Light control device

Abstract

To provide a dimmer compatible with a greater number of types of a load.SOLUTION: A pair of input terminals 11, 12 is electrically connected between a load 7 and an alternating current power supply 8. A bidirectional switch 2 is configured to switch interruption and passage of a current between the pair of input terminals 11, 12, and includes two controllable semiconductor switches. A phase detection unit 3 detects a phase of an alternating voltage of an alternating current power supply 8. A dimming level for specifying a magnitude of output of the load 7 is input into an input unit 4. The power supply unit 5 is supplied with power from the alternating current power supply 8 to generate power for a control unit 6. An opening / closing unit (stop unit 13) can supply or interrupt the power from the alternating current power supply 8 to the power supply unit 5. The control unit 6 controls the bidirectional switch 2 to an ON state using a control signal of each of the two semiconductor switches as a first signal during a first interval from a first point in a half cycle interval of the alternating voltage to a second point when a first period corresponding to the dimming level elapses.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dimmer for dimming a lighting load. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a dimming device for dimming a lighting load is known (for example, Patent Document 1).

[0003] The dimming device described in Patent Document 1 includes a pair of terminals, a control circuit unit, a control power supply unit that supplies control power to the control circuit unit, and a dimming operation unit that sets the dimming level of the lighting load.

[0004] A control circuit section and a control power supply section are connected in parallel between a pair of terminals. A series circuit of an AC power supply and a lighting load is also connected between the pair of terminals. The lighting load includes a plurality of LED (Light Emitting Diode) elements and a power supply circuit that lights up each of the LED elements. The power supply circuit includes a smoothing circuit of a diode and an electrolytic capacitor.

[0005] The control circuit unit includes a switch unit that phase-controls the AC voltage supplied to the lighting load, a switch drive unit that drives the switch unit, and a control unit that controls the switch drive unit and the control power supply unit.

[0006] The control power supply unit is connected in parallel to the switch unit. The control power supply unit converts the AC voltage of the AC power supply into the control power. The control power supply unit includes an electrolytic capacitor that stores the control power.

[0007] The control unit is supplied with control power from the control power supply unit through an electrolytic capacitor. The control unit includes a microcomputer. The microcomputer performs reverse phase control to cut off power supply to the lighting load in the middle of each half cycle of the AC voltage according to the dimming level set by the dimming operation unit. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2013-149498 A Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a dimmer device capable of handling a greater variety of loads. [Means for solving the problem]

[0010] A dimming device according to one aspect of the present invention includes a pair of input terminals electrically connected between a load and an AC power source, a bidirectional switch including two controllable semiconductor switches capable of switching between blocking and passing a bidirectional current between the pair of input terminals, an input unit to which a dimming level is input, a control unit to control the bidirectional switch in response to the dimming level, and a control power supply unit that is supplied with power from the AC power source and generates power for the control unit. AC power supply During a half-cycle period of the AC voltage, the bidirectional switch is controlled to an off state by using both control signals of the two semiconductor switches as first signals in accordance with the dimming level, and after controlling the bidirectional switch to the off state, the bidirectional switch is controlled to an on state by using both control signals of the two semiconductor switches as second signals, and with the bidirectional switch in the off state, control is performed so that power is supplied from the AC power source to the controlled power supply unit. Effect of the Invention

[0011] The present invention has the advantage that it can accommodate a greater variety of loads. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic circuit diagram showing a configuration of a light control device according to a first embodiment. [Diagram 2]4 is a timing chart showing the operation of the light control device according to the first embodiment. [Diagram 3] 4 is a timing chart used for comparing the light control device according to the first embodiment with a comparative example. [Figure 4] 1 is a schematic circuit diagram showing a configuration of a light control device according to a first modified example of the first embodiment. [Diagram 5] 10 is a schematic circuit diagram showing a configuration of a light control device according to a second modified example of the first embodiment. FIG. [Figure 6] 11 is a timing chart showing the operation of the light control device according to Modification 2 of the first embodiment. [Figure 7] FIG. 11 is a schematic circuit diagram showing a configuration of a light control device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Embodiment 1) (1.1) Structure The dimming device 1 of this embodiment will be described below. However, the configuration described below is merely one example of the present invention, and the present invention is not limited to the following embodiment. Even if it is not the embodiment, various modifications are possible according to the design, etc., as long as it does not deviate from the technical idea of ​​the present invention. As shown in FIG. 1, the dimming device 1 of this embodiment includes a pair of input terminals 11, 12, a bidirectional switch 2, a phase detection unit 3, an input unit 4, a power supply unit 5, a control unit 6, a switch driving unit 9, diodes D1, D2, and a stop unit 13.

[0014] The pair of input terminals 11, 12 are electrically connected between a load 7 that lights up when energized and an AC power source 8. The bidirectional switch 2 is configured to switch between blocking / conducting a bidirectional current between the pair of input terminals 11, 12. The phase detection unit 3 detects the phase of the AC voltage Vac of the AC power source 8. The input unit 4 receives a dimming level that specifies the magnitude of the light output of the load 7. The power supply unit 5 is electrically connected between the pair of input terminals 11, 12, and generates a control power supply using power supplied from the AC power source 8.

[0015] The control unit 6 operates by receiving a control power supply from the power supply unit 5. Based on the detection signal from the phase detection unit 3, the control unit 6 controls the bidirectional switch 2 so that the bidirectional switch 2 is in the OFF state from a first time point at which a first time has elapsed from the start point of a half cycle of the AC voltage Vac. The control unit 6 controls the bidirectional switch 2 so that the bidirectional switch 2 is in the ON state from the first time point to a second time point at which a second time according to a dimming level has elapsed. The control unit 6 also controls the bidirectional switch 2 so that the bidirectional switch 2 is in the OFF state from the second time point to the end point of the half cycle.

[0016] Here, the expression "from time point A" includes time point A. For example, "from the first time point" includes the first time point. On the other hand, the expression "up to time point A" does not include time point A and means up to just before time point A. For example, "up to the first time point" does not include the first time point and means up to just before the first time point. Also, the "input terminal" here does not have to have an actual physical form as a component (terminal) for connecting an electric wire or the like, and may be, for example, a lead of an electronic component or a part of a conductor included in a circuit board.

[0017] The dimmer 1 is a two-wire dimmer, and is used in a state where a load 7 is electrically connected in series to an AC power source 8. The load 7 lights up when power is applied. The load 7 includes an LED element as a light source and a lighting circuit for lighting the LED element. The AC power source 8 is, for example, a single-phase 100 [V], 60 [Hz] commercial power source. The dimmer 1 can be applied to, for example, a wall switch.

[0018] The bidirectional switch 2 is composed of, for example, two elements, a first switch element Q1 and a second switch element Q2, electrically connected in series between input terminals 11 and 12. For example, each of the switch elements Q1 and Q2 is a semiconductor switch element composed of an enhancement type n-channel Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET).

