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WO2012008002A1 - Dispositif de commande de diode électroluminescente et dispositif semi-conducteur de commande de diode électroluminescente - Google Patents

Dispositif de commande de diode électroluminescente et dispositif semi-conducteur de commande de diode électroluminescente Download PDF

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Publication number
WO2012008002A1
WO2012008002A1 PCT/JP2010/006790 JP2010006790W WO2012008002A1 WO 2012008002 A1 WO2012008002 A1 WO 2012008002A1 JP 2010006790 W JP2010006790 W JP 2010006790W WO 2012008002 A1 WO2012008002 A1 WO 2012008002A1
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WIPO (PCT)
Prior art keywords
switching element
circuit
current
value
emitting diode
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PCT/JP2010/006790
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English (en)
Japanese (ja)
Inventor
崇 國松
敏史 石田
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Panasonic Corp
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Panasonic Corp
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]

Definitions

  • the present invention relates to a light emitting diode driving device and a semiconductor device used for driving the light emitting diode, and more particularly to a step-down chopper type driving device.
  • a light emitting diode driving device for driving a light emitting diode (hereinafter referred to as an LED (Light Emitting Diode)) and a light emitting diode driving semiconductor device used for driving the LED have been developed and put into practical use.
  • mass production of lighting devices such as LED bulbs using white LEDs as a light source has been actively performed.
  • Various drive circuits for appropriately driving LEDs have been proposed. For example, when a plurality of LEDs are connected in series, if a specific LED becomes open, the output voltage may rise unnecessarily, increasing the load on the components, or excessively high drive circuitry. There was a risk of voltage being applied.
  • Patent Document 1 a light emitting diode driving device (illumination device) having a function of detecting such LED open and switching to a safe operation mode is disclosed.
  • FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus described in Patent Document 1.
  • FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus described in Patent Document 1.
  • the conventional light emitting diode driving device 11 is connected to an LED light source unit 18 including a plurality of LEDs 18a connected in series, and controls lighting of the plurality of LEDs 18a. As shown in FIG. 8, the conventional LED driving device 11 flows through the LED light source unit 18 and the lighting circuit unit 12 including a converter that converts the power supply voltage into a predetermined DC voltage and outputs the voltage to the LED light source unit 18. And a current detection resistor 13 for detecting a current. Further, the conventional light emitting diode driving device 11 includes a voltage detection circuit unit 19.
  • the lighting circuit unit 12 is a so-called step-up DC / DC converter, and includes an inductance element 14, a diode 15, a switching element 16, a capacitance element 20, and a drive control circuit 17.
  • the inductance element 14 is connected to the high voltage side of the DC power supply VE.
  • the diode 15 is a backflow preventing diode having an anode connected to the other end of the inductance element 14.
  • the switching element 16 is a power element such as an FET (Field Effect Transistor) connected between the other end of the inductance element 14 and the low voltage side of the DC power supply VE.
  • Capacitance element 20 is connected between the cathode of diode 15 and the low voltage side of DC power supply VE.
  • the drive control circuit 17 controls the output voltage V of the lighting circuit unit 12.
  • the drive control circuit 17 controls on and off of the switching element 16 while monitoring the output of the lighting circuit unit 12 by the voltage detection circuit unit 19 and the current detection resistor 13.
  • the drive control circuit 17 has a control function and a mode setting function.
  • the control function is a function for controlling on and off of the switching element 16.
  • the mode setting function is a function for setting the operation mode of the lighting circuit unit 12 to a normal mode or a standby mode for non-connection (no load) (or a stop mode) depending on the connection state of the LED light source unit 18.
  • the current detection resistor 13 is a resistor connected between the cathode of the LED light source unit 18 and the low voltage side of the DC power source VE.
  • the current detection resistor 13 converts the current I flowing through the LED light source unit 18 into voltage information and feeds it back to the feedback terminal FB of the drive control circuit 17.
  • the drive control circuit 17 determines that the LED light source unit 18 is connected if the current I detected by the current detection resistor 13 exceeds a predetermined threshold value.
  • the drive control circuit 17 operates in a normal mode in which the output voltage of the converter is adjusted so that the current flowing through the LED light source unit 18 becomes a predetermined set value.
  • the drive control circuit 17 determines that the LED light source unit 18 is not connected and operates in the standby mode or the stop mode.
  • the standby mode is a mode in which the output voltage is decreased to a predetermined value
  • the stop mode is a mode in which the output of the lighting circuit unit 12 is stopped.
  • the predetermined threshold value is set such that when the LED light source unit 18 is normally connected, the current flowing through the LED light source unit 18 is at least a value exceeding the threshold value.
  • the conventional light-emitting diode driving device described in Patent Document 1 requires a current detection resistor for detecting the current flowing through the LED.
  • the drive control circuit requires a terminal for inputting the current detection information detected by the current detection resistor, thereby reducing the size and space of the driving device, the size of the lighting circuit IC, and the size of the terminal. It becomes a problem when it is realized. Further, since the LED current flows through the current detection resistor, the loss of power consumption in the current detection resistor is large.
  • a step-down drive circuit is effective to efficiently supply a high voltage rectified and smoothed based on a commercial AC power supply (AC100V / 240V, etc.) to an LED light source that is lower than the input power supply voltage. It is.
  • AC100V / 240V, etc. a commercial AC power supply
  • the potential of the current detection resistor becomes a high voltage, and thus a high voltage element is required in the drive control circuit in order to input the detected information to the drive control circuit.
  • a smoothing capacitor and a dummy resistor are often connected in parallel in the immediate vicinity of the LED light source in order to reduce ripples in the current waveform flowing through the LED light source and to prevent noise. In such a case, even if the LED is open, current may flow through the smoothing capacitor and the dummy resistor, so the drive control circuit may not be able to detect normally.
  • An object of the present invention is to provide a light-emitting diode driving device and a light-emitting diode driving semiconductor device capable of normally detecting LED open.
  • a light-emitting diode driving device is a step-down chopper type light-emitting diode driving device that drives one or more light-emitting diodes.
  • An LED light source unit a choke coil connected in series to the LED light source unit, a series connection loop circuit including a diode for supplying back electromotive force generated in the choke coil to the LED light source unit, and the series connection
  • a power supply unit that is connected to a loop circuit and supplies an input voltage to the LED light source unit and the choke coil, and a switching unit that is connected to the series connection loop circuit and that controls the current flowing through the LED light source unit.
  • a driving circuit comprising: a switching element block; a control circuit block;
  • the switching element block includes a switching element that is connected in series to the series connection loop circuit and intermittently supplies an input voltage supplied by the power supply unit to the LED light source unit and the choke coil
  • the control circuit block includes a SW control circuit that controls switching of the switching element on and off, and a current value of a current that flows through the switching element when the switching element is turned off.
  • An upper limit determination circuit for determining whether the current value of the current flowing through the switching element is equal to or higher than a predetermined lower limit reference value; The current value of the current flowing through the switching element is equal to or lower than the upper limit reference value by the upper limit determination circuit.
  • the switching element is controlled by a method different from that in the first operation mode.
  • the current flowing through the switching element is used to detect the opening of the LED, a dedicated resistor and terminal are not required. That is, since a resistor for detecting the current flowing through the LED light source unit is not required, it is not necessary to consider a loss in the resistor, and high-efficiency driving is possible.
  • the current value of the current flowing through the switching element when the switching element is turned off is equal to or lower than the upper limit reference value, the current flows through the switching element due to the open of the LED (high load impedance state of the LED light source unit). It can be detected that the current has decreased. Therefore, since it is possible to determine whether the LED light source unit is open using the current flowing through the switching element, an additional terminal is not required, and the light emitting diode driving device can be reduced in size and space can be saved.
  • the value of the current flowing through the switching element is greater than or equal to the lower limit reference value
  • the value of the current flowing through the switching element is low even if the LED is normal (for example, when the input voltage is low, or when a smoothing capacitor or the like is connected in parallel with the LED, it is possible to prevent erroneous detection that the LED is open.
  • the number of times that the value of the current flowing through the switching element is less than or equal to the upper limit reference value and greater than or equal to the lower limit reference value is measured and the measured number is compared with the determination reference value, the LED continuously The case where it is open can be detected.
  • the dedicated resistor and terminal are not required, and even when the input voltage is low and when the smoothing capacitor or the like is connected in parallel to the LED, the LED normally Open can be detected.
