T02.7 - Design Method of Impedance Transformation Network for Robust Resonant Power Converters with Wide Load Impedance Variation

The output performance of resonant power converters is affected by the load impedance variations. This paper proposes a design method for an impedance transformation network that achieves the robustness of a resonant power converter across a wide load impedance variation range. An impedance conversion characteristic of a general two-port passive network is utilized. Thus, the proposed design method does not require case studies of several resonant network topologies. It enables the design of impedance transformation networks that satisfy various industry-required robust properties, such as constant current (CC), constant voltage (CV), and constant power (CP). Experimental results from 3.3-kW, 150-kHz DC-DC converter prototypes with CP capability validate the feasibility and the effectiveness of the proposed method. The prototype system can deliver a constant output power over a twofold output voltage variation, from 400-V to 800-V, with only 10% of input voltage variation, from 415-V to 450-V. The peak efficiency is shown as 95.2 % with the lowest output DC voltage.