Automotive lighting continues to evolve by leaps and bounds. While LED light sources offer increased efficiency and unique vehicle styling, original equipment manufacturers (OEMs) are now implementing novel and useful lighting use cases. In this technical article, I would like to highlight several semiconductor technologies that are impacting the roadmap for headlight, taillight and interior lighting systems.

Adaptive Headlight Systems

Adaptive headlamp systems and adaptive high beam headlamp systems adjust the shape of the low beam and high beam respectively. While adaptive headlights are available for European production vehicles, U.S. automakers do not have access to these advanced lights. However, this situation may soon change. Adaptive systems use high-power LEDs as light sources, which require high-power LED drivers to regulate the current and achieve the desired brightness. The switching LED driver must be used to achieve high efficiency and implement a two-stage power handling topology for thermal management.

The first stage is a boost regulator. It manages the widely varying automotive input voltage and creates a stable intermediate power rail. The second stage is a step-down current regulator, which can be implemented with low output capacitance suitable for dynamic LED loads. However, since the LED driver is used as a switching regulator, you will have to deal with electromagnetic compatibility (EMC) challenges.

LED Driver and Matrix Manager Features and Options

Considering the speed at which headlight systems evolve, design flexibility is critical. In an adaptive system, you can use the new TPS92682-Q1 dual-channel, dual-phase LED controller as a constant-voltage boost regulator for the first stage of the headlamp. If you have static headlights on your roadmap, configure the device as a constant-current buck-boost/boost/single-ended primary inductor converter (SEPIC) LED driver. the TPS92682-Q1 also features programmable spread spectrum modulation to help easily meet EMC requirements.

For the second stage of the buck current regulator, another device, the TPS92520-Q1, offers high power density in a small solution size, which is achieved with a single, dual synchronous buck constant current LED driver with up to 2.2MHz switching frequency and serial peripheral interface. In addition to the high integration and power density offered by the TPS92520-Q1, its control architecture provides true average current regulation, as well as dynamic and matrix load compatibility.

While the TPS92682-Q1 and TPS92520-Q1 can be found in any headlight system as drivers for the headlight electronic control unit (ECU), the matrix manager IC is responsible for regulating the beam shape of the headlight. Located on the headlamp's pixel board, the matrix manager controls the intensity of each pixel precisely to generate different beam patterns and illuminate the entire field of view while avoiding oncoming glare.

The TPS9266X-Q1 provides a robust and lightweight communication interface, as well as a full set of diagnostics to detect and report pixel-level LED failures directly to the ECU, since the LED pixel board is typically connected to the ECU via a wiring harness, and therefore requires reliable communication and reduced harness size.

Headlight ECU Reference Design

DLP® Technology Features and Options

Headlamps based on TI DLP technology not only enable high-resolution adjustment of the headlamp beam shape; they also enable symbol projection to assist the driver. The symbols can communicate with the driver and others on the road. The DLP5531-Q1 chipset is suitable for automotive industry standards and has been optimized for headlamp applications and today's roads. View the DLP Automatic Headlamp Reference Design.

Motor Functions and Options

Another way to change the beam is headlamp leveling, in which the beam illuminates the road regardless of the slope of the road or whether the driver is accelerating or decelerating. Pointing the headlights at the road improves driving safety by improving visibility, especially when driving at night. Bipolar stepper motors are typically used to control headlight levels. the DRV8899-Q1 stepper motor driver not only has the power stage to drive the motor, but also has a stall detection function that eliminates the need for additional sensors.

With the expansion of communication technology-based lighting control modules, Texas Instruments' family of Controller Area Network (CAN) transceivers (e.g., TCAN1044-Q1), Local Interconnect Network (LIN) transceiver products (e.g., TLIN1029-Q1), and system-based chips (e.g., TCAN4550-Q1 and TLIN14415-Q1) are good choices for automotive lighting applications.

