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Foaad
Guest
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 Posted:
Thu Feb 10, 2005 7:21 am Post subject:
Ac to DC without transformer |
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Hi, I was wondering if there were any single chip solutions to
convert from 120V AC to DC
We are currently using a transformer but its a bit bulky to put on a
printed circuit board.
The chip will have to provide 5V DC for a couple of IC's.
0.1A is maximum current required.
Thanks in advance.
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Tim Wescott
Guest
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| Posted:
Thu Feb 10, 2005 7:26 am Post subject:
Re: Ac to DC without transformer |
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Foaad wrote:
| Quote: | Hi, I was wondering if there were any single chip solutions to
convert from 120V AC to DC
We are currently using a transformer but its a bit bulky to put on a
printed circuit board.
The chip will have to provide 5V DC for a couple of IC's.
0.1A is maximum current required.
Thanks in advance.
|
Do a web search on off line power, or off line switcher. Lots of info.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com |
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Paul Mathews
Guest
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| Posted:
Thu Feb 10, 2005 10:42 pm Post subject:
Re: Ac to DC without transformer |
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At these power levels (1/2 Watt), switchers aren't much smaller than
linear transformers. If ALL of your circuitry is isolated properly,
you can consider using series capacitance instead of a transformer, but
you'll need about 3uF, and properly rated capacitor(s) could also be
about as large as a 1VA transformer. You might want to put your
energies into looking for the smallest possible linear transformer,
especially if your product has any exposed metal.
Paul Mathews
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Rock
Guest
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| Posted:
Thu Feb 10, 2005 11:38 pm Post subject:
Re: Ac to DC without transformer |
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No single chips that I know of, but check out Power Integrations and
their LNK304 series of chips (www.powerint.com). This takes at least 10
other components to make it work, but it works well and they are cheap
solution.
At .1A you need too big a series cap to do a simple ac coupled bridge
converter for it to be cheap, however, if you can lower current to
about 20ma it is a good way to go.
Of course I'm thinking you don't need isolation?
Rocky |
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Alan Turner
Guest
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| Posted:
Fri Feb 11, 2005 8:22 pm Post subject:
Re: Ac to DC without transformer |
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Hi,
On Wed, 09 Feb 2005 17:21:14 -0800, Foaad wrote:
| Quote: | Hi, I was wondering if there were any single chip solutions to
convert from 120V AC to DC
We are currently using a transformer but its a bit bulky to put on a
printed circuit board.
The chip will have to provide 5V DC for a couple of IC's.
0.1A is maximum current required.
Thanks in advance.
|
If you're after a "transformerless" power supply you might consider
looking at an ATT2406. I played with one of these several years ago - I
still have one or two lying about, but I can't seem to find the datasheet
on the 'net.
My memory of the details of this IC are very hazy, so take what follows
with a grain of salt. The IC detected zero crossings and charged a
capacitor directly from the mains right at the start of a half-cycle. When
the instantaneous mains voltage reached some threshold the capacitor was
disconnected from the mains and used to supply a linear regulator. The IC
came in a plastic DIP8 package
I don't know if this IC would meet your current requirement of 100mA. Also
note that it does not provide isolation (which may or may not be important
for your application).
I'd avoid transformerless power supplies unless I were desperate.
Regards,
Alan
--
Alan R. Turner | Live never to be ashamed of anything you do or say.
To reply by email, remove Mr Blobby. |
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