Electric compressor for vehicles

Abstract

To make it possible to suppress an increase in power consumption of a battery.SOLUTION: An electric compressor 20 for a vehicle, comprises a control device 33 and a detection circuit 51. The detection circuit 51 comprises an AD conversion circuit 61. The AD conversion circuit 61 converts an ignition voltage from an analog signal to a digital signal. The control device 33 recognizes a value of the ignition voltage by the digital signal. The control device 33 determines that the battery 11 is in an over-voltage condition when the value of ignition voltage is greater than a threshold value for over-voltage determination.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electric compressor for a vehicle. [Background technology]

[0002] The power supply control device disclosed in Patent Document 1 includes a control device and two voltage dividing resistors. An ignition voltage is applied to the two voltage dividing resistors. The ignition voltage is a voltage applied from a battery via an ignition switch. When the ignition switch is turned on, the battery and the two voltage dividing resistors are electrically connected, and the ignition voltage is applied to the two voltage dividing resistors. A voltage divided by the two voltage dividing resistors is applied to the control device. The control device determines whether the ignition voltage is greater than a threshold value from the voltage divided by the two voltage dividing resistors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-341595 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power supply control device disclosed in Patent Document 1, current always flows through the voltage dividing resistor while the ignition switch is on, which increases the power consumption of the battery. [Means for solving the problem]

[0005] An electric compressor for a vehicle that solves the above problem includes an electric motor, an inverter that supplies AC power to the electric motor, a high-voltage circuit including a control device that controls the inverter, a compression unit driven by the electric motor, and a low-voltage circuit including a detection circuit that detects ignition voltage applied from a battery via an ignition switch of the vehicle, wherein the detection circuit includes an AD conversion circuit that converts the ignition voltage from an analog signal to a digital signal, a switching element that is provided on the input side of the ignition voltage relative to the AD conversion circuit, and a switching unit that turns on the switching element when a wake-up signal is input, and the control device determines that the battery is overvoltage when the value of the ignition voltage recognized by the digital signal is greater than an overvoltage determination threshold, and stops the electric compressor for the vehicle.

[0006] The AD conversion circuit converts the ignition voltage into a digital signal. The control device can recognize the value of the ignition voltage from the digital signal. The control device can determine whether an overvoltage has occurred based on the value of the ignition voltage. Because the control device can determine whether an overvoltage has occurred without using a voltage dividing resistor, it is possible to suppress an increase in battery power consumption caused by current flowing through the voltage dividing resistor.

[0007] With respect to the above-mentioned vehicle electric compressor, the control device may determine that the battery is at a low voltage when the value of the ignition voltage recognized by the digital signal is smaller than a low voltage determination threshold, and stop the vehicle electric compressor.

[0008] An electric compressor for a vehicle that solves the above problem includes an electric motor, an inverter that supplies AC power to the electric motor, a high-voltage circuit including a control device that controls the inverter, a compression unit driven by the electric motor, and a low-voltage circuit including a detection circuit that detects ignition voltage applied from a battery via an ignition switch of the vehicle, wherein the detection circuit includes an AD conversion circuit that converts the ignition voltage from an analog signal to a digital signal, a switching element that is provided on the input side of the ignition voltage relative to the AD conversion circuit, and a switching unit that turns on the switching element when a wake-up signal is input, and when the value of the ignition voltage recognized by the digital signal is smaller than a low-voltage determination threshold, the control device determines that the battery is at a low voltage and stops the electric compressor for the vehicle.

[0009] The AD conversion circuit converts the ignition voltage into a digital signal. The control device can recognize the value of the ignition voltage from the digital signal. The control device can determine whether the voltage is low based on the value of the ignition voltage. Because the control device can determine whether the voltage is low without using a voltage divider resistor, it is possible to suppress an increase in battery power consumption caused by current flowing through the voltage divider resistor.

[0010] In the above-described vehicle electric compressor, the AD conversion circuit may convert the analog signal into bit information. [Effects of the Invention]

[0011] According to the present invention, an increase in battery power consumption can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a configuration of an electric compressor for a vehicle. [Figure 2] FIG. 10 is a diagram illustrating a low-voltage circuit of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of an electric compressor for a vehicle will be described. As shown in FIG. 1, a vehicle 10 includes a battery 11, an ignition switch 12, a high-voltage battery 13, and an electric compressor 20 for the vehicle.

