### Author Topic: How can I calculate mosfet heat dissappation?  (Read 1131 times)

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#### alank2

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##### How can I calculate mosfet heat dissappation?
« on: August 31, 2014, 02:00:36 am »
Hi Everyone,

I'm feeding it a 8kHz PWM signal and it is switching a 40mA load (which I realize is very little for a mosfet).

It is a IRLD024PBF-ND.

Thanks,

Alan

#### T3sl4co1l

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##### Re: How can I calculate mosfet heat dissappation?
« Reply #1 on: August 31, 2014, 02:42:52 am »
Circuit?
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#### Pedram

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##### Re: How can I calculate mosfet heat dissappation?
« Reply #2 on: August 31, 2014, 03:49:13 am »
it depends on RDS(on) , gate voltage , frequency , driver's output impedance and gate capacitance

according to datasheet, RDS(on) is 0.1ohms on 5V DC Gate voltage.  at 50ma it dissipate less than 250uW

#### DanielS

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##### Re: How can I calculate mosfet heat dissappation?
« Reply #3 on: August 31, 2014, 12:03:35 pm »
The fundamental way of calculating dissipation in any component is: sum of integral of i(t)v(t) on all pins averaged over a number of complete operating cycles.

A simplified ballpark figure if the rise/fall curves are roughly linear: ((trise + tfall)*IDSrise+fall average*VDSoff/2 + ton * RDSon * Ids^2) / period.

The exact rise/fall waveforms can vary considerably depending on circuit design and operating region. If the MOSFET drives an inductor operating in continuous mode at 10A average current and has a 500ns rise/fall time, 30V input voltage and 0.02 RDSon, you lose about 15W from rise/fall and 1W from ON-time.

Smf