  • the control circuit block further includes a current detection circuit that detects a current value of a current flowing through the switching element, and the upper limit determination circuit is configured such that the current value detected by the current detection circuit is equal to the upper limit reference.
  • the lower limit determination circuit may determine whether or not the current value detected by the current detection circuit is equal to or greater than the lower limit reference value.
  • both the comparison with the upper limit reference value (upper limit determination) and the comparison with the lower limit reference value (lower limit determination) use the current value detected by the current detection circuit, the determination is easily performed. be able to. For example, by performing the upper limit determination and the lower limit determination at the same time, a circuit for temporarily holding one of the determination results is not required, so that the circuit configuration necessary for the determination can be simplified.
  • the SW control circuit switches the switching element from OFF to ON at a preset period, and the upper limit determination circuit is a period during which the switching element is ON in the period.
  • the maximum duty period that is the maximum value of the switching element is set, and the period during which the switching element is on reaches the maximum duty period, the current value of the current flowing through the switching element is less than or equal to the upper reference value You may have the maximum duty detection circuit to determine.
  • the period during which the switching element is on in the cycle reaches the maximum duty period (maximum duty drive).
  • the open state of the LED can be detected by counting the number of times when the maximum duty drive is performed. At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the maximum duty drive is performed, so that the open detection accuracy can be improved.
  • the SW control circuit turns on the switching element after a predetermined period from when the switching element is turned off, and the upper limit determination circuit turns on the switching element.
  • a maximum on-period that is a maximum value of a certain period of time is set, and when the period during which the switching element is on reaches the maximum on-period, the current value of the current flowing through the switching element is less than or equal to the upper reference value You may have the maximum ON period detection circuit determined to exist.
  • the period during which the switching element is on reaches the maximum on period (maximum on-time driving).
  • the current flowing through the switching element is equal to or lower than the upper reference value. Therefore, regardless of whether or not the current flowing through the switching element reaches a preset upper limit reference value, it is possible to detect the opening of the LED by counting the number of times when the maximum on-time driving is performed. . At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the driving is the maximum on-time driving, so that the open detection accuracy can be improved.
  • the control circuit block further includes a peak current detection circuit that outputs a peak current detection signal when the current value of the current flowing through the switching element reaches a preset peak value, and the SW control The circuit may turn off the switching element when the peak current detection signal is input in the first operation mode, and the upper reference value may be a value equal to or lower than the peak value.
  • the upper limit reference value can be arbitrarily set according to the current value of the LED light source unit, it is possible to improve the detection accuracy of LED open.
  • the control circuit block may further include a current adjustment circuit that dynamically changes the peak value according to a value input from the outside.
  • the current adjustment circuit may further change the upper limit reference value in accordance with the change of the peak value.
  • the open detection accuracy of the LED light source unit can be improved.
  • the power supply unit may include an AC power source that generates an AC voltage, and a rectifier circuit that generates the input voltage that is a pulsating voltage by rectifying the AC voltage.
  • the control circuit block further includes an input voltage detection circuit for determining whether or not the input voltage is equal to or higher than a predetermined set voltage, and the SW control when the input voltage is equal to or higher than the set voltage.
  • an input voltage detection circuit for determining whether or not the input voltage is equal to or higher than a predetermined set voltage
  • the SW control circuit causes the switching element to turn on and off in the first operation mode.
  • a start / stop circuit for stopping the switching.
  • the switching operation of the switching element (on / off switching control) is stopped. Therefore, the switching operation can be stopped before the input voltage value and the output voltage value are close to each other and the on-time of the switching element is extended to reach the maximum on-time or the maximum on-duty. The possibility of false detection is low.
  • the series connection loop circuit further includes a resistor connected in parallel to the LED light source unit, and the lower limit reference value is a current of a current flowing through the resistor when at least one of the light emitting diodes is open. It may be a value less than or equal to the value.
  • the lower limit determination circuit detects that the current is flowing because the LED light source unit is open. be able to. Therefore, the detection accuracy of LED open can be improved.
  • the series-connected loop circuit further includes a capacitor connected in parallel to the LED light source unit, and the lower limit reference value is a current flowing through the capacitor when at least one of the light emitting diodes is open. It may be a value less than or equal to the value.
  • the lower limit determination circuit detects that the current is flowing because the LED light source unit is open. be able to. Therefore, the detection accuracy of LED open can be improved.
  • the series connection loop circuit further includes a resistor connected in parallel to the LED light source unit, and a capacitor connected in series to the resistor and connected in parallel to the LED light source unit, and the lower limit reference value is When the at least one light emitting diode is open, it may be a value equal to or smaller than the current value of the current flowing through the resistor and the capacitor.
  • the lower limit determination circuit may reset the determination result each time the switching element is turned on.
  • the determination result by the lower limit determination circuit is reset for each switching cycle of the switching element, the possibility of erroneous detection can be reduced.
  • the lower limit determination circuit may determine whether a current value of a current flowing through the switching element is equal to or higher than the lower limit reference value during a period from when the switching element is turned on to when the switching element is turned off. .
  • the count circuit may reset the number of times when the measured number does not increase in synchronization with the timing at which the switching element is turned off.
  • the number of counts is reset when the current flowing through the switching element is continuously exceeding the upper limit reference value or the peak value is reached while the number of counts is continuously increasing. Can be lowered.
  • the count circuit may reset the measured number of times when the switching of the switching element is stopped.
  • the SW control circuit may stop the switching element from latching as the second operation mode.
  • the SW control circuit may perform a timer intermittent operation in which the switching element is driven and stopped at regular intervals as the second operation mode.
  • the energy output by the switching operation is reduced, so that it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element.
  • the light emitting diode driving device may further include an abnormality processing circuit that outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit is equal to or greater than the determination reference value. Good.
  • an abnormality determination signal is output. Therefore, the supply of input voltage is stopped using this abnormality determination signal, and the peripheral device is informed that the LED light source unit is open. By transmitting or sounding an alarm, the user can be informed that the LED light source unit is abnormal.
  • a semiconductor device for driving a light emitting diode is a semiconductor device for driving a light emitting diode, and includes the switching element block and the control circuit block. And the control circuit block are formed on the same semiconductor substrate or incorporated in the same package.
  • the switching element and the control circuit can be incorporated into one package. Therefore, if the light emitting diode driving device is configured using this semiconductor device, the number of parts of the light emitting diode driving device can be greatly reduced, and the light emitting diode driving device can be easily reduced in size, weight and cost. Can be realized.
  • a dedicated resistor and terminal are not required, and even when the input voltage is low and when a smoothing capacitor or the like is connected in parallel to the LED, the open of the LED is normally detected. be able to.
  • FIG. 1 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 2A is a waveform diagram showing a waveform of an input voltage and an operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 2B is a waveform diagram showing the waveform of the input voltage and the operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 3 is a waveform diagram showing an example of a waveform of a current flowing through the switching element according to Embodiment 1 of the present invention.
  • FIG. 1 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 2A is a waveform diagram showing a waveform of an input voltage and an operation period of the light emitting diode driving apparatus according to Embodiment 1 of the present invention.
  • FIG. 4 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 2 of the present invention.
  • FIG. 5 is a waveform diagram showing an example of a waveform of a current flowing through the switching element according to Embodiment 2 of the present invention.
  • FIG. 6A is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention.
  • FIG. 6B is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention.
  • FIG. 6C is a circuit diagram showing an example of a serial connection loop circuit according to Embodiment 3 of the present invention.
  • FIG. 7 is a circuit diagram showing an example of a light-emitting diode driving apparatus according to Embodiment 4 of the present invention.
  • FIG. 8 is a circuit diagram showing a configuration of a conventional light emitting diode driving apparatus.
  • the light-emitting diode driving apparatus is a step-down chopper type driving apparatus that drives one or more light-emitting diodes (LEDs), and the current flowing through the switching element at a predetermined timing is the upper limit reference. It is determined whether it is less than the value and greater than or equal to the lower limit reference value. Then, the LED driving apparatus according to Embodiment 1 of the present invention counts the number of times that the current flowing through the switching element is determined to be equal to or lower than the upper limit reference value and equal to or higher than the lower limit reference value, and the number of times counted When the value is equal to or greater than a predetermined criterion value, abnormality processing is performed.
  • FIG. 1 is a circuit diagram showing an example of the configuration of the light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention.
