CN108243538B

CN108243538B - Load control device

Info

Publication number: CN108243538B
Application number: CN201711446815.2A
Authority: CN
Inventors: 三宅智裕; 工藤弘行; 斋藤裕
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2016-12-27
Filing date: 2017-12-27
Publication date: 2020-12-29
Anticipated expiration: 2037-12-27
Also published as: TW201824950A; JP2018106564A; TWI658749B; CN108243538A; JP6830204B2

Abstract

The present invention relates to a load control device capable of supporting a wider variety of loads. The load control device includes a bidirectional switch, a phase detection unit, a switching power supply, and a stop unit. The bidirectional switch is electrically connected in series with a load with respect to an ac power supply, and performs phase control of an ac voltage (Vac) supplied to the load. The phase detection unit detects the phase of the alternating voltage (Vac). The switching power supply is electrically connected in parallel to the bidirectional switch, and performs a conversion operation of converting a drive voltage (Vc1), which is a dc voltage generated by the supply of electric power from the ac power supply, into a control voltage (Vc2) by a switching operation of the switching element. The stop unit electrically separates the switching power supply from the AC power supply or stops the switching operation of the switching power supply during an exclusion period (T0) including a detection timing at which the phase detection unit detects the phase.

Description

Load control device

Technical Field

The present invention relates generally to a load control device, and more particularly, to a load control device that performs phase control of an ac voltage supplied to a load.

Background

Conventionally, a dimming device that dims a lighting load is known (for example, document 1: JP 2013-149498A).

The light control device described in document 1 includes: a pair of terminals; a control circuit section; a switching power supply for supplying a control power to the control circuit unit; and a dimming operation unit for setting a dimming level of the lighting load.

Between the pair of terminals, a control circuit unit and a switching power supply are connected in parallel, respectively. Further, a series circuit of an ac power source and a lighting load is connected between the pair of terminals. The lighting load includes a plurality of LED (Light Emitting Diode) elements and a power supply circuit for lighting the LED elements. The power supply circuit includes a smoothing circuit including a diode and an electrolytic capacitor.

The control circuit unit includes: a switching unit for performing phase control on an alternating voltage supplied to the lighting load; a switch driving unit for driving the switch unit; and a control unit for controlling the switch drive unit and the switching power supply.

The switching power supply is connected in parallel with the switching section. The switching power supply converts alternating voltage of an alternating current power supply into a control power supply. The switching power supply includes an electrolytic capacitor for storing a control power supply.

The control power is supplied from the switching power supply to the control unit through the electrolytic capacitor. The control unit is provided with a microcomputer. The microcomputer performs the following phase inversion control: the power supply to the lighting load is cut off halfway in each half cycle of the alternating current voltage in accordance with the dimming level set by the dimming operation unit.

Disclosure of Invention

Problems to be solved by the invention

In addition, a load control device such as a dimmer device can be electrically connected to various loads such as various lighting loads. Therefore, depending on the load connected to the load control device, the load control device or the load may perform an abnormal operation.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a load control device capable of supporting a wider variety of loads.

Means for solving the problems

A load control device according to an aspect of the present invention includes a bidirectional switch, a phase detection unit, a switching power supply, and a stop unit. The bidirectional switch is electrically connected in series with a load with respect to an alternating current power supply, and performs phase control of an alternating current voltage supplied to the load. The phase detection unit detects a phase of the alternating voltage. The switching power supply is electrically connected in parallel to the bidirectional switch, and performs a conversion operation of converting a direct-current voltage generated by the power supplied from the alternating-current power supply into a control voltage by a switching operation of a switching element. The stop unit electrically separates the switching power supply from the ac power supply or stops the switching operation of the switching power supply during an exclusion period including a detection timing at which the phase detection unit detects the phase.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention has the advantage of being able to support a wider variety of loads.

Drawings

Fig. 1 is a schematic circuit diagram of a load control device according to embodiment 1 of the present invention.

Fig. 2 is a timing chart showing the operation of the load control device as described above.

Fig. 3 is a timing chart showing an operation in the case where the electric energy stored in the capacitive element is insufficient in the load control device as described above.

Fig. 4 is a timing chart showing an operation of the load control device according to modification 1 of embodiment 1 of the present invention.

Fig. 5 is a timing chart showing the operation of the load control device according to embodiment 2 of the present invention.

Fig. 6 is a timing chart showing the operation of the load control device according to embodiment 3 of the present invention.

Fig. 7 is a timing chart showing the operation of the load control device according to embodiment 4 of the present invention.

Description of the reference numerals

1: a load control device; 2: a bi-directional switch; 3: a phase detection unit; 7: a load; 8: an alternating current power supply; 51: a step-down power supply; 52: a switching power supply; 53: a detection unit; 61: a control unit; 62: a stop portion; 63: a switching unit; c1: a capacitive element; t0: during the elimination period; t1: a first period; t2: a second period; t3: a third period; t4: a fourth period; vac: an alternating voltage; vc 1: a driving voltage (direct current voltage); vc 2: controlling the voltage; vth 1: and (4) a threshold value.

Detailed Description

The configuration described below is merely an example of the present invention, and the present invention is not limited to the following embodiments, and various modifications can be made in accordance with design and the like as long as the modifications do not depart from the technical idea of the present invention.

(embodiment mode 1)

(1) Summary of the invention

As shown in fig. 1, the load control device 1 according to the present embodiment includes a bidirectional switch 2 electrically connected in series to a load 7 with respect to an ac power supply 8. The load control device 1 performs phase control of an ac voltage Vac supplied from an ac power supply 8 to a load 7 by using a bidirectional switch 2. The "phase control" referred to herein means the following method: the alternating voltage Vac supplied (applied) to the load 7 is controlled by changing a phase angle (conduction angle) at which energization to the load 7 is started or ended every half cycle of the alternating voltage Vac. That is, the load control device 1 controls the load 7 such as an illumination load, a heater, or a fan by performing phase control on the ac voltage Vac supplied to the load 7.

In the present embodiment, a case will be described as an example where the load 7 is an illumination load including a plurality of LED elements and a power supply circuit for lighting the plurality of LED elements. That is, the load control device 1 constitutes a dimming device that adjusts the magnitude of the light output of the load 7 constituted by the illumination load by phase control. The ac power supply 8 is, for example, a single-phase 100 [ V ] or 60 [ Hz ] commercial power supply. The load control device 1 can be applied to a wall switch or the like as an example.

Here, the load control device 1 according to the present embodiment is a two-wire type, and is connected between the ac power supply 8 and the load 7 such that the bidirectional switch 2 is electrically connected in series with the load 7 with respect to the ac power supply 8. In other words, two wires, i.e., a wire connected to the ac power supply 8 and a wire connected to the load 7, are connected to the load control device 1, and the bidirectional switch 2 is inserted between the two wires. Therefore, if the bidirectional switch 2 is in the conductive state, the voltage from the ac power supply 8 is applied to the load 7 and the power is supplied to the load 7, and if the bidirectional switch 2 is in the non-conductive state, the voltage from the ac power supply 8 is applied to the load control device 1 and the power supply to the load 7 is stopped. The load control device 1 receives the operation electric power of the load control device 1 itself from the ac power supply 8 through the two electric wires, and controls the bidirectional switch 2. That is, since the load control device 1 generates its own operation electric power by the power supply unit 5 described later when the bidirectional switch 2 is in the non-conductive state, the two-wire load control device 1 can be realized.

(2) Structure of the product

As shown in fig. 1, the load control device 1 according to the present embodiment includes a pair of

input terminals

11 and 12, a bidirectional switch 2, a phase detection unit 3, an interface unit 4, a power supply unit 5, a control circuit 6, a switch drive unit 9, a detection unit 53, and diodes D1 and D2. The control circuit 6 includes a control unit 61, a stop unit 62, and a switching unit 63. The "input terminal" referred to herein may not be a member (terminal) for connecting an electric wire or the like, and may be, for example, a lead wire of an electronic component or a part of a conductor included in a circuit board.

The bidirectional switch 2 includes, for example, two elements of a first switching element Q1 and a second switching element Q2 electrically connected in series between the

input terminals

11, 12. For example, the switching elements Q1 and Q2 are Semiconductor switching elements each formed of an enhancement-mode n-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor).

The switching elements Q1 and Q2 are connected in a so-called anti-series connection between the

input terminals

11 and 12. That is, the sources of the switching elements Q1 and Q2 are connected to each other. The drain of the switching element Q1 is connected to the input terminal 11, and the drain of the switching element Q2 is connected to the input terminal 12. The sources of the two switching elements Q1 and Q2 are connected to the ground terminal of the power supply unit 5. The ground of the power supply unit 5 is a reference potential for the internal circuit of the load control device 1.

The bidirectional switch 2 can switch four states by a combination of on and off of the switching elements Q1 and Q2. The four states include a bidirectional off state in which both the switching elements Q1, Q2 are off, a bidirectional on state in which both the switching elements Q1, Q2 are on, and two unidirectional on states in which only one of the switching elements Q1, Q2 is on. In the unidirectional on state, the pair of

input terminals

11 and 12 are unidirectionally conducted from the on one of the switching elements Q1 and Q2 through the parasitic diode of the off one of the switching elements. For example, when the switching element Q1 is on and the switching element Q2 is off, a first unidirectional on state is established in which a current flows from the input terminal 11 to the input terminal 12. When switching element Q2 is on and switching element Q1 is off, the second unidirectional on state is established in which current flows from input terminal 12 to input terminal 11. Therefore, when the ac voltage Vac is applied from the ac power supply 8 to between the

input terminals

11 and 12, the first unidirectional on state is the "forward on state" and the second unidirectional on state is the "reverse on state" in the half cycle in which the ac voltage Vac is positive, that is, the input terminal 11 is on the high potential side and the input terminal 12 is on the low potential side. On the other hand, in a half cycle in which the ac voltage Vac has a negative polarity, that is, the input terminal 11 is on the low potential side and the input terminal 12 is on the high potential side, the second unidirectional on state is the "forward on state" and the first unidirectional on state is the "reverse on state".

