Control apparatus and control method of the control apparatus

Abstract

To provide a control apparatus capable of achieving both of suppression of a leakage current and reduction of a conduction noise in accordance with a type of an AC power supply, and provide a control method of the control apparatus.SOLUTION: A control apparatus according to an embodiment of the present invention, comprises a noise suppression circuit, a leakage current suppression circuit, and a control part. The noise suppression circuit is connected to an AC power supply, includes a first capacitor and a second capacitor that are connected in series between lines of the AC power supply, and suppresses a common mode noise. The leakage current suppression circuit has switching means of switching a first mode that is connected between a connection point of the first capacitor and the second capacitor and a ground, and in which suppression of a leakage current is prioritized and a second mode in which the suppression of the common mode noise is prioritized. The control part controls the switching means in accordance with a predetermined switching condition. The control apparatus has a determination part for determining a type of the AC power supply to be connected, and sets the switching condition on the basis of the type of the AC power supply determined by the determination part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device used in an air conditioner or the like, and a control method for the control device. [Background technology]

[0002] A motor control device that achieves both suppression of leakage current and reduction of conduction noise is known. For example, Patent Document 1 discloses a motor control device that controls a motor of a compressor of an air conditioner. In this motor control device, a first capacitor and a second capacitor are connected in series between an AC power supply line, and a leakage current suppression circuit is provided between a connection point of the first capacitor and the second capacitor and a housing. In addition, two surge absorbers with different operating voltages are connected in parallel to the leakage current suppression circuit, and a switch is connected in series to the surge absorber with the lower operating voltage. The switch is switched on or off according to a predetermined condition. As a result, in an operating state in which the leakage current flowing to the housing via the compressor is likely to be high, the leakage current is suppressed by turning off the switch, and in an operating state in which the leakage current is likely to be low, the conduction noise is reduced by turning on the switch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-137837 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the leakage current flowing through the housing includes not only the leakage current through the compressor but also the leakage current through the Y capacitor as the first capacitor and the second capacitor, and it is necessary to suppress the total leakage current. In an air conditioner that operates with a single-phase AC power supply, there are cases where it is connected to a single-phase AC power supply and cases where it is connected to two of the three wires of a three-phase AC power supply. The leakage current through the Y capacitor differs depending on the type of AC power supply to which the air conditioner is connected, that is, whether it is single-phase or three-phase, and in the case of three-phase, what the connection method is. For example, in the case of a single phase, no leakage current flows from the Y capacitor to the ground, but in the case of a three-phase, leakage current flows. In addition, in the case of a three-phase, the leakage current is larger in a Δ connection than in a Y connection. Therefore, if the switch is switched on and off based on the operating state regardless of the type of AC power supply, the total leakage current may become too large, or the conduction noise may be unnecessarily increased even though the leakage current is small.

[0005] In view of the above circumstances, an object of the present invention is to provide a control device and a control method for the control device that can simultaneously suppress leakage current and reduce conducted noise depending on the type of AC power supply. [Means for solving the problem]

[0006] A control device according to an embodiment of the present invention includes a noise suppression circuit, a leakage current suppression circuit, and a control unit. The noise suppression circuit is connected to an AC power supply, includes a first capacitor and a second capacitor connected in series between AC power supply lines, and suppresses common mode noise. The leakage current suppression circuit is connected between the connection point between the first capacitor and the second capacitor and ground, and has a switching means for switching between a first mode in which suppression of leakage current is prioritized and a second mode in which suppression of common mode noise is prioritized. The control unit controls the switching means in accordance with a predetermined switching condition. The control unit also has a determination unit that determines a type of the connected AC power supply, and sets the switching condition based on the type of the AC power supply determined by the determination unit.

[0007] In the control device, a switching condition is set based on the type of AC power supply, and a switching means for switching between a first mode in which leakage current suppression is prioritized and a second mode in which common mode noise suppression is prioritized is controlled according to the switching condition. In this way, by differentiating between prioritizing leakage current suppression and noise suppression based on the type of AC power supply, it is possible to achieve both leakage current suppression and noise reduction regardless of the type of AC power supply.

[0008] The switching conditions include a first switching condition when the type of the AC power supply is three-phase and a second switching condition when the type of the AC power supply is single-phase, and the second switching condition may be determined to make it easier to switch to the second mode than the first switching condition.

