Adjust the forward current to adjust the brightness to change the brightness of the LED is very easy to achieve. The first thought is to change the drive current, because the brightness of the led dimming technology is almost directly proportional to its drive current.
1.1 to adjust the forward current
Current sense resistor to adjust the LED current to the most simple way is to change and LED load series, almost all DC-DC constant current chip has a detection current interface is detected by the voltage and chip internal reference voltage to control current constant. But the sense resistor value is usually very small, only a few tenths of Europe, if you want installed in the wall a few tenths of Europe’s potentiometer to adjust the current is unlikely to lead resistance there will be a few tenths of Europe. Some chips provide a control voltage interface, changing the input control voltage can change its output constant current value.
Forward current of 1.2 tone makes chromatography offset
However, to adjust the forward current to adjust the brightness will have a problem, that is, adjust brightness while also change the spectrum and color temperature. Because the white led high bay excitation with blue light LED yellow phosphor, yellow phosphor thickness without a proportionate thinning, when the forward current is reduced, the blue led high bay brightness increase, making it the dominant wavelength of the spectrum increased.
Of course, these problems in the general led dimming technology may not be a big problem. RGB LED system, however, will cause the color offset, the human eye color deviation is very sensitive, and therefore cannot be allowed.