A High Conversion Ratio Quasi-Resonant Flying Capacitor DC-DC Converter

A new single-stage wide-range DC-DC converter topology that is well suited for emerging high step-down low-power applications is presented. The topology fully utilizes the energy stored in the flying capacitor thus minimizing its size compared to other flying capacitor-based solutions. Depending on the load value, the converter can operate in either continuous or discontinuous inductor current conduction while providing soft switching. These advantages are achieved by having a discontinuous voltage across the flying capacitor. It is charged from zero to the full input voltage. Thus, the switching losses, which are the largest contributors to the overall losses in high step down low current applications, are minimized.The effectiveness of this single-stage converter is verified with an experiment silicon-based prototype, providing up to 6.5 A of current at the output and operating with various conversion ratios. For operations at 48V-5V, 48V-3.3V, 48V-1V and 24V-1V the topology achieves a peak efficiency of 92%, 90%, 84% and 88%, respectively. In the targeted low power range, and to the best of our knowledge, the efficiency of the introduced topology is comparable to the arguably most efficient single-stage GaN based solutions [1], without a penalty paid in the overall volume of the converter.