Rapid battery charging circuit with overvoltage shunt

• US 5,736,833 A
• Filed: 06/28/1996
• Issued: 04/07/1998
• Est. Priority Date: 06/28/1996
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Symbios Logic Incorporated (Broadcom, Inc.)
• Inventors: Farris, Richard D.
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/676,019
• Time in Patent Office: 648 Days
• Field of Search: 320/5, 320/6, 320/11, 320/12, 320/20, 320/21, 320/27, 320/30, 320/39, 320/37
• US Class Current: 320/163
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

A circuit for charging a battery comprising a charging source, a transistor and a charge control device for switching the transistor. When saturated and switched on, the transistor permits flow of charge to the battery from the charging source. The charge control device senses when main power is lost and switches the transistor off to prevent discharge of the battery through the charging source. After the battery is charged the transistor provides a path of least resistance to bleed off unwanted charge from other sources thereby preventing overcharging of the battery. The circuit therefore charges a battery rapidly and prevents overcharging of the battery. The charge control device is operable from a constant supply voltage supplied by a main power source when available or from the charged battery to continue operation despite loss of main power.

Claims

1. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a transistor connected in series between said charging potential source and said battery, wherein said transistor is switchable between a first state in which current linearly flows through said transistor from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

a charge control device connected to said transistor to switch said transistor between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value.

2. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a transistor connected in series between said charging potential source and said battery, wherein said transistor is switchable between a first state in which current flows through said transistor from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

a charge control device connected to said transistor to switch said transistor between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value, and wherein said charge control device comprises a comparator device which compares said main power source potential to said predetermined threshold value.

3. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a transistor connected in series between said charging potential source and said battery, wherein said transistor is switchable between a first state in which current flows through said transistor from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

a charge control device connected to said transistor to switch said transistor between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value, and wherein said predetermined threshold value is substantially fixed regardless of said main power source potential.

4. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a transistor connected in series between said charging potential source and said battery, wherein said transistor is switchable between a first state in which current flows through said transistor from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

a charge control device connected to said transistor to switch said transistor between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value, and wherein said predetermined threshold value is derived from said main power source potential when said main power source potential is above said predetermined threshold value, and wherein said predetermined threshold value is derived from said battery when said main power source potential is below said predetermined threshold value.

5. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a switching device connected in series between said charging potential source and said battery, wherein said switching device is switchable between a first state in which current linearly flows through said switching device from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

charge control means connected to said switching device to switch said switching device between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value.

6. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a switching device connected in series between said charging potential source and said battery, wherein said switching device is switchable between a first state in which current flows through said switching device from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

charge control means connected to said switching device to switch said switching device between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value, and wherein said charge control device comprises a comparator device which compares said main power source potential to said predetermined threshold value.

7. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a switching device connected in series between said charging potential source and said battery, wherein said switching device is switchable between a first state in which current flows through said switching device from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

charge control means connected to said switching device to switch said switching device between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value, and wherein said predetermined threshold value is substantially fixed regardless of said main power source potential.

8. A circuit for charging a battery comprising:

a charging potential source which derives its power from a main power source potential;

a switching device connected in series between said charging potential source and said battery, wherein said switching device is switchable between a first state in which current flows through said switching device from said charging potential source and said battery and a second state in which no current flows from said charging potential source and said battery; and

charge control means connected to said switching device to switch said switching device between said first state and said second state, wherein said charge control device derives operational power from said main power source potential when said main power source potential is above a predetermined threshold value, and wherein said charge control device derives operational power from said battery when said main power source potential is below said predetermined threshold value, and wherein said predetermined threshold value is derived from said main power source potential when said main power source potential is above said predetermined threshold value, and wherein said predetermined threshold value is derived from said battery when said main power source potential is below said predetermined threshold value.

9. In combination:

a transistor connected between a charging power source and a battery, wherein charge current periodically flows through said transistor from said charging power source to said battery; and

a diode connected between said battery and a load, wherein said transistor periodically shunts leakage current from the diode away from the battery.

10. In combination:

a main power source that provides power to a load;

a charging power source that provides power to a battery;

a diode coupled between said battery and said load; and

a transistor coupled between said charging power source and said battery, wherein current flows through said transistor from said diode to said charging power source.

11. A dual-function electrical device that provides current to a battery when the battery is not charged, and shunts current away from the battery when the battery is charged.

12. The device of claim 11, wherein the dual-function electrical device is a transistor.

13. A method for maintaining a battery, comprising the steps of:

providing current from a power source to the battery through an electrical device during a first cycle; and

shunting current away from the battery to the power source through the electrical device during a second cycle.

14. The method of claim 13, wherein the dual-function electrical device is a transistor.