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250V 21Amp N-MOS — Parallax Forums

250V 21Amp N-MOS

Beau SchwabeBeau Schwabe Posts: 6,572
edited 2009-12-08 06:35 in General Discussion
Mouser has this for $1.65 which isn't a bad deal.

IRFS 654B

DataSheet

What I'm looking for is something with an RdsON lower than .14 Ohms without running a couple of these MOSFETS in Parallel.

Anyone have a part number for a reasonably priced MOSFET with less than .08 Ohms RdsON? The actual current I need is about 10 Amps, so 21 is there for a little padding, but I absolutely need the 250V

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 12/5/2009 8:59:49 PM GMT

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-12-05 21:51
    ST Micro's STW75NF30. Is $6.53/1 reasonable?

    -Phil
  • Beau SchwabeBeau Schwabe Posts: 6,572
    edited 2009-12-05 22:17
    Phil,

    Thanks, that's roughly the equivalent of 4 of the IRFS 654B's in Parallel and would definitely work for my application.

    Right now with each unit I have about 1000 Watts using two IRFS 654B's in Parallel (total of 8 for the H-Bridge). If I go with a single STW75NF30 (total of 4 for the H-Bridge), I could make the units capable of roughly 2000 Watts. Hmmm... I'll have to think about that.

    Either way, the price in dollars per watt is very close...

    8x $1.65 = $13.20 --> 1000 Watts
    4x $6.53 = $26.12 --> 2000 Watts


    Thanks!

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-12-06 00:00
    There may be some that are cheaper if you don't need logic-level drive. Since you're using nMOSFETs in all four quadrants of an H-bridge, I'm guessing you don't. (Besides, those things have such a high gate capacitance, you'll need a MOSFET driver anyway if you're going to PWM them.)

    -Phil

    Addendum: Here is one for $1.75.

    Post Edited (Phil Pilgrim (PhiPi)) : 12/6/2009 12:13:55 AM GMT
  • Beau SchwabeBeau Schwabe Posts: 6,572
    edited 2009-12-06 00:28
    Phil,

    I have a MOSFET driver that I'm using capable of driving up to 600V mosfets. My application is for a pure sine wave inverter, that's a little bit reverse engineered from one that I bought about a year ago. Originally the design was rated for 350Watts, and I have that now working at 1000Watts. After the DC-DC converter stage, I totally re-built the output stage so that I can even use a "modified sine" inverter's DC-DC converter stage and still get a pure sine wave on the output.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • Beau SchwabeBeau Schwabe Posts: 6,572
    edited 2009-12-08 06:35
    Phil,

    Just an update...

    I think for now my limitation is going to be right at about 1000 Watts. Using the STW75NF30's will reduce the size a little bit and keep things cool on the output side. The weak link is in the DC-to-DC converter section where I have 3 switching power transformers rated at 30 Amps a piece. (see attached schematic) A single transformer solution is out of my hobby budget at the moment. I could parallel the output of the transformers to save a little bit more space and go with a single "20Amp puck" bridge rectifier. This is still WIP as well as a personal learning curve, so if I find something along the way who knows.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.

    Post Edited (Beau Schwabe (Parallax)) : 12/8/2009 6:47:28 AM GMT
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