Circuits and methods for impedance determination using active measurement cancelation

摘要

A delta signal and opposite delta signal are generated such that a sum of the two signals is substantially zero. The delta signal is applied across a first set of electrochemical cells. The opposite delta signal is applied across a second set of electrochemical cells series connected to the first set. A first held voltage is established as the voltage across the first set. A second held voltage is established as the voltage across the second set. A first delta signal is added to the first held voltage and applied to the first set. A second delta signal is added to the second held voltage and applied to the second set. The current responses due to the added delta voltages travel only into the set associated with its delta voltage. The delta voltages and the current responses are used to calculate the impedances of their associated cells.

主权项

1. An impedance measurement circuit, comprising:
a signal creator configured to generate a delta signal and an opposite delta signal, which is substantially equal and opposite in amplitude to the delta signal, such that a sum of the delta signal and the opposite delta signal is substantially zero at any instant of time; a first application circuit configured to apply the delta signal across a first set of cells comprising one or more electrochemical cells of a plurality of electrochemical cells, wherein the plurality of electrochemical cells are operably coupled in series between a first end terminal and a second end terminal; a second application circuit configured to apply the opposite delta signal while the delta signal is being applied and across a second set of cells comprising one or more electrochemical cells of the plurality of electrochemical cells; and a measurement unit configured to measure a response signal across the second set of cells when the delta signal and the opposite delta signal are being applied; wherein the second set of cells is different from the first set of cells and there is substantially no change in current between the first end terminal and the second end terminal due to the application of the delta signal and the opposite delta signal.