[0014] Any type of battery can be used as the battery 11 as long as it is capable of being charged and discharged. For example, a lead storage battery can be used as the battery 11. The ignition switch 12 is connected to the battery 11. The ignition switch 12 is a switch that is turned on when starting the vehicle 10. The ignition switch 12 is also sometimes called a start switch.

[0015] Any type of battery can be used as the high-voltage battery 13 as long as it is chargeable and dischargeable. For example, a lithium-ion secondary battery can be used as the high-voltage battery 13. The rated output voltage of the high-voltage battery 13 is higher than the rated output voltage of the battery 11.

[0016] <Electric compressor for vehicles> The electric compressor 20 for a vehicle includes a compression unit 21, a high-voltage circuit 30, a low-voltage circuit 40, and an insulating element 71. The electric compressor 20 for a vehicle is used, for example, to supply refrigerant to an external refrigerant circuit provided for heating and cooling the interior of the vehicle.

[0017] The compression unit 21 compresses and discharges the fluid that is drawn in. The fluid is, for example, a refrigerant. The compression unit 21 is realized by, for example, a scroll type, a piston type, a vane type, or the like.

[0018] The high-voltage circuit 30 includes an inverter 31, an electric motor 32, and a control device 33. The high-voltage circuit 30 operates by receiving power from the high-voltage battery 13. The inverter 31 is a three-phase inverter that converts DC power supplied from the high-voltage battery 13 into AC power and outputs the AC power. The inverter 31 converts DC power into AC power by, for example, the switching operation of a switching element.

[0019] The electric motor 32 is a three-phase motor. The inverter 31 and the electric motor 32 are electrically connected. The electric motor 32 is driven by AC power supplied from the inverter 31. The compression unit 21 is driven by the driving of the electric motor 32.

[0020] The control device 33 controls the inverter 31. For example, the control device 33 controls the switching elements of the inverter 31 to cause the inverter 31 to convert DC power into AC power. The control device 33 includes, for example, a processor and a memory as hardware configurations.

[0021] The low-voltage circuit 40 includes a connection line 41, a power supply circuit 42, a filter circuit 43, a diode 47, a capacitor 48, and a detection circuit 51. The low-voltage circuit 40 is powered by the battery 11.

[0022] The connection line 41 is connected to the ignition switch 12. When the ignition switch 12 is turned on, the voltage of the battery 11 is applied to the connection line 41. The voltage applied from the battery 11 via the ignition switch 12 is referred to as the ignition voltage.

[0023] The power supply circuit 42 is connected to the connection line 41. An ignition voltage is applied to the power supply circuit 42 via the connection line 41. The power supply circuit 42 transforms and outputs the voltage supplied from the battery 11. The power supply circuit 42 includes, for example, a transformer and a switching element.

[0024] The filter circuit 43 is provided between the ignition switch 12 and the power supply circuit 42. The filter circuit 43 includes one inductor 44 and two capacitors 45 and 46. The inductor 44 is provided on the connection line 41. The two capacitors 45 and 46 are provided on either side of the inductor 44. The two capacitors 45 and 46 connect the connection line 41 to ground.

[0025] The diode 47 is provided between the ignition switch 12 and the filter circuit 43. The anode of the diode 47 is connected to the ignition switch 12. The cathode of the diode 47 is connected to the filter circuit 43.

[0026] The capacitor 48 is provided between the filter circuit 43 and the power supply circuit 42. The capacitor 48 connects the connection line 41 to the ground. <Detection circuit> The detection circuit 51 includes a power supply terminal 52, a signal input terminal 53, an input terminal 54, an output terminal 55, a switching element 56, a switching unit 57, other circuits 58, and an ignition voltage detection circuit 60. The detection circuit 51 is a circuit for detecting the ignition voltage.

[0027] A portion of the connection line 41 between the filter circuit 43 and the capacitor 48 is connected to the power supply terminal 52. A wake-up signal Si transmitted from a higher-level control device is input to the signal input terminal 53. A portion of the connection line 41 between the filter circuit 43 and the capacitor 48 is connected to the input terminal 54. An isolation element 71 is connected to the output terminal 55.

[0028] The switching element 56 is provided between the power supply terminal 52 and the ignition voltage detection circuit 60. When the switching element 56 is turned on, an ignition voltage is applied to the ignition voltage detection circuit 60 from the connection line 41. This causes the ignition voltage detection circuit 60 to operate. When the switching element 56 is turned off, the ignition voltage is no longer applied to the ignition voltage detection circuit 60 from the connection line 41. Any element can be used as the switching element 56. In this embodiment, a transistor is used as the switching element 56. The collector of the switching element 56 is connected to the power supply terminal 52. The emitter of the switching element 56 is connected to the ignition voltage detection circuit 60.

