JP6710621B2 - Ground fault detection circuit Reverse voltage protection circuit - Google Patents

Description

The present invention relates to a ground fault detection circuit and a power supply device.

Generally, in an electric vehicle, a fuel cell vehicle, and a hybrid electric vehicle, a high-voltage power supply unit connected to a high-voltage battery is insulated from a vehicle body. When a ground fault occurs in the high-voltage power supply unit, the risk of electric shock increases. Therefore, a circuit for detecting the ground fault of the high-voltage power supply unit is required for the purpose of preventing electric shock due to the ground fault.

For example, as a ground fault detection device that determines a ground fault between a high voltage power supply unit and a vehicle body, a ground fault detection device as described in Patent Document 1 below is known.
In Patent Document 1, an output terminal of a high-voltage power supply is connected to one end side of an input coupling capacitor, a pulse signal is applied to a measurement point on the other end side of the coupling capacitor, and the voltage value generated at the measurement point is measured. It is detected and the ground fault of the high voltage power supply is judged.

JP, 2006-177840, A

Since the input coupling capacitor used in the ground fault detection circuit is connected to a high voltage battery of several hundreds of volts, a high capacity capacitor is used so that the output voltage difference becomes large depending on the presence or absence of a ground fault. Therefore, electrolytic capacitors are mainly used.

This ground fault detection circuit is connected to the + side or − side of the high voltage battery, and the ground fault detection circuit terminal is applied with a high voltage of several hundred to several kV of both positive and negative poles in a test regarding insulation between low voltage and high voltage and withstand voltage. May be done. Further, the ground fault detection circuit terminal may be connected reversely to the high voltage battery side which should be originally connected due to an incorrect connection or the like, so that the electrolytic capacitor of the ground fault detection circuit needs to have a high withstand voltage of both positive and negative polarities.

The electrolytic capacitor has a resistance of several volts to several hundreds of volts against a positive voltage, while it has a resistance to a reverse voltage of about 1 V in general, and the reverse voltage resistance is very weak. When a voltage higher than the reverse withstand voltage is applied to the electrolytic capacitor, a current flows and gas is generated due to an internal chemical reaction, which may cause deterioration of the electrolytic capacitor. That is, the electrolytic capacitor used as the input coupling capacitor of the ground fault detection circuit needs protection against reverse voltage.

A ground fault detection circuit according to the present invention is a ground fault detection circuit that detects a ground fault of a high-voltage battery, and has an AC signal generation unit that generates an AC signal , has polarity, and has the AC signal generation unit and the An input capacitive element provided between the high voltage battery and one end side thereof, a voltage dividing circuit for dividing the voltage of the one end side of the high voltage battery, and the high voltage based on an input ground fault detection signal. A ground fault detection unit that detects a ground fault of the voltage battery, provided between the voltage dividing circuit and the ground fault detecting unit, of the voltage on one end side of the high voltage battery that is divided by the voltage dividing circuit. A detection capacitive element for inputting an AC component as the ground fault detection signal to the ground fault detection unit, and a plurality of the input capacitive elements are connected in series and the plurality of input capacitive elements are connected. An AC signal transmission circuit section configured by a plurality of bias resistors for suppressing capacity variation and a plurality of diodes functioning as a reverse voltage protection circuit for the input capacitive element; and the plurality of input capacitive elements . The element is connected to a first capacitive element group composed of input capacitive elements whose polarities are connected in a first direction, and a second direction whose polarity is opposite to the first direction. A second capacitive element group including an input capacitive element, and the plurality of diodes each include a diode reversely connected to each input capacitive element belonging to the first capacitive element group. It includes a first diode group and a second diode group formed of diodes that are respectively reversely connected to the input capacitive elements belonging to the second capacitive element group.

According to the present invention, the electrolytic capacitor used as the input coupling capacitor of the ground fault detection circuit can be protected from the reverse voltage.

It is a figure which shows the structure of the power supply device by one Embodiment of this invention. It is a figure which shows the relationship between the ratio of Vin and Vout in Formula (1), and leak resistance. 7 is an example of a voltage waveform applied to the AD input terminal 2 of the microprocessor 11 when a ground fault occurs. It is a figure which shows the structure of the power supply device by one Embodiment of this invention. It is a figure which shows the structure of the power supply device by one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Structure of power supply device)
FIG. 1 is a diagram showing a configuration of a power supply device according to an embodiment of the present invention.

