Engineer It - How to test power supplies - Measuring Stability

TI's Bob Hanrahan demonstrates how to measure stability when testing power supplies.
For more videos on testing power supplies, check out:
Overview: www.ti.com/testingpoweroverview
Measuring efficiency: www.ti.com/measuringefficiency
Measuring noise: www.ti.com/measuringnoise

[@justintimber5058]

I grew up with TI's products and I'm still a big fan of TI. The video shown is good and informative. Thanks.

[@diocorissosa4448]

Thank you for this valuable video!

[@alejandroalfonso6651]

Does TI let consumers rent the equipment such as the Signal Analyzer to perform these measurements?

[@tamyboy1]

Beautiful

[@irgski]

So, what are appropriate allowable ranges for both phase and gain margins?

[@roberthanrahan6993]

+irgski I hate saying that it depends, but it very much depends on the design and the application. Trade-offs exists when it comes to transient response (reaction time to load changes) and phase margin which is effected by part tolerance, and parametric variation over temperature and time. Most of us have safe margin limits that we use that might provide a safety margin wider than needed for applications where response time must be minimized. If you search the subject you will find much written about the subject, both theory and opinion which you may want to sift through. Thanks for the question.

[@reyjaime]

Hi, sorry to bother you, I have a question. What if I have a current controlled power supply with high side current sensing, where will the signal get injected/read? Thanks in advance.

[@TexasInstruments]

+Jaime Salinas This really depends on the current sense scheme employed. You can inject anywhere in the feedback loop as long as you stay within the allowable voltage range of the FRA and you have a high enough impedance to disturb the loop with the FRA output. You may sense across the current sense resistor if the voltage isn’t too high. The injection signal should be isolated as shown in this article (www.edn.com/design/power-management/4412230/1/Testing-a-power-supply---Stability--Part-three) and the gain may need to be increased to get an appropriate signal back into the FRA receiver, depending on the value of the shunt (s) and drive current.

[@reyjaime]

+Texas Instruments Thank you

[@KikusuiElectronics]

GREAT!