LED gradually replaces traditional light sources with unique advantages, and it also occupies a major market in automotive lighting. Today, the editor will introduce to you the solution of ON Semiconductor‘s LED car headlights. The scheme is aimed at improving the conversion efficiency and reducing the system cost. The design is simple and effective, and it is the preferred choice for the LED automotive headlamp scheme.

1. LED light source

After years of technological development, LED light sources have become the mainstream in the field of lighting, and their advantages over traditional light sources have been continuously improved. In addition to high luminous efficiency and small size, long life is also the main feature, as shown in the figure. 

All conventional light sources degrade (lower lumen output) over time, even LEDs. The failure of traditional light sources is often due to the open circuit of the filament after working for a period of time, which can lead to no longer use; while LEDs degrade very slowly under the conditions of reasonable drive design (constant current drive), and their service life is much longer than that of traditional light sources.

On the other hand, because the response time of the LED light source is extremely fast, only 60 nanoseconds, which is much shorter than the hundreds of milliseconds of ordinary traditional light sources. This is used in automotive lighting, which undoubtedly greatly increases the safety factor, so that LEDs will also Become the mainstream of automotive lighting.

2. BOOST-BUCK topology

During the working process of the LED, the heat generation is large, and the temperature affects its various parameters, which requires that the LED driver should use a constant current source. In practical applications, different LEDs have different parameters, and together with the design requirements of different lighting methods, it is difficult to find a general design solution to match. ON Semiconductor provides a complete solution for high-current LED drivers for vehicles. The BOOST-BUCK topology is used, and the parameters of each device can be configured through programming. A design that does not need to be applied, especially in automotive headlights.

Main features of BOOST-BUCK topology:

·The only solution that can maintain stable output in a wide load range

Boosting can make the drive power more stable and filter the external power ripple at the same time

Step-down constant current output responds faster and is the best LED current regulator

·High dimming frequency to avoid flickering effect

The same hardware can support different LED string configurations

·Can deal with the adjustment of LED light string voltage sudden change

Highly integrated, built-in step-down switch, dimming, functional diagnosis, etc.

Helps to reduce the total cost of the system

The automotive-grade LED dedicated drive BOOST controller launched by ON Semiconductor is a single-chip high-efficiency multi-phase boost controller that supports multiple chip combinations, can synchronize clock and multi-phase output, and obtain higher output power at the same time. It also has better filtering effect. The constant current BUCK controller is paired with the BOOST controller, and the suitable chip model and the number of output light strings are selected according to the load. They are all configurable via SPI communication, come with on-chip diagnostics, and drive LED strings safely and reliably.

3. LED headlamp scheme

LED FRONT LIGHTING is ON Semiconductor‘s BOOST controller and BUCK controller‘s programmable platform solution for LED car headlights. As shown in the figure, the BOOST-BUCK topology circuit can drive two LED strings quickly and stably with constant current. Simultaneously independently control low beams, high beams, corner lights, turn signals and daytime running lights, support CAN communication control and hard-wire control, and support a modular design platform. The same module is used for different models and headlights. In practice In applications, customers create a piece of hardware and reuse it, speeding up their design cycle, ease of design and cost-effectiveness. It is a platform-based, programmable, and low-cost solution.

Program advantages:

• Vehicle-grade hardware architecture;

• Use automotive-grade chips, which are safe and reliable;

• The highest stable output is more than 100W;

• Low quiescent current;

• Support CAN and hard wire control;

• Programmable configuration, safe and flexible;

• Programmable configuration of output voltage and current;

• Self-contained diagnostic function, safe and reliable;

• Can be adapted to LED loads with different parameters;

• Flexible software resources;

• Provide general software library to easily realize porting between different MCUs;

• Complete software design framework reference to shorten your product development time;

• Provide a complete hardware design solution;

• Provide complete software development underlying support.