An apparatus such as a DC-DC power converter including a switch, an ON-time controller, and a compensator operates in a constant ON-time control mode. Over multiple control cycles, the ON-time controller controls an ON-time duration of activating the switch and generation of an output voltage to power a dynamic load. The compensator, in communication with the ON-time controller, adjusts the ON-time duration of activating the switch depending on a magnitude of output current delivered by the output voltage to the dynamic load. For example, during heavier load conditions when the dynamic load consumes a higher amount of current, and in which internal resistive losses of the power supply become more substantial, the compensator increases the ON-time duration of activating the switch, resulting in operation of the power supply and switch closer to a desired frequency setpoint.