Lab Power Supply Circuit Variable 30 Volt

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In this tutorial, we are going to show you how to make a low-cost, good quality stable, and adjustable power supply circuit. It is easy to build and can be used as a lab power supply. A power supply is a device that converts one type of electrical energy into another. The output of this power supply circuit is 2.5V to 27.5V DC.

The IC that we are using in this project is TL431, it is a three-terminal adjustable shunt regulator IC which is able to deliver output voltage from 2.5V to 36V with only a few external components. It is precise and has built-in thermal stability circuitry with low output noise and low cost. It is available in small and surface mount packaging and can be used to build all sorts of power supplies.

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Hardware Components

The following components are required to make Lab Power Supply Circuit

S.no	Component	Value	Qty
1.	Step down Transformer	230V-25V	1
2.	Diode	1N4001	1
3.	Resistor	470Ω, 1K, 2.7K	1, 1, 1
4.	Variable resistor	10K	1
5.	Electrolytic Capacitor	4700µF/50V, 470µF/50V	1
6.	Ceramic Capacitor	0.1µF	2
7.	Transistor	2SC3807	1
8.	Transistor	2SC2922	1
9.	Adjustable Shunt (Zener) Regulator IC	TL431	1

TL431 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of TL431

Lab Power Supply Circuit

Working Explanation

This circuit is simple, we are using two transistors, one IC, and a few other components. Supply is given to the circuit through a transformer T1 it steps down the voltage from 230V to 25V which is given to the bridge rectifier.

It converts the AC supply into DC. The input is now passed through capacitors for noise cancellation, two transistors are used to amplify the signals and then fed onto the IC. A variable resistor of 10K ohms is used to set the desired output voltage, more capacitors are used for further noise cancellation of the output.