Electric Compressor

Abstract

To provide a technique for preventing power for controlling an electric compressor from flowing into a vehicle system.SOLUTION: An electric compressor 1 includes an electric motor 11, a filter circuit 13, a capacitor C13, an inverter circuit 12, a drive circuit 14, a power supply circuit 16, a switch 20 that connects or disconnects a power supply path that supplies power from the power supply circuit 16 to the drive circuit 14, and a control circuit 15 that controls an operation of the switch 20. The control circuit 15 connects the power supply path in a case where a voltage between the capacitor C13 and the inverter circuit 12 is higher than a voltage between the power supply circuit 16 and the drive circuit 14, and disconnects the power supply path in a case where the voltage between the capacitor C13 and the inverter circuit 12 is lower than the voltage between the power supply circuit 16 and the drive circuit 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric compressor, and more particularly to an electric compressor that can operate using DC power from a vehicle battery. [Background technology]

[0002] Conventionally, vehicles such as hybrid vehicles, electric vehicles, and fuel cell vehicles are equipped with electric compressors used in vehicle air conditioners, etc. For example, JP 2020-159320 A (Patent Document 1) discloses an electric compressor that converts DC power from a high-voltage battery mounted on a vehicle system into AC power and supplies it to an electric motor. The electric compressor disclosed in Patent Document 1 includes an inverter circuit that converts DC power from the high-voltage battery into AC power based on the control of a control computer, and a low-voltage power supply that supplies power lower than the power from the high-voltage battery to the control computer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-159320 A Summary of the Invention [Problem to be solved by the invention]

[0004] The electric compressor disclosed in Patent Document 1 can convert DC power from a high-voltage battery of a vehicle system into AC power and supply it to an electric motor by driving an inverter circuit under the control of a control computer. However, for example, when the vehicle system is stopped and the voltage on the high-voltage battery side becomes lower than the voltage applied to the control computer from a low-voltage power supply, there is a risk that electric charge will accumulate in a capacitor inside or outside the electric compressor due to the electric power from the low-voltage power supply. In such a case, the electric charge accumulated in the capacitor may damage or shorten the lifespan of devices in the vehicle system. Such problems are not limited to vehicle air conditioners, but exist in all systems in which an electric compressor is operated by electric power from an external battery.

[0005] The present invention has been made to solve the above-mentioned problems, and has as its object to provide a technology that prevents the power for controlling an electric compressor from damaging or shortening the lifespan of equipment in a system in which the electric compressor is installed. [Means for solving the problem]

[0006] An electric compressor according to an aspect of the present disclosure includes an electric motor, a filter circuit, a capacitor, an inverter circuit, a drive circuit, a power supply circuit, a switch, and a control circuit. The filter circuit reduces noise in power supplied from an external battery. The capacitor constitutes the filter circuit. The inverter circuit converts power supplied from the battery via the filter circuit from direct current to alternating current and supplies the power to the electric motor. The drive circuit is connected to a power supply path from the inverter circuit to the electric motor and controls the operation of the inverter circuit. The power supply circuit transforms power supplied from the battery and supplies the power to the drive circuit. The switch connects or disconnects a power supply path that supplies power from the power supply circuit to the drive circuit. The control circuit controls the operation of the switch. The control circuit connects the power supply path when a voltage between the capacitor and the inverter circuit is higher than a voltage between the power supply circuit and the drive circuit, and disconnects the power supply path when a voltage between the capacitor and the inverter circuit is lower than a voltage between the power supply circuit and the drive circuit.

[0007] According to the above configuration, the electric compressor can use a switch to connect or disconnect the power path through which power is supplied from the power supply circuit to the drive circuit. This prevents the electric compressor from accumulating electric charge in the capacitor inside the electric compressor due to the electric power supplied from the power supply circuit to the drive circuit, and therefore prevents the electric power for controlling the electric compressor from damaging or shortening the lifespan of devices in the system in which the electric compressor is installed.

