The invention provides a regulator for DC-DC hybrid-mode power regulation of an output voltage and a load current. The regulator may include a controller and a back-end circuit. The controller controls the output voltage and the load current by charging a connection node when a driving signal is at an on-level, and stopping charging the connection node when the driving signal is at an off-level. The back-end circuit is coupled to the controller, capable of switching between a first mode and a second mode to control transition of the driving signal by different schemes. The back-end circuit switches from the second mode to the first mode when a mode-switch criterion is satisfied, and whether the mode-switch criterion is satisfied is independent of a measurement of the output voltage.