JP4623220B2 - Power circuit - Google Patents

Description

  The present invention relates to a power supply circuit for an air conditioner including an inverter motor.

  A power supply circuit of an air conditioner that performs a refrigeration cycle by circulating a refrigerant through a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion valve, and a use side heat exchanger are connected to a pipe is connected to the power supply circuit. A main relay is provided in the current path of the power supply circuit in order to cut off the energization to the inverter motor that drives the compressor and stop the inverter motor. Conventionally, the main relay has been provided on the current path between the external power supply and the rectifier circuit that rectifies AC power in the power supply circuit (see, for example, Patent Document 1 (air conditioner main switch 21)).

JP 2001-45679 A

  In the case of a power supply circuit in which the main relay is provided on an AC current path as shown in Patent Document 1, the main relay is required for each AC power supply line of each phase connected to an external power supply. Increases the size and cost of the power circuit.

  If the main relay is provided on the DC current path between the rectifier circuit and the smoothing section, there is no need to provide a main relay on the AC power line for each phase, and the size and cost of the power circuit can be reduced. to become. However, in this case, the possibility of the deterioration and welding of the main relay increases for the following reasons.

  Since the inverter motor is connected to the power supply circuit, a large current flows through the current path in the power supply circuit when the inverter motor is driven. Therefore, for example, when opening the main relay to stop the inverter motor that is being driven when an abnormality occurs in the refrigeration cycle, if the main relay is opened in an energized state, a large burden is applied to the contact of the main relay, The contact of the main relay may be deteriorated or welded.

  In a power circuit in which the main relay is provided on an AC current path, the main relay is opened in a non-energized state by opening the main relay at a zero cross point of AC power supplied from the external power source. , Deterioration and welding of the contact of the main relay can be prevented.

  On the other hand, in the power supply circuit in which the main relay is provided on the direct current path, the main relay cannot be opened at the zero cross point, so that the possibility of deterioration or welding of the main relay increases.

  The present invention has been made to solve such problems, and can reliably stop the inverter motor included in the air conditioner when the refrigeration cycle is abnormal, and can also prevent deterioration and welding of the contacts of the main relay. An object is to provide a power supply circuit that can be prevented at low cost.

A power supply circuit for an air conditioner according to one aspect of the present invention includes a refrigeration cycle in which a refrigerant is circulated through a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion valve, and a use side heat exchanger are piped. An air conditioner power circuit to be executed,
A rectifier circuit (RC) for rectifying AC power supplied from an external power source;
A smoothing section (C) for smoothing the output of the rectifier circuit (RC);
A main relay (10) provided on a current path between the rectifier circuit (RC) and the smoothing unit (C);
An inverter circuit (30) that is connected between the smoothing section (C) and an inverter motor (M) that is a load, and generates AC power supplied to the inverter motor (M);
A main relay opening / closing control unit (120) for outputting an opening / closing control signal for instructing opening / closing to the main relay (10), an inverter circuit control unit (110) for outputting a driving signal to the inverter circuit (30), the air conditioner abnormality detecting section for detecting the abnormality the inverter circuit control unit a hardware (200) to a high impedance automatically driving signal output when the abnormal signal to be output when the abnormality detection is input (110) waveform forced cutoff unit to cut off electrically the (130), and wherein separately from the main relay switching control unit (120), the waveform forced cutoff unit (130) to the abnormality signal before Symbol main when entered A cutoff signal output unit (140) for outputting a cutoff signal, which is a control signal for opening the relay (10), to the main relay (10); A microcomputer (100) for controlling opening and closing operation and the operation of the inverter circuit (30) of the main relay (10),
The cut- off signal is input on the wiring connecting the cut-off signal output unit (140) and the main relay (10), and the cut-off signal is sent to the main relay (10) after a predetermined time from the input. ) To output a delay circuit (40),
When the main relay (10) is in a closed state and the abnormal signal is input to the waveform forced cutoff unit (130), the waveform forced cutoff unit (130) 110) is electrically cut off, and the cut-off signal output from the cut-off signal output unit (140) is input to the main relay (10) via the delay circuit (40), and the main relay (10) Is opened by the input of the cutoff signal.

