Re: Logic level HV fet...
From: Genome (ilike_spam_at_yahoo.co.uk)
Date: 01/27/05
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Date: Thu, 27 Jan 2005 13:38:52 GMT
"Fred Bloggs" <nospam@nospam.com> wrote in message
news:41F8ED17.3080900@nospam.com...
>
>
> Genome wrote:
> > "Mike Deblis" <mdeblis@hotmail.com> wrote in message
> > news:35ru47F4mkh6eU1@individual.net...
> >
> >>Hi,
> >>
> >>I'm looking for a 200 - 250V FET with low Qg, low RDSon (only needs
maybe
> >
> > 3A
> >
> >>peak Ids, but low RDSon for efficiency) and LOGIC LEVEL GATE for use in
an
> >>SMPS that only has a 9V supply - the SMPS is in boost configuration to
> >
> > give
> >
> >>180V @ 20mA out, probably going to use the LTC1872 if I can.
> >>
> >>Any ideas would be appreciated - I've not had a lot of luck so far - I
> >
> > know
> >
> >>its a tall order. An SMD footprint would also be good.
> >>
> >>Thanks
> >>
> >>Mike
> >>
> >>
> >
> >
> > Use a voltage boosted boost converter. You tap the inductor so that the
FET
> > sees a fraction of the output voltage.
> >
> >
> > ----nnnnnnnnnnnn----->|-----
> > |
> > |
> > |--
> > |<-
> > |--
> > |
> > |
> > -------------------------------
> >
> >
> > DNA
> >
> >
>
> Although diode sees a multiple of reverse output voltage,
Yes, that's the caveat.
DNA
the duty D can
> be significantly reduced from the 95% required of single inductor 20:1
> multiplication of 9V->180V. Good idea.
>
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