An Inner Phase Shift Control Scheme for the CLLC Converter

The CLLC converter is a promising topology for bidirectional power conversion applications, such as vehicle-to-grid (V2G) systems and battery energy storage systems. In these applications, a wide output voltage range is needed. However, traditional pulse frequency modulation (PFM) control is not suitable for wide output range applications because of its wide switching frequency range. In this paper, a novel inner phase shift (IPS) control is proposed for CLLC converters. By modulating the IPS angle between the primary-side bridge legs, the output voltage can be regulated with a wide variation range (voltage gain less than 1) at resonant frequency. Moreover, the primary-side zero voltage switching and secondary-side zero current switching features are also guaranteed. The proposed IPS control can replace the above resonance operation of PFM control, narrowing the switching frequency range significantly.