JP2014170880A - Light-emitting element switch-on device and light source device - Google Patents

Abstract

The present invention provides a lighting device and the like that can generate a small amount of heat by an electric circuit and can be turned on and off freely.
An apparatus for controlling turning on / off of a plurality of light emitting elements LED1 to 8 connected in series, and is connected to the plurality of light emitting elements LED1 to 8 to increase and decrease the voltage to supply power to each light emitting element. Converter 11, a plurality of switch circuits SW 1 to 8 each connected in parallel to one of the plurality of light emitting elements LED 1 to 8, and a switch control unit that individually controls the open / closed states of the plurality of switch circuits SW 1 to 8 15 is a lighting device for a light emitting element.
[Selection] Figure 1

Description

  The present invention relates to a technique for controlling turning on / off of a plurality of light emitting elements.

  As a vehicular lamp such as a stop lamp and a turn lamp, one using a plurality of LEDs (Light Emitting Diodes) is known. As a method of driving a plurality of LEDs, for example, a plurality of LEDs are connected in series, and a voltage corresponding to the sum of forward voltages of the LEDs is supplied to the LEDs by a buck-boost converter circuit. A method of driving with a constant current is conceivable (see, for example, JP-A-2001-215913). This method has a simple circuit configuration, and even if the number of LEDs is increased, it can be handled by increasing the output voltage of the buck-boost converter. Therefore, the number of components does not increase, and this is advantageous in terms of cost. In addition, since constant current control by a switching DC-DC converter is possible, the conversion efficiency of the circuit is high, heat generation is small, and it is advantageous for downsizing of the circuit. However, due to the configuration in which a plurality of LEDs are connected in series, it is difficult to turn off and turn off individual LEDs independently.

  On the other hand, a method is also conceivable in which a plurality of LEDs are connected in parallel, and each LED is associated with a constant current control IC, and each LED is subjected to constant current control. According to this, it is easy to individually turn on / off each LED, but as the number of LEDs increases, it is necessary to increase the constant current control IC, so that the number of parts increases and the cost increases. There is a disadvantage that the circuit configuration becomes complicated. In addition, each constant current control IC operates as a drop power supply when supplying a constant current to each LED. Therefore, when the LED drive current is relatively large, the circuit loss also increases in proportion to the output current. Therefore, the heat generation of the current control IC increases. In order to cope with the heat generation from the constant current control IC, it is necessary to increase the mounting board area for heat dissipation, and it is difficult to reduce the size of the electric circuit.

  On the other hand, a method is conceivable in which a plurality of LEDs are connected in parallel, and a current limiting resistor is connected in series with each LED, and a voltage is supplied to each LED. In this case, if a switch is provided for each LED together with the current limiting resistor, each LED can be individually turned on and off by opening and closing the switches individually. However, in this case, when the number of LEDs increases, it is necessary to increase the number of current limiting resistance elements, which increases the number of parts, increases the cost, and complicates the circuit configuration. Further, since the current is set by each current limiting resistance element connected to each LED, the heat generation from the current limiting resistance element increases as the LED current increases. For this reason, as an actual circuit configuration, it is necessary to disperse overheating by using a plurality of current limiting resistance elements in combination with each LED in preparation for an increase in heat generation. Therefore, a large resistive element and a substrate area for heat dissipation are required, which disadvantageously increases the size of the electric circuit.

JP 2001-215913 A

  A specific aspect according to the present invention is to provide a lighting device and a light source device that generate less heat by an electric circuit, can be downsized, and can freely turn on and off a plurality of light emitting elements. One.

  A lighting device for a light-emitting element according to one aspect of the present invention is a device for controlling turning on / off of a plurality of light-emitting elements connected in series, and (a) the light-emitting elements connected to the plurality of light-emitting elements A step-up / down converter for supplying power to the element; (b) a plurality of switch circuits each connected in parallel to one of the plurality of light emitting elements; and (c) an open / closed state of each of the plurality of switch circuits. It is the lighting device of the light emitting element containing the switch control part to perform.

