Telonic explores Switch Mode Power Supply Noise Measurement.
Channel: TelonicInstruments
Date: 2013-04-12

A perfect DC power supply would have pure DC at its output terminals with no noise and no regulation under load, but the Real World doesn't quite work like that.  Charles (an engineer at Telonic Instruments) shows how to recognise and measure the several sources of noise in the output of a mains-powered switch mode power supply.  He discusses how the various types of imperfections occur, and why the output capacitors can suffer an early death in poorly designed units.  Charles shows appropriate probing techniques and how to avoid common mistakes.  A near-field probe is also used.  Finally he shows how to determine the efficiency of the unit.

The test power supply is powered from a Kikusui PCR2000M AC source.  This provides a very clean and stable variable voltage/frequency source of mains for the various tests.  Between the PCR2000M and the test unit sits a Kikusui KPM1000 Digital Power Meter -- this gives a precise measure of the input current and power (including phase angle).  The test unit is loaded with a Kikusui PLZ-150U Electronic Load, enabling various precise load conditions to be simulated.  Finally, a RIGOL DS4054  4GSa/s 'scope gives an accurate display of the various signals coming out of the test unit.