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Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Jan, 2kVA is a lot of power, especially hard-switched. Even if you have like 90% efficient driver which is excellent, you still need to get rid of 100-200W of heat which is pretty hard. As far as I see your heatsinks are quite small!
You need to give them lots of cooling to get close to their rated current. I'm not sure if small to247 packages are capable of dissipating all this!
Update- one of the gate drivers was blown but I believe this was the result of the failure (gate voltage went too high/ outputting to short etc.)
That's why I always vote for a GDT. It's very easy to get working, from my point of view, easier and with much less possible bugs than bootstrapped driver.
Other important thing, it drives the gate NEGATIVE, and with some deadtime you can perfectly avoid shootthrough.
I say nothing is good for circuits of that kind like SG3525 and a GDT. You can feed up to 40V into SG3525 collectors and use stepdown GDT 2:1 or even 3:1 for really great performance.
Don't give up by a chance, make sure to fix it soon and photograph the monster arc
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Marko wrote ...
Jan, 2kVA is a lot of power, especially hard-switched. Even if you have like 90% efficient driver which is excellent, you still need to get rid of 100-200W of heat which is pretty hard. As far as I see your heatsinks are quite small!
You need to give them lots of cooling to get close to their rated current. I'm not sure if small to247 packages are capable of dissipating all this!
Marko, it was nowhere near 2kva, I think it was more like something little over 1kva now (when I said before 1kva it was not as much, as I found out later my DMM acted up near the driver, it was really more like 600-700W previously.)
The heatsinks were just slightly warm to touch after a minute of operation, so this was not an issue. I think each igbt was not over 20W.
I've later included a 3R3 resistor/ 10n capacitor series combo on the output of the bridge, which slowed down the voltage rise on the igbts on turn-off, and made them run slightly cooler. Could this have lead to the failure? I don't think so.
Maybe some time in the future when I'm ready to blow another two $6 devices, I'll resurrect the driver.
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IGBT flyback driver
