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The principle of led color temperature adjustment brightness

Mar 26, 2019

The principle of led color temperature adjustment brightness


Led color temperature is the ratio of changing different light. Increase red light, warmer color temperature, increase blue light, and cool color temperature. Adjust the brightness, change the current flowing through the LED, the current is larger, it will be brighter. On the contrary, it is darker. The regulation of the current is achieved by changing the PWM. The so-called PWM is the pulse width adjustment. The method of pulse width adjustment, the most fundamental is to change the value of the resistance and capacitance value that determines its width. If the product of RC is large, the width will be larger. The specifics should be discussed in conjunction with the circuit diagram.


1 color temperature

The color temperature of the light source is an ideal model, also called a complete radiator, by comparing its color and theoretical thermal black body radiator (abbreviated as black body, the absorption rate of radiant energy at any temperature is equal to 1 at any temperature). ) to determine. The spectrum emitted by the heat radiation source is continuous and smooth. For the black body, the temperature is different and the color is different. There is a unique correspondence between the color of the black body and the temperature.


When expressing the color of a light source, the color of the light source is often compared with the color of the blackbody. If the color of the light source is the same as the color of the blackbody at a certain temperature, the color of the light source is regarded as a black body. The color at this temperature is called "temperature color", referred to as "warm color". Obviously, "warm color" refers to "color", which is the color of a black body at a certain temperature. However, due to long-standing conventions, this concept is now commonly referred to as "color temperature."


For incandescent lamps and other thermal radiation sources, because their spectral distribution is close to that of blackbody, their chromaticity coordinate points are basically on the black body trajectory, and the concept of visible color temperature can properly describe the light color of incandescent lamps.


However, for other lights other than incandescent lamps, the spectral distribution is far from the black body, and the chromaticity coordinates determined by the relative spectral power distribution at their temperature T do not necessarily fall accurately on the black body temperature trajectory of the chromaticity diagram. The color temperature of the light source can only be determined by the color of the light source and the black body trajectory, which is called the correlated color temperature (CCT).