Compared with traditional lamps such as xenon lamps and halogen lamps, LEDs have the advantages of low energy consumption and high energy efficiency, which can reduce CO2 emissions and achieve energy-saving tasks in all aspects of automobiles for automotive engineers. Automotive headlamp applications, including high beam, low beam, daytime running lights (DRL) and position lights, are an area where LEDs can be significantly energy efficient and achieve energy efficiency improvements, while energy efficiency benefits can be Direct conversion to save fuel consumption. This has not yet addressed the important advantages of LED-based headlamp modules over other lamps, such as long life, design flexibility and greater functionality. Successfully developing and applying cost-effective, energy-efficient lamp modules that include multiple strings of high-brightness (HB) LEDs depends on the design of electronic control units (ECUs) that utilize the same energy-efficient system-on-chip (SoC) solution; The SoC integrates all the necessary specific headlight functions, including diagnostics and connectivity. Early application of LED in the automotive field Among the passenger car applications, the first large-scale LED is the central high-position stop light (CHMSL). The ability to utilize a single string of LEDs in an unobtrusive low-profile housing is an excellent match for high-level parking lights. Subsequently, LED-based interior lighting and integrated taillights (RCL) with integrated turn signals, taillights and brake lights were also used in a number of applications. Especially in combined taillight assemblies, LEDs can help greatly simplify the design of lenses and reflectors. LEDs are more durable and have a longer life expectancy (about 30,000 hours versus 1,000 hours) compared to incandescent bulbs, making designers more willing to adopt this newer technology. Application of high brightness LED in headlights Rapid advances in technology have helped accelerate the introduction of HB LEDs with significantly improved light output, so the use of LEDs in headlamp applications has become a reality. Xenon lamps and halogen lamps have entered a stagnation period in terms of technology, maximum energy efficiency and cost reduction, but LEDs are still in the early stages of the same journey, so the advantage of using HB LEDs over the prior art is increasing year by year. The first generation of LEDs in headlamps was used as daytime running lights. Although it only provides low light output and therefore low energy consumption, daytime running lights are defined as long as the car engine is running, so the daytime running lights are always consuming extra fuel. LED-based daytime running lights consume only about 9 W of power, which can reduce this extra fuel consumption to an absolute minimum. HB LEDs are likely to meet all existing headlamp applications including high beam, low beam, daytime running lights, turn signals and fog lights, and are possible to provide excellent solutions for beam adjustment Emerging functions such as road concentrating. In the evolutionary path of fully adopting LED lighting with the headlight module, some automakers currently only choose to provide the greatest advantage in terms of energy savings (ie better fuel economy) for early switching to LEDs. The aforementioned daytime running lights are an example and are becoming a statutory requirement in more and more countries. Another example is the decision to temporarily maintain the use of a halogen high beam – the thinking process behind it is that the high beam is used for a very short time (only at night and in the opposite direction when no vehicle is approaching), the corresponding total energy savings / Very little fuel. HB LED costs are lower and overall performance is improving, and the trend toward LED adoption in new automotive designs will accelerate. Strong, energy-efficient (90%) system-on-chip LED drivers such as the ON Semiconductor NCV786XX series will further drive this trend; the NCV786XX has taken a big step forward with switching regulators, with headlamps in the middle Wait until the high power requirements, its dual LED driver application diagram shown in Figure 1. Figure 1: Schematic diagram of ON Semiconductor's NCV78663 dual LED driver application Considering the automotive headlamp module, in addition to the inherent low-power, energy-efficient properties of HB LEDs relative to incandescent, halogen and xenon lamps, consideration should be given to places where other automotive applications can save power. For example, in order to provide advanced safety-critical functions such as headlight beaming, conventional headlamps use motor-driven shutters or other moving parts to block, adjust, or steer the beam. When using HB LED strings to provide this functionality, the desired effect can be provided by simply turning a particular LED in the LED string on or off. The use of SoC LED drivers to control the intelligent and flexible performance of HB LED strings has driven the addition of exciting new features to headlamp designs. For example, dynamic beam adjustment and direction adjustment, including highway concentrating, can be applied by feeding GPS information to the SoC driver. The GPS input can even show which country the vehicle is driving, and is therefore used