A Demagnetization Circuit for Single-Ended Forward Converter

This paper presents a novel demagnetization scheme for single-ended forward converter. In the past, many prior transformer core reset methods have been proposed in order to avoid the transformer saturation, such as tertiary transformer winding, RCD clamp, resonant reset, active clamp and two-switch forward topology etc.. However, the lower efficiency, complicated transformer winding structure and the cost of too many added elements are the main drawbacks. In this paper, a novel demagnetization scheme for single-ended forward converter is presented. The proposed demagnetization circuit is very simple and the transformer demagnetization can be reached by adding two diodes and a clamping capacitor. In addition, the transformer design and PWM control circuit for the single-ended forward converter with proposed demagnetization circuit is the same as conventional forward converter. Finally, the operation and circuit performance of the single-ended forward converter with proposed demagnetization circuit are demonstrated with an experimental prototype that delivers a 5 V/10 A output from a 36-72 V input at the maximum efficiency of 88%.