JP2013149399A - Two-line light control switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-line light control switch capable of stabilizing the brightness of an LED bulb connected as an illumination load.SOLUTION: The two-line light control switch comprises: a main open/close circuit 10 having a triac 11 as a main switching element; a frequency detection circuit 17 that detects the frequency of an AC power 2; an auxiliary open/close circuit 18 having a thyristor as an auxiliary switch element that flows a load current when the main switch element is not conductive; a light control amount setting circuit 4 which is operated by a user; and a control circuit 16 that detects a frequency of the AC power 2 based on a signal detected by the frequency detection circuit 17 to estimate a voltage zero-cross point, and starts drive signal output for establishing the conduction of the auxiliary open/close circuit 18 at a first timing, and terminates the output of drive signal at a second timing before a predetermined time with respect to the next estimated voltage zero-cross point. Even when the load current value is small and the main open/close circuit 10 is not conductive, the auxiliary open/close circuit 18 continuously flows the load current.

Description

  The present invention relates to a two-wire dimmer switch for adjusting the brightness of a lighting load, for example.

  Conventionally, a dimming switch using a semiconductor switch element such as a triac has been put into practical use for the purpose of dimming an incandescent bulb. FIG. 8 shows a basic circuit configuration (first conventional example) of the two-wire dimmer switch 50 using the triac 51. The two-wire dimmer switch 50 is connected in series to the AC power source 2 and the illumination load (incandescent light bulb) 3. The two-wire dimming switch 50 is connected to the triac 51, the gate electrode of the triac 51, and for example, a diac (trigger diode) 52 for inputting a gate drive signal, and a variable connected to an operation member operated by a user. It comprises a resistor 53, a fixed resistor 54, a capacitor 55, a filter element 56, and the like.

  In the two-wire dimmer switch 50, when the switch 57 is turned on, the capacitor 55 is charged from the AC power supply 2 through the variable resistor 53, and when the voltage across the capacitor 55 reaches the breakover voltage of the diac 52, the triac 51 Is conducted. The triac 51 is extinguished at the voltage zero cross point of the AC power supply. That is, the trigger (conduction) and self-extinguishing (non-conduction) of the triac 51 by the diac 52 are repeated every half cycle of the AC power supply. The illumination load 3 can be dimmed by adjusting the resistance value of the variable resistor 53 and controlling the phase of the firing period of the triac 51.

  Since the two-wire dimming switch 50 of the first conventional example adjusts the illumination load 3 by changing the resistance value of the variable resistor 53, the loss due to the variable resistor 53 is large. Further, since the voltage of the AC power supply 2 is directly applied to the variable resistor 53, the variable resistor 53 itself cannot be downsized, and downsizing of the two-wire dimmer switch 50 has a limit. Furthermore, when other devices connected to the same AC power supply 2 operate, a voltage change occurs in the AC power supply 2 and the brightness of the illumination load 3 changes instantaneously.

  In order to solve the problem of the two-wire dimmer switch 50 of the first conventional example, Japanese Patent Application Laid-Open No. 2004-228561 uses a microcomputer or the like to set the timing for turning on the semiconductor switch element, that is, the timing for outputting the gate drive signal. A dimmer switch has been proposed for controlling the light. Although the dimming switch described in Patent Document 1 is a three-wire type, FIG. 9 shows a circuit configuration (second conventional example) in which the configuration of Patent Document 1 is applied to a two-wire dimming switch. In the two-wire dimmer switch 60 of the second conventional example, the secondary side phototriac 63 of the phototriac coupler 62 is connected to the gate electrode of the triac 61. Further, a rectifier circuit 65 is connected between the other electrodes of the triac 61, and the power that has been full-wave rectified by the rectifier circuit 65 is input to the power supply unit 66. The control unit 67 is driven by DC power converted by the power supply unit 66. Here, the voltage of the AC power source 2, for example, AC 100 V is applied to the rectifier circuit 65. On the other hand, the control part 67 is driven by DC3-6V, for example. The phototriac coupler 62 optically isolates the control unit 67 and the semiconductor switch element 61. The control unit 67 makes the transistor 69 conductive at a timing stored in advance in the look-up table according to the resistance value of the variable resistor 68 connected to the operation member operated by the user. When the transistor 69 is turned on, a current flows through the light emitting diode 64 on the primary side of the phototriac coupler 62, and the secondary side phototriac 63 is turned on. When the secondary side phototriac 63 of the phototriac coupler 62 becomes conductive, the load current starts to flow and the gate voltage of the triac 61 increases. When the gate voltage of the triac 61 exceeds the threshold value, the triac 61 becomes conductive, and the current flowing from the AC power supply 2 to the lighting load 3 is commutated from the phototriac 63 to the triac 61 in the two-wire dimming switch 60, and the phototriac 63 becomes non-conductive.

