Recently I've had terrible luck buying those little DC-DC boards from China off of eBay.

We've been trying to build projects where we have some sort of wobbly input DC off of a car or solar, batteries and things.

So I've started trying to learn how to design and build my own DC-DC SMPS circuits.

I'm very new at this, so I'm looking for something that I can use as a calculator (input Vin and Vout, etc) but also I need to understand what's I'm doing and what's going on.

To start with I've decided to take one of our projects which needs an SMPS and build it, something which these little boards off of eBay would probably be unsuitable for.

Project: A portable, battery powered audio amplifier.

I'm going to buy a DIY amp board, deliberately choosing one which requires a high voltage to run (http://goo.gl/Idwos8 or http://goo.gl/11S6TJ perhaps) and are cheap so I won't get upset if I blow it up.

Then, take something cheap and wholly unsuitable to run it off, such as 4xAA batteries.

So, about ~6V in and I need ~30V out.

So there we go, where can I get a design which lets you calculate how to build a 6V to 30V SMPS?

Once I've done that I need to then build something useful.

I though I'd start with a 12V VRLA battery, step that up to 36V.

Problem then is how do I, you know, make it not melt when there is hundreds of watts happening?

  • \$\begingroup\$ My advice to you would be to start with something a bit "simpler" than what you have in mind, like for example an LED flashlight. In my experience, it helps if you at first work with cheap components that you'll be able to burn repeatedly, like cheap LEDs. Audio amplifiers are a bit problematic here, because they are often sensitive to noise on the power supply lines. The ones you linked to are class D, so they should be a bit more immune, but still my advice is to start with something simpler and then "graduate" to say power supply for an audio amplifier. \$\endgroup\$
    – AndrejaKo
    Oct 3 '14 at 12:30
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    \$\begingroup\$ This question is impossibly broad. There are curricula dedicated to power electronics and power conversion in universities worldwide, hundreds of books on the market and hundreds of approaches to "how do I convert X into Y?". Start with a book that teaches the fundamentals of power conversion, and once you get the basics down, analyze one of those 'poor' DC/DC boards and figure out why it's poor before designing a replacement. After all, without the right knowledge, are you a competent judge of why your chosen DC/DC converters are poor? \$\endgroup\$ Oct 3 '14 at 12:42
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    \$\begingroup\$ By all means try and learn about SMPS design, but if your main objective is to solve the power supply issues with your projects then there are DC-DC converter modules available from reputable manufacturers to meet almost every requirement, and the cost isn't much compared to the time it might take to design and troubleshoot your own. Just be aware whether the converter's output is actually regulated or just ratiometric to the input voltage. \$\endgroup\$
    – nekomatic
    Oct 3 '14 at 12:42
  • \$\begingroup\$ Also, your question title is about learning SMPS design, and the body of your question is asking specific design questions (which are more appropriate for this site). Choose one or the other please. \$\endgroup\$ Oct 3 '14 at 12:43
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    \$\begingroup\$ I agree take a step back and learn the basics. You are proposing running a 200W audio amp off of 4 AA batteries. (Once you learn a bit more you'll see how silly that is.) Please don't be offended by my comments. \$\endgroup\$ Oct 3 '14 at 12:44

If you are keen to learn lots there is a free version of a book called

Principles and Elements of POWER ELECTRONICS

By Barry W Williams

Google for it.

It is very good and maybe overkill for you right now. However, reading certain sections lightly might help. I am still plowing my way through it to update knowledge I learnt 25 years ago.

From Adam Davis's comment. Here is a link that you could download the book in various chapters.

Book Link

Again to pull good information out of the comments here is a link to more info about types of modern Power supplies. Has the added advantage of an online PSU calculators of various subtypes, Buck, Boost etc.

PSU Calculator Site

  • \$\begingroup\$ Many Thanks, time to brush off the kindle! :) Looks pretty overkill but at the same time reference stuff is highly useful. \$\endgroup\$
    – RoboJ1M
    Oct 3 '14 at 12:58
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    \$\begingroup\$ Search engines appear to be bringing up a lot of document websites requiring registration, fees, or making poor ad choices. The website with the latest version from Barry is here: project.eee.strath.ac.uk/textbook/website/index.php The latest version does require registration, but it's simple and otherwise ad free, unlikely to cause spam to your email. The first edition is free without registration. \$\endgroup\$
    – Adam Davis
    Oct 3 '14 at 14:23
  • \$\begingroup\$ Question's locked now and it probably can't be fixed, but I found this elsewhere on the site and I think this combined with the book gives me what I need. Feel free to add it to your answer, schmidt-walter.eit.h-da.de/smps_e/smps_e.html I've read the summary of the book and it looks to contain all the information I could possibly need. @kingchris \$\endgroup\$
    – RoboJ1M
    Oct 6 '14 at 8:37
  • \$\begingroup\$ Excellent find @RoboJ1M. This will be useful for my own re-education. One can plug in various values to see what might happen and understand some of the maths behind the hardware. \$\endgroup\$
    – kingchris
    Oct 7 '14 at 4:19

Great online free course: Introduction to Power Electronics from University of Colorado Boulder:

The course is an introduction to switched-mode power converters. It provides a basic knowledge of circuitry for the control and conversion of electrical power with high efficiency. These converters can change and regulate the voltage, current, or power; dc-dc converters, ac-dc rectifiers, dc-ac inverters, and ac-ac cycloconverters are in common use. Applications include electronic power supplies, aerospace and vehicular power systems, and renewable energy systems.

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    \$\begingroup\$ Nice book too. (I finished ~80% of that online course last year, which I understand is typical.) \$\endgroup\$ Oct 3 '14 at 13:07
  • \$\begingroup\$ Fantastic, thank you very much. Just watched the intro video, everything on there is something I want to know, understand and build! :) Now I just need to get to the point where I'd understand the course material. \$\endgroup\$
    – RoboJ1M
    Oct 3 '14 at 13:17
  • \$\begingroup\$ @m.Alin Have you taken this course? \$\endgroup\$ Oct 3 '14 at 15:22
  • \$\begingroup\$ @Nick I only watched a few video lessons \$\endgroup\$
    – m.Alin
    Oct 3 '14 at 15:41

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