HB LEDs present several advantages over traditional lighting technologies: they do not contain hazardous materials such as the mercury in CCFLs, they consume less power, and they have much longer lifespans. Moreover, HB LEDs are now highly cost competitive with traditional technologies, especially when the total cost of ownership (i.e., operating and maintenance costs) is accounted for.

Yet, HB LEDs also pose unique challenges, particularly when used in the harsh operating environment of automotive applications. This application note provides an overview of HB LED driver selection criteria, reviews driver topologies, and recommends configurations for different automotive lighting applications, including dome lighting, daytime running lights (DRL), rear combination lights (RCL), fog lamps, and low-/high-beam lights.

The color of an HB LED varies with the current flowing through it. Therefore, it is typically better to dim HB LEDs by pulse-width modulating (PWM) a constant current than by actually changing the current magnitude. That is, to maintain the emission spectrum over different brightness levels, it is best to keep the DC current at values specified by the HB LED manufacturers and chop the current at a certain frequency and duty cycle.

Read more: How to Select HB LED Drivers for Automotive Lighting Applications