A Novel Dual-Bridge LLC Resonant Converter with Wide Range of Low Input Voltage

Abstract

A dual-bridge (DB) LLC resonant converter for dc/dc conversion with a wide range of low input voltage is proposed in this paper. The proposed converter front stage is based on switch integration technique, integrating the buck-boost converter at the front stage with the full-bridge (FB) LLC and half-bridge (HB) LLC as a new single stage DB LLC. Since the front buck-boost converter allows the DB LLC resonant converter to obtain a greater input voltage, thus the transformer turns ratio increases to lower the resonant current value, the primary conduction loss. In addition, the design of the magnetizing inductance can be maximized. Furthermore, the DB LLC resonant converter uses different phase-shift modulation gains MD at different input voltages to easily achieve a wide input voltage range with only slight change in frequency. Finally, different actual duty ratios are provided at different light load conditions to achieve minimum power loss. Therefore, the prosed system has high efficiencies at light load conditions and its voltage regulation is reduced. The simulated results on the proposed converter with 100V-200V DC input and 480W (24V / 20A) output is provided to verify the system performance.