[0009] The motor drive system may have an inverter that converts input DC power into drive power for driving a motor and supplies the drive power to the motor, and the second switching condition may be determined such that the second mode is always maintained at least while the motor is being driven.

[0010] The control device may further include a detection unit that detects a phase difference of voltage between the AC power supply lines, and the determination unit may determine a type of the AC power supply based on the phase difference of the voltage detected by the detection unit.

[0011] A control method for the control device may include determining a type of the AC power source when power is supplied to the control device, setting the switching condition based on the type of the AC power source after the type of the AC power source has been determined, and controlling the switching means based on the set switching condition. Effect of the Invention

[0012] According to the present invention, it is possible to suppress leakage current and reduce conducted noise in accordance with the type of AC power supply. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram showing a configuration example of a control device according to the present invention; [Diagram 2] FIG. 13 is a diagram showing a simulation result of leakage current depending on the type of AC power supply. [Diagram 3] FIG. 1 is a diagram showing a mechanism by which leakage current in a single-phase AC power supply becomes zero. [Figure 4] FIG. 1 is a diagram for explaining leakage current in a three-phase Y-connection. [Diagram 5] FIG. 13 is a diagram for explaining leakage current in a three-phase Δ connection. [Figure 6] 4 is a flowchart showing a control process of a microcomputer.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] [Configuration of control device 100] FIG. 1 is a diagram showing an example of the configuration of a control device 100 according to the present invention.

[0016] The control device 100 converts AC power from an external AC power source 1 into drive power for driving a compressor 4 mounted on the air conditioner, and supplies the drive power to the compressor 4. The control device 100 is a device that operates in a single phase (hereinafter, referred to as a single-phase model). In this embodiment, the control device 100, which is a single-phase model, is connected to various types of AC power sources (single-phase or three-phase).

[0017] 1, in this embodiment, the control device 100 has a noise suppression circuit 10, a bridge diode 2, a boost circuit 20, an inverter (IPM) 3, a leakage current suppression circuit 5, a detection unit 7, and a microcomputer 8 which is a control unit. The bridge diode 2, the inverter 3, the compressor 4, the leakage current suppression circuit 5, the detection unit 7, the microcomputer 8, the noise suppression circuit 10, and the boost circuit 20 are housed in a housing 30.

[0018] In addition to the above, the housing 30 may house an outdoor heat exchanger, an outdoor fan, various control circuits, and the like.

[0019] The noise suppression circuit 10 suppresses common mode noise. In this embodiment, the noise suppression circuit 10 has a first coil 11, a second coil 12, a first capacitor 13, and a second capacitor 14. The first coil 11 and the second coil 12 are provided on an AC power supply line on the output side of the AC power supply 1. The first capacitor 13 and the second capacitor 14 are connected in series between the AC power supply lines on the input side of the bridge diode 2, and are provided on the rear side of the first coil 11 and the second coil 12.

[0020] The bridge diode 2 rectifies the input AC voltage.

[0021] The boost circuit 20 boosts the DC voltage input from the bridge diode 2 and improves the power factor by switching a first switch 25 and a second switch 26 described later, and outputs the boosted voltage to the inverter 3.

[0022] In this embodiment, the boost circuit 20 has a third coil 21 and a fourth coil 22 connected in parallel. The boost circuit 20 also has a first diode 23 connected between the third coil 21 and the inverter 3, and a second diode 24 connected between the fourth coil 22 and the inverter 3.

[0023] The boost circuit 20 also has a first switch 25 and a second switch 26 each formed of a switching element such as a transistor. The first switch 25 is connected in parallel with the inverter 3 and is connected between the third coil 21 and the first diode 23. The second switch 26 is connected in parallel with the inverter 3 and is connected between the fourth coil 22 and the second diode 24.

[0024] The boost circuit 20 also includes a smoothing capacitor 27. The smoothing capacitor 27 is connected in parallel to the first switch section 25 and the second switch section 26, and is connected between the inverter 3 and the first diode 23 and the second diode 24.

[0025] The inverter 3 converts the DC power input from the boost circuit 20 into driving power (AC power) for driving the motor of the compressor 4, and supplies the driving power to the motor.

