JP2010146527A - Load control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load control device for correctly controlling an opening/closing timing, while reducing the number of switching elements. <P>SOLUTION: After receiving a charging completion signal of a buffer capacitor 29 from a voltage detecting part 18, a control part 13 outputs a first pulse so as to make a main opening/closing part 11 conductive only for a first predetermined time. After a zero-cross detecting part 19 detects the zero-cross point of a load current, the control part 13 outputs a second pulse so as to restrict the opening state of the main opening/closing part 11 for a second predetermined time which is less than the half period of the load current. A main opening/closing control part 25 calculates the logical AND of the first and second pulses, and outputs the result of the logical AND to the main opening/closing part 11. Consequently, the main opening/closing part 11 closes and is made conductive only during a period in which the first predetermined time when the first pulse is rising overlaps the second predetermined time when the second pulse is rising. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a two-wire load control device connected in series between a load such as an AC power source and a lighting device.

  Conventionally, load control devices for lighting devices using contactless switching elements such as triacs and thyristors have been put into practical use. These load control devices generally have a two-wire connection from the viewpoint of reduced wiring, and are connected in series between an AC power source and a load. Thus, in a load control device connected in series between an AC power supply and a load, how to secure its own circuit power supply becomes a problem.

  A load control device 50 of the first conventional example shown in FIG. 6 is connected in series between an AC power source 2 and a load 3, and includes a main switching unit 51, a rectifying unit 52, a control unit 53, and a control unit 53. A first power supply unit 54 for supplying stable power, a second power supply unit 55 for supplying power to the first power supply unit 54 when power to the load 3 is stopped, and power supply to the load 3 are performed. The third power source unit 56 supplies power to the first power source unit 54 when it is connected, and an auxiliary opening / closing unit 57 that energizes a minute current in the load current. The switch element 51a of the main opening / closing part 51 is configured by a triac.

  In the off state of the load control device 50 in which no power is supplied to the load 3, the voltage applied from the AC power supply 2 to the load control device 50 is supplied to the second power supply unit 55 via the rectification unit 52. The second power supply unit 55 is a constant voltage circuit composed of a resistor and a Zener diode. The current flowing through the load 3 at this time is a minute current that does not cause the load 3 to malfunction, the current consumption of the control unit 53 is small, and the impedance of the second power supply unit 55 is set to be kept high.

  On the other hand, in the ON state of the load control device 50 in which power is supplied to the load 3, the third power supply unit 56 is turned on by the control signal from the control unit 53, and the impedance of the load control device 50 is lowered to reduce the load 3 As the amount of current flowing through the first power supply unit 56 increases, the current flowing through the third power supply unit 56 also flows through the first power supply unit 54 and starts charging the buffer capacitor 59. When the charging voltage of the buffer capacitor 59 becomes higher than a predetermined threshold value, the Zener diode 56a constituting the third power supply unit 56 breaks down and current starts to flow, current flows into the gate of the auxiliary switching unit 57, and the auxiliary switching unit 57 conducts (closed state). As a result, the current flowing from the rectifying unit 52 to the third power supply unit 56 is commutated to the auxiliary switching unit 57 and further flows into the gate of the switch element 51a of the main switching unit 51, and the main switching unit 51 becomes conductive (closed state). ). Therefore, almost all the electric power is supplied to the load 61. Once the main opening / closing part 51 becomes conductive (closed state), the current continues to flow. However, when the alternating current reaches the zero cross point, the switch element 51a self-extinguishes and the main opening / closing part 51 becomes non-conductive (open state). become. When the main opening / closing part 51 becomes non-conductive (open state), a current flows again from the rectifying part 52 through the third power supply part 56 to the first power supply part 54, and the operation for securing the self-circuit power supply of the load control device 50 is performed. . In other words, the self-circuit power supply securing of the load control device 50, the conduction of the auxiliary opening / closing part 57, and the conduction operation of the main opening / closing part 51 are repeated every half cycle of the alternating current.

  The load control device 60 of the second conventional example shown in FIG. 7 is connected in series between the AC power source 2 and the load 3, and is connected to the main switching unit 61, the rectifying unit 62, the control unit 63, and the control unit 63. The first power supply unit 64 for supplying stable power, the second power supply unit 65 for supplying power to the first power supply unit 64 when the power to the load 3 is stopped, and the power supply to the load 3 are performed. The third power source unit 66 supplies power to the first power source unit 64 when the power source is disconnected, and the zero cross detection unit 67 detects the zero cross point of the load current. A MOSFET is used as the switch element 61a of the main opening / closing part 61, and an incandescent lamp is used as a load to be controlled.

