Analysis of the Anti - high - frequency Interference Circuit of Safety Capacitor

Safety capacitor is divided into X capacitor and Y capacitor, they are used for EMI / RFI suppression. EMI (Electro Magnetic Interference) for electromagnetic interference, RFI (Radio Frequency Interference) means radio frequency interference. As shown in Figure 5-36 is the X capacitor and Y capacitor application circuit, which is 220V AC switching power supply input circuit, also known as transient filter circuit, or EMI filter. R1 in the circuit for the varistor, L1 and L2 is the ferrite coil, F1 for the fuse. Figure 5-37 shows the switching power supply in the X capacitor and Y capacitor physical map.

EMI filter function explanation

EMI filter set in the 220V AC line between the incoming and rectifier circuit, used to filter out the city power grid voltage transients and high frequency interference, but also to prevent switching power supply in the high-frequency interference generated by the switch to the city grid , The formation of high-frequency interference with other electrical appliances.