How to do a lot with few , i mean , quite an exaustive study
of output stage protection circuitry , the most complete i ve seen so far,
congrats , mike , for this usefull paper.
of output stage protection circuitry , the most complete i ve seen so far,
congrats , mike , for this usefull paper.
Excellent! I think I have prodded Michael for at least the last 10 years to publish his work on SOA. A very worthwhile read!
jan
jan
Almost all that content was published in EW in Oct 2002. I've been using his VI limiter methodology in my Excel spreadsheets to build accurate protection ever since!
Brian.
Has anyone considered SOA protection in which the protection transistors are removed from the forward path of the amplifier and, instead, opto-coupled to a bistable which drops out the output relay?
The protection locus would have to be conservative as it would have to accomodate the fact that it may take up to ten milliseconds to drop out the relay.
The protection locus would have to be conservative as it would have to accomodate the fact that it may take up to ten milliseconds to drop out the relay.
Use solid state relay. Fast (50-200 us), great repetitive current handling capability (100A no problem), and can handle inductive energy up to 500mJ.
Here is one example: Solid State Relay with PCB Layout
There are quite a few others on DIY audio as well.
Here is one example: Solid State Relay with PCB Layout
There are quite a few others on DIY audio as well.
I am not sure why there is a "sudden" interest in SOA protection in numerous threads at the moment. Haven't we DIYers (not professional Electrical Engineers) known about this forever and deliberately decided to accept the risks? I can understand it being extremely important to Electrical Engineers designing consumer products.
Just a couple of points about "reference 3" in the paper. Elliott is spelt with 2 t's and Phil Allison is well known in Australia as a Toaster Repairman with a potty mouth, Phil Allison - Australia | LinkedIn.
Just a couple of points about "reference 3" in the paper. Elliott is spelt with 2 t's and Phil Allison is well known in Australia as a Toaster Repairman with a potty mouth, Phil Allison - Australia | LinkedIn.
Can those relays be used to turn off the supply rails instead of having them in series with the output?
In other words, if SOA protection is invoked or DC offset detected, then disconnect the DC supplies from the amplifier.
A latch would be necessary as you don't want the supply rails re-connected to the amplifier unless power is cycled.
Actually I suspect those folk who "accept the risks" do so because they don't know better. The purpose of the paper is to enlighten them.
Can those relays be used to turn off the supply rails instead of having them in series with the output?
In other words, if SOA protection is invoked or DC offset detected, then disconnect the DC supplies from the amplifier.
A latch would be necessary as you don't want the supply rails re-connected to the amplifier unless power is cycled.
I use this(similar, a bit upgraded) power supplay with all needed protection. http://www.diyaudio.com/forums/powe...iplier-electronic-protection.html#post2901733
Yes, you could switch the rails - in fact it would probably be easier than the speaker. I have toyed with the idea but not organized my thoughts into a circuit yet.
You can take a look at my circuit diagram and, maybe take some ideas from it(as I took some from JLH)
http://www.diyaudio.com/forums/powe...iplier-electronic-protection.html#post2901733
Thanks dadod.
There seems to have been a profusion of protection circuits lately - driven I believe by fast MOSFET switches, cheap bipolar output transistors and more use of simulators.
There seems to have been a profusion of protection circuits lately - driven I believe by fast MOSFET switches, cheap bipolar output transistors and more use of simulators.
This one was built and it is in daily use in my TT amp with no problem, even ones saved my speaker coused by amp bad solder connection.
dado
Dadod, I think you use a regulated power supply? There is no need for a regulated power supply for power amps.
The idea I proposed is to have solid state switches in the unregulated supplies of the amp. to disconnect them from the amp. in the event of SOA violation or DC offset.
The idea I proposed is to have solid state switches in the unregulated supplies of the amp. to disconnect them from the amp. in the event of SOA violation or DC offset.
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