Three Noise Elimination Circuits

As shown in Figure a, a commonly used anti-interference measure for electronic products is to connect two bypass capacitors from the primary side of the power transformer to the ground (chassis). When C1 and C2 are selected with small capacities, they can only bypass pulses with steep front edges and narrow widths. To overcome pulse interference with large energy, at least its fundamental wave and third harmonics need to be filtered out. , so C1 and C2 should be larger. However, it will be dangerous if the case is electrified. After experiments, connecting a 0.47~2μF (withstand voltage 500~750) capacitor to the power grid as shown in Figure b can not only eliminate interference, but also The chassis will be charged, which is very beneficial to protect the safety of people and equipment. Connecting Cp to the power grid will undoubtedly play a positive role in improving the power factor of the power grid. In order to make Cp fully play its role, it can be connected to the power grid at the entrance of the home. The upper end of the knife gate S, as shown in Figure c.