ZVS Analysis and Design for Half Bridge Bidirectional LLC-DCX Converter With Consideration of Nonlinear Capacitance and Different Load Under Synchronous Turn-On and Turn-Off Modulation

Abstract

In the application of bidirectional LLC -DCX converter, synchronous turn-on and turn-off modulation can be adopted to simplify the control. In view of zero-voltage switching (ZVS) performance, conventionally, the magnetizing inductance is regarded as a current source to discharge output capacitance of primary switches, neglecting the effect of secondary output capacitance and load, which leads to insufficient accuracy and non-ZVS. This article presents the ZVS analysis and design for half-bridge LLC -DCX converter with consideration of nonlinear capacitance and different load values under the synchronous turn-on and turn-off modulation. With consideration of nonlinear capacitance and different load values, the charging and discharging process of the output capacitance during the dead time is analyzed in detail. The analysis indicates that the ZVS conditions are not only affected by the dead time and magnetizing inductance as in the previous study but also related to the load and other parameters. Based on in-depth analysis, more precise ZVS conditions on the magnetizing inductance, dead time, load, and resonant parameters are revealed. In addition, based on the obtained ZVS conditions, the guidance for parameters design is given to achieve full-load-range ZVS. Finally, the effectiveness of the proposed solution has been verified through experimental results.