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Registered Member #1694
Joined: Sat Sept 13 2008, 09:13AM
Location: Australia
Posts: 108
Hi,
Is it possible to run MOSFETs in parallel? I'm trying to make a high power boost converter, the largest MOSFETs I have are rated 900V 7A. I'm need one rated 800V 15 amps, at least.
I've bid on some 1000V 50amp IGBTs on ebay, but if I don't win them it would be nice to know I if I could use these MOSFETs instead.
I plan on driving the gate with a 555. The 555 will be run at 12V.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I use paralleled mosfets at the rated current of a single in my induction heater without problems. However trying to push more current through them than a single mosfet is rated for doesn't work well, and you're better to parallel them to reduce power dissipation instead.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Mosfets to be run in parallel having the same part number but from different manufacturers should be avoided, as they will have different mask designs, which may result in small - but significant - differences in turn on delay time. (The mosfet with the shortest turn-on delay and quickest rise-time will hog most of the current) So choose mosfets from the same manufacturer - and from the same batch if possible - for best results in parallel operation.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Further to my comments about turn-on time, parallel MOSFETs must be mounted close together so that their gate drive impedances are as near the same as can be managed in practice, and all devices switch simultaneously.
I've often thought that some of the unexpected effects and malfunctions reported on this forum may be due to undiagnosed parasitic oscillation of multiple devices, a problem address in this paper below:
Eliminating Parasitic Oscillation between Parallel MOSFETs
There's really nothing complicated about it, and no reason why you shouldn't do it with a minimum of fuss. It's a common enough circuit configuration.
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MOSFETs in parallel?
