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The LED light failure compensation scheme

by:ALLTOP      2020-12-03
High power LED performance varies with time and temperature decline has been recognized, this is a high power LED lighting currently facing an important problem. Because of the high power LED price is relatively high, if you want to gain relative to other LED light source a better return on investment, it must rely on long service life and save electricity as much as possible to make up for the high price of lamps and lanterns. At present domestic high-power LED lighting to solve the problem of droop, typically in front of the lamps and lanterns to life expectancy, provide more than needed luminous flux of lamps and lanterns, luminous flux in the process of the use of lamps and lanterns gradually reduce, when got to the life expectancy of the luminous flux of lamps and lanterns of lamps and lanterns is close to the actual need to value. This approach is simple, but there is no doubt that wasted energy, excessive lighting also affect the service life of lamps and lanterns, so find better droop solution, it is very meaningful.
from the normal use of the LED, the main factors affecting the service life of the LED is hot. A source of heat, heat produced mainly LED, high power leds will be 20 - 30% of its electricity into light, around 70% of the converted into heat, and if the drive with built-in method, also increase the LED heat dissipation of the drive. The accumulation of heat makes the temperature rise and temperature makes the performance of the chip recession, material aging and degeneration. Current, high power LED light failure is mainly determined by the chip itself, improper application ( Improper power supply, heat dissipation, etc. ) Is also a cause of droop, as shown in figure 1.
the LED light failure is related to its junction temperature, the so-called junction temperature is the temperature of the semiconductor PN junction, the junction temperature, the higher the earlier appear light failure, namely the shorter service life. Can be seen from the figure 1, if the junction temperature is 105 degrees, the brightness of 70% life only more than ten thousand hours, 20000 hours, 95 degrees and the junction temperature down to 75 degrees, life 40000 hours, 65 degrees more can be extended to 90000 hours. So prolong life is the key point is to reduce the junction temperature. But the fact is due to the size and the cost control of lamps and lanterns, the LED junction temperature is compared commonly difficult to control in a lower value, light failure situation is always lingering shadow in the design of LED lamps and lanterns. For a specific LED chip, the traditional solution is to set the output current to meet the LED light source lumens requires the corresponding value of the rated life arrived. This will make use of first LED lamp output lumens count for more than 130% of the rated even higher, as shown in figure 2.
so traditional LED lighting design, in front of the lamps and lanterns of life always is in a state of excessive lighting lamps and lanterns, for the new lamp lighting may even more than 30%, and through the intelligent droop compensation mode, can make the lamps and lanterns in the life cycle constant work in the state of flux, to meet the needs of users will be excessive lighting is a waste of energy savings, but also extend the life span of the light source and drives.
the feit electronic presents a new intelligent control to solve the droop compensation solution.
in the first place according to the temperature of the LED chip is LED from the LED chip datasheet droop characteristic curve, the mathematical model is established. Then calculated by internal control chip as shown in the figure below the curve of the output current increases slowly. LED driver can control its output current with LED light source total lighting was increased with time, and then implement increases with the increase of the total lighting time LED light source output of luminous flux, realize droop compensation, so as to ensure the luminous flux of LED light source output can be constant with the increase of the total illumination time always needs in the illumination area, as shown in figure 3. Control the basic diagram, as shown in figure 4.
droop compensation controller contains a compensation design unit, a timing control unit and an output unit. Reference level of output by controlling the drive current feedback control, which makes the output current drive with the change of the design of the controller. And external Rset can be used to set up different compensation curve, as shown in figure 5.
in addition, there is no built-in droop compensation to the existing LED drive, as long as the drive can be 0 10 v dimmer, the external droop compensation controller to realize droop compensation, specific implementation, as shown in figure 6.
the feit electronic the droop of compensation technology is put forward, and the existing early compared to excess illumination compensation droop method, to drive the LED light source, do not need to reserve a current, thus saving energy, prolong the life of lamps and lanterns, reasonable design can also reduce the cost of light source of lamps and lanterns. Described by changing the droop line resistance regulation, make the same LED driver in driving different light failure rate of the LED light source can realize different droop compensation characteristics, improve the generality of the plant. In addition, if you want to achieve more accurate droop compensation, the British who can for the customer in advance before they go out in the controller write custom procedures. And in the near future, this will droop compensation controller can controller integrated together, and other functions, to realize more functions of the LED control.
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