LED light power deviation analysis

Recently, various media frequently reported that the national and local quality inspection departments randomly checked the quality of LED light sources and LED lamps. The high-quality "quality door" incident seriously damaged the company's own image and the brand image of China's LED industry on the international stage. The situation is alarming.

In the unqualified test project, the actual test power of the luminaire does not match the declared power of the product. As early as 2010, China has issued the National Standard GB/T24908-2010 "Performance Requirements for Self-ballasted LED Lamps for General Lighting", Article 5.3 requires "when the lamp is working at rated voltage and rated frequency, its actual power consumption and rated power difference should not exceed 15% or 0.5W". The International Electrotechnical Commission also requires in paragraph 7 of IEC62722-1 that "the deviation between the nominal value of the electrical parameters of the luminaire and the actual value should not exceed 10%".

The author believes that the reasons for the product power deviation are as follows:

First, due to cost pressure, 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  (Vf) drops out of control, causing the actual power of the lamp to deviate from the lower limit.

Thirdly, the thermal power supply of the selected driving power supply 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.