Dimmer, change the luminous flux of the light source in the lighting device, and adjust the level of illumination. The purpose of the dimmer is to adjust the brightness of the light. By reducing or increasing the RMS voltage to cause the average power of the light produced by the different intensity of the light output. Although variable voltage devices can be used for a variety of purposes, this regulation is intended to control lighting.
There are three types of LED dimmer:
1. Pulse width modulation (Pulse Width Modulation, referred to as PWM) will power the square wave digitization, and control the square wave duty cycle, so as to achieve the purpose of control current.
2. Constant current power regulation Analog linear technology can easily adjust the size of the current.
3. Group control will be more LED grouping, with a simple packet control.
The above 1.2. Two methods can be used to adjust the adjustable resistance knob for stepless control. As the PWM module technology mature, cost reduction. It is difficult to determine from the price side is the use of what way the flow control. However, the adjustable resistor itself is not a very reliable component. Often because of the dust into the manufacturing process or not tight, in the operation of adjustable resistance when there will be a moment of jumping fault, then the light will flash. This flashing in the case of PWM is less obvious, in the use of linear technology to control the current situation is more obvious.
Regardless of the way in which the current is regulated, it can be changed to a Tact Switch or a separate packet switch (eg a packetizer, remote control) to control the light. This quality is relatively reliable, the service life is much longer. It is necessary to use adjustable resistance to do fine lighting control, it is recommended to use high-quality adjustable resistance (usually a few dollars to 10 dollars).
Whether the LED is driven by a buck, boost, buck / boost or linear regulator, the most common thread that connects each drive circuit is the need to control the output of light. Today, only a very small number of applications only need to open and close the simple function, the vast majority need to 0 ~ 100% to fine-tune the light. At present, for the photometric control, the main two solutions for the linear adjustment of the LED current (analog dimming) or in the naked eye can not detect the high frequency, so that the drive current from 0 to the target current value between the switch back and forth (digital Light). The use of pulse width modulation (PWM) to set the cycle and the duty cycle may be the simplest way to achieve digital dimming, because the same technology can be used to control most of the switching converters.
Dimming system introduction:
Slotted switch dimming:
The use of the wall of the ordinary light switch can achieve 4-channel dimming, the first open for the whole light, the second open 60% brightness, the third open for 40% brightness, the fourth open to 20% brightness. The advantage of this system is that you can use ordinary wall switches to achieve dimming. And its power factor up to 0.92 or more. There is no interference signal generated. The disadvantage is that it can not be dimmed continuously. There are some trouble operating.
Remote control dimming:
Infrared remote control to achieve dimming LED. This is of course the ideal solution. Can be realized switch lights, and with PWM continuous dimming. The disadvantage is the high cost, there is no uniform specifications, can only be used for high-end residential.
In fact, we should come back to think about what we want to be the main purpose of dimming. All of the previously mentioned dimming purposes are designed to meet the needs of home people in different occasions need different light intensity. For example, when watching TV may be dark, read the time may be bright. Most of these are in the house. Very few offices, shopping malls, factories, schools installed dimming lights. And the vast majority of these places are installed fluorescent lamps, energy-saving lamps, it is impossible to dim or difficult to achieve continuous dimming.
Epoch-making for energy saving and dimming:
Since human consciousness must do everything possible to reduce energy consumption, in order to solve the urgent problems of atmospheric warming, how to reduce lighting electricity as an important issue mentioned on the agenda up. Because the lighting power consumption accounted for 20% of the total energy consumption.However, there has been a highly efficient energy-saving LED, LED itself more than 5 times more energy than incandescent than fluorescent lamps, energy-saving lamps have to save about twice, not like fluorescent lamps, energy-saving lamps Containing mercury. If you can also use dimming to save energy, then it is also very important means of energy conservation. But in the past all the light is very easy to achieve dimming, and easy dimming LED is a great advantage. Because in many occasions it is not necessary to turn on the lights or at least not so bright, but the lights are very bright, such as the middle of the night to the dawn of the street lights; subway car from the ground to the suburbs of the ground when the car lights; Is in the sunny hours near the window of the office, schools, factories and other fluorescent lights are still open there. These places do not know how much energy to waste every day! In the past because of high pressure sodium lamp, fluorescent lamps, ceiling lamps, energy-saving lamps can not be dimmed, can only forget. Now switch to LED, you can freely dimmer, and these energy can be saved down. So for the dimming light, the family wall dimming is not the main application, the market is also very small. But is the street lights, offices, shopping malls, schools, factories on-demand dimming is more important occasions, not only the market is huge, and energy-saving considerable. These occasions do not need manual dimming but automatic dimming, intelligent dimming.
