Switching Power Supplies

08/19/2001


A special Note before we start our Technical Discussion:

Regardless of what some folks may tell you, NEVER EVER turn on a Switching Power Supply without some kind of a load. Granted, there are some that you can safely turn on without a load, but when testing Switching Power Supplies, ALWAYS assume that these units need some kind of a load! It is simply much safer that way.

I had preached this in the classroom for years, and one year one of my students wanted to prove me wrong with a Switching Power Supply he had turned on & off a few times. He brought it over, set it up, and while about half of the class was watching and with a big smile on his face he turned it on with no load. Unfortunately, his smile disappeared when smoke and fire exuded from the unit (while those in the class watched). I then said, "I guess you need to repair the damage. You're married to it until it's fixed". He was not a Happy Camper.

Introduction

For the material presented here, it would be helpful to print out the Switching Power Supply Schematic ( 76 Kb pdf file).

Switching Power Supplies can be divided into 3 Physical Parts:

  1. The Primary Section
  2. The Secondary Section
  3. The Control Circuit(s)

You must also think about:

  1. Other Considerations
  2. Safety
  3. Troubleshooting Procedures

The Primary Section

Note: The highlighted areas here are not Links, but are references to your printed Switching Power Supply Schematic

The Secondary Section

The highlighted areas are references to the Switching Power Supply Schematic.

The Control Circuit(s)

The highlighted areas are references to the Switching Power Supply Schematic.

Other Considerations

Safety

Troubleshooting Methods and Procedures