Adjustable regulator for 50v - diyAudio
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Old 14th April 2007, 03:23 PM   #1
Dengbej is offline Dengbej  Isle of Man
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Default Adjustable regulator for 50v

I need an adjustable voltage regulator like LM338 but LM338's datasheet confirms that maximum load is 35v. But i have 45v dc need to regulate about 34-36v.
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Old 14th April 2007, 03:40 PM   #2
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take a look at national semiconductor "Linear Brief 47" -- this will show you how to do it.

jack
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Old 14th April 2007, 11:49 PM   #3
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If you can make do with 700mA of current, you could go for the TL783... http://focus.ti.com/docs/prod/folders/print/tl783.html
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Old 15th April 2007, 12:39 AM   #4
Dengbej is offline Dengbej  Isle of Man
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Thank you for reply. But i need to 5 amp regulator for using in regulated gainclone project.
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Old 15th April 2007, 01:05 AM   #5
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That amount of voltage drop and current in a regulator will likely dwarf the chip amp in complexity and heatsinking. Best use a different transformer, or look for a more suitable amp project. AAK's symasym version would work on those rails, and likely sound better than a chip amp anyway.
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Old 15th April 2007, 01:22 AM   #6
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Also, as eeka chu says above = take a look at page 10: http://focus.ti.com/lit/ds/symlink/tl783.pdf

High current and higher voltage (to 125 VDC), adjustable = no worry mate
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Old 19th April 2007, 05:52 AM   #7
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Default Adjustable Regulator

Consider using the LM317/LM337 regulators. They are available in both positive and negative polarities and are designed for floating applications. In other words, they can regulate any input voltage as long as the input to output voltage difference is less than aprox 35V. The output voltage is set by a ratio of two external resistors. I have used these devices in many applications, and they are reliable and easy to design with.

For a 5A supply, you will need to use an external pass transistor, but National Semi has an example shown in their application notes (look under LM317 or LM337 on their website).

Hope this helps.

JCM
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Old 19th April 2007, 12:51 PM   #8
AMV8 is offline AMV8  United Kingdom
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Hi

I have used lm devices with pass transistor as analogue guy says and I found it worked just fine. I used it for a JLH amplifier.

Recently I prefer to simply use the pass transistor/mosfet with zeners to set the voltage without using the lm devices as I find this approach sounds the best. You can use either pass transistors or mosfets; either will work just fine. If you are not familiar with this concept there is a 4 page explanation of how to design and build a power supply using pass mosfets or transistors by Nelson Pass in the The Zen Variations part three "Active supply Regulation" at Passdiy. A superb article by Nelson as always and well worth a read if you have not done this before.

I also add capacitors between the positive and negative rails and audio ground just before the amplifier modules. I do not know the details of your amplifiers but I usually use 1000uf capacitors in thsse locations. I also use high quality 105 degree capacitors.

Don
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Old 19th April 2007, 02:40 PM   #9
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I used LM317 and some 2N3055's to make a pass supply(with lots of help from friendly members).

http://www.diyaudio.com/forums/showt...03#post1046703
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Old 19th April 2007, 05:52 PM   #10
Bone is offline Bone  United Kingdom
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Why not use the LM317HV see http://www.national.com/pf/LM/LM317HV.html

Tony.
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