The performance of HB LEDs has dramatically improved over the last few years. The question commonly raised regarding LEDs in automotive lighting has changed from “Can LEDs be efficient enough to compete with other lighting technologies?” to “How can we maximize the extraction of light from the LED system?”
The best commercially available white LEDs are now fast approaching 100 lm/W.
However, the actual light output from an LED in a system application depends on the electrical system to deliver the right current, the thermal management system to maintain the junction temperature at an acceptable level, and the optical system to extract the light out of the package.
The objective of the design of an LED driver is to maximize the efficiency of conversion to the desired constant current at the lowest possible cost under electrical and physical conditions of a particular power source.
The configuration of the driver can be a combination of integrated circuits (ICs) and discrete devices. The use of dissipative resistors for current regulation for HB LEDs is omnipresent; however, these are the least efficient solutions. Linear regulators, which are transistorized resistors, offer better efficiencies –more than 50%. As the sophistication of drivers progresses from linear regulators to switch mode drivers with pulse width modulation (PWM) for dimming and colour changing LEDs, the drivers incorporate ICs in the circuitry
In 2007, the total market for HB LED driver ICs was $979 million.
In automotive applications the use of LEDs is not necessarily accompanied by driver ICs, especially for signaling. But the increasing penetration of LED headlamps, as well as the increasing use of high power white LEDs in interior lighting, will increase the sales of driver IC s to the automotive segment in the next five years.