Ground fault detector for vehicle

A ground fault detector for evaluating ground faults in an electrical system of a vehicle, the electrical system including a power source, the detector comprising:

• an output terminal of the power source connected to one side of a coupling capacitor;
• pulse generating means for applying a pulse signal at a prescribed oscillation frequency to a measurement point on an opposite side of the capacitor;
• voltage detection means for detecting a voltage amplitude generated at the measurement point when the pulse signal is applied;
• ground fault detection means for detecting an occurrence of a ground fault of the circuit based on the voltage amplitude detected by the voltage detection means;
• and
• cause-of-ground-fault judgment means for changing an oscillation frequency of the pulse signal applied to the measurement point and for determining a cause of the ground fault based on a change in the voltage amplitude detected before and after change of the oscillation frequency.

A ground fault detection method for an electric system for a vehicle, the electrical system comprising a power source and at least one unit coupled to the power source to receive power from the power source, the method comprising:

• applying a pulse signal to a measurement point at one end of a coupling capacitor, the other end of the coupling capacitor coupled to the power source;
• detecting a voltage amplitude generated at the measurement point;
• detecting a presence or an absence of a ground fault of the system based on comparing the voltage amplitude to an amplitude of the pulse signal;
• changing an oscillation frequency of the pulse signal when the presence of the ground fault is detected;
• comparing a change in the voltage amplitude before and after the changing of the oscillation frequency, the change indicating a cause of the ground fault;
• and
• outputting a signal corresponding to the cause of the ground fault.