Power supply control circuit and air conditioner including the same

Abstract

To provide a power supply control circuit capable of controlling two switching circuits with one microcomputer.SOLUTION: In a power supply control circuit 100, the reference potential of a second switching circuit 25B is different from that of a first switching circuit 25A. A microcomputer 40 outputs a first control signal PWM-1 for the first switching circuit 25A and a second control signal PWM-2 for the second switching circuit 25B. A first potential conversion unit 46A converts the potential of the second control signal PWM-2. In the power supply control circuit 100, the potential of either one of the two control signals can be converted by the first potential conversion unit 46A, such that one microcomputer can control two switching circuits with different reference potentials.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In a three-phase four-wire 400V air conditioner, as a device for controlling an AC400V system motor and an AC200V system motor using the N phase, for example, a control device disclosed in Patent Document 1 (WO2017 / 200027) is known. In this control device, a signal for controlling the compressor motor and a signal for controlling the fan motor are output from the microcomputer. However, since the ground of the microcomputer and the fan motor is not common, the signal for controlling the fan motor is input to the fan motor via a photocoupler.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, the fan motor described in Patent Document 1 incorporates a microcomputer, a drive circuit, and a switching circuit, and substantially two microcomputers are required. Therefore, from the viewpoint of cost reduction, it is desirable to control two switching circuits with one microcomputer.

Means for Solving the Problems

[0004] The power control circuit of the first aspect is a power control circuit mounted on a printed wiring board configured such that the R phase, S phase, T phase, and N phase are input from an AC power supply that supplies three-phase alternating current 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 phase, S phase, and T phase. The second rectifier circuit rectifies the AC voltage between any one of the R phase, S phase, and T phase 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 directed to the first switching circuit and a second control signal directed 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 control circuit that controls two switching circuits with different reference potentials, since the potentials of the control signals output to each switching circuit are different, a microcomputer corresponding to each switching circuit was required.

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

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

[0008] In this power control circuit, the delay in the transmission speed due to the operation time of the first potential conversion unit is suppressed.

[0009] The power control circuit from the third perspective is the power control circuit from the first perspective or the second perspective, and further includes 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 as a first current detection signal to the microcontroller. The second current detection unit detects the load current of the second switching circuit, and outputs the detected current value as a second current detection signal to the microcontroller. The third potential conversion unit converts the potential of the signal whose reference potential is different from the reference potential of the microcontroller among the first current detection signal and the second current detection signal.

[0010] The power control circuit from the fourth perspective is the power control circuit from the first perspective or the second perspective, and further includes a first voltage detection unit, a second voltage detection unit, and a second potential conversion unit. The first voltage detection unit detects the voltage across the first smoothing capacitor that smoothes the output voltage from the first rectifier circuit, and outputs the detected voltage value as a first voltage detection signal to the microcontroller. The second voltage detection unit detects the voltage across the second smoothing capacitor that smoothes the output voltage from the second rectifier circuit, and outputs the detected voltage value as a second voltage detection signal to the microcontroller. The second potential conversion unit converts the potential of the signal whose reference potential is different from the reference potential of the microcontroller among the first voltage detection signal and the second voltage detection signal.

[0011] The power control circuit from the fifth perspective is any one of the power control circuits from the first perspective to the fourth perspective, and 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 smaller than the shortest distance from the microcontroller to the first potential conversion unit.

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

[0013] The power control circuit from the sixth perspective is any one of the power control circuits from the first to the fifth perspectives, and 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 in one package.

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

[0015] The power control circuit from the seventh perspective is a power control circuit mounted on a printed wiring board configured such that the R phase, S phase, T phase, and N phase are input 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 phase, S phase, and T phase. 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 for the first switching circuit and a third control signal for 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 control circuit that controls two switching circuits with different reference potentials, since the potentials of the control signals output to each switching circuit are different, a microcomputer corresponding to each switching circuit was required.

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

[0018] The power control circuit from the eighth perspective is the power control circuit from the seventh perspective, and the transmission speed of the first potential conversion unit is 10 Mbps or more.

[0019] In this power control circuit, the delay in the transmission speed due to the operation time of the first potential conversion unit is suppressed.

[0020] The power control circuit of the ninth aspect is the power control circuit of the seventh aspect or the eighth aspect, and further includes a first current detection unit, a third 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 third current detection unit detects the 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 the signal whose reference potential is different from the reference potential of the microcomputer among the first current detection signal and the third current detection signal.

[0021] The power control circuit of the tenth aspect is the power control circuit of the seventh aspect or the eighth aspect, and further includes a first voltage detection unit, a third voltage detection unit, and a second potential conversion unit. The first voltage detection unit detects the voltage across the first smoothing capacitor that smoothes the output voltage from the first rectifying circuit, and outputs the detected voltage value to the microcomputer as a first voltage detection signal. The third voltage detection unit detects the voltage across the 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 the signal whose reference potential is different from the reference potential of the microcomputer among the first voltage detection signal and the third voltage detection signal.

[0022] The power control circuit of the eleventh aspect is any one of the power control circuits from the seventh aspect to the tenth aspect, and 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 smaller than the shortest distance from the microcomputer to the first potential conversion unit.

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

[0024] The power control circuit according to the 12th aspect is any one of the power control circuits according to the 7th to 11th aspects, and the third switching circuit is a power module in which a plurality of switching elements for generating a compensation current for suppressing harmonic current are built in one package.

