3.3vdc power from 24vac

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#1
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For many years I've powered my projects with LM1806 or similar regulator, usually running it through a full wave bridge so you can use just about any off the shelf wallwart.

I'm now looking at a project where the power input available is 24VAC, and this presses the LM1806 a bit hard and creates a lot of heat. So I'm looking for
a better solution.

I need 250MA @ 3.3v

I'd like it to be somewhat cost effective (IE no $10 solutions). Anyone have any suggestions?

Maybe I can use the LM1806 just used in a different configuration?

Thanks,

Mycal

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Using a linear regulator you'll need to waste around 7-8W therefore things are going to get hot. You'll need to look at a switchmode style of supply. Something like the National Semiconductor 'simple switcher' range. For a one-off the cost of parts may run into the $10 range.

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Use the full-bridge to convert the input to DC. Then use a DC-DC step-down converter like TI's MC33063AQDRQ1.

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I'd be looking at the 34063 also. Generic, easy to get and adequate.

http://www.hsmc.com.tw/pdf/H34063A.pdf

oddbudman

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Thanks for the input, the H34063A looks good but I can't find a place that sells it for proto types or price info.

My friend suggested I use the LM2595 as he has used it with success in a project with a power supply section cost of around $4 in low qtys.

I'm leaning towards that unless I find something better to try.

-M

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woops over looked the MC33063AQDRQ1, this looks very interesting I may look into that too. Cost looks quite a bit cheaper.

Thanks!

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mycal, the 34063 is a generic switching regulator. Many companies make a version of this. st, taiwan semiconductor, onsemi etc etc

Use the '34063' number in your keyword search and you should find some options.

oddbudman

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Ooops, didn't make the connection, now I do, thanks.

-M