Low-cost EMC (Electro Magnetic Compatibility) circuit and system for suppressing switching power supply

The utility model discloses a low-cost EMC circuit and system for suppressing a switching power supply, and relates to the field of switching power supplies, the low-cost EMC circuit comprises a circuit unit 1 and a circuit unit 2, the circuit unit 1 comprises a two-stage filter circuit composed of LF1, CX1 and LF2 for suppressing electromagnetic interference of alternating current input, a common mode inductor LF1 is connected with a common mode inductor LF2, the common mode inductor LF1 is connected to a zero line end N and a live line end L, and the zero line end N is connected with a power line end L; and a capacitor CX and a capacitor CX1 are sequentially connected between the common mode inductor LF1 and the common mode inductor LF2. The LF1, the CX1 and the LF2 in the circuit unit 1 form a two-stage filter circuit to suppress electromagnetic interference of alternating current input; common-mode interference is suppressed through a filter circuit composed of CY1, CY2, R2, CY3 and CY4 in the circuit uni