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Old 31st December 2010, 04:15 PM   #1
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Default Need Negative High Voltage Regulator Circuit

Can someone point me to a good voltage regulator circuit for a high (-70V) supply? The transformer rating is: 50V, 0.1A out @ 120V, 60Hz in. I don't need a dual polarity supply, just the one single supply.

So far all of the voltage regulator IC circuits I've found top out well short of the voltage I'm using; using separate components isn't a problem.

Thanks.

EBS
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Old 31st December 2010, 05:13 PM   #2
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Almost any voltage regulator needs more input voltage than output voltage.
Depending on the load your 50V transformer may not even supply 70V DC
let alone the 72Vdc or higher you will need. Do the math 50VAC X 1.41
= 70.5 VDC - ~2V ( droped across the bridge rectifier) = 68,5 VDC so you
don't even have 70VDC let alone any extra for the regulator to play with.
But at a verry light load that transformer will probably be closer to 60VAC
so you may want to build a DC supply and test it under your expected load
to see if you do have some voltage to work with.
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Old 31st December 2010, 05:33 PM   #3
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Woody:

Thanks for the reply.

I can tolerate some drop in the actual working voltage. If I wind up with something in the 60 - 65V range it will be fine. If I have to use a bigger transformer to get there that's fine too. It's the regulator circuit that's got me stumped at the moment.

EBS
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Old 31st December 2010, 05:51 PM   #4
iko is offline iko  Canada
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You can use a voltage doubler to deal with the voltage drop across the regulator. How large a current does the load circuit draw?
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Old 31st December 2010, 06:28 PM   #5
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Use the TL783 high voltage regulator and reverse the outpots
as is discused in this link.

Re: Voltage regulator
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Old 31st December 2010, 08:34 PM   #6
tatus is offline tatus  Germany
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Quote:
Originally Posted by EBSDallas View Post
I can tolerate some drop in the actual working voltage.
Don't understand this. If you can tolerate that the regulator does not regulate, why do you then need a regulator?

Have a look at the old-age but still interesting LM317, it's nothing that has not been done with it... For example: www.national.com/ms/LB/LB-47.pdf
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Old 31st December 2010, 09:16 PM   #7
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Quote:
Originally Posted by tatus View Post
Don't understand this. If you can tolerate that the regulator does not regulate, why do you then need a regulator?

Have a look at the old-age but still interesting LM317, it's nothing that has not been done with it... For example: www.national.com/ms/LB/LB-47.pdf
Sorry.

I can accept some voltage less than -70V due to the requirements of the regulator circuit. Say -65Volts as long as the -65Volts is regulated.

Thanks.

EBS
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Old 31st December 2010, 09:36 PM   #8
tatus is offline tatus  Germany
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okay understood!
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Old 1st January 2011, 09:02 AM   #9
Elvee is offline Elvee  Belgium
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Why not go for something discrete?
It is barely more complex than an integrated regulator, but more flexible and more robust.
Here is an example: the performances are comparable to an integrated regulator, and as a bonus, it is low drop-out.
Attached Images
File Type: jpg HVreg1.jpg (163.4 KB, 738 views)
File Type: jpg HVreg2.jpg (167.7 KB, 657 views)
File Type: jpg HVreg3.jpg (166.1 KB, 627 views)
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Old 1st January 2011, 11:54 AM   #10
tatus is offline tatus  Germany
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Nice circuit, has better PSRR than a LM317. To my opinion the drawback is missing current limit and thermal protection. How are line and load transient response, temperature stability?
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