[0029] The switching unit 57 is connected to the signal input terminal 53. The switching unit 57 switches the switching element 56 on and off in response to the input of a wake-up signal Si. When the wake-up signal Si is input via the signal input terminal 53, the switching unit 57 turns on the switching element 56. When a sleep signal is input from a higher-level control device, for example, the switching unit 57 turns off the switching element 56. The switching unit 57 includes, for example, a processor and a memory as hardware configuration.

[0030] The other circuit 58 is connected to the emitter of the switching element 56. When the switching element 56 is turned on, an ignition voltage is applied to the other circuit 58 from the connection line 41. The other circuit 58 includes a drive circuit. The drive circuit drives the power supply circuit 42 by operating a switching element included in the power supply circuit 42.

[0031] The ignition voltage detection circuit 60 includes an AD conversion circuit 61 and a conversion unit 62. A switching element 56 is provided between the power supply terminal 52 and the ignition voltage detection circuit 60, and is provided closer to the input side of the ignition voltage than the AD conversion circuit 61.

[0032] The AD conversion circuit 61 is connected to the input terminal 54. An ignition voltage is input to the AD conversion circuit 61 from the input terminal 54. The AD conversion circuit 61 converts the ignition voltage input from the input terminal 54 from an analog signal to a digital signal. The AD conversion circuit 61 converts the ignition voltage into bit information represented by two values. The AD conversion circuit 61 outputs a digital signal corresponding to the bit information. For example, the digital signal is a pulse wave in which 0 is a low level and 1 is a high level out of the two values.

[0033] The conversion unit 62 includes a first switching element 63 and a second switching element 64. The first switching element 63 is a p-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The second switching element 64 is an n-channel MOSFET. The first switching element 63 and the second switching element 64 are connected in series to each other. The drain of the first switching element 63 is connected to a power supply. The source of the first switching element 63 is connected to the drain of the second switching element 64. The source of the second switching element 64 is connected to ground. The gate of the first switching element 63 is connected to the AD conversion circuit 61. The gate of the second switching element 64 is connected to the AD conversion circuit 61. The connection point between the first switching element 63 and the second switching element 64 is connected to the output terminal 55.

[0034] In the conversion unit 62, the first switching element 63 and the second switching element 64 are switched by the digital signal output from the AD conversion circuit 61. As a result, the conversion unit 62 converts the voltage of the digital signal into a voltage that can be recognized by the isolation element 71. When the AD conversion circuit 61 outputs a low-level signal, the first switching element 63 is turned off and the second switching element 64 is turned on. In this case, conduction between the ground and the output terminal 55 causes the conversion unit 62 to output a low-level signal. When the AD conversion circuit 61 outputs a high-level signal, the first switching element 63 is turned on and the second switching element 64 is turned off. In this case, conduction between the power supply and the output terminal 55 causes the conversion unit 62 to output a high-level signal.

[0035] The isolation element 71 is connected to the control device 33. The isolation element 71 connects the AD conversion circuit 61 and the control device 33 via the conversion unit 62. The isolation element 71 transmits a digital signal to the control device 33 while maintaining insulation between the low voltage circuit 40 and the high voltage circuit 30. The digital signal output from the AD conversion circuit 61 is input to the isolation element 71 via the conversion unit 62. The isolation element 71 outputs the digital signal to the control device 33. For example, an isolator or a photocoupler can be used as the isolation element 71.

[0036] A digital signal is input to the control device 33 from the insulating element 71. The control device 33 can recognize the value [V] of the ignition voltage from the digital signal. If the value of the ignition voltage is greater than an overvoltage determination threshold, the control device 33 determines that the battery 11 is at an overvoltage. The overvoltage determination threshold is a predetermined value. The overvoltage determination threshold is stored in the memory of the control device 33. If the value of the ignition voltage is less than a low voltage determination threshold, the control device 33 determines that the battery 11 is at an undervoltage. The low voltage determination threshold is a predetermined value. The low voltage determination threshold is stored in the memory of the control device 33. The control device 33 determines both whether the battery 11 is at an overvoltage and whether the battery 11 is at an undervoltage, but it may be configured to perform only one of these determinations.

