JP2009170240A - LED dimmer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dimming device of an LED capable of controlling an LED load at low loss with an alternating-current power source, and that, capable of avoiding dimming mistakes. <P>SOLUTION: With the LED dimming device, a control circuit 7 changes a phase of a trigger point t10 by a phase control signal FC11 as a trigger signal outputted to a photo triac coupler 3 in a variable range R11 narrower than a half cycle of the alternating-current voltage SV. With this, the control circuit 7 can avoid outputting a trigger signal into the photo triac coupler 3 in the vicinity of a zero cross point of the alternating-current voltage SV out of the half cycle of the alternating-current voltage SV. Thus, a phenomenon that the LED does not at all light itself can be avoided despite a setting of light dimming near an upper limit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dimming device for an LED that causes a plurality of LEDs (Light Emitting Diodes) connected in series to emit light using an AC power supply, an LED power supply module including the LED dimming device, and an LED lighting device.

  In recent years, the luminous efficiency of LEDs has been rapidly improved and the price has been reduced, so that they have been used not only for conventional display devices but also for small-scale lighting fixtures.

  When using LEDs in lighting fixtures, it is necessary to consider replacing with conventional incandescent bulbs and fluorescent lighting fixtures. Considering price and reliability, power supply circuits and control circuits have as many parts as possible. A small and simple circuit configuration is desired.

  The LED has a direction in which a current flows and the reverse breakdown voltage is smaller than that of a normal diode or the like, so that it has been conventionally driven by a DC power source. Also, lighting fixtures are often used by converting a commercial power source into a relatively low DC voltage using a power source using a power transformer, a rectifier diode, a smoothing capacitor, or a switching power source. Further, a device having a dimming function requires a circuit that changes the switching duty of the switching power supply, and has a more complicated circuit configuration.

  By the way, although LED is an element for direct current | flow, it can be used also by alternating current power supply by connecting a polarity in parallel in a reverse direction and adding a rectifier diode. Further, by connecting a plurality in series, the difference between the forward voltage of the entire LED load and the commercial power supply voltage is reduced, and the commercial AC power supply need not be stepped down. That is, if only the LED is lit, a lighting circuit can be configured with only the LED and the current limiting resistor.

  In fact, LED lighting fixtures using the above-described method and LED units called AC LEDs that can be directly connected to a commercial power source have been commercialized in recent years.

  On the other hand, as a method of using an AC power supply as an LED power supply and dimming this LED, conventionally, a bidirectional switching element such as a triac is connected between the AC power supply and the LED load (light source) and the switching element is turned on. A phase control method is often used in which the effective value of the AC voltage is varied by changing the phase angle.

  In addition, this phase control method can be configured with a bidirectional switching element and a relatively simple circuit for changing the phase of the trigger signal, and is therefore often used as a means for dimming an incandescent lamp.

  Techniques for using such a phase control method even when an LED is used as a load are disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-194071) and Patent Documents 2-5 (Japanese Patent Laid-Open No. 2006-3320, JP, No. 2006-32031, JP-A-2006-32032, and JP-A-2006-32033).

  By the way, in order to light a plurality of LEDs directly with a commercial power source in lighting or the like using LEDs, the plurality of LEDs are connected in series, and the entire forward voltage of the plurality of LED loads connected in series. Generally, a method of reducing the power loss in the current limiting resistor by increasing the current limiting resistor and reducing the current limiting resistor is common. In this case, the LED is not lit in a region where the power supply voltage of the commercial power supply is lower than the forward voltage of the LEDs connected in series.

  However, even if the LED is not lit at the portion where the power supply voltage of the commercial power supply is low, the area of the portion where the power supply voltage is low is small when considering the entire area of the AC waveform of the power supply voltage. If the current limiting resistance is set small, there will be no problem with the brightness of the LED.

However, when such an LED load is dimmed by a conventional pulse trigger type phase control circuit, even if a trigger signal is input to the switching element in a region where the power supply voltage is lower than the forward voltage of the LED load, the switching element Therefore, there is a problem that the self-holding function of the switching element does not work. This problem occurs near the upper and lower limits of dimming, and in particular, when it occurs near the upper limit, there is a phenomenon that the LED does not light at all even though the setting is near the upper limit of dimming. Therefore, it becomes a big problem.
JP 2007-140771 A Japanese Patent Laid-Open No. 2006-32030 JP 2006-32031 A JP 2006-32032 A JP 2006-32033 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an LED dimming device that can dimm an LED load with an AC power source with low loss and prevent dimming errors.

In order to solve the above-described problem, the LED dimming device of the present invention is a closed circuit connected between an LED load unit having a plurality of light emitting diodes connected in series so that the forward direction is the same and an AC power supply. And a bidirectional switching element having a self-holding function,
A trigger signal is output to the bidirectional switching element to turn on the bidirectional switching element, and the trigger signal is input to the LED load unit by changing the phase of the trigger signal within a variable range narrower than a half cycle of the AC voltage. And a pulse trigger type phase control unit that performs light control by changing effective power.

