AMS OSRAM RGBi series: a new tool for playing with interior ambient lighting

With the rapid development of new energy vehicles, cars are gradually evolving from simple means of transportation to mobile spaces that are both practical and emotional. The continuous innovation and breakthroughs in the field of automotive lighting provide a strong impetus for this evolution. Among them, ambient lighting, as a new element of the future cockpit, is bringing drivers and passengers a more comfortable and pleasant driving experience with its colorful lighting effects and personalized customization experience.

As a leading global supplier of optical solutions, ams OSRAM's interior lighting RGBi series products make the vehicle interior environment more comfortable and personalized by providing a variety of color and brightness options, providing automakers with new opportunities to enhance their brand image and market competitiveness.

Image source: ams-osram

1 Application Trends of Car Ambient Lighting

At present, the colorful atmosphere lights of cars are evolving in the following directions: First, from monochrome to full color, the atmosphere lights are not only visible at night, but also can show good effects during the day. Moreover, the dynamic effects of the atmosphere lights will be richer, and the number of light sources will also increase significantly, achieving more delicate and smooth lighting changes. Furthermore, the atmosphere lights located in different positions should present highly consistent colors to avoid visual discomfort caused by color difference. In addition, the atmosphere lights are gradually beginning to adopt surface light source design and applied to free-form surfaces. Finally, users will be able to control the atmosphere lights through the car system or mobile phone APP.

The resulting product demands include: a rich RGB product line, single high-power or multiple low-power products, which are characterized by high brightness, high efficiency, precise color adjustment and high integration, can finely grade brightness and color temperature, and have easy-to-use temperature compensation functions. The packaging should be diverse, and for ambient lights that need to be applied to free-form surfaces, PCB boards that can be flexibly soldered should be used. Open hardware is also necessary to facilitate secondary development and customization by third-party manufacturers.

At present, colorful ambient light is mainly used for static decoration in specific areas, such as interior lighting, to enhance the beauty and atmosphere of the interior environment. In the future, ambient light will be used in various scenes such as decoration, warning, more interaction, touch display, etc. to realize dynamic interactive functions.

Image source: ams-osram

2 OSIRE® product family of colorful ambient light from ams OSRAM

ams OSRAM is a leader in the field of colorful ambient lighting, and its OSIRE® product family provides customers with comprehensive solutions. The OSIRE® product family is divided into three categories: standard LEDs, LEDs with QR codes, and smart LEDs with built-in drivers.

● Standard LED: without calibration data, externally driven, and with a new 1/4 fine brightness binning. Representative models include OSIRE® E3635, OSIRE® E5515 and OSIRE® E3323. Compared with competitors, ams OSRAM's standard LED products have been subdivided in the brightness bin division, making the span of each brightness bin narrower. The advantage of this design is that even without calibration, the color point distribution accuracy of white light mixing with fine binning can reach about ±0.01.

● LED with QR code: can obtain calibration data through QR code, with external drive and new 1/4 fine brightness division features. Representative models include OSIRE® E3323 and OSIRE® E5515.

● Intelligent LED with built-in driver: It has the features of built-in standard data, built-in driver and open protocol (OSP:Open System Protocol). The representative model is OSIRE® E3731i.

Image source: ams-osram

3 Intelligent RGB LED OSIRE® E3731i based on open protocol (OSP)

As the body electronic architecture evolves from distributed electronic control units (ECUs) to central pre-control, the architecture of automotive ambient lighting has also changed. Traditional distributed ambient lighting control systems use CAN/LIN buses to connect multiple independent RGB light modules, which are controlled by the body control unit (BCU). Under the body central domain control architecture, the ambient lighting system uses RGBi (intelligent RGB) light strips, which are centrally controlled by microcontrollers and domain controllers to achieve more precise lighting effects and lighting synchronization.

In this trend, OSIRE® 3731i from ams OSRAM came into being. This is an integrated intelligent RGB LED based on an open protocol, which can support up to 1,000 LEDs per channel. Its PWM accuracy is up to 15/14 bits (at 500/1000 Hz), which can achieve up to 32768 colors. At the same time, the drive current can be selected as 10 mA or 50 mA. The built-in three-color raw data can be read and processed by the controller, and the brightness of each color can be independently driven to a maximum of 50 mA, and the maximum brightness of white light exceeds 5000 mcd.