This power supply device is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and charges the high voltage battery 1 when driving the motor 7 of the vehicle or collecting the regenerative electric power generated by the motor 7. Performs discharge control.

The high voltage battery 1 is insulated from the vehicle body. The power supply device according to the present embodiment has a ground fault detection circuit. This ground fault detection circuit detects that the insulation between the high-voltage battery 1 and the motor 7 has deteriorated and a ground fault has occurred.

The power supply device includes a precharge resistor 2, relays 3 to 5, an inverter 6, an MCU 21, a driver circuit 22, a capacitor 8, a total voltage detection circuit 9, a current sensor 10, a microprocessor 11, a resistor 13, an input coupling capacitor 14, It has a detection coupling capacitor 15 and an amplifier 16.

The high-voltage battery 1 is, for example, a lithium-ion battery, and is configured by connecting a plurality of cells in which a manganese-based material is used for a positive electrode and an amorphous carbon material is used for a negative electrode in series. High voltage battery 1 has a rated capacity of 5.5 Ah, for example, and a rated voltage of 3.6 V, for example.

The high voltage battery 1 and the inverter 6 are connected via relays 3-5. The relays 3 to 5 are controlled by the MCU 21 that controls the inverter 6 to switch between on and off. A large-capacity capacitor 8 for smoothing a pulsed charging/discharging current is connected to the input terminal side of the inverter 6. A precharge resistor 2 for preventing inrush current is provided between the high voltage battery 1 and the inverter 6. Precharge resistor 2 has a resistance value of 390Ω, for example. When the energization of the high voltage battery 1 to the inverter 6 is started, the relays 4 and 5 are closed, so that the high voltage battery 1 and the inverter 6 are connected via the precharge resistor 2. This limits the inrush current flowing through the capacitor 8 and protects the contacts of the relays 3-5. After that, the relay 3 is closed and the relay 4 is opened, so that the high-voltage battery 1 and the inverter 6 are connected without the interposition of the precharge resistor 2. In this way, the connection states of the high voltage battery 1 and the inverter 6 are switched by the relays 3-5.

The inverter 6 is connected to a motor 7 mounted on the vehicle, converts the DC power output from the high-voltage battery 1 into three-phase AC power, outputs the three-phase AC power to the motor 7, and drives the motor 7. Further, the regenerative power generated by using the motor 7 as a generator is converted into DC power and output to the high-voltage battery 1 to charge the high-voltage battery 1. That is, the inverter 6 has a bidirectional input/output characteristic and functions as a charge/discharge load of the high-voltage battery 1.

The total voltage detection circuit 9 detects the total voltage of the high voltage battery 1 and outputs a voltage corresponding to the detected value as a voltage detection signal. The total voltage detection circuit 9 has resistors 17 to 20 and a differential amplifier 21 that form a voltage dividing circuit. The voltage detection signal output from the total voltage detection circuit 9 is the output from the differential amplifier 21. The current sensor 10 detects a current input to and output from the high voltage battery 1 and outputs a voltage corresponding to the detected value as a current detection signal. The current detection signal output from the current sensor 10 and the voltage detection signal output from the total voltage detection circuit 9 are input to the AD input terminals 1 and 3 of the microprocessor 11, respectively.

The high-voltage side of the high-voltage battery 1, that is, the positive-side terminal is connected to the AD input terminal 2 of the microprocessor 11 via the resistor 17, the detection coupling capacitor 15, and the amplifier 16 in the total voltage detection circuit 9. ing. The amplifier 16 detects the voltage on the high voltage side of the high voltage battery 1, and outputs a voltage corresponding to the detected value to the AD input terminal 2 of the microprocessor 11 as a ground fault detection signal. The high-voltage side terminal of the high-voltage battery 1 is connected to one of the two input terminals of the differential amplifier 21 via the resistor 17. The voltage input from the high voltage side terminal of the high voltage battery 1 to the detection coupling capacitor 15 and the differential amplifier 21 is divided by the resistors 17 and 19. Therefore, the withstand voltage of the detection coupling capacitor 15 and the differential amplifier 21 may be low.

