Diode losses in switching power supply


I couldn't find a simple approx formula for calculating diode reverse recovery losses!
I am not doing any rocket science, so I just need an approx formula (not worried much about temperature effects and small variation in parameters). I have been searching in Google for answer, most of answer refer to an litterateur, which has detailed calculation including "n" number of variables. Please suggest a basic formula for approximating diode recovery losses.

Best Answer

The following information is taken from the slides for Coursera's Introduction to Power Electronics class, which is based on ECEN5797 at the University of Colorado Boulder.

You will need to know the following parameters, which come from your design and the diode datasheet:

\$t_{r}\$: Diode reverse recovery time (typically tens of nanoseconds)

\$Q_{r}\$: Reverse recovery charge (not sure what's typical -- hundreds of nanocoulombs?)

\$I_L\$: Average inductor current

\$V_{DR}\$: Diode reverse voltage -- equal to the input voltage \$V_g\$ (for a buck converter) or the output voltage \$V\$ (for a boost converter)

\$T_S\$: The switching period

Assume that the diode changes at the end of the reverse recovery transient. This is a pessimistic assumption. These graphs show the transistor and diode waveforms for a buck converter:

Transistor and diode waveforms for reverse recovery

Using this assumption, the reverse recovery power loss can be approximated as:

$$V_{DR}(\frac{t_r I_L}{T_S} + \frac{Q_r}{T_S})$$