LME49830 with Foldback Current Limit and 2sk1530 - diyAudio
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Old 18th October 2012, 07:19 AM   #1
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Cool LME49830 with Foldback Current Limit and 2sk1530

Hello!

I designed a LME49830 with foldback current limit and the popular 2sk1530/2sj201, the circuit is similar to the an1850 from ti.

Unfortunately I can only simulate the circuit in tina-ti because I don't have the LME in lt-spice. BUT I don't have the 2sk1530 mosfets in tina-ti So I tried to simulate it with irfp240 and irfp9240 and it nearly worked. The only thing were the low distortions on the takeover point but I think it is because of wrong bias current and the "wrong" mosfets in the simulation. The current limitier worked very well

So now, a question to the specialists here in the fomum, will this amp work??

Is it a good idea to take the expensive 2sk1530 / 2sj201 mosfets instead of the cheaper irfp240 / 9240?

Thanks in advance ;-)

regards
bernhard
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File Type: png lme49830_foldback.png (22.1 KB, 447 views)

Last edited by mantabernd; 18th October 2012 at 07:23 AM. Reason: no picture added :(
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Old 18th October 2012, 01:17 PM   #2
AndrewT is online now AndrewT  Scotland
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are the sources inside the LME sufficiently protected such that when the protection triggers, your circuit does not blow up the LME?
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Old 18th October 2012, 01:26 PM   #3
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Hello Andrew,

good Question, I don't know about fues inside the LME. In the datasheet is only a thermal fuse listed.

How can I protect the LME? With extra transistors for driving the mosfets?
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Old 19th October 2012, 11:02 AM   #4
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No one else any suggestions/comments ?
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Old 19th October 2012, 11:43 AM   #5
pergo is offline pergo  Italy
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LME's drivers are current limited to 56mA.
Datasheet shows that drivers can be shorted with a 10ohm resistor without problems.

That circuit will work.
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Old 19th October 2012, 12:17 PM   #6
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Oh ok I didn't see this detail. Thanks for this information!!

So that's my first own amplifier design - I'm very excited about building it. I hope it won't fire it up ... Maybe, if I got the time for it I will test it this evening.
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Old 19th October 2012, 12:23 PM   #7
AndrewT is online now AndrewT  Scotland
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I think that both Pass and ESP websites shown a method & circuit to allow non destructive testing of current limiting circuits.
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Old 19th October 2012, 03:29 PM   #8
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Sorry for the question but do you have links for the circuits? I didn't find them and I like non destructive solutions ;-)
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Old 24th October 2012, 07:26 AM   #9
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Default Fold back current limiter

i have a regulated bus supply of 28 volts now i want to design foldback current limiter circuit which limits load current when it exceeds above 5 ampere. can any one has any idea..

Thanks in advance..
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Old 26th October 2012, 12:08 PM   #10
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Default I built it :)

I finally built that circuit above with only one pair of mosfets and it worked. I had some problems with oscillations at the beginning, it is very important to have only one big gnd point. After I changed this the oscillations were gone

So can't say anything about the sound quality because my testspeaker is very bad but I measured it.

The current limiter needs a bit tuning, the negative side seems to limit correctly but the positive side looks very very strange.

I tested it by putting a 2R4 Ohms resistant from output to gnd.

Supply voltage was +/- 60V. The Voltage at the gate of 2sk1530 was 1,758V and on the 2SJ201 it was -1,537. After putting the 2R4 Ohms at the output the voltage at the 2sk1530 was 1,501V and on the 2SJ201 it was -0,499V.

So it doesn't work simultaneously

I added two pictures, one of normal operating mode and another with the resistant at the output.

Anyone any suggestion what to change?
Attached Images
File Type: jpg IMG_0968.jpg (285.8 KB, 291 views)
File Type: jpg IMG_0969.jpg (244.1 KB, 260 views)

Last edited by mantabernd; 26th October 2012 at 12:11 PM.
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