Study on high-efficiency, low cost, and high power density on-board charger system using center-tapped clamping voltage-source circuit

Abstract

In this dissertation, a new clamp circuit, which consists of two diodes and one capacitor, is proposed. With this very simple structure, the proposed clamp circuit can solve many limitations in conventional phase-shifted full-bridge (PSFB) converters, so that high efficiency, low cost, and high power density are achieved in electric-vehicle battery charger applications. The proposed center-tapped clamp circuit provides the clamping path and allows the secondary voltage stress to be clamped to the secondary-reflected input voltage. This results in a greatly reduced conduction loss in the secondary full-bridge rectifier (FBR) due to the low forward-voltage drop of low voltage-rated diodes. In addition, the circulating current in the primary side is removed without any duty-cycle loss. Furthermore, the turn-off switching loss in the FBR is substantially reduced due to the decreased reverse-recovery current and the reduced reverse voltage. With these advantages, high efficiency can be achieved. Besides, the size of the output inductor is considerably reduced with the aid of clamping voltage, resulting in a high power density with saving the cost. In order to confirm the effectiveness of the proposed converter, a 3.3-kW prototype was tested. Experimental results show that the proposed converter achieves high efficiency over the entire conditions.