Buck converter using NE555 and N-Channel MOSFET

Published by MKDas on

Sometimes making a high amp regulator become very complex using linear regulator ICs. But using a buck converter can be very easy if the circuit work is simplified. Especially for motor-type loads. In this article, we will make a simple motor regulator using buck converter utilizing N-Channel MOSFET and NE555 ic. So let’s start our Buck converter using NE555.

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In the previous article, we have learned about the basic operation of a buck converter using N-Channel MOSFET. For basics, you should read that before reading this article.

Table of Contents

Concept:

The basic buck converter uses P-Channel MOSFET which is a little complex to use without proper gate driving IC. But if the configuration is modified a little, it becomes easier to handle. Here the basic circuit is this:

Buck converter with N channel MOSFET

This circuit can be further modified to a practical one. But first, we need to replace the clock source with a circuit. Here, the most common and easiest timer IC NE555 can be used.

NE555 as PWM generator:

NE555 timer IC can be used in different modes. One of those is the PWM generator. You can read these Application note1, Application note2 to know more about NE555 timer IC. There is an article on this you can read it too.

PWM generation using NE555

Also, there is a simulation video for better understanding:

Adding this PWM generator to our buck converter:

Now we can use this PWM generation circuit to out buck converter circuit.

Buck converter using NE555
Full circuit

Now the circuit is ready for operation. We used 12V as input and NE555 is directly supplied 12V. So there is no need to use any extra optocoupler P817C as the output is over 10V from NE555.

The circuit is also designed in PCB. Here is the PCB layout:

PCB:

Buck converter using NE555
Buck converter using NE555

After making the PCB, I tested the circuit with a lamp. Here is the test result:

Test result:

Conclusion:

This circuit is very simple and useful for small to medium inductive and resistive loads only. Where linear regulators are not suitable this converter can be used alternatively. Comparing with the linear one, the conversion loss is pretty low. A small heatsink is enough for normal loads, but I recommend using a suitable heatsink with the MOSFET for long-lasting.

Thanks for reading this article, I hope this will help you a lot. For more helpful articles, don’t forget to subscribe.

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Check this: 6V Lead-Acid battery charger circuit


MKDas

I'm Mithun K. Das; B.Sc. in EEE from KUET, Bangladesh. Blog: https://labprojectsbd.com. "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 (https://mlabsbd.com). 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.

9 Comments

  • Asimiyu · June 17, 2021 at 7:50 am

    Good day sir. It has been long . Hope you are fine sir. Pls from the posted circuit above, buck converter using NE555 timer as a clock pulse. Is any formula to find the value of inductor to suit a desired output voltage.
    (2) can this circuit be remodified to charge mobile phones as mobile power bank

      MKDas · June 17, 2021 at 10:18 am

      You can use any buck converter calculation. It’s just rearranged in position. No, it’s not suitable for mobile phone chargers. There are dedicated ICs for mobile phone chargers. This design is suitable for Motors and resistive loads.

        Asimiyu · June 17, 2021 at 6:53 pm

        Ok sir. Thank you

    djalltra · July 20, 2021 at 12:42 am

    the circuits efficiency will be low as it does not have a feedback network

      MKDas · July 20, 2021 at 12:48 pm

      Yes, but sometimes it becomes effective depending on load size.

    Seun · August 18, 2021 at 2:25 pm

    It seems your inductor does not have ferrite core, is it OK from efficiency. How can I add feedback for good efficiency

      MKDas · August 18, 2021 at 2:39 pm

      This converter is a very basic one. If you want to keep feedback then use a different clock source that you can control such as a microcontroller. Use optocouplers for feedback. and yes, using a ferrite core will improve the inductor performance.

    Seun · August 25, 2021 at 5:51 pm

    Please can this circuit be used as simple mppt system for solar system.

    I have tried this circuit before but I have difficulty in knowing the appropriate inductor despite using the calculator, please guide

    I want to use this to step down from 48v to 5v and 12v to charge phone and basic 12v loads, please advise accordingly.

    Thanks Sir.

      MKDas · August 26, 2021 at 6:31 pm

      This circuit is not suitable for MPPTs. You can check my other article on MPPT.

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