The low-voltage side terminal of the high-voltage battery 1, that is, the negative-side terminal is connected to the other one of the two input terminals of the differential amplifier 21 via the resistor 18 in the total voltage detection circuit 9. The voltage input from the low voltage side terminal of the high voltage battery 1 to the differential amplifier 21 is divided by the resistors 18 and 20.

The differential amplifier 21 compares the voltages input to the two input terminals and outputs a signal corresponding to the difference to the AD input terminal 3 of the microprocessor 11 as a voltage detection signal from the total voltage detection circuit 9. .. This voltage detection signal represents the voltage difference between the high voltage side and the low voltage side of the high voltage battery 1, that is, the total voltage.

The microprocessor 11 is a battery controller that manages the entire power supply device including the high voltage battery 1. The microprocessor 11 has a built-in oscillation circuit. The oscillator circuit generates a predetermined AC signal, for example, a rectangular wave having a frequency of 10 Hz and an amplitude of 0 to 5 V, and outputs the rectangular wave from an AC output terminal. The AC output terminal of the microprocessor 11 is connected to the terminal on the high voltage side of the high voltage battery 1 via the resistor 13 and the input coupling capacitor 14.

The microprocessor 11 further includes an AD converter. The current detection signal from the current sensor 10, the ground fault detection signal from the amplifier 16, and the voltage detection signal from the total voltage detection circuit 9 are supplied to the AD converter of the microprocessor 11 via the AD input terminals 1 to 3, respectively. Is entered. The AD converter measures these signals within a predetermined measurement range, for example, a measurement range of 0 to 5V, and converts them into digital values. Based on the measured value after the digital conversion, the microprocessor 11 measures the total voltage and the input/output current of the high voltage battery 1, and also detects the ground fault with respect to the vehicle body between the high voltage battery 1 and the motor 7.

(Explanation of ground fault detection operation)
A voltage Vout represented by the following equation (1) is applied to the AD input terminal 2 of the microprocessor 11 as a ground fault detection signal. In the following equation (1), α is a value obtained by multiplying the voltage division ratio of the resistors 17 and 19 by the amplification factor of the amplifier 16, and Vin is applied from the AC output terminal of the microprocessor 11 to the high voltage side of the high voltage battery 1. R1 is the resistance value of the leak resistance 12, R2 is the resistance value of the resistance 13, and Z is the impedance of the input coupling capacitor 14.

Vout≈αVin (R1/(R1+R2+Z))... Formula (1)
When the leak resistance 12 occurs, that is, when a ground fault occurs between the high voltage battery 1 and the motor 7, the signal is input to the AD input terminal 2 of the microprocessor 11 according to the above equation (1). The amplitude of the ground fault detection signal changes. Therefore, the microprocessor 11 can detect the occurrence of the ground fault.

Further, when the detection coupling capacitor 15 is opened due to a failure or the like, a ground fault detection signal different from that in the normal state appears at the AD input terminal 2, so that the abnormality can be detected.

Furthermore, when the input coupling capacitor 14 is opened and the AC signal is not applied to the high voltage side of the high voltage battery 1, the AC component is not included in the ground fault detection signal appearing at the AD input terminal 2, The microprocessor 11 can still detect an abnormality.

In the total voltage detection circuit 9, the voltage dividing circuit including the resistors 17 to 20 must have sufficiently high resistance with respect to the chassis GND when viewed from the high voltage battery 1 side. Further, the voltage division ratios of the combination of the resistors 17 and 19 and the resistors 18 and 20 are equal to each other, and even if one terminal of the high-voltage battery 1 is short-circuited to the chassis GND, the differential amplifier 21 does. Set it within the voltage range that allows normal amplification.

The amplification factor of the amplifier 16 corrects the amplitude reduction of the AC signal output from the microprocessor 11, and is set to an amplification factor with which the ground fault detection signal can sufficiently detect the ground fault with the resolution of the AD converter of the microprocessor 11. Set. Further, when the transient response generated at the time of connecting the relays 3 to 5 is sufficiently stable thereafter and the ground fault can be sufficiently detected, the ground fault detection signal exceeds the input voltage range of the AD converter of the microprocessor 11. Set not to.