[0019] The switch elements Q1 and Q2 are connected in what is called an anti-series configuration between the input terminals 11 and 12. That is, the sources of the switch elements Q1 and Q2 are connected to each other. The drain of the switch element Q1 is connected to the input terminal 11, and the drain of the switch element Q2 is connected to the input terminal 12. The sources of both switch elements Q1 and Q2 are connected to the ground of the power supply unit 5. The ground of the power supply unit 5 serves as a reference potential for the internal circuit of the dimmer 1.

[0020] The bidirectional switch 2 can switch between four states by combinations of ON and OFF of the switch elements Q1 and Q2. The four states include a bidirectional OFF state in which both switch elements Q1 and Q2 are OFF, a bidirectional ON state in which both switch elements Q1 and Q2 are ON, and two types of unidirectional ON states in which only one of the switch elements Q1 and Q2 is ON. In the unidirectional ON state, one of the switch elements Q1 and Q2 is turned ON, and a pair of input terminals 11 and 12 is unidirectionally connected through a parasitic diode of the switch element that is turned OFF. For example, when the switch element Q1 is turned ON and the switch element Q2 is turned OFF, a first unidirectional ON state is established in which a current flows from the input terminal 11 to the input terminal 12. When the switch element Q2 is turned ON and the switch element Q1 is turned OFF, a second unidirectional ON state is established in which a current flows from the input terminal 12 to the input terminal 11. Therefore, when AC voltage Vac is applied between input terminals 11 and 12 from AC power supply 8, the first unidirectional on state becomes the "forward on state" and the second unidirectional on state becomes the "reverse on state" during the half cycle when AC voltage Vac is positive, i.e., when input terminal 11 is positive. On the other hand, when AC voltage Vac is negative, i.e., when input terminal 12 is positive, the second unidirectional on state becomes the "forward on state" and the first unidirectional on state becomes the "reverse on state."

[0021] Here, the bidirectional switch 2 is in the on state in both the "bidirectional on state" and the "forward on state", and in the off state in both the "bidirectional off state" and the "reverse on state".

[0022] The phase detector 3 detects the phase of the AC voltage Vac applied between the input terminals 11 and 12. The "phase" here includes the zero-crossing point of the AC voltage Vac and the polarity (positive polarity, negative polarity) of the AC voltage Vac. The phase detector 3 is configured to output a detection signal to the controller 6 when it detects the zero-crossing point of the AC voltage Vac. The phase detector 3 has a diode D31, a first detector 31, a diode D32, and a second detector 32. The first detector 31 is electrically connected to the input terminal 11 via the diode D31. The second detector 32 is electrically connected to the input terminal 12 via the diode D32. The first detector 31 detects the zero-crossing point when the AC voltage Vac transitions from a negative half cycle to a positive half cycle. The second detector 32 detects the zero-crossing point when the AC voltage Vac transitions from a positive half cycle to a negative half cycle.

[0023] That is, when the first detection unit 31 detects that the voltage with the input terminal 11 as the positive pole has shifted from a state below the specified value to a state above the specified value, it determines that it is a zero crossing point. Similarly, when the second detection unit 32 detects that the voltage with the input terminal 12 as the positive pole has shifted from a state below the specified value to a state above the specified value, it determines that it is a zero crossing point. The specified value is a value (absolute value) set near 0 [V]. For example, the specified value of the first detection unit 31 is about a positive number [V], and the specified value of the second detection unit 32 is about a negative number [V]. Therefore, the detection point of the zero crossing point detected by the first detection unit 31 and the second detection unit 32 is slightly delayed in time from the zero crossing point (0 [V]) in the strict sense.

[0024] The input unit 4 receives a signal representing a dimming level from an operation unit operated by a user, and outputs the signal as a dimming signal to the control unit 6. When outputting the dimming signal, the input unit 4 may or may not process the received signal. The dimming signal is a numerical value or the like that specifies the magnitude of the light output of the load 7, and may include an "OFF level" that turns off the load 7. The operation unit may be configured to output a signal representing a dimming level to the input unit 4 in response to a user's operation, and may be, for example, a variable resistor, a rotary switch, a touch panel, a remote controller, or a communication terminal such as a smartphone.

[0025] The control unit 6 controls the bidirectional switch 2 based on the detection signal from the phase detection unit 3 and the dimming signal from the input unit 4. The control unit 6 controls each of the switch elements Q1 and Q2 separately. Specifically, the control unit 6 controls the switch element Q1 with a first control signal and controls the switch element Q2 with a second control signal.

[0026] The control unit 6 mainly comprises, for example, a microcomputer. The microcomputer executes a program recorded in the memory of the microcomputer with a CPU (Central Processing Unit), thereby realizing the function of the control unit 6. The program may be recorded in the memory of the microcomputer in advance, or may be provided by being recorded on a recording medium such as a memory card, or may be provided through an electric communication line. In other words, the above program is a program for causing a computer (here, a microcomputer) to function as the control unit 6.

[0027] The switch driver 9 has a first driver 91 that drives (ON / OFF control) the switch element Q1, and a second driver 92 that drives (ON / OFF control) the switch element Q2. The first driver 91 receives a first control signal from the controller 6 and applies a gate voltage to the switch element Q1. This causes the first driver 91 to control the switch element Q1 to be turned on and off. Similarly, the second driver 92 receives a second control signal from the controller 6 and applies a gate voltage to the switch element Q2. This causes the second driver 92 to control the switch element Q2 to be turned on and off. The first driver 91 generates a gate voltage based on the potential of the source of the switch element Q1. The same is true for the second driver 92.

[0028] The power supply unit 5 has a control power supply unit 51 that generates a control power supply, a drive power supply unit 52 that generates a drive power supply, and a capacitive element (capacitor) C1. The control power supply is a power supply for operating the control unit 6. The drive power supply is a power supply for driving the switch drive unit 9. The capacitive element C1 is electrically connected to an output terminal of the control power supply unit 51, and is charged by the output current of the control power supply unit 51.

[0029] The power supply unit 5 is electrically connected to the input terminal 11 via the diode D1, and is electrically connected to the input terminal 12 via the diode D2. Thus, the AC voltage Vac applied between the input terminals 11 and 12 is full-wave rectified in a diode bridge formed of a pair of diodes D1 and D2 and the parasitic diodes of the switch elements Q1 and Q2, and is supplied to the power supply unit 5. The drive power supply unit 52 smoothes the full-wave rectified AC voltage Vac to generate a drive power supply. The drive power supply unit 52 supplies the drive power supply to the switch drive unit 9 and the control power supply unit 51. The drive power supply is, for example, 10 [V]. The control power supply unit 51 generates a control power supply by stepping down the drive power supply supplied from the drive power supply unit 52, and outputs it to the capacitive element C1. The control power supply is, for example, 3 [V]. The control power supply unit 51 may generate the control power supply directly from the full-wave rectified AC voltage Vac without going through the drive power supply unit 52. In other words, the power supply unit 5 generates a control power supply and a drive power supply using the power supplied from the AC power supply 8.

