Voltage detecting circuit

• US 20100073004A1
• Filed: 09/21/2009
• Published: 03/25/2010
• Est. Priority Date: 09/25/2008
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Miyamoto, Manabu
• Granted Patent: US 8,400,163 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 19/10 Measuring sum, difference or ratio
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A voltage detecting circuit includes a switch group that selects any one of a plurality of battery cells connected in series, a sampling capacitor that maintains a potential difference between a positive electrode terminal and a negative electrode terminal of a battery cell selected by the switch group, a measuring part that outputs a detected voltage value signal corresponding to the potential difference between ends of the sampling capacitor, a transfer switch that transfers, to the measuring part, the potential difference caused between the ends of the sampling capacitor, a correction capacitor provided in parallel to input terminals of the measuring part, and between the transfer switch and the measuring part, and a discharge switch provided in parallel to the correction capacitor, and controlled so that a switching condition of the discharge switch is mutually exclusive with that of the transfer switch.

Claims

1. A voltage detecting circuit, comprising:

a switch group that selects any one of a plurality of battery cells connected in series;

a sampling capacitor that maintains a potential difference between a positive electrode terminal and a negative electrode terminal of a battery cell selected by the switch group;

a measuring part that outputs a detected voltage value signal corresponding to the potential difference between ends of the sampling capacitor;

a transfer switch that transfers, to the measuring part, the potential difference caused between the ends of the sampling capacitor;

a correction capacitor provided in parallel to input terminals of the measuring part, and between the transfer switch and the measuring part; and

a discharge switch provided in parallel to the correction capacitor, and controlled so that a switching condition of the discharge switch is mutually exclusive with that of the transfer switch.

2. The voltage detecting circuit according to claim 1,

wherein the correction capacitor has a capacity value corresponding to a capacity value of parasitic capacitance added to the transfer switch.

3. The voltage detecting circuit according to claim 1,

wherein, in the correction capacitor, a capacity value is switchable to a larger value in a case of measurement of a battery cell connected to a high potential side of the plurality of battery cells.

4. The voltage detecting circuit according to claim 3,

wherein the capacity value of the correction capacitor is determined in accordance with a potential difference between a potential of a positive electrode terminal of a battery cell corresponding to the high potential side transfer switch, and a potential of a negative electrode terminal of a battery cell connected to a lowest potential side, the positive electrode terminal being connected to the correction capacitor.

5. The voltage detecting circuit according to claim 1,

wherein the correction capacitor is disconnected from the transfer switch and the measuring part in a case of measurement of the battery cell connected to a lowest potential side of the plurality of battery cells.

6. The voltage detecting circuit according to claim 1,

wherein the sampling capacitor comprises a capacitor externally added to the voltage detecting circuit, and

wherein the voltage detecting circuit further comprises:

first and second external terminals to which the sampling capacitor is connected.

7. The voltage detecting circuit according to claim 6,

wherein the correction capacitor has a capacity value corresponding to a capacity value of parasitic capacitance added to the transfer switch and the first and second external terminals.

8. The voltage detecting circuit according to claim 1, further comprising:

a switch control circuit that controls a switching condition of each switching circuit included in the switch group and that of the transfer switch.

9. The voltage detecting circuit according to claim 1,

wherein the transfer switch includes:

a low potential side transfer switch that connects a low potential side terminal of the sampling capacitor to a low potential side input terminal of the measuring part; and

a high potential side transfer switch that connects a high potential side terminal of the sampling capacitor to a high potential side input terminal of the measuring part.

10. The voltage detecting circuit according to claim 1,

wherein the transfer switch includes:

a low potential side transfer switch that connects a low potential side terminal of the sampling capacitor to a low potential side input terminal of the measuring part; and

a plurality of high potential side transfer switches that each connect a high potential side terminal of the sampling capacitor to a high potential side input terminal of the measuring part, a number of the high potential side transfer switches corresponding to a number of the plurality of battery cells,

wherein the correction capacitor and the discharge switch are connected to each high potential side transfer switch of the plurality of high potential side transfer switches except for a high potential side transfer switch corresponding to the battery cell connected to a lowest potential side.

11. The voltage detecting circuit according to claim 1, further comprising:

a register that stores respective voltage values of the plurality of battery cells measured by the measuring part,

wherein the voltage detecting circuit sequentially measures the plurality of battery cells in a predetermined cycle, and stores results of the measurement in the register, and

wherein the voltage detecting circuit outputs the value stored in the register in response to a request from another circuit.