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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: LTSpice model for a SiC MOSFET
Date: Thu, 22 May 2025 03:52:59 +1000
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On 22/05/2025 1:43 am, Edward Rawde wrote:
> "john larkin" <jl@glen--canyon.com> wrote in message news:8osr2klq9oepgqsva13nljp4aikmh75rkv@4ax.com...
>> On Wed, 21 May 2025 09:42:11 -0400, "Edward Rawde"
>> <invalid@invalid.invalid> wrote:
>>
>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:100jsf2$2n1hq$2@dont-email.me...
>>>> On 21/05/2025 3:44 am, Edward Rawde wrote:
>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:100ibpi$2at8a$2@dont-email.me...
>>>>>> On 20/05/2025 11:38 pm, Edward Rawde wrote:
>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:100hb9s$24itl$3@dont-email.me...
>>>>>>>> On 20/05/2025 4:26 am, Edward Rawde wrote:
>>>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:100epio$1h4ca$1@dont-email.me...
>>>>>>>>>> On 19/05/2025 1:38 pm, john larkin wrote:
>>>>>>>>>>> On Mon, 19 May 2025 12:23:54 +1000, Bill Sloman <bill.sloman@ieee.org>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> On 19/05/2025 12:15 am, john larkin wrote:
>>>>>>>>>>>>> On Sun, 18 May 2025 18:11:58 +1000, 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?
>>>>>>>>>>>>>
>>>>>>>>>>>>> I use a Cree/Wolfspeed 1200v part, C2M0280120D, in my Pockels Cell
>>>>>>>>>>>>> driver.
>>>>>>>>>>>>>
>>>>>>>>>>>>> https://www.dropbox.com/scl/fi/5arhyamrp0bl3tgb2fasn/DSC02771.JPG?rlkey=3ttcc2yt6s9nrtdouuv3aneol&raw=1
>>>>>>>>>>>>>
>>>>>>>>>>>>> They do have an LT Spice model library that works.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Gate drive for SiC parts is a bear. I did it myself, but I think there
>>>>>>>>>>>>> are chips for that now.
>>>>>>>>>>>>>
>>>>>>>>>>>>> There are multi-kilovolt silicon mosfets too.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Baxandal looks to be inefficient and expensive as a low power
>>>>>>>>>>>>> converter. The drain swing is 2x the supply voltage, and it needs two
>>>>>>>>>>>>> fets and a difficult custom transformer.
>>>>>>>>>>>>
>>>>>>>>>>>> It isn't going to be inefficient. That configuration is famous efficient.
>>>>>>>>>>>>
>>>>>>>>>>>> The drain swing is actually 1.67 times the supply voltage, but it does
>>>>>>>>>>>> need two switching devices and a specially wound transformer (and we
>>>>>>>>>>>> know how reluctant you are to design them or get them made).
>>>>>>>>>>>>
>>>>>>>>>>>> It is probably going to be too expensive for the application, and we'd
>>>>>>>>>>>> be grateful for your insights into a cheaper alternative. I can't think
>>>>>>>>>>>> of one.
>>>>>>>>>>>
>>>>>>>>>>> I'm not sure what the specs are, but I have a few ideas.
>>>>>>>>>>>
>>>>>>>>>>> One could make a flyback converter with a high-ratio transformer.
>>>>>>>>>>> Coilcraft makes some, capacitor charging transformers and CCFLs. There
>>>>>>>>>>> must be crazy cheap Indian or Chinese CCFL transformers.
>>>>>>>>>>>
>>>>>>>>>>> ST makes a 1400v NPN transistor for under a dollar.
>>>>>>>>>>
>>>>>>>>>> But you can't be bothered to post the part number.
>>>>>>>>>
>>>>>>>>> What you should have said is that you couldn't be bothered to use a search engine.
>>>>>>>>
>>>>>>>> I need at least 1.7kV. A 1400V part isn't interesting.
>>>>>>>
>>>>>>> Centuries ago they'd put two transistors in series in the TV horizontal deflection department because a single one didn't
>>>>>>> have
>>>>>>> enough Vce max.
>>>>>>
>>>>>> The transistor was invented in the 1950's. Decades ago is closer to the mark.
>>>>>
>>>>> LOL sane people would have known what I meant without needing to point that out Bill.
>>>>
>>>> Sane people don't say "centuries" when they mean "decades".
>>>
>>> Does the word "hyperbole" mean anything to you Bill?
>>
>> He's obviously unwell.
> 
> Yes I think you're right so I'm going to leave it there.

I think I'll rely on my doctor. She's got a medical degree, and does 
seem to know what she is talking about.

-- 
Bill Sloman, Sydney