Electrical – Wiring LEDs in series and parallel


I am looking to build a light stick.

I am quite new to electronics and have just been experimenting so far. My light needs to be portable so I am using a 3.7v LiPo battery (I am into RC so have some lying around). I initially thought that wiring my LEDs in parallel would be best as it requires no voltage boost but I seems like it will use more battery that way.

I looked at linking them up in series but I have about 16 and need a voltage of around 51-52V to run them in series. From what I have read this uses fewer amps for better efficiency but I don't know if this is correct.

The voltage regulators seem to get quite bulky when you up to a higher voltage. What I was thinking of was creating segments of LEDs in series and put the segments in parallel using multiple step up voltage converters in one project.

Would it be ok to use more than one and would you recommend using a pre-made one or incorporate it into my design and have it on the board.

Best Answer

It's generally ill-advised to place two diodes (including LEDs) in parallel due to the negative temperature coefficient of a diode - a thermal runaway can result.

Two diodes in parallel will have the same voltage applied across them (i.e. forward voltages are the same), but due to differences in the diodes (manufacturing variation, thermal path differences, etc), one will draw more current than the other. The negative temperature coefficient will cause the diode drawing more current to draw even more current, and so forth, eventually causing it to overheat if left unchecked.

Boosting from 3.7V to ~50V could be tough, so you may have luck with using a few smaller strings of LEDs. A tri-channel boost LED driver such as the LT3797 would keep the boost ratio (V_out / V_in) reasonable.