KR20140102271A - Two-line dimmer switch - Google Patents

Abstract

A main switching element 10 which uses the triac 11 as a main switching element, a frequency detection circuit 17 which detects the frequency of the AC power supply 2, and a thyristor as an auxiliary switching element, A light amount setting circuit 4 operated by the user, and a control circuit 17 for controlling the frequency of the AC power source 2 based on the detection signal of the frequency detection circuit 17. The auxiliary switching circuit 18, The voltage zero cross point is estimated and the output of the drive signal for causing the auxiliary open / close circuit 18 to conduct at the first timing is started, and at the second timing which is a predetermined time before the next estimated voltage zero cross point When the load current value is small and the main switching circuit 10 becomes non-conductive, the auxiliary switching circuit 18 continues to supply the load current continuously Flow The. This stabilizes the brightness of the LED bulb and reduces flicker and flicker, even when the LED bulb is connected as a lighting load.

Description

TWO-LINE DIMMER SWITCH

The present invention relates to a two-wire dimming switch for adjusting the brightness of an illumination load.

Conventionally, dimming switches using semiconductor switch elements such as triac have 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 dimming switch 50 using the triac 51. Fig. The two-wire dimming switch 50 is connected in series to the AC power supply 2 and the lighting load (incandescent lamp) 3. The two-wire dimming switch 50 is connected to the gate electrodes of the triac 51 and the triac 51, and is connected to a gate of the triac 51 via a diode (trigger diode) 52, for example, A fixed resistor 54, a capacitor 55, a filter element 56, and the like connected to the operating member which is operated by the operating member.

In the two-wire dimming switch 50, when the switch 57 is turned on, the capacitor 55 is charged from the alternating-current power supply 2 through the variable resistor 53 and the voltage across the capacitor 55 is supplied to the diode 52 ), The triac 51 becomes conductive. Then, the triac 51 extinguishes at a voltage zero cross point of the AC power source. That is, the trigger (conduction) and self-extinguishing (non-conduction) of the triac 51 by the diaphragm 52 are repeated every half cycle of the AC power. The illumination load 3 can be dimmed by adjusting the resistance value of the variable resistor 53 to control the phase of the ignition period of the triac 51.

The two-wire dimming switch 50 of the first conventional example has a large loss due to the variable resistor 53 because it dims the illumination load 3 by changing the resistance value of the variable resistor 53. Moreover, since the voltage of the AC power supply 2 is directly applied to the variable resistor 53, the variable resistor 53 itself can not be downsized, and the downsizing of the two-wire dimming switch 50 is also limited. Further, when another device connected to the same AC power supply 2 operates, a voltage variation occurs in the AC power supply 2, and the brightness of the illumination load 3 instantaneously fluctuates.

In order to solve the problem of the two-wire dimming switch 50 of the first conventional example, Japanese Unexamined Patent Application Publication No. 11-67479 discloses a technique in which the timing for turning on the semiconductor switch element, There has been proposed a dimmer switch which is controlled by using a computer or the like. This dimming switch is of a three-wire type, and FIG. 9 shows a circuit configuration (second conventional example) in which it is applied to a two-wire dimming switch.

In the two-wire type dimming switch 60 of the second conventional example, the secondary side phototransistor 63 of the phototriac coupler 62 is connected to the gate electrode of the triac 61. A rectifying circuit 65 is connected between the other electrodes of the triac 61 and the power that has been subjected to full-wave rectification by the rectifying circuit 65 is input to the power supply unit 66. [ The control unit 67 is driven by the DC power converted by the power supply unit 66. Here, the voltage of the AC power source 2, for example, AC (AC) 100 V is applied to the rectifying circuit 65. On the other hand, the control unit 67 is driven with DC (DC) 3 to 6V, for example. The photo-triac coupler 62 optically isolates the control section 67 and the semiconductor switch element 61 from each other. The control unit 67 conducts the transistor 69 at a timing previously stored in the lookup table in accordance with the resistance value of the variable resistor 68 connected to the operating member operated by the user. When the transistor 69 conducts, a current flows to the light emitting diode 64 on the primary side of the phototriac coupler 62, and the secondary side phototransistor 63 conducts. When the secondary side phototransistor 63 of the phototriac coupler 62 conducts, a load current begins to flow and the gate voltage of the triac 61 increases. When the gate voltage of the triac 61 becomes equal to or higher than the threshold value, the triac 61 is conducted, and the current flowing from the ac power source 2 to the illumination load 3 is supplied to the phototri Current flows from the liquid 63 to the triac 61 and the phototriac 63 becomes non-conductive.

