Engineering Custom LED Circuits
What is the future of custom LED lighting? We believe the future is world where system designers and engineers can communicate ideas more effectively. Unfortunately today, much confusion remains due to inconsistencies with LED lights and terminology. Manufactures of LED lamps publish data for LED bulbs according to different formats, and base standards according to different terms. Ultimately, the consumer ends up paying a price for such inconsistencies. At Lunar Accents Design Corporation, we believe the first step to a better future begins with an education in LED lights. This is why we have dedicated an entire section of our website specifically towards educating designers and consumers about the various technical aspects of LED lighting.
LED Bulbs Datasheets
Without previous experience, interpreting datasheets for custom LED lights can be a daunting and time-consuming task. The following tutorial will guide you through each section of our example datasheet for LED bulbs, provided courtesy of Nichia America. Our tutorial architecture follows the general format of our sample datasheet. The datasheet contains numerous sections, as well as numerous subsections within each. Specific values for LED lamps are contained within each section or subsection. Fortunately, most datasheets follow a relatively similar format. However, specific values will vary dramatically. This tutorial is for educational purposes only. It is important to consult with the LED manufacture for specific values prior to designing an LED home lighting or similar system.
Understanding LED Lamps Efficiency
LED efficiency is the measurement of visible light expressed in lumens compared to overall power dissipation expressed in watts. Logically, the common expression, "lumens per watt", refers to the ratio of visible light per watt of available power. In an LED home lighting project, an array of LED lights producing ten lumens per watt is more efficient than one producing only eight lumens per watt. In this example, assuming that total power dissipation of both LED bulbs is equal, the LED lamps producing eight lumens per watt is actually more efficient at producing heat when compared with the LED producing ten lumens per watt. Since heat is an undesirable byproduct, the LED producing eight lumens per watt is less efficient in terms of photometric output. Theoretically, LED efficiency could refer to optical or thermal efficiency, but since light is the desired product, heat is considered as waste.
Custom LED Home Lighting
We have all heard our share about some of the extraordinary benefits offered by modern LED lights and technology. Many consumers wonder why LED bulbs are rarely utilized in common LED home lighting applications, such as floor lamps and ceiling fixtures. If custom LED lamps are so superior, why have they not replaced all of our traditional incandescent lighting fixtures? The following articles will compare numerous aspects of modern LED lighting with the traditional incandescent bulbs found in most household lighting applications today. The examples found within the following context refer to a standard incandescent bulb and a popular high power LED. We have selected the Philips "Natural Light" 100-watt A19 bulb as our example for incandescent lighting. This is a very common bulb found in your typical household lighting application. We selected the Nichia Rigel NFSL036BT as our example for LED lighting. This is a modern high power LED manufactured by one of the world's leading and most reputable LED manufacturers.
LED Driver and Power Management
Modern LED lights operate at approximately 2-4 volts DC, and can draw between 10 mA and 1500 mA each. Power management involves the science of designing efficient circuitry and tailoring corresponding electronics to provide sufficient power to the circuitry. Simple drive circuits for LED lamps consist of series resistors to limit current while more advanced drive circuitry may consist of buck, boost, buck-boost, or charge-pump converters. The following context describes several basic drive concepts for modern LED bulbs which may be found in many common LED home lighting projects.
Understanding LED Thermal Management
All LED lights produce energy not only as light, but also in the form of heat. It is a common misconception that LED bulbs produce no heat at all. However, they do dissipate less heat into the surrounding atmosphere in direct proximity to the LED lamps. This is because most of the thermal energy produced radiates in the reverse direction, into the printed circuit board on which the device is mounted. The success of a custom LED home lighting design may depend upon the attention devoted to thermal management. Modern LEDs produce not only extreme amounts of light, but also heat. Recent advances in technology can now permit an LED to produce even more light due to its ability to withstand extreme temperatures as high as 185 degrees Celsius, within the internal junction. As a result, thermal management becomes more important than ever before. Maintaining a reasonable operating temperature not only ensures maximum performance, but also promotes an extended lifespan.
Warm White LED Designs
A variety of modern lighting applications now incorporate some form of white LED technology. Most of us who are at least somewhat familiar with LED lighting have seen white LED lights in operation. A slight bluish tint is defiantly a notable characteristic of the light produced by most white LED bulbs. It is fair to conclude that this slight bluish tint is somewhat comparable to the appearance of traditional fluorescent lighting. On the other hand, incandescent lighting appears more natural, like sunlight. A special kind of white LED lamps referred to as "warm white" actually produces light very similar to the incandescent bulb. Studies have proven that people generally feel more comfortable within an LED home lighting environment illuminated by a light source that mimics natural lighting. To realize why, it is important to understand the relationship between color temperature and color rendering.
LED Optical Characteristics
LED is an acronym that stands for light emitting diode. A diode is a common electronic component classified as a semiconductor, and contains a PN junction. A light emitting diode is simply a diode that converts electrical energy to light by releasing photons directly from the PN junction. An LED lights optical characteristics can describe how the LED bulbs might appear to humans and what functionally it might serve in an LED home lighting environment. A good understanding of basic optical characteristics associated with LED lamps, as well as associated terms will play a critical role during the initial developmental stages of a custom LED design project.
LED Lifespan
LED lifespan is perhaps the single most misunderstood aspect of LED lighting technologies. The misconception dates back to a time when many people believed in the 100,000-hour life span. Although LED lights may survive this long, it will not produce nearly as much light as it did within its first few hours of operation! As the LED bulbs age, the luminous output will continuously degrade. This degradation is due to growing defects within the molecular structure of the die. Overtime, the LED lamps become less efficient at producing light. In addition, lens yellowing can also decrease the luminous output as the LED ages. Lens yellowing occurs from ultra-violet radiation as it passes through the epoxy lens. This is why ultra-violet (UV) LEDs have a very limited lifespan and may not be suitable for LED home lighting projects. The intense ultra-violet radiation causes lens yellowing at an accelerated rate.