6. Transformer Block
Diagram
Transformer :
A step-down transformer is used to reduce the dangerously high mains
voltage to a safer level
In Our power supply the output of the transformer is an AC stepped down to
15 V.
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7. Block
Diagram
Bridge Rectifier
Converts the AC voltage to DC
Available in the form of packages of combination of four diodes
forming a bridge
Bridge rectifier and output is obtained from the corner positive
and negatively marked terminals
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Page 7
8. Block
Diagram
Filtering
Filtering is technique in which a pure DC is obtained
The output of a bridge rectifier is not a pure DC and needs to be converted
into pure form
A capacitive circuit is used as a filter or a smoother
It converts the pulsating DC into a pure DC with a little ripples.
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9. Block
Regulator Diagram
Eliminates ripple by setting DC output to a fixed voltage
Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or
variable output voltages
Each regulator has its own data sheet and pin configuration
LM 7815 and 7915 were used in our supply.
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11. 15 V DC power
supply
Circuit Designing
Designing a circuit
Simulating the circuit in any of the friendly
interfaced simulating software.
The software used by us was Multisim .
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Page 11
12. Simulation
U1
LM7815CT
11 LINE VREG XSC1
VOLTAGE
COMMON
V1 Ext T rig
+
13 8
15 Vrms C1 C3 _
A B
50 Hz 2 D1 4.7mF 2.2mF + _ + _
0°
4 1 0
9
V2
3 1B4B42 C4
15 Vrms C2 2.2mF
50 Hz 4.7mF
COMMON
0°
6 VOLTAGE 7
VREG LINE
12
U2
LM7915CT
It resulted in a pure waveform in which remaining ripples were also
eliminated
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13. 15 V DC power
supply
SIMULATED CIRCUIT
U1
LM7815CT R1
1 LINE VREG
9 6
VOLTAGE
8 1kΩ
COMMON
V1
15 Vrms C1 C3 LED1
50 Hz 2 D1 4.7mF 2.2mF
0° 0
4 1
2
V2
3 1B4B42 C4
15 Vrms C2 2.2mF
4.7mF LED2
50 Hz
COMMON
0° 12 10 R2
VOLTAGE 4
VREG LINE
3
U2 1kΩ
LM7915CT
• Whole of the circuit was simulated which shows various stages of regulation
of 15 Volts DC
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14. 15 V DC power
supply
Components Purchased
A list of components purchased
NO. COMPONENTS SPECIFICATIONS QUANTITY
1
Transformer 15x2 Volts 1
2
Bridge Rectifier 2 Ampere 1
3
Capacitor 4700uF 2
4
Voltage Regulator LM 7815 1
5
Voltage Regulator LM 7915 1
6
Capacitor 2200uF 2
7
Resistance 1 kilo ohm 2
8
Light Emitting Diodes (LEDs) 2
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15. 15 V DC power
supply
•
Bread Board Testing
For testing the circuit, a step by step procedure was adopted as was done in
simulation. And in each step the functionality was checked using Cathode Ray
Oscilloscope and also a Digital Multimeter (DMM).
• 1. First of all, a wire and a plug were connected to the wires of transformer
primary. The transformer output was measured using DMM. It is a step down
transformer and provides an output of 15 Volts at its output.
• 2. The transformer AC output of 15 Volts was converted to DC using a bridge
rectifier.
• 3. The ripples of positive DC output were removed by connecting a capacitor of
4700 µF in parallel with the bridge rectifier side which provides positive output
voltage.
• 4. For regulating this filtered voltage at +15 Volts a voltage regulator, LM-7815
was connected across the capacitor (in series or in parallel).
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16. 5. Any ripples remaining in this regulated voltage were then removed
using another filter capacitor of worth 2200 µF connected in parallel with
this circuit.
6. The output was now a regulated DC voltage of +15 Volts as was
the requirement of our supply design.
7. The same procedure was repeated for the regulation of -15 Volts. In its
regulation voltage regulator LM 7915 was used.
8. To check the functionality of the circuit LEDs were connected across
the circuit with the help of two series resistors of 1kΩ.
• Green LED for -15 Volts
• Red LED for +15 Volts
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20. CON_IN
1 2 3
done
4 2
C
A
C
A
3 1
-
V
+
V
G
N
Br_Rectifier
D
4 C 4 C
7 7
2 1
0 0
0 0
u u
1
2
U
1
I
N
U
2
I
2
N
G
N
1
G LM7915 LM7815
D
N
O
D
U
O
T
U
T
3
3
Powerpoint Templates
Schematic
2 Cap
Pol1 C 2 Cap
Pol1 C
2 2
4 3
0 0
0 0
u u
5 Res2 R(load)
0
5 Res2 R(load)1
0
L L
E E
D D
2 1
corresponding to which the PCB simulation is
The schematic in Altium Design Suite is made
Page 20
21. PCB Design circuit
Corresponding to the Schematic a PCB
simulated circuit is obtained
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Page 21
22. Routing
Process in which the tracks are created in the
Design and the length and thickness of these
tracks can be altered according to the
requirement
The print of this design is taken on a sticker
paper.
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24. 15 V DC power
supply
Print On Sticker Sheet
The print of the routed PCB is taken on a sticker paper so that it could be
pasted on the copper board
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25. Lamination 15 V DC power
supply
This is the process in which the print of the PCB taken on a sticker sheet
using a laser printer is transferred to the copper board.
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27. We used an alternate procedure of ironing the
printed sticker sheet over the copper board
In this process the sticker sheet was ironed over
the copper board and after sometime it was
observed that the print was imprinted over the
copper board
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28. Etching
ETCHED TANK PA 310
Etching is a chemical process in which the copper (extra) is removed from
the copper board resulting in a PCB to be Drilled
An Etched PCB
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29. Etching (continued) 15 Vsupply
DC power
The etching process depends upon the chemical used mostly it is an acid
The acid is heated to particular temperature then it is maintained
For this purpose a machine known as PCB etch tank is used
The Copper board is placed in the heated acid for about 2 minutes
This process also depends on the quality of the chemical used
If the chemical used is old it might take a long time
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30. Drilling 15 V DC power
supply
Process in which holes are drilled at the appropriate places for the
components to be soldered
This process is carried out using a drill machine
It can be manually drilled as in our case
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31. Soldering 15 V DC power
supply
Place the PCB, with its components, in steady position when soldering iron
is to be used
The heated soldering iron should then be placed in contact with the PCB and
the component and allowed to heat them up. Once they are heated the
solder can be applied. The solder should flow through and around the
component and the track of PCB
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32. Testing of PCB 15 V DC power
supply
Finally the PCB was tested
Connector connected to the output of the Transformer.
Two glowing LEDs show that the PCB is working.
Also the output voltage and current of the transformer were checked.
Output seen on CRO for the final check.
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