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

[0026] The power control circuit according to the 13th aspect is any one of the power control circuits according to the 1st to 12th aspects, and further includes a power factor improvement circuit. The power factor improvement circuit has a first switching element, a rectifying element, and a reactor, inputs the voltage rectified by the first rectifying circuit, and the microcomputer controls the on / off of the first switching element to improve the power factor of the AC power supply.

[0027] The power control circuit according to the 14th aspect is the power control circuit according to the 13th aspect, and is a power module in which at least the first switching element and the rectifying element are built in one package.

[0028] In this power control circuit, the modularization facilitates the design of the peripheral circuit of the power factor improvement circuit on the printed wiring board.

[0029] The air conditioner according to the 15th aspect is an air conditioner provided with any one of the power control circuits according to the 1st to 14th aspects.

Brief Description of Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

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

[0032] The power 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 AC power of the R phase, S phase, and T phase. The second rectifier circuit 20B rectifies the AC power of any one of the R phase, S phase, and T phase and the N phase.

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

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

[0036] 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.

[0037] 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.

[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 conversion unit 46A converts the potential of the first control signal PWM-1 or the second control signal PWM-2.

[0040] The second potential conversion unit 46B converts the potential of the signal among the first voltage detection signal and the second voltage detection signal whose reference potential is different from the reference potential of the microcomputer 40.

[0041] The third potential conversion unit 46C converts the potential of the signal among the first current detection signal and the second current detection signal whose reference potential is different from the reference potential of the microcomputer 40.

[0042] The power control circuit 100 of the present disclosure is mounted on, for example, the outdoor unit of a three-phase 4-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 laminated with an insulator layer in between.

[0044] Mounted on the printed wiring board 10 are the input terminal 9, the first rectifier circuit 20A, the second rectifier circuit 20B, the first switching circuit 25A, the second switching circuit 25B, the switching power supply 31, the refrigerant control circuit 42, the first potential conversion unit 46A, the second potential conversion unit 46B, the third potential conversion unit 46C, which are components of the power control circuit 100, and the microcomputer 40 that controls these components.

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

[0047] The first rectifier circuit 20A is a diode module in which six diode chips connected in a bridge are built in 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 the AC power input from the fourth wiring 14 connected to the N phase and the fifth wiring 15 branched from the first wiring 11. The wiring for branching the fifth wiring 15 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 diode chips connected in a bridge are built in 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 detection unit 23A The first voltage detection unit 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 detection unit 23A is configured such that two resistors connected in series with each other are connected in parallel to the smoothing capacitor 22, and the voltage across the first smoothing capacitor 22A is divided. The voltage value at the connection point between those two resistors is input to the microcomputer 40.

[0052] The first voltage detection unit 23A is not necessarily required and can be replaced by other means.

[0053] (2-6) Second voltage detection unit 23B The second voltage detection unit 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 detection unit 23B is configured such that two resistors connected in series with 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 those two resistors is input to the microcomputer 40.

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

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

[0056] The first current detection unit 24A may be composed of an amplification circuit using a shunt resistor and an operational amplifier for amplifying the voltage across both ends of the resistor. The motor current detected by the first current detection unit 24A is input to the microcomputer 40.

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

[0058] The second current detection unit 24B may be composed of an amplification circuit using a shunt resistor and an operational amplifier for amplifying the voltage across both ends of the resistor. The motor current detected by the second current detection unit 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 configurations of the first switching circuit 25A and the second switching circuit 25B are the same, they will be described as the switching circuit 25.

[0060] Figure 2 is a configuration diagram of the switching circuit 25 and the gate drive circuit 26 that drives it. In Figure 2, the 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, Q5b and a plurality of reflux diodes D3a, D3b, D4a, D4b, D5a, D5b.

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

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

[0063] The first switching circuit 25A and the second switching circuit 25B are power modules in which the upper arm side switching elements (Q3a, Q4a, Q5a, D3a, D4a, D5a) and the lower arm side switching elements (Q3b, Q4b, Q5b, D3b, D4b, D5b) are built in one 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 states of the transistors Q3a to Q5b of the first switching circuit 25A based on the first control signal PWM-1 from the microcomputer 40. The second gate drive circuit 26B changes the on / off states of the transistors Q3a to Q5b of the second switching circuit 25B based on the second control signal PWM-2 from the microcomputer 40.

[0066] Since the configurations of the first gate drive circuit 26A and the second gate drive circuit 26B are the same, they will be described as the gate drive circuit 26.

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

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

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

[0071] Furthermore, the microcomputer 40 also functions as a refrigerant control microcomputer. For example, it controls the refrigerant control circuit 42 of the air conditioner, and adjusts the circulation direction of the refrigerant in the refrigerant circuit, the evaporation temperature of the refrigerant, the superheat degree, and the subcooling degree.

[0072] (2-12) Switching power supply 31 The switching power supply 31 converts the AC power input from the sixth wiring 16 branched from the third wiring 13 and the seventh wiring 17 branched from the fourth wiring 14 into DC power of a predetermined voltage and supplies it to the microcomputer 40 and the like. The wiring that branches the sixth wiring 16 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 the command from the microcomputer 40, the refrigerant control circuit 42 controls the operation of the four-way switching valve 71 that switches the circulation direction of the refrigerant circulating in the refrigerant circuit of the air conditioner, and the operation of the electric expansion valve 72 that adjusts the evaporation temperature, superheat degree, and subcooling degree of the refrigerant.

