Performance Optimization of Single-phase On-Board Chargers with Ripple Port

Abstract:
This paper introduces a new modulation method for a ripple port integrated in an On-Board Charger (OBC), that includes an isolated resonant LLC DCDC stage. The ripple port switching frequency is synchronized with the variable frequency of the LLC, and is phase-shifted so that the combined DC link current ripple is reduced. The voltage offset applied to the ripple port capacitor is controlled to achieve ZVS operation of the ripple port switches across a broad range of switching frequencies, while limiting excessive current stress. Results show substantial reduction in the DC link capacitor current ripple.