Selecting one or many LEDs for constant-current driver? Answered
I'd like to build a flashlight with several LEDs, perhaps different colors, perhaps different beam characteristics, and allow the user to select one or more of them to be active at once.
With primitive electronics, this is simple: Each LED gets its own current-limiting resistor in series with it, and then all the LEDs with individual switches go in parallel across the power bus.
But I'd like to use a constant-current driver (buckpuck or similar) for better efficiency and stability across varying input voltages. This means the LEDs should be in series. To take one out of the circuit, I'd simply short across it, bypassing it so the current still flows through the other(s). This is pretty simple with two LEDs, as I could use a center-off toggle switch to short A, neither, or B. But if I try for three LEDs in series, the logic of allowing any combination to be bypassed *except* all of them (because a dead short would damage the driver circuit) quickly gets complicated.
Is there something simple I'm overlooking? Or do people simply avoid doing it this way for this reason? (The obvious solution is to use a constant-current circuit for each LED and run them all in parallel, but that gets expensive in a hurry!)