  According to the LED light control device of the present invention, the phase control unit sets the phase of the trigger point of the bidirectional switching element by the trigger signal to a half of the AC voltage with respect to the AC voltage output from the AC power supply. Change within a variable range narrower than the cycle. Thereby, the said phase control part can avoid outputting a trigger signal to the said bidirectional | two-way switching element in the zero cross point vicinity of the said alternating voltage of the half cycle of the said alternating voltage. Therefore, according to the present invention, it is possible to avoid the phenomenon that the LED does not light at all even though the setting is near the upper limit of dimming.

  Therefore, according to the present invention, the LED load can be dimmed with an AC power source with low loss, and a dimming error can be prevented.

Further, in the LED light control device according to one embodiment, the phase control unit includes:
A zero cross detection circuit for detecting a zero cross point at which the absolute value of the AC voltage of the AC power supply becomes 0 V;
A control circuit that does not make the predetermined range from the zero cross point detected by the zero cross detection circuit out of the period during which the absolute value of the AC voltage increases as the variable range of the phase of the trigger signal.

  According to this embodiment, the phase control unit does not output a trigger signal to the bidirectional switching element in a predetermined period in which the absolute value of the AC voltage increases from a zero cross point where the absolute value of the AC voltage becomes 0V. Therefore, it is possible to reliably avoid the phenomenon that the LED does not light at all even though the setting is near the upper limit of dimming.

Moreover, in the LED light control device of one embodiment, the control circuit includes:
Of the period during which the absolute value of the AC voltage decreases, the period from when the absolute value of the AC voltage is a predetermined value to the zero cross point detected by the zero cross detection circuit is not set as the variable range of the phase of the trigger signal.

  According to this embodiment, it is possible not only to avoid a trigger error near the upper limit of dimming but also to avoid a trigger error near the lower limit of dimming.

  In one embodiment of the LED light control device, the trigger signal output by the phase control unit is on until the next zero cross point of the AC voltage.

  According to this embodiment, it is possible to perform normal pulse trigger phase control while avoiding an on-miss of the bidirectional switching element due to the trigger signal.

The LED dimming device according to an embodiment includes a load current detection unit that detects a current flowing through the LED load unit and outputs a load current detection signal to the phase control unit,
The phase control unit is
When the load current detection signal is received from the load current detection unit, the trigger signal is turned off.

  According to this embodiment, the pulse width of the trigger signal can be shortened.

In one embodiment of the LED light control device, the trigger signal has a pulse width longer than the turn-on time of the bidirectional switching element,
The control circuit is
The variable range of the phase of the trigger signal is made wider by one half of the longer pulse width than the turn-on time from both ends of the range in which the current greater than the holding current flows in the bidirectional switching element.

  According to this embodiment, the current in the LED exceeds the set control range due to variations in the forward voltage due to manufacturing problems of the LEDs used in the LED load section and changes in the forward voltage due to temperature changes during use. When the flow range becomes narrow, it is possible to avoid the phenomenon of not lighting near the upper limit of the output setting. Further, according to the phase control unit of this embodiment, when the range in which the current flows to the LED becomes wider than the set control range due to the variation or change in the forward voltage, the 0 to 0 in the wide range is set. The phenomenon that 100% dimming cannot be performed can be avoided.

The LED dimming device according to an embodiment includes a load current detection unit that detects a current flowing through the LED load unit and outputs a load current detection signal to the phase control unit,
The phase control unit is
The trigger signal phase is set near the minimum value of the absolute value of the AC voltage within the variable range of the trigger signal phase, and the load current detection signal from the load current detection unit is received. If not, the trigger signal phase is changed.

  According to this embodiment, when the trigger error due to the trigger signal occurs, the phase control unit can re-trigger the bidirectional switching element by automatically changing the phase of the trigger signal. it can.

  In one embodiment of the LED light control device, the load current detection unit includes a phototransistor coupler connected in series to the LED load unit in the closed circuit.

  Further, in the LED light control device according to an embodiment, even if no current flows through the LED load portion, a holding current that causes a current equal to or higher than the holding current to flow through the bidirectional switching element except for the zero cross point of the AC power supply. It has a securing circuit.

  According to this embodiment, the range in which normal phase control can be performed can be expanded.

  In one embodiment of the LED light control device, the holding current securing circuit is a resistance element connected in parallel to the LED load section.

  According to this embodiment, the holding current securing circuit can be simplified.

  In one embodiment of the LED dimming device, the holding current securing circuit is a constant current element or a constant current circuit connected in parallel to the LED load.

  According to this embodiment, the loss can be reduced by the holding current securing circuit.

  Moreover, the LED power supply module of one Embodiment was equipped with the said LED light control apparatus.

  Moreover, the LED illuminating device of one Embodiment was equipped with the said LED light control apparatus.

  According to the LED light control device of the present invention, the phase control unit can avoid outputting a trigger signal to the bidirectional switching element in the vicinity of the zero cross point of the AC voltage in a half cycle of the AC voltage. Therefore, according to the present invention, it is possible to avoid the phenomenon that the LED does not light at all even though the setting is near the upper limit of dimming. Therefore, according to the present invention, the LED load can be dimmed with an AC power source with low loss, and a dimming error can be prevented.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 shows a basic configuration of a first embodiment of the LED light control device of the present invention. This light control device includes a phototriac coupler 3 as a bidirectional switching element that is connected between a commercial power source (AC 100 V) 1 as an AC power source and an LED load unit 2 to form a closed circuit. A current limiting resistor R <b> 1 is connected between the secondary side of the phototriac coupler 3 and the LED load unit 2.

