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Old 28th February 2009, 11:37 PM   #1
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Default -500V Maida regulator inquiry

I am about to embark on my second Maida regulator design. I am a bit concerned, though. I am unable to find a pass device rated for a voltage greater than the raw DC supply voltage. Is this only a concern if you want the supply to survive a short circuit? I am willing to live with destruction of the components if I am dumb enough to short the output.

I am planning on making a -500V regulator with about -560V raw DC.
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Old 1st March 2009, 12:11 AM   #2
SY is offline SY  United States
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Power on and power off are a concern. I haven't tried a Zener across the pass device yet, but that might give you some protection.
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Old 1st March 2009, 12:24 AM   #3
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I don't plan on having any downstream capacitance, so I guess I'll try a zener across the pass device and see how reliable that is. With minimal capacitance there won't be much pinning the output to ground at power-up or a bunch of energy to bleed off at power-down. Hopefully, the Zener won't see any huge current surges.

I've also thought about two pass devices in series. Dropout voltage would be higher, though.

I just wish there was an 800V p-channel FET.
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Old 1st March 2009, 02:21 AM   #4
Colt45 is offline Colt45  Serbia
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if you have a seperate winding for the -500v, just regulate the high (ground) side... then you can use Nch stuff.
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Old 1st March 2009, 02:44 AM   #5
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Quote:
Originally posted by Colt45
if you have a seperate winding for the -500v, just regulate the high (ground) side... then you can use Nch stuff.

As recommended in "The Art of Electronics".

If you have to do the high-side there are a lot of HV MOSFETs.
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Old 1st March 2009, 04:08 AM   #6
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I was going to use a Hammond 278CX(800VCT) to create a +-500V supply, so windings are not separate. I guess I could consider a custom wind from Edcor. That may be the most reliable solution.
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Old 1st March 2009, 10:05 AM   #7
disco is offline disco  Netherlands
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Did you consider the T-reg or the Swenson Reg instead ?
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