±12V dual power supply using 12V/1W Zener diodes.

A simple ±12V dual power supply using 12V/1W Zener diodes

Introduction 

Dual power supplies that provide both positive and negative voltage (specifically, ±12V) are very useful for people who enjoy working with electronics and for professionals in technology. They offer a straightforward, affordable, and dependable source of direct current (DC) power.

This project focuses on building a simple ±12V dual power supply using 12V/1W Zener diodes.

Understanding Zener Diodes

A Zener diode is a special type of electronic component made from silicon. Unlike regular diodes, which only allow current to flow in one direction, a Zener diode allows current to flow in both the forward and reverse directions.

The key feature of a Zener diode is its reverse-breakdown voltage. When the voltage applied in the reverse direction reaches this specific point, the diode starts conducting electricity. Importantly, it can continue operating in this "reverse-bias" mode without being damaged. This precise breakdown voltage makes Zener diodes excellent for voltage regulation.

Know your circuit 

Kindly go through the circuit schematic thoroughly, so that you know how the DC supply after the bridge rectifier has been bifurcated into positive as well as negative supplies with the common '0' potential.  The circuit schematic is very simple and straightforward.

Parts List

230V to 15V step-down power transformer----- 1 no. 

D1 to D4 1N4001 Rectifier diode               ----- 4 nos. 

12V 1W Zener diode of the type 1N5349B------ 2 nos. 

150 ohms Resistors                                ------ 2 nos. 

250 MFD 40V Electrolytic capacitor          ------ 1 no. 

Know your design

Study the circuit schematic and understand how it has been configured using 2 Zener diodes to obtain both positive and negative power supplies from the single DC source. 

How the Power Supply Works

The main part of this circuit is the 12V/1W Zener diode, which acts as a voltage regulator. Here is a step-by-step breakdown of how the circuit converts standard household AC power into regulated DC power:

1. Voltage Step-Down: A standard 230V input (AC) is fed into a transformer. The transformer reduces this voltage to 15V (AC) while keeping the frequency at 50Hz.

2. AC to DC Conversion: The 15V AC signal passes through a bridge rectifier (made up of four 1N4001 diodes). This converts the alternating current into a pulsating (rippling) direct current.

3. Smoothing: The rippling DC signal goes through a 250uF capacitor. This capacitor smooths out the ripples and removes any remaining noise.

4. Voltage Regulation: The smoothed DC signal is then regulated by two Zener diodes. Because Zener diodes maintain a constant voltage in the breakdown region, they produce a stable, regulated output of ±12V.

Know your assembly 

The circuit can be assembled on a general-purpose veroboard. If one wants a PCB pattern, it is readily available in the market. One can procure and assemble it. The power transformer is mounted outside the PCB. All other parts are as usual in assembling a normal power supply design.  

If you like to build a 6V DC power supply circuit, visit this blog. 

Conclusion 

A simple but effective dual power supply circuit is highly essential in one's lab for practical purposes. Hence it is discussed this readymade power supply is discussed for the benefit of electronic enthusiasts. 

Applications

A dual DC power supply like this has several practical uses:
Controlling Motors: It can be used to apply a variable voltage to small DC motors.
Testing Projects: It is commonly used for testing small electronic projects and do-it-yourself (DIY) circuits.

In some designs, Operational Amplifiers such as IC 741 require a dual power supply like this. In that case, this circuit will be handy to power such OP ICs.