Active reset circuit for forward converter to reduce losses and to increase duty cycle range

This paper presents a circuit that can reset single or multiple forward converters without additional voltage stress beyond the optimum value. This circuit allows for a maximum duty cycle well in excess of 50%, and recovers the magnetization energy. The transformer core(s) is reset to residual under all conditions and third quadrant reset is accomplished over most of the operating range. Data is presented to demonstrate the action of this circuit and design equations are developed. The traditional reset methods are reviewed as a comparison to the new circuits operation