Power supply control circuit and air conditioner comprising same

Abstract

The purpose of the present disclosure is to provide a power supply control circuit that is capable of controlling two switching circuits with a single microcomputer. In a power supply control circuit (100), the reference potential of a second switching circuit (25B) differs from that of a first switching circuit (25A). A microcomputer (40) outputs a first control signal (PWM-1) which is directed to the first switching circuit (25A) and a second control signal (PWM-2) which is directed to the second switching circuit (25B). A first potential conversion unit (46A) converts the potential of the second control signal (PWM-2). The power supply control circuit (100) makes it possible to use the first potential conversion unit (46A) to convert the potential of one of the two control signals, and therefore makes it possible to control, with a single microcomputer, two switching circuits having different reference potentials.

Description

Power supply control circuit and air conditioner equipped with the same

[0001] This invention relates to a power supply control circuit mounted on a three-phase, four-wire, 400V air conditioner.

[0002] For example, a control device disclosed in Patent Document 1 (WO2017 / 200027) is known as a device for controlling an AC 400V motor and an AC 200V motor using an N-phase in a three-phase, four-wire, 400V air conditioner. In this control device, a signal for controlling the compressor motor and a signal for controlling the fan motor are output from a microcomputer. However, because the microcomputer and the fan motor do not share a common ground, the signal for controlling the fan motor is input to the fan motor via a photocoupler.

[0003] However, the fan motor described in Patent Document 1 includes a microcomputer, a drive circuit, and a switching circuit, which essentially requires two microcomputers. Therefore, from the perspective of cost reduction, it is desirable to control two switching circuits with one microcomputer.

[0004] A first aspect of the power supply control circuit is mounted on a printed wiring board configured to receive R, S, T, and N phases from an AC power supply that supplies three-phase AC in a three-phase, four-wire system, and includes a first rectifier circuit, a second rectifier circuit, a first switching circuit, a second switching circuit, a microcomputer, and a first potential conversion unit. The first rectifier circuit rectifies the AC voltages of the R, S, and T phases. The second rectifier circuit rectifies the AC voltages of any one of the R, S, and T phases and the N phase. The first switching circuit is connected to the first rectifier circuit. The second switching circuit is connected to the second rectifier circuit and has a reference potential different from that of the first switching circuit. The microcomputer outputs a first control signal to the first switching circuit and a second control signal to the second switching circuit. The first potential conversion unit converts the potential of the first control signal or the second control signal.

[0005] Conventionally, in a power supply control circuit that controls two switching circuits with different reference potentials, the potentials of the control signals output to each switching circuit are different, so a microcomputer corresponding to each switching circuit is required.

[0006] However, in this power supply control circuit, the potential of either of the two control signals can be converted by the first potential conversion unit, making it possible to control two switching circuits with different reference potentials using a single microcomputer.

[0007] A power supply control circuit according to a second aspect is the power supply control circuit according to the first aspect, wherein the transmission speed of the first potential conversion unit is 10 Mbps or more.

[0008] In this power supply control circuit, delays in the transmission speed caused by the operation time of the first potential conversion unit are suppressed.

[0009] A power supply control circuit according to a third aspect is the power supply control circuit according to the first or second aspect, further comprising a first current detection unit, a second current detection unit, and a third potential conversion unit. The first current detection unit detects the load current of the first switching circuit and outputs the detected current value to the microcomputer as a first current detection signal. The second current detection unit detects the load current of the second switching circuit and outputs the detected current value to the microcomputer as a second current detection signal. The third potential conversion unit converts the potential of either the first or second current detection signal, whichever has a reference potential different from the reference potential of the microcomputer.

[0010] A power supply control circuit according to a fourth aspect is the power supply control circuit according to the first or second aspect, further comprising a first voltage detection unit, a second voltage detection unit, and a second potential conversion unit. The first voltage detection unit detects a voltage across a first smoothing capacitor that smoothes the output voltage from the first rectifier circuit and outputs the detected voltage value to the microcomputer as a first voltage detection signal. The second voltage detection unit detects a voltage across a second smoothing capacitor that smoothes the output voltage from the second rectifier circuit and outputs the detected voltage value to the microcomputer as a second voltage detection signal. The second potential conversion unit converts the potential of either the first or second voltage detection signal, whichever has a reference potential different from the reference potential of the microcomputer.

[0011] A power supply control circuit according to a fifth aspect is a power supply control circuit according to any one of the first aspect to the fourth aspect, in which the shortest distance from the first potential conversion unit to the first switching circuit or the shortest distance from the first potential conversion unit to the second switching circuit is shorter than the shortest distance from the microcontroller to the first potential conversion unit.

[0012] In this power supply control circuit, the shorter the distance from the first potential conversion section to each switching circuit, the smaller the size of the printed wiring board, which contributes to miniaturization of the power supply control circuit.

[0013] A power supply control circuit according to a sixth aspect is a power supply control circuit according to any one of the first aspect to the fifth aspect, in which at least one of the first switching circuit and the second switching circuit is a power module in which a plurality of switching elements that convert DC power into AC power of a predetermined frequency are built into one package.

[0014] In this power supply control circuit, modularization of the switching circuit facilitates the design of peripheral circuits of the switching circuit on a printed wiring board.

[0015] A seventh aspect of the power supply control circuit is a power supply control circuit mounted on a printed wiring board configured to receive R, S, T, and N phases from an AC power supply that supplies three-phase AC in a three-phase, four-wire system, and includes a first rectifier circuit, a first switching circuit, a third switching circuit, a microcomputer, and a first potential conversion unit. The first rectifier circuit rectifies the AC voltages of the R, S, and T phases. The first switching circuit is connected to the first rectifier circuit. The third switching circuit is connected in parallel between the AC power supply and the first rectifier circuit and has a reference potential different from that of the first switching circuit. The microcomputer outputs a first control signal to the first switching circuit and a third control signal to the third switching circuit. The first potential conversion unit converts the potential of the first control signal or the third control signal.

[0016] Conventionally, in a power supply control circuit that controls two switching circuits with different reference potentials, the potentials of the control signals output to each switching circuit are different, and therefore a microcomputer corresponding to each switching circuit is required.

[0017] However, in this power supply control circuit, the potential of either of the two control signals can be converted by the first potential conversion unit, making it possible to control two switching circuits with different reference potentials using a single microcomputer.

[0018] A power supply control circuit according to an eighth aspect is the power supply control circuit according to the seventh aspect, wherein the transmission speed of the first potential conversion unit is 10 Mbps or more.

[0019] In this power supply control circuit, delays in the transmission speed caused by the operation time of the first potential conversion unit are suppressed.

[0020] A power supply control circuit according to a ninth aspect is the power supply control circuit according to the seventh or eighth aspect, further comprising a first current detection unit, a third current detection unit, and a third potential conversion unit. The first current detection unit detects a load current of the first switching circuit and outputs the detected current value to the microcomputer as a first current detection signal. The third current detection unit detects a bus current of the third switching circuit and outputs the detected current value to the microcomputer as a third current detection signal. The third current conversion unit converts the potential of either the first or third current detection signal, whichever has a reference potential different from the reference potential of the microcomputer.

[0021] A power supply control circuit according to a tenth aspect is the power supply control circuit according to the seventh or eighth aspect, further comprising a first voltage detection unit, a third voltage detection unit, and a second potential conversion unit. The first voltage detection unit detects a voltage across a first smoothing capacitor that smoothes the output voltage from the first rectifier circuit and outputs the detected voltage value to the microcomputer as a first voltage detection signal. The third voltage detection unit detects a voltage across a third smoothing capacitor that smoothes the output voltage from the third switching circuit and outputs the detected voltage value to the microcomputer as a third voltage detection signal. The second potential conversion unit converts the potential of either the first or third voltage detection signal, whichever has a reference potential different from the reference potential of the microcomputer.

[0022] The power supply control circuit of an eleventh aspect is a power supply control circuit of any one of the seventh aspect to the tenth aspect, in which the shortest distance from the first potential conversion unit to the first switching circuit or the shortest distance from the first potential conversion unit to the third switching circuit is shorter than the shortest distance from the microcontroller to the first potential conversion unit.

[0023] In this power supply control circuit, the shorter the distance from the first potential conversion section to each switching circuit, the smaller the size of the printed wiring board, which contributes to miniaturization of the power supply control circuit.

[0024] A power supply control circuit according to a twelfth aspect is a power supply control circuit according to any one of the seventh aspect to the eleventh aspect, in which the third switching circuit is a power module in which a plurality of switching elements that generate compensation currents for suppressing harmonic currents are built into one package.

[0025] In this power supply control circuit, modularization of the third switching circuit facilitates the design of peripheral circuits of the third switching circuit on a printed wiring board.

[0026] A power supply control circuit according to a thirteenth aspect is the power supply control circuit according to any one of the first to twelfth aspects, further comprising a power factor correction circuit. The power factor correction circuit has a first switching element, a rectifying element, and a reactor, and improves the power factor of the AC power supply by inputting a voltage rectified by the first rectifying circuit and controlling the on / off of the first switching element by a microcomputer.

