Switching power supply circuit is mainly composed of fuse, thermistor, mutual inductance filter, bridge rectifier circuit, filter capacitor, switching oscillation integrated circuit, switching transformer and so on. A thermistor is usually added after the fuse to limit the current. The mutual inductance filter is made of two groups of coils symmetrically wound, and its function is to eliminate the interference pulse of the external circuit into the circuit through the mutual inductance effect, and the pulse signal in the circuit will not radiate interference to the power grid.