  The LED load section 2 is formed by connecting two sets of units U1 and U2 in which 25 white LEDs are connected in series so that the polarities are in opposite directions. The phototriac coupler 3 is an optical coupling element in which the input-side LED 3B and the output-side phototriac 3A are insulated, and the output-side phototriac 3A is triggered by passing a current through the input-side LED 3B. The

  The commercial power supply 1 is connected to a zero cross detection circuit 5 and a microcomputer power supply circuit 6. This zero cross detection circuit 5 is a circuit in which a photocoupler 5A is connected to a commercial power source 1 via a resistor 5B. When the voltage of the commercial power source 1 is large, the LED 11 or 12 on the input side of the photocoupler 5A is lit, so the output transistor 13 is turned on, while the LEDs 11 and 12 are turned off near the zero cross where the voltage of the commercial power source 1 is small. Therefore, the output transistor 13 is turned off. Thereby, the zero cross detection circuit 5 detects the zero cross point of the commercial power source 1 and outputs a zero cross detection signal. In the zero cross detection circuit 5 shown in FIG. 1, the emitter of the output transistor 13 is connected to the ground, and the collector is connected to the microcomputer MC1 that is pulled up internally. The microcomputer MC1 constitutes a control circuit 7. The control circuit 7 and the zero cross detection circuit 5 constitute a phase control unit.

  The zero-cross detection signal ZC output from the zero-cross detection circuit 5 has a signal waveform as shown in the (g) column of FIG. 5A. That is, in such a zero-cross detection circuit 5, since the input-side LEDs 11 and 12 are not lit before and after the power supply voltage of the commercial power supply 1 becomes 0V, the zero-cross detection signal ZC is higher than the actual zero-cross point of the power supply voltage. It is output a little earlier and has a certain pulse width.

  In the embodiment of FIG. 1, the pulse width of the zero-cross detection signal ZC output from the zero-cross detection circuit 5 has a width of about 400 μs, and the signal is output 200 μs before the actual zero-cross point. In the embodiment of FIG. 1, the zero-cross detection circuit 5 has the input-side LEDs 11 and 12 connected in antiparallel called an AC input type, but the input polarity of two normal phototransistor couplers is set. The operation is the same in the reverse connection configuration and the circuit in which the diode bridge is inserted in front of the phototransistor coupler.

  The microcomputer power supply circuit 6 rectifies the AC power from the commercial power supply 1 and outputs the DC power to the microcomputer MC1 constituting the control circuit 7. The microcomputer power supply circuit 6 is configured by a simple circuit that does not use a transformer (transformer) because the required current is 10 mA or less and voltage accuracy is not required.

  In this embodiment, the microcomputer MC1 is a microcomputer called PIC (Peripheral Interface Controller) that writes a control program before being mounted on a circuit. This PIC contains an oscillation circuit, timer circuit, comparator, data storage memory, etc. in one package, and many control programs are written in the flash memory, and the contents disappear even when the power is turned off. Absent. Further, since this PIC is low in price, has a low power consumption of several mA, and has a wide operating power supply range, even a simple power supply circuit 6 as shown in FIG. In addition, the program can be easily changed, and the conditions can be finely classified according to the type of LED load to be used.

  The input / output terminals of the microcomputer MC1 can be switched by a program, and pull-up and pull-down resistors can be set. Further, as shown in FIG. 1, the microcomputer MC1 operates only by connection to a power source and input / output signal terminals, and other components are unnecessary. The role of the microcomputer MC1 is to trigger the phototriac coupler 3 at a set position within a half cycle of the AC power supply voltage SV of the commercial power supply 1 based on the zero cross signal input from the zero cross detection circuit 5 to the input signal terminal ZX. It is to output a phase control signal FC as a trigger signal as a signal. The phase control signal FC is input from the output terminal OUT of the microcomputer MC1 to the LED 3B on the input side of the phototriac coupler 3 via the resistor R0.

  In this embodiment, since the LED load unit 2 is directly lit by alternating current from the commercial power source 1, there is no loss that occurs during voltage conversion or rectification, and the power consumption of the control circuit 7 is as low as several tens of mW. Drive with high efficiency.

  Further, this embodiment includes a switch unit 15 connected to the control circuit 7, and the switch unit 15 is configured by a normal push button switch. The switch unit 15 includes three switches 15A, 15B, and 15C. The switch 15C is connected to the terminal ON / OFF of the control circuit 7 to turn on / off the power source. The switch 15A is connected to the terminal UP of the control circuit 7. By turning on the switch 15A, the phase of the phase control signal FC output from the control circuit 7 is advanced, and the trigger point of the phototriac coupler 3 is moved in the upper limit direction. The switch 15B is connected to the terminal DOWN of the control circuit 7. By turning on the switch 15B, the phase of the phase control signal FC is delayed, and the trigger point of the phototriac coupler 3 is moved in the lower limit direction. It should be noted that a remote controller receiving circuit is provided in place of the switches 15A to 15C, and a signal is input to the remote controller receiving circuit from the remote controller so that the control circuit 7 can be turned on and off, and the upper and lower limits of the trigger point. You may operate to move in the direction.

