Ćuk converter employing indirect current control loop for TEG energy harvesting devices

This paper presents a custom DC-DC Ćuk converter developed for charging batteries from serially connected thermoelectric generators (TEGs). Present DC-DC converters are designed for a single power source resulting in low output power if the harvested heat energy source has low temperature. This drawback can be eliminated with Buck-Boost DC-DC converters able to adjust the output current accordingly to the variation of the available heat source temperature. In order to increase the efficiency, the proposed Ćuk converter employs two N-Mos switches where the second replaces the diode from the original topology. An isolation transformer is used to revert the output polarity and high resolution nanosecond adjustable timing will be used to prevent the cross conduction of the switches. The converter employs an indirect current control loop by measuring only the output voltage of the thermoelectrical generators, eliminating the need for a current sensor. An a priori built look-up table stores the voltage - internal resistance correspondence of the TEG and is used to compute the actual current the converter is sourcing to the battery pack.