Working principle of capacitive step-down(I)

    The working principle of capacitor step-down is not complicated. His principle is to limit the maximum operating current by using capacitive reactance generated by capacitors at a certain AC signal frequency. For example, at the power frequency of 50Hz, the capacitance of a 1uF produces a capacitance resistance about 3180 ohms. When the AC voltage of 220 V is applied to the two ends of the capacitor, the maximum current flowing through the capacitor is about 70mA. Although the current flowing through the capacitor is 70mA, it does not produce power consumption on the capacitor. If the capacitor is ideal, the current flowing through the capacitor is a virtual, and the work it does is useless. According to this characteristic, if we connect a resistive element in series on a capacitor of 1uF, the voltage at both ends of the resistive element and the power consumption generated by the resistive element depend entirely on the characteristics of the resistive element. For example, we connect a 110V/8W bulb with a 1uF capacitor, and on the AC voltage to the 220V/50Hz, the light bulb is lit up with normal brightness without burning. Because the current required for the 110V/8W bulb is 8W / 110V / 72mA, it coincides with the current limiting characteristics generated by the 1uF capacitor. In the same way, we can connect the 5W/65V bulb in series with the 1uF capacitor to the alternating current of the 220V/50Hz, and the bulb will also be lit and not destroyed. Because the working current of the 5W/65V bulb is about 70mA.