[0074] The ground potential of the refrigerant control circuit 42 is the same GND-A 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 and 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 and the output signal from the second potential conversion unit 46B to the microcomputer 40. However, the second voltage detection unit 23B does not necessarily need to be provided, and in that case, the second potential conversion unit 46B is unnecessary.

[0077] The third potential conversion unit 46C is provided between the microcomputer 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 and the output signal from the third potential conversion unit 46C to the microcomputer 40 are insulated.

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

[0081] Insulation ICs such as high-speed photocouplers and digital isolators are adopted for the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C. In this embodiment, a high-speed photocoupler with a transmission speed of 10 Mbps or more is adopted.

[0082] When the transmission speeds from the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C become low, a delay time of the circuit occurs. Specifically, for example, when the transmission speed from the third potential conversion unit 46C becomes low, overcurrent protection and current detection cannot be performed. Therefore, by setting it to a high speed of 10 Mbps or more, the influence of the delay time of the circuit is minimized.

[0083] (3) Relationship between the microcomputer 40 and the first to third potential conversion units (46A to 46C) 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-B of the circuit from the second rectifier circuit 20B to the second switching circuit 25B.

[0084] When 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] In addition, the microcomputer must receive voltage detection signals with different ground potentials from the first voltage detection unit 23A and the second voltage detection unit 23B, respectively.

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

[0087] Therefore, a plurality of microcomputers are required. As a result, the cost increases.

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

[0090] Also, the second voltage detection signal directed from the second voltage detection unit 23B to the microcomputer 40 is converted to a different ground potential in the second potential conversion unit 46B.

[0091] Therefore, the first voltage detection signal directed from the first voltage detection unit 23A to the microcomputer 40 and the second voltage detection signal directed 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 in the third potential conversion unit 46C.

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

[0094] (3-1) First control signal PWM-1 for the first switching circuit 25A The microcomputer 40 generates the first control signal PWM-1 with a 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 gate pulses by the first gate drive circuit 26A. The switching elements of each upper and lower arm of the first switching circuit 25A are controlled to be turned on and off by the gate pulses, and a three-phase alternating voltage is supplied to the first motor 51A.

[0096] (3-2) Second control signal PWM-2 for the second switching circuit 25B Also, the microcomputer 40 generates the second control signal PWM-2 with a 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 second control signal PWM-2 that has been subjected to potential conversion is converted into gate pulses by the second gate drive circuit 26B. Each switching element of the upper and lower arms of the second switching circuit 25B is turned on and off by the gate pulses, and a three-phase AC voltage is supplied to the second motor 51B.

[0099] (3-3) The first voltage detection signal of the first voltage detection unit 23A directed to the 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 directly input to the microcomputer 40 (3-4) The second voltage detection signal of the second voltage detection unit 23B directed to the 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. The 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 microcomputer 40 receives the second voltage detection signal that has been subjected to potential conversion.

[0100] (3-5) The first current detection signal of the first current detection unit 24A directed to the 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 directly input to the microcomputer 40 (3-6) The second current detection signal of the second current detection unit 24B directed to the 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. The 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 microcomputer 40 receives the second current detection signal whose potential has been converted.

[0101] (3-7) Effect In this embodiment, since the 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, the delay in the transmission speed due to the operation time of the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C is suppressed.

[0102] Also, since the input signal and the output signal of the first potential conversion unit 46A are insulated, even when there is an influence of noise, it does not directly affect the signal input to the second gate drive circuit 26B.

[0103] Also, although the ground potentials of the first switching circuit 25A and the second switching circuit 25B are different, since 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, malfunction can be prevented.

[0104] Also, since the input signals and the output signals of the second potential conversion unit 46B and the third potential conversion unit 46C are insulated respectively, even when there is an influence of noise, it does not directly affect the signal input to the microcomputer 40.

[0105] Also, although the ground potentials of the first voltage detection unit 23A and the first current detection unit 24A are different from those of the second voltage detection unit 23B and the second current detection unit 24B, 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 sides of the second potential conversion unit 46B and the third potential conversion unit 46C, respectively, so malfunction can be prevented.

[0106] As a result, the refrigerant control circuit 42, the first switching circuit 25A, and the second switching circuit 25B are controlled by one microcomputer 40.

[0107] (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 for the first switching circuit 25A and a second control signal PWM-2 for the second switching circuit 25B. The first potential conversion unit 46A converts the potential of the second control signal PWM-2. In the power supply control circuit 100, since the potential of either one of the two control signals can be converted by the first potential conversion unit 46A, it is possible to control two switching circuits with different reference potentials using one microcomputer.

[0108] (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.

[0109] (4-3) In the power 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.

[0110] (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 control circuit 100, the delay in the transmission speed due to the operation time of the first potential conversion unit 46A, the second potential conversion unit 46B, and the third potential conversion unit 46C is suppressed.

[0111] (4-5) The first switching circuit 25A and the second switching circuit 25B are power modules in which a plurality of switching elements for converting DC power into AC power of a predetermined frequency are built in one package. The modularization of each switching circuit facilitates the design of the peripheral circuits of each switching circuit on the printed wiring board 10.

[0112] <Second Embodiment> FIG. 3 is a circuit diagram showing the configuration of a power control circuit 102 according to the second embodiment of the present disclosure. In FIG. 3, since 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 that of the first embodiment, the same reference numerals as those in the first embodiment are used and the description thereof is omitted.

