Comment by lutusp

> So is there something like a purely current protector that doesn't change the voltage much?

First, in a regulated power supply, you control the current by (a) monitoring current, and (b) adjusting voltage.

Second, a switching power supply can easily be designed to regulate load current, which is what you want for an LED load, because the voltage across the LED changes with both current and temperature. The point of a switching design is that very little power is dissipated by anything except the load.

In your present circuit, the 22 ohm resistor is dissipating at least half the available power, all to protect the LED from overcurrent. I should add that, in any LED driving circuit, a way must be provided to limit the LED's current, or it may experience thermal runaway and failure. A switching power supply is an ideal way to do this, but only if it senses current in the load, not voltage.

Apropos, I designed switching power supplies for the NASA Space Shuttle. They were about 90% efficient, in spite of the fact that they had to deliver widely varying voltages and currents.