Occasionally we need dc power source which is adjustable along with protections. This slide will help you to create a circuit that can adjust the dc voltage and apply thereby.

1. Presented By:
MUHSIN BAKHTIAR FAHIM
DEPARTMENT OF ECE, KUET
Adjustable DC Power Supply
KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY
Department of Electronics & Communication Engineering

2. W E L C O M E
E V E R Y O N E
2KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

3. C O N T E N T S
OBJECTIVES
CIRCUIT ANALYSIS
CIRCUIT DESIGN
ADVANTAGES & LIMITATIONS
APPLICATIONS
3KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

4. GOALS
1
6
5
2 4
3
Backup supply to be enlisted
Very marginal and
refined tuning
Low cost & lightweight
circuit
An adjustable DC
power supply
Ensuring short circuit
protection
Ensuring under voltage
protection
OBJECTIVES
4KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

5. W H Y W O U L D W E P R E F E R T H I S ?
SIZE HANDYDESIGN WEIGHT
The size of the device we
built was small and easy
doing.
The compact shape is
also noteworthy!
The light weight of this
device makes it easier to
deal with.
The design is much more
convenient.
Although similar types of devices are found in the market doing the same functions, but why would
just we go with our projected circuit? Yes, its because of some preferable dominating advantages
stated above.
5KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

6. 1
2
3
4
5
BLOCK
NETWORK
DIAGRAM
INPUT AC
SUPPLY
BRIDGE &
RECTIFIER
CIRCUIT UNDER &
OVER
VOLTAGE
PROTECTION
CIRCUIT
VOLTAGE
REGULATION
SHORT
CIRCUIT
PROTECTION
BACKUP
DESIRED OUTPUT
6KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

7. D E T A I L S O F E A C H B L O C K
In this part the AC input is converted to DC. First
rectifier gives us pulsating Dc, then filter circuit gives
us smooth DC.
BRIDGE RECTIFIER & FILTER CIRCUIT1
The backup circuit consists of a battery & some
specific conditions. If the circuit is isolated either over
voltage or under voltage, then the circuit gives power
to the output.
BACKUP CIRCUIT2
The regulator gives us regulated output. By this we
can get our desired voltage level in output.
REGULATOR CIRCUIT3
If the output of the circuit gets shorted to ground, this
circuit protects the internal device being damaged by
limiting current.
SHORT CIRCUIT PROTECTION4
In this part if the rectified output gets over a range
determined by the designer the circuit gets isolated,
hence protecting the output.
OVER VOLTAGE PROTECTION5
In this part if the rectified output gets under a range
determined by the designer the circuit gets isolated,
hence protecting the output.
UNDER VOLTAGE PROTECTION6
7KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

8. RECTIFIE
R
CIRCUIT
INTRODUCTION
INSTRUMENTATION:
1. FUSE
2.TRANSFORMER
3. DIODES
4. BRIDGE RECTIFIER
5. CAPACITORS
8KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

9. REGULATE
D DC
SUPPLY
INSTRUMENTATION:
1. IC LM317T acts as a regulator
2. Resistors
3. CAPACITORS C2 acts as a
ripple remover & C3 reduces
transient effect
4. VARIABLE resistor is for
regulation of output
9KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

10. SHORT
CIRCUIT
PROTECTIO
N
INSTRUMENTATION:
1. Here R2 & Red LED
acts as a trigger.
2. If the load is shorted the transistor Q2
goes off hence Q2 goes off state. So the
current flows through R2 & Red LED
indicating short circuit.
3. Transistor 2N2905 & 2N2222 are used.
10KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

11. OVER
VOLTAGE
INTRODUCTION
INSTRUMENTATION:
1. Zener diode for reference voltage
2. Rectified output applied across
voltage divider portion.
3. When rectified output goes above
reference voltage then comparator gives
output voltage and Q4 becomes on
* One thing to say that the relay 1 is
switched to operate this region.
* Activated for over 34 volts.
11KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

12. UNDER
VOLTAGE
INTRODUCTION
INSTRUMENTATION:
1. Rectified output is applied across
voltage divider portion.
2. Using zener diode as a reference
voltage
3. When rectified output goes under the
reference voltage then comparator gives
output voltage and LED becomes on
*Activated for less than 22 volts.
12KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

13. C I R C U I T
D I A G R A M
13KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

14. RESULT
ANALYSIS
1. Transformer input=220 V ac.
2. Transformer output=28 V ac,
1000mA ac.
3. Output voltage after filtering=36.4V
DC.
4. Output current after filtering=600 mA
5. Over voltage= 34 volts
6. Under voltage= 22 volts
7. Regulated output=2.3~34.2 V DC.
8. Maximum output current=300 mA.
9. Maximum short circuit current =68
mA DC.
10. Lowest resistence to get shorted=
105 ohm.
14KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

15. MAJOR PROBLEM AND
RELATED SOLUTION
We were not able to design an uninterrupted circuit if two cases
occurred and they are over voltage situation and under voltage
situation. If the over voltage or under voltage situation occurred
the relay would turn on & then it was grounded. That’s when the
rest of the circuits operation stopped and we were not able to
get the required output.
For getting uninterrupted circuit we had to use a backup
battery of 27V so that when the relay goes on the backup
battery will give the needed supply to run the rest of the
circuit operation.
i.e. when the circuit is interrupted by short circuited or over
or under voltage protected the backup battery will provide
continuous power supply for the time being.
15KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

16. L I M I T A T I O N S
1
The circuit is vulnerable
2
The load is limited as output
voltage
3
Its output voltage range is only
2.3~37.2
4
Circuit efficiency is not so
reasonable
5
Current rating is very low
6
No lifetime guarantee
16KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

17. A P P L I C A T I O N S
AC
ADAPTERS
LIKE MOBILE
C H AR GER S LABORATORY
DEVICES
LIGHTING
SPEAKERS
AND
CHARGER
FANS
CENTRAL
POWER
DISTRIBUTION
VEHICLES
SPACE
STATION
17KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY

18. T H AT ’ S A L L !
Thank you for coming today!
IF YOU HAVE ANY QUERY THEN DO ASK ABOUT THAT TO US. 
18KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY