Download AC to DC converter with zener diode regulation

AC to DC converter with zener diode regulation
Nazmus Sakib
Department of EEE, Ahsanullah University of Science & Technology,Dhaka,Bangladesh.
Email : [email protected]
Abstract:The
basic objective of the thesis is to
construct a circuit that can give a constant dc 5volt. The
output voltage must not have an output voltage ripple
greater than one percent for its given output.The first
concept to make a 5volt dc power supply is to design for a
rectifier circuit to convert AC power into DC.After getting
pulsating dc we have to filter it to get smooth waveshape
.Then we will use zener diode to regulate the voltage and
thus we will get a nearly constant 5 volt
Keyword: Diode,Rectifier,Filter,Pulsating DC, Ripple
voltage,Transformer,Zener diode, Regulation.
A DC supply consists of the following parts:
1. A transformer to change the voltage as required
and to isolate the DC circuit from the line.
2. A rectifier consisting of one or more diodes, to
change
AC
to
DC.
3. A smoothing circuit using inductors and
capacitors.
4. A zener diode to regulate the voltage.
2. Equipments and Components
1.Introduction
Electric energy is most often delivered in the form of
alternating current . the voltage and the
current alternate sinusoidally between two extremes.
This cycle is repeated 50 times a second . Very often,
however, and particularly for electronic circuits,
direct current is desired . voltage and/or current
which are stable in time. The degree of stability of
the voltage varies according to how the DC is
produced. A power supple converting AC to DC
may, on the other hand, have a good long
term stability but rather poor short term stability. In
this case fast but often small variations called
ripple originate from the AC input leaking through
the
AC
to
DC
converter.
The aim when designing a DC supply is of course to
get an output voltage with good stability.
Serial
No.
Component
Details
Specification
Quantity
1.
Transformer
220V/12V
1 piece
2.
p-n junction
diode
1N4007
4 piece
3.
Resistor
1KΩ
1 piece
4.
Capacitor
1000uf
1 piece
5.
Zener diode
1N4733A
1 piece
6.
Bread Board
7.
Wire
1 unit
as
required
3.Transformation
The first step is to transfer 220 volt into 12
volt to make a5 volt power supply .So we
have to use a transformer to convert the
voltage.. The transformer the first block of
thethe converter required the ac input. A
basic two pin ac plug connector was
connected to the transformer allowing it to
be plugged into any standard wall plug. For
safety reasons we affixed the transformer in
a metal case and wrapped the outside of the
box in a layer of electric tape.The
transformer is used for this project which is
a step down control transformer.The
transformer is designed to connect in series
for AC-DC converter design. It is needed to
input at 220 Vac, and output at 12 Vac.Here
we used a center tapped & shell type
transformer. The rating of this transformerInput : 220V~50Hz
Output : 12V X 2 1000mA
Fig1. Centre tapped transformer
4.Rectification
We can convert ac signal to dc signal by using a
rectifier.A rectifier is an electrical device that
converts alternating current (AC), which periodically
reverses direction, to direct current (DC), which
flows in only one direction. The process is known as
rectification.There are two types of rectifier.
1.Half
wave
rectifier.
2.Full
wave
rectifier.
Half wave rectifier:In half wave rectification of a
single-phase supply, either the positive or negative
half of the AC wave is passed, while the other half is
blocked. Because only one half of the input
waveform reaches the output, mean voltage is lower.
Half-wave rectification requires a single diode in a
single-phase supply, or three in a three-phase supply.
Rectifiers yield a unidirectional but pulsating direct
current; half-wave rectifiers produce far more ripple
than full-wave rectifiers, and much more filtering is
needed to eliminate harmonics of the AC frequency
from the output.
Full wave rectifier:A full-wave rectifier converts the
whole of the input waveform to one of constant
polarity (positive or negative) at its output. Full-wave
rectification converts both polarities of the input
waveform to pulsating DC (direct current), and yields
a higher average output voltage. Two diodes and a
center tapped transformer, or four diodes in a bridge
configuration and any AC source (including a
transformer without center tap), are needed.[3] Single
semiconductor diodes, double diodes with common
cathode or common anode, and four-diode bridges,
are manufactured as single components.
Fig3.Full wave rectifier
The major disadvantages of half wave rectifier are:
1.Load recieves half of input power,
2.Average DC voltage is low,
3.Due to presence of ripple output voltage is not
smooth one.
The advantages of full wave rectifier:
1.wastage of power is less
2.Average DC input increase significantly.
3.Waveshape become smoother.
Vripple=
11.25
1k∗50∗𝐶
10.44
Disadvantages are:
1.Require more space and bulky in use.
2.not cost effective for transformer.
Or, 0.22 = 1k∗50∗𝐶
Or, C = 1000 uf.
Here we use full wave rectifier for high efficiency.
Vrectified (Experimental):
Output voltage of transformer, Vrms= 13.4 V
Peak voltage, VM =13.4* 2 V
= 19.04V
We know,
Vrectified = 0.318*2(VM-2*Vth)
Here, Vth= Threshold voltage of silicon diode=0.7V
So,
Vrectified = 0.318*2(17.81-2*0.7)
= 11.25 V
5.
Filtering:
To get real dc from pulsating dc we have to
filter.Actually we have to make a low pass filter
because a low-pass filter is an electronic filter that
passes low-frequency signals and attenuates signals
with frequencies higher than the cutoff frequency.If
we can reduce the value of ripple voltage we will get
smooth waveshape.The most common meaning of
ripple in electrical science is the small unwanted
residual periodic variation of the direct current (dc)
output of a power supply which has been derived
from an alternating current (ac) source. This ripple is
due to incomplete suppression of the alternating
waveform within the power supply.In other words v
ripple is the difference of maximum and minimum
voltage.To reduce v ripple we can use a bigger value
of capacior as the ripple voltage is inversely
propotional to the value of capacitor.The equation is
given below-
Calculation for choosing capacitor value:
We know, Vripple=
Vrectified
RL∗𝑓∗𝐶
Vripple= Ripple Votage  0.22 V [Assumed]
Vrectified= Rectified voltage=10.44V.
f= Frequency of the ripple voltage=50Hz.
C= Value of the capacitor.
6. Voltage regulation:
Any electrical or electronic device that maintains the
voltage of a power source within acceptable limits.
The voltage regulator is needed to keep voltages
within the prescribed range that can be tolerated by
the electrical equipment using that voltage. Voltage
can be ragulated many ways such a susing IC or
Zener diode .We have zener diode to regulate voltage
here.As we wan to make a5 volt power supply we
have used a zener diode which threshold voltage is 5
volt.So we have got 5. volt across zener diode.We
havent got exact 5 volt because the zener diode
voltage depends upon the resistor in series with it
which is used to limit the current flow.
Simulation and circuit diagram:
Fig.4 : Circuit diagram.
Fig 5.Simulated waveshape
7. Conclusion:
The AC-DC converter design has been tested with
computer simulation and analysis . It has achieved
the voltage output range requirement ( 5V) . But
however, the testing results also show some
uncertainties about the power output of this AC-DC
converter, which is below our expectation. The
problem is most likely is caused by the old
transformer which we obtained from the electronics
shop and became inoperable after the demonstration.
8. References
1.
2.
3.
Electronic Devices and Circuit Theory (Tenth
Edition) by ROBERT BOYLESTEAD AND
LOUIS
NASHELSKY.
(
Chapter1:Semiconductor diodes, Chapter 2:
Diode application)
Microelectronic circuits (Fifth Edition) by
Sedra/Smith. ( Chapter 3: Diodes)
Class lecture of Ziaur Rahman sir.