A Study of 220 V AC - 5V DC Converter Sabrina Chowdhury

Department of EEE, Ahsanullah University of Sciene And Technology, Dhaka, Bangladesh. E-mail : Sabrina.chowdhury29@gmail.com

Abstract — AC-DC converters are widely used in industrial and domestic applications. Input AC voltage is rectified andfiltered using filtering circuit which consists of large electrolytic capacitors. These capacitors draw a largeamount of current and the efficiency of the converter system decreases drastically. large ripple factor have made the converter system inefficient .This paperanalyses about different converter topology and proposes a different design which is based on converting Ac signal to specified Dc signal of about 5V by which ripple factor can be reduced to make the system enough efficient. The implification of this project is for charging or operating semiconductor devices .The results of respective topologies are shown through P-simulation program with integrated circuit emphasis (PSPICE) simulation and theirparameters are calculated. Three parameters are considered for the comparison of these topologies.

Keywords— Bridge Rectifier, Rectification, Filtering, Zener Diode, Transformer, Ripple Voltage.

I. INTRODUCTION

This Paper analyses about different converter topology and different design which is based upon converting AC signal to specified Dc signal. Regarding the quality of the current waveform, pure sinusoidal waveforms are best butthat usually cost very high. So there are the so called “single stage converters” that offer many advantages, which composed of a diode bridge and filters. The general supplied voltage is 220V AC which is above the limit rating of the semiconductor devices. Due to the characteristics of semiconductor devices, we need DC voltage to operate or charge it. Hence, we need to convert the AC voltage to particular DC voltage in which range the device will be able to take it. We converted to 5V DC as we would use it as a mobile phone charger.

The four steps which were taken are charted below:

II. 220V AC-5V DC CONVERTER SYSTEM PROCEDURE TABLE I Specification of the components

A. USING TRANSFORMER

We used a shell type step down transformer with specific rating in this project to transform the voltage level from 220V AC to around 12V AC maintaining the same frequency.

Input: 220V~50Hz Output:12V~1000mA

We used the transformer to confirm safety because 220V AC is a human hazard.

B. RECTIFICATION

Serial no.

Components Specification Quantity

1. p-n junction diode

1N4007 4 piece

2. Resistor 1KΩ,2KΩ 1 piece each

3. Capacitor 1000uF 1 piece4. Zener Diode 5 volts 1 piece5. AC supply 220V~50 Hz6. Transformer I/P:220V~50 Hz

O/P:12*12V~1000 mA

1 unit

7. LED(Red) 1.8 volts 1 piece8. Bread Board 1 unit9. Chords and

wires10. Digital

Multimeter1 unit

The second obligatory step of converting the AC signal to DC signal is rectification. Rectification is a process through which we can get a one way signal .There are two types of rectification-half wave and a full wave rectification. We used a diode bridge rectification process to get a half wave output for the better performance.

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current (AC) input into a direct current (DC) output, it is known as a bridge rectifier . A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a shell type transformer

While one set of diodes is forward biased the other set is reverse biased and effectively eliminated from the circuit. For both positive and negative swings of the transformer, there is a forward path through the diode bridge. Both conduction paths cause current to flow in the same direction through the load resistor, accomplishing full-wave rectification.

In this model the output voltage will be 0.636 times if output peak voltage.

In this model the output voltage will be 0.636 times if output peak voltage.From the measurement,

¿0.636 × (18.625−1.4 ) V ¿10.95 V ≈ 10.94 V We got this 10.94V experimentally from the circuit.Its called the rectified unfiltered voltage which is quite near to the DC signal.

C. FILTERING

In this step Filtering is done to make the output signal smoother. For many applications, especially with single phase AC where the full-wave bridge serves to convert an AC input into a DC output, the addition of a capacitor may be desired because the bridge alone supplies an output of pulsed DC.

The function of this capacitor, known as a reservoir capacitor (or smoothing capacitor) is to lessen the variation in (or 'smooth') the rectified AC output voltage waveform from the bridge. There is still some variation, known as "ripple". One explanation of 'smoothing' is that the capacitor provides a low impedance path to the AC component of the output, reducing the AC voltage across, and AC current through, the resistive load. In less technical terms, any drop in the output voltage and current of the bridge tends to be cancelled by loss of charge in the capacitor. This charge flows out as additional current through the load. Thus the change of load current and voltage is reduced relative to what would occur without the capacitor. Increases of voltage correspondingly store excess charge in the capacitor, thus moderating the change in output voltage / current.