[0027] A power supply control circuit according to a fourteenth aspect is the power supply control circuit according to the thirteenth aspect, which is a power module in which at least the first switching element and the rectifying element are built into one package.

[0028] In this power supply control circuit, modularization makes it easier to design the peripheral circuits of the power factor correction circuit on the printed wiring board.

[0029] An air conditioner according to a fifteenth aspect is an air conditioner including the power supply control circuit according to any one of the first to fourteenth aspects.

[0030] FIG. 1 is a circuit diagram showing the configuration of a power supply control circuit according to a first embodiment of the present disclosure. FIG. 2 is a configuration diagram of a switching circuit and a gate drive circuit that drives it. FIG. 3 is a circuit diagram showing the configuration of a power supply control circuit according to a second embodiment of the present disclosure. FIG. 4 is a configuration diagram of a third switching circuit and a gate drive circuit that drives it. FIG. 5 is a circuit diagram showing the configuration of a power supply control circuit according to a first modified example of the first embodiment. FIG. 6 is a circuit diagram showing the configuration of a power supply control circuit according to a first modified example of the second embodiment. FIG. 7 is a partial plan view of a printed wiring board showing the positional relationship of a first switching circuit, a second switching circuit, a microcomputer, and a potential conversion unit according to a second modified example of the first embodiment. FIG. 8 is a circuit diagram showing the configuration of a power supply control circuit according to another embodiment. FIG. 9 is a configuration diagram of a PWM converter and a fourth gate drive circuit that drives it.

[0031] First Embodiment (1) Overview of Power Supply Control Circuit 100 Fig. 1 is a circuit diagram showing the configuration of a power supply control circuit 100 according to a first embodiment of the present disclosure. In Fig. 1, the power supply control circuit 100 is mounted on a printed wiring board 10 configured to receive R-phase, S-phase, T-phase, and N-phase inputs from an AC power supply 91 that supplies three-phase AC in a three-phase, four-wire system.

[0032] The power supply control circuit 100 includes a first rectifier circuit 20A, a second rectifier circuit 20B, a first voltage detection unit 23A, a second voltage detection unit 23B, a first current detection unit 24A, a second current detection unit 24B, a first switching circuit 25A, a second switching circuit 25B, a microcomputer 40, a first potential conversion unit 46A, a second potential conversion unit 46B, and a third potential conversion unit 46C.

[0033] The first rectifier circuit 20A rectifies the R-phase, S-phase, and T-phase AC power. The second rectifier circuit 20B rectifies any one of the R-phase, S-phase, and T-phase AC power and the N-phase AC power.

[0034] The first voltage detection unit 23A detects the voltage across the first smoothing capacitor 22A, which smoothes the output voltage from the first rectifier circuit 20A, and outputs the detected voltage value to the microcomputer 40 as a first voltage detection signal.

[0035] The second voltage detection unit 23B detects the voltage across the second smoothing capacitor 22B, which smoothes the output voltage from the second rectifier circuit 20B, and outputs the detected voltage value to the microcomputer 40 as a second voltage detection signal.

[0036] The first current detection unit 24A detects the load current of the first switching circuit 25A and outputs the detected current value to the microcomputer 40 as a first current detection signal.

[0037] The second current detection unit 24B detects the load current of the second switching circuit 25B and outputs the detected current value to the microcomputer 40 as a second current detection signal.

[0038] The first switching circuit 25A is connected to the first rectifier circuit 20A. The second switching circuit 25B is connected to the second rectifier circuit 20B, and has a reference potential different from that of the first switching circuit 25A.

[0039] The microcomputer 40 outputs a first control signal PWM-1 to the first switching circuit 25A and a second control signal PWM-2 to the second switching circuit 25B. The first potential converter 46A converts the potential of the first control signal PWM-1 or the second control signal PWM-2.

[0040] The second potential converter 46B converts the potential of either the first voltage detection signal or the second voltage detection signal, whichever has a reference potential different from the reference potential of the microcomputer 40 .

[0041] The third potential converter 46C converts the potential of either the first or second current detection signal, whichever has a reference potential different from the reference potential of the microcomputer 40 .

[0042] The power supply control circuit 100 of the present disclosure is mounted on, for example, an outdoor unit of a three-phase, four-wire, 400V air conditioner.

[0043] (2) Detailed Configuration (2-1) Printed Wiring Board 10 The printed wiring board 10 is a multilayer printed wiring board having a plurality of conductive pattern layers stacked with insulating layers sandwiched therebetween.

[0044] The printed wiring board 10 is mounted with the following components of the power supply control circuit 100: an input terminal 9, a first rectifier circuit 20A, a second rectifier circuit 20B, a first switching circuit 25A, a second switching circuit 25B, a switching power supply 31, a refrigerant control circuit 42, a first potential conversion unit 46A, a second potential conversion unit 46B, a third potential conversion unit 46C, and a microcomputer 40 that controls these components.

[0045] The input terminal 9 is configured to receive R, S, T, and N phases from an AC power supply 91 that supplies three-phase AC in a three-phase, four-wire system. A first wiring 11, a second wiring 12, a third wiring 13, and a fourth wiring 14, which are conductive patterns, are connected to the R, S, T, and N phases of the AC power supply 91 via the input terminal 9, respectively.

[0046] (2-2) First Rectifier Circuit 20A The first rectifier circuit 20A is a three-phase diode bridge that full-wave rectifies AC power input from a first wiring 11 connected to the R phase, a second wiring 12 connected to the S phase, and a third wiring 13 connected to the T phase.

[0047] The first rectifier circuit 20A is a diode module in which six bridge-connected diode chips are built into one package, and is mounted on the first surface 10a of the printed wiring board 10.

[0048] (2-3) Second Rectifier Circuit 20B The second rectifier circuit 20B is a single-phase diode bridge that full-wave rectifies AC power input from a fourth wiring 14 connected to the N phase and a fifth wiring 15 branching from the first wiring 11. The wiring from which the fifth wiring 15 branches may be any of the first wiring 11, the second wiring 12, and the third wiring 13.

[0049] The second rectifier circuit 20B is a diode module in which four bridge-connected diode chips are built into one package.

[0050] (2-4) First Smoothing Capacitor 22A, Second Smoothing Capacitor 22B The first smoothing capacitor 22A smoothes the output voltage from the first rectifier circuit 20A. The second smoothing capacitor 22B smoothes the output voltage from the second rectifier circuit 20B.

[0051] (2-5) First Voltage Detector 23A The first voltage detector 23A is connected to the output side of the first smoothing capacitor 22A and detects the voltage across the first smoothing capacitor 22A. The first voltage detector 23A is configured such that two resistors connected in series to each other are connected in parallel to the smoothing capacitor 22A, and the voltage across the first smoothing capacitor 22A is divided. The voltage value at the connection point between these two resistors is input to the microcomputer 40.

[0052] The first voltage detection unit 23A does not necessarily have to be provided, and can be replaced by other means.

[0053] (2-6) Second Voltage Detector 23B The second voltage detector 23B is connected to the output side of the second smoothing capacitor 22B and detects the voltage across the second smoothing capacitor 22B. The second voltage detector 23B is configured such that two resistors connected in series to each other are connected in parallel to the second smoothing capacitor 22B, and the voltage across the second smoothing capacitor 22B is divided. The voltage value at the connection point between these two resistors is input to the microcomputer 40.

[0054] The second voltage detection unit 23B does not necessarily have to be provided, and can be replaced by other means.

[0055] (2-7) First Current Detector 24A The first current detector 24A is connected between the first smoothing capacitor 22A and the first switching circuit 25A and to the negative output terminal side of the first smoothing capacitor 22A. After the first motor 51A is started, the first current detector 24A detects the motor current flowing through the first motor 51A.

[0056] The first current detection unit 24A may be configured with an amplifier circuit using a shunt resistor and an operational amplifier that amplifies the voltage across the resistor. The motor current detected by the first current detection unit 24A is input to the microcomputer 40.

[0057] (2-8) Second Current Detector 24B The second current detector 24B is connected between the second smoothing capacitor 22B and the second switching circuit 25B and to the negative output terminal side of the second smoothing capacitor 22B. After the second motor 51B is started, the second current detector 24B detects the motor current flowing through the second motor 51B.

[0058] The second current detector 24B may be configured with an amplifier circuit using a shunt resistor and an operational amplifier that amplifies the voltage across the resistor. The motor current detected by the second current detector 24B is input to the microcomputer 40.

[0059] (2-9) First Switching Circuit 25A, Second Switching Circuit 25B The first switching circuit 25A is an inverter circuit connected to the output side of the first smoothing capacitor 22A. The second switching circuit 25B is an inverter circuit connected to the output side of the second smoothing capacitor 22B. Since the first switching circuit 25A and the second switching circuit 25B have the same configuration, they will be described as switching circuits 25.

[0060] 2 is a configuration diagram of switching circuit 25 and gate drive circuit 26 that drives it. In Fig. 2, switching circuit 25 includes, as switching elements, a plurality of insulated gate bipolar transistors (hereinafter simply referred to as transistors) Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b, and a plurality of freewheeling diodes D3a, D3b, D4a, D4b, D5a, and D5b.

