DESIGN IDEAS Simple Converter Drives Luxeon
White LEDs from Batteries by Michael Nootbaar
Introduction current drive. Existing boost circuits
generally use voltage feedback switching converters with extra circuitry to The high output 1W white LEDs from
Luxeon and Nichia provide illumination levels close to 12W incandescent
levels while dissipating only 1W and
lasting for 50,000 hours or more. These
devices promise enormous power savings and reduced maintenance cost
for many lamp applications. However,
these LEDs must be driven with a
constant current to maintain proper
brightness. The forward voltage drop
varies between 2.8V and 4.0V over
process and temperature extremes.
The circuit used to drive the LED must
compensate for this forward voltage
variation while maintaining constant The LTC3490 provides a
simple solution for boosting
a single or dual cell battery
voltage to the necessary
LED forward voltage and
regulating the current
through the LED load. …