In recent years, LED bulbs using LEDs (Light Emitting Diodes) have been put into practical use to replace incandescent bulbs. Along with this, LED light bulbs that can be dimmed are put to practical use. As shown in Fig. 10, the LED bulb consists of a plurality of LED elements and a driving circuit thereof, while the incandescent bulb is the resistor itself. The LED driving circuit 70 includes a rectifying circuit 71 for rectifying AC power, an inductor 72, a buffer capacitor 73 for collecting power, an LED array 77, an LED array 77, A field effect transistor (FET) 75 for causing a constant current to flow through the LED array 77, a driving IC 74 and the like. That is, the LED bulb is an electronic circuit composed of a diode or an IC as a load. 11 (a) shows waveforms of the load voltage and the load current of the incandescent bulb at 1/2 period of the AC power source, and Fig. 11 (b) shows the waveforms of the load voltage and the load current of the LED bulb. The incandescent lamp has a power factor of 1, and the voltage and the current show almost the same waveform. On the other hand, in the case of the 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 it immediately becomes smaller.

If the LED bulb exhibiting such characteristics is controlled to be dimmed with the two-wire dimming switch 50 of the first conventional example, the following problems arise. 12 shows a problem in the case where the LED bulb is subjected to light control by the two-wire dimming switch 50 of the first conventional example. As shown in Fig. 12, when the triac 51 becomes conductive, a large load current instantaneously flows, but it immediately becomes smaller. When the value of the load current becomes less than the holding current of the triac 51, the triac 51 becomes self-extinguished and becomes non-conducting. When the triac 51 becomes non-conductive, the voltage of the capacitor 73 drops, and the drive IC 74 controls the current flowing through the FET 75 to be small. As a result, the current flowing through the LED array 77 decreases and the brightness of the LED bulb is lowered. The load current temporarily decreases due to the influence of the noise superimposed on the AC power supply 2 or as shown in Fig. 13, by the operation of other equipments connected to the same AC power supply 2, the AC power supply 2 ), The brightness of the LED bulb is lowered.

On the other hand, in the case of the two-wire dimming switch 60 of the second conventional example, if the current continues to flow through the phototriac 63 on the secondary side of the phototriac coupler 62, the load current can be kept flowing. Since a current of several mA to several tens mA flows in the phototriac 63, a large amount of power is consumed to maintain conduction for a long time. Particularly, since the LED bulb is substantially the same as the above-described electronic circuit itself and consumes a small amount of power, there is a possibility that the LED bulb may be out of control if a large amount of power is consumed by the two-wire dimming switch 60 side.

The object of the present invention is to provide a two-wire dimming switch which stabilizes the brightness of an LED bulb and has less flicker or flicker even when an LED bulb is connected as an illuminating load do.

A two-wire dimming switch according to the present invention is connected in series to an AC power source and an illumination 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 a first semiconductor switching element as a main switching element,

A rectifying circuit connected between the first connection terminal and the second connection terminal,

A power supply circuit connected to the dc side of the rectifying circuit for securing an internal power supply of the two-wire dimming switch,

A frequency detection circuit connected to the DC side of the rectifying circuit for outputting a predetermined detection signal for detecting the frequency of the AC power supply,

A second semiconductor switch element is used as an auxiliary switch element and a load current is caused to flow when the main switch element is not conducting and the main switch element or other main switch element is connected to the DC or AC side of the rectifying circuit, An auxiliary switching circuit for outputting a gate driving signal for conducting the semiconductor switch element,

An illumination light amount setting circuit operated by a user to set an illumination light amount for adjusting the brightness of the illumination load,

A frequency zero crossing point of the alternating current power supply is detected based on the detection signal outputted from the frequency detection circuit, and the zero crossing point of the alternating current power supply is estimated, The control circuit starts outputting a drive signal for causing the auxiliary open / close circuit to conduct at a first timing determined based on a cross point, And a control circuit for stopping the output of the drive signal at a timing.

