Voltage profile charge control system

• US 6,268,715 B1
• Filed: 04/29/2000
• Issued: 07/31/2001
• Est. Priority Date: 04/29/2000
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Herrmann, John Edward, Oglesbee, John Wendell, Ramsden, Martin Hague
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/562,267
• Time in Patent Office: 458 Days
• Field of Search: 320/127, 320/128, 320/133, 320/148, 320/156, 320/157, 320/158, 320/159, 320/161, 320/162, 320/163, 320/164
• US Class Current: 320/156
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

This invention is a battery charging system that charges rechargeable battery cells by tracking a voltage profile charging curve across time. As all lithium based, like voltage cells have the same voltage profile across time, regardless of capacity, the invention presents a preferred embodiment of a universal charger capable of charging lithium batteries of varying capacities. Current is treated as a variable dependent upon voltage. Thus, in a preferred embodiment, cells of varying capacities will be charged at an optimal rate, thereby optimizing battery performance. One embodiment uses frequency selection to vary the rate of change in the output voltage of the system, thereby tracking the voltage profile charging curve across time.

Claims

1. A battery charging system comprising:

A) a power source;

B) means for modulating the power input electrically coupled to the power source;

C) logic means for modulating clock signals electrically coupled to the means for modulating the power input; and

D) terminals for connecting to a rechargeable battery cell, the terminals being electrically coupled to the means for modulating the power input;

wherein the logic circuitry causes the means for modulating the power input to track at least one monotonically increasing voltage curve across time to charge the rechargeable battery cell.

2. The system of claim 1, wherein the monotonically increasing curve is a voltage profile charging curve.

3. The system of claim 2, wherein the logic means for modulating clock signals comprises:

A) a cell detector;

B) initialization logic electrically coupled to the cell detector;

C) oscillator logic electrically coupled to the initialization logic; and

D) means for converting digital signals to analog signals, electrically coupled to the oscillator logic, having at least one digital input and at least one analog output;

wherein the oscillator logic selects from at least one frequency corresponding to at least one rate of charging.

4. The system of claim 3, wherein the battery cell detector comprises logic for actuating a start control signal that initializes the system.

5. The system of claim 4, wherein the oscillator logic comprises:

A) a resistor-capacitor oscillator having at least one frequency control input;

B) digital logic for processing the at least one frequency control input;

C) a counter having at least one digital count output; and

D) a decoder having at least one select control input at least one frequency control output, the decoder being capable of selecting at least one frequency control output based upon the at least one count output.

6. The system of claim 5, wherein the output of the means for converting digital signals to analog signals sets the output voltage level of the means for modulating the power input.

7. The system of claim 6, wherein the system further comprises a means for comparing the output of the means for converting digital signals to analog signals and the output of the means for modulating the power input, such that when the output of the means for modulating the power input exceeds the output of the means for converting digital signals to analog signals, a comparison control signal is asserted.

8. The system of claim 7, wherein the system further comprises an initialization offset voltage.

9. The system of claim 8, wherein when the rechargeable battery cell is coupled to the means for modulating the power input, the system increases the output of the means for modulating the power input until it reaches a predetermined point, and thereafter the means for modulating the power input tracks the voltage profile charging curve across time.

10. The system of claim 4, wherein the oscillator logic comprises:

A) a digital frequency oscillator having at least one frequency control input;

B) a fixed clock electrically coupled to the digital frequency oscillator; and

C) a counter having at least one digital count output.

11. The system of claim 10, wherein the oscillator further comprises a memory having stored therein at least one digital bit corresponding to at least one synthesizer frequency.

12. The system of claim 4, wherein the oscillator logic comprises:

A) a microprocessor having at least one data control input;

B) a digital clock electrically coupled to the microprocessor; and

C) a memory having stored therein at least one digital bit corresponding to at least one synthesizer frequency.

13. The system of claim 4, wherein the oscillator logic comprises:

A) voltage controlled clock modulation; and

B) logic circuitry electrically coupled to the voltage controlled clock modulation;

wherein the logic circuitry and voltage controlled clock modulation comprise at least one semiconductor die.

14. The system of claim 4, wherein the oscillator logic comprises:

A) current controlled clock modulation; and

B) logic circuitry electrically coupled to the current controlled clock modulation;

wherein the logic circuitry and current controlled clock modulation comprise at least one semiconductor die.