I need your advice on high power device selection.

I'm working with a similar application to this schematic, with the descriptions being in this forum. Without reading through the dozens of pages (and several bad Oprah jokes that I don't get): it's a motor driver circuit for an electric vehicle.

Think 500A, 144V driven with PWM at 16kHz. Parallel NMOS looks like the best solution, though I'm open to suggestions for monster parts that would be in the same price range and handle the full load...

With this kind of power, I'm thinking it's very important to have minimum losses (the original gate driver is described as an "Ultrafast MOSFET Driver", and the NMOS is rated at 11 milli ohms). Price is a consideration, but should be compared to the losses adding up with daily driving use over years and taking range into consideration.

The driver in the schematic is EOL from what I can tell, so I need a recommendation on the driver as well.

In summary: I need selection help for MOSFET, flyback diodes and gate driver IC for this application.

  • \$\begingroup\$ EOL? Does that mean you can't get it any more? \$\endgroup\$ – Andy aka Oct 10 '13 at 12:49
  • \$\begingroup\$ End of life. So you could get it on ebay no doubt, but supply is uncertain and it's not really a good part to put in a design: you might not be able to find them if you might ever need to do repairs or if you might want to make one for a friend in the future. I stay away from EOL parts, and for something as commonly needed as a gate driver, there has to be an excellent (maybe better?) alternative. \$\endgroup\$ – Bob Oct 10 '13 at 13:07
  • \$\begingroup\$ Have you considered using an IGBT? \$\endgroup\$ – Scott Winder Oct 10 '13 at 13:41
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    \$\begingroup\$ You can find IGBT modules at your favorite distributor that should meet your requirements--they can be a bit pricey, but ought to pay you back over time, as you've suggested. \$\endgroup\$ – Scott Winder Oct 10 '13 at 13:50
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    \$\begingroup\$ Found a great FET vs. IGBT here on stack exchange. \$\endgroup\$ – Bob Oct 10 '13 at 14:11

FAN3121 and FAN3122 MOSFET drivers from Fairchild look good and are "about" the same spec as the IDXX414. They have a peak drive capability of about 9A and from a quick look it seems their pin out is nominally the same.

The IRFP260N is good for operating at 170ºC and is rated at 200V, 50A with an on resistance of 0.04 ohms. Gate drive at 10V is surprisingly low for this type of device too. There are probably better devices but I've used one of these before and given it a fair bit of stick.


  • IRFP260 drops about 0.8V at 20A - 16W per device
  • IPP110 drops about 0.2V at 20A - 4W per device
  • IRFP4668 drops about 0.18V at 20A - 3.6W per device
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  • \$\begingroup\$ Thanks for the answer! I think the IRFP260N might be a little too low powered at 50A, but then, 25 of them in parallel might be cheaper (and maybe even lower resistance) than fewer high-powered devices, with less risk if just one fails... I'll mull it over. The heat sink would have to be huge, though! \$\endgroup\$ – Bob Oct 10 '13 at 13:31
  • \$\begingroup\$ @Bob The IRFP4227 does 20A and drops 0.4V = 8W per device dissipation. The IXFH120N drops 0.3V at 20A = 6W and these are all TO-247 packs for convenience. Might get better devices in TO-3 package? \$\endgroup\$ – Andy aka Oct 10 '13 at 13:52

Not exactly an answer on the question, but anyway.

The big problem of this schematic is not the part selection, but the electrical and mechanical construction. On 500A and 16kHz, you have very serious problems with the PCB design, current paths, EMI, etc, etc...

BTW, the total power loss will be something like 500W (This is very good value) and the cooling of the MOSFETS can be an important part of the design.

Don't forget about the accumulator (battery) heating as well. It will probably need cooling system. For example "Tesla roadster" with 53kWh battery packs has cooling system with liquid coolant that is driven by a 146W pump and works even when the car is switched off (if the battery is charged more than 90%).

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  • \$\begingroup\$ What do you mean by "accumulator"? The thread of forum posts actually gets a number like 500W for power loss, so nice job! The thread has the board layout and heat sink discussion (at great length): the guy is using 5ounce copper board. I haven't seen any discussion so far of EMI causing problems, but I haven't gotten through all 5000+ posts on the thread... Though it didn't answer the question,thanks very much for the input! \$\endgroup\$ – Bob Oct 10 '13 at 14:27
  • \$\begingroup\$ By accumulator I mean the battery. It has some internal resistance and there will be some power loss as well and this power could be even higher than in the MOSFETS. \$\endgroup\$ – johnfound Oct 10 '13 at 15:02

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