Measuring circuit using switched capacitors for measuring voltage and related systems, methods, and devices
Measuring circuits including switched capacitors, and related systems, methods, and devices are disclosed. A measurement circuit includes a flying capacitor, a grounded capacitor, a first switch, a second switch, a third switch, and a fourth switch. The first switch is configured to selectively electrically connect an electrochemical cell cathode node to a first terminal of the flying capacitor. The second switch is configured to selectively electrically connect an electrochemical cell anode node to a second terminal of the flying capacitor. The third switch is configured to selectively electrically connect the first terminal of the flying capacitor to a third terminal of the grounded capacitor. The fourth switch is configured to electrically connect the second terminal of the flying capacitor to a fourth terminal of the grounded capacitor. The fourth terminal is electrically connected to the reference voltage potential node.
1. A measurement circuit, comprising:
a flying capacitor comprising a first terminal and a second terminal;
an electrochemical cell cathode node;
an electrochemical cell anode node;
a first set of switches including a first switch and a second switch, the first switch between the electrochemical cell cathode node and the first terminal of the flying capacitor, the second switch between the electrochemical cell anode node and the second terminal of the flying capacitor;
a reference voltage potential node;
a grounded capacitor including a third terminal and a fourth terminal, the fourth terminal electrically connected to the reference voltage potential node;
a second set of switches including a third switch and a fourth switch, the third switch between the first terminal of the flying capacitor and the third terminal of the grounded capacitor, the fourth switch between the second terminal of the flying capacitor and the fourth terminal of the grounded capacitor; and
a controller to provide a first signal and a second signal to the first set of switches and the second set of switches, respectively, to control opening and closing of the first set of switches and the second set of switches;
wherein, the first signal and second signal are complementary signals having a dead time between opening of the first set of switches and closing of the second set of switches and between opening of the second set of switches and closing of the first set of switches.
2. The measurement circuit of claim 1 , wherein the controller includes an analog to digital converter input electrically connected to the third terminal of the grounded capacitor.
3. The measurement circuit of claim 2 , wherein the controller is to control the first set of switches and the second set of switches to alternatingly close the first set of switches and the second set of switches such that the flying capacitor is alternatingly electrically connected to the electrochemical cell cathode node and the electrochemical cell anode node and to the third terminal and the fourth terminal of the grounded capacitor.
4. The measurement circuit of claim 1 , comprising a multiplexer including a first plurality of inputs and a second plurality of inputs, the first plurality of inputs selectively electrically connectable to the electrochemical cell cathode node, the second plurality of inputs selectively electrically connectable to the electrochemical cell anode node.
5. The measurement circuit of claim 4 , wherein the first plurality of inputs are electrically connected to cathodes of respective electrochemical cells of a string of series-connected electrochemical cells and the second plurality of inputs of the multiplexer are electrically connected to anodes of respective electrochemical cells of the string of series-connected electrochemical cells.
6. The measurement circuit of claim 5 , comprising a controller electrically connected to the multiplexer, the controller to control the multiplexer to selectively electrically connect a cathode and an anode of each of the electrochemical cells, one at a time, to the electrochemical cell cathode node and the electrochemical cell anode node, respectively.
7. The measurement circuit of claim 6 , wherein the controller is to control switching of the first set of switches and the second set of switches.
8. The measurement circuit of claim 1 , wherein the reference voltage potential node is electrically connected to a ground terminal of the measurement circuit.
9. An electrochemical cell charging system, comprising:
a string of series-connected electrochemical cells comprising a plurality of electrochemical cells, each of the plurality of electrochemical cells including a cathode and an anode;
a multiplexer including a plurality of electrochemical cell terminal inputs, two outputs, and multiplexer control inputs, the plurality of electrochemical cell terminal inputs of the multiplexer respectively electrically connected to the cathode and the anode of each of the plurality of electrochemical cells, the two outputs respectively electrically connected to an electrochemical cell cathode node and an electrochemical cell anode node, the multiplexer to selectively electrically connect the cathode of a selected electrochemical cell to the electrochemical cell cathode node and the anode of the selected electrochemical cell to the electrochemical cell anode node responsive to multiplexer control signals received at the multiplexer control inputs;
a flying capacitor including a first terminal and a second terminal;
a first set of switches including a first switch and a second switch, the first switch to selectively electrically connect the electrochemical cell cathode node to the first terminal of the flying capacitor, the second switch to selectively electrically connect the electrochemical cell anode node to the second terminal of the flying capacitor;
a grounded capacitor including a third terminal and a fourth terminal, the fourth terminal electrically connected to a reference voltage potential node;
a second set of switches including a third switch and a fourth switch, the third switch to selectively electrically connect the first terminal of the flying capacitor to the third terminal of the grounded capacitor, the fourth switch to selectively electrically connect the second terminal of the flying capacitor to the fourth terminal of the grounded capacitor; and
a controller including an analog to digital converter, the analog to digital converter including an input electrically connected to the third terminal of the grounded capacitor.
10. The electrochemical cell charging system of claim 9 , wherein the controller is to generate the multiplexer control signals.
11. The electrochemical cell charging system of claim 9 , wherein the controller is to control the first set of switches and the second set of switches to alternatingly close the first set of switches and the second set of switches so as to provide a cell voltage potential difference across the selected electrochemical cell to the analog to digital converter input.
12. The electrochemical cell charging system of claim 9 , wherein the controller is to balance charging of the plurality of electrochemical cells.
13. The electrochemical cell charging system of claim 9 , wherein the reference voltage potential node is electrically connected to a ground node of the electrochemical cell charging system.
14. The electrochemical cell charging system of claim 9 , wherein the controller is to sample, at the analog to digital converter input, a cell voltage potential corresponding to a cell voltage potential difference of the selected electrochemical cell.
15. The electrochemical cell charging system of claim 9 , wherein the controller is to generate switch control signals to control switching of the first set of switches and the second set of switches.
16. The electrochemical cell charging system of claim 15 , wherein the controller is to provide the switch control signals from complementary waveform generator pins of the controller.
17. A method comprising:
controlling, with a controller, a multiplexer to electrically connect a cathode and an anode of a selected electrochemical cell of a string of electrochemical cells to respective electrochemical cell terminal nodes;
alternatingly closing, with the controller, a first set of switches and a second set of switches, the first set of switches electrically connected between a flying capacitor and the electrochemical cell terminal nodes, the second set of switches electrically connected between the flying capacitor and a grounded capacitor;
sampling, with the controller, a cell voltage potential at the grounded capacitor, the cell voltage potential corresponding to a cell voltage potential difference across the selected electrochemical cell; and
balancing, with the controller, charging of the electrochemical cells based at least in part on the sampled cell voltage potential.
18. The method of claim 17 , comprising controlling, with the controller, charging of the selected electrochemical cell based at least in part on the sampled cell voltage potential.