How to Test Switch-Mode Power Supplies

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Mixed Signal Oscilloscope
+ Mixed Signal Oscilloscope
Mixed Signal Oscilloscope
+ Mixed Signal Oscilloscope

Characterizing switch-mode power supplies with an oscilloscope

Characterizing the operation of switch-mode power supplies requires a broad range of measurements using an oscilloscope. You must analyze the power supply's input, switching, and output. You will also need to make frequency response measurements like power supply rejection ratio (PSRR) and control loop response. These measurements are typically made with a vector network analyzer (VNA).

Perform these measurements using an oscilloscope with power measurement software, a deskew fixture, a high-voltage differential probe, a current probe, and a passive voltage probe. The deskew fixture nulls the difference in propagation delay between the probes for more accurate measurements. Deskewing is critical for the switching loss measurement. Time delay can cause significant differences in power and energy measurements during the turn-on and turn-off phases of transistor switching.

Switch-mode power supply characterization solution

Characterizing a switch-mode power supply requires deskewing to equalize the time delay between probes. The Keysight InfiniiVision 4000 X-Series oscilloscope, paired with power analysis software, enables quick power measurements using differential and current probes calibrated by a deskew fixture. The U1880A power measurement deskew fixture deskews the time delay between voltage and current, driving both probes with the same pulse signal.
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