Lighting is a key differentiating factor in automotive design, playing an increasingly important role in personalization and safety, and semiconductor is undoubtedly a key component in driving automotive lighting innovation trends. Thanks to the small size of LEDs, the ability to change brightness according to current, to provide engineers with more design flexibility, and energy saving and high efficiency, LED lights are expected to become a trend of automotive lighting.
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Advanced LEDs for automotive technology and future â€œstyling, safety, fuel efficiencyâ€
LED drivers are essential in LED lighting applications, and automotive engineers can use it to achieve energy savings, enhance safety and create unique and beautiful designs. The LED driver provides a constant light output by adjusting the power of an LED or LED string, that is, even if the power may vary, it is stably supplied to the LED. Engineers need to select the right LED driver for a specific application to maximize energy efficiency and provide adjustability for functions such as soft start or emergency light, depending on different requirements such as series or parallel, high or low power, and cost or function.
When selecting an LED driver, in terms of design complexity, cost, performance, etc., it is necessary to select and design a suitable topology according to the total LED power, the applied electronic ambient temperature, and the flexibility of changing the LED configuration. For example, switch drivers are more energy efficient, lower power consumption than linear actuators, can withstand higher electronic ambient temperatures, and can be used in applications with higher brightness requirements; brightness adjustment of light can use reference voltage control and pulse width modulation control, etc. Multiple methods are available; a wide operating power range configurable power supply and number of LEDs that can be driven. In terms of integration, it is necessary to judge which application is more suitable according to the characteristics 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 need to be flexible: use the same platform to reduce design cycles and react to changes in system requirements, while enabling the system to scale to each LED string to support different applications that will be available on the market to meet the needs of automotive OEMs. System Requirements. In today's luxury cars, we see headlamp systems that use a combination of high pressure gas discharge lamps (HID) and LED solutions. Looking ahead, the full LED system will begin to gain growth momentum. As the car moves toward a more intelligent direction, the drive will incorporate more features such as the Advanced Driver Assistance System (ADAS), and engineers must consider enhanced troubleshooting capabilities to improve system reliability.
Luxury lighting solutions across the mid- to low-end car market
From an application perspective, automotive lighting is divided into internal and external lighting. Most of today's automotive interior lighting uses bright white LED drivers and RGB red, green and blue programmable drivers. External lighting is no longer limited to headlights and taillights. Body lighting (such as signage and door handles) and external RGB have been used in luxury cars and are expected to penetrate mid- to low-end cars.
1, today's car interior lighting - white light
White LEDs are mainly used for ceiling lamps, reading lamps, cargo compartment lights and other applications where brightness is relatively high. It is different from standard bulbs and provides a warm and comfortable atmosphere for drivers. Automotive OEMs use white LEDs to provide different ambient light options, from simple discrete white LED drivers to on/off to more complex dimming slopes to create unique and differentiated shapes and effects, such as gradual closure or Involute to produce dramatic effects. ON Semiconductor offers discrete or constant current stabilized silicon solutions for this type of application.
2, today's car interior lighting - RGB
RGB and white LEDs complement each other, and their development is driven by the power to further personalize the vehicle. It is used as a programmable internal light source, including special effects such as instrument panel, center console, navigation/audio and other regional lighting and ambient lights. ON Semiconductor offers a Linear System Basis Chip (SBC) for this type of application, and 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, the NCV7430, which enables current control through 3 LEDs while providing full chromatogram and intensity. A unique feature of the device is 24-bit true color, which can output 16 million different colors via LIN commands for security features such as vehicle theft and create a personalized interior atmosphere. This solution saves board space compared to current solutions consisting of microcontrollers and LIN-SBC, and can use an optional ballast control pin to drive more power to drive an external low-cost BJT transistor. Thus transferring power from the IC to the external transistor makes thermal management easier. In addition, the NCV7430's individual LIN nodes acquire addresses via pre-programmed or LIN commands, making design flexible and cost-effective.
Figure 1. RGB driver for automotive interior lighting
3, today's car taillights
From the single LED in the past to the current opaque and uniform light row, from the animated signal to the swept flashing light, the driver is an important part of the evolution of the car's taillights. In addition to continuous innovation in the appearance of cars such as shapes and images, Increasing the safety factor, and supporting start-stop pressure drop, and adaptive ambient lighting conditions are key to meeting the energy requirements of automotive manufacturers and governments. For such applications, ON Semiconductor offers linear current regulators and controllers.
Figure 2. Car taillights
4, today's car headlights
LED headlamps are commonly used in daytime running lights (DRL). The two most common solutions are light guide LEDs and LED strings. These DRL applications not only provide better visibility to oncoming vehicles, but car manufacturers also rely on the flexibility of LEDs and LED drivers to personalize their vehicles and build a unique "visual" brand.
Advanced headlamps for luxury cars are not limited to DRL, high beam and low beam. Automotive manufacturers can also choose LED turn signals, LED fog lights and high-speed street spotlights, as well as a combination of HID and LED solutions. The headlight system, and even the future full LED lights. Driven by a more personalized, safer and more energy-efficient trend, consider modularizing the platform, from low-cost â€œentry-level low beamâ€ to high-end full-featured â€œadvanced lighting systemâ€, offering a variety of automotive manufacturers. Innovation.
Figure 3. Advanced headlights for luxury cars
In terms of cost, advanced lighting systems are more expensive than standard lighting systems, but can be reduced in function to cater to low-cost cars. In addition, it is scalable and can be expanded as needed for a wide range of vehicles.
Further system development will add the ability to control the motor. ON Semiconductor offers dual-channel LED drivers and stepper motor drivers for adaptive headlamp systems (AFS). Each car can integrate up to six ON Semiconductor dual-channel LED drivers and three ON Semiconductor stepper motor drivers. These systems overcome the deficiencies of traditional headlamps, automatically leveling to reduce glare, and automatically rotating the lighting blind spots that illuminate traditional headlamps. The dual-channel LED driver is a system-on-chip with integrated power LEDs that can operate at temperatures up to 125 degrees Celsius for medium to high total power. Stepper motor drivers offer bipolar stepper drive, microstepping, stall detection, LIN, I2C, and SPI interfaces, as well as ambient temperatures up to 125 degrees Celsius.
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