Capacitor resistance and voltage reduction principle (I)

Current supply

This type of circuit is often used to obtain non-isolated, low-current power at low cost. Its output voltage can usually be in the range of several volts to three tens of volts, depending on the Zener regulator used. The amount of current that can be supplied is proportional to the current limit

Capacitance capacity. When using half-wave rectification, the current (average) per microfarad capacitor is: (International Standard Unit)

I(AV)=0.44*V/Zc=0.44*220*2*Pi*f*C

=0.44*220*2*3.14*50*C=30000C

=30000*0.000001=0.03A=30mA

0.44: Mean coefficient of half-wave rectification

F: power frequency unit HZ;

C: capacitor capacitance unit F farad;

V: power supply voltage unit volts V;

Zc = 2 * Pi * f * C: impedance resistance unit ohms.

If you use full-wave rectification, you can get double the current (average) as:

I(AV)=0.89*V/Zc=0.89*220*2*Pi*f*C

=0.89*220*2*3.14*50*C=60000C

=60000*0.000001=0.06A=60mA

In general, the full-wave rectification of this kind of circuit is slightly larger, but because of floating, stability and safety are worse than those of half-wave rectification, so it is less.