[0030] The stop unit 13 stops the generation of the control power supply in the power supply unit 5 during the stop period. In this embodiment, the stop unit 13 stops the generation of the control power supply in the power supply unit 5 by electrically cutting off the power supply unit 5 or controlling a semiconductor switch element included in the power supply unit 5. In the example of FIG. 1, the stop unit 13 forms a series circuit with the power supply unit 5, and the series circuit of the stop unit 13 and the power supply unit 5 is electrically connected in parallel with the bidirectional switch 2 between the pair of input terminals 11 and 12. As will be described in detail in the section "(1.2.2) Dimming Operation", the stop period is a period set excluding at least the period during which the bidirectional switch 2 is in a bidirectional off state. Specifically, the stop unit 13 is a switch electrically connected between the connection point of the pair of diodes D1 and D2 and the power supply unit 5, and turns off upon receiving a cutoff signal from the control unit 6 to electrically separate the power supply unit 5 from the input terminals 11 and 12.

[0031] The light control device 1 of this embodiment also includes a mask unit 61. Upon receiving a detection signal from the phase detection unit 3, the mask unit 61 disables the detection signal for a certain length of mask time. In this embodiment, the mask unit 61 is provided integrally with the control unit 6 as one function of the control unit 6. This will be described in detail in the section "(1.2.2) Light Control Operation," but the mask unit 61 disables the detection signal from the phase detection unit 3 during the mask time, making the control unit 6 less susceptible to the influence of erroneous detection of the zero crossing point by the phase detection unit 3. It is preferable that the mask unit 61 disables the detection signal for each of the first detection unit 31 and the second detection unit 32 separately.

[0032] The lighting circuit of the load 7 reads the dimming level from the waveform of the AC voltage Vac phase-controlled by the dimmer 1, and changes the magnitude of the light output of the LED element. Here, the lighting circuit has a circuit for securing current, such as a bleeder circuit, for example. Therefore, it is possible to pass current to the load 7 even during the period when the bidirectional switch 2 of the dimmer 1 is not conducting.

[0033] (1.2) Operation (1.2.1) Start-up behavior First, a start-up operation at the start of energization of the light control device 1 of this embodiment will be described.

[0034] According to the dimming device 1 configured as described above, when the AC power supply 8 is connected between the input terminals 11, 12 via the load 7, the AC voltage Vac applied from the AC power supply 8 between the input terminals 11, 12 is rectified and supplied to the drive power supply unit 52. The drive power generated by the drive power supply unit 52 is supplied to the switch drive unit 9 and also to the control power supply unit 51. When the control power generated by the control power supply unit 51 is supplied to the control unit 6, the control unit 6 is started up.

[0035] When the control unit 6 is started, the control unit 6 determines the frequency of the AC power supply 8 based on the detection signal of the phase detection unit 3. Then, the control unit 6 refers to a numerical value table stored in advance in a memory according to the determined frequency, and sets various parameters such as time (for example, a mask time and a stop period described later). Here, if the dimming level input to the input unit 4 is the "OFF level", the control unit 6 maintains the impedance between the pair of input terminals 11, 12 in a high impedance state by maintaining the bidirectional switch 2 in a bidirectional OFF state. As a result, the load 7 is maintained in an off state.

[0036] (1.2.2) Dimming Operation Next, the dimming operation of the dimming device 1 of the present embodiment will be described with reference to FIG. 2. FIG. 2 shows the AC voltage "Vac", the first detection signal "ZC1", the first mask processing "MASK1", the second detection signal "ZC2", the second mask processing "MASK2", the first control signal "Sb1", the second control signal "Sb2", and the cutoff signal "Ss1". Here, the first detection signal ZC1 is a detection signal by the first detection unit 31, and the second detection signal ZC2 is a detection signal by the second detection unit 32. The first mask processing MASK1 is a mask processing (nullification processing) by the mask unit 61 for the first detection signal ZC1, and the second mask processing MASK2 is a mask processing by the mask unit 61 for the second detection signal ZC2. Here, it is assumed that the first detection signal ZC1 is generated when the first detection signal ZC1 changes from the "H" level to the "L" level. Moreover, the second detection signal ZC2 is deemed to have been generated when the second detection signal ZC2 changes from the “H” level to the “L” level. In other words, the first detection signal ZC1 and the second detection signal ZC2 are signals that change from the “H” level to the “L” level when a zero-crossing point is detected.

[0037] First, the operation of the dimmer 1 in a half cycle in which the AC voltage Vac is positive will be described. In the dimmer 1, the phase detector 3 detects the zero-cross point of the AC voltage Vac, which is the reference for phase control. When the AC voltage Vac transitions from a half cycle in which the AC voltage Vac is negative to a half cycle in which the AC voltage Vac is positive, the first detector 31 outputs a first detection signal ZC1 when the AC voltage Vac reaches a specified value "Vzc" of positive polarity. Upon receiving the first detection signal ZC1, the controller 6 sets the first control signal Sb1 and the second control signal Sb2 to "OFF" signals.

[0038] As a result, in a first period T1 from the start point (zero crossing point) t0 of the half cycle to the first time point t1 at which the first time has elapsed, both of the switch elements Q1 and Q2 are turned off, and the bidirectional switch 2 is in a bidirectional off state. In this embodiment, the time point at which the first detection signal ZC1 is generated is defined as a "detection point", and the first period T1 is defined as the sum of the period from the start point (zero crossing point) t0 of the half cycle to the detection point and the period from the detection point until a certain time (for example, 300 μs) has elapsed. That is, in this embodiment, the control unit 6 controls the bidirectional switch 2 to a bidirectional off state not only after the detection point, but also during the period from the start point (zero crossing point) t0 of the half cycle to the detection point. Here, if the frequency of the AC voltage Vac is constant, the time from the start point (zero crossing point) t0 of the half cycle to the detection point is a constant length of time, so the first time in this embodiment (the time from the start point t0 of the half cycle to the first time point t1) is a constant length of time.

[0039] When a certain time (for example, 300 μs) has elapsed from the detection point, that is, at the first time point t1, the control unit 6 sets the first control signal Sb1 and the second control signal Sb2 to "ON" signals.

[0040] The second time point t2 is a time point when a second time corresponding to the dimming signal has elapsed from the first time point t1. At the second time point t2, the control unit 6 changes the first control signal Sb1 to an "OFF" signal while maintaining the second control signal Sb2 as an "ON" signal. As a result, during the second period T2 from the first time point t1 to the second time point t2, both switch elements Q1 and Q2 are turned on, and the bidirectional switch 2 is in a bidirectional ON state. Therefore, during the second period T2, power is supplied from the AC power source 8 to the load 7 via the bidirectional switch 2, and the load 7 is turned on.

[0041] The third point in time t3 is a fixed time (e.g., 300 μs) before the end point (zero cross point) t4 of the half cycle. At the third point in time t3, the control unit 6 sets the first control signal Sb1 and the second control signal Sb2 to "OFF" signals. As a result, during the third period T3 from the second point in time t2 to the third point in time t3, only the switch element Q1 of the switch elements Q1 and Q2 is turned off, and the bidirectional switch 2 is in the reverse ON state (i.e., the OFF state). Therefore, during the third period T3, the power from the AC power source 8 to the load 7 is cut off.

