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This article proposes a highly efficient current-fed half-bridge resonant converter over a wide range of the output voltages. By adding a bidirectional switch across center nodes of the voltage doubler and applying corresponding switching modulation, the converter accomplishes almost zero-voltage switching at the turn-off instant under the wide output voltage variations. Moreover, the circuit experiences very little instantaneous reactive current even when the output voltage varies widely. Primary-side duty cycle fixed at 0.5 balances the voltages across the capacitors at the primary side and at the secondary side each irrespective of the output voltage variation; it also limits the voltage stress at the active power components. Therefore, the proposed converter delivers high efficiency and compact component size. We fabricated a 400-W experimental prototype to validate the superior properties of the proposed converter. [ABSTRACT FROM AUTHOR]

This article presents a bidirectional soft-switching push–pull resonant converter that is highly efficient over a wide range of battery voltages. It is derived by integrating a current-fed push–pull circuit and an active voltage doubler circuit with a bidirectional switch. The converter operates as a pulsewidth modulation (PWM) current-fed push–pull resonant-boost converter in the forward direction, but as a PWM half-bridge resonant converter in the backward direction. The most attractive feature of the proposed converter is that, by employing the bidirectional switch and corresponding switching modulation, it can achieve almost ZVS at turn-off instants under wide variations of battery voltages. Therefore, the proposed converter achieves high efficiency even during high-frequency operation. Moreover, no instantaneous reactive current flows through the circuit under wide variations of battery voltages and loads. Furthermore, the proposed bidirectional resonant converter has a high conversion ratio in both power flow directions without using a transformer that has high turns-ratio. The operating principles and characteristics of the proposed bidirectional resonant converter are presented in detail. Experimental results using a 1-kW prototype verified the feasibility and efficiency of the proposed converter. [ABSTRACT FROM AUTHOR]