A very simple high efficiency white LED driver electronic project can be designed using the MAX1573 integrated circuit , manufactured by Maxim Semiconductor.
This white LED driver electronic project drives as many as four white LEDs in parallel from a 3.3V source, and adjusts the total LED current from 1mA to 106mA, in 64 steps of 1dB each .
To control the LED brightness, op amp U2 monitors the difference between the high-side voltage and the wiper voltage of digital potentiometer U1. The op amp then multiplies that voltage by a gain to set the maximum output current.
Zero resistance at the pot's W1 terminal corresponds to minimum LED current, and therefore minimum brightness. Because the SET voltage is fixed (at 0.6V), any voltage change at the left side of R5 changes ISET, and the resulting change in LED currents changes their brightness level. R5 sets the maximum LED current: R5 = 215x0.6/ILED(Desired) (ILED is the current through one LED) .
U1 is a digital potentiometer with logarithmic taper and an analog-voltage wiper for which each tap corresponds to 1dB of attenuation between H1 and W1 (pins 11 and 9).