Here, two states of "bidirectional on state" and "forward on state" of the bidirectional switch 2 are on states, and two states of "bidirectional off state" and "reverse on state" are off states.

The phase detection unit 3 detects the phase of the ac voltage Vac applied between the

input terminals

11 and 12. The "phase" referred to herein includes a zero-cross point of the ac voltage Vac, and the phase detection unit 3 is configured to output a detection signal to the control circuit 6 when the zero-cross point of the ac voltage Vac is detected. The phase detector 3 includes a diode D31, a first detector 31, a diode D32, and a second detector 32. The first detection unit 31 is electrically connected to the input terminal 11 via a diode D31. The second detection unit 32 is electrically connected to the input terminal 12 via a diode D32. The first detection unit 31 detects a zero-crossing point when the alternating voltage Vac transitions from a negative half cycle to a positive half cycle. The second detection unit 32 detects a zero cross point when the alternating voltage Vac transitions from a positive half cycle to a negative half cycle.

That is, when detecting that the voltage at the high side of the input terminal 11 and the voltage at the low side of the input terminal 12 has shifted from a state smaller than a predetermined value to a state equal to or larger than a predetermined value, the first detector 31 determines that the voltage is a zero cross point, and outputs the first detection signal ZC1 to the control circuit 6. Similarly, when detecting that the voltage of the input terminal 11 on the low potential side and the voltage of the input terminal 12 on the high potential side has shifted from a state smaller than a predetermined value to a state equal to or larger than a predetermined value, the second detector 32 determines that the voltage is a zero cross point, and outputs a second detection signal ZC2 to the control circuit 6. The predetermined value is a value (absolute value) set to a value near 0 [ V ]. For example, the predetermined value of the first detector 31 is about several [ V ], and the predetermined value of the second detector 32 is about several [ V ]. Therefore, the detection point of the zero cross point detected by the first detection unit 31 and the second detection unit 32 is delayed a little time from the zero cross point (0 [ V ]) in a strict sense.

The interface unit 4 receives an input level for defining a phase angle (conduction angle) at which the ac voltage Vac starts or ends to be supplied to the load 7 every half cycle. That is, the input level defines the timing at which the bidirectional switch 2 is turned on or off in the half cycle of the ac voltage Vac. In the present embodiment, since the load control device 1 is a dimming device, the interface unit 4 receives an operation by a user and receives an input of a dimming level as an input level. The interface unit 4 outputs a dimming signal indicating a dimming level to the control circuit 6. The dimming signal is a numerical value or the like for specifying the magnitude of the light output of the load 7, and may include an "OFF level" for turning OFF the load 7. In the present embodiment, the interface unit 4 has a touch panel that receives a touch operation by a user, for example. The interface unit 4 may be any configuration as long as it outputs a signal indicating an input level (dimming level), and may be, for example, a variable resistor, a rotary switch, or the like. The interface unit may be a receiving unit that receives a signal from a communication terminal such as a remote controller or a smartphone.

In the present embodiment, the interface unit 4 further includes a display unit (indicator) for displaying the input level (dimming level) that is input. The interface unit 4 includes, for example, a display unit including a plurality of LED elements, and displays an input level by the number of LED elements turned on.

The control circuit 6 functions as a control unit 61, a stop unit 62, and a switching unit 63. The control unit 61 controls the bidirectional switch 2 based on the detection signal from the phase detection unit 3 and the dimming signal from the interface unit 4. The controller 61 controls the switching elements Q1 and Q2, respectively. Specifically, the controller 61 controls the switching element Q1 with the first control signal Sb1, and controls the switching element Q2 with the second control signal Sb 2. The stop unit 62 electrically disconnects the switching power supply 52, which will be described later, from the ac power supply 8 during the exclusion period, or stops the conversion operation of the switching power supply 52. The "exclusion period" referred to herein is a period including the detection timing of the phase detection unit 3 to detect the phase, and when the phase detection unit 3 detects the zero cross point, the exclusion period is a period including the zero cross point. The switching unit 63 switches the function of the stopping unit 62 between enabled and disabled. The stop unit 62 and the switching unit 63 are described in detail in the column of "(3.3) operation of the power supply unit".

The control circuit 6 includes, for example, a microcomputer as a main structure. The microcomputer realizes the function as the control circuit 6 by executing a program recorded in a memory of the microcomputer in a CPU (Central Processing Unit). The program may be recorded in advance in a memory of the microcomputer, may be provided by being recorded in a recording medium such as a memory card, or may be provided through an electric communication line. In other words, the program is a program for causing a computer (here, a microcomputer) to function as the control circuit 6.

The switch driving unit 9 includes a first driving unit 91 that drives (on/off controls) the switching element Q1, and a second driving unit 92 that drives (on/off controls) the switching element Q2. The first driver 91 receives the first control signal Sb1 from the control circuit 6 and applies a gate voltage to the switching element Q1. Thereby, the first driving unit 91 on/off-controls the switching element Q1. Similarly, the second driver 92 receives the second control signal Sb2 from the control circuit 6, and applies a gate voltage to the switching element Q2. Thus, the second driving unit 92 on/off-controls the switching element Q2. The first driving unit 91 generates a gate voltage with reference to the potential of the source of the switching element Q1. The same applies to the second driving unit 92.

The power supply unit 5 includes a step-down power supply 51 that generates drive power (electric energy) for operating the switch drive unit 9 and the like, and a switching power supply 52 that generates control power. The drive power is power for operating the switch drive unit 9 and the like. The control power is power for operating the interface unit 4, the control circuit 6, and the like. The power supply unit 5 performs the following generating operation: electric energy (driving power) is generated by the step-down power supply 51 by the supply power from the ac power supply 8. The electric energy (driving power) generated by the step-down power supply 51 is converted into control power by the switching power supply 52.

The power supply unit 5 is electrically connected to the input terminal 11 via a diode D1, and is electrically connected to the input terminal 12 via a diode D2. Thus, the ac voltage Vac applied between the

input terminals

11 and 12 is full-wave rectified by the diode bridge including the parasitic diodes of the diodes D1 and D2 and the switching elements Q1 and Q2, and supplied to the power supply unit 5. Therefore, when the bidirectional switch 2 is in the non-conduction state, the full-wave rectified ac voltage Vac (pulsating voltage output from the diode bridge) is applied to the power supply unit 5.

The step-down power supply 51 has a first circuit 511 and a capacitive element (capacitor) C1. The step-down power supply 51 is a series regulator type power supply circuit, and applies a full-wave rectified ac voltage Vac to step down and smooth the applied voltage, thereby generating a dc drive voltage Vc 1. That is, when the full-wave rectified ac voltage Vac is applied to the first circuit 511, the capacitive element C1 is charged, and the drive voltage Vc1 is generated across the capacitive element C1. The step-down power supply 51 supplies the electric energy stored in the capacitive element C1 to the switch driving unit 9 and the switching power supply 52 as driving power. The drive voltage Vc1 is, for example, 15 [ V ].

The switching power supply 52 has a second circuit 521 and a capacitive element (capacitor) C2. The switching power supply 52 is a switching DC-DC converter such as a step-down chopper circuit, and generates a DC control voltage Vc2 by applying a drive voltage Vc1 from the step-down power supply 51 to step down an applied DC voltage (drive voltage Vc 1). That is, when the driving voltage Vc1 is applied to the second circuit 521, the capacitive element C2 is charged, and the control voltage Vc2 is generated across the capacitive element C2. The second circuit 521 includes a switching element (semiconductor switch), and generates a control voltage Vc2 by stepping down the drive voltage Vc1 by a switching operation of the switching element. In short, the switching power supply 52 performs a conversion operation of converting the dc voltage generated by the electric power supplied from the ac power supply 8 into the control voltage Vc2 by the switching operation of the switching element. The control power generated by the switching operation of the switching power supply 52 is supplied to the interface unit 4, the control circuit 6, and the like. The control voltage Vc2 is, for example, 3.5 [ V ].

Therefore, during the switching operation of the switching power supply 52, electric power is supplied from the capacitive element C1 of the power supply unit 5 to the control circuit 6 (control unit 61) via the switching power supply 52. The control circuit 6 (control unit 61) operates using electric energy (control power) from the power supply unit 5.

The step-down power supply 51 and the switching power supply 52 are configured to be controllable by the control unit 61. In other words, the control unit 61 has a function of controlling the power supply unit 5. Thus, the control unit 61 controls whether or not the power supply unit 5 performs a generating operation of generating electric energy (driving power) to be stored in the capacitive element C1. The control unit 61 controls whether or not the power supply unit 5 performs a conversion operation for generating electric energy (control power) to be stored in the capacitive element C2.

