Resonant reset forward converter circuit diagram

Crystal Resonator 2.0*1.6mm 2016 25MHZ (25.000MHZ) 20PF 10PPM

Forward converters have a variety of reset modes: resonant reset; third winding reset; RCD reset; active clamp. Here is a low-cost compromise solution: resonant RCD reset.
As shown in (a), the resonant reset forward converter is a capacitor C connected in parallel with the main switch S, and a sine wave is generated by the capacitor C and the transformer magnetizing inductance Lm to reset the transformer. Figure (b) is the main operating waveform of the resonant reset forward converter, where VT is the voltage across the transformer and iLm is the excitation current of the transformer. These waveforms take into account the presence of transformer leakage inductance and are waveforms under heavy loads. The resonant reset voltage should be a sine wave if the leakage inductance is not considered or the load current is zero. When the switch is turned off, there is a voltage spike on the transformer, which is caused by the transfer of energy stored in the leakage inductance Ls to the resonant capacitor C, which is the leakage inductance of the transformer and the resonance of the capacitor C. This resonance period is much smaller than the resonance period of the magnetizing inductance and the capacitance C.

(a) Resonant reset forward converter

(b) Resonant reset forward converter operating waveform