• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 279 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC2897A: Inductance setting

KIM Andy
Expert 2530 points

Part Number: UCC2897A

Hi

My Customer is current 22W active clamp forward circuit configuration of UCC2897A.

The first problem I found is that the output inductor is applied to 22uF and the circuit oscillates after a certain time, when the output capacitor is 540uH (270x2).

Conversely, lowering the output inductance to 1.5uF improves the problem.

I implemented the circuit with caculator and webench.

In this circuit, the output inductor was increased to about 120 uF and the output capacitor was reduced to 10 uH.

However, testing the current board and increasing the output inductor will cause the circuit to start oscillating at 5uH.

Can the trans L value affect this? Or what should we look at? We tried to change the trans L value, but there was no big change.

Is it possible to reduce the inductance to 1.5 uF, which is different from the calculated value?

I attach the test contents of the customer's company.

The current customer plans to design 44W through the next version development.

  • 0
    TI__Mastermind 31580 points
    HI Andy

    I suspect you have a control loop instability issue. Please use the power stage designer tool on TI.com to calculate the power stage component values. Power stage designer will also calculate the control loop values. Please compare theses values to the values used in your design.

    When you use the 3.3uH output inductor the output current is discontinuous, when the output inductor is 22uH the inductor current is continuous, it does not fall to zero for 1A and 2A load currents. In continuous mode the voltage control loop will have higher gain and it is more likely to oscillate if it is not designed correctly.

    Regards

    Pteer
  • 0 in reply to Peter Meaney
    TI__Mastermind 31580 points
    Hi Andy,

    I hope you have made some progress in the meantime. Since there has been no activity on this post for nearly two weeks now I am closing the post.

    Please open a new post if you have more questions.

    Regards

    Peter