[0042] During a fourth period T4 from the third point in time t3 to the end point (zero crossing point) t4 of the half cycle, both switch elements Q1 and Q2 are turned off, and the bidirectional switch 2 is in a bidirectional off state.

[0043] Moreover, the operation of the light control device 1 in a half cycle in which the AC voltage Vac has a negative polarity is basically the same as that in a half cycle in which the AC voltage Vac has a positive polarity.

[0044] In a negative half cycle, the period from the start point (zero crossing point) t0 (t4) of the half cycle to the first time point t1 at which the first time has elapsed is defined as the first period T1. In this embodiment, the time point at which the second detection signal ZC2 is generated is defined as the "detection point", and the sum of the period from the start point (zero crossing point) t0 (t4) of the half cycle to the detection point and the period from the detection point until a certain time (for example, 300 [μs]) has elapsed is defined as the first period T1. The second time point t2 is the time at which a second time corresponding to the dimming signal has elapsed from the first time point t1, and the third time point t3 is the time a certain time (for example, 300 [μs]) before the end point (zero crossing point) t4 (t0) of the half cycle. That is, when the AC voltage Vac reaches the negative polarity specified value "-Vzc", the second detection unit 32 outputs the second detection signal ZC2. Upon receiving the second detection signal ZC2, the control unit 6 sets the first control signal Sb1 and the second control signal Sb2 to "OFF" signals. As a result, the bidirectional switch 2 is in a bidirectional OFF state during the first period T1. Then, at the first time point t1, the control unit 6 sets the first control signal Sb1 and the second control signal Sb2 to "ON" signals.

[0045] At the second time point t2, the control unit 6 changes the second control signal Sb2 to an "OFF" signal while maintaining the first control signal Sb1 as an "ON" signal. As a result, during the second period T2 from the first time point t1 to the second time point t2, both switch elements Q1 and Q2 are turned on and the bidirectional switch 2 is in a bidirectional ON state. Therefore, during the second period T2, power is supplied from the AC power source 8 to the load 7 via the bidirectional switch 2, and the load 7 is turned on.

[0046] At the third time point t3, the control unit 6 sets the first control signal Sb1 and the second control signal Sb2 to "OFF" signals. As a result, during the third period T3 from the second time point t2 to the third time point t3, only the switch element Q2 of the switch elements Q1 and Q2 is turned off, and the bidirectional switch 2 is in the reverse ON state (i.e., the OFF state). Therefore, during the third period T3, the power from the AC power supply 8 to the load 7 is cut off.

[0047] The dimming device 1 of this embodiment performs dimming of the load 7 by alternately repeating the above-described positive polarity half-cycle operation and negative polarity half-cycle operation for each half cycle of the AC voltage Vac. The bidirectional switch is in the off state during the period from the start point (zero cross point) t0 of the half cycle to the first time point t1, and the bidirectional switch is in the off state during the period from the second time point t2 to the end point (zero cross point) t4 of the half cycle. Therefore, when focusing on two consecutive half cycles, the bidirectional switch is in the off state from the second time point t2 of the first half cycle to the first time point t1 of the next half cycle (i.e., the second half cycle).

[0048] Here, the time from the first time point t1 to the second time point t2 (the second time) corresponds to the dimming level input to the input unit 4, so the time during which the input terminals 11 and 12 are conductive in a half cycle is determined according to the dimming level. That is, the second time is determined to be short when the light output of the load 7 is reduced, and the second time is determined to be long when the light output of the load 7 is increased. Therefore, it is possible to change the magnitude of the light output of the load 7 according to the dimming level input to the input unit 4. In addition, there are periods (the first period T1 and the fourth period T4) during which the bidirectional switch 2 is in a bidirectional off state before and after the zero-crossing point of the AC voltage Vac, respectively, so that the dimmer 1 can ensure the power supply from the AC power source 8 to the power source unit 5 by using these periods. In this embodiment, the power supply from the AC power source 8 to the power source unit 5 can be ensured during at least one of the first period T1 and the fourth period T4. In addition, when the user operates the operating unit to maximize the light output of the load 7, priority may be given to ensuring the first period T1 and the fourth period T4, and the second period T2 may be controlled to be shorter than the length required to maximize the light output.

[0049] Incidentally, the light control device 1 of the present embodiment includes a mask unit 61, and performs mask processing to invalidate the detection signal of the zero crossing point thereafter for a certain length of mask time after receiving the detection signal of the zero crossing point. That is, after receiving the first detection signal ZC1 from the first detection unit 31, the mask unit 61 turns the first mask processing MASK1 "ON" and invalidates the first detection signal ZC1 until the mask time has elapsed. Similarly, after receiving the second detection signal ZC2 from the second detection unit 32, the mask unit 61 turns the second mask processing MASK2 "ON" and invalidates the second detection signal ZC2 until the mask time has elapsed. The length of the mask time is set based on the half cycle of the AC voltage Vac. Here, as an example, the mask time is set to a time slightly shorter than twice the half cycle (i.e., one cycle). In FIG. 2, the first detection signal ZC1 and the second detection signal ZC2 during the invalidated period are indicated by dashed lines.

[0050] As a result, once a zero-crossing point is detected, masking is performed up to the vicinity of the next zero-crossing point. For example, even if a zero-crossing point is erroneously detected due to noise at a point 1 / 4 of a cycle after a zero-crossing point is detected, the detection signal generated by the erroneous detection is invalidated by masking. Therefore, the control unit 6 is less susceptible to the effects of erroneous detection of zero-crossing points by the phase detection unit 3.

[0051] Further, the light control device 1 of the present embodiment controls the stop unit 13 by the shutoff signal Ss1. During the shutoff period, the stop unit 13 electrically shuts off the power supply unit 5 or controls a semiconductor switch element included in the power supply unit 5, thereby stopping the generation of the control power supply in the power supply unit 5. That is, the control unit 6 electrically disconnects the power supply unit 5 from the input terminals 11 and 12 by turning off the shutoff signal Ss1 to an "OFF" signal during the shutoff period to turn off the stop unit 13. The shutoff period is a period set excluding at least the period (first period T1, fourth period T4) during which the bidirectional switch 2 is in a bidirectional off state. That is, the shutoff period is set within the second period T2 during which the bidirectional switch 2 is in a bidirectional on state and the third period T3 during which the bidirectional switch 2 is in a unidirectional on state (reverse on state). Here, as an example, the shutoff period is set so that the start point is a time point set between the first time point t1 and the second time point t2 and the end point is the third time point t3. That is, the shutoff period is set within a period during which power may be supplied from the AC power supply 8 to the load 7.

