Efficiency-Optimized Current-Source Resonant Converter for USB-C Power Delivery

This paper presents a resonant dc-dc converter capable of providing load-independent output current without the need for active current control. This converter comprises an LC
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L resonant tank, with inductance and capacitance values selected based on a new design methodology that achieves two objectives: 1) the converter’s output current is independent of its output voltage, and 2) the resonant tank losses are minimized. The design methodology is based on minimizing inductive energy storage to improve the power conversion efficiency. This design methodology makes the converter suitable for applications that require constant current over a wide range of output voltages, such as USB-C power delivery (PD) based battery charging. An efficiency-optimized current-source LC
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L converter prototype operating from 20-V input and delivering 6 A current with USB-C PD output voltages in the range from 5 V to 15 V is designed, built and tested. The prototype achieves a peak efficiency of 92%, maintains >87% efficiency over the entire output voltage range, and is also shown to have >10% lower losses compared to a conventionally designed prototype. A loss breakdown demonstrates how reduced inductive energy storage results in lower system losses.