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changing dc power supply output voltage???

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seaball

New Member
can this be done easily?

specifically, i would like to see a 2 volt output from an old pc power supply that is rated at 12v,4.8 amps and 5v,18 amps.

can i create a simple external curcuit that i could attach to either output (12v or 5v) to get a 2v output with decent current capabilites (10amp+)?

many thanks in advance for your help.

chris.
 

stevez

Active Member
If efficiency isn't a problem you could add a power resistor (or several) to get rid of 3 volts from the 5 volt end but unless the load is constant there would be no regulation of voltage.

You might use a voltage regulator with pass transistors - 3 volts drop is just a little more than the minimum for come common types. Look up LM317 for data sheets - I think the sheet describes pass transistor requirements and configuration.

Both of the above are wasteful but are external and parts count is limited. Internal modification of the supply certainly seems possible but it would also seem that there are so many variations that you'd have to provide more detail on the supply.
 

Roff

Well-Known Member
Here is a cookbook design I found at the Maxim website. If you need 2 volts with no adjustability, you can toss U2 (a D/A converter) and R2, and change R10 to 6.2k and R11 to 10k. Layout is very important in high current supplies. You should read some of the app notes available from Maxim before proceeding. Also, read the MAX1864 datasheet.
Sebi might be able to provide more assistance (sorry, Sebi).
 

seaball

New Member
thank you again for your quick responses. i am no electonics wiz...like you couldn't tell. i do however dabble enough to need the answers to a few of these question. this forum is great.

many thanks.
 
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