By：Simon Kuo/Technical Service Center
simon.kuo@meanwell.com

MEAN WELL, established in 1982, has been known for superior quality and high cost-performance in the power supply industry for nearly four decades. For switched-mode power supplies, the number of the components could be from dozens to hundreds, depending on the wattage and topology. Each component is applied to the design with its necessity. The assurance of exact lifetime and evaluation of the reliability is the know-how in the power supply industry. We could assess the quality of a power supply or whether the product is well examined by checking MTBF or life cycle parameters. This article will analyze the MTBF and the lifecycle parameters generally considered in the early product implementation phase. 

MTBF (Mean Time Between Failure) and Life Cycle are both indicators of reliability. MTBF can be calculated by two different methodologies: "part count" and "stress analysis". The regulations of MIL-HDBK-217F Notice 2 and TELCORDIA SR/TR-332(Bellcore) are commonly used to calculate MTBF. MIL-HDBK-217F is a United States military standard, and TELCORDIA SR/TR-332(Bellcore) is commercial regulation. Life Cycle is founded by using the temperature rise of electrolytic capacitors under maximum operating temperature at full load condition to estimate the approximate life of the power supply. Both parameters have a certain reference value. The only difference is that they are derived from differential equations.

Unlike the Life Cycle that only utilizes parameters from the temperature rise of electrolytic capacitors for its equation, MTBF is more complicated than that. As we all know, the equation for electrical component failure rate during MTBF calculation contains many variations, as shown in Eq. 1, including quality factor, environment factor, basic failure factor…etc. When these factors combine with the stress or the number of the components, the result turns differently. But people don't know is that some of the factors improve over time. The following paragraph will explain in more detail.

Equation of electrical component generic failure rate

As the world tries to keep up with Moore's law, material technology and the craft of the processes grow together. That can be applied to electrical components as well. For example, a component with the same size and specification today surely possesses better quality and stability during production compared to the past. This is the reason why the MTBF updates once in a while to optimize the database. Therefore, even with the same design, by simply changing the component to a higher grade or optimizing the quality, it is possible to adjust the quality parameter πQ in the equation to enhance a higher reading of MTBF. 

Continuous pursuit of innovation and optimization has been a mission to MEAN WELL since day one. As a result, MEAN WELL keeps evolving and reaching a higher level of quality by improving research volume and strictly selecting the components and suppliers. The MTBF reading of the MEAN WELL products has been relatively conservative. The reading no longer matches the quality nowadays, which makes no advantage when competing with other brands, especially when customers face government bids or project competitions. Fortunately, the quality guarantee with a long lifecycle and warranty still maintains MEAN WELL's competitive edge in the market. To resolve the issue that continuously encounters, to fulfil our mission "Continuous pursuit of innovation and optimization", MEAN WELL re-examined the MTBF parameters of TELCORDIA SR/TR-332(Bellcore) and implemented an optimization. MEAN WELL reviewing the supplier quality policy and accompanying with IQC/OQC/FQC…etc., all the ways to after-sales service, ensure preventing recurrence, which not only brings the quality of MEAN WELL products to another level, but it also changes the status of the quality factor πQ of the MTBF equation as shown in Table 1 according to TELCORDIA SR/TR-332(Bellcore) regulation. Leading the MTBF reading can be optimized from Level 0~I to Level I~II.

Table 1. Device Quality Level Description and Factor of TELCORDIA SR/TR-332(Bellcore)

MEAN WELL continuously announces long warranty products (7 yeas warranty of HLG series/6 years warranty of HEP series/5 years warranty of DPU/DRP series…etc.) because of the lifecycle parameters and warranty closer to general user's expectation of quality control. Either MTBF or lifecycle is a commitment of product design. Through this event, MEAN WELL re-examined the parameters and optimized the MTBF of TELCORDIA SR/TR-332(Bellcore), making the MTBF closer to the high quality of MEAN WELL's products today. Improve the overall competitiveness of MEAN WELL products from specification aspects.