  When power is supplied to the load 3, the switch element 61a of the main switching unit 61 is turned on only during a period according to the dimming level inputted externally, but at the timing when the zero-cross detection unit 67 detects the zero-cross point of the voltage. 61a is made conductive (closed state), and the switch element 61a is made nonconductive (open state) after the above period. While the main opening / closing part 61 is non-conductive (open state), the self-circuit power supply of the load control device 60 is secured as in the first conventional example. When the main opening / closing part 61 is made non-conductive (open state), the zero cross detection part 67 again detects the zero cross point and repeats the operation of making the switch element 61a conductive (closed state) every half cycle of AC. .

  When the switch element of the main switching unit 51 is a triac or thyristor as in the load control device 50 of the first conventional example, to reduce noise generated when power is supplied to the load 3, and to supply power to the load 3. In order to prevent malfunction caused by noise propagated from the power supply 2 when stopping the power supply, it is necessary to provide a filter. However, the size of the coil 58 constituting the filter and the heat generated by the coil become problems, and the load control device is downsized. Is difficult.

  In order to reduce noise caused by the load control device without using a filter, for example, in the load control device described in Patent Document 1 (third conventional example), in addition to the switch element of the main switching unit, The second switch portion having a larger on-resistance than the first switch portion is provided, and the first switch portion is turned on after the second switch portion is turned on. However, in the third conventional example, the number of switch elements increases, the circuit configuration becomes complicated, and the control of switch-on timing becomes complicated.

  Further, when the switch element 61a of the main opening / closing part 61 is a transistor as in the load control device 60 of the first conventional example, the load is like an incandescent lamp and the load current and the load voltage have the same phase (power factor 1). It is limited to.

Further, a triac or a transistor used as a switching element of the main opening / closing section is generally composed of Si, and a vertical type in which current flows in the vertical direction of the element. In the case of a triac, since a PN junction exists in the energization path, a loss is generated because the barrier is overcome. Further, in the case of a transistor, a loss occurs during energization because it is necessary to connect the two elements in opposite directions and the resistance of the low carrier concentration layer serving as the withstand voltage maintaining layer is high. Due to these losses, the switch element itself generates a large amount of heat and requires a large heat sink, which hinders an increase in capacity and size of the load control device. In general, such a load control device is used by being housed in a metal box or the like provided on a wall surface. However, since there is a limit to downsizing of a conventional load control device, it is currently generally used. Depending on the size of the box used, the load control device cannot be used in combination with other sensors or switches. Therefore, further reduction in size of the load control device is required in order to allow the load control device and other sensors, switches, and the like to be provided in a box having a general size.
JP 2006-92859 A

  The present invention has been made to solve the above-described problems of the conventional example, and an object thereof is to provide a load control device capable of accurately controlling the opening / closing timing while reducing the number of switch elements.

  In order to achieve the above object, the invention according to claim 1 includes a switch element having a transistor structure, a main opening / closing part that controls supply of power to a load, and a switch element having a thyristor structure. An auxiliary opening / closing part for controlling the supply of power to the load when the part is non-conductive, a control part for controlling the opening / closing of the main opening / closing part and the auxiliary opening / closing part, and a rectifying part from both ends of the main opening / closing part When the power supply to the load is stopped, the first power supply unit that supplies power via the rectifier unit and the first power supply unit that supplies a stable voltage to the control unit and the rectifier unit are stopped. A second power source that supplies power to the first power source, and the first power source when the main switching unit or the auxiliary switching unit is in a closed state to supply power to the load. A load control device having a third power supply for supplying power to And a voltage detection unit that detects a voltage input to the third power supply unit, and a zero cross detection unit that detects a zero cross point of the load current, and the control unit supplies power to the load. A first predetermined time counted from when the voltage input to the third power source reaches a predetermined threshold by the voltage detector, and a count after the zero cross detector detects the zero cross point of the load current. The main opening / closing part is turned on only during a time that overlaps with a second predetermined time that is less than a half cycle of the load current to be generated.

  According to a second aspect of the present invention, in the load control device according to the first aspect, the control unit causes the auxiliary opening / closing part to be conductive for a third predetermined time when the main opening / closing part is non-conductive.

