JPS57182224A - Method for inhibiting overcurrent of power supply - Google Patents

Abstract

PURPOSE:To obtain a drooping characteristic which does not cause unstable operations, suh as hunting, etc., when an overcurrent is generated, by giving a hysteresis characteristic to a control signal produced based on a peak-hold detected value of an instantaneous value at a half cycle of the main current flowing through a semiconductor device for controlling electric power. CONSTITUTION:The main current of a semiconductor device for controlling electric power Tr is detected by a current detector Dc. The output of the detector Dc outputs an inhibit signal CL to a controlling circuit Av at an instantaneous value of a half cycle of the main current in an overcurrent inhibiting circuit. The circuit Av controls the device Tr with the signal CL, and outputs a constant voltage of a power source E to terminals T1 and T2 through a transformer T and rectifier elements D1, D2, L, and C. When the peak-hold detected value is higher than a reference level, the signal CL lowers the reference level to a lower level, and, when the peak-hold value exceeds the lower level, inhibits the delivery of a drive signal Ds from the circuit Av. In this way, a power unit having a drooping characteristic which does not cause any hunting can be obtained by utilizing the hysteresis characteristic between the two levels.