Roff
Well-Known Member
What do you mean,
?there was a waveform with the switcher across the sense resistor
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?there was a waveform with the switcher across the sense resistor
I was confused by your dangling participle.there was a waveform with the switcher across the sense resistor
Sorry, but I don't remember seeing a 1Meg pot in any of your schematics. Can you post what you have now?So I'd like to use a single 10 turn pot for adjustment. Slim pickins for a 1M precision pot it seems. If I change it back to 100K I need to go with a lower reference voltage right?
I would do it like this. You can scale the pots up by as much as 20 times (10k each), or anywhere in between, so long as you scale R2 proportionally. This way, you can use any value that you can find.I changed the 100k pot to 1Meg when I changed the reference method. Here is a current schematic.
I had recommended that you replace them with C4 and R9.Oh cool, I'll do that. R6,8 and C2,3 are for stability (at least that's what I was told in one of the articles I read). Are they not needed?
I can't guarantee that my solution is better than what you were using, because (1) I don't have a model of your power module, and (2) I wouldn't trust it if I did.Oh, ok. I missed the part about C4,R9 being replacements for those compnents.
Well, damn. I made the changes and ran it at 10A for a while. No problems. Ramped it up to 20A, no prob. Ran it at 27A and the module shorted again. Did find out that the switcher will do 60A for about 2 sec before protection kicks in. Impressive.
Unfortunately I did not get a picture on the scope before it went.
Here are meter readings from the dead module:
E-C 4.3
B-E 43.3
B-C 39.3
Bx-E 4.3
Bx-C .4
B-Bx 39.3
What's excellent is nothing is acting like a diode now. Swapping leads gave the same readings.
Here's a good one for comparison.
E-C FWD 382K REV 8.3K
B-E FWD 97 REV 97
B-C FWD 8.35K REV 358K
Bx-E FWD 54 REV 54
Bx-C FWD 8.23K REV 336K
B-Bx FWD 42.6 REV 42.6