  According to a third aspect of the present invention, in the load control device according to the first or second aspect of the present invention, the load control device further includes a current detection unit that detects a current flowing through the auxiliary opening / closing unit, and the control unit has a current greater than or equal to a predetermined threshold value. When the main opening / closing part flows into the auxiliary opening / closing part, the main opening / closing part is once rendered conductive, and then the auxiliary opening / closing part is made conductive when the main opening / closing part becomes non-conductive.

  According to the first aspect of the present invention, when the voltage detection unit detects that the voltage input to the third power supply unit has reached a predetermined threshold value, the control unit causes the main opening / closing unit to conduct (closed) for a first predetermined time. Therefore, most of the time in the half cycle of the commercial power supply is supplied from the main switching unit to the load. Further, when the second predetermined time has elapsed even within the first predetermined time, the control unit causes the main opening / closing unit to become non-conductive (open state). Even if the start timing is delayed, the main switching unit is surely turned off before the load current becomes zero. As a result, the main opening / closing portion is prevented from conducting beyond the zero cross of the load current.

  According to the invention of claim 2, when the main opening / closing part becomes non-conductive after the first predetermined time elapses, the auxiliary opening / closing part is made conductive for the third predetermined time, so that most of the half period of the commercial power supply After power is supplied from the main opening / closing unit to the load, power is supplied to the load from the auxiliary opening / closing unit after the energization current decreases. Since these operations are performed with respect to the load current, the load is not limited to one having a power factor of 1 even if the main switching unit is configured by a switch element having a transistor structure, and it can be applied to either a fluorescent lamp or an incandescent lamp. A suitable two-wire load control device can be realized. Further, since the level of noise generated during operation of the load control device can be kept low, it is possible to realize a load control device that is small and has a wide compatible load range.

  According to the invention of claim 3, when the current detection unit detects that the current exceeding the allowable value flows in the auxiliary opening / closing unit, the main opening / closing unit is once brought into conduction (closed). The switch element can be constructed with a small switch element, and the load control device can be miniaturized. improves.

(First embodiment)
A load control device according to a first embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing a configuration of a load control device 1A according to the first embodiment, and FIGS. 2 to 4 are time charts showing signal waveforms in respective parts of the load control device 1A.

  A load control device 1A according to the first embodiment shown in FIG. 1 is connected in series between an AC power supply 2 and a load 3, and has a main switching unit 11 that controls supply of power to the load 3, and a rectification unit 12 A control unit 13 that controls the entire load control device 1A, a first power supply unit 14 for supplying stable power to the control unit 13, and a first power supply unit 14 when the power to the load 3 is stopped. The second power supply unit 15 that supplies power, the third power supply unit 16 that supplies power to the first power supply unit 14 when the power supply to the load 3 is performed, and the energization of a minute current out of the load current The auxiliary opening / closing part 17 is configured to be performed. The third power supply unit 16 includes a voltage detection unit 18 that detects a voltage input to the third power supply unit and a zero cross detection unit 19 that detects a zero cross point of the load current. The main opening / closing part 11 has a switch element 11a having a transistor structure, and the auxiliary opening / closing part 17 has a switch element 17a having a thyristor structure. In addition, the control unit 13 is provided with a main control unit 20 configured by a CPU or the like, a first pulse output unit 21, a second pulse output unit 22, and a third pulse output unit 23.

  After receiving the charge completion signal for the buffer capacitor 29 from the voltage detection unit 18, the first pulse output unit 21 outputs a first pulse so that the main switching unit 11 is turned on for a first predetermined time. That is, the first pulse rises in response to a charge completion signal from the voltage detector 18 and falls after the first predetermined time has elapsed. The second pulse output unit 22 outputs the second pulse so as to limit the open state of the main switching unit 11 for a second predetermined time after the zero cross detection unit 19 detects the zero cross point of the load current. That is, the second pulse rises in response to the zero cross detection signal from the zero cross detection unit 19 and falls after the second predetermined time has elapsed. The third pulse output unit 23 detects that the main opening / closing unit 11 has become non-conducting (open state), and then causes the auxiliary opening / closing unit 17 to conduct only for a third predetermined time. Output a signal. In other words, the second pulse rises upon detecting that the main opening / closing part 11 has become non-conductive (open state), and falls after the third predetermined time has elapsed.

  Even in the off state of the load control device 1A in which power supply to the load 3 is not performed, a current flows from the power source 2 to the second power source unit 15 via the rectifying unit 12, and therefore a minute current also flows to the load 3. However, the current is kept low enough not to cause the load 3 to malfunction, and the impedance of the second power supply unit 15 is maintained at a high value.

