Battery charger that employs current sharing to simultaneously power an application and charge a battery

• US 7,535,195 B1
• Filed: 08/25/2005
• Issued: 05/19/2009
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Vu, Luan, Horovitz, Neal Lane
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): Tran; Nguyen
• Application Number:
  US11/212,171
• Time in Patent Office: 1,363 Days
• Field of Search: 320/141, 320/145, 320/106
• US Class Current: 320/106
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• 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

Circuitry for powering a load and charging of a battery from a power source by a smart power supply is provided. The smart power supply controls the maximum current for battery charging based in part upon variables such as the maximum rate of charge of the battery and maximum source current. The smart power supply is thus capable of providing the power requested by the load, and use the remaining power for battery charging.

Claims

1. A method of charging a battery and powering a load, comprising:

setting a first variable to represent a maximum source current available from a power source;

setting a second variable to represent a maximum rate of charge for the battery;

employing a state machine to calculate a first battery charging control signal that indicates a first current value that represents a maximum charging current for the battery based upon the first variable and the second variable;

employing the state machine to calculate a second battery charging control signal that indicates a second current value that represents a threshold load current based upon the first variable and the second variable;

supplying a current to the load via a power supply circuit; and

supplying an actual charging current to the battery by providing the first battery charging control signal and the second battery charging control signal to the power supply circuit, wherein the actual charging current is based, at least in part, on a sensed magnitude of the load current such that if the load current is less than the threshold load current, the actual charging current is not greater than the maximum charging current; and

such that if the load current is greater than the threshold load current, the actual charging current is not greater than the difference between the maximum source current and the load current.

2. The method of claim 1, further comprising:

determining if the battery voltage is above or below a fullrate charging threshold; and

if the battery voltage is below the fullrate charging threshold, supplying an actual charging current to the battery which is substantially less than the maximum charging current.

3. The method of claim 1, wherein setting the first and second variables is accomplished by digitally storing the first variable and the second variable in flip-flops;

and

wherein calculating the maximum charging current and the threshold load current is accomplished by digital calculations.

4. The method of claim 2, wherein calculating the maximum charging current includes:

calculating the maximum charging current by taking the minimum value of;

the maximum rate of charge and the maximum source current; and

wherein calculating the threshold load current includes;

if the battery voltage is above the fullrate charging threshold, calculating the threshold load current by subtracting the maximum rate of charge from the maximum source current; and

if the battery voltage is below the fullrate charging threshold, calculating the threshold load current by subtracting a constant from the maximum source current.

5. The method of claim 1, further comprising:

determining if the battery voltage is above a fullrate charging threshold;

determining if the battery voltage is above a constant voltage charging threshold, wherein the constant voltage charging threshold is above the fullrate charging threshold; and

if the battery voltage is below the fullrate charging threshold,

calculating the maximum charging current by taking the minimum value of the maximum rate of charge and the maximum source current;

calculating the threshold load current by subtracting a constant from the maximum source current; and

supplying an actual charging current to the battery which is substantially less than the maximum charging current; and

if the battery voltage is above the fullrate charging threshold but below the constant voltage charging threshold,

calculating the maximum charging current by taking the minimum value of the maximum rate of charge and the maximum source current; and

calculating the threshold load current by subtracting the maximum rate of charge from the maximum source current; and

supplying an actual charging current to the battery such that, during a current regulation, if the load current is less than the threshold load current, the actual charging current is the maximum charging current; and

such that if the toad current is greater than the threshold load current, the actual charging current is the difference between the maximum source current and the load current.

6. A power supply for a supplying electrical power to a load, comprising:

a power supply circuit that is connectable to a power source, a battery, and a load circuit, wherein the power supply circuit is operable to charge the battery during a charging cycle and to provide a toad current to the load circuit;

the charging cycle includes current regulation;

the power supply circuit is further operable to receive one or more battery charging control signals; and

to set one or more operational parameters utilized in the charging of the battery based, in part, on the battery charging control signals such that the current regulation is based, in part, on the battery charging control signals; and

a battery charger control circuit operable to provide the one or more battery charging control signals, wherein the battery charger control circuit includes;

one or more registers operable to store one or more battery charging variables; and

a state machine configured to read at least one of the one or more registers and to calculate the one or more battery charging control signals based, in part, one or more battery charging variables and based, in part, on a sensed magnitude of the load current,

wherein the one or more registers include;

a first register that is operable to store a first variable of the one or more battery charging variables, wherein the first variable represents an available source current from the power source; and

a second register that is operable to store a second variable of the one or more battery charging variables, wherein the second variable represents a maximum rate of charge for the battery; and

wherein the one or more battery charging control signals include;

a first battery charging control signal that indicates first current value that represents a maximum desired charging current for the battery, wherein the state machine is operable to provide the first battery charging control signal based upon the first variable and the second variable; and

a second battery charging control signal that indicates a second current value that represents a maximum load current to be supplied before the power supply circuit reduces an actual charging current from the maximum desired charging current, wherein the state machine is operable to provide the second battery charging control signal based upon the first variable and the second variable.