JP 11-67479 A

  In recent years, LED bulbs using LEDs have been put to practical use in order to replace incandescent bulbs. Along with this, LED bulbs that can be dimmed have been put into practical use. An incandescent bulb is a resistor itself, whereas an LED bulb is composed of a plurality of LED elements and their drive circuits, as shown in FIG. The LED drive circuit 70 includes a rectifier circuit 71 that rectifies AC power, an inductor 72, a buffer capacitor 73 for storing power, an LED array 77, a capacitor 76 connected in parallel to the LED array 77, an LED The array 77 includes a FET 75 for supplying a constant current to the array 77 and a driving IC 74 thereof. That is, the LED bulb is an electronic circuit composed of a diode or an IC as a load. Fig.11 (a) shows the waveform of the load voltage and load current of an incandescent lamp in the 1/2 cycle of AC power supply, and FIG.11 (b) shows the waveform of the load voltage and load current of an LED bulb. An incandescent bulb has a power factor of 1, and the voltage and current show almost the same waveform. On the other hand, in the case of an LED bulb, the load current is mainly for charging the capacitor 73, and instantaneously shows a large value simultaneously with the conduction of the triac, but soon decreases.

  If an LED bulb having such characteristics is to be dimmed and controlled by the two-wire dimmer switch 50 of the first conventional example, the following problems occur. FIG. 12 shows a problem when the LED bulb is dimmed and controlled by the two-wire dimmer switch 50 of the first conventional example. As shown in FIG. 12, when the triac 51 is turned on, a large load current flows instantaneously, but immediately decreases. When the value of the load current becomes less than the holding current of the triac 51, the triac 51 is self-extinguished and becomes non-conductive. When the triac 51 becomes non-conductive, the voltage of the capacitor 73 decreases, and the drive IC 74 controls to reduce the current flowing through the FET 75. If it does so, the electric current which flows into the LED array 77 will decrease, and the brightness of an LED bulb will fall. Further, the load current temporarily decreases due to the influence of noise superimposed on the AC power supply 2, or the voltage is applied to the AC power supply 2 by the operation of other devices connected to the same AC power supply 2 as shown in FIG. When the fluctuation occurs, the brightness of the LED bulb decreases.

  On the other hand, in the case of the two-wire dimmer switch 60 of the second conventional example, if a current is continuously supplied to the phototriac 63 on the secondary side of the phototriac coupler 62, a load current can be continuously supplied. However, since a current of several mA to several tens of mA flows through the phototriac 63, a large amount of power is consumed to maintain the conduction for a long time. In particular, the LED bulb is substantially an electronic circuit as described above and consumes little power. Therefore, if a large amount of power is consumed on the two-wire dimmer switch 60 side, it may become uncontrollable.

  The present invention has been made to solve the above-described problems of the conventional example, and even when an LED bulb is connected as an illumination load, the brightness of the LED bulb is stabilized, and there is little flickering or fluctuation 2 An object is to provide a linear dimmer switch.

In order to achieve the above object, a two-wire dimmer switch according to the present invention is connected in series to an AC power source and a lighting load,
A first connection terminal and a second connection terminal to which AC power is input;
A main switching circuit connected between the first connection terminal and the second connection terminal and having the first semiconductor switch element as a main switch element;
A rectifier circuit connected between the first connection terminal and the second connection terminal;
A power supply circuit connected to the DC side of the rectifier circuit and securing an internal power supply of the two-wire dimmer switch;
A frequency detection circuit connected to the DC side of the rectifier circuit and outputting a predetermined detection signal for detecting the frequency of the AC power supply;
Connected to the DC side or AC side of the rectifier circuit, the second semiconductor switch element is used as an auxiliary switch element, and a load current flows when the main switch element is not conducting, and the main switch element or other semiconductor An auxiliary switching circuit for outputting a gate drive signal for conducting the switch element;
A dimming amount setting circuit for setting a dimming amount to be adjusted by the user to adjust the brightness of the illumination load;
Based on the detection signal output from the frequency detection circuit, the frequency of the AC power supply is detected, the voltage zero cross point of the AC power supply is estimated, and the light control amount and the estimation set by the light control amount setting circuit Output of a driving signal for conducting the auxiliary switching circuit at a first timing determined based on the voltage zero-cross point thus determined, with respect to the estimated voltage zero-cross point next to the estimated voltage zero-cross point And a control circuit for stopping the output of the drive signal at a second timing before a predetermined time.

