Three-Bridge LLC-LC Resonant Converter with Wide Output Voltage Control Ranges

This paper presents an enhanced three-bridge LLC-LC DC-DC converter featuring notch filters implemented with an LC parallel resonant circuit. The proposed topology enables seamless output voltage regulation from the rated output voltage down to 0 VDC. To ensure stable operation over a wide output voltage range while maintaining a limited switching frequency variation, the converter adopts five operating-mode transitions, allowing effective voltage regulation even with a relatively large magnetizing inductance. Furthermore, excessive current in the LC parallel resonant tank is significantly reduced by restricting the voltage applied to the resonant circuit to one-quarter of the input voltage, even when operating at the LC resonant frequency. The operating principles of the proposed converter are thoroughly analyzed, and its performance and feasibility are validated experimentally.