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How do I make a 230V SMPS to replace my linear transformers?

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Full Member level 5
Jan 4, 2012
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Hi. I've been doing electronics for a couple of years now and for every project that has needed a 230V supply I've used a linear transformer. I'm very comfortable with this simple design, but linear transformers are as you know very big and very expensive, is it a good idea to shift my focus to SM supplies instead? Are they difficult to make and what do I need to know?

Looks very interesting. Why would I design a high frequency transformer, don't I just buy one? Also, how do I go about making a dual sided SMPS? As I only know the basic operation of these supplies and I'm a little worried when dealing with 230V (safety first), the best thing would be to simply copy a schematic and a part list, perhaps even the board layout?

At home you wont be successful in developing or making 230V switch mode power supplies (SMPS). You can only buy them the same way you buy a mains transformer.
To get into SMPS start developing and making boost and buck converters. They are useful interesting and no danger involved.

Why won't I be successful in making a 230V SMPS?

When you develop circuits for the first time many things don't work well. Working with high voltages doesn't allow you to probe your circuit and find the faults.
Other than that, you will get better answer to your question when you try to make SMPS at home.

You are better off to buy and test SMPS or use PC PSU and learn before attempting to design anything. Magnetic property selection can be complex with saturation.

Can't I just use some voltage divider to be able to probe my circuit? Aren't there designs out there I can copy by the way? I've looked inside some small 230V SMPS and many of them look very simple, surely there are board layouts and component lists I can follow to make a safe and solid SMPS?

I've looked at mouser for switched supplies, but dual sided supplies are hard to come by and those single sided supplies I do find aren't that much cheaper than linear transformers. The component cost of something like this can't be much at all, still it cost 11USD:


Each SMPS has its transformer designed for it, there are no standard transformers to by. Making the SMPS transformer is as hard as making the mains transformer that you buy.
You are better starting with making SMPS for low voltages, less chance of burning your fingers with them.

Could you explain why there are no standard high frequency transformers? How many different factors can there be when designing a transformer?

Why won't I be successful in making a 230V SMPS?

Because you can't run without learning to walk first.
In this same forum, I have advised beginners over and over: You want to learn about SMPS? Good! Start with a low voltage, low power one.

Line powered SMPS circuits are unforgiving. If you make a mistake, and rest assured that as a novice you will make plenty, and you could damage your test equipment, shock yourself, and start a small fire.

And you have to read, read, read. Read datasheets, read appnotes, read good SMPS books.

If after building a small SMPS you still want to go further, my advice is to purchase an Evaluation Kit available from many suppliers. Its advantage is that it is already a fully functional circuit which is well documented and explained, has a wide layout and plenty of test point for easy probing, and usually has options to modify or customize it.

It may cost around $50 US, but as I also have repeatedly stated, education is never free.

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Check for instance, the following Reference Design from OnSemi:

Power Integrations has reference designs and recommended transformers from 1W - 200W, for a newbie, easy to follow and get going, all parts COTS (common off the shelf)
you guys ever design a power supply before? lots of transformers off-the shelf that are made for exactly the original poster's needs. the transformers are designed to suit some existing off-the shelf controllers. it couldn't be easier, especially using 230Vac as the input since this is such a common value. if you have to meet some specific customer spec, that's different.. but if its just a one-off for personal use in the 5 to 30W range? couldn't be easier.

I agree with Anna Conda. PI's reference material is pretty good though they ALWAYS encourage you to wind your own transformer which i hate.
also, youtube flyback transformer design. there is like a 10 series video that is fairly decent.

off the shelf transformer suppleirs:

there are others

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