IGBT overheats - Page 1
Forum section: electronics / beginners

author: GbR
author_rank: Contributor
timestamp: August 13, 2023, 04:24:29 pm
content: .Edit:This clown thinks it's OK to post a bunch of stuff on forums and then remove them just to be a jerk. For this reason, he is in the naughty corner.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: August 14, 2023, 11:38:54 am
content: I'm not an IGBT expert but.. the FGN60N60 has a total switching loss of 1.7mJ. The AUIRGPS4067D1 has a total switching loss of 13.8mJ. So every time it switches you are dissipating 10 times the energy you used to during the transition. Seems like the kind of thing that would add up?

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 11:54:31 am
content: .

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2023, 01:01:38 pm
content: You are testing with no heatsink and complaining of "overheating"? This is not design...

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 01:21:43 pm
content: .

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2023, 02:02:39 pm
content: Hm, I wonder how one might go about figuring out someone's knowledge on a topic? Thumbing throughold postswould surely be enlightening, but tedious / low-information. The keywords and statements they put on theirprofilemight be a clue, but to be fair those are self-admitted and could be fabrication. Perhaps checking theirwebsitewould be relevant, though to be fair, not everyone can publish articles on private work, and one might have todigto find aresume, or contacts or other related information that might suggest whether one has SMPS knoledge .To clarify:- Switching losses are in the datasheet, usually specified at typical parameters, and plotted with respect to Ic and Rg.- Power dissipation is in the datasheet, or if not for Ta = 25C parameters, then this is typical for the package and any TO-247 (or whatever) package can be looked up for its typical performance.- Offhand, a TO-247 with no heatsink will be disastrously hot from just a couple of watts. 10W will fail in less than a minute.- You are right to be suspicious of parts from uncontrolled / 3rd party sources. There is a series of tests that can be performed to confirm performance. Putting devices into a random application in which temperature is uncontrolled (and perhaps voltage and current too, I don't know, no schematic has been provided), is likely not one of them; but, if the parameters are well defined, measurement in an application can be a part of those tests.Tim

author: moffy
author_rank: Super Contributor
timestamp: August 14, 2023, 02:54:05 pm
content: Quote from: GbR on August 14, 2023, 01:21:43 pmIf T3sl4co1l offers advice on switching supplies or a broad range of other topics it is always wise to listen, he is very knowledgeable on the topic.P.S. The AUPS device looks like it has been sanded unless you did that while clamping. Who was the supplier?

author: jmelson
author_rank: Super Contributor
timestamp: August 14, 2023, 02:58:02 pm
content: Well, 10 W at 40 V is 0.25A. 0.25A * about 1 V drop in the IGBT is 1/4 W. That should not be getting super hot. What kind of gate drive are you using? IGBTs need to be switched hard to prevent them from being in the linear region. When in the linear region, part of the die can "current hog" because the transistor has a positive temperature coefficient, meaning the warmer region conducts more current, so it gets hotter. This is usually a destructive cycle and leads to rapid (microseconds) failure, but at low current might not get that far. But, due to what I guess is a huge gate charge you mignt not have enough gate drive to turn it on rapidly.Jon

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 03:39:25 pm
content: .

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2023, 03:43:57 pm
content: Quote from: jmelson on August 14, 2023, 02:58:02 pmIGBTs tend to be rather generous/gentle to drive, on the whole; typical R_G around 10 ohms (with diminishing returns near there) is not uncommon.Now, the AUIR's Eon, Eoff vs. Rg (Fig.15) cuts off around 4 ohms, and switching is specified at 4.7 ohms. Relative to the 240nC typ. Qg, that's pretty modest; but that's quite a large Qg as discrete devices go, and, if the transformers I'm seeing in the photo are for gate drive (ed: aha, they probably are), their characteristic impedance could well be on the 10-20 ohm range, or more, and this really is a huge charge to attempt to drive via transformer, or even by bootstrap driver for that matter.Note that turn-on loss dominates here, largely I think because of the slow diode; Eon will be much lower in a typical forward converter or resonant application, for example, where hard switching is not incurred. (It will be relevant, during part of the cycle or in certain operating conditions, for the motor drive applications this part is probably intended for.) Turn-off losses can be snubbed to some extent (moreso in resonant applications), but the only solution to a slow diode is buying a better co-pack.Again, it's not clear if Eon or Eoff strictly applies in this case, because load current, and schematic in general, are completely undefined. If nothing else (literally unloaded), capacitance (Coes) will set switching loss; somewhat more than a watt, I think, but how much more is hard to say without simulation.Also curiously, this seems to be a planar device (as opposed to Superjunction, where Coes changes abruptly around 20-30V). That's kind of neither here nor there, for IGBTs, but interesting that it's such a big die from a more or less traditional process.Tim