[0113] (1) Outline of the power control circuit 102 As shown in FIG. 3, the power control circuit 102 is mounted on a printed wiring board 10 configured such that the R phase, S phase, T phase, and N phase are input from an AC power supply 91 that supplies three-phase alternating current in a three-phase four-wire system.

[0114] The power 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 microcomputer 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.

[0115] The first rectifier circuit 20A rectifies the AC power of the R-phase, S-phase, and T-phase. The first voltage detection unit 23A detects the voltage across both ends of the first smoothing capacitor 22A that smooths 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.

[0116] 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.

[0117] The first switching circuit 25A is connected to the first rectifier circuit 20A. The active filter circuit 60 includes a third switching circuit 25C.

[0118] 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.

[0119] The third voltage detection unit 56 detects the voltage across both ends of the third smoothing capacitor 52 that smooths 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.

[0120] The third current detection unit 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The first potential conversion unit 47A converts the potential of the first control signal PWM-1 or the third control signal PWM-3.

[0125] The second potential conversion unit 47B converts the potential of the signal whose reference potential is different from the reference potential of the microcomputer 40 among the first voltage detection signal and the third voltage detection signal.

[0126] The third potential conversion unit 47C converts the potential of the signal whose reference potential is different from the reference potential of the microcomputer 40 among the first current detection signal and the third current detection signal.

[0127] The fourth potential conversion unit 47D converts the potential of the signal whose reference potential is different from the reference potential of the microcomputer 40 among the first current detection signal and the fourth current detection signal.

[0128] The fifth potential conversion unit 47E converts the potential of the signal whose reference potential is different from the reference potential of the microcomputer 40 among the first current detection signal and the fifth current detection signal.

[0129] The power control circuit 102 of the present disclosure is mounted on, for example, the outdoor unit of a three-phase four-wire 400V air conditioner.

[0130] (2) Detailed configuration (2-1) Active filter circuit 60 The active filter circuit 60 includes a third switching circuit 25C, a third gate drive circuit 26C, a third smoothing capacitor 52, a carrier filter 53, a coupling 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.

[0131] (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 composed of a plurality of switching elements that generate a compensation current for suppressing harmonic currents.

[0132] The third switching circuit 25C is controlled to perform a switching operation 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, it cancels out the harmonic current flowing out from the first switching circuit 25A to the power line.

[0133] Since the configuration of the third switching circuit 25C is the same as that of the first switching circuit 25A, the transistors and diodes, which are the switching elements, are given the same reference numerals as those of the transistors and diodes in the first switching circuit 25A.

[0134] The third switching circuit 25C is a power module in which the upper arm side switching elements (Q3a, Q4a, Q5a, D3a, D4a, D5a) and the lower arm side switching elements (Q3b, Q4b, Q5b, D3b, D4b, D5b) are built in one package.

[0135] (2-1-2) Third gate drive circuit 26C The third gate drive circuit 26C controls the switching elements. Since the configuration and function of the third gate drive circuit 26C are the same as those of the first gate drive circuit 26A, the description is omitted.

[0136] (2-1-3) Third smoothing capacitor 52 The third smoothing capacitor 52 is a capacitor that smooths the output voltage of the third switching circuit 25C.

[0137] (2-1-4) Carrier filter 53 The carrier filter 53 removes noise associated with the switching of the third switching circuit 25C. Specifically, the carrier filter 53 removes the high-frequency component of the compensation current generated by the switching of the third switching circuit 25C.

[0138] (2-1-5) Link reactor 54 The link reactor 54 connects the third switching circuit 25C and the power line.

[0139] (2-1-6) Third voltage detection unit 56 The third voltage detection unit 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 detection unit 56 is configured such that, for example, two resistors connected in series with 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 those two resistors is input to the microcomputer 40.

[0140] The third voltage detection unit 56 is not necessarily provided and can be replaced by other means.

[0141] (2-1-7) Third current detection unit 57 The third current detection unit 57 is 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 detection unit 57 detects the bus current of the third switching circuit 25C.

[0142] The third current detection unit 57 may be configured by, for example, 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.

[0143] (2-1-8) U-phase current detection unit 58u and W-phase current detection unit 58w The U-phase current detection unit 58u detects the compensation current flowing in the U-phase. The W-phase current detection unit 58w detects the compensation current flowing in the W-phase.

[0144] (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.

[0145] Also, the microcomputer 40 is connected to the third gate drive circuit 26C via the first potential conversion unit 47A. Also, the microcomputer 40 is connected to the third voltage detection unit 56 via the second potential conversion unit 47B. Also, the microcomputer 40 is connected to the third current detection unit 57 via the third potential conversion unit 47C. Also, the microcomputer 40 is connected to the U-phase current detection unit 58u via the fourth potential conversion unit 47D. Furthermore, the microcomputer 40 is connected to the W-phase current detection unit 58w via the fifth potential conversion unit 47E.

[0146] The microcomputer 40 performs control to switch on / off 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.

[0147] Furthermore, the microcomputer 40 also has a function as a refrigerant control microcomputer. For example, it controls the refrigerant control circuit 42 of the air conditioner to adjust the circulation direction of the refrigerant in the refrigerant circuit, the evaporation temperature of the refrigerant, the superheat degree, and the subcooling degree.

[0148] (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 the input signal from the microcomputer 40 to the first potential conversion unit 47A and the output signal from the first potential conversion unit 47A to the third gate drive circuit 26C are insulated.

