Modeling of common-mode noise in phase-shift full-bridge converter

The common-mode (CM) noise modeling for a power converter mainly focuses on the identification of high dv/dt nodes in the circuit and the related parasitic capacitance. For phase-shift full-bridge (PSFB) converter, the inter-winding capacitance of the transformer and the parasitic capacitance between the mid-point nodes from each leg and the ground are critical parasitic capacitance for CM noise, owning to high dv/dt characteristics of the transformer terminals and the mid-point nodes. Due to the existence of the resonant inductor, the electric potential of the transformer primary terminals is not only related with the electric potential of the mid-point nodes, but also influenced by the voltage vLr across the resonant inductor. In this paper, the voltage vLr is considered and added into the CM noise model of PSFB converter, and the CM noise equivalent circuit is derived. By comparing the calculated CM noise from the derived equivalent circuit with the simulated result, the CM noise modeling of PSFB converter is verified.