Comprehensive evolution of LED drivers to make automotive LED lighting perfect

LED lighting is widely used in the automotive industry due to its high brightness, low energy consumption, long life and fast response. LED headlights, daytime running lights, brake lights and turn signals have become standard features of many models. At the same time, with the advancement of intelligent driving technology, automotive LED lighting solutions are also moving towards intelligence. For example, the adaptive headlight system can automatically adjust the beam distribution according to road conditions and vehicle speed, thereby significantly improving driving safety; and the interior LED lighting supports multiple mode switching to create a more comfortable riding experience for passengers.

The realization of all these functions is inseparable from the high-performance LED driver. It ensures the stable operation of the LED light source and prolongs its service life by accurately controlling the current and voltage. In addition, the LED driver can also adjust the light intensity according to different application scenarios to meet diverse needs. Most importantly, an efficient LED driver helps reduce energy consumption and is in line with the trend of green energy saving.

With the increasing popularity of automotive LED technology, automotive LED drivers have evolved a variety of features to meet the needs of various lighting scenarios. These features not only reflect the maturity and progress of automotive LED driver technology, but also provide more abundant and flexible options for automotive lighting systems.

High-efficiency LED drivers not only provide higher brightness output, but also significantly reduce energy consumption, thereby improving the overall energy efficiency of the vehicle. The intelligent and programmable features enable the LED driver to automatically adjust the beam distribution according to road and environmental conditions, thereby improving driving comfort and safety, and allowing users to personalize settings through digital communication interfaces such as I2C and SPI. In addition, the use of advanced materials and design technologies makes the LED driver highly reliable and long-life, able to work stably under various harsh environmental conditions, and effectively reduce maintenance costs.

Fast response and high-frequency PWM control technology provide smoother dimming, reduce flicker, improve visual comfort, and quickly provide the required lighting level in emergency situations. This technology is critical to improving driver attention and reaction speed, especially at night or in low visibility conditions.

Finally, the trend towards miniaturization and integration also makes it easier for LED drivers to be integrated into various components of the vehicle, reducing the number of components and improving the overall reliability and performance of the system. This design optimization not only helps reduce vehicle weight, but also helps simplify the manufacturing process and reduce costs.

The headlights include low beam, high beam, daytime running lights, width lights, turn signals and fog lights. As the total power of the system is very large and many functions are integrated, more heat dissipation is required and the design is relatively complex.

Matrix/pixel headlights are the new favorite in headlights. Through hundreds or even thousands of tiny LED lamp beads forming a matrix or pixel array, precise control and adjustment of the lighting area are achieved. This design enables the headlight to intelligently adjust the shape, size and brightness of the light beam according to actual road conditions and driving needs. The pixel is an LED lamp bead in the LED array. Each pixel has an area illuminated by a beam, which can adapt to driving intentions and traffic conditions to improve safety. Its modular design can adapt to any architecture.

Matrix LEDs use switch-type LED driver chips to provide high-power output to drive LED lamp beads, and work with matrix management chips to achieve independent on/off control of individual LEDs (single pixels). For example, ON Semiconductor 's NCV78702 and NCV78723 (dual-channel buck) work with pixel lamp control chips to form a complete solution that can drive multiple LED strings up to 60V .

Figure 1: Headlight module capable of driving multiple LED strings

Among them, NCV78702 is a single-chip high-efficiency boost converter for LED driving, designed for automotive headlight applications such as high beam, high beam, DRL (daytime running light), turn indicator, fog light, static cornering, etc. It includes a current mode voltage boost controller with minimal external components and customizable output voltage. Two NCV78702s can be combined together to form a multi-phase boost circuit to further optimize the filtering effect of the booster and reduce BOM cost.

NCV78723 can drive 2 strings of LED lights up to 60V. It includes 2 independent current regulators for LED strings and diagnostic functions required for automotive headlights. The chip does not require any external sense resistor to adjust the buck current and can customize the output current. When more than 2 LED channels are required on a module, 2, 3 or more NCV78723 can be combined together.

The rear lights are used to remind surrounding vehicles and pedestrians of the vehicle's upcoming driving intentions, including turning, braking, parking, etc. At the same time, the various shapes on the body can also be used as a sign of the vehicle's identity. The working current is generally less than 100mA. The rear combination lights have these advanced functions: enhanced parking lights, tail lights, and turn lights are dynamic segmented light signals, and can also achieve branding, welcoming, animation and other effects with light beams. They can drive single-string and multi-string LED lamp beads, with higher energy efficiency, less loss, and safety diagnostic functions.

The NCV7683 consists of eight 100mA linear programmable constant current sources for LED based rear tail combination lamp dimming and control and blinking functions in automotive applications. System designs with the NCV7683 enable two levels of cutoff programming (100% duty cycle) and tail lighting (programmable duty cycle), and can also implement optional external PWM control. LED brightness can be easily programmed with two external resistors (cutoff programming as absolute current value, tail programming as duty cycle). The use of an optional external ballast FET enables power distribution on designs that require high current. Back-off power limiting reduces the drive current under overvoltage conditions. This is most useful for low power applications where external FETs are not used.

Since LED has great advantages in color temperature, color rendering index, brightness, etc., it is very suitable for short-term use in the car. Common ones include instrument lights, step lights, door lights, trunk lights, reading lights, ceiling lights, etc. In addition, LED can also be used to represent the status of the vehicle. For example, whether the door is closed can be reflected by the LED light. At the same time, another outstanding advantage of using LED lights in the interior lighting system is that it can reduce interference with the driver's vision, thereby effectively reducing the driver's dazzle.

ON Semiconductor offers a wide range of discrete and integrated solutions to meet the needs of a wide range of lighting applications. These include simple solutions such as a double-ended constant current regulator (CCR), an economical but robust device that provides an effective current regulation solution for cost-sensitive automotive LED lighting; some more complex solutions include LIN RGB LED drivers, which combine a LIN transceiver with an RGB LED driver and memory to form a single-chip RGB driver for monitoring multi-color LED applications.

The NSI45020J adjustable constant current regulator (CCR) is a simple, economical and rugged device suitable for providing a cost-effective solution for regulating current in LEDs (similar to constant current diodes CCDs). The CCR is based on self-biased transistor (SBT) technology and regulates current over a wide voltage range. It uses a negative temperature coefficient to protect the LED from thermal runaway at extreme voltages and currents.

RGB and white LEDs complement each other, and their development is driven by the drive to further personalize vehicles as programmable interior light sources, including area lighting such as instrument panels, center consoles, navigation/audio, and special effects applications such as mood lighting. The NCV7430 is a single-chip RGB driver for specialized multi-color LED applications. This RGB LED driver includes a LIN interface (slave interface) for parameterized programming of LED color and chromaticity. The device receives instructions via the LIN bus and then drives the LEDs individually. The NCV7430 acts as a slave node on the LIN bus, and the master node can request specific status information (parameter values ​​and error flags). The LIN address of the NCV7430 is programmable in the internal memory of the device. A feature of the device is 24-bit true color, which allows the module to output 16 million different colors via LIN commands for creating a personalized interior atmosphere in the car.

ON Semiconductor provides comprehensive semiconductor solutions for applications such as headlights, matrix/pixel lights, and rear combination lights. These solutions not only have high energy efficiency, high integration, and excellent reliability, but also achieve excellent scalability and flexibility thanks to the platform-based design concept. This undoubtedly brings great convenience to designers, helping them to move forward unimpeded on the road of innovation, while simplifying and accelerating the product development process. In addition, ON Semiconductor's intelligent power combined with advanced intelligent sensing technology has laid a solid foundation for improving road traffic safety.