  When power is supplied to the load 3, the impedance of the third power supply unit 16 is lowered, a current is supplied to the circuit side inside the load control device 1 </ b> A, and the buffer capacitor 29 of the first power supply unit 14 is charged. As described above, the third power supply unit 16 is provided with the voltage detection unit (charge monitoring unit) 18 and detects the voltage input to the third power supply unit 16. When the voltage detection unit 18 detects that the voltage input to the third power supply unit 16 has reached a predetermined threshold value, the voltage detection unit 18 outputs a predetermined detection signal to the control unit 13. When the control unit 13 receives the detection signal from the voltage detection unit 18, the control unit 13 makes the main opening / closing unit 11 conductive for a first predetermined time (closed). In FIG. 1, the first pulse output unit 21 configured by hardware using a dedicated IC or the like is used to directly output the first pulse signal according to the detection signal from the voltage detection unit 18. The example of a structure provided as a part of control part 13 is shown. Alternatively, the configuration is not limited to the illustrated configuration, and the output from the voltage detection unit 18 may be input to the main control unit 20 configured by a CPU or the like, and the first pulse signal may be output by software. Good. The first predetermined time for conducting the main opening / closing part 11 is preferably set to a time slightly shorter than a half cycle of the commercial frequency power supply.

  Next, when the main opening / closing unit 11 starts an operation of becoming non-conductive (open state) after the first predetermined time has elapsed, the control unit 13 opens the auxiliary opening / closing unit 17 for a third predetermined time (for example, several hundred μm). For 2 seconds). For this operation, the auxiliary opening / closing part 17 is only required to become non-conductive (open state) slightly later than the main opening / closing part 11. Alternatively, the main control unit 20 may output a pulse signal to the auxiliary opening / closing unit 17 that is longer than the first pulse signal output to the main opening / closing unit 11 by a third predetermined time. Alternatively, the delay circuit may be configured using a diode or a capacitor.

  By these operations, after the charging of the buffer capacitor 29 is completed, power is supplied from the main switching unit 11 to the load 3 for most of the half cycle of the commercial power supply. The power is supplied from 17 to the load 3. Since the auxiliary opening / closing part 17 includes the switch element 17a having a thyristor structure, the auxiliary opening / closing part 17 becomes non-conductive (open state) when the current value becomes zero (zero cross point). When the auxiliary opening / closing part 17 becomes non-conductive (open state), the current again flows into the third power supply part 16, and thus the above operation is repeated every half cycle of the commercial power supply.

  FIG. 2 shows signal waveforms in each part of the load control device 1A at high load, and FIGS. 3 and 4 show signal waveforms in each part of the load control device 1A at low load. 3 shows a case where the main switching unit 11 is controlled using only the first pulse, and FIG. 4 shows a case where the main switching unit 11 is controlled using the first pulse and the second pulse. Show.

  When the load is high, that is, when the connected load 3 has a high capacity, as shown in FIG. 2, the buffer capacitor 29 is charged in a short time, and after the completion of the charging, most of the half cycle of the commercial power supply Is supplied to the load 3 from the main switching unit 11. At this time, since the first predetermined time is set so that the main opening / closing part 11 is turned off before the time when the current value becomes zero (zero crossing point), the main opening / closing part 11 exceeds the zero crossing point. There is no conduction.

  However, when the load is low, that is, when the connected load 3 has a low capacity, the load current is small, so that a long time is required for charging. Therefore, as shown in FIG. 3, the time from when the zero cross detection unit 19 detects the zero cross until the voltage detection unit 18 detects the completion of charging becomes longer, and the rising of the first pulse is delayed. Since the first predetermined time is set according to the above-described high load, if the rise of the first pulse is excessively delayed, the first pulse falls after the load current exceeds the zero cross point. Therefore, in the case of controlling the main switching unit 11 using only the first pulse, the main switching unit 11 is brought into a conducting state beyond the zero cross point at low load, and the charging operation for each half cycle is not stable.

  Therefore, in this embodiment, the second pulse output from the second pulse output unit 22 is used to limit the open state of the main opening / closing unit 11 for the second predetermined time. The second pulse rises in response to the detection of the zero cross by the zero cross detector 19 and falls after the elapse of the second predetermined time. This second predetermined time is set shorter than a half cycle of the load current.