  • the light-emitting diode driving apparatus 100 according to Embodiment 1 of the present invention is a step-down chopper type driving apparatus that drives one or more LEDs.
  • the light emitting diode driving device 100 includes a power supply unit 110, a series connection loop circuit 120, a switching driving circuit 200, a capacitor 130, and a resistor 140.
  • the switching drive circuit 200 is an example of a semiconductor device according to the first embodiment of the present invention.
  • the power supply unit 110 is connected to the series connection loop circuit 120 and supplies an input voltage to the LED light source unit 121 and the choke coil 122 included in the series connection loop circuit 120. As shown in FIG. 1, the power supply unit 110 includes an AC power supply 111, a rectifier circuit 112, and a smoothing capacitor 113.
  • AC power supply 111 generates an AC voltage.
  • the AC power supply 111 is a commercial power supply.
  • the rectifier circuit 112 is connected to the AC power source 111 and generates a pulsating voltage by rectifying the AC voltage.
  • the rectifier circuit 112 is a full-wave rectifier circuit, for example, and generates a full-wave rectified voltage from an AC voltage.
  • the high potential side of the rectifier circuit 112 is connected to the series connection loop circuit 120, and the low potential side is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the smoothing capacitor 113 generates the input voltage Vin by smoothing the full-wave rectified voltage generated by the rectifier circuit 112.
  • the high potential side of the smoothing capacitor 113 is connected to the series connection loop circuit 120, and the low potential side is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the generated input voltage Vin is supplied to the LED light source unit 121 and the choke coil 122.
  • the waveform of the input voltage Vin is sufficiently smoothed or becomes a pulsating waveform depending on the capacitance value of the smoothing capacitor 113.
  • the case where the input voltage waveform is a pulsating voltage waveform as shown in FIG. 2A will be described as an example.
  • the series connection loop circuit 120 includes an LED light source unit 121, a choke coil 122, and a diode 123. As shown in FIG. 1, the LED light source unit 121, the choke coil 122, and the diode 123 form a loop.
  • the LED light source unit 121 includes a plurality of light emitting diodes (LEDs). The plurality of LEDs are connected in series.
  • the choke coil 122 is connected to the LED light source unit 121 in series.
  • the diode 123 is connected in parallel to the LED light source unit 121 and the choke coil 122, and supplies back electromotive force generated in the choke coil 122 to the LED light source unit 121.
  • the high potential side of the rectifier circuit 112 and the smoothing capacitor 113 is connected to the anode terminal side of the LED light source 121 and the cathode terminal side of the diode 123.
  • the common connection point between the choke coil 122 and the anode terminal of the diode 123 is connected to the high potential side terminal DRN of the switching drive circuit 200.
  • the choke coil 122 is connected to the cathode terminal side of the LED light source unit 121, but may be connected to the anode terminal side. Further, an LED light source in which a plurality of light emitting diodes are connected in series will be described as an example. However, it is sufficient that the number of light emitting diodes is one or more.
  • the plurality of light emitting diodes may be connected not only in series but also in a matrix. The same applies to the embodiments described below.
  • the switching drive circuit 200 is an example of a light emitting diode driving semiconductor device according to Embodiment 1 of the present invention, and is a semiconductor device for constant current control of the current flowing through the LED light source unit 121. As shown in FIG. 1, the switching drive circuit 200 includes a switching element block 210 and a control circuit block 220. The switching drive circuit 200 has five terminals (rectified voltage application terminal IN, high potential side terminal DRN, low potential side terminal GND, power supply terminal VCC, and external current adjustment terminal EX) connected to the outside.
  • the rectified voltage application terminal IN is connected to the high potential side of the rectifier circuit 112, and an input voltage Vin having a pulsating voltage waveform is input thereto.
  • the high potential side terminal DRN is connected to the series connection loop circuit 120 as described above.
  • the low potential side terminal GND is a ground terminal connected to the ground potential of the control circuit block 220 and serves as a reference potential (ground potential).
  • the capacitor 130 is connected between the power supply terminal VCC and the low potential side terminal GND.
  • the external current adjustment terminal EX is connected to the power supply terminal VCC via the resistor 140.
  • the switching element block 210 includes a switching element 211 and a current detection switching element 212.
  • the switching element 211 is connected in series to the series connection loop circuit 120 and intermittently supplies the input voltage Vin supplied from the power supply unit 110 to the LED light source unit 121 and the choke coil 122. Specifically, the switching element 211 is connected between the series connection loop circuit 120 and the grounded low potential side terminal GND.
  • the current detection switching element 212 is connected in parallel with the switching element 211 so that a current having a constant current ratio flows smaller than the current flowing through the switching element 211.
  • the high potential side terminal of the switching element 211 and the high potential side terminal of the current detection switching element 212 are connected in common and connected to the high potential side terminal DRN of the switching drive circuit 200.
  • the control terminal of the switching element 211 and the control terminal of the current detection switching element 212 are connected in common, and the control signal Vg is applied from the control circuit block 220.
  • the low potential side terminal of the switching element 211 is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the low potential side terminal of the current detection switching element 212 is connected to one end of a resistor 221 included in the control circuit block 220. The other end of the resistor 221 is connected to the low potential side terminal GND of the switching drive circuit 200.
  • the switching element 211 and the current detection switching element 212 are supplied with a common control signal Vg at their commonly connected control terminals, the switching operation is performed simultaneously. That is, the switching element 211 and the current detection switching element 212 are turned on or turned off at the same timing.
  • the control circuit block 220 includes a resistor 221, a junction FET 222, a regulator circuit 223, an input voltage detection circuit 224, a start / stop circuit 225, a current adjustment circuit 226, a peak current detection circuit 227, and a SW control circuit. 228, a count circuit 229, and a current determination circuit 230.
  • the resistor 221 and the current detection switching element 212 are an example of a current detection circuit that detects a current value of a current flowing through the switching element 211.
  • the resistor 221 has one end connected to the low potential side terminal of the current detection switching element 212 and the other end connected to the low potential side terminal GND.
  • the resistor 221 is a resistor for converting a current flowing through the current detection switching element 212 into a voltage. That is, in the embodiment of the present invention, the current flowing through the switching element 211 is detected as voltage information.
  • the resistor 221 does not directly measure the current flowing through the switching element 211 but measures the current flowing through the current detection switching element 212. Since the current flowing through the switching element 212 for current detection is proportional to the current flowing through the switching element 211, the current value of the current flowing through the switching element 211 is indirectly measured by the configuration according to the embodiment of the present invention. be able to.
  • the high potential side terminal of the junction FET 222 is connected to the rectified voltage application terminal IN.
  • the low potential side terminal of the junction FET 222 is connected to the regulator circuit 223 and the input voltage detection circuit 224.
  • the regulator circuit 223 outputs the low potential side voltage of the junction FET 222 to the capacitor 130 via the power supply terminal VCC.
  • the regulator circuit 223 operates so that the voltage of the capacitor 130 (the voltage Vcc of the power supply terminal VCC) becomes constant.
  • the operation power supply voltage of the control circuit block 220 is generated using the voltage obtained by rectifying the AC voltage from the commercial power supply (AC power supply 111), the voltage during operation of the control circuit block 220 can be kept constant. it can. Therefore, on / off control (switching control) of the switching element 211 by the control circuit block 220 can be stabilized.
  • the input voltage detection circuit 224 determines whether or not the input voltage generated by the power supply unit 110 is equal to or higher than a predetermined set voltage. Specifically, the input voltage detection circuit 224 receives the low potential side voltage of the junction FET 222 and compares it with an internal reference voltage to detect whether the input power supply voltage Vin is equal to or higher than the set voltage. . Then, the input voltage detection circuit 224 outputs a detection signal whose state changes according to the detection result. Specifically, the signal level is high when the input power supply voltage Vin is equal to or higher than the set voltage, and a low level signal is output when the input power voltage Vin is lower than the set voltage.
  • the output terminal of the input voltage detection circuit 224 is connected to the input terminal of the start / stop circuit 225.
  • both the regulator circuit 223 and the input voltage detection circuit 224 are configured to be connected to the junction FET 222, but the present invention is not limited to this.
  • Various other circuits for converting the input voltage, which is a high voltage, into the power supply voltage Vcc of the switching drive circuit 200 are provided and are well known to those skilled in the art.
  • the configuration of the input voltage detection circuit 224 is not limited to this.
