As a light source, dimming is very important. Not only to get a more comfortable environment in the home, today, the purpose of reducing unnecessary electric light to further achieve energy saving and emission reduction is even more important. Moreover, for LED light sources, dimming is easier to implement than other fluorescent lamps, energy-saving lamps, high-pressure sodium lamps, etc., so it is necessary to add dimming function to various types of LED lamps.
The first part adopts the dimming technology of DC power LED
one. Adjust the brightness by adjusting the forward current
To change the brightness of the LED is very easy to achieve. The first thing that comes to mind is to change its drive current because the brightness of the LED is almost directly proportional to its drive current. Figure 1 shows the relative intensity and forward current of Cree's XLampXP-G output.
Figure 1. The relationship between the relative intensity and forward current of the XLampXP-G output.
As can be seen from the figure, if the light output at 350 mA is taken as 100%, the light output at 200 mA is about 60%, and at 100 mA is about 25%. Therefore, the current can be adjusted easily by adjusting the current.
1.1 Method of adjusting forward current
The easiest way to adjust the LED current is to change the current sense resistor in series with the LED load (Figure 2a). Almost all DC-DC constant current chips have an interface for detecting current, which is the detected voltage and the internal reference voltage of the chip. Compare to control the constant current. However, the value of this sense resistor is usually very small, only a few ohms. If you want to install a potentiometer of a few ohms on the wall to adjust the current is not possible, because the lead resistance will also have a few ohms. Therefore, some chips provide a control voltage interface, which can change the output constant current value by changing the input control voltage. For example, Linear Technology's LT3478 (Fig. 2b) can change the constant current value of its output as long as the ratio of R1 and R2 is changed.
Figure 2 Output constant current value adjustment
4 years of manufacturing experience. High cooler rendering index luminous efficiency with soft light output. PC shade high transmittance, weather resistance high cooler rendering inde luminous. Efficiency with soft light output. Low power consumption.Lower heating during operation. Lumen decay: 3 within 1000 hours. Then Lumens be stable. Low power consumption.Lower heating during operation.Lumen decay: 3 within 1000 hours. Then Lumens be stable. No mercury, enviromental protection. The shell of LED Downlights adopt integrated design, it optimize efficiency of heat dissipation.
*Related Products:exterior downlights,Dimmable LED Downlight,light fittings,detachable led,led recessed light,adjustable downlight.
Led Downlights,Dimmable Downlight,Smd Downlights
SHENZHEN KEHEI LIGHTING TECHNOLOGY CO.LTD , http://www.keheiled.com