  According to the above configuration, the plurality of LEDs can be turned on and off freely. In addition, according to the step-up / down converter circuit, a DC drop voltage which is a difference between the input voltage and the actual LED lighting voltage is not generated, so that the circuit loss is small, and overheating of the control IC and the current limiting resistor element is considered. There is no need. In addition, since each LED can be collectively controlled in series without individually controlling constant current, the number of components is small and there is no need to provide a separate board area for heat dissipation. Easy.

  In the above lighting device, it is also preferable that the switch control unit controls the plurality of switch circuits in an open state or a closed state in order at different timings.

  Thereby, for example, by controlling each switch circuit in an open state or a closed state with a time difference in accordance with the order of arrangement of the light emitting elements, it is possible to produce an effect in which light flows in appearance.

  The lighting device preferably further includes a PWM control unit that PWM-controls the power supplied by the step-up / down converter circuit.

  As a result, the light emission intensity of each light emitting element connected in series can be increased or decreased in a lump.For example, after each light emitting element is turned on, PWM dimming is performed to gradually leave afterglow due to afterglow. It is possible to produce effects such as turning off all LEDs.

  In the above lighting device, when a plurality of switch circuits are controlled to be open at different timings by the switch control unit, by detecting a voltage across the series circuit in which a plurality of light emitting elements are connected corresponding to each timing, It is also preferable to further include a disconnection and short circuit detection means for detecting a disconnection and a short circuit in any of the plurality of light emitting elements.

  Thereby, since the sum of the forward voltage of each light emitting element and an actual voltage can be compared, it can be determined whether the light emitting element is disconnected or short-circuited.

  A light source device according to an aspect of the present invention includes any one of the lighting devices described above and a plurality of light emitting elements connected in series to each other and connected to the lighting device.

  According to the above configuration, it is possible to obtain a light source device that generates less heat by an electric circuit, can be downsized, and can freely turn on and off a plurality of light emitting elements.

FIG. 1 is a block diagram illustrating a configuration of a lighting device for a light emitting element according to an embodiment. FIG. 2 is a block diagram illustrating a detailed configuration example of the microcomputer control unit and the like. FIG. 3 is a circuit diagram showing a configuration example of a switch circuit connected in parallel to each LED.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the meaning of “connection” in the present specification includes the case where other circuit elements are interposed between circuit elements such as circuit elements in a form that does not hinder the operation necessary for obtaining the intended technical effect. Shall also be included.

  FIG. 1 is a block diagram illustrating a configuration of a lighting device for a light emitting element according to an embodiment. The lighting device shown in FIG. 1 is for driving a plurality (eight in this example) of LEDs 1 to 8 connected in series, and eight switch circuits SW1 to SW1 connected in association with the LEDs 1 to 8, respectively. 8, an input filter 10, a buck-boost converter circuit 11, a current detection unit 12, an output filter 13, a power supply control IC 14, and a microcomputer control unit 15. In addition, a light source device is comprised including this lighting device and LED1-8.

  The switch circuit SW1 is connected in parallel to the LED1. Similarly, the switch circuit SW2 is parallel to LED2, the switch circuit SW3 is parallel to LED3, the switch circuit SW4 is parallel to LED4, the switch circuit SW5 is parallel to LED5, and the switch circuit SW6. Are parallel to LED 6, switch circuit SW 7 is parallel to LED 7, and switch circuit SW 8 is parallel to LED 8. These switch circuits SW1 to SW8 can be individually opened and closed under the control of the microcomputer control unit 15. For this reason, it becomes possible to short-circuit / open arbitrarily between the anode and cathode of each LED1-8, and it becomes possible to control lighting / extinction of each LED1-8 separately.

