Light-load efficiency improvement strategy for LLC resonant converter utilizing a step-gap transformer

An inductance-based control strategy, for further optimize parameter design which is conducted through inductance adaptive variation on LLC resonant converter, is proposed. A simple switch concept is applied to set the desired magnetizing inductance, the main control factor, to achieve light load efficiency improving and overall required switching frequency range narrowing. Evaluation for showing the enhancement effect of this control method is verified theoretically in a deriving mathematic model based on the relation between magnetizing inductance and air gap of LLC transformer. Two platforms using LLC resonant converter demonstrates the effectiveness of this control strategy experimentally.