The auxiliary switching circuit is made conductive by the gate driving signal outputted from the auxiliary switching circuit and flows the load current when the main switching element is not conducting after the auxiliary switching circuit is conducted, It is preferable to further include a quasi main opening / closing circuit for outputting a driving signal for conducting.

The main switch element is triac,

It is preferable that the auxiliary switching circuit is a thyristor connected to the DC side of the rectifying circuit as an auxiliary switching element.

Alternatively, the main switch element is triac,

It is preferable that the auxiliary switching circuit is two auxiliary thyristors connected alternately to the rectifying circuit and alternately conducting according to the polarity of the AC power source.

The photodetector of the phototriac coupler is connected in parallel with the main switch element, and one terminal of the phototriac coupler is connected to the main switch element A light emitting diode on the primary side of the phototriac coupler is connected in series with the auxiliary opening / closing circuit,

It is preferable that the holding current value of the phototriac is smaller than the holding current value of the triac.

The control circuit preferably outputs the first drive signal for causing the auxiliary open / close circuit to conduct at a predetermined timing in the vicinity of the estimated voltage zero cross point when starting dimming control of the illumination load.

According to the two-wire dimming switch, there is provided an auxiliary opening / closing circuit for allowing a load current to flow when the main switch element is not conducting and outputting a gate drive signal for conducting the main switch element or other semiconductor switch element , A drive signal for conducting the auxiliary open / close circuit is switched from the first timing determined based on the illumination amount set by the illumination light amount setting circuit and the voltage zero cross point to the second timing which is a predetermined time before the next voltage zero cross point And the auxiliary open / close circuit maintains the conduction state. Therefore, even if the load is the LED bulb and the load current flows from the auxiliary switching circuit or the like to the main switching circuit, the load current value becomes less than the holding current of the main switching element and the main switching circuit becomes nonconductive, The load current can be kept flowing through the open / close circuit and the like. As a result, the brightness of the LED bulb can be stabilized, and the flicker or the shake can be reduced.

1 is a circuit diagram showing a configuration of a two-wire dimming switch according to a first embodiment of the present invention;
2 is a waveform diagram of a load voltage, a load current of a LED bulb, and a gate driving signal for conducting a thyristor of an auxiliary opening / closing circuit in the first embodiment;
Fig. 3 is a waveform diagram of a load voltage, a load current, and a gate drive signal for causing the thyristor of the auxiliary open / close circuit to conduct, in the first embodiment, the load voltage of the LED bulb showing the influence of the load current by the other device.
4 is a circuit diagram showing a configuration of a two-wire dimming switch according to a second embodiment of the present invention;
5 is a circuit diagram showing a configuration of a two-wire dimming switch according to a third embodiment of the present invention;
6 is a circuit diagram showing a configuration of a two-wire dimming switch according to a fourth embodiment of the present invention;
Fig. 7 is a waveform diagram of each part in the control method of the two-wire dimming switch according to the fifth embodiment of the present invention; Fig.
8 is a circuit diagram showing a configuration of a two-wire dimming switch related to the first conventional example;
9 is a circuit diagram showing a configuration of a two-wire dimming switch related to the second conventional example;
10 is a circuit diagram showing a configuration of a driving circuit of a general LED bulb;
11 is a graph showing the difference in load voltage and load current between an incandescent lamp and an LED bulb;
Fig. 12 is a diagram showing a state in which a triac self-extinguishes when the load current value becomes less than the holding current value of the triac in the conventional two-wire dimming switch. Fig.
13 is a diagram showing a state in which a load voltage of an LED bulb fluctuates due to a load current of another device connected to the same AC current in a conventional two-wire dimming switch.

