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Old 10th September 2003, 10:02 PM   #1
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Question current boosted lm317..

wanna build agood regulated linear ps. for a small car amp. which
iuse it here at home, the ICs inside works directly from a 12v.
source, iwanna current boost the lm317 regulator using the
common 2N3055 pass transistor,
idid a search & found this one attached, iuse a 12-0-12 center
tapped 10A trans. with 15A bridge rectifier ,have about 30,000
or more as needed filter capacitance ,ijust wanna make sure that
the ps. would give about 6A continously for the amp.

so how much current this schematic would produce?
any mods. needed to achieve the requireds?

thanks alot guys..
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Old 11th September 2003, 04:02 AM   #2
paulb is offline paulb  Canada
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It should work. But watch out for the power being dissipated in the 2N3055. If you use a standard full wave bridge you'll get about 30 volts from your transformer, with 12 volts output at 6 amps, the transistor will give off (30-12)*6 = 108 watts of heat, which is not practical. Consider parallelling a bunch of output transistors.
A full wave centre tap (2 diodes) instead might work.
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Old 11th September 2003, 04:37 AM   #3
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parallel the transformer outputs - will give enough voltage and reduce the drop over the 2N3055
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Old 11th September 2003, 05:56 AM   #4
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Default Consider using a Darlinton

I would switch to a Darlington transistor you can then decrease the drive current. Also, the LM317 and LM337 and be biased with a zenner. The regulator will also work at 1/4 National recomended biasing with out losing regulation. Of course you could just use a 7812.
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Old 11th September 2003, 10:33 AM   #5
hacknet is offline hacknet  Singapore
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why not you use a computer psu which will solve all ur power supply problems...
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Old 11th September 2003, 01:14 PM   #6
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Quote:
Originally posted by paulb
It should work. But watch out for the power being dissipated in the 2N3055. If you use a standard full wave bridge you'll get about 30 volts from your transformer, with 12 volts output at 6 amps, the transistor will give off (30-12)*6 = 108 watts of heat, which is not practical. Consider parallelling a bunch of output transistors.
A full wave centre tap (2 diodes) instead might work.
the transformer iuse is 12-0-12 , so after rectification iwould get
about 18v. , as i use only the +12 & the ground not the both rails.
so what do u think now?

Quote:
Originally posted by hacknet
why not you use a computer psu which will solve all ur power supply problems...
itried to use the computer ps. to power it up ,but it presented much noise into the subwoofer, some "zzzzz" sound when moving
the mouse.. other when opening progs...etc
u ve any ideas about this?!
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Old 11th September 2003, 02:30 PM   #7
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Check out this project on Rod Elliots page.
http://sound.westhost.com/project77.htm

You cannot use the same power supply in your computer for your amp, as you have experienced. You have to go buy a computer power supply or get one from an old computer or something and use it for your amp.
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