  • the input voltage is input from the rectified voltage application terminal IN to the switching drive circuit 200 through a voltage reduction resistor, and the divided voltage using resistance division is compared with the internal reference voltage inside the switching drive circuit 200, thereby obtaining the input voltage.
  • both the input signal to the regulator circuit 223 and the input signal to the input voltage detection circuit 224 need not be applied from the rectified voltage application terminal IN, and may be configured to have separate application terminals.
  • the start / stop circuit 225 causes the SW control circuit 228 in the first operation mode to start switching on and off of the switching element when the input voltage is equal to or higher than the set voltage. Further, the start / stop circuit 225 causes the SW control circuit 228 to stop switching of the switching element on and off when the input voltage is less than the set voltage.
  • the SW control circuit 228 and its operation mode will be described later.
  • the start / stop circuit 225 outputs either an ENABLE signal or a DISABLE signal according to the signal level from the input voltage detection circuit 224.
  • a signal (ENABLE signal or DISABLE signal) output from the start / stop circuit 225 is input to the SW control circuit 228 and the count circuit 229.
  • the ENABLE signal is a signal that enables switching control of the switching element 211 (that is, switching of the switching element 211 on and off), for example, a signal having a high signal level.
  • the DISABLE signal is a signal for stopping the switching control of the switching element 211, for example, a signal having a low signal level.
  • the current adjustment circuit 226 is connected to the external current adjustment terminal EX.
  • the current adjustment circuit 226 is connected to the peak current detection circuit 227.
  • the current adjustment circuit 226 inputs a signal corresponding to the current value applied from the external current adjustment terminal EX to the peak current detection circuit 227. That is, the current adjustment circuit 226 adjusts the reference voltage Vref according to the current value input from the external current adjustment terminal EX, and outputs a signal indicating the adjusted reference voltage Vref.
  • the peak current detection circuit 227 detects whether or not the current flowing through the switching element 211 has reached a preset peak value. When the current flowing through the switching element 211 reaches a preset peak value, the peak current detection circuit 227 outputs a peak current detection signal ILIMIT indicating that fact.
  • the peak current detection circuit 227 is a comparator having a plus input terminal, a minus input terminal, and an output terminal.
  • a connection portion between the current detection switching element 212 and the resistor 221 is connected to the positive input terminal, and a detection voltage Vsn generated in the resistor 221 by the current flowing through the current detection switching element 212 is input.
  • the reference voltage Vref adjusted by the current adjustment circuit 226 is input to the negative input terminal.
  • the output terminal is connected to the SW control circuit 228.
  • the peak current detection circuit 227 outputs a peak current detection signal ILIMIT having a high signal level when the detection voltage Vsn applied to the plus input terminal becomes equal to or higher than the reference voltage Vref.
  • the peak current detection signal ILIMIT output from the peak current detection circuit 227 is input to the SW control circuit 228. Since the reference voltage Vref is determined by the power supply voltage Vcc and the value of the resistor 140, it can be changed to an arbitrary value by changing the value of the resistor 140.
  • the current flowing through the current detection switching element 212 and the resistor 221 has a constant current ratio with respect to the current ID flowing through the switching element 211. Therefore, the peak current detection circuit 227 detects whether or not the current ID flowing through the switching element 211 has reached a predetermined peak value Ip by comparing the reference voltage Vref and the detection voltage Vsn. Can do. In addition, since the current flowing through the current detection switching element 212 and the resistor 221 is smaller than the current flowing through the switching element 211, the power loss can be reduced as compared with the case where the current flowing through the switching element 211 is directly detected by the resistor.
  • the peak current detection circuit 227 can compare the internal reference voltage Vref and the detection voltage Vsn.
  • the method for detecting the current flowing through the switching element 211 is not limited to these methods, and the detection method is not limited.
  • the current adjustment circuit 226 may dynamically change the peak value according to a value input from the outside. That is, the current adjustment circuit 226 may change the peak value by changing the reference voltage Vref according to the current value input from the external current adjustment terminal EX. Further, the current adjustment circuit 226 may change an upper limit reference value to be described later with the change of the peak value.
  • SW control circuit 228 controls on / off switching of switching element 211 in the first operation mode. Further, as will be described later, when the number of times measured by the count circuit 229 is equal to or greater than a predetermined determination reference value, the SW control circuit 228 is set to the first operation mode in the second operation mode for abnormality processing. Controls the switching element 211 in a different manner. As the determination reference value (number of times) for the number of counts, an optimum value is selected from about a dozen times depending on the oscillation frequency of the switching element 211 and the off time in the first operation mode.
  • the first operation mode is a normal operation mode and is a mode that is executed when it is determined that the LED light source unit 121 is not open. That is, the first operation mode is a mode in which switching control of the switching element 211 is performed according to a predetermined control method.
  • the second operation mode is an operation mode that is different from the first operation mode, and is an operation mode that is executed when any abnormality is detected in the series connection loop circuit 120. For example, in the second operation mode, the switching control of the switching element 211 is stopped.
  • the determination reference value is determined to such an extent that the switching element 211, the current detecting switching element 212, and other components can be prevented from being destroyed by applying an excessive voltage. Specifically, the determination reference value is determined based on the oscillation frequency of the switching element 211, the current value flowing through the switching element 211 when the LED light source unit 121 is opened, and the like.
  • the SW control circuit 228 performs switching control of the switching element 211 as an operation in the first operation mode during a period in which the ENABLE signal is input from the start / stop circuit 225.
  • the SW control circuit 228 inputs the switching control signal Vg to the switching element 211 at a preset timing, thereby turning on the switching element 211 and causing a current to flow through the switching element 211.
  • the SW control circuit 228 turns off the switching element 211 at the timing when the peak current detection signal ILIMIT output from the peak current detection circuit 227 is input. Thereby, the SW control circuit 228 performs control so that the peak current value of the current ID flowing through the switching element 211 is always the peak value Ip.
  • the SW control circuit 228 stops the operation of the switching element 211 during a period in which the DISABLE signal is input from the start / stop circuit 225.
  • the switching control method of the switching element 211 includes a PWM (Pulse Width Modulation) system that controls the on-duty of switching, a current mode PWM control system that changes the peak value of the current flowing through the switching element 211, and the like.
  • PWM Pulse Width Modulation
  • a current mode PWM control system that changes the peak value of the current flowing through the switching element 211
  • the control method is not limited.
  • the configuration based on these control systems is not shown in FIG.
  • the current determination circuit 230 is connected to a common connection portion between the current detection switching element 212 and the resistor 221 and receives the detection voltage Vsn. As shown in FIG. 1, the current determination circuit 230 includes an integration circuit 231, two comparators 232 and 233, and an AND circuit 234.
  • Integral circuit 231 receives detection voltage Vsn and outputs the maximum value of detection voltage Vsn. Note that when the switching element 211 is turned off, the output signal of the integrating circuit 231 is reset.
  • the comparator 232 is an example of an upper limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or lower than a predetermined upper limit reference value when the switching element 211 is turned off. In the present embodiment, the comparator 232 determines whether or not the current value detected by the resistor 221 is equal to or lower than the upper limit reference value.
  • the upper reference value is a value equal to or less than the peak value Ip.
  • the upper limit reference voltage IDH is input to the plus input terminal, and the maximum value of the detection voltage Vsn corresponding to the current value detected by the resistor 221 is input to the minus input terminal.
  • the upper limit reference voltage IDH is set to a value smaller than a voltage corresponding to the peak value Ip (specifically, the reference voltage Vref).
  • the comparator 232 outputs a high level signal to the AND circuit 234 when the maximum value of the detection voltage Vsn is smaller than the upper limit reference voltage IDH.
  • the comparator 233 is an example of a lower limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or higher than a predetermined lower limit reference value. In the present embodiment, the comparator 233 determines whether or not the current value detected by the resistor 221 is greater than or equal to the lower limit reference value.
  • the comparator 233 the maximum value of the detection voltage Vsn corresponding to the current value detected by the resistor 221 is input to the plus input terminal, and the lower limit reference voltage IDL is input to the minus input terminal.
  • the comparator 233 outputs a high level signal to the AND circuit 234 when the maximum value of the detection voltage Vsn is higher than the lower limit reference voltage IDL.
  • both the comparators 232 and 233 perform determination at the timing when the switching element 211 is turned off. Since the current flowing through the switching element 211 is maximized immediately before the switching element 211 is turned off, the comparators 232 and 233 use the maximum value of the current flowing through the switching element 211 (actually, the corresponding detection voltage Vsn). Make a decision.
