Power supply circuit with load protection function

Abstract

A power supply circuit interrupts power to a load in response to a short-circuit or an open-circuit condition and automatically restores power after a momentary short-circuit. A short-circuit detector monitors the current flowing through the load and generates a short-circuit signal if the current exceeds a predetermined level. An open-circuit detector monitors the load voltage and generates an open-circuit signal if the voltage exceeds a predetermined level. A latch converts the short-circuit signal to a latch signal. A logic unit combines the latch signal with the open-circuit signal and a pulse signal from a pulse generator to generate a drive signal. A driver uses the drive signal to control a switch which is connected between the power source and the load to interrupt power to the load. During a short-circuit, a timer generates a periodic pulse signal that toggles the latch signal and intermittently restarts the power to the load. If the short-circuit was of short duration, power is restored to the load. If the short-circuit persists, the power supply circuit continues to intermittently restore power to the load until the short-circuit is removed. The logic unit also generates a fault signal in response to the latch signal and the open-circuit signal. A display unit generates a visual alarm in response to the fault signal to indicate an abnormal state.