"Nico Coesel" Measure the RMS voltage across it and the RMS current through it for
** Absolute BULLSHIT !!That gives a quantity called Volt Amps or VA.
..... Phil
Measuring Power dissipation emperically
Apr 13, 2008
21 Replies
You are spot on there. Only if you take simultaneous measurement samples, multiply them, and take the average, you will get watts. For instance, I made a simulation of a simple boost converter. The MOSFET reads 16.57 volts RMS and its current is 8.47 amps RMS (140.3 VA), yet the dissipation is
1.767 W.It drives a 2 ohm resistor at 129 watts (16.06 volts RMS), and the input is
11.73 amps RMS at 12 volts, or 140.8 watts. There's 11 watts lost in the circuit, so it must be in the inductor and the diode. Yes, 5.57 watts in the inductor (0.041 ohms), and 4.12 watts in the diode. (Yeah, it's gonna burn up!)So, reading the MOSFET VA is pretty close to the total watts of the circuit and load, but useless for MOSFET dissipation.
Paul
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required