ABSTRACT
A proper evaluation of the loop gain of the system serves to provide the essential information for tailoring the final loop gain response for stable system operation. If gain adjustment is required to tailor the loop gain for better phase or gain margin, it can then be accomplished by adjusting the closed-loop gain of the error amplifier. In a power converter, negative feedback is employed around a loop containing amplifier(s), comparator, modulator, and filter components. At zero or very low frequencies, the loop gain exhibits a phase lag of approximately 180° by virtue of the negative polarity of the feedback signal. The higher the switching frequency, the wider the frequency band available for manipulating the loop response. It is worthy of consideration that the phase and amplitude responses are interrelated. The phase margin is observed as the phase at the frequency where the magnitude response has declined to the 0-dB level.
