One of the major problems with the electronics circuits is the extent of noise they generate. Power Supplies are not an exception. Whether the regulator IC used on the board or an external power supply used for the board, most often they are the culprits of noise generation. Noise with power supplies is in terms of emissions. The emissions are either common-mode emissions or differential-mode emissions. Engineers fret over to see such emissions. We have all the below possibilities to reduce emissions:
- Add components like capacitors (power line filters)
- Have a layout which doesn't allow emissions (not always possible, though)
- Frequency Dithering
In switching power supply circuits, we provide PWM input. When power supply is operated, the emissions are over a narrow band. Now, the PWM duty cycle can be varied which we call dithering. when dithering is applied, the emissions spread over a wide band, there by reducing the emission levels. One main drawback of dithering is that it might increase the switching losses.
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