  According to this configuration, the main relay is provided on a DC current path between the rectifier circuit and the smoothing unit, and opens and closes the current path. Therefore, unlike the case where the main relay, which requires the main relay for each phase AC power line connected to the external power source, is provided on the AC power line on the external power source side of the rectifier circuit, the AC of each phase Since it is not necessary to provide the main relay on the power line, the size and cost of the power circuit can be reduced.

  Furthermore, according to this configuration, when the main relay is in a closed state when an abnormality occurs in the refrigeration cycle, and the abnormality signal is input to the waveform forced cutoff unit, the waveform forced cutoff unit is the inverter. The inverter motor is stopped by electrically cutting off the circuit control unit. Therefore, the inverter motor can be reliably stopped when an abnormality occurs in the refrigeration cycle. In addition, since the abnormal signal is input to the waveform forced cutoff unit and the cutoff signal output from the cutoff signal output unit is input to the main relay via the delay circuit, the inverter motor Is stopped, that is, in a state where the main relay is not energized, the main relay is opened. Therefore, when the main relay is opened when an abnormality occurs in the refrigeration cycle, it is possible to prevent deterioration and welding of the contacts of the main relay.

  The said structure WHEREIN: It is preferable that the said inverter motor to which the said inverter circuit is connected is an inverter motor which drives the said compressor. According to this configuration, since the compressor is stopped when an abnormality occurs in the refrigeration cycle, the refrigeration cycle in which an abnormality has occurred can be stopped.

  In the above configuration, the abnormality detection unit is a high pressure switch that detects an abnormal increase in the high pressure of the refrigeration cycle, and the abnormal signal is output by the high pressure switch when the high pressure of the refrigeration cycle is abnormally increased. It can be an abnormal signal.

According to this configuration, when the high pressure of the refrigeration cycle is abnormally increased, the compressor can be stopped reliably and the refrigeration cycle can be stopped, so that the safety of the air conditioner can be improved .

  According to the power supply circuit for an air conditioner according to the present invention, when an abnormality occurs in the refrigeration cycle, the inverter motor included in the air conditioner can be stopped reliably, and deterioration and welding of the contacts of the main relay can be prevented. be able to. Therefore, the safety of the air conditioner can be improved and the life of the main relay can be extended.

It is a circuit diagram which shows the power supply circuit which concerns on Embodiment 1 of this invention. It is a time chart which shows operation | movement of the power supply circuit which concerns on Embodiment 1 of this invention. (A) is a high voltage abnormality signal state, (B) is a drive signal state, (C) is a waveform output state of a current output from a power supply circuit, and (D) is an open / close state of an electromagnetic contactor. It is shown, respectively. It is a circuit diagram which shows the power supply circuit which concerns on Embodiment 2 of this invention. It is a time chart which shows operation | movement of the power supply circuit which concerns on Embodiment 2 of this invention. (A) is a high voltage abnormality signal state, (B) is a drive signal state, (C) is a waveform output state of a current output from a power supply circuit, and (D) is an open / close state of an electromagnetic contactor. It is shown, respectively. It is a circuit diagram which shows the power supply circuit which concerns on Embodiment 3 of this invention.

  Hereinafter, power supply circuits according to Embodiments 1 to 3 of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>
FIG. 1 is a circuit diagram showing a power supply circuit according to Embodiment 1 of the present invention. The power supply circuit 1 is a power supply device that drives an inverter motor M of a compressor provided in an air conditioner (not shown), for example, and includes a rectifier circuit RC, a coil L, a main relay 10, and a capacitor C (smoothing unit). The voltage detection circuit 20, the shunt resistor R3, the inverter circuit 30, the delay circuit 40, and the microcomputer 100 are configured.

