Capacitor resistance and voltage reduction principle (II)

When using this circuit, the following things need attention:

(1) Is not isolated from 220V AC high voltage, please pay attention to safety and prevent electric shock!

(2) The current-limiting capacitor must be connected to the line of fire, and the withstand voltage should be large enough (greater than 400V). It should also be added with a series of surge-proof surge resistors and a discharge resistor.

(3) Pay attention to the power consumption of the Zener tube, and it is strictly prohibited that the Zener tube should be disconnected.

2. Capacitive buck power supply converts AC to low voltage DC

The operating principle of the capacitor buck is not complicated. His working principle is to limit the maximum operating current by using the capacitive reactance generated by the capacitor at a certain frequency of the AC signal. For example, a capacitance of 1uF produces a capacitive reactance of about 3180 ohms at 50Hz power frequency. When 220V AC voltage is applied across the capacitor, the maximum current flowing through the capacitor is approximately 70mA. Although the current flowing through the capacitor is 70mA, no power is dissipated in the capacitor. It should be that if the capacitor is an ideal capacitor, the current flowing through the capacitor is the imaginary current, and the work done by it is reactive power. According to this feature, if we connect a resistive element in series with a 1uF capacitor, the voltage across the resistive element and the power dissipation it generates will depend entirely on the characteristics of the resistive element.