How to measure Loop Gain and Phase of switching power supply

KevinMEL

Hello,

I have read the Application Report "Optimizing Transient Response of Internally Compensated dc-dc Converters With Feedforward Capacitor" SLVA289B to measure and optimize the phase margin of my design.

In section 2.3 "Determining the Crossover Frequency Using Frequency Analysis" How the loop Gain and Phase are measured ? The only solution is the FRA technique ?

Best Regard's,

over 5 years ago

0 Garrett Roecker over 5 years ago

TI__Mastermind 21720 points

Hi KevinMEL

Thanks for reaching out with your questions.

Using a frequency response analyzer is the easiest way to measure the loop. However if there you don't have access to this piece of equipment a function generator, oscilloscope and transformer can be used to measure the loop. Please take a look at this application note to help implement the measurements.

-Garrett

0 Youhao Xi over 5 years ago

TI__Guru* 78270 points

Hi Kevin,

Basically you need a frequency response analyzer to measure the Bode Plots. There are many vendors producing the analyzer, including Keysight, Venable and Ridley, different vendors but the method is the same. For your reference, you can read the article at the below link for the loop measurement.

http://www.ridleyengineering.com/hardware/ap310-analyzer/ap300-application/ap300-measurement-techniques.html

Another method, which is for experienced engineer without an frequency response analyzer, is presented in the article below.

http://www.ti.com/lit/an/snva364a/snva364a.pdf

Thanks,

Youhao Xi, Applications Engineer

0 KevinMEL over 5 years ago

Prodigy 70 points

Hello,

Thank you for your useful informations

Best Regard's,

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How to measure Loop Gain and Phase of switching power supply