In an embodiment, a method includes generating a pulse-width-modulated signal having a duty cycle, and isolating a power-supply output node in response to the duty cycle corresponding to a signal magnitude that is less than a magnitude of an output signal on the power-supply output node. For example, where a power supply has a non-zero residual output signal (e.g., output voltage) on its output node after the power supply is deactivated, a power-supply controller can use such a technique to reduce or eliminate a drop in the residual output signal caused by, or that would be caused by, a restarting of the power supply.