Reducing the Common-Mode Noise in Phase-Shifted Full-Bridge Converter

The phase-shifted full-bridge (PSFB) converter features soft-switching for power switches and simple topology, and it has been widely used in medium-to-high power applications. Due to the phase-shift control, the electric potentials of the two phase-leg midpoints change at different time. As a result, the displacement current flowing through the parasitic capacitance between the phase-leg midpoints and the protective earth (PE), as well as the transformer inter-winding capacitance, cannot cancel by each other. As mentioned in Chaps.  6 and 7 , the PSFB converter does not have the CM noise cancellation capability, and the shielding-based methods can not reduce its CM noise. In this chapter, the CM noise reduction in the PSFB converter is investigated. Based on the CM noise model of the PSFB converter, the method of symmetrical resonant inductor and symmetrical transformer configuration is proposed, which eliminates the effect of resonant inductor voltage on the CM noise. Then, the passive cancellation circuit is introduced for further eliminating the effect of two phase-leg midpoint voltages on the CM noise. Finally, the proposed method is verified by the experimental results.