(basic action)
Next, the basic operation will be described. The microcomputer MC1 converts the phase control signal FC that becomes the trigger signal of the phototriac coupler 3 into the zero cross detection signal ZC for a set time within the phase variable range between the upper limit and the lower limit of the trigger point of the phototriac coupler 3. Output from the output terminal OUT. The increment in which the phase of the zero cross detection signal ZC is shifted is a phase width obtained by dividing the phase variable range into, for example, 256 equal parts (in the case of 8-bit variables).

  Here, the phase range of the normal trigger point as a comparative example is a half cycle of the AC commercial power supply 1, and in the case of 60 Hz, the inside of about 8.3 ms is divided into 256 equal parts, so about 32.6 μs. The trigger point can be varied in steps. That is, the zero step of the 256 equal steps is 0% from the zero cross signal and 0% (power is 100%) phase control is performed, and the 255 step is delayed by 8.3 ms from the zero cross signal. Phase control of 100% (power is 0%) is performed at the position.

  As described above, when the zero cross detection signal ZC is deviated from the actual zero cross point, the correction of the phase control is necessary. This correction is performed by the control circuit 7. In the case of this embodiment, the trigger point is a time added by 200 μs from the phase control position. The pulse width of the phase control signal FC that is a trigger signal input to the phototriac coupler 3 only needs to be longer than the turn-on time of the phototriac 3A, and 100 μs is sufficient. Further, considering the current consumption of the control circuit 7 and the deterioration of the LED 3B of the phototriac coupler 3, it is desirable that the pulse width is as short as possible.

(Operation of Comparative Example 1)
Here, in the light control device shown in FIG. 1, instead of the LED load unit 2, a resistance load such as an incandescent lamp is connected, and the power supply voltage SV and load current when this resistance load is phase-controlled by the conventional method. The waveform of LIa is shown in FIG. In the waveforms of the power supply voltage SV and the load current LIa shown in FIG. 3, the resistance change with respect to the temperature change of the filament of the incandescent lamp is ignored. In this comparative example 1, by outputting the phase control signal FC1 every half cycle of the power supply voltage SV, the phototriac 3A is turned on by this phase control signal FC1, and the load current LIa flows until the next zero cross point. In the left cycle of the zero cross point Z1 shown in FIG. 3, about 75% phase control is performed, and in the right cycle of the zero cross point Z1, about 20% phase control is performed.

(Operation of Reference Example 1)
Next, in the (a) column of the waveform diagram of FIG. 4, when a resistive load such as an incandescent lamp is connected to the AC power supply 1 that generates the power supply voltage SV, the load current LIb flowing through the resistive load is indicated by a broken line. In FIG. 4B, the waveform of the load current LIc flowing through the LED load unit 2 when the LED load unit 2 shown in FIG. FIG. 2 shows, as an example, the relationship between the forward voltage VF and the forward current IF of the LED load section in which 25 white LEDs are connected in series.

  As can be seen from the two waveforms of the power supply voltage SV and the load current LIc shown in the column (b) of FIG. 4, the forward voltage of each LED is synthesized and increased in the LED load section in which a large number of LEDs are connected in series. When the power supply voltage SV is lower than the synthesized forward voltage, it can be seen that the load current LIc hardly flows through the LED load portion.

(Operation of Comparative Example 2)
Next, with reference to columns (c) and (d) of FIG. 4, the waveform of the load current LId when the LED load unit 2 shown in FIG. In the (d) column of FIG. 4, the positions of the trigger points TP1 to TP4 are changed in each half cycle t1 to t4 of the power supply voltage SV for the sake of explanation. The waveform of the two half cycles t1 and t2 on the left side of the power supply voltage SV in the column (d) of FIG. 4 is in a region where the power supply voltage SV is larger than the forward voltage VF of the LED load section 2. There are trigger points TP1 and TP2 by the phase control signal FC1 shown in the column (c) of FIG. Therefore, normal phase control by the phase control signal FC1 is performed at the trigger points TP1 and TP2. That is, while the phase control signal FC1 is on, a current equal to or greater than the holding current Ih of the phototriac 3A flows to the phototriac 3A, and the load current LI flows to the LED load unit 2.

  On the other hand, regarding the waveforms of the two half cycles t3 and t4 on the right side of the power supply voltage SV in the column (d) of FIG. 4, the forward voltage VF of the LED load unit 2 is larger than the power supply voltage SV. There are trigger points TP3 and TP4 by the phase control signal FC1 shown in the column (c) of FIG. Therefore, at the trigger points TP3 and TP4, even if the phase control signal FC1 is input to the LED 3B of the phototriac coupler 3 with a normal pulse width, the holding current Ih of the phototriac 3A is maintained while the phase control signal FC1 is on. The above current does not flow to the phototriac 3A. For this reason, the self-holding function of the phototriac 3A does not operate in the two half cycles t3 and t4 on the right side of the power supply voltage SV in the column (d) of FIG.

  It should be noted that even when the phase control is normal (when the self-holding function of the phototriac 3A is activated) with the output setting near the lower limit as in the trigger point TP4 in the half cycle t4 in the column (d) of FIG. Since the load unit 2 is an area where the light does not light, a trigger error does not become a problem. On the other hand, in the output setting near the upper limit like the trigger point TP3 in the half cycle t3, the LED of the LED load unit 2 does not light at all even though the LED load unit 2 should be near the maximum output. Therefore, a trigger mistake becomes a big problem.