In addition, OSIRE® 3731i also has a built-in temperature sensor, allowing users to accurately compensate for the temperature of each color of R, G, and B to ensure color consistency. Its system architecture supports daisy chain loopback transmission and connects sensors through an open protocol universal interface to achieve extended functions. The product has built-in diagnostic functions to achieve over-temperature protection, open circuit, voltage and communication error detection.

OSIRE® 3731i includes memory, controller and driver. Among them, the OTP storage stores the color and highlight data of R, G, B used for color calibration. The communication process is as follows: 1) Initialization, each LED on the link automatically assigns an address, and the controller reads the original brightness and wavelength information of each LED red, green and blue chip. 2) Color mixing: MCU calculates according to the original value of each LED and the target value of color mixing, and sends different PWM values ​​to the corresponding LED. MCU can read the temperature information of the LED in real time and compensate when necessary. 3) Output: The built-in PWM driver of each LED outputs according to the instructions of the MCU, and the output continues until the MCU refreshes the instruction.

OSIRE® 3731i communication process (Image source: ams OSRAM)

4. Installed as soon as it is released, why is OSIRE® E3731i so popular?

Once released, OSIRE® E3731i was quickly recognized and adopted by many well-known car companies. Currently, models such as Lynk & Co 08, Zeekr 007 and Zeekr 009 Brilliant Edition are already equipped with this advanced RGBi lighting solution. In addition, 3-4 German luxury pure electric platforms that will be mass-produced in 2025 and 2 American top pure electric brand sedans that will be mass-produced by the end of 2024 are also actively adopting OSIRE® E3731i.

OSIRE® E3731i is so popular in the market due to its many advantages:

Image source: ams-osram

4.1 Stable and EMC robust

Currently, many competitors or products on the market have a major disadvantage, which is the stability of cross-board transmission. In the complex electromagnetic environment inside the car, LEDs are easily interfered by external signals, and may also affect surrounding equipment (such as audio) during transmission and output. Therefore, EMC (electromagnetic compatibility) and EMI (electromagnetic interference) are important indicators that vehicle-mounted equipment must be compatible with.

The open protocol-based system architecture of ams OSRAM's RGBi system solves this problem very well. When the company simulated the worst environment in a car and transmitted data across boards via a 15-meter-long twisted pair cable, the OSIRE® E3731i demonstrated stable and EMC-robust long-distance transmission across boards.

Image source: ams-osram

4.2 High cost performance

OSIRE® E3731i also has significant cost advantages compared to common dynamic atmosphere lighting solutions: OSIRE® E3731i has simpler wiring; fewer PCB layers, only a single layer is required, while traditional solutions usually require multiple layers of PCB boards; the calibration cost of dedicated RGB driver chips is high, and the hardware cost and time are also high, while RGBi and ISELED do not require calibration. Even at different RGB light strip numbers, RGBi is cheaper than dedicated driver chips and ISELED.

It is worth mentioning that based on the OSP open protocol, ams OSRAM has developed an independent LED driver SAID system architecture. ams OSRAM combined the OSIRE® E3731i and SAID modules to create a demo system. They work together in a link, and the boards are connected via LVDS or CAN FD to achieve two-way communication. The SAID module acts as a relay for the communication protocol to achieve interactive scene switching. The demo demonstrates an efficient and flexible LED driver and control system based on the OSP protocol, which is suitable for complex in-vehicle environments and provides a highly reliable and compatible solution.

Image source: ams-osram

ams OSRAM is committed to building an ecosystem based on the OSP open protocol, aiming to provide more efficient, flexible, reliable and compatible solutions for automotive lighting applications.

OSP protocol support can be connected to any microcontroller or gateway, and all devices compatible with OSP protocol can be connected to the network. This allows lighting solutions such as ams OSRAM's RGBi intelligent RGB LED and SAID independent intelligent driver to be easily integrated with other manufacturers' products, providing customers with more flexible choices.