[0149] The second potential conversion unit 47B is provided between the microcomputer 40 and the third voltage detection unit 56, and the input signal from the third voltage detection unit 56 to the second potential conversion unit 47B and the output signal from the second potential conversion unit 47B to the microcomputer 40 are insulated. However, since the third voltage detection unit 56 does not necessarily need to be provided, in that case, the second potential conversion unit 47B is unnecessary.

[0150] The third potential conversion unit 47C is provided between the microcomputer 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 and the output signal from the third potential conversion unit 47C to the microcomputer 40 are insulated.

[0151] The fourth potential conversion unit 47D is provided between the microcomputer 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 conversion unit 47D and the output signal from the fourth potential conversion unit 47D to the microcomputer 40 are insulated.

[0152] The fifth potential conversion unit 47E is provided between the microcomputer 40 and the W-phase current detection unit 58w, and the input signal from the W-phase current detection unit 58w to the fifth potential conversion unit 47E and the output signal from the fifth potential conversion unit 47E to the microcomputer 40 are insulated.

[0153] Insulated ICs such as high-speed photocouplers and digital isolators are employed 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 adopted.

[0154] When the transmission speed from 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 becomes low, a delay time of the circuit occurs. Specifically, for example, when the transmission speed from the third potential conversion unit 47C becomes low, overcurrent protection and current detection become impossible. Therefore, by making it high-speed at 10 Mbps or more, the influence of the delay time of the circuit is minimized.

[0155] (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 different from the ground potential GND-C of the active filter circuit 60.

[0156] When 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.

[0157] Also, the microcomputer must receive voltage detection signals with different ground potentials from the first voltage detection unit 23A and the third voltage detection unit 56 respectively.

[0158] 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.

[0159] Therefore, a plurality of microcomputers are required. As a result, the cost increases.

[0160] 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.

[0161] Therefore, the ground potentials of the first control signal PWM-1 directed to the first switching circuit 25A and the third control signal PWM-3 directed to the third switching circuit 25C output from the microcomputer 40 may be the same ground potential GND-A.

[0162] Also, the third voltage detection signal directed from the third voltage detection unit 56 to the microcomputer 40 is converted to a different ground potential in the second potential conversion unit 47B.

[0163] Therefore, even if the first voltage detection signal directed from the first voltage detection unit 23A to the microcomputer 40 and the second voltage detection signal directed from the third voltage detection unit 56 to the microcomputer 40 have different ground potentials, it may be acceptable.

[0164] Also, the third current detection signal directed from the third current detection unit 57 to the microcomputer 40 is converted to different ground potentials in the third potential conversion unit 47C.

[0165] Therefore, even if the first current detection signal directed from the first current detection unit 24A to the microcomputer 40 and the third current detection signal directed from the third current detection unit 57 to the microcomputer 40 have different ground potentials, it may be acceptable.

[0166] Also, the fourth current detection signal directed from the U-phase current detection unit 58u to the microcomputer 40 is converted to different ground potentials in the fourth potential conversion unit 47D.

[0167] Therefore, even if the first current detection signal directed from the first current detection unit 24A to the microcomputer 40 and the fourth current detection signal directed from the U-phase current detection unit 58u to the microcomputer 40 have different ground potentials, it may be acceptable.

[0168] Furthermore, the fifth current detection signal directed from the W-phase current detection unit 58w to the microcomputer 40 is converted to different ground potentials in the fifth potential conversion unit 47E.

[0169] Therefore, even if the first current detection signal directed from the first current detection unit 24A to the microcomputer 40 and the fifth current detection signal directed from the W-phase current detection unit 58w to the microcomputer 40 have different ground potentials, it may be acceptable.

[0170] (3-1) The first control signal PWM-1 for the first switching circuit 25A The microcomputer 40 generates the first control signal PWM-1 with the switching power supply 31 as the 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.

[0171] The first control signal PWM-1 is converted into a gate pulse by the first gate drive circuit 26A. The switching elements of each upper and lower arm of the first switching circuit 25A are turned on and off by the gate pulse, and a three-phase AC voltage is supplied to the first motor 51A.

[0172] (3-2) The third control signal PWM-3 for the third switching circuit 25C Also, the microcomputer 40 generates the third control signal PWM-3 with the switching power supply 31 as the 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.

[0173] Since the first potential conversion unit 47A is provided between the microcomputer 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.

[0174] The potential-converted third control signal PWM-3 is converted into a gate pulse by the third gate drive circuit 26C. The switching elements of each upper and lower arm of the third switching circuit 25C are turned on and off by the gate pulse.

[0175] (3-3) The first voltage detection signal of the first voltage detection unit 23A for the 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 directly input to the microcomputer 40 (3-4) The third voltage detection signal of the third voltage detection unit 56 for the 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 microcomputer 40 receives the potential-converted third voltage detection signal.

[0176] (3-5) First current detection signal of the first current detection unit 24A directed to the 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 directly input to the microcomputer 40 (3-6) Third current detection signal of the third current detection unit 57 directed to the 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. The 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 microcomputer 40 receives the potential-converted third current detection signal.

[0177] (3-7) Fourth current detection signal of the U-phase current detection unit 58u directed to the microcomputer 40 The ground potential of the U-phase current detection unit 58u is the same as the ground potential GND-C of the third switching circuit 25C. The fourth potential conversion unit 47D is provided between the 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 conversion unit 47D is converted to the same potential as the ground potential GND-A on the output side of the fourth potential conversion unit 47D. The microcomputer 40 receives the potential-converted fourth current detection signal.

