JP2006278009A - Dimmer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to perform measurement with accuracy of a reference time of phase control of a dimmer. <P>SOLUTION: A closed circuit is structured by serially connecting a two-way switching element Q1 with a self-retaining function, an illumination load 4 with a capacitative element C2 connected in parallel and an alternate current power source 1, a zero-cross detection circuit 24 is connected at an output end of a rectifying circuit 22 rectifying in full wave the alternate current power source 1, and time measurement is carried out from a rising edge or a trailing edge of a zero-cross detection signal obtained, whereby a phase controlling circuit of a DC trigger system for deciding an arcing phase angle of the two-way switching element Q1, and a chopper circuit of boosting or boosting/stepping down type is connected to an output end of the rectifying circuit connected to the zero-cross detection circuit 24 as a switching power source 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light control device that adjusts the illuminance of a light source such as an incandescent bulb or LED.

  Conventionally, a phase control dimmer is often used as means for dimming an incandescent lamp. Phase control dimmers are generally connected in series between a commercial AC power supply and an incandescent lamp load, and control the phase angle (triggering phase angle) at which the triac, which is a switching element inside the dimmer, turns on. In this way, the effective value of the commercial AC voltage supplied to the incandescent lamp load is varied to control the dimming of the incandescent lamp load. FIG. 9 shows operation waveforms of the phase control dimmer. In an incandescent lamp load, since the power supply voltage and the load current are in phase, the load current can be turned off if it is turned off at the zero cross point of the power supply.

  As a lighting circuit for a low-voltage halogen bulb, an electronic transformer is well known as a means for converting a commercial AC voltage into a high frequency of several tens of KHz and further converting it into a high-frequency low voltage of 12 V using a step-down transformer. It is also a general technique to perform dimming control by combining an electronic transformer for a low-voltage halogen bulb with the above-described phase control type dimmer.

  FIG. 10 shows a circuit configuration when the phase control dimmer and the electronic transformer are used in combination. In the figure, 1 is an AC power source, 2 is a phase control dimmer, 3 is an electronic transformer, and 4 is a load. In this configuration, since the filter capacitor C1 is connected in parallel to the series connection of the triac Q1 which is a bidirectional switching element and the filter choke L1, and the noise prevention capacitor C2 on the electronic transformer side is further connected in series, the triac Q1. When the current flowing in is used at a commercial frequency, the phase of the power supply voltage may be advanced due to the influence of the capacitive element.

  The circuit operation will be described with reference to FIG. Here, as the phase control signal, not the pulse trigger system that applies the gate voltage only at the turn-on time but the DC trigger system that continues to apply the gate voltage during the turn-on period. The triac Q1 is an element that turns off when the phase control signal is turned off and then becomes a current equal to or lower than the holding current. Is commutated across the zero cross point, and when the current exceeding the holding current flows at the moment when the phase control signal is turned off, the TRIAC Q1 cannot be turned off, so that the current becomes zero over the next half cycle of the AC power supply. Until that time, the triac Q1 remains on.

  Therefore, conventionally, in order to solve this problem, as shown in FIG. 12, time is set so that the phase control signal is turned off before the current flowing in the triac Q1 crosses the zero cross point at the design stage. The problem of dimming operation was avoided. In the figure, the triac Q1 cannot be turned off even if the phase control signal is turned off at the timing t1, but the triac Q1 can be turned off by turning off the phase control signal at the timing t2.

  As one of the specific means, a system (Japanese Patent Application No. 2004-206741) for avoiding the dimming problem due to the phase advance current by separately providing a circuit for detecting the zero cross point of the current flowing in the triac Q1, or a microcomputer A method for avoiding the problem of dimming operation due to the phase advance current by setting the time by using the current (Japanese Patent Application No. 2004-206742), and further increasing the reactive current by connecting the resistor element in parallel with the capacitor C2 to triac The current flowing in Q1 is increased, and the phase of the phase control signal is turned off from the zero point of the main switch current without considering the off timing of the switching element by making the phase of the power supply voltage and the main switch current substantially the same. A system configuration (Japanese Patent Application No. 2004-2067) in which a malfunction can be avoided by being in front. No. 3) and has already proposed.

