Looking for transformers to build +5V, +12V power supply for CD-ROM drive

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Saurav

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Joined 2002
I'd like to build a linear power supply for my CD-ROM drive. I looked at Avel-Lindberg, but didn't find any transformers with different output voltage secondaries. One option is to buy separate transformers for the two supplies (say 15V and 8V secondaries or something). I guess another option would be to build a 12V supply and use a voltage divider to get the 5V? But then a sag in one supply would make the other one sag too... but a voltage regulator will probably take care of that?

Has anyone done this before? Are there any transformers out there that I can use for this? Anything else I need to know or watch out for?

Thanks,
Saurav
 
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Saurav

Member
Joined 2002
I know what the LM7812 does (I have LT1085 so I'd use those), I'm not familiar with the MAX724. So it's a 'switching regulator'... takes in the 12V, and produces 5V using PWM? Doesn't this defeat the purpose of building a linear power supply though, if I use a switching regulator?
 
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sayang001

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Joined 2003
vanleusden.xs4all.nl
I used the MAX724 to limit the dissipation loss in de regulator.

12Vac => 15V dc under load. The CDRom player I have uses about 1.5A on the 5V line, with a linear regulator this would be a loss of 1.5A x 10V = 15W. in the regulator. With the MAX724 I reduced the loss to 4W. You can add an output filter to make the dc more smooth, see the datasheet for examples.

You can find the MAX724 datasheet here:

http://www.maxim-ic.com/quick_view2.cfm?qv_pk=1269
 
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