  The rectifier circuit RC is composed of, for example, a diode bridge circuit, is connected to output terminals T1 to T3 of an external power source E that is a commercial power source, for example, and rectifies AC power output from the external power source E.

  The coil L, the main relay 10 and the capacitor C are connected in series. Both terminals of this series circuit are connected to the respective output terminals of the rectifier circuit RC. The capacitor C forms a smoothing circuit and smoothes the output of the rectifier circuit RC. The coil L is a reactor provided for improving the power factor of the inverter circuit 30.

  The main relay 10 includes an electromagnetic contactor 11 (52C) and an unillustrated thermal relay. The main relay 10, more correctly, the magnetic contactor 11, is provided on the current path between the rectifier circuit RC and the capacitor C, and opens and closes the current path. Here, it is assumed that the main relay 10 is provided on the AC power supply line closer to the external power supply E than the rectifier circuit RC. In this case, since the main relay 10 is required for each AC power line of each phase connected to the external power source E, the power circuit 1 is increased in size and cost. On the other hand, in the present embodiment, the main relay 10 is provided on the current path between the rectifier circuit RC and the capacitor C, that is, on the direct current side. Therefore, it is necessary to provide the main relay 10 on the AC power supply line of each phase. no. As a result, the size and cost of the power supply circuit can be reduced.

  The voltage detection circuit 20 is a circuit in which two voltage dividing resistors R1 and R2 are connected in series between both electrodes of the capacitor C in order to detect a voltage between both electrodes of the capacitor C. A connection point between the voltage dividing resistor R1 and the voltage dividing resistor R2 is connected to an inverter circuit control unit 110 included in the microcomputer 100 via a signal line L11, and a voltage value at the connection point is output to the inverter circuit control unit 110. .

  The shunt resistor R3 is connected on the current path between the capacitor C and the inverter circuit 30 in order to monitor the current for driving the inverter motor M, and the current value after passing through the shunt resistor R3 is the signal line L12. Is output to the inverter circuit control unit 110.

  The inverter circuit 30 is composed of, for example, a switching element, a diode, or the like, which is an insulated gate bipolar transistor (IGBT), and converts the DC power output from the capacitor C into AC power having a predetermined frequency. Then, the inverter motor M is driven. The inverter circuit 30 receives a drive signal, which is a PWM signal output from the inverter circuit control unit 110 and input to the inverter circuit 30 via the signal line L15, and turns the IGBT on and off, so that the DC power is Convert to AC power.

  The microcomputer 100 controls the operation of the air conditioner by controlling the drive of the inverter motor M and the fan motor that drive the compressor and the opening degrees of the plurality of electric valves included in the air conditioner. The microcomputer 100 includes an inverter circuit control unit 110, a main relay opening / closing control unit 120, a waveform forced cutoff unit 130, and a cutoff signal output unit 140.

  The inverter circuit control unit 110 is connected to a connection point between the voltage dividing resistors R1 and R2 through the signal line L11, is connected to the shunt resistor R3 through the signal line L12, and is connected to the inverter circuit 30 through the signal line L13. Various electrical signals that are connected and sent via the signal lines L11 to L13 are monitored. In response to the electric signal, the inverter circuit control unit 110 outputs a drive signal, which is a PWM signal, to the inverter circuit 30 through the signal line L15 so that the drive frequency of the inverter motor M becomes a predetermined value. The inverter circuit 30 is controlled.

  The main relay opening / closing control unit 120 outputs an opening / closing control signal for instructing opening / closing of the magnetic contactor 11 to the main relay 10 via the signal line L16, and is provided on a current path between the rectifier circuit RC and the capacitor C. The electromagnetic contactor 11 is opened and closed. The main relay opening / closing control unit 120 closes the electromagnetic contactor 11 at the start of the operation of the air conditioner or at the time of return after the abnormality is resolved. At this time, the current path becomes conductive, the output from the rectifier circuit RC is supplied to the capacitor C and the inverter circuit 30, and the inverter motor M starts driving. On the other hand, when the operation of the air conditioner is stopped or when an abnormality is detected, the main relay opening / closing control unit 120 opens the electromagnetic contactor 11. At this time, the current path is interrupted, the output from the rectifier circuit RC is not supplied to the capacitor C and the inverter circuit 30, and the inverter motor M stops.