[0061] The transistors Q3a and Q3b, Q4a and Q4b, and Q5a and Q5b are connected in series with each other, and the diodes D3a to D5b are connected in parallel with each other so that the collector terminal of the transistor and the cathode terminal of the diode are connected to each of the transistors Q3a to Q5b, and the emitter terminal of the transistor and the anode terminal of the diode are connected to each of the transistors Q3a to Q5b.

[0062] The switching circuit 25 generates drive voltages SU, SV, SW for driving the motor by applying a DC voltage from the smoothing capacitor 22 and turning on and off each of the transistors Q3a to Q5b at timings instructed by the gate drive circuit 26. These drive voltages SU, SV, SW are output to the motor from connection points NU, NV, NW between the transistors Q3a and Q3b, Q4a and Q4b, and Q5a and Q5b, respectively.

[0063] The first switching circuit 25A and the second switching circuit 25B are power modules in which upper arm switching elements (Q3a, Q4a, Q5a, D3a, D4a, D5a) and lower arm switching elements (Q3b, Q4b, Q5b, D3b, D4b, D5b) are built into a single package.

[0064] The first switching circuit 25A and the second switching circuit 25B are mounted on the first surface 10a of the printed wiring board 10.

[0065] (2-10) First Gate Drive Circuit 26A, Second Gate Drive Circuit 26B The first gate drive circuit 26A changes the on / off state of each of the transistors Q3a to Q5b of the first switching circuit 25A based on a first control signal PWM-1 from the microcomputer 40. The second gate drive circuit 26B changes the on / off state of each of the transistors Q3a to Q5b of the second switching circuit 25B based on a second control signal PWM-2 from the microcomputer 40.

[0066] The first gate drive circuit 26A and the second gate drive circuit 26B have the same configuration, and therefore will be described as the gate drive circuit 26.

[0067] 2, the gate drive circuit 26 generates gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz to be applied to the gates of the transistors Q3a to Q5b so that drive voltages SU, SV, and SW having duty ratios determined by the microcomputer 40 are output to the motor from the switching circuit 25. The generated gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz are applied to the gate terminals of the respective transistors Q3a to Q5b.

[0068] (2-11) Microcomputer 40 The microcomputer 40 is connected to the first voltage detection unit 23A, the first current detection unit 24A, and the first gate drive circuit 26A. The microcomputer 40 controls the first gate drive circuit 26A to drive the first motor 51A. The first motor 51A is a motor that drives the compressor.

[0069] The microcomputer 40 is also connected to the second gate drive circuit 26B via the first potential converter 46A. The microcomputer 40 controls the second gate drive circuit 26B to drive the second motor 51B. The second motor 51B drives a fan.

[0070] The microcomputer 40 is also connected to the second voltage detection unit 23B via a second potential conversion unit 46B, and to the second current detection unit 24B via a third potential conversion unit 46C.

[0071] Furthermore, the microcomputer 40 also functions as a refrigerant control microcomputer, for example, controlling the refrigerant control circuit 42 of the air conditioner and adjusting the circulation direction of the refrigerant in the refrigerant circuit, the evaporation temperature of the refrigerant, and the degree of superheat and subcool.

[0072] (2-12) Switching Power Supply 31 The switching power supply 31 converts AC power input from the sixth wiring 16 branching from the third wiring 13 and the seventh wiring 17 branching from the fourth wiring 14 into DC power of a predetermined voltage, and supplies it to the microcomputer 40, etc. The wiring from which the sixth wiring 16 branches may be any of the first wiring 11, the second wiring 12, and the third wiring 13.

[0073] (2-13) Refrigerant Control Circuit 42 Based on commands from the microcomputer 40, the refrigerant control circuit 42 controls the operation of the four-way switching valve 71, which switches the circulation direction of the refrigerant circulating through the refrigerant circuit of the air conditioner, and the operation of the electric expansion valve 72, which adjusts the evaporation temperature, degree of superheat, and degree of subcooling of the refrigerant.

[0074] The ground potential of the refrigerant control circuit 42 is GND-A, which is the same as the ground potential of the first switching circuit 25A.

[0075] (2-14) First to third potential conversion units (46A to 46C) The first potential conversion unit 46A is provided between the microcomputer 40 and the second gate drive circuit 26B, and insulates the input signal from the microcomputer 40 to the first potential conversion unit 46A from the output signal from the first potential conversion unit 46A to the second gate drive circuit 26B.

[0076] The second potential conversion unit 46B is provided between the microcomputer 40 and the second voltage detection unit 23B, and insulates the input signal from the second voltage detection unit 23B to the second potential conversion unit 46B from the output signal from the second potential conversion unit 46B to the microcomputer 40. However, the second voltage detection unit 23B does not necessarily have to be provided, and in that case the second potential conversion unit 46B is not necessary.

[0077] The third potential conversion unit 46C is provided between the microcontroller 40 and the second current detection unit 24B, and the input signal from the second current detection unit 24B to the third potential conversion unit 46C is insulated from the output signal from the third potential conversion unit 46C to the microcontroller 40.

[0078] The ground potential on the input side of the first potential conversion section 46A is GND-A, and the ground potential on the output side is GND-B.

[0079] The ground potential on the input side of the second potential conversion section 46B is GND-B, and the ground potential on the output side is GND-A.

[0080] The ground potential on the input side of the third potential converter 46C is GND-B, and the ground potential on the output side is GND-A.

[0081] The first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C employ an insulating IC such as a high-speed photocoupler or a digital isolator. In this embodiment, a high-speed photocoupler with a transmission speed of 10 Mbps or more is employed.

[0082] When the transmission speeds from the first potential converter 46A, the second potential converter 46B, and the third potential converter 46C become slow, a circuit delay occurs. Specifically, for example, when the transmission speed from the third potential converter 46C becomes slow, overcurrent protection and current detection become impossible. Therefore, by setting the transmission speed at 10 Mbps or higher, the influence of the circuit delay time is minimized.

[0083] (3) Relationship between the microcontroller 40 and the first to third potential conversion units (46A to 46C) In this embodiment, the ground potential GND-A of the circuit extending from the first rectifier circuit 20A to the first switching circuit 25A is a different potential from the ground potential GND-B of the circuit extending from the second rectifier circuit 20B to the second switching circuit 25B.

[0084] If the ground potentials are different, the microcomputer must supply control signals with different ground potentials to the first switching circuit 25A and the second switching circuit 25B, respectively.

[0085] Furthermore, the microcomputer must receive voltage detection signals having different ground potentials from the first voltage detection unit 23A and the second voltage detection unit 23B.

[0086] Furthermore, the microcomputer must receive current detection signals having different ground potentials from the first current detection unit 24A and the second current detection unit 24B.

[0087] Therefore, multiple microcontrollers are required, which results in increased costs.

[0088] Therefore, in this embodiment, since one microcomputer 40 controls the first switching circuit 25A and the second switching circuit 25B, the ground potential of the second control signal PWM-2 directed to the second switching circuit 25B is converted to a different ground potential in the first potential conversion unit 46A.

[0089] Therefore, the ground potential of the first control signal PWM-1 output from the microcomputer 40 to the first switching circuit 25A and the second control signal PWM-2 output from the microcomputer 40 to the second switching circuit 25B may be the same ground potential GND-A.

[0090] Furthermore, the second voltage detection signal sent from the second voltage detection unit 23B to the microcomputer 40 is converted into a different ground potential by the second potential conversion unit 46B.

[0091] Therefore, the first voltage detection signal from the first voltage detection unit 23A to the microcomputer 40 and the second voltage detection signal from the second voltage detection unit 23B to the microcomputer 40 may have different ground potentials.

[0092] Furthermore, the second current detection signal sent from the second current detection unit 24B to the microcomputer 40 is converted to a different ground potential by the third potential conversion unit 46C.

[0093] Therefore, the first current detection signal from the first current detection unit 24A to the microcomputer 40 and the second current detection signal from the second current detection unit 24B to the microcomputer 40 may have different ground potentials.

[0094] (3-1) First Control Signal PWM-1 to First Switching Circuit 25A The microcomputer 40 generates a first control signal PWM-1 using the switching power supply 31 as a reference potential and outputs it to the first gate drive circuit 26A. The first control signal PWM-1 has a predetermined duty ratio for controlling the rotation of the first motor 51A.

[0095] The first control signal PWM-1 is converted into a gate pulse by the first gate drive circuit 26A. The gate pulse controls the on / off of the switching elements of the upper and lower arms of the first switching circuit 25A, and a three-phase AC voltage is supplied to the first motor 51A.

[0096] (3-2) Second Control Signal PWM-2 Directed to Second Switching Circuit 25B The microcomputer 40 generates a second control signal PWM-2 using the switching power supply 31 as a reference potential. The second control signal PWM-2 has a predetermined duty ratio for controlling the rotation of the second motor 51B.

[0097] Since the first potential conversion unit 46A is provided between the microcomputer 40 and the second gate drive circuit 26B, the ground potential GND-A of the second control signal PWM-2 input to the first potential conversion unit 46A is converted to the same potential as the ground potential GND-B on the output side of the first potential conversion unit 46A.

