DC-Protect Circuitry - Page 2

parsecaudio · 3rd September 2006, 12:28 PM

Hi Leolabs
The speed of this circuit is due to the speed relay.
Some high speed responce relay are very expensive,and the response time are approx. 5 m. sec.A standard relay have a response time over 15-25 m.sec.

When I have ended to mount my last high power amp I have disconnect the + supply rail from the supply,with a loudspeaker connected.
- 77 V DC on the output, the relay disconnect,and loudspeaker saved...

AndrewT · 3rd September 2006, 01:01 PM

Hi Parsec,
re post6
What do D4 & D6 do with their associated Rs & Cs?
They appear to be across the supplies only.

Can a dual comparator be used for the window detectors?

parsecaudio · 3rd September 2006, 01:39 PM

AndrewT
I have made an error.

Thank you for your answer.

This is the right circuit

I never used a comparator for this circuit you can be use this for the detectors,but with a single TL084 or similar,you save space and cost

AndrewT · 3rd September 2006, 08:21 PM

Hi Par,
can you explain what D6 does?

anatech · 3rd September 2006, 08:29 PM

Hi Andrew,
D6 discharges C3 when you power down.

However, X4 is a waste. It's not needed as you only have to light the LED. Just hook the LED across the FET as a protection indicator. It's operating current should cause any problems at all.

-Chris

parsecaudio · 4th September 2006, 01:10 AM

Hi Chris
The blinking circuit is only for indicate when the protection is activated.
When using a quadruple op amp like this circuit,your current charge is not a problem, a LED indicator should be used for protection indicator.

His current charge are the same if it is supplied from the op amp,or directly (with the same value of resistor)by the power supply.

It is better to use a single quad op amp (like a TL 084) because this save cost, component number and spacing...

anatech · 4th September 2006, 04:00 AM

Hi parsecaudio,
I like to keep things simple. Less to break.

I would attempt to reduce the op amp count to two anyway, use a transistor or two if you have to. That's just my take on these things.

Nothing worse than having the protection circuit fail and the amp is fine!

-Chris

fab · 4th September 2006, 04:18 AM

Quote:

Originally posted by anatech
Hi parsecaudio,
I like to keep things simple. Less to break.

I would attempt to reduce the op amp count to two anyway, use a transistor or two if you have to. That's just my take on these things.

Nothing worse than having the protection circuit fail and the amp is fine!

-Chris

On the same note I do not use ICs which contain too many transistors to detect simple voltage with no precision needed. Only a few transistors can do the job. The goal should be that the protection circuit be a lot more reliable than the audio amp circuitry...

parsecaudio · 4th September 2006, 10:12 AM

Hi chris and fab
A simple question:
you are sure that he is simpler to mount a single quad op amp(14 pins=14 holes and/or solders points ) or some transistors(minimum count of 4 + their associated components= minimum 18 holes / solders point on PCB)?

Fab,it is right that a simple discrete transistors can do the same function.Are less expensive four transistors or one single standard operational amp?

No precision needed?Why?

When I designing a circuit,I like that it works as I want

Thank you very much for your answer

jacco vermeulen · 4th September 2006, 10:47 AM

Quote:

A simple question

The chance of an opamp failure in a circuit with 4 opamps is 4 times as high as one with 1 single opamp.
Is the chance of failure of a Quad opamp higher than that of a single opamp ?

3rd September 2006, 01:01 PM	#12
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi Parsec, re post6 What do D4 & D6 do with their associated Rs & Cs? They appear to be across the supplies only. Can a dual comparator be used for the window detectors? __________________ regards Andrew T.

3rd September 2006, 08:21 PM	#14
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi Par, can you explain what D6 does? __________________ regards Andrew T.

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3rd September 2006, 12:28 PM	#11
parsecaudio diyAudio Member Join Date: Apr 2004 Location: ventimiglia	Hi Leolabs The speed of this circuit is due to the speed relay. Some high speed responce relay are very expensive,and the response time are approx. 5 m. sec.A standard relay have a response time over 15-25 m.sec. When I have ended to mount my last high power amp I have disconnect the + supply rail from the supply,with a loudspeaker connected. - 77 V DC on the output, the relay disconnect,and loudspeaker saved...

3rd September 2006, 08:29 PM	#15
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Andrew, D6 discharges C3 when you power down. However, X4 is a waste. It's not needed as you only have to light the LED. Just hook the LED across the FET as a protection indicator. It's operating current should cause any problems at all. -Chris

4th September 2006, 01:10 AM	#16
parsecaudio diyAudio Member Join Date: Apr 2004 Location: ventimiglia	Hi Chris The blinking circuit is only for indicate when the protection is activated. When using a quadruple op amp like this circuit,your current charge is not a problem, a LED indicator should be used for protection indicator. His current charge are the same if it is supplied from the op amp,or directly (with the same value of resistor)by the power supply. It is better to use a single quad op amp (like a TL 084) because this save cost, component number and spacing...

4th September 2006, 04:00 AM	#17
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi parsecaudio, I like to keep things simple. Less to break. I would attempt to reduce the op amp count to two anyway, use a transistor or two if you have to. That's just my take on these things. Nothing worse than having the protection circuit fail and the amp is fine! -Chris

4th September 2006, 10:12 AM	#19
parsecaudio diyAudio Member Join Date: Apr 2004 Location: ventimiglia	Hi chris and fab A simple question: you are sure that he is simpler to mount a single quad op amp(14 pins=14 holes and/or solders points ) or some transistors(minimum count of 4 + their associated components= minimum 18 holes / solders point on PCB)? Fab,it is right that a simple discrete transistors can do the same function.Are less expensive four transistors or one single standard operational amp? No precision needed?Why? When I designing a circuit,I like that it works as I want Thank you very much for your answer

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