[0008] Preferably, the control circuit controls the switch to connect the power supply path when power supply from the battery to the inverter circuit begins while the power supply path is interrupted and the voltage between the capacitor and the inverter circuit becomes equal to or greater than a first threshold value.

[0009] According to the above configuration, when the power supply path of the electric compressor starts to be supplied from the battery to the inverter circuit while the power supply path is cut off, and the voltage between the capacitor and the inverter circuit, in other words the voltage of the power supplied from the battery to the inverter circuit, becomes equal to or higher than the first threshold value, the electric power path is connected by the switch, thereby preventing the voltage of the power supplied from the power supply circuit to the drive circuit from becoming higher than the voltage on the high-voltage side and preventing an electric charge from accumulating in the capacitor in the electric compressor due to the power supplied from the power supply circuit to the drive circuit.

[0010] Preferably, when a voltage between the capacitor and the inverter circuit drops to a second threshold while the power supply path is connected, the control circuit controls the switch to cut off the power supply path.

[0011] According to the above configuration, when the voltage between the capacitor and the inverter circuit, in other words the voltage of the power supplied from the battery to the inverter circuit, drops to the second threshold while the power supply path is connected, the electric compressor cuts off the power supply path using a switch, thereby preventing electric charge from accumulating in the capacitor inside the electric compressor due to the power supplied from the power supply circuit to the drive circuit. Effect of the Invention

[0012] According to the present disclosure, it is possible to prevent the power for controlling the electric compressor from damaging or shortening the lifespan of equipment within a system in which the electric compressor is installed. [Brief description of the drawings]

[0013] [Figure 1] 1 is a circuit diagram showing a configuration of an electric compressor according to an embodiment; [Diagram 2] 1 is a circuit diagram showing a configuration of a vehicle system according to an embodiment; [Diagram 3] 2 is a circuit diagram showing a configuration of a drive unit of a drive circuit according to an embodiment; FIG. [Figure 4] FIG. 13 is a diagram showing an example of an effect of residual charge on a vehicle system. [Diagram 5] 5 is a flowchart showing a switch control process performed by the control circuit according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters, and the description thereof will not be repeated.

[0015] [Electric compressor configuration] The configuration of an electric compressor 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram showing the configuration of an electric compressor 1 according to an embodiment.

[0016] The electric compressor 1 is an electric compressor used in vehicle air conditioners and the like. As shown in Fig. 1, the electric compressor 1 can be connected to a vehicle system 3 by connecting a cable 35 to connection points T1 and T2. Connection points T1 and T2 are attached to a housing of the electric compressor 1 as connectors (not shown). The vehicle system 3 includes a switch 30, a battery 40, a drive unit 80, a gear 81, and drive wheels 82. The battery 40 corresponds to the "external battery" in this disclosure.

[0017] The drive device 80 drives drive wheels 82 via gears 81 using power supplied from the battery 40. The electric compressor 1 is an auxiliary device that converts DC power from the battery 40 used in the drive device 80 into AC power and supplies the AC power to an electric motor 11, which will be described later.

[0018] The battery 40 is composed of a chargeable and dischargeable secondary battery such as a lithium ion secondary battery, a nickel metal hydride battery, or a lead storage battery. In vehicles such as hybrid cars, electric cars, or fuel cell cars, a secondary battery of 200V to 400V may be applied as the battery 40. In FIG. 1, the voltage of the power supplied from the battery 40 is indicated as "HV." The positive terminal of the battery 40 is connected to a connection point T1 via the switch 30. The negative terminal of the battery 40 is connected to a connection point T2.

[0019] The switch 30 electrically connects or disconnects a path between the battery 40 and the electric compressor 1. A specific configuration of the switch 30 will be described later with reference to FIG.

[0020] The electric compressor 1 includes a positive electrode line PL, a negative electrode line NL, an electric motor 11, an inverter circuit 12, a filter circuit 13, a drive circuit 14, a control circuit 15, and a power supply circuit 16.

