UC2843A: output voltage go higher than setting

Ben Kuo

Part Number: UC2843A

Dear expert,

I have one issue as title with UC2843A.

Output will go higher than my setting with out load transient.

I have check FB and RT/CT waveform, looks like sometimes PWM will have higher duty than normal.(please find the waveform as below picture in red circle.)

Could you let me know which Pin or waveform I have to check? Thanks!

over 5 years ago

0 Joe Leisten over 5 years ago

TI__Expert 3095 points

Hi Ben Kuo,

Sorry that you are having issues.

Could you please capture the COMP pin waveform instead of the RT/CT waveform.

FB should be an input to the device that is proportional to output voltage. It appears from your trace that something is affecting this input. Assuming that device is not damaged I think most likely is that the COMP network is causing this disturbance.

My current thinking is that this may be a stability issue.

Please could you share your schematic. If you are not willing to post it on E2E then you can send it to my Email address.

Thanks

Joe Leisten (j-leisten@ti.com)

0 Ben Kuo over 5 years ago in reply to Joe Leisten

TI__Expert 6715 points

Hi Joe,

I have sent a mail to you. Let's discuss it via mail.
Thanks for your support.

-Ben

0 Joe Leisten over 5 years ago in reply to Ben Kuo

TI__Expert 3095 points

Hi Ben,
I am closing this post since we are covering the detail by Email.
Thanks
Joe

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UC2843A: output voltage go higher than setting