Wide Input Voltage Range LLC Resonant Converter Based on Fuzzy PI Control

In order to broaden the input voltage range of the LLC resonant converter and improve its stability under input voltage fluctuations, this paper utilizes the topology transition between the full-bridge (FB) and half-bridge (HB) LLC resonant converter with twofold voltage gain ratio, which can greatly expand its voltage gain range. However, there is an abrupt change in the output voltage during the transition between FB and HB topology, using the traditional PI control strategy in the face of abrupt changes in the operating conditions of the system, it is often difficult to achieve the desired fast dynamic response speed and stability requirements. Therefore, this paper proposes the use of fuzzy PI control, through the fuzzy logic dynamic adjustment of the parameters of the PI controller, to improve the output voltage stability of the system when transition between FB and HB modes under input voltage fluctuation. Simulation experiments show that the fuzzy PI control strategy greatly reduces the output voltage fluctuation and improves the stability of the system when transition between FB and HB modes under input voltage fluctuation compared with the traditional PI control strategy.