Did synchronous rectifier has other function?

Hi folks, I have designing the flyback SMPS using on-semi ic NCP1937 and reference to EV board DN05044 ( https://www.onsemi.cn/pub/Collateral/DN05044-D.PDF ) to develop my design.
There have 3 parts of the EV board, flyback/PFC controller, low standby controller and synchronous rectifier.
I have very few knowledge about synchronous rectifier, so I find from internet to get more information about this, here is my understanding:
The synchronous rectifier is used to increase efficiency when the output voltage is lower, it can compensate the rectifier diode voltage drop, if output voltage is lower(let say 5V out), the voltage drop from rectifier diode (0.5~1V) is much obviously affect the efficiency.
Is this correct? did the synchronous rectifier has other usage/ function from above EV board? If my voltage output is 30V, and parallel the rectifier diode to make the voltage drop lesser, can I ignore the synchronous rectifier?
Thanks all!

Hi,

Synchronous rectifier: usally a (controlled) Mosfet is used in parallel to the rectifier diode to decrease voltage drop and thus increase efficiency.

and parallel the rectifier diode to make the voltage drop lesser,

Click to expand...

Paralleling diodes won't reduce voltage drop significantly.

Klaus

make sure you drive sync rects properly...be wary of current reversing seriously in the inductor or seconday of flyback etc