Testing Power Supplies with an Electronic Load

A programmable electronic load is the proper tool for validating a power supply design. Without one, you're just hoping your design handles load transients correctly.

Load regulation: set the load to draw nominal current and measure the output voltage. Then step the load to 10% of nominal and measure again. Good supplies maintain regulation within 1-2% across the full load range. Transient response: rapidly switch the load from 10% to 100% and back while watching the output on an oscilloscope. You'll see a voltage dip when load increases and a spike when it decreases — these transients should settle within microseconds for a well-designed supply.

Current limiting: test that the supply's current limit activates before any component stress. Set the load above the current limit, verify the supply folds back cleanly, and verify the supply recovers when the overload is removed. A supply that latches off on overcurrent (hiccup mode) is fine; one that sits in an undefined state is a design problem.