Re: LTSpice model for a SiC MOSFET

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'd keep it simple and repurpose a backwards commodity CCFL ($0.50)
 transformer, in a low frequency (20-50KHz) buck regulator 'of sorts'.

A 1KV mosfet (why SIC?) would act as it's own TVS if the source was
really self-limited. 2$

Trickle charge for start-up, with all control power on the LV side;
an intermediate 8-20V rail.

From there it's a matter of your techy arranging 'who's on first'
in a sensible manner.

RL