  The step-up / down converter circuit 11 is supplied with the battery voltage via the input filter 10 and supplies power to the series circuit of the LEDs 1 to 8 via the output filter 13. This step-up / down converter circuit 11 is a switching type DC-DC step-up / down converter, and can convert a battery voltage into a forward voltage necessary for LED lighting with high efficiency.

  The current detector 12 detects the magnitude of the current flowing from the step-up / down converter circuit 11 to the series circuit of the LEDs 1 to 8 and feeds it back to the power supply control IC 14.

  The power supply control IC 14 controls the voltage supplied to the buck-boost converter circuit 11 according to the magnitude of the current fed back from the current detector 12.

  The microcomputer control unit 15 controls the overall operation of the lighting device such as controlling the open / closed state of the switch circuits SW1 to SW8.

  The configuration of the lighting device of the present embodiment is as described above. Next, the operation thereof will be described. For the LEDs 1 to 8 connected in series, the step-up / down converter circuit 11 supplies an output voltage in accordance with the LED forward voltage so as to have a preset current value. At this time, when a specific LED (LED1 as an example here) is turned off, the switch circuit 1 provided in parallel with the LED1 is closed under the control of the microcomputer control unit 15. As a result, the current is bypassed by the switch circuit SW1, and since no current flows through LED1, LED1 is turned off. The same applies to other LEDs, and any one of the LEDs can be selected and extinguished by individually controlling the switch circuits SW1 to SW8 by the microcomputer controller 15.

  At this time, constant current control is performed for the current flowing through the series circuit of the LEDs 1 to 8, so that there is no effect even if the switch circuit connected in parallel to any LED is in a closed state (short circuit state). Further, when all the LEDs are turned off, all the switch circuits are closed. Even in this case, the output current set by the constant current control flows. The step-up / down converter circuit 11 starts to operate after the turn-on input is input. For example, if all the switch circuits SW1 to SW8 connected in parallel to the LEDs 1 to 8 are first short-circuited, the entire LEDs are turned off. State (all off). For example, if the switch circuits SW1, SW2,... 8 are sequentially opened after the preset timing, the LEDs are turned on one by one in the order of LEDs 1, 2,. Therefore, for example, if the LEDs 1 to 8 are arranged in a row in the horizontal direction, it is possible to realize a turn lamp in which light flows visually from right to left (or vice versa).

  FIG. 2 is a block diagram illustrating a detailed configuration example of the microcomputer control unit and the like. Components common to those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  When the power supply voltage is applied to the turn lighting input, the voltage is supplied to the buck-boost converter circuit 11 and the power supply IC 16 that supplies the 5V power supply for the microcomputer, and the microcomputer control unit 15 starts the initial setting. First, the microcomputer control unit 15 controls the switch circuits SW1 to SW8 to be closed in order to turn off the LEDs 1 to 8. Further, the microcomputer control unit 15 starts operating the power supply control IC 14 of the step-up / step-down converter circuit 11 and attempts to increase the output voltage for lighting the LEDs 1 to 8. However, since the buck-boost converter circuit 11 makes the LED current constant by constant current control, the output voltage hardly rises when all LEDs are short-circuited.

  Here, in the case of the turn control of the turn lighting, the LED lighting timing sequence control unit 151 sends a control signal to one closed switch circuit in order to turn on one LED. Is opened. In this case, only one LED is lit, and the other LEDs remain off because the switch circuits connected in parallel to each other are closed. Even in this case, the current flowing in the series circuit of the LEDs 1 to 8 by the constant current control is controlled to a constant current value as in the case of the entire short circuit. Similarly, when the LEDs are sequentially turned on at time intervals based on the sequence control, the viewing angle effect of turning lighting that flows is obtained.

