GROUND FAULT DETECTION APPARATUS
FIG1 is a block diagram illustrating a configuration of a ground fault detection apparatus according to an embodiment of the present invention
Embodiments of the present invention will be described in detail with reference to the drawings. FIG1 is a block diagram illustrating a configuration of a ground fault detection apparatus 100 according to an embodiment of the present invention. As shown, the ground fault detection apparatus 100 is a flying capacitor type apparatus which is connected to a non-grounded high-voltage battery 300 and detects a ground fault of a system provided with the high-voltage battery 300. Herein, an insulation resistor between a positive-electrode side of the high-voltage battery 300 and a ground is represented as RLp, and an insulation resistor between a negative-electrode side of the high-voltage battery 300 and the ground is represented as RLn. High voltage means a voltage higher than a low-voltage battery (generally 12 V) for driving various devices (lamps, wipers, etc.) in a vehicle, and the high-voltage battery 300 is a battery used for driving of a vehicle travelling. As illustrated in FIG1, the positive-electrode-side C contact switch 111 and the negative-electrode-side C contact switch 112 are independently controlled and switched by the control device 120. The control device 120 switches the measurement path by controlling switching of the positive-electrode-side C contact switch 111, the negative-electrode-side C contact switch 112, and the switching element Sa independently, and performs charging and discharging of the detection capacitor C1 and measuring a charging voltage. Further, in the example of this figure, a parallel resistor of the resistor Ra11 and the resistor Ra12 plays a role of the resistor Ra, and a parallel resistor of the resistor Rb11 and the resistor Rb12 plays the role of the resistor Rb. Therefore, in the case of using the same resistance as in FIG1, resistance Ra11 = resistance Ra12 = resistance Rb11 = resistance Rb12 = 2 × the resistance Ra = 2 × resistance Rb.
block diagram
100
ground fault detection apparatus
302
negative-electrode-side power supply line
300
high-voltage battery
112
negative-electrode-side C contact switch
120
control device
['1. A ground fault detection apparatus that is connected to a non-grounded high-voltage battery (300) and detects a ground fault of a system provided with the high-voltage battery, the ground fault detection apparatus comprising: a control unit (120); a detection capacitor (C1) that operates as a flying capacitor; a positive-electrode-side first resistor (Ra) connected to a positive-electrode side of the high-voltage battery; a negative-electrode-side first resistor (Rb) connected to a negative-electrode side of the high-voltage battery; a positive-electrode-side second resistor (R3) having a first end grounded and a second end, a voltage of the second end being measured by the control unit; a negative-electrode-side second resistor (R4) having a first end grounded; a positive-electrode-side C contact switch (111) that is formed as a twin relay having relays (111a, 111b) operating in conjunction with each other and connected in parallel, and that is configured to alternatively switch a connection destination of a first end of the detection capacitor between a path including the positive-electrode-side first resistor and a path including the positive-electrode-side second resistor based on an instruction from the control unit; a negative-electrode-side C contact switch (112) that is formed  as a twin relay having relays (112a, 112b) operating in conjunction with each  other and connected in parallel, and that is configured to alternatively switch a connection destination of a second end of the detection capacitor between a path including the negative-electrode-side first resistor and a path including the negative-electrode-side second resistor based on an instruction from the control unit; and a path switching C contact switch (113) formed as a twin relay having relays configured to operate in conjunction with each other, one (113a) of the relays of the path switching C contact switch being configured to switch one of the relays of the positive-electrode-side C contact switch to the connection destination of the first end of the detection capacitor, and another one (113b) of the relays of the path switching C contact switch being configured to switch one of the relays of the negative-electrode-side C contact switch to a connection destination of the second end of the detection capacitor.']