(First Embodiment)

 The two-wire dimming switch according to the first embodiment of the present invention will be described. Fig. 1 shows a circuit configuration of a two-wire dimming switch 1A according to the first embodiment. The two-wire dimming switch 1A is connected in series with respect to the alternating-current power supply 2 and the illumination load 3. The switch 5 may be provided separately for controlling the ON / OFF of the illumination load 3 integrally with the dimming variable resistor 4 of the 2-wire dimming switch 1A . In the following description, the case where the switch 5 is provided separately from the two-wire dimming switch 1A will be illustrated.

The first connection terminal 1a and the second connection terminal 1b of the two-wire dimming switch 1A are connected to the AC power supply 2 or the illumination load 3 and the switch 5. A main switching circuit 10 having a first semiconductor switching element such as triac as a main switching element 11 is connected between the first connection terminal 1a and the second connection terminal 1b. The rectifying circuit 12 is connected between the first connecting terminal 1a and the second connecting terminal 1b in parallel with the main switching circuit 10. The rectifying circuit 12 is connected to the two- 1A are connected to a power supply circuit 13 for securing the internal power. The power supply circuit 13 includes a first transistor element 13a and a second transistor element 13b connected in a Darling tone manner and a Zener diode 13c and a resistor 13d connected to the base of the second transistor element 13b, And a constant voltage circuit (such as a three-terminal regulator) 14 and a buffer capacitor 15 for supplying a constant-voltage direct-current power to the control circuit 16 constituted by a microprocessor or the like.

When the switch 5 is turned on, the pulsating current rectified by the rectifying circuit 12 is input to the power supply circuit 13, and the power whose output voltage is governed by the Zener voltage of the Zener diode 13c is output from the power supply circuit . This electric power is supplied to the control circuit 16 while being charged to a predetermined voltage (for example, 3 V) by the constant voltage circuit 14 while charging the buffer capacitor 15. [ Here, when the resistance value of the resistor 13d of the power supply circuit 13 is set to a high value such that the current required for the operation of the second transistor element 13b flows, the current value flowing to the ground through the Zener diode 13c is made low And 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 rectifying circuit 12 and a predetermined detection signal outputted from the frequency detection circuit 17 is supplied to the control circuit 16). The DC output terminal of the rectifying circuit 12 is connected to the output terminal of the lighting load 3 when the main switching device 11 of the main switching circuit 10 conducts or when the main switching device 11 does not conduct Is connected to an auxiliary open / close circuit 18 using a second semiconductor switch element such as a thyristor as an auxiliary switch element. To the control circuit 16, a light intensity setting circuit 4 composed of a variable resistor or the like operated by a user is connected. In the following description, the main switch element is referred to as a triac 11, and the auxiliary switching element or auxiliary switching element is referred to as a thyristor 18, if necessary.

The frequency detecting circuit 17 is configured so that the pulsating current outputted from the rectifying circuit 12 is inputted to the base of the transistor element 17a and is detected from the frequency detecting circuit 17 in accordance with the frequency of the ac power source 2 A signal is input to the control circuit 16. 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 thereon. Then, the gate drive signal is inputted to the gate terminal of the thyristor 18 on the basis of the detected frequency and the estimated voltage zero cross point or the like. 2 shows waveforms of the load voltage, the load current and the gate drive signal in the 1/2 cycle of the AC power supply 2 when the LED bulb is used as the illumination load 3. In Fig. The rise of the gate drive signal (the first timing at which the thyristor 18 conducts) is determined by searching the lookup table previously stored in the control circuit 16 based on the resistance value of the illumination light amount setting circuit (variable resistor) . The second timing at which the gate drive signal falls (the second timing at which the thyristor 18 becomes non-conductive) is set at a predetermined time? T (for example, 1 ms) from the voltage zero cross point of the AC power supply 2. This predetermined time? T is a time sufficient for the control circuit 16 to estimate the next voltage zero crossing point based on the detection signal from the frequency detecting circuit 17, for example.

