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    This joule thief led or high efficiency LED with 1.5 volt driver is a tried and tested circuit built around some discrete electronics components. A common 5 mm high-efficiency white LED (D1) is the key component in this design.

    Technical specification of the high-efficiency LED used is shown below
    tested circuit

    • White color, water clear lens
    • 5mm Round type
    • Material: GaN/SiC
    • Viewing angle: 15 degrees
    • Forward current: 20mA
    • Forward voltage: 3.0-3.6V
    • Luminous intensity: 15000-20000 mcd

    With the help of an ordinary low power npn transistor (T1-C547B-Philips) we can drive this 3.6 Volt LED using a single 1.5 Volt AA cell.

    Here, the transistor functions as a high-frequency oscillator to generate the required voltage (DC-DC Boost Conversion) for the white LED. Next important component is a home-made toroid core inductor (L1). Total current consumption of the circuit is near 50mA.

    If you can’t find a toroid core for L1, note that toroid (ferrite) cores are largely used in Compact Fluorescent Lamps. Just take the core from the PCB of a discarded CFL and wind 10 turns of 30SWG enamelled copper wire. Pull out a centre tap and then wind another 10 turns.

    components toroid transistor

    Finally connect the inductor leads to the circuit as shown in circuit (ie Start by winding 10 turns, the start is the collector winding.
    Pull out the tap for the battery +ve connection, and then wind an additional 10 turns for the base winding).

    Joule Thief LED Driver circuit schematic

    high efficiency led circuit schematic

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    7 Responses to "Joule Thief High Efficiency LED with 1.5 Volt"

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    1. nice idea.the pcb size is interesting.Good work

    2. Hi Mr. Tridev Kripa

      I have tried but was unable to get above inductor based circuit for 6V. Needing to drive a number of LEDS (5 or 10 or more) from an inductor based circuit designed for 6V. Observed increased life and brightness so am avoiding resistance method.


    3. a.m.hoseinpoori says: on April 24, 2011 at 1:10 am

      i want drive high power LED with this circuit , but my LED need about 200mA
      can i change T1 or R1 & get more current?
      plz help me…

    4. There is no need for the 51R resistor.
      The 100R is far too low a value.
      A BC338 is a better transistor.

    5. Very good & useful circuit.
      Sir I want to drive 1 watt LED of forward current 350 ma. from 6 volt battery. pls. help.

    6. to use a toroid with a 6volt
      voltage winding 40 and the
      winding number of the well
      40, and then use that leads
      to the base resistor 1k ohm,
      and for best results use TIP32C transistor (npn) , good jobs

    7. it is working

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