[0098] The potential-converted second control signal PWM-2 is converted into a gate pulse by the second gate drive circuit 26B. The gate pulse controls the on / off of the switching elements of the upper and lower arms of the second switching circuit 25B, and a three-phase AC voltage is supplied to the second motor 51B.

[0099] (3-3) First Voltage Detection Signal of First Voltage Detection Unit 23A Sent to Microcomputer 40 The ground potential of the first voltage detection unit 23A is the same as the ground potential GND-A of the first switching circuit 25A and the microcomputer 40. Therefore, the first voltage detection signal from the first voltage detection unit 23A is input directly to the microcomputer 40.

[0100] (3-4) Second Voltage Detection Signal of Second Voltage Detection Unit 23B Intended for Microcomputer 40 The ground potential of the second voltage detection unit 23B is the same as the ground potential GND-B of the second switching circuit 25B. A second potential conversion unit 46B is provided between the second voltage detection unit 23B and the microcomputer 40. Therefore, the ground potential GND-B of the second voltage detection signal input to the second potential conversion unit 46B is converted to the same potential as the ground potential GND-A on the output side of the second potential conversion unit 46B. The potential-converted second voltage detection signal is input to the microcomputer 40.

[0101] (3-5) First Current Detection Signal of First Current Detection Unit 24A Sent to Microcomputer 40 The ground potential of the first current detection unit 24A is the same as the ground potential GND-A of the first switching circuit 25A and the microcomputer 40. Therefore, the first current detection signal from the first current detection unit 24A is input directly to the microcomputer 40.

[0102] (3-6) Second Current Detection Signal of Second Current Detection Unit 24B Intended for Microcomputer 40 The ground potential of the second current detection unit 24B is the same as the ground potential GND-B of the second switching circuit 25B. A third potential conversion unit 46C is provided between the second current detection unit 24B and the microcomputer 40. Therefore, the ground potential GND-B of the second current detection signal input to the third potential conversion unit 46C is converted to the same potential as the ground potential GND-A on the output side of the third potential conversion unit 46C. The potential-converted second current detection signal is input to the microcomputer 40.

[0103] (3-7) Effect In this embodiment, high-speed photocouplers are used as the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C, so delays in transmission speed caused by the operating times of the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C are suppressed.

[0104] Furthermore, since the input signal and output signal of the first potential conversion unit 46A are insulated, even if there is an effect of noise, the signal input to the second gate drive circuit 26B is not directly affected.

[0105] Furthermore, although the ground potentials of the first switching circuit 25A and the second switching circuit 25B are different, the ground potentials of the second gate drive circuit 26B and the second switching circuit 25B are common to the ground potential GND-B on the output side of the first potential conversion unit 46A, thereby preventing malfunction.

[0106] Furthermore, since the input and output signals of the second potential conversion unit 46B and the third potential conversion unit 46C are insulated, even if there is an effect of noise, it does not directly affect the signal input to the microcomputer 40.

[0107] Furthermore, although the ground potentials of the first voltage detection unit 23A and the first current detection unit 24A and the second voltage detection unit 23B and the second current detection unit 24B are different, the ground potentials of the first voltage detection unit 23A and the first current detection unit 24A are common to the ground potential GND-A on the output side of the second potential conversion unit 46B and the third potential conversion unit 46C, respectively, thereby preventing malfunction.

[0108] As a result, the refrigerant control circuit 42 , the first switching circuit 25A, and the second switching circuit 25B are controlled by a single microcomputer 40 .

[0109] (4) Features of the First Embodiment (4-1) In the power supply control circuit 100, the reference potential of the second switching circuit 25B is different from that of the first switching circuit 25A. The microcomputer 40 outputs a first control signal PWM-1 to the first switching circuit 25A and a second control signal PWM-2 to the second switching circuit 25B. The first potential converter 46A converts the potential of the second control signal PWM-2. In the power supply control circuit 100, the potential of either of the two control signals can be converted by the first potential converter 46A, making it possible to control two switching circuits with different reference potentials using a single microcomputer.

[0110] (4-2) In the power supply control circuit 100, the first voltage detection unit 23A detects the voltage across the first smoothing capacitor 22A and outputs the detected voltage value as a first voltage detection signal to the microcomputer 40. The second voltage detection unit 23B detects the voltage across the second smoothing capacitor 22B and outputs the detected voltage value as a second voltage detection signal to the microcomputer 40. The second potential conversion unit 46B converts the reference potential of the second voltage detection signal.

[0111] (4-3) In the power supply control circuit 100, the first current detection unit 24A detects the load current of the first switching circuit 25A and outputs the detected current value as a first current detection signal to the microcomputer 40. The second current detection unit 24B detects the load current of the second switching circuit 25B and outputs the detected current value as a second current detection signal to the microcomputer 40. The third potential conversion unit 46C converts the reference potential of the second current detection signal.

[0112] (4-4) The first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C are high-speed photocouplers with a transmission speed of 10 Mbps or more. In the power supply control circuit 100, delays in the transmission speed caused by the operation times of the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C are suppressed.

[0113] (4-5) First switching circuit 25A and second switching circuit 25B are power modules in which multiple switching elements that convert DC power into AC power of a predetermined frequency are built into a single package. Modularization of each switching circuit facilitates the design of peripheral circuits for each switching circuit on printed wiring board 10.

[0114] 3 is a circuit diagram showing the configuration of a power supply control circuit 102 according to a second embodiment of the present disclosure. In FIG. 3, the circuit configuration from the AC power supply 91 to the first motor 51A and from the AC power supply 91 to the switching power supply 31 is the same as in the first embodiment, so the same reference numerals as in the first embodiment are used and the description thereof will be omitted.

[0115] (1) Overview of the power supply control circuit 102 As shown in FIG. 3, the power supply control circuit 102 is mounted on a printed wiring board 10 configured to receive R-phase, S-phase, T-phase, and N-phase inputs from an AC power supply 91 that supplies three-phase AC in a three-phase, four-wire system.

[0116] The power supply control circuit 102 includes a first rectifier circuit 20A, a first voltage detection unit 23A, a first current detection unit 24A, a first switching circuit 25A, a third voltage detection unit 56, a third current detection unit 57, a U-phase current detection unit 58u, a W-phase current detection unit 58w, an active filter circuit 60, a microcontroller 40, a first potential conversion unit 47A, a second potential conversion unit 47B, a third potential conversion unit 47C, a fourth potential conversion unit 47D, and a fifth potential conversion unit 47E.

[0117] The first rectifier circuit 20A rectifies the AC power of the R phase, S phase, and T phase. The first voltage detector 23A detects the voltage across a first smoothing capacitor 22A that smoothes the output voltage from the first rectifier circuit 20A, and outputs the detected voltage value to the microcomputer 40 as a first voltage detection signal.

[0118] The first current detection unit 24A detects the load current of the first switching circuit 25A and outputs the detected current value to the microcomputer 40 as a first current detection signal.

[0119] The first switching circuit 25A is connected to the first rectifier circuit 20A. The active filter circuit 60 includes a third switching circuit 25C.

[0120] The third switching circuit 25C is connected in parallel between the AC power supply 91 and the first rectifier circuit 20A, and has a reference potential different from that of the first switching circuit 25A.

[0121] The third voltage detector 56 detects the voltage across the third smoothing capacitor 52 that smoothes the output voltage from the third switching circuit 25C, and outputs the detected voltage value to the microcomputer 40 as a third voltage detection signal.

[0122] The third current detector 57 detects the bus current of the third switching circuit 25C and outputs the detected current value to the microcomputer 40 as a third current detection signal.

[0123] The U-phase current detection unit 58u detects the current flowing through the U-phase of the third switching circuit 25C, and outputs the detected current value to the microcomputer 40 as a fourth current detection signal.

[0124] The W-phase current detector 58w detects the current flowing through the W-phase of the third switching circuit 25C, and outputs the detected current value to the microcomputer 40 as a fifth current detection signal.

[0125] The microcomputer 40 outputs a first control signal PWM-1 to the first switching circuit 25A and a third control signal PWM-3 to the third switching circuit 25C.

[0126] The first potential converter 47A converts the potential of the first control signal PWM-1 or the third control signal PWM-3.

[0127] The second potential converter 47B converts the potential of either the first voltage detection signal or the third voltage detection signal, whichever has a reference potential different from the reference potential of the microcomputer 40 .

[0128] The third potential converter 47C converts the potential of either the first or third current detection signal, whichever has a reference potential different from the reference potential of the microcomputer 40 .

[0129] The fourth potential converter 47D converts the potential of either the first current detection signal or the fourth current detection signal, whichever has a reference potential different from the reference potential of the microcomputer 40 .

[0130] The fifth potential converter 47E converts the potential of either the first current detection signal or the fifth current detection signal, whichever has a reference potential different from the reference potential of the microcomputer 40 .

[0131] The power supply control circuit 102 of the present disclosure is mounted on, for example, an outdoor unit of a three-phase, four-wire, 400V air conditioner.

[0132] (2) Detailed Configuration (2-1) Active Filter Circuit 60 The active filter circuit 60 has a third switching circuit 25C, a third gate drive circuit 26C, a third smoothing capacitor 52, a carrier filter 53, a linking reactor 54, a third voltage detection unit 56, a third current detection unit 57, a U-phase current detection unit 58u, and a W-phase current detection unit 58w.