In Patent Document 1, when dimming an inverter-type discharge lamp lighting device by phase control, a boost chopper circuit is connected to the output terminal of a full-wave rectifier so that the inverter circuit can be connected regardless of the phase control angle. A technology that enables dimming control while improving the input power factor by making the input DC voltage substantially constant and inputting phase control angle information as a dimming signal to the inverter circuit is disclosed. However, the phase control signal is not limited to the DC trigger method, and the problem of erroneous firing due to the phase advance load is not suggested.
JP-A-11-135290

  Each of the above-mentioned Japanese Patent Application Nos. 2004-206741 to 3 uses any means, and the timing at which the phase control signal of the DC trigger method is turned off is earlier than the timing at which the current of the triac Q1 becomes zero. However, the time reference for determining the ON and OFF timing of the phase control signal is the rising or falling edge of the zero-cross detection signal of the input voltage.

  As shown in FIG. 2, this rising or falling edge is generated by a switch such as a transistor Tr1 in a valley portion (low voltage region) of a full-wave rectified waveform after the input voltage is rectified by a rectifier circuit 21 such as a diode bridge. The section in which the element is turned off and an H level signal is input to the microcomputer input terminal is defined as a voltage zero cross section, and the rising edge of the voltage zero cross is handled as a reference for starting the timer count of the microcomputer. When the control power supply voltage Vcc of the microcomputer and its peripheral circuits is supplied using a step-down chopper type switching power supply in the subsequent stage, the output voltage of the switching power supply cannot be lower than the control power supply voltage Vcc. The voltage on the output side of the diode bridge is completely zero It can not be in the belt.

  In addition, each diode element itself of the diode bridge has a slight stray capacitance, and the value is different for each element. As a result, the rising edge of the voltage zero cross signal is negative when the power supply voltage is positive → negative and negative → The timing for crossing the detection threshold value Vref differs depending on whether it is positive. In other words, the rise time of the voltage zero-cross detection signal and the time until the true AC voltage zero-cross point every half cycle differ depending on whether the power supply voltage changes from positive to negative and from negative to positive. It will be.

  Therefore, since the on / off timing of the phase control signal differs for each half cycle of the power supply, the DC trigger type phase control is performed more than the timing at which the current of the triac Q1 considered at the design stage becomes zero. There may be a problem that the timing at which the signal is turned off is delayed, which causes a malfunction of light control.

  In order to solve this problem, a resistance element is connected in parallel to the rectified output side of the diode bridge, so that a current flows through the diode bridge even in the power supply trough so that the output voltage becomes approximately zero volts in the power supply trough. However, since the resistance element is a heat generating element, it is an inappropriate measure for a product with severe size restrictions and an element that deteriorates the circuit efficiency.

  It is an object of the present invention to eliminate the above-described inconveniences and to accurately measure a reference time that is important in determining the on / off timing of phase control.

  In order to solve the above-described problem, the dimming device according to claim 1 is a lighting load 4 in which a bidirectional switching element Q1 having a self-holding function and a capacitive element C2 are connected in parallel as shown in FIG. And the AC power supply 1 are connected in series to form a closed circuit, and a phase control circuit that makes the effective power to the illumination load 4 variable by changing the ignition phase angle of the bidirectional switching element Q1 is provided. A dimming device, wherein a zero-cross detection circuit 24 for detecting a zero-cross of an input voltage is connected to an output terminal of a full-wave rectifier circuit 21 connected in parallel with the AC power supply 1, and the phase control circuit includes the zero-cross detection circuit The firing phase angle of the bidirectional switching element Q1 is determined by measuring time from the rising or falling edge of the zero-crossing detection signal obtained in 24, and the ON period of the bidirectional switching element Q1 Is a DC trigger type phase control circuit that continues to provide a drive voltage, and a step-up or step-up / step-down chopper circuit is connected as a switching power supply 22 to the output terminal of the full-wave rectifier circuit 21 to which the zero-cross detection circuit 24 is connected. It is characterized by this.

  In order to solve the same problem, the dimming device of claim 2 includes a bidirectional switching element Q1 having a self-holding function and a lighting load 4 in which a capacitive element C2 is connected in parallel, as shown in FIG. And a phase control circuit that connects the AC power source 1 in series to form a closed circuit, and makes the effective power to the illumination load 4 variable by changing the ignition phase angle of the bidirectional switching element Q1. In the optical device, a peak detection circuit 26 for detecting a timing when the input voltage reaches a peak is connected to an output terminal of a full-wave rectifier circuit 21 connected in parallel with the AC power supply 1, and the phase control circuit includes the peak control circuit The firing phase angle of the bidirectional switching element Q1 is determined by measuring time from the rising or falling edge of the peak detection signal obtained by the detection circuit 26, and during the ON period of the bidirectional switching element Q1 It is characterized in that a phase control circuit of the DC trigger system continue to provide driving voltage.