In the present embodiment, the control unit 61 switches between a state in which the power supply unit 5 performs the generating operation and a state in which the generating operation of the power supply unit 5 is stopped by controlling the semiconductor switch included in the step-down power supply 51. Specifically, the control section 61 controls the semiconductor switch of the step-down power supply 51 by the first power supply signal Ss 1. The control unit 61 stops the operation of the first circuit 511 to increase the input impedance of the step-down power supply 51, thereby stopping the generation operation of the step-down power supply 51. When the generation operation of the step-down power supply 51 is stopped by the first power supply signal Ss1, the generation of the electric energy (driving power) in the power supply section 5 is stopped. The control unit 61 controls the switching element included in the switching power supply 52 to switch between a state in which the power supply unit 5 performs the conversion operation and a state in which the conversion operation of the power supply unit 5 is stopped. Specifically, the control section 61 controls the switching element of the switching power supply 52 by the second power supply signal Ss 2. When the switching operation of the switching power supply 52 is stopped, the generation of electric energy (control power) in the power supply unit 5 is stopped.

The detection unit 53 detects the magnitude of the electric energy stored in the capacitive element C1. In the present embodiment, the detection unit 53 is configured to detect the magnitude of the drive voltage Vc1, which is the voltage across the capacitive element C1. The detection unit 53 is, for example, a voltage dividing resistor connected between both ends of the capacitive element C1, and outputs a voltage corresponding to the drive voltage Vc1 as a detection value to the control circuit 6. That is, the detector 53 detects the voltage (the drive voltage Vc1) between both ends of the capacitive element C1, thereby directly detecting the magnitude of the electric energy stored in the capacitive element C1. Next, the detection value of the detection unit 53 is equal to the drive voltage Vc 1. However, the present invention is not limited to this configuration, and the detection unit 53 may be configured as follows: the magnitude of the electric energy stored in the capacitive element C1 is indirectly detected by detecting the control voltage Vc2, which is the voltage across the capacitive element C2.

The lighting circuit of the load 7 reads the dimming level from the waveform of the ac voltage Vac phase-controlled by the load control device 1, and changes the magnitude of the light output of the LED element. Here, the lighting circuit includes, as an example, a current securing circuit such as a bleeder circuit. Therefore, even when the bidirectional switch 2 of the load control device 1 is non-conductive, a current can flow to the load 7.

(3) Movement of

(3.1) Start action

First, a start operation at the start of energization of the load control device 1 according to the present embodiment will be described.

According to the load control device 1 configured as described above, when the ac power supply 8 is connected between the

input terminals

11 and 12 via the load 7, the ac voltage Vac applied from the ac power supply 8 to between the

input terminals

11 and 12 is rectified and supplied to the step-down power supply 51. The drive power generated by the step-down power supply 51 is supplied to the switch drive section 9 and to the switching power supply 52. When the control power generated by the switching power supply 52 is supplied to the control circuit 6 and the interface section 4, the control circuit 6 and the interface section 4 are started.

When the control circuit 6 is activated, the control circuit 6 determines the frequency of the ac power supply 8 based on the detection signal of the phase detection unit 3. Then, the control circuit 6 refers to a numerical table stored in advance in a memory according to the determined frequency, and sets parameters such as various times. Here, if the dimming level input to the interface unit 4 is the "OFF level", the control circuit 6 maintains the bidirectional switch 2 in the bidirectional OFF state, thereby maintaining the impedance between the pair of

input terminals

11, 12 in the high impedance state. Thereby, the load 7 maintains the extinguished state.

(3.2) load control action

Next, a load control operation of the load control device 1 according to the present embodiment will be described with reference to fig. 2. In fig. 2, the alternating-current voltage "Vac", the first detection signal "ZC 1", the second detection signal "ZC 2", the first control signal "Sb 1", the second control signal "Sb 2", the first power supply signal "Ss 1", and the drive voltage "Vc 1" are shown.

In the present embodiment, the first detection signal ZC1 is generated when the first detection signal ZC1 changes from the "H" Level (High Level: High Level) to the "L" Level (Low Level: Low Level). When the second detection signal ZC2 changes from the "H" level to the "L" level, a second detection signal ZC2 is generated. That is, the first detection signal ZC1 and the second detection signal ZC2 are signals that change from "H" level to "L" level when the phase (zero-cross point) is detected by the phase detector 3. The first power supply signal Ss1 and the drive voltage Vc1 are described in the column of "(3.3) control power generation operation".

The control unit 61 divides the 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, and controls the bidirectional switch 2. The "half cycle" referred to herein is a period between zero-crossing points of consecutive two times of the alternating voltage Vac. In the first period T1 and the fourth period T4, the control unit 61 sets the bidirectional switch 2 in a non-conductive state. In the second period T2, the control unit 61 turns on the bidirectional switch 2. In the third period T3, the control unit 61 sets the bidirectional switch 2 to the non-conductive state.

Next, the operations of the load control device 1 in the first period T1, the second period T2, the third period T3, and the fourth period T4 will be described in further detail.

First, the operation of the load control device 1 in a half cycle in which the ac voltage Vac has a positive polarity will be described. The load control device 1 detects a zero cross point of the ac voltage Vac as a reference of the phase control by the phase detection unit 3. When the ac voltage Vac has changed from the negative half cycle to the positive half cycle, the first detector 31 outputs a first detection signal ZC1 when the ac voltage Vac has reached a predetermined positive value "Vzc". The controller 61 sets the first time point t1 after the time point t11 at which the first detection signal ZC1 is generated, that is, after the detection timing of the phase (zero cross point) by the phase detector 3 is detected, and sets the first control signal Sb1 and the second control signal Sb2 to "ON" signals at the first time point t 1. In other words, in the example of fig. 2, the phase detector 3 detects the phase at time t11, and the controller 61 sets the bidirectional switch 2 to the bidirectional on state at the first time t1 after that. A period from the start point (zero crossing point) T0 of the half cycle of positive polarity to the first time point T1 is a first period T1. In the first period T1, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to OFF signals. Thus, in the first period T1, the switching elements Q1 and Q2 are both off, and the bidirectional switch 2 is in the bidirectional off state (non-conductive state). Therefore, during the first period T1, the power supply from the ac power supply 8 to the load 7 is interrupted.

The second time t2 is a time when an on time having a length corresponding to the dimming signal has elapsed from the detection timing (time t11) at which the phase (zero cross point) is detected by the phase detection unit 3. At a second time point t2, the controller 61 maintains the second control signal Sb2 as an "ON" signal and the first control signal Sb1 as an "OFF" signal. Thus, in the second period T2 from the first time point T1 to the second time point T2, both the switching elements Q1 and Q2 are turned on, and the bidirectional switch 2 is in the bidirectional on state (on state). Therefore, during the second period T2, power is supplied from the ac power supply 8 to the load 7 via the bidirectional switch 2.

The third time point t3 is a time point that is advanced by a fixed time (e.g., 300 [ mu ] s ] from the end point of the half cycle (zero crossing) t 4. That is, when the time point after the lapse of the time obtained by subtracting the first period T1 from the time of the half cycle from the detection timing (time point T11) at which the zero cross point is detected by the phase detection unit 3 is estimated as the end point T4, the third time point T3 is a time point before the fixed time of the end point T4. In the timing diagram of fig. 2, the diagram is: the third time point t3 coincides with the timing at which the ac voltage Vac reaches the positive predetermined value "Vzc" and the timing at which the ac voltage Vac reaches the negative predetermined value "-Vzc". However, the third time point t3 is actually determined regardless of the timing at which the ac voltage Vac crosses the positive predetermined value "Vzc" or the negative predetermined value "-Vzc".

At a third time point t3, the control circuit 6 makes the first control signal Sb1 and the second control signal Sb2 "OFF" signals. Thus, in the third period T3 from the second time point T2 to the third time point T3, only the switching element Q1 of the switching elements Q1 and Q2 is turned off, and the bidirectional switch 2 is in the reverse on state (non-conductive state). Therefore, during the third period T3, the power supply from the ac power supply 8 to the load 7 is interrupted.

During a fourth period T4 from the third time point T3 to the end point (zero-crossing point) T4 of the half cycle, both the switching elements Q1, Q2 are turned off, and the bidirectional switch 2 is in a bidirectional off state (non-conductive state).

The operation of the load control device 1 in the half cycle in which the ac voltage Vac has a negative polarity is substantially the same as that in the half cycle having a positive polarity.

In the negative half cycle, when the ac voltage Vac reaches the negative predetermined value "-Vzc", the second detector 32 outputs a second detection signal ZC 2. In the present embodiment, a period from the start point T0(T4) of the negative half cycle to the first time point T1 set after the generation time point of the second detection signal ZC2, that is, after the detection timing (time point T11) at which the phase detector 3 detects the phase (zero cross point), is the first period T1. The second time t2 is a time after the elapse of an on time corresponding to the dimming signal from the detection timing (time t11) at which the phase (zero cross point) is detected by the phase detection unit 3, and the third time t3 is a time advanced by a fixed time (for example, 300 μ s) from the end point t4(t0) of the half cycle.

In the first period T1, the controller 61 turns the first control signal Sb1 and the second control signal Sb2 OFF. Thereby, the bidirectional switch 2 is in the bidirectional off state (non-conductive state) in the first period T1. Then, at the first time point t1, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to "ON" signals. Thus, in the second period T2 from the first time point T1 to the second time point T2, both the switching elements Q1 and Q2 are turned on, and the bidirectional switch 2 is in the bidirectional on state (on state). Therefore, during the second period T2, power is supplied from the ac power supply 8 to the load 7 via the bidirectional switch 2.

At a second time point t2, the controller 61 maintains the first control signal Sb1 as an "ON" signal and the second control signal Sb2 as an "OFF" signal. At a third time point t3, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to "OFF" signals. Thus, in the third period T3 from the second time point T2 to the third time point T3, only the switching element Q2 of the switching elements Q1 and Q2 is turned off, and the bidirectional switch 2 is in the reverse on state (non-conductive state). Therefore, during the third period T3, the power supply from the ac power supply 8 to the load 7 is interrupted. During a fourth period T4 from the third time point T3 to the end point T4 of the half cycle, both the switching elements Q1, Q2 are turned off, and the bidirectional switch 2 is in a bidirectional off state (non-conductive state).