[0026] The leakage current suppression circuit 5 is connected between the ground and the connection point between the first capacitor 13 and the second capacitor 14, and has a switching means 6 for switching between a first mode in which the suppression of leakage current takes precedence and a second mode in which the suppression of common mode noise takes precedence. In this embodiment, the switching means 6 is a switch, and is controlled by the microcomputer 8 to be switched between on (closed) and off (open) according to predetermined switching conditions described later.

[0027] The first mode is a state in which the switch serving as the switching means 6 is turned off, and the second mode is a state in which the switch serving as the switching means 6 is turned on.

[0028] In order to suppress the leakage current flowing through the housing 30, in addition to the leakage current through the compressor 4, it is necessary to suppress the leakage current through the noise suppression circuit 10, i.e., the first capacitor 13 and the second capacitor 14, which are Y capacitors.

[0029] In this embodiment, in the first mode, the switch serving as the switching means 6 is turned off, so that leakage current between the Y capacitor and ground is less likely to flow, and the leakage current can be suppressed. On the other hand, common mode noise increases because common mode noise cannot flow to ground. In the second mode, the switch serving as the switching means 6 is turned on, so that common mode noise flows along with the leakage current between the Y capacitor and ground, and while the common mode noise is suppressed, the leakage current increases.

[0030] The switching means 6 of the leakage current suppression circuit 5 is not limited, and may have any configuration as long as it can switch between the first mode and the second mode. For example, the leakage current suppression circuit 5 may be configured such that two surge absorbers with different operating voltages are connected in parallel, and a switch as the switching means 6 is provided in series with the surge absorber with the lower operating voltage. In this case, when the suppression of the leakage current is prioritized (first mode), the switch is turned off so that the leakage current between the Y capacitor and the ground flows through the surge absorber with the higher operating voltage, thereby suppressing the leakage current. Furthermore, when the suppression of the common mode noise is prioritized (second mode), the switch is turned on so that the leakage current between the Y capacitor and the ground flows through the surge absorber with the lower operating voltage, thereby making it easier for the leakage current to flow and for the common mode noise to be easily removed, thereby suppressing the common mode noise.

[0031] The detection unit 7 detects the phase difference of the voltage between the AC power supply lines (live, neutral). For example, the detection unit 7 is an AC voltage detection circuit capable of detecting the voltage of each AC power supply line. Also, for example, the detection unit 7 detects the voltage phase difference based on the time difference between the timings at which the voltages of the AC power supply lines become 0V. The voltage phase difference detected by the detection unit 7 is output to the microcomputer 8.

[0032] The microcomputer 8 controls the switching means 6 according to a predetermined switching condition. In this embodiment, the microcomputer 8 determines the type of the AC power supply 1 to which the control device 100 is connected, based on the phase difference of the voltage between the AC power supply lines detected by the detection unit 7. The microcomputer 8 sets the switching condition based on this determination result (type of the AC power supply 1).

[0033] That is, in this embodiment, the microcomputer 8 functions as a control unit that controls the switching means in accordance with a predetermined switching condition, and as a determination unit that determines the type of the connected AC power supply.

[0034] The switching condition includes a first switching condition when the type of the AC power supply 1 is three-phase and a second switching condition when the type of the AC power supply 1 is single-phase. In this embodiment, the second switching condition is determined so as to make it easier to switch to the second mode than the first switching condition.

[0035] Here, "easily switched" means that the second switching condition is a more lenient condition for switching to the second mode than the first switching condition. In other words, when the microcomputer 8 controls the switching means according to the second switching condition, the operation time in the second mode is longer than when the microcomputer 8 controls the switching means according to the first switching condition.

[0036] The reason why the second switching condition is determined to make it easier to switch to the second mode than the first switching condition is that, as shown in Figs. 2 and 3 described later, when the AC power supply 1 is single-phase, the leakage current is zero and suppression of common mode noise needs to be prioritized over the leakage current.

[0037] For example, the first switching condition is determined as the operating current of the compressor 4 exceeding a predetermined threshold current value, and the second switching condition is determined as the control device 100 being supplied with power. In this case, if the type of AC power source 1 is three-phase, the compressor 4 is in the first mode until the rotation speed increases after startup and the operating current reaches a predetermined threshold current value, and switches to the second mode when the operating current exceeds the predetermined threshold current value. On the other hand, if the type of AC power source 1 is single-phase, the mode switches to the second mode at the point when power is supplied to the control device 100. In other words, the second switching condition is determined so that the time during which the compressor 4 operates in the second mode is longer than that of the first switching condition, that is, so that the mode is easily switched to the second mode.

