Joule Thief

[Dave45]

Thinking about it, for the most part bemf is always feeding the load.

[Dave45]

bemf feed

[Dave45]

With sequential synchronous switching it could be done using three chokes.   

[Pirate88179]

Here is an update on my Micro Joule Thief efforts:

https://www.youtube.com/watch?v=J6B4_EHmOIQ&feature=youtu.be

I made these lights using the NCP 1402 chip which will switch down to .3 volts.  I have been attempting to make a commercial light that will run on dead batteries and finally decided that modifying an existing light is the way to go.  This video shows my progression from making an entire light myself, to finding a good light to modify.  By rewiring the light in parallel from series, I can now operate using just a single battery, or two, or the three the lights were designed to use.  Using three batteries will give a very long run time.

I am now working on seeing just how long that is, along with some other testing before making these available on my website.

Bill

[MarkE]

Here is an update on my Micro Joule Thief efforts:

https://www.youtube.com/watch?v=J6B4_EHmOIQ&feature=youtu.be

I made these lights using the NCP 1402 chip which will switch down to .3 volts.  I have been attempting to make a commercial light that will run on dead batteries and finally decided that modifying an existing light is the way to go.  This video shows my progression from making an entire light myself, to finding a good light to modify.  By rewiring the light in parallel from series, I can now operate using just a single battery, of two, or the three the lights were designed to use.  Using three batteries will give a very long run time.

I am now working on seeing just how long that is, along with some other testing before making these available on my website.

Bill

The NCP1402 is a good choice provided that you have a current limiting mechanism on the load side.  If you do not then the LED current can be highly variable and other problems can occur.  One way around the problem would be to steal the circuitry out of one of those garden stick lights.  They are limited int he total power that they can deliver, but they can generally operate to pretty low input voltages, are efficient and drive the LEDs with a current instead of a voltage.