For example, say the average current draw is 5A. A typical IGBT would drop about 2V, giving a 10W power loss, whereas a MOSFET with an RDSon of say 200mohm loses only 5*5*0.2 = 5W, giving much lesser junction temperature, with similar cooling arrangements. However, it is fairly easy to see that an RDSon = 500mohm would put the MOSFET (approximately) at par with the IGBT, improving neither efficiency nor reliability (stresses).
It therefore, depends on what MOSFET you end up choosing. The point nevertheless is that at high currents the MOSFET's losses are proportional to the square of the current, whereas those of the IGBT would still (only) be largely proportional to it. Thus, MOSFETs win at low-medium power levels while IGBTs win at very high power (>5kW).
Thanks for that, this is the kind of info I was hoping to find here ...
Because the board uses copper in the pcb and not large additional heatsinks the package type would have to be D2PAK or TO-220 modified to be surface mounted.
the 2 resonating caps are behind the toroid inductor L9. the igbt halfbridge is driven at 50% dutycycle, adn varying freqeuncy to regulate the voltage.
thgere is a point in the resonance curve where the output voltage is almost independent of the load. some of these designs are offered on the diyaudio.
read up on LLC resonant converters... imho igbt´s fare more rugged than mosfets, just not as efficient in switching as nmosfets, but when the freq is low igbt´s are just fine.
thgere is a point in the resonance curve where the output voltage is almost independent of the load. some of these designs are offered on the diyaudio.
read up on LLC resonant converters... imho igbt´s fare more rugged than mosfets, just not as efficient in switching as nmosfets, but when the freq is low igbt´s are just fine.
It looks like I'll just have to go with what I can get ... having real trouble finding anything suitable (IGBT or Mosfet) in stock at a reasonable price here in UK in D2PAK or TO-220 ....
What about this Infineon IGBT that comes up on their cross reference search:
https://www.infineon.com/cms/en/search.html#!term=stgb19nc60kdt4&view=crossReference
Close to original parameters, plenty in stock, cheap shipping ... although I've no idea where they ship from.
Have any of you bought from Infineon directly? ... certainly a lot cheaper than buying from Mouser for me...
https://www.infineon.com/cms/en/search.html#!term=stgb19nc60kdt4&view=crossReference
Close to original parameters, plenty in stock, cheap shipping ... although I've no idea where they ship from.
Have any of you bought from Infineon directly? ... certainly a lot cheaper than buying from Mouser for me...
found this part at st estores: STGB20V60DF
https://estore.st.com/en/stgb20v60df-cpn.html
it has 2x higher gatecharge, but at 102khz the driver should be able to handle it. keep an eye on the irs temp , otherwise glue a heatsink on top of the package.
it is in stock
https://estore.st.com/en/stgb20v60df-cpn.html
it has 2x higher gatecharge, but at 102khz the driver should be able to handle it. keep an eye on the irs temp , otherwise glue a heatsink on top of the package.
it is in stock
Trimming is OK if both packages have similar thermal resistances from junction to case, but needs to be avoided as far as possible, since the part would be subject to mechanical vibrations while being cut to size.
I don't understand why you would want that 15V supply at all when your IR2110 seems to be working perfectly well, as seen from the wave-forms in post #5!! If I were you, I would now focus on getting the half-bridge working correctly, which is easily verified by measuring VS w.r.t. COM. It may also be worth checking if the capacitor midpoint (labelled W8 / NEUTRAL2 / LUG1) is correctly balanced at 330/2 = 165V w.r.t. COM.
All the devices I suggested are spare parts (used in domestic appliances) that are likely to be locally available in most countries. So, it may be time to get off the internet and try the nearest electronics bazaar in your area.
It would be a last resort.
I've been meaning to dig out the power supply for about a year now for other things (it's also a 48v phantom supply) , yes I know the 2110 is working, the object for me is not just to repair as fast as possible but to also develop a strategy for future repair troubleshooting and to learn more about Class D & associated SMPS, so I wanted to dig it out and just connect it up for practice, I'm just coming back to electronics after a long gap just doing bits and pieces.
Lug 1 is half voltage @ 161v = 322/2.
