EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: mrpackethead on July 17, 2015, 02:08:52 am
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Hi, I'm looking for a reference design for a very low cost Switching supply, it needs to be Isolated, and i need .2A @ 5V..
Any suggestions.
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I seriously doubt that you can do better than to copy the usual crappy USB charger designs, albeit hopefully with proper safety (2500V isolation in the transformer, enough mechanical strength it won't fall apart on the user, properly rated X/Y caps if used, a fuse, etc.)
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Buy a phone charger and take out the guts
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Actually better than buying a charger, go to some random hotel with your phone in hand. Tell them you think you left your phone charger in a room and they will bring a box of chargers for you to choose from. Once you have this, take out the guts and install it in a project box with small isolation transformer on the input. If you can't find a small 1:1 transformer, then get two line to 12V transformers and then connect them secondary to secondary and you will have a small isolation transformer.
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He's looking for a design, not a charger :-//
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He did say extremely low cost. Doesn't get any cheaper than a genuine Won Hun Lo micro usb charger, cough up a few bucks and they will send a 10 pack of them your way with free shipping.
Tho the isolated part might be debatable with those, since they have a pretty liberal definition of isolated at the good ol Hun Lo co.
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He's looking for a design, not a charger :-//
Yes you are right, he asked for a design, not something purchase. :palm:
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buy one of these :
http://www.dx.com/p/isolated-switching-power-supply-module-green-5v-600ma-240410#.Vak9GWZG1Uw (http://www.dx.com/p/isolated-switching-power-supply-module-green-5v-600ma-240410#.Vak9GWZG1Uw)
then reverse engeneer it there is quite nothing inside should be easy...
(http://img.dxcdn.com/productimages/sku_240410_1.jpg)
or use texas search engine for power supply :
http://webench.ti.com/webench5/power/webench5.cgi?lang_chosen=en_US&VinMin=85&VinMax=260&source=AC&line_fsw=50&O1V=5.0&O1I=0.5&op_TA=30 (http://webench.ti.com/webench5/power/webench5.cgi?lang_chosen=en_US&VinMin=85&VinMax=260&source=AC&line_fsw=50&O1V=5.0&O1I=0.5&op_TA=30)
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buy one of these :
http://www.dx.com/p/isolated-switching-power-supply-module-green-5v-600ma-240410#.Vak9GWZG1Uw (http://www.dx.com/p/isolated-switching-power-supply-module-green-5v-600ma-240410#.Vak9GWZG1Uw)
then reverse engeneer it there is quite nothing inside should be easy...
And how would you go about sourcing the unmarked IC and transformer?
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Getting a properly designed brand charger and reverse-engineering it would make a lot of sense, as you will learn practical things that are lacking from the simplest designs - especially related to safety and EMI. Ebay/DX chargers could give wrong ideas, or nothing extra compared to simplest flyback example design you can find on Google image search for schematic, although that would still be a good starting point.
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Hi,
Look at the offerings from Power Integrations:
https://ac-dc.power.com/products/tinyswitch-family/tinyswitch-4/ (https://ac-dc.power.com/products/tinyswitch-family/tinyswitch-4/)
They may have lower power products but this is a start.
Jay_Diddy_B
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buy one of these :
http://www.dx.com/p/isolated-switching-power-supply-module-green-5v-600ma-240410#.Vak9GWZG1Uw (http://www.dx.com/p/isolated-switching-power-supply-module-green-5v-600ma-240410#.Vak9GWZG1Uw)
then reverse engeneer it there is quite nothing inside should be easy...
And how would you go about sourcing the unmarked IC and transformer?
99% chance the IC is a UC3842 ...