ON Semiconductor's solutions to meet automotive lighting design trends

Lighting is a key differentiating factor in automotive design, playing an increasingly important role in personalization and safety, and semiconductors are undoubtedly the key components driving the trend of automotive lighting innovation. Thanks to the small size of LEDs, the ability to change brightness according to current, which provides engineers with more design flexibility, and the advantages of energy saving and high efficiency, LED headlights are expected to become a trend in automotive lighting.

 

Advanced LEDs for automotive technology and future "styling, safety, fuel efficiency"

 

LED drivers are essential in LED lighting applications, and automotive engineers can use them to achieve energy saving, safety advantages, and unique and beautiful design needs. LED drivers provide constant light output by adjusting the power of an LED or LED string, which means that even if the power may vary, it still stably supplies power to the LED. Engineers need to choose the right LED driver for a specific application based on different requirements such as series or parallel, high power or low power, cost or function, etc. to maximize energy efficiency and provide adjustability for functions such as soft start or emergency lights.

 

When selecting LED drivers, in terms of design complexity, cost, performance, etc., it is necessary to select and design the appropriate topology based on the total LED power, the electronic ambient temperature of the application, and the flexibility of changing the LED configuration. For example, switch drivers have higher energy efficiency and lower power consumption than linear drivers, can withstand higher electronic ambient temperatures, and can be used in applications with higher brightness requirements; light brightness adjustment can be achieved using a variety of methods such as reference voltage control and pulse width modulation control; a wide operating power supply range can configure the power supply and the number of LEDs that can be driven. In terms of integration, it is necessary to determine which application is more suitable based on the features supported by each solution (such as automatic dimming, individual LED control, color change, etc.) and safety and fault diagnosis standards.

 

In the future, lighting drivers will need to be flexible: using the same platform to shorten design cycles and respond to changes in system requirements, while enabling the system to scale according to each LED string to support different applications that will be on the market and meet the system requirements of automotive manufacturers. In today's luxury cars, we see headlight systems that use a combination of high-pressure gas discharge lamps (HID) and LED solutions. Looking to the future, full LED systems will begin to gain momentum. As cars move towards a more intelligent direction, drivers will incorporate more functions such as advanced driver assistance systems (ADAS), and engineers must consider enhancing fault diagnostics to improve system reliability.

 

Luxury lighting solutions span the mid-range and low-end car market

From the application level, automotive lighting is divided into interior and exterior lighting. Today's automotive interior lighting mostly uses bright white light LED drivers and RGB red, green and blue programmable drivers. Exterior lighting is no longer limited to headlights and taillights. Body lighting (such as logo lights and door handles) and exterior RGB have been used in luxury cars and are expected to penetrate into mid- and low-end cars.

 

1. Today’s automotive interior lighting – white light

White LEDs are mainly used in applications with relatively high brightness requirements, such as ceiling lights, reading lights, and cargo compartment lights. Unlike standard bulbs, they can provide drivers with a warm and comfortable atmosphere. Automotive manufacturers can use white LEDs to provide different ambient lighting options, from simple on/off control with discrete white LED drivers to more complex dimming slopes to produce unique and differentiated shapes and effects, such as gradual closing or opening to create dramatic effects. ON Semiconductor provides discrete or constant current stabilization silicon solutions for such applications.

 

2. Today’s automotive interior lighting – RGB 

RGB and white LEDs complement each other, and their development is driven by the drive to further personalize vehicles, and are used as programmable interior light sources, including special effects applications such as instrument panels, center consoles, navigation/audio area lighting, and mood lighting. ON Semiconductor can provide linear system basis chips (SBCs) for such applications. The SBC interface provides all the functions of driving RGB LEDs via the LIN bus.

