A low forward voltage drop schottky diode is used as a rectifier diode to reduce its power dissipation and improve efficiency. Using 80% derating on VOUT for ringing on the switch node, the rectifier diode minimum reverse break-down voltage is given by Equation 41.
The power dissipation in the diode is estimated by Equation 44.
For this design, the maximum power dissipation is estimated as 1 W. Reviewing 30-V and 40-V schottky diodes, the MBRS340T3, 40-V, 3-A diode in an SMC package is selected. This diode has a forward voltage drop of 0.48 V at 6 A, so the conduction power dissipation is approximately 960 mW, less than half its rated power dissipation.