In some embodiments, a power extractor's control loop detects changes in power and controls the duty cycle of the switching circuitry in response to the detected changes in power, thereby controlling the power transfer. The control loop may include a signal generator to control the duty cycle, and the frequency of the generated signal may be changed to optimize the energy transfer efficiency. The switching circuitry may control the rate at which circuits store and release the energy in response to the control signal and thereby seek to obtain a rate of storage and release that results in no detected changes in power. Other embodiments are described and claimed.