ON Semiconductor's automotive lighting innovation meets the automotive trend of personalization, safety and energy saving-EEWORLD

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In today's rapidly evolving automotive lighting market, LED drivers play a particularly important role: providing automakers with more energy-efficient options to meet consumers' demands for fuel economy, improving visibility and safety to reduce or avoid traffic accidents, and creating a personalized vehicle atmosphere to meet consumers' expectations for unique car styling...

In the next eight years, the overall annual compound growth rate of automotive lighting systems will reach nearly 10%, and the market development potential is huge, and the drivers used in such systems will also have similar growth.

Driver requirements for automotive lighting

LEDs are devices that change brightness based on current, and LED drivers provide constant light output by adjusting the power of an LED or LED string. Each automotive lighting solution requires a unique driver design, and engineers need to select the right LED driver for a specific application to maximize energy efficiency based on different requirements such as series or parallel, high power or low power, and cost or functionality.

Factors that determine which LED driver is best for your application include:

-Total LED power for each function? -This is key to determine the LED driver topology.

- Electronics ambient temperature? - For example, if a taillight requires a brighter LED, it is better to choose a more energy-efficient switching driver rather than a high-power linear driver to keep it cooler at higher power levels.

-Flexibility to change LED configuration - Light adjustment can be done using various brightness methods such as reference voltage control and pulse width modulation control. Wide operating

The power supply range provides the power supply configuration and the number of LEDs that can be driven.

- Supported features - such as automatic dimming, individual LED control, color change.

- Supports fault diagnostics and safety standards compliance - such as thermal warning, thermal shutdown, open/short circuit, over-current protection, over/under voltage and single LED failure.

Figure 1: Driver solution for LED lighting

Future lighting drivers will need to include the following elements to support automotive manufacturers’ system requirements:

- Scalable, with flexible hardware to support different automotive applications and requirements that will come to market;

- Different driver requirements in the same module: high-pressure gas discharge lamp (HID), LED, etc.

-As more functions are added to the drive, consideration should be given to enhancing the fault diagnostics capabilities;

-Reliable LED current control, improving driver reliability.

Automotive Lighting Innovations from ON Semiconductor

Automotive lighting applications will surge inside and outside the car, and lighting systems will become more and more popular in all automotive market segments. The expansion of the market will correspondingly drive more silicon development. ON Semiconductor actively cooperates with this market trend, focusing on linear, switch-mode drivers, and bulk commercial/general and system integration solutions, and continues to promote energy-efficient innovation in the automotive lighting market.

1. Today’s automotive interior lighting

Today's automotive interior lighting mostly uses white light LED drivers and RGB red, green and blue programmable drivers.

Bright white LEDs are mainly used in applications with relatively high brightness requirements, such as ceiling lights, reading lights, and cargo compartment lights. However, unlike standard bulbs, they can provide drivers with a warm and comfortable atmosphere, and their dimming slope characteristics can produce unique and differentiated shapes and effects. ON Semiconductor provides discrete or constant current silicon solutions for such applications.

RGB and white light LEDs complement each other, and their development is driven by the motivation to further personalize vehicles. They are used as programmable interior light sources, including special effects applications such as instrument panels, center consoles, navigation/audio and other regional lighting and atmosphere lighting. Its color accuracy needs to be calibrated, and a separate LIN corresponds to one RGB, plus regional dimming, which are important features to meet the requirements of automobile manufacturers. ON Semiconductor can provide linear system basis chips (SBCs) for such applications. The SBC interface provides all functions for driving RGB LEDs via the LIN bus.

Figure 2: RGB drivers for automotive interior lighting

(II) Today’s automotive exterior lighting – taillights

From single LEDs in the past to opaque and uniform light rows today, from animated signals to sweeping flashing signal lights, drivers are an important part of the evolution of car taillights. In addition to continuous innovation in the appearance of cars such as shape and image, they also improve safety factors, support start-stop voltage drops, and adapt to ambient lighting conditions. They are the key to meeting the energy-saving requirements of automakers and governments. For such applications, ON Semiconductor provides linear current regulators and controllers.

Figure 3: Car taillights

(III) Today’s automotive exterior lighting – headlights

LED headlamps are commonly used in daytime running lights (DRLs), and the two most common solutions are light-guiding LEDs and LED strings (as shown in Figure 4). These DRL applications not only provide better visibility to oncoming vehicles, but automakers also rely on the flexibility of LEDs and LED drivers to personalize their vehicles and establish a unique "visual" brand.

Figure 4. Two common solutions for LED headlights in DRL applications

Advanced headlights for luxury cars are no longer limited to DRL, high beam and low beam. Automakers can also choose designs such as LED turn signals, LED fog lights and high-speed road spotlights, as well as headlight systems that combine HID and LED solutions, and even full LED lights in the future. Driven by the trend of more personalized, safer and more energy-efficient, consider making the platform modular, from low-cost "entry-level low beam" to high-end full-function "advanced lighting system", to provide automakers with a variety of innovations.

In terms of cost, the advanced lighting system is more expensive than the standard lighting system, but the functions can be reduced accordingly to cater to low- and medium-cost vehicles. In addition, it is scalable and can be appropriately expanded to various types of vehicles as needed.

ON Semiconductor provides dual-channel LED drivers and stepper motor drivers for adaptive front lighting systems (AFS). These systems further enhance safety levels by providing lighting units that can move and rotate according to driving conditions, speed and vehicle load. Features of dual-channel LED drivers include: integrated power LEDs, system-level chips, and up to 125 dc ambient, suitable for medium and high total power. Stepper motor drivers provide bipolar stepper drive, microstepping, stall detection, LIN, I2C and SPI interfaces, and up to 125 dc ambient.

Future automotive lighting solutions - pixel/matrix headlights

Moving from motor control to the use of pixel/matrix headlight systems is a major trend in future automotive lighting. It adopts a system modular platform design, provides many advantages beyond the current headlight solutions, enhances the image of the car through high-tech and innovative design, supports 50% to 80% or even more use of full static non-glare high beams, can adjust the lighting system according to the environment and oncoming cars, and provide drivers with higher visibility in all situations. It uses LED technology, has no moving parts, and is safer and more reliable. In addition, due to multiple blank areas, adjustable luminous power of each pixel, and fast switching, more functions can be expanded.

LED AFS pixel/matrix systems are composed of LED application-specific standard products (ASSP), FETs, LDOs, rectifiers, logic, Zener, protection and other components. ON Semiconductor can now provide all semiconductor components except the microcontroller. As the system becomes more standardized, this microcontroller can be embedded into an application-specific integrated circuit (ASIC), supporting potential ON Semiconductor single-chip silicon solutions.

ON Semiconductor’s NCV78247 pixel/matrix controller can drive four LED strings, has an integrated dimming controller, built-in overvoltage/undervoltage, overtemperature, short/open circuit detection (including LED bypass open), SPI interface, output fault, configurable output segments, SPI communication, onboard microcontroller, and more (Figure 5).

Figure 5. NCV78247 pixel/matrix controller

Conclusion

The automotive lighting driver market will continue to require driver combinations, supporting solutions from the simplest discrete devices to the use of combination technology, providing more possibilities for automotive exterior design and improving driving safety and fuel economy. Pixel/matrix headlights are the key trend of future headlights. In response to market development, ON Semiconductor continues to promote innovation in the automotive lighting market and provides a series of high-efficiency drivers and controllers that can meet the safety, energy saving and styling needs of low-, medium- and high-end automotive lighting.

Keywords：Safety Reference address：ON Semiconductor's automotive lighting innovation meets the automotive trend of personalization, safety and energy saving

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