  A high-pressure abnormality signal output when the high-pressure switch 200 (abnormality detection unit) that detects an abnormal increase in the high-pressure pressure in the refrigeration cycle detects an abnormal increase in the high-pressure pressure is displayed on the waveform forced cutoff unit 130 as a signal line L14. Is input through. The waveform forced cutoff unit 130 is a so-called POE (Port Output Enable), and when the high voltage abnormality signal is input, the drive signal output from the signal line L15 by the inverter circuit control unit 110 is automatically set to high impedance. The inverter circuit control unit 110 is electrically disconnected.

  When the high voltage abnormality signal is input to the waveform forced cutoff unit 130, the cutoff signal output unit 140 sends a cutoff signal, which is a control signal for opening the electromagnetic contactor 11, to the main relay 10 via the signal line L17. and outputs it to.

  The delay circuit 40 is an RC circuit including, for example, a resistor and a capacitor provided on the signal line L17. The cutoff signal output by the cutoff signal output unit 140 is input to the delay circuit 40, and after a predetermined time from the input, the delay circuit 40 outputs the cutoff signal to the main relay 10.

  Next, based on the time chart shown in FIG. 2, the operation of the power supply circuit 1 when the electromagnetic contactor 11 is in the closed state and the high-voltage abnormal signal is input to the waveform forced cutoff unit 130 will be described. . 2A is the state of the high voltage abnormality signal, FIG. 2B is the state of the drive signal, FIG. 2C is the state of the waveform output of the current output from the power supply circuit 1, and FIG. The time-dependent change of the open / close state of the contactor 11 (52C) is shown.

  When the magnetic contactor 11 is in the closed state (FIG. 2D), when the high voltage abnormality signal is input to the waveform forced cutoff unit 130 (FIG. 2A), the waveform forced cutoff unit 130 controls the inverter circuit. Since the unit 110 is electrically cut off, the output of the drive signal from the inverter circuit control unit 110 is stopped (FIG. 2B). Therefore, the waveform output from the power supply circuit 1 is stopped (FIG. 2C), and the drive of the inverter motor M is also stopped. At this time, the cutoff signal output unit 140 outputs the cutoff signal to the main relay 10, but the cutoff signal is input to the main relay 10 via the delay circuit 40, so that waveform output from the power supply circuit 1 is stopped. After that, the electromagnetic contactor 11 is opened in a non-energized state (FIG. 2D). Note that the waveform output again after the waveform output from the power supply circuit 1 is stopped is a waveform due to capacitor discharge for discharging the electric power charged in the capacitor C to the inverter motor M for safety (FIG. 2). (D)).

  When the inverter motor M is driven, a large current flows through the electromagnetic contactor 11. Accordingly, in the power supply circuit in which the main relay 10 is provided on the AC power supply line closer to the external power supply E than the rectifier circuit RC, when the inverter motor M being driven is stopped by opening the electromagnetic contactor 11, the external power supply E Unless the electromagnetic contactor 11 is opened at the zero cross point of the supplied AC power, a large load is applied to the contact of the electromagnetic contactor 11, and the contact of the electromagnetic contactor 11 may be deteriorated or welded. However, a certain amount of time is required to detect the zero cross point. Therefore, with this configuration, it is difficult to immediately open the electromagnetic contactor 11 and stop the inverter motor M when the high pressure of the refrigeration cycle increases abnormally.

  On the other hand, in the power supply circuit 1, the waveform forced cutoff unit 130 stops the inverter motor M by electrically cutting off the inverter circuit control unit 110. Therefore, when the high pressure of the refrigeration cycle increases abnormally, the inverter motor M can be stopped immediately to stop the refrigeration cycle.

