Active Cooling A cooling process that uses power for cooling components such as fans to actively exhaust heat from components.
Amp A measure of electrical current. Current (Amps) = Power (Watts) / Voltage (Volts).
Binning The grouping of LEDs (from production) according to specifications, such as light output, color, and voltage so that LEDs of similar light performance are grouped.
Candela (cd) A measure of luminous intensity, or power emitted by a light source in a particular direction. A common candle emits light with a luminous intensity of roughly one candela.
Correlated Color Temperature (CCT) The temperature of the surface of an ideal black body radiator measured in Kelvin (K), which ranges from warm (i.e., red to yellow, generally 3000K and below) to cool (i.e., blue, generally 5000K and above) tones.
Color Rendering Index (CRI) A measurement of the ability of a light source to reproduce the colors of various objects in comparison to natural light. The optimum colour rendition index is Ra = 100.
Cutoff Luminaire To avoid light pollution, a cutoff luminaire is one in which the luminous intensity (in candelas) at or above an angle of 90° above nadir does not numerically exceed 2.5% of the luminous flux (in lumens) of the lamp or lamps in the luminaire, and the luminous intensity (in candelas) at or above a vertical angle of 80° above nadir does not numerically exceed 10% of the luminous flux (in lumens) of the lamp or lamps in the luminaire.
Chip A term used for the board or “light engine” to which the LEDs are applied. The chip or “light engine” is a circuitry board for the LED.
DMX512 A standard for digital communication networks that are commonly used for theatrical or stage lighting. A single DMX universe has 512 addressable channels.
Diode A two-terminal device commonly used as a one-way switch allowing the flow of electric current in one direction (called the forward-biased condition), and blocking the flow of the current in the opposite direction (the reverse-biased condition).
Driver An LED power supply that provides either a constant levels of current, or a constant level of voltage.
Driver Efficiency A measure of luminaire efficiency that focuses on the performance of driver, or power supply, components.
Efficacy The light output of a light source divided by the total electrical power input to that source, measured in lumens per watt.
Fully Rated Life The end of the life of an LED is determined by the point at which the LED fails to deliver at least 70% of initial lumen output. LEDs are commonly marketed as having 50,000 hours of fully-rated lives.
Glare Collective term for the reduction of visual performance or the impairment of perception due to high luminances or luminance contrasts in the visual surroundings. A distinction is made between discomfort glare and disability glare: the former concerns an objective reduction in vision and the latter a subjective impairment due to any disparity between the luminance and information content of the observed area. The glare can be caused by the lamp itself (direct glare) or by reflection of the lamp (reflected glare).
Heat Dissipation The intentional transition of thermal energy from a hotter object (such as a sensitive electronic device) to a cooler object. Heat dissipation is achieved with LEDs primarily by mounting them on heat sinks made on high-quality aluminum and other alloys.
Heat Sink An object that absorbs and dissipates heat from another object using thermal contact (either direct or radiant).
High Power LEDs LEDs designed to operate at several hundred milliamps and a watt or more of power. Since these devices create substantial heat, which would destroy the unit if special steps were not taken, specialized heat dissipation technologies must be employed.
Illuminance The intensity of light falling on a surface area. If the area is measured in square feet, the unit of illuminance is footcandles, while if the area is measured in square meters, the unit of illuminance is lux(lx).
Kelvin Temperature (K) Term used to measure the comparative color appearance of a light source when compared to absolute black.
Light Emitting Diode (LED) A Light Emitting Diode is a solid state lighting device that converts electrical energy directly into light. The semiconductor is composed of a p-region which carries positive electrical charges and an n-region which contains negative electrical charges. When the LED is turned on the electrons flow from the n-region to the p-region releasing energy that produces photons.
LED Array An arrangement of LEDs onto a printed circuit board(PCB) or other surface that is capable of producing light when powered.
LED Driver An electronic circuit that converts input power into a current source which remains constant despite fluctuations in voltage.
Lumen (lm) Unit of measurement for the total amount of visible light emitted from a source, essentially a measure of brightness.
Lumens per Watt (LPW) The ratio of light produced by an LED device, measured in lumens, divided by the power, measured in watts, required to operate the device used to measure LED performance.
Luminous Flux Measure, usually given in lumens, of the total amount of visible light.
Lux (lx) The international unit of illuminance, typically measured in lumens per square meter.
L70 An abbreviation for 70% of initial lumens levels delivered from an LED, which is a common definition of the useful life of an LED.
LED Efficiency A measure of the light output of an LED device, generally measured in lumens, divided by the power, generally measured in watts, required to operated the device.
LED Junction Temperature (TJ) The temperature of the p/n junction inside the LED. Although TJ cannot be directly measured, there are a number of widely-used, reliable methods of accurately estimating TJ.
Milliamp (mA) A measure of electrical current, the milliamp is one thousandth of an amp.
Phosphors A substance that exhibits phosphorescence, which is the process of glowing occurring after exposure to energized particles. Many white LEDs are produced by combining GaN or InGaN LEDs, which produce blue light, with YAG (yttrium aluminum garnet) phosphors.
P/N Junction The border region in a semiconductor device formed by placing P-type (or materials carrying a positive charge) and N-type (or materials carrying a positive charge) semiconductor materials together in close proximity. It is the location in an LED where light is created, as well as the location inside the LED where heat is created.
Power Factor A measure of the ratio of the real power flowing to a load divided by the apparent power. A load with low power factor draws more current than a load with a high power factor (which is generally defined as higher than 0.9) for the same amount of useful power transferred.
Power Supply A generic term for any device that supplies electrical or other types of energy to a load. In lighting, common power supplies include fluorescent and HID ballasts, various types of transformers, and LED drivers. The latter are available as devices providing either constant current or constant voltage.
Printed Circuit Board (PCB) A material used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. Common types include FR-4 (Flame Retardant 4) and metal-core PCBs.
Retrofit The retrofit LED is a bulb or trim that is designed to convert an existing line voltage luminaire housing to an energy efficient LED luminaire.
Solid State Electronic components and systems based on the use of semiconductors rather than vacuum tubes. Common types of solid state components include integrated circuits, liquid-crystal displays, and LEDs.
Thermal Efficiency A measure of luminaire efficiency that focuses on the ability of the luminaire system to transfer heat from sensitive components, such asLEDs, to the outside environment.
Volt A measurement of the electrical potential difference between oppositely charged conductors.
Voltage Electrical potential difference, which is commonly expressed as (VA − VB). Voltage is conceptualized as the electrical driving force that drives a conventional electric current in the direction A to B. LED voltage is determined by the physical structure of the semiconductor material, and the level of light produced by the LED is determined largely by the level of current flowing to the LEDs.
Watts A measure of power, or the rate of energy conversion. The watts consumed by an LED are typically derived from a relatively fixed voltage level and varying levels of current. Power (Watts) = Current (Amps) X Voltage (Volts).