Battery charging and monitoring system

• US 5,349,282 A
• Filed: 04/23/1991
• Issued: 09/20/1994
• Est. Priority Date: 12/11/1990
• Status: Expired due to Term

• Current Assignee: SPAN Incorporated
• Original Assignee: SPAN Incorporated
• Inventors: McClure, Malcolm S.
• Primary Examiner(s): KINCAID, KRISTINE LYNN
• Application Number:
  US07/690,203
• Time in Patent Office: 1,246 Days
• Field of Search: 320/31, 320/32, 320/37, 320/38, 320/39, 320/40, 320/43, 320/44, 320/48, 320/22, 320/23, 320/24, 324/426, 324/427, 324/433
• US Class Current: 320/136
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02M 3/155 using semiconductor devices only
• CPC Class Codes: H02M 7/217 using semiconductor devices only

Abstract

This invention relates to the use of rechargeable batteries for supply of electrical power. Devices are provided which are highly efficient and which provide accurate and reliable control and indications, while using a small number of component parts and being otherwise readily and economically manufacturable. Devices of the invention are compact and such that they can be readily included, if desired, as integral parts of battery packs such as those used for supplying power to lap-computers and other types of portable equipment.

Claims

1. A rechargeable battery pack comprising:

housing means, battery means disposed within said housing means and providing a pair of battery terminals, terminal means on said housing means for connecting said pair of battery terminals to a load and to a charging current source, monitoring means within said housing means connected to said pair of battery terminals and operative to monitor operation of said battery means to determine the state of charge of said battery means, data output terminal means on said housing means, and transmitting means associated with said monitoring means for transmitting through said data output terminal means digital data indicating the state of charge of said battery means, further including charge done output terminal means on said housing means, and transmitting means associated with said monitoring means for transmitting through said charge done output terminal means a signal indicating a full state of charge of said battery means.

2. Apparatus as defined in claim 1, wherein said data transmitting means operates to transmit a serial output signal.

3. Apparatus as defined in claim 2, wherein said serial output signal is transmitted in a RS-232 format.

4. Apparatus as defined in claim 2, wherein said microprocessor means operates to develop said serial output signal at an output pin thereof.

5. Apparatus including a battery charge condition monitor which comprises:

battery voltage sensing means for developing a voltage proportional to voltage of a battery, ramp voltage generator means for development of a ramp voltage, voltage comparator means for comparing said ramp voltage developed by said ramp voltage generator means and said voltage developed by said battery voltage sensing means to develop an output signal, and microprocessor means operative for controlling operation of said ramp voltage generator means and for measuring an elapsed time from development of said ramp voltage by said ramp voltage generator means and development of said output signal from said voltage comparator means, said ramp voltage generator means including a ramp capacitor, means coupling said ramp capacitor to a source of charging current, said microprocessor means having an output pin directly coupled to said ramp capacitor and operative between one state in which said ramp capacitor is held in a discharged condition and a second state in which charging of said capacitor from said source of charging current is allowed and in which said ramp voltage is thereby developed across said ramp capacitor.

6. Apparatus as defined in claim 5, further including second voltage sensing means, and a second voltage comparator means for comparing said ramp voltage developed by said ramp generator means and a voltage developed by said second voltage sensing means to develop a second output signal, said microprocessor means being operative for measuring an elapsed time starting from development of said ramp voltage applied to said second voltage comparator means and ending with development of said output signal from said second voltage comparator means.

7. Apparatus as defined in claim 5, further including current supply means for supplying said charging current to said battery, battery current sensing means for sensing said charging current supplied to said battery, and charging current control means coupled to said battery current sensing means and to said current supply means for maintaining said charging current at a controlled value.

8. Apparatus as defined in claim 7, further including means associated with said charging current control means for selectively setting a low controlled value of said charging current for a trickle charge operation and a high controlled value of said charging current for a fast charge operation.