[0037] When the control device 33 determines that the battery 11 has an overvoltage, it stops the vehicle electric compressor 20. For example, the control device 33 stops the inverter 31. When the control device 33 determines that the battery 11 has a low voltage, it stops the vehicle electric compressor 20.

[0038] [Operation of this embodiment] A low-voltage circuit of a comparative example will be described below. In the low-voltage circuit of the comparative example, the same components as those in the low-voltage circuit 40 of the embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0039] As shown in FIG. 2, a low-voltage circuit 80 of the comparative example includes a connection line 41, a power supply circuit 42, a capacitor 48, a detection circuit 81, a load switch 91, resistive elements 92 and 93, Zener diodes 94 and 95, and a voltage dividing resistor 96.

[0040] The detection circuit 81 includes a power supply terminal 52, a signal input terminal 53, a switching terminal 82, a first input terminal 83, a second input terminal 84, a switching element 56, a switching unit 57, other circuits 58, and an ignition voltage detection circuit 85. The switching terminal 82 is connected to the collector of the switching element 56. The first input terminal 83 and the second input terminal 84 are connected to the ignition voltage detection circuit 85.

[0041] The load switch 91 is provided between the filter circuit 43 and the power supply circuit 42. Any switching element can be used as the load switch 91. In this embodiment, a p-channel MOSFET is used as the load switch 91. The gate of the load switch 91 is connected to the switching terminal 82 via a resistor element 92. The resistor element 93 is connected between the source and gate of the load switch 91. The Zener diode 94 is connected between the source and gate of the load switch 91.

[0042] The Zener diode 95 is provided between the load switch 91 and the filter circuit 43. The Zener diode 95 connects the connection line 41 to the ground. The voltage dividing resistor 96 is provided between the load switch 91 and the power supply circuit 42. The voltage dividing resistor 96 includes a first voltage dividing resistor element 97, a second voltage dividing resistor element 98, and a third voltage dividing resistor element 99. The first voltage dividing resistor element 97, the second voltage dividing resistor element 98, and the third voltage dividing resistor element 99 are connected in series with each other between the connection line 41 and ground.

[0043] The connection point between the first voltage dividing resistor element 97 and the second voltage dividing resistor element 98 is connected to the first input terminal 83. The connection point between the second voltage dividing resistor element 98 and the third voltage dividing resistor element 99 is connected to the second input terminal 84.

[0044] The ignition voltage detection circuit 85 is a comparator. The ignition voltage detection circuit 85 compares signals input from the first input terminal 83 and the second input terminal 84 to determine whether the ignition voltage is greater than the overvoltage determination threshold. The ignition voltage detection circuit 85 outputs a low-level signal when the ignition voltage is equal to or less than the overvoltage determination threshold. The ignition voltage detection circuit 85 outputs a high-level signal when the ignition voltage is greater than the overvoltage determination threshold. The ignition voltage detection circuit 85 is connected to the control device 33 via an insulating element, as in the embodiment. When the control device 33 receives a high-level signal from the ignition voltage detection circuit 85, it determines that the battery 11 is overvoltage. Although not shown, the low voltage circuit 80 includes a voltage dividing resistor for low voltage determination, an ignition voltage detection circuit for low voltage determination, and an insulating element for low voltage determination. The ignition voltage detection circuit for low voltage determination outputs a low-level signal when the ignition voltage is equal to or greater than the low voltage determination threshold. The ignition voltage detection circuit for low voltage determination outputs a high-level signal when the ignition voltage is lower than the low-voltage determination threshold. When the high-level signal is input from the ignition voltage detection circuit for low voltage determination, the control device 33 determines that the battery 11 is at a low voltage.

[0045] When the wake-up signal Si is input to the switching unit 57, the switching element 56 is turned on, which turns on the load switch 91. The ignition voltage is applied to the ignition voltage detection circuit 85, the other circuit 58, and the voltage dividing resistor 96. This causes the ignition voltage detection circuit 85 and the other circuit 58 to operate.

[0046] In the low-voltage circuit 80 of the comparative example, it is necessary to provide a voltage-dividing resistor 96 in order to set the overvoltage determination threshold and the undervoltage determination threshold. When the wake-up signal Si is not input, the load switch 91 is not turned on, and therefore power consumption of the battery 11 due to current flowing through the voltage-dividing resistor 96 is suppressed. However, in the low-voltage circuit 80 of the comparative example, it is necessary to provide the load switch 91 in order to prevent current from flowing through the voltage-dividing resistor 96 when the wake-up signal Si is not input.

