Zero-current-switched quasiresonant converters with one additional fully regulated output

A solution is proposed in order to obtain an additional fully regulated output in zero-current-switched quasi-resonant converters (ZCS-QRCs). The solution consists of connecting a low-power pulsewidth-modulation (PWM) topology to the resonant switch and modulating the duty cycle (besides the switching frequency) in the power transistor. The PWM topology must have a transformer or a tapped-inductor to overcome a constraint between the output voltage gain in both outputs. The converter obtained has nonzero-current switching, but the increase in switching losses is very small if the power handled by the new output is much smaller than that delivered by the main output