-200 VDC regulator

jogas · 3rd January 2008, 12:18 PM

Hi,

I need to reduce a -270 VDC down to -200 at 20 mA.
Is there any three pin component available?
I only found a VB408 that is a positive regulator

Thanks in advance for your help
Giuseppe

Nordic · 3rd January 2008, 12:21 PM

a fat 3k5 resistor maybe? 2 - 5W

70/3500 = 0.02A

jogas · 3rd January 2008, 12:40 PM

.... I do need a very precise and stable and current independent -200VDC...

theAnonymous1 · 3rd January 2008, 01:12 PM

Is it not possible to use two LM137HV? Use one to pre-regulate down to around -235v and the other to drop down to -200v.

BWRX · 3rd January 2008, 01:39 PM

Quote:

Originally posted by jogas
I need to reduce a -270 VDC down to -200 at 20 mA.
Is there any three pin component available?

Have you thought about just using a zener (or a string of zeners), resistor(s), and pnp transistor? A 70V drop across a transistor sinking 20mA is only 1.4W. You could also put a resistor in series with the collector to reduce the transistor's dissipation.

jan.didden · 3rd January 2008, 01:58 PM

Quote:

Originally posted by jogas
Hi,

I need to reduce a -270 VDC down to -200 at 20 mA.
Is there any three pin component available?
I only found a VB408 that is a positive regulator

Thanks in advance for your help
Giuseppe

If your raw supply is floating you can use a pos regulator. Just ground the pos terminal and use the common terminal (which normally would be grounded) as the neg terminal. Works like a charm.

Jan Didden

SY · 3rd January 2008, 01:59 PM

I'd use a Maida regulator with a 337 and either a HV PNP bipolar or HV p-channel MOSFET. Simple, stable, low output impedance, low noise. And reliable.

jogas · 3rd January 2008, 02:06 PM

Thanks for the answers, yes, the easiest way is to use apositive regulator with the output grounde...

SY what is a maida regulator?

Giuseppe

SY · 3rd January 2008, 02:11 PM

Poke around National Semiconductor's site. There's a nice paper by Michael Maida on using a HV bipolar to limit the voltage across a 317-type regulator. I think the paper is Linear Brief LB-47. This paper only shows positive regulators, but by using PNP (or p-channel FET), a 337, and turning around the diodes, you can make a negative regulator.

Or you could use the positive regulator as published inserted in the ground leg of your raw supply.

3rd January 2008, 12:18 PM	#1
jogas diyAudio Member Join Date: Jun 2004 Location: Milan	-200 VDC regulator Hi, I need to reduce a -270 VDC down to -200 at 20 mA. Is there any three pin component available? I only found a VB408 that is a positive regulator Thanks in advance for your help Giuseppe

3rd January 2008, 01:12 PM	#4
theAnonymous1 diyAudio Member Join Date: Feb 2004 Location: Anonymityville	Is it not possible to use two LM137HV? Use one to pre-regulate down to around -235v and the other to drop down to -200v. __________________ "If you don't like funerals don't kick sand in Ninja's face." - Ninja

3rd January 2008, 01:59 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	I'd use a Maida regulator with a 337 and either a HV PNP bipolar or HV p-channel MOSFET. Simple, stable, low output impedance, low noise. And reliable. __________________ If there's a sucker born every minute, where do the rest of them come from?

3rd January 2008, 02:11 PM	#9
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Poke around National Semiconductor's site. There's a nice paper by Michael Maida on using a HV bipolar to limit the voltage across a 317-type regulator. I think the paper is Linear Brief LB-47. This paper only shows positive regulators, but by using PNP (or p-channel FET), a 337, and turning around the diodes, you can make a negative regulator. Or you could use the positive regulator as published inserted in the ground leg of your raw supply. __________________ If there's a sucker born every minute, where do the rest of them come from?

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3rd January 2008, 12:21 PM	#2
Nordic diyAudio Member Join Date: Sep 2005	a fat 3k5 resistor maybe? 2 - 5W 70/3500 = 0.02A

3rd January 2008, 12:40 PM	#3
jogas diyAudio Member Join Date: Jun 2004 Location: Milan	.... I do need a very precise and stable and current independent -200VDC...

3rd January 2008, 02:06 PM	#8
jogas diyAudio Member Join Date: Jun 2004 Location: Milan	Thanks for the answers, yes, the easiest way is to use apositive regulator with the output grounde... SY what is a maida regulator? Giuseppe

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