Common Mode or Differential Mode Noise from Boost Converter

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basit701

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Hello Guys!

Hope you are doing great.

I am working on feedback of non isolated boost converter. For voltage sensing i am using an ADC. However, the output voltage from the converter has noise. I searched on the Internet and its written that there are two types of noise Common Mode Noise and Differential Mode Noise. I cannot figure out what type of noise the converter is producing and how to mitigate it. I am attaching the waveforms(took snapshot).

Probe +VE and -VE tip connected to ground terminal


Probe +VE and -VE tip connected to Vout terminal


Probe +VE tip connected to Vout and -VE tip to ground terminal
 

There's obviously common noise involved, as the first measurement indicates. It also proves that the oscilloscope probe picks up common mode noise. This is primarily a measurement artifact introduced by the external cabling. Internal signals may be O.K. if you remove the probe. The downside is that you can't acquire the internal signals correctly without a better measurement setup (e.g. using differential probes, common mode chokes, etc.).
 

For your feedback signal, make sure it is in a narrow area current loop. -Then it will pick up less noise.
The capacitor that you put in the feedback of the error amplifier should get rid of some noise for you.
But yes, your boost smps will produce both common and diff mode noise.
 

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