3.6V Joule Thief (32) 5mm LED (3.6V - 210 mA .75 Watts)

Playing around with finding the right balance for Lithium Ion Joule Thief circuits and came up with this lamp configuration which puts out pretty darn good light for .75 watts. Normally, as to not burn out the LEDs and add protection based on full voltage (4.2V), the 32 5mm's would require 32 resistors at 33 ohms each. This would equate to resistors dissipating 422.4 mW of HEAT alone, drawing 640 mA from the source. Total power consumption would be 2.7 watts. In this scenario, no substantial heat can be detected, and total power consumption is about .75 watts, or 750 milliwatts. When you consider that driving these LEDs with the same battery, normally, the resistors dissipate over 50% of this JT circuit's total power dissipation... even if the circuit is only 75% efficient, theoretically you should be ahead of the game, no? I like it anyway.. :) It is fun to do the final tuning of JT's as you find the right capacitance for the setup, watch the lumens go up, and the draw go down.. :)
Be the first to comment