Primary only control quasi resonant convertor

摘要

A power supply apparatus and method of regulating is provided. A converter circuit includes a primary switching element and an auxiliary switching element. The auxiliary switching element is for transferring a reflected voltage signal. A transformer includes a primary and a secondary, the primary is coupled with the converter circuit. The primary and secondary each include a single winding. An output rectifier circuit is coupled with the secondary of the transformer. A resonant circuit is included in the converter circuit and is coupled with the primary. The resonant circuit includes one or more resonance capacitors that are configured for providing a transformer resonance. The transformer resonance comprises the reflected voltage signal, the capacitance of the one or more resonance capacitors and a parasitic capacitance of the transformer. The reflected voltage signal is reflected from the secondary to the primary. A virtual output voltage feedback loop provides an output voltage reference signal to the converter circuit via the resonant circuit. The converter circuit is responsive to the output voltage reference signal in regulating an output voltage.