The load control device 1 of the present embodiment alternately repeats the above-described operation of the positive half cycle and the operation of the negative half cycle for each half cycle of the ac voltage Vac, thereby dimming the load 7. Here, since the "bidirectional on state" is a conductive state and the "reverse on state" is a non-conductive state, the bidirectional switch 2 is switched from the conductive state to the non-conductive state at the end of the second period, that is, at the second time point t 2. The end point of the second period (second time point t2) is defined according to the dimming level input to the interface unit 4. If the positive predetermined value "Vzc" and the negative predetermined value "-Vzc" are fixed values, the time from the start point t0 of the half cycle to the detection timing (time point t11) at which the phase detector 3 detects the phase (zero cross point) is a substantially fixed time.

Therefore, the length of the "variable time" which is a time obtained by adding the time from the start point T0 of the half cycle to the second time point T2, that is, the first period T1 and the second period T2 whose length varies according to the dimming level. In other words, the phase angle (conduction angle) at the second time point t2 at which the load 7 is energized at the end of each half cycle of the ac voltage Vac changes in accordance with the dimming level. That is, when the light output of the load 7 is small, the variable time is defined to be short (the phase angle is defined to be small), and when the light output of the load 7 is large, the variable time is defined to be long (the phase angle is defined to be large). Therefore, the load control device 1 can change the magnitude of the light output of the load 7 in accordance with the dimming level input to the interface unit 4.

In addition, in the periods (the first period T1, the third period T3, and the fourth period T4) other than the period (the second period T2) from the first time point T1 to the second time point T2 in the half cycle of the ac voltage Vac, the bidirectional switch 2 is in the non-conduction state (the reverse on state or the bidirectional off state). The load control device 1 can ensure the supply of power from the ac power supply 8 to the power supply unit 5 using the periods in which the bidirectional switch 2 is in the non-conductive state. The operation of the power supply unit 5 is described in detail in the column of "(3.3) operation of the power supply unit".

Here, the expression "from the time point a" means that the time point a is included. For example, "from a first point in time" means including the first point in time. On the other hand, the expression "to the time point a" means that the time point a is not included until immediately before the time point a. For example, "to the end of the half cycle" means not including the end of the half cycle until immediately before the end of the half cycle.

(3.3) operation of Power supply section

Next, the operation of the power supply unit 5 will be described with reference to fig. 2.

The control unit 61 divides the 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, and controls the power supply unit 5. In the first period T1 and the fourth period T4, the controller 61 causes the step-down power supply 51 to perform the generating operation. In the second period T2, the control unit 61 stops the generation operation of the step-down power supply 51. In the third period T3, the control unit 61 stops the generation operation of the step-down power supply 51. That is, the step-down power supply 51 performs the generating operation of generating the electric energy (driving power) by the power supplied from the ac power supply 8 only in the first period T1 and the fourth period T4 in the half cycle of the ac voltage Vac.

Specifically, the control unit 61 causes the power supply unit 5 to perform the generating operation by turning the first power supply signal Ss1 to the "ON" signal (for example, H level) only in the first period T1 and the fourth period T4 of the half cycle of the ac voltage Vac. The control unit 61 stops the generation operation of the power supply unit 5 by setting the first power supply signal Ss1 to the "OFF" signal (for example, L level) in the second period T2 and the third period T3. In short, while the first power supply signal Ss1 is the "ON" signal, the power supply unit 5 performs a generating operation for generating electric energy (drive power) by the step-down power supply 51. At this time, the switching power supply 52 of the power supply unit 5 performs a switching operation. On the other hand, while the first power supply signal Ss1 is the "OFF" signal, the power supply section 5 stops the generation of the electric energy (driving power) in the step-down power supply 51, thereby stopping the generation operation. The switching power supply 52 does not immediately stop the conversion operation when the first power supply signal Ss1 becomes the "OFF" signal, but continues the conversion operation by the electric charge accumulated in the capacitive element C1 while the first power supply signal Ss1 is the "ON" signal. That is, as long as sufficient electric energy (driving power) is accumulated in the capacitive element C1, the switching power supply 52 can continue the conversion operation even while the operation of generating electric energy (driving power) in the step-down power supply 51 is stopped.

However, in the load control device 1, the timing at which the first power signal Ss1 changes from the "OFF" signal to the "ON" signal does not necessarily coincide with the third time point t3 at which the first control signal Sb1 and the second control signal Sb2 change to the "OFF" signal. For example, the first power supply signal Ss1 may be turned to the "ON" signal at a timing earlier than the third time point t3, that is, at any timing between the second time point t2 and the third time point t 3. In this case, the timing at which the first power supply signal Ss1 changes from the "OFF" signal to the "ON" signal is at the boundary between the third period T3 and the fourth period T4. That is, since the bidirectional switch 2 is in the non-conductive state before and after the third time point T3, the first power supply signal Ss1 may be changed to the "ON" signal at a timing earlier than the third time point T3, and the fourth period T4 may be started.

By operating the power supply unit 5 as described above, the drive voltage Vc1 rises in the first period T1 and the fourth period T4 of the half cycle of the ac voltage Vac, and the drive voltage Vc1 falls in the second period T2 and the third period T3. Therefore, when looking at two consecutive half cycles, the driving voltage Vc1 rises from the third time point t3 of the first half cycle to the first time point t1 of the next half cycle (that is, the 2 nd half cycle).

During the switching operation of the switching power supply 52, the following may occur: the impedance of the power supply unit 5 varies due to the switching operation of the switching element, and a current flowing from the ac power supply 8 to the power supply unit 5 pulsates (ripple). That is, although a DC-DC converter of a switching operation system such as the switching power supply 52 has higher efficiency than a power supply circuit of a series regulator system, it is likely to be a source of noise. When the current flowing from the ac power supply 8 to the power supply section 5 pulsates (ripple), there are cases where: due to this influence, the phase detection unit 3 decreases the accuracy of detecting the phase of the ac voltage Vac. That is, since the phase detection unit 3 monitors a relatively small voltage of about several [ V ] to detect the zero-crossing point of the ac voltage Vac, there are cases where: even if the current fluctuates only slightly under the influence of noise generated by the switching power supply 52, the detection accuracy of the phase is degraded.

Therefore, as shown in fig. 2, in the load control device 1 according to the present embodiment, the stop unit 62 electrically disconnects the switching power supply 52 from the ac power supply 8 during the exclusion period T0 including the detection timing (time T11) when the phase detection unit 3 detects the phase. The stop unit 62 stops the operation of the first circuit 511 by, for example, the first power supply signal Ss1, thereby increasing the input impedance of the step-down power supply 51 and stopping the generation operation of the step-down power supply 51. When the generation operation of the step-down power supply 51 is stopped by the first power supply signal Ss1, the switching power supply 52 is electrically disconnected from the ac power supply 8.

That is, the switching power supply 52 is not always electrically connected to the ac power supply 8, and is electrically disconnected from the ac power supply 8 during the exclusion period T0. As shown in fig. 2, the exclusion period T0 is a period defined to include a detection timing at which the phase detector 3 detects the phase (zero cross point), that is, a time point T11 which is a generation time point of the first detection signal ZC1 or the second detection signal ZC 2. In the present embodiment, the start point T21 of the exclusion period T0 is set within the fourth period T4 (the period from T3 to T4), and the end point T22 of the exclusion period T0 is set within the first period T1 (the period from T0 to T1). That is, the exclusion period T0 is defined to span 2 periods of the fourth period T4 and the first period T1. More specifically, the end point T22 of the exclusion period T0 is set to a period (period from T11 to T1) after the detection timing (time point T11) at which the phase detector 3 detects the phase in the first period T1. Thus, the timing of detection of the phase by the phase detector 3 (time T11) is included in the exclusion period T0.

Specifically, the stopping unit 62 stops the operation of the first circuit 511 by the first power supply signal Ss1 in the exclusion period T0 in the half cycle of the ac voltage Vac, thereby increasing the input impedance of the step-down power supply 51 and stopping the generation operation of the step-down power supply 51. While the generation operation of the step-down power supply 51 is stopped by the first power supply signal Ss1, the switching power supply 52 is electrically disconnected from the ac power supply 8. That is, the stop unit 62 turns the first power signal Ss1 to the "OFF" signal during a period from a start point T21 set in the fourth period T4 (the period from T3 to T4) to an end point T22 set in the first period T1 (the period from T0 to T1). Thus, in the exclusion period T0 (the period from T21 to T22) of the fourth period T4 and the first period T1, the generation operation of the step-down power supply 51 is stopped, and the switching power supply 52 is electrically disconnected from the ac power supply 8.

Thus, in the exclusion period T0, the variation in the impedance of the power supply unit 5 due to the switching operation of the switching power supply 52 is suppressed, and the current flowing from the ac power supply 8 to the power supply unit 5 is less likely to generate a ripple (ripple). As a result, at the detection timing (time T11) included in the exclusion period T0, the decrease in the detection accuracy of the phase detector 3 is suppressed.

The end point T22 of the exclusion period T0 may coincide with the detection timing (time point T11) at which the phase detector 3 detects the phase. That is, since the switching operation of the switching power supply 52 does not affect the detection accuracy of the phase detection unit 3 as long as the phase detection unit 3 detects the phase, the exclusion period T0 may end at the detection timing when the phase detection unit 3 detects the phase.

