As LED technology continues to improve the application and the gradual decline in the cost, LED lights on through the years in the automotive technology validation, concept car shows, etc. After the initial conceptual stage, closer to large-scale systems used in production cars prospects. Electronic systems from the Audi R8 full use of LED lights begin to Mercedes-Benz, BMW, Cadillac, Toyota and other companies also launched its own alternative to traditional incandescent light LED lights, HID lights of car models, a variety of colorful LED lights for the new car considerably, attracting the attention of consumers, but also for the future of automotive design offers a new highlight, I believe that soon there will be more car manufacturers will be LED lights as automotive lighting, direction, light and decoration preferred.
LED is suitable for a variety of automotive lighting applications, including headlights (high beam and low beam lamps), fog lights, tail lights, brake lights, turn signals, daytime running lights, pedals, lights, interior lights, showing the wide lights, navigation, entertainment systems, instrument lights and LED backlighting, etc. LED lights used in automotive systems the following main advantages: First, color saturation, the output light more clear and soft, in line with the characteristics of automotive headlight applications; second, long life, durable, strong earthquake , can exceed 10,000 hours, while traditional halogen life is generally 300 hours; third, high efficiency, low excess loss, compared to the complexity of the traditional lamp cooling system, LED lights can be seen that the heat loss is much smaller, conversion efficiency can reach 85%, in particular, focus on energy saving for the future of automotive design; fourth, fast response, different from the traditional incandescent light, HID lamps require a longer drive light delay, but also reflect real-time vehicle speed and road conditions, leaving give drivers more time to judge, to reduce vehicle accidents; fifth, small size, light weight, can achieve a more compact lamps, designed for other models to save more space; sixth, LED lights are but The light color is very good, no infrared, ultraviolet and other light, heat, radiation rarely suitable for automotive interior lighting, backlighting applications.
LED lights use in cars, which now focuses on headlights, taillights, lights, GPS and so the use of the backlight, especially tail, which accounts for 10% of the market.
Five technical challenges
The size of the domestic automotive LED automotive lighting market currently accounts for only a small share of about 10%, now mainly concentrated in the high-end vehicle applications. Although LED lights cost continued to decline, but comparable to traditional light sources to achieve, but also in terms of quality and production gradually increased, in order to reduce the cost of LED, LED automotive electronics to expand market share.
Not delay the high cost of LED lamps in automotive applications the only factor, some of the technical performance aspects of the problem is the need to solve, such as a single LED light intensity is still insufficient, it will not be able to arbitrarily reduce the number of LED lamps reduce volume; while smaller size is not conducive to heat sources, which requires manufacturers to make products LED thermal management, in order to more fully exploit the advantages of LED, or both for the life of the LED can provide better color rendering state, otherwise it can only be counterproductive, reducing the quality of products; LED drive current conversion efficiency is more critical problem points, many programs in high-power applications, while taking into account the cost of conversion efficiency is not high; also present, China’s LED lamp applications In the automotive electronics are all high-end cars and high-end cars are most in control of foreign auto manufacturers, foreign manufacturers of LED supplier selection and certification are very harsh, very difficult to enter the domestic LED enterprises in their supply chain; another country’s LED lights also stay in the majority of production levels within the requirements of civilian products, it is difficult to reach automotive applications, even though its application to automotive manufacturers may be some production capacity and ensure product consistency, etc. do not necessarily enough, it is difficult to meet production of large quantities of high quality automotive needs.
Therefore, in order to accelerate the LED light source in the car on the share, you must first solve these issues to increase the intensity, the thermal management issues as described above, production costs and product consistency, and so on.
Automotive LED drive power requirements of discrete
With a constant voltage source driving the LED brightness can not guarantee the consistency and reliability of LED life and lumen. Therefore, LED constant current source driver must be used. Most LED has a current value required, you can use the configuration for the current source to drive the linear regulator, linear regulator with a reduced number of parts and reduce electromagnetic interference (EMI) benefits, but in the efficiency and heat consumption has serious drawbacks, not suitable for high power applications, with switch-mode power supply (SMPS) is more suitable for a variety of applications.
SMPS current mode LED driver using the power of the market mainstream, but also combinations of discrete components into an integrated manner and IC, IC integration patterns such as Taiwan Macroblock (MacroBlock), Zetex (Diodes), TI and the NSC, the main feature is the built- MOSFET and driver circuit, while some integrated multi-drive, automatically dimming and various protection functions, the application circuit is simple, small, easy to control costs, but because of this application-driven current, the design is not flexible enough to control the accuracy not high, the boost mode can not be achieved because, in most automotive applications are very limited, and the PWM control chip and the external MOSFET to achieve the separation mode, you can achieve high-power automotive electronics, high efficiency and high stability of the application, it can be a different topology, combined with the LED for voltage, current and power requirements, in line with the system to achieve the overall objective. With the amount of the cost will be gradually reduced.
