PFM-PWM DC-DC converter providing DC offset correction to PWM error amplifier and equalizing regulated voltage conditions when transitioning between PFM and PWM modes

摘要

To prevent a voltage glitch in the regulated DC output voltage of a PWM/PFM DC-DC converter when switching between PFM and PMW modes, the error amplifier of the converter's PWM regulation path is provided with a DC voltage offset correction mechanism. This mechanism “zeros-out” DC voltage offsets that may be present in the voltage regulation path, thereby enabling the error amplifier to accurately regulate the converter's output voltage. When the converter transitions between PFM and PWM modes, the DC offset correction mechanism establishes initial conditions of the error amplifier that effectively ensure that the converter's regulated output voltage at the beginning of a new “switched-to” PWM mode cycle is DC offset-free.