In general, the street lights to the middle of the night after no use, so the usual practice is to turn off the lights after 12 or half of the brightness. But the most reasonable approach is based on traffic flow to control the brightness of street lamps, and even fully adaptive control of brightness.
And in order to achieve this intelligent dimming, in fact, is also very simple. As long as the region's traffic flow statistics curve into a single-chip, according to the curve given PWM dimming signal to the constant current drive source can be achieved.
Photosensitive automatic dimming LED lights:
In order to reduce unnecessary lighting in strong sunlight, you can use light-sensitive auto-dimming LED fluorescent lamp (or any other LED lamps).
The effect of the photosensitive element is to feel the surrounding daylight, and if the daylight is stronger, then a PWM signal is output to all the LED lamps near the daylight (such as the LED fluorescent lamp), and their brightness is dimmed. A dimming signal generator can adjust a lot of LED lamps, as long as these lamps constant current drive source with PWM dimming control interface. The efficiency of this dimming system itself is as high as 92% or more. And there is no compatibility with any of the walled thyristor lines. This automatic energy-saving dimming is any fluorescent lamp, energy-saving lamps, high pressure sodium lamp and other gas discharge tube simply can not be achieved, but it is the best LED lights.
Today's LED industry, I am most optimistic about the temporary LED dimming technology and LED drive power. LED driver power supply mainly for the aspects of LED lights power. And this time we mainly say that LED dimming technology. At present, LED dimming technology mainly has the following kinds:
1: SCR dimming This development in the incandescent dimming technology, because the incandescent lamp for the pure resistive load, the use of SCR chopping technology, can successfully achieve dimming, but the LED is not practical, from the At present, compatible with thyristor dimming power supply, usually very low efficiency, 80% are difficult to achieve, which is contrary to the original intention of LED energy saving, and secondly, it is difficult to achieve high power factor, again, only work in a single Of the input voltage, this dimming technology will die due to the extinction of incandescent, but because of the high market penetration, there will be a period of time.
2: linear dimming using constant current chip dedicated dimming feet, adjust the LED current, to achieve the purpose of dimming, this technology is good, but the wiring is complex, is not conducive to fluorescent lamps and other lighting, lamp a lot of this method.
3: PWM dimming This method is similar to linear dimming, and with the linear dimming together to occupy most of the lights table lamp. This PWM dimming user and customer are also very happy.
4: remote control dimming infrared remote control and wireless remote control two, to achieve more complex, but can be achieved to change the color temperature, color and other dimming methods can not achieve the effect, the current mainly for panel light dimming, there are some bulbs The lights use some dimming methods.
5: Section dimming This dimming method utilizes the switch on the wall of the switch for a specified period of time to achieve the purpose of dimming. The advantage of this method is that no additional dimming elements are required, according to the existing installation method, Can be achieved dimming, and the other, because the dimming entirely by the power switch chip internal control, full voltage range, regardless of what kind of brightness, can achieve high efficiency and high power factor, the disadvantage is only in advance Set the brightness cycle adjustment, can not achieve stepless dimming, there is, at present, such a small number of IC types, and the current regulation rate is not satisfactory, but I think with the technology mature, IC manufacturers will be more Home improvement, personal feel that this dimming technology, will become the mainstream of dimming technology.
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