Analysis for LLC Resonant Converter Considering Parasitic Components at Very Light Load Condition

Abstract

The LLC resonant converter has a critical problem that the output voltage cannot be regulated at very light load condition, although switching frequency is widely changed. This letter proposes time domain analysis considering parasitic components at very light load condition. Based on the proposed analysis, the essential reason of the regulation problem of the LLC resonant converter at very light load condition is described and the clear solution is suggested. To confirm the validity of the proposed analysis, the experimental results with 200 W prototype is presented.