9. Apparatus as defined in claim 8, further including means controlled by said microprocessor means for selectively setting said high controlled value of said charging current for said fast charge operation prior to attainment of a full charge condition and to then set said low controlled value of said charging current to thereafter obtain said trickle charge operation.

10. Apparatus including a battery charge condition monitor which comprises:

voltage sensing means, ramp voltage generator means for development of a ramp voltage, voltage comparator means for comparing said ramp voltage developed by said ramp voltage generator means and a voltage developed by said battery voltage sensing means to develop an output signal, and microprocessor means for controlling operation of said ramp voltage generator means and for measuring an elapsed time starting from development of said ramp voltage by said ramp voltage generator means and ending with development of said output signal from said voltage comparator means, said ramp voltage generator means including a ramp capacitor, means coupling said ramp capacitor to a source of charging current, further including current supply means for supply of said charging current to said battery, battery current sensing means for sensing said charging current supplied to said battery, and charging current control means coupled to said battery current sensing means and to said current supply means and operable for maintaining said charging current at a controlled value.

11. Apparatus as defined in claim 10, wherein said voltage sensing means operates to sense battery voltage, and wherein said microprocessor means periodically operates said ramp voltage generator means for measurement of said battery voltage and determination of the attainment of a full battery charge condition.

12. Battery charger apparatus comprising:

current supply means for supplying charging current to a battery, said current supply means including power transistor means for conducting said charging current, means including microprocessor means for monitoring battery voltage, battery current sensing means operable independently of said microprocessor means for developing a battery current signal proportional to said charging current supplied to said battery, charging current control means coupled to said power transistor means and to said battery current sensing means and operable in response to a control signal applied thereto and in response to said battery current signal for maintaining said charging current at a value proportional to said control signal applied thereto, said microprocessor means being operable to develop a charge done signal upon charging of said battery to a substantially full charge condition, and said microprocessor means being operable to apply a first control signal to said charging current control means to obtain a high charging current for a fast charge operation prior to development of said charge done signal and to then apply a second control signal to said charging current control means to obtain a low charging current for a trickle charge operation, an inductor coupled in series with said power transistor means to store energy during conduction of said charging current by said power transistor means, and diode means connected to operate during periods of non-conduction of said power transistor means to apply said stored energy in continuing conduction of said charging current to said battery means.

13. Battery charger apparatus, comprising:

first and second output terminals for connection to terminals of a battery to be charged, first and second power input terminals for connection to a source of charging current with said first power input terminal forming a circuit ground connection, means for connecting said second output terminal to said second power input terminal, MOSFET transistor means having first and second output electrodes and having a gate electrode for control of current flow between said first and second output electrodes, means coupling said first output electrode to said first output terminal, a battery current sensing resistor coupled between said second output electrode and said circuit ground connection and operative for developing a control voltage proportional to battery current, and control circuit means having an input coupled to said battery current sensing resistor and having an output coupled to said gate electrode of said MOSFET transistor means to control conduction of said MOSFET transistor means and to thereby control battery charging current as a function of said control voltage developed by said battery current sensing resistor.

14. Apparatus as defined in claim 13, said MOSFET transistor means including an N-channel MOSFET transistor.

15. Battery charger apparatus, comprising:

first and second output terminals for connection to terminals of a battery to be charged, first and second power input terminals for connection to a source of charging current with said first power input terminal forming a circuit ground connection, means for connecting said second output terminal to said second power input terminal, transistor means having first and second output electrodes and having a control electrode for control of current flow between said first and second output electrodes, means coupling said first output electrode to said first output terminal, a battery current sensing resistor coupled between said second output electrode and said circuit ground connection and operative for developing a control voltage proportional to battery current, and control circuit means having an input coupled to said battery current sensing resistor and having an output coupled to said control electrode of said transistor means to control conduction of said transistor means and to thereby control battery charging current as a function of said control voltage developed by said battery current sensing resistor, said apparatus further including monitoring means coupled to said ground connection and to said first and second output terminals and operative for developing a voltage proportional to battery voltage from the difference between voltages at said first and second output terminals with respect to ground.