16 Ways to Design a Switch-Mode Power Supply (.PDF Download)

July 5, 2017
16 Ways to Design a Switch-Mode Power Supply (.PDF Download)

Simply put, designing a power supply is a major undertaking. After making your build vs. buy decision, you face a myriad of circuit choices—more than you probably realize.  Building a power supply used to be relatively straightforward, but with switch-mode methods dominating these days, it has become a complex specialty. If you’re not a power-supply expert and/or this is one of your first designs, you may need some guidance. The information presented here should help you identify your options and zero in on one to follow through with.

Step 1: A Good Specification

It all begins with a good specification. It’s critical to take the time to research your needs and write a detailed specification. As a starting point, list the following key features:

  • Input-voltage (ac or dc) range
  • Output voltages (dc or ac) and tolerances
  • Output-current requirements
  • Ripple maximum
  • Estimated total power required
  • Efficiency requirements, if any
  • Electromagnetic-interference (EMI) considerations, if any

Step 2: A First Decision

With these specifications, you should be able to make your first big choice: linear vs. switch-mode design. Yes, linear supplies are still an option even in the current switch-mode dominant environment. If your design can accept the lower efficiency of a linear supply, you may appreciate its benefits. The major advantages of a linear supply are simplicity of design, lower cost, abundant relevant components, proven techniques, and low EMI emissions.


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