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.