In both military and commercial applications, every electronic system needs a power supply. As is the case with commercial power supplies, the three configurations of military power supplies are AC to DC, DC to DC and DC to AC; consequently, some may be inclined to believe that military and commercial power supplies are one and the same, however, they are not. What is the difference between military power supplies and their commercial off the shelf (COTS) counterparts? In a word, reliability.
While commercial power supplies may be adequate for some commercial applications, they are not appropriate for aircraft, sea craft or other military transportation equipment. That is because in these applications, a more robust power source is needed. Most commercial power supplies have a shorter mean time between failure (MTBF) rating than military power supplies. That means they are more likely to experience interruptions, often without warning. In a commercial or military transportation application, a loss of power can be cataclysmic – often, life-threatening. These applications require a more robust power supply with a long MTBF, which military power supplies are designed to provide.
Another advantage that military power supplies offer is the ability to recognize any impending failures in the system. As the demand for predictability increases, new power conversion products are equipped to make the user aware of specific glitches that may be around the corner. Finally, military power supplies are subject to greater scrutiny than commercial power supplies. The military power supply industry is strongly regulated, with specific requirements involving the selection of parts, the design process and specifications for use in varying environments.
There are many fine commercial power supply products, but most are not suitable for military applications. When the defense market builds systems using COTS power supplies, it must understand the risks involved – obsolescence, process changes, environmental vulnerability, faulty electrical performance or EMI issues – and modify the system to compensate for said risks. The cost and manpower spent on those modifications can be avoided by bypassing COTS power supplies in the first place, and opting for power supplies that are engineered and designed for military applications.