Switching-mode power supply design problem

Because of its emphasis on efficiency, switching-mode power supply design minimizes the use of lossy components such as resistors and uses components that are ideally lossless such as switches, capacitors, inductors, and transformers. The primary design problem is how to interconnect these components and control the switches so the desired results are obtained. The secondary design problem is to select, design, or overcome the performance characteristics of less than ideal components. Protection techniques and parts derating are used to circumvent the fact that real parts tend to fail when overstressed.

The design process is successful when a proper topology and control has been chosen that exceed the performance requirements and when protection techniques, parts selection, and derating have been used that exceed the required reliability. Both normal and abnormal operating environments the circuit will encounter over its useful life must be considered throughout the design process.

Note that the design goal is to exceed, not to just meet, the performance and reliability requirements. This comes from the philosophy that given fixed resources the engineer's task is to get the most from these resources. For example, if analysis shows that it will take 25 parts worth $50 and one month development time to just meet requirements, the goal then shifts from just meeting requirements to getting the absolute best performance out of these parts in the allotted time -- exceeding and not just meeting requirements if this is possible. This is not "gold plating" but just good engineering. Because of the critical nature of power supplies in all equipment, this approach improves both the performance and reliability of the total system at no additional cost. It often keeps the power supply off the critical-path schedule when increasing requirements might force a redesign resulting in a schedule slip.