There are two ways to make DC power supply
- Linear
- Switching
Linear Power Supply
Continous control of voltage is done at any instance of time. It uses a pass transistor with an error amplifier to regulate the voltage supply.
example: 7805, 7905, LM317 etc
Switching Power Supply
It also uses the pass transistor along with an inductor and a capacitor to store the energy and release the energy. By controlling the switching of the pass transistor, the Voltage is regulated. It is more complex than the linear power supply.
The advantage of switching is that the transformer size gets reduced. Which reduced the cost of the power supply. The Reduced size also reduced the weight; which further increases the portability of the power supply.
I am using a step-down transformer. Which transformer 220V 50Hz AC to 12 Vrms AC.
The Vrms is converted to Vdc which is dc equivalent voltage.
So, 12 Vrms = 12 x 1.414 Vdc
= 16.968 (approx.) Vdc
this Vdc is passed through the bridge rectifier which drops 1.5V to 1.8V
= 16.968 – 1.8
= 15.168 V
which is then filtered through the Capacitor filter
C = ( I x t ) / V
I is the amount of current passing through the capacitor at maximum load.
Let I = 1A
t is the ripple time which is taken 10 mS if using 50Hz cycles.
C = [1 x 10 x 10^(-3) ] / 15.168
= 6.59 x 10^(-4) F
= 659 micro Frad
So we will use a standard capacitor that is either equal to or bigger than the above value i.e 1000uF will OK.
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