[0133] (2-1-1) Third Switching Circuit 25C Fig. 4 is a detailed configuration diagram of the third switching circuit 25C. In Fig. 4, the third switching circuit 25C is made up of a plurality of switching elements that generate compensation currents for suppressing harmonic currents.

[0134] The switching operation of the third switching circuit 25C is controlled by the third gate drive circuit 26C, and by controlling the current flowing between the AC power supply 91 and the third switching circuit 25C, harmonic current flowing from the first switching circuit 25A to the power supply line is cancelled out.

[0135] The configuration of the third switching circuit 25C is the same as that of the first switching circuit 25A, and therefore the transistors and diodes that are switching elements are given the same reference numerals as the transistors and diodes of the first switching circuit 25A.

[0136] The third switching circuit 25C is a power module in which upper arm switching elements (Q3a, Q4a, Q5a, D3a, D4a, D5a) and lower arm switching elements (Q3b, Q4b, Q5b, D3b, D4b, D5b) are built into a single package.

[0137] (2-1-2) Third Gate Drive Circuit 26C The third gate drive circuit 26C controls the switching elements. The configuration and function of the third gate drive circuit 26C are similar to those of the first gate drive circuit 26A, and therefore a description thereof will be omitted.

[0138] (2-1-3) Third Smoothing Capacitor 52 The third smoothing capacitor 52 is a capacitor that smoothes the output voltage of the third switching circuit 25C.

[0139] (2-1-4) Carrier Filter 53 The carrier filter 53 removes noise caused by the switching of the third switching circuit 25 C. Specifically, the carrier filter 53 removes high-frequency components of the compensation current generated by the switching of the third switching circuit 25 C.

[0140] (2-1-5) Linking Reactor 54 The linking reactor 54 links the third switching circuit 25C and the power supply line.

[0141] (2-1-6) Third Voltage Detector 56 The third voltage detector 56 is connected to the output side of the third smoothing capacitor 52 and detects the voltage across the third smoothing capacitor 52. The third voltage detector 56 is configured, for example, such that two resistors connected in series to each other are connected in parallel to the third smoothing capacitor 52, and the voltage across the third smoothing capacitor 52 is divided. The voltage value at the connection point between these two resistors is input to the microcomputer 40.

[0142] The third voltage detection unit 56 does not necessarily have to be provided, and can be replaced by other means.

[0143] (2-1-7) Third Current Detector 57 The third current detector 57 is located between the third smoothing capacitor 52 and the third switching circuit 25C and is connected to the negative output terminal side of the third smoothing capacitor 52. The third current detector 57 detects the bus current of the third switching circuit 25C.

[0144] The third current detection unit 57 may be configured, for example, by an amplifier circuit using a shunt resistor and an operational amplifier that amplifies the voltage across the resistor. The current detected by the third current detection unit 57 is input to the microcomputer 40.

[0145] (2-1-8) U-Phase Current Detector 58u and W-Phase Current Detector 58w The U-phase current detector 58u detects the compensation current flowing in the U-phase. The W-phase current detector 58w detects the compensation current flowing in the W-phase.

[0146] (2-2) Microcomputer 40 The microcomputer 40 is connected to the first voltage detection unit 23A, the first current detection unit 24A, and the first gate drive circuit 26A. The microcomputer 40 controls the first gate drive circuit 26A to drive the first motor 51A.

[0147] The microcomputer 40 is also connected to the third gate drive circuit 26C via a first potential converter 47A. The microcomputer 40 is also connected to the third voltage detector 56 via a second potential converter 47B. The microcomputer 40 is also connected to the third current detector 57 via a third potential converter 47C. The microcomputer 40 is also connected to the U-phase current detector 58u via a fourth potential converter 47D. The microcomputer 40 is also connected to the W-phase current detector 58w via a fifth potential converter 47E.

[0148] The microcontroller 40 controls the on / off switching of each switching element of the third switching circuit 25C based on the detection values ​​of the third voltage detection unit 56, the third current detection unit 57, the U-phase current detection unit 58u, and the W-phase current detection unit 58w.

[0149] Furthermore, the microcomputer 40 also functions as a refrigerant control microcomputer, for example, controlling the refrigerant control circuit 42 of the air conditioner and adjusting the circulation direction of the refrigerant in the refrigerant circuit, the evaporation temperature of the refrigerant, and the degree of superheat and subcool.

[0150] (2-3) First to fifth potential conversion units (47A to 47E) The first potential conversion unit 47A is provided between the microcomputer 40 and the third gate drive circuit 26C, and insulates the input signal from the microcomputer 40 to the first potential conversion unit 47A from the output signal from the first potential conversion unit 47A to the third gate drive circuit 26C.

[0151] The second potential conversion unit 47B is provided between the microcomputer 40 and the third voltage detection unit 56, and insulates the input signal from the third voltage detection unit 56 to the second potential conversion unit 47B from the output signal from the second potential conversion unit 47B to the microcomputer 40. However, the third voltage detection unit 56 does not necessarily have to be provided, and in that case the second potential conversion unit 47B is not necessary.

[0152] The third potential conversion unit 47C is provided between the microcontroller 40 and the third current detection unit 57, and the input signal from the third current detection unit 57 to the third potential conversion unit 47C is insulated from the output signal from the third potential conversion unit 47C to the microcontroller 40.

[0153] The fourth potential converter 47D is provided between the microcontroller 40 and the U-phase current detection unit 58u, and the input signal from the U-phase current detection unit 58u to the fourth potential converter 47D is insulated from the output signal from the fourth potential converter 47D to the microcontroller 40.

[0154] The fifth potential converter 47E is provided between the microcontroller 40 and the W-phase current detector 58w, and the input signal from the W-phase current detector 58w to the fifth potential converter 47E is insulated from the output signal from the fifth potential converter 47E to the microcontroller 40.

[0155] An insulating IC such as a high-speed photocoupler or a digital isolator is used for the first potential conversion unit 47A, the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D, and the fifth potential conversion unit 47E. In this embodiment, a high-speed photocoupler with a transmission speed of 10 Mbps or more is used.

[0156] When the transmission speed from the first potential converter 47A, the second potential converter 47B, the third potential converter 47C, the fourth potential converter 47D, and the fifth potential converter 47E becomes slow, a circuit delay time occurs. Specifically, for example, when the transmission speed from the third potential converter 47C becomes slow, overcurrent protection and current detection become impossible. Therefore, by setting the transmission speed at 10 Mbps or higher, the influence of the circuit delay time is minimized.

[0157] (3) Relationship between the microcomputer 40 and the first to fifth potential conversion units (47A to 47E) In this embodiment, the ground potential GND-A of the circuit from the first rectifier circuit 20A to the first switching circuit 25A is a different potential from the ground potential GND-C of the active filter circuit 60.

[0158] If the ground potentials are different, the microcomputer must supply control signals with different ground potentials to the first switching circuit 25A and the third switching circuit 25C, respectively.

[0159] Furthermore, the microcomputer must receive voltage detection signals having different ground potentials from the first voltage detection unit 23A and the third voltage detection unit 56, respectively.

[0160] Furthermore, the microcomputer must receive current detection signals with different ground potentials from the first current detection unit 24A, the third current detection unit 57, the U-phase current detection unit 58u, and the W-phase current detection unit 58w.

[0161] Therefore, multiple microcontrollers are required, which results in increased costs.

[0162] Therefore, in this embodiment, since one microcomputer 40 controls the first switching circuit 25A and the third switching circuit 25C, the ground potential of the third control signal PWM-3 directed to the third switching circuit 25C is converted to a different ground potential in the first potential conversion unit 47A.

[0163] Therefore, the ground potential of the first control signal PWM-1 output from the microcomputer 40 to the first switching circuit 25A and the third control signal PWM-3 output from the microcomputer 40 to the third switching circuit 25C may be the same ground potential GND-A.

[0164] Furthermore, the third voltage detection signal sent from the third voltage detection unit 56 to the microcomputer 40 is converted into a different ground potential by the second potential conversion unit 47B.

[0165] Therefore, the first voltage detection signal from the first voltage detection unit 23A to the microcomputer 40 and the second voltage detection signal from the third voltage detection unit 56 to the microcomputer 40 may be at different ground potentials.

[0166] Furthermore, the third current detection signal sent from the third current detection unit 57 to the microcomputer 40 is converted into a different ground potential by the third potential conversion unit 47C.

[0167] Therefore, the first current detection signal from the first current detection unit 24A to the microcomputer 40 and the third current detection signal from the third current detection unit 57 to the microcomputer 40 may be at different ground potentials.

[0168] Furthermore, the fourth current detection signal sent from the U-phase current detector 58u to the microcomputer 40 is converted to a different ground potential by the fourth potential converter 47D.

[0169] Therefore, the first current detection signal from the first current detection unit 24A to the microcomputer 40 and the fourth current detection signal from the U-phase current detection unit 58u to the microcomputer 40 may have different ground potentials.

[0170] Furthermore, the fifth current detection signal sent from the W-phase current detector 58w to the microcomputer 40 is converted to a different ground potential by the fifth potential converter 47E.