  In addition, it is turned on by the gate drive signal output from the auxiliary switching circuit, and after the auxiliary switching circuit is turned on, a load current is passed when the main switch element is not turned on, and the main switch element is turned on. It is preferable to further include a quasi-main switching circuit that outputs a drive signal for the purpose.

The main switch element is a triac,
The auxiliary switching circuit preferably uses a thyristor connected to the DC side of the rectifier circuit as an auxiliary switch element.

Or the main switch element is a triac;
Preferably, the auxiliary switching circuit includes two thyristors that are connected to the AC side of the rectifier circuit and are alternately turned on according to the polarity of the AC power supply as auxiliary switch elements.

The quasi-main switching circuit has a phototriac coupler as a switch element, a phototriac on the secondary side of the phototriac coupler is connected in parallel with the main switch element, and one terminal is a gate of the main switch element. A light emitting diode on the primary side of the phototriac coupler is connected in series with the auxiliary switching circuit;
The holding current value of the phototriac is preferably smaller than the holding current value of the triac.

  When the control circuit starts dimming control of the illumination load, it preferably outputs an initial drive signal for conducting the auxiliary switching circuit at a predetermined timing near the estimated voltage zero-cross point. .

  According to the present invention, the auxiliary switching circuit includes an auxiliary switching circuit that supplies a load current when the main switching element is not conducting and outputs a gate drive signal for conducting the main switching element or other semiconductor switching elements. The second timing that is a predetermined time before the next voltage zero-cross point from the first timing in which the drive signal for turning on the power is determined based on the dimming amount set by the dimming amount setting circuit and the voltage zero-cross point The auxiliary open / close circuit is maintained in a conductive state until the output is continued. Therefore, it is assumed that the lighting load is an LED bulb, and the load current becomes less than the holding current of the main switch element after the load current is commutated from the auxiliary switch circuit to the main switch circuit, and the main switch circuit becomes non-conductive. However, the load current can continue to flow through an auxiliary switching circuit or the like. As a result, the brightness of the LED bulb can be stabilized, and flicker and fluctuation can be reduced.

1 is a circuit diagram showing a configuration of a two-wire dimmer switch according to a first embodiment of the present invention. The wave form diagram of the gate drive signal for making the thyristor of the load voltage of an LED bulb | bulb, load current, and an auxiliary | assistant switch circuit in 1st Embodiment conduct. In 1st Embodiment, the waveform figure of the gate drive signal for making the thyristor of the load voltage of an LED bulb | bulb, load current, and an auxiliary | assistant switch circuit which show the influence of the load current by another apparatus conduct. The circuit diagram which shows the structure of the two-wire dimmer switch which concerns on 2nd Embodiment of this invention. The circuit diagram which shows the structure of the two-wire dimmer switch which concerns on 3rd Embodiment of this invention. The circuit diagram which shows the structure of the two-wire dimmer switch which concerns on 4th Embodiment of this invention. The wave form diagram of each part in the control method of the two-wire dimmer switch which concerns on 5th Embodiment of this invention. The circuit diagram which shows the structure of the two-wire dimmer switch which concerns on a 1st prior art example. The circuit diagram which shows the structure of the 2 wire type light control switch which concerns on a 2nd prior art example. The circuit diagram which shows the structure of the drive circuit of a general LED bulb. The figure which shows the difference of the load voltage and load current of an incandescent bulb and an LED bulb. The figure which shows a mode that a triac self-extinguishes when the load current value becomes less than the holding current value of a triac in the conventional 2-wire dimmer switch. The figure which shows a mode that the load voltage of a LED bulb fluctuates with the load current of the other apparatus connected to the same alternating current in the conventional 2-wire dimmer switch.

