Control of computer AC adapter output voltage via battery pack feedback

• US 5,684,382 A
• Filed: 07/19/1996
• Issued: 11/04/1997
• Est. Priority Date: 07/19/1996
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Sawyers, Thomas P., Schneider, Michael E., Watts, Robert K., Hallowell, William C., Stobert, Norman D., Fritz, Brian C.
• Primary Examiner(s): Tso, Edward
• Application Number:
  US08/684,686
• Time in Patent Office: 473 Days
• Field of Search: 320/5, 320/30, 320/31, 320/32, 320/35, 320/39, 320/48, 320/49, 320/9, 320/10
• US Class Current: 320/164
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A computer system including circuitry for accurately and economically controlling the charge voltage and charge current at the terminals of its rechargeable battery. During a battery recharge, sensor circuitry coupled to the battery provides accurate data to a battery microcontroller regarding the charge voltage and charge current present at the battery terminals. A battery microcontroller relays this information to a multipurpose microcontroller. The battery microcontroller also provides the desired charging voltage and current as determined by the battery pack'"'"'s charging algorithm. The multipurpose microcontroller uses the battery status information to program an addressable potentiometer. In turn, the potentiometer generates an adjustment signal that controls the output voltage of the computer'"'"'s AC adapter. Preferably, the AC adapter is capable of being operated in a constant-power mode. Adjustment of the potentiometer allows the output of the AC adapter to be dithered up or down as needed to provide the desired charging voltage and charging current to the battery.

Claims

1. A computer system, comprising:

a rechargeable battery;

a monitoring circuit coupled to said rechargeable battery for measuring the present voltage and current at the terminals of said rechargeable battery;

a battery microcontroller coupled to said monitoring circuit and implementing a recharging routine capable of generating a desired voltage for the terminals of said rechargeable battery;

a multipurpose microcontroller coupled to said battery microcontroller and adapted to generate an adjustment signal based on the present battery terminal voltage and current and the desired battery terminal voltage;

an adjustable output AC adapter having an output voltage signal line coupled to a terminal of said rechargeable battery, and a control input for altering the output voltage signal of said AC adapter; and

a dither control circuit coupled to said multipurpose microcontroller and said control input of said AC adapter, said dither control circuit receiving the adjustment signal and communicating a corresponding control signal to said control input of said AC adapter.

2. The computer system of claim 1, further including a serial communications bus coupling said dither control circuit, said multipurpose microcontroller, and said battery microcontroller.

3. The computer system of claim 2, wherein said serial communications bus is essentially compliant with the I² C-bus standard.

4. The computer system of claim 1, wherein said rechargeable battery, said monitoring circuit and said battery microcontroller are incorporated in a detachable battery pack.

5. The computer system of claim 1, wherein said dither control circuit comprises an addressable potentiometer.

6. The computer system of claim 1, wherein said rechargeable battery is comprised of one of the following types:

lithium-ion, nickel-metal-hydride, lithium polymer, or zinc-air.

7. A computer system, comprising:

a rechargeable battery;

a monitoring circuit coupled to said rechargeable battery for measuring the present voltage and current at the terminals of said rechargeable battery;

a battery microcontroller coupled to said monitoring circuit and implementing a recharging routine generating a desired voltage for the terminals of said rechargeable battery;

said battery microcontroller further generating an adjustment signal based on the present battery terminal voltage and current and the desired battery terminal voltage;

an adjustable output AC adapter having an output voltage signal line coupled to a terminal of said rechargeable battery, and a control input for altering the output voltage signal of said AC adapter; and

a dither control circuit coupled to said battery microcontroller and said control input of said AC adapter, said dither control circuit receiving the adjustment signal and communicating a corresponding control signal to said control input of said AC adapter.

8. The computer system of claim 7, further including a serial communications bus coupling said dither control circuit and said battery microcontroller.

9. The computer system of claim 8, wherein said serial communications bus is essentially compliant with the I² C-bus standard.

10. The computer system of claim 7, wherein said rechargeable battery, said monitoring circuit and said battery microcontroller are incorporated in a detachable battery pack.

11. The computer system of claim 7, wherein said dither control circuit comprises an addressable potentiometer.

12. The computer system of claim 7, wherein said rechargeable battery is comprised of one of the following types:

lithium-ion, nickel-metal-hydride, lithium polymer, or zinc-air.

13. A method for controlling the voltage at the terminals of a rechargeable battery in a computer system incorporating an adjustable output AC adapter, the computer system further comprising a monitoring circuit for measuring the voltage and current at the terminals of the rechargeable battery, a battery microcontroller for implementing a recharging algorithm, and a dither control circuit for adjusting the output of the AC adapter, the method comprising the steps of:

retrieving the present voltage and current at the terminals of the rechargeable battery as determined by the monitoring circuit;

calculating the desired voltage and current at the terminals of the rechargeable battery as determined by the recharging algorithm;

generating an adjustment signal based on the present voltage and current and the desired voltage and current; and

communicating the adjustment signal to the dither control circuit to modify the AC adapter output voltage such that the adjusted voltage at the terminals of the rechargeable battery approaches the desired voltage.

14. The method of claim 13, wherein the claimed steps are repeatedly performed until the adjusted voltage at the terminals of the rechargeable battery equals the desired voltage.

15. The method of claim 13, wherein the steps of generating an adjustment signal and communicating the adjustment signal to the dither control circuit are performed by a multipurpose microcontroller coupled to the battery micro controller and the dither control circuit.