[0178] (3-8) The fifth current detection signal of the W-phase current detection unit 58w for the 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. The fifth potential conversion unit 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 conversion unit 47E is converted to the same potential as the ground potential GND-A on the output side of the fifth potential conversion unit 47E. The microcomputer 40 receives the fifth current detection signal whose potential has been converted.

[0179] (3-9) Effects In this embodiment, since the 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, the delay in the transmission speed due to the operation time 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 is suppressed.

[0180] Also, the input signal and the output signal of the first potential conversion unit 47A are insulated, and even if there is an influence of noise, it does not directly affect the signal input to the third gate drive circuit 26C.

[0181] Also, although the ground potentials of the first switching circuit 25A and the third switching circuit 25C are different, since 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, malfunction can be prevented.

[0182] Also, since the input signals and the 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 respectively, even if there is an influence of noise, it does not directly affect the signal input to the microcomputer 40.

[0183] Further, 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 potential of each of the first voltage detection unit 23A and the first current detection unit 24A is common with the ground potential GND-A on the output side of each 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. Therefore, malfunction can be prevented.

[0184] As a result, the refrigerant control circuit 42, the first switching circuit 25A, and the third switching circuit 25C are controlled by one microcomputer 40.

[0185] (4) Features of the Second Embodiment (4-1) In the power supply control circuit 102, the reference potential of the third switching circuit 25C is different from that of the first switching circuit 25A. The microcomputer 40 outputs a first control signal PWM-1 for the first switching circuit 25A and a third control signal PWM-3 for the third switching circuit 25C. The first potential conversion unit 47A converts the potential of the third control signal PWM-3. In the power supply control circuit 102, since the potential of either one of the two control signals can be converted by the first potential conversion unit 47A, it becomes possible to control two switching circuits having different reference potentials with one microcomputer.

[0186] (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.

[0187] (4-3) In the power 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.

[0188] (4-4) In the power control circuit 102, the U-phase current detection unit 58u detects the current flowing in 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.

[0189] (4-5) In the power control circuit 102, the W-phase current detection unit 58w detects the current flowing in 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.

[0190] (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 control circuit 102, the delay in the transmission speed due to the operation time 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 is suppressed.

[0191] (4-7) The third switching circuit 25C is a power module in which a plurality of switching elements for generating a compensation current for suppressing harmonic current are built in one package. The modularization of the third switching circuit 25C facilitates the design of the peripheral circuit of the third switching circuit on the printed wiring board 10.

[0192] <Modifications Common to the First and Second Embodiments> (1) First Modification FIG. 5 is a circuit diagram showing the configuration of the power control circuit 100 according to the first modification of the first embodiment. Further, FIG. 6 is a circuit diagram showing the configuration of the power control circuit 102 according to the first modification of the second embodiment.

[0193] In FIG. 5, the difference between the first modification of the first embodiment and the first embodiment is that a power factor improvement circuit 21 is interposed between the first rectifier circuit 20A and the first smoothing capacitor 22A, and the other configurations are the same as those of the first embodiment. Similarly, in FIG. 6, the difference between the first modification of the second embodiment and the second embodiment is that a power factor improvement circuit 21 is interposed between the first rectifier circuit 20A and the first smoothing capacitor 22A, and the other configurations are the same as those of the second embodiment. Therefore, only the power factor improvement circuit 21 will be described here.

[0194] The power factor improvement circuit 21 includes 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 plus side of the first rectifier circuit 20A and the plus side of the first smoothing capacitor 22A. The diode 212 is connected so as to be in the forward direction from the boost reactor 211 toward the plus side of the first smoothing capacitor 22A.

[0195] The switching element 213 is provided so as to be able to be turned on or off by a control signal given from the microcomputer 40 between the boost reactor 211 and the diode 212 and between the minus side of the first rectifier circuit 20A and the minus side of the first smoothing capacitor 22A.

[0196] In the power factor improvement circuit 21, the switching element 213 is turned on and off based on a control signal input from the microcomputer 40 to the switching element 213, and the direct current input from the first rectifier circuit 20A via the boost reactor 211 is chopped at high speed. Thereby, the voltage obtained by charging the first smoothing capacitor 22A with the direct current from the first rectifier circuit 20A is adjusted.

[0197] The microcomputer 40 detects the voltage of the first smoothing capacitor 22A, and by changing the on / off of the switching element 213 based on the detection result or the like by a control signal, the supply voltage to the first switching circuit 25A is adjusted to improve the power factor.

[0198] Since the microcomputer 40 and the power factor improvement circuit 21 have a common ground potential GND-A, the control signal is input without passing through the potential conversion unit.

[0199] The series circuit of the switching element 213 and the diode 212 may be a power module built in one package.

[0200] With the above configuration, in the first modification of the first embodiment, the refrigerant control circuit 42, the power factor improvement circuit 21, the first switching circuit 25A, and the second switching circuit 25B having a ground potential different from that of the first switching circuit 25A can be controlled by one microcomputer 40.

[0201] Similarly, in the first modification of the second embodiment, the refrigerant control circuit 42, the power factor improvement circuit 21, the first switching circuit 25A, and the third switching circuit 25C having a ground potential different from that of the first switching circuit 25A can be controlled by one microcomputer 40.

