PFM-PSM Hybrid Controlled CLLC Resonant Converter for Electric Vehicles

This paper describes the new design and control of pulse-frequency modulation (PFM) - phase shift modulation (PSM) hybrid controlled CLLC resonant converter (H-CLLC), which significantly reduces the operating frequency region and improves overall efficiency and reliability. In conventional PFM controlled CLLC resonant converter, bi-directional operation over the wide voltage range of HVB causes wide operating switching frequency range especially in step-down operation. This leads to drawbacks such as high switching loss and first harmonic approximation errors, which reduce the overall efficiency and reliability. To solve these issues, several hybrid control methods have been proposed. However, conventional hybrid control methods induce inoperative region, which reduce overall reliability, stability, and efficiency. To overcome the aforementioned problems of conventional PFM and hybrid control methods, the new PFM-PSM hybrid controlled CLLC resonant converter is proposed. Its operations and design considerations are firstly analyzed. Then, its performance is evaluated by simulation test.