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Computing switching losses in Power MOSFET

manish sharma2
Prodigy 150 points

I  have a Query on TI article on Improving Power Supply Efficiency –The Global Perspective. 

  1. The equation 4 on page 9, the switching losses in Drain capacitance VDS (the voltage change across CDS) is mentioned. That Vds is the RMS value or peak value (As in my system at the Drain there is Full wave rectified voltage waveform is there, So RMS and peak value are different)
  2.     In Equation 5 on page 9, Switching Overlap

                               P = 0.5×VDS × I ON× t TR× fSW

 

What is t TR mentioned here?

VDS is RMS value or Peak value?
I ON is RMS current that is flowing through the MOSFET?

I am attaching the Document along with this mail for your reference.

conduction and switching losses.pdf

  • 0
    TI__Intellectual 1615 points
    1. the value should be instantaneous value. If your input is DC, you can just use that voltage. If the input voltage varies like AC, you need to integrate alone the cycle and do the average
    2. tTR is the transition time. Generally, when MOSET turns on and off, there is time the MOSFET carries high voltage and high current at the same time. The tTR would be the overlapping time.