High-Voltage LED Driver (CHEAP)

Intro: High-Voltage LED Driver (CHEAP)

Based off dan (MonkeyLectric) page:

https://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/step11/an-even-simpler-current-source/

Background:
I needed a low power, very bright tail light for my Electric Bike (E-bike).  I wanted something SIMPLE.  I've looked up designs for LED drivers that had MANY parts.  Dan's design only had 3 cheap parts.  I found components that would work in my voltage range (Max ~60v).

I was previously using a standard 1157 (12v) automotive bulb (~20watt output) at ~15lm/watt = 300lm
Because it was a 12v bulb I needed a voltage regulator that was only ~50% Efficient, so previous power draw was 300lm/50watt or 6lm/Watt.

The new LED design has a ~10 fold increase in efficiency.  ~50lm/watt

STEP 1: High-Voltage (60v) LED Driver (CHEAP)

High Efficiency (~85%) driver for E-bike Lights
I’m using this as my low power tail light.
Input Voltage (50-60v) – 50v input min is based off the 46v LED unit.  A different unit would have a lower input voltage, but would reduce efficiency of the regulator.

This regulator is rated at 300mA at 60v.  Use of many 3.3 or 5v LED is also possible in series.
LED is rated at 125mA with a forward Bias Voltage of 46v - 55v

This Design Current ~100mA (Adjustable with different resistor value)  Regulator is rated up to ~1.5A, so plenty of power capacity left in the design.

LED current in amps = 1.25 / R3

Capacitor Value - CAP ALUM 22UF 63V 20% RADIAL
Resistor Value - RES 12.4 OHM 1/4W 1% AXIAL
Regulator – IC REG LDO ADJ 1.5A TO220-3

All Part Numbers are from Digi-Key

For more details, please look up the part numbers listed below.

LED – (XMLHVW-Q2-0000-0000LT351CT-ND) - $5.72
LED Mounting Board – (BER272-ND) – $1.01
Regulator – (LM317HVT-ND) – $2.40
Capacitor – (P5190-ND) – $0.22
Resistor – (CMF12.4QFCT-ND) – $0.31
Heat sink – (SV-LED-113E-ND) - $2.22
Heat Sink Mounting Tape (1168-1715-ND) – $0.26

Total $12.14

Comments

[iqlogic]

LM317 and high efficiency? You are joking, right?

[amandaghassaei]

cool, do you really such a big heat sink, or is it for artistic purposes?

[CircusJeff]

After about 20min of running in 70deg air (no air blowing) the heat sink is almost hot enough to burn you... so, I would say it is for function, not looks.

[pfred2]

Are you sure it is the LED that is making the heat and not the voltage regulator you have attached to the heatsink too? While your voltage regulator may be able to supply up to 1.5 amps in some circumstances at 60 volts it can only supply about 250 milliamperes. So you have fair headroom for what you're doing but I wouldn't go tossing another load on there. If you think it is hot now ...

[CircusJeff]

Agree... Regulator is burning ~1watt. It is absolutely adding to the heat of the heat-sink. I could have a separate sink for the regulator, but I wanted a single package...

[Lectric Wizard]

You should include values for the components so people who don't use Digikey can still build this. Cheers!