  • the AND circuit 234 has two input terminals and an output terminal, calculates a logical product of signals input to the input terminal, and outputs the calculation result from the output terminal. Specifically, the output signals of the comparators 232 and 233 are input to the two input terminals, respectively, and the logical product of the output signals of the comparators 232 and 233 is output to the count circuit 229.
  • the values of the upper limit reference voltage IDH and the lower limit reference voltage IDL are arbitrary values set in advance so that Vref> IDH> IDL is satisfied.
  • the value of the upper limit reference voltage IDH may be adjusted according to the value of the reference voltage Vref adjusted by the current adjustment circuit 226.
  • the current determination circuit 230 outputs a high-level signal to the count circuit 229 when the maximum value of the detection voltage Vsn has a relationship of not less than IDL and not more than IDH.
  • the count circuit 229 measures the number of times that the current value of the current flowing through the switching element 211 is determined to be equal to or lower than the upper limit reference value by the upper limit determination circuit and is determined to be equal to or higher than the lower limit reference value by the lower limit determination circuit. .
  • the count circuit 229 is a circuit that counts the number of high-level signals output from the current determination circuit 230.
  • the count circuit 229 outputs an open signal to the SW control circuit 228 when the count number reaches a predetermined determination number (determination reference value).
  • the count circuit 229 receives an output signal (ENABLE signal or DISABLE signal) from the start / stop circuit 225.
  • an output signal ENABLE signal or DISABLE signal
  • the count number of the count circuit 229 is reset.
  • 2A and 2B are waveform diagrams showing an example of an input voltage waveform and an operation period of the light emitting diode driving apparatus 100 according to Embodiment 1 of the present invention.
  • FIG. 2A is a diagram showing the relationship between the input voltage waveform and the detection voltage Vinuv of the input voltage detection circuit 224.
  • the period of the input voltage Vin> the detection voltage Vinuv is a period in which the switching drive circuit 200 and the control circuit block 220 can operate.
  • the switching element 211 stops operating.
  • FIG. 2B is a diagram showing a waveform when the input voltage gradually increases when the input voltage is a pulsating waveform.
  • the switching drive circuit 200 and the control circuit block 220 are not operating, so the switching element 211 is also not operating.
  • the control circuit block 220 can operate in the period T2 in which the input voltage Vin is higher than the detection voltage Vinuv and lower than the output voltage VF_LED. Therefore, the SW control circuit 228 inputs the switching control signal Vg to the switching element 211, and the switching element 211 starts a switching operation, but no current flows through the switching element 211.
  • a waveform of a current flowing through the switching element 211 during normal operation is indicated by IDS1 in FIG.
  • the current waveform IDS1 is a simple increase current waveform having a slope (Vin ⁇ VF_LED) / L determined from the inductance value L of the choke coil 122 and the voltage difference (Vin ⁇ VF_LED) between the two terminals of the LED light source 121. It becomes.
  • the SW control circuit 228 When the current ID flowing through the switching element 211 reaches a preset peak value Ip, the SW control circuit 228 outputs a control signal Vg that turns off the switching element 211, thereby causing the peak of the current flowing through the switching element 211.
  • the value is always controlled to be constant at Ip.
  • the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220 (that is, the detection voltage Vsn detected by the resistor 221), the upper limit reference voltage IDH, and the lower limit reference voltage IDL is expressed as “the maximum value of Vsn> IDH. Since “> IDL”, the current determination circuit 230 does not output a high level signal to the count circuit 229.
  • the internal control circuit block 220 and the switching element 211 start on and off control (switching operation).
  • the period T2 no current flows through the switching element 211 as described above.
  • the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220, the upper limit reference voltage IDH, and the lower limit reference voltage IDL is “IDH> IDL> Vsn maximum value”.
  • the circuit 230 does not output a high level signal to the count circuit 229.
  • the open failure of the light-emitting diode can be classified into two types, a case where it is completely electrically insulated and a half-open state where a resistance component remains.
  • the input voltage Vin is not applied to the choke coil 122 and the switching element 211. For this reason, there is no possibility that a high voltage is applied to the choke coil 122 and the switching element 211 even if the LED light source 121 is opened.
  • the current that flows through the switching element 211 when the LED light source unit 121 is in a semi-open state is shown in IDS2 of FIG.
  • the impedance is higher than that in the normal state, and the current increase rate is reduced.
  • the switching element 211 is turned off according to the control method of the SW control circuit 228 without the maximum value of the current ID flowing through the switching element 211 reaching the peak value Ip.
  • the relationship between the maximum value of the detection voltage Vsn inside the control circuit block 220, the upper limit reference voltage IDH, and the lower limit reference voltage IDL is “IDH> maximum value of Vsn> IDL”.
  • a high level signal is output to the count circuit 229.
  • the count circuit 229 determines that the LED light source 121 that is a load is open when the number of counts is equal to or greater than a predetermined determination reference value, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped as the second operation mode for abnormality processing.
  • the light emitting diode driving apparatus 100 configured as described above does not require a dedicated resistor for detecting the current flowing through the LED light source unit 121, and is a current flowing through the switching element 211.
  • the open determination of the LED light source part 121 is possible.
  • the switching drive circuit 200 does not require an additional terminal, and the light emitting diode drive device 100 can be reduced in size and space.
  • the light-emitting-diode drive device 100 includes the count circuit 229, and determines a state where the LED light source unit 121 may be open a plurality of times. For example, as described above, when the input voltage is low, such as when the power is turned on, there is a case where it is determined that the LED light source unit 121 is open even if the LED light source unit 121 is not open. In this case, it is determined that the input voltage is not open (that is, normal) as the input voltage increases.
  • the determination is performed a plurality of times, even if it is determined that the circuit is open a predetermined number of times or less, it is not open. judge. Therefore, according to the light emitting diode drive device 100 according to Embodiment 1 of the present invention, erroneous detection can be prevented by setting the determination reference value to an appropriate value.
  • the light emitting diode driving apparatus 100 includes the current adjustment circuit 226, and can adjust the peak value Ip flowing through the switching element 211 to an appropriate value from the outside. Therefore, the LED open detection accuracy can be improved by arbitrarily setting the upper limit reference voltage IDH and the lower limit reference voltage IDL.
  • the light-emitting diode driving apparatus 100 includes the input voltage detection circuit 224, and stops the on / off control (switching operation) of the switching element 211 when the input voltage decreases. Therefore, the switching operation can be stopped before the input voltage value and the output voltage value are close to each other and the ON time of the switching element 211 is extended to reach the maximum ON time or the maximum ON duty period. The possibility of false detection of open is low.
  • the switching operation of the switching element 211 is stopped by the input voltage detection circuit 224.
  • the count is reset. That is, the count circuit 229 resets the measured number of times when the switching (switching operation) of the switching element 211 is stopped. For this reason, when the switching operation of the switching element 211 is restarted by the input voltage detection circuit 224 next, the number of counts is not held, so the possibility of erroneous detection is reduced.
  • the switching element block 210 and the control circuit block 220 are integrated on the same substrate, or the switching drive circuit 200 is configured as a semiconductor device incorporated in the same package, whereby a light emitting diode drive device (illumination device) is formed. ) Can be significantly reduced.
  • the present configuration is not limited to the light emitting diode driving device according to the first embodiment of the present invention, and can also be applied to light emitting diode driving devices according to other embodiments described below.
  • the full-wave rectifier circuit is used as the rectifier circuit 112 that rectifies the AC voltage, it is obvious that the same effect can be obtained even if the half-wave rectifier circuit is used. Furthermore, the effect of the present invention can be enjoyed even when a DC power supply is used instead of the AC power supply 111. The same applies to the embodiments described below.
  • the light emitting diode driving device determines whether or not the current flowing through the switching element is equal to or lower than the upper limit reference value by determining whether or not the maximum duty driving is performed.
  • the maximum duty drive is a control method in which the switching element is driven at a constant period, and when the period during which the switching element is on reaches a preset maximum period (maximum duty), the switching element is turned off. That is.
  • the current flowing through the switching element reaches the peak value and the switching element is turned off by the maximum duty drive before the switching element is turned off.
  • the current flowing through the switching element is not more than the upper reference value.
