20-09-2013, 04:26 PM
5V DC POWER SUPPLY
POWER SUPPLY.docx (Size: 15.28 KB / Downloads: 65)
INTRODUCTION
A 220v ac to 12-0-12v transformer is used and for rectification, four diodes IN4007 are connected for rectification of the step down ac supply. Filter capacitor of 1000 is used. It is regulated to +5v using a regulator 7805
DESCRIPTION:-
Transformer:-
A bridge rectifier coupled with a step down transformer is used for our design. The voltage rating of transformer used is 0-12V and the current rating is 500mA. When AC voltage of 230V is applied across the primary winding an output AC voltage of 12V is obtained. One alteration of input causes the top of transformer to be positive and the bottom negative. The next alteration will temporarily cause the reverse.
Rectifier:-
In the power supply unit, rectification is normally achieved using a solid state diode. Diode has the property that will let the electron flow easily at one direction at proper biasing condition. Bridge rectifiers of 4 diodes are used to achieve full wave rectification. Two diodes will conduct during the negative cycle and the other two will conduct during the positive half cycle.
Filtering unit :-
filter circuit which is usually a capacitor acts as a surge arrester always follows the rectifier unit. This capacitor is also called as a decoupling capacitor or a bypass capacitor, is used not only to short the ripple with frequency to ground but also leave the frequency of the DC to appear at the output.
Regulators:-
The voltage regulators play an important role in any power supply unit. The primary purpose of a regulator is to aid the rectifier and filter circuit in providing a constant DC voltage to the device. Power supplies without regulators have an inherent problem of changing DC voltage values due to variations in the load or due to fluctuations in the AC line voltage. With a regulator connected to DC output, the voltage can be maintained within a close tolerant region of the desired output. IC 7805 regulator is used in this project for providing a DC voltage of +5V