Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: LTSpice model for a SiC MOSFET
Date: Wed, 21 May 2025 17:20:48 +1000
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On 21/05/2025 3:47 am, KevinJ93 wrote:
> On 5/20/25 1:46 AM, Bill Sloman wrote:
>> On 20/05/2025 1:13 am, Liz Tuddenham wrote:
>>> Bill Sloman <bill.sloman@ieee.org> 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?
>>>
>>> How about a piezoelectric transformer run in reverse?
>>
>> The piezoelectric transformer is an interesting idea.
>>
>>> Neon tubes illuminating a solar cell? 
>>
>> Neither is all that efficient.
>>
>>> Capacitive divider using a spare core in the
>>> mains supply lead as one plate of the capacitor?  (Depending on supply
>>> frequency and required output current.)
>>
>> I can't see how that could work. Charging up lots of capacitor is 
>> series, and discharging them in parallel is one mode of current 
>> multiplication, but about the only kind of switch that would work 
>> would be a reed relay, and they are slow and don't last long when 
>> cycled fast.
>>
>> Dry reeds are good for 10 million closures, mercury-wetted reeds for 
>> about 100 million, and neither is all that cheap or compact.
>>
> 
> The Art of Engineering #3 (I think) - describes a "Reverse Marx 
> Generator" that does exactly that (charging caps in series and 
> discharging in parallel). It uses diodes as the switching element.

The forward diode drop is inconsequential at 1kV, but inconvenient at 
3.3V. And you'd need 250 stages in this application.

I've got AOE3. It's index doesn't point to any "reverse Marx generator".
Google search throws up links, but nothing useful.

The classic Marx generator uses spark gaps as its switches. I have used 
them myself (to start a xenon arc lamp), but they wouldn't be useful here.

-- 
Bill Sloman, Sydney