How to Test Switch-Mode Power Supplies
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
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![N7026A AC/DC High Sensitivity Clamp-On Current Probe]()
N7026A AC/DC High Sensitivity Clamp-On Current Probe
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![D4000BDLB Ultimate Software Bundle for the 4000 X-Series]()
D4000BDLB Ultimate Software Bundle for the 4000 X-Series
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![U1880A Power Measurement Deskew Fixture]()
U1880A Power Measurement Deskew Fixture
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![MSOX4154A Mixed Signal Oscilloscope: 1.5 GHz, 4 Analog Plus 16 Digital Channels]()
MSOX4154A Mixed Signal Oscilloscope: 1.5 GHz, 4 Analog Plus 16 Digital Channels
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![N2790A High-Voltage Differential Probe, 100 MHz]()
N2790A High-Voltage Differential Probe, 100 MHz
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![DSOX4WAVEGEN2 WaveGen Built-in Dual-chan Function and Arbitrary Waveform Generator for 4000 X-Series Oscilloscopes]()
DSOX4WAVEGEN2 WaveGen Built-in Dual-chan Function and Arbitrary Waveform Generator for 4000 X-Series Oscilloscopes
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