How Long Can It Go? An Introduction to Power Supply Reliability Information

Engineers looking for a power supply have to sort through countless choices. There are countless available models to evaluate, each with a product description or datasheet that touts important characteristics relating to the supply’s performance and operating features. The description may even include pricing information. But when you take a deeper dive into the product information, you’ll see acronyms like MTBF and MTTF. They may not mean much if they go into machines that will only see sporadic use. But, when your device is expected to run 24/7 or go into, for example, a life-saving medical device, reliability should be very high on a designer’s list of selection criteria. If a power supply fails, it can disable a system and also cause major damage to critical equipment.

This blog series will review basic power supply reliability concepts, including mean time between failure (MTBF) and mean time to failure (MTTF). Both terms are deceptively similar yet very different. Moreover, power supply manufacturers use different standards and methodologies to calculate reliability ratings. We’ll also discuss power supplies with internal electrolytic capacitors and how a cap’s lifetime can be just as important as MTBF and MTTF when predicting system reliability. This series intends to help foster a better understanding of the information available to buyers looking to select a power supply that will meet the reliability requirements that their application demands.