The future of lighting – What will come after the LED?
LED lighting is already being used to replace incandescent bulbs everywhere. Even for applications where the accuracy of the light output pattern is important, such as car headlights, we see manufacturers start creating shaped diodes to emit light in that precise pattern.
Even as the popularity of light-emitting diode (LED) lighting grows, the vast majority of end users still have simple needs. Turn it on, turn it off; light and darkness. Nothing sophisticated.
But that's changing, and change is coming fast. LED lighting systems must be smart and efficient. "Being able to adjust the light, not only the brightness but also the color, is very important," said Steve Kennelly, senior manager of lighting and medicine at Microchip Technology Inc. Each other."
This is happening everywhere, in cameras, refrigerators, streetlights and machine vision systems. In medicine, doctors, for example, want to increase or decrease lighting or even change colors in exam rooms and operating rooms. Automakers want to be able to modify the colors of the interior lighting of their vehicles. And they want smart headlights.
Beyond On and Off…
Only electronic lighting can meet these needs and "you need intelligent control," Kennelly said. That's why project engineers are looking for a new generation of LED drivers.
However, to understand why LED drivers are important, you first need to understand what they do. In their simplest form, they look a lot like ballasts in fluorescent lights, which reconfigure the input current and voltage to drive the LED chip. In analog lighting, a printed circuit board with an energy conversion section containing oscillators and inductors and an integrated circuit tell components what to do.
Of course, some LED drivers do little more than on and off. "The predominant number of cars using LED headlights does nothing sophisticated," said Bryan Legates, director of electrical product design engineering at Linear Technology Corp. "It's just a high light and a low light and it works like the old halogen bulb incandescent."
But today's LED drivers can do much more than that if needed. Texas Instruments (TI's LM3466 LED driver), for example, allows LED chains to "talk" to each other. By doing so, you can balance the current between the chains, even when there is a fault or a chain is short-circuited.
"It's about making sure that no matter what happens to parallel LED chains, the current relationship between them is always identical," said John Perry, marketing manager for the IT lighting and energy products business. "So if you have a constant source of 1A, and you fall from four to three, the current is rebalanced so that each chain gets 333 mA, instead of 250 mA."
For many LED users, the main goal is to have good current regulation over time. In automated factories, for example, LEDs are applied in conjunction with machine vision systems. To ensure that these systems can always read the markings on the parts, users employ controllers that can precisely control the current of nearby light sources. Linear Technology offers a variety of such controllers, including LT3763, LT3744, and LT3791, to perform such tasks. "Customers want good regulation today, so once they calibrate the light source, it stays the same for the lifetime," Legates said.
However, in some cases, the new generation of drivers is allowing LEDs to do things that could not have been done before. An example of this is the "matrix headlight", which allows the vehicle to work with sensors to "see" the approaching traffic and then dim the bright lights to prevent drivers from being blind. The key is that it does it selectively, attenuating specific blinding LEDs while keeping the light on the road.
"Many of the newer vehicles already have the sensors and information needed to make that happen," Legates said. "Now they're just feeding him to the headlights."
Such "smart beacons" have existed, but they were electromechanical. LEDs and LED controllers, such as Linear Technology's LT3965, eliminate the need for complicated actuator arrays to move the oncoming incandescent beam away from the approaching conductor. "In the past, automakers used halogen lights and engines, but they couldn't change the shape of light so quickly and ended up with a very complicated system that didn't work as well," Legates said.