US Department of Energy LED Driver Reliability Test: Significant Performance Improvement

  As is well known, LED drivers, like LED components themselves, are crucial for optimal light quality. A suitable driver design can eliminate flickering and provide uniform lighting. And the driver is also the most likely component in LED lights or lighting fixtures to malfunction. After realizing the importance of drivers, DOE began a long-term driver testing project in 2017. This project involves single channel and multi-channel drivers, which can be used for fixing devices such as ceiling grooves.

  The US Department of Energy has previously released two reports on the testing process and progress, and now the third test data report is being released, which covers product test results running under AST conditions for 6000-7500 hours.

  In fact, the industry does not have as much time to test drives in normal operating environments for many years. On the contrary, the US Department of Energy and its contractor RTI International have tested the drive in what they call a 7575 environment – with indoor humidity and temperature consistently maintained at 75° C. This test involves two stages of driver testing, independent of the channel. Single stage design costs less, but it lacks a separate circuit that first converts AC to DC and then regulates the current, which is unique to two-stage design.

  The US Department of Energy report states that in tests conducted on 11 different drives, all drives were run for 1000 hours in a 7575 environment. When the drive is located in the environmental room, the LED load connected to the drive is located under outdoor environmental conditions, so the AST environment only affects the drive. DOE did not link the runtime under AST conditions to the runtime under normal conditions. The first batch of devices failed after running for 1250 hours, although some devices are still in operation. After testing for 4800 hours, 64% of the devices failed. Nevertheless, considering the harsh testing environment, these results are already very good.

  Researchers have found that most faults occur in the first stage of the driver, especially in power factor correction (PFC) and electromagnetic interference (EMI) suppression circuits. In both stages of the driver, MOSFETs also have faults. In addition to indicating areas such as PFC and MOSFET that can improve driver design, this AST also indicates that faults can usually be predicted based on monitoring driver performance. For example, monitoring power factor and surge current can detect early faults in advance. An increase in flashing also indicates that a malfunction is imminent.

  For a long time, DOE’s SSL program has been conducting important testing and research in the SSL field, including application scenario product testing under the Gateway project and commercial product performance testing under the Caliper project.

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