[0047] In contrast, in the embodiment, the ignition voltage is converted into a digital signal by the AD conversion circuit 61. The digital signal is then output to the control device 33, causing the control device 33 to determine whether the voltage is overvoltage or undervoltage. Since the low voltage circuit 40 does not need to include the voltage dividing resistor 96, there is no need to provide a load switch 91.

[0048] [Effects of this embodiment] (1) The AD conversion circuit 61 converts the ignition voltage from an analog signal to a digital signal. The control device 33 can recognize the value of the ignition voltage from the digital signal. The control device 33 can determine whether an overvoltage exists based on the value of the ignition voltage. When a comparator is used as the ignition voltage detection circuit 85, as in the comparative example, it is necessary to input a voltage divided by a voltage dividing resistor 96 to the comparator. In contrast, by using the AD conversion circuit 61, it is possible to determine whether an overvoltage exists without using the voltage dividing resistor 96. An increase in power consumption of the battery 11 caused by current flowing through the voltage dividing resistor 96 can be suppressed.

[0049] Furthermore, when the switching element 56 is on, the ignition voltage is applied to the ignition voltage detection circuit 60 and the other circuits 58. When the switching element 56 is off, the ignition voltage is not applied to the ignition voltage detection circuit 60 and the other circuits 58, so that an increase in power consumption of the battery 11 can be suppressed.

[0050] (2) The control device 33 can determine whether the voltage is low based on the value of the ignition voltage. By using the AD conversion circuit 61, the low voltage determination can be performed without using the voltage dividing resistor 96. An increase in the power consumption of the battery 11 caused by a current flowing through the voltage dividing resistor 96 can be suppressed.

[0051] (3) The AD conversion circuit 61 converts an analog signal into bit information, which can improve the accuracy of measuring the ignition voltage compared to AD conversion circuits 61 that perform PFM conversion or PWM conversion.

[0052] (4) When using the low-voltage circuit 80 of the comparative example, changing the overvoltage determination threshold and the undervoltage determination threshold requires changing the resistance values ​​of the voltage-dividing resistor elements 97 to 99. In contrast, when using the low-voltage circuit 40, the overvoltage determination threshold and the undervoltage determination threshold can be easily changed by simply rewriting the overvoltage determination threshold and the undervoltage determination threshold stored in the memory.

[0053] (5) When the low-voltage circuit 80 of the comparative example is used, the control device 33 can determine whether the ignition voltage is greater than the overvoltage determination threshold and whether the ignition voltage is less than the low-voltage determination threshold. However, the control device 33 cannot recognize the value of the ignition voltage. In contrast, when the low-voltage circuit 40 of the embodiment is used, the control device 33 can recognize the value of the ignition voltage.

[0054] (6) When the low-voltage circuit 80 of the comparative example is used, even if the output of the ignition voltage detection circuit 85 is maintained at a low level, the control device 33 cannot determine whether the ignition voltage detection circuit 85 has failed. In contrast, when the low-voltage circuit 40 of the embodiment is used, if the digital signal is maintained at a high level or a low level, it can be said that the ignition voltage detection circuit 60 has failed. The control device 33 can determine whether the ignition voltage detection circuit 60 has failed from the digital signal.

[0055] (7) When using the low-voltage circuit 80 of the comparative example, the vehicle electric compressor 20 needs to have separate insulating elements for determining overvoltage and undervoltage. In contrast, when using the low-voltage circuit 40 of the embodiment, it is sufficient to have the insulating element 71 that transmits digital signals, and the number of insulating elements 71 can be reduced. This reduces the number of times the function of the insulating elements 71 is checked, thereby reducing the management burden. Furthermore, when an isolator is used as the insulating element 71, the isolator may become a noise source. Reducing the number of insulating elements 71 reduces noise.

[0056] (8) When the low-voltage circuit 80 of the comparative example is used, a voltage drop occurs due to the load switch 91. In contrast, when the low-voltage circuit 40 of the embodiment is used, no voltage drop occurs due to the load switch 91, and therefore, loss can be reduced.

[0057] (9) When the low-voltage circuit 80 of the comparative example is used, an inrush current occurs when the load switch 91 is turned on. In contrast, when the low-voltage circuit 40 is used, the inrush current can be reduced, allowing the fuse of the vehicle 10 to be smaller.

