[sdiy] ot: class d audio amp

[Alex Stettler]

Hello,

I just built a sort of 3-channel class D amplifier. I use it to generate
3-phase / 450 Hz power
for my Alcatel Turbopump. It is based on a look-up-table (calculated in
MATLAB), clock-generator
and driver / MOSFET-power stage. The whole amplifier is very efficient. With
full output power
of 300 VA (cos(phi) is estimated to be about 0.7) the losses in the power
stage are only about 12 Watts.
Also the sinewave is very nice, watched on a scope. I didn't measure the THD
so far, but I'll do in the next
days. In my application the amplifier is even simpler, because you don't
need the output filter network.
The stator winding of the pump motor plays the role of the lowpass-filter.
(BTW: Most modern frequency converters for ac-motors are simpler forms of
class-D amplifiers)
As a future project I intend to build a audio class D ampfifier as you, too.
Because this type of amplifier is interesting
in two ways: You can get 800 Watts or more of audio power out of 1U / 19"
case (high power per volume) and because of the working principle and the
design of the different components involved with this type of amplifier
(Switching Mode Power Supply, PWM-Modulation, DSP-Processing,
Control-Circuits etc.)
But first I've two finish my SMPS (based on L5991) for my 3-phase
generator/amplifier.
With the experience I've made with this class of amplifiers, I'm very
optimistic to get a class D audio amp running with low THD and other good
technical specs. But in comparison to the amp I've built, the audio capable
version will need much more of design effort, because of the much bigger
bandwith and other differences. My generator/amp has only to cover a
frequency range of about 400 - 1200 Hz.

Regards,
Alex



> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Czech Martin
> Sent: Monday, October 20, 2003 4:19 PM
> To: Sdiy (E-mail)
> Subject: [sdiy] ot: class d audio amp
>
>
> Could anyone point me to diy audio amp project switch class D?
> So far I only could find some theoretical paper or commercials.
>
> m.c.
>