Driver options for Low Vf 2.0-2.2 red Leds?

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mountainair26's picture
Last seen: 19 hours 11 min ago
Joined: 09/10/2016 - 18:10
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Driver options for Low Vf 2.0-2.2 red Leds?

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. 

kiriba-ru's picture
Last seen: 1 hour 18 min ago
Joined: 01/17/2016 - 02:34
Posts: 1092
Location: Russia

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.

Meanwhile in Russia:

Lexel's picture
Last seen: 1 hour 28 min ago
Joined: 11/01/2016 - 08:00
Posts: 2340
Location: Germany

AMC 7135s


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).