This paper introduces a low-power non-isolated step-up hybrid quasi-resonant converter and a complementary mixed-signal controller, capable of producing conversion ratios exceeding 50x, while maintaining relatively high power processing efficiency. At low power levels, from a fraction of a watt to few watts, conventional ultra-high step-up solutions operate at efficiency not exceeding 45%, mostly limited by switching losses, the introduced solution exhibits efficiencies exceeding 70%. The improvements are obtained by modifying the previously reported fully soft-switching quasi-resonant boost converter and strategically incorporating a charge pump in the circuit. The solution exhibits load-independent soft-switching for all the active switches, at all voltage-conversion ratios. The soft switching is achieved by utilizing a small flying capacitor that is fully charged and discharged, resonantly with the inductor. The operation and performance are experimentally verified with a discrete prototype with input voltage of 3.6 V, common high output voltages of 55 V, 80 V, 105 V, 150 V, 200 V and 250 V, and load currents ranging from 1 mA to 20 mA.
