Current limit circuit in single-ended forward converter utilizing core reset to initiate power switch conduction

摘要

Current limit protection against current overload is obtained in a core-reset, forward-type converter by inserting a properly selected impedance in the flyback current path. The voltage developed across the impedance is impressed against the secondary winding of the power transformer. During current overload, the voltage drop across the impedance maintains a voltage drop across the secondary winding delaying a zero crossing of the voltage and, hence, delaying the initialization of conduction in the converter power switch. The time delay in conduction initiation in the power switch reduces current output and effectively counteracts the overload current.