I was going to investigate the sweet sport for the MT9284 boost convertors. Instead, after some reflection, I brought some MT3609L boost convertors. As expected, with the lower resistance of the switching element (FET) the efficiency was much higher, around 90% measured, than I achieved with the MT9284 (50-60%).
However, two things really stood out. Firstly, a large number of inductors which work in the MT9284 circuit simply do not work with a MT3608L for reasons I do not presently understand. The MT3608L datasheet recommends an inductor of 4.7uh to 22uH. With the exception of two different 8.2uH inductors and one 3.3uH inductor, I found 22uH was the minimum inductance that would work.
Secondly, for the three 22uH inductors tested I achieved the following efficiencies:
22uh MT3608L MT3608L LED Power MT9284 MT9284 LED Power
small 24% 0.008W 20% 0.49W
large 24% 0.008W 52% 1.3W
Ferrite Chip 51% 0.023W 18% 0.47W
With a similar switching frequency and the same 4 meters being used to measure voltage and current simultaneously the results for make little sense to me.
I have the output current pin floating which the datasheet suggesting "The OC pin can be floating, the
current limit will be set by Internal 2.5A current limit." I will try attaching a 22k resistor to program the output current to 2.4Amps to see if this makes any difference.
No comments:
Post a Comment