[0171] Therefore, the first current detection signal from the first current detection unit 24A to the microcomputer 40 and the fifth current detection signal from the W-phase current detection unit 58w to the microcomputer 40 may have different ground potentials.

[0172] (3-1) First Control Signal PWM-1 to First Switching Circuit 25A The microcomputer 40 generates a first control signal PWM-1 using the switching power supply 31 as a reference potential and outputs it to the first gate drive circuit 26A. The first control signal PWM-1 has a predetermined duty ratio for controlling the rotation of the first motor 51A.

[0173] The first control signal PWM-1 is converted into a gate pulse by the first gate drive circuit 26A. The gate pulse controls the on / off of the switching elements of the upper and lower arms of the first switching circuit 25A, and a three-phase AC voltage is supplied to the first motor 51A.

[0174] (3-2) Third Control Signal PWM-3 Directed to Third Switching Circuit 25C The microcomputer 40 generates a third control signal PWM-3 using the switching power supply 31 as a reference potential. The third control signal PWM-3 has a predetermined duty ratio for switching on / off each switching element of the third switching circuit 25C.

[0175] Since the first potential conversion unit 47A is provided between the microcontroller 40 and the third gate drive circuit 26C, the ground potential GND-A of the third control signal PWM-3 input to the first potential conversion unit 47A is converted to the same potential as the ground potential GND-C on the output side of the first potential conversion unit 47A.

[0176] The potential-converted third control signal PWM-3 is converted into a gate pulse by the third gate drive circuit 26C. The gate pulse controls the on / off of the switching elements of the upper and lower arms of the third switching circuit 25C.

[0177] (3-3) First Voltage Detection Signal of First Voltage Detection Unit 23A Sent to Microcomputer 40 The ground potential of the first voltage detection unit 23A is the same as the ground potential GND-A of the first switching circuit 25A and the microcomputer 40. Therefore, the first voltage detection signal from the first voltage detection unit 23A is input directly to the microcomputer 40.

[0178] (3-4) Third Voltage Detection Signal of Third Voltage Detection Unit 56 Sent to Microcomputer 40 The ground potential of the third voltage detection unit 56 is the same as the ground potential GND-C of the third switching circuit 25C. The second potential conversion unit 47B is provided between the third voltage detection unit 56 and the microcomputer 40. Therefore, the ground potential GND-C of the third voltage detection signal input to the second potential conversion unit 47B is converted to the same potential as the ground potential GND-A on the output side of the second potential conversion unit 47B. The potential-converted third voltage detection signal is input to the microcomputer 40.

[0179] (3-5) First Current Detection Signal of First Current Detection Unit 24A Sent to Microcomputer 40 The ground potential of the first current detection unit 24A is the same as the ground potential GND-A of the first switching circuit 25A and the microcomputer 40. Therefore, the first current detection signal from the first current detection unit 24A is input directly to the microcomputer 40.

[0180] (3-6) Third Current Detection Signal of Third Current Detection Unit 57 Sent to Microcomputer 40 The ground potential of the third current detection unit 57 is the same as the ground potential GND-C of the third switching circuit 25C. A third potential conversion unit 47C is provided between the third current detection unit 57 and the microcomputer 40. Therefore, the ground potential GND-C of the third current detection signal input to the third potential conversion unit 47C is converted to the same potential as the ground potential GND-A on the output side of the third potential conversion unit 47C. The potential-converted third current detection signal is input to the microcomputer 40.

[0181] (3-7) Fourth Current Detection Signal of U-Phase Current Detection Unit 58u Sent to Microcomputer 40 The ground potential of U-phase current detection unit 58u is the same as the ground potential GND-C of the third switching circuit 25C. A fourth potential converter 47D is provided between U-phase current detection unit 58u and the microcomputer 40. Therefore, the ground potential GND-C of the fourth current detection signal input to the fourth potential converter 47D is converted to the same potential as the ground potential GND-A on the output side of the fourth potential converter 47D. The potential-converted fourth current detection signal is input to the microcomputer 40.

[0182] (3-8) Fifth Current Detection Signal of W-Phase Current Detection Unit 58w Sent to Microcomputer 40 The ground potential of the W-phase current detection unit 58w is the same as the ground potential GND-C of the third switching circuit 25C. A fifth potential converter 47E is provided between the W-phase current detection unit 58w and the microcomputer 40. Therefore, the ground potential GND-C of the fifth current detection signal input to the fifth potential converter 47E is converted to the same potential as the ground potential GND-A on the output side of the fifth potential converter 47E. The potential-converted fifth current detection signal is input to the microcomputer 40.

[0183] (3-9) Effects In this embodiment, high-speed photocouplers are used as the first potential conversion unit 47A, the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D, and the fifth potential conversion unit 47E, thereby suppressing delays in transmission speed caused by the operating times of the first potential conversion unit 47A, the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D, and the fifth potential conversion unit 47E.

[0184] Furthermore, the input signal and output signal of the first potential conversion unit 47A are insulated, and even if there is an effect of noise, the signal input to the third gate drive circuit 26C is not directly affected.

[0185] Furthermore, although the ground potentials of the first switching circuit 25A and the third switching circuit 25C are different, the ground potentials of the third gate drive circuit 26C and the third switching circuit 25C are common to the ground potential GND-C on the output side of the first potential conversion unit 47A, thereby preventing malfunction.

[0186] Furthermore, since the input signals and output signals of the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D and the fifth potential conversion unit 47E are insulated, even if there is an influence of noise, it does not directly affect the signal input to the microcontroller 40.

[0187] Furthermore, although the ground potentials of the first voltage detection unit 23A and the first current detection unit 24A are different from those of the third voltage detection unit 56, the third current detection unit 57, the U-phase current detection unit 58u and the W-phase current detection unit 58w, the ground potentials of the first voltage detection unit 23A and the first current detection unit 24A are common to the ground potential GND-A on the output side of the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D and the fifth potential conversion unit 47E, thereby preventing malfunction.

[0188] As a result, the refrigerant control circuit 42, the first switching circuit 25A, and the third switching circuit 25C are controlled by a single microcomputer 40.

[0189] (4) Features of the Second Embodiment (4-1) In the power supply control circuit 102, the third switching circuit 25C has a reference potential different from that of the first switching circuit 25A. The microcomputer 40 outputs a first control signal PWM-1 directed to the first switching circuit 25A and a third control signal PWM-3 directed to the third switching circuit 25C. The first potential converter 47A converts the potential of the third control signal PWM-3. In the power supply control circuit 102, the first potential converter 47A can convert the potential of either of the two control signals, making it possible to control two switching circuits with different reference potentials using a single microcomputer.

[0190] (4-2) In the power supply control circuit 102, the first voltage detection unit 23A detects the voltage across the first smoothing capacitor 22A and outputs the detected voltage value as a first voltage detection signal to the microcomputer 40. The third voltage detection unit 56 detects the voltage across the third smoothing capacitor 52 and outputs the detected voltage value as a third voltage detection signal to the microcomputer 40. The second potential conversion unit 47B converts the reference potential of the third voltage detection signal.

[0191] (4-3) In the power supply control circuit 102, the first current detection unit 24A detects the load current of the first switching circuit and outputs the detected current value as a first current detection signal to the microcomputer 40. The third current detection unit 57 detects the bus current of the third switching circuit 25C and outputs the detected current value as a third current detection signal to the microcomputer 40. The third potential conversion unit 47C converts the reference potential of the third current detection signal.

[0192] (4-4) In the power supply control circuit 102, the U-phase current detection unit 58u detects the current flowing through the U-phase of the third switching circuit 25C and outputs the detected current value as a fourth current detection signal to the microcomputer 40. The fourth potential conversion unit 47D converts the reference potential of the fourth current detection signal.

[0193] (4-5) In the power supply control circuit 102, the W-phase current detection unit 58w detects the current flowing through the W-phase of the third switching circuit 25C and outputs the detected current value as a fifth current detection signal to the microcomputer 40. The fifth potential conversion unit 47E converts the reference potential of the fifth current detection signal.

[0194] (4-6) The first potential conversion unit 47A, the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D, and the fifth potential conversion unit 47E are high-speed photocouplers with a transmission speed of 10 Mbps or more. In the power supply control circuit 102, delays in the transmission speed caused by the operation times of the first potential conversion unit 47A, the second potential conversion unit 47B, the third potential conversion unit 47C, the fourth potential conversion unit 47D, and the fifth potential conversion unit 47E are suppressed.

[0195] (4-7) The third switching circuit 25C is a power module in which multiple switching elements that generate compensation currents to suppress harmonic currents are built into one package. Modularization of the third switching circuit 25C facilitates the design of peripheral circuits of the third switching circuit on the printed wiring board 10.

[0196] <Modifications common to the first and second embodiments> (1) First Modification Fig. 5 is a circuit diagram showing the configuration of a power supply control circuit 100 according to a first modification of the first embodiment. Fig. 6 is a circuit diagram showing the configuration of a power supply control circuit 102 according to a first modification of the second embodiment.