(First embodiment)
A two-wire dimmer switch according to a first embodiment of the present invention will be described. FIG. 1 shows a circuit configuration of a two-wire dimmer switch 1A according to the first embodiment. The two-wire dimmer switch 1 </ b> A is connected in series to the AC power source 2 and the illumination load 3. A switch 5 for controlling lighting and extinction of the illumination load 3 may be provided integrally with the dimming variable resistor 4 of the two-wire dimming switch 1A, or the switch 5 may be provided separately. In the following description, a case where the switch 5 is provided separately from the two-wire dimmer switch 1A is illustrated.

  The first connection terminal 1 a and the second connection terminal 1 b of the two-wire dimmer switch 1 </ b> A are connected to the AC power supply 2 or the illumination load 3 and the switch 5. Connected between the first connection terminal 1a and the second connection terminal 1b is a main switching circuit 10 having a first semiconductor switch element such as a triac as a main switch element 11. In parallel with the main switching circuit 10, a rectifier circuit 12 is connected between the first connection terminal 1a and the second connection terminal 1b. The rectifier circuit 12 receives the internal power of the two-wire dimmer switch 1A. A power supply circuit 13 for securing is connected. The power supply circuit 13 includes a switching circuit composed of a first transistor element 13a and a second transistor element 13b connected in Darlington, a Zener diode 13c and a resistor 13d connected to the base of the second transistor element 13b, and the like. A constant voltage circuit (such as a three-terminal regulator) 14 and a buffer capacitor 15 for supplying DC constant voltage power to a control circuit 16 constituted by a processor or the like are included.

  When the switch 5 is turned on, the pulsating current rectified by the rectifier circuit 12 is input to the power supply circuit 13, and power whose output voltage is governed by the Zener voltage of the Zener diode 13c is output from the power supply circuit. The electric power charges the buffer capacitor 15 and is stepped down to a predetermined voltage (for example, 3 V) by the constant voltage circuit 14 and is supplied to the control circuit 16. Here, if the resistance value of the resistor 13d of the power supply circuit 13 is set to a value high enough to allow the current necessary for the operation of the second transistor element 13b to flow, the value of the current flowing to the ground via the Zener diode 13c is obtained. Therefore, the power loss can be reduced.

  A frequency detection circuit 17 for detecting the frequency of the AC power supply 2 is connected to the DC output terminal of the rectifier circuit 12, and a predetermined detection signal output from the frequency detection circuit 17 is input to the control circuit 16. Further, the DC side output terminal of the rectifier circuit 12 is a thyristor for passing a current through the illumination load 3 until the main switch element 11 of the main switching circuit 10 is turned on or when the main switch element 11 is not turned on. An auxiliary switching circuit 18 having the second semiconductor switch element as an auxiliary switch element is connected. The control circuit 16 is connected to a dimming amount setting circuit 4 composed of a variable resistor or the like operated by a user. In the following description, the main switch element is referred to as a triac 11 and the auxiliary switching circuit or auxiliary switch element is referred to as a thyristor 18 as necessary.

  The frequency detection circuit 17 is configured such that the pulsating current output from the rectifier circuit 12 is input to the base of the transistor element 17a, and a predetermined detection signal is transmitted from the frequency detection circuit 17 in accordance with the frequency of the AC power supply 2. 16 is input. The control circuit 16 detects the frequency (50 Hz or 60 Hz) of the AC power supply 2 from the detection signal of the frequency detection circuit 17 and estimates the voltage zero cross point based on the detection. Then, a gate drive signal is input to the gate terminal of the thyristor 18 based on the detected frequency and the estimated voltage zero cross point. FIG. 2 shows respective waveforms of the load voltage, load current, and gate drive signal in a half cycle of the AC power supply 2 when an LED bulb is used as the illumination load 3. The rising edge of the gate drive signal (the first timing when the thyristor 18 is turned on) searches a lookup table stored in advance in the control circuit 16 based on the resistance value of the light adjustment amount setting circuit (variable resistor) 4. To be determined. The fall of the gate drive signal (second timing when the thyristor 18 becomes non-conductive) is set to a short time Δt (for example, 1 ms) from the voltage zero cross point of the AC power supply 2. The predetermined time Δt is a time sufficient for the control circuit 16 to estimate the next voltage zero-cross point based on the detection signal from the frequency detection circuit 17, for example.