7. The power supply of claim 6, wherein the current regulation is controlled, based in part, on a magnitude of current that is supplied to the battery and at least one of the one or more battery charging control signals.

8. The power supply of claim 6, wherein the state machine is configured to receive an input representing a state of the battery.

9. The power supply of claim 6, wherein the state machine is configured to receive one or more inputs representing a state of one or more power sources.

10. The power supply of claim 6, wherein the battery charger control circuit further includes a microprocessor interface configured to receive a signal that enables an update of a battery charging variable.

11. A power supply for a supplying electrical power to a load, comprising:

a power supply circuit that is connectable to a power source, a battery, and a load circuit, wherein the power supply circuit is operable to charge the battery during a charging cycle and to provide a load current to the load circuit;

the charging cycle includes current regulation;

the power supply circuit is further operable to receive one or more battery charging control signals; and

to set one or more operational parameters utilized in the charging of the battery based, in part, on the battery charging control signals such that the current regulation is based, in part, on the battery charging control signals; and

a battery charger control circuit operable to provide the one or more battery charging control signals, wherein the battery charger control circuit includes;

one or more registers operable to store one or more battery charging variables; and

a state machine configured to read at least one of the one or more registers and to calculate the one or more battery charging control signals based, in part, on the one

or more battery charging variables and based, in part, on a sensed magnitude of the load current,

wherein the one or more registers include;

a first register that is operable to store a first variable of the one or more battery charging variables, wherein the first variable represents an available source current from the power source; and

a second register that is operable to store a second variable of the one or more battery charging variables, wherein the second variable represents a maximum rate of charge for the battery; and

wherein the one or more battery charging control signals include;

a first battery charging control signal that indicates first current value that represents a maximum desired charging current for the battery, wherein the state machine is operable to provide the first battery charging control signal such that the first battery charging control signal is the minimum of the first variable and the second variable; and

a second battery charging control signal that indicates a second current value that represents a maximum load current to be supplied before the power supply circuit reduces an actual charging current from the maximum desired charging current, wherein the state machine is operable to provide the second battery charging control signal such that the second battery charging control signal is the difference of the first variable and the second variable; and

wherein the power supply circuit is operable to supply &

load current and an actual charging current to the battery, wherein the load draws the load current from the power supply and the actual charging current is regulated as follows during the current regulation;

if the load current is less than the second current value, then the actual charging current is regulated such that it is the first current value;

otherwise the actual charging current is regulated such that it is equal to the difference between the first current value and the toad current.

12. A processor-readable medium having processor executable code stored therein, which when executed by one or more processors, enables actions, comprising:

setting a first variable to represent an available source current from a power source;

setting a second variable to represent a maximum rate of charge for a battery;

calculating a first battery charging control signal that indicates a first current value that represents a maximum charging current for the battery based upon the first variable and the second variable;

calculating a second battery charging control signal that indicates a second current value that represents a threshold load current based upon the first variable and the second variable;

supplying a current to the load via a power supply circuit; and

supplying an actual charging current to the battery by providing the first battery charging control signal and the second battery charging control signal to the power supply circuit, wherein the actual charging current is based, at least in part, on a sensed magnitude of the load current, such that if the load current is less than the threshold load current, the actual charging current is not greater than the maximum charging current; and

such that if the load current is greater than the threshold load current, the actual charging current is not greater than the difference between the maximum source current and the load current.

13. The processor-readable medium of claim 12, which when executed by one or more processors, enables further actions, comprising:

determining if the battery voltage is above or below a fullrate charging threshold; and

if the battery voltage is below the fullrate charging threshold, supplying an actual charging current to the battery which is substantially less than the maximum charging current.

14. The processor-readable medium of claim 12, wherein setting the first and second variables is accomplished by digitally storing the first variable and the second variable in flip-flops;

and

wherein calculating the maximum charging current and the threshold load current is accomplished by digital calculations.

15. The processor-readable medium of claim 13, wherein calculating the maximum charging current includes:

if the battery voltage is above the fullrate charging threshold, calculating the maximum charging current by taking the minimum value of the maximum rate of charge and the maximum source current; and

if the battery voltage is below the fullrate charging threshold, calculating the maximum charging current by taking the minimum value of the maximum rate of charge and the maximum source current; and

wherein calculating the threshold load current includes;

if the battery voltage is above the fullrate charging threshold, calculating the threshold load current by subtracting the maximum rate of charge from the maximum source current; and

if the battery voltage is below the fullrate charging threshold, calculating the threshold load current by subtracting a constant from the maximum source current.

16. The processor-readable medium of claim 12, wherein setting the first variable includes setting the first variable in a first register, and wherein setting the second variable includes setting the second variable in a second register.

17. The processor-readable medium of claim 12, wherein calculating the first battery charging control signal is carried out with a state machine, and wherein calculating the second battery charging control signal is carried out with the state machine.

18. The processor-readable medium of claim 12, wherein the enabled actions further include setting one or more operational parameters utilized in the charging of the battery based, in part, on the first battery control signal and the second battery control signal such that current regulation is based, in part, on first battery control signal and the second battery control signal.