What is ripple and noise voltage in a power supply?
Ripple and noise voltage is the alternating current voltage superimposed on the output voltage. In the case of a switched-mode power supply, this is specified in mVpp (millivolts peak-to- peak).
- The superimposed alternating current voltage consists of three components:
- Ripple voltage with mains frequency
- Output noise with the switching frequency of the converter
- Voltage spikes in the MHz range caused by the switching processes of the internal switching transistors and diodes
The peak-to-peak figures given in the datasheets of the PULS power supplies include all three components.
Hints on measuring the ripple and noise voltage: The measurement must be made directly at the output of the power supply with a short twisted-pair earth cable (no loops) and a series capacitor (e.g. parallel connection of a 100 nF capacitor and a 560 µF electrolytic capacitor). The oscilloscope must be set to 50 ohm AC measurement. A bandwidth limit of 20 MHz must be set.