[0021] The positive electrode line PL is connected via a connection point T1 to a positive terminal of the battery 40. The negative electrode line NL is connected via a connection point T2 to a negative terminal of the battery 40. In addition, the negative electrode line NL is connected to a ground terminal GND.

[0022] Electric motor 11 is a so-called three-phase AC motor, and includes U-phase coil 11U, V-phase coil 11V, and W-phase coil 11W. Coils 11U, 11V, and 11W are connected in a Y-connection, for example. Electric motor 11 rotates a rotor (not shown) and a rotating shaft connected to the rotor by supplying power to each of coils 11U, 11V, and 11W.

[0023] The inverter circuit 12 constitutes a so-called three-phase inverter. The inverter circuit 12 includes switching elements TU1 and TU2 connected in series between a positive electrode line PL and a negative electrode line NL, switching elements TV1 and TV2 connected in series between a positive electrode line PL and a negative electrode line NL, and switching elements TW1 and TW2 connected in series between a positive electrode line PL and a negative electrode line NL. In the following description, any or all of the switching elements TU1, TU2, TV1, TV2, TW1, and TW2 will also be simply referred to as "switching elements."

[0024] Each switching element is configured by a semiconductor transistor such as an insulated gate bipolar transistor (IGBT) or a field effect transistor (FET). In FIG. 1, an example in which each switching element is configured by an IGBT is shown.

[0025] Switching element TU1 constitutes a U-phase upper arm. Switching element TU2 constitutes a U-phase lower arm. Switching element TV1 constitutes a V-phase upper arm. Switching element TV2 constitutes a V-phase lower arm. Switching element TW1 constitutes a W-phase upper arm. Switching element TW2 constitutes a W-phase lower arm.

[0026] Specifically, the collector of the switching element TU1 is connected to the positive electrode line PL, and the emitter of the switching element TU1 is connected to the collector of the switching element TU2. The emitter of the switching element TU2 is connected to the negative electrode line NL. The collector of the switching element TV1 is connected to the positive electrode line PL, and the emitter of the switching element TV1 is connected to the collector of the switching element TV2. The emitter of the switching element TV2 is connected to the negative electrode line NL. The collector of the switching element TW1 is connected to the positive electrode line PL, and the emitter of the switching element TW1 is connected to the collector of the switching element TW2. The emitter of the switching element TW2 is connected to the negative electrode line NL.

[0027] A node N1 between the emitter of the switching element TU1 and the collector of the switching element TU2 is connected to a coil 11U. A node N2 between the emitter of the switching element TV1 and the collector of the switching element TV2 is connected to a coil 11V. A node N3 between the emitter of the switching element TW1 and the collector of the switching element TW2 is connected to a coil 11W.

[0028] Furthermore, the inverter circuit 12 includes a diode DU1 connected in parallel with the switching element TU1, a diode DU2 connected in parallel with the switching element TU2, a diode DV1 connected in parallel with the switching element TV1, a diode DV2 connected in parallel with the switching element TV2, a diode DW1 connected in parallel with the switching element TW1, and a diode DW2 connected in parallel with the switching element TW2.

[0029] The anode of the diode DU1 is connected to the emitter of the switching element TU1, and the cathode of the diode DU1 is connected to the collector of the switching element TU1. The anode of the diode DU2 is connected to the emitter of the switching element TU2, and the cathode of the diode DU2 is connected to the collector of the switching element TU2. The anode of the diode DV1 is connected to the emitter of the switching element TV1, and the cathode of the diode DV1 is connected to the collector of the switching element TV1. The anode of the diode DV2 is connected to the emitter of the switching element TV2, and the cathode of the diode DV2 is connected to the collector of the switching element TV2. The anode of the diode DW1 is connected to the emitter of the switching element TW1, and the cathode of the diode DW1 is connected to the collector of the switching element TW1. The anode of the diode DW2 is connected to the emitter of the switching element TW2, and the cathode of the diode DW2 is connected to the collector of the switching element TW2.

