What is the difference between diode rectification and synchronous rectification?

DC/DC Switching Regulators

Nisshinbo Micro Device's step-down DCDC converters use diode rectifier and synchronous rectifier.
The diode rectifier type uses a schottky diode and the synchronous rectifier type uses a MOS transistor in the low-side switches.

The high-side and low-side MOS transistors are built in most of the Nisshinbo Micro Device's DCDC converters except for the R1242, which uses synchronous rectifier and an external low-side MOS transistor.

• R1240 (Diode Rectifier Type)

  

• RP500 (Synchronous Rectifier Type)