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Class D Switching Power Amplifiers and Power D/A conversion

My design L20D IRS2092+IRFI4020H  200W8R
My design L20D IRS2092+IRFI4020H  200W8R
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Old 17th June 2018, 04:55 AM   #1081
serafis is offline serafis  New Zealand
diyAudio Member
Join Date: Jun 2008
That's bad luck! While I haven't used the L25D boards myself, I've blown up and then fixed a couple of L15D's, and I believe the basic circuitry is very similar.

If there's high voltage at output, I would immediately suspect that either or both IRFB4020 MOSFETs are blown. Pretty easy to check, just put a meter across them and check whether they're shorted

The other transistor on the heatsink may have blown too, and depending on what caused the fault, the surface mounted IRS2092 chip on the underside of the board as well.

To be on the safe side, I'd replace all of those components (they're pretty cheap and readily available - I bought a few spares from Aliexpress just in case), and also check all the other semiconductors too (i.e. diodes and zeners).

Then, before powering up again, you need to determine what caused the fault in the first place. Could be a speaker short, or too low impedance speakers (I believe the L25D's don't like much below 8 ohms), or a wiring, connection or soldering problem on the board. Or possibly no heat transfer compound between the transistors and the heatsink, causing the MOSFETs to overheat - I've heard this is not uncommon in pre-assembled boards, and might explain why it worked for a while before failing.

If you didn't assemble the board yourself, I'd also check (and reflow) all solder joints (the solder joints on pre-assembled boards I've had weren't great quality which is why I prefer to assemble them myself). And I'd double check that all components are correct and in the correct places.

When I first blew up an L15D (my own fault for not checking speaker shorts before switching on!), I ordered another one as a spare, plus MOSFETS, transistor and IRS2092 components to fix the blown one. That means I now always have a spare working board, so if I have a a blow-up in the future, I can just swap out the faulty board and fix it in my own time.

Hope this helps and it all works out.



Last edited by serafis; 17th June 2018 at 04:58 AM.
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Old 28th June 2018, 11:48 AM   #1082
ghitus is offline ghitus
diyAudio Member
Join Date: Nov 2017
Hi everyone, I bought two l20d to drive a subwoofer, where each module will drive a double coil loudspeaker. With the coils connected in series. The impedance is of 6.5 ohms. Having to chose the feeding voltage of the SMPS, according to you, which one should I prefer? 60 or 72 volts? The SMPS will probably be Connex SMPS800RE.
Many thanks,
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