Next, a specific operation of the two-wire dimming switch 1A according to the first embodiment will be described. When the switch 5 is in the off state, it can be considered that the charge of the buffer capacitor 15 is almost discharged and the control circuit 16 is not functioning. Here, when the switch 5 is turned on, full-wave rectified pulsating current is outputted from the rectifying circuit 12, for example. The buffer capacitor 15 is charged and the 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, a detection signal is input from the frequency detection circuit 17 to the control circuit 16, so that the control circuit 16 estimates the frequency of the AC power supply 2 and its zero cross point. Then, the control circuit 16 starts outputting the gate driving signal at the first timing (raises the gate driving signal) based on the resistance value of the light intensity setting circuit (variable resistor) 4. When the gate driving signal is inputted to the gate terminal of the thyristor 18, the thyristor 18 is turned on, and a current starts to flow in the lighting load 3. Since the current flowing through the thyristor 18 flows also to the gate electrode of the triac 11, when the voltage and the current become equal to or higher than the gate voltage threshold and the turn-on current of the triac 11, Thus, the load current flows from the thyristor 18 to the triac 11. When the triac 11 conducts, almost no current flows through the rectifying circuit 12 and almost no current flows through the thyristor 18, the power supply circuit 13, and the frequency detecting circuit 17. [ When the current does not flow in the power supply circuit 13, the discharge of the electric power from the buffer capacitor 15 is started, and the driving power of the control circuit 16 is secured accordingly. At this time, since the gate drive signal is continuously inputted from the control circuit 16 to the gate electrode of the thyristor 18, the thyristor 18 is in the conduction state.

When the lighting load 3 is an LED bulb, the load current instantaneously shows a large value at the same time as the thyristor 18 or the triac 11 is energized as described above, but it immediately becomes smaller. When the value of the load current becomes less than the holding current of the triac 11, the triac 11 becomes self-extinguished and becomes non-conductive. However, since the thyristor 18 conducts, ). Then, the control circuit 16 stops outputting the gate drive signal (lowers the gate drive signal) at the second timing which is ahead of the voltage zero cross point of the AC power supply 2 by the predetermined time? T. At this stage, the load current hardly flows, and even when the thyristor 18 becomes non-conductive, the brightness of the illumination load 3 hardly changes. When the thyristor 18 becomes non-conductive, the pulsating current output from the rectifying circuit 12 flows from the thyristor 18 to the power supply circuit 13 and the frequency detecting circuit 17, The next voltage zero cross point of the AC power source 2 can be estimated based on the detection signal from the circuit 17 and the output of the next gate drive signal is started on the basis of the estimated voltage zero cross point Timing can be controlled.

As described above, the two-wire dimming switch 1A is turned on during the period until the main switch element (triac) 11 of the main switching circuit 10 conducts, or when the main switching element 11 is not conducting (Thyristor) 18 for allowing a current to flow through the load 3, the value of the load current becomes less than the holding current of the triac 11, and the triac 11 becomes non- The load current continues to flow through the thyristor 18 because the thyristor 18 is conducting. As a result, the brightness of the LED bulb is stabilized, and flickering or blurring which can be seen by the naked eye hardly occurs. Also, even when the maximum value of the load current is less than the holding current of the triac 11, the current can be kept flowing through the auxiliary opening / closing circuit (thyristor) 18. The gate drive signal inputted to the gate electrode of the thyristor 18 is stopped at the second timing which is ahead of the voltage zero cross point of the ac power supply 2 by the predetermined time? T, The cross point can be accurately estimated. 3, even if other equipment connected to the same AC power supply 2 operates, the load current continues to flow through the thyristor 18, so that the brightness of the lighting load 3 hardly changes Do not. In addition, the load voltage waveform does not change much. It is needless to say that the triac 11 is selected and used particularly with a small holding current value.