  The first pulse output from the first pulse output unit 21 and the second pulse output from the second pulse output unit 22 are input to the main opening / closing control unit 25. The main opening / closing control unit 25 includes an AND circuit 25 a, calculates a logical product of the first pulse and the second pulse, and outputs the logical product to the main opening / closing unit 11. As a result, the main opening / closing part 11 is closed only for the overlapping time of the first predetermined time when the first pulse rises and the second predetermined time when the second pulse rises. As described above, the second pulse rises at the timing when the zero-cross detection unit 19 detects the zero-cross point, and falls in the second predetermined period shorter than the half cycle of the load current. Therefore, the completion of charging of the buffer capacitor 29 is detected. Even when the timing, i.e., the timing at which the first predetermined time starts later, shifts beyond the zero cross point of the power supply frequency, the main opening / closing part 11 is not closed. Thereby, it can charge reliably for every half cycle and the operation | movement stability is achieved. Since these operations are performed with respect to the load current, the load 3 is not limited to one with a power factor of 1, even if the main switching unit 11 is configured by a switch element 11a having a transistor structure. A two-wire load control device suitable for any of the above can be realized, and the main open / close part is a dual gate transistor switch element, so the load control device can be reduced in size and capacity at the same time. can do.

  According to the load control apparatus 1A according to the first embodiment, when the voltage detection unit 18 detects that the voltage input to the third power supply unit 16 has reached a predetermined threshold, the control unit 13 11 is turned on (closed) for a first predetermined time, so that power is supplied from the main switching unit 11 to the load during most of the half cycle of the commercial power supply. Further, when the second predetermined time elapses even within the first predetermined time, the control unit 13 makes the main opening / closing unit 11 non-conductive (opens). Even if the timing at which the time is started is delayed, the main switching unit 11 is turned off before the load current becomes zero. As a result, the main opening / closing part 11 is not conducted beyond the zero cross of the load current, so that charging can be performed reliably during a half cycle of the AC power supply.

  In addition, when the main opening / closing part 11 becomes non-conductive after the first predetermined time has elapsed, the auxiliary opening / closing part 17 is made conductive only for the second predetermined time, so that most of the half time of the commercial power supply is from the main opening / closing part. After the power is supplied to the load, the power is supplied from the auxiliary opening / closing unit 17 after the energization current decreases. Since these operations are performed with respect to the load current, the load is not limited to one with a power factor of 1, even if the main switching unit 11 is configured by a switch element 11a having a transistor structure. A two-wire load control device suitable for both can be realized. Further, since the level of noise generated during operation of the load control device can be kept low, it is possible to realize a load control device that is small and has a wide compatible load range.

(Second Embodiment)
A load control device according to a second embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing a configuration of a load control device 1B according to the second embodiment. The load control device 1 </ b> B is further provided with a current detection unit 26 for detecting a current flowing through the auxiliary opening / closing unit 17 and an OR circuit 25 b that operates according to a signal output from the current detection unit 26. Unlike the load control device 1 </ b> A according to the embodiment, the rest is the same. The OR circuit 25 b is provided at the subsequent stage of the AND circuit 25 a of the main opening / closing control unit 25.

  The auxiliary opening / closing part 17 is originally intended to detect a zero-cross point of the current, and is not intended to be energized, and is expected to be composed of a small switch element. However, if the frequency shifts in the commercial power supply or if the load control device is to be operated with both 50 Hz and 60 Hz, the time from when the main switching unit becomes non-conductive until the zero cross point of the current becomes long, the load Energization of the auxiliary opening / closing part is started before the current becomes sufficiently small. In addition, when an overload connection is made as a load, even if the energization time in the auxiliary opening / closing part is the same, the energization loss may increase, and the switch element constituting the auxiliary opening / closing part 17 may be damaged. Therefore, in the second embodiment, the current detection unit 26 detects the current value flowing through the auxiliary opening / closing unit 17, and when a current exceeding the allowable current value of the auxiliary opening / closing unit 17 flows again (for the fourth predetermined time). The main opening / closing part 11 is made conductive (closed) only for a period of time, and then the auxiliary opening / closing part 17 is made conductive again when the main opening / closing part 11 becomes non-conductive (open state).

