Lighting Emitting Diode Tutorial

What is an LED?
Think light emitting diodes (LEDs) are just for flashlights and cell phone displays? Think again. Once relegated to humble indicator lights in electronic devices, LEDs have advanced at remarkable rights to enable an entirely new category of lighting that's projected to reach $30 billion by 2025.

These very same sources will one day light our homes and everyday spaces. Why? Because they're highly efficient, long lasting, environmentally friendly and inherently controllable - enabling both new and traditional applications of light. Promising future aside, LED systems already illuminate famous buildings, bridges, retail shops, television studios, theater stages, hotels, casinos, hospitals, restaurants and celebrity-filled nightclubs around the world.

What's so different?
First let's take a look at the traditional light bulb or "lamp" as it's called by the industry.

The light in most homes is produced by incandescent sources. The bulb structure is produced when hot glass is blown into molds and then cooled and coated with diffusing material. Placed inside the bulb is a very thin and fragile, coiled tungsten filament (.0017 inches thick). For the bulb to produce light an electric current is passed through a conductor and the tungsten is heated to the point at which it gives off light. Unfortunately, these bulbs, like many of their relatives, are not very energy efficient; roughly 10% of the energy is used to make visible light.

How do LEDs work?
The structure of the LED is completely different than that of the light bulb. Amazingly, the LED has a simple and strong structure. The beauty of the structure is that it is designed to be versatile, allowing for assembly into many different shapes. The light-emitting semiconductor material is what determines the LED's color.

As indicated by its name, the LED is a diode that emits light. A diode is a device that allows current to flow in only one direction. Almost any two conductive materials will form a diode when placed in contact with each other. When electricity is passed through the diode the atoms in one material (within the semiconductor chip) are excited to a higher energy level. The atoms in that first material have too much energy and need to release that energy. The energy is then released as the atoms shed electrons to the other material within the chip. During this energy release light is created. The color of the light from the LED is a function of the ingredients (materials) and recipes (processes) that make up the chip.

What are the advantages of LEDs?
LEDs have a variety of advantages over other light sources:

• High-levels of brightness and intensity
• High-efficiency
• Low-voltage and current requirements
• Low radiated heat
• High reliability (resistant to shock and vibration)
• No UV Rays
• Long source life
• Can be easily controlled and programmed

Why are LEDs becoming so popular?
Over the past decade, LED technology has advanced at light speed. In the past, lack of colors and the low intensity made LEDs useful only as indicator lights. As manufacturing methods and technology improved, the LED quickly found homes in more and more applications. These days, the LED is becoming a preferred light source for much more than simple indicators. In fact, today Philips illuminates the world's largest spherical building (Globen arena), the world's largest observation wheel (Singapore Flyer), and the world's tallest free-standing tower (CN Tower) with LEDs!.

LED sources are also gaining popularity due to the growing energy conservation movement. According to the U.S. Department Energy, no other lighting technology offers as much potential to save energy and enhance the quality of our building environments.

Summary
Today is an exciting time for those working closely with LED lighting systems, which allow completely new uses of light.

Far surpassing the simple enclosure of LEDs on a circuit board, Philips excels in all the critical areas that are vital to high-performing LED lighting systems - from thermal management, binning and optics to high-efficiency LED drivers and advanced power components. We have also developed important proprietary technologies to reduce the cost and complexity of LED lighting control, operation and installation - in turn accelerating market adoption.

Though it's been shown to affect the way people live, work, and feel, light has long been considered an afterthought. Philips strives to change that notion, advancing LED lighting technology to create experiences, inspire new applications, and even mitigate strain on our world's resources.