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Old 23rd June 2009, 07:29 PM   #1
purpf is offline purpf  Lithuania
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Default 35v to 18v

Hi,
What's the best way to drop the voltage of a PSU from 35v to 18v? Im thinking about a shunt voltage stabilizer.
What's your opinion?
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Old 23rd June 2009, 08:11 PM   #2
mjf is offline mjf  Austria
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hello.
do you want to use the psu with a preamp.......or something else?
current consumption?
greetings..........
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Old 23rd June 2009, 08:58 PM   #3
acid_k2 is offline acid_k2  Italy
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Other questions:
Do you need stable voltage? intermittent or continuos load? low ripple? low noise? low heat dissipation? small space available? other specification?
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Old 23rd June 2009, 09:08 PM   #4
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There is no way to give you a good answer without knowing your requirements: power level, regulation, noise and ripple, overload protection, efficiency, etc. Nonetheless, a current mode buck regulator would be a good choice.
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Old 24th June 2009, 12:20 AM   #5
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Going from 35V to 18V is a 17V drop. If you want to draw even a measly 200mA, you'll dissipate 3.4W. Maybe that's ok, but the suggestion of a switching buck regulator is a very good one if you need any significant amount of current. There's a reason you'll almost never find a shunt regulator in commercial equipment (non-audio) other than as a voltage reference- they're a bad choice in almost any imaginable application.
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Old 24th June 2009, 02:24 AM   #6
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Quote:
Originally posted by Conrad Hoffman
There's a reason you'll almost never find a shunt regulator in commercial equipment (non-audio) other than as a voltage reference- they're a bad choice in almost any imaginable application.
Except to save yourself warm in upstate NY winters.
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Old 24th June 2009, 10:50 PM   #7
purpf is offline purpf  Lithuania
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I'm thinking of using a 2x24v toroidal core transformer with 2 PS units. 1 PSU to power an LM3875 chip amp and the other to power a preamp. Unless I can find a preamp powered by ~35v, I need to lover the voltage to about 18v.
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Old 24th June 2009, 10:50 PM   #8
purpf is offline purpf  Lithuania
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I need stable DC current, the simplest solution is always the best
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Old 24th June 2009, 11:49 PM   #9
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Though I don't have schematics handy, I think there have been a variety of discrete preamps over the years that ran on 35 and higher voltish single ended supplies. The claimed advantage was headroom on transients.
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Old 25th June 2009, 12:32 AM   #10
wwenze is offline wwenze  Singapore
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Hmm? I know of op-amps that can handle +-17V. You can get a rail splitter to split the +35V to +-17V
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