Dynamic taillights

LED light sources are becoming more versatile when it comes to taillight signaling functions such as brake lights and turn indicators, and can now even cover dynamic and/or personalized lighting messages.

Static Lighting

The automotive two-stage (SEPIC + linear) static LED driver module reference design for taillights shows a two-stage LED driver. Its first stage voltage regulator is implemented via the LM5155-Q1 configured in a SEPIC topology. This buck-boost topology allows the light to operate at low battery voltages and to be regulated down at high battery voltages in order to optimize the second stage LED driver from a thermal management perspective.

Dynamic Lighting

Texas Instruments' new 12-channel high-side LED driver, the TPS929120-Q1, was developed specifically for dynamic lighting applications. The device uses FlexWire, a Texas Instruments-exclusive interface, for individual pixel control. FlexWire is a Universal Asynchronous Receiver Transmitter (UART) based interface with automatic baud rate detection, so high LED counting systems can be independently dimmable. A complete diagnostic and fail-safe mode ensures the reliability of the complete LED lamp.

Digital Interface LED Driver Module Reference Design

The TPS929120-Q1 includes 12-bit pulse width modulation (PWM) dimming capability and provides off-board support - for taillight implementations that may span the entire length of the vehicle, as shown in Figure 1. As shown in the digital interface LED driver module reference design, the TPS929120-Q1 can be connected to a CAN or LIN communication transceiver for improved communication stability.

Other taillight trends

New ways of signaling that combine style and personalization are being implemented for taillights. One example is sliding turns, where the turn indicator LEDs light sequentially rather than all at once, making it appear as if you are sliding the turn indicators. Another trend is the use of taillights to display a welcome message for the driver, or even a message alert for the driver behind the wheel.

Personalized interior lighting

Lighting in the cockpit is also changing. One such change is the use of a large number of LEDs to display personal messages (such as a welcome message) or to adapt the beam to shine in specific locations (such as on the front passenger seat when moving).

The TLC6C5724-Q1 is a 24-channel red, green and blue LED driver that controls each channel independently, which is critical for zoning applications. The LED driver is perfectly combined with a front-end buck converter such as the LMR33630-Q1 or LMR36015 for individual interior lighting, such as zoned dome lights or RGB lighting. The front-end buck regulator improves the thermal performance of solutions such as the EMC-tested automotive pixelated headlamp reference design for interior lighting.

Brighter, custom puddle lights

The original purpose of ground projection (sometimes called "puddle lights" or "light carpets") was to illuminate near the vehicle to help drivers drive in. The next generation of puddle lights will use DLP technology to enable dynamic ground projection. This technology not only dynamically changes the position of the projection, but also the content of the projection. This feature can be used to send a message to drivers before they enter the vehicle, to warn people around the car or to provide branding opportunities for automakers. Vehicles with static puddle lights that project static symbols, such as logos, are now available.

Transparent car window displays

As the carpooling wave continues to grow, a system needs to be developed to display sharing-related messages to customers. In addition, the trend toward self-driving cars requires ways for cars to communicate with other vehicles and pedestrians.

One space where such messages can be displayed is the car window. DLP technology projects messages on the window while the car is parked and keeps the window view clear while the car is moving. This DLP projector, combined with specialized screen technology, can also display promotional advertising on the car windows. This is an attractive prospect for automotive OEMs.

There are several types of screen technologies that enable transparent window displays, and for many of them, DLP projectors are naturally suited to illuminate the screen. One technology is a light-emitting phosphor film embedded in the window that is excited by 405 nm light from inside the DLP projector. Texas Instruments' DLP3034-Q1 and DLP5534-Q1 both support 405 nm-based illumination sources.

Conclusion

New and exciting capabilities are being implemented throughout vehicle lighting systems. From Nevsemi you could find the related hot chips. Texas Instruments' semiconductor products make these features and reference designs easier, giving you a better starting point for design and reducing time to market.

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