At present, in the Australia, Europe and the United States market， the people demand for the dimming products. Europe has a smaller market, but it also accounts for a large share. Most of the dimming products are used with the Triac dimmer. Therefore, the research on LED lighting products for Triac dimming is very meaningful. In recent years, with the rise of the global led commercial lighting market, many led manufacturers, including China, have led commercial lighting products in the market development of an important position. Especially because of the recent Japan, Europe and the United States and other major markets on LED lighting products, high efficiency, long-life, high-power factor, flexible expansion, adjustable light and so on, making the LED driver IC and the power industry is facing a new change. Therefore, in the next two years, LED lighting intelligent dimming, especially in commercial lighting application of the proportion will be expected to be rapidly improved.
The main challenge now is that led light source prices are falling, but there is not much innovation in driving electronic technology, prices have been high, the cost of pressure. Second, due to the LED lighting more use of current-driven mode, and the existing dimmer is mostly voltage dimming, so in the compatibility of the challenge is quite large. In addition, the trend of the light power supply also requires the LED driver to have a smaller volume. As consumers, LED lighting products need to be driven by the use of IC dimming technology to provide consumers with unique sensory experience.
According to the survey report, the U.S. market is currently the demand for dimmer products, almost 100% are dimming products. Europe has a smaller market, but it also accounts for a larger share. In addition, smart LED bulbs are likely to appear large-scale commercially this year. And most of these dimming products are used in conjunction with the Triac dimmer. Therefore, the research on LED lighting products for Triac dimming is very meaningful.
1. Introduction of Triac Dimming
Analysis of traditional dimming system, such as incandescent lamp, halogen light, because compared with LED lights, incandescent and halogen lamps are pure resistive devices, which means that its current waveform and voltage waveform is always the same, when the use of Triac to adjust the light, the input voltage waveform due to Triac conduction angle change and deviate from the sine wave, That is to change the effective value of input voltage, you can achieve the purpose of dimming.
The controllable silicon potentiometer has a switch that is connected to the input end of N and is used to control the switch of the lamp. In the controllable silicon conduction process, changing the pressure ratio of the internal adjustable resistor, changing its conduction angle, can change its output voltage valid value, thus realizes the dimming function. In addition to Triac, there are transistor cutting edge, and later along the dimming technology, the basic principles are similar. 2. The shortcomings and problems of Triac dimming
When dimming with Triac dimmer switch, there will be a series of problems as follows.
(1) During the dimming process, with the change of the internal conduction angle, the input voltage sine wave is destroyed by Triac, which reduces the power factor value (PF), usually PF is less than 0.5, and when dimming, with the smaller conduction angle, the lower the power factor value (1/4 brightness is only 0.25).
(2) If the sine wave of the input voltage is destroyed, the sinusoidal waveform increases the harmonic coefficient.
(3) The input of non sinusoidal voltage waveform in LED drive circuit will cause serious interference signal (EMI) on the line.
(4) During the dimming process, it is easy to maintain the unstable current due to the low load, and the solution is to add a discharge resistor. Normally this discharge resistor consumes at least 1-2 watts of power, which reduces the efficiency of the constant current source circuit.
(5) When the Triac dimming circuit is used to adjust the light of the incandescent lamp, when the input-end LC Filter and Triac are oscillating, the human eye cannot see the oscillation due to the thermal inertia of the incandescent lamp. When the Triac dimming circuit and the LED driving circuit supporting the use, will produce audio noise and flicker, this is often unacceptable.
3. The advantages of Triac dimming
Lighting market development so far, although the Triac dimming there are many shortcomings and problems, but because of its long history, mature technology and stable, and incandescent lamps and halogen lamp perfect combination, occupies a very large dimming market. In most areas of dimming, where Triac dimming incandescent bulbs or halogen lamps have been installed, consumers have installed two of connecting wires to the luminaire on the walls, as well as the switch boxes and knobs of the Triac dimmer on the walls. For consumers, if you can simply replace the incandescent lamp or halogen light on the lamp, instead of replacing the Triac switch on the wall or the number of additional connections, it is a simpler solution and is acceptable to the more general consumer. This means that the LED lighting products really need to be compatible with the Triac dimming if they want to replace incandescent lamps and halogen lamps fully with the tunable light applications that match the Triac dimmer. This is also the current LED driver IC developers and designers have to face a common problem. How to develop a suitable IC is very important for Triac dimming and special driving mode of LED.
4, compatible with Triac dimming problems and shortcomings
So far, many big chip companies have introduced chips and solutions specifically compatible with existing Triac dimming, but there are still some drawbacks to these solutions. At the same time, compatible with Triac dimming LED is still in the market is limited, market acceptance is not so high, the reasons are as follows:
(1) The development of controllable silicon technology has been a obsolete technology for more than half a century. It has many shortcomings as deTriacibed earlier and is a technology that should be eliminated early. Social development requires a more advanced and smarter product to replace it.
(2) Currently compatible with Triac dimming LED driver IC, many claiming to have a PFC, can achieve a higher power factor, in fact, it only improves the load of the power factor, so that the overall circuit looks closer to the pure resistance, and actually does not improve the entire system including Triac power factor.
(3) As mentioned above, in order to maintain a controllable silicon maintenance current is not enough, many compatible Triac led dimming system needs additional leakage resistance, thereby increasing loss, so that the overall efficiency of LED dimming system is very low, which completely damage the LED energy efficiency of the original intention.
(4) At present, Triac dimming LED system market development is uneven, the real match compatible with all Triac dimmer led driver basically not, this virtually increased the great development task. In addition, the real matching of all Triac dimmer led driver is still to be long time reliability verification.
(5) The installation of Triac dimming incandescent lamp and halogen light accounted for less than one out of 10,000, while the wall installed Triac switch ratio in the Triac dimming lamps even one out of 10,000, because most of the installation of Triac dimming is a table lamp, bedside lamp, light. What's more, there are dozens of different specifications of Triac and transistor dimmer switch, in fact, the development of IC can not be compatible with all Triac switches, but only a small part of the compatibility.
(6) LED is a new technology of Genesis, it has unparalleled superiority. In the face of the increasingly mature dimming LED lighting products market demand, Triac dimming led driver development needs to be sustained.
The Triac dimmer is widely used in traditional lighting market, such as incandescent lamp, which is easy to be used by consumers and conforms to people's usage habits. Therefore, the promotion of LED Triac has a good market prospects.
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