  In order to solve the same problem, the light control device according to claim 3 includes a bidirectional switching element Q1 having a self-holding function and a lighting load 4 in which a capacitive element C2 is connected in parallel, as shown in FIG. And a phase control circuit that connects the AC power source 1 in series to form a closed circuit, and makes the effective power to the illumination load 4 variable by changing the ignition phase angle of the bidirectional switching element Q1. In the optical device, the phase control circuit measures the time of the bidirectional switching element Q1 by measuring time from the rising or falling edge of the zero-cross detection signal obtained by the zero-cross detection circuit 24 that detects the zero-cross of the AC power supply 1. It is a DC trigger type phase control circuit that determines the ignition phase angle and continues to provide a drive voltage during the ON period of the bidirectional switching element Q1, and the zero-cross detection circuit 24 includes: A first rectifier circuit 21a for detecting the voltage zero crossing in the positive half-wave of the flow source 1, is characterized in that it has a second rectifier circuit 21b for detecting the voltage zero crossing in the negative half-wave.

  According to a fourth aspect of the present invention, there is provided the light control device according to the third aspect, wherein the zero-crossing detection circuit 24 detects the timing at which the rectified output voltages of the first rectifier circuit 21a and the second rectifier circuit 21b rise. It is characterized by having.

  According to the invention of each claim, it is possible to avoid that the rising or falling timing of the zero cross detection signal of the AC voltage, which is the time reference of the ON / OFF timing of the phase control, is shifted every half cycle of the AC power supply. Since the time accuracy can be improved, inconveniences such as false firing can be reliably prevented.

(Embodiment 1)
A circuit diagram of Embodiment 1 of the present invention is shown in FIG. The AC power supply 1 is connected in parallel with a noise preventing capacitor C1. One end of the capacitor C <b> 1 is connected to one end of the AC input terminal of the rectifier circuit 21, and the other end is connected to the other end of the AC input terminal of the rectifier circuit 21 via the fuse F. A surge absorbing element ZNR is connected in parallel to both ends of the AC input terminal of the rectifier circuit 21, and a switching power supply 22 is connected to both ends of the DC output terminal. The switching power supply 22 is composed of a step-up or step-up / step-down chopper circuit, and a switching current flows even near the zero cross of the AC power supply 1. A smoothing capacitor C3 is connected in parallel to the output terminal of the switching power supply 22.

  In the triac Q1 as a bidirectional switching element for phase control, a phototriac Q4 and a resistance voltage dividing circuit are connected between main electrodes, and an output of the resistance voltage dividing circuit is applied to a gate electrode. A noise preventing capacitor is connected in parallel between the gate electrode and one of the main electrodes. One end of the filter choke L1 is connected to the other main electrode of the triac Q1, and the other end of the filter choke L1 is connected to one end of the AC power source 1 via a noise preventing capacitor C2. The other end of the AC power source 1 is connected to the one main electrode of the triac Q1, and the AC power source 1, the triac Q1, the filter choke L1, and the capacitor C2 constitute a series closed circuit. Both ends of the capacitor C2 serve as output ends of the phase control dimmer, and a load 4 is connected in parallel between the output ends. As the load 4, in addition to an incandescent bulb, an electronic transformer, an LED load, or the like is appropriately connected.

  FIG. 3 shows the internal configuration of the switching power supply 22. In the figure, Vin is a full-wave rectified pulsating voltage output from the rectifier circuit 21, and Vout is a smoothed DC output voltage. (A) is a step-down chopper shown as a comparative example, and when Vin <Vcc, no current can be drawn from the power supply. Therefore, when the pulsating voltage is lower than Vcc at the valley of the rectified output voltage, No current flows. FIG. 5B shows the step-up chopper shown as an embodiment. When electromagnetic energy is accumulated in the inductor L3 in a section in which the switching element Q3 is closed and then the switching element Q3 is turned off, the capacitor C3 is connected via the diode D3. Therefore, the input current cannot flow even in the valley portion of the rectified output voltage.

