Interface circuit with adjustable bias voltage enabling maximum power point tracking of capacitive energy harvesting devices

Abstract

The operation analysis of a new interface circuit for electrostatic vibration energy harvesting with adjustable bias voltage is carried out in this paper. Two configurations determined by the open or closed states of an electronic switch are examined. The increase of the voltage across a biasing capacitor, occurring when the switch is open, is proved theoretically and experimentally. With the decrease of this biasing voltage which occurs naturally when the switch is closed due to imperfections of the circuit, the bias voltage can be maintained close to a target value by appropriate ON and OFF control of the switch. As the energy converted by the variable capacitor on each cycle depends on the bias voltage, this energy can be therefore accurately controlled. This feature opens up promising perspectives for optimization the power harvested by electrostatic devices. Simulation results with and without electromechanical coupling effect are presented. In experimental tests, a simple switch control enabling to stabilize the bias voltage is described.

A Novel Characterization Method for Accurate Lumped Parameter Modeling of Electret Electrostatic Vibration Energy Harvesters

“…To estimate the influence of random error sources on the measurement using (5)(6), E is first estimated at 20V, by a surface potential measurement done 1mm on top of the device using a contact-less electrostatic voltmeter. The four values of η are measured by synchronous detection, and δ V is measured as 25mV.…”

“…where ξ :" C S {C min and η :" C max {C min . From (5)(6), it comes that the measurement uncertainty due to random error sources decreases by decreasing C S . However, decreasing C S increases the electromechanical coupling effect on the e-VEH's dynamics, thereby inducing a systematic measurement error on C max and E. This is because equations (3-4) are derived from (1-2) assuming that pC max , C min q with circuit HW1 (in (1)) are equal to pC max , C min q with circuit HW2 (in (2)).…”

Optimization of a Piezoelectric Energy Harvester and Design of a Charge Pump Converter for CMOS-MEMS Monolithic Integration

“…This is a critical limitation for the circuit miniaturization; in addition, inductances of such high values are relatively expensive. A charge pump circuit is an alternative to the SSHI that only uses capacitors [28,29]. It is a switching regulator that delivers the power by only charging and discharging capacitors.…”