[0052] As a result, the dimming device 1 can maintain the impedance between the input terminals 11, 12 high during the stop period by the amount of the power supply unit 5 being disconnected from the input terminals 11, 12. That is, the dimming device 1 supplies power from the AC power source 8 to the power supply unit 5 during the period when the bidirectional switch 2 is in the bidirectional off state, and can maintain the impedance between the input terminals 11, 12 high during the period when power is not supplied to the power supply unit 5 (stop period). For example, by maintaining the impedance between the input terminals 11, 12 high during the third period T3 when the bidirectional switch 2 is in the reverse on state, it is possible to prevent power from being supplied to the load 7 due to leakage current. As a result, the magnitude of the light output of the load 7 can be changed in response to small changes in the dimming level, and the responsiveness of the load 7 is improved.

[0053] (1.3) Summary of the light control device according to the first embodiment As described above, the light control device 1 according to this embodiment includes the bidirectional switch 2, the phase detection unit 3, the power supply unit 5, and the control unit 6.

[0054] The bidirectional switch 2 is connected in series with the load 7 and the AC power supply 8, and controls the phase of the AC voltage Vac supplied to the load 7. The phase detection unit 3 detects the phase of the AC voltage Vac of the AC power supply 8. The power supply unit 5 is connected in parallel with the bidirectional switch 2, and performs a conversion operation to convert the AC power supply 8 into a predetermined control power supply, and has a capacitive element C1 that accumulates the control power supply.

[0055] The control unit 6 receives control power from the power supply unit 5 through the capacitive element C1 and divides each half cycle of the AC voltage Vac into a first period T1, a second period T2, a third period T3, and a fourth period T4 based on the phase detected by the phase detection unit 3. In the first period T1 and the fourth period T4, the control unit 6 controls the bidirectional switch 2 to be non-conductive to cut off the power supply to the load 7 and causes the power supply unit 5 to perform a conversion operation. In the second period T2, the control unit 6 controls the bidirectional switch 2 to be conductive to supply power to the load 7 and causes the power supply unit 5 to stop the conversion operation. In the third period T3, the control unit 6 controls the bidirectional switch 2 to be non-conductive to cut off the power supply to the load 7.

[0056] The "non-conduction control" here means control for turning off the bidirectional switch 2. Moreover, the "conduction control" means control for turning on the bidirectional switch 2. Moreover, the "conversion operation" means an operation for converting the AC power supply 8 into a predetermined control power supply in the power supply unit 5, that is, an operation for generating a control power supply from the power supplied from the AC power supply 8.

[0057] Moreover, the light control device 1 may further include a stop unit 13 that switches between execution and stop of the conversion operation of the power supply unit 5. In this case, for example, in the third period (T3), the control unit 6 may control the bidirectional switch 2 to be non-conductive to cut off the power supply to the load 7, and the stop unit 13 may also stop the conversion operation of the power supply unit 5.

[0058] (1.4) Comparison with Comparative Examples Hereinafter, an anti-phase control method different from that of this embodiment will be used as a comparative example, and the differences between the control method of this embodiment and the control method of the comparative example will be described with reference to FIG.

[0059] In the comparative example shown here, the operation of the control unit 6 (the control method of the bidirectional switch 2) is different from that of this embodiment, but the circuit configuration is the same as that of this embodiment, so in the following, components similar to those of this embodiment are denoted by the same reference numerals. Fig. 3 shows the AC voltage "Vac", the first control signal "Sa1" and the second control signal "Sa2" of the comparative example, and the first control signal "Sb1" and the second control signal "Sb2" of this embodiment.

[0060] The dimmer of the comparative example alternately turns on the first control signal Sa1 and the second control signal Sa2 in the same cycle as the AC voltage Vac. According to this comparative example, the bidirectional switch 2 is conductive during the period when the switch element on the high potential side of the AC voltage Vac, out of the switch elements Q1 and Q2, is on. That is, in the comparative example, so-called anti-phase control is realized in which the pair of input terminals 11 and 12 are conductive during the period Ta1 from the zero crossing point of the AC voltage Vac to the middle of the half cycle in FIG. 3. Therefore, by adjusting the phase difference between the first control signal Sa1 and the second control signal Sa2 and the AC voltage Vac, the conductive time of the bidirectional switch 2 can be adjusted.

[0061] Therefore, when comparing this embodiment with the above-mentioned comparative example, the two differ in the following points 1 and 2.

[0062] [Difference 1] As indicated by [X] in FIG. 3, the present embodiment differs from the comparative example in that there is a period (second period T2) during which the bidirectional switch 2 is in a bidirectional on state, whereas there is no period in which the bidirectional switch 2 is in a bidirectional on state in the comparative example.

[0063] That is, in the comparative example, the bidirectional switch 2 is in a unidirectional on state (forward on state) to establish conduction between the pair of input terminals 11, 12, whereas in this embodiment, the bidirectional switch 2 is in a bidirectional on state to establish conduction between the pair of input terminals 11, 12. In this manner, in the dimmer 1 of this embodiment, the bidirectional switch 2 is in a bidirectional on state when conduction is established between the pair of input terminals 11, 12, so that the conduction loss in the bidirectional switch 2 can be kept small compared to the comparative example in which the bidirectional switch 2 is in a unidirectional on state.

[0064] [Difference 2] As indicated by [Y] in FIG. 3, before and after the zero-crossing points of the AC voltage Vac, there are periods (first period T1, fourth period T4) in which the bidirectional switch 2 is in a bidirectional off state in this embodiment, whereas in the comparative example, no such periods exist.

[0065] That is, in the comparative example, the pair of input terminals 11 and 12 are conductive during the period Ta1 from the zero crossing point of the AC voltage Vac to the middle of the half cycle, so that the opportunity to supply power from the AC power source 8 to the power source unit 5 is ensured only in the latter half of the half cycle. However, depending on the type of load 7, such as the load 7 that employs a capacitor input type lighting circuit, there are cases where no current flows through the load 7 in the latter half of the half cycle of the AC voltage Vac. Therefore, in the comparative example, a sufficient current cannot be flowed through the power source unit 5 during the period when the pair of input terminals 11 and 12 are not conductive, and it is possible that the supply of power from the AC power source 8 to the power source unit 5 cannot be sufficiently ensured. As a result, in the comparative example, it is possible that the supply of control power from the power source unit 5 to the control unit 6 cannot be maintained.

[0066] In contrast, the dimmer 1 of this embodiment keeps the bidirectional switch 2 in a bidirectional off state during the period (first period T1) from the start point (zero cross point) t0 of the half cycle to the first time point t1, and can therefore use this period to supply power to the power supply unit 5. Although the dimmer 1 of this embodiment basically employs reverse phase control, it provides a period (first period T1) during which the bidirectional switch 2 is non-conductive during the first half of the half cycle of the AC voltage Vac, thereby ensuring an opportunity for power supply from the AC power source 8 to the power supply unit 5 during the first half of the half cycle. Therefore, the dimmer 1 of this embodiment can maintain power supply from the power supply unit 5 to the control unit 6 in response to more types of loads 7 than the comparative example.

[0067] Furthermore, since the dimmer 1 keeps the bidirectional switch 2 in the bidirectional off state also during the period from the third time point t3 to the end point t4 of the half cycle (the fourth period T4), this period can also be used to supply power to the power supply unit 5. In other words, by providing the period (the fourth period T4) in which the bidirectional switch 2 is non-conductive also during the second half of the half cycle, the dimmer 1 can ensure an opportunity for power supply from the AC power supply 8 to the power supply unit 5 also during the second half of the half cycle.

