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UCC28070: About VSENSE and VINAC Resistor Configuration

Hide
Guru 21045 points
Part Number: UCC28070

Hi Team,

 

I have two questions.

 

---------

[Q1]

I understand that “It is necessary that the attenuation (kR) of the two divider networks be equivalent for proper PFC operation.”

If the attenuation (kR) of the two divider networks is different, what kind of concern is there?

 

<For example>

UCC28070 can’t output the target output voltage etc.

---------

 

[Q2]

If VSENSE KR is 0.0078(23.5k/(2990k+23.5k)) and VINAC KR is 0.0086(26k/(2990k+26k)) so the two divider networks is different,

what kind of concern is there?

 

And, could you please let us know “Difference of permissible KR” if you have any information?

 

<For example>

OK case: Difference of kR is less than 0.1

NG case: Difference of kR is more than 0.1

---------

 

Regards,

Hide

  • 0
    TI__Mastermind 34465 points

    Hello Hide,

    The UCC28070 has an internal current synthesizer and this is used to predict the down slope of the inductor current.

    This synthesizer relies on equal divider ratios for VINAC and VSENSE.

    You will get the best accuracy with equal didivder ratios.

    If the divider ratios are unequal then you can expect a slight increase in current distortion

    If you are happy with the test results for the divider ratios you have chosen then there is no reason to change.

    Regards

    John

  • 0 in reply to John Griffin1
    Guru 21045 points

    Hi John-san,

    Thank you for your response.

    I greatly appreciate your cooperation.

    Regards,

    Hide