Device and method for charge equalization of series-connected individual cells of an energy accumulator

• US 7,812,572 B2
• Filed: 03/22/2006
• Issued: 10/12/2010
• Est. Priority Date: 03/24/2005
• Status: Expired due to Fees

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Continental Automotive GmbH (Continental AG)
• Inventors: Bolz, Stephan, Knorr, Rainer, Gotzenberger, Martin
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): OMAR, AHMED H
• Application Number:
  US11/909,513
• Publication Number:
  US 20080211456A1
• Time in Patent Office: 1,665 Days
• Field of Search: 320/166, 320/167
• US Class Current: 320/166
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Abstract

A device and a method equalize a charge of series-connected individual cells of an energy accumulator with a DC/DC converter. The DC/DC converter draws energy from the energy accumulator or from another power source for charging an intermediate circuit capacitor whose voltage is inverted in a DC/AC converter and the alternating voltage is converted into an intermittent direct current by a rectifier via an AC bus and a coupling element. A switch is placed between the AC bus and each cell thereby enabling the cell to be coupled to the AC bus or disconnected therefrom.

Claims

1. A device for charge equalizing series-connected individual cells of an energy accumulator, the device comprising:

an energy accumulator including a plurality of individual cells connected in series, the energy accumulator having a connection;

a DC/DC converter including an input and an output;

a switch having a first switching state connecting said input of said DC/DC converter to the connection of the energy accumulator to remove energy from the energy accumulator, said switch having a second switching state connecting said input of said DC/DC converter to a further power source;

a DC/AC converter connected to said output of said DC/DC converter, said DC/AC converter having an intermediate circuit capacitor and a bridge connection;

AC buses disposed downstream of said DC/AC converter;

a rectifier;

coupling elements, a series connection of respective one of said coupling elements and said rectifier is disposed between each of the cells and a respective one of said AC buses; and

selector switches, at least one of said selector switches disposed between said respective AC bus and each of the cells, the cells being electrically coupled to said respective AC bus or electrically disconnected from said respective AC bus through said selector switches.

2. The device according to claim 1, wherein:

said rectifier has a plurality of diodes connected to said coupling elements being coupling capacitors; and

a respective coupling capacitor of said coupling capacitors each connected to a first diode and second diode of said diodes, said first diode connected to said respective coupling capacitor so that said first diode (D_xa, D_xc, wherein x=1 to n) is conductive from a connection of said respective coupling capacitor facing away from said respective AC bus to a positive connection of a respective cell and said second diode is conductive from a negative connection of the respective cell to said connection of said respective coupling capacitor facing away from said respective AC bus.

3. The device according to claim 1, further comprising a further switch and said DC/DC converter may be connected to a further power source through said further switch.

4. The device according to claim 1, wherein said DC/DC converter is a current-regulated voltage reduction unit.

5. The device according to claim 1, wherein said bridge connection of said DC/AC converter includes a half-bridge with two series transistors connected parallel to said intermediate circuit capacitor.

6. The device according to claim 1, wherein said bridge connection of said DC/AC converter has a configuration with multi-phases, each of said phases is a half-bridge having two series transistors connected parallel to said intermediate circuit capacitor.

7. The device according to claim 1, wherein the energy accumulator is a double-layer capacitor.

8. The device according to claim 1, wherein the energy accumulator contains a series connection of accumulators.

9. The device according to claim 5, wherein said bridge connection of said DC/AC converter is self-clocked.

10. The device according to claim 6, wherein said bridge connection of said DC/AC converter is self-clocked.

11. The device according to claim 1, further comprising a common housing, the energy accumulator, said rectifier, said coupling elements and said AC buses are integrated in said common housing.

12. A method for operating a device for charge equalizing series-connected individual cells of an energy accumulator, the device including an energy accumulator including a plurality of individual cells connected in series, the energy accumulator having a connection, a DC/DC converter including an input and an output, a switch having a switching state connecting the input of the DC/DC converter to the connection of the energy accumulator to remove energy from the energy accumulator and a second switching state connecting the input of the DC/DC converter to a further power source, a DC/AC converter connected to the output of the DC/DC converter, the DC/AC converter having an intermediate circuit capacitor and a bridge connection, AC buses disposed downstream of the DC/AC converter, a rectifier, coupling elements, a series connection of a respective one of the coupling elements and the rectifier is disposed between each of the cells and a respective one of the AC buses, and selector switches, at least one of the selector switches is disposed between the respective AC bus and each of the cells, the cells being electrically coupled to the respective AC bus or electrically disconnected from the respective AC bus by the selector switches, the method which comprises the steps of:

supplying the DC/DC converter from one of the energy accumulator and the further power source, the DC/DC converter supplying a current to the intermediate circuit capacitor resulting in a voltage being automatically established at the intermediate circuit capacitor for charging the cells;

inverting the voltage in a DC/AC converter;

supplying, from the DC/AC converter, an inverted, pulsating charging current via the AC buses, the coupling elements and diodes of the rectifier; and

selecting at least one cell to be charged via at least one of the selector switches.

13. The method according to claim 12, which further comprises:

providing the DC/AC converter as a multi-phase DC/AC converter providing a charging current for the cell with a lowest cell voltage flowing in a first phase from the intermediate circuit capacitor via a first transistor, a first AC bus, a first selector switch, a first coupling element and a first diode, through the cell and back via a second diode, a second coupling element, a second selector switch, a second AC bus and a fourth transistor to the intermediate circuit capacitor and a charging current flows in a second phase from the intermediate circuit capacitor via a third transistor, the second AC bus, the second selector switch, the second coupling element and a third diode, through the cell and back via a fourth diode, the first coupling element, the first selector switch, the first AC bus and a second transistor to the intermediate circuit capacitor.