[0030] Filter circuit 13 is disposed on the input side of electric compressor 1 and constitutes an LC filter. When power is supplied from battery 40 to inverter circuit 12, filter circuit 13 suppresses high-frequency components (noise) of power from passing through inverter circuit 12. Filter circuit 13 includes an inductor L13 provided on positive electrode line PL, and a capacitor C13 connected between positive electrode line PL and negative electrode line NL.

[0031] The drive circuit 14 is connected to the gates of the switching elements of the inverter circuit 12 and to nodes N1, N2, and N3, and is communicatively connected to the control circuit 15. The drive circuit 14 includes a drive unit 50 that drives each switching element. The drive unit 50 controls each switching element to an ON or OFF state based on a PWM signal from the control circuit 15. As a result, the DC power supplied from the battery 40 is converted to AC power by the inverter circuit 12 and supplied to the electric motor 11. The drive circuit 14 is connected to a power supply path from the inverter circuit 12 to the electric motor 11 at nodes N1, N2, and N3. It can also be said that the electric motor 11 and the drive circuit 14 are connected to the inverter circuit 12 so as to branch off from the nodes N1, N2, and N3.

[0032] The control circuit 15 includes a processor such as a CPU (Central Processing Unit), an FPGA (Field-Programmable Gate Array), and a GPU (Graphics Processing Unit), and a memory such as a RAM (Random Access Memory) or a ROM (Read-Only Memory), and is configured so that the processor controls the drive circuit 14 based on data stored in the memory. Specifically, the control circuit 15 controls the drive circuit 14 by a PWM signal to control each switching element of the inverter circuit 12 to an ON or OFF state. As a result, the control circuit 15 converts DC power supplied from the battery 40 into AC power by the inverter circuit 12 and supplies it to the electric motor 11, thereby driving the electric motor 11.

[0033] The power supply circuit 16 is an internal power supply for the electric compressor 1. The power supply circuit 16 supplies power supplied from a 12V low-voltage battery 90 included in the vehicle system 3 to the control circuit 15 and the drive circuit 14 via different paths. For example, the power supply circuit 16 converts the power from the low-voltage battery 90 to 5V or 10V power by a regulator (not shown) and supplies the power to the control circuit 15 via a power path 26. The power supply circuit 16 also converts the power from the low-voltage battery 90 to 15V power by a regulator (not shown) and supplies the power to the drive circuit 14 via a power path 25. The power path 25 corresponds to the "power supply path" in this disclosure. In this manner, the power supply circuit 16 supplies power lower than the power supplied from the battery 40 to the inverter circuit 12 to the control circuit 15 and the drive circuit 14 via different paths. In FIG. 1, the voltage of the power supplied from the low-voltage battery 90 is indicated by "LV". The low-voltage battery 90, like the battery 40, corresponds to the "external battery" in this disclosure. The battery 40 and the low-voltage battery 90 may be integrated into a single battery, and power may be supplied from this battery to the power supply circuit 16 after being reduced in pressure via a converter.

[0034] Note that the control circuit 15 does not need to be supplied with power from the same power supply circuit as the drive circuit 14 (power supply circuit 16 in this example), and may be supplied with power from, for example, a power supply circuit different from the power supply circuit 16 of the drive circuit 14.

[0035] [Vehicle system configuration] The configuration of a vehicle system 3 according to an embodiment will be described with reference to Fig. 2. Fig. 2 is a circuit diagram showing the configuration of a vehicle system 3 according to an embodiment. Note that Fig. 3 shows the configuration of a portion of the vehicle system 3 to which an electric compressor 1 can be connected.

[0036] As shown in FIG. 2, the vehicle system 3 includes a battery 40, a switch 30, a resistor R1, a capacitor C1, and a capacitor C2.

