FUNCTIONAL ON/OFF SWITCH FOR SWITCHED-MODE POWER SUPPLY CIRCUIT WITH BURST MODE OPERATION

摘要

A switched-mode power supply circuit having an operating mode and a stand-by mode, includes a functional ON/OFF switch. The switched-mode power supply circuit includes a transformer and a controllable switch connected to a primary winding of the transformer for switchably connecting the primary winding to a source of d.c. voltage. In the stand-by mode, based on a detected voltage level at an input of a controller IC, the switched-mode power supply circuit is arranged to switchable connect the primary winding to the d.c. voltage source in bursts which occur at a low frequency. By switchably connecting this input to a power source for the switched-mode power supply circuit, the controlled IC detects the absence of this power source, and turns off the switched-mode power supply circuit allowing a minimum current consumption by the switched-mode power supply circuit.