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Old 28th September 2011, 12:57 PM   #1371
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Quote:
Originally Posted by CPX View Post
Supply rail protection will have to wait for the bypass capacitors to discarge...and you need reaction time in the microsecond range.
Yes, I forgot that.. But something come to my mind.. What if I put protection bettwen main capacitors and amp and when protection starts, BC238 is opened and momentaly make short on main relay, then raley is off and it realise time is 8ms. Now active led is off too because relay is in short, I have complite indication of whole situation..

Relay is 24V on example on +-60V, relay resistor is 1.5K (relay current is 24mA).
When reley is short, current through BC238 will be 40mA and his current raiting is 200mA, it can handle.. For sure maybe is good to put stronger transistor like BD139
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Last edited by Dzony988; 28th September 2011 at 01:01 PM.
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Old 28th September 2011, 01:24 PM   #1372
CPX is offline CPX  Romania
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The problem with your aproach is that this will not only save the the transistors in the event of a sudden short(like when the speaker burns)...an efective protection for the transistors must be very fast both in detection and in action.Detector has to be put on output or on the leg of irfp250 after bypass capacitor 470uf but i recomand it on output.
Protector has to stop input signal and/or transistor oscilation ..only the relay will not work..thre is no point in doing just an overload protection and not a complete fast short protection...
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Old 28th September 2011, 03:36 PM   #1373
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ok. What if I shut down TIP41C.
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Old 28th September 2011, 03:51 PM   #1374
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SD pin of IR2110. that is the solution
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Old 28th September 2011, 03:53 PM   #1375
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SD pin is conected to Ucc-. How to activate it?
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Old 28th September 2011, 03:55 PM   #1376
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put a 1k resistor from sd to vcc- then
pin 3 of the ic has 12v. it's enough even 5 i think.

try it
it should stop
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Old 28th September 2011, 03:58 PM   #1377
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Yes, Pin3 of NE555 has 12V
1K from SD pin to Ucc-, and pin 3 of NE555 directly to SD!?
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Old 28th September 2011, 04:01 PM   #1378
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i was refering to pin 3 of IR2110 :P

when you have 12v to sd pin of ir2110 it will shut down.
read the ir2110. you could even make cycle by cycle over-current protection
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Old 28th September 2011, 04:12 PM   #1379
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Ok, thank you Savu. I saw on Luka's schematics that he conect pin 3 (out) of NE555 directly to SD pin and SD pin is conected across 10K to Ucc-.
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Old 28th September 2011, 04:15 PM   #1380
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u have prot circuit grounded to GND not vcc-.

that is a big no no.

ground the prot circuitry to vcc-, or just use luka's prot circuitry
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