  Next, the operation of this embodiment will be described with reference to the (W) column and (a) to (h) columns of the waveform diagram of FIG. 5A.

  First, in the (W) column of FIG. 5A, the waveform of the power supply voltage SV of the AC power supply 1 and the waveform of the load current LIc flowing through the LED load section 2 when the LED load section 2 is connected to the AC power supply 1 are shown. Is indicated by a broken line. 5A shows an example of the phase control signal FC1 according to the above-described comparative example 2, and the trigger point variable range R1 according to the phase control signal FC1.

  Next, the (b) column of FIG. 5A shows the phase control signal FC11 as the trigger signal of the first example output from the control circuit 7 according to this embodiment. The phase variable range R11 of the phase control signal FC11 does not include the phase ranges S1 and S2 from the zero cross point of the power supply voltage SV until the power supply voltage SV reaches the forward voltage VF of the LED load section 2. That is, the phase variable range R11 of the phase control signal FC11 starts from the time t10 when the power supply voltage SV exceeds the forward voltage VF, and then from the time t30 when the power supply voltage SV reaches the zero cross point. This is the range up to time t20 after subtracting the pulse width.

  The phase control signal FC11 of the first example is not output in the phase ranges S1 and S2 in which the power supply voltage SV is equal to or lower than the forward voltage VF. Therefore, the output control is performed near the upper limit as in the comparative example 2 described above. Regardless, the problem that the LED of the LED load unit 2 does not light at all can be solved.

  Next, the column (c) of FIG. 5A shows the phase control signal FC12 as the trigger signal of the second example output from the control circuit 7 according to this embodiment. The phase variable range R12 of the phase control signal FC12 does not include the phase ranges S1 and S2 from when the power supply voltage SV reaches the forward voltage VF of the LED load unit 2 from the zero cross point of the power supply voltage SV, and It does not include the phase ranges S3 and S4 from when the power supply voltage SV decreases below the forward voltage VF of the LED load section 2 until the next zero cross point is reached. That is, the phase variable range R12 of the phase control signal FC12 is limited to a range in which the power supply voltage SV exceeds the forward voltage VF.

  According to the phase control signal FC12 of the second example, as in the case of the phase control signal FC11 of the first example, the LED is not output in the phase ranges S1 and S2. The problem that the LED of the load unit 2 does not light at all can be solved. Further, according to the phase control signal FC12 of the second example, since it is not output not only in the phase ranges S1 and S2 but also in the phase ranges S3 and S4, the original fine adjustment (256 in the range in which the LED of the LED load unit 2 is lit). This is effective when you want to perform (Step). Moreover, it is effective when it becomes a problem that the output can be set in the lower limit direction even after the LED load unit 2 is turned off.

  Next, the (d) column of FIG. 5A shows the phase control signal FC13 as the trigger signal of the third example output from the control circuit 7 of this embodiment. The phase control signal FC13 corresponds to a signal obtained by increasing the pulse width of the phase control signal FC12 of the second example. That is, the phase control signal FC13 has a pulse width that is three times the pulse width of the phase control signal FC12 of the second example. The phase control signal FC13 has a phase variable range R13 that is wider than the phase variable range R12 of the phase control signal FC12 by the pulse width of the phase control signal FC12 in the upper limit direction and in the lower limit direction. Wide enough for the pulse width. According to the phase control signal FC13 of the third example, it is set by the variation of the forward voltage VF due to the manufacturing problem of the LED used in the LED load section 2 or the change of the forward voltage VF due to the temperature change during use. When the range in which the current flows in the LED becomes narrower than the control range, the phenomenon of not lighting near the upper limit of the output setting can be avoided. Further, according to the phase control signal FC13 of the third example, when the range in which the current flows through the LED becomes wider than the set control range due to the variation or change in the forward voltage VF, the widened range. It is possible to avoid the phenomenon that 0 to 100% dimming cannot be performed.

  Note that the pulse width of the phase control signal FC13 in the third example may be set based on possible variations in the forward voltage VF and temperature characteristics of the forward voltage VF. However, even when the lower limit is set within the phase variable range, it is necessary to set the phase control signal to a range that is off at the next zero cross point. This is because if the phase control signal is turned on at the next zero cross point, the output setting becomes 100% at the maximum.

  Next, the (e) column of FIG. 5A shows the phase control signal FC14 of the fourth example output from the control circuit 7 of this embodiment. The phase control signal FC14 has a variable range R14 similar to the trigger point variable range R1 by the phase control signal FC1 according to the comparative example 2 shown in the column (a) of FIG. 5A. As illustrated in the column (e) of FIG. 5A, the phase control signal FC14 is from the rising time (trigger point) Ts until the next zero cross signal is input to the control circuit 7 (up to the end of the variable range R14). The pulse width is

  According to the phase control signal FC14 of the fourth example, the trigger point Ts is also in the vicinity of the next zero cross point even when the output is set near the upper limit where the current flowing through the phototriac coupler 3 that is a bidirectional switching element is equal to or less than the holding current. Stays on until. For this reason, when the power supply voltage SV increases and exceeds the forward voltage VF of the LED load section 2, the phototriac coupler 3 that is a bidirectional switching element is turned on, and normal phase control can be performed while avoiding an on-miss. .

