Re: LTSpice model for a SiC MOSFET

On Wed, 28 May 2025 00:28:12 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

On 27/05/2025 11:46 pm, john larkin wrote:

On Tue, 27 May 2025 14:16:11 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
>

Bill Sloman <bill.sloman@ieee.org> wrote:
>

On 27/05/2025 9:09 am, john larkin wrote:

>
[...]

The specs, as far as I can tell, suggest 1KV at 1 ma in and 3.3v at 3
ma out. The required efficiency is then 1%.

>
Actually 1kV at 10uA in.

>
Good grief!   A 10-megohm quarter watt resistor with a zener diode is
the obvious answer.

>
A 3.3v real zener will probably leak more than 10uA. Low voltage
zeners are awful.
>
And he wants 3 mA out... I think.

>
The guy I was talking to had 10uA at 1kV, and wanted a 3.3V output. 1mW
at 3.3V is 3mA. The 3ma is the upper limit the circuit could supply.

 Geez, check your work before you post it. 3.3v * 3 mA is 10 mW.
 I have a few kids that I'm teaching to design electronics. They
already have EE degrees.
 One of the fundamental concepts: check your work.
 

>
[...]

Misunderstanding the constraints can lead people to propose
inappropriate solutions.

>
How can anyone misunderstand something they have never been told?

>
You managed it.
>

Bill was the confused person.

>
John Larkin does like to think that.
>

The problem gets much more interesting with 10 uA in and 99%
efficiency requirement.

>
There never was an efficiency requirement. 50% would have been nice.
>

A Baxandall isn't going pull microamps at 1 KV.

>
Keeping a resonant tank resonating at a couple of kV is going to use up
power in the winding resistance. I think I can get 245H out of RM14
core. If we can keep the parallel capacitance down to 25pF that would
resonate at 2kHz and the reactive impedance would be 3 Mohm, giving a
peak current 0f 1mA. The resistance of the winding is going to be about
480R, so I^2.R is 500uW, or 0.5uA at 1kV.
>
A properly designed Baxandall might well pull less than 1uA if lightly
loaded.

 Build it.