Transformerless power supply with Viper12A

Published by MKDas on

One of the very useful transformerless power supplies using Viper12A IC can be used in many applications. It is sufficient to run micro-controllers, sensors, displays, relays, and so on. With very few numbers of components, we can get a reliable transformerless power supply with Viper12A.

Disclaimer: Electricity is always dangerous. Proper skill is required to work with electricity. Do work at your own risk. The author will not be responsible for any misuse or harmful act or any mistake you make. The contents of this website are unique and copyright protected. Kindly don’t do any nonsensical act copying and claiming it as yours. Most of the articles published here are kept as open-source to help you. Take the knowledge for free and use it, but if you are interested you can buy the ready resources offered here. If you need any help or guide feel free to comment below, the author will try to help you. Thanks.

***Warning: An electrocution hazard exists during experimentation with transformerless circuits that interface to wall power. There is no transformer for power-line isolation in the following circuits, so the user must be very careful and assess the risks from line transients in the user’s application. An isolation transformer should be used when probing the following circuits.

Table of Contents

About Viper12A:

This is actually a PWM controller with high voltage power MOSFET inside. Usually used in low power standby power supplies, battery chargers, auxiliary power supply, etc.

Datasheet of Viper12A.

You can check this article too: Transformerless power supply design guide in detail with calculator

Circuit diagram using Viper12A:

transformer less power supply with Viper12A

Circuit explanation of power supply with Viper12A:

Here, R1 is used to limit the inrush current and L1 and C1&2 are used to rectify the AC with a filter to get DC voltage. The L2 is the main inductor in this circuit. In this circuit, the inductor should not be used less than 1mH. Diode D2 is supplying the power to VDD and D3 & D4 are generating the feedback voltage. If you need another voltage rather than 12, change the value of this Zener diode D4. C5 and C6 are used to filter the noise from the feedback signal. And finally, C4 is used as the main filter capacitor for the low voltage side. A safety Zener diode D6 of 15V (higher than the output voltage) is used to limit the initial voltage spike during startup. And D5 is the freewheeling diode. Must be used any Ultra Fast diode.


This article was a serial port of the previous post (Transformerless power supply design guide). As this circuit performs much better than the capacitor or resistor-based power supplies and I’ve been using this circuit in many applications and field running (24/7) devices for a long time so I decided to share the diagram. If you can design the PCB carefully keeping sufficient PCB space as a heatsink, this circuit will last a long time. The average power delivery is 100mA. And most interesting this is this circuit works from 15V to 300V wide (maybe extra-wide) range.

I hope this project was helpful to you. If you make one for yourself, it will be a great pleasure for me. Anywhere you need help, let me know. Please share this project and subscribe to my blog. Thank you.

Don’t forget to subscribe for the next update.


JLCPCB – Only $2 for PCB Prototype (Any Color)

24 Hours fast turnaround, Excellent quality & Unbeatable prices

$18 Welcome Bonus for new registrations Now!!!

Check this out: 5 coolest multimeters you can buy


I'm Mithun K. Das; B.Sc. in EEE from KUET, Bangladesh. Blog: "First, electronics was my passion, then it was my education, and finally, electronics is now my profession." I run my own electronics lab, M's Lab ( Where I work with the creation of new products from ideas to something in real life. Besides this is my personal blog where I write for hobbyists and newcomers in the electronics arena. I also have a YouTube channel where I publish other helpful videos, you can find the link inside the articles. I always try to keep it simple so that it becomes easy to understand. I hope these will help them to learn electronics and apply the knowledge in their real life.

1 Comment

  • Joy · February 12, 2021 at 11:51 am

    Thank you… Nice Project..

    Leave a Reply

    Avatar placeholder

    Your email address will not be published. Required fields are marked *