MDA-400 (Some hidden features)

[Workhorse]

Originally Posted by AP2

Hi,

Meanwhile, the simple protection of the output stage Vs.current load.
In this recent years has proved effective and robust protecting the amp short circuit on the load, thus helping the response to reactive load.
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short, some parts of the schema (as special ALC) and audio measurements.

Regards

Originally Posted by AP2

I have always paid special attention to the protection circuits.
not enough to have a good current sensing device if then are left out some important functions, such as when in the presence of short circuit

Your protection of short circuit involves an AC [opto leds connected in inverse parallel] optocoupler which has a flaw in sensing the current. Only the positive direction LED receives the bias from +/-60V rails thru resistors which helps in turning on the LED during overcurrent condition sensed thru 60m Ohm shunt.

But when the negative cycle occurs, the bias resistors have no contribution at all and the INVERTED LED has to rely on the sheer drop across the 60m Ohm resistor alone. Which states that the threshold for sensing of current is not SYMMETRICAL at all.

During short circuit, there is no surety which polarity is at work in that instant.

[AP2]

Originally Posted by Workhorse

Your protection of short circuit involves a AC[leds connected inverse parallel] optocoupler which has a flaw in sensing the current. Only the positive direction LED receives the bias from +/-60V rails thru resistors which helps in turning on the LED during overcurrent condition sensed thru 60m Ohm shunt.

But when the negative cycle occurs, the bias resistors have no contribution at all and the INVERTED LED has to rely on the sheer drop across the 60m Ohm resistor alone. Which states that the threshold for sensing of current is not SYMMETRICAL at all.

During short circuit, there is no surety which polarity is at work in that instant.

Chip H11AA1 is double diode inverted (ac). +/- rail cretes a threshold to help the ddp that derives from the shunt.
the threshold depending on the polarity of the mature ddp, sum or subtract. this is very clever in my opinion, unless the amp perfectly. has been well tested in 5 years. also, 60mR is not a limitation as you think, considering that the drain is directly connected to vcc.

[Workhorse]

Originally Posted by AP2

Chip H11AA1 is double diode inverted (ac). +/- rail cretes a threshold to help the ddp that derives from the shunt.
the threshold depending on the polarity of the mature ddp, sum or subtract. this is very clever in my opinion, unless the amp perfectly. has been well tested in 5 years. also, 60mR is not a limitation as you think, considering that the drain is directly connected to vcc.

See what i wrote above, i am not saying 60mR is limitation, What i am saying is the thresholds for sensing positive and negative cycle currents are NOT SAME. Because the 100k resistors bias the opto during positive cycle only.

I know you won't understand

[AP2]

why not refresh your brain with "principle of Kirchhoff" before try understand this simple network resistive?
threshold is zero without ddp.

[AP2]

Originally Posted by Workhorse

I already simulated it and the results are in my favor, better try it before hurling advices

show me your simulation,i'm sure you have not connected all... just you not see how it running (principle).
apart this, just this amplifier you can shortcut at output, repeated at one sec. forever (while is at 90% of power output)

[Workhorse]

Here is the simulation results, the waveform is taken at the both optocouplers OR'ed collectors which is clearly showing that there is considerable difference in thresholds sensing of both polarities.

Anyone skilled in the art can see the verdict.

[AP2]

Originally Posted by Workhorse

Here is the simulation results, the waveform is taken at the both optocouplers OR'ed collectors which is clearly showing that there is considerable difference in thresholds sensing of both polarities.

Anyone skilled in the art can see the verdict.

Anyone... study well,before attak.
I not want explain at you,becouse your simulation is wrong. I imagine other wrong in your study.
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The collector of the photodiode, closes perfectly(to zero), both on the positive and negative, as can be seen from the simulation. considers that a closing pulse is sufficient, even of only 2us, for the type of circuit to which is connected the protection.

[Workhorse]

See this simulation which shows symmetric behavior of waveform for both polarities.

AP2,
Please feel safe, no one is attacking you. You don't even know what an attack means. Showing a flaw is not attacking.

Your simulation itself is showing asymmetry in itself, your red waveform has varying pulse width, no doubt you can sense a full short circuit with it. But the precision is totally missing and you are missing what my point is.

Below is the way which shows how to do a SYMMETRIC SENSING.

If you still don't get it, then its not my fault.

[AP2]

My protection running very well con very few parts employed. (this is the best side of an enginner that companies search)
when I want to make things more complex, not use simulators.
Have no doubt that you can improve. the problem in my case, it's not that I do not know how to make it better, but finding a reliable solution in the easiest way.
this amplifier has a very high peak current,> 16Amp. it is not necessary to detect the current with precision, right you only have a quick break. honestly, today, I must say that was really reliable.

[Workhorse]

Originally Posted by AP2

Anyone... study well,before attak.
I not want explain at you,becouse your simulation is wrong. I imagine other wrong in your study.
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The collector of the photodiode, closes perfectly(to zero), both on the positive and negative, as can be seen from the simulation. considers that a closing pulse is sufficient, even of only 2us, for the type of circuit to which is connected the protection.

See the difference , your own simulations speaks in favour of my results.