Input source detection for a battery charger

• US 7,782,022 B2
• Filed: 10/19/2007
• Issued: 08/24/2010
• Est. Priority Date: 10/19/2007
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Reed, Byron, Xu, Zhenxue
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): RAMADAN, RAMY O
• Application Number:
  US11/975,617
• Publication Number:
  US 20090102429A1
• Time in Patent Office: 1,040 Days
• Field of Search: 320/145, 320/152, 320157-159, 320162-164
• US Class Current: 320/164
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters

Abstract

A system and method for determining if a USB port can source sufficient current to charge a rechargeable battery at a predetermined peak current level. Detection circuitry is disposed between the USB port and the battery. The detection circuitry includes a current source that is controlled to provide to the battery an increasing current that is sourced by the USB port. As the source current is increased from an initial value to a predetermined peak current source value, the output voltage of the USB port is monitored. If the USB port output voltage drops below a specified threshold voltage before the current source has ramped to the peak current source value, the load current is removed from the battery and an indication is provided that the USB port cannot provide the specified current. The detection process is then repeated after a specified delay interval. If the current source ramps up to the peak source current value and the USB port voltage has not decreased below the specified threshold voltage, charging of the rechargeable battery from the USB port continues at the peak source current.

Claims

1. A method for determining in detection circuitry disposed between a power source and a rechargeable battery whether the power source can source a predetermined peak charging current to charge the rechargeable battery, wherein the power source has an output voltage, the method comprising the steps of:

in a first controlling step, controlling, in the detection circuitry, the application of a charging current sourced by the power source and provided to the rechargeable battery so that the charging current increases from an initial charging current toward said peak charging current in a predetermined manner;

monitoring the power source output voltage to determine whether the power source output voltage decreases below a predetermined threshold voltage as said charging current increases from said initial charging current toward said peak charging current;

in the event the charging current reaches the peak charging current and said monitoring step has not produced an indication that said power source output voltage has dropped below said predetermined threshold voltage, in a second controlling step, controlling, in the detection circuitry, the sourcing of charging current from said power source to said rechargeable battery at said peak charging current; and

in the event the monitoring step results in an indication that said power source output voltage has dropped below said predetermined threshold voltage before said charging current has reached said peak charging current, in a third controlling step, controlling said detection circuitry so as to discontinue sourcing of said charging current from said power source to said rechargeable battery.

2. The method of claim 1 wherein said controlling step comprises the step of controlling in the detection circuitry the application of a charging current sourced by a USB port and provided to the rechargeable battery so that the charging current increases from an initial charging current of approximately 0 milliamps toward said peak charging current in a predetermined manner.

3. The method of claim 1 wherein said controlling step comprises the step of controlling in the detection circuitry the application of a charging current sourced by the power source and provided to the rechargeable battery so that the charging current increases from an initial charging current toward said peak charging current in a generally linear manner.

4. The method of claim 1 wherein said controlling step comprises the step of controlling, in the detection circuitry, the application of a charging current sourced by the power source and provided to the rechargeable battery so that the charging current increases from an initial charging current toward said peak charging current in a generally non-linear manner.

5. The method of claim 1 further including the steps of:

generating a delay of a predetermined time interval in the event said monitoring step results in a determination that said power source output voltage has dropped below said predetermined threshold voltage; and

following said delay repeating said first controlling step, said monitoring step and said second and third controlling steps, as applicable.

6. The method of claim 1 wherein said first controlling step comprises the step of controlling a pulse width modulator within said detection circuitry to control the application of said charging current sourced by the power source and provided to the rechargeable battery so that the charging current increases from said initial charging current toward said peak charging current in said predetermined manner.

7. The method of claim 1 wherein said first controlling step comprises the step of controlling a linear current source within said detection circuitry to control the application of said charging current sourced by the power source and provided to the rechargeable battery so that the charging current increases from said initial charging current toward said peak charging current in said predetermined manner.

8. The method of claim 1 wherein said power source comprises a Universal Serial Bus (USB) port.

9. Circuitry for coupling between a power source having an output voltage and a rechargeable battery, said circuitry comprising:

an input for coupling to a power connection of said power source and an output for coupling to said rechargeable battery;

a controllable current source disposed between said input and said output;

a controller for controlling via said controllable current source, a charging current sourced from said power connection and provided to said rechargeable battery, said controller operative to control said controllable current source such that said charging current increases from an initial charging current toward a predetermined peak charging current in a predetermined manner;

a comparator operative to provide an indication if said power source output voltage decreases below a predetermined threshold voltage while said charging current is increasing from said initial charging current toward said peak charging current;

said controller, operative in response to an indication from said comparator that said power source output voltage has dropped below said predetermined threshold voltage before said charging current has reached said predetermined peak charging current to control said controllable current source so as to terminate sourcing of charging current from said power source to said rechargeable battery via said controllable current source; and

said controller, operative in response to an indication from said comparator that said power source output voltage has not dropped below said predetermined threshold voltage before said charging current has reached said predetermined peak charging current to control said controllable current source so as to continue the sourcing of charging current from said power source to said rechargeable battery via said controllable current source at said peak charging current.

10. The circuitry of claim 9 wherein said initial charging current is approximately 0 milliamps.

11. The circuitry of claim 9 wherein said controller is operative to control said controllable current source so as to increase said charging current in a generally linear manner from said initial charging current toward said peak charging current.

12. The circuitry of claim 9 wherein said controller is operative to control said controllable current source so as to increase said charging current in a generally non-linear manner from said initial charging current toward said peak charging current.

13. The circuitry of claim 9 further including delay circuitry operative to generate a predetermined delay in response to a determination by said comparator that a USB port output voltage has dropped below said predetermined threshold voltage, said control circuitry operative to control said controllable current source to re-initiate charging of said rechargeable battery with a charging current increasing from said initial charging current toward said peak charging current following said predetermined delay.

14. The circuitry of claim 9 wherein said controllable current source includes a pulse width modulator operative to provide said charging current for charging said battery in response to a control input.

15. The circuitry of claim 9 wherein said controllable current source includes a linear current source operative to provide said charging current for charging said battery in response to a control input.

16. The circuitry of claim 9 wherein said power source comprises a Universal Serial Bus (USB) port.

17. A system for determining whether a power source can source a predetermined peak charging current to a rechargeable battery:

a Universal Serial Bus (USB) output port having a power connection, said output port having an output voltage;

a rechargeable battery;

detection circuitry in electrical communication with said USB output port and said rechargeable battery, said detection circuitry including;

an input for receiving power from said power connection and an output for coupling to said rechargeable battery;

a controllable current source disposed between said input and said output;

a controller for controlling, via said controllable current source, a charging current sourced from said power connection and provided to said rechargeable battery, said controller operative to control said controllable current source such that said charging current increases from an initial charging current toward a predetermined peak charging current in a predetermined manner;

a comparator operative to provide an indication if said USB port output voltage decreases below a predetermined threshold voltage while said charging current is increasing from said initial charging current toward said peak charging current;

said controller, operative in response to an indication from said comparator that said USB port output voltage has dropped below said predetermined threshold voltage before said charging current has reached said predetermined peak charging current to control said controllable current source so as to terminate sourcing of charging current from said USB port to said rechargeable battery via said controllable current source; and

said controller, operative in response to an indication from said comparator that said USB port output voltage has not dropped below said predetermined threshold voltage before said charging current has reached said predetermined peak charging current to control said controllable current source so as to continue the sourcing of charging current from said USB port to said rechargeable battery via said controllable current source at said peak charging current.