  Moreover, since the waveform forced cutoff unit 130 is hardware that functions independently of the control program executed by the microcomputer 100, the inverter motor can be used even when an abnormal increase in high pressure occurs when an error occurs in the control program. The refrigeration cycle can be stopped by reliably stopping M. Therefore, the safety | security of an air conditioner can be improved by using the power supply circuit 1 for an air conditioner.

  Further, according to the power supply circuit 1, the cutoff signal output from the cutoff signal output unit 140 in response to the input of the high voltage abnormality signal to the waveform forced cutoff unit 130 is input to the main relay 10 via the delay circuit 40. It is. Therefore, the electromagnetic contactor 11 is opened after the inverter motor M is stopped, that is, in a state where the electromagnetic contactor 11 is not energized. Therefore, when the electromagnetic contactor 11 is opened when the high pressure of the refrigeration cycle is abnormally increased, contact deterioration of the electromagnetic contactor 11 and welding can be prevented.

<Embodiment 2>
A power supply circuit 2 according to Embodiment 2 of the present invention will be described below. Note that description of points that are not different from the power supply circuit 1 according to the first embodiment is omitted unless necessary. FIG. 3 is a circuit diagram showing the power supply circuit 2. The same components as those of the power supply circuit 1 are denoted by the same reference numerals. The power supply circuit 2 is configured by removing the cutoff signal output unit 140 and the delay circuit 40 from the power supply circuit 1. Therefore, the microcomputer 100A included in the power supply circuit 2 includes the inverter circuit control unit 110, the main relay opening / closing control unit 120, and the waveform forced cutoff unit 130, and is configured by removing the cutoff signal output unit 140 from the microcomputer 100 included in the power supply circuit 1. It becomes.

  Thus, since the power supply circuit 2 is different in configuration from the power supply circuit 1, as described below based on the time chart shown in FIG. 4, the electromagnetic contactor 11 is in a closed state, and the high voltage abnormality signal is The operation of the power supply circuit 2 when input to the waveform forced cutoff unit 130 is different from that of the power supply circuit 1. 4A shows the state of the high voltage abnormality signal, FIG. 4B shows the state of the drive signal, FIG. 4C shows the state of waveform output of the current output from the power supply circuit 2, and FIG. 4D. Indicates time-dependent changes in the open / close state of the magnetic contactor 11 (52C).

  When the magnetic contactor 11 is in a closed state (FIG. 4D), when the high voltage abnormality signal is input to the waveform forced cutoff unit 130 (FIG. 4A), the waveform forced cutoff unit 130 controls the inverter circuit. Since the unit 110 is electrically cut off, the output of the drive signal from the inverter circuit control unit 110 is stopped (FIG. 4B). Therefore, the waveform output from the power supply circuit 2 is stopped (FIG. 4C). At this time, the main relay open / close control unit 120 maintains the electromagnetic contactor 11 in the closed state without outputting the open / close control signal to the main relay 10 (FIG. 4D). That is, when the electromagnetic contactor 11 is in the closed state, the power supply circuit 2 is in phase with the power supply circuit 1 in that the electromagnetic contactor 11 remains closed even if the high voltage abnormality signal is input to the waveform forced cutoff unit 130. It is different.

  Thus, in the power supply circuit 2, the main relay switching control unit 120 maintains the electromagnetic contactor 11 in the closed state when the high pressure of the refrigeration cycle is abnormally increased, so that the electromagnetic contactor 11 is opened when energized. Degradation and welding of the generated contact of the electromagnetic contactor 11 can be prevented.

  Moreover, since the electromagnetic contactor 11 is in the closed state, it is possible to drive the fan motor of a heat exchanger (not shown) connected to the power supply circuit 3 together with the inverter motor M. Therefore, since the heat exchange efficiency between the refrigerant, the indoor air, and the outdoor air in the heat exchanger does not decrease, the return from the high pressure abnormality of the air conditioner is faster than when the electromagnetic contactor 11 is opened.

