A dual-loop voltage control for optocoupler feedback in capacitive output filter converter

This paper proposes a dual-loop voltage control for optocoupler feedback in capacitive output filter converter to mitigate the detrimental effect of the optocoupler on regulation performance. The dual-loop consists of primary-side regulation (PSR) loop and reference voltage correction loop. PSR loop performs output voltage regulation with indirectly sensed output voltage across tertiary winding of transformer, while reference voltage correction loop generates accurate reference voltage of PSR loop based on actual output voltage and transfers the signal through optocoupler. As a result, it is possible to achieve precise output voltage regulation and non-degraded system performance simultaneously. The design considerations for the proposed method are presented. Experimental results with a 288-W half-bridge LLC resonant converter verify the feasibility of the proposed method.