Shanghai Longmao Microelectronics Co., Ltd. Mao Yuhai
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, adjusting the current size makes it easy to adjust the brightness.
1.1.1 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 voltage detected and the internal reference of the chip. Voltage comparison to control the current constant. 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: Adjustment of the output constant current value
1.25Mm Wire To Board Connectors are avialable in different terminations and sizes intended for use on a variety of applications. These connectors provide power and signal with different body styles, termination options, and centerlines. To find the wire to board set required, click on the appropriate sub section below.
Description
1.25mm wire-to-board connector system is designed for a wide variety of applications in Industrial, Automotive, and Consumer markets.
The comprehensive range consists of terminals, crimp housings and PCB headers in straight and right angle, surface mount and through-hole configurations. It is available in 2 to 15 circuits in a single row. 1.25mm wire-to-board solution conforms to the EU Industry Safety Standard. Pcb Header material meets halogen-free requirements and can be operated in the temperature range from -40°C to +105°C.
Saves space with a 1.25mm pitch
Suitable for Industrial, Automotive, and Consumer markets
Crimp housing with friction feature
Conforms to EU Industry Safety Standard
Accommodates wire range up to 32AWG-28AWG
Features
Three plating versions - Tin 15μin Gold, 30μin Gold and Gold Flash
Fully polarized housings
Crimp housing with friction feature
Tape and Reel packaging with pick up cap
UL94V-0 flammability rated LCP material
Halogen-free resin material
RoHS compliant and lead-free
Benefits
Supports applications in a wide range of environments
Prevents accidental mismating
Provides additional retention and prevents harness-to-header mismating
Pick and place for SMT production process
High flammability rating
Meets environmental requirement
Meets environmental, health and safety requirement
Applications
Consumers
Car Audio
Industrial & Instrumentation
Industry Control
Instrumentation/Metering
Office Equipment
Small Motor/Robot Control
Security
Alarm Systems
Vending POS Machine
1.25mm Wire To Board Connectors
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ShenZhen Antenk Electronics Co,Ltd , http://www.antenk.com