  Other effects of the power supply circuit 2 are the same as those of the power supply circuit 1.

<Embodiment 3>
A power supply circuit 3 according to Embodiment 3 of the present invention will be described below. In addition, about the point which is not different from Embodiment 1 and 2, description is abbreviate | omitted unless it is required. FIG. 3 is a circuit diagram showing the power supply circuit 3. The same components as those of the power supply circuits 1 and 2 are denoted by the same reference numerals. The power supply circuit 3 requires the gate IC 101 for driving the inverter circuit 30B, and stops the inverter motor M by cutting off the drive signal output to the inverter circuit 30B by the gate IC 101 when the high pressure of the refrigeration cycle rises abnormally. In this respect, it differs from the power supply circuit 2.

  The power supply circuit 3 includes a rectifier circuit RC, a coil L, a main relay 10, a capacitor C (smoothing unit), a voltage detection circuit 20, a shunt resistor R3, an inverter circuit 30B, a microcomputer 100B, and a gate IC 101. It is configured with. The rectifier circuit RC, the coil L, the main relay 10, the capacitor C, the voltage detection circuit 20, the shunt resistor R3, and the inverter circuit 30B are connected to each other in the same manner as the power supply circuits 1 and 2.

  Inverter circuit 30B, like power supply circuits 1 and 2, is composed of an IGBT (switching element), a diode, and the like, and converts the DC power output from capacitor C into AC power having a predetermined frequency to convert the inverter motor. Drive M. The inverter circuit 30B receives a drive signal that is a PWM signal that is output from the drive signal output unit 170 included in the gate IC 101 and is input to the inverter circuit 30B via the signal line L15B2, and turns the IGBT on and off. Conversion from DC power to AC power.

  Similarly to the power supply circuits 1 and 2, the microcomputer 100B controls the inverter motor M and the fan motor that drive the compressor, and controls the opening of a plurality of electric valves included in the air conditioner, thereby operating the air conditioner. to control. The microcomputer 100B includes a gate IC control unit 150 instead of the inverter circuit control unit 110, and the waveform forced cutoff unit 130 is different from the microcomputer 100A of the power supply circuit 2 in that it is provided in the gate IC 101 instead of the microcomputer 100B. .

  The gate IC control unit 150 is connected to a connection point between the voltage dividing resistors R1 and R2 via the signal line L11, connected to the shunt resistor R3 via the signal line L12, and connected to the inverter circuit 30 via the signal line L13. Various electrical signals that are connected and sent via the signal lines L11 to L13 are monitored. In response to the electric signal, the gate IC control unit 150 controls the gate IC 101 by outputting a control signal to the gate IC 101 via the signal line L15B1 so that the drive frequency of the inverter motor M becomes a predetermined value. to.

  The gate IC 101 includes a control signal input unit 160, a drive signal output unit 170, and a waveform forced cutoff unit 130. A control signal output from the gate IC control unit 150 is input to the control signal input unit 160 via the signal line L15B1. The drive signal output unit 170 generates a PWM signal corresponding to the control signal input to the control signal input unit 160 as a drive signal, and outputs the drive signal to the inverter circuit 30 via the signal line L15B2.

  When the magnetic contactor 11 is in a closed state, and the high-voltage abnormality signal is input to the waveform forced cutoff unit 130, the state of the high-voltage abnormality signal, the state of the drive signal, and the power supply circuit 3 The time-dependent changes in the waveform output state of the output current and the open / close state of the magnetic contactor 11 are the same as those in the power supply circuit 2 shown in the time chart of FIG.

  By using the power supply circuit 3 for the air conditioner, the same effects as those of the second embodiment can be obtained.

  As described above, the power supply circuits 1 to 3 according to the first to third embodiments of the present invention have been described. However, the present invention is not limited to this, and for example, the following modified embodiments can be taken.