Here, the switching power supply 52 does not stop the conversion operation immediately when it is electrically disconnected from the ac power supply 8, but continues the conversion operation by the electric charge accumulated in the capacitive element C1 while the first power supply signal Ss1 is the "ON" signal. That is, as long as sufficient electric energy (driving power) is accumulated in the capacitive element C1, the switching power supply 52 can continue the conversion operation even during the exclusion period T0.

In the present embodiment, the length of the exclusion period T0 is a fixed length. That is, the length of the exclusion period T0 in which the switching power supply 52 and the ac power supply 8 are electrically separated from each other is determined in advance for a predetermined time and does not change. For example, the length of the exclusion period T0 can be determined in consideration of the deviation of the detection timing of the phase detected by the phase detector 3. For example, the detection timing of the phase detected by the phase detector 3 in the half cycle of the ac voltage Vac may vary depending on the load 7 or may vary depending on the dimming level. Therefore, the length of the exclusion period T0 is determined based on the magnitude (dispersion) of the deviation of the detection timing of the phase detected by the phase detector 3 so that the detection timing converges within the exclusion period T0 even if there is a deviation in the detection.

On the other hand, the position of the exclusion period T0 in the half cycle of the ac voltage Vac may be changed. That is, the relative position of the start point T21 or the end point T22 of the exclusion period T0 with respect to the start point T0 of the half cycle of the alternating voltage Vac can be changed. Specifically, the stop unit 62 performs a search process for searching for a position at the detection timing (time t11) at which the phase detector 3 detects the phase in the half cycle of the ac voltage Vac. Stop unit 62 determines the position of exclusion period T0 in the half cycle of ac voltage Vac based on the result of the search process. In short, when the position of the detection timing in the half cycle of the ac voltage Vac is found by the search processing, the stopping unit 62 determines the position of the exclusion period T0 in consideration of the magnitude of the deviation of the detection timing so that the detection timing falls within the exclusion period T0. For example, the search process by the stop unit 62 and the determination of the position of the exclusion period T0 are performed immediately after the control circuit 6 is started and the frequency of the ac power supply 8 is determined.

Here, in the load control device 1 according to the present embodiment, the switching unit 63 can switch the function of the stopping unit 62 between being enabled and disabled. That is, the function of the stopping unit 62 that electrically disconnects the switching power supply 52 from the ac power supply 8 or stops the switching operation of the switching power supply 52 during the exclusion period T0 may not always be enabled, but may be disabled by the switching unit 63. The switching unit 63 automatically switches the function of the stopping unit 62 between enabled and disabled according to, for example, the state of the load 7 or the remaining amount of electric energy (control power) stored in the capacitive element C2. That is, for example, depending on the load 7, there is a case where the elimination period T0 is not required to be provided, and the current flowing from the ac power supply 8 to the power supply unit 5 does not generate a ripple (ripple) or the like during the switching operation of the switching power supply 52. In this case, it is preferable that the switching unit 63 disable the function of the stopping unit 62. The switching unit 63 may switch the function of the stop unit 62 between enabled and disabled according to, for example, a user operation received by the interface unit 4.

In addition, depending on the load 7, there are cases where: in the first period T1 and the fourth period T4, the power supply unit 5 cannot receive sufficient power supply from the ac power supply 8, and the electric energy stored in the capacitive element C1 is insufficient, so that the normal operation of the load control device 1 cannot be maintained. That is, the following may occur depending on the load 7: the electric power (driving power) generated by the step-down power supply 51 during the half cycle of the alternating voltage Vac is lower than the electric power consumed by the load control apparatus 1 during the half cycle of the alternating voltage Vac. In this case, the electric energy accumulated in the capacitive element C1 of the step-down power supply 51 gradually decreases by a half cycle of the ac voltage Vac. If this state continues, the electric energy stored in the capacitive element C1 may be insufficient sooner or later, and the normal operation of the load control device 1 may no longer be maintained. When the drive voltage Vc1 drops to some extent due to a decrease in the electric energy accumulated in the capacitive element C1, for example, there are cases where: the generation of the control power in the switching power supply 52 using the drive power becomes unstable, or the operation of the interface unit 4 and the like becomes unstable. As a result, for example, there is a possibility that an abnormal operation of the load control apparatus 1 or the load 7 may occur, such as a sudden and sudden display or flickering of the display unit of the interface unit 4 or a sudden and sudden flickering of the load 7.

Therefore, in the present embodiment, the stop unit 62 is configured to shorten the elimination period T0 by the shortened time based on the detection result of the detection unit 53, thereby lengthening the target period by the shortened time. The target period referred to here is a period that is regarded as an extended target by the stop unit 62, and includes at least one of the first period T1 and the fourth period T4.

That is, as shown in fig. 3, in the load control device 1 according to the present embodiment, the stop unit 62 shortens the exclusion period T0 based on the detection result of the detection unit 53, and extends the target period by the time corresponding to the shortening time of the exclusion period T0. In the example of fig. 3, the stop unit 62 eliminates the elimination period T0, thereby shortening the elimination period T0 by a shortening time equivalent to the entire elimination period T0. In the example of fig. 3, by removing the exclusion period T0 that spans both the fourth period T4 and the first period T1, both the fourth period T4 and the first period T1 are extended, and therefore both the fourth period T4 and the first period T1 are target periods. Fig. 3 is a timing chart similar to fig. 2 in the case where the electric energy stored in the capacitive element C1 is insufficient due to the load 7.

In other words, the stopping unit 62 shortens the exclusion period T0 included in the target period, thereby shortening the period (exclusion period T0) during which the generation operation of the step-down power supply 51 is stopped in the target period. Thus, at least a part of the exclusion period T0 during which the generation operation of the step-down power supply 51 is originally stopped is stolen as the target period during which the generation operation of the step-down power supply 51 is performed, and the target period is substantially extended.

Specifically, when the detection result of the detector 53 is smaller than the predetermined threshold Vth1 (see fig. 3), the stopper 62 shortens the exclusion period T0 and extends the target period (both the first period T1 and the fourth period T4) by the time required to shorten the exclusion period T0. For example, as shown in fig. 3, when the detection result of the detector 53 is lower than the threshold Vth1 in the third period T3 of the second half cycle in the figure, the third period T3 of the second half cycle is the detection period. Then, the stopping unit 62 shortens the exclusion period T0 and extends the target period from the first target period after the end of the detection period (the third period T3 of the second half period), that is, the fourth period T4 of the second half period.

In this way, when the electric energy stored in the capacitive element C1 is insufficient, the detection unit 53 detects a decrease in the electric energy, and the stop unit 62 extends the target period (the first period T1 and the fourth period T4) for the electric energy generating operation by the power supply unit 5. Therefore, the electric energy (drive power) generated by the power supply unit 5 in the target period increases in accordance with the extension of the target period, and as a result, the shortage of the electric energy stored in the capacitive element C1 is suppressed.

However, the stop unit 62 is not limited to the configuration in which the exclusion period T0 is shortened by eliminating the exclusion period T0, and may be, for example, a configuration in which the length of the exclusion period T0 is shortened to half, a configuration in which the length of the exclusion period T0 is shortened by a fixed time, or the like.

In the case of the present embodiment, since the half cycle of the ac voltage Vac is divided by preferentially securing the supply of power from the ac power supply 8 to the power supply unit 5, the length of the second period T2 may not be defined according to the dimming level input to the interface unit 4. For example, there are the following cases: even if the user operates the interface unit 4 so as to maximize the light output of the load 7, the exclusion period T0 is preferentially secured, and the start point of the second period T2 is not set as the dimming signal from the interface unit 4.

In addition, in the control method of the load control device 1, there is a positive phase control method (leading edge method) in addition to the opposite phase control method (trailing edge method), that is, conduction between the pair of

input terminals

11 and 12 is performed during a period from the middle of the half cycle of the alternating voltage Vac to the zero cross point. The reverse phase control method supplies power to the load 7 including the LED element as the light source from the zero cross point, and therefore can suppress distortion of the current waveform at the time of starting power supply. Thus, there are the following advantages: the number of loads 7 (the number of lamps) that can be connected to the load control device 1 is increased, or the generation of a buzzer sound can be suppressed.

The load control device 1 of the present embodiment basically adopts the anti-phase control method, but starts supplying power to the load 7 at a first time point t1 slightly later than the start point (zero-cross point) t0 of the half cycle. Therefore, the current waveform distortion may become larger than in the anti-phase control method in which the supply of power to the load 7 is started at the zero-cross point. However, the absolute value of the alternating voltage Vac at the first time point t1 is not so large, and therefore the influence of the current waveform distortion is small enough to be ignored.

Further, in the load control device 1 of the present embodiment, since the bidirectional switch 2 is turned on in the reverse direction during the period from the second time point T2 to the third time point T3 (the third period T3), it is possible to reduce the false detection by the phase detector 3. That is, the following may occur depending on the load 7: the absolute value of the voltage across the load 7 is higher than the absolute value of the ac voltage Vac, and as a result, a voltage having a polarity opposite to that of the ac voltage Vac (hereinafter referred to as "reverse polarity voltage") is applied to the pair of

input terminals

11 and 12. For example, in the case of a load 7 such as the load 7 provided with a relatively large-capacity snubber capacitor, in which the voltage across the terminals is not likely to drop, such a reverse polarity voltage is likely to be generated. When a reverse polarity voltage is generated, the phase detection unit 3 may erroneously detect a zero cross point at a place other than the zero cross point of the ac voltage Vac. There is also a load 7 that generates a reverse polarity voltage or does not generate a reverse polarity voltage depending on the dimming level, and in such a load 7, the zero cross point abruptly changes when the dimming level changes. In the third period T3, since the bidirectional switch 2 is in the reverse on state, the generation of the reverse polarity voltage is suppressed, and therefore, the erroneous detection of the phase detection unit 3 by the reverse polarity voltage can be reduced.

