Question

please solve it and thank you

converting 220v Ac to 12V DC :

1. Design specification

2. Specification of each of the component used in the project

3. Transformers, Step-down transformer, transformer ac input/ ac output specifications

4. Rectifier (forward and reverse biasing diode, half wave rectifier, full wave recifier)

5. Peak Inverse Voltage, Calculation of Peak inverse voltage

6. Filter capacitor

7. Unregulated Power Supply

8. Voltage regulation using an IC 7812

9. Percent regulation with Zener diode and 7812

10. Comparison of design specification with actual result.

Answer 1

Things you need to design the circuit

1. 220/12v transformer (You can buy either 0.5A or 1 A depending upon your usage)
2. 7812 IC voltage regulator
3. IN4001 (4) silicon diodes
4. Capacitor 1000uF
5. Dot board/ bread board/ PCB board.
6. Connecting wires (As required)
7. Power chord

1. Step Down the Voltage Level

The step-down converters are used for converting the high voltage into low voltage. The converter with output voltage less than the input voltage is called as a step-down converter, and the converter with output voltage greater than the input voltage is called as step-up converter. There are step-up and step-down transformers which are used to step up or step down the voltage levels. 230V AC is converted into 12V AC using a step-down transformer. 12V output of stepdown transformer is an RMS value and its peak value is given by the product of square root of two with RMS value, which is approximately 17V.

Step-down transformer consists of two windings, namely primary and secondary windings where primary can be designed using a less-gauge wire with more number of turns as it is used for carrying low-current high-voltage power, and the secondary winding using a high-gauge wire with less number of turns as it is used for carrying high-current low-voltage power. Transformers works on the principle of Faraday’s laws of electromagnetic induction.

2. Convert AC to DC

220V AC power is converted into 12V AC (12V RMS value wherein the peak value is around 17V), but the required power is 12V DC; for this purpose, 17V AC power must be primarily converted into DC power then it can be stepped down to the 12V DC. But first and foremost, we must know how to convert AC to DC? AC power can be converted into DC using one of the power electronic converters called as Rectifier. There are different types of rectifiers, such as half-wave rectifier, full-wave rectifier and bridge rectifier. Due to the advantages of the bridge rectifier over the half and full wave rectifier, the bridge rectifier is frequently used for converting AC to DC.

Bridge rectifier consists of four diodes which are connected in the form a bridge. We know that the diode is an uncontrolled rectifier which will conduct only forward bias and will not conduct during the reverse bias. If the diode anode voltage is greater than the cathode voltage then the diode is said to be in forward bias. During positive half cycle, diodes D2 and D4 will conduct and during negative half cycle diodes D1 and D3 will conduct. Thus, AC is converted into DC; here the obtained is not a pure DC as it consists of pulses. Hence, it is called as pulsating DC power. But voltage drop across the diodes is (2*0.7V) 1.4V; therefore, the peak voltage at the output of this retifier circuit is 15V (17-1.4) approx.

3. Smoothing the Ripples using Filter

15V DC can be regulated into 12V DC using a step-down converter, but before this, it is required to obtain pure DC power. The output of the diode bridge is a DC consisting of ripples also called as pulsating DC. This pulsating DC can be filtered using an inductor filter or a capacitor filter or a resistor-capacitor-coupled filter for removing the ripples. Consider a capacitor filter which is frequently used in most cases for smoothing.

We know that a capacitor is an energy storing element. In the circuit, capacitor stores energy while the input increases from zero to a peak value and, while the supply voltage decreases from peak value to zero, capacitor starts discharging. This charging and discharging of the capacitor will make the pulsating DC into pure DC.

4. Regulating 12V DC into 12V DC using Voltage Regulator

15V DC voltage can be stepped down to 5V DC voltage using a DC step-down converter called as voltage regulatorIC7805. The first two digits ‘78’ of IC7812 voltage regulator represent positive series voltage regulators and the last two digits ‘12’ represents the output voltage of the voltage regulator.the ic7812 is shown below..