Here a simple 1 watt LED driver circuit based on a modified joule thief design, runs on a 1.5V single AA or AAA cell.
I got the concept of this circuit few years back from a LED torch, which was powered by a single AA battery. This circuit is pretty efficient and it can power a 1 watt white LED quite brightly.
This LED driver was constructed on a little PCB, unfortunately I don’t have the the torch any more to show you some pictures.
1 watt LED driver circuit diagram and part list
Part list >
- One BC557 transistor
- One BC337 transistor
- One 47kOhm resistor
- One 33pF capacitor
- Inductor coil, 40 turn on a 5x2mm ferrite toroid.
- One 1N4148 Diode
- One 47uF electrolytic capacitor
- One 1 watt white LED
- A battery of cource, AA or AAA NiMH/Alkaline or Zinc Carbon
You can make the Inductor coil easily by winding 30-40 turns of enameled copper wire on a small toroid salvaged from a old CFL, or even you could wrap the wire on a 5mm Iron screw.
The circuit diagram >
Working of this 1 watt LED driver circuit > Two transistors, BC557 and BC337 along with the 33pF capacitor and 47k Ohm resistor forms a simple oscilator circuit, supplying the inductor coil a pulsed DC current.
The coil produces high voltage pulses, the high voltage pulses got filtered by the 1N4148 diode, smoothed by the 47uF capacitor and eventually lights up the 1 watt LED.
You can construct this circuit easily on a strip board, a 1.5cmx2cm piece of strip board is enough.