Power management circuit and methodology for battery-powered systems

• US 20060145665A1
• Filed: 12/30/2004
• Published: 07/06/2006
• Est. Priority Date: 12/30/2004
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Bell, David B., Zemke, Roger A.
• Granted Patent: US 7,548,041 B2
• Time in Patent Office: Days
• US Class Current: 320/133
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A power management system including a battery-powered application, in which an input current is supplied by a source of current that may be a current-constrained source, such as a USB port, to a battery for charging the battery and to an application load. Battery charging current is supplied to the battery for a period of time based on magnitude of battery charging current, so that charging current of lesser magnitude is applied to the battery for a greater period of time. In accord with one implementation, battery charging current is determined by monitoring the difference between a programmed charging current, dependent on battery type, and magnitude of current used by the load. Change of battery charging current due to voltage mode charging, when charge current begins to drop as the battery approaches full charge, is detected, and in response, the charging period is set to a fixed charging period based on the battery.

Claims

1. For a battery powered application, a power management method, comprising steps for:

supplying a current to the battery for a charging period to charge the battery; and

controlling the charging period in accordance with current magnitude.

2. A method in accordance with claim 1, wherein the charging period is controlled inversely to current magnitude.

3. A method in accordance with claim 1, including a step for detecting when a change of current is due to voltage mode charging, and in response, setting the charging period to a prescribed charging period.

4. A method in accordance with claim 3, in which the prescribed charging period is dependent on battery type.

5. A method in accordance with claim 1, wherein input current is supplied to (1) the battery for charging the battery and (2) a load, including an additional step for determining charging current magnitude, wherein the step for supplying current to the battery is controlled in accordance with a difference between (a) a prescribed current dependent on battery type and (b) load current magnitude.

6. A method in accordance with claim 5, in which the input current is obtained from a USB port.

7. A power management system for implementation in a battery powered application, comprising:

an input current node to which a current source is applied for providing input current to a battery and a load;

a first circuit coupled to the input current node and configured for supplying a charging current to the battery for a charging period;

a second circuit configured for determining magnitude of current supplied to the battery by the first circuit; and

a third circuit, coupled to the first circuit and responsive to magnitude of the charging current, for controlling the charging period.

8. A system in accordance with claim 7, including:

a fourth circuit for monitoring load current;

wherein the third circuit is configured for supplying current to the battery in accordance with a difference between (a) a prescribed current of magnitude dependent on battery type and (b) load current magnitude monitored by the fourth circuit.

9. A system in accordance with claim 8, including:

a fifth circuit configured for detecting when a change of charging current is due to a voltage mode charging, and in response, setting the charging period to a prescribed charging period.

10. A system in accordance with claim 9, in which the prescribed charging period is dependent on battery type.

11. A system in accordance with claim 8, wherein the input current source is a USB port.

12. A power management system for implementation in a battery powered application, comprising:

an input current source for supplying an input current to a battery and a load;

a load current monitor circuit for determining load current magnitude;

a variable period timer;

a charging circuit coupled to the timer for controlling supply of current to the battery for a charging period determined by the timer; and

a control circuit responsive to load current magnitude for controlling the timer period.

13. A system in accordance with claim 12, including:

a charge mode detector circuit, coupled to the battery and a source of reference voltage, for detecting voltage mode charging of the battery, and in response, setting the charging period of the timer to a prescribed charging period.

14. A system in accordance with claim 13, in which the prescribed charging period is dependent on battery type.

15. A system in accordance with claim 12, wherein the charging circuit is coupled to the load current monitor circuit and configured to control magnitude of battery current in accordance with (a) a prescribed current of magnitude dependent on type of battery and (b) load current.

16. A system in accordance with claim 12, wherein the input current source is a USB port.

17. A system in accordance with claim 15, wherein the magnitude of battery current is controlled in accordance with a difference between the prescribed and load currents.

19. A system in accordance with claim 17, including fourth means for monitoring load current, and wherein the first means determines battery current magnitude in accordance with a difference between (a) a prescribed current dependent on battery type and (b) the load current.

18. A power management system for implementation in a battery powered application, comprising:

an input current source for supplying input current to (1) a battery for charging the battery and (2) a load;

first means for determining battery current magnitude;

a variable period timer;

second means for controlling supply of current to the battery for a charging period determined by the timer; and

third means for controlling the timer period in accordance with magnitude of battery current.

20. A system in accordance with claim 18, including fifth means for detecting when a change of battery current is due to voltage mode charging, and in response, setting the charging period to a prescribed charging period.