Fullbridge Class D PA ultra high power

Current sense resistors should be of lower value, it will become hot on full power sinewave tests (and 1/4 of power dissipation of resistors on highly compressed music)

OCP on lowside can be replaced with IR25750L + comparator so that OCP will have no dissipation, can be adjusted without compromise, also cheaper than milliohm current sense resistors.

For highside, a digital isolator can be used, though complexity and cost will increase.

http://www.infineon.com/dgdl/ir25750lpbf.pdf?fileId=5546d462533600a4015355ca1d0e16f7

thanks lester for sharing . cool ocp chip
 

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and this I did simulate, have quite low distortion because of multipole faseshift for self oscillation, the carrier stays quite stable now with overdrive.

Harmonic distortion is with 40 volts peak in 8 ohm, carrier 800 Khz, amp has 50 Khz bandwidth and there still -80 dB hd.

Just give it a try, I have not build it, just sim, I am now busy with a circlotron.

regards
 

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i wanted to use ir2110chip so that i can use irfb4227 n channel only fets +/-75volts full bridge. will the above dual lm311 work with ir2110 in ucd??:confused:

This one maybe, ir2110 chip need opposite fase input? now you need not two lm 311, I am not check that. A very fast comparator is a must for low distortion, also a fast integrator opamp with minimum 50 Khz bandwidth so feedback do have low propagation delay.
 

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Current sense resistors should be of lower value, it will become hot on full power sinewave tests (and 1/4 of power dissipation of resistors on highly compressed music)

OCP on lowside can be replaced with IR25750L + comparator so that OCP will have no dissipation, can be adjusted without compromise, also cheaper than milliohm current sense resistors.

For highside, a digital isolator can be used, though complexity and cost will increase.

http://www.infineon.com/dgdl/ir25750lpbf.pdf?fileId=5546d462533600a4015355ca1d0e16f7

The reason is for simplicity.
That resistor is about 20W dissipation at continuous. But music never as continuous signal. In practical, no signififant temperature rise.
 
this one is quite simple, and has a power comparator , need a good pcb layout.

test with very high voltage output, but it do work on 2 x 30 or 50 volts, what I did is not right then I need to change the comparator value,s.

The output is -40 dB down Harmonics but output is then almost to rails, keep carrier quite stable in this fase shift type class D..
 

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Again, you are talking about OVER LOAD.

Do you really want to tell what I talk about??? Trust me (or don't trust, just read again), I talked explicitely about short circuit. But you have only 1 circuit for both purpose.

Short circuit characteristic is very different. It is momentary

At least you test it this way. But nobody can assure it is really momentary. It can happen any time, any duration and at any signal voltage. Short circuit in real life is not intentional. You can not control it.

and can have very huge energy, instantly.

Short circuit is PASSIVE. The amp is what provides energy.

The OCP speed is not fixed but higher current the faster OCP to initiate.

Yes it is not fixed. I calculated the fastest possible reaction time what is already too high. But it can be slower. Do you think I ought have to calculate the slower one? :)

Sparks or not doesn't matter. It is only YOUR personal preference
.

It is not a preference. I don't care wether you like sparks or not. It is an indicator of short circuit current.

From my test, it is very simple judgement: no burning mosfet on repeat event event continue shorted. No temperature rise as well to the heatsink which may continue to thermal runaway.

No temperature rise either due to normal operation in the test, but in reality it can happen, therefore the test does not represent worst case. Not worst case also because of other reasons:
- natural variance of parts
- variable signal
And these are the smaller problems. The bigger is that you don't offer the real circuit you tested, only a theoretical schematic without exact part numbers and layout. Your design is on the borderline of safe operation. Any deviance from your unpublished building and testing habits can push it to the burning side.

Third is MY SECRET. There are always 4 diodes arround the inductor in my design. Whatever energy generated in the coil, it cannot be more than voltage supply as the diodes act like pipe. Any generated voltage more than voltage supply will be drained by that diodes to supply cap. This is wy my design is very stable. Even you can play connect or disconnect, short, whatever, on and off power without smoke.

This is my "secret": If I write current, then I mean current. Nobody cares how you limited voltage when the test is about a "short" circuit, and high currents, not about voltages.

And I mentioned many times an important test without any reply: short your single ended discrete amps with a piece of long and thick wire, without signal, and measure supply voltage!

I dont know what you mean from last statement.
Only the last one?
 
this one is quite simple, and has a power comparator , need a good pcb layout.

test with very high voltage output, but it do work on 2 x 30 or 50 volts, what I did is not right then I need to change the comparator value,s.

The output is -40 dB down Harmonics but output is then almost to rails, keep carrier quite stable in this fase shift type class D..

please kees , post schematic
 
I just found this incidentally:
SOA:
Of course the IRFP4668 can handle more than 4kW, especially when used at lower frequencies. And of course you will find plenty designs that do not consider worst case situations and also no theoretical SOA check at all.
When looking to selfoscillating class D amps, then the critical situation will never be normal operation, because you only have the high currents at high modulation levels where you have low switching frequencies. This is definitely a very fortunate nature of the selfoscillating designs.
But when looking to the described worst case scenario:
-Output running into a shorted wire ==> i.e. 50m Ohms
-Input signal small, but enough to go for approx. 3V output into 50m Ohms
Then you will still have the high switching frequency and 60Amax and almost no rail sagging ==> That's the worst case scenario.

This is what a real engineer (Chocoholic) says.