LED Glossary 

Wattage (W)

The unit of electrical power consumed by an electrical device during its operation. Many lighting sources come with rating in watts to indicate their power consumption. A light source with higher lumen per watt value is more efficient. For example, a standard halogen or incandescent bulb operate at 50W, while a LED offers the same brightness but using only approximately a quarter of the watts or less.

Ampere (A)

The ampere is a measure of the amount of electric charge passing a point in an electric circuit per unit time

Voltage (V)

The term used to designate electrical pressure or force that causes electrical current to flow.

Luminous Flux

Luminous flux is a quantitative expression of the brilliance of a source of visible light, which is electromagnetic energy within the wavelength range of approximately 390 nanometer s (nm) to 770 nm. This quantity is measured in terms of the power emitted per unit solid angle from an isotropic radiator, a theoretical point source that radiates equally in all directions in three-dimensional space. The standard unit of luminous flux is the lumen (lm).

Luminous Intensity

Luminous intensity is an expression of the amount of light power emanating from a point source within a solid angle of one steradian. The candela was defined and adopted as the standard unit of luminous intensity. One candela (1 cd) is the magnitude of an electromagnetic field ( EM-field ), in a specified direction, that has a power level equivalent to a visible-light field of 1/683 watt (1.46 x 10 -3 W) per steradian at 540 THz.


Luminance is the luminous intensity, projected on a given area and direction. Luminance is an objectively measurable attribute. The unit is 'Candela per Square Meter' (cd/m2). So, different monitors can be adjusted to the same luminous intensity by measuring the luminance in cd/m2.


Illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception.

Colour Temperature

Colour temperature is a simplified way to characterize the spectral properties of a light source. While in reality the colour of light is determined by how much each point on the spectral curve contributes to its output, the result can still be summarized on a linear scale. Standard unit for colour temperature is Kelvin (K).

Colour Rendering index

Effect of an illuminant on the colour appearance of objects by conscious or subconscious comparison with their colour appearance under a reference illuminant. The Standard unit for colour temperature is Ra.

Lumen (lm)

The unit of measurement to express how much illumination a light source produces.

Lumen Depreciation

The percentage of light lost relative to the original lumen output.

Luminous Efficacy

Refers to the light output in lumen (lm) divided by the total electrical power input in wattage (W) to the light source, that is expressed in lumens per watt (lm/W). It measures how efficient the light source is, the higher the lumen and the lower the wattage, the more efficient it is.

Beam Angle

Beam angle is the measure of distribution of light, which is measured in degrees. Beam angles are commonly 80, 90, 120 degrees depending on the type of luminaire. This is controled by type of shade that is attached to the LED unit.


An electronic circuit that is used to reduce the voltage in order to allow specific luminaire to work. For example, a 12V Lamp requires a driver/transformer to reduce the voltage from 110 ~ 240V to 12V in order for it to operate. It also protects the lighting product from voltage fluctuations, over-voltages and voltage spikes.

Lamp Starter

A lamp starter is used in conjunction with a ballast to preheat the traditional fluorescent tube in order to light up the tube.

Heat Sink

A heat sink is a passive heat exchanger that cools a device by dissipating heat into the surrounding medium. Heat sinks are used with high-power semiconductor devices such as power transistors and optoelectronics such as lasers and light emitting diodes (LEDs), where the heat dissipation ability of the basic device is insufficient to moderate its temperature.

Surface Area Technology

Surface-Mount Technology or known as SMT is in which LED components are bonded onto a PCB for better heat dissipation and higher component density. This technology has now surpass the Through-Hole Technology in terms of overall performance and quality such as higher energy efficiency, higher lumen output, higher CRI, slower lumen depreciation for commercial and residential lighting applications.


COB or also known as Chip-On-Board is a new technology in which multiple LED chips are packaged as one lighting module. Technology provides significant advantages over surface mount technology (SMT). It has better temperature management, smaller LED module for greater lumen output and energy efficiency.

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