Design considerations of asymmetric step-up/down dual-resonator charger for lithium-ion battery applications

In Lithium-ion battery charging applications, wide step-up/down voltage gain range converters are commonly used. The resonant frequency ratio and quality factor can seriously affect the switching frequency range and voltage gain characteristics of the step-up/down dual-resonator converter. Therefore, combined with two asymmetric voltage gain cases, by matching the appropriate resonant frequency ratio and minimum quality factor, the required step-up and step-down voltage gain range can be achieved in a specific frequency range above the critical resonance point. On the basis of the impacts and issues, a comprehensive design method is proposed in this paper for improving the voltage gain characteristics and switching frequency range utilization in asymmetric wide conversion range lithium-ion battery charging applications. Moreover, a prototype with 20 V​ input to 10–60 V output is built and tested to verify the proposed design method.