Research on a Wide-Output Resonant Converter with Multi-Mode Switching

In this article, a resonant converter based on a series-parallel self-adjusting rectifier structure is proposed. By changing the driving signal of the switch, the converter has four working modes: full-bridge structure frequency modulation control, full-bridge structure phase-shift control, half-bridge structure frequency modulation control and half-bridge structure phase-shift control. The newly proposed resonant converter retains the soft switching characteristics of the LLC resonant converter and the mode switching can be completed only through software control without adding additional switches. Different modes correspond to different gain ranges. By changing the control strategy of the modes, the newly proposed converter can meet the design requirements of wide output. Finally, an experimental prototype with an input voltage of 25 V and an output voltage of 9 V to 35 V is built. The experimental results prove the correctness of the wide output characteristics of the converter proposed in the article and, in the four operating modes, it can realize zero-voltage turn-on of the active switch on the primary side and zero-current turn-off of the rectifier diode on the secondary side, which preserves the high efficiency of the resonant converter.