A soft-switching coupled inductor bidirectional DC–DC converter with high-conversion ratio

Design and Implementation of a Soft-Switching Converter With High Step-Up Ratio

“…9; at this time, the resonance inductor current i Lr has risen to I Lm1 − I Lm2 and the auxiliary switch S 1r maintains conducted, the resonance inductor current i Lr will continue to increase gradually, and the resonance capacitor C r begins discharging, thus the resonance inductor L r and the resonance capacitor C r form a resonance trough. The circuit equation of this mode is represented in (12), where v Cr (t) and i Lr (t) as in ( 13) can be solved from (12), and the resonance impedance Z o and the angular resonance frequency ω o can be represented in (14). When the resonance capacitor voltage v Cr reduces to zero, at this time ω o (t − t 1 ) = π 2 , therefore, the resonance inductor current i Lr and auxiliary switch current i S1r can be derived from ( 13) to arrive at (15); the operating time of the operating mode can also be derived as shown in ( 16) from (13), then the body diode of the main switch S 1 will begin conduction and enter Mode 3.…”

“…For traditional hard-switching DC-DC converters [5], [6], the conversion efficiency is low, the voltage step-up ratio is low, and the switching stress of the power switch is large. Although they can be combined with the soft-switching technique [7], [8], [9], [10], [11], [12], [13], [14] so that they have benefits of fewer circuit components, simpler structure, and ease of control while increasing the conversion efficiency, however, since power switch operation is bounded by the normal duty cycle, the voltage conversion ratio is limited. Furthermore, when higher DC voltage output is needed, the switch component needs to work under a greater duty cycle, but the greater duty cycle will cause the current which passes through the power switch to increase, which may lead to burn-out due to overheating if the power switch is operated for extended time under high duty cycle.…”