  • FIG. 4 is a circuit diagram showing an example of the light emitting diode driving apparatus 300 according to Embodiment 2 of the present invention. 4, constituent elements corresponding to those shown in FIG. 1 are given the same reference numerals as those in FIG. 1, and descriptions thereof are omitted.
  • the light emitting diode driving device 300 according to the second embodiment of the present invention is different from the first embodiment in the configuration of the control circuit block 420 of the switching driving circuit 400. Further, the connection relationship of the resistor 140 is different. Other configurations are the same as those in the first embodiment.
  • the SW control circuit 228 switches the switching element 211 from off to on in a preset cycle in the first operation mode (normal operation mode). Further, when the current flowing through the switching element 211 reaches the peak value Ip, that is, when the peak current detection signal ILIMIT is input, the switching element 211 is turned off.
  • the control circuit block 420 includes a count circuit 429, a comparator 433, a flip-flop circuit 435, and a clock generator 436 as shown in FIG. 4 instead of the count circuit 229 and the current determination circuit 230.
  • the resistor 140 is connected to the high potential side of the rectifier circuit 112 and the smoothing capacitor 113.
  • the reference voltage Vref set by the current adjustment circuit 226 changes according to the waveform of the input voltage.
  • the clock generator 436 is an example of a maximum duty detection circuit, and sets a maximum duty period (also described as maximum on-duty).
  • the maximum duty period is a maximum value of a period during which the switching element 211 is on in a cycle in which the switching element 211 is switched from on to off.
  • the clock generator 436 has a current value of the current flowing through the switching element 211 equal to or lower than the above upper limit reference value (IDH). It is determined that
  • the clock generator 436 includes an oscillator and outputs a CLOCK signal that determines the turn-on timing of each cycle of the switching element 211 and a MAXDUTY signal that determines the maximum on-duty.
  • the CLOCK signal is input to the SW control circuit 228, the SW control circuit 228 outputs the control signal Vg to the switching element 211, thereby turning on the switching element 211.
  • the peak current detection circuit 227 When the current ID flowing through the switching element 211 reaches a preset peak value Ip, that is, when the detection voltage Vsn input to the peak current detection circuit 227 reaches the reference voltage Vref, the peak current detection circuit 227 is The peak current detection signal ILIMIT is output to the SW control circuit 228. As a result, the SW control circuit 228 outputs a control signal Vg for turning off the switching element 211. By this control, control is performed so that the peak value of the current flowing through the switching element 211 is always constant at Ip.
  • the clock generator 436 when the clock generator 436 outputs the MAXDUTY signal to the SW control circuit 228 before the peak current detection circuit 227 outputs the peak current detection signal ILIMIT to the SW control circuit 228, the SW control circuit 228 causes the switching element 211 to be switched. A control signal Vg for turning off is output. Although not shown in FIG. 4, actually, when the SW control circuit 228 outputs the control signal Vg for turning off the switching element 211 by the peak current detection signal ILIMIT, the clock generator 436 does not output the MAXDUTY signal.
  • the comparator 433 is a part of a lower limit determination circuit that determines whether or not the current value of the current flowing through the switching element 211 is equal to or higher than a predetermined lower limit reference value.
  • the detection voltage Vsn is input to the plus input terminal, and the lower limit reference voltage IDL is input to the minus input terminal.
  • the comparator 433 outputs a high level signal to the flip-flop circuit 435 when the detection voltage Vsn is greater than the lower limit reference voltage IDL.
  • the comparator 433 determines whether the current value of the current flowing through the switching element 211 is greater than or equal to the lower limit reference value between the time when the switching element 211 is turned on and the time when the switching element 211 is turned off. Then, the determination result is held by the flip-flop circuit 435.
  • the flip-flop circuit 435 is a part of the lower limit determination circuit, and holds the determination result by the comparator 433. Each time the switching element 211 is turned on, the determination result is reset.
  • the flip-flop circuit 435 is, for example, an RS flip-flop circuit having a set terminal, a reset terminal, and an output terminal.
  • the output signal of the comparator 433 is input to the set terminal, and the CLOCK signal is input from the clock generator 436 to the reset terminal.
  • the output terminal is connected to the count circuit 429, and outputs an output signal to the count circuit 429 until a signal is input to the reset terminal after a signal is input to the set terminal.
  • the output signal is reset every time the CLOCK signal is output from the clock generator 436. That is, at the timing when the switching element 211 is turned on, the output of the flip-flop circuit 435 is reset once and then set by the output signal from the comparator 433.
  • the count circuit 429 measures the number of times that the current value of the current flowing through the switching element 211 is determined to be less than or equal to the upper limit reference value and greater than or equal to the lower limit reference value.
  • the current value of the current flowing through the switching element 211 is compared with the upper reference value by detecting the time until the peak value is reached instead of directly comparing the current values. .
  • the count circuit 429 includes a peak current detection signal ILIMIT from the peak current detection circuit 227, a MAXDUTY signal from the clock generator 436, and a start / stop circuit 225.
  • Output signal (ENABLE signal or DISABLE signal).
  • the count circuit 429 increases the number of counts by one when the output signal from the flip-flop circuit 435 and the MAXDUTY signal from the clock generator 436 are input.
  • count circuit 429 outputs an open signal to SW control circuit 228.
  • the count circuit 429 resets the number of counts.
  • Embodiment 2 of the present invention configured as described above, the operation when the LED light source unit 121 is normal will be described.
  • the waveform of the current flowing through the switching element 211 during normal operation and the signal waveform of the control circuit block 420 are shown in IDS1 of FIG.
  • the current waveform IDS1 at this time is a simple increase current having a slope (Vin ⁇ VF_LED) / L determined from the inductance value L of the choke coil 122 and the voltage difference (Vin ⁇ VF_LED) between both terminals of the LED light source 121. It becomes a waveform.
  • the control circuit block 420 and the switching element 211 in the internal control circuit block 420 and the switching element 211 start on and off control, but in the period in which no current flows through the switching element 211,
  • the relationship between the detection voltage Vsn inside 420 and the lower limit reference voltage IDL is IDL> Vsn. For this reason, the count circuit 429 does not increase the number of counts.
  • the number of counts is reset by the peak current detection signal ILIMIT from the peak current detection circuit 227.
  • the on-period of the switching element 211 reaches the maximum on-duty defined by the clock generator 436 without the maximum value of the current ID flowing through the switching element 211 reaching the peak value Ip.
  • the clock generator 436 outputs a MAXDUTY signal
  • the SW control circuit 228 outputs a control signal Vg for turning off the switching element 211.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433.
  • the output signal is output to the count circuit 429.
  • the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty every time.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the flip-flop circuit 435 When the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn> IDL due to the spike current flowing in the switching element 211, the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. . Even if the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn ⁇ IDL during the ON period of the switching element 211, the output signal of the flip-flop circuit 435 does not change. Therefore, when the MAXDUTY signal is output from the clock generator 436 to the count circuit, the count circuit 429 can increase the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty every time.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the light emitting diode driving apparatus 300 performs maximum duty driving when the value of the current flowing through the switching element 211 does not reach the peak value. That is, when the period during which the switching element 211 is on reaches a preset maximum duty period, the switching element 211 is turned off.
  • the current mode PWM control method for changing the peak value of the current flowing through the switching element 211 is described as an example of the control method for the switching element 211.
  • the present invention is not limited to this. Absent. Even in the case of the PWM method for controlling the switching on-duty, it is possible to perform the same control as in the second embodiment by defining the maximum on-duty of the switching element 211.
  • the same control as that of the second embodiment is performed also in the off-time fixed control method in which the off-time of the switching element 211 is fixed at a preset value or the PFM control method in which the oscillation frequency is changed.
  • Can do For example, first, a maximum time during which the switching element 211 can be turned on for each pulse, that is, a maximum ON period is defined.
  • the output signal from the flip-flop circuit 435 and a signal (not shown in FIG. 4) indicating that the maximum on-period has elapsed are applied to the count circuit 429, the number of counts is increased by one. Thus, the same effect can be obtained.
  • the light emitting diode driving apparatus determines whether or not the current flowing in the switching element 211 is equal to or lower than the upper reference value by determining whether or not the driving is the maximum on-time driving. Determine whether or not.
  • the maximum on-time driving is to turn off the switching element 211 when the period during which the switching element 211 is on reaches a preset maximum period (maximum on period). That is, in the light emitting diode driving device according to the modification of the second embodiment of the present invention, the current flowing through the switching element 211 reaches the peak value and is turned off by the maximum on-time driving before the switching element 211 is turned off. By detecting this, it is detected that the current flowing through the switching element 211 is equal to or lower than the upper limit reference value.