to trigger a cut-off line that adjusts the low beam (by turning a specific LED on or off), allowing the car to automatically drive safely at night. Configuration, regardless of the country's traffic regulations, is based on the left or right side of the road. System level challenges driving LED headlamps High temperature (up to 125) for any LED headlamp module driver due to its proximity to the center of the engine compartment and integrated multi-string LEDs to provide high beam, low beam, turn signal and daytime running lights °C) Performance and space utilization are prerequisites. Switching regulators are capable of meeting temperature specifications; however, they lack system integration and require a large number of external components. SoC devices such as the ON Semiconductor NCV786XX family integrate most of the required functions, keeping the number of external components at an absolute minimum. If the integrated driver can support 2 instead of 1 HB LED string like the NCV786XX (up to 60 V per string), the space, weight and cost savings will increase. In addition to the advantages of HB LEDs relative to xenon or halogen lamps, it is also important to consider the key factors of the SoC energy efficiency level used to drive the headlamp LEDs. The total power requirement of HB LED modules including high beam, low beam, daytime running lights, corner lights and turn signals will be in the 90 W range, so the importance of the driver (NCV786XX) providing about 90% of the rated energy efficiency is very important. . Moreover, the high energy efficiency of LED drivers means less heat is generated, so smaller heat sinks can be used. This not only reduces the total cost, but also significantly reduces weight. There are many other system-level challenges you may encounter with integrated SoC LED drivers, and these challenges increase as the headlamp unit has more features. First and foremost is the ability to support pulse width modulation (PWM) dimming; this allows the use of LED strings to provide more than one function, such as when using remote unlock (RKE) to unlock the door lock, daytime running lights reduce light output It can be used as a so-called "welcome" function. In order to provide stable and reliable operation, it is important to stabilize the current with low ripple and accurate average current when driving HB LED strings. SoC headlamp LED drivers like ON Semiconductor's NCV786XX series meet this requirement to provide only 15% of the rated ripple current; in comparison, conventional buck-boost drivers provide about 200% ripple current. Providing low electromagnetic emissions to the battery and for LED switching and dimming is important to improve overall system reliability and minimize the number of externally filtered components (because this adds cost, weight and valuable space). In a headlamp design that uses a single halogen or xenon bulb to perform functions such as low beam, the drive can be clearly perceived if the bulb fails. In contrast, if one or two LEDs in the LED string designed to perform the same function fail, the driver is not noticeable unless a careful visual inspection of the LED string is performed. Not only that, because it is necessary to illuminate the road ahead, some LEDs in the LED string fail, which will affect safety. This is why diagnostics is an example of the important features of an integrated SoC LED driver. This information can be communicated to the drive using software via the body electronics controller to quickly identify and correct any problems. Automating the standardization of components for automotive platforms wherever possible is also beneficial to automakers because it simplifies production planning and it may be economical to purchase larger quantities of the same components relative to each of the different components. SoC LED drivers like the NCV786XX series achieve this in a number of ways. First, by providing built-in interface capabilities for traditional lighting electronic control units (ECUs), LED drivers can be used on automotive platform-derived models that specify the use of conventional halogen or xenon headlamps instead of HB LEDs. Second, by supporting the LED configuration with software rather than hardware, headlamp applications can be driven across the entire vehicle range with different variants of the same device. Finally, a Serial Peripheral Interface (SPI) is provided, optionally with external microcontroller and dynamic control system parameters. summary The use of HB LEDs for daytime running lights has made a low-key start for the use of headlamps. The improvement of HB LED technology while reducing the price and the relative advantages of xenon lamps and halogen lamps is accelerating the application of HB LED technology in new car platforms. Robust and energy-efficient SoC drivers are critical for successful application in new designs because they meet a wide range of system challenges, integrate diagnostics, and provide design flexibility for connecting external microcontrollers to traditional bulb ECUs. The environmentally friendly (fuel saving), safety and convenience of full-featured HB LED headlamps provide automotive designers with an excellent way to meet their future needs and differentiate their products. 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