(4) Modification example

(4.1) modification 1

In the load control device 1 according to modification 1 of embodiment 1, the stop unit 62 stops the switching operation of the switching power supply 52 during the exclusion period T0 without electrically separating the switching power supply 52 from the ac power supply 8. Specifically, as shown in fig. 4, the stop unit 62 stops the operation of the second circuit 521 by the second power supply signal Ss2, thereby stopping the conversion operation of the switching power supply 52. In fig. 4, the alternating-current voltage "Vac", the first detection signal "ZC 1", the second detection signal "ZC 2", the first control signal "Sb 1", the second control signal "Sb 2", the first power supply signal "Ss 1", the second power supply signal "Ss 2", and the drive voltage "Vc 1" are shown.

In this case, too, in the exclusion period T0, the ripple of the current flowing from the ac power supply 8 to the power supply unit 5 due to the switching operation of the switching element of the switching power supply 52 is suppressed. The exclusion period T0 is a period sufficiently shorter than the half cycle of the ac voltage Vac, and therefore, the operation of the control circuit 6 and the like is maintained by the electric energy (control power) stored in the capacitive element C2 of the switching power supply 52. However, in this case, even if the exclusion period T0 is shortened by the shortening time, the target period is not lengthened by the shortening time.

According to the configuration of the present modification, since the generating operation of the step-down power supply 51 can be continued even in the exclusion period T0, the electric energy (drive power) can be efficiently generated by the step-down power supply 51.

(4.2) other modifications

Next, a modification of embodiment 1 will be described.

The load control device 1 according to embodiment 1 and modification 1 described above is not limited to application to the load 7 using an LED element as a light source, and can be applied to a light source that has a high impedance and is lit with a small current and that is equipped with a capacitor input type circuit. Examples of such a light source include an organic el (electroluminescence) element. The load control device 1 can be applied to, for example, loads 7 of various light sources such as discharge lamps.

The load 7 controlled by the load control device 1 is not limited to the lighting load, and may be, for example, a heater, a fan, or the like. In the case where the load 7 is a heater, the load control device 1 adjusts the amount of heat generation of the heater by adjusting the average power supplied to the heater. In addition, when the load 7 is a fan, the load control device 1 constitutes a regulator that regulates the rotation speed of the fan.

The bidirectional switch 2 is not limited to an enhancement-type n-channel MOSFET, and may be formed of, for example, two IGBTs (Insulated Gate Bipolar transistors) connected in anti-series. In the bidirectional switch 2, the rectifying element (diode) for realizing the unidirectional on state is not limited to the parasitic diode of the switching elements Q1 and Q2, and may be an external diode. The diode may be built in the same package as the switching elements Q1 and Q2. The bidirectional switch 2 may be a semiconductor element having a double gate (dual gate) structure using a semiconductor material having a wide band gap such as GaN (gallium nitride). With this configuration, the conduction loss of the bidirectional switch 2 can be reduced.

The switching power supply 52 may directly generate the control voltage Vc2 from the full-wave rectified ac voltage Vac without using the step-down power supply 51. The control unit 61 may control the switching power supply 52 to switch whether or not to execute the generating operation of generating the electric energy (control power) to be stored in the capacitive element C2. In this case, the detection unit 53 may detect the magnitude of the electric energy (control power) stored in the capacitive element C2 of the switching power supply 52. The detector 53 detects, for example, the magnitude of the control voltage Vc2 which is the voltage across the capacitive element C2.

In addition, in the control of the bidirectional switch 2, the "forward on state" may be controlled instead of the "bidirectional on state", and conversely, the "bidirectional on state" may be controlled instead of the "forward on state". In addition, the "reverse on state" may be controlled instead of the "bidirectional off state", and the "bidirectional off state" may be controlled instead of the "reverse on state". That is, the state of the on state or the off state of the bidirectional switch 2 may be unchanged.

The control method of the bidirectional switch 2 by the control circuit 6 is not limited to the above example, and may be, for example, the following method: the first control signal Sb1 and the second control signal Sb2 are alternately turned to "ON" signals at the same cycle as the alternating voltage Vac. In this case, the bidirectional switch 2 is turned on while the switching element on the high potential side of the ac voltage Vac, out of the switching elements Q1 and Q2, is turned on. That is, in this modification, so-called anti-phase control is realized in which conduction is performed between the pair of

input terminals

11 and 12 from the zero-crossing point of the ac voltage Vac to the halfway point of the half cycle. In this case, the on time of the bidirectional switch 2 can be adjusted by adjusting the phase difference between the ac voltage Vac and the first and second control signals.

The control method of the control unit 61 of the load control device 1 may be a general control method that can support both the positive phase control method and the negative phase control method.

The control unit 61 is not limited to the configuration of switching whether or not to cause the power supply unit 5 to perform the generating operation based on the first power supply signal Ss 1. For example, the control unit 61 may have the following configuration: the generation operation is stopped by disconnecting a switch provided between at least one of the pair of

input terminals

11 and 12 and the power supply unit 5 (step-down power supply 51) and electrically separating the power supply unit 5 from the ac power supply 8.

The detection unit 53 is not limited to a configuration that always detects the magnitude of the electric energy stored in the capacitive element C1 (the magnitude of the drive voltage Vc1), and may detect the electric energy only during a part of the half cycle of the ac voltage Vac. For example, the detector 53 may detect the magnitude of the electric energy stored in the capacitive element C1 only in the fourth period T4.

The length of the exclusion period T0 is not limited to a fixed length, and may be a variable length. In this case, for example, the length of the exclusion period T0 may be automatically adjusted according to the state of the load 7 or the remaining amount of the electric energy (control power) stored in the capacitive element C2.

The function of the stop unit 62 to shorten the exclusion period T0 is not essential to the load control device 1, and may be omitted as appropriate. When the stopping unit 62 does not shorten the exclusion period T0, the detecting unit 53 may be omitted.

The detection unit 53 may be provided in the control circuit 6, for example. In this case, for example, if the capacitive element C1 is connected to the a/D conversion input terminal of the control circuit 6, the drive voltage Vc1 can be input to the control circuit 6 as an analog value.

The switch driving unit 9 is not necessarily required for the load control device 1, and may be omitted as appropriate. In the case where the switch driving unit 9 is omitted, the bidirectional switch 2 is directly driven by the control circuit 6. When the switch driver 9 is omitted, the step-down power supply 51 may be omitted.

The first time point t1 is not limited to the generation time point of the first detection signal ZC1 or the second detection signal ZC2, and may be a time point after a fixed delay time (e.g., 300 μ s) has elapsed from the generation time point of the first detection signal ZC1 or the second detection signal ZC 2. The delay time is not limited to 300 [ mu ] s, and can be set as appropriate within a range of 0 [ mu ] s to 500 [ mu ] s.

The third time point t3 may be before the end point (zero-crossing point) t4 of the half cycle, and the length from the third time point t3 to the end point t4 of the half cycle can be set as appropriate. For example, when the time length from the first time point t1 to the third time point t3 is shorter than the half period by a predetermined time, the predetermined time is not limited to 300 μ s, and can be set within a range of 100 μ s to 500 μ s.

The diodes D1 and D2 in embodiment 1 are not essential to the load control device 1, and the diodes D1 and D2 may be omitted as appropriate.

In embodiment 1, the case where the load control device 1 is of a two-wire type has been described, but the configuration is not limited to this, and the load control device 1 may be a so-called three-way switch capable of connecting three wires, a so-called four-way switch capable of connecting four wires, or the like, for example. When the load control devices 1 constitute a three-way switch, the state of current supply to the load 7 can be switched between two places, for example, an upper floor part and a lower floor part of a floor in a building, by combining two load control devices 1.

In comparison between two values such as the ac voltage Vac and the predetermined value Vzc, "equal to or greater than" includes both a case where the two values are equal to each other and a case where one of the two values exceeds the other. However, the meaning of "more than" may be the same as that of "more than" including only the case where one of the two values exceeds the other. That is, since whether or not the two values are equal can be arbitrarily changed according to the setting such as the predetermined value Vzc, there is no technical difference between "above" and "above". Likewise, "less than" may be the same as "below".

(embodiment mode 2)

The load control device 1 according to the present embodiment is different from the load control device 1 according to embodiment 1 in the control method of the control unit 61. In the following, the same configurations as those in embodiment 1 are denoted by common reference numerals and description thereof is omitted as appropriate.

In the present embodiment, as shown in fig. 5, the control unit 61 divides the half cycle of the ac voltage Vac into the first period T1, the second period T2, and the third period T3 based on the phase detected by the phase detection unit 3. In fig. 5, the alternating-current voltage "Vac", the first detection signal "ZC 1", the second detection signal "ZC 2", the first control signal "Sb 1", the second control signal "Sb 2", the first power supply signal "Ss 1", the second power supply signal "Ss 2", and the drive voltage "Vc 1" are shown.

Here, a period from the start point (zero crossing point) T0 of the half cycle of the ac voltage Vac to the first time point T1 is a first period T1. The period from the first time point T1 to the second time point T2 is a second period T2. The second time point t2 is a time point after a lapse of a time of a length corresponding to the dimming signal from the detection timing (time point t11) at which the phase (zero cross point) is detected by the phase detection unit 3. A period from the second time point T2 to the end point T3 of the half cycle of the ac voltage Vac is a third period T3.

