Fast-charging device for rechargeable batteries

• US 5,717,311 A
• Filed: 04/24/1996
• Issued: 02/10/1998
• Est. Priority Date: 04/24/1995
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Im, Sang-Tae, Choi, Byung-Cho, Seoung, Hwan-Ho
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/639,088
• Time in Patent Office: 657 Days
• Field of Search: 320/20, 320/21, 320/22, 320/23, 320/30, 320/32, 320/33, 320/27
• US Class Current: 320/164
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• 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: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 320/22 Line impedance, e.g. resistor

Abstract

A battery charging device for providing a fast charging a rechargeable battery and controlling the charging process to prevent overcharging. The battery charging device detects a decrease in the voltage of the rechargeable battery as it is being charged and approaches a full charge, and modulates the switching of a switching power supply supplying current to the rechargeable battery in response thereto. The battery charging device has a first resistor in series with the rechargeable battery which is to be charged, a power supply which charges the rechargeable battery, a charging control unit which detects a decrease in the voltage across the rechargeable battery using capacitors and which outputs battery condition signals and battery error signals in response thereto, and a power supply control unit which accepts a mode change signal and a battery error signal from the charging control unit and outputs a control signals for controlling the power supply.

Claims

1. A battery charging device, comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a power supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery;

charging control means, connected to said rechargeable battery and said first resistor, for detecting a decrease in a voltage across said rechargeable battery and outputting a battery condition signal indicating that said voltage across said rechargeable battery has decreased, wherein said charging control means comprises;

a first capacitor having a negative electrode connected to a negative electrode of said rechargeable battery;

a second resistor connected in series with said first capacitor;

a first operation amplifier having a negative input terminal connected in series with said series connection of said first capacitor and said second resistor, and having a positive input terminal connected to a positive electrode of said rechargeable battery;

a diode having a cathode connected to an output terminal of said first operation amplifier and having an anode connected to said negative input terminal of said first operation amplifier;

a second capacitor connected in parallel with said diode;

a second operation amplifier having a positive input terminal connected to said positive input terminal of said first operation amplifier, and having a negative input terminal connected to an output terminal of said second operational amplifier; and

a first comparator having a positive input terminal connected to said output terminal of said first operation amplifier, and having a negative input terminal connected to said output terminal of said second operation amplifier; and

power supply control means for controlling said power supply in accordance with said battery condition signal.

2. The battery charging device according to claim 1, wherein said charging control means further comprises:

battery condition output means for outputting said battery condition signal only if said voltage of said rechargeable battery is higher than a predetermined first reference voltage.

3. The battery charging device according to claim 2, wherein said battery condition output means comprises:

a second comparator having a positive input terminal connected to said output terminal of said second amplifier, and having a negative input terminal connected to said first predetermined reference voltage; and

a first NAND gate having a first input terminal connected to said output terminal of said first comparator, and having a second input terminal connected to said output terminal of said second comparator.

4. The battery charging device according to any one of claims 1 to 3, wherein said charging control means further comprises:

battery error signal output means for outputting a battery error signal if said voltage of said rechargeable battery is at least one of;

lower than a predetermined second reference voltage, and higher than a predetermined third reference voltage.

5. The battery charging device according to any one of claims 1 to 3, wherein said charging control means further comprises:

filter means for filtering high frequency noise from said voltage of said rechargeable battery.

6. The battery charging device according to any one of claims 1 to 3, wherein said charging control means further comprises:

mode change means for outputting a mode change signal corresponding to said battery condition signal.

7. The battery charging device according to any one of claims 1 to 3, wherein said power supply control means comprises:

compensation means for detecting a current through said first resistor and compensating said current through said first resistor to be constant.

8. A battery charging device, comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a power supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery;

charging control means, connected to said rechargeable battery and said first resistor, for detecting a decrease in a voltage across said rechargeable battery and outputting a battery condition signal indicating that said voltage across said rechargeable battery has decreased, wherein said charging control means comprises;

filter means for filtering high frequency noise from said voltage of said rechargeable battery; and

power supply control means for controlling said power supply in accordance with said battery condition signal.

9. A battery charging device comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a power supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery;

charging control means connected to said rechargeable battery and said first resistor, for detecting a decrease in a voltage across said rechargeable battery and outputting a battery condition signal indicating that said voltage across said rechargeable battery has decreased, wherein said charging control means comprises;

battery error signal output means for outputting a battery error signal if said voltage of said rechargeable battery is at least one of;

lower than a predetermined second reference voltage, and higher than a predetermined third reference voltage; and

power supply control means for controlling said power supply in accordance with said battery condition signal.

10. A battery charging device, comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a switching power supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery sufficient for a fast-charging operation of said rechargeable battery in less than approximately one hour;

a charging control unit, connected to said rechargeable battery, for detecting, while said rechargeable battery is being recharged, a decrease in a voltage across said rechargeable battery due to a full charge condition of said rechargeable battery, said charging control unit outputting a battery condition signal when said decrease in said voltage across said rechargeable battery has been detected; and

power supply control means for terminating said fast-charging operation of said rechargeable battery in accordance with an occurrence of said battery condition signal, said power supply control means controls a switching operation of said switching power supply in accordance with said battery condition signal.

11. A battery charging device, comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery sufficient for a fast-charging operation of said rechargeable battery in less than approximately one hour;

a charging control unit connected to said rechargeable battery, for detecting, while said rechargeable battery is being recharged, a decrease in a voltage across said rechargeable battery due to a full charge condition of said rechargeable battery, said charging control unit outputting a battery condition signal when said decrease in said voltage across said rechargeable control has been detected, wherein said charging control unit comprises;

a first capacitor and a second resistor connected in series, said series connection of said first capacitor and said second resistor being connected so that said first capacitor is charged in parallel with said rechargeable battery, a voltage of said first capacitor decreasing in correspondence with said decrease in said voltage of said rechargeable battery; and

power supply control means for terminating said fast-charging operation of said rechargeable battery in accordance with an occurrence of said battery condition signal.

12. A battery charging device, comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a power supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery sufficient for a fast-charging operation of said rechargeable battery in less than approximately one hour;

a charging control unit, connected to said rechargeable battery, for detecting, while said rechargeable battery is being recharged, a decrease in a voltage across said rechargeable battery due to a full charge condition of said rechargeable battery, said charging control unit outputting a battery condition signal when said decrease in said voltage across said rechargeable battery has been detected;

power supply control means for terminating said fast-charging operation of said rechargeable battery in accordance with an occurrence of said battery condition signal; and

a latch to latch said battery condition signal such that said decrease in said voltage across said rechargeable battery need only be detected once during a recharging cycle.

13. A battery charging device, comprising:

a first resistor connected in series with a rechargeable battery to be charged;

a power supply connected to supply electrical current through said series connection of said first resistor and said rechargeable battery;

charging control means, connected to said rechargeable battery and said first resistor, for detecting a decrease in a voltage across said rechargeable battery and outputting a battery condition signal indicating that said voltage across said rechargeable battery has decreased; and

power supply control means for controlling said power supply in accordance with said battery condition signal, wherein said power supply control means comprises;

compensation means for detecting a current through said first resistor and compensating said current through said first resistor to be constant.