Selection Of Driving Power Supply For LED Light Bar Dimming Application
- Dec 29, 2018 -

The application of LED in lighting lamps is more and more extensive, and it is superior to the traditional lighting mode. In addition to improving the quality of life, improving the efficiency of light source and prolonging the life of lamps, it uses its unique adjustable light function to change the color temperature and brightness of lights, and fully achieves the greatest advantage of energy-saving application.

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

Generally speaking, LED light sources can be divided into two categories: single LED diode light source or LED diode light source with resistance. In application, sometimes the LED light source will be designed as a module with DC-DC converter. Such complex modules are not discussed in 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 input current of the LED, so the choice of the LED driving power supply should refer to this characteristic. The HLG/ELG family of Mingwei Company is characterized by adjustable current, and can be controlled by external 1-10VDC* or 10VPWM pulse width modulation or even through a simple external variable resistance. Modulation. Another kind of LED diode light source with resistors (commonly known as LED lamp bar or LED STRIP), LED lamp bar is widely used with LED diode series resistance, so the voltage is relatively stable, so users can use any fixed voltage power supply on the market to drive the LED lamp bar. Common LED lamp is usually driven by 12VDC or 24VDC, but it may be difficult to use in the dimming of LED lamp. This paper describes the application of current amplitude dimming driver in LED lamp bar, and also discusses some common dimming problems. At the same time, it introduces the dimming LED power driver with output pulse width (PWM) modulation. The PWM family series introduced by Mingwei Company and affirmed by the National Technology Innovation Product Award is the most suitable and simplest LED lamp on the market at present. Dimming scheme.

Common poor LED dimming conditions:

Dimming sounds like a simple thing. In fact, many factors need to be considered in order to have a 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

Deadtravelling is a common problem when using an LED power driver with adjustable output current to dim the light of an LED lamp. Although it works well when the LED driver power supply is fully loaded (as shown in Fig. 1-a), when the LED driver is not fully loaded, it is obvious that the dimming is not smooth.


Figure 1: The bright-weft LED driver HLG-100 is connected to the LED lamp bar under different load (length): (a) 100% full load - can produce the best dimming performance; (b) 70% load - shows the imperfect dimming effect; (c) 30% load - shows the poor dimming result, because the dimming range is too narrow.

Output Pulse Width Modulation (Output PWM) Solution

If the LED driver power is used to dim the light of the LED lamp under full load, there is no deadtraveling problem. The above argument is correct, but it is not very practical. In fact, LED light bars are often used in various applications (decorative lighting/auxiliary lighting/advertising lighting) because the length can not be accurately predicted, so the simplest and best application solution is to correctly select the LED driver power supply with output pulse width PWM dimming function to achieve the dimming requirements of LED light bars. The output brightness can be reduced by the load cycle of dimming signal. The important parameter of driving power supply is the frequency of dimming resolution and output pulse width modulation PWM. The lowest dimming capability should be as low as 0.1%. The dimming resolution of 8 bits can meet all LED lamp bar dimming applications, and the output pulse width modulation PWM frequency should be as good as possible. It can be improved to prevent the glint problem mentioned in Table (1). According to the related technical research literature, the frequency is recommended to be at least higher than 1.25 kHz in order to reduce the ghost glint visible to the human eye.


The best LED lamp dimming scheme is to use output pulse width modulation PWM dimming function to solve the common deadtravelling dimming problem. The PWM model provided by Mingwei Company covers four series, such as 40/60/90/120W. It is a very suitable LED driver for various LED lamp dimming applications.