-200 VDC regulator

[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

 

[Nordic]

a fat 3k5 resistor maybe? 2 - 5W

70/3500 = 0.02A

 

[jogas]

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

 

[theAnonymous1]

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]

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]

Re: Re: -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

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]

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]

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]

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.