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# Calculating power loss in switching MOSFETs

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re: Calculating power loss in switching MOSFETs
3/22/2013 1:21:43 AM
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Nice article and some good comments. It would be good to have a similar introduction in NPN switch.

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re: Calculating power loss in switching MOSFETs
1/15/2012 8:49:58 AM
I stand by your side. The two power loss you mentioned are very serious in the motor drive.

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re: Calculating power loss in switching MOSFETs
8/10/2011 4:53:45 PM
Switch too fast trying to reduce linear transition losses and reverse recovery down stream rears its ugly head. so you can only switch so fast for your devices selected. Topswitch would be wise to offer a part that will drive an external trenchFET in // with the integrated FET on chip. allow the power level (current peak level) to set when these switch over or // up external fet. So as to have lowes switching losses from standby to full power. You have my resume on file btw

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re: Calculating power loss in switching MOSFETs
8/4/2011 12:46:28 PM
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We should always keep in mind the Miller effect that may dramatically increase the input capacitance in a common source connection. In full- and half-bridge configurations the lower MOSFETs are often hotter than the upper ones and require higher current for the gate drive (if both are driven correctly). Therefore the formula for switching power dissipation becomes far more complicated.

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re: Calculating power loss in switching MOSFETs
8/4/2011 6:30:31 AM
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rayji2008, there are trench devices above 200V that are not superjunction - 250V, 300V and even 500V trench FETs. See IRFB812PBF for example.

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re: Calculating power loss in switching MOSFETs
8/2/2011 11:55:14 PM
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I can think of another two causes of power loss: 1) One thinks of a switching MOSFET as being either hard on or hard off. In reality it takes finite time to switch, and during this time the MOSFET is in linear mode and the power dissipation can be huge. 2) In an H-Bridge configuration or in a Buck regulator, there is a "Deadtime" during which both MOSFETS are off. However the load current still has to flow, and it flows through the body diode of the MOSFET and dissipates power. An article on Calculating power loss in switching MOSFETs should address these mechanisms.

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re: Calculating power loss in switching MOSFETs
8/2/2011 3:00:30 AM
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A good basic overview of the power issues relative to switching MOSFETs. I must confess to a little bit of deja-vu when reading the article as it seems to repeat basic facts a few times. Still overall a nice review of the issues.

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re: Calculating power loss in switching MOSFETs
8/1/2011 2:25:53 AM
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I believe there is no "Trench" MOSFET beyond 200V range at this moment. What referred to as "Trench" in this article is rather Planar or Super Junction technology-based high-voltage MOSFETs, which has "vertical" current flow path rather than "lateral". I hope the author is aware of this terminology difference.