  FIG. 2C shows a step-up / step-down chopper (No. 1) shown as a preferred embodiment, and the polarity of the output voltage Vout is opposite to that of the input voltage Vin. FIG. 4D is a step-up / step-down chopper (part 2) shown as a further preferred embodiment, and the switching elements Q2 and Q3 perform switching in synchronization. Electromagnetic energy is accumulated in the inductor L3 while the switching elements Q2 and Q3 are on, and when the switching elements Q2 and Q3 are off, the electromagnetic energy accumulated through the diodes D2 and D3 is supplied to the capacitor C3. The operation is the same as that of the step-up chopper in that energy is stored in the inductor L3 when the switch is turned on and is supplied to the output side when the switch is turned off.

  When the step-up / step-down chopper as shown in FIGS. 3C and 3D is used as the switching power source 22, a DC voltage obtained by stepping up or stepping down the output voltage of the rectifier circuit 21 is obtained in the smoothing capacitor C3. The control power supply voltage Vcc can be obtained relatively easily. On the other hand, when a step-up chopper as shown in FIG. 3B is used as the switching power supply 22, a high DC voltage obtained by boosting the output voltage of the rectifier circuit 21 is obtained in the smoothing capacitor C3. The voltage is stepped down by a resistor or a subsequent step-down chopper and converted to a DC low voltage, or a secondary winding is provided in a choke coil (inductor) for chopper, and the output is rectified and smoothed to obtain a DC low voltage. After that, this DC low voltage is suitably stabilized by a three-terminal regulator or the like and supplied to the control circuit 23 as the control power supply voltage Vcc.

  The control circuit 23 includes a microcomputer and its peripheral circuits, and outputs a phase control signal as a drive signal for the phototriac Q4. Here, a DC trigger method (also referred to as a solid trigger method) is used as a phase control signal, not a pulse trigger method that applies a drive voltage only at turn-on, but a drive voltage that is continuously applied during the turn-on period.

  The control circuit 23 detects the zero cross point of the AC power supply 1 by the zero cross detection circuit 24 connected to the DC output terminal of the rectifier circuit 21, and starts the timer count of the microcomputer based on the detected zero cross point. A phase control signal synchronized with the power supply cycle of the AC power supply 1 can be output.

  An example of the circuit configuration of the zero-cross detection circuit 24 is shown in FIG. In this example, a series circuit of voltage dividing resistors R1, R2, and R3 is connected to the DC output terminal of the rectifier circuit 21 formed of a diode bridge, and the voltage across the resistor R3 is supplied between the base and emitter of the transistor Tr1. Yes. The emitter of the transistor Tr1 is connected to the ground, and the collector is connected to the control power supply voltage Vcc line via a pull-up resistor R4.

  Next, the basic operation of this circuit will be described. When the microcomputer of the control circuit 23 recognizes the rising edge of the zero-crossing detection signal of the input AC voltage from the AC power supply 1, the timer count operation is started from there, and the timing at which the TRIAC Q1, which is the main switch, is turned on. It is determined by reading the analog input from the provided variable resistor VR. As this analog input, a DC voltage of 0 to Vcc obtained by dividing the control power supply voltage Vcc by the variable resistor VR is used.

  On the other hand, the triac Q1 is turned off by counting the time determined from the rise of the voltage zero-cross signal at the design stage and turning it off when a predetermined time elapses. In addition, when the current detecting means for detecting the current flowing through the triac Q1 is used in combination, the predetermined time during which the phase control signal is given to the triac Q1 is from the rise of the voltage zero cross signal until the current detecting means detects the zero cross point. The time is set to be shorter than the time.

  As described above, this dimming device starts the timer count operation of the microcomputer from the rising edge of the voltage zero cross signal, outputs the on timing and off timing from the microcomputer, and performs the dimming operation every half cycle of the power supply. Yes.

  An important design requirement for performing this circuit operation is to accurately capture the zero-crossing timing of the input AC voltage from the AC power supply 1 as a signal and to set the timing of timer count start by the microcomputer with high accuracy.

  In such a case, if a step-down chopper circuit is used as the switching power supply 22, the current cannot be drawn from the input side to the output side of the rectifier circuit 21 at the power source trough, and the current flows into the rectifier circuit 21. As a result, the valley waveform of the output voltage of the rectifier circuit 21 does not become 0V.

