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It is reported that the United States Department of Energy (DOE) recently released the third LED driver reliability report based on long-term accelerated life test. Researchers of Solid-state lighting (SSL) of the United States Department of Energy believe that the latest results have confirmed the accelerated pressure test (AST) method, which has shown good performance under various harsh conditions. In addition, the test results and measured failure factors can inform driver developers of relevant strategies to further improve reliability.

As is well known, LED drivers, like LED components themselves, are crucial for optimal light quality. A suitable driver design can eliminate flicker 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 United States Department of Energy has previously released two reports on the test process and progress. Now it is the third test data report, which involves the product test results of 6000-7500 hours of operation under AST conditions.

In fact, the industry does not have so much time to test drives in normal operating environments for many years. On the contrary, the United States Department of Energy and its contractor RTI International have tested the actuator in what they call the 7575 environment – the indoor humidity and temperature are 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 United States Department of Energy reported that in the test of 11 different drives, all the drives ran for 1000 hours in a 7575 environment. When the drive is located in an 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 associate the operating time under AST conditions with the operating time under normal environments. The first batch of devices failed after 1250 hours of operation, 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 specifying areas such as PFC and MOSFET that can improve driver design, this AST also indicates that faults can usually be predicted based on monitoring the performance of the driver. For example, monitoring power factor and surge current can detect early faults in advance. The increase in flashing also indicates that a malfunction is about to occur.

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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