A Bidirectional Isolated LLC Resonant Converter with Configurable Structure for Wide Output Voltage Range Applications

This paper proposes a novel bidirectional isolated LLC resonant converter to realize wide output voltage range. The proposed converter overcome the dilemma of conventional LLC resonant converter between wide voltage gain and wide switching frequency range. It is achieved by the two operation configurations when the switches of configurable structure (CS) adopt different duty cycle. The CS is beneficial to narrow switching frequency range and increase magnetizing inductance of the converter that benefits the design of the magnetic components and reduces the conduction losses, respectively. Meanwhile, the switching frequency doubler modulation (SFDM) that makes the frequency of the resonant tank twice the switching frequency is adopted to further reduce the size of resonant components and greatly reduce switching losses. Moreover, the proposed converter can achieve soft-switching which ensures high efficiency throughout the wide voltage gain for both forward and reverse operation. In addition, the voltage stress of all switches is halved compared to full- bridge and half-bridge converters. The simulations and a 100W prototype have been built to verify the operation principal and its performance.