METHOD FOR LIMITING BATTERY DISCHARGING CURRENT IN BATTERY CHARGER AND DISCHARGER CIRCUIT

• US 20120139500A1
• Filed: 05/13/2011
• Published: 06/07/2012
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Ye, Mao, Qian, Jinrong, Chen, Suheng, Stair, Richard
• Granted Patent: US 9,136,724 B2
• Time in Patent Office: Days
• US Class Current: 320/135
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• 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: H02M 1/10 Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from ac or dc
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: Y02T 90/12 Electric charging stations

Abstract

A power supply system includes a rechargeable battery to deliver a supply current to a load and a circuit to limit a discharge current when the rechargeable battery is supplying power to the load. The power supply system may further include an integrator for integrating a discharge voltage representing the discharge current that exceeds a predetermined limit, a pulse-width-modulation (PWM) circuit for producing a control signal having a PWM duty cycle representing the discharge voltage, and a driver circuit for delivering the supply current to said load according to said control signal. In one embodiment, a digital register is used to set the battery discharging current limit, in another embodiment an analog circuit is used to set the battery discharging current limit, and in yet another embodiment or a combination of the digital register and analog circuit is used to set the battery discharging current limit.

Claims

1. A power supply system, comprising:

a rechargeable battery connectable to deliver a supply current to a load;

a circuit to limit a discharge current from said rechargeable battery when said rechargeable battery is supplying power to said load.

2. The power supply system of claim 1 further comprising:

buck mode circuitry;

boost mode circuitry;

and switching circuitry to switch from said buck mode circuitry to said boost mode circuitry to supply current to said load above a predetermined limit, and wherein said rechargeable battery supplies additional current when said boost mode circuitry is switched to supply said supply current above said predetermined limit.

3. The power supply system of claim 1 wherein said circuit to limit a discharge current comprises:

a digital register for containing a digital value representing a desired discharge current limit;

a d/a converter to convert said digital value to a reference voltage;

a circuit to sense a discharge current from said rechargeable battery to produce a discharge voltage representing said discharge current;

and an operational amplifier to amplify said reference voltage value with said discharge voltage to produce an output that follows said discharge voltage when said discharge voltage is larger than said reference voltage.

4. The power supply system of claim 3 wherein said digital value is established by a host computer.

5. The power supply system of claim 3 further comprising:

an integrator for integrating said output from said operational amplifier;

a pulse-width-modulation (PWM) circuit for producing a control signal having a PWM duty cycle representing said discharge voltage;

and a driver circuit for delivering said supply current to said load according to said control signal.

6. The power supply system of claim 1 wherein said circuit to limit a discharge current comprises:

a reference voltage source to produce a reference voltage;

a circuit to sense a discharge current from said rechargeable battery to produce a discharge voltage representing said discharge current;

and an operational amplifier to amplify said reference voltage with said discharge voltage to produce an output that follows said discharge voltage when said discharge voltage is larger than said reference voltage.

7. The power supply system of claim 6 wherein said reference voltage is established by a resistor voltage divider.

8. The power supply system of claim 6 wherein said reference voltage is set by a user.

9. The power supply system of claim 6 further comprising:

an integrator for integrating said output from said operational amplifier;

a pulse-width-modulation (PWM) circuit for producing a control signal having a PWM duty cycle representing said discharge voltage;

and a driver circuit for delivering said supply current to said load according to said control signal.

10. The power supply system of claim 1 wherein said circuit to limit a discharge current comprises:

a circuit to sense a discharge current from said rechargeable battery to produce a discharge voltage representing said discharge current;

a digital register for containing a digital value representing a desired discharge current limit;

a d/a converter to convert said digital value to a first reference voltage;

a reference voltage source to produce a second reference voltage;

a first operational amplifier to amplify said first reference voltage with said discharge voltage to produce a first output that follows said discharge voltage when said discharge voltage is larger than said first reference voltage;

a second operational amplifier to amplify said second reference voltage with said discharge voltage produce a second output that follows said discharge voltage when said discharge voltage is larger than said second reference voltage; and

a circuit to produce a combined voltage from said first and second outputs.

11. The power supply system of claim 10 wherein said digital value is established by a host computer.

12. The power supply system of claim 10 wherein said reference voltage source is adjusted by a user.

13. The power supply system of claim 10 further comprising:

an integrator for integrating said combined voltage;

a pulse-width-modulation (PWM) circuit for receiving said combined voltage and producing a control signal having a PWM duty cycle representing said discharge voltage;

and a driver circuit for delivering said supply current to said load according to said control signal.

14. A method for operating a power supply system, comprising:

providing a rechargeable battery connectable to deliver a supply current to a load; and

providing a circuit to limit a discharge current from said rechargeable battery when said rechargeable battery is supplying power to said load.

15. The method of claim 14 further comprising switching from a buck mode of operation to a boost mode of operation in which said rechargeable battery supplies additional supply current to said load.

16. The method of claim 14 further comprising:

when said discharge current exceeds a predetermined limit, generating a control signal having a duty cycle corresponding to an amount by which discharge current exceeds said predetermined limit;

and using said control signal to control the supply current to limit said discharge current.

17. The method of claim 14 wherein said providing a circuit to limit a discharge current from said rechargeable battery when said rechargeable battery is supplying power to said load comprises providing a digital register containing a digital value set by a host to represent a discharge current limit.

18. The method of claim 17 further comprising converting said digital value to an analog voltage representing said discharge current.

19. The method of claim 14 wherein said providing a circuit to limit a discharge current from said rechargeable battery when said rechargeable battery is supplying power to said load comprises providing a user settable reference voltage to represent a discharge current limit.

20. The method of claim 14 wherein said providing a circuit to limit a discharge current from said rechargeable battery when said rechargeable battery is supplying power to said load comprises providing a digital register containing a digital value set by a host to represent a first discharge current limit, providing a user settable reference voltage to represent a second discharge current limit, and using the lower of said first and second discharge current limits to limit said discharge current.