A multiphase power supply including a controller and phases can respond to a drop in load level by reducing all but one active phase to reduce power consumption. If the load level drops further, further reduction of the power consumption could be achieved by reducing, changing, or disabling the functions of some circuits within the active phase during these conditions. Estimating these conditions, however, may be difficult for a controller when the communication between the controller and the phase is limited. The disclosure describes an active phase that estimates a state of the load based on a sensed output current and a pulse width modulation control signal. The active phase may change its operating mode to match the estimated state of the load so that lighter load conditions consume less power. Furthermore, the idle phase(s) may nearly turn off all function except PWM detection to save power. Because this mode change is local to the phase, no additional communication with the controller is required.