Fully Soft-Switching Flying Capacitor Based Quasi-Resonant Boost Converter

A quasi-resonant converter and a complementary mixed-signal controller suitable for low-power step-up applications are introduced. The converter has the same structure as a 3-level flying capacitor boost but operates in a different manner achieving soft switching on all transition edges, thus having flat and high efficiency curve. The advantages are obtained by fully charging/ discharging the flying capacitor as a resonant element through a specific control technique ensuring proper timing. The operation is verified with an experimental prototype with $V_{in}\in[3V,\ 5V], V_{out}\in[12V,\ 18V], I_{load}\in[10mA, 200mA$ and $f_{sw}\in[10kHz, 200kHz]$, demonstrating flat efficiency curves of up to 89.2%.