Patent ID: 8294443

Claim:
A level-switching device for a PWM converter, comprising: a voltage divider coupled to an output node of the PWM converter to generate a feedback signal related to an output voltage at the output node, and having a feedback node to provide the feedback signal; a resistor and a MOS serially coupled to the feedback node to switch a voltage dividing ratio of the signal VFB to the output voltage; and an undershoot/overshoot eliminator coupled to the MOS for the MOS changing from a totally on state to a totally off state or vice versa softly when switching the MOS, the undershoot/overshoot eliminator comprising: a first impedance network coupled between a drain and a gate of the MOS; a second impedance network coupled between the gate of the MOS and a ground node; a third impedance network coupled between the drain of the MOS and the ground node; and a current source coupled to the gate of the MOS for controlling turning-on/turning-off of the MOS.