blog; Motor Controller Options for 2015

[DampRobot]

Originally Posted by apples000

Switching to a higher frequency also makes the system less efficient. Although the more efficient sign-magnitude switching could make up for this loss, you'd see higher efficiency if it switched at 10kHz than 15kHz. The reason is that the faster you switch the FETs, the more time they'll end up spending in their switching state. The transition is not instantaneous, and as you increase frequency, they'll spend more time in between, which is inefficient.

While I agree that in theory faster switching will decrease efficiency, I'm not sure that it'll be that large of an effect in practice.

At 15 kHz, a MOSFET would switch on and off twice every 1/(15 kHz), which is a switch about every 30,000 ns at 50% duty cycle. The MOSFETs I've seen on the market nowadays all switch faster than 10 ns, and some even faster than 5 ns IIRC. That's about .03% of each state at 50% duty cycle. Of course, as switch your FETs at closer to 0% or 100% duty cycle, the effect you're describing will be more important, but I don't think it'll significantly decrease the efficiency of the controller.

EDIT: For what it's worth, I'm not an EE either. But that could change in the future.