Selection of driving power supply for LED light bar dimming application

October 31 10:04 2022

LED is more and more widely used in lighting fixtures. In addition to its unique advantages over traditional lighting methods, in addition to improving the quality of life, improving the efficiency of light sources and prolonging the service life of lighting fixtures, LED uses its unique dimming function to change the color temperature and brightness of light, and fully achieves the greatest advantage of energy-saving applications.

The dimming efficiency of LED lighting fixtures depends on the matched LED light source and driving power supply.

In general, LED light sources can be divided into two categories: single LED diode light source or LED diode light source with resistance. In application, sometimes LED light sources are designed as a module containing DC-DC converter, and such complex modules are not discussed in this article. If the LED light source or module is a separate LED diode itself, the common dimming method is to adjust the amplitude of LED input current, so the selection of LED drive power should refer to this feature.

Common LED poor dimming conditions:

When the LED power driver with adjustable output current is used for dimming LED lights, deadtravel is a common problem. Although the LED driver power supply can work well when it is in full load, it is obvious that the dimming is not smooth when the LED driver is not in full load.

Solution of Output Pulse Width Modulation (Output PWM)

If the LED driver power is used for LED light bar dimming under full load, there is no problem of deadtravel. The above argument is true, but it is not very practical. In fact, LED light strips are often used in various applications (decorative lighting/auxiliary lighting/advertising lighting) where the length cannot be accurately estimated. Therefore, the simplest and best application solution is to correctly select LED driver power with output pulse width PWM dimming function to achieve the dimming requirements of LED light strips. The output brightness can reduce the dimming change of the brightness by virtue of the load cycle of the dimming signal. The important parameters for selecting the drive power supply are dimming resolution and the frequency of output pulse width modulation PWM. The minimum dimming capacity should be as low as 0.1% to achieve the 8bit dimming resolution to meet all LED light bar dimming applications. The output pulse width modulation PWM frequency should be as high as possible, To prevent the light flicker problem mentioned in Table (I), according to the relevant technical research literature, the frequency is recommended to be at least higher than 1.25 kHz to reduce the flicker of ghosts visible to human eyes.

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