  The above problem in the zero cross detection operation will be described with reference to FIG. In the zero cross detection circuit 24 shown in FIG. 2, when a step-down chopper as shown in FIG. 3A is used as the switching power supply 22 on the output side of the rectifier circuit 21, the pulsating current output from the rectifier circuit 21 is used. The voltage waveform is as shown by the solid line in FIG. 4A, and does not become zero even near the zero cross of the AC power supply 1. Therefore, it is impossible to detect a true voltage zero cross point. In actual voltage zero cross detection, a point close to the zero cross point is detected by using switching of the transistor Tr1, and a trough portion of the power supply voltage is zero crossed. It is captured at the rise or fall of the detection pulse, and the timer count is started from there.

  When the AC input voltage from the AC power source 1 is ideally rectified, the waveform is as shown by the broken line in FIG. 4A, and the starting point of the timer count is as shown in FIG. ), The time ta can be set with high precision (zero cross voltage rising) or late (voltage zero cross falling).

  However, when the output voltage of the rectifier circuit 21 does not become 0 V at the power source trough, the rising or rising of the voltage zero cross signal is detected with a deviation of tb from the true value. Then, as shown in FIG. 4 (c), the start point of the timer count is shifted (ta-tb) from the design value, so that the timing at which the triac Q1 as the main switch is turned off is delayed by that amount. In some cases, the phase control signal is turned off after the commutation of the main switch current, causing a false firing.

  Further, even if it does not cause false firing, the effective value of the load current changes every half cycle of the power supply due to the timing of turning on / off the TRIAC Q1, which is the main switch, causing flickering. In particular, when the load 4 is connected to a load having a small wattage such as an LED, the load 4 appears remarkably.

  In the present embodiment, countermeasures are taken against the above-described problem. Conventionally, a step-down chopper as shown in FIG. 3A has been used as the switching power supply 22, but in this embodiment, the switching power supply 22 is used. As a feature, a step-up chopper as shown in FIG. 3B or a step-up / step-down chopper circuit as shown in FIGS. 3C and 3D is used.

  In the step-down chopper, as shown in FIG. 3A, since the output terminal is connected to the closed loop in which the input current flows while the switching element Q3 is on, the power supply voltage (rectified output voltage) decreases. When Vin = Vout, the current through the switching element Q3 can no longer be drawn from the input side to the output side, so that the current cannot flow through the rectifier circuit 21 at the trough of the power supply voltage and floats. It becomes a state.

  On the other hand, as shown in FIG. 3 (b), the step-up chopper has a mode in which current is temporarily stored when the switching element Q3 is turned on. In this case, current flows also through the rectifier circuit 21 in the valley portion of the power supply voltage. Therefore, the output voltage of the rectifier circuit 21 can be set to approximately 0 V at the power source valley.

  The step-up / step-down chopper shown in FIGS. 3C and 3D is the same as the step-up chopper in that it has a mode for temporarily storing electromagnetic energy in the chopper choke L3. For this reason, it is better to use a step-up chopper or a step-up / step-down chopper than a step-down chopper in that the rising timing of the voltage zero cross signal can be accurately detected in the power source trough every half cycle of the power source. Further, for the purpose of supplying power to a microcomputer or the like, it is more appropriate to use a buck-boost chopper than a boost chopper.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIGS. Since the main circuit configuration is the same as that of the first embodiment, redundant description is omitted. In the first embodiment, a step-up chopper or a step-up / step-down chopper is used as the switching power supply 22. However, in the present embodiment, the switching power supply 22 is a step-down chopper. Further, as a configuration significantly different from the first embodiment, pre-smoothing voltage detection means 25a and post-smoothing voltage detection means 25b for detecting the voltage before and after the rectified output voltage of the rectifier circuit 21 is smoothed by the smoothing capacitor C3 are provided. A voltage peak detection circuit 26 is provided for generating a voltage peak detection signal based on the signals detected by the voltage detection means 25a and 25b. The voltage peak detection circuit 26 includes, for example, a voltage comparison circuit (comparator).

  In the present embodiment, the phenomenon that the voltage zero-cross signal rise / fall timing differs every half cycle of the power supply due to the occurrence of the voltage indefinite region in the power supply valley as described in the first embodiment is solved. Instead, the configuration is such that the voltage is detected at the peak portion of the rectified output voltage at which the rectified voltage can be surely taken out every cycle at the same phase angle.