When the leak resistance R1 (the resistance value of the leak resistance 12) in the equation (1) is 0, that is, when the high voltage battery 1 is completely grounded, the equation (1) is simplified to the equation (2).

Vout=0... Formula (2)
FIG. 2 is a diagram showing the relationship between the ratio of Vin to Vout in the equation (1) and the leak resistance. In this embodiment, the insulation resistance value can be monitored in the entire voltage range applied with Vin, and the insulation resistance measurement accuracy can be improved.

FIG. 3 is an example of a voltage waveform of a ground fault detection signal applied to the AD input terminal 2 of the microprocessor 11 when a ground fault occurs between the positive electrode terminal side of the high voltage battery 1 and the motor 7.

When the input voltage range of the AD converter in the microprocessor 11 is 0 to 5 V, Vout may be outside the input voltage range of the AD converter due to voltage fluctuations that occur when a ground fault occurs.

In the present embodiment, by adjusting the amplitude, it is possible to monitor the amplitude immediately after the occurrence of the ground fault and minimize the delay in the ground fault detection operation.

When detecting the occurrence of a ground fault, the microprocessor 11 may open the relays 3 to 5 to disconnect the high voltage battery 1 from the inverter 6 and the motor 7. Alternatively, the microprocessor 11 that has detected the occurrence of the ground fault may perform an operation other than opening the relays 3 to 5. For example, the user may be notified of the occurrence of the ground fault by turning on a warning light prepared in advance. These operations and various other operations may be combined.

The above is the description of the ground fault detection operation.

The present invention is an invention relating to protection of the ground fault detection circuit against positive and negative overvoltages.

In the circuit configuration in which the ground fault detection circuit of FIG. 1 is connected to the + side of the high voltage battery, a plurality of electrolytic capacitors 14 are connected in series according to a desired breakdown voltage with respect to the positive overvoltage to the ground fault detection circuit, so that the entire breakdown voltage is increased. It is conceivable to increase the circuit configuration. FIG. 1 shows a 4-series connection configuration as an example. At this time, in the multi-series connection of the electrolytic capacitors 14, the voltage applied to each electrolytic capacitor 14 varies due to the variation in electrostatic capacitance. Therefore, the bias resistor 24 is connected in parallel to each electrolytic capacitor 14 to reduce the variation in applied voltage. Can be done.

If a negative overvoltage is applied to the negative overvoltage to the ground fault detection circuit by connecting a reverse connection protection diode 23 to the cathode of the electrolytic capacitor 14 on the + side and an anode on the − side of the electrolytic capacitor 14, the reverse connection protection diode 23 is forwarded to the reverse connection protection diode 23. A current flows, and only the forward voltage Vf can be applied to the electrolytic capacitor 14. Depending on the negative overvoltage value, the resistance value of the resistor 13 is adjusted so that the forward current is sufficiently small so that only the forward voltage Vf of 1 V or less is applied to the electrolytic capacitor 14, thereby protecting the electrolytic capacitor 14 against the negative overvoltage. be able to.

Further, when the ground fault detection circuit is connected to the negative side of the high voltage battery 1, since the connection to the negative potential is made with respect to the ground fault detection circuit, a circuit configuration in which the polarity of the electrolytic capacitor is reversed as shown in FIG. Become. With respect to the negative overvoltage to the ground fault detection circuit, a circuit configuration in which a plurality of electrolytic capacitors 14 are connected in series according to a desired withstand voltage to raise the overall withstand voltage can be considered. FIG. 4 shows a 4-series connection configuration as an example. At this time, in the multi-series connection of the electrolytic capacitors 14, the voltage applied to each electrolytic capacitor 14 varies due to the variation in electrostatic capacitance. Therefore, the bias resistor 24 is connected in parallel to each electrolytic capacitor 14 to reduce the variation in applied voltage. Can be done.

When a negative overvoltage is applied by connecting the reverse connection protection diode 23 to the cathode of the electrolytic capacitor 14 on the positive side and the anode on the negative side of the positive overvoltage to the ground fault detection circuit, the reverse connection protection diode 23 is forwarded to the reverse connection protection diode 23. A current flows, and only the forward voltage Vf can be applied to the electrolytic capacitor 14. Depending on the negative overvoltage value, the resistance value of the resistor 13 is adjusted so that the forward current is sufficiently small so that only the forward voltage Vf of 1 V or less is applied to the electrolytic capacitor 14, thereby protecting the electrolytic capacitor 14 against the negative overvoltage. be able to.

