I have a cheap bad torch (flashlight) and I want to improve it's performance by increasing the current. It uses two white 5 mm LEDs and two AAA batteries to drive them. At 2.7 V, the current is just over 2 mA which is surely ~1 mA per LED! At 3.0 V this rises to 7 mA total or 3.5 mA per LED. I figure most cheap white LEDs are rated to take 20 mA which would make for 40 mA total. There is some IC called QX5252 which is some kind of joule thief whose current output is determined by the inductor attached externally. I was hoping could corroborate my interpretation of the datasheet before I order the parts.
The LEDs need 4.1 V to get 40 mA of current to them. That's 164 mW. I'm providing 2.4 V (dropping to ~1.6 V) .
Inductor needed at full charge = 2 x 2.4 V x 10E-6 / 0.164 W = 29 uH. Is that calculation correct?
Also, I think the energy is delivered in pulses but the datasheet is pretty rubbish and doesn't give any indication on the width of the pulses so I don't know what effect a capaitor would have for smoothing the pulses out.