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On 29/05/2025 3:56 am, john larkin wrote:On Thu, 29 May 2025 02:24:01 +1000, Bill Sloman <bill.sloman@ieee.org>>
wrote:
On 29/05/2025 12:26 am, john larkin wrote:On Wed, 28 May 2025 21:03:03 +1000, Bill Sloman <bill.sloman@ieee.org>>
wrote:
>On 28/05/2025 3:08 am, Joe Gwinn wrote:>On Tue, 27 May 2025 07:53:12 -0700, john larkin <jl@glen--canyon.com>>
wrote:
>On Tue, 27 May 2025 10:02:27 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
>On Tue, 27 May 2025 20:32:49 +1000, Chris Jones>
<lugnut808@spam.yahoo.com> wrote:
>On 18/05/2025 6:11 pm, Bill Sloman wrote:>I'm looking at a problem where somebody wants to step down a 1kV low>
current source to 3.3V.
>
The Baxandall class-D oscillator could do it, but it needs a pair 1.7kV
MOSFETs for the job. The Infineon SiC IMH170R450M1 would do it - though
it's a much higher current part (10A) than the job needs (about 1mA).
>
I've dived into the Infineon rabbit-hole which promises LTSpice models,
but wasn't able to find one.
>
Does anybody know of a similar - ideally cheaper and smaller - part for
which there is an LTSpice model?
>
Maybe use an electrostatic motor driving a small generator!
Maybe DON'T FEED THE TROLL?
It is an interesting problem, designing a logic supply that runs off a
1 KV DC supply. Even when the requirements are confused.
>
Actually, the uncertainty opens up more circuit possibilities to
consider. We can thank Sloman for being confused.
I don't think that John Larkin needs my help to get confused.
>Finally, a purpose ...>
The first line of my original post was.
>
"I'm looking at a problem where somebody wants to step down a 1kV low
current source to 3.3V. "
>
That's been the purpose all along.
Your (still confused and unresolved) specifications opened up a wide
range of possible implementations. Thanks.
Since I've now at least got a PSpice model for the IXTH1N450HV 4.5KV
FET, I can - with luck - get on with being confused by an actual (if
simulated circuit). Typical Ciss is depressingly high at 1700pF.
>
The higher current (but lower voltage) Infineon IMWH170R450M1 has a
typical Ciss of 506pF and is cheaper than $US45 IXYS part.
>
You may find the specification to be confused and unresolved. I haven't
spelt it out in detail because - as the subject line spells out - that's
not what I'm here for. As far as I can see I've been consistent about
what I believe my contact is seeking, and what you are complaining about
is the way you have misconstrued passing comments.
What are the requirements? 1 mA, 3 mA, 1 mW, 10 mW, some microamps,
where? There have been all sorts of numbers.
The basic idea is that my contact has 1kV source capable of delivering
about 10uA - 10mW - and wants to use it to power some logic from a 3.3V
power rail. He'd like better than 50% efficiency, so presumaby he wants
something approaching 1.5mA. About the only other number I recall
posting was the idea that a switching MOSFET might need to handle up to
1mA rather than the 1A the IXTH1N450HV can manage or the 10A the
Infineon part offers.
>
I've now had an interesting an potentially patentable idea that I'm
obviously not going to post on a public forum. Like most patentable
ideas it is unlikely to actually work, let alone be be practicable.
>Does cost matter?>
He does want it to be inexpensive. There doesn't seem to be any
specialised market where a few customers can afford to pay a lot of
money for a few devices, or if there is he hasn't mentioned it to me
(and probably wouldn't) if there was.
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