I have a question about power a portable LED light source. I understand the various ways to power an LED array but my question is more about the best practical approach. I have created a portable “LED Light Bar”/“Book Light” for lighting sheet music. In order to spread out the light for a more even cast with less shadows, I have created the following layout:

12 LEDs, each LED has the following specs: 6.1 V / 117 lm / 150 mA / 4000 K / 90 CRI (Luminus Devices MP-3030-2100-40-90), that are paralleled and spaced 10 mm from each other on a 10 mm x 200 mm aluminum PCB.

I would like to power this with a 2S LiPo (7.4 V – 8.4 V) supply. I wanted the supply to be as small, simple and fail-proof as possible. The light will only be needed for about 30 min per use so battery efficiency is not a concern. I was thinking about using just a single resistor or a single AL5809 (SOD123 120 mA CCS AL5809-120P1-7) on each of the 12 LEDs. I was leaning a little more toward the AL5809 since the level of light would remain more constant as the battery voltage changes.

One other thought I had in order to not use resistors or CCS on each LED, was just to power the LED board through a 5.6 V linear regulator, which is below the 6.1 V drop of the LED.

Again the goal is for the smallest, simplest, fail-safe, portable LED light source that produces a good quality of light for 30 min at a time.


Because you do not care about efficiency a single constant voltage supply with resistors will work fine. But current limiting resistors are inefficient and the brightness will diminish as the battery discharges. The AL5809 CCR will provide "a good quality of light"

Battery operated projects should NOT use current limiting resistors. A CCR like your AL5809 will keep the current constant over a wide range of voltages (e.g. 3-6V)

For $15, 2 Panasonic 3350mAh 18650 NCR18650B Li-ion Battery may do better than a no-name Li-po battery pack.

Other possible CCRs
On-Semi NSI50150ADT4G Adjustable Constant Current Regulator & LED Driver
or the Microchip MIC4801


The smallest would be Lumiled's Luxeon Color C Line

The most efficient (and small) would be the Cree XP-G3

The most efficient Color LEDs are OSRAM Olson SSL


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