Apparatus and method for dual mode battery charger with linear and switched control modes based on operating conditions

• US 7,498,769 B1
• Filed: 03/04/2005
• Issued: 03/03/2009
• Est. Priority Date: 03/04/2005
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Potanina, Elena, Potanin, Vladislav
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): BOATENG, ALEXIS ASIEDUA
• Application Number:
  US11/073,135
• Time in Patent Office: 1,460 Days
• Field of Search: 320/141, 320/143, 320/148, 324/433
• US Class Current: 320/125
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007192 in response to temperature
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage

Abstract

A circuit for battery charging is provided. The circuit provides a charge current to a battery, and regulates the charge current with either linear regulation or switching regulation, based on operating conditions. In one embodiment, if the input voltage minus the battery voltage is less than a threshold (e.g. 100 mV), linear regulation is employed, and if the input voltage minus the battery voltage is greater than the threshold (e.g. 100 mV), switching regulation is employed. The threshold may be fixed, or the threshold may be adjustable based on die temperature or charge current.

Claims

1. A method for charging a battery, comprising:

employing linear regulation to provide a charge current to the battery;

monitoring at least one operating condition of the charging;

based on the at least one monitored operating condition, determining whether a first pre-determined condition is satisfied;

if the first pre-determined condition is satisfied, employing switching regulation to provide the charge current;

providing a voltage error signal that is based, in part, on a voltage of the battery; and

providing a current error signal that is based, in part, on the charge current, wherein;

employing linear regulation includes;

providing a linear regulation control signal by performing a majority function on the voltage error signal and the current error signal; and

driving the gate of the power transistor based on the linear regulation control signal; and

wherein employing switching regulation includes;

providing a switching regulation control signal based on pulse modulating a clock signal with the voltage error signal, and further based on employing the current error signal as a current limit; and

driving the gate of the power transistor based on the switching regulation control signal.

2. The method of claim 1, wherein:

the at least one monitored operating condition includes an input voltage;

the first pre-determined condition is satisfied if the input voltage minus the battery voltages exceeds a first threshold;

the switching regulation is performed as buck pulse charge switching regulation if the input voltage minus the battery voltage exceeds a second threshold, wherein the second threshold is greater than the first threshold;

an inductor is coupled between the power transistor and a node;

the switching regulation is performed as modified buck pulse charge switching regulation if the input voltage minus the battery voltage is greater than the first threshold and less than the second threshold; and

wherein performing the switching regulation as modified buck pulse charge switching regulation includes;

when the power transistor is closed, coupling the node to ground; and

when the power transistor is open, coupling the node to the battery voltage.

3. The method of claim 1, wherein the at least one monitored operating condition includes at least one of the input voltage, a die temperature, or the charge current.

4. A circuit for charging a battery, comprising:

an input monitor circuit that is arranged to compare an input voltage to a battery voltage; and

to provide an input monitor output signal based on the comparison;

a control circuit that is arranged to provide a control signal to a power transistor to enable the power transistor to regulate a charge current based on the input voltage and the control signal, using the input voltage as the power source for the regulation, wherein

the control circuit is configured to provide the control signal such that;

the control signal is based, in part, on the charge current;

the power transistor performs linear regulation if a pre-determined condition is not satisfied; and

such that the power transistor performs switching regulation if the pre-determined condition is satisfied;

wherein the pre-determined condition is based, at least in part, on the input monitor output signal; and

wherein the input monitor circuit is arranged to assert the input monitor output signal if the input voltage exceeds the battery voltage by a first threshold;

a current sense error amplifier that is arranged to provide a current error signal that is based, in part, on the charge current;

a voltage divider that is arranged to provide a feedback voltage from the battery voltage;

a feedback voltage error amplifier having at least a first input that is arranged to receive the feedback voltage, a second input that is arranged to receive a reference voltage, and an output that is configured to provide a voltage error signal based on a difference between the feedback voltage and the reference voltage,

wherein the control circuit further includes;

a CC-CV linear regulation control circuit that includes a majority function circuit having at least a first input that is arranged to receive the current error signal, a second input that is arranged to receive the voltage error signal, and an output that is configured to provide a linear regulation control signal that substantially corresponds the greater of the current error signal and the voltage error signal;

a CC-CV switching regulation control circuit that is arranged to provide a switching regulation control based, in part, on the current error signal and the voltage error signal, wherein the CC-CV switching regulation control circuit includes a pulse modulation circuit and a current limit comparator; and

a multiplexer circuit that is arranged to receive the linear regulation control signal, the switching regulation control circuit, and a multiplexer select signal, and further arranged to provide the first control signal by multiplexing the linear regulation control signal and the switching regulation control signal based on the multiplexer select signal, wherein the multiplexer select signal is based, at least in part, on the input monitor output signal.