[0038] Also, for example, both the first switching condition and the second switching condition may be determined such that the operating current of the compressor 4 exceeds a predetermined threshold current value, and the threshold current value in the second switching condition may be determined to be lower than the threshold current value in the first switching condition. In this case, too, the second switching condition is determined so as to facilitate switching to the second mode, since the operating current of the compressor 4 reaches the threshold current value more quickly under the second switching condition.

[0039] The configuration of the microcomputer 8 is not limited, and may be, for example, composed of a communication unit that receives the detection result of the detector 7, a storage unit that stores the switching conditions, and a CPU that controls the switching means 6 in accordance with the switching conditions.

[0040] Here, the difference in leakage current due to the difference in the type of AC power supply will be described later with reference to FIGS.

[0041] FIG. 2 is a diagram showing the simulation results of leakage current depending on the type of AC power supply.

[0042] As shown in Fig. 2, AC power supplies are classified into single-phase and three-phase AC (Y-connection and Δ-connection). The phase difference of the voltage between the AC power supply lines is 180° for single-phase and 120° for three-phase. Furthermore, when the AC power supply is three-phase, a leakage current flows between the Y capacitor (first capacitor 13 and second capacitor 14) and the ground, but does not flow (0 mA) in the case of single-phase. Furthermore, when the AC power supply is three-phase, the leakage current flowing between the Y capacitor and the ground is larger in the case of Δ-connection than in the case of Y-connection.

[0043] Fig. 3 is a diagram showing a mechanism by which leakage current becomes 0 when the control device 100, which is a single-phase model, is connected to a single-phase AC power supply. Fig. 3A is a diagram showing a current waveform flowing through a Y capacitor when the control device 100 is connected to a single-phase AC power supply 1. Fig. 3B is a diagram showing a simulation result of leakage current.

[0044] In FIG. 3A, a control device 100 is connected to a single-phase AC power supply, a first Y capacitor Y1 is connected between a first electric wire L1 and ground GND, and a second Y capacitor Y2 is connected between a second electric wire L2 and ground GND.

[0045] Since the phase difference between the voltage waveform 41 of the first wire L1 phase and the voltage waveform 42 of the second wire L2 phase is 180 degrees, the phase difference between the current (leakage current) 43 flowing through the first Y capacitor Y1 and the current (leakage current) 44 flowing through the second Y capacitor Y2 is also 180 degrees.

[0046] Therefore, as shown in FIG. 3B, a combined leakage current 45 flowing between the Y capacitor and the ground becomes zero because the leakage current 43 and the leakage current 44 always cancel each other out.

[0047] Fig. 4 is a diagram for explaining leakage current when the control device 100, which is a single-phase model, is connected to a three-phase Y-connection. Fig. 4A is a diagram showing a current waveform flowing through a Y capacitor when the control device 100 is connected to a three-phase Y-connection AC power source 1. Fig. 4B is a diagram showing a simulation result of the leakage current.

[0048] As shown in Fig. 4A, a first ungrounded electric wire L1 and a second ungrounded electric wire L2 of a three-phase Y-connection AC power source 50 (e.g., phase voltage 120 V, line voltage 208 V) are connected to the control device 100. Fig. 4A also shows a third Y capacitor Y3 connected between the first ungrounded electric wire L1 and the ground, and a fourth Y capacitor Y4 connected between the second ungrounded electric wire L2 and the ground.

[0049] In the case of a three-phase Y-connection AC power supply 50, the phase difference between the voltages of the first ungrounded electric wire L1 and the second ungrounded electric wire L2 is 120 degrees, and therefore the phase difference between the leakage current 51 flowing through the third Y capacitor Y3 and the leakage current 52 flowing through the fourth Y capacitor Y4 is also 120 degrees.

[0050] Fig. 5 is a diagram for explaining leakage current when the control device 100, which is a single-phase model, is connected to a three-phase Δ connection. Fig. 5A is a diagram showing a current waveform flowing through a Y capacitor when the control device 100 is connected to an AC power source 1 with a three-phase Δ connection. Fig. 5B is a diagram showing a simulation result of leakage current.