A circuit configuration in which electric field capacitors are alternately arranged as shown in FIG. 5 is also conceivable.
With this circuit configuration, it is possible to connect the positive side of the high voltage battery having a positive potential to the ground fault detection circuit and the negative side of the high voltage battery 1 having a negative potential.
Although FIG. 5 shows a 4-series connection configuration as an example, a desired breakdown voltage can be obtained by connecting a plurality of series connections, and the electrolytic capacitor 14 can also be protected from reverse voltage.

As a modified example of the present embodiment, the present invention can be applied to a system that uses a rechargeable battery other than a lithium-ion battery, a system that does not use an inverter and a motor, such as a system other than an electric vehicle.

Further, as a modified example of this embodiment, the output of the amplifier 16 may be input to circuits and devices other than the microprocessor 11. Further, the circuit and the device other than the microprocessor 11 may perform the operation according to the detection of the occurrence of the ground fault. For example, the power supply device may be configured so that the inverter 6 opens the relays 3 to 5.

The present embodiment is not limited to the above embodiments as long as the characteristics of the present embodiment are not impaired, and other forms considered within the scope of the technical idea of the present invention are also within the scope of the present invention. included.

DESCRIPTION OF SYMBOLS 1... High voltage battery, 2... Precharge resistance, 3-5... Relay, 6... Inverter, 7... Motor, 8... Capacitor, 9... Total voltage detection circuit, 10... Current sensor, 11... Microprocessor, 12... Leakage Resistors, 13... Resistors, 14... Input coupling capacitors, 15... Detection coupling capacitors, 16... Amplifiers, 17-20... Resistors, 21... Differential amplifiers, 22... Driver circuits, 23... Reverse voltage protection diodes, 24... Bias resistor

Claims (5)

A ground fault detection circuit for detecting a ground fault of a high voltage battery,
An AC signal generator that generates an AC signal;
An input capacitive element having polarity and provided between the AC signal generator and one end of the high-voltage battery;
A voltage divider circuit that divides the voltage at one end of the high-voltage battery,
Based on the input ground fault detection signal, a ground fault detection unit that detects a ground fault of the high-voltage battery,
The ground fault detecting unit is provided between the voltage dividing circuit and the ground fault detecting unit, and uses the AC component of the voltage on one end side of the high-voltage battery divided by the voltage dividing circuit as the ground fault detecting signal. A capacitive element for detection for input to
A plurality of input capacitive elements are connected in series, and a plurality of bias resistors that suppress the capacitance variation of the plurality of input capacitive elements and a plurality of bias resistors that function as a reverse voltage protection circuit for the input capacitive elements . An alternating current signal transmission circuit section composed of a diode ,
The plurality of input capacitive elements have a first capacitive element group composed of input capacitive elements whose polarities are connected in a first direction, and the polarities opposite to those in the first direction. A second capacitive element group composed of input capacitive elements connected in a second direction,
The plurality of diodes include a first diode group formed of diodes that are reversely connected to respective input capacitive elements belonging to the first capacitive element group, and respective inputs belonging to the second capacitive element group. A ground fault detection circuit including a capacitive element for use and a second diode group including diodes that are reversely connected to each other . The ground fault detection circuit according to claim 1,
Wherein the plurality of bias resistors and said plurality of diodes of the AC signal transmitting circuit is electrically connected in parallel respectively provided and the input capacitive element in accordance with the number of the input capacitive element Ground fault detection circuit. The ground fault detection circuit according to claim 1,
The ground fault detection circuit further provided with the total voltage detection circuit which detects the voltage of the said high voltage battery using the said voltage divider circuit. A power supply device comprising: the ground fault detection circuit according to claim 1; and a battery controller that manages the high-voltage battery that is an assembled battery configured by a plurality of battery cells. The power supply device according to claim 4,
Further comprising a relay that switches a connection state between the high-voltage battery and a load driven by the high-voltage battery,
The battery controller is a power supply device that controls the relay and disconnects between the high-voltage battery and the load in response to the detection of the ground fault by the ground fault detection unit.

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