Low Common Mode Noise Half-Bridge LLC DC–DC Converter With an Asymmetric Center Tapped Rectifier

Half-bridge LLC dc-dc converter is popular in electric vehicle on-board charger due to its soft switching, high-power density, and low cost. But, it also has serious electromagnetic interference problems in that the half-bridge structure brings asymmetry common mode (CM) noise source by switching. So, this letter proposes an asymmetric center tapped rectifier (ACTR) to reduce the CM noise in half-bridge LLC without additional components. With ACTR, the CM noise source on primary winding is cancelled by CM noise sources on secondary windings. The CM noise reduction of the proposed ACTR is verified by a 1.1-kW half-bridge LLC prototype with 800 V input and 300-450 V output.