  In the phase control signal FC14 of the fourth example of this embodiment, there is no need to consider the difference in the forward voltage VF depending on the number of LEDs included in the LED load unit 2 and the variation in the forward voltage VF.

  However, in the phase control signal FC14 of the fourth example, the on-time is significantly increased, so that the current consumption increases particularly when the vicinity of the upper limit is set. Further, the deterioration of the LED 3B of the phototriac coupler 3 is accelerated. In addition, since the variable range of the trigger point is wider than the range in which the LED load unit 2 is actually lit, there is a region where the light amount does not change even if the setting is changed near the upper limit or lower limit of the output. However, in actuality, if the UP button for dimming attached to the switch 15A or the DOWN button attached to the switch 15B is kept pressed, the phase of the trigger point Ts changes at high speed in fine steps such as 256 steps. In addition, it is difficult to understand that there is a region where the light amount does not change near the lower limit, and this is not a big problem as a light control device.

  Note that the phase control signals FC11 to FC14 of the first to fourth examples in the columns (b) to (e) of FIG. 5A are obtained only by changing the program of the microcomputer MC1 in the dimming device shown in FIG. It is feasible.

(Second embodiment)
Next, the basic configuration of the second embodiment of the LED light control device of the present invention will be described with reference to the circuit diagram of FIG. The dimming device of FIG. 6 includes only the phototransistor coupler 60 connected between the phototriac coupler 3 and the current limiting resistor R1 of the dimming device of the first embodiment described above. 1 different from the dimmer. Therefore, in the second embodiment, differences from the first embodiment will be mainly described.

  The phototransistor coupler 60 detects a current flowing through the LED load unit 2. That is, when the phototriac coupler 3 is turned on and a current flows through the LED load unit 2, the LED unit 60A on the input side of the phototransistor coupler 60 is also lit, and the phototransistor 60B on the output side is turned on. Current flows. This output-side phototransistor 60B is connected to the terminal ON of the microcomputer MC1, which is pulled up internally, as in the zero-cross detection circuit 5.

  Thus, the load current detection signal DS input from the phototransistor coupler 60 to the terminal ON of the microcomputer MC1 has a waveform shown in the column (h) of FIG. 5A.

  In the second embodiment, the control circuit 7 turns off the phase control signal FC15 shown in the column (f) of FIG. 5A by using the load current detection signal DS input from the phototransistor coupler 60. The phase control signal FC15 has a variable range R15 similar to the phase control signal FC14 in the (e) column of FIG. 5A as shown in the (f) column of FIG. 5A. The phase control signal FC15 has a pulse width from the rising time (trigger point) Ts to the falling time Td of the load current detection signal DS as shown in the column (f) of FIG. 5A. That is, the phase control signal FC15 is turned off at the point where the current starts to flow through the LED load unit 2.

  In the region where the power supply voltage SV is larger than the forward voltage VF of the LED load section, the phototriac 3A is turned on immediately after the phase control signal FC15 is input to the phototriac coupler 3, so that the phase control signal FC15 is very high. Shorter. In this region, when the phase control signal FC15 becomes too short and the turn-on is not normally performed, or when the current flowing through the LED load unit 2 is large, it is parallel to the LED unit 60A that is the primary side of the phototransistor coupler 60. It is only necessary to connect a resistance element to and lower the detection sensitivity.

  Here, the used phototransistor coupler 60 also has input-side LEDs 61 and 62 connected in reverse parallel for AC input, like the zero cross detection circuit 5, but the input polarity of two normal phototransistor couplers. The operation is the same in a configuration in which the diodes are connected in reverse or in a circuit in which a diode bridge is inserted in front of the phototransistor coupler.

  In the phase control signal FC15, it is detected that the load current flows at the fall of the load current detection signal DS, and the phase control signal FC15 shown in the column (f) of FIG. 5A is turned off. The phase control signal FC15 may be turned off by detecting that the load current does not flow at the rise time Tu of the detection signal DS (the LED load unit 2 is turned off).

  In the second embodiment, it is possible to eliminate the phenomenon that the trigger point Ts of the phase control signal FC15 exceeds the range R12 in which the phase can be normally controlled for some reason and is completely turned off near the upper limit.

  The following (1) and (2) are examples in which the trigger point Ts of the phase control signal FC15 is automatically changed in the variable range R15.

   (1) If the dimming is continued from the normal state in the upper limit direction (pressing the UP button for dimming attached to the switch 15A) and turned off, the setting immediately before turning off is restored.

   (2) If the setting is within the range from the output 50% to the output upper limit, if the light does not turn on from the beginning, or if the light is turned off halfway, the power supply voltage SV with the highest output voltage SV is set. Change to trigger point.

  Next, FIG. 7 shows a first modification of the light control device of the first embodiment shown in FIG. In this modification, a resistance element 70 for securing a holding current is connected to the LED load unit 2 in parallel. In this case, even when the power supply voltage SV is smaller than the forward voltage VF of the LED load unit 2 and no current flows through the LED load unit 2, the current flows through the resistance element 70 for securing the holding current. Therefore, a current equal to or higher than the holding current flows in the phototriac 3A except for the zero cross point of the power supply voltage SV as in a current waveform If indicated by a dotted line in the column (i) of FIG. 5B. Therefore, the range in which normal phase control can be performed can be expanded.

