another HV power supply

Why not just put some more turns on L2 and use 1 diode?

Your time scale is in mS I think? Top right HV generator:

Seems like a lot of stress on the poor tranny.

What diode is that? What's the big square thing? Where is the oscillator? Does it regulate?

Yes, the sim runs for 300 ms. That's about 5 minutes in real time, which leaves lots of time to pretty up the schematic. And make snacks.

We have all those parts in stock.

A single diode would have a kilovolt or so across it, which would be a lot of stress on the PCB.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

John Larkin admits the possiblity of getting special purpose transformers wound, but he prefers not to have it done

Transformers should be wound for the job you want them to do. It's not the kind of intellectual load you like to cope with, but it can be done.

Who cares.Jan can make things that work. He doesn't seem to put them into production.

But you don't have a transformer winding machine, reels of wire, stocks of coil formers and the ferrite cores you plug into them.

There are Teflon insulated standoffs, that you can plug into a circular hole in the PCB, which can stand-off a few kV. I used them from time to time at Cambridge Instruments, mostly for photomultiplier dynode chains.

Oh, on the transfromer wire perhaps, seems to not mind

No idea, SK11 or SK10? some thing that does HV

What's the big square thing?

OLED display LM096

Microchip PIC 18F14K22 It has build in PWM with cycle by cycle current limit (analog comparot in)

So, yes. And you can set voltage and PWM and a lot of other stuff via USB It has GPS too

??

Na. never noticed :-)

This one is on 24/7 on my desk: uses a voltage doubler, some old potcore I found. Now runs on 12V via a mains adaptor, records radiation level 24/7 to a file, since.. 2010? The detector is from an old army surplus set.

When I moved house:

Microchip PICs are nice, use hardly any power, have good build in hardware functions (ADC, PWM, analog comparator, DAC, what not), reliable and simple to program in asm.

There is a lot more to it, just ask.

Obviously. That DRQ127 is surface-mount and costs 86 cents and required no engineering design, no drawings, no quotations, no prototypes, and has multiple sources. Leakage inductance is tiny. The C-W multiplier lets the tranny work at low voltage stress.

The diodes are dual SOT23s which cost 5 cents per dual. The HV supply is a minor side issue on the HV pulse generator project. [1]

It's easy for Bill Sloman to theorize when he doesn't actually design anything to be built.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I'm not theorising - I'm just telling you what worked for me in the past. The stuff got built and put into production, and if final test didn't like it they would try to get me to change the design to one that they liked better - mostly they'd got the wrong end of the stick. The one design change I did make was when they couldn't get my set-up procedure to work - I actually set up the offending unit in ten minutes, but they'd struggled for hours, and switching to a laser-trimmed part only cost (in cash terms) about twenty minutes of final test labour.

No you're not. You're insulting him. Insulting others seems to be what you do best. That and bragging about how you set the unit up in ten minutes after others had struggled for hours.

To avoid this becoming another silly mega thread I won't reply to any reply to this.

Hmmm, a lot of stress is when you do a straight flyback to 5kV, like ours. Making the "tranny" is a real pain of course, so they work for years 24/7. (we do it on RM8 cores). The advantage of flyback is that it regulates well down to well below 500V (users need different voltages for different detectors, for Ge I have seen anything between

The diodes I found by sheer chance and I am not sure I know how to get some more again - good thing I got a decent supply back then (ebay or aliexpress, not sure which). Look like microwave HV diodes only they are fast, really low losses, something like 10kV rated IIRC. 10-12mm long, about 3mm diameter.

====================================================== Dimiter Popoff, TGI

That LTC3803 flyback controller is really nice.

We try to surface-mount everything, and use parts that we already have in stock. And avoid ebay or amazon or ali parts.

I'd guess that a classic (line freq transformer type) microwave would have slow-recovery diodes.

