New hybrid control for wide input full-bridge LLC resonant DC/DC converter

Abstract

In order to achieve low switching frequency range and high efficiency for a wide-input LLC resonant converter, a new hybrid control combining pulse-frequency modulation (PFM) and phase-shift pulse-width modulation (PS-PWM) is proposed. In the new control, the LLC converter has two operation modes, i.e PFM and PFM+PS-PWM. The new control scheme and operation principle is analyzed deeply, and then efficiency optimization can be carried out by the proposed design procedure for the resonant tank of LLC converter. Finally, a prototype is developed with input voltage range from 22V to 45V, and rated power of 250W and output voltage of 380V. The experiment shows that the peak efficiency of LLC converter reaches to 96.2%, and verifies the proposed control scheme, design.