System and apparatus for generating a continuosly variable reference signal for controlling battery cell charging

• US 5,847,546 A
• Filed: 05/14/1997
• Issued: 12/08/1998
• Est. Priority Date: 11/13/1992
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: Packard Bell NEC
• Inventors: Turnbull, Robert R., Shah, Rajesh A., Sengupta, Upal, Fritz, Brian Carl
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/858,202
• Time in Patent Office: 573 Days
• Field of Search: 320/106, 320/124, 320/132, 320/137, 320/136, 320/144, 320/149, 320/150, 320/153, 320/158, 320/163, 320/101, 320/129, 320/131, 320/134, 320/138, 320/147
• US Class Current: 320/144
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• 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: 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
• CPC Class Codes: Y10S 320/10 Nonbattery load controls charging

Abstract

A power supply system, for example, for use with a portable personal computer, includes a smart battery pack and a charging system. The smart battery pack is provided with a dedicated microcontroller for controlling the charging level of the battery charger system. In particular, the status of the battery including the voltage and temperature of the battery is applied to the microcontroller along with a signal representative of the current load demand of the computer system. The micro controller, in turn, provides a control signal in the form of fixed frequency, variable duty cycle pulse width modulated (PWM) signal for controlling the charging level of the battery charger system. The duty cycle of the PWM signal is used to regulate the charging current supplied by the battery charger. In particular, the DC value of the PWM signal is used as a reference to control the charging current of the regulator to provide a variable output charging current with a relatively wide current range. As such, the battery charger is adapted to efficiently utilize the residual capacity of the battery charger system for optimizing charging of the battery packs during all operating conditions of the computer system. Moreover, the use of a PWM signal from the battery pack to control the battery charger enables a single type of battery charger to be utilized for various battery technologies.

Claims

1. A smart battery pack for providing a source of portable electrical power, comprising:

one or more predetermined battery cells;

charging current sensing means for sensing the charging current supplied to said one or more battery cells;

temperature sensing means for sensing the temperature of said one or more battery cells;

voltage sensing means for sensing the voltage of said one or more battery cells; and

means responsive to said charging current sensing means, said temperature sensing means and said voltage sensing means for controlling the charging current applied to said one or more battery cells by generating a charge control signal, said charge control signal being a continuously variable reference signal which varies as a predetermined function of the load current and the voltage and temperature of said one or more battery cells.

2. A smart battery pack as recited in claim 1, further including means for sensing the load current supplied by said one or more battery cells.

3. A smart battery pack as recited in claim 2, wherein said controlling means includes means for generating a charge control signal which varies as a predetermined function of the load current supplied by said one or more battery cells, the charging current supplied to said one or more battery cells and the voltage and current of said one or more battery cells.

4. A smart battery pack as recited in claim 1, wherein said charging current sensing means includes a resistor serially connected to said one or more battery cells.

5. A smart battery pack as recited in claim 1, wherein said controlling means includes means for generating pulse width modulated (PWM) charge control signals whose duty cycles vary as a function of the charging current supplied to said one or more battery cells and the voltage and temperature of said one or more battery cells.

6. A smart battery pack as recited in claim 1, further including a housing for housing said one or more battery cells and said controlling means, means for enabling said smart battery pack to be connected to one or more external electrical circuits.

7. A smart battery pack as recited in claim 6, wherein said enabling means includes means for enabling said battery pack to be connected to a predetermined external electrical load.

8. A smart battery pack as recited in claim 7, wherein said enabling means includes means for enabling said smart battery pack to be electrically connected to an external load and to an external supply of charging current at the same time.

9. A smart battery pack for providing a source of portable electrical power comprising:

one or more predetermined battery cells;

load current sensing means for sensing the load current being supplied by said one or more battery cells;

temperature sensing means for sensing the temperature of said one or more battery cells;

voltage sensing means for sensing the voltages of said one or more battery cells; and

means responsive to said load current sensing means, said temperature sensing means and said voltage sensing means for controlling the charging current applied to said one or more battery cells by generating a charge control signal, said charge control signal being a continuously variable reference signal which varies as a predetermined function of the load current and the voltage and temperature of said one or more battery cells.

10. A smart battery pack as recited in claim 9, wherein said controlling means includes means for generating pulse width modulated (PWM) control signals, whose duty cycles vary as a function of the load current being supplied to said or more battery cells and the voltage and temperature of said one or more battery cells.

11. A smart battery pack as recited in claim 9 further including a housing for housing said one or more battery cells and said controlling means, and means for enabling said smart battery pack to be connected to one or more external circuits.

12. A smart battery pack as recited in claim 11 wherein said enabling means includes means for enabling said battery pack to be connected to a predetermined external load and to an external supply of charging current at the same time.