High frequency soft switching and pulse width modulation full bridge DC / DC converter with reduced circulating current

摘要

An improved soft switching topology of a full bridge PWM DC/DC converter is described. The new topology employs an energy recovery snubber to minimize a circulating current flowing through the transformer and switching devices. By using an energy recovery snubber instead of adding a tapped inductor and a saturable reactor to reduce RMS current stress, the converter achieves nearly zero current switching for the right leg of the full bridge circuit due to the minimized circulating current, and achieves zero voltage switching for the left leg of the full bridge circuit due to the reflected output current during the interval of left leg transition. The converter achieves soft switching for secondary side rectifier and freewheeling diode because at the turn-on time of the primary switching device, the energy recovery snubber provides a low impedance path.