  Specifically, as shown in FIG. 6A, the smoothed voltage Vb generated by the smoothing capacitor C3 is input as a reference voltage to one terminal of the comparator, and the rectified voltage Va before smoothing is input to the other terminal of the comparator. If input, the output of the comparator can be used as a voltage peak detection signal in the vicinity of the peak of the rectified output voltage, as shown in FIG.

  FIG. 6B shows a voltage zero cross signal detected at the power source trough, and the rising timing and the interval between the true voltage zero cross points are t1 and t2 between the positive half cycle and the negative half cycle. , It is scattered. Therefore, when the timer count operation is started at the timings t1 and t2, variations occur in the ON timing and OFF timing of the phase control signal, as shown in FIG. 6C.

  On the other hand, as shown in FIG. 6D, when the voltage peak detection signal is used, the rising timing and the interval between the true voltage zero cross points are stable as t3 and t4. Therefore, if the timer count operation is started at the rising edge of the voltage peak detection signal, the ON timing and OFF timing of the phase control signal can be set with high accuracy.

  In the first embodiment, the step-up chopper or the step-up / step-down chopper is used as the switching power supply 22. However, considering that the output of the switching power supply 22 is used as a control power supply voltage Vcc for a microcomputer, the switching power supply 22 is used. This embodiment using a step-down chopper is more convenient.

(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIGS. The present embodiment is characterized in that the rectifier circuit 21 is not a full-wave rectifier circuit using a diode bridge, but two half-wave rectifier circuits that rectify a positive half-wave and a negative half-wave.

  When a full-wave rectifier circuit is used as the rectifier circuit 21 as in the above-described second embodiment, a predetermined discharge is performed in the power source trough due to the stray capacitance component of each diode constituting the rectifier bridge circuit. Since time is required, the output voltage of the rectifier circuit 21 is not completely zero. That is, as shown in FIG. 6A, since the voltage polarity of the AC power supply 1 is inverted without the electric charge accumulated in the stray capacitance being completely discharged, the residual charge in the power source valley is charged again and completely removed. It will never be.

  In this case, when the rectified output voltage Va in FIG. 6 (a) falls below the threshold voltage, the zero-cross detection signal rises. However, the rise timing is determined by the value of the stray capacitance and the threshold voltage. Therefore, it is difficult to design the timer count start timing with high accuracy. In addition, when the threshold voltage is exceeded at the rising portion of the rectified output voltage Va in FIG. 6A, the zero cross detection signal falls. However, if the timing of the timer count start is set using the timing, Since charging is performed again by reversing the polarity of the AC voltage from the state where the voltage remains, in the full-wave rectifier circuit, the valley of the rectified output voltage Va is never filled.

  When trying to take a zero cross detection signal at such a power source trough waveform, the timing at which the rectified output voltage Va crosses the threshold voltage differs depending on the magnitude of the stray capacitance value at the rise or fall of the zero cross detection signal. The rising / falling timing of the zero cross detection signal is shifted, and the start timing of the timer count cannot be designed with high accuracy.

  Therefore, in the present embodiment, the first rectifier circuit 21a and the second rectifier circuit 21b are provided as rectifier circuits, and the positive half wave and the negative half wave are rectified independently.

  Here, the first rectifier circuit 21a and the second rectifier circuit 21b are formed of diodes for half-wave rectification, and the first and second impedances 27a and 27b are formed of voltage dividing resistors, for example.

  FIG. 8A shows the detection voltage VA generated in the first impedance 27a by the rectified output voltage of the first rectifier circuit 21a, and FIG. 8B shows the second impedance 27b by the rectified output voltage of the second rectifier circuit 21b. The generated detection voltage VB, FIG. 8C, is a zero cross detection signal output from the voltage comparison circuit 28. As shown in FIG. 8C, the voltage comparison circuit 28 outputs an L level signal when the detection voltages VA, VB of the first or second impedances 27a, 27b exceed a predetermined threshold voltage Vref. The voltage comparison circuit outputs an H level signal when the detection voltages VA and VB of the first and second impedances 27a and 27b do not exceed a predetermined threshold voltage Vref.

  In this embodiment, the timer count operation of the microcomputer for generating the phase control signal is started using the falling timing instead of the rising timing of the zero cross detection signal shown in FIG.

