Patent ID: 6919726

Claim:
A leakage detection apparatus for detecting the presence or absence of leakage between a high-voltage circuit and a low-voltage circuit, comprising: a signal generator for generating a signal whose frequency is set variably; a resistant element for attenuating the signal from the signal generator in cooperation with an insulation resistor between the high-voltage circuit and the low-voltage circuit; a capacitive element for capacitance-coupling one end of the resistant element to the high-voltage circuit; a low-pass filter whose cut-off frequency is set variably so as to pass a signal with a frequency set in the signal generator, for attenuating a high-frequency component via the capacitive element to be superimposed on the signal via the resistant element; a leakage detection portion for comparing an amplitude level of a signal via the low-pass filter with a predetermined threshold value, and detecting the presence or absence of leakage between the high-voltage circuit and the low-voltage circuit; and a control portion for setting the signal frequency of the signal generator and the cut-off frequency of the low-pass filter after startup of the low-voltage circuit and before startup of the high-voltage circuit to be higher than those after startup of the high-voltage circuit.