Compact LED driver comes out to eat the car lighting circuit

LED demand for flexible, integrated, networked driver electronics is getting closer and closer in 2011. For European OEMs, it means that the time limit for implementing ECE R87 is approaching. As early as in 2008, the European Union has announced that starting in February 2011, new cars and small trucks will be equipped with daytime running lights (DRL), and other trucks and buses will also be available on August 7, 2012. Audi's A8, R8 and A4 series have been equipped with LED daytime running lights. From the perspective of the famous automakers actively following up on the daytime running, the LED adoption rate is the highest. It is clear that the EU's move will further accelerate the growth of the automotive LED market. .

Although the price of LED is still less than civilians compared to traditional lighting, but the financial industry is not bad money. As a luxury luxury, the soul of a car is quality. LED has successfully entered the automotive market with its long life and low power consumption. According to the statistics of the U.S. Department of Energy, the service life of LEDs is 20 to 25 times that of traditional light sources and 10 times longer than halogen lamps. Compared with traditional light sources, the lumen output of the same power LED is 3 to 4 times higher than that of an ordinary light bulb and 2 to 3 times higher than that of a halogen light. Using LEDs also helps improve fuel economy and effectively reduce carbon dioxide emissions. In terms of daytime running lights, the average CO2 emissions per kilometer of ordinary light bulbs is 1.2g, while that of LEDs is reduced to 0.58g.

Compared with conventional lighting solutions and LED lighting circuits, increasing the integration of LED lighting control modules not only reduces the chip's footprint, but also helps to increase system reliability and reduce system costs by reducing the amount of components used in the circuit.

NXP's fully integrated highly flexible driver chips ASL1010NTK and ASL1010PHN integrate many core functions such as direct LED temperature feedback, LED fault detection, internal pulse width modulation (PWM) and short circuit protection. The use of this compact chip does not require an external MCU to build an LED lighting control circuit. In addition, in the current input conduction process, the ripple current will be clearly reflected in the LED performance, generally through the filter to avoid the impact of ripple current on the LED, this solution effectively eliminates the ripple current to avoid the use of external filters, significantly Reduce the external components required for the drive circuit. In the reference design given by Drue Freeman, the chip with 11 external components can realize the circuit function that the same LED drive scheme requires more than 20 components.

ASL1010NTK is 8-pin version, 3x3mm package size can be integrated with the LED on the same printed circuit board, ASL1010PHN is the same series of 16-pin version, with direct classification resistance input, and increase the short circuit protection function to prevent connection Wait for the error to damage the LED. The two products will be launched in December this year, the first samples will be officially put into production next year.

Flexible support for multiple LED solutions to prevent overheating of LEDs

Drue Freeman said that the challenge of LEDs for exterior lighting is the need for integrated, flexible, and networked drives.

LED has been widely used in automotive lighting. Even hard-to-eat headlights have the courage to eat crabs. However, in different automotive lighting applications, the number of LEDs used in the lighting module is different, and the driving circuits are also different. Lighting control devices need more powerful and more flexible solutions to quickly introduce LED designs and give full play to LED energy-saving advantages. The system solution introduced by NXP can support 1 to 20 LEDs in series, with an output voltage range of 6V to 60V, and can support different automotive platforms, including hybrid vehicles.

In addition, there are differences in characteristics among different LED manufacturers and different LED batches, and the steep forward characteristic of the LED causes a slight change in the driving voltage to cause a strong fluctuation of the driving current. Therefore, LED manufacturers must classify different levels according to the color and brightness of the LED. In the past, it was necessary to design and optimize the LED Driver circuits according to each level. It is not difficult to understand that the LED lighting industry has fixed the lock-in effect to certain LED manufacturers. NXP's ASL1010 PHN (16-pin version) is expected to be loosened for LED lighting. It can distribute the classification resistance according to the characteristics of different LED's to achieve the flexibility of the drive circuit, giving system manufacturers more freedom when designing and purchasing LED lights. degree.

Due to the limitation of current LED technology, the photoelectric conversion efficiency of LED has yet to be improved, and the lost energy is released in the form of thermal energy, which leads to high temperature around the LED and causes serious light failure. What's worse, the service life of LED is greatly reduced. High-power headlamps consume large amounts of power, and the heat dissipation problem is the most prominent. This is also the crux of the difficulty in the popularity of LED headlamps. The ASL1010NTK and ASL1010PHN use temperature feedback and combine PWM to regulate the current flowing through the LED to prevent overheating of the LED.

These two products are NXP's first products for automotive LED lighting drivers. The veteran car electronics supplier NXP has the blood of the split Philips lamp before it is believed. He believes that his plan for automotive LED lighting will not stop there. Drue Freeman revealed that NXP has a long-term plan for automotive LED driver chips. In the near future, it will focus on low-current driver integrated power switches, integrated bus interface (CAN\LIN interface), and multi-channel drivers for driving the light group to form the speed of light. Effect. The most exciting thing is that NXP will push the LED driver's integration to a new level—sensorless temperature sensing. The LED driver chip will sense the temperature of the LED without a temperature feedback resistor.

Source: University of Michigan Institute of Transportation LED driver circuit engineering, integration program single-handedly With the continuous maturity of LED technology, the automotive industry, LED is used in dashboards, car interior lighting has long been familiar with the road, LED is gradually capturing brake lights, fog Lights, low beam, high beam, daytime running lights, and adaptive front lights (AFS). Although it is of great benefit to use LED in automotive lighting, there are still many problems to be overcome in system design. Drue Freeman, vice president of global sales and marketing at NXP Automotive Electronics, points out that the challenge of LEDs for exterior lighting is the need for integrated, flexible, and networked drives.

A typical automotive lighting architecture relies on body control modules to achieve control lighting. The traditional light bulb solution only requires one switch to execute the commands of the body control module, and the control circuit is relatively simple. Once turned to LED lighting solutions, the lighting control circuit immediately becomes complicated. Since the LED's color temperature, output light flux, and ambient temperature are closely related, it is necessary to use the MCU as a control center to adjust the brightness of the LED in real time according to the ambient temperature and the light signal, collect the information on the LED, and feed it back to the body control module, thereby increasing the voltage regulation. , signal conditioning, temperature feedback, short circuit protection, electromagnetic filtering and a series of electronic devices. In terms of cost, the cost of the LED architecture is higher than that of a conventional lighting source driver circuit. From the perspective of system design, the complex circuit virtually increases the risk of the system, and the difficulty in troubleshooting electronic components also increases.