## Dual Power Supply Circuit

### Description

The circuit given here is of a regulated dual power supply that provides +12V and -12V from the AC mains. A power supply like this is a very essential tool on the work bench of an electronic hobbyist.
The transformer T1 steps down the AC mains voltage and diodes D1, D2, D3 and D4 does the job of rectification. Capacitors C1 and C2 does the job of filtering.C3, C4, C7and C8 are decoupling capacitors. IC 7812 and 7912 are used for the purpose of voltage regulation in which the former is a positive 12V regulator and later is a negative 12V regulator. The output of 7812 will be +12V and that of 7912 will be -12V.

### Circuit diagram with Parts list

#### Notes

• Assemble the circuit on a good quality PCB.
• Transformer T1 can be a 230V primary; 15-0-15 V, 1A secondary step-down transformer.
• Fuse F1 can be a 500mA fuse.
• Capacitor C1,C2,C5 and C6 must be rated at least 50V.

1. Abhijeet shinde

Build a regulated power supply on general purpose pcb to obtain -12v using LM IC 7912

I want 12v 2amp DC output .but they are not available 12v transformer.in this case 23v transformer how can convert in to 12v 2amp.tell me sir it’s possible or not.whether possible then can draw or send the circuit diagram please sir. I can make one DC power supply use for battery charger.please tell me the solution sir .reply pls

3. varsha mahajan

Send me a connection image of dual power supply of 12v using IC7812 and 7912

4. Jitendra bhandarkar

my circuit can not give the positive output

5. hi,
i want to know can we build variable power supply (12-0. 0- -12) using lm7812 and lm7912?
thank you.

6. arif hussain

I need a schematic diagram of Dual power supply of -30v to +30v….plz send it…….

7. Dear Sir,

I’ve actually built this circuit as you’ve specified, but found that the output voltage in +ve and -ve are not quite balance. (+12.0 vs -11.9) I’ve tried to replace all components, including the 7812 and 7912 pair, and the unbalance is not quite solve, so my next step, if all I have used up my options, would be using a trimmer to help fine tuning the 0V output. (Current drawn will be minimal, but the voltage must be fully balanced, or I will have a baised output at the device I am driving with this)
What would you suggest other than adding the trimmer?

8. Seetharaman

Hi Sunil use the above circuit add Red LED in positive Bus and Green LED in negative bus use a LED current limiting resistance of 1k ohms for each LED.

9. Sunil deka

I want to design a dual mode power supply with 12V out put voltage and 500mA in PCB using diodes IN4007and regulator chips IC 7812 and IC 7912 and LED

10. santosh naik

hi
sir my name is santosh naik i am studing at diploma power electroninc i make one project dueal power supply but idont have circuit digram pls send me sir that diagram

regarding
santosh naik
8971314064

11. seetharaman

Hi Kabelo This way it is ok, if step down transformer secondary current is 500mA.
you cannot use the other way round. That is 1.5amp transformer with 500mA bridge rectifier.

12. can i use a 1.5amp bridge rectifier and a 500mA step down transformer?

13. i want to disign a dual power suply with 12v out put voltage and 150mA

14. I need a dual variable regulated supply with 0-50V/5A !! Somebody help me !! 🙁

15. seetharaman

Hi Charles this can be designed. the drawback will be as the filter capacitor comes after yhyrister. the output cannot be changed fast. without actual load you have disconnect filter capacitor use a small value capacitor set the voltage and connect the main filter capacitor and the load. i will be submitting soon a circuit in this column.

16. can you make a design of power supply using thyristors

17. seetharaman

Ni Leena D1 & D3 with respect to transformer center tap is a full wave rectifier. It will develop 15 X rt2 (1.414) voltage across C1, that is +21 volts DC. This voltage is fed to a fixed voltage regulator to 15 Volt DC. C3 & C7 are used to take care of the inductive component of the electrolytic capacitors at high frequeny. similarly with D2 & D4 produces the negative voltage. If you want any further details please contact me through email here the space is in sufficient. seethasub@hotmail.com

18. twits4twats

Might I suggest that if you can’t design one yourself that you shouldn’t be asking for one.
30VDC is enough to kill.

19. I want a variable power supply circuit from a range of 0-50v/5A DC with digital voltage display.

20. i want a variable power supply’s circuit diagram……
it’s in between 0 to 30 volt dual