I have been shown an IC that is a current sink PWM dimmable LED regulator. It happens to be a WS2811. While this works well for low drive currents (up to about 20mA), I was approached with the idea of making it drive power LEDs (~1 amp @ 3 volts).
I immediately thought of using a PNP transistor in this configuration:
simulate this circuit – Schematic created using CircuitLab
While it does demonstrate power gain, the efficiency is terrible!
We would like to make this solution use as few components as possible. Since this is not an opinion-based site, please illustrate examples of highly efficient methods of "multiplying" current sinks, say by a factor of 100. The major constraint is component count.
Answer
Your circuit has another issue, if you were to try to build more than one of them you would find that the LED current would vary dramatically from unit to unit.
That's because the beta of a 2N3906 (or most transistors for that matter) varies widely.
Your requirements are somewhat contradictory. To get efficiency you need a switching current regulator, which necessarily has a controller, an inductor and at least a few other parts.
One example is here: http://www.ti.com/lit/ds/symlink/lm3434.pdf
You can find other solutions (and depending on how much current you really want some more highly integrated solutions) by searching the TI website or many other semiconductor manufacturers.
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