  Next, a specific operation of the two-wire dimmer switch 1A according to the first embodiment will be described. In the state where the switch 5 is OFF, the charge of the buffer capacitor 15 is almost discharged, and it is considered that the control circuit 16 is not functioning. Here, when the switch 5 is turned on, for example, a full-wave rectified pulsating flow is output from the rectifier circuit 12. As a result, the buffer capacitor 15 is charged, and DC power is supplied from the constant voltage circuit 14 to the control circuit 16 so that the control circuit 16 is activated. In parallel with this, since a detection signal is input from the frequency detection circuit 17 to the control circuit 16, the control circuit 16 detects the frequency of the AC power supply 2 and estimates its voltage zero-cross point. Then, the control circuit 16 starts outputting the gate drive signal at the first timing based on the resistance value of the light control amount setting circuit (variable resistor) 4 (rises the gate drive signal). When the gate drive signal is input to the gate terminal of the thyristor 18, the thyristor 18 becomes conductive and current starts to flow through the lighting load 3. Further, since the current flowing through the thyristor 18 also flows through the gate electrode of the triac 11, the triac 11 becomes conductive when the voltage and current exceed the gate voltage threshold value and the turn-on current of the triac 11, and the load current flows from the thyristor 18 to the triac 11. To commutate. When the triac 11 is turned on, almost no current flows through the rectifier circuit 12, and little current flows through the thyristor 18, the power supply circuit 13, and the frequency detection circuit 17. When no current flows through the power supply circuit 13, the power starts to be discharged from the buffer capacitor 15, thereby securing the driving power of the control circuit 16. At this time, since the gate drive signal is continuously input from the control circuit 16 to the gate electrode of the thyristor 18, the thyristor 18 is in a conductive state.

  When the lighting load 3 is an LED bulb, the load current instantaneously shows a large value simultaneously with the conduction of the thyristor 18 or the triac 11 as described above, but immediately becomes small. When the value of the load current becomes less than the holding current of the triac 11, the triac 11 is self-extinguished and becomes non-conductive. However, since the thyristor 18 is conductive, the load current flows through the thyristor 18. to continue. Then, the control circuit 16 stops the output of the gate drive signal (falls the gate drive signal) at a second timing just before the voltage zero cross point of the AC power supply 2 by a predetermined time Δt. At this stage, almost no load current flows, and even if the thyristor 18 becomes non-conductive, the brightness of the lighting load 3 hardly changes. When the thyristor 18 becomes non-conductive, the pulsating current output from the rectifier circuit 12 is diverted from the thyristor 18 to the power supply circuit 13 and the frequency detection circuit 17, so that the control circuit 16 is based on the detection signal from the frequency detection circuit 17. Thus, the next voltage zero cross point of the AC power supply 2 can be estimated, and the timing of starting the output of the next gate drive signal can be controlled with the estimated voltage zero cross point as a reference.

  In this way, the two-wire dimmer switch 1A allows a current to flow through the illumination load 3 until the main switch element (triac) 11 of the main switching circuit 10 is turned on or when the main switch element 11 is not turned on. Since the auxiliary open / close circuit (thyristor) 18 is provided, the load current value is less than the holding current of the triac 11 and the thyristor 18 is conductive even when the triac 11 is nonconductive. Continues to flow through thyristor 18. As a result, the brightness of the LED bulb is stabilized, and flickering and fluctuation that can be seen with the naked eye hardly occur. Even when the maximum value of the load current is less than the holding current of the triac 11, the current can continue to flow through the load via the auxiliary switching circuit (thyristor) 18. Furthermore, the gate drive signal input to the gate electrode of the thyristor 18 is stopped at a second timing just before the voltage zero cross point of the AC power source 2 by a predetermined time Δt, so that the next voltage zero cross point of the AC power source 2 can be accurately determined. Can be estimated. Further, as shown in FIG. 3, even if other devices connected to the same AC power supply 2 operate, the load current continues to flow through the thyristor 18, so that the brightness of the illumination load 3 hardly changes. Also, the load voltage waveform does not change much. Needless to say, a triac 11 having a small holding current value is selected and used.