[0037] The switches 30 include switches 31 and 32 provided between the positive terminal of the battery 40 and the electric compressor 1, and switches 33 and 34 provided between the negative terminal of the battery 40 and the electric compressor 1. Each of the switches 31 to 34 is constituted by a switch such as an electromagnetic contactor or an electromagnetic switch (magnetic switch), and electrically connects or disconnects a path between the battery 40 and the electric compressor 1.

[0038] One end of the switch 31 is connected to the positive terminal of the battery 40, and the other end of the switch 31 is connected to a connection point T1 of the electric compressor 1 via a resistor R1. One end of the switch 32 is connected to the positive terminal of the battery 40, and the other end of the switch 32 is connected to the connection point T1 of the electric compressor 1.

[0039] One end of the switch 33 is connected to the negative terminal of the battery 40, and the other end of the switch 33 is connected to a connection point T1 of the electric compressor 1 via a capacitor C1. One end of the switch 34 is connected to the negative terminal of the battery 40, and the other end of the switch 34 is connected to a connection point T2 of the electric compressor 1.

[0040] The resistor R1 is connected between the switch 31 and the connection point T1 of the electric compressor 1, and functions as a pre-charge resistor.

[0041] Capacitor C1 is connected to connection point T1 between switch 33 and electric compressor 1, and functions as a smoothing capacitor.

[0042] Capacitor C2 is connected to node T1 and node T2 of electric compressor 1, and functions as a smoothing capacitor.

[0043] In the vehicle system 3 configured as described above, when the system is started up (for example, when the vehicle ignition switch is turned on), the switch 30 is controlled to the on state, thereby electrically connecting the battery 40 and the electric compressor 1. Specifically, when the vehicle system 3 is started up, the switch 33 is switched from the off state to the on state, and the switch 34 is switched from the off state to the on state. Then, after the switch 31 is switched from the off state to the on state, the switch 32 is switched from the off state to the on state. Thereafter, the switch 31 is switched from the on state to the off state. As a result, the battery 40 and the electric compressor 1 are electrically connected, and the supply of power from the battery 40 to the electric compressor 1 begins.

[0044] Meanwhile, in the vehicle system 3, when the system is stopped (for example, when the vehicle ignition switch is turned off), the switch 30 is controlled to the off state, thereby electrically disconnecting the battery 40 and the electric compressor 1. Specifically, when the vehicle system 3 is stopped, the switch 32 is switched from the on state to the off state. Thereafter, the switch 33 is switched from the on state to the off state, and the switch 34 is switched from the on state to the off state. This electrically disconnects the battery 40 and the electric compressor 1, and the supply of power from the battery 40 to the electric compressor 1 is stopped.

[0045] [Drive circuit drive section configuration] The configuration of the drive unit 50 of the drive circuit 14 according to the embodiment will be described with reference to Fig. 3. Fig. 3 is a circuit diagram showing the configuration of the drive unit 50 of the drive circuit 14 according to the embodiment. Note that, in Fig. 3, of the multiple switching elements of the inverter circuit 12, only switching element TU1 and switching element TU2 are shown, and the other switching elements are omitted. Also, in Fig. 3, the power path from the drive unit 50 is connected only to the gate of the switching element TU1, but in reality, the power paths from the drive unit 50 are also connected to the gates of the other switching elements.

[0046] As shown in FIG. 3, the driving unit 50 includes a driver IC (Integrated Circuit) 51, a capacitor C51, a capacitor C52, a resistor R51, a resistor R52, a resistor R53, and a diode D51.

[0047] The driver IC 51 is an integrated circuit for controlling each switching element of the inverter circuit 12 to an ON or OFF state based on a PWM signal from the control circuit 15. The driver IC 51 includes terminals 511-515, a switching element 521, and a switching element 522.

[0048] The terminal 511 is connected to the power supply circuit 16 and is connected to the ground terminal GND via the capacitor C51. The terminal 512 is connected to the ground terminal GND. The terminal 513 is connected to the power supply circuit 16 via the resistor R53 and the diode D51 and is connected to the terminal 515 via the capacitor C52. The anode of the diode D51 is connected to the resistor R53, and the cathode of the diode D51 is connected to the terminal 513 and the capacitor C52. The terminal 514 is connected to the gate of the switching element TU1 via the resistor R51. The terminal 515 is connected to the emitter of the switching element TU1 and the collector of the switching element TU2 via the resistor R52.