[0068] (1.5) Advantages In addition to the reverse phase control method (trailing edge method), the control method for the dimmer device includes the positive phase control method (leading edge method) in which a pair of input terminals 11, 12 are conductive in the period from the middle of a half cycle of the AC voltage Vac to the zero cross point. The reverse phase control method starts supplying power to the load 7 equipped with an LED element as a light source from the zero cross point, so it is possible to minimize distortion of the current waveform at the start of power supply. This has the advantage of increasing the number of loads 7 (number of lights) that can be connected to the dimmer device and suppressing the generation of humming noise.

[0069] The dimmer 1 of this embodiment basically employs an inverse phase control method, but provides an opportunity for power supply from the AC power source 8 to the power supply unit 5 in the first half of the half cycle of the AC voltage Vac. Therefore, power supply to the load 7 starts at the first time point t1 when the first time has elapsed from the zero cross point, so there is a possibility that the current waveform distortion will be larger than in the inverse phase control method as in the comparative example. However, since the absolute value of the AC voltage Vac at the first time point t1 is not so large, the effect of the current waveform distortion is negligibly small. On the other hand, there is an advantage that the control power supply required for the operation of the control unit 6 can be reliably secured, allowing stable operation.

[0070] Furthermore, in the dimming device 1 of the present embodiment, the bidirectional switch 2 is in the reverse on state during the period from the second time point t2 to the third time point t3 (third period T3), so that erroneous detection by the phase detection unit 3 can be reduced. That is, depending on the load 7, the absolute value of the voltage across the load 7 may exceed the absolute value of the AC voltage Vac, and as a result, a voltage of the opposite polarity to the AC voltage Vac (hereinafter referred to as the "reverse polarity voltage") may be applied to the pair of input terminals 11, 12. For example, in the case of a load 7 in which the voltage across both ends is unlikely to decrease, such as a load 7 provided with a buffer capacitor with a relatively large capacity, such a reverse polarity voltage is likely to occur. When a reverse polarity voltage occurs, the phase detection unit 3 may erroneously detect a zero cross point at a point other than the zero cross point of the AC voltage Vac. There are also loads 7 in which a reverse polarity voltage may or may not occur depending on the dimming level, and in such loads 7, the zero cross point changes suddenly when the dimming level changes. In the third period T3, the bidirectional switch 2 is in the reverse ON state, which suppresses the occurrence of such a reverse polarity voltage, thereby reducing erroneous detection by the phase detection unit 3 caused by the reverse polarity voltage. Of course, even during the period in which the bidirectional switch 2 is in the reverse ON state (third period T3), there is no conduction between the pair of input terminals 11, 12. Therefore, by setting the interruption signal to an “ON” signal, this period can be used to supply power to the power supply unit 5.

[0071] The light control device 1 can maintain the power supply from the power supply unit 5 to the control unit 6, and thus can prevent abnormal operation of the load 7, such as blinking or flickering.

[0072] In controlling the bidirectional switch 2 in this embodiment, it is possible to control it to a "forward on state" instead of the "bidirectional on state", and conversely, it is also possible to control it to a "bidirectional on state" instead of the "forward on state". It is also possible to control it to a "reverse on state" instead of the "bidirectional off state", and it is also possible to control it to a "bidirectional off state" instead of the "reverse on state". In other words, it is sufficient if the bidirectional switch 2 does not change between the on state or the off state.

[0073] As in the present embodiment, the bidirectional switch 2 is preferably configured to be switchable between a bidirectional off state in which a bidirectional current is blocked, a bidirectional on state in which a bidirectional current is passed, and a unidirectional on state in which a unidirectional current is passed between the input terminals 11 and 12. In this case, the control unit 6 is preferably configured to control the bidirectional switch 2 so that the bidirectional switch 2 is in a reverse on state from the second time point t2 to a third time point t3 between the second time point t2 and the end point of the half cycle. The "reverse on state" is a unidirectional on state in which the bidirectional switch 2 passes a current from the input terminal on the low potential side of the AC power supply 8 to the input terminal on the high potential side of the input terminals 11 and 12. With this configuration, the generation of a reverse polarity voltage is suppressed from the second time point t2 to the third time point t3, so that erroneous detection by the phase detection unit 3 caused by the reverse polarity voltage can be reduced.

[0074] Moreover, as in this embodiment, it is preferable that the power supply unit 5 has a capacitive element C1. According to this configuration, the power supply unit 5 can store the power supplied from the AC power supply 8 in the period when the input terminals 11 and 12 are not conductive, in the capacitive element C1. Therefore, even in the period when the input terminals 11 and 12 are conductive, the power supply unit 5 can secure the control power supply for the control unit 6. However, it is not essential for the dimmer 1 that the power supply unit 5 has the capacitive element C1, and the capacitive element C1 may be omitted as appropriate.

[0075] Also, as in this embodiment, it is preferable that the first time period is a fixed time period. With this configuration, the control unit 6 controls the bidirectional switch 2 to the bidirectional off state during the period (first period T1) from the start point (zero crossing point) t0 of the half cycle until the fixed first time period has elapsed. Therefore, the processing of the control unit 6 is simpler than when the length of the first time period varies.

[0076] Although the processing by the control unit 6 becomes complicated, it is also possible to make the length of the first time different between the first period T1 in the positive half cycle and the first period T1 in the negative half cycle.

[0077] As in this embodiment, the phase detection unit 3 is preferably configured to output a detection signal when it detects a zero-cross point of the AC voltage Vac. In this case, the dimmer 1 preferably further includes a mask unit 61 that invalidates the detection signal for a certain length of mask time when it receives a detection signal from the phase detection unit 3. The mask unit 61 in this embodiment is not an essential component of the dimmer 1, and the mask unit 61 may be omitted as appropriate.

[0078] Moreover, as in this embodiment, it is preferable that the dimmer 1 further includes a stop unit 13 that stops the generation of control power in the power supply unit 5 during the stop period. The stop period is a period that is set excluding at least the period during which the bidirectional switch 2 is in an off state. The stop unit 13 in this embodiment is not an essential component of the dimmer 1, and the stop unit 13 may be omitted as appropriate.

[0079] Moreover, as in this embodiment, the bidirectional switch 2 preferably includes switch elements Q1, Q2 electrically connected in series between a pair of input terminals 11, 12.

[0080] (1.6) Variations (1.6.1) Variation 1 4, a light control device 1A according to Modification 1 of Embodiment 1 differs from the light control device 1 of Embodiment 1 in a portion corresponding to a bidirectional switch 2. Hereinafter, common reference symbols are used for configurations similar to those of Embodiment 1, and descriptions thereof will be omitted as appropriate.

