LED (Light Emitting Diode), light-emitting diode, is a solid-state semiconductor devices, which can be converted directly into electricity to light. In recent years, the applications continue to expand, from the portable device backlight traditional to large size LCD display / LCD TV backlighting, automotive and general lighting field. This article will be devoted to a variety of LED driver solutions, suitable for car light, This paper will be devoted to the various LED drive scheme suitable for automotive lighting applications, and discusses some typical applications. and discuss some typical applications. LED offers many advantages for automotive lighting applications,LED applications is very wide in car field, but can be summarized as interior lighting and exterior lighting (see Figure 1).
but simply classified into internal and external lighting lighting . External lighting as the headlight, Obe Terua, interior lighting including internal convenient and comfortable lighting and instrument panel backlight.
A lot of factors to promote the application of automotive LED lighting. With headlamp for example, the use of LED as a light source has many advantages:
1.1 to design led flexible or novel
LED physical size is very small, can be used to develop extremely compact, thin modules. Compared with halogen and xenon lights, multi-string LED module requires a smaller, simpler lens and a light-diffusing sheet hardware. And a plurality of LED light source is easier to guide,
greatly reduce the impact that project in engineering design.
1.2 light intensity and energy efficiency continues to improve LED light intensity is fast on the lift curve, showing every 18-24 months flux will double trend. LED light output has more than halogen lamps,
future LED optical performance will also be able to rival the xenon lamp.
1.3 high reliability and long life
As long as the car headlamp effective thermal management module to maintain a low junction temperature, and protect it from the switch is turned on / off, the impact of the pulse and the battery current spikes may occur during can’t affect. Expect them to continue to use in the whole life cycle of the car.
1.4 significant energy savings
Compared with other solutions, car headlamps use fuel / energy is much less. Use high efficiency intelligent power Technology / chip, rather than a number of external components required general IC, can be more energy efficient.Therefore, LED automotive lighting applications in increasing, and by many car manufacturers as a design selling point.
2 LED driver solutions compare
LED automotive lighting applications in a variety of different applications of LED current requirements also vary, so the need to combine specific application requirements, select the appropriate LED driver solution.
One of the main features LED driver solution is the steady flow in a variety of working conditions, regardless of the input conditions and forward voltage variations. Driver programs must comply with energy efficiency, form factor, cost and safety aspects of the application requirements. Meanwhile, the selected solutions must be easy to use and strong enough, to meet strict environmental application specific.The typical LED driver program in automotive applications including resistors, linear LED driver, LED driver and innovative lighting switch management LED driver. In general, according to the size of LED current in the application, in low current application of 20 to 200 mA, can using discrete components (i.e. resistance) or linear driving solutions; in the secondary current application of 200 to 500 mA, can choose linear or switch driver solutions; and in high current applications is greater than 500 mA， in general please selection switch drive solutions.
In fact, the resistance is the easiest, lowest cost ,LED current limiting solutions, but they are not “steady flow”, but the LED forward voltage variation and input supply voltage variation and lead to current changes, will be causing the LED brightness variation, simply LED maximum current limit. Although the low cost of such programs, but also the lowest energy efficiency, and the existence of LED thermal runaway screening costs and thermal runaway problem.CCR is a higher performance solution and it has more lower cost than the switch driver. suitable for LED lighting applications in current is less than 200 mA. CCR cheap and rugged, providing a constant brightness over a wide voltage range, CCR maximum operating voltage of 50 V, the battery can withstand load dump. CCR provides SOD123, SOT123 and DPAK different packages to work (125 ℃)
This solution can reduce or eliminate the generation LED filter stock, so that a lower total cost of the program. CCR maximum operating voltage of 50 V, CCR provides SOD123, SOT123 and DPAK in different packaging, can work under strict thermal environment (125 ℃), In addition, CCR does not generate electromagnetic interference, easy to design.
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