[0049] The switching element 521 and the switching element 522 are configured by semiconductor transistors such as IGBTs or FETs. Fig. 3 shows an example in which the switching element 521 and the switching element 522 are configured by FETs. Inside the driver IC 51, the drain of the switching element 521 is connected to a terminal 513, and the source of the switching element 521 is connected to a drain of the switching element 522. The source of the switching element 522 is connected to a terminal 515. The source of the switching element 521 and the drain of the switching element 522 are connected to a terminal 514.

[0050] The drive circuit 14 configured as described above controls each switching element of the inverter circuit 12 to an on or off state based on a PWM signal from the control circuit 15 by driving the driver IC 51 using power supplied from the power supply circuit 16.

[0051] [Phenomenon that occurs when vehicle systems are shut down] As described above, in the vehicle system 3, when the system is stopped (when the ignition switch is turned off), the switch 30 is controlled to the off state, and the power supply from the battery 40 to the electric compressor 1 is stopped. Immediately after the power supply from the battery 40 is stopped, electric charges are stored in the capacitors C2 and C13 on the high voltage side, but the residual electric charges stored in the capacitors C2 and C13 are gradually discharged by the driving of the drive device 80. As a result, the voltage on the high voltage side on the vehicle system 3 side gradually decreases. In such a situation, if the voltage on the high voltage side becomes lower than the voltage of the electric power supplied from the power supply circuit 16 to the drive circuit 14 due to the power being maintained from the power supply circuit 16, there is a risk that the electric power from the power supply circuit 16 will leak into the high voltage side via the inverter circuit 12.

[0052] 3, the current due to the power supplied from the power supply circuit 16 is input to the terminal 513 of the driver IC51 via the resistor R53 and the diode D51, and is output from the terminal 515 of the driver IC51 via the switching elements 521 and 522. Specifically, when the system is stopped (when the ignition switch is off), the gate voltages of the switching elements 521 and 522 become 0V, and the switching elements 521 and 522 are controlled to be in the on state. As a result, the current due to the power supplied from the power supply circuit 16 passes through the switching elements 521 and 522 and is output from the terminal 515 of the driver IC51.

[0053] The current output from the power supply circuit 16 at the terminal 515 is input to the node N1 of the inverter circuit 12 via the resistor R52. In the inverter circuit 12, the gate voltage of the switching element TU1 becomes 0V and the switching element TU1 is controlled to be in the off state, so that the current output from the power supply circuit 16 at the terminal 515 is output from the inverter circuit 12 to the vehicle system 3 via the diode DU1. The current output from the power supply circuit 16 at the inverter circuit 12 passes through the capacitor C13, while passing through the capacitor C2 of the vehicle system 3 via the inductor L13. Similarly, the current output from another terminal (not shown) of the driver IC51 is input to the nodes N2 and N3, and finally passes through the capacitors C13 and C2.

[0054] As described above, the current from the power supply circuit 16 flows into the high-voltage side capacitors C2 and C13, causing electric charge (for example, an amount of electric charge equivalent to about 10 V) to accumulate in the capacitors C2 and C13. The electric charge remaining in the capacitors C2 and C13 may damage or shorten the lifespan of devices in the vehicle system 3.

[0055] For example, Fig. 4 is a diagram showing an example of the effect of residual charge on the vehicle system 3. As shown in Fig. 4, when the vehicle system 3 is started (the ignition switch is turned on) with residual charge stored in the capacitor C2 or the capacitor C13 (not shown), the switch 33 switches from the off state to the on state, and the switch 34 switches from the off state to the on state. At this time, a closed circuit is formed by the path passing through the switch 33, the capacitor C1, the capacitor C2, and the switch 34, and the residual charge stored in the capacitor C2 is suddenly released, which may cause a spark in the switch 34. This may shorten the life of the switch 34 due to rough damage to the contacts of the switch 34, or cause a malfunction due to welding of the contacts of the switch 34.

