Method and apparatus for converting the output of a thermoelectric generator to voltages compatible with implantable medical devices is provided. One apparatus includes an implantable thermoelectric generator. The apparatus includes an input terminal for receiving an input voltage generated by a thermoelectric energy converter and a charging inductor connected in series with the input terminal. The apparatus also includes a switching Field Effect Transistor (FET) connected to the inductor, and a capacitor connected to the FET and the input terminal via a diode. The FET is switched with a frequency and duty cycle such that a voltage level at an output terminal is compatible with an implantable medical device. According to various embodiments, the FET is switched using a closed loop feedback system that controls the frequency and duty cycle based on an observed voltage level at the output terminal. Other aspects and embodiments are provided herein.