  Further, after the last LED is turned on, the dimming dimming PWM timer control unit 152 intermittently outputs the output from the step-up / down converter circuit 11 by sending a dimming signal to the power supply control IC 14 of the step-up / down converter circuit 11. Turn on and off. As a result, each LED is gradually turned off gradually while leaving the afterglow due to afterglow by PWM dimming the lighting state of each LED. In this embodiment, since the individual LEDs are connected in series and controlled at a constant current, if the buck-boost converter circuit 11 is dimmed by PWM control, each LED can be dimmed at the same time. Dimming can be easily performed at low cost compared to the case where PWM dimming is performed individually in parallel connection. After all the LEDs are turned off, the turn-on lighting is repeated after the first LED is turned on again in a state where the vehicle turn signal is input.

  The LED open abnormality detection unit 154 detects the output voltage of the buck-boost converter circuit 11 in order to detect an abnormal state of the circuit and the LED. As a result, at the time of disconnection on the output side and when the LED is open, an increase in the output voltage due to the current not flowing in the constant current control is detected, and if the threshold of the open voltage higher than the steady state is exceeded, an abnormality is detected. judge.

  The LED short abnormality detecting unit 153 detects the forward voltage of the first lit LED at the time of turning on, and further detects the forward voltage of two LEDs in the second lit state. Next, the forward voltage of the three LEDs in the state where the third LED is also lit is detected, and by sequentially obtaining the difference, it is detected whether each LED is in a short-circuited state. That is, during normal LED lighting, the LED forward voltage is about 2V to 4V. If the detected forward voltage difference of each LED is lower than 2V, the LED may be short-circuited, and it can be determined that the LED is in an abnormal state.

  The fail stop determination unit 155 determines whether one or a plurality of short-circuited LEDs are generated. When a predetermined number of short-circuited LEDs are generated, the fail stop determination unit 155 sends a control signal to the power supply control IC 14 to stop the turn lighting. In addition, the abnormal output unit 156 sends an abnormal output (teletail signal) to the vehicle side. This abnormal signal can be detected even when the LED is open and completely turned off, and a warning can be issued in the same manner.

  As the output of the abnormal signal, for example, a logic that outputs an open-collector Lo signal when the output is normal and outputs a Lo signal when the transistor is abnormal can be considered. Similarly, the case of reversing the logic of Hi / Lo at normal time and abnormal time can also be considered. Further, a logic that turns on and off the transistor to output a pulse signal when normal and outputs Lo when abnormal can be considered. Thus, it is possible to warn the vehicle side as a different output signal when the LED state is normal and abnormal, stop the converter part of the lighting circuit, and make the output voltage of the power supply circuit zero.

  The LED chip short detection unit 17 detects an abnormality due to a short circuit of the LED by detecting the LED forward voltage when all the LEDs 1 to 8 are turned on. When the turn is not turned on, that is, when only the turn input is connected to the power supply and the answerback input is off, the LEDs are not sequentially turned on, so individual LED forward voltages cannot be detected. By detecting the LED forward voltage, it is possible to detect an abnormal output voltage when a plurality of LEDs are short-circuited. That is, when the minimum forward voltage is 2V, the output voltage should be 16V or more when the LEDs are lit in series, but in this case, a voltage lower than 16V is detected. Then, a short-circuited LED is generated. Accordingly, it is possible to detect an LED abnormality and send an abnormal output (teletail signal) to give a warning.

  The input voltage detector 157 detects the battery input voltage. When the battery is lowered from the idling stop on the vehicle side when the engine is re-started, the abnormal output (teletail signal) may not be generated when the voltage falls below the minimum input battery voltage that can maintain the lighting of the LED. That is, the abnormal decrease in battery voltage is not caused by an LED failure, and the LED lighting is resumed by the return of the battery voltage, and therefore it is determined that it is appropriate for the vehicle side not to generate an abnormal signal. It is also possible. For this reason, when the input voltage detection unit 157 detects a decrease in the input battery voltage, the fail stop determination unit 155 determines that an abnormal output is unnecessary.