(Second Embodiment)

A two-wire dimming switch according to a second embodiment of the present invention will be described. 4 shows a circuit configuration of a two-wire dimming switch 1B according to the second embodiment. The two-wire dimming switch 1B is obtained by adding a phototriac coupler 20 as a quasi opening / closing circuit to the two-wire dimming switch 1A according to the first embodiment. The secondary side phototriac liquid 21 of the phototriac coupler 20 is connected in parallel to the main opening and closing circuit (triac) 11 and the primary side light emitting diode 22 is connected in series to the auxiliary opening and closing part (thyristor) Respectively. Other configurations are the same. As the phototriac 21, the holding current value is selected to be smaller than the holding current value of the triac 11 of the main opening / closing circuit.

Next, the specific operation of the 2-wise dimming switch 1B according to the second embodiment will be described focusing on the difference. Current flows to the rectifying circuit 12 when the triacol 11 and the phototriacic liquid 21 are extinguished at the voltage zero cross point of the alternating current power supply 2. Thereafter, The gate drive signal is input to the gate terminal of the thyristor 18, and the thyristor 18 is turned on to allow the load current to flow through the thyristor 18. [ At this time, the primary side light emitting diode 22 of the photo-triac coupler 20 emits light, the gate drive signal is inputted to the gate terminal of the secondary side phototriac 21, and the phototriac 21 is energized . When the phototriac liquid 21 conducts, the load current flows to the phototriac 21. When the load current value is small and is less than the holding current value of the triac 11 of the main opening / closing circuit, the triac 11 of the main opening / closing circuit does not conduct, As shown in FIG. On the other hand, when the load current value is large and becomes equal to or more than the holding current value of the triac 11 of the main opening / closing circuit, the triac 11 of the main opening / closing circuit conducts and the load current flows to the triac 11. If the load current is less than the holding current of the triac 11, the triac 11 is self-extinguished and becomes non-conducting, but the thyristor 18 is conductive Thus, the load current temporarily flows to the thyristor 18. The primary side light emitting diode 22 of the phototriac coupler 20 emits light and the secondary side phototransistor 21 conducts and the load current flows to the phototriac 21. Since the holding current value of the photo-triac 21 is smaller than the holding current value of the triac 11 as described above, the load current can be stably kept flowing.

The two-wire dimming switch 1B according to the second embodiment is different from the two-wire dimming switch 1A according to the first embodiment in that a phototriac coupler 20 is added as a quasi opening / The structure is complicated and the cost is increased accordingly. However, even after the triac 11 becomes non-conducting, since the load current flows only through the phototriac 21 on the upstream side (AC side) of the rectifying circuit 12, that is, the load current flows through the diode bridge It does not pass, and the loss due to the diode bridge is lost. As a result, the change in brightness of the LED bulb becomes very small, so that flickering or blurring that can be seen with the naked eye hardly occurs.

(Third Embodiment)

A two-wire dimming switch according to a third embodiment of the present invention will be described. Fig. 5 shows a circuit configuration of a two-wire dimming switch 1C according to the third embodiment. The two-wire dimming switch 1C is provided with two auxiliary opening / closing circuits (thyristors) 18a and 18b in the two-wire dimming switch 1A according to the first embodiment, and the anode of each thyristor is rectified And the cathode is connected to the DC side minus terminal of the rectifying circuit 12 on the AC side of the circuit 12. [ 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 opening / closing circuit according to the polarity of the AC power source 2. [ Other configurations and operations are the same as those of the two-wire dimming switch 1A according to the first embodiment.

The two-wire dimming switch 1C according to the third embodiment is different from the two-wire dimming switch 1A according to the first embodiment in that thyristors, resistors, and capacitors constituting the auxiliary opening / closing circuit are added, The structure is complicated and the cost is increased accordingly. However, after the triac 11 becomes non-conducting, the load current does not pass through one diode constituting the rectifying circuit 12, and thus the loss is reduced accordingly. When the lighting load (3) is an LED bulb, since the load current value is very small, the smaller the loss of one diode, the smaller the flicker or the shake of the LED bulb can be.

