Drive power selection for LED dimming application
LED is more and more widely used in lighting, and it is superior to traditional lighting. In addition to improving the quality of life, improving the efficiency of the light source and prolonging the life of the lamp, it uses its unique dimming function to change the color temperature and brightness of the light, and fully achieves energy-saving application as its biggest advantage.
The dimming efficiency of LED lighting fixtures depends on the matching LED light source and driving power supply.
In general, LED light sources can be divided into two simple categories: LED diode light sources alone or LED diode light sources with resistors. In applications, LED light sources are sometimes designed as a module containing a DC-DC converter. Such complex modules are beyond the scope of this article. If the LED light source or module is a single LED diode itself, the common dimming method is to adjust the amplitude of the LED input current, so the selection of LED driving power should refer to this feature. The mingwei HLG/ELG family features current adjustment and can be controlled by external 1-10VDC* or 10VPWM pulse width adjustment or even by a simple external variable resistor. And another LED diode light source with a resistor (generally known as LED strip or LEDSTRIP), LED strip is widely used with LED diode series resistance, so the voltage is relatively stable, so the user can use any fixed voltage power supply to drive the LED strip. The common LED strip is usually driven by 12VDC or 24VDC, but it may be difficult to apply the dimming of the LED strip. In this paper, the application of current amplitude dimming driver in LED strip is explained, and some common dimming problems are also discussed. Meanwhile, the DIMming LED power driver with output pulse width modulation (PWM) is introduced. The PWM family, which is launched by Mingwei Company and has won the national Technical Innovation product award, is introduced. It is the most appropriate and simplest LED strip dimming scheme on the market.
Common poor LED dimming conditions:
Dimming sounds like a simple thing, but in fact many factors need to be considered in order to have good and smooth dimming performance. There are many common cases of poor LED dimming, as shown in table 1 below:
Table 1: Common dimming problems
Deadtravel is a common problem when dimming LED lights using an LED power driver with adjustable output current. Although the LED driver works well when it is fully loaded (as shown in Figure 1-a), poor dimming is evident when the LED driver is not fully loaded.
Output pulse width modulation (output PWM) solution
Deadtravel is not an issue when using LED drive power for LED strip dimming applications under full load conditions. The above argument is true, but it's not very practical. In fact, LED strips are often used in a variety of applications (decorative lighting/auxiliary lighting/advertising lighting) where the length cannot be accurately predicted. Therefore, the simplest and best application solution is to correctly choose the LED drive power supply with output pulse width PWM dimming function to achieve LED strip dimming requirements. The output brightness depends on the load cycle of the dimming signal to achieve the dimming change of reduced brightness. The important parameters for selecting the driving power supply are the dimming resolution and the output pulse width to adjust the PWM frequency. The minimum dimming capacity should be as low as 0.1% to achieve 8bit dimming resolution to meet all LED light bar dimming applications. Output pulse width modulation PWM frequency should be as high as possible to prevent table (1) mentioned light flicker problem, according to relevant technical research literature reports, recommended frequency at least higher than 1.25kHz, to reduce the visible ghost flicker.
The best LED strip dimming solution is to use the output pulse width modulation PWM dimming function to solve the common deadtravel dimming problem. The PWM models provided by Mingwei company cover 40/60/90/120W and other four series, which are very suitable for various LED dimming applications.