5. The circuit of claim 4, wherein the input monitor circuit is configured such that the first threshold is a fixed value in a range from about 100 mV to 200 mV.

6. The circuit of claim 4, wherein the input monitor circuit is configured such that the first threshold varies based on a die temperature.

7. The circuit of claim 4, wherein the current sense error amplifier has at least:

a first input that is arrange to receive the current sense signal, a second input, and an output that is configured to provide the current error signal;

the circuit further comprising;

a comparator that is arranged to assert a full charge signal if the battery voltage is greater than a pre-determined minimum safe operating voltage;

a resistor that is coupled to the second input of the current sense error amplifier circuit, wherein the first threshold varies based, in part, on a voltage drop across the resistor; and

a current source that is arranged to provide a current to the resistor at a first level if the full charge signal is asserted, and further arranged to provide the current to the resistor at a second level if the full charge is unasserted, wherein the second level is approximately one-tenth of the first level.

8. The circuit of claim 4, wherein the pre-determined condition is satisfied if the input monitor output signal is asserted.

9. The circuit of claim 8, further comprising a die temperature detection circuit, wherein the pre-determined condition is also satisfied if a die temperature exceeds a pre-determined temperature.

10. The circuit of claim 4, wherein the multiplexer select signal is the input monitor output signal.

11. The circuit of claim 4, further comprising:

a die temperature detection circuit that is arranged to provide a temperature signal that is substantially proportional to the die temperature;

a comparator that is arranged to provide a temperature limit signal based on the temperature signal; and

an OR gate having at least an output that is configured to provide the multiplexer select signal, a first input that is arranged to receive the input monitor signal at the first input, and a second input that is arranged to receive the temperature limit signal at the second input.

12. The circuit of claim 4, wherein the input voltage is provided from at least one of a wall adapter, a car adapter, or a power bus.

13. A circuit for charging a battery, comprising:

an input monitor circuit that is arranged to compare an input voltage to a battery voltage; and

to provide an input monitor output signal based on the comparison;

a control circuit that is arranged to provide a control signal to a power transistor to enable the power transistor to regulate a charge current based on an input voltage and the control signal, wherein

the control circuit is configured to provide the control signal such that;

the control signal is based, in part, on the charge current;

the power transistor performs linear regulation if a pre-determined condition is not satisfied; and

such that the power transistor performs switching regulation if the pre-determined condition is satisfied;

the pre-determined condition is based, at least in part, on the input monitor output signal; and

wherein the input monitor circuit is arranged to assert the input monitor output signal if the input voltage exceed the battery voltage by a first threshold;

a first switch circuit that is coupled between a first node and an output node, wherein the first switch circuit is arranged to close if a second control signal is asserted, and to open if the second control signal is unasserted;

a second switch circuit that is coupled between the first node and ground, wherein

the second switch circuit is arranged to close if a third control signal is asserted, and to open if the third control signal is unasserted;

the circuit for charging the battery is arranged to operate with an inductor coupled between a second node and the first node, with the power transistor coupled between an input node and the second node, and with the power transistor receiving the input voltage at the input node; and

wherein the control circuit is further arranged to provide the second and third control signals such that;

if the input voltage minus the battery voltage is less than the first threshold, the power transistor performs linear regulation;

if the input voltage minus the battery voltage is greater than the first threshed and a second threshold, the power transistor performs buck pulse switching regulation;

if the input voltage minus the battery voltage is greater than the first threshold, and less than the second threshold, the power transistor performs modified buck pulse switching regulation, wherein during the buck pulse seihng regulation and the modified buck pulse switching regulation, the control signal is provided such that the power transistor is closed during a first phase of a clock cycle, and such that the power transistor is open during a second phase of the clock cycle;

during the linear regulation and the buck pulse switching regulation, the second control signal is asserted and the third control signal is unasserted; and

such that during the modified buck pulse switching regulation;

the second control signal is asserted during the first phase of the clock cycle and unasserted during the second phase of the clock cycle; and

the third control signal is unasserted during the first phase of the clock cycle and asserted during the second phase of the clock cycle.

14. The circuit of claim 13, wherein the first threshold is a value from about 100 mV to 200 mV, and wherein the second threshold is about 1V.

15. The circuit of claim 13, wherein the first threshold is the value from about 100 mV to 200 mV at about room temperature, the first threshold is substantially proportional to a die temperature, and wherein the second threshold is about 1V.

