Power management systems with current sensors

• US 7,868,483 B2
• Filed: 01/18/2008
• Issued: 01/11/2011
• Est. Priority Date: 09/06/2007
• Status: Expired due to Fees

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Lu, Chun, Su, Xinhe
• Primary Examiner(s): Fureman; Jared J
• Assistant Examiner(s): Amrany; Adi
• Application Number:
  US12/009,466
• Publication Number:
  US 20090066161A1
• Time in Patent Office: 1,089 Days
• Field of Search: 307 43- 44, 307/48, 307 51- 52, 307/62, 307/64, 307/66, 307/70
• US Class Current: 307/85
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence

Abstract

A power management system includes a power management unit (PMU) and a current sensor. The PMU is operable for controlling a first power source and a second power source. The second power source is operable for being charged by the first power source via a charging path. The current sensor has a first terminal coupled to the first power source and the second power source and has a second terminal coupled to the second power source via the charging path. The current sensor is operable for sensing a first current flowing from the first power source through the current sensor and for sensing a second current flowing from the second power source through the current sensor.

Claims

1. A power management system comprising:

a power management unit for controlling a first power source and a second power source, wherein said second power source is charged by said first power source through a charging path, and wherein said first power source and said second power source selectively provide power to a load; and

a current sensor having a first terminal for being electrically coupled to said first power source and also electrically coupled to said second power source and having a second terminal for being coupled to said second power source via said charging path, wherein said current sensor senses a first current flowing from said first power source through said current sensor and a second current flowing from said second power source through said current sensor, and wherein said power management unit determines whether a short-circuit condition or an over-voltage condition occurs based upon the sensed information from said current sensor.

2. The power management system of claim 1, wherein said power management unit is operable for triggering a protection action if one of said first current and said second current is greater than a predetermined threshold.

3. The power management system of claim 1, further comprising:

a switch coupled to said current sensor in series and for being turned off if one of said first current and said second current is greater than a predetermined threshold.

4. The power management system of claim 1, further comprising

a DC-DC converter coupled to said current sensor and coupled between a first output terminal and a second output terminal, wherein said DC-DC converter converts a first output voltage at said first output terminal to a second output voltage at said second output terminal.

5. The power management system of claim 4, wherein said DC-DC converter comprises a switch for being turned off if one of said first current and said second current is greater than a predetermined threshold.

6. The power management system of claim 1, wherein said first current comprises a load current from said first power source to said load coupled to said second terminal.

7. The power management system of claim 1, wherein said first current comprises a charging current flowing through said charging path from said first power source to said second power source and a load current from said first power source to said load coupled to said second terminal.

8. The power management system of claim 7, wherein said charging path comprises a switch, an inductor and a charging sensor coupled in series, wherein said charging sensor senses said charging current, and wherein said switch is turned off if said charging current is greater than a preset threshold.

9. The power management system of claim 1, wherein said second current comprises a load current from said second power source to said load coupled to said second terminal.

10. The power management system of claim 1, wherein said power management unit comprises:

an amplifier coupled across said current sensor and for generating a voltage signal indicating a level of said first current or said second current;

a first comparator coupled to said amplifier and for comparing said voltage signal with a short-circuit threshold voltage to determine whether said short-circuit condition occurs; and

a second comparator coupled to said amplifier and for comparing said voltage signal with an over-voltage threshold voltage to determine whether said over-voltage condition occurs.

11. An electronic system comprising:

a load;

a power management system for managing power to said load, said power management system comprising;

a power management unit for controlling a first power source and a second power source, wherein said second power source is charged by said first power source through a charging path, and wherein said first power source and said second power source selectively provide said power to said load;

a current sensor having a first terminal electrically coupled to said first power source and also electrically coupled to said second power source and having a second terminal coupled to said second power source via said charging path, wherein said current sensor senses a first current flowing from said first power source through said current sensor and a second current flowing from said second power source through said current sensor, and wherein said power management unit determines whether a short-circuit condition or an over-voltage condition occurs based upon sensed information from said current sensor.

12. The electronic system of claim 11, wherein said power management unit is operable for triggering a protection action if one of said first current and said second current is greater than a predetermined threshold.

13. The electronic system of claim 11, wherein said power management system further comprises:

a switch coupled to said current sensor in series and for being turned off if one of said first current and said second current is greater than a predetermined threshold.

14. The electronic system of claim 11, wherein said power management system further comprises:

a DC-DC converter coupled to said current sensor and coupled between a first output terminal and a second output terminal, wherein said DC-DC converter converts a first output voltage at said first output terminal to a second output voltage at said second output terminal.

15. The electronic system of claim 14, wherein said DC-DC converter comprises a switch for being turned off if one of said first current and said second current is greater than a predetermined threshold.

16. The electronic system of claim 14, wherein said power management unit comprises:

an amplifier coupled across said current sensor and for generating a voltage signal indicating a level of said first current or said second current;

a first comparator coupled to said amplifier and for comparing said voltage signal with a short-circuit threshold voltage to determine whether said short-circuit condition occurs; and

a second comparator coupled to said amplifier and for comparing said voltage signal with an over-voltage threshold voltage to determine whether said over-voltage condition occurs.

17. The electronic system of claim 11, wherein said charging path comprises a switch, an inductor and a charging sensor coupled in series, wherein said charging sensor senses said charging current, and wherein said switch is turned off if said charging current is greater than a preset threshold.

18. A method for managing power from a first power source and a second power source, comprising:

charging said second power source by said first power source via a charging path;

sensing a first current flowing from said first power source through a current sensor by said current sensor;

sensing a second current flowing from said second power source through said current sensor by said current sensor; and

determining whether a short-circuit condition or an over-current condition occurs based upon sensed information from said current sensor,

wherein said current sensor has a first terminal electrically coupled to said first power source and electrically coupled to said second power source and has a second terminal coupled to said second power source via said charging path.

19. The method of claim 18, further comprising:

triggering a protection action if one of said first current and said second current is greater than a predetermined threshold.

20. The method of claim 18, wherein said first current comprises a load current from said first power source to a load.

21. The method of claim 18, wherein said first current comprises a charging current flowing through said charging path from said first power source to said second power source and a load current from said first power source to a load.

22. The method of claim 18, wherein said second current comprises a load current from said second power source to a load.

23. The method of claim 18, further comprising:

generating a voltage signal indicative of a level of said first current or said second current;

comparing said voltage signal with a short-circuit threshold voltage;

determining whether said short-circuit condition occurs based upon a first comparison result;

comparing said voltage signal with an over-voltage threshold voltage; and

determining whether said over-voltage condition occurs based upon a second comparison result.