A Mixed Modulation Strategy for DC/DC Converter in Wide Input Voltage Range

Aiming at the problem of traditional LLC resonant converters in wide input voltage range, an improved variable mode hybrid modulation strategy combining frequency modulation and asymmetric PWM is proposed. When the input voltage is lower than the switching voltage, the frequency modulation strategy is used to implement the boosting; when the input voltage is higher than the switching voltage, the asymmetric PWM modulation strategy is used to implement the step-down. In this paper, the working principle and circuit characteristics of LLC resonant DC/DC converters with two modulation strategies are analyzed in detail. Finally, the experiment results prove the correctness of the theoretical analysis and the feasibility of the circuit scheme.