  FIG. 8 shows a second modification of the light control device of the first embodiment shown in FIG. In this modification, a constant current diode unit 80 including constant current diodes 80A and 80B is connected in parallel with the LED load unit 2 as a constant current element for securing a holding current. In this case, even when the power supply voltage SV is smaller than the forward voltage VF of the LED load unit 2 and no current flows through the LED load unit 2, a current flows through the constant current diode unit 80 for securing the holding current. Therefore, as in the current waveform Ik indicated by the broken line in the column (i) of FIG. 5B, a current equal to or higher than the holding current flows in the phototriac 3A except for the zero cross point of the power supply voltage SV. Therefore, the range in which normal phase control can be performed can be expanded.

  The resistance value of the resistance element 70 of the first modification and the characteristics of the constant current diode section 80 of the second modification are determined by the holding current of the phototriac coupler 3 that is a bidirectional switching element. For example, in the case of the phototriac 3A of this embodiment, since the holding current is about 100 μA, when the resistance element 70 of FIG. 7 is provided, good results are obtained at about several tens kΩ to 100 kΩ. With such a resistance value, the power consumed by the resistor is small and the capacitance of the resistor is small. On the other hand, when the load of the load unit 2 is large and a power triac or the like is used for the bidirectional switching element, the holding current also increases. Therefore, the resistance value of the resistance element 70 needs to be reduced. When the resistance value of the resistance element 70 is reduced, the power consumed by the resistance element 70 increases, and the current flowing through the resistance element 70 is further increased in a region where the power supply voltage is unnecessary and the loss due to the resistance element 70 can be ignored. Disappear.

  As described above, when the holding current of the bidirectional switching element is large, a second modification in which the constant current element unit 80 capable of flowing a constant current regardless of the applied voltage is connected in parallel with the LED load unit 2. Is preferred. In the second modification, the constant current diodes 80A and 80B that are often used for the purpose of supplying a constant current to the LED are employed as the constant current element. As the constant current diodes 80A and 80B, there are diodes that flow a constant current of several hundred μA to several tens of mA. Further, as the constant current diodes 80A and 80B, those having a reverse withstand voltage of about 150V are employed. In the case of an AC load, as shown in FIG. 8, two constant current diodes 80A and 80B may be connected so that the polarities are reversed.

  In the second modification, a small and simple constant current diode is used. However, a constant current circuit using a transistor, a Zener diode, or the like may be provided.

  Further, in the first and second embodiments described above, the LED load unit 51 and the rectifier diode bridge 52 shown in FIG. In this LED load section 51, two sets of LED units 51A and 51B are connected in parallel, and each LED unit 51A and 51B includes a plurality of LEDs connected in series and current limiting resistors R2 and R3. Further, the LED array directions of the LED units 51A and 51B are the same in the forward direction. The rectifier diode bridge 52 rectifies the AC current from the commercial power supply 1 so that it always flows in the forward direction with respect to the LED load 51.

  When the current flowing through the LED load section 2 is large, as shown in FIG. 10, a triac 61 is connected between the commercial power source 1 and the current limiting resistor R1, and the triac 61 is turned on by the phototriac coupler 3. You may make it arc. Further, instead of the phototriac coupler 3, a normal triac (not shown) is connected to the gate of the triac 61, and the gate of the triac (not shown) is directly controlled by a phase control signal output from the control circuit 7. You may make it do.

