Cell equalizing circuit

• US 7,061,207 B2
• Filed: 08/09/2002
• Issued: 06/13/2006
• Est. Priority Date: 08/09/2002
• Status: Expired due to Fees

• Current Assignee: H2Eye Limited
• Original Assignee: H2Eye Limited
• Inventors: Patel, Sanjay, Shelton, Chris D, Tyson, Lawrence S
• Primary Examiner(s): Sparks, Donald
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US10/216,090
• Publication Number:
  US 20040027092A1
• Time in Patent Office: 1,404 Days
• Field of Search: 320/119, 320/116, 320/118, 320/120, 320/121, 320/140, 363/15, 363/30, 363/34
• US Class Current: 320/119
• CPC Class Codes: H02J 7/0018 using separate charge circuits

Abstract

An electric circuit for equalizing voltages between serially arranged cells. The circuit is operable to generate AC voltages at amplitudes dependent on the DC voltages of the received cells. The AC voltages are all connected to an inductive coupling circuit. The inductive coupling allows higher-voltage cells to induce a recharging current flow in lower voltage cells and so equalize the cell voltages. The circuit also operates to ensure that cell voltages are maintained in equilibrium during charging or discharging of received cells, irrespective of the individual charging and discharging characteristics of the cells. The circuit thus prevents individual cells in a battery from being over-charged or over-discharged and allows more efficient use of the full capacity of a battery without risking damage to the individual cells. The cell equalizing circuit is thus especially useful for rechargeable cells, such as lithium-ion cells, which are sensitive to damage by over-charging and over-discharging.

Claims

1. An electric circuit for receiving a battery of cells in series, comprising:

a plurality of DC-to-AC converters each having a DC-side arranged to connect across positive and negative terminals of cells received by the circuit and an AC-side for carrying an AC voltage converted from the DC-side; and

an inductive coupling between the AC-sides of the DC-to-AC converters to provide an effective current transfer between cells responsive to differences in DC voltages between them; and

wherein each of the DC-to-AC converters comprises a first switch responsive to a first control signal for providing a first polarity of the AC voltage and a second switch responsive to a second control signal for providing a second polarity of the AC voltage.

2. The electric circuit according to claim 1, wherein the inductive coupling comprises transformer windings.

3. The electric circuit according to claim 2, wherein each of the transformer windings comprises a center-tap between two end-taps such that alternate phases of the AC voltages are applied between the center-tap and one or other of the end-taps.

4. An electrically powered device including an electric circuit according to claim 2.

5. The electrically powered device according to claim 4, wherein the electrically powered device is one of a portable computer, a portable video camera, a digital camera, a global positioning receiver, a portable television, a mobile telephone, a submarines, an electric vehicles, or a wheel chair.

6. The electric circuit according to claim 1, wherein the control signals are coupled to the switches via one or more control signal capacitors.

7. An electrically powered device including an electric circuit according to claim 6.

8. The electrically powered device according to claim 7, wherein the electrically powered device is one of a portable computer, a portable video camera, a digital camera, a global positioning receiver, a portable television, a mobile telephone, a submarines, an electric vehicles, or a wheel chair.

9. An electrically powered device including an electric circuit according to claim 1.

10. The electric circuit according to claim 1, wherein the first and second switches are field effect transistors.

11. An electrically powered device including an electric circuit according to claim 10.

12. The electrically powered device according to claim 11, wherein the electrically powered device is one of a portable computer, a portable video camera, a digital camera, a global positioning receiver, a portable television, a mobile telephone, a submarines, an electric vehicles, or a wheel chair.

13. The electric circuit according to claim 1, wherein the control signals are coupled to the switches via one or more control signal transformers.

14. An electrically powered device including an electric circuit according to claim 13.

15. The electrically powered device according to claim 14, wherein the electrically powered device is one of a portable computer, a portable video camera, a digital camera, a global positioning receiver, a portable television, a mobile telephone, a submarines, an electric vehicles, or a wheel chair.

19. The electrically powered device according to claim 9, wherein the electrically powered device is one of a portable computer, a portable video camera, a digital camera, a global positioning receiver, a portable television, a mobile telephone, a submarines, an electric vehicles, or a wheel chair.

16. An electric circuit for receiving a battery of cells in series, comprising:

a plurality of DC-to-AC converters each having a DC-side arranged to connect across positive and negative terminals of cells received by the circuit and an AC-side for carrying an AC voltage converted from the DC-side;

an inductive coupling between the AC-sides of the DC-to-AC converters to provide an effective current transfer between cells responsive to differences in DC voltages between them; and

a comparator configured to output a status responsive to a comparison between a first voltage dependent on a first group of cells and a second voltage dependent on a second group of cells.

17. An electrically powered device including an electric circuit according to claim 16.

18. The electrically powered device according to claim 17, wherein the electrically powered device is one of a portable computer, a portable video camera, a digital camera, a global positioning receiver, a portable television, a mobile telephone, a submarines, an electric vehicles, or a wheel chair.