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Old 10th January 2017, 04:16 AM   #11
Pafi is offline Pafi  Hungary
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Eva,
What do you mean no current limiting? Rail current is sensed, and shutdown activated, however not correctly, depending on modulation index, and slowly.
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Old 10th January 2017, 04:39 AM   #12
kartino is offline kartino  Indonesia
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Quote:
Originally Posted by Pafi View Post
Eva,
What do you mean no current limiting? Rail current is sensed, and shutdown activated, however not correctly, depending on modulation index, and slowly.
What do you mean not correctly and slowly?
What is your basis of judgement?
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Old 10th January 2017, 04:42 AM   #13
kartino is offline kartino  Indonesia
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Quote:
Originally Posted by Eva View Post
And? Even TPA chips have a basic short circuit detector. Otherwise in case of output short DC protection relay opens but it does not open until output stage is toasted enough to produce DC.

I'm ubiquitous, I'm never leaving or coming back.
Yes, seen the decoupling, some superstition taking place hehe
Main protection is shut down the IR2110.
Cut the relay is just optional.
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Old 10th January 2017, 06:45 AM   #14
Pafi is offline Pafi  Hungary
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Quote:
Originally Posted by kartino View Post
What do you mean not correctly and slowly?
What is your basis of judgement?
- Calculation I already presented in the other topic.
- Seen too big sparks on your testing videos.
- Shunt is shunted by 2 electrolytic capacitor. This gives unpredictable result for spikes, since sensed voltage depends on ESR and parasitic inductances that depends on layout that is not defined yet.
+ the well known fact that bridge cancels a very high part of rail current at low modulation index.
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Old 10th January 2017, 08:06 AM   #15
kartino is offline kartino  Indonesia
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Quote:
Originally Posted by Pafi View Post
- Calculation I already presented in the other topic.
- Seen too big sparks on your testing videos.
- Shunt is shunted by 2 electrolytic capacitor. This gives unpredictable result for spikes, since sensed voltage depends on ESR and parasitic inductances that depends on layout that is not defined yet.
+ the well known fact that bridge cancels a very high part of rail current at low modulation index.
Again, you are talking about OVER LOAD. Short circuit characteristic is very different. It is momentary and can have very huge energy, instantly. The OCP speed is not fixed but higher current the faster OCP to initiate.

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

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.

I dont know what you mean from last statement.

Last edited by kartino; 10th January 2017 at 08:17 AM.
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Old 10th January 2017, 03:47 PM   #16
stewin is offline stewin  Kenya
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Quote:
Originally Posted by Pafi View Post
- Calculation I already presented in the other topic.
- Seen too big sparks on your testing videos.
- Shunt is shunted by 2 electrolytic capacitor. This gives unpredictable result for spikes, since sensed voltage depends on ESR and parasitic inductances that depends on layout that is not defined yet.
+ the well known fact that bridge cancels a very high part of rail current at low modulation index.
hi paffi please post a schematic explaining this
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Old 10th January 2017, 03:49 PM   #17
stewin is offline stewin  Kenya
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Quote:
Originally Posted by Eva View Post
No current limiting and no way to implement it without changing to a different driver IC scheme or a different supply/ground topology, or adding a few dozen parts either as rail sense or floating sense. Pre-filter feedback, so more useful for LF duty.

TL07x is not the best choice for this application because that kind of chips are OK for their pricing but have a funny -PSRR charactetistic: around crossover frequency (3Mhz) the output exhibits amplification for the voltage difference between the output and negative rail, so any fast spike either as input command or as output load causes HF output bounce. In practice TL07x is OK when the spikes and related inaccuracy do not matter (linear circuits with no spikes, or proper consideration with spikes at the input and/or (100r,1n) to GND at the output to avoid disturbance entering. LM83x and MC3307x is a different kind of audio op-amp in the same price range that does not have the vulnerabilities of TL07x but have other, high input noise current, dictating the use of low value resistors, but this is always less trouble than bounce at the output of an op-amp used as class D modulator.

hi eva , nice to see you. eva can lm311 be used in sigma delta instead of tloxx???
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Old 10th January 2017, 04:13 PM   #18
stewin is offline stewin  Kenya
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hi katrino, why don,t you use ucd like the below diagram. ucd is more stable than sigma except containing the noise is the hardest part , to make a good layout
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Old 10th January 2017, 04:38 PM   #19
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by stewin View Post
hi katrino, why don,t you use ucd like the below diagram. ucd is more stable than sigma except containing the noise is the hardest part , to make a good layout
Why not using a two output comparator? things can be simpler.
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Old 10th January 2017, 04:53 PM   #20
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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/ir25750...5355ca1d0e16f7

Last edited by JLesterP; 10th January 2017 at 05:06 PM.
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