Common Mode Noise Reduction for an LLC Resonant Converter by Using Passive Noise Cancellation

Abstract

This paper describes the application of a passive noise cancellation method to a prototype inductor-inductor-capacitor (LLC) resonant converter by placing a compensation winding in a transformer to reduce common mode noise. The connection method for the compensation winding is investigated. A circuit analysis is implemented for the displacement currents between the primary and secondary windings in the transformer. The analyzed displacement currents are verified by performing a circuit simulation and a proper compensation winding connection that reduces common mode noise is found. The measurement results show that common mode noise is reduced effectively up to 20 dB in the 1 to 7 MHz frequency region for the prototype LLC resonant converter by using the proposed passive noise cancellation method. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ⓒ

Design Considerations of Resonant Network and Transformer Magnetics for High Frequency LLC Resonant Converter

“…Generally, the primary and secondary windings of the LLC resonant converter are separated to obtain large and controllable values of the leakage inductance for low switching frequency as shown in Fig. 9 (a) [23]. However, for the high frequency operation such as 500 kHz, the winding structure should be changed because a leakage inductance in the LLC resonant converter is much smaller than the case of low frequency.…”