Analysis and Design of Constant AC Current Output Isolated Resonant Inverter with Coupled Inductors

This article proposes a novel isolated resonant inverter with constant ac current output. Within wide load range, the proposed isolated resonant inverter can achieve low voltage stress across the switch and zero voltage turn-on. A detailed characteristics analysis of the proposed isolated resonant inverter is performed in time domain, obtaining the constant ac output, zero-voltage switching conditions and parameter design procedure. For galvanic isolation, coupled inductors are added to the proposed isolated resonant inverter to replace the input choke inductor and output filter inductor. Finally, the 13.56 MHz experimental prototype of 90.9% peak efficiency is implemented to verify the above analysis. Without closed-loop control, the protype can achieve 2 A ac constant output when the load varies from 1 and 30 Ω.