LED CONTROL

Efficient LED Control
LEDs must be driven with a source of constant current. Most LEDs have
a specified current level that will achieve the maximum brightness for that
LED without premature failures. An LED could be driven with a linear voltage
regulator configured as a constant current source. However, this approach is
not practical for higher power LEDs due to power dissipation in the regulator
circuit. A switch-mode power supply (SMPS) provides a much more efficient
solution to drive the LED. An LED will have a forward voltage drop across its
terminals for a given current drive level. The power supply voltage and the
LED forward voltage characteristics determine the SMPS topology that is
required. Multiple LEDs can be connected in series to increase the forward
voltage drop at the chosen drive current level.
The SMPS circuit topologies adopted to regulate current in LED lighting
applications are the same used to control voltage in a power supply
application.