The capacitor and the load resistance have a typical time constant τ = RC where C and R are the capacitance and load resistance respectively. As long as the load resistor is large enough so that this time constant is much longer than the time of one ripple cycle, the above configuration will produce a smoothed DC voltage across the load.

The ripple voltage is inverse proportional to the value of the capacitor. The equation for calculating the value of the capacitor is given below:

Vripple=VrectifiedfRC

⋯⋯⋯⋯(1)

According to the equation if we want to lessen the ripple voltage,we have to put a larger value of the capacitor.

We assumed the ripple voltage to be 0.0729V. Hence we got the value of 1000uF of the capacitor.

The calculation is given below:-

Vrectified=10.94 V

f =50 Hz

R=¿3K

∴C= 10.9450 ×3×1000 ×0.0729

F

=1000uF

Here in this project we used a 1000uF smoothing capacitor to get a smooth output DC signal voltage.

D. REGULATION

After filtering we did regulation in this project to get a specific voltage after filtering. A Zener diode is used here to regulate the circuit to give 5V DC output signal voltage. Zener Diode is a general purpose diode, which behaves like a normal diode when forward biased. But when it is reverse biased above a certain voltage known as zener breakdown voltage or zener voltage or avalanche point or zener knee voltage the voltage remains constant for a wide range of current. The purpose of a voltage regulator is to maintain a constant voltage across a load regardless of variations in the applied input voltage and variations in the load current.

The function of a regulator is to provide a constant output voltage to a load connected in parallel with it in spite of the ripples in the supply voltage or the variation in the load current and the zener diode will continue to regulate the voltage until the diodes current falls below the minimum IZ(min) value in the reverse breakdown region. It permits current to flow in the forward direction as normal, but will also allow it to flow in the reverse direction when the voltage is above a certain value - the breakdown voltage known as the Zener voltage.

We found some limitations in the regulation of the circuit which is given below-

i. Load Range.ii. Current Range

iii. Input voltage Range In spite of doing the project properly through rectification, filtering and regulation, It couldn’t be able to exceed the limitations. Lastly we got 4.90V as an output DC signal voltage.

III. SIMULATION IN PSPICE

We simulated the circuit using Pspice to show the voltage signal curve across the capacitor,which was almost DC signal.We also showed the curve across the zener diode.It was around 5.0013V.

The simulated circuit along with the curves are given below:

IV. ASSUMPTIONS AND EXTRAS

a) We assumed that the input voltage of the circuit is the peak voltage.

b) We used LED in series with the zener diode to get the indication of current flow.

c) As the resistance of the LED was unknown, we measured the current of the branch and then the voltage across the LED to get the resistance of it.

d) We assumed the ripple voltage be 0.0729V to get the value of an available capacitor.

V. LIMITATIONSa) A zener diode voltage depends on the load in

parallel with it. so there is a maximum and minimum range of the load.

b) The zener diode voltage also depends on the value of the resistance in series with it, which was used to limit the current flow.

c) A higher value of the capacitor was used, it took a bit time to discharge fully after being switched off.

d) The input voltage range acts an important role to give a constant voltage output across the zener diode. If this range exceeds, the constant voltage rises or fall.

VI. CONCLUSIONFrom the above discussion, it is clear that the rectification, filtering and the regulation process is obligatory for this prject. It is the most fundamental process of converting the AC signal to DC signal. The rectification section employs bridge rectification that comprises of four (4) diodes IN4007 while the smoothing was carried out using two 1000 μF capacitors. Since the desired regulated output voltage is 5V.Zener diode acts as a regulator to

give a constant 5V output DC signal voltage. This project is implemented unanimously indoor ,outdoor and industrial purposes.

VII. REFERENCES

[1] Electronic Devices 9th edition by Thomas L Floyd.

[2] Electronics Devices and circuit theory 7th edition by Robert

Boylestad.

[3] N. Mohan, T.M. Undeland and W.P. Robbins “Power

Electronics: Converters, Applications, and Design”, New York:

NY, USA,

John Wiley & Sons, Inc., 1995.

[4] S. B. Dewan, “Optimum Input and Output Filters for a Single-

phase Rectifier Power Supply”, IEEE Trans. Industry Appl., vol.

IA-17, no. 3, pp. 282-288, 1981.

[5]Electronics One in all for Dummies by Doug Lowe.

[6]Electronics Principles 7th edition by Albart Malvino.

[7]Encyclopedia of Electronic components (vol-1)