A sampled-data model for a digitally controlled self oscillating series-parallel resonant converter with the parasitic effects and the control loop delay

The paper describes a new methodology for predicting the steady state and dynamic operation of the digitally controlled self-oscillating series parallel resonant converter for the voltage regulator modules (VRMs) applications. It takes into account the effect of the transformer leakage inductance, the output capacitor filter parasitic resistance and the control delay effect in the control loop, which are crucial for the high frequency operation. The generalized piecewise linear state space models are derived, and then employed to predict the static and dynamic behavior. The steps are translated into a MATLAB program that is 20 times faster and 100 times less capacity than that of the PSIM software. It proves the fact that the parasitic effects vary the waveforms of the resonant tank extensively and hence a new design procedure should be considered. Analytical, simulation and experimental results are given to prove the validity of the developed models.