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Common-Mode EMI Noise Reduction for Interleaved Multichannel GaN-Based PFC Converter

CM noise
Fig. 1. Measured common mode noise compare for cases without balance and with balance in the MHz GaN-based totem-pole PFC
  By adopting a GaN device in power factor correction (PFC) con- verters, switching frequency can be increased up to the MHz range, with dramatic improvement in power density and without costing efficiency. Furthermore, the inductor value is reduced dramatically with more opportunities to integrate PCB windings into magnetics. With a PCB-based winding structure, opportunities for high-frequency EMI common-mode (CM) noise reduction, previously inconceivable due to the uncontrollable equivalent parallel capacitor (EPC) and equivalent parallel resistor (EPR), is possible to be realized with a balance technique.
  To enhance the high-frequency balance in a PFC converter, a novel PCB winding structure with an integrated coupled inductor is proposed. A CM-noise model and balance conditions for minimizing CM noise is derived. Moreover, ground loop impacts for high-frequency noise are studied.
  A two-phase, interleaved totem-pole PFC converter with GaN device (1-3 MHz switching frequency) is built up to verify the pro- posed balance inductor structure. Two balance inductors are introduced in the return path for CM noise reduction. All four of the in- ductors in the PFC circuit are integrated into a single EI magnetic core with six layers of PCB windings. Experimental results show that balance conditions are achieved in the whole interested frequency range (150 kHz–30 MHz) with 20 dB uniform CM noise reduction. At the same time, resonant frequency due to ground loop is increased beyond 30 MHz so that the ground loop impact in the interested frequency range is eliminated.
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