# US 7,612,537 B2 · Galvanically isolated charge balance system

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- Number: US 7,612,537 B2
- Document ID: US7612537B2
- Status: Granted
- Kind: B2
- Application number: 11/657,824
- Filed: 2007-01-25
- Published: 2008-07-31
- Granted: 2009-11-03
- Earliest claimed: 2007-01-25
- Assignees: Analog Devices, Inc.
- Inventors: John Wynne; Eamon Hynes
- Web page: https://patentgrep.com/patent/US7612537B2

## CPC

- H02J 7/54: Passive balancing, e.g. using resistors or parallel MOSFETs
- H02J 7/52: for charge balancing, e.g. equalisation of charge between batteries
- H02J 7/82: Control of state of charge [SOC]
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY

## Abstract

A galvanically isolated charge balance system for a multicell battery includes a balancing circuit associated with each cell; each balancing circuit including a flying capacitor; a variable conductance switch; and a biasing circuit for the variable conductance switch; and a galvanically isolating MEMS switching device for selectively connecting the flying capacitor to a voltage supply to charge it to a predetermined voltage and to the biasing circuit for setting the variable conductance switch to adjust the charge on its associated cell to a preselected level.

## Claims

### Claim 1

A galvanically isolated charge balance system for a multicell battery comprising:
a balancing circuit associated with each cell; each balancing circuit including a flying capacitor; a variable conductance switch; and a biasing circuit for said variable conductance switch; and
a galvanically isolating MEMS switching device for selectively connecting said flying capacitor to a voltage supply to charge it to a predetermined voltage and to said biasing circuit for setting said variable conductance switch to adjust the charge on its associated cell to a preselected level.

### Claim 2 (depends on 1)

The galvanically isolated charge balance system of claim 1 in which said variable conductance switch includes a transistor.

### Claim 3 (depends on 2)

The galvanically isolated charge balance system of claim 2 in which said transistor includes a MOSFET.

### Claim 4 (depends on 1)

The galvanically isolated charge balance system of claim 1 in which said biasing circuit includes a capacitor.

### Claim 5 (depends on 1)

The galvanically isolated charge balance system of claim 1 in which said predetermined voltage sets said variable conductance switch to discharge said cell to said predetermined level.

### Claim 6 (depends on 1)

The galvanically isolated charge balance system of claim 1 in which said predetermined voltage sets said variable conductance switch to charge said cell to said predetermined level.

### Claim 7 (depends on 1)

The galvanically isolated charge balance system of claim 1 in which said predetermined voltage sets said variable conductance switch to charge said cell to said predetermined level with a current level which is a predetermined percentage of an external current source.

### Claim 8

A galvanically isolated charge balance system for a multicell battery comprising:
a balancing circuit associated with each cell; each balancing circuit including a flying capacitor; a variable conductance switch; and a biasing circuit for said variable conductance switch; and
a galvanically isolating MEMS switching device for selectively connecting said flying capacitor to a voltage supply to charge it to a predetermined voltage and to said biasing circuit for setting said variable conductance switch to discharge its associated cell to a preselected level.

### Claim 9

A galvanically isolated charge balance system for a multicell battery comprising:
a balancing circuit associated with each cell; each balancing circuit including a flying capacitor; a variable conductance switch; and a biasing circuit for said variable conductance switch; and
a galvanically isolating MEMS switching device for selectively connecting said flying capacitor to a voltage supply to charge it to a predetermined voltage and to said biasing circuit for setting said variable conductance switch to charge its associated cell to a preselected level.