When I reviewed the datasheet for the MT9284 boost converter I noted the suggested inductor size of 4.7uH to 22uH. The datasheet contemplates led currents of 20mA. I'm pushing the chip almost 10 times past the 20mA.
Which begs the question what inductance should I be using? I did a series of measurements and after a lot of thought concluded the right amount of inductance is around 8.2-10uH. The following chart shows measured efficiency, with outliers removed, and two trend lines for 10uH and under, and 10uH and over. By inspection these trend lines intersect around 9uH. If I drop the 10uH observations the intersection of the trend lines shifts towards 8.2uH.
I've ordered some more inductors to confirm this is the sweet spot.
This will be a good starting point for the lower loss boost converter I will be receiving in the same parts shipment.
No comments:
Post a Comment