TPS53313: Why the oscillation frequency of transient voltage in closed loop is equal to the crossover frequency

Zach Xia

Part Number: TPS53313

I have been learning voltage mode control of Buck recently, and I am study how the transient response is influenced by the crossover frequency. I find many materials tell that the oscillation frequency of transient voltage in closed loop is equal to the crossover frequency of the loop. So I am just wondering how to derive this conclusion.

over 2 years ago

0 Yitzhak Bolurian over 2 years ago

TI__Mastermind 18370 points

Hi Zach,

The following application note does address your question.

https://www.ti.com › lit › pdf › slva381

Basically the ringing after a transient is an indication of stability and the phase at cross over frequency (Phase margin).

Regards,

Yitzhak Bolurian

0 Zach Xia over 2 years ago in reply to Yitzhak Bolurian

TI__Expert 5065 points

Hi Yitzhak,

Thanks for your reply! The note you provide is very helpful to understand the relation between stability with phase margin.

I have acknowledged that the ringing frequency can be estimated by dominant pole approximation. That is, for a step input, the frequency of response oscillation is very close to the crossover frequency, because the dominant poles lie around the crossover frequency, by inverse Laplace transform, the expression in time domain will be sin/cos functions of the poles.

Best Regards,

Zach Xia

0 Yitzhak Bolurian over 2 years ago in reply to Zach Xia

TI__Mastermind 18370 points

Hi Zach,

Thanks for the explanation.
We all learn something new everyday.

Regards,

Yitzhak

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TPS53313: Why the oscillation frequency of transient voltage in closed loop is equal to the crossover frequency