In the first period T1, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to OFF signals, and sets the bidirectional switch 2 in a non-conductive state. In the second period T2, the controller 61 turns the first control signal Sb1 and the second control signal Sb2 to the "ON" signal, and turns the bidirectional switch 2 to the ON state. In the third period T3, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to OFF signals, and sets the bidirectional switch 2 in a non-conductive state.

In the first period T1, the control unit 61 sets the first power supply signal Ss1 to the "ON" signal, and causes the step-down power supply 51 to perform the generating operation. In the second period T2, the control unit 61 turns the first power supply signal Ss1 to an "OFF" signal, and stops the generation operation of the step-down power supply 51. In the third period T3, the control unit 61 turns the first power supply signal Ss1 to an "OFF" signal, and stops the generation operation of the step-down power supply 51. That is, the step-down power supply 51 performs a generating operation for generating electric energy (driving power) by the power supplied from the ac power supply 8 only in the first period T1 in the half cycle of the ac voltage Vac.

Here, the exclusion period T0 is set to the first period T1 so as to include a time point T11 that is a detection timing at which the phase detector 3 detects the phase (zero cross point), that is, a generation time point of the first detection signal ZC1 or the second detection signal ZC 2. The start point T21 of the exclusion period T0 coincides with the start point T0 of the half cycle of the alternating voltage Vac. The end point T22 of the exclusion period T0 is set to a period (period from T11 to T1) after the detection timing (time point T11) at which the phase detector 3 detects the phase in the first period T1.

In the load control device 1 according to the present embodiment, the stop unit 62 stops the switching operation of the switching power supply 52 during the exclusion period T0, as in modification 1 of embodiment 1. Specifically, as shown in fig. 5, the stop unit 62 stops the operation of the second circuit 521 by the second power supply signal Ss2, thereby stopping the conversion operation of the switching power supply 52.

In the configuration of the present embodiment, also in the exclusion period T0, the ripple of the current flowing from the ac power supply 8 to the power supply unit 5 due to the switching operation of the switching element of the switching power supply 52 is suppressed.

The configuration of the load control device 1 according to embodiment 2 can be appropriately combined with the configuration of embodiment 1 (including the modified examples).

(embodiment mode 3)

The load control device 1 according to the present embodiment adopts a positive phase control method as a control method, that is, a method in which the pair of

input terminals

11 and 12 are conducted during a period from the halfway of the half cycle of the ac voltage Vac to the zero cross point.

In the present embodiment, as shown in fig. 6, the control unit 61 divides the half cycle of the ac voltage Vac into the first period T1, the second period T2, and the third period T3 based on the phase detected by the phase detection unit 3. In fig. 6, the alternating-current voltage "Vac", the first detection signal "ZC 1", the second detection signal "ZC 2", the first control signal "Sb 1", the second control signal "Sb 2", the first power supply signal "Ss 1", the second power supply signal "Ss 2", and the drive voltage "Vc 1" are shown.

Here, a period from the start point (zero crossing point) T0 of the half cycle of the ac voltage Vac to the first time point T1 is a first period T1. The first time point t1 is a time point when a time of a length corresponding to the dimming signal has elapsed from the detection timing (time point t11) at which the phase (zero cross point) is detected by the phase detection unit 3. The period from the first time point T1 to the second time point T2 is a second period T2. A period from the second time point T2 to the end point T3 of the half cycle of the ac voltage Vac is a third period T3.

In the first period T1, the control unit 61 turns the first power supply signal Ss1 to an "OFF" signal, and stops the generation operation of the step-down power supply 51. In the second period T2, the control unit 61 turns the first power supply signal Ss1 to an "OFF" signal, and stops the generation operation of the step-down power supply 51. In the third period T3, the control unit 61 sets the first power supply signal Ss1 to the "ON" signal, and causes the step-down power supply 51 to perform the generating operation. That is, the step-down power supply 51 performs a generating operation for generating electric energy (driving power) by the power supplied from the ac power supply 8 only in the third period T3 in the half cycle of the ac voltage Vac.

Here, the exclusion period T0 is set to the third period T3 so as to include a time point T11 that is a detection timing at which the phase detector 3 detects the phase (zero cross point), that is, a generation time point of the first detection signal ZC1 or the second detection signal ZC 2. The start point T21 of the exclusion period T0 is set to a period (period from T2 to T11) before the detection timing (time point T11) at which the phase detector 3 detects the phase in the third period T3. The end T22 of the exclusion period T0 coincides with the end T3 of the half cycle of the alternating voltage Vac.

In the load control device 1 according to the present embodiment, the stop unit 62 stops the switching operation of the switching power supply 52 during the exclusion period T0, as in modification 1 of embodiment 1. Specifically, as shown in fig. 6, the stop unit 62 stops the operation of the second circuit 521 by the second power supply signal Ss2, thereby stopping the conversion operation of the switching power supply 52.

The configuration of the load control device 1 according to embodiment 3 can be appropriately combined with the configuration of embodiment 1 (including the modified examples).

(embodiment mode 4)

input terminals

11 and 12 are conducted during a period from the halfway of the half cycle of the ac voltage Vac to the zero cross point. In the present embodiment, the bidirectional switch 2 is composed of, for example, a three-terminal triac (triac), and the control circuit 6 turns on the bidirectional switch 2 in the middle of a half cycle of the ac voltage Vac (second time point t 2). The bidirectional switch 2 formed of a bidirectional thyristor becomes non-conductive in the vicinity of a zero cross point (0 [ V ]) of the alternating voltage Vac.

In the present embodiment, as shown in fig. 7, the control unit 61 divides the half cycle of the ac voltage Vac into the first period T1, the second period T2, and the third period T3 based on the phase detected by the phase detection unit 3. In fig. 7, the alternating-current voltage "Vac", the first detection signal "ZC 1", the second detection signal "ZC 2", the first control signal "Sb 1", the second control signal "Sb 2", the first power supply signal "Ss 1", the second power supply signal "Ss 2", and the drive voltage "Vc 1" are shown.

In the first period T1, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to OFF signals, and sets the bidirectional switch 2 in a non-conductive state. In the second period T2, the controller 61 sets the first control signal Sb1 and the second control signal Sb2 to OFF signals, and sets the bidirectional switch 2 in a non-conductive state. In the third period T3, the controller 61 turns the first control signal Sb1 and the second control signal Sb2 ON and turns the bidirectional switch 2 ON.

In the first period T1, the control unit 61 sets the first power supply signal Ss1 to the "ON" signal, and causes the step-down power supply 51 to perform the generating operation. In the second period T2, the control unit 61 turns the first power supply signal Ss1 to the OFF signal, and stops the generation operation of the step-down power supply 51. In the third period T3, the control unit 61 turns the first power supply signal Ss1 to an "OFF" signal, and stops the generation operation of the step-down power supply 51. That is, the step-down power supply 51 performs a generating operation for generating electric energy (driving power) by the power supplied from the ac power supply 8 only in the first period T1 in the half cycle of the ac voltage Vac.

In the load control device 1 according to the present embodiment, the stop unit 62 stops the switching operation of the switching power supply 52 during the exclusion period T0, as in modification 1 of embodiment 1. Specifically, as shown in fig. 7, the stop unit 62 stops the operation of the second circuit 521 by the second power supply signal Ss2, thereby stopping the conversion operation of the switching power supply 52.

The configuration of the load control device 1 according to embodiment 4 can be appropriately combined with the configuration of embodiment 1 (including the modified examples).

(conclusion)

As described above, the load control device 1 according to the first embodiment includes the bidirectional switch 2, the phase detection unit 3, the switching power supply 52, and the stop unit 62. The bidirectional switch 2 is electrically connected in series to a load 7 with respect to an ac power supply 8, and performs phase control on an ac voltage Vac supplied to the load 7. The phase detection unit 3 detects the phase of the ac voltage Vac. The switching power supply 52 is electrically connected in parallel to the bidirectional switch 2, and performs a conversion operation of converting a dc voltage (drive voltage Vc1) generated by the power supplied from the ac power supply 8 into a control voltage Vc2 by a switching operation of the switching element. The stop unit 62 electrically disconnects the switching power supply 52 from the ac power supply 8 or stops the switching operation of the switching power supply 52 during an exclusion period T0 including the detection timing of the phase detected by the phase detection unit 3.

According to this configuration, the stop unit 62 electrically disconnects the switching power supply 52 from the ac power supply 8 or stops the switching operation of the switching power supply 52 during the exclusion period T0 including the detection timing of the phase detected by the phase detection unit 3. Therefore, at the timing when the phase detection unit 3 detects the phase, the ripple (ripple) generated in the current flowing from the ac power supply 8 to the power supply unit 5 due to the switching operation of the switching element of the switching power supply 52 is suppressed. Therefore, the decrease in the detection accuracy of the phase in the phase detection unit 3 due to the influence of the noise generated by the switching power supply 52 is suppressed. If the detection accuracy of the phase of the ac voltage Vac in the phase detection unit 3 is improved, it is easy to maintain the normal operation of the load control device 1 or the load 7. Therefore, the load control device 1 has an advantage of being able to support a wider variety of loads 7.

In the second aspect, the load control device 1 according to the first aspect preferably further includes a switching unit 63 that switches between enabling and disabling the function of the stopping unit 62. According to this configuration, for example, when the normal operation of the load control device 1 and the load 7 can be maintained by the load 7, the efficiency of the switching power supply 52 can be improved by disabling the function of the stop unit 62. However, this configuration is not essential to the load control device 1, and the switching unit 63 may be omitted as appropriate.

