FAULT CONTROL CIRCUIT FOR SWITCHED POWER SUPPLY

摘要

PURPOSE: A fault control circuit is provided to control switched power supplies in such apparatus during current overload conditions by utilizing a control circuit otherwise present for switching the power supply, for example an auxiliary power supply, on and off when changing between the run and standby modes of operation mode. CONSTITUTION: A voltage source, a transformer and a switching controller are coupled for switched mode generation of a regulated output supply voltage. A switching circuit responsive to an on/off signal turns the power supply on and off by establishing a conductive condition in a conductive path. A fault detector establishes a non conductive condition in a part of the conduction path responsive to an overload condition. A delay circuit establishes a conductive condition in an auxiliary conduction path for a period of time after the power supply is turned on. The auxiliary conduction path becomes non-conductive when the fault detector establishes a conductive condition in the part of the conduction path. The part of the conduction path remains conductive absent an overload condition. A latch arrangement including the delay circuit maintains the non conductive condition in the auxiliary conduction path until the power supply is turned off.