12V Regulated Power Supply Using LM2940T IC

A 12V Regulated power supply is an integral part of any DC supply unit used in electronic equipment. It serves as an interface between a wall outlet and common power electronic equipment. In this project, we are going to design a simple 12V Regulated power supply circuit using an LM2940T-12 voltage regulator IC.

The LM2940/LM2940T positive voltage regulator has the ability to source 1A of output current with a dropout voltage of typically 0.5V and a maximum of 1V over the entire temperature range. Furthermore, the IC package hs a quiescent current reduction circuit which reduces the ground current when the differential between the input voltage and the output voltage exceeds approximately 3V.

Hardware Components

The following components are required to make a 12V Regulated Power Supply Circuit

S.no	Component	Value	Qty
1.	Voltage regulator IC	LM2940T-12	1
2.	Stepdown Transformer	230V to 12V/1A	1
3.	Bridge Rectifier	1N4007	4
4.	Ceramic Capacitor	100nF	1
5.	Electrolytic Capacitors	1000μF/50V, 33μF	1
6.	Breadboard	–	1

LM2940T Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of LM2940T

12V Regulated Power Supply Circuit

Working Explanation

An input voltage of 230V/110V is applied at the primary of a non-CT transformer which steps it down to 12V 1A through mutual induction of the primary & secondary windings while maintaining the frequency at 50Hz. After which the 12V AC signal goes through a bridge rectifier (1N4007 diodes) that converts the AC signal into a rippling DC signal.

The DC signal then passes through smoothing capacitors C1 (1000µF) & C2 (100nF) before passing on to an LM2904T-12 voltage regulator IC which produces a constant regulated 12V DC signal at the output. The DC signal then passes through capacitor C3 (33µF) to remove any residual noise before going on towards the output.

Applications

• A Variable power supply serves in applications such as applying a variable voltage to DC motors.
• Commonly used in testing & troubleshooting small electronic projects.