[0051] As shown in Fig. 5A, a first ungrounded electric wire L1, a second ungrounded electric wire L2, and a grounded electric wire L3 of a three-phase Δ-connection AC power source 60 (for example, line voltage 240 V) are connected to the control device 100. Fig. 5A also shows a fifth Y capacitor Y5 connected between the first ungrounded electric wire L1 and ground GND, and a sixth Y capacitor Y6 connected between the second ungrounded electric wire L2 and ground GND.

[0052] In the case of a three-phase delta-connection AC power supply 60, the phase difference between the voltages of the first ungrounded electric wire L1 and the second ungrounded electric wire L2 is 120 degrees, and therefore the phase difference between the leakage current 61 flowing through the fifth Y capacitor Y5 and the leakage current 62 flowing through the sixth Y capacitor Y6 is also 120 degrees.

[0053] 4B and 5B, the combined leakage current (53 and 63) in a three-phase AC power supply is different from that in a single-phase AC power supply in that the leakage current 51 (61) and the leakage current 52 (62) do not cancel each other out, and therefore the leakage current flowing through the Y capacitor is larger than that in a single-phase AC power supply.

[0054] Next, the reason why there is a difference in the magnitude of leakage current between a three-phase Y connection and a three-phase Δ connection will be explained. For example, in the three-phase Y connection shown in Fig. 4A, the potential of each phase is 120V. On the other hand, in the three-phase Δ connection shown in Fig. 5A, the potential of each phase is 240V.

[0055] The leakage current flowing through the Y capacitor can be calculated using the following formula: I=2πf×V×C

[0056] Here, f is the power supply frequency, V is the power supply voltage (potential), and C is the capacitance of the Y capacitor.

[0057] According to the above formula, even if the line voltages are the same, a three-phase delta connection, which has a higher power supply voltage (potential), will have a larger leakage current than a three-phase wye connection.

[0058] [Microcontroller 8 sequence diagram] FIG. 6 is a flowchart showing the control process of the microcomputer 8.

[0059] As shown in FIG. 6, when power is supplied to the control device 100, the detection unit 7 detects the phase difference of the voltage between the AC power supply lines (step 101).

[0060] The microcomputer 8 determines whether the phase difference of the detected voltages is 180 degrees or not (step 102). That is, the microcomputer 8 determines whether the AC power supply 1 is single-phase or three-phase.

[0061] If the microcomputer 8 determines that the voltage phase difference is 180 degrees (YES in step 102), that is, if the type of the AC power supply 1 is single-phase, the switching condition is set to the second switching condition (step 103).

[0062] Here, when the AC power supply type is single-phase, no leakage current flows between the Y capacitor and the ground, and therefore the total leakage current of the leakage current flowing between the Y capacitor and the ground and the leakage current through the compressor 4 is unlikely to be large. Therefore, compared to when the AC power supply type is three-phase, there is less need to prioritize suppression of the leakage current. Therefore, in this embodiment, the second switching condition is determined to be that power is being supplied to the control device 100. As will be described later, in this case, the second switching condition is always satisfied as long as the power supply is turned on, and the second mode in which common mode noise is prioritized is selected.

[0063] Alternatively, the second switching condition may be determined to be that the operating current of the compressor 4 exceeds a predetermined threshold current value. In this case, the first switching condition described below is also determined to be that the operating current of the compressor 4 exceeds a predetermined threshold current value, and the predetermined threshold current value of the second switching condition may be set lower than the predetermined threshold current value of the first switching condition. In other words, the second switching condition may be determined to make it easier to switch to the second mode than the first switching condition. The reason why the first switching condition or the second switching condition may be determined to be that the operating current of the compressor 4 exceeds a predetermined threshold current value will be described in detail later.

[0064] Next, the microcomputer 8 starts the compressor 4 (step 104). Then, the microcomputer 8 judges whether or not the second switching condition is satisfied (step 105). In this embodiment, the second switching condition is that power is supplied to the control device 100. Since power is supplied to the control device 100 in step 101, the second switching condition is always satisfied in this embodiment (YES in step 105). Therefore, the microcomputer 8 turns on the switch that is the switching means 6 (step 106). That is, as shown in FIG. 2 and FIG. 3, when the AC power source 1 is single-phase, the leakage current flowing between the Y capacitor and the ground is zero, and therefore the switching means 6 switches to the second mode in which suppression of common mode noise is prioritized. Since the processes from step 105 to step 106 are performed substantially simultaneously, the second mode is always maintained while the motor of the compressor 4 is driven.