  Even in this embodiment, the residual charge is accumulated due to the stray capacitance at the fall of the rectified output voltage, and the rectified output voltage does not immediately reach zero even at the zero cross point. At the voltage rising portion, in the case of the half-wave rectification method, the discharge of the residual charge due to the stray capacitance can be almost completed during the period of the power supply half cycle. The time until the rectified output voltage rising from the true zero cross point at the time of application reaches the threshold voltage Vref (falling timing of the zero cross detection signal) is not affected by residual charge, etc., so the voltage zero cross timing is accurately detected. can do.

  That is, with respect to the falling timing of the zero cross detection signal in FIG. 8C, the time delay from the true voltage zero cross point is not affected by the residual charge of the stray capacitance, so the timer count operation of the microcomputer is started at this timing. Thus, the ON timing and OFF timing of the phase control signal can be set with high accuracy.

It is a circuit diagram of Embodiment 1 of the present invention. It is a circuit diagram which shows an example of the voltage zero crossing detection circuit used for Embodiment 1 of this invention. It is a circuit diagram which shows the example of the switching power supply used for Embodiment 1 and a comparative example of this invention. It is a wave form diagram for operation | movement description of Embodiment 1 of this invention and a comparative example. It is a circuit diagram of Embodiment 2 of the present invention. It is a wave form diagram for explanation of operation of Embodiment 2 of the present invention. It is a circuit diagram of Embodiment 3 of the present invention. It is a wave form diagram for description of operation | movement of Embodiment 3 of this invention. It is a wave form diagram for the principle explanation of the conventional phase control type light control device. It is a circuit diagram of a prior art example. It is a wave form diagram for demonstrating the trouble of a prior art example. It is a wave form diagram for explanation of operation of other conventional examples.

Explanation of symbols

1 AC power supply Q1 Bidirectional switching element (Triac)
L1 Filter choke C2 Noise prevention capacitor 21 Rectifier circuit 22 Switching power supply 23 Control circuit 24 Zero cross detection circuit 4 Load

Claims (4)

A bidirectional switching element with a self-holding function, a lighting load in which capacitive elements are connected in parallel, and an AC power supply are connected in series to form a closed circuit, and the firing phase angle of the bidirectional switching element is variable. A dimmer equipped with a phase control circuit that makes the effective power to the lighting load variable, and detects a zero cross of the input voltage at the output terminal of a full-wave rectifier circuit connected in parallel with the AC power supply Connect the detection circuit, the phase control circuit determines the ignition phase angle of the bidirectional switching element by measuring time from the rising or falling edge of the zero cross detection signal obtained by the zero cross detection circuit, both A DC trigger type phase control circuit that continuously applies a drive voltage during the ON period of the direction switching element, and the full-wave rectification circuit to which the zero cross detection circuit is connected Boost or Buck-light control apparatus characterized by connecting the chopper circuit of the output end of the. A bidirectional switching element with a self-holding function, a lighting load in which capacitive elements are connected in parallel, and an AC power supply are connected in series to form a closed circuit, and the firing phase angle of the bidirectional switching element is variable. The dimming device having a phase control circuit that makes the effective power to the lighting load variable, and the timing at which the input voltage peaks at the output terminal of the full-wave rectifier circuit connected in parallel with the AC power supply. Connect the peak detection circuit to detect, the phase control circuit determines the firing phase angle of the bidirectional switching element by measuring time from the rising or falling edge of the peak detection signal obtained by the peak detection circuit The light control device is a DC trigger type phase control circuit that continuously applies a drive voltage during the ON period of the bidirectional switching element. A bidirectional switching element with a self-holding function, a lighting load in which capacitive elements are connected in parallel, and an AC power supply are connected in series to form a closed circuit, and the firing phase angle of the bidirectional switching element is variable. A dimming device comprising a phase control circuit that makes the effective power to the illumination load variable, wherein the phase control circuit is a zero cross detection signal obtained by a zero cross detection circuit that detects a zero cross of an AC power supply. A DC trigger type phase control circuit that determines a firing phase angle of a bidirectional switching element by measuring time from a rising edge or a falling edge, and continuously applies a drive voltage during an ON period of the bidirectional switching element, The zero-cross detection circuit detects a voltage zero-cross in the positive half-wave of the AC power supply and a voltage zero-cross in the negative half-wave. Dimmer, characterized in that it comprises a second rectifier circuit for. 4. The dimming device according to claim 3, wherein the zero-crossing detection circuit includes a voltage comparison circuit that detects a timing at which the rectified output voltages of the first rectifier circuit and the second rectifier circuit rise.

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