LLC resonant converters for PHEV battery chargers

The load-dependent properties of LLC resonant converter leads to enormous difficulty in regular design of the converter, even when the load characteristic is usually assumed to be passive for the design simplification. For a battery charger, the output voltage requirement is quite different and is more challenging compared with the passive load. In this paper, an optimal design methodology for LLC resonant converter is presented and verified in a 400V/4kW charger for plug in hybrid electric vehicle (PHEV) applications with peak efficiency of 97%.