New HB LED Driver for High Power Automotive LED Headlight Design

The need to provide higher performance and higher cost performance for LEDs has never been met, prompting the rapid adoption of LED headlamps for a variety of new models. The new LED driver IC meets these needs. It has constant current, high efficiency, wide dimming ratio range, and various protection functions to achieve system reliability. In the solution proposed in this paper, the LED driver circuit occupies a very compact, flat and high thermal footprint.

By 2015, the market for high-brightness (HB) LEDs is expected to reach $20.2 billion (source: Strategies Unlimited). One of the key application areas driving this growth is the LEDs used in automotive design, including headlights, daytime running lights, brake lights, instrument panel backlighting, and various interior dressing lighting. This amazing growth rate is not only due to the high reliability, low power consumption and compact form factor of LEDs, but also because LEDs can be used to achieve innovative designs such as steerable headlights and anti-glare dimming. In an automotive environment, all of these improvements must be optimized while still withstanding the rigors of automotive electrical and physical environments. Needless to say, these solutions must also be very flat, with a very compact footprint and an overall price/performance ratio.

Although LEDs have been used for daytime running lights, brake lights, turn indicators and interior lighting for many years, a few headlamp-specific applications have only recently appeared, such as those used in the Audi A8 and R8 and the Lexus LS600h. However, in the past year, several car manufacturers have introduced LED headlights in their most popular models. In 2014, Toyota introduced LED headlights for its best-selling Corolla models. In addition, several other Toyota models also used LED headlights. Honda, Nissan, Porsche and Audi also introduced LED headlights in most of the upcoming models. Many people estimate that the LED headlamp market will exceed $3 billion in 2014.

One of the biggest challenges for automotive lighting system designers is how to take advantage of all the benefits of the latest generation of HB LEDs. HB LEDs typically require an accurate and efficient DC current source and a dimming method. LED driver IC designs must be able to meet these requirements under a variety of conditions. Therefore, power conversion solutions must be very efficient, functionally reliable, and must be very compact and cost effective. It can be said that one of the most demanding applications for driving HB LEDs is automotive headlamp applications, because such applications must withstand the rigors of automotive electrical environments and must provide significant power (generally 50W~75W) must be able to fit into a housing with limited heat and space, while maintaining an attractive cost structure.