[0202] (2) Second modification FIG. 7 is a partial plan view of the printed wiring board 10 showing the positional relationship among 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 the second modification of the first embodiment.

[0203] In FIG. 7, the first switching circuit 25A and the second switching circuit 25B are adjacent to each other. However, it is not always necessary to make them adjacent.

[0204] The first potential conversion unit 46A is provided between the microcomputer 40 and the second switching circuit 25B, similar to the first embodiment, and the input signal from the microcomputer 40 to the first potential conversion unit 46A and the output signal from the first potential conversion unit 46A to the second switching circuit 25B are insulated.

[0205] 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 smaller than the shortest distance Lo from the microcomputer 40 to the first potential conversion unit 46A.

[0206] Desirably, both 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 smaller than the shortest distance Lo from the microcomputer 40 to the first potential conversion unit 46A.

[0207] 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, and the smaller the size of the printed wiring board 10, thus contributing to the miniaturization of the power control circuit 100.

[0208] Also, if the second switching circuit 25B in FIG. 7 is replaced with a third switching circuit 25C, it can be applied as a second modification of the second embodiment.

[0209] In such a case, since 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 smaller than the shortest distance from the microcomputer 40 to the first potential conversion unit 47A, it contributes to the miniaturization of the power control circuit 102.

[0210] <Other Embodiments> (1) Outline of the power control circuit 103 FIG. 8 is a circuit diagram showing the configuration of the power control circuit 103 according to another embodiment. In FIG. 8, the power control circuit 103 is mounted on a printed wiring board 10 configured such that the R phase, S phase, T phase, and N phase are input from an AC power supply that supplies three-phase alternating current in a three-phase four-wire system.

[0211] The power control circuit 103 includes a PWM converter 19, a first switching circuit 25A, a microcomputer 40, and a potential conversion unit 48.

[0212] The PWM converter 19 converts the AC power of the R phase, S phase, and T phase into DC power. The first switching circuit 25A is connected to the PWM converter 19. The reference potential of the PWM converter 19 is different from that of the first switching circuit 25A.

[0213] The microcomputer 40 outputs a first control signal PWM-1 for the first switching circuit 25A and a fourth control signal PWM-4 for 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.

[0214] The power control circuit 103 of the present disclosure is mounted, for example, on the outdoor unit of an air conditioner with a three-phase four-wire 400V.

[0215] (2) Detailed Configuration In FIG. 8, among the components excluding the PWM converter 19, the components with the same reference numerals as those of the power control circuit 100 described in FIG. 1 are described in the first embodiment, so the description is omitted here.

[0216] (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, Q2b and a plurality of diodes D0a, D0b, D1a, D1b, D2a, D2b.

[0217] Transistors Q0a and Q0b are connected in series with each other to form upper and lower arms, and the connection point formed thereby is connected to the output side of the R phase of the AC power supply 91. Transistors Q1a and Q1b are connected in series with each other to form upper and lower arms, and the connection point formed thereby is connected to the output side of the S phase of the AC power supply 91. Transistors Q2a and Q2b are connected in series with each other to form upper and lower arms, and the connection point formed thereby is connected to the output side of the T phase of the AC power supply 91.

[0218] 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 and the cathode terminal of the diode, and the emitter terminal of the transistor and the anode terminal of the diode are connected.

[0219] The PWM converter 19 causes each of the transistors Q0a to Q2b to turn on and off at the timing instructed by the fourth gate drive circuit 26D. Thereby, the power supply current is made substantially sinusoidal, and suppression of power supply harmonics and improvement of the power supply power factor are achieved.

[0220] (2-2) Fourth Gate Drive Circuit 26D The fourth gate drive circuit 26D changes the on and off states of each of the transistors Q0a to Q2b of the PWM converter 19 based on the fourth control signal PWM-4 from the microcomputer 40. The fourth gate drive circuit 26D generates pulse-shaped 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.

[0221] (2-3) Potential Conversion Unit 48 The potential conversion unit 48 is provided between the microcomputer 40 and the PWM converter 19, and insulates the input signal from the microcomputer 40 to the potential conversion unit 48 and the output signal from the potential conversion unit 48 to the PWM converter 19.

[0222] For the potential conversion unit 48, insulation ICs such as high-speed photocouplers and digital isolators are adopted. In this embodiment, a high-speed photocoupler with a transmission speed of 10 Mbps or more is adopted.

[0223] When the transmission speed from the potential conversion unit 48 becomes low, a delay time of the circuit occurs, and overcurrent protection and current detection cannot be performed. Therefore, by making it high-speed at 10 Mbps or more, the influence of the delay time of the circuit is minimized.

[0224] (3) Relationship between the microcomputer 40 and the potential conversion unit 48 In this embodiment, the ground potential GND-D of the PWM converter 19 is a potential different from the ground potential GND-A of the first switching circuit 25A.

[0225] When 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, and a plurality of microcomputers are required. As a result, the cost increases.

[0226] 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 for the PWM converter 19 is converted to a different ground potential in the potential conversion unit 48.

[0227] Therefore, the ground potentials of the first control signal PWM-1 for the first switching circuit 25A output from the microcomputer 40 and the fourth control signal PWM-4 for the PWM converter 19 are the same ground potential GND-A.

[0228] (3-1) The first control signal PWM-1 for the first switching circuit 25A The microcomputer 40 generates a first control signal PWM-1 with a reference potential of the switching power supply 31 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.

