The development of LED lighting dimming function is also one of the keys to its ability to further replace traditional lighting. Needless to say, LED lighting is definitely the future trend. The reasons for this observation include the long life of LED lighting, power saving and reliability. . That is, LED lamps can not only light or dark two options, but must be like traditional incandescent lamps can provide dimming function, so that LED lamps have the advantages of both traditional lighting and LED lighting, it will inevitably promote LED lighting more popular. On the whole, with the rapid development of the LED lighting application market and the continuous expansion of the application range, the demand for products has been continuously increased. In the LED lighting terminal products, the need for LED brightness adjustment of this function has also become necessary. It will be a topic that needs continuous attention from suppliers of LED lamps and related components.
For example, in the lighting of street lamps, with the development of technology, when the service life and stability reach a certain level, whether or not the street lamp is dimmable will become another emphasis. Basically, although LED street lighting standards are not yet complete and product specifications vary from place to place, more and more LED street lamp manufacturers have incorporated intelligent control into one of their LED street light functions for power management and future maintenance. From the point of view, the intelligentization of LED street lights is also imperative. Its function is to determine whether or not a human vehicle passes light control according to the needs of the environment, so as to increase the service life of LED lights and achieve energy saving effects.
For the necessity of LED street light dimming function, Everlight Electronics stated that the company launched a second generation of new Dolphin LED street lamps, lighting efficiency up to 100lm / W, and equipped with adjustable light control function, according to the current ambient brightness adjustment LED Brightness, this design can save unnecessary power waste. Another example is the new LED street light special power supply that Jinruitong Technology recently announced, which is mainly aimed at improving the current market as a dimming control but cannot achieve a constant voltage. This power supply can be performed under a certain voltage. Dimming, providing linear changes in the signal control, the output of the constant current can correspond to the control signal for linear changes in the adjustment, to adjust the current intensity does not produce electromagnetic interference effects.
It is understood that based on the LED street light system developed by this power supply, about 75% of the electricity can be saved. In addition, Shenzhen Spark's upgraded version of the LED street light also uses a new intelligent drive power, the introduction of a central control system, remote monitoring of the light fixtures, can instantly adjust the brightness of the light (0-100%). The company stated that by setting the LED lamps, the LED lights can maintain strong illuminance during busy periods, and automatic dimming can be started when there are few people in the middle of the night, so that the LED street lights can maintain illumination with low illuminance. Overall, the main advantage of intelligently controlling LED street lamps is that they can significantly reduce the consumption. Of course, not only LED street lights need to have a dimming function, LED lighting in other various application fields is also gradually required to have a dimming function. Basically, LEDs use the constant current method to adjust the LED output brightness as the most effective method at present. The method can be divided into analog (Analog) current regulation and Pulse-Width Modulation (PWM).
Two different ways of dimming
First of all, the analog dimming mode uses the current size adjustment method to change the peak value of the LED forward current so as to achieve different brightness adjustments. For example, by reducing the forward current of half the LED, you can get half the brightness. However, this method may cause Peak Wavelength or ColorShift. In addition, the pulse width modulation (PWM) dimming technology uses continuous ON and OFF switching methods to change the duty cycle of the LED forward current. This technique does not change the forward current peak. This method can avoid peak wavelength or color shift problems, and has a linear dimming function that can effectively reduce power consumption.
In summary, PWM dimming can significantly reduce LED color variations and have different brightness levels, providing additional logic to establish PWM wavelengths. Analog dimming is a relatively simple circuit, but it is not suitable for applications that require a constant color temperature. In terms of the dimming response time, PWM dimming is widely used in practical applications due to its fast response speed and ability to dim more accurately. Many semiconductor companies have launched relevant driver ICs for PWM dimming needs. Tony Armstrong, director of product marketing for Linear's power products division, pointed out that one of the key performance features that today's LED driver ICs must have is to fully tune the LED. Light. With the increase in demand for high-brightness (HB) LEDs, Linear Technology has also introduced a corresponding product. For example, the LT3956 can be dimmed by TrueColor pulse width modulators (PWM), and can be used for dimming up to 3,000 to one. Provides fixed LED color in the range.
Spark Opto LED street light - intelligent drive power
In addition, NXP has also performed excellent work in the field of LED dimming. The company's dimmable LED solution SSL2101 is a small-sized switch mode power supply (SMPS) controller IC designed to drive LED devices. And design, and provide dimmable capabilities. SSL2101 can drive a variety of lighting systems with different power requirements, including LED retrofit lamps, LED modules, LED spotlights, spotlights, and LED light strings for store displays. The company stated that the NXP SSL2101 is fully compatible with today's lighting infrastructure, can use rectified mains power directly in conjunction with phase dimmers, and contains a high voltage power switch that can be started directly from the rectified mains voltage, eliminating the need for an external startup circuit. To support dimming capabilities, the SSL2101 also includes two integrated high-voltage switches for voltage divider operation and one input to sense real-time lamp power and initiate additional voltage divider operation when needed.
It is worth mentioning that NXP agent - Pinjia company has applied SSL2101 dimming IC to complete the LED dimming bulb lamp DEMO, while using Samsung's 2W LED light source (2W LED luminous flux reaches 150LM), it can With the existing dimming system, the LED bulb light can be continuously adjusted in the range of 0%-100%, and the efficiency can reach over 70%. The power supply drives three 2-watt Samsung LEDs with a total power of 6 watts and an input voltage of 220V and an output of 0.18A/30V.
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