12V Regulated Power Supply Using LM2940T IC

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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.

LM2940-12V-Low-Dropout-Regulator

Hardware Components

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

S.noComponentValueQty
1.Voltage regulator ICLM2940T-121
2.Stepdown Transformer230V to 12V/1A 1
3.Bridge Rectifier 1N40074
4.Ceramic Capacitor100nF1
5.Electrolytic Capacitors1000μF/50V, 33μF1
6.Breadboard1

LM2940T Pinout

LM2940-12V-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.