Utilizing Zero Voltage Switching for Efficiency Enhancement in Pulse Width Modulation Controlled Series Resonant Converter’s Boost Operation

Resonant converters are mainly used due to their high power density and high efficiency in electric vehicle (EV) charging systems. As the battery voltage of an EV increases from 400 V to 800 V, the wide range of power voltage of resonant converters becomes a great advantage. Among resonant converters, series resonant converters (SRCs) are widely used due to their high efficiency caused by low circulating current. However, due to the characteristics of SRC, the maximum voltage gain is 1, and high efficiency is obtained by operating at the resonance point. Therefore, if the goal is to achieve high efficiency at the resonant point, then pulse width modulation (PWM) control is required to obtain a wide output voltage range. Through the PWM control, the secondary-side full-bridge rectifier can be converted into a double-voltage rectifier to obtain double voltage gain curves. As a result, a wide output voltage range and high efficiency can be obtained simultaneously. However, in the SRC operated by PWM control, achieving zero voltage switching (ZVS) operation may be difficult due to low magnetization current circulation, which may increase switching loss and reduce converter efficiency. This study proposes a control technique to achieve full-range ZVS operation in SRC operated with PWM control for obtaining a wide output voltage range.