700v regulator circuit help???

I have posted several circuits.

You'll need at least 175 watts of heat-dissipating capability to handle a short, so you'll need more than one power MOSFET, even if you add foldback current limiting, which you should certainly consider. What's the unregulated input voltage? How much higher will it soar at high AC line and low load?

MOSFETs are preferred because unlike BJTs they don't suffer from second breakdown, which severely limits a BJT's high- voltage linear power-handling ability.

On a sunny day (Mon, 08 Oct 2007 05:32:57 -0700) it happened Winfield wrote in :

Is not normal practice to use a switcher or switcher before the linear regulator? That way, although the switcher is slow, the dissipation is only for a few milliseconds. I did this for a telco with thyristor followed by linear regulator many decades ago. The thyristor switcher regulated so there always was about a few volt across the linear regulator so it could filter 100Hz ripple...

P from Mars

Where might one find them? I'm considering a similar regulator for a circuit. (~600-650Vin,and perhaps,450-500Vout. maybe about 450ma max.)

In your case, you want the absolute simplest circuit you can get away with. Your question contains absolutely no information about the application in so far as describing the load characteristics or regulator performance. You might as well be asking for a space qualified ruggedized laboratory grade power supply.

Wonder if he could get by with an electronic circuit breaker instead if the current limiter. This would get away from the huge power dissipation requirement. I would configure this to both turn off the pass transistor, and open the AC.

Tam

You didn't specify AC or DC ?, so i'll assume DC voltage to the source? And you didn't specify what kind of control you have over this assumed already existing 700V at 250ma source?

--
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

It is for a power supply for a Vacuum tube military transmitter for which I do not have the power supply I need to build one. The power supply that would have came with the Tx used a number of chokes which were very heavy. I want to build something a bit more modern and not so heavy. The transmitter uses CW and SSB / RTTY modes of operation I have a toroid transformer for this purpose which is

Yes, That explains a lot thank you. :) Simple phase controller on the primary that can be biased. Use a comparator with voltage divider and protection on the HV side to drive a opto-coupler. You would need a cap at the voltage divider so that you can pad the small ripple that will be there. The output on the other side can be part of a RC network to create a slow change to a bias point for the phase angle timing. I did something like this once before but not for a transmitter. it was to stabilize a lab high voltage supply. I used a very crap design of a a phase control . something you would see in a simple light dimmer. :) the isolated feed back circuit worked with the DIAC to adjust the firing point. I got to say, for something that was very cheap and dirty, it worked very good and still in use. This supply I speak of goes from 0..25k DC . the original designed just used an autoxformer to drive the main xformer.

--
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

You really don't need very good regulation for this. 720V with a choke input supply would give you close to 700VDC out . You would have to guarantee some minimum load to keep the output from shooting up to 1000V. I would also check the ICAS rating for the tube to see if it can be run at 1000V (720VAC with capacitor input). I have never heard of an amateur transmitter that used a regulated supply, except for grid and screen voltages. The gold plated stuff was choke input. Tam

@

suggest

I know exactly where you can find several versions for this HV regulator. I have built a few myself, both solid state and with tube regulators. The answer is a few inches away (at least on my computer) in the rec.audio.tubes newsgroup. Many fine and experience rodents there, more than happy to help you. Mention my name.

Cordially, west

"West" wrote in news:vXvOi.3092$Cd7.1898@trnddc03:

If you're feeling adventurous you can look here;

though Jamie's suggestion would probably work best for you...

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----

The #1 Newsgroup Service in the World! 120,000+ Newsgroups

----= East and West-Coast Server Farms - Total Privacy via Encryption =----

"spock"

** I do.

So you have a 360 VA toroidal tranny that must weigh 4 kg.

And you are baulking at adding a filter choke that might weigh 400gm.

So you want to add a HV linear regulator that will, with heatsink, weigh more ?

Bet you have no licence for that transmitter and or it is on an illegal frequency.

...... Phil

Well, you are are wrong on both counts my operation is quit legal I have authority from the powers that be. The biggest problem is finding a choke big enough, they are getting scarce BTW for a choke to handle 250mA would weight at least 9lbs which would double the weight remeber it is 8H @ 250mA the heat sink would not weight half that. I don't want what YOU think I can't do I posted here to find out what will work!

Thank you

Last I heard, that place got overrun by trolls. Over the noise you might get an answer, but frankly, you're as well off here as anywhere else.

For that matter, most of us RATs went off to geek.scorpiorising.ca.

Tim

-- Deep Fryer: A very philosophical monk. Website @

"spock" = Top Posting PITA Fool

** Well, you would says that, wouldn't you.

** Absolute nonsense.

** No need exists for a size like 8H.

The Hammond " 158S " and " 158T " are rated at 250 and 300mA respectively - they both weigh 1.5 lbs.

Using 100 uF caps for input and post choke will reduce 100Hz ripple to around 100mV rms.

** You do NOT get to control the answers on Usenet - pal. ** Then stop acting like a know-all wanker.

And STOP BLOODY TOP POSTING !!!!!!

....... Phil

By trying to insult me you lose your Credibility, do you think I will listen to you if you do this, not really. The radios maker used a 8H choke Are you saying you know more than Rockwell Collins.

I am not a know it all, why did I post my question because I wanted to know what WILL work, not what will not work if you are going to be rude I will ignore you in the future BTW are you an Electronics Engineer? What are your qualified as?

"spock" = Top Posting PITA Fuckwit"

** It is simply not possible to insult an utter ass like YOU .

The English language lacks appropriate words.

** Did the original maker use a toroidal transformer and silicon diodes too ??

What a massively STUPID remark to make.

** Then STOP telling the folk who have post good replies they are wrong.

Cos YOU have no FUCKING IDEA .

.......... Phil

250 ma x 700V ~ 200W. A light dimmer switch plugged into 120VAC, feeding primary of a "step-up" transformer , stepped up to 6x out the secondary. From that you rectifier the voltage from the secondary, and filter it. What's your ripple spec on the output? Ken