  More specifically, the current detection unit 26 that has detected that a current exceeding the allowable current value of the auxiliary opening / closing unit 17 flows, outputs a signal to that effect to the OR circuit 25b of the main opening / closing control unit 25. When receiving either the output signal from the AND circuit 25a or the output signal from the current detection unit 26, the OR circuit 25b makes the main switching unit 11 conductive for a short time to protect the auxiliary switching unit 17. To do. By repeatedly switching the main opening / closing part 11 and the auxiliary opening / closing part 17 in this way, the switch element of the auxiliary opening / closing part 17 is prevented from being damaged, and the compatibility with the type of commercial power source and the overload are improved.

  According to the load control device 1B according to the second embodiment, when the current detection unit 26 detects that a current exceeding the allowable value flows through the auxiliary opening / closing unit 17, the main opening / closing unit is once turned on (closed). ), And then turn off. As a result, the switch element of the auxiliary opening / closing part 17 can be prevented from being damaged, and the auxiliary opening / closing part 17 can be configured with a small switch element, so that the load control device can be miniaturized, and the compatibility with the type of commercial power supply can be achieved. And improved response to overload.

  The present invention is not limited to the configuration of the above-described embodiment, and at least the control unit 13 receives a first charge completion signal of the buffer capacitor 29 from the voltage detection unit 18 and outputs the first pulse, and the zero cross detection unit 19 loads the load current. The operation of the main opening / closing part 11 may be controlled based on the logical product with the second pulse that receives and outputs the zero cross point detection signal. The present invention can be modified in various ways. For example, as for the second pulse, the output from the zero cross detector 19 is input to the main controller 20 constituted by a CPU or the like, and the first pulse is realized by software. You may comprise so that a signal may be output.

The circuit diagram which shows the structure of the load control apparatus which concerns on 1st Embodiment of this invention. The time chart which shows the signal waveform of each part at the time of the high load of the load control apparatus which concerns on 1st Embodiment. The time chart which shows the signal waveform of each part at the time of assuming that the 2nd predetermined time is not used for control of the main opening / closing part at the time of low load of the load control apparatus which concerns on 1st Embodiment. The time chart which shows the signal waveform of each part at the time of low load of the load control apparatus which concerns on 1st Embodiment at the time of using 2nd predetermined time for control of the main opening / closing part. The circuit diagram which shows the structure of the load control apparatus which concerns on 2nd Embodiment of this invention. The circuit diagram which shows the structure of the load control apparatus which concerns on a 1st prior art example. The circuit diagram which shows the structure of the load control apparatus which concerns on a 2nd prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B Load control apparatus 2 Power supply 3 Load 11 Main switching part 11a Switch element 12 Rectification part 13 Control part 14 1st power supply part 15 2nd power supply part 16 3rd power supply part 17 Auxiliary opening / closing part 17a Switch element 18 Voltage detection part 19 Zero cross detection unit 20 Main control unit 21 First pulse output unit 22 Second pulse output unit 23 Third pulse output unit 26 Current detection unit

Claims (3)

A main switching unit having a transistor-structure switch element and controlling supply of power to a load;
An auxiliary opening / closing part that has a thyristor-type switching element and controls supply of power to a load when the main opening / closing part is non-conductive;
A control unit that controls opening and closing of the main opening and closing unit and the auxiliary opening and closing unit;
A first power supply unit that is supplied with power from both ends of the main switching unit via a rectifying unit and supplies a stable voltage to the control unit;
A second power supply unit that supplies power to the first power supply unit when power is supplied from both ends of the main opening / closing unit via the rectification unit and power supply to the load is stopped;
In the load control device including a third power supply unit that supplies power to the first power supply unit when the main opening / closing unit or the auxiliary opening / closing unit is in a closed state and supplying power to the load,
A voltage detection unit that detects a voltage input to the third power supply unit; and a zero-cross detection unit that detects a zero-cross point of the load current;
The control unit is configured to supply a power to a load, the voltage detection unit counts a first predetermined time counted from when a voltage input to the third power supply unit reaches a predetermined threshold; A load characterized in that the main switching unit is made to conduct only for a time that overlaps with a second predetermined time that is less than a half cycle of the load current counted after the zero cross detection unit detects the zero cross point of the load current. Control device.   2. The load control device according to claim 1, wherein the control unit causes the auxiliary opening / closing part to conduct for a third predetermined time when the main opening / closing part is non-conducting. A current detection unit for detecting a current flowing through the auxiliary opening / closing unit;
When a current of a predetermined threshold value or more flows through the auxiliary opening / closing part, the control unit temporarily turns the main opening / closing part on, and then turns on the auxiliary opening / closing part when the main opening / closing part becomes non-conductive. The load control device according to claim 2, wherein:

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