Wednesday, March 23, 2016

LED lights dimming applications under the LED drive power options



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     In LED lighting applications more widely, with better than traditional lighting methods unique, in addition to improving the quality of life, improve performance and extend lamp life light source, the use of its unique function dimmable lighting color temperature and brightness changes, and fully achieve energy saving applications for its biggest advantage.

Dimming performance LED lighting but depends on the mix of LED light source and drive power.

Generally speaking, LED light source can be simply divided into two categories: individual LED diode light source with a resistor or LED diode light source, in the application, sometimes LED light source is designed as a module containing the DC-DC converter this complex modules are not within the scope of this article. If the LED light source or modules for individual LED diode itself, the common dimming method to adjust the LED input current amplitude, so the LED drive power of choice should refer to this feature, Ming-wai's HLG / ELG family is characterized by currents adjustments can only be controlled modulation of the output current from an external 1-10VDC * or 10V PWM pulse width modulation, or even through a simple external variable resistor. And the other with a resistor LED diode light source (generally referred to as LED light bar or LED STRIP), LED lights are widely used LED diode having a resistor in series, the voltage is relatively stable, so the user can access any commercially available constant-voltage power supply to drive the LED light bar. Common LED lights generally based on 12VDC or 24VDC drive, but because of the dimming applications LED light bar can be a bit difficult. This article describes the use of the current amplitude dimming drive application of the LED light bar, and also discuss some common dimming issue, and also introduced an adjustable using the output pulse width (PWM) modulated light LED power driver, Ming Wei launched by the company and access to national technology innovation award recognizes a family of PWM, is currently on the market the most appropriate and easiest LED lights dimming scheme.

Common LED dimming poor condition:

Dimming may sound like a simple thing, in fact, want to have a good and smooth dimming performance is the need to consider many factors, the situation is common LED dimming poor are many.
When using the LED output current adjustable power driver for LED lights dimming when, dead travel is a recurring problem. Although when the LED drive power is in fully loaded condition (as illustrated 1-a) can be operated when the ground is very good, but when the LED driver in a non-full, not smooth dimming state is very obvious.

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   Meanwell LED Driver HLG-100 at different loads (length) coupled to the LED status lights: (a) 100% of full load - can produce the best dimming performance; (b) 70% of the load - it shows the imperfect dimming effect; (c) 30% of the load - shows poor dimming results because dimmable too restrictive.

The output pulse width modulation (output PWM) Solutions

If you are used under full load conditions LED driver power supply LED lights dimming applications, dead travel problems would not exist. The above argument is true, but not very practical, in fact, LED lights are often used in a variety of applications (Decorative lighting / auxiliary lighting / Advertising Lighting) can not be accurately estimated at length because of circumstances, so the easiest is the best application solutions is the right choice should be an output pulse width of the PWM LED dimming drive power to achieve LED lights dimming requirements. While the output brightness is by virtue of the duty cycle of the dimming signals to achieve lower brightness dimming changes, important parameters of the drive power is dimming resolution and output pulse width modulation PWM frequency, minimum dimming capability should be as low as 0.1 %, in order to achieve 8bit dimming resolution to meet all LED lights dimming applications, the output pulse width modulation PWM frequency should be able to raise as much as possible, to prevent the table (a) said light flicker problem, according to the relevant Research reported in the literature, the frequency is recommended at least above 1.25kHz, to reduce ghosting visible to human eyes blink.

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