(Second Embodiment)
A two-wire dimmer switch according to a second embodiment of the present invention will be described. FIG. 4 shows a circuit configuration of a two-wire dimmer switch 1B according to the second embodiment. The two-wire dimmer switch 1B is obtained by adding a phototriac coupler 20 as a quasi-main switching circuit to the two-wire dimmer switch 1A according to the first embodiment. A secondary side phototriac 21 of the phototriac coupler 20 is connected in parallel to a main switching circuit (triac) 11, and a primary side light emitting diode 22 is connected in series to an auxiliary switching unit (thyristor) 18. Other configurations are the same. As the phototriac 21, one having a holding current value smaller than the holding current value of the triac 11 of the main switching circuit is selected.

  Next, a specific operation of the two-wire dimmer switch 1B according to the second embodiment will be described focusing on the differences. When the triac 11 and the photo triac 21 are extinguished at the voltage zero cross point of the AC power supply 2, a current flows through the rectifier circuit 12, and then a gate drive signal is input to the gate terminal of the thyristor 18 at a predetermined first timing. Is conducted, and the load current flows through the thyristor 18. At this time, the primary side light emitting diode 22 of the phototriac coupler 20 emits light, a gate drive signal is input to the gate terminal of the secondary side phototriac 21, and the phototriac 21 becomes conductive. When the phototriac 21 is turned on, the load current is commutated to the phototriac 21. Here, when the load current value is small and less than the holding current value of the TRIAC 11 of the main switching circuit, the TRIAC 11 of the main switching circuit is not conducted, and the load current remains as it is in the phototriac 21 that is a quasi-main switching circuit. Flowing through. On the other hand, when the load current value is large and exceeds the holding current value of the triac 11 of the main switching circuit, the triac 11 of the main switching circuit becomes conductive, and the load current is commutated to the triac 11. When the illumination load 3 is an LED bulb, when the load current value is less than the holding current of the triac 11, the triac 11 is self-extinguished and becomes non-conductive, but the thyristor 18 is conductive and the load current is the thyristor 18. To commutate temporarily. Then, the primary side light emitting diode 22 of the phototriac coupler 20 emits light, the secondary side phototriac 21 is turned on, and the load current is commutated to the phototriac 21. Since the holding current value of the phototriac 21 is smaller than the holding current value of the triac 11 as described above, the load current can continue to flow stably.

  The two-wire dimmer switch 1B according to the second embodiment is slightly different from the two-wire dimmer switch 1A according to the first embodiment in that a phototriac coupler 20 is added as a quasi-main switching circuit. The structure is complicated, which increases the cost. However, even after the triac 11 is turned off, the load current flows exclusively through the phototriac 21 on the upstream side (AC side) of the rectifier circuit 12, that is, the load current does not pass through the diode bridge. Loss due to bridging is eliminated. As a result, the change in the brightness of the LED bulb becomes very small, and there is almost no flickering or fluctuation that can be seen with the naked eye.

(Third embodiment)
A two-wire dimmer switch according to a third embodiment of the present invention will be described. FIG. 5 shows a circuit configuration of a two-wire dimmer switch 1C according to the third embodiment. The two-wire dimmer switch 1C is provided with two auxiliary open / close circuits (thyristors) 18a and 18b in the two-wire dimmer switch 1A according to the first embodiment, and the anode of each thyristor is an alternating current of the rectifier circuit 12. The cathode is connected to the DC negative terminal of the rectifier circuit 12 on the side. The gate drive signal output from the control circuit 16 is branched by the diodes 25a and 25b and input to the gate terminals of the thyristors 18a and 18b. That is, one of the two thyristors 18a and 18b is used as an auxiliary switching circuit depending on the polarity of the AC power supply 2. Other configurations and operations are the same as those of the two-wire dimmer switch 1A according to the first embodiment.

  Since the two-wire dimmer switch 1C according to the third embodiment is added with a thyristor, a resistor, and a capacitor constituting an auxiliary switching circuit, compared to the two-wire dimmer switch 1A according to the first embodiment. The structure is slightly complicated, which increases the cost. However, since the load current does not pass through one diode constituting the rectifier circuit 12 after the triac 11 is turned off, the loss is reduced accordingly. When the illumination load 3 is an LED bulb, the load current value is very small. Therefore, the smaller the loss of one diode, the smaller the flickering and fluctuation of the LED bulb.

