DC to DC converters

Hi All,
I need a 5V to 12V DC to DC converter (at least 500mA). I'd like to find one that doesn't require external components but that is proving to be
difficult. Anyone know of any part numbers off hand? Thanks.
-Dave
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On Mon, 2 Feb 2004, it was written:

Dave -
It's much easier to go the other way (from 12V down to 5V). (just put the 12V into a 5V regulator and you're ready to go)
To go 5V up to 12V, you will need to design a "chopper" circuit. The output of the Chopper will get fed into a step-up transformer (probably want to go up to about 24 volts out of the transformer). The output of the transformer will go thru a rectifier and filter (the output of the filter should be around 16VDC). This will then go into a 12V regulator.
---Keith Lehman University of Wisconsin - Milwaukee
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This is true.

This is not.
Its fairly straight forward to build a "boost" switching regulator that will take 5V in and produce 12V out, however it won't be "without external components." Fortunately a number of places sell "potted" DC-DC converters that take in 5V and output 12V.
Consider the Nichion part # ZHR060512C http://www.nichicon-us.com/english/seihin/pdfs/e-hi_dc.pdf
A 6W, 5V in to 12V out, DC-DC converter in a single package.
--Chuck
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Thanks all. Of course I've found some boost converters that do the job, but not without external components, mainly the inductor and a couple of bypass capacitors, it's no big deal really, but I like to reduce component counts whenever possible. I did also find some of the "variety" to quote Chuck but they are $$$. Maxim 761 is probably what I'll use, cheap and easy. In my robot, I'm adding an active cooling system to a voltage regulator that gets hot. I'm using a mini-CPU fan out of an old computer which requires 12 volts @ 90mA from a 6 cell pack, hence the need for the converter. Regards,
-Dave

will
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Call me stupid but wouldn't it be easier to find a 5 volt fan. I know sunon make them, I just don't know where you would buy one.
Dave wrote:

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Yes you can get them, but I don't have a 5 volt fan and they're rather expensive. It does run at 5 volts but too slow to be all that useful. Regards,
-Dave

converters
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Hmm, I don't know what fans you been looking at but a google search for '5v fan' turns up its first hit with a $3.50 fan that might work for you. http://www.cascadesurplus.com/new/catalog/product_info.php/products_id/50
-C http://hossweb.com
"Dave" <blank> wrote:

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Locally of course at computer shops they're expensive. Aside from that, Digikey and Jameco are the usual suppliers I check first. Thanks for the link, now I have another place I can check. Regards,
-Dave
wrote:

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Also have you tried to run the fan from 5 volts it may run ok just a bit slower. Or tried a larger heatsink.
Dave wrote:

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On Tue, 3 Feb 2004, Chuck McManis wrote:

I was not aware of these devices. was going by OLD experience.
---Keith Lehman
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I was trying to use some of the National DC-DC converter chips myself. I was looking to convert 13.6v into 24v and or into 36v. National's webbased app was interesting. Most of the resistor parts came out at around zero ohms or close t it. It had me wondering if it would work or not. For example: http://www.national.com/appinfo/power/webench / Using a LM3478 with 10.6 to 14.5 volts input 24.5 volts output at 2.0 amperes Comes up with some interesting custom parts. It has me wondering if just the resistance of a length of PCB trace would do it for things like 0.01668 ohms and 0.00022 ohms or whether the solder joint would be sufficient? The power transistor would be an interesting choice too. If I built it, would the magic smoke leave the chips or transistor or not. It has me curious.

will
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Dave wrote:

Try Jameco. -- D. Jay Newman http://enerd.ws/robots /
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