  • the SW control circuit 228 turns on the switching element 211 after a predetermined period after the switching element 211 is turned off by the fixed off time control method. . As described above, the SW control circuit 228 turns off the switching element 211 when the current flowing through the switching element 211 reaches the peak value Ip, that is, when the peak current detection signal ILIMIT is input. .
  • the clock generator 436 is an example of a maximum on-period detection circuit, and sets a maximum on-period that is the maximum value of the period during which the switching element 211 is on. Then, when the period during which the switching element 211 is on reaches the maximum on-period (that is, when the maximum on-time driving is performed), it is determined that the current value of the current flowing through the switching element 211 is equal to or less than the upper limit reference value. Is done.
  • the number of times when the maximum on-time driving is performed is counted, thereby detecting LED open. It can be performed. At this time, it is not necessary to detect the current for comparison with the upper limit reference value, and it is only necessary to determine whether or not the driving is the maximum on-time driving, so that the open detection accuracy can be improved.
  • the CLOCK signal for turning on the switching element 211 from the clock generator 436 is applied to the reset terminal of the flip-flop circuit 435, and detection is performed every switching cycle of the switching element 211. Less likely.
  • the count circuit 429 resets the number of times when the measured number does not increase in synchronization with the timing at which the switching element 211 is turned off. Thereby, the possibility of erroneous detection can be reduced.
  • the light emitting diode driving device is characterized in that a resistor, a capacitor, or a resistor and a capacitor connected in series with each other are connected in parallel to the LED light source unit.
  • the third embodiment is different from the first and second embodiments in the configuration of the series connection loop circuit 120. More specifically, an additional component is connected in parallel with the LED light source unit 121.
  • FIG. 6A to 6C are circuit diagrams showing an example of the configuration of the series connection loop circuit according to the third embodiment of the present invention.
  • the switching drive circuit light emitting diode drive semiconductor device
  • the power supply unit for driving these series-connected loop circuits are the circuit shown in FIG. 1 and the implementation shown in FIG. Either of the circuits shown in Embodiment 2 can be used.
  • 6A includes a LED light source unit 121, a choke coil 122, a diode 123, and a resistor 524.
  • the open failure of the light emitting diode can be classified into two types, that is, a case where it is completely electrically insulated (fully open state) and a semi-open state where a resistance component remains.
  • the resistance load is determined by the resistor 524 in the fully open state, and the residual high resistance and the resistor 524 are in the half open state. And combined resistance load.
  • a case where the LED light source unit 121 is in a completely open state will be described as an example.
  • the impedance becomes higher than that in the normal state, and the current increase rate becomes lower.
  • the maximum value of the current ID flowing through the switching element 211 does not reach the peak value Ip, and the ON period of the switching element 211 is determined by the clock generator 436.
  • the clock generator 436 outputs a MAXDUTY signal.
  • the SW control circuit 228 outputs a control signal Vg that turns off the switching element 211.
  • the value of the lower limit reference voltage IDL is set in advance to be “a current value corresponding to IR524> IDL”. That is, the lower limit reference value is set to a value equal to or smaller than the current value of the current flowing through the resistor 524 when at least one light emitting diode included in the LED light source unit 121 is open.
  • the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the lower limit reference voltage IDL may be a fixed value set inside in advance, or may be configured to be freely adjustable by the user from the outside. Further, the user sets the value of the resistor 524 according to the set IDL value and the number of connected light emitting diodes connected to the LED light source unit 121, that is, according to the value of VF_LED, “current value corresponding to IDL ⁇ VF_LED. / R524 "is adjusted. Thereby, in the period T2 of FIG. 2B, it is not erroneously determined that the LED light source unit 121 is open.
  • the current flowing through the switching element 211 and the signal waveform of the control circuit block 420 are similar to those of the IDS 3 in FIG. Also in this case, in the period T2 described with reference to FIG. 2B, the value of the lower limit reference voltage IDL and the maximum value of the current flowing through the resistor 524 are “current value corresponding to IDL> IRP524 (that is, the maximum value of the current)”. Therefore, the number of counts of the count circuit 429 does not increase.
  • the flip-flop circuit 435 when the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn> IDL due to the spike current flowing in the switching element 211, the flip-flop circuit 435 is set by the output signal from the comparator 433. The output signal is output to the count circuit 429. Even when the relationship between the detection voltage Vsn and the lower limit reference voltage IDL becomes Vsn ⁇ IDL during the ON period of the switching element 211, the output signal of the flip-flop circuit 435 does not change. Therefore, when the MAXDUTY signal is output from the clock generator 436 to the count circuit 429, the count circuit 429 can increase the number of counts by one.
  • the series connection loop circuit 520b shown in FIG. 6B includes an LED light source unit 121, a choke coil 122, a diode 123, and a smoothing capacitor 525. As shown in FIG. 6B, a smoothing capacitor 525 is connected in parallel with the LED light source unit 121.
  • the value of the lower limit reference voltage IDL is “IC525> IDL beforehand. It is set so that it corresponds to the “current value”. That is, the lower limit reference value is set to a value equal to or smaller than the current value of the current flowing through the smoothing capacitor 525 when at least one light emitting diode included in the LED light source unit 121 is open.
  • the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty. When the number of counts is equal to or greater than a predetermined determination reference value, the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228. When the open signal is input, the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the open state of the LED light source 121 can be accurately detected by the same operation as in FIG. 6A.
  • the series connection loop circuit 520c shown in FIG. 6C includes an LED light source unit 121, a choke coil 122, a diode 123, a resistor 524, and a smoothing capacitor 525. As shown in FIG. 6C, a smoothing capacitor 525 and a resistor 524 connected in series are connected to the LED light source unit 121 in parallel.
  • the LED light source 121 when the LED light source 121 is opened, a current flows through the smoothing capacitor 525 and the resistor 524. Further, the value of the flowing current is limited by the resistance value R524 of the resistor 524. Therefore, as in the period T2 described with reference to FIG. 2B, the maximum value of the current that flows during the period in which the input voltage Vin is lower than the output voltage VF_LED is determined by the IRP 524.
  • IR524 VF_LED / R524 is determined, and the value of the lower limit reference voltage IDL is set in advance so that “current value corresponding to IDL> IRP524”. For this reason, the current corresponding to the lower limit reference voltage IDL does not flow through the switching element 211 during the period T2.
  • the value of the lower limit reference voltage IDL is set in advance such that “current value corresponding to IR524> IDL”. That is, the lower limit reference value is set to a value equal to or less than the current value of the current flowing through the resistor 524 and the smoothing capacitor 525 when at least one light emitting diode included in the LED light source unit 121 is open.
  • the relationship between the detection voltage Vsn in the control circuit block 420 and the lower limit reference voltage IDL is set in advance so that Vsn> IDL.
  • the flip-flop circuit 435 is set by the output signal from the comparator 433 and outputs the output signal to the count circuit 429. Further, the MAXDUTY signal is output from the clock generator 436 to the count circuit 429. For this reason, the count circuit 429 increases the number of counts by one.
  • the count circuit 429 resets the number of counts when the peak current detection circuit 227 outputs the peak current detection signal ILIMIT. The number of counts increases only when the ON period of the switching element 211 is the maximum ON duty.
  • the count circuit 429 determines that the LED light source unit 121 that is a load is open, and outputs an open signal to the SW control circuit 228.
  • the SW control circuit 228 turns off the switching element 211 and holds the state where the switching operation is stopped. That is, the SW control circuit 228 latches and stops the switching element 211 as the second operation mode for abnormality processing.
  • the user can connect the set IDL value and the LED light source by connecting a resistor 524 in series with the smoothing capacitor 525.
  • a resistor 524 in series with the smoothing capacitor 525.
  • erroneous detection of the LED light source unit 121 can be easily prevented. That is, by adjusting the value of the resistor 524 in accordance with the value of VF_LED so as to be in the range of “current value corresponding to IDL ⁇ VF_LED / R524”, the LED light source unit 121 is erroneously set in the period T2 of FIG. 2B. It is possible to easily adjust so that it is not determined to be open.
  • the open state of the LED light source unit 121 can be accurately detected by the same operation as in FIG. 6A.
