Not really, in fact. I mean, you never want your amp to be overloaded, right ? As long as you keep a decent damping factor, the protection will stay quiet and watching. Make a short circuit, and, because of the internal resistance of the power devices, you'll run out of current: Voltage in the output will decrease enough to fire the protection.
It is because the damping factor is a produce of the feedback, trying to compensate the voltage errors. In case of short circuits, you run out of feedback range. No more feedback, the amp is in open loop or near, saturating.
Note that, for an industrial product, where you know the exact amps gain factor, you can save the two adjustable resistances, replacing them with fixed resistances.
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Hello Andrew T
greetings fist of all which is better a latch to hold on the protection
or when the speaker wires are shorted protection works but relay goes on
and off i have tested another dc and short circuit protection on high power
PA amps same result on shorting speaker wires relay goes on or off is that
right i think its not ok because large currents on relay contacts can spoil
contacts these all are simple dc and overload protections with low cost
components at least expensive transistors and speakers are saved THATS
the main goal i think
warm regards
Andrew
greetings fist of all which is better a latch to hold on the protection
or when the speaker wires are shorted protection works but relay goes on
and off i have tested another dc and short circuit protection on high power
PA amps same result on shorting speaker wires relay goes on or off is that
right i think its not ok because large currents on relay contacts can spoil
contacts these all are simple dc and overload protections with low cost
components at least expensive transistors and speakers are saved THATS
the main goal i think
warm regards
Andrew
It is supposed to have a 2 second delay after the trouble has ended before the relay re-connect the speakers.
"The 470µF provide the "Power ON" delay of 6 seconds, while the 2MΩ and 2K resistances are in charge of setting a threshold in such a way that the protection will not fire with little voltage errors noises, and offset of the previous OPAs. On the other side, the diode the resistance and the 0.33µF cap allow a fast switching and a slow recovery (2s)"
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Of course. Short circuits of speakers wires are not supposed to happens, so, it is the main target of this protection: protect your speakers in case of amp failure. And the protection will stay fired as long as the offset will be present.
I thought everything has been explained.
You can adjust sensitivity for the protection fire in less than 10ms at 35mV of offset ;-)
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if you are interested, I have made a version with protection not recovering itself after activation, but with a "reset button".
Just the add of 4 resistances, a diode and a CD4027B.
I added 2 more relays for the A <> B speakers and connected the coils to the collector of the protection transistor.
This forces 2 relays to shut off when a problem occurs
I used an AC photodetector to detect 5v DC either way on the amp output to SCR gate turning off the driver transistor. this forces a power off reset
This forces 2 relays to shut off when a problem occurs
I used an AC photodetector to detect 5v DC either way on the amp output to SCR gate turning off the driver transistor. this forces a power off reset
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Hello Esperado
greetings yes i am interested with the protection not recovering
itself after protection please can you post schematic just tested
overload current protection with yellow core CT current sensor
QSC PL380 amplifier uses this technique with success just 1 ic
2 trs few resistaces and caps for stereo overload protection
warm regards
Andrew
greetings yes i am interested with the protection not recovering
itself after protection please can you post schematic just tested
overload current protection with yellow core CT current sensor
QSC PL380 amplifier uses this technique with success just 1 ic
2 trs few resistaces and caps for stereo overload protection
warm regards
Andrew
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