The Charge Control for the Single Stage LLC Resonant AC/DC Converter with Matrix Switches

With the development of renewable energy and the widespread use of electric vehicles, the AC/DC converter, which plays an important role as an interface to the power grid, has drawn much attention. Compared to the two stage AC/DC converter, the single stage AC/DC converter has the merits of high power density and high efficiency. with introducing the LLC resonant tank, the converter can achieve soft switching operation and wide voltage range. However, in the LLC-type single stage AC/DC converter, the control method is usually the Pulse Frequency Modulation (PFM), which has less outstanding dynamic response faced with sudden changes in load. To improve the dynamic response, this paper proposes a charge control strategy for the single stage AC/DC converter. By introducing charge control as the inner loop, the bandwidth can be extended. The simulation of an LLC-type matrix AC/DC converter is implemented to verify the proposed control strategy. A 1kW prototype is built and the preliminary experiment is conducted. The simulation and the preliminary experimental results are in good agreement with the theoretical analysis.