UCC2897A: external slope compensation circuit

kura

Genius 4840 points

Part Number: UCC2897A

Tool/software:

This question is about the external slope compensation circuit for the UCC2897A.

Our customer is considering an external slope compensation circuit, referring to the document at the following URL:

External Slope Compensation for UCC2897A in Some Special Applications

https://www.ti.com/jp/lit/an/slua548/slua548.pdf

They want to determine the RS resistor value in Figure 6. External Compensation Circuit in this document, but the document does not include instructions on how to design the RS resistor.

Please let us know the formula for determining the RS resistor.

Regards,

Kura

1 month ago

0 Hong Huang 1 month ago

TI__Guru 73265 points

Hi,

For initial design, you can use the below to get the parameter values to start to test. You would need to tune up Rs on bench debugging.

Please see the correction in the next reply.

0 Hong Huang 1 month ago in reply to Hong Huang

TI__Guru 73265 points

Hi,

The formula needs to correct as the below.

0 kura 1 month ago in reply to Hong Huang

Genius 4840 points

Thank you for your reply.

I think the information you provided is the calculation formula for when a current detection resistor is used on the source terminal side of the primary-side FET.

Could you please let us know the formula for detecting primary-side current using a current transformer?

Regards,

Kura

0 Hong Huang 1 month ago in reply to kura

TI__Guru 73265 points

Hi,

Substitute Rcs with Rct/Nct in that formula based on the below.

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UCC2897A: external slope compensation circuit