[0197] In Fig. 5, the first modified example of the first embodiment differs from the first embodiment in that a power factor correction circuit 21 is interposed between the first rectifier circuit 20A and the first smoothing capacitor 22A, with the remaining configuration being the same as that of the first embodiment. Similarly, in Fig. 6, the first modified example of the second embodiment differs from the second embodiment in that a power factor correction circuit 21 is interposed between the first rectifier circuit 20A and the first smoothing capacitor 22A, with the remaining configuration being the same as that of the second embodiment. Therefore, only the power factor correction circuit 21 will be described here.

[0198] The power factor correction circuit 21 has a boost reactor 211, a diode 212, and a switching element 213. The boost reactor 211 and the diode 212 are connected in series between the positive side of the first rectifier circuit 20A and the positive side of the first smoothing capacitor 22A. The diode 212 is connected in the forward direction from the boost reactor 211 toward the positive side of the first smoothing capacitor 22A.

[0199] The switching element 213 is arranged so that it can conduct or cut off electricity between the boost reactor 211 and the diode 212, and between the negative side of the first rectifier circuit 20A and the negative side of the first smoothing capacitor 22A, based on a control signal provided by the microcomputer 40.

[0200] In the power factor correction circuit 21, the switching element 213 is turned on and off based on a control signal input to the switching element 213 from the microcomputer 40, and chops at high speed the DC current input from the first rectifier circuit 20A via the boost reactor 211. This adjusts the voltage obtained when the DC current from the first rectifier circuit 20A charges the first smoothing capacitor 22A.

[0201] The microcomputer 40 detects the voltage of the first smoothing capacitor 22A and changes the on / off state of the switching element 213 using a control signal based on the detection results, thereby adjusting the voltage supplied to the first switching circuit 25A and improving the power factor.

[0202] Since the microcomputer 40 and the power factor correction circuit 21 share a common ground potential GND-A, the control signal is input without passing through the potential conversion unit.

[0203] The series circuit of the switching element 213 and the diode 212 may be a power module built into a single package.

[0204] With the above configuration, in the first variant of the first embodiment, the refrigerant control circuit 42, the power factor correction circuit 21, the first switching circuit 25A, and the second switching circuit 25B, which has a different ground potential from the first switching circuit 25A, can be controlled by a single microcomputer 40.

[0205] Similarly, in the first variant of the second embodiment, the refrigerant control circuit 42, the power factor correction circuit 21, the first switching circuit 25A, and the third switching circuit 25C, which has a different ground potential from the first switching circuit 25A, can be controlled by a single microcomputer 40.

[0206] (2) Second Modification FIG. 7 is a partial plan view of the printed wiring board 10 showing the positional relationship between the first switching circuit 25A, the second switching circuit 25B, the microcomputer 40, and the first potential conversion unit 46A of the power supply control circuit 100 according to a second modification of the first embodiment.

[0207] 7, the first switching circuit 25A and the second switching circuit 25B are adjacent to each other, but they do not necessarily have to be adjacent to each other.

[0208] As in the first embodiment, the first potential conversion unit 46A is provided between the microcomputer 40 and the second switching circuit 25B, and the input signal from the microcomputer 40 to the first potential conversion unit 46A is insulated from the output signal from the first potential conversion unit 46A to the second switching circuit 25B.

[0209] The shortest distance La from the first potential conversion unit 46A to the first switching circuit 25A or the shortest distance Lb from the first potential conversion unit 46A to the second switching circuit 25B is shorter than the shortest distance Lo from the microcomputer 40 to the first potential conversion unit 46A.

[0210] It is desirable that the shortest distance La from the first potential conversion unit 46A to the first switching circuit 25A and the shortest distance Lb from the first potential conversion unit 46A to the second switching circuit 25B are both shorter than the shortest distance Lo from the microcontroller 40 to the first potential conversion unit 46A.

[0211] The shorter the distance from the first potential conversion unit 46A to the switching circuit, the simpler the routing of the conductive pattern connecting the first potential conversion unit 46A and the switching circuit becomes, and the smaller the size of the printed wiring board 10 becomes, which contributes to the miniaturization of the power supply control circuit 100.

[0212] Moreover, if the second switching circuit 25B in FIG. 7 is replaced with a third switching circuit 25C, this can be applied as a second modification of the second embodiment.

[0213] In such a case, the shortest distance from the first potential conversion unit 47A to the first switching circuit 25A or the shortest distance from the first potential conversion unit 47A to the third switching circuit 25C is shorter than the shortest distance from the microcontroller 40 to the first potential conversion unit 47A, which contributes to the miniaturization of the power supply control circuit 102.

[0214] <Other Embodiments> (1) Overview of Power Supply Control Circuit 103 Fig. 8 is a circuit diagram showing the configuration of a power supply control circuit 103 according to another embodiment. In Fig. 8, the power supply control circuit 103 is mounted on a printed wiring board 10 configured to receive R-phase, S-phase, T-phase, and N-phase inputs from an AC power supply that supplies three-phase AC in a three-phase, four-wire system.

[0215] The power supply control circuit 103 includes a PWM converter 19 , a first switching circuit 25A, a microcomputer 40 , and a potential conversion unit 48 .

[0216] The PWM converter 19 converts the R-phase, S-phase, and T-phase AC power into DC power. The first switching circuit 25A is connected to the PWM converter 19. The PWM converter 19 has a reference potential different from that of the first switching circuit 25A.

[0217] The microcomputer 40 outputs a first control signal PWM-1 to the first switching circuit 25A and a fourth control signal PWM-4 to the PWM converter 19. The potential conversion unit 48 converts the potential of the first control signal PWM-1 or the fourth control signal PWM-4.

[0218] The power supply control circuit 103 of the present disclosure is mounted on, for example, an outdoor unit of a three-phase, four-wire, 400V air conditioner.

[0219] (2) Detailed Configuration In FIG. 8, among the components other than the PWM converter 19, the components denoted by the same reference numerals as the components of the power supply control circuit 100 shown in FIG. 1 have been explained in the first embodiment, and therefore explanation thereof will be omitted here.

[0220] (2-1) PWM Converter 19 Fig. 9 is a configuration diagram of the PWM converter 19 and a fourth gate drive circuit 26D that drives it. In Fig. 9, the PWM converter 19 includes a plurality of IGBTs (insulated gate bipolar transistors, hereinafter simply referred to as transistors) Q0a, Q0b, Q1a, Q1b, Q2a, and Q2b, and a plurality of diodes D0a, D0b, D1a, D1b, D2a, and D2b.

[0221] The transistors Q0a and Q0b are connected in series to form upper and lower arms, and the junction formed thereby is connected to the R-phase output side of the AC power supply 91. The transistors Q1a and Q1b are connected in series to form upper and lower arms, and the junction formed thereby is connected to the S-phase output side of the AC power supply 91. The transistors Q2a and Q2b are connected in series to form upper and lower arms, and the junction formed thereby is connected to the T-phase output side of the AC power supply 91.

[0222] Each of the diodes D0a to D2b is connected in parallel to each of the transistors Q0a to Q2b such that the collector terminal of the transistor is connected to the cathode terminal of the diode, and the emitter terminal of the transistor is connected to the anode terminal of the diode.

[0223] In the PWM converter 19, the transistors Q0a to Q2b are turned on and off at timings instructed by the fourth gate drive circuit 26D, thereby making the power supply current a nearly sinusoidal wave, suppressing power supply harmonics, and improving the power supply power factor.

[0224] (2-2) Fourth Gate Drive Circuit 26D The fourth gate drive circuit 26D changes the on / off state of each of the transistors Q0a to Q2b of the PWM converter 19 based on a fourth control signal PWM-4 from the microcomputer 40. The fourth gate drive circuit 26D generates pulsed gate control voltages Go, Gp, Gq, Gr, Gs, and Gt having a duty ratio determined by the microcomputer 40. The generated gate control voltages Go, Gp, Gq, Gr, Gs, and Gt are applied to the gate terminals of the respective transistors Q0a to Q2b.

[0225] (2-3) Potential Converter 48 The potential converter 48 is provided between the microcomputer 40 and the PWM converter 19, and insulates the input signal from the microcomputer 40 to the potential converter 48 from the output signal from the potential converter 48 to the PWM converter 19.

[0226] An insulating IC such as a high-speed photocoupler or a digital isolator is used for the potential conversion unit 48. In this embodiment, a high-speed photocoupler with a transmission speed of 10 Mbps or more is used.

[0227] If the transmission speed from the potential conversion unit 48 becomes slow, a circuit delay occurs, making it impossible to perform overcurrent protection or current detection. Therefore, by setting the transmission speed at 10 Mbps or higher, the effect of the circuit delay is minimized.

[0228] (3) Relationship Between the Microcomputer 40 and the Potential Converter 48 In this embodiment, the ground potential GND-D of the PWM converter 19 is different from the ground potential GND-A of the first switching circuit 25A.

[0229] If the ground potentials are different, control signals with different ground potentials must be supplied to the PWM converter 19 and the first switching circuit 25A, respectively, which requires multiple microcomputers, resulting in increased costs.

[0230] Therefore, in this embodiment, since one microcomputer 40 controls the PWM converter 19 and the first switching circuit 25A, the ground potential of the fourth control signal PWM-4 directed to the PWM converter 19 is converted to a different ground potential in the potential conversion unit 48.