[0058] (10) When the low-voltage circuit 80 of the comparative example is used, it is necessary to provide a Zener diode 94 to protect the load switch 91. In contrast, when the low-voltage circuit 40 of the embodiment is used, it is not necessary to provide the Zener diode 94. Noise caused by the Zener diode 94 can be reduced.

[0059] (11) When the low-voltage circuit 80 of the comparative example is used, the load switch 91 needs to be turned on, which increases the time from when the wake-up signal Si is input until the ignition voltage is applied to the connection line 41. In contrast, when the low-voltage circuit 40 of the embodiment is used, the process of turning on the load switch 91 is eliminated, which shortens the time from when the wake-up signal Si is input until the ignition voltage is applied to the connection line 41.

[0060] (12) When the filter circuit 43 resonates, the ignition voltage increases. In the low-voltage circuit 40 of the embodiment, the load switch 91 is not required, and the capacitance of the capacitor 48 can be increased. This prevents the ignition voltage from increasing when the filter circuit 43 resonates.

[0061] [Example of change] The embodiment can be modified as follows: The embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0062] If the voltage of the digital signal output from the AD conversion circuit 61 is a voltage that can be recognized by the insulating element 71, the ignition voltage detection circuit 60 does not need to include the conversion unit 62.

[0063] The detection circuit 51 may be configured to output information other than the value of the ignition voltage to the control device 33. For example, the detection circuit 51 may be configured to output the temperature of an object to be measured to the control device 33.

[0064] If the control device 33 and the detection circuit 51 are provided in a circuit with the same voltage level, the vehicle electric compressor 20 does not need to include the insulating element 71. The AD conversion circuit 61 may convert the analog signal into a digital signal by PFM (Pulse Frequency Modulation) conversion, which converts the analog signal into a digital signal with a frequency proportional to the voltage.

[0065] The AD conversion circuit 61 may convert the analog signal into a digital signal by PWM (Pulse Width Modulation) conversion, which converts the analog signal into a digital signal with a pulse width proportional to the voltage. [Explanation of symbols]

[0066] Si...wake-up signal, 11...battery, 12...ignition switch, 20...vehicle electric compressor, 21...compression unit, 30...high voltage circuit, 31...inverter, 32...electric motor, 33...control device, 40...low voltage circuit, 51...detection circuit, 56...switching element, 57...switching unit, 61...AD conversion circuit.

Claims

1. An electric motor; an inverter for supplying AC power to the electric motor; a high voltage circuit including a control device that controls the inverter; a compression unit driven by the electric motor; a low-voltage circuit including a detection circuit that detects an ignition voltage applied from a battery via an ignition switch of the vehicle, The detection circuit a power supply terminal electrically connected to the battery; a signal input terminal to which a wake-up signal from a higher-level control device is input; an AD conversion circuit that converts the ignition voltage from an analog signal to a digital signal; a switching element that is provided on the input side of the ignition voltage relative to the AD conversion circuit and is connected to the power supply terminal; a switching unit that connects the signal input terminal and the switching element but is not connected to the power supply terminal, and turns on the switching element when the wake-up signal is input from the signal input terminal; The control device determines that the battery is overvoltage when the value of the ignition voltage recognized by the digital signal is greater than an overvoltage determination threshold, and stops the vehicle electric compressor.

2. 2. The electric compressor for a vehicle according to claim 1, wherein the control device determines that the battery is at a low voltage when the value of the ignition voltage recognized by the digital signal is smaller than a low voltage determination threshold, and stops the electric compressor for a vehicle.

3. An electric motor; an inverter for supplying AC power to the electric motor; a high voltage circuit including a control device that controls the inverter; a compression unit driven by the electric motor; a low-voltage circuit including a detection circuit that detects an ignition voltage applied from a battery via an ignition switch of the vehicle, The detection circuit a power supply terminal electrically connected to the battery; a signal input terminal to which a wake-up signal from a higher-level control device is input; an AD conversion circuit that converts the ignition voltage from an analog signal to a digital signal; a switching element that is provided on the input side of the ignition voltage relative to the AD conversion circuit and is connected to the power supply terminal; a switching unit that connects the signal input terminal and the switching element but is not connected to the power supply terminal, and turns on the switching element when the wake-up signal is input from the signal input terminal; The control device determines that the battery is at a low voltage when the value of the ignition voltage recognized by the digital signal is smaller than a low voltage determination threshold, and stops the vehicle electric compressor.

4. The electric compressor for a vehicle according to claim 1 , wherein the AD conversion circuit converts the analog signal into bit information.

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