Energy harvesters [1] power energy-autonomous wireless sensor systems by converting ambient environmental energy into electrical energy. Thermoelectric generators (TEG's) are a suitable compact power supply for both on-the-body and industrial sensors. Due to changing conditions, the generated power and voltage vary. Therefore a power management circuit (PMC) has to store the generated energy in a rechargeable battery or capacitor. It contains a DC/DC-converter with variable conversion factor and a controller that sets the conversion factor.

Power autonomy is an important requirement for wireless sensor nodes. Thermoelectric generators can produce sufficient power for low power applications. Due to varying temperature, a power management circuit will be required. This paper presents such a power management circuit, realized in the AMIS I3T80 CMOS technology. It contains a Dickson charge pump with a variable number of stages as a DC/DC converter. A controller optimizes the number of stages of the charge pump, consuming 1.4 muA. The maximum efficiency of the charge pump is 82%, leading to a total efficiency that can reach up to 58%.

Energy scavenging is an emerging method to power energy-autonomous wireless sensor systems by converting ambient environmental energy into electrical energy. Miniature as well as micro-machined thermoelectric generators (TEG) can become a suitable compact power supply for both on-the-body and industrial sensors. To minimize the overall size of the power supply, the generator has to work at its maximum power point. Due to varying thermal conditions, the generated power and voltage are not constant. Typically the output voltage is lower than the power supply voltage of the sensor. For these reasons, a power management circuit (PMC) with maximum power-point tracking capability and containing a DC/DC-converter with variable conversion factor is required that stores the generated energy in a rechargeable battery or capacitor.