(Fourth Embodiment)

A two-wire dimming switch according to a fourth embodiment of the present invention will be described. Fig. 6 shows the circuit configuration of the 2-wire dimming switch 1D according to the fourth embodiment. The two-wire dimming switch 1D is a combination of the features of the two-wire dimming switch 1B related to the second embodiment and the two-wire dimming switch 1C related to the third embodiment, A coupler 20, and two auxiliary switching circuits (thyristors) 18a and 18b. The two-wire dimming switch 1D according to the fourth embodiment configures the rectifier circuit 12 when the load current flows through the thyristor 18a or 18b in the same manner as the two-wire dimming switch 1C according to the third embodiment It does not pass through one diode, so the loss is reduced accordingly. Therefore, as compared with the two-wire dimming switch 1B according to the second embodiment, the voltage fluctuation when the load current flows from the thyristor 18a or 18b to the phototriac 21 becomes small, 3). As a result, the change in brightness of the LED bulb is further reduced, and flickering or fluctuation hardly occurs.

(Fifth Embodiment)

Although the first to fourth embodiments relate to the structure of the two-wire dimming switch, the fifth embodiment relates to a control method in any one of the two-wire dimming switches 1A to 1D. The two-wire dimming switches 1A to 1D and the LED bulb drive circuit 70 shown in Fig. 10 all have a circuit configuration for converting AC power into DC power and storing electric power in the buffer capacitor. Therefore, for example, when the switch 5 is turned off for a long time, it can be considered that any buffer capacitor is discharged and no power remains. When the switch 5 is turned on, the two-wire dimming switches 1A to 1D are started, and the control circuit 16 outputs a gate drive signal to start supplying power to the illumination load 3. [ In the case where the lighting load 3 is an LED bulb, since the driving circuit 70 is not started even when the power supply is started, the operation and the impedance characteristic are different from those in the normal lighting. That is, when the power supply to the drive circuit 70 of the LED bulb is started, the buffer capacitor 73 is charged for the first time. Therefore, when the LED bulb is started, the capacitance component of the buffer capacitor 73 exhibits a dominant impedance characteristic. When the voltage of the AC power source 2 is relatively high, when the current starts to flow in the drive circuit 70 of the LED bulb, the buffer capacitor 73 is rapidly charged and the two-wire dimming switches 1A to 1D and the LED bulb A large power factor difference arises between the drive circuit 70 of FIG.

Assuming that the phase of the voltage applied is different from the phase of the AC power supply 2 and the load voltage is -30 V, for example, when the voltage of the AC power supply 2 is 100 V, (Voltage between switches) between the connection terminals 1a and 1b of the dimmer switches 1A to 1D becomes 130V. That is, the voltage zero cross point of the AC power supply 2 and the zero cross point of the switches of the two-wire dimming switches 1A to 1D are different. The two-wire dimming switches 1A to 1D originally intended to perform control based on the voltage zero cross point of the AC power supply 2, And a zero-cross point of the inter-switch voltage is estimated from the output to perform dim control. Therefore, if control is performed at a timing different from the voltage zero cross point of the AC power supply 2 (the gate drive signal is output), there is a possibility that stable light control can not be inherently performed.

Fig. 7 shows the waveforms of the respective parts according to the control method according to the fifth embodiment. Until the start of dimming, the phase of the voltage waveform of the AC power supply 2 coincides with the phase of the inter-switch voltage waveform of the two-wire dimming switches 1A to 1D. In the control method according to the fifth embodiment, at the start of the dimming control of the illumination load 3, the first gate drive signal inputted from the control circuit 16 to the gate terminal of the thyristor 18 of the auxiliary opening / (For example, within ± several milliseconds with respect to the inter-switch voltage zero cross point) estimated from the output of the detection circuit 17. The timing for outputting the first gate driving signal is not always required to be ahead of the voltage zero cross point but may be after the voltage zero cross point. By doing so, the charging of the buffer capacitor 73 of the drive circuit 70 of the LED bulb can be started from the low level of the AC power supply 2. As described above, since the power supply to the drive circuit 70 of the LED bulb is started from around the voltage zero cross point (0 V), the impedance change of the two-wire dimming switches 1A to 1D and the drive circuit 70 of the LED bulb becomes abrupt And the power of 1/2 period of the AC power source 2 can be divided by the two-wire dimming switches 1A to 1D and the driving circuit 70 of the LED bulb. In addition, since a large power factor difference does not occur between the two-wire dimming switches 1A to 1D and the drive circuit 70 of the LED bulb, stable dimming control can be performed.

