Hello Madhu and fellow PICsters,

I am confused to why we add dissipated power instead of taking a weighted
average.  For example, if a device is periodically dissipating 5W for 1ms
followed by 0W for 1ms shouldn't the average dissipated power be 2.5W
(5W*(1ms/2ms) + 0W*(1ms/2ms)) and the peak dissipated power be 5W.  For the
calculations below relating to a MOSFET in a motor controller, shouldn't the
total losses per cycle of the PWM signal be a waited average and not the
sum?  If at no time the MOSFET is dissipating 80W I fail to see how it can
be dissipating 80W per cycle.  Please explain.  Thanks.

Regards,
Donovan Parks
AUVic Team Leader



> (7) Turn on losses = [0.55 * Vb * (Iload + Irrm)^2 * f * 2E-9] / Di/Dt =
> 8.475 Watts
> (8) Turn off losses = Vb^2 * ILoad E-9 * f / (dv/dt) = 6.667 Watts
> (9) Conduction Losses = RdsonTj * ILoad^2 = 64 Watts.
> (10) Total Losses are approximately 80 Watts per cycle of your PWM
> waveform.

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