Figure 2: Design of the power management part for regulated TENG outputs.

(a) Circuit diagram of the power management circuit. (b) Theoretical calculation of the optimized charging time to demonstrate the design of the power management circuit. (c) Board efficiency measurement results. (d) Measurement of the maximum d.c. power of this system driven by human biomechanical energy. (e,f) Total efficiency measurement results. (e) Measurement of the a.c.-harvested power from a resistor. (f) Measurement of the d.c.-harvested power from the power management circuit. (g) Comparison of the charging current between direct charging and board charging.