LED theory


Forward current, which flows across the LED module, so that the LED will receive sufficient energy to emit light. In MST module marked value of If should be divided by the amount of strings in a specific product to have a value of single LED current.


Forward voltage, which must be applied across the LED module, in order to turn the LED on. In MST module marked value of Uf should be divided by the amount of diodes connected in series in a specific product to have a value of single LED voltage.


Highest permissible current flowing through the LED module. Operating the LED beyond the listed maximum ratings may affect module reliability and cause permanent damage.


Temperature at the Tp-point is maximum operated temperature to which the rated performance characteristics are declared by the manufacturer. Temperature at Tp is relevant to the light output and life time of a LED module. For the MST LED module product’s Tp point is placed at the same point as Tc.


Highest permissible temperature which may occur on the outer surface (at the indicated place) under normal operating conditions. Tc is measured at thermally stable condition.


Colour Rendering Index is a quantitative measure of the ability of a light source to reproduce the colours of illuminated objects accurately when compared to a reference light source.


Correlated Colour Temperature of a light source is the temperature of an ideal black-body radiator that radiates light of comparable hue to that of the light source. Colour temperature gives a numerical estimate of what reference light source best approximates particular artificial light.


Standard Deviation of Colour Matching – has the same meaning as a "MacAdam" ellipse and refer to the size of an ellipse around the black body locus. Staying within this ellipse results in a consistency of light which ensures that no colour difference is perceivable between one LED line and another with the naked eye in most applications.


Global consortium of the light industry. Its overall aim is to develop interface specifications that allow LED light sources from different suppliers to be used interchangeably, without changing the luminaire design. Zhaga standard specific cover physical dimensions as well as photometric, electrical and thermal parameters of LED light engines.