In March a friend asked me if I would like to design something simple
with the IRS2092. First I was not enthusiastic, because I had doubts that
it would work to achieve something better than the IRAUD7 and its clones.
Better means: Improved speaker control (==> post filter feedback), less noise and at least not worse distortion.
Nevertheless I had look into the topic.
My first attempts were fitting more or less to my expectations.
Good control of the filter and speaker, blameless step response, but harmonics in the -70db category all over the place. Ugh..
Also the gap between simulation and reality was to big for my taste.
Operating frequency and distortion figures did not fit sufficiently.
I digged deeper into the non documented weaknesses of the IRS2092.
Key points:
Transfer function of the OTA
Noise of the OTA
Jittery / ambitious flipping of the comparator
Internal delay times
After all this I updated my simulation model of the IRS2092 and soon came to
a changed structure, which behaves fine in simulation and reality.
Can't tell an official name for the structure.
With a good portion of phantasy we could call it a post filter feedback sigma delta modulator.
Above 60kHz F1(s) and F2(s) together are acting like an integrator for the 1Bit data stream coming from the half bridge...
In the mean time the results by far surpass the IRAUD7, but the complexity is very similar.
Step response is blameless with rise times below 5us, output noise is below 100uVrms, very low THD and nice dual tone behavior.
It is promising enough that I intend to go for a proper PCB.
Attached a scheme of the control structure and some measurements at 10W into 4R.
with the IRS2092. First I was not enthusiastic, because I had doubts that
it would work to achieve something better than the IRAUD7 and its clones.
Better means: Improved speaker control (==> post filter feedback), less noise and at least not worse distortion.
Nevertheless I had look into the topic.
My first attempts were fitting more or less to my expectations.
Good control of the filter and speaker, blameless step response, but harmonics in the -70db category all over the place. Ugh..
Also the gap between simulation and reality was to big for my taste.
Operating frequency and distortion figures did not fit sufficiently.
I digged deeper into the non documented weaknesses of the IRS2092.
Key points:
Transfer function of the OTA
Noise of the OTA
Jittery / ambitious flipping of the comparator
Internal delay times
After all this I updated my simulation model of the IRS2092 and soon came to
a changed structure, which behaves fine in simulation and reality.
Can't tell an official name for the structure.
With a good portion of phantasy we could call it a post filter feedback sigma delta modulator.
Above 60kHz F1(s) and F2(s) together are acting like an integrator for the 1Bit data stream coming from the half bridge...
In the mean time the results by far surpass the IRAUD7, but the complexity is very similar.
Step response is blameless with rise times below 5us, output noise is below 100uVrms, very low THD and nice dual tone behavior.
It is promising enough that I intend to go for a proper PCB.
Attached a scheme of the control structure and some measurements at 10W into 4R.