[0081] In this modification, the bidirectional switch 2A includes a switch element Q3 with a double gate structure. The switch element Q3 is a semiconductor element with a double gate (dual gate) structure using a wide band gap semiconductor material such as GaN (gallium nitride). The bidirectional switch 2A further includes a pair of diodes D3 and D4 connected in so-called anti-series between the input terminals 11 and 12. The cathode of the diode D3 is connected to the input terminal 11, and the cathode of the diode D4 is connected to the input terminal 12. The anodes of both diodes D3 and D4 are electrically connected to the ground of the power supply unit 5. In this modification, the pair of diodes D3 and D4, together with the pair of diodes D1 and D2, form a diode bridge.

[0082] According to the configuration of this modified example, the bidirectional switch 2A can further reduce the conduction loss compared to the bidirectional switch 2.

[0083] (1.6.2) Variation 2 A dimming device 1B according to Modification 2 of the first embodiment differs from the dimming device 1 of the first embodiment in that a control unit 6B is configured to estimate a zero-crossing point of the AC voltage Vac more than a half cycle ahead based on a detection signal of one zero-crossing point, as shown in Fig. 5. The circuit configuration of the dimming device 1B is the same as that of the dimming device 1 of the first embodiment. Hereinafter, the same configurations as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0084] As in the first embodiment, the phase detector 3 is configured to output a detection signal when it detects a zero-cross point of the AC voltage Vac.

[0085] In this modification, the control unit 6B estimates a zero cross point that is more than a half cycle ahead of the AC voltage Vac as a virtual zero cross point every time it receives a detection signal from the phase detection unit 3 based on the frequency of the AC voltage Vac, and generates a virtual signal at the timing of the virtual zero cross point. Specifically, as shown in FIG. 6, the control unit 6B generates a first virtual signal Si1 when a waiting time Tzc equivalent to one cycle of the AC voltage Vac has elapsed since the first detection signal ZC1 has been received. Similarly, the control unit 6B generates a second virtual signal Si2 when a waiting time Tzc equivalent to one cycle of the AC voltage Vac has elapsed since the second detection signal ZC2 has been received. Here, the waiting time Tzc is set to be slightly longer than one cycle of the AC voltage Vac so that the first virtual signal Si1 is not generated before the next first detection signal ZC1. Also, the waiting time Tzc is set to be slightly longer than one cycle of the AC voltage Vac so that the second virtual signal Si2 is not generated before the next second detection signal ZC2.

[0086] Then, the control unit 6B uses the logical sum of the first detection signal ZC1 and the first virtual signal Si1 as a trigger signal that determines the timing of control of the bidirectional switch 2. Similarly, the control unit 6B uses the logical sum of the second detection signal ZC2 and the second virtual signal Si2 as a trigger signal that determines the timing of control of the bidirectional switch 2. Therefore, even if the phase detection unit 3 fails to detect a zero-crossing point, the control unit 6B can determine the timing of control of the bidirectional switch 2 by using a virtual signal generated at a virtual zero-crossing point as a trigger signal instead of the detection signal from the phase detection unit 3.

[0087] The control unit 6B may be configured to estimate the virtual zero-crossing point two or more times for one zero-crossing point detection signal. In this case, the control unit 6B generates a virtual signal every time the standby time Tzc has elapsed since the detection signal was received. Here, the length of the standby time Tzc may be changed so that the first standby time Tzc is slightly longer than one cycle of the AC voltage Vac, and the second and subsequent standby times Tzc are approximately the same length as one cycle of the AC voltage Vac.

[0088] Furthermore, the waiting time Tzc for generating the virtual signal may be set based on a half cycle of the AC voltage Vac, and may be set based on one cycle, a half cycle, three times the half cycle (i.e., 1.5 cycles), four times the half cycle (i.e., two cycles) or more. When the waiting time Tzc is set based on an odd multiple of a half cycle, the control unit 6B generates the second virtual signal Si2 when the waiting time Tzc has elapsed based on the first detection signal ZC1. In this case, the control unit 6B generates the first virtual signal Si1 when the waiting time Tzc has elapsed based on the second detection signal ZC2. Therefore, the control unit 6B may be configured to generate the first virtual signal Si1 and the second virtual signal Si2 from only one of the first detection signal ZC1 and the second detection signal ZC2.

[0089] According to the configuration of this modified example, even if the phase detection unit 3 cannot detect the zero-cross point due to the influence of accidental noise or the like, or even if a shift in the zero-cross point occurs due to an instantaneous drop in the AC voltage Vac, the control unit 6B performs stable inverse phase control in synchronization with the period of the AC voltage Vac.

[0090] (1.6.3) Other Modifications Below, modifications of the first embodiment other than the above-mentioned modifications 1 and 2 will be listed.

[0091] The light control devices of the first embodiment and the first and second modifications described above are not limited to loads 7 using LED elements as light sources, but are applicable to light sources that have a capacitor input type circuit, have high impedance, and are turned on with a small current. An example of this type of light source is an organic EL (Electroluminescence) element. The light control devices are also applicable to loads 7 that are various light sources, such as discharge lamps.

[0092] Furthermore, the switch driving section 9 is not an essential component of the light control device 1 and may be omitted as appropriate. When the switch driving section 9 is omitted, the control section 6 drives the bidirectional switch 2 directly.

[0093] The mask unit 61 may have any configuration as long as it can invalidate the detection signal over a certain length of mask time, and is not limited to being provided integrally with the control unit 6. That is, the mask unit 61 may be provided integrally with, for example, the phase detection unit 3. In this case, the mask unit 61 can invalidate the detection signal by stopping the operation of the phase detection unit 3 over the mask period. The mask unit 61 may also be provided separately from the control unit 6 and the phase detection unit 3.

[0094] Furthermore, the masking time may be any time that is preset based on a half cycle of the AC voltage Vac, and is not limited to a time slightly shorter than twice the half cycle (i.e., one cycle) as exemplified in the first embodiment. For example, the masking time may be a time slightly shorter than the half cycle, or a time slightly shorter than three times the half cycle (i.e., 1.5 cycles). The masking time may also be set based on four times the half cycle (i.e., two cycles) or more.

[0095] Moreover, each of the switch elements Q1 and Q2 constituting the bidirectional switch 2 is not limited to an enhancement-type n-channel MOSFET, but may be, for example, an IGBT (Insulated Gate Bipolar Transistor). Furthermore, in the bidirectional switch 2, the rectifying element (diode) for realizing the unidirectional on-state is not limited to the parasitic diode of the switch elements Q1 and Q2, but may be an external diode as in Modification 1. The diode may be built into the same package as each of the switch elements Q1 and Q2.

[0096] In addition, the first time may be a fixed length of time, and the length can be set appropriately. For example, if the first time period T1 is the sum of the period from the start point (zero cross point) t0 of the half cycle to the detection point and the period from the detection point until a fixed delay time has elapsed, the delay time is not limited to 300 μs and can be set appropriately within the range of 0 μs to 500 μs.

[0097] In addition, the third point t3 may be located just before the end point (zero cross point) t4 of the half cycle, and the length from the third point t3 to the end point t4 of the half cycle can be set appropriately. For example, if the time length from the detection point to the third point t3 is shorter than the half cycle by a certain specified time, the specified time is not limited to 300 μs, but is set appropriately in the range of 100 μs to 500 μs.

