An overall scheme for a LLC series resonant control based 500 V/25 A charging module of off-board charger for electric vehicles is described. The main circuit topology and control circuit topology in this module are also given. A method of resolving the problem of module output voltage increasing under non-load or small load is provided， and the relationship between such parameters as the input voltage， switching frequency and output voltage of this module at different working frequencies is detailed. Experimental results on a 12.5 kW prototype show that all switches have realized zero voltage switching（ZVS） and a high efficiency of 96% can be obtained， with the performance completely meeting the design requirements.