THE FUTURE OF LIGHTING - WHAT WILL COME AFTER LED?

The 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 that manufacturers begin to create 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. Uncool.

But that is changing, and change is coming fast. LED lighting systems must be intelligent and efficient. "Being able to adjust the light, not only the brightness but also the color, is very important," said Steve Kennelly, senior lighting and medicine manager at Microchip Technology Inc. to each other. "

This is happening everywhere, in cameras, refrigerators, street lamps, and artificial vision systems. In medicine, doctors, for example, want to increase or decrease lighting or even change colors in exam rooms and operating rooms. Car manufacturers 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 is why project engineers are looking for a new generation of LED controllers.

However, to understand why LED drivers are important, it is first necessary 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 the components what to do.

Of course, some LED drivers do little more than on and off. "The predominant number of cars that use LED headlights does nothing fancy," said Bryan Legates, director of design engineering for electrical products at Linear Technology Corp. "It's just a high beam and a low beam and works like the old halogen bulb. incandescent."

But today's LED drivers can do much more than that if necessary. The Texas Instruments LM3466 LED driver (TI), for example, allows LED strings 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 shorted.

"It's about making sure that no matter what happens with parallel LED strings, the current relationship between them is always identical," said John Perry, marketing manager for the IT lighting and energy products business. "Then, 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 objective is to have a good regulation of the current over time. In automated factories, for example, LEDs are applied together with artificial vision systems. To ensure that these systems can always read the markings on the parts, users use controllers that can precisely control the current from nearby light sources.

However, in some cases, the new generation of controllers 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 so selectively, dimming specific blinding LEDs while maintaining light on the road.

Such "intelligent headlights" have existed, but they were electromechanical. LEDs and LED controllers, such as Linear Technology LT3965, eliminate the need for complicated actuator arrangements to keep the incandescent beam away from the approaching driver. "In the past, car manufacturers used halogen lights and motors, but they couldn't change the shape of the light so quickly and they ended up with a very complicated system that didn't work so well," said Legates.