[0056] Therefore, as shown in FIG. 1, the electric compressor 1 according to the embodiment includes a switch 20 that connects or disconnects a power path 25 through which power is supplied from a power supply circuit 16 to a drive circuit 14. Furthermore, the electric compressor 1 includes a current sensor 60 that measures a current flowing through the inverter circuit 12, and a voltage sensor 70 that measures a voltage applied to the inverter circuit 12. It can also be said that the voltage sensor 70 measures a voltage between the capacitor C13 and the inverter circuit 12. The control circuit 15 controls the switch 20 based on a voltage value measured by the voltage sensor 70. Alternatively, the control circuit 15 may calculate the power supplied from the battery 40 to the inverter circuit 12 based on the current value measured by the current sensor 60 and the voltage value measured by the voltage sensor 70, and control the switch 20 based on the calculated power. More specifically, the voltage sensor 70 measures the voltage between the capacitor C13 and the inverter circuit 12.

[0057] The switch 20 is configured by a switching circuit, such as a relay or a transistor, that connects or disconnects the power path 25. In the electric compressor 1, for example, an LDO (Low Drop Out) regulator is used as the switch 20.

[0058] As described above, power supply circuit 16 is configured to supply power to control circuit 15 via power path 26, while supplying power to drive circuit 14 via power path 25. Therefore, even if power path 25 is cut off by switch 20, power path 26, through which power is supplied from power supply circuit 16 to control circuit 15, is not cut off.

[0059] [Switch control processing by the control circuit] Control processing of the switch 20 by the control circuit 15 according to the embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing control processing of the switch 20 by the control circuit 15 according to the embodiment. The flowchart in Fig. 5 is called from a main routine (not shown) when a predetermined condition is met, and is executed periodically. Each step of the control circuit 15 is realized by the processor executing a program stored in memory. Hereinafter, step is abbreviated as S.

[0060] 5, the control circuit 15 determines whether or not the power path 25 is interrupted (S1). When the power path 25 is interrupted (YES in S1), the control circuit 15 determines whether or not the voltage applied from the battery 40 to the inverter circuit 12 is equal to or greater than a first threshold (S2). The "first threshold" may be any value equal to or greater than the voltage applied from the power supply circuit 16 to the drive circuit 14, more specifically, any value equal to or greater than the voltage between the power supply circuit 16 and the drive circuit 14, and may be, for example, the minimum operating voltage of the electric compressor 1.

[0061] When the voltage applied from the battery 40 to the inverter circuit 12 is equal to or higher than the first threshold (YES in S2), the control circuit 15 controls the switch 30 to the on state to connect the power path 25 (S3). On the other hand, when the voltage applied from the battery 40 to the inverter circuit 12 is not equal to or higher than the first threshold (NO in S2) or after the process of S3, the control circuit 15 returns the process to the main routine.

[0062] In this way, when the vehicle system 3 is started (the ignition switch is turned on) while the power path 25 is interrupted, the application of voltage to the inverter circuit 12 begins, the voltage applied from the battery 40 to the inverter circuit 12 gradually increases, and when the voltage applied to the inverter circuit 12 becomes equal to or higher than the first threshold, the power path 25 is connected by the switch 30. In this way, the control circuit 15 can prevent the voltage applied from the power supply circuit 16 to the drive circuit 14 from becoming higher than the voltage on the high voltage side and can prevent the voltage applied from the power supply circuit 16 to the drive circuit 14 from flowing to the high voltage side, thereby preventing the power for controlling the electric compressor 1 from damaging or shortening the lifespan of devices in the vehicle system 3.