[0065] In the case of the second switching condition in this embodiment, the second switching condition is always satisfied in step 105. However, depending on the setting of the second switching condition, the second switching condition may not be satisfied (NO in step 105). In this case, the microcomputer 8 turns off the switch serving as the switching means 6 (step 107). That is, the switching means 6 goes into the first mode in which suppression of leakage current is prioritized. Then, the microcomputer 8 returns the process to step 105. That is, the microcomputer 8 repeats the processes of steps 105 and 107 until the second switching condition is satisfied.

[0066] In this way, when the AC power supply type is single-phase, as shown in Figure 3, the leakage current flowing between the Y capacitor and ground is zero, so the first mode is not performed and the second mode is always executed, and therefore unnecessary opening and closing of the switch is not performed. Also, if the initial state of the switch is set to on and the on state is maintained even if the power supply is cut off, the switch is always on and opening and closing of the switch can be completely eliminated. This makes it possible to extend the life of the parts without deteriorating them. In addition, common mode noise can easily flow between the Y capacitor and ground, ensuring emission performance.

[0067] Moreover, if the microcomputer 8 determines that the voltage phase difference is not 180 degrees (NO in step 102), that is, if the type of the AC power supply 1 is three-phase, the switching condition is set to the first switching condition (step 108).

[0068] Here, when the type of AC power supply is three-phase, a leakage current is likely to flow between the Y capacitor and the ground, and therefore the total leakage current of the leakage current flowing between the Y capacitor and the ground and the leakage current through the compressor 4 is likely to become large. Therefore, it is necessary to set the first switching condition so that the first mode and the second mode can be switched, taking into account the magnitude of the leakage current through the compressor 4.

[0069] The magnitude of the leakage current flowing through the compressor 4 to the housing 30 depends on the density of the dielectric (the refrigerant sealed in the air conditioner) that fills the periphery of the winding of the motor of the compressor 4. For example, when the refrigerant is in the liquid phase, the density of the liquid is greater than that of the gas, so the leakage current flows more easily than when the refrigerant is in the gas phase. Therefore, when the refrigerant is in the liquid phase or two-phase gas-liquid phase, the leakage current through the compressor 4 is larger than when the refrigerant is in the gas phase. Also, the lower the rotation speed of the motor of the compressor 4, the less heat is generated by the compressor 4, so the refrigerant in the compressor 4 is more likely to become two-phase gas-liquid. Therefore, the leakage current through the compressor 4 is larger. On the other hand, when the rotation speed of the motor of the compressor 4 is higher, the heat generated by the compressor 4 is greater, so the refrigerant in the compressor 4 is more likely to become gas-liquid. Therefore, the leakage current through the compressor 4 is smaller.

[0070] Therefore, in this embodiment, the first switching condition is set as the operating current of the compressor 4 exceeding a predetermined threshold current value. Here, the threshold current value is a current value that is sufficiently high to the extent that it can be assumed that the refrigerant around the motor windings of the compressor 4 is in a gas phase, and is determined in advance by an experiment or the like. In other words, if the operating current of the compressor 4 exceeds the predetermined threshold current value, it is assumed that the rotation speed of the compressor 4 is high and the refrigerant around the motor windings of the compressor 4 is in a gas phase. Therefore, since the leakage current through the compressor 4 is considered to be small, it can be determined that it is acceptable to switch from the first mode, in which suppression of the leakage current is prioritized, to the second mode, in which suppression of the common mode noise is prioritized.

[0071] Alternatively, the first switching condition may be determined to be that the rotation speed of the compressor 4 exceeds a predetermined value. If the rotation speed of the compressor 4 exceeds the predetermined value, it is presumed that the refrigerant around the windings of the motor of the compressor 4 is in a gas phase. Therefore, since the leakage current through the compressor 4 is considered to be small, it can be determined that the first mode, in which suppression of the leakage current is prioritized, may be switched to the second mode, in which suppression of the common mode noise is prioritized.

