Charging a secondary battery

• US 7,786,698 B2
• Filed: 01/27/2009
• Issued: 08/31/2010
• Est. Priority Date: 12/17/2004
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: SigmaTel Incorporated (NXP Semiconductors NV)
• Inventors: Felder, Matthew, Schultz, Russell A.
• Primary Examiner(s): Vu, Bao Q
• Assistant Examiner(s): Zhang, Jue
• Application Number:
  US12/360,628
• Publication Number:
  US 20090212739A1
• Time in Patent Office: 581 Days
• Field of Search: 320/128, 320/104, 320/118, 320/132, 320/134, 320/149, 320162-164
• US Class Current: 320/128
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

A method of charging a battery includes applying a charging current from a semiconductor device to the battery during a first battery charging time period. The method also includes measuring a charging voltage level at the battery during the first battery charging time period. During a non-charging voltage measurement time interval, the method includes temporarily stopping application of the charging current from the semiconductor device to the battery and measuring a non-charging voltage level at the battery while the charging current is not being applied to the battery.

Claims

1. A method of charging a battery, the method comprising:

applying a charging current from a semiconductor device to a battery during a first battery charging time period;

measuring a charging voltage level at the battery during the first battery charging time period; and

controlling the charging current applied by an adjustable current source to the battery using the semiconductor device, wherein during the first battery charging time, a constant current is applied to the battery from the start of charging to when an upper threshold voltage level of the battery is reached without turning off the constant current, and wherein during a second battery charging time, the semiconductor device selectively provides a signal to turn off the charging current supplied by the adjustable current source, wherein a first voltage at the battery is measured during a time period when the charging current is turned on and a second voltage at the battery is measured during a time period when the charging current is turned off, and wherein the semiconductor device provides the signal to turn off the charging current when a difference between the first voltage and the second voltage is less than a threshold value.

2. The method of claim 1, wherein the second battery charging time is less than the first battery charging time.

3. The method of claim 1, wherein the battery comprises a non-aqueous battery.

4. The method of claim 1, wherein the battery comprises a lithium-ion type battery.

5. The method of claim 1, further comprising displaying a charging status of the battery at a display device.

8. The method of claim 1, further comprising sending a stop charging signal from the semiconductor device to the adjustable current source when the difference between the first voltage and the second voltage is less than the threshold value.

6. A method, comprising:

sending a charging current from an interface coupled to an adjustable current source to an external battery;

monitoring a voltage level at the external battery;

comparing the voltage level to a limit voltage; and

controlling the charging current applied by the adjustable current source to the external battery using a control module, wherein the control module operates in a first phase of a charging cycle in which a constant current is applied to the external battery from the start of charging to when an upper threshold voltage level of the external battery is reached without turning off the constant current, and wherein the control module operates in a second phase of a charging cycle wherein the control module selectively provides a signal to turn off the current supplied by the adjustable current source, wherein a first voltage at the external battery is measured during a time period when the current is turned on and a second voltage at the external battery is measured during a time period when the current is turned off, and wherein the control module provides the signal to turn off the current when a difference between the first voltage and the second voltage is less than a threshold value.

7. The method of claim 6, further comprising sending a stop charging signal from the control module to the adjustable current source when the difference is less than the threshold value.

9. The method of claim 6, wherein the external battery comprises a non-aqueous battery.

10. The method of claim 6, wherein the external battery comprises a lithium-ion type battery.

11. The method of claim 6, further comprising displaying a charging status of the external battery at a display device.