A Thermoelectric generator, or TEG (also called a Seebeck generator) is a solid state device that converts heat (temperature differences) directly into electrical energy through a phenomenon called the Seebeck effect (a form of thermoelectric effect). Thermoelectric generators function like heat engines.
The circuit is built by a 5v Thermo electric Module, Schottky diode 1N5817 and DC-DC boost converter module. Working of this small DC-DC boost converter module is based on pulse frequency modulation (PFM) technique.
A PFM converter is an alternative DC-DC power converter architecture that uses a variable frequency clock to drive power switches and transfer energy from input to output. Because the drive signal’s frequency is directly controlled to regulate the output voltage, this architecture is referred to as PFM. DC-DC converter with constant-on-time or constant-off-time control is a typical example of this architecture.
In the circuit diagram, the negative terminal (black wire) of Module is treated as the positive output terminal, connected to PFM module (board 1) through polarity guard diode 1N5817 (D1). The PFM module is connected across buffer capacitor (C1) to get a USB-standard 5V DC output through its USB (A-type) connector. You can connect the mobile with data cable and charge your mobile from the output of DC-DC Boost Convertor.