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 04:14:32 pm
content: .

author: strawberry
author_rank: Super Contributor
timestamp: August 14, 2023, 04:15:04 pm
content: ~40K/W =~ 2W@~100Cfor 1kW SMPS is fineloss will increase with voltage and currentferrite inductor and iron powder transformer? I guess, one of them will work poorly with PWM modulation

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 04:22:24 pm
content: .der transformer.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2023, 04:37:33 pm
content: Diagrams are a start. We need characteristics. What are the RLC parameters of the GDTs? Resistance, magnetizing and leakage inductance, capacitance; saturation flux; or core type and size, winding schedule (number of turns, what wire, how arranged).Likewise the power transformer(s).What are component values for everything else? PCB layout?Tim

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 05:05:06 pm
content: Quote from: T3sl4co1l on August 14, 2023, 04:37:33 pmPlease NOTE: The issue only arises when I replace the FGN60N60 with either the AUPS4067D1 or the 120N60B3D.

author: uer166
author_rank: Super Contributor
timestamp: August 14, 2023, 06:49:47 pm
content: What is your actual gate drive voltage? Your scope shot shows ~1.2V which obviously can't be correct.

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 06:55:17 pm
content: .

author: uer166
author_rank: Super Contributor
timestamp: August 14, 2023, 07:01:59 pm
content: Some quick napkin math: assuming 20R gate drive at 12V, and 150Qg, then you'll switch at about 250ns (really rough approximation). The switching losses would be in the order of 2*Fsw*Tswich*Power_out, which works out to 1.2W, which could overheat your FETs but not in a few seconds..Something doesn't quite add up, and without more info, scope shots of the switching edges and current, it's impossible to say what might be going on. Start by answering Tim's questions since they're good ones. I'd like to see more scope shots to see the transition time of Vgs and Vds simultaneously (with a low inductance ground clip!).

author: uer166
author_rank: Super Contributor
timestamp: August 14, 2023, 07:06:31 pm
content: Quote from: T3sl4co1l on August 14, 2023, 04:37:33 pmThey look like custom OEM harvested parts out of another PSU, so it's unlikely you'll get those answers unless OP characterizes them.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2023, 08:17:08 pm
content: Quote from: uer166 on August 14, 2023, 07:06:31 pmIndeed, I do both! Design from calculations,andmeasure to verify design correctness.Knowing how to characterize transformers is a valuable skill. Consider an equivalent circuit like this:Assuming LL < Lm (Lm isn't shown on the diagram separately, but can be assumed part of the transformer having k = 1), they are easily measured (as referred to a given winding) when short-circuiting all other windings, or leaving all open.Tim

author: GbR
author_rank: Contributor
timestamp: August 14, 2023, 09:49:42 pm
content: [qu

author: andru123
author_rank: Newbie
timestamp: August 14, 2023, 10:51:52 pm
content: Why would you go and delete your posts? So the secret knowledge is not shared with others?Now this thread does not make sense.

author: uer166
author_rank: Super Contributor
timestamp: August 15, 2023, 06:34:01 pm
content: This is actually an interesting topic, and I was really curious what the issue was. Shame it was all deleted!

author: MK14
author_rank: Super Contributor
timestamp: August 15, 2023, 06:52:16 pm
content: Quote from: uer166 on August 15, 2023, 06:34:01 pmYou're right, I've accessed Google Cache and maybe other sources (such as anything my computer still has about that thread, that I can readily find), to get the following:QuoteQuoteQuoteOne source(s) link, that could easily NOT work, as the google caches get deleted, I think, or overwritten/updated.https://www.eevblog.com/forum/projects/igbt-overheats/Actually, that is the wrong link, so here is some (I cut out the apparently irrelevant, bottom of it) of the raw source cache:Quote

author: magic
author_rank: Super Contributor
timestamp: August 15, 2023, 08:07:44 pm
content: Quote from: uer166 on August 15, 2023, 06:34:01 pmPossibly a fairly boring case of counterfeit components. Or the OP was doing something too embarrassing (or "innovative") to disclose publicly

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 15, 2023, 08:31:58 pm
content: I might've quipped back too strongly. The resulting whiplash seemed effective, but it's hard to say how they really felt...I don't have reason to doubt the components, it's a concern of course, and can be tested (but, the whole testing fixture, and signals, and what to do and why, is a wholething), and I think their level of knowledge wasn't enough to twig on that, or just overwhelmed by the combination of not-necessarily-constructive-sounding information, and their ignorance being put on such plain display (and to be clear, that's fine, remember, the cure for ignorance is knowledge), maybe, dunno?I guess the real issue is we're starved for good SMPS content here and all jumped on this thread like sharks to chum?..Tim