(Fourth embodiment)
A two-wire dimmer switch according to a fourth embodiment of the present invention will be described. FIG. 6 shows a circuit configuration of a two-wire dimmer switch 1D according to the fourth embodiment. The two-wire dimmer switch 1D is a combination of the features of the two-wire dimmer switch 1B according to the second embodiment and the two-wire dimmer switch 1C according to the third embodiment. A phototriac coupler 20 and two auxiliary switching circuits (thyristors) 18a and 18b are provided. In the two-wire dimming switch 1D according to the fourth embodiment, as in the two-wire dimming switch 1C according to the third embodiment, a diode that forms the rectifier circuit 12 when a load current flows through the thyristor 18a or 18b. Since it does not pass through one, the loss is reduced accordingly. Therefore, as compared with the two-wire dimmer switch 1B according to the second embodiment, voltage fluctuation when the load current is commutated from the thyristor 18a or 18b to the phototriac 21 is reduced, and stable power is supplied to the lighting load 3. Can be supplied. As a result, the change in brightness of the LED bulb is further reduced, and flickering and fluctuation hardly occur.

(Fifth embodiment)
The first to fourth embodiments described above relate to the structure of the two-wire dimmer switch, but the fifth embodiment relates to a control method in the two-wire dimmer switches 1A to 1D that are shifted. The two-wire dimmer switches 1A to 1D and the LED bulb driving circuit 70 shown in FIG. 10 each have a circuit configuration for converting AC power into DC power and storing the power in a buffer capacitor. Therefore, for example, when the switch 5 is turned off for a long time, it is considered that any buffer capacitor is discharged and no electric power remains. When the switch 5 is turned on, the two-wire dimming switches 1A to 1D are activated, and the control circuit 16 outputs a gate drive signal, whereby supply of power to the lighting load 3 is started. When the illumination load 3 is an LED bulb, the drive circuit 70 is not activated even when the supply of power is started, and thus the operation and impedance characteristics are different from those during steady lighting. That is, when the supply of power to the LED bulb driving circuit 70 is started, the buffer capacitor 73 is charged first. Therefore, when the LED bulb is started, the capacitance component of the buffer capacitor 73 exhibits dominant impedance characteristics. When a current starts to flow through the LED bulb driving circuit 70 when the voltage of the AC power supply 2 is relatively high, the buffer capacitor 73 is rapidly charged, and the two-wire dimmer switches 1A to 1D and the LED bulb driving circuit are charged. A large power factor difference with 70 occurs.

  Between impedances with greatly different power factors, the phase of the voltage applied to each of them differs from the phase of the AC power supply 2. For example, when the voltage of the AC power supply 2 is 100V and the load voltage is −30V, The voltage between the connection terminals 1a and 1b of the two-wire dimmer switches 1A to 1D (referred to as an inter-switch voltage) is 130V. That is, the voltage zero cross point of the AC power supply 2 is different from the inter-switch voltage zero cross point of the two-wire dimmer switches 1A to 1D. The two-wire dimmer switches 1A to 1D are originally intended to perform control with reference to the voltage zero cross point of the AC power supply 2, but the control circuit 16 detects the inter-switch voltage zero cross point from the output of the frequency detection circuit 17. Dimming control is performed by estimating. Therefore, if the control is performed at a timing different from the voltage zero cross point of the AC power supply 2 (a gate drive signal is output), there is a possibility that the original stable light control cannot be performed.

  FIG. 7 shows the waveforms of the respective parts according to the control method according to the fifth embodiment. Until the dimming is started, the phase of the voltage waveform of the AC power supply 2 and the phase of the voltage waveform between the switches of the two-wire dimmer switches 1A to 1D match. In the control method according to the fifth embodiment, when the dimming control of the lighting load 3 is started, the first gate drive signal input to the gate terminal from the control circuit 16 to the thyristor 18 of the auxiliary switching circuit is obtained from the output of the frequency detection circuit 17. Output near the estimated inter-switch voltage zero cross point (for example, within ± several ms with respect to the inter-switch voltage zero cross point). The timing for outputting the first gate drive signal does not necessarily need to be before the voltage zero-cross point, and may be after the voltage zero-cross point. By doing so, charging of the buffer capacitor 73 of the LED bulb driving circuit 70 can be started from a low level of the voltage of the AC power supply 2. Thus, by starting the power supply to the LED bulb driving circuit 70 from around the voltage zero cross point (0 V), the impedance change between the two-wire dimmer switches 1A to 1D and the LED bulb driving circuit 70 is abrupt. The power of 1/2 cycle of the AC power source 2 can be shared by the two-wire dimmer switches 1A to 1D and the LED bulb driving circuit 70. In addition, since a large power factor difference does not occur between the two-wire dimmer switches 1A to 1D and the LED bulb driving circuit 70, stable dimming control can be performed.

