Circuits and methods for impedance determination using active measurement cancelation

An impedance measurement circuit, comprising;

• an active measurement unit configured to:
• generate a delta signal;
• 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 couples in series between a first end terminal and a second end terminal;
• and
• measure a response signal across the first set of cells when the delta signal is being applied;
• an inverter unit configured to generate 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;
• and
• a cancelation unit 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;
• 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.

An impedance measurement circuit, comprising:

• a signal creator configured to generate a delta signal;
• an application unit configured to apply the delta signal across at least one electrochemical cell 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;
• an inverter unit configured to generate 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 plurality of cancelation circuits, each cancelation circuit configured to apply a portion of the opposite delta signal across a corresponding electrochemical cell of the plurality of electrochemical cells while the delta signal is being and such that 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;
• and
• a measurement unit configured to measure a response signal across the at least one electrochemical cell when the delta signal and the opposite delta signal are being applied.

A method of measuring impedance, comprising:

• generating a delta signal;
• generating 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 during an application period for the delta signal and the opposite delta signal;
• applying 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;
• applying the opposite delta signal across a second set of cells comprising one or more electrochemical cells of the plurality of electrochemical cells, wherein the second set of cells is different from the first set of cells and such that 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;
• and
• measuring a current response signal into the second set of cells when the delta signal and the opposite delta signal are being applied.