  FIG. 3 is a circuit diagram showing a configuration example of a switch circuit connected in parallel to each LED. As described above, each of the switch circuits SW1 to SW8 is connected in parallel to one corresponding LED, and short-circuits or opens the anode and cathode of each LED. Each switch circuit SW1-8 has a common configuration. When the PWM-8 signal is Hi input to the base of the bipolar transistor Q5 of the lowermost switch circuit SW8, the collector and emitter of the bipolar transistor Q5 are turned on (conductive state). As a result, a negative potential is biased to the gate of the P-channel field effect transistor Q4 of the switch circuit SW8, and the drain and source are turned on (conductive state). Thereby, the anode and cathode of the LED 8 are short-circuited, and the LED 8 is turned off. When the LED 8 is lit, the P-channel field effect transistor Q4 is turned off (non-conducting state) by setting the PWM-8 signal to Lo. Thereby, since an electric current flows into LED8, LED8 lights. The same applies when other LEDs are turned on and off.

  Therefore, by sequentially outputting PWM-1 signal, PWM-2 signal,..., PWM-8 signal from Hi to Lo from the microcomputer control unit 15, each P channel type field effect transistor is sequentially applied from the lowest stage. Since Q4 is turned off and the short circuit state of each LED1-8 is opened, it is possible to sequentially turn on the LED1-8 so as to flow to the uppermost stage with a time difference. Further, by simultaneously changing the PWM-1 signal, the PWM-2 signal,..., The PWM-8 signal from Hi to Lo, it is possible to start lighting all the LEDs 1 to 8 at a time. At the same time, the PWM-1 signal, the PWM-2 signal,..., The PWM-8 signal are simultaneously changed from Lo to Hi, so that all the LEDs 1 to 8 can be turned off at a time.

  According to the embodiment as described above, it is possible to freely turn on / off each of the plurality of LEDs. In addition, according to the step-up / down converter circuit, a DC drop voltage which is a difference between the input voltage and the actual LED lighting voltage is not generated, so that the circuit loss is small, and overheating of the control IC and the current limiting resistor element is considered. There is no need. In addition, since each LED can be collectively controlled in series without individually controlling constant current, the number of components is small and there is no need to provide a separate board area for heat dissipation. Easy.

  In addition, when the turn is turned on, the forward voltage of all the LEDs that are lit is detected each time the LEDs are lit sequentially, and the individual LED forward voltage that is lit by each LED is detected as a difference from the converter output voltage. Therefore, each LED short-circuit abnormality can be easily detected and determined.

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously.

10: Input filter 11: Buck-boost converter circuit 12: Current detection unit 13: Output filter 14: Power supply control IC
15: Microcomputer control unit 16: Power supply IC
17: LED chip short detection unit 151: LED lighting timing sequence control unit 152: Dimming dimming PWM timer control unit 153: LED short abnormality detection unit 154: LED open abnormality detection unit 155: Fail stop determination unit 156: Abnormal output unit 157: Input voltage detector

Claims (5)

An apparatus for controlling turning on / off of a plurality of light emitting elements connected in series,
A step-up / down converter connected to the plurality of light emitting elements and supplying power to each of the light emitting elements;
A plurality of switch circuits each connected in parallel to any of the plurality of light emitting elements;
A switch control unit for individually controlling the open / closed state of each of the plurality of switch circuits;
A lighting device for a light emitting element. The switch control unit controls the plurality of switch circuits in an open state or a closed state in order at different timings, respectively.
The lighting device of the light emitting element according to claim 1. A PWM controller for PWM-controlling the power supplied by the buck-boost converter circuit;
The lighting device for a light emitting element according to claim 1, further comprising: When the plurality of switch circuits are controlled to be opened at different timings by the switch control unit, the plurality of the plurality of switch circuits are detected by detecting voltages across the series circuit in which the plurality of light emitting elements are connected corresponding to each timing. Disconnection and short circuit detection means for detecting disconnection and short circuit in any of the light emitting elements,
The lighting device for a light emitting element according to claim 1, further comprising: The lighting device according to any one of claims 1 to 4,
A plurality of light emitting elements connected in series with each other, connected to the lighting device,
A light source device.

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