above is the led I'd like to power from a single ~3.7-4v lithium ion, but it has a vf of only 2.2 at 700ma and 2 at 300ma. Are there buck drivers that can handle that task? I'd like to use them in a P60 drop-in or something similar with an18650 or 16340, otherwise two or three nimh cells would be a good power source for a buck driver. Modes aren't that important, just want it to get the voltages somewhat close without damaging anything. Thanks for any suggestions on drivers for low vf leds.
You can use 7135 based driver if efficincy is not so important.
Buck like ld-4 from i-o should work well, but you will need to change resistor to set required current value.
The maximum junction temperature ratings of AMC7135 should not be exceeded under continuous normal load
conditions. When power consumption is over about 700mW (SOT-89 package, at TA=70°C), additional heat sink is required to control the junction temperature below 120°C.
and we mount them on a copper PCB that is close to the flashlight body and they reduce current when too hot
TJ = PD (θJT +θCS θSA ) TA
so also like 25-35°C/W from PCB cooling from PCB
PD : Dissipated power.
θJT: Thermal resistance from the junction to the mounting tab of the package.
For SOT-89 package, θJT = 35.0 °C /W. For TO-252 package, θJT = 7.0 °C /W.
θCS: Thermal resistance through the interface between the IC and the surface on which it is mounted.
(typically, θCS < 1.0°C /W)
θSA: Thermal resistance from the mounting surface to ambient (thermal resistance of the heat sink).