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5kV 40uA from 120VAC

I think all Tek scopes use C-W multipliers. Some up to 7 X. Some used a single diode to get the negative cathode supply (about -3kV) from the same winding. Only issue is you need fast HV diodes when inverters are used. But they are cheap.

There are one chip off line MOSFET drivers available for a few bucks that would work nice for this. Grab a bit of feedback from the base voltage from the first capacitor junction to get a bit of regulation. They also provide some short circuit and overcurrent protection for when one of the HV caps short.

tm

Reply to
tm
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On a sunny day (Thu, 7 Jul 2011 13:12:23 -0700 (PDT)) it happened Kooner wrote in :

Any old BW TV transistor circuit should give you 15kV at that current. Just turn it down a bit :-) Must be tons of those along the road.

Reply to
Jan Panteltje

On a sunny day (Thu, 7 Jul 2011 23:55:40 -0400) it happened "P E Schoen" wrote in :

Old HeNe laser power supply, here I use one with volatge controlled by a PIC:

formatting link

It now does only 1.5 kV or so, but you can get 5 no problem, more too. Runs of a 12 V wall wart.

Reply to
Jan Panteltje

Am 08.07.2011 06:32, schrieb John Larkin:

very nice! What type of diodes do you use in your multiplier?

Regards, Alexander

Reply to
Alexander

Those are MMBD204's. They are cheap, as I recall.

I did evaluate some VMI packaged C-W multipliers, but they had very low capacitor values and were insanely expensive.

Actually, small potted HV supplies aren't real expensive. It might have been more rational to just buy some.

John

Reply to
John Larkin 

--
You call it whining; I call it showing you up for the bullshit artist
you are.
Reply to
John Fields

Am 08.07.2011 15:33, schrieb John Larkin:

I had a quick look in the datsheet. Unfortunately they can only handle 300V.

'insanely expensive' is absolutely true! A couple of years ago I had to replace a 2kV diode from Philips which had been discontinued. When I asked VMI for a replacement type I thought they were joking.

Reagrds, Alexander

Reply to
Alexander 

--
You may have missed it, but I didn't critique his "cheap but big"
suggestion, and criticized his CW entry only because of the CW
overkill since the same thing can be done with a transformer, a
half-wave rectifier, and a capacitor:


.                3600 RMS              5000 DC
.               /            40µA-->  / 
.120ACD>----+  +--[HV RECT>]--+------+
.           |  |              |      |
.           P||S              |      |Rl
.         n R||E 30n        [39n]  [125M]
.           I||C              |      |
.           |  |              |      | 
.120AC>-----+  +--------------+------+

39nF will allow about 17V of ripple on the output, and I'm assuming a
transformer with a turns ratio of 1:30 with the I²R loss in the
secondary and the drop across the diode to drop the extra 64 VRMS out
of the secondary.
Reply to
John Fields

I often suspected that Larkin was gay. After all, he does live in San Fransicko, Californica :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

They overshoot to some ridiculous voltage at turn-on, so you have to be careful.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
Reply to
Phil Hobbs

You said you loved me. I always thought you were a repulsive idiot.

Let the world decide.

John

Reply to
John Larkin

That's why you use lots of them!

John

Reply to
John Larkin

Freaking moron. I was praising Alex, not myself.

You offered to post stuff, then chickened out.

You dared me to post a C-W HV circuit, and I did, and all you do is whine.

We're discussing HV circuits, and you've sniveling.

And you didn't answer the question about why a lower-ratio transformer and a multiplier is often a better design.

Idiot old hen.

John

Reply to
John Larkin

Hey, Jan's schematics are even fuzzier than yours!

I should send you each a Boston electric pencil sharpener.

I'm old enough to have taken *two semisters* of engineering drawing, and they pounded linework quality into us. We even had to ink our own borders and title blocks.

John

Reply to
John Larkin

On a sunny day (Fri, 08 Jul 2011 11:13:45 -0400) it happened Phil Hobbs wrote in :

That is why the voltage feedback via the PIC, PWM modulated output. The original circuit I got the cascade and transformer from had a 555 timer :-)

Reply to
Jan Panteltje

On a sunny day (Fri, 08 Jul 2011 08:48:11 -0700) it happened John Larkin wrote in :

For ciruits this simple who needs a schematic?

Reply to
Jan Panteltje 

--
If that's what you really wanted, then you'd admit that the context
of the post was fraternal and not at all sexual.

But since it isn't, and what you really want is to demean me, what you
do is try to use lies and innuendo to try to get the world to decide
in your favor.

Shame on you, cheater.
Reply to
John Fields

Abuse, he gives me, and on my first Friday afternoon in my new office, too. I bought a nice Brother B-size all-in-one, and I'll have you know that my hand-drawn schematics now reproduce *beautifully*. Jan's look like the Dead Sea Scrolls after a late night partying.

So a loud and juicy raspberry to you and your hifalutin engineering school penmanship.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
Reply to
Phil Hobbs

Where are those great cavitation photos?

John

Reply to
John Larkin

I was at a hardware store (Mountain Hardware in Truckee, aka Mountain Macy's) and they had a thing that looks just like a tennis racket, but has two high-voltage grids. You swat a bug with it and it goes ZAAAPPPP!

John

Reply to
John Larkin

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