LED lamp power deviation analysis

LED lighting products "quality door" incidents are high, on the one hand, industry norms and regulatory vacancies, on the other hand, the company's own weak quality awareness, design capabilities, process level defects.

In this paper, the power deviation of LED lamps is out of control as an example. The theoretical calculation combines case calculations to analyze the constant current accuracy of the driving power supply and the influence of the LED forward voltage drop distribution on the deviation of the lamp power for designers to improve the design quality of LED products.

First, due to cost pressures, the production process cut corners and reduced the necessary product testing process. The unqualified products were not removed from the factory and shoddy to the market.

Second, the LED lamp bead heat dissipation design margin is insufficient, the assembly process, the deviation of the incoming material causes the lamp bead to overheat, and the forward voltage drop (Vf) drops out of control, causing the actual power of the lamp to deviate from the lower limit.

Thirdly, the thermal stability of drive power of lamp is poor, and the output current temperature drifts greatly, which directly causes the lamp power to deviate in a wide range.

Fourth, in order to reduce the procurement cost of LED lamp bead. The lamp bead purchase did not select the LED Vf distribution BIN according to the design requirements, causing the actual power consumption of the LED to deviate from the design center value.

Fifth, the optional drive power supply has a low constant current accuracy (typically 5%-8%) and cannot be adapted to the Vf BIN with various lamp beads.

If the constant current precision 5% drive power is used, the minimum voltage drop of the string is required to be 34.27V and the maximum value is 37.72V.

Compared with the Vf BIN distribution table of the lamp bead, it is not difficult to find that nearly half of the lamp beads cannot be used in mass production without taking effective BIN measures, and the cost of lamp bead purchase is indirectly increased.

If the constant current accuracy is 1%, the minimum voltage drop is 32.79V and the maximum value is 39.204V, which completely covers the lamp bead Vf BIN. No need to mix BIN measures, the production cost and procurement cost are greatly reduced.

Through the comparison and analysis of the above cases, it is not difficult to see that the high-precision driving power supply can effectively avoid the troubles of the cumbersome and unpredictable proportion of lamp bead mixing in the lamp factory, greatly reduce the system comprehensive cost, and the "small cost" of the power supply in exchange for the "big gain" of the system. ".

LED lighting competition has become increasingly hot, and product prices continue to fall, and low-cost strategies at the expense of product quality and even against industry norms and regulatory requirements are not desirable. LED industry practitioners must explore low-cost solutions based on the quality requirements of the product, so that ordinary people can afford high-quality LED lighting products.