Spikes on output of AC-DC Converter

A.S.Bhushan

I observed spikes on output of AC-DC converter in oscilloscope (image attached), when I switch OFF or ON of AC fan as per connection shown in block diagram. Here I did not connect earth. We connected Phase and neutral only.

I observed not only in our power supplies, almost all power supplies even in Lamda, Meanwell, etc.,

Here I am attaching image showing that spikes on 24V output. Maximum peak was 36.9V

What could be the reason? What is the solution to solve this?Image.pdf

over 6 years ago

0 Benjamin Lough over 6 years ago

TI__Mastermind 27135 points

Hi A.S. Bhushan,

Can you share a schematic for your AC/DC converter and tell me where on the converter you are measuring the output? Directly on the output cap? At the end of a wire? Can you repeat the measurement using tip and barrel?

https://www.eetimes.com/document.asp?doc_id=1273282#

Best Regards,

Ben Lough

0 Benjamin Lough over 6 years ago in reply to Benjamin Lough

TI__Mastermind 27135 points

Hi A.S. Bhushan,

Did you have a chance to retake the measurement using tip and barrel?

Best Regards,

Ben Lough

0 A.S.Bhushan over 6 years ago in reply to Benjamin Lough

Expert 1060 points

Hi Ben Lough,

Today I tried with tip and barrel method. It works fine. There is no spikes at output.

Good results.

What could be the problem? Why spikes are coming from input to output even it is isolated?

Is there any pickup in air?

0 Benjamin Lough over 6 years ago in reply to A.S.Bhushan

TI__Mastermind 27135 points

Hi A.S.Bhushan,

The ground clip on many passive probes can act as an antenna and pick up noise in air. For noise spikes such as what you described, it is a good idea to use tip and barrel to confirm the noise is real or is simply noise coupling into the probe measurement from elsewhere.

Best Regards,

Ben Lough

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Spikes on output of AC-DC Converter