+-45vdc regulated power supply schematics needed. - diyAudio
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Old 12th August 2012, 10:05 AM   #1
Maroof is offline Maroof  Pakistan
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Default +-45vdc regulated power supply schematics needed.

Hi,
I want to build a +-45v dc regulated power supply for my TDA7293 stereo amplifier. But the problem is i have a 36-0-36 v ac 1000va transformer and the max voltage for TDA7293 is +-50v dc . can someone give me schematics for +-45v dc regulated power supply?
Sorry for English.
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Old 12th August 2012, 12:00 PM   #2
AndrewT is offline AndrewT  Scotland
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Buy the correct transformer.
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Old 12th August 2012, 12:56 PM   #3
d a o is offline d a o  Denmark
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If you use "Full-Wave Bridge Rectifier" it is necessary voltage drop 0.7 volts for each diode is in series, ie 0.7 * 2 = 1.4 volts for a "Full-Wave Bridge Rectifier".
In time of need you can put 2 or 3 "Full-Wave Bridge Rectifier" after each other, ie 2 units = 2.8 volts or 3 units = 4.2 volts.
In other words, 36 volts AC * SQR (2) = 51 volts AC minus 1.4 volts per "you use and at 2" Full-Wave Bridge Rectifier "will be about 48.2 volts at 3" Full-Wave Bridge Rectifier "is the 46.8 volts.
But the best is to have the correct AC voltage transformer and 1 "Full-Wave Bridge Rectifier"

http://hyperphysics.phy-astr.gsu.edu...ic/rectct.html
http://www.otherpower.com/rectifiers/image002.jpg
http://wiki.answers.com/Q/How_you_co...t_by_equations
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Last edited by d a o; 12th August 2012 at 01:06 PM.
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Old 12th August 2012, 06:06 PM   #4
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Your transformer is ideal for an unregulated supply.
for a regulator , try PA100 DIY 2x LM3886 in parallel gainclone audio amplifier
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Old 12th August 2012, 06:42 PM   #5
Maroof is offline Maroof  Pakistan
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Quote:
Originally Posted by whizgeek View Post
Your transformer is ideal for an unregulated supply.
for a regulator , try PA100 DIY 2x LM3886 in parallel gainclone audio amplifier
Thanks for help.
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Old 13th August 2012, 04:54 AM   #6
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Do not try the LM317 for 45 volts output. It will get damaged as it can withstand 35 volts across itself.

At power-on, there will be zero volts at the output.

Search for transistor assisted zener regulator.

Gajanan Phadte
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Old 13th August 2012, 10:14 AM   #7
AndrewT is offline AndrewT  Scotland
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Use a Zener across 317 IN/OUT to limit the start up voltage drop.
That same Zener acts as the 317 protection against reverse voltage at shut down.
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Old 13th August 2012, 10:27 AM   #8
AJT is offline AJT  Philippines
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Quote:
Originally Posted by Maroof View Post
Hi,
I want to build a +-45v dc regulated power supply for my TDA7293 stereo amplifier. But the problem is i have a 36-0-36 v ac 1000va transformer and the max voltage for TDA7293 is +-50v dc . can someone give me schematics for +-45v dc regulated power supply?
Sorry for English.
how heavy is your traffo? what is the primary dc resistance? how high does your power line go?

if you know the answers to my question then we can say if you can use your traffo....as it stands, yours is on the brink....

36-0-36 v ac 1000va transformer looks huge for 7293 you can power half a dozen of such amps easy....

36-0-36 v ac will give you +-50volts dc unloaded, but loaded it will still drop....
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Old 13th August 2012, 10:30 AM   #9
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Tony View Post
36-0-36 v ac will give you +-50volts unloaded,
this is very misleading.
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Old 13th August 2012, 02:04 PM   #10
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Quote:
Originally Posted by AndrewT View Post
this is very misleading.
i guess you thinking of regards to main voltage?
i can confirm that 2*36V transformer gives +/-50.5V unloaded with dual rectifier bridges and CRC with R at 0.11ohm, on 234V mains. this was with a 500VA transformer.
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