Common-Mode Noise Reduction in Phase-Shifted Full-Bridge Converter by Common-Mode Voltage Cancellation

Full-bridge (FB) converter is a widely adopted topology in medium-to-high power conversion applications, and soft switching can be realized with phase-shifted control to achieve high efficiency. As the diagonal switches turns on (off) at different time, the displacement current flowing through associated parasitic capacitances (including the transformer inter-winding capacitance and the parasitic capacitance between two midpoints and the ground) cannot be cancelled by each other, which makes the common-mode (CM) noise severe in phase-shifted full-bridge (PSFB) converter. In this paper, a CM voltage cancellation (CMVC) method is proposed, which is realized by inserting a cancellation voltage source into the input power cord, and canceling the CM noise. The cancellation voltage source is realized by CM winding, which is coupled with the CM voltage sensing winding connected between the middle of the transformer primary winding and the primary ground. By utilizing the magnetizing current through the CM voltage sensing winding, the load range for zero-voltage switching (ZVS) can also be extended by applying this method. The effectiveness of CMVC method has been verified by simulation.