  • Embodiment 3 of the present invention configured as described above, a current flows through the components connected in parallel even when the LED light source 121 is opened, but the comparator is an example of a lower limit determination circuit. Since it is detectable by 433, the detection accuracy of LED open improves.
  • the light emitting diode driving device includes an abnormality processing circuit that outputs an abnormality determination signal when the number of counts is equal to or greater than a predetermined determination reference value.
  • FIG. 7 is a circuit diagram showing an example of a light-emitting diode driving apparatus 600 according to Embodiment 4 of the present invention.
  • the fourth embodiment includes a new abnormality processing circuit 650, a power supply unit 610 instead of the power supply unit 110, and a switching drive circuit 700 instead of the switching drive circuit 400. The point to prepare is different.
  • the switching drive circuit 700 newly has an external connection terminal OP, and outputs the open signal output from the count circuit 429 to the abnormality processing circuit 650 via the external connection terminal OP.
  • the abnormality processing circuit 650 outputs an abnormality determination signal indicating an abnormality when the number of times measured by the count circuit 429 is greater than or equal to the determination reference value. Specifically, the abnormality processing circuit 650 outputs an abnormality determination signal to the switch 614 included in the power supply unit 610 when an open signal is input via the external connection terminal OP.
  • the power supply unit 610 newly includes a switch 614.
  • the switch 614 is connected in series between the rectifier circuit 112 and the series connection loop circuit 120, and determines whether or not to apply the input voltage Vin to the LED light source unit 121 and the choke coil 122. Specifically, when an abnormality determination signal is input from the abnormality processing circuit 650, the switch 614 is turned off and stops supplying the input voltage Vin.
  • the count circuit 429 determines that the LED light source 121 that is a load is open when the number of counts exceeds a predetermined determination reference value, and outputs an open signal to the SW control circuit 228. Further, the open signal is also output to the abnormality processing circuit 650 via the external connection terminal OP.
  • the abnormality processing circuit 650 When the open signal is input, the abnormality processing circuit 650 outputs an abnormality determination signal to turn off the switch 614 so that the input voltage Vin is not supplied to the LED light source unit 121 side. As a result, it is possible to prevent an excessive voltage from being applied to peripheral components and switching elements.
  • the SW control circuit 228 may turn off the switching element 211 and hold the state where the switching operation is stopped.
  • the switching element 211 is stopped, and the input voltage is not applied, so that safety can be further improved.
  • the open signal output from the external connection terminal OP terminal may be configured to transmit a signal to another drive device different from the light emitting diode drive device. That is, the abnormality processing circuit 650 may output an abnormality determination signal to an external device in order to notify the user that the LED light source unit 121 is abnormal.
  • an open signal may be transmitted to another device to indicate that an abnormality has occurred to a third party.
  • the abnormality processing circuit 650 can display on the display unit that the LED light source unit 121 is open by outputting an abnormality determination signal to an external display unit.
  • the abnormality processing circuit 650 can notify the user that the LED light source unit 121 is open by an alarm sound or the like by outputting an abnormality determination signal to an external sound output unit.
  • the light emitting diode driving device 600 configured as described above outputs an abnormality determination signal when detecting the open of the LED. For this reason, the supply of input voltage is stopped using this output signal, the peripheral device is notified that the LED light source is open, an alarm is sounded, and the user is notified of an abnormality in the LED light source unit. it can.
  • the light emitting diode driving device and the light emitting diode driving semiconductor device according to the present invention have been described based on the embodiments, but the present invention is not limited to these embodiments. Unless it deviates from the meaning of this invention, the form which carried out the various deformation
  • the SW control circuit 228 may perform a timer intermittent operation that repeats driving and stopping of the switching element 211 at regular intervals as the second operation mode for abnormality processing. According to this, when the opening of the LED is detected, the energy output by the switching operation is reduced, so that it is possible to prevent an excessive voltage from being applied to the peripheral component or the switching element 211.
  • comparison with the lower limit reference value may not be performed. That is, when the number of times that the current value of the current flowing through the switching element 211 is determined to be less than or equal to the upper limit reference value by the upper limit determination circuit is greater than or equal to a predetermined determination reference value, the count circuit 229 or 429 outputs the open signal. It may be output. Then, the SW control circuit 228 executes the second operation mode for abnormality processing when it is continuously detected a plurality of times that the current flowing through the switching element 211 is equal to or lower than the upper limit reference value. Thereby, it can be detected that the LED light source unit 121 is open.
  • the comparison with the upper limit reference value (upper limit determination) and the comparison with the lower limit reference value (lower limit determination) may be performed simultaneously.
  • a circuit (specifically, the flip-flop circuit 435) for temporarily holding any determination result is not required, and thus a circuit configuration necessary for the determination is provided. It can be simplified.
  • the light-emitting diode driving device and the semiconductor device for driving a light-emitting diode according to the present invention can be used for all devices and devices using light-emitting diodes, and are useful as, for example, LED bulbs or LED lighting devices.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Led Devices (AREA)

Abstract

L'invention concerne un dispositif (100) de commande de DEL du type hacheur abaisseur, qui comporte: une unité (121) de source lumineuse à DEL; une unité (110) de source d'alimentation pour fournir une tension d'entrée; et un circuit (200) de commande de commutation pour maintenir à un niveau constant le courant appliqué à l'unité (121) de source lumineuse à DEL. Le circuit (200) de commande de commutation comprend: un élément (211) de commutation qui fournit de manière intermittente une tension d'entrée à l'unité (121) de source lumineuse à DEL; un circuit (228) de commande SW qui commande la commutation marche/arrêt de l'élément de commutation (211); des comparateurs (232, 233) qui déterminent si la valeur de courant du courant appliqué à l'élément de commutation (211) est inférieure à une valeur de référence supérieure, et supérieure à une valeur de référence inférieure; et un circuit (229) de comptage qui mesure le nombre de fois où la valeur de courant est inférieure à la valeur de référence supérieure, et supérieure à la valeur de référence inférieure. Le circuit (228) de commande SW exécute un mode de traitement d'erreur quand ledit nombre mesuré est supérieur à une valeur de critère acceptable.
PCT/JP2010/006790 2010-07-16 2010-11-19 Dispositif de commande de diode électroluminescente et dispositif semi-conducteur de commande de diode électroluminescente Ceased WO2012008002A1 (fr)

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JP2010161549A JP2012023277A (ja) 2010-07-16 2010-07-16 発光ダイオード駆動装置及び発光ダイオード駆動用半導体装置

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JP6146970B2 (ja) * 2012-08-09 2017-06-14 三菱電機株式会社 光源点灯装置及び照明器具
JP5988207B2 (ja) 2012-09-07 2016-09-07 パナソニックＩｐマネジメント株式会社 固体発光素子駆動装置及び照明装置、照明器具
EP2709426A3 (fr) * 2012-09-14 2017-04-19 Panasonic Intellectual Property Management Co., Ltd. Dispositif de commande d'élément électroluminescent à l'état solide, système d'éclairage et appareil d'éclairage
TWI524811B (zh) 2013-08-14 2016-03-01 Richtek Technology Corp Light emitting diode system and voltage conversion device
JP6295816B2 (ja) * 2014-05-14 2018-03-20 三菱電機株式会社 照明器具
JP6422056B2 (ja) * 2015-01-06 2018-11-14 パナソニックＩｐマネジメント株式会社 点灯装置およびそれを用いた照明器具
JP6587054B2 (ja) 2015-06-19 2019-10-09 パナソニックＩｐマネジメント株式会社 点灯装置及び照明器具
JP6803560B2 (ja) * 2016-12-22 2020-12-23 パナソニックＩｐマネジメント株式会社 点灯装置及び照明器具
JP2019054582A (ja) * 2017-09-13 2019-04-04 パナソニックＩｐマネジメント株式会社 制御回路、半導体光源駆動装置、及び電子機器
JP7148469B2 (ja) * 2019-09-12 2022-10-05 株式会社東芝 半導体回路及び半導体システム
JP7581959B2 (ja) * 2021-02-26 2024-11-13 日本精機株式会社 車両用表示装置

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JP2008235530A (ja) * 2007-03-20 2008-10-02 Matsushita Electric Ind Co Ltd 発光ダイオード駆動装置、及びそれを用いた照明装置
JP2009117121A (ja) * 2007-11-05 2009-05-28 Denso Corp Ｌｅｄ駆動回路

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