Charge balancing circuit

Patent 6806686 Issued on October 19, 2004. Estimated Expiration Date:

April 25, 2023. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

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Inventor

Thrap, Guy C.

Assignee

Maxwell Technologies, Inc.

Application

No. 10423708 filed on 04/25/2003

US Classes:

320/118With discharge of cells or batteries

Examiners

Primary: Tso, Edward H.

Attorney, Agent or Firm

Foley & Lardner LLP

International Class

H02J 700

Abstract

A charge balancing circuit is disclosed that is configured to provide charge balancing for a bank of series connected charge storage devices such as capacitors. One embodiment of the charge balancing circuit comprises a voltage divider, an operational amplifier, and a negative feedback resistor connected between every two capacitors. The circuit is configured to monitor the voltage in each of the capacitors and, if the voltage in one of the capacitors is higher than the other, the circuit transfers energy from the higher charged capacitor to the lower charged capacitor until the capacitors are balanced. A current limiting resistor can be included for limiting the output current of the operational amplifier to a safe value and for providing feedback information regarding the health of the capacitor. An additional gain stage can also be included for increasing the output current of the operational amplifier for banks of large charge storage devices such as capacitors.