18 volt transformer less power supply

18 volt transformer less power supply, In this article I am going to discuss how to design inexpensive power supply. Linear power supplies contain transformer. Transformer is expensive component from all other parts in linear power supplies. In this article you will learn how to design 18 volt and 40mA power supply without using transformer. you can use this power supply for low power projects. To power microcontrollers and for testing of low power components. I have already posted one article on transformerless power supply for microcontrollers. You can also check it by clicking on following link:

Transformerless power supply for microcontrollers

What is transformerless power supply :

Many people also called transformerless power to capacitor fed power supply. Beasue capacitor is used between high voltage supply and low voltage. High voltage side is main AC power and input to transformerless power supply. Capacitor power supply is very risky to use.

Circuit diagram of transformer less power supply :

Circuit diagram of 18v and 40mA transformer less power supply is given below.

Transfromer less power supply

Transfromer less power supply

Four diodes are used in this project. Two diodes are zener diodes and other two diodes are rectifier diodes. Rectifier diodes are used to rectify AC voltage into pulsating DC voltage. Two 18 volt zener diodes are used which produce pulsating output voltage at the output of full bridge not more than 18 volt.  The output voltage will never be greater than 18 volt due to these two zener diodes. Zener diodes used as regulator.

10 ohm resistor is used a safety fuse resistor as a current limiting resistor with combination of .47uf two capacitors which acts as a oscillator. 100uf capacitor is used to filter pulsating AC voltage and provide constant DC voltage at the output. List of components  are given below.

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List of components:

Category,Reference,Value,Order Code

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