Hello!

I am making PWM generator for SMPS.

There is one problem, so I ask a question.


<My circuit diagram, 60KHz>


<My circuit connection>


<My PWM output scope>


<My PWM waveform with noise>

What should I do to get rid of the above noise? What should I learn?
Any help would be appreciated.

Thanks.

 

I'd start with a low pass filter on the scope options and then on the board.

 

I'd start with a low pass filter on the scope options and then on the board.

Thanks for the reply. You mean, the oscilloscope itself has a low pass filter function?

 

You mean, the oscilloscope itself has a low pass filter function?

Well, mine does but it is a newer Digital scope. I don't think that LG model you are using has one. Try building a quick RC lo pass filter to feed the signal into. Or just ignore it... Is it causing a problem?

 

Well, mine does but it is a newer Digital scope. I don't think that LG model you are using has one. Try building a quick RC lo pass filter to feed the signal into. Or just ignore it... Is it causing a problem?

Thanks for any help. Most of the noise seems to be reduced. My Mosfet no longer malfunctions.

Thanks!

 

A plug-in breadboard is a poor way to build such a circuit.
All the long flying leads are prone to generating and pickup of noise.
If you built it on a vector board with a ground plane, you likely would see a lot less noise.

 

A plug-in breadboard is a poor way to build such a circuit.
All the long flying leads are prone to generating and pickup of noise.
If you built it on a vector board with a ground plane, you likely would see a lot less noise.

I thought similar to yours.
Thank you for telling us about that possibility as well.
As you said, I used to think that there could be noise coming from many pins of the breadboard.

 

The PWM circuit is quite similar to a switching-mode power supply, and so certainly filtering will be required. If this is intended to serve as a PWM audio power amplifier then yes, you need a low pass filter able to handle the power level that IC provides.The low pass filter cutoff frequency should be a bit above the top audio output frequency you require.