I guess the newer microwaves have switchers. I think some actually have semiconductors instead of magnetrons... but magnetrons are cheap.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

You missed the point. I'd developed the circuit, and I knew that the set-up procedure I'd described had worked for me and did take about ten minutes. The problem was that I hadn't described it well enough to let the final test guys do it at all. There's no brag in admitting that you hadn't been able to describe a fairly simple - if tedious and repetitive

- procedure well enough to let final test techicians (who were good at that sort of stuff) make it work. My expectation had been that they could do it faster than I could, and I was wrong about that.

The underlying point was John Larkin doesn't seem to realise that I've done at least as much hand-on work as he has.

Why would you bother? You don't like being told that you have missed the point, and you always do.

We have used some of theirs and they work OK, but I still prefer to have more control over the loop and do 1/2 74HC123, 1/2 LMC6482 plus driver and FET (like on this board, where noise is critical and there are what, 8 voltages in addition to the HV.

Same here. Throuhole come into play when they can save board area at the expense of height, when available. Ali got me by a nice surprise when I found there some coaxial connectors which had disappeared at Mouser etc., at a much more reasonable cost. So I tried again, this time for some mini-melf resistors we had run out of; guess what, they track better than the previous we had, from some reputable source... (tracking is crucial at a few points on this board, we specify <30ppm/C gain drift, ship <20ppm, and *one* unit came out around *0*, could not be measured, can you believe it!). I also got some chips there (two types), yet to try these out though (both are not to be found at Mouser/Digikey etc.).

Yes, these are ubiquitous and not usable. I was surprised to find the fast ones some 15 years ago, we had run out of a supply of an older type I had, Philips or something like that, were up to 3mA and lossy but worked. The new ones are much better, I think 10mA - no, 25! Located some datasheet I must have found then, G10FS is the part name (or one of the neighbour ones), 100ns is pretty good.

No idea, I have only dismantled a dead microwave once to take the magnets... :-)

Where you can find semiconductors that can work at 2.4 GHz at power level of few hundred watts?

Gallium Nitride devices. Quorvo T1G4020036-FL in the US. EXIM rules apply.

Joe Gwinn

Apparently GaN.

We'll be driving GaN fets with the 700v power supply that I mentioned.

The GaNs are wonderful to drive. They only need 5 volts on the gate and the drain-gate capacitance is essentially zero.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It won't be "essentially zero", but something small but finite that a serious designer would know about, even if they didn't have to do anything about it.

Joe Gwinn has identified a similar part - the 50V Qorvo T1G4020036_FL

Measuring it wouldn't be difficult. You could probably get a Spice model out of the manufacturers if you asked, but it would need to include lead inductances and would be messy.

It must be a drag to always dispute everything so literally. That instantly kills any traces of creativity.

"Essentially zero" means "too small to matter" to us. The PCB has more d-g capacitance that the fets we are using.

My my, you made yet another spelling error!

That's an RF part and has RF specs, narrowband s-params and Smith stuff, presumably to be used with slide rules. We use switch-type parts that have proper specs, with c-v curves.

Many or maybe most RF parts have wirebonds that tune it for one specific RF band, wherever they think the money is.

The bias procedure is typical for RF parts. Slowly adjust the gate voltage until it works. I see no DC curves. It's probably a depletion part.

Some day people will use Spice to simulate RF systems, and provide proper device models.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Not a spelling error but a typo - an omission. We all do it. If it creates a comic effect it can be worth commenting on.

Smith charts - or the tabulated data used to construct them - could be used as inputs to a computer program. I've never seen such a program, but I suspect that examples do exist.

But you didn't offer a link to a data sheet or even a part number to back up your "essentially zero" nonsense.

Another unsupported speculation.

It's actually possible to concoct your own Spice models - Gummel and Poon aren't the only people who have done it. It's the sort of tedious slog that gets inflicted on graduate students, and interns.

It's almost certain that some poor graduate student has been stuck with doing that for an RF part to get a Ph.D. The part will probably be obsolete before the thesis is submitted, but the student will be remarkably employable after graduation. Not by you, of course.