The principle of pressure reduction of the safety capacitor

The principle of the safety capacitor buck is to limit the maximum working current by using the capacitive reactance generated by the capacitor at a certain AC signal frequency. That is, the terminal load pulls down the output voltage after the current limiting. The safety capacitor actually acts as a limiting current. And dynamically assign the role of capacitor and voltage across the load. For example, the mains power in China is 220V/50Hz, and a 1μF capacitor capacitance is about Xc=(2mfC)=1/(2×3.14×501×10-6)=3180Ω. When 220V AC voltage is applied across the capacitor, the maximum current flowing through the capacitor is approximately IC=U÷Xc=220÷3180=70mA. Knowing this calculation method, it is possible to select the safety capacitor value based on the operating current of the appliance.

When using a safety capacitor for buck, the following points can be noted:

1) The step-down capacitor must use a non-polarity capacitor. Never use an electrolytic capacitor. And the pressure resistance of the capacitor must be above 400V.

2) Capacitor buck is not suitable for dynamic loads, nor is it suitable for capacitive and inductive loads.

3) When dc operation is required, use half-wave rectification as much as possible, preferably with a suitable regulator.

4) Do not change the capacitance value arbitrarily while maintaining the electric capacity depressurizing the electrical apparatus.