LM25037: Practical Implementation of Slope Compensation

Istvan Adam

Part Number: LM25037

Tool/software:

Hello,

I am an electrical engineering student, and I am working on designing a push-pull converter using the LM25037. Throughout the design process, I am trying to understand everything, but I am having some difficulty with the practical implementation of slope compensation. The datasheet includes equation (6) for determining Rslope, but I am unsure how to express the equation. How can it be derived?

Is the equation based on determining the time dependency of the RAMP voltage? I have attempted this but ended up with a transcendental equation, which makes it difficult to express Rslope.

I would like to understand it thoroughly, as I also want to examine the effect of Cfilter on slope compensation. If I am correct, this has been neglected in the equation.

Thank you in advance for your help.

1 month ago

0 Steven Mappus1 1 month ago

TI__Mastermind 27715 points

Search "Slope Compensation E2E"...this subject has been covered many times.

Steve

0 Istvan Adam 1 month ago in reply to Steven Mappus1

Prodigy 10 points

Hi Steven,

Of course, I searched for it, but I couldn't find a satisfactory answer, which is why I asked the question.

0 Steven Mappus1 1 month ago in reply to Istvan Adam

TI__Mastermind 27715 points

If you want to derive an equation for slope comp, attached is the way I've done it. If you want to derive the exact equation6 from the data sheet...I'll leave that as an exercise for the student.

Steve

0 Istvan Adam 1 month ago in reply to Steven Mappus1

Prodigy 10 points

Thank you for your help. This is how far I've gotten with the task so far:

0 Istvan Adam 1 month ago in reply to Steven Mappus1

Prodigy 10 points

Unfortunately, I am struggling with the problem, so I shouldn't expect specific help from TI?

0 Steven Mappus1 1 month ago in reply to Istvan Adam

TI__Mastermind 27715 points

The issue of slope compensation has been around since peak current mode control was first introduced. Of course TI supports our customer to help design stable converter loops and avoid subharmonic instability. There are many TI references describing subharmonic oscillation and how to calculate/implement slope comp. You seem to be taking an academic approach where the equation is provided but you want the derivation. If you are having difficulty setting up the controller, TI Application Engineers are here to help. If you need help with your homework, you should see the TA.

Steve

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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LM25037: Practical Implementation of Slope Compensation