Overview:
LED street lights are an important part of urban lighting. Traditional street lamps often use high-pressure sodium lamps. High-pressure sodium lamps emit 360-degree light. The shortcomings of large light loss cause huge waste of energy. At present, the global environment is deteriorating and countries are developing clean energy. With the rapid growth of the national economy, the contradiction between China's energy supply and demand has become increasingly prominent, and there is a serious shortage of power supply. Energy conservation is an urgent problem to be solved. Therefore, the development of new high-efficiency, energy-saving, long-life, high color rendering index, environmentally friendly LED street lights is of great significance for urban lighting energy conservation. Road lighting is closely related to people's production and life. With the acceleration of urbanization in China, LED street lights gradually take advantage of directional illumination, low power consumption, good driving characteristics, fast response, high seismic capacity, long service life and environmental protection. Entering people's vision and becoming the new generation of energy-saving light source in the world that has the advantage of replacing traditional light source, LED street light will become the best choice for energy-saving renovation of road lighting.
Lixun Technology has published a series of LED lighting driver ICs in recent years. It has also been concerned about the development of LED street lamps. This paper mainly aims at the application of several different LED street lamps, proposes a suitable architecture, and analyzes the advantages and disadvantages. Let readers find the most suitable solution according to their company's situation and the scope of application of the designed street lamp. The same architecture can also be used in the design of other high-power luminaires.
1. Direct AC input, respectively, for 6 strings of LEDs to make constant current control alternating current, referred to as AC. Its most basic form is sinusoidal current. The standard frequency of AC power supply in China is 50 Hz, and that in Japan and other countries is 60 Hz. AC power changes over time can be expressed in a variety of forms. The range of applications and effects of alternating currents of different expressions are also different. The law of current changes with time, it can be seen that sinusoidal alternating current needs to be described by three physical quantities: frequency, peak and phase. The basic problem to be discussed in AC is the current, voltage relationship and power (or energy) distribution in the circuit. Since the alternating current has a characteristic of changing with time, a series of characteristics different from the direct current circuit are produced. The components used in the AC circuit not only have resistance, but also have capacitive and inductive components. The components used are many, and the phenomena and laws are complicated.
Among the following solutions, this should be the most efficient and lowest cost circuit. The output voltage is adjusted directly by the back-to-back control of the primary side by the Photo-coupler. Compared to other traditional solutions, one less switchinglose. The CSpin voltage is fixed at 0. 25V, and the current is controlled for the 6 strings of LEDs. The IC will detect the position of each string of FBs, and fix the string with the lowest voltage, that is, the highest sum of Vf, at 0.5V. At this time, due to the difference in the sum of the LEDVf values ​​of the strings, the excess voltage caused by the Vf difference will fall on the MOS, causing some loss. If it is a general LED for Vf after BIN, the loss should be controlled within 2%. Less than the usual switchinglose. If you use the primary side of the LLC architecture, you have the opportunity to make the overall power efficiency close to 90%. Based on the current stage, LED factories are not inclined to provide high-power LEDVf sub-Bin services. Therefore, it is necessary for the user to adjust the sum of the LEDs of each string, which causes troubles in mass production. At present, this method is more suitable for programs that have extreme pursuit of efficiency, especially those that are priced by the amount of power saving.
Advantages: high efficiency and low cost
Disadvantages: AC input, the design of the primary side is more complicated, and the power efficiency is related to the difference of the Vf of each string.
Suitable for street lamps that are highly efficient (please read the PDF for details)
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