Hi Graham I think it is a misunderstanding to think that the power supply
must supply peaks of current. This is what the choke avoids, there will be
some ripple on the supply but it should be quite minor (I must put a current
probe on mine, sometime). The current flowing from the psu when the
"switch" is on, does not stop flowing when it goes "off", the current is
diverted into the shunt capacitor. This is why the most important
calculation in the design is the power required which determines the size
needed for this cap. So the current drain on the psu should be reasonably
constant. As Mal says you dont need a stabilised supply for this type of
operation (or a class C stage), just a "stiff" one capable of supplying the
current without distress.
Alan
----- Original Message -----
From: "Graham" <[email protected]>
To: <[email protected]>
Sent: Saturday, March 08, 2008 3:22 PM
Subject: Re: LF: Re: Smaller DC feeding choke in class E amplifier
> Ok Alan,
>
> Ok , no problem on the 'isolation' using a inductor , I was thinking
more
> of the power supply demand/regulation side of things , looks like these
> things are a bit tricky to feed 'dc' interms of peak demand on the suppy
> ... this slides into calcuations of actual power supplied, form factors
etc
> , these must affect power supply design in terms of regulation bandwith ,
> parasitic inductance etc ? , that was the link to mobile phones !
>
> G ..
>
>
>
> ----- Original Message -----
> From: "Alan Melia" <[email protected]>
> To: <[email protected]>
> Sent: Saturday, March 08, 2008 1:40 PM
> Subject: Re: LF: Re: Smaller DC feeding choke in class E amplifier
>
>
> > Hi Graham, well there is not a lot of difference between "pulse amps"
and
> > any other sort really from that point of view. The choke "opposes
changes
> > in
> > current" and also allows the signal to go to the load rather than be
short
> > circuited by the PSU. At HF the situation is slightly different as you
can
> > run into resonances as well, but as I understand most mobile phones use
> > Class E for efficiency and battery life in just the same way as we use
'em
> > on LF....that is if you ever switch em on (I hardly ever do !!) Being
> > digital they dont need to be linear.
> >
> > Alan
> >
> > ----- Original Message -----
> > From: "Graham" <[email protected]>
> > To: <[email protected]>
> > Sent: Saturday, March 08, 2008 11:43 AM
> > Subject: Re: LF: Re: Smaller DC feeding choke in class E amplifier
> >
> >
> >> Hi Alan,
> >>
> >> I never could get a handle on using passive components to feed pulse
> >> amps
> > ,
> >> a sort of
> >> contradiction ? what do they do in a mobile phone ?
> >>
> >> G ..
> >>
> >>
> >> ----- Original Message -----
> >> From: "Alan Melia" <[email protected]>
> >> To: <[email protected]>
> >> Sent: Saturday, March 08, 2008 12:30 AM
> >> Subject: Re: LF: Re: Smaller DC feeding choke in class E amplifier
> >>
> >>
> >> > Hi Joe , Thanks for the "plug" :-))
> >> > Yes the circulating currents get pretty large with the low impednces
> > when
> >> > you try to put high power out with 12 supply. It doesnt do some caps
a
> > lot
> >> > of good either (think of the current density in the thin foil!). Most
> >> > of
> >> > my
> >> > tests were done at 35v or higher and that is a lot easier.
> >> > Best Wishes de Alan G3NYK
> >> >
> >> > ----- Original Message -----
> >> > From: <[email protected]>
> >> > To: <[email protected]>
> >> > Sent: Friday, March 07, 2008 11:47 PM
> >> > Subject: Re: LF: Re: Smaller DC feeding choke in class E amplifier
> >> >
> >> >
> >> >> Alan, Johan and group,
> >> >>
> >> >> Since experimenting on LF I have discovered the joys of Class E,
> >> >> many thanks to Alan. My first 100W TX used an IRF-640 as
> >> >> suggested on Alan's web page. A dozen of them could be had for
about
> > $10
> >> >> in 2003. Unfortunately, they are have gone up quite a bit since
then,
> >> >> although much cheaper than a 6146! There seems to be a new
> >> >> generation
> >> >> of hexfet such as the IRFP260 and perhaps it might be possible to
use
> >> >> this
> >> >> in a 12volt 100w amp. Unfortunately, many 640's came to an
untimely
> >> >> demise in my unsuccessful attempts to get 100 watts with a 12 V
> >> >> supply.
> >> >>
> >> >>
> >> >> 73
> >> >> Joe VO1NA
> >> >>
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > No virus found in this incoming message.
> >> > Checked by AVG Free Edition.
> >> > Version: 7.5.516 / Virus Database: 269.21.6/1317 - Release Date:
> > 3/7/2008
> >> > 08:15
> >> >
> >>
> >>
> >>
> >
> >
> >
> >
> >
> > --
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.5.516 / Virus Database: 269.21.6/1317 - Release Date:
3/7/2008
> > 08:15
> >
> >
>
>
>
|