 

ON Semiconductor also offers the fully integrated addressable LIN RGB single-chip solution NCV7430, which enables current control through 3 LEDs while providing full color spectrum and intensity. A unique feature of this device is 24-bit true color. This module can output 16 million different colors through LIN commands for security features such as vehicle anti-theft and creating a personalized interior atmosphere. This solution saves circuit board space compared to the current solution consisting of a microcontroller and LIN-SBC on the market, and can use an optional ballast control pin to output more power to drive an external low-cost BJT transistor, thereby transferring power consumption from the IC to the external transistor to make thermal management simpler. In addition, the NCV7430's individual LIN nodes obtain addresses via pre-programming or LIN commands, making the design flexible and reducing costs.

 

Figure 1. RGB driver for automotive interior lighting

 

3. Today’s car 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 2. Car taillights

 

4. Today’s car headlights

LED headlights are commonly used in daytime running lights (DRL), and the two most common solutions are light-guided LEDs and LED strings. 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 unique "visual" brands.

 

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.

 

Figure 3. Advanced headlights for luxury cars

 

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.

 

Further system development will add motor control capabilities. ON Semiconductor provides dual-channel LED drivers and stepper motor drivers for adaptive front lighting systems (AFS). Each vehicle can integrate up to 6 ON Semiconductor dual-channel LED drivers and 3 ON Semiconductor stepper motor drivers. These systems overcome the shortcomings of traditional headlights and can automatically level to reduce glare, as well as automatically rotate to illuminate the blind spots of traditional headlights. The dual-channel LED driver is a system-level chip with integrated power LEDs, with an ambient temperature of up to 125 degrees Celsius, suitable for medium and high total power. The stepper motor driver provides bipolar stepper drive, microstepping, stall detection, LIN, I2C and SPI interfaces, and ambient temperatures up to 125 degrees Celsius.

 

In particular, ON Semiconductor's innovative automotive LED headlight solution NCV78663 uses power ballasts and dual LED drivers to provide segmented glare-free high beams, integrated intelligent electronics, and sensors, cameras, and navigation controls to automatically adapt the car to various road conditions and enhance safety by maximizing the lighting area. Its most advanced function is: if there is no oncoming car, the headlights will have maximum light output; but when an oncoming car approaches, the headlights will automatically separate from the specific location of the oncoming car and turn on the high beam mode. The closer the car is, the wider the gap is as the car approaches. The gap becomes wider until the car passes, and then returns to the high beam mode. The solution supports a modular design platform, which is easy to design and cost-effective.

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Future automotive lighting solutions

1. "Sweep" indicator light

Headlight systems will continue to be driven by safety and visibility. According to tests, if a car is equipped with a "sweeping" indicator light, the driver's accuracy in detecting the direction ahead will increase from the normal 72% to 90%, and the reaction time will be improved by 32%.

 

Figure 4. "Sweep" indicator light

 

In addition, based on some regional regulations, LED drivers must be able to provide light equivalent to the full brightness of an incandescent lamp.

 

2. Pixel/matrix light

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.

 

Figure 5. Pixel/matrix light

 

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 and onboard microcontroller, etc. (Figure 6).

 

Figure 6. NCV78247 pixel/matrix controller

 

Conclusion

Many future automotive lighting solutions will be based on current R&D and usage experience, and driven by the silicon development and cost reduction trends in the semiconductor industry. The market will continue to need driver combinations, supporting solutions from the simplest discrete devices to those using combined technology, providing more possibilities for automotive exterior design, and improving driving safety and fuel economy. Systems that add motor control capabilities can be adjusted according to driving conditions, speed and vehicle load to further improve safety levels. In order to obtain high visibility in specific light areas, headlight systems will move from motor control to the use of pixel or matrix LEDs. ON Semiconductor can provide all semiconductor components (except microcontrollers) that make up the LED AFS pixel/matrix system, such as LED application-specific standard products (ASSP), FETs, LDOs, rectifiers, logic, Zeners, protection, etc. As the system becomes more standardized, the microcontroller will be embedded in an application-specific integrated circuit (ASIC), which will support potential ON Semiconductor single-chip silicon solutions, helping engineers simplify designs and accelerate time to market.