Powering R+B+G light sources

I have been musing over ways to supply red green and blue led with a fixed ratio of currents to produce a dimmable 'white' light source - there is a thread on current ratios in the LED forum.

So far, my best idea is a Boost (Edited, was wrongly 'buck') topology with three inductors in series, each with a Schottky, capacitor and one of the three leds.

By operating in continuous mode (Edited, was discontinuous mode, and sizing the inductors), the current ratio can be fixed, but the total current can be varied.

Any ideas?

forgive the lack of diag

Steve

It might be easier to run the LEDs in series, and vary the ratio of colors. An example

- Lux III Red
- Lux III 1 green, 1 cyan
- Lux III blue or royal blue

Drive in series as 700ma - comes out very close to the white point. It is not perfect, but might be acceptable for your application.