Switching BEC Test Results

[BrianG]

I picked up a couple of the cheap (~$10) UBEC units from eBay. This is what I use in my Hyper 8 and it works well so far, but I decided to run some tests to see how well they really work.

First, some pics:







This unit is based on the LM2596 switching regulator IC and use a very minimum amount of parts. The design of these units are assembled just about verbatim from the example circuit in the datasheet (in the link above).

Now, some numbers. I hooked them up to a linear adjustable 12v power supply I made and loaded them with various resistors. Pay attention to the output voltage, output current, and efficiency ratings.



Typical of switchers, they tend to be most efficient when run closer to their rated output current. I did overload it (4.4A) to see how it would react and I was quite happy. The voltage sagged a little, but the AC ripple was pretty constant for about 5 seconds when the switching frequency dropped, AC ripple increased, and the unit started to get quite warm (~125*F). So, it can take short durations of current draw beyond its rating. Under normal conditions, the temperature stayed under 105*F. And AC voltage ripple was quite low at a nominal of 2.2mV.

I was a little disappointed to see the output voltage was not quite what it claimed. The 5v setting fell a little short, and the 6v setting fell at least 0.5v short.

Dropout voltage is a little high at about 1v. This means that your input voltage has to be at least 1v higher than the output voltage you want. Still, it will still work for 6 cells/2s lipo should you choose to do so.

Edited for spelling :)