Re: Transistor Veb rating... plus Patent Update


"Tony Williams" <tonyw@xxxxxxxxxxxxxxxxxxx> wrote in message
news:4eb60cfe9dtonyw@xxxxxxxxxxxxxxxxxxxxxx
In article <t7gBh.7840$fa.3709@xxxxxxxxxxxxxxxxxxxx>,
Genome <mrspamizgood@xxxxxxxxxxx> wrote:

On the new page, with the new PFC circuit, I had to provide drive
waveforms that do what you describe to achieve the effect.

http://www.genomerics.org/patent/newpfc.html

Yes ok thanks. A quick Run of newpfc shows that
the -20A pulse nicely straddles the mosfet drive
negative-going edge.

On the first page the turn off current source is -20.1A so only
100mA is available to turn the device off. Clamping the device
with a diode would mean that you don't provide sufficient
reverse bias to remove the stored charge.

But maybe some means of defining the maximum Veb
is going to be neccessary?

A quick glance at the IR data *** mentioned
earlier shows that there is some form of body
diode in an IGBT. Does your model contain that?

'Hmm... reminiscent of commutating an SCR.'

There was mention of that but I sort of discounted it. I suppose
they might be concerned that if what I am proposing for an IGBT
has already been done with SCRs then the patent might not be
valid on the grounds of obviousness. OTOH if it were so obvious
because it is done with SCRs why is it not being done with IGBTs?

Well, commutation is a generic word. Here you are
applying a form of commutation to the new and specific
application of speeding up the turnoff of an IGBT.

--
Tony Williams.

Apologies for not doing this in line, never works for me.

Yes some sort of Oh ***! protection might be prudent. However the method
shown in the second circuit does provide a reasonably well defined reverse
bias level..... Ignoring the ringing.

I have found a data *** for a high voltage switching transistor which goes
as far as specifying a repetitive Veb avalanche energy.... It's probably the
case that it is permissible to operate many things under such conditions but
they just haven't been qualified for that mode of operation.

Yes.... I have commented out the clamp diode from the original model so if
you downloaded it from the website it's not there.

As to obviousness or newnesss.... I'm with you on that one. That's to be
expected but at the level I've seen patents operate it should qualify as
being valid.... if it really hasn't been done before.


I've had a look around the interwank for the 'expert' that responded and I
have found information that causes me some doubts as to wether he is truly
qualified to give a valued judgement about the method. He seems too far
removed from the technical guts of things.

Hmmmmmm, obviously I've got a blinkered view about this.. Either he phoned
me up to give a company approved whitewash or he phoned me up to blither and
reported blither to the non-technical side who took his advice and cancelled
interest.

Ho hum

DNA


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