  In the first and second embodiments described above, the dimming device having the configuration shown in FIGS. 1 and 6 has been described. However, the zero-cross detection circuit 5 and the phototransistor coupler 60 for detecting the load current are different from each other. Detection means may be used. Of course, the AC power source is not limited to the commercial power source 1. In the first and second embodiments, an inexpensive one-chip microcomputer (microcomputer MC1) is used as the control circuit 7 so that the trigger point of the phase control signal can be easily changed by a program. In one embodiment, instead of the microcomputer MC1 as the control circuit 7, a control circuit composed of two timer circuits and a variable resistor that changes the time of the timer can be employed. In other words, the first timer circuit that receives the zero-crossing detection signal from the zero-crossing detection circuit 5 and starts timekeeping and measures the time for a set time, and uses the trigger point of the phase control signal as a trigger point. The second timer circuit in which the period up to this time is set to the pulse width of the phase control signal and the time setting circuit for changing the time measuring time of the first and second timer circuits may be constituted by a variable resistor or the like. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a first embodiment of an LED light control device according to the present invention. It is a characteristic view which shows the relationship between the forward voltage VF and forward current IF of the LED load part which connected 25 white LED in series. It is a wave form diagram which shows AC power supply voltage SV which drives resistive loads, such as an incandescent lamp, load current LIa, and phase control signal FC1. The (a) column shows the waveform of the power supply voltage SV and the load current LIb when the load is a resistive load such as an incandescent lamp, and the (b) column shows the power supply voltage SV and the load current LIc when the load is an LED load unit. The movement control signal FC1 in the comparative example 2 is shown in the (c) column, and the waveform of the power supply voltage SV and the load current LId in the comparative example 2 is shown in the (d) column. The (W) column shows the waveform of the power supply voltage SV and the load current LIc of the AC power supply, the (a) column shows the waveform of the phase control signal FC1, and the (b), (c), (d), (e) columns Shows the waveforms of the phase control signals FC11, FC12, FC13, and FC14 as first, second, third, and fourth examples of the trigger signal in the first embodiment, and the trigger signal in the second embodiment is shown in (f) column. The waveform of the phase control signal FC15 is shown, the waveform of the zero-cross detection signal ZC in the first and second embodiments is shown in the (g) column, and the load current detection signal DS in the second embodiment is shown in the (h) column. It is a wave form diagram which shows a waveform. It is a wave form diagram which shows current waveform If and Ik in the 1st, 2nd modification of the said 1st Embodiment in the (i) column. It is a circuit diagram which shows 2nd Embodiment of the LED light modulation apparatus of this invention. It is a circuit diagram which shows the 1st modification of the said 1st Embodiment. It is a circuit diagram which shows the 2nd modification of the said 1st Embodiment. It is a circuit diagram which shows the modification of the said 1st Embodiment. It is a circuit diagram which shows the modification of the said 1st Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 LED load part 3 Phototriac coupler 3A Phototriac 3B LED
5 Zero cross detection circuit 5A Photocoupler 5B Resistance 6 Microcomputer power supply circuit 7 Control circuit 11, 12 LED
15 Switch unit 15A to 15C Switch 60 Phototransistor coupler 60A LED unit 60B Phototransistors 61 and 62 LED
70 Resistance element 80 Constant current diode part 80A, 80B Constant current diode DS Load current detection signals FC1, FC11 to FC15 Phase control signals LIa to LIc Load current MC1 Microcomputer SV Power supply voltage Ts Rise time Td Fall time Z1 Zero cross point ZC Zero cross detection signal ZX Input signal terminal

Claims (13)

A bidirectional switching element that is connected between an LED load unit having a plurality of light emitting diodes connected in series so as to have the same forward direction and an AC power source to form a closed circuit and has a self-holding function;
The LED is generated by outputting a trigger signal to the bidirectional switching element to turn on the bidirectional switching element and changing the phase of the trigger signal within a variable range narrower than a half cycle of the AC voltage output from the AC power supply. An LED light control device comprising: a pulse trigger type phase control unit that performs light control by changing effective power input to a load unit. The LED light control device according to claim 1,
The phase control unit is
A zero cross detection circuit for detecting a zero cross point at which the absolute value of the AC voltage of the AC power supply becomes 0 V;
A control circuit that includes a control circuit that does not make the predetermined period from the zero cross point detected by the zero cross detection circuit within the variable range of the phase of the trigger signal out of the period during which the absolute value of the AC voltage increases. Optical device. The LED light control device according to claim 2,
The control circuit is
Of the period in which the absolute value of the AC voltage decreases, the period from the time when the absolute value of the AC voltage is a predetermined value to the zero cross point detected by the zero cross detection circuit is not set as the variable range of the phase of the trigger signal. LED dimmer characterized by the above. The LED light control device according to claim 1 or 2,
The LED dimming device according to claim 1, wherein the trigger signal output from the phase control unit is on until the next zero cross point of the AC voltage. The LED light control device according to claim 1 or 2,
A load current detection unit that detects a current flowing through the LED load unit and outputs a load current detection signal to the phase control unit;
The phase control unit is
The LED light control device, wherein the trigger signal is turned off when the load current detection signal is received from the load current detection unit. In the LED light control device of Claim 3,
The trigger signal has a pulse width longer than the turn-on time of the bidirectional switching element,
The control circuit is
The variable range of the phase of the trigger signal is widened from both ends of the range in which a current equal to or higher than the holding current flows in the bidirectional switching element by one half of the pulse width longer than the turn-on time. LED dimmer. In the light control device of LED as described in any one of Claim 1 to 6,
A load current detection unit that detects a current flowing through the LED load unit and outputs a load current detection signal to the phase control unit;
The phase control unit is
The trigger signal phase is set near the minimum value of the absolute value of the AC voltage within the variable range of the trigger signal phase, and the load current detection signal from the load current detection unit is received. A dimming device for an LED, wherein the phase of the trigger signal is changed in the absence of the trigger signal. The LED light control device according to claim 5 or 7,
The load current detector is
An LED light control device comprising a phototransistor coupler connected in series to the LED load section in the closed circuit. In the light control device of LED as described in any one of Claim 1 to 8,
A dimming LED having a holding current securing circuit for supplying a current equal to or higher than a holding current to the bidirectional switching element except for a zero cross point of the AC power supply even when no current flows in the LED load section apparatus. The LED light control device according to claim 9,
The holding current securing circuit is
A dimming device for an LED, comprising a resistance element connected in parallel to the LED load section. The LED light control device according to claim 9,
The holding current securing circuit is
An LED light control device, comprising: a constant current element or a constant current circuit connected in parallel to the LED load.   The LED power supply module provided with the light control apparatus of LED as described in any one of Claim 1 to 11.   An LED lighting device comprising the LED light control device according to any one of claims 1 to 11.

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