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Why is it important to achieve a reasonable phase margin in the design?
Phase margin indicates relative stability, the tendency to oscillate during its damped response to an input change such as a step function. Gain margin indicates absolute stability and the degree to which the system will oscillate, without limit, given any disturbance.
What values of gain margin and phase margin are considered good enough as a thumb rule?
The more commonly used metric is phase margin, perhaps because it comes with a handy rule of thumb: an amplifier should be designed to have a phase margin of at least 45°.
What does INF gain margin mean?
A gain margin of infinty means that no matter how much you increase the gain, the system will always be stable.
What should the phase margin be on a DC DC converter?
Figure 2: An example Gain-phase (Bode) plot of a DC-DC converter with the cross-over frequency, phase margin and gain margin values marked. It is customary to mandate a minimum phase margin of 45 degrees and a gain margin of 10 dB.
What’s the minimum phase margin you can use?
Typically many designers use 45 degrees as the absolute minimum acceptable phase margin over component tolerances, etc. and 60 as a typical target. Gain margin is important as well, but it doesn’t give as much information about the response of the system.
Why is phase margin considered in switch mode power supply?
The explanation is relatively simple: The phase margin (resp. gain margin) gives you the additional (unwanted) phase shift (resp. additional gain) which will bring the closed-loop into the region of instability.
Is there a way to increase the gain margin?
One thought: The gain margin is the gain for which the system is critically stable. Therefore moving the dominant pole further away from the origin could help increase the gain margin. As for increasing the phase margin to a specific value I have no idea. Phase margin is my main concern to be honest.