Re: Amplifone Design... Wonders me

this is for geting the the line in the right place. Cause the current lags
in a coil "CIVIL" u need to bump up the voltage
to get the line in the right place. When the coil lags the currnet in the
resistor is compered to the input voltage and the
error is ampified to fix the coils lag.

          V -----+
                 |
                 )
                 ( Yoke
                 )
                 |
          FB ----+
                 |
                 /
                 \ Resistor
                 /
                 |
                ---
                 -

ps this is just what i think this also make a grate audio amp ehheeh :P
----- Original Message -----
From: "Zonn" <zonn@zonn.com>
To: <vectorlist@vectorlist.org>
Sent: Wednesday, March 10, 2004 1:40 PM
Subject: Re: VECTOR: Amplifone Design... Wonders me

> On Tue, 9 Mar 2004 23:31:10 +0100, "mypearl" <mypearl@dds.nl> wrote:
>
> >My concern now is why the amplifone deflection board is so sensitive to
power supply ripple...
> >
> >I have never seen any home stereo amp with regulation. They have very
good ripple rejection though... I don't suppose those are voltage feedback
amplifiers makes a difference for PSRRR ?
>
> I *believe* the voltage feedback amplifier, compared to current feedback
does
> make a difference. But I'm a software guy, so anybody more knowledgeable
than
> me, *please* jump in!
>
> Here's my feeble analysis...(including the part I'm not so sure of).
>
> Both amplifiers are running in voltage feedback mode. The difference is
that
> the audio amplifier looks at the voltage directly across the speaker, it
holds
> that voltage regardless of what the power supply is doing, therefore the
power
> supply does not need much regulation, just filtering.
>
> The deflection amplifier needs to current control the yoke, it does this
by
> placing a resistor in series with the yoke. Since controlling the voltage
on
> the resistor controls the current through it, it also controls the current
> through the yoke, like this:
>
> (Fixed Font warning, ASCII art ahead)
>
> V -----+
> |
> )
> ( Yoke
> )
> |
> FB ----+
> |
> /
> \ Resistor
> /
> |
> ---
> -
>
> The power supply voltage is V, the feedback point is FB. The deflection
> amplifier runs as a voltage feedback amplifier holding the voltage at FB
to a
> specific value, and therefore regulating the current through the resistor
and
> yoke.
>
> Now here's where my lack of analog skills kick in and is something that
has
> always bothered me in my attempts to understand this circuit.
>
> Let's say V is 25v, and FB is being held to 1v. Now let's say the
unregulated V
> voltage jumps to 30v.
>
> The amplifier will hold FB at 1v, which will keep the current flowing
through
> the resistor, and yoke, constant. But here's my dilemma:
>
> Since the Yoke and Resistor act like a voltage divider, and the voltage at
FB is
> held constant, then when V is at 25v, there is 1v across FB and 24v across
the
> yoke. Now when V jumps up to 30v, FB is still held to 1v, but now there
is 29v
> across the yoke.
>
> My gut feeling is that increasing the voltage across the yoke from 24v to
29v
> *will* have an affect on the display, even if the current is held
constant.
> Which leads me to think deflection amplifiers need to be run from
regulated
> power supplies, much like the design that WG originally came up with.
>
> Is my thinking correct on this? Hopefully someone more versed in analog
> electronics than me, can answer this question, it's bothered me since I
first
> started working on X/Y monitors.
>
> -Zonn
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Received on Wed Mar 10 03:51:52 2004