Author: Shandong Wang Xiufeng
In terms of luminous efficiency, commercial LEDs are 30 to 501 m/W, which is superior to incandescent lamps, second only to fluorescent lamps. 1001m/W LEDs will be put on the market soon.
The US semiconductor lighting research and development project has a luminous efficiency of 200 lm/W, which is almost twice as high as that of high-pressure sodium and metal halide lamps. Two or three years ago, the operating current of LEDs generally did not exceed 30 mA. The Luxeon LEDs that Lumileds Lighting put on the market have white, blue, red, green and other light colors. LEDs with operating currents of 220mA, 350mA, 500/550mA and 700mA, 1000mA will soon be commercialized. This high-current LED can replace incandescent and tungsten halogen lamps for landscape lighting, automotive and indoor lighting .
Figure 1 shows an LED driver circuit consisting of a step-down transformer and a bridge rectifier filter circuit. The LXHL-MWlD has an operating current of 350mA and a forward voltage drop of 3.5V. This kind of driving circuit is relatively simple, but the current regulation rate can be higher than ±25% when the AC voltage changes by ±10%. At the same time, when the AC voltage rises instantaneously, the LED is easily damaged.
Figure 2 shows an LED driver circuit using a flyback switching regulator. The switching power supply input is 180 ~ 265VAc, the output voltage is 3.5V (drive one LED) ~ 28V (drive 8 LED), the output current is 350mA. In the picture.
ICl is an intelligent power switching regulator integrated with PWM control circuit and 730V/10.7A power MOSFET produced by ST. IC2 is TSMll01l with built-in 2.5V reference voltage and dual comparator. R6 in the secondary circuit of the transformer is a current sampling resistor, which forms a current control loop with a current comparator in IC2. The voltage dividers R4 and R5 and the voltage comparators in IC2 form a voltage control loop. Secondary to primary feedback is achieved by optocoupler IC3.
The circuit efficiency of Figure 2 is more than 80%, and provides constant current and constant voltage working conditions for the LED. If you use TSMl04 instead of TSMlloll, you can also achieve O% ~ 90% dimming function.
In addition, ON Semiconductor has designed an integrated current source NUD4001 for 350mA LEDs. Power consumption can be reduced, but a power frequency power transformer is still required.
Rocker Switches
Rocker Switches is also called a boat switch, an IO switch, and a power switch. The structure of the rocker switch is the same as that of a Toggle Switches and Slide Switches, except that the handle of the rocker is replaced by a ship. This On Off Rocker Switches often used as the power switch of electronic equipment. Its contacts are divided into single-pole single-throw and double-pole double-throw, and some switches also have indicator lights.
It is a household circuit switch hardware product. Custom Rocker Switches are used in drinking fountains, treadmills, computer speakers, car batteries, motorcycles, plasma TVs, coffee pots, plugs, massage machines, etc., involving commonly used household appliances.
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