The embodiment of the invention discloses an active EMI (Electro-Magnetic Interference) filter. The active EMI filter comprises an auxiliary source circuit, a current detection circuit, an inverse amplifying circuit, a
noise injection circuit, a differential mode
capacitor and a differential mode
inductor, wherein the earth impedance of a
positive power line and the earth impedance of a
negative power line are different; the differential mode
capacitor is connected between the
positive power line and the
negative power line; the differential mode
inductor is connected on the power line with higher earth impedance in the
positive power line and the
negative power line; one end of the differential mode
inductor is connected to the connected node of the auxiliary source circuit and the power line, and the other end of the differential mode inductor is connected to the connected node of the differential mode
capacitor and the power line. The differential mode capacitor can enlarge the impedance for the power line with higher earth impedance, so that more low-frequency common-mode
noise circuits are merged to the power line with lower earth impedance through the differential mode capacitor. The embodiment of the invention further discloses a
power management device, and the
power management device comprises the active EMI filter. Through the adoption of the active EMI filter and the
power management device, the filtering effect for low-frequency common-mode
noise current can be enhanced, and the stability of the active EMI filter is improved.