[0072] The first switching condition may be determined to be that the compressor 4 is driven by the flux-weakening control. The flux-weakening control is a control that is implemented to further increase the rotation speed when the rotation speed of the motor of the compressor 4 is high and the back electromotive force is large. For example, the microcomputer 8 implements the flux-weakening control when the required capacity of the air conditioner cannot be satisfied unless the rotation speed of the motor of the compressor 4 is further increased. If the compressor 4 is driven by the flux-weakening control, the rotation speed of the compressor 4 is high, so it is presumed that the refrigerant around the winding of the motor of the compressor 4 is in a gas phase. Therefore, it is considered that the leakage current through the compressor 4 is small, and it can be determined that it is acceptable to switch from the first mode, in which suppression of leakage current is prioritized, to the second mode, in which suppression of common mode noise is prioritized.

[0073] The first switching condition may be determined as a temperature difference ΔT obtained by subtracting the high-pressure saturation temperature from the main body temperature of the compressor 4 exceeds a predetermined value. The high-pressure saturation temperature is a value determined according to the pressure of the refrigerant discharged from the compressor 4, depending on the physical properties of each type of refrigerant. When the temperature difference ΔT is a positive value, the temperature of the refrigerant inside the compressor 4 is higher than the high-pressure saturation temperature, and the refrigerant inside the compressor 4 is in a superheated state, that is, in a gas phase. When the temperature difference ΔT is 0, the temperature of the refrigerant inside the compressor 4 is equal to the high-pressure saturation temperature, and the refrigerant inside the compressor 4 is in a gas-liquid two-phase state, saturated liquid, or saturated gas. Therefore, when the temperature difference ΔT is a positive value, it means that the refrigerant inside the compressor 4 is completely in a gas phase. Therefore, if the temperature difference ΔT is a predetermined value (a value greater than 0, for example 2), it is considered that the leakage current through the compressor 4 is small, and it can be determined that the first mode, in which suppression of the leakage current is prioritized, may be switched to the second mode, in which suppression of the common mode noise is prioritized.

[0074] That is, the first switching condition may be determined based on various conditions under which it can be assumed that the leakage current from the compressor 4 has become small.

[0075] Next, the microcomputer 8 starts the compressor 4 (step 109). Then, the microcomputer 8 determines whether or not the first switching condition is satisfied (step 110). As described above, in this embodiment, the first switching condition is that the operating current of the compressor 4 exceeds a predetermined threshold current value.

[0076] When the first switching condition is satisfied, that is, when the operating current of the compressor 4 exceeds a predetermined threshold current value (YES in step 110), the microcomputer 8 turns on the switch serving as the switching means 6 (step 111). That is, the switching means 6 goes into the second mode in which suppression of common mode noise is prioritized.

[0077] If the first switching condition is not satisfied, that is, if the operating current of the compressor 4 does not exceed the predetermined threshold current value (NO in step 110), the microcomputer 8 turns off the switch serving as the switching means 6 (step 112). That is, the switching means 6 goes into the first mode in which suppression of leakage current takes priority. Then, the microcomputer 8 returns the process to step 110. That is, the microcomputer 8 repeats the processes of steps 110 and 112 until the first switching condition is satisfied.

[0078] In this way, when the type of AC power supply is three-phase, since leakage current easily flows between the Y capacitor and the ground, the total leakage current of the leakage current flowing between the Y capacitor and the ground and the leakage current through the compressor 4 tends to become large. Therefore, while the leakage current through the compressor 4 is large after the compressor 4 is started, the switch is turned off (first mode) to suppress the leakage current flowing between the Y capacitor and the ground, thereby suppressing the total leakage current of the leakage current flowing between the Y capacitor and the ground and the leakage current through the compressor 4. Furthermore, after the compressor 4 is started, when the first switching condition is satisfied, that is, when the rotation speed of the compressor 4 increases and the leakage current through the compressor 4 becomes small, the switch is turned on (second mode) to suppress the common mode noise. This makes it possible to ensure the emission performance after the start. Furthermore, after the compressor 4 is started, the suppression of the leakage current takes precedence over the suppression of the common mode noise until the first switching condition is satisfied, so that the emission performance deteriorates, but the impact is small because the rotation speed of the compressor 4 is low, the current is low, and the noise is low.