[0231] Therefore, the ground potential of the first control signal PWM-1 output from the microcomputer 40 to the first switching circuit 25A and the fourth control signal PWM-4 output from the microcomputer 40 to the PWM converter 19 is the same ground potential GND-A.

[0232] (3-1) First Control Signal PWM-1 to First Switching Circuit 25A The microcomputer 40 generates a first control signal PWM-1 using the switching power supply 31 as a reference potential and outputs it to the first gate drive circuit 26A. The first control signal PWM-1 has a predetermined duty ratio for controlling the rotation of the first motor 51A.

[0233] The first control signal PWM-1 is converted into a gate pulse by the first gate drive circuit 26A. The gate pulse controls the on / off of the switching elements of the upper and lower arms of the first switching circuit 25A, and a three-phase AC voltage is supplied to the first motor 51A.

[0234] (3-2) Fourth Control Signal PWM-4 for PWM Converter 19 The microcomputer 40 generates a fourth control signal PWM-4 using the switching power supply 31 as a reference potential. The fourth control signal PWM-4 has a predetermined duty ratio for switching on / off each switching element of the PWM converter 19.

[0235] Since the potential conversion unit 48 is provided between the microcontroller 40 and the PWM converter 19, the ground potential GND-A of the fourth control signal PWM-4 input to the potential conversion unit 48 is converted to the same potential as the ground potential GND-D on the output side of the potential conversion unit 48.

[0236] The potential-converted fourth control signal PWM-4 is converted into a gate pulse by the PWM converter 19. The gate pulse controls the on / off of the switching elements of the upper and lower arms of the PWM converter 19.

[0237] (3-3) Effects In this embodiment, a high-speed photocoupler is used as the potential conversion unit 48, which suppresses delays in transmission speed caused by the operation time of the potential conversion unit 48. Furthermore, the input and output signals of the potential conversion unit 48 are insulated, and even if there is an effect of noise, the signal input to the PWM converter 19 is not directly affected.

[0238] Furthermore, although the ground potentials of the first switching circuit 25A and the PWM converter 19 are different, the ground potential of the fourth gate drive circuit 26D and the PWM converter 19 is common to the ground potential GND-D on the output side of the potential conversion unit 48, thereby preventing malfunction.

[0239] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0240] 10 Printed wiring board 20A First rectifier circuit 20B Second rectifier circuit 21 Power factor correction circuit 22A First smoothing capacitor 22B Second smoothing capacitor 23A First voltage detection unit 23B Second voltage detection unit 24A First current detection unit 24B Second current detection unit 25A First switching circuit 25B Second switching circuit 25C Third switching circuit 40 Microcomputer 46A First potential conversion unit 46B Second potential conversion unit 46C Third potential conversion unit 47A First potential conversion unit 47B Second potential conversion unit 47C Third potential conversion unit 47D Fourth potential conversion unit 47E Fifth potential conversion unit 52 Third smoothing capacitor 56 Third voltage detection unit 57 Third current detection unit 58u U-phase current detection unit 58w W-phase current detection unit 100 Power supply control circuit 102 Power supply control circuit 211 Reactor 212 Diode (rectifying element) 213 Switching element (first switching element)

[0241] WO2017 / 200027

Claims

1. A power supply control circuit mounted on a printed wiring board (10) configured to receive an R phase, an S phase, a T phase, and an N phase from an AC power supply that supplies three-phase AC in a three-phase four-wire system, the power supply control circuit comprising: a first rectifier circuit (20A) that rectifies AC voltages of the R phase, the S phase, and the T phase; a second rectifier circuit (20B) that rectifies AC voltages of any one of the R phase, the S phase, and the T phase, and the N phase; a first switching circuit (25A) connected to the first rectifier circuit (20A); a second switching circuit (25B) connected to the second rectifier circuit (20B) and having a reference potential different from that of the first switching circuit (25A); a microcomputer (40) that outputs a first control signal directed to the first switching circuit (25A) and a second control signal directed to the second switching circuit (25B); and a first potential conversion unit (46A) that converts a potential of the first control signal or the second control signal.

2. The power supply control circuit (100) according to claim 1, wherein the transmission speed of the first potential conversion unit (46A) is 10 Mbps or more.

3. A power supply control circuit (100) according to claim 1 or 2, further comprising: a first current detection unit (24A) that detects a load current of the first switching circuit (25A) and outputs the detected current value as a first current detection signal to the microcomputer (40); a second current detection unit (24B) that detects a load current of the second switching circuit (25B) and outputs the detected current value as a second current detection signal to the microcomputer (40); and a third potential conversion unit (46C) that converts the potential of one of the first and second current detection signals, the reference potential of which differs from the reference potential of the microcomputer (40).

4. The power supply control circuit (100) according to claim 1 or 2, further comprising: a first voltage detection unit (23A) that detects a voltage across both ends of a first smoothing capacitor (22A) that smoothes the output voltage from the first rectifier circuit (20A) and outputs the detected voltage value to the microcomputer (40) as a first voltage detection signal; a second voltage detection unit (23B) that detects a voltage across both ends of a second smoothing capacitor (22B) that smoothes the output voltage from the second rectifier circuit (20B) and outputs the detected voltage value to the microcomputer (40) as a second voltage detection signal; and a second potential conversion unit (46B) that converts the potential of one of the first and second voltage detection signals, the reference potential of which is different from the reference potential of the microcomputer (40).

5. A power supply control circuit (100) as described in any one of claims 1 to 4, wherein the shortest distance from the first potential conversion unit (46A) to the first switching circuit (25A) or the shortest distance from the first potential conversion unit (46A) to the second switching circuit (25B) is shorter than the shortest distance from the microcomputer (40) to the first potential conversion unit (46A).

6. The power supply control circuit (100) according to any one of claims 1 to 5, wherein at least one of the first switching circuit (25A) and the second switching circuit (25B) is a power module in which a plurality of switching elements for converting DC power into AC power of a predetermined frequency are built into one package.

7. A power supply control circuit mounted on a printed wiring board (10) configured to receive R, S, T and N phases from an AC power supply that supplies three-phase AC in a three-phase four-wire system, the power supply control circuit (102) comprising: a first rectifier circuit (20A) that rectifies AC voltages of the R, S and T phases; a first switching circuit (25A) connected to the first rectifier circuit (20A); a third switching circuit (25C) that is connected in parallel between the AC power supply and the first rectifier circuit (20A) and has a reference potential different from that of the first switching circuit (25A); a microcomputer (40) that outputs a first control signal directed to the first switching circuit (25A) and a third control signal directed to the third switching circuit (25C); and a first potential conversion unit (47A) that converts a potential of the first control signal or the third control signal.

8. The power supply control circuit (102) according to claim 7, wherein the transmission speed of the first potential conversion unit (47A) is 10 Mbps or more.

9. A power supply control circuit (102) as claimed in claim 7 or claim 8, further comprising: a first current detection unit (24A) that detects a load current of the first switching circuit (25A) and outputs the detected current value as a first current detection signal to the microcomputer (40); a third current detection unit (57) that detects a bus current of the third switching circuit (25C) and outputs the detected current value as a third current detection signal to the microcomputer (40); and a third potential conversion unit (47C) that converts the potential of one of the first and third current detection signals, the reference potential of which is different from the reference potential of the microcomputer (40).

10. A power supply control circuit (102) as claimed in claim 7 or 8, further comprising: a first voltage detection unit (23A) that detects a voltage across both ends of a first smoothing capacitor (22A) that smoothes the output voltage from the first rectifier circuit (20A) and outputs the detected voltage value to the microcomputer (40) as a first voltage detection signal; a third voltage detection unit (56) that detects a voltage across both ends of a third smoothing capacitor (52) that smoothes the output voltage from the third switching circuit (25C) and outputs the detected voltage value to the microcomputer (40) as a third voltage detection signal; and a second potential conversion unit (47B) that converts the potential of one of the first and third voltage detection signals, the reference potential of which is different from the reference potential of the microcomputer (40).

11. A power supply control circuit (102) as described in any one of claims 7 to 10, wherein the shortest distance from the first potential conversion unit (47A) to the first switching circuit (25A) or the shortest distance from the first potential conversion unit (47A) to the third switching circuit (25C) is shorter than the shortest distance from the microcomputer (40) to the first potential conversion unit (47A).

12. The power supply control circuit (102) according to any one of claims 7 to 11, wherein the third switching circuit (25C) is a power module in which a plurality of switching elements that generate compensation currents for suppressing harmonic currents are built into one package.

13. The power supply control circuit (100, 102) according to any one of claims 1 to 12, further comprising a power factor correction circuit (21) having a first switching element (213), a rectifying element (212), and a reactor (211), inputting a voltage rectified by the first rectifying circuit (20A), and the microcomputer (40) controlling the on / off of the first switching element (213) to improve the power factor of the AC power supply.

14. The power supply control circuit (100, 102) according to claim 13, wherein at least the first switching element (213) and the rectifier element (212) are a power module built into a single package.

15. An air conditioner comprising a power supply control circuit (100) according to any one of claims 1 to 14.

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