  (1) In the power supply circuit 3 according to the third embodiment, the inverter circuit 30B that requires the gate IC 101 for driving is used as the inverter circuit. However, instead of the inverter circuit 30B, the control signal input unit 160, the drive signal output A so-called intelligent power module having the function of a gate IC having the unit 170 and the waveform forced cutoff unit 130 can be used as an inverter circuit. By using an intelligent power module, it is possible to reduce the cost by reducing the size of the power supply circuit and the number of parts.

  (2) In the first to third embodiments, only one main relay 10 is provided in the power supply circuit. However, in the case of a large capacity power supply circuit, a plurality of main relays may be provided in parallel. . As a result, it is not necessary to use a large capacity main relay, so that it is easy to procure the main relay and it is possible to reduce the cost.

C capacitor (smoothing part)
E External power supply M Inverter motor RC Rectifier circuit 1-3 Power supply circuit 10 Main relay 11 Magnetic contactor 30, 30B Inverter circuit 40 Delay circuit 100, 100A, 100B Microcomputer 101 Gate IC
DESCRIPTION OF SYMBOLS 110 Inverter circuit control part 120 Main relay opening / closing control part 130 Waveform forced cutoff part 140 Shutdown signal output part 150 Gate IC control part 160 Control signal input part 170 Drive signal output part 200 High pressure switch (abnormality detection part)

Claims (3)

A compressor, a heat source side heat exchanger, an expansion valve, and a utilization side heat exchanger are air conditioner power supply circuits that circulate refrigerant in a refrigerant circuit connected by piping and execute a refrigeration cycle,
A rectifier circuit (RC) for rectifying AC power supplied from an external power source;
A smoothing section (C) for smoothing the output of the rectifier circuit (RC);
A main relay (10) provided on a current path between the rectifier circuit (RC) and the smoothing unit (C);
An inverter circuit (30) that is connected between the smoothing section (C) and an inverter motor (M) that is a load, and generates AC power supplied to the inverter motor (M);
A main relay opening / closing control unit (120) for outputting an opening / closing control signal for instructing opening / closing to the main relay (10), an inverter circuit control unit (110) for outputting a driving signal to the inverter circuit (30), the air conditioner The abnormality detection unit (200) for detecting the abnormality of the hardware automatically sets the drive signal output to high impedance when the abnormality signal output at the time of abnormality detection is input, and the inverter circuit control unit (110) waveform forced cutoff unit to cut off electrically the (130), and wherein separately from the main relay switching control unit (120), the waveform forced cutoff unit (130) to the abnormality signal before Symbol main when entered A cutoff signal output unit (140) for outputting a cutoff signal, which is a control signal for opening the relay (10), to the main relay (10); A microcomputer (100) for controlling opening and closing operation and the operation of the inverter circuit (30) of the main relay (10),
The cut- off signal is input on the wiring connecting the cut-off signal output unit (140) and the main relay (10), and the cut-off signal is sent to the main relay (10) after a predetermined time from the input. ) To output a delay circuit (40),
When the main relay (10) is in a closed state and the abnormal signal is input to the waveform forced cutoff unit (130), the waveform forced cutoff unit (130) 110) is electrically cut off, and the cut-off signal output from the cut-off signal output unit (140) is input to the main relay (10) via the delay circuit (40), and the main relay (10) Is a power supply circuit (1) which is opened by the input of the cutoff signal.   The power supply circuit (1) according to claim 1, wherein the inverter motor to which the inverter circuit (30) is connected is an inverter motor (M) that drives the compressor. The abnormality detection unit is a high pressure switch (200) that detects an abnormal increase in the high pressure of the refrigeration cycle,
The power supply circuit according to claim 2, wherein the abnormal signal is a high-pressure abnormal signal that is output when the high-pressure switch (200) abnormally increases the high-pressure pressure of the refrigeration cycle.

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