16. The circuit of claim 13, further comprising:

a current sense error amplifier that is arranged to provide a current error signal that is based, in part, on the charge current;

a voltage divider that is arranged to provide a feedback voltage from the battery voltage;

a feedback voltage error amplifier having at least a first input that is arranged to receive the feedback voltage, a second input that is arranged to receive a reference voltage, and an output that is configured to provide a voltage error signal based on a difference between the feedback voltage and the reference voltage,

wherein the control circuit further includes;

a CC-CV linear regulation control circuit that includes a majority function circuit having at least a first input that is arranged to receive the current error signal, a second input that is arranged to receive the voltage error signal, and an output that is configured to provide a linear regulation control signal that substantially corresponds the greater of the current error signal and the voltage error signal;

a CC-CV switching regulation control circuit that is arranged to provide a switching regulation control based, in part, on the current error signal and the voltage error signal, wherein the CC-CV switching regulation control circuit includes a pulse modulation circuit and a current limit comparator; and

a multiplexer circuit that is arranged to receive the linear regulation control signal, the switching regulation control circuit, and a multiplexer select signal, and further arranged to provide the first control signal by multiplexing the linear regulation control signal and the switching regulation control signal based on the multiplexer select signal, wherein the multiplexer select signal is based, at least in part, on the input monitor output signal.

17. The circuit of claim 13,

wherein the control circuit includes:

a linear regulation control circuit that is operable to provide a linear regulation control signal;

a switching regulation control circuit that is operable to provide a switching regulation control, wherein the switching regulation control circuit includes a pulse modulation circuit; and

a multiplexer circuit that is arranged to receive the linear regulation control signal, the switching regulation control circuit, and a multiplexer select signal, and further arranged to provide the first control signal by multiplexing the linear regulation control signal and the switching regulation control signal based on the multiplexer select signal.

18. The circuit of claim 13, wherein the control circuit includes a pulse modulation circuit, the pulse modulation circuit is operable to perform pulse modulation, and wherein the switching regulation is based, at least in part, on the pulse modulation.

19. The circuit of claim 18, wherein the pulse modulation circuit is a pulse width modulation circuit.

20. The circuit of claim 18, wherein the pulse modulation circuit is a pulse frequency modulation circuit.

21. A circuit for charging a battery, comprising:

a current sense error amplifier that is arranged to provide a current error signal that is based, in part, on a charge current; and

a control circuit that is arranged to provide a control signal to a power transistor to enable the power transistor to regulate the charge current based on an input voltage and the control signal, using the input voltage as the power source for the regulation, wherein

the control circuit is configured to provide the control signal such that;

the control signal is based, in part, on the current error signal;

the power transistor performs linear regulation if a pre-determined condition is not satisfied; and

such that the power transistor performs switching regulation if the pre-determined condition is satisfied; and

wherein the pre-determined condition is based, at least in part, on at least one of the input voltage, a die temperature, or the charge current.

22. A circuit for charging a battery, comprising:

an input monitor circuit that is arranged to compare an input voltage to a battery voltage; and

to provide an input monitor output signal based on the comparison; and

a control circuit that is arranged to provide a control signal to a power transistor to enable the power transistor to regulate a charge current based on the input voltage and the control signal, using the input voltage as the power source for the regulation, wherein

the control circuit is configured to provide the control signal such that;

the control signal is based, in part, on the charge current;

the power transistor performs linear regulation if a pre-determined condition is not satisfied; and

such that the power transistor performs switching regulation if the pre-determined condition is satisfied; and

wherein the pre-determined condition is based, at least in part, on the input monitor output signal.

23. The circuit of claim 22, wherein the input voltage is provided from at least one of a wall adapter, a car adapter, or a power bus.

24. A method for charging a battery, comprising:

employing linear regulation to provide a charge current to the battery, using an input voltage as the power source for the regulation;

monitoring at least one operating condition of the charging;

based on the at least one monitored operating condition, determining whether a first pre-determined condition is satisfied; and

if the first pre-determined condition is satisfied, employing switching regulation to provide the charge current, wherein the at least one monitored operating condition includes at least one of the input voltage, a die temperature, or the charge current.

25. The method of claim 24, wherein the at least one monitored operating condition includes the input voltage, and wherein the first pre-determined condition is satisfied if the input voltage minus the battery voltage exceeds a first threshold.

26. The method of claim 25, wherein the at least one monitoerd operating condition further includes a die temperature, wherein the first threshold is a value from approximately 100 mV to 200 mV if the die temperature corresponds to approximately room temperature, and wherein the first threshold is substantially proportional to the die temperature.