A Modulation method for DCX LLC Converter to Achieve Fixed Voltage Gain and Bidirectional Power Transfer with Power Limitation Capability

The LLC resonant converter can be used as a dc–dc transformer (DCX) to provide isolation and fixed voltage transfer ratio. In this paper, a modulation strategy is proposed to achieve natural bidirectional power flow for DCX-LLC converters without exchanging the PWM logics and without auxiliary SR circuit. Without loss of generality, the proposed modulation can achieve ZVS of one side switches and ZCS of another side switches. In addition, the converter gain is fixed as long as the converter resonant current is discontinuous. Meanwhile, two additional diodes are added to achieve the constant output power limitation under overload condition.