|Thread Links||Date Links|
|Thread Prev||Thread Next||Thread Index||Date Prev||Date Next||Date Index|
I think there are good arguments on both sides, I’d like to give some information that may be useful to know about.
This is about efficiency, which depends on selecting a typical low cost schottky diode bridge versus selecting an expensive active (FET) bridge.
In the case of 51W PD, a low cost bridge (schottky rectifiers) will introduce close to 0.9 W x 2, which is a real concern for PD equipment makers, who struggle with thermal and efficiency.
If now we look at the whole PSE-PD-cable ecosystem, this has high impact on system efficiency, which partly defeats the purpose of driving 4P.
It is true that using an active bridge could eliminate a high portion of that loss, typically probably 75% of it, but it then becomes a quite expensive solution.
On the other hand, a single rectifier solution can be based on any of these two options:
1. single schottky diode: can already remove 50% of that loss with negligible cost,
2. one-FET solution: eliminate about 90% of the loss with just one FET (much simpler and lower cost) instead a full FET bridge (4 FET).
And we all know how cost-sensitive the PD equipment market is.
I fully understand the concerns mentioned below, and I’m sure they are valid concerns, but I think that efficiency and cost should also be part of the discussion.