LLC resonant converter utilizing a step‐gap transformer structure for holdup time improvement

Summary This letter presents a current‐controlled variable magnetizing inductance of transformer for further improving the holdup time on half‐bridge LLC converter. When the input voltage is failed, the magnetizing inductance of transformer can be decreased sharply; therefore, the LLC converter holdup time can be improved without adding additional auxiliary circuit. The mathematic model between magnetizing inductance and step‐gap structure of transformer is proposed, and the benefit effects using this step‐gap structure of transformer have been verified in this letter. Finally, a 180‐W, LLC converter utilizing step‐gap structure of transformer has been achieved, and detailed analysis and design of the proposed step‐gap structure are described. This letter presents a current‐controlled variable magnetizing inductance of transformer for further improving the holdup time on half‐bridge LLC converter. When the input voltage is failed, the magnetizing inductance of transformer can be decreased sharply; therefore, the LLC converter holdup time can be improved without adding additional auxiliary circuit. The mathematic model between magnetizing inductance and step‐gap structure of transformer is proposed, and the benefit effects using this step‐gap structure of transformer have been verified in this letter. Finally, a 180‐W, LLC converter utilizing step‐gap structure of transformer has been achieved, and detailed analysis and design of the proposed step‐gap structure are described