[0063] When the power path 25 is not interrupted (NO in S1), the control circuit 15 determines whether or not the voltage applied from the battery 40 to the inverter circuit 12 has dropped to a second threshold value (S4). The "second threshold value" may be any value equal to or greater than the voltage applied from the power supply circuit 16 to the drive circuit 14, more specifically, any value equal to or greater than the voltage between the power supply circuit 16 and the drive circuit 14, and may be, for example, the minimum operating voltage of the electric compressor 1. The first threshold value may be the same value as the second threshold value, or may be a value different from the second threshold value.

[0064] When the voltage applied from the battery 40 to the inverter circuit 12 falls to the second threshold (YES in S4), the control circuit 15 controls the switch 30 to the off state to cut off the power path 25 (S5). On the other hand, when the voltage applied from the battery 40 to the inverter circuit 12 has not fallen to the second threshold (NO in S4) or after the processing of S5, the control circuit 15 returns the processing to the main routine.

[0065] In this manner, when the vehicle system 3 is stopped (the ignition switch is turned off) while the power path 25 is connected, the power supply to the inverter circuit 12 is stopped, the voltage applied from the battery 40 to the inverter circuit 12 gradually decreases, and when the voltage applied to the inverter circuit 12 decreases to the second threshold, the power path 25 is interrupted by the switch 30. That is, before the voltage applied to the inverter circuit 12 becomes less than the second threshold, the power path 25 is interrupted by the switch 30. In this manner, the control circuit 15 can prevent the voltage applied from the power supply circuit 16 to the drive circuit 14 from becoming higher than the voltage on the high voltage side and can prevent the power supplied from the power supply circuit 16 to the drive circuit 14 from flowing to the high voltage side, thereby preventing the power for controlling the electric compressor 1 from damaging or shortening the lifespan of the devices in the vehicle system 3.

[0066] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0067] 1 electric compressor, 3 vehicle system, 11 electric motor, 11U, 11V, 11W coil, 12 inverter circuit, 13 filter circuit, 14 drive circuit, 15 control circuit, 16 power circuit, 20, 30, 31, 32, 33, 34 switch, 25, 26 power path, 35 cable, 40 battery, 50 drive unit, 51 driver IC, 60 current sensor, 70 voltage sensor, 80 drive device, 81 gear, 82 drive wheel, 90 low voltage battery, 511, 512, 513, 514, 515 terminal, 521, 522, TU1, TU2, TV1, TV2, TW1, TW2 switching element, C1, C2, C13, C51, C52 capacitor, D51, DU1, DU2, DV1, DV2, DW1, DW2 Diode, GND ground terminal, L13 inductor, N1, N2, N3 nodes, NL negative line, PL positive line, R1, R51, R52, R53 resistors, T1, T2 connection point.

Claims

1. An electric motor; a filter circuit for reducing noise in the power supplied from the external battery; A capacitor constituting the filter circuit; an inverter circuit that converts the power supplied from the battery through the filter circuit from direct current to alternating current and supplies the alternating current to the electric motor; a drive circuit connected to a power supply path from the inverter circuit to the electric motor, the drive circuit controlling the operation of the inverter circuit; a power supply circuit that transforms the power supplied from the battery and supplies the transformed power to the drive circuit; a switch that connects or disconnects a power supply path that supplies power from the power supply circuit to the drive circuit; A control circuit for controlling an operation of the switch, the control circuit connects the power supply path when the voltage between the capacitor and the inverter circuit is higher than the voltage between the power supply circuit and the drive circuit, and cuts off the power supply path when the voltage between the capacitor and the inverter circuit is lower than the voltage between the power supply circuit and the drive circuit.

2. 2. The electric compressor according to claim 1, wherein the control circuit controls the switch to connect the power supply path when power supply from the battery to the inverter circuit starts while the power supply path is interrupted and a voltage between the capacitor and the inverter circuit becomes equal to or higher than a first threshold value.

3. 2. The electric compressor according to claim 1, wherein the control circuit controls the switch to interrupt the power supply path when a voltage between the capacitor and the inverter circuit drops to a second threshold while the power supply path is connected.

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