Using a switching regulator as an LED driver requires the designer to convert a voltage regulator into a current regulator. Beyond the challenge of changing the feedback system to control current, the LEDs themselves present a load characteristic that is much different than the digital devices and other loads that require constant voltage. The LED WEBENCH® online design environment predicts and simulates the response of an LED to constant current while taking into account several potential design parameters that are new to designers of traditional switching regulators.– Article quote
The topics discussed inside the application note including the output voltage changes, pitfalls of Parallel LED arrays, selecting LED ripple current, dynamic resistance, and many more.
Source : Chris Richardson (National Semiconductor Application Notes)
Find more details about the switching led drivers design challenges from the National Semiconductor by downloading the pdf document from the following source (national.com) :
Design Challenges of Switching LED Drivers DOWNLOAD