[0079] As described above, according to this embodiment, the switching condition is set based on the type of the AC power supply 1, and the switching means 6 for switching between the first mode in which the suppression of leakage current is prioritized and the second mode in which the suppression of common mode noise is prioritized is controlled in accordance with the switching condition. As a result, whether the emphasis is placed on the suppression of leakage current or on the suppression of noise is differentiated based on the type of the AC power supply, so that it is possible to achieve both the suppression of leakage current and the reduction of noise regardless of the type of the AC power supply.

[0080] Furthermore, according to this embodiment, the switching conditions include a first switching condition when the type of the AC power supply 1 is three-phase, and a second switching condition when the type of the AC power supply 1 is single-phase. The second switching condition is determined so that the switching to the second mode is easier than the first switching condition. As a result, since the leakage current is smaller when the type of the AC power supply 1 is single-phase than when it is three-phase, by determining the condition so that the switching is easier to prioritize noise suppression when it is single-phase, it is possible to achieve both the suppression of leakage current and the reduction of conducted noise.

[0081] Furthermore, according to this embodiment, the control device 100 has an inverter 3 that converts the input DC power into drive power for driving the motor of the compressor 4 and supplies the drive power to the motor of the compressor 4. The second switching condition is determined so that the second mode is always maintained at least while the motor of the compressor 4 is being driven. As a result, when the AC power source type is single-phase, emphasis is always placed on noise suppression, so that the leakage current does not become a problem and the conducted noise can always be reduced. Also, when the AC power source type is single-phase, switching between the first mode and the second mode is not performed, so that the switch is not opened or closed, and therefore defects due to the lifespan of the switch can be prevented.

[0082] Furthermore, according to this embodiment, the control device 100 has a detection unit 7 that detects a phase difference in voltage between AC power supply lines. The microcomputer 8 determines the type of the AC power supply 1 based on the phase difference in voltage detected by the detection unit 7. This makes it possible to determine the type of the AC power supply by a simple means.

[0083] Furthermore, according to this embodiment, the control method of the control device 100 is to determine the type of the AC power supply 1 when power is supplied to the control device 100, and after the type of the AC power supply 1 is determined, set a switching condition based on the type of the AC power supply 1, and control the switching means 6 based on the set switching condition. As a result, by placing importance on either leakage current suppression or noise suppression based on the type of AC power supply, it is possible to achieve both leakage current suppression and noise reduction regardless of the type of AC power supply. [Explanation of symbols]

[0084] 1…AC power supply 3…Inverter 4. Compressor 5. Leakage current suppression circuit 6...Switching means 7…Detection section 8. Microcomputer 10...Noise suppression circuit 20...Boost circuit 30…Housing 100...Control device

Claims

1. a noise suppression circuit connected to an AC power supply, the noise suppression circuit including a first capacitor and a second capacitor connected in series between AC power supply lines, the noise suppression circuit suppressing common mode noise; a leakage current suppression circuit connected between a connection point between the first capacitor and the second capacitor and ground, the leakage current suppression circuit having a switching means for switching between a first mode in which a priority is given to suppression of leakage current and a second mode in which a priority is given to suppression of common mode noise; A control unit that controls the switching means in accordance with a predetermined switching condition; Equipped with The control unit has a determination unit that determines a type of the connected AC power supply, The control unit sets the switching condition based on the type of the AC power supply determined by the determination unit. Control device.

2. The control device according to claim 1 , the switching condition includes a first switching condition when the type of the AC power supply is three-phase and a second switching condition when the type of the AC power supply is single-phase, The second switching condition is determined so that the switching to the second mode is easier than the first switching condition. Control device.

3. The control device according to claim 2, an inverter that converts input DC power into drive power for driving a motor and supplies the drive power to the motor; The second switching condition is determined so that the second mode is always maintained at least while the motor is being driven. Control device.

4. The control device according to claim 1, further comprising: a detection unit for detecting a phase difference of a voltage between the AC power supply lines, The determination unit determines a type of the AC power supply based on the phase difference of the voltage detected by the detection unit. Control device.

5. A control method for the control device according to any one of claims 1 to 4, When power is supplied to the control device, a type of the AC power source is determined; After the type of the AC power source is determined, the switching condition is set based on the type of the AC power source; The switching means is controlled based on the set switching condition. A control method for a control device.

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