Power sharing method and circuit for simultaneously charging multiple loads

• US 6,445,159 B1
• Filed: 09/24/2001
• Issued: 09/03/2002
• Est. Priority Date: 09/24/2001
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ramsden, Martin H.
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/957,953
• Time in Patent Office: 344 Days
• Field of Search: 320/106, 320/107, 320/110, 320/112, 320/116, 320/118, 320/119, 320/125
• US Class Current: 320/119
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

This invention includes a circuit for charging multiple batteries simultaneously. The circuit monitors the amount of current being delivered to a first battery and compares it to a maximum available current. The circuit then delivers the difference to at least a second battery. The circuit includes a current sensing resistor and comparator for actuating a series switch to electrically couple and decouple a second battery depending upon the demands of the first battery. An optional microprocessor can manipulate a reference threshold to allow simultaneous charging of multiple batteries. The invention greatly reduces the time needed to charge a primary and spare battery.

Claims

1. A charging circuit comprising:

a. a power supply electrically coupled to the charging circuit;

b. at least two connections for electrically coupling to at least two rechargeable batteries;

c. current sensing circuitry electrically coupled to a first connection for electrically coupling to a first rechargeable battery;

d. a reference voltage;

e. circuitry for comparing an output of the current sensing circuitry to the reference voltage; and

f. a switch electrically coupled serially between the power supply and at least a second connection for electrically coupling to at least a second rechargeable battery;

wherein when the output of the current sensing circuitry exceeds the reference voltage, the circuitry for comparing the output of the current sensing circuitry actuates the switch.

2. The circuit of claim 1, wherein the current sensing circuitry actuates the switch by a method selected from the group consisting of opening the switch, closing the switch, and operating the switch in a linear mode.

3. The circuit of claim 2, wherein the circuitry for comparing an output of the sensing circuitry to the reference voltage comprises a comparator.

4. The circuit of claim 3, wherein the switch is selected from the group consisting of metal oxide semiconductor field effect transistors, bipolar junction transistors, junction field effect transistors, circuit breakers and relays.

5. The circuit of claim 4, further comprising a microprocessor.

6. The circuit of claim 5, wherein the microprocessor is able to adjust an output level of the voltage reference.

7. A charger for charging two or more batteries, the charger comprising:

a. at least two pockets, the at least two pockets comprising at least one first pocket and at least one second pocket;

b. a power supply electrically coupled to the at least two pockets;

c. a means for monitoring the current delivered to the at least one first pocket;

d. a means of comparing the current delivered to the at least one first pocket to a predetermined threshold; and

e. a means of electrically decoupling the at least one second pocket from the power supply when the current delivered to the at least one first pocket exceeds the predetermined threshold.

8. The charger of claim 7, wherein the means of comparing current comprises a comparator.

9. The charger of claim 8, wherein the means of electrically decoupling comprises a transistor.

10. The charger of claim 9, wherein the means of monitoring the current comprises a resistor.

11. The charger of claim 10, wherein the resistor has a value of between zero and one hundred ohms.