Analysis and Suppression of Common Mode Interference in Flyback Switching Power Supplies

Abstract

In the flyback power supply, with the increase of switching frequency, the electromagnetic interference caused by the power switch becomes more and more serious. In order to control the interference problem, the common mode (CM) interference noise source and transmission path of the flyback power supply are analyzed, the equivalent model of the transmission path is established, and the parameters affecting the common mode noise magnitude are deduced. On this basis, an active gate driver (AGD) circuit is proposed to suppress the noise generated by interference sources. The AGD circuit reduces the du/dt of the power switching tube by reducing the driving current during the turn-off dynamic period and thus achieves the reduction of the common-mode noise. Compared with traditional drive mode, the AGD can increase switching losses less at the same target. Finally, the feasibility of the AGD method is verified by experiments on the test platform.