Transformerless Power supply | AC to DC Power supply | How to make 12 volt dc power supply

Transformerless Power supply requirements and capacitor selection:

  

Below is the table for output current and output voltage (without the Load), of different values of X-rated capacitors:

Capacitor Code	Capacitor value	Voltage	Current
104k	0.1 uF	4 v	8 mA
334k	0.33 uF	10 v	22 mA
474k	0.47 uF	12 v	25 mA
684k	0.68 uF	18 v	100 mA
105k	1 uF	24 v	40 mA
225k	2.2 uF	24 v	100 mA

Selection of voltage dropping capacitor is important, it is based on Reactance of Capacitor and  the amount of current to be withdrawn. The Reactance of the capacitor is given by below formula:

X = 1 / 2¶fC

X = Reactance of Capacitor

f = frequency of AC

C = Capacitance of X rated capacitor

We have used 474k means 0.47uF capacitor and frequency of AV mains is 50 Hz so the Reactance X is:

X = 1 / 2*3.14*50*0.47*10-6 = 6776 ohm (approx)

Now we can calculate the current (I) in the circuit:

I = V/X = 230/6775 = 34mA

So that’s how the Reactance and Current is calculated.