In the third aspect, the length of the exclusion period T0 in the load control device 1 according to the first or second aspect is preferably a fixed length. With this configuration, the process for setting the exclusion period T0 is simplified. However, this configuration is not essential to the load control device 1, and the length of the exclusion period T0 may be variable.

In a fourth aspect, it is preferable that the stopping unit 62 of the load control device 1 according to any one of the first to third aspects is configured to: search processing is performed, and the position of the exclusion period T0 in the half cycle is determined based on the result of the search processing. The search process is a process of searching for the position of the detection timing in the half cycle constituted by the period between consecutive secondary zero-crossing points of the ac voltage Vac. According to this configuration, even when the position of the detection timing in the half cycle is shifted according to the load 7, for example, the elimination period T0 can be set at an appropriate position according to the position of the detection timing in the half cycle. However, this configuration is not essential to the load control device 1, and the search process may be appropriately omitted.

In a fifth aspect, the load control device 1 according to any one of the first to fourth aspects further includes a step-down power supply 51 and a control unit 61. The step-down power supply 51 has a capacitive element C1 that stores electric energy, is electrically connected in parallel to the bidirectional switch 2, and performs a generating operation that generates electric energy using electric power supplied from the ac power supply 8. The control unit 61 controls the bidirectional switch 2 and the step-down power supply 51. The switching power supply 52 is configured to: the voltage across the capacitive element C1 (drive voltage Vc1) is converted into a control voltage Vc2 by a conversion operation. The control unit 61 divides a half cycle, which is formed by a period between consecutive secondary zero-crossing points 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. The control unit 61 sets the bidirectional switch 2 to the non-conductive state and causes the step-down power supply 51 to perform the generating operation in the first period T1 and the fourth period T4. In the second period T2, the control unit 61 turns on the bidirectional switch 2 and stops the generating operation of the step-down power supply 51. In the third period T3, the control unit 61 sets the bidirectional switch 2 to the non-conductive state and stops the generating operation of the step-down power supply 51. The exclusion period T0 is set to at least one of the first period T1 and the fourth period T4. According to this structure, the following advantages are obtained as compared with the positive phase control method: it is possible to suppress the distortion of the current waveform at the time of starting the supply of electric power to the load 7, to increase the number of loads 7 connected to the load control device 1, and to suppress the generation of a buzzer sound.

In a sixth aspect, the load control device 1 according to any one of the first to fourth aspects further includes a step-down power supply 51 and a control unit 61. The step-down power supply 51 has a capacitive element C1 that stores electric energy, is electrically connected in parallel to the bidirectional switch 2, and performs a generating operation that generates electric energy using electric power supplied from the ac power supply 8. The control unit 61 controls the bidirectional switch 2 and the step-down power supply 51. The switching power supply 52 is configured to: the voltage across the capacitive element C1 (drive voltage Vc1) is converted into a control voltage Vc2 by a conversion operation. The control unit 61 divides a half cycle, which is formed by a period between consecutive secondary zero-crossing points of the ac voltage Vac, into a first period T1, a second period T2, and a third period T3 based on the phase detected by the phase detection unit 3. The control unit 61 sets the bidirectional switch 2 to the non-conductive state in the first period T1, and causes the step-down power supply 51 to perform the generating operation. In the second period T2, the control unit 61 turns on the bidirectional switch 2 and stops the generating operation of the step-down power supply 51. In the third period T3, the control unit 61 sets the bidirectional switch 2 to the non-conductive state and stops the generating operation of the step-down power supply 51. The exclusion period T0 is set at the first period T1. According to this structure, the following advantages are obtained as compared with the positive phase control method: it is possible to suppress the distortion of the current waveform at the time of starting the supply of electric power to the load 7, to increase the number of loads 7 connected to the load control device 1, and to suppress the generation of a buzzer sound.

The load control device 1 according to the seventh aspect further includes a step-down power supply 51 and a control unit 61. The step-down power supply 51 has a capacitive element C1 that stores electric energy, is electrically connected in parallel to the bidirectional switch 2, and performs a generating operation that generates electric energy using electric power supplied from the ac power supply 8. The control unit 61 controls the bidirectional switch 2 and the step-down power supply 51. The switching power supply 52 is configured to: the voltage across the capacitive element C1 (drive voltage Vc1) is converted into a control voltage Vc2 by a conversion operation. The control unit 61 divides a half cycle, which is formed by a period between consecutive secondary zero-crossing points of the ac voltage Vac, into a first period T1, a second period T2, and a third period T3 based on the phase detected by the phase detection unit 3. In the first period T1, the control unit 61 sets the bidirectional switch 2 to the non-conductive state and stops the generating operation of the step-down power supply 51. In the second period T2, the control unit 61 turns on the bidirectional switch 2 and stops the generating operation of the step-down power supply 51. In the third period T3, the control unit 61 sets the bidirectional switch 2 to the non-conductive state and causes the step-down power supply 51 to perform the generating operation. The exclusion period T0 is set to the third period T3. According to this structure, there are the following advantages: even the load control device 1 of the positive phase control system can support a wider variety of loads 7.

The load control device 1 according to the eighth aspect further includes a step-down power supply 51 and a control unit 61. The step-down power supply 51 has a capacitive element C1 that stores electric energy, is electrically connected in parallel to the bidirectional switch 2, and performs a generating operation that generates electric energy using electric power supplied from the ac power supply 8. The control unit 61 controls the bidirectional switch 2 and the step-down power supply 51. The switching power supply 52 is configured to: the voltage across the capacitive element C1 (drive voltage Vc1) is converted into a control voltage Vc2 by a conversion operation. The control unit 61 divides a half cycle, which is formed by a period between consecutive secondary zero-crossing points of the ac voltage Vac, into a first period T1, a second period T2, and a third period T3 based on the phase detected by the phase detection unit 3. The control unit 61 sets the bidirectional switch 2 to the non-conductive state in the first period T1, and causes the step-down power supply 51 to perform the generating operation. The control unit 61 sets the bidirectional switch 2 to the non-conductive state in the second period T2, and stops the generating operation of the step-down power supply 51. The control unit 61 turns on the bidirectional switch 2 in the third period T3 to stop the generating operation of the step-down power supply 51. The exclusion period T0 is set at the first period T1. According to this structure, there are the following advantages: even in the positive phase control type load control device 1. A greater variety of loads 7 can also be supported.

Claims

1. A load control device is provided with:

a bidirectional switch electrically connected in series to a load with respect to an ac power supply, the bidirectional switch performing phase control of an ac voltage supplied to the load;

a phase detection unit that detects a phase of the ac voltage;

a switching power supply electrically connected in parallel to the bidirectional switch and performing a conversion operation of converting a direct-current voltage generated by the power supplied from the alternating-current power supply into a control voltage by a switching operation of a switching element; and

a stop unit that electrically disconnects the switching power supply from the alternating-current power supply or stops the switching operation of the switching power supply during a period excluding a detection timing when the phase detection unit detects the phase,

during the excluding, the bi-directional switch is in a non-conductive state.

2. The load control device according to claim 1,

and a switching unit for switching between the activation and deactivation of the function of the stopping unit.

3. The load control device according to claim 1,

the length of the exclusion period is a fixed length.

4. The load control device according to claim 1,

the stopping unit is configured to: and a step of performing a search process for searching for a position of the detection timing in a half cycle, the half cycle being configured by a period between consecutive secondary zero-crossing points of the alternating-current voltage, and determining a position of the exclusion period in the half cycle based on a result of the search process.

5. The load control device according to claim 2,

6. The load control device according to claim 3,

7. The load control device according to any one of claims 1 to 6, further comprising:

a step-down power supply having a capacitive element for accumulating electric energy, electrically connected in parallel to the bidirectional switch, and performing a generating operation for generating the electric energy by using electric power supplied from the ac power supply; and

a control section that controls the bidirectional switch and the step-down power supply,

the switching power supply is configured to: transforming the voltage across the capacitive element into the control voltage by the transforming action,

the control unit is configured to:

dividing a half period formed by a period between consecutive secondary zero-crossing points of the alternating-current voltage into a first period, a second period, a third period, and a fourth period based on the phase detected by the phase detection unit,

in the first period and the fourth period, the bidirectional switch is set to a non-conductive state, and the step-down power supply is caused to perform the generating operation,

in the second period, the bidirectional switch is turned on to stop the generating operation of the step-down power supply,

in the third period, the bidirectional switch is set to a non-conducting state to stop the generating operation of the step-down power supply,

the exclusion period is set to at least one of the first period and the fourth period.

8. The load control device according to any one of claims 1 to 6, further comprising:

the control unit is configured to:

dividing a half period, which is formed by a period between consecutive secondary zero-crossing points of the alternating-current voltage, into a first period, a second period, and a third period based on the phase detected by the phase detection unit,

in the first period, the bidirectional switch is set to a non-conducting state, and the step-down power supply is caused to perform the generating operation,

the exclusion period is set at the first period.

9. The load control device according to any one of claims 1 to 6, further comprising:

the control unit is configured to:

in the first period, the bidirectional switch is set to a non-conducting state to stop the generating operation of the step-down power supply,

in the third period, the bidirectional switch is set to a non-conductive state, and the step-down power supply is caused to perform the generating operation,

the excluding period is set to the third period.

10. The load control device according to any one of claims 1 to 6, further comprising:

the control unit is configured to:

in the second period, the bidirectional switch is set to a non-conducting state to stop the generating operation of the step-down power supply,

in the third period, the bidirectional switch is turned on to stop the generating operation of the step-down power supply,

the exclusion period is set at the first period.