Installed before the market mainstream in Europe
MCU + MCP1630 program currently used in a wide range of applications in Europe, accounting for 70% of the market in Europe pre-installed over the market, mainly used in the headlights (high beam), tail lights, flashing lights and other applications, the chip is its high reliability, high efficient, flexible functionality, cost-effective applications in the automotive LED driver to establish a good reputation, some large foreign companies for the LED driver of choice, while, with the amount increasing, MCP1630 cost advantages are increasingly obviously, can apply in the low-end models, to better address the thermal management in LED drivers, efficiency, product consistency and other issues.
MCP1630 is used to develop intelligent power of a high-speed pulse width modulator. MCP1630 in peak current mode can be achieved 1MHz frequency, CMOS output driver can directly control the MOSFET drivers or low-N channel MOSFET, provides an external reference power, flexibility of the output voltage and current regulation set; internal high-speed comparator, high-speed bandwidth / error amplifier can achieve faster and more accurate current sensing, and integrated over-temperature protection, under voltage lockout function, to better achieve better thermal management. When conjunction with a microcontroller, it can control the power system duty cycle to provide a stable output voltage or current. SCM is used to adjust the output voltage or current, switching frequency, maximum duty cycle and can improve the power system more intelligent and regulating of other features.
In the LED driver system, if the supply voltage exceeds the total LED voltage, you need to step-down converter. If the LED pack voltage exceeds the supply voltage, you need to step-up converter. In the automotive power system, LED voltage may be higher or lower than the supply voltage, so it should be a buck / boost or single-ended primary inductance converter (SEPIC) and other power supply topology. MCP1630 to achieve the above topology design needs. While adhering to the Microchip products in a consistent style (high stability and product consistency), the LED production costs and quality have been improved. Here’s to Microchip’s MCP1630 High Speed PWM chip, for example, through the SEPIC topology to explain the program in automotive applications, the applicability.
Microchip introduced the use PIC12F1823 + MCP1630 SEPIC topology for the car’s tail light / flash applications DEMO, enables +9 V to +16 V input voltage, the maximum output voltage to 55V @ 350mA, 10 1.5WLED driving lights, while achieving the grade dimming, undervoltage, overtemperature protection and other functions, the conversion efficiency of 85%.
MCP1630 enables the application of LED load current under the influence of various factors are controlled in the pre-designed level, the circuit will be a reference voltage or current signal Vref and the LED load voltage or current signal FB into the signal control module for comparison, the error signal is processed and returned to the primary control IC for processing, when the load current due to changes resulting from various factors, the primary control IC can control the switch so that the load current back to the initial design value. Through feedback and over-temperature detection, can achieve very good thermal management.
Topology used on the, SEPIC converter efficiency, although not as buck or boost regulator, but it also has its advantages, SEPIC, and buck-boost also has the ability, especially for vehicles in cold start when the voltage may be as low as 4.5V, while the other hand, in the case of auto overload voltage will suddenly rise to the sudden rise more than 40V dump application, another very popular in automotive applications, the advantages of interest among its circuit capacitor, it can be provided between the input and output isolation is very effective. Of course, the SEPIC converter there is an obvious disadvantage is the need to operate two inductors. This application method will be two inductors wound in concentric circles separated into two opposing components, saving both cost and size. MCP1630 at the same time the peak current mode due to the presence of high-speed comparator, you can respond quickly to within 12ns, fast high-precision current loop. Meanwhile PIC12F1823 detection can be achieved through the AD voltage detection, to achieve efficient control.
In addition to the application as a SEPIC topology, MCP1630 can be applied to separate boost / buck circuit, mainly used in automotive headlights and daytime running lights, etc., can be achieved LED in series to achieve more efficient control applications
In addition to the application MCP1630, Microchip has introduced a low-cost MCU with integrated LED driver applications, such as PIC12HV615, PIC16HV785, its internal high voltage regulator integrated, high-speed hardware PWM module, comparator, ADC, operational amplifier, voltage reference, etc., can boost or step-down control, backlight used in automotive equipment, instrument backlighting, brake lights and other small power applications, will turn into a traditional CCFL backlight LED backlight. MCU’s rich resources can achieve more intelligent features, highly integrated applications reduce costs, simplify design, save space and also help to overcome the thermal management and improve efficiency. However, the application is still not suitable for high power applications.