In the above description, the triac as a single bidirectional semiconductor switch element is exemplified as the main switch element, but the present invention is not limited to this, and it may be a structure having a structure capable of flowing current in both directions like the triac, An insulated gate bipolar transistor (IGBT) or an inverse-parallel-connected FET may be used.

1A to 1D: 2-wire dimming switch 2: AC power source
3: Lighting load 4: Lighting amount setting circuit (Variable resistor)
5: Switch 10: Main switching circuit
11: main switch element (triac) 12: rectifying circuit
13: power supply circuit 16: control circuit
17: Frequency detection circuit
18, 18a, 18b: auxiliary switching circuit (auxiliary switching element, thyristor)
20: Substance open / close circuit (phototriac coupler)
21: Photo triac 22: Light emitting diode

Claims (6)

A two-wire dimming switch connected in series to an AC power source and an illumination 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 a first semiconductor switching element as a main switching element,
A rectifying circuit connected between the first connection terminal and the second connection terminal,
A power supply circuit connected to the dc side of the rectifying circuit for securing an internal power supply of the two-wire dimming switch,
A frequency detection circuit connected to the DC side of the rectifying circuit for outputting a predetermined detection signal for detecting the frequency of the AC power supply,
A second semiconductor switch element is used as an auxiliary switch element and a load current is caused to flow when the main switch element is not conducting and the main switch element or other main switch element is connected to the DC or AC side of the rectifying circuit, An auxiliary switching circuit for outputting a gate driving signal for conducting the semiconductor switch element,
An illumination light amount setting circuit operated by a user to set an illumination light amount for adjusting the brightness of the illumination load,
A frequency zero crossing point of the alternating current power supply is detected based on the detection signal outputted from the frequency detection circuit, and the zero crossing point of the alternating current power supply is estimated, The control circuit starts outputting a drive signal for causing the auxiliary open / close circuit to conduct at a first timing determined based on a cross point, And a control circuit for stopping the output of the drive signal at a timing when the two-wire type dimming switch is turned on. The method according to claim 1,
Wherein the main switch element is made conductive by the gate drive signal outputted from the auxiliary open / close circuit, and after the auxiliary open / close circuit is conducted, a load current is caused to flow when the main switch element is not conducting, Further comprising a quasi main opening / closing circuit for outputting a driving signal for driving the light source. The method according to claim 1 or 2,
The main switch element is a triac,
Wherein the auxiliary switching circuit comprises a thyristor connected to the DC side of the rectifying circuit as an auxiliary switching element. The method according to claim 1 or 2,
The main switch element is a triac,
Wherein the auxiliary switching circuit is connected to the AC side of the rectifying circuit and two thyristors alternately conducting in accordance with the polarity of the AC power supply are used as auxiliary switching elements. Claim 3 or claim 2 dependent on claim 2, claim 4 or claim 5 dependent on claim 2,
Wherein the phototriac coupler is a switch element, the phototriac of the phototriac coupler on the secondary side is connected in parallel with the main switch element, and one of the terminals is connected to the gate terminal The light emitting diode on the primary side of the phototriac coupler is connected in series with the auxiliary opening / closing circuit,
Wherein the holding current value of the phototriac is smaller than the holding current value of the triac. The method according to any one of claims 1 to 5,
Wherein the control circuit outputs a first drive signal for causing the auxiliary open / close circuit to conduct at a predetermined timing near the estimated voltage zero cross point when the dimming control of the illumination load is started Linear dimming switch.

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