Safety capacitors are used in situations where the capacitor fails, which will not cause electric shock and endanger personal safety. It includes x capacitor and y capacitor. X-capacitor is a capacitor connected across two lines (L-N) of the power line, and metal film capacitor is generally selected; Y capacitors are capacitors connected between the power line and the ground (L-E, N-E) respectively, and generally appear in pairs. Due to the limitation of leakage current, the value of Y capacitor should not be too large. Generally, the X capacitance is uF level and the Y capacitance is nF level. X capacitor suppresses differential mode interference, and Y capacitor suppresses * * * mode interference.