There are no electronics bazaars here & haven't been for many years now, internet is the only choice (like I said earlier up till 2 years ago I could get literally any part next working day delivery here for free, now it's like living in a desert), I looked for the parts you suggested in all of the suppliers here including mouser etc. & there are none available without very long lead times ... some into next year. The part I mentioned above is about the only suitable part I've found that I can actually order immediately. What do you think of it? it's D2PAK so would not need trimming.
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You may use that (IKB20N60) if you don't get anything else. But do keep in mind that the original device that had more or less similar specifications actually managed to get damaged, possibly under normal operating conditions....
However, for some extra money, you could get more reliable devices and avoid the problem from occurring ever again:
D2PAK
https://www.infineon.com/cms/en/product/power/mosfet/automotive-mosfet/ipb65r050cfd7a/
https://www.infineon.com/cms/en/product/power/mosfet/automotive-mosfet/ipb65r099cfd7a/
TO-220
https://www.infineon.com/cms/en/product/power/mosfet/automotive-mosfet/ipp65r050cfd7a/
https://www.infineon.com/cms/en/product/power/mosfet/automotive-mosfet/ipp65r099cfd7a/
The original devices were damaged by the previous owner plugging the amp into an ancient set of speaker cabs that had very low impedance due to probably shorted voice coils. These amps actually have quite a good record for reliability (when used within spec.) but I am always interested in any info you have about adding reliability.
Thanks for looking these out, there is a fair difference in price though, I'm going to go and have a good look at the parametrics vs original. Do you think it's really worth the (almost 5x) extra money e.g. for the 1st one you list? ...
Neither, it's the product of the two that needs to be as low as possible. Qg decides the gate driver IC (2110) switching losses while Rds on governs the heat on the device itself. However, your SMPS could literally work with any compatible transistor as long as things are within the capabilities of the driver IC.
Also, did you verify the suspected fault on the bridge? I would suggest getting the cheapest transistors in town, at least until basic functionality is restored. The reliability improvements could be brought in later, as a value addition. Once you get the thing operational, you could then probe different points within the SMPS to learn how it operates etc. But until then, it's going to be just repair and nothing else.
Besides, it was assumed from post #1 that you had cleared all downstream faults within the Class-D section. In case you haven't done that yet, any of those faults could keep coming back to blow up your power supply over and over again until they're all resolved.
Also, did you verify the suspected fault on the bridge? I would suggest getting the cheapest transistors in town, at least until basic functionality is restored. The reliability improvements could be brought in later, as a value addition. Once you get the thing operational, you could then probe different points within the SMPS to learn how it operates etc. But until then, it's going to be just repair and nothing else.
Besides, it was assumed from post #1 that you had cleared all downstream faults within the Class-D section. In case you haven't done that yet, any of those faults could keep coming back to blow up your power supply over and over again until they're all resolved.
I meant when comparing IGBT's & Mosfets. It's IGBT's I don't have experience with.
Sorry yes meant to put that in earlier, only 15v DC on VS. I've got the way the SMPS works in this amp now. The problem is there are no "cheapest transistors in town" ... ordering any small amount of parts here at the moment incurs significant shipping costs. Only ebay is cheap but 99.9% of sellers are just re-selling fake chinese transistors. Mind you I do have replacements for the amp Mosfets (IRF4227) ... I could try them ... (edit: no Vds is only 200v). Just to put things into perspective for ordering here, those amp mosfets took almost 4 months to come into stock (supplier said 1 week lead time when I ordered).
Yes both driver IC's & all four amp output Mosfets removed until SMPS fixed.
That actually brings me to a question that I was going to ask later ... for other classes of amplifier repair we have variac & lamp limiters to save further damage to replaced components if faults still exist. What is the best check & power up procedure for powering up these Class D after replacing faulty parts?
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Well, an IGBT is a MOSFET followed by a BJT, and so its Qg is defined similarly. The IGBT (even at zero collector current) has a minimum voltage drop of about 1V across it, whereas the MOSFET that doesn't share this property makes the Rds-based comparison a really bad one.
The best way to test a Class-D amp is to run it on a conventional power supply, after bypassing the on-board SMPS.
Thanks for that ...it's starting to become clearer.
With the test Mosfets in place the SMPS function and all secondary voltages are restored.
Are you talking about testing sections at a time or using multiple supplies?