[0098] Furthermore, the stop period during which the stop unit 13 electrically disconnects the pair of input terminals 11, 12 from the power supply unit 5 may be any period set excluding at least the periods during which the bidirectional switch 2 is in a bidirectional off state (the first period T1 and the fourth period T4). Therefore, the stop period is not limited to a period starting at a time point between the first time point t1 and the second time point t2 and ending at the third time point t3 as in the first embodiment, but may start at the first time point t1 and end before the third time point t3, for example.

[0099] Furthermore, stopping unit 13 may be configured to stop the generation of the control power supply in power supply unit 5 during the stop period. Therefore, stopping unit 13 is not limited to a configuration that stops the generation of the control power supply in power supply unit 5 by electrically disconnecting at least one of a pair of input terminals 11, 12 and power supply unit 5, or by controlling a semiconductor switch element included in power supply unit 5. For example, stopping unit 13 may be configured to stop the generation of the control power supply in power supply unit 5 by increasing the input impedance of power supply unit 5 by stopping the output (output of the control power supply) of power supply unit 5.

[0100] In this embodiment, the diodes D1 and D2 are not essential components of the light control device 1, and the diodes D1 and D2 may be omitted as appropriate.

[0101] (Embodiment 2) The light control device 1C of this embodiment differs from the light control device 1 of the first embodiment in that it further includes a voltage detection unit 53 that detects the voltage of the control power supply (the voltage of the capacitive element C1) as shown in Fig. 7. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0102] In this embodiment, the first time is not a fixed time length, but is a time length from the start point (zero cross point) t0 of a half cycle of the AC voltage Vac until the voltage detected by the voltage detection unit 53 (the voltage of the capacitive element C1) reaches a predetermined threshold value. That is, the first time in this embodiment is not a fixed time length, but a variable time length that changes according to the detection value of the voltage detection unit 53.

[0103] Specifically, the voltage detection unit 53 is provided in the power supply unit 5C. The voltage detection unit 53 detects the voltage across the capacitive element C1 of the power supply unit 5C and outputs the detection value to the control unit 6C. After receiving a detection signal from the phase detection unit 3, the control unit 6C compares the detection value of the voltage detection unit 53 with a predetermined threshold, and determines that the first time has elapsed (i.e., the first time point t1) when the detection value reaches the threshold. Here, the threshold is set to the voltage across the capacitive element C1 when the capacitive element C1 is charged to an extent that the operation of the control unit 6 can be ensured at least until the end point (zero cross point) t4 of the half cycle of the AC voltage Vac.

[0104] As described above, the light control device 1C of this embodiment further includes a voltage detection unit 53 that detects the voltage of the control power supply, and the first time is the time from the start of the half cycle until the voltage detected by the voltage detection unit 53 reaches a predetermined threshold. According to this embodiment, the control unit 6 can put the bidirectional switch 2 into a bidirectional ON state at the time when the capacitive element C1 is charged to an extent that the control power supply necessary for the operation of the control unit 6 can be secured. Therefore, the light control device 1C of this embodiment can shorten the time from the start point (zero cross point) t0 of the half cycle of the AC voltage Vac to the time when the input terminals 11 and 12 are conductive as much as possible while reliably securing the control power supply necessary for the operation of the control unit 6. The capacitive element C1 may be a parasitic capacitance, in which case there is no separate capacitive element.

[0105] Other configurations and functions are the same as those of embodiment 1. The configuration of this embodiment can be applied in combination with each of the configurations described in embodiment 1 (including the modified examples).

[0106] (Other embodiments) In the above-described first embodiment (including the modified example) and second embodiment, the power supply from the AC power supply 8 to the power supply unit 5 is ensured over the period before and after (the first period T1 and the fourth period T4) the start point (zero cross point) t0 of the half cycle of the AC voltage Vac, but this is not limited to the above.

[0107] The power supply from the AC power source 8 to the power supply unit 5 may be ensured for a certain time only after the start point (zero cross point) t0 of the half cycle of the AC voltage Vac (first period T1). Alternatively, the power supply from the AC power source 8 to the power supply unit 5 may be ensured for a certain time only before the start point (zero cross point) t0 of the half cycle of the AC voltage Vac (fourth period T4). Even in this case, the first period T1 or the fourth period T4 is set by prioritizing the assurance of the power supply from the AC power source 8 to the power supply unit 5, so that the second period T2 for supplying power to the load 7 according to the dimming level input to the input unit 4 may not be set. For example, this is the case when the user operates the operation unit to maximize the light output of the load 7.

[0108] By setting the above-mentioned certain time period so that the power supply from the AC power source 8 to the power source unit 5 can be sufficiently performed, it is possible to suppress distortion of the current waveform and ensure stable operation of the control unit 6. [Explanation of symbols]

[0109] 1,1A,1B,1C dimmer 2,2A two-way switch (opening / closing part) 3 Phase detection section 4 Input section (setting section) 5,5C power supply section 6,6B,6C Control section 7. Load 8 AC power supply 11 Input terminal (terminal) 12 Input terminal (terminal) 13 Stop part 53 Voltage detection section 61 Mask section C1 Capacitive element Q1 Switch element Q2 Switch element Q3 Switch element t0 Start of half cycle (zero crossing point) t1 Time 1 t2 Time 2 t3 Third time point t4 End of half cycle (zero crossing point) Vac AC voltage ZC1 First detection signal ZC2 Second detection signal

Claims

1. A pair of input terminals electrically connected between the load and the AC power source; a bidirectional switch including two controllable semiconductor switches that can switch between blocking and passing a bidirectional current between the pair of input terminals; an input section for inputting a dimming level; a control unit that controls the bidirectional switch in response to the dimming level; a control power supply unit that receives power from the AC power supply and generates power for the control unit; The control unit is during a half cycle of the AC voltage of the AC power supply, controlling the bidirectional switch to an off state by using both control signals of the two semiconductor switches as a first signal in response to the dimming level; After controlling the bidirectional switch to the off state, controlling the bidirectional switch to an on state by using both control signals of the two semiconductor switches as second signals; When the bidirectional switch is in the off state, control is performed so that power is supplied from the AC power supply to the control power supply unit. Dimmer.

2. the control unit controls the bidirectional switch to be in the on state so as to stop the supply of power from the AC power source to the control power source unit. The light control device according to claim 1 .

3. an opening / closing unit connected between the pair of input terminals and the control power supply unit and capable of supplying or cutting off power from the AC power supply to the control power supply unit; the control unit controls the opening / closing unit to supply power from the AC power source to the control power source unit when the bidirectional switch is in the off state. The light control device according to claim 1 or 2.

4. an opening / closing unit connected between the pair of input terminals and the control power supply unit and capable of supplying or cutting off power from the AC power supply to the control power supply unit; the control unit controls the opening / closing unit to cut off the supply of power from the AC power source to the control power source unit when the bidirectional switch is in the on state. The light control device according to any one of claims 1 to 3.

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