Existing Y-capacitor-free electromagnetic interference (EMI) filter design methods suffer from large volume and high cost. To achieve miniaturization

this study focuses on the Y-capacitor-free EMI filter of the PFC+QR flyback circuit. Based on the analysis of noise transmission mechanism

a mathematical model of insertion loss for the Y-capacitor-free EMI filter considering high-frequency parasitic parameters and noise source internal impedance is established. It is clarified that the noise source internal impedance

common-mode inductor

and coupling coefficient of differential-mode inductor are the key factors affecting the insertion loss characteristics of the Y-capacitor-free EMI filter. Drawing on the insertion loss mathematical model

through the coordination analysis of differential and common-mode filtering capabilities

a Y-capacitor-free EMI filter design method based on optimization of the common-mode noise-source internal impedance combined with magnetically integrated differential-mode inductor is proposed

and the design criteria for the magnetically integrated differential-mode inductor are given. Finally

experimental results verify that the proposed EMI filter design method can effectively achieve the miniaturization of the Y-capacitor-free EMI filter.