  In the above description, the triac that is a single bidirectional semiconductor switching element is exemplified as the main switching element. However, the present invention is not limited to this, and the main switching element is not limited to the triac as long as it has a structure that allows current to flow bidirectionally. For example, IGBTs or FETs connected in reverse parallel may be used.

1A to 1D 2-wire dimmer switch 2 AC power supply 3 Lighting load 4 Dimming amount setting circuit (variable resistor)
5 Switch 10 Main switching circuit 11 Main switch element (Triac)
DESCRIPTION OF SYMBOLS 12 Rectifier circuit 13 Power supply circuit 16 Control circuit 17 Frequency detection circuit 18, 18a, 18b Auxiliary switching circuit (auxiliary switch element, thyristor)
20 Quasi-main switching circuit (Phototriac coupler)
21 Phototriac 22 Light-emitting diode

Claims (6)

A two-wire dimming switch connected in series with an AC power source and a lighting load,
A first connection terminal and a second connection terminal to which AC power is input;
A main switching circuit connected between the first connection terminal and the second connection terminal and having the first semiconductor switch element as a main switch element;
A rectifier circuit connected between the first connection terminal and the second connection terminal;
A power supply circuit connected to the DC side of the rectifier circuit and securing an internal power supply of the two-wire dimmer switch;
A frequency detection circuit connected to the DC side of the rectifier circuit and outputting a predetermined detection signal for detecting the frequency of the AC power supply;
Connected to the DC side or AC side of the rectifier circuit, the second semiconductor switch element is used as an auxiliary switch element, and a load current flows when the main switch element is not conducting, and the main switch element or other semiconductor An auxiliary switching circuit for outputting a gate drive signal for conducting the switch element;
A dimming amount setting circuit for setting a dimming amount to be adjusted by the user to adjust the brightness of the illumination load;
Based on the detection signal output from the frequency detection circuit, the frequency of the AC power supply is detected, the voltage zero cross point of the AC power supply is estimated, and the light control amount and the estimation set by the light control amount setting circuit Output of a driving signal for conducting the auxiliary switching circuit at a first timing determined based on the voltage zero-cross point thus determined, with respect to the estimated voltage zero-cross point next to the estimated voltage zero-cross point And a control circuit for stopping the output of the drive signal at a second timing before a predetermined time.   To conduct a load current when the main switch element is not conducted after the auxiliary switch circuit is conducted after the gate drive signal outputted from the auxiliary switch circuit is conducted, and to conduct the main switch element The two-wire dimmer switch according to claim 1, further comprising a quasi-main switching circuit that outputs a driving signal of The main switch element is a triac;
The two-wire dimmer switch according to claim 1 or 2, wherein the auxiliary switching circuit uses a thyristor connected to the DC side of the rectifier circuit as an auxiliary switch element. The main switch element is a triac;
3. The auxiliary switch circuit according to claim 1, wherein two auxiliary thyristors are connected to the AC side of the rectifier circuit and alternately turned on according to the polarity of the AC power supply. A two-wire dimmer switch according to 1. The quasi-main switching circuit uses a phototriac coupler as a switch element, a phototriac on the secondary side of the phototriac coupler is connected in parallel with the main switch element, and one terminal is connected to the gate terminal of the main switch element. A light emitting diode on the primary side of the phototriac coupler is connected in series with the auxiliary switching circuit;
The two-wire according to claim 2, subordinate to claim 2, subordinate to claim 2, or subordinate to claim 2, wherein the holding current value of the phototriac is smaller than the holding current value of the triac. Dimmer switch.   The control circuit outputs a first drive signal for turning on the auxiliary switching circuit at a predetermined timing near the estimated voltage zero-cross point when the dimming control of the lighting load is started. The two-wire dimmer switch according to any one of claims 1 to 5.

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