[0229] The first control signal PWM-1 is converted into a gate pulse by the first gate drive circuit 26A. Each switching element of the upper and lower arms of the first switching circuit 25A is turned on and off by the gate pulse, and a three-phase alternating voltage is supplied to the first motor 51A.

[0230] (3-2) Fourth control signal PWM-4 for the PWM converter 19 Also, the microcomputer 40 generates a fourth control signal PWM-4 with a reference potential of the switching power supply 31. The fourth control signal PWM-4 has a predetermined duty ratio for switching on / off each switching element of the PWM converter 19.

[0231] Since the potential conversion unit 48 is provided between the microcomputer 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.

[0232] The fourth control signal PWM-4 whose potential has been converted is converted into a gate pulse by the PWM converter 19. Each switching element of the upper and lower arms of the PWM converter 19 is turned on and off by the gate pulse.

[0233] (3-3) Effect In this embodiment, since the high-speed photocoupler is used as the potential conversion unit 48, the delay in the transmission speed due to the operation time of the potential conversion unit 48 is suppressed. Also, the input signal and the output signal of the potential conversion unit 48 are insulated, and even when there is an influence of noise, it does not directly affect the signal input to the PWM converter 19.

[0234] Also, although the ground potentials of the first switching circuit 25A and the PWM converter 19 are different, since the ground potentials of the fourth gate drive circuit 26D and the PWM converter 19 are common with the ground potential GND-D on the output side of the potential conversion unit 48, malfunction can be prevented.

[0235] As described above, the embodiments of the present disclosure have been described. 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 described in the claims.

Explanation of Reference Numerals

[0236] 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 control circuit 102 Power control circuit 211 Reactor 212 Diode (Rectifying Element) 213 Switching Element (First Switching Element)

Prior Art Documents

Patent Documents

[0237]

Patent Document 1

Claims

1. A power control circuit mounted on a printed wiring board (10) configured to receive the R-phase, S-phase, T-phase, and N-phase from an AC power supply that supplies three-phase alternating current in a three-phase four-wire system, comprising: a first rectifying circuit (20A) that rectifies the AC voltages of the R-phase, S-phase, and T-phase; a second rectifying circuit (20B) that rectifies the AC voltage of any one of the R-phase, S-phase, and T-phase and the N-phase; a first switching circuit (25A) connected to the first rectifying circuit (20A); a second switching circuit (25B) connected to the second rectifying 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); a first potential conversion unit (46A) that converts the potential of the first control signal or the second control signal; and a power control circuit (100).

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

3. a first current detection unit (24A) that 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); a second current detection unit (24B) that 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); a third potential conversion unit (46C) that converts the potential of the signal of the first current detection signal and the second current detection signal whose reference potential is different from the reference potential of the microcomputer (40); further comprising The power control circuit (100) according to claim 1 or claim 2.

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

5. 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). The power control circuit (100) according to claim 1 or claim 2.

6. 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 in one package. The power control circuit (100) according to claim 1 or claim 2.

7. A power control circuit mounted on a printed wiring board (10) configured to receive the R phase, S phase, T phase, and N phase from an AC power source that supplies three-phase alternating current in a three-phase four-wire system, a first rectifying circuit (20A) for rectifying the AC voltages of the R phase, S phase, and T phase; a first switching circuit (25A) connected to the first rectifying circuit (20A); a third switching circuit (25C) connected in parallel between the AC power source and the first rectifying circuit (20A) 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 third control signal directed to the third switching circuit (25C); a first potential conversion unit (47A) for converting the potential of the first control signal or the third control signal; comprising a power control circuit (102).

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

9. a first current detection unit (24A) that 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); a third current detection unit (57) that 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); a third potential conversion unit (47C) for converting the potential of the signal among the first current detection signal and the third current detection signal whose reference potential is different from the reference potential of the microcomputer (40); further comprising The power control circuit (102) according to claim 7 or claim 8.

10. A first voltage detection unit (23A) that detects the voltage across a first smoothing capacitor (22A) that smooths the output voltage from the first rectifying circuit (20A), and outputs the detected voltage value as a first voltage detection signal to the microcomputer (40); A third voltage detection unit (56) that detects the voltage across a third smoothing capacitor (52) that smooths the output voltage from the third switching circuit (25C), and outputs the detected voltage value as a third voltage detection signal to the microcomputer (40); A second potential conversion unit (47B) that converts the potential of the signal whose reference potential is different from the reference potential of the microcomputer (40) among the first voltage detection signal and the third voltage detection signal; further comprising The power control circuit (102) according to claim 7 or claim 8.

11. 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 smaller than the shortest distance from the microcomputer (40) to the first potential conversion unit (47A), The power control circuit (102) according to claim 7 or claim 8.

12. The third switching circuit (25C) is a power module in which a plurality of switching elements that generate a compensation current for suppressing harmonic current are built in one package, The power control circuit (102) according to claim 7 or claim 8.

13. A power factor improvement circuit (21) having a first switching element (213), a rectifying element (212), and a reactor (211), inputting the voltage rectified by the first rectifying circuit (20A), and the microcomputer (40) controls the first switching element (213) to be turned on and off to improve the power factor of the AC power supply, further comprising The power control circuit (100, 102) according to claim 1 or claim 7.

14. At least the first switching element (213) and the rectifying element (212) are power modules built in one package, The power control circuit (100, 102) according to claim 13.

15. An air conditioner comprising the power control circuit (100) according to claim 1 or claim 7.

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