Paul asked a question:
If you increase the resistor and the [supply] intake current reduces, what does the efficiency do?
Paul has asked several questions about Joule Thiefs that I had not thought about previously, and they’ve brought up some thoughts that may be important and should be examined further.
I have calculated the efficiency of a Joule Thief, but I haven’t done a graph with points for supply current versus efficiency for a certain combination of transistor, coil, etc., and I would expect that the info would only apply to that particular JT, not to others. I’m speculating about this, but since the current is less, the Vce(sat) will be lower, and the loss across the transistor will be less. Also the gain will be a bit higher, so it should help lower the power wasted on the base bias. But there may be other factors that I haven’t considered that may influence the results, such as core losses and frequency changes.
