The US Department of Energy (DOE) has recently released its third reliability report on LED drivers based on long-term accelerated life testing. Researchers from the US Department of Energy’s Solid State Lighting (SSL) believe that the latest results confirm the excellent performance of the Accelerated Pressure Test (AST) method 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 US Department of Energy has previously released two reports on the testing process and progress, and now it is the third test data report, which covers product testing results running under AST conditions for 6000 to 7500 hours.

In fact, the industry does not have so 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 – both indoor humidity and temperature are 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 reported that in tests conducted on 11 different drives, all drives were operated in a 7575 environment for 1000 hours. 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 at the Gateway