Circuit and method of operation for an electrical power supply

• US 20040164708A1
• Filed: 02/21/2003
• Published: 08/26/2004
• Est. Priority Date: 02/21/2003
• Status: Active Grant

• Current Assignee: Fundamental Innovation Systems International LLC (Fundamental Innovation Systems International Holdings LLC)
• Original Assignee: Blackberry Limited
• Inventors: Veselic, Dusan, Guthrie, Martin G. A.
• Granted Patent: US 7,791,319 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/0071 with a programmable schedule

Abstract

A battery charging circuit comprising: a semiconductor switch having an output connected to a rechargeable battery; a battery charge controller for receiving power from an external source, and supplying output power to a portable device and the input of the semiconductor switch, the current output of the battery charge controller being controllable; and a voltage sensing circuit for: measuring the voltage drop across the battery charge controller; and responding to the voltage drop across the battery charge controller by modulating the semiconductor switch to reduce the quantity of current supplied to the rechargeable battery when the voltage drop is too great; whereby the total power dissipated by the battery charge controller is controlled, the portable device receiving the power it needs to operate and the rechargeable battery receiving any additional available power.

Claims

1. A battery charging circuit comprising:

a semiconductor switch having an output connected to a rechargeable battery;

a battery charge controller for receiving power from an external source, and supplying output power to a portable device and the input of said semiconductor switch, the current output of said battery charge controller being controllable; and

a voltage sensing circuit for;

measuring the voltage drop across said battery charge controller; and

responding to said voltage drop across said battery charge controller by modulating said semiconductor switch to reduce the quantity of current supplied to said rechargeable battery when said voltage drop is too great;

whereby the total power dissipated by said battery charge controller is controlled, said portable device receiving the power it needs to operate and said rechargeable battery receiving any additional available power.

2. The battery charging circuit of claim 1, wherein said battery charge controller further comprises an external driving semiconductor for carrying supply current to said portable device and said semiconductor switch, whereby load current passes through said external driving semiconductor rather than through said battery charge controller.

3. The battery charging circuit of claim 2, wherein said voltage sensing circuit comprises an operational amplifier.

4. The battery charging circuit of claim 3 where said voltage sensing circuit comprises:

an operational amplifier for receiving a voltage signal from the output of said battery charge controller and a reference voltage signal, and responds to said voltage signal being less than said reference voltage by reducing the current flow through said semiconductor switch.

5. The battery charging circuit of claim 3, wherein said voltage sensing circuit comprises an operational amplifier for comparing the voltage on the output of said battery charge controller to a reference voltage.

6. The battery charging circuit of claim 2 where low-power, critical components of said portable device are fed from said battery charge controller, and high-power, non-critical components of said portable device are fed from said rechargeable battery.

7. The battery charging circuit of claim 6 where said low-power, critical components include at least one of:

a memory and a microprocessor.

8. The battery charging circuit of claim 6 where said high-power, non-critical components include at least one of:

a back lighting system and a vibrator.

9. The battery charging circuit of claim 2, wherein said external driving semiconductor comprises a transistor.

10. The battery charging circuit of claim 4 wherein:

said operational amplifier circuit further comprises a voltage divider for scaling down said voltage signal from said battery charge controller and said reference voltage signal is scaled down proportionally.

11. The battery charging circuit of claim 10 where said external power supply comprises a computer data bus having a power node.

12. The battery charging circuit of claim 11 wherein:

said computer data bus is a Universal Serial Bus (USB).

13. The battery charging circuit of claim 2, wherein the maximum current said battery charge controller will provide is limited by an external resistance to ground.

14. The battery charging circuit of claim 13, wherein the maximum current said battery charge controller will provide is limited by multiple sets of external resistors and semiconductor switches, allowing said battery charge controller to be controlled to provide varying levels of current.

15. The battery charging circuit of claim 14, wherein said semiconductor switch comprises a MOSFET (metal oxide silicon field effect transistor).

16. The battery charging circuit of claim 15 wherein:

said regulating circuit further comprises a capacitor coupling the output of said operational amplifier to ground, thereby smoothing out variances in the output of said operational amplifier.

17. A battery charging circuit comprising:

a battery charge controller connected to said external power supply and electrifying a battery and a portable device, and having a maximum current setting; and

a regulating circuit for sensing the voltage drop across said battery charge controller, and modulating the current to said battery to keep the power dissipated by said battery charge controller below a predetermined level.

18. A method for charging a battery of a portable device via an external power supply, said method comprising the steps of:

connecting the input of a battery charge controller to said external power supply;

connecting the output of said battery charge controller, in parallel, to said portable device and the input of a semiconductor switch;

connecting the output of said semiconductor switch to said battery;

controlling the current output of said battery charge controller;

measuring the voltage drop across said battery charge controller; and

responding to said voltage drop across said battery charge controller by modulating said semiconductor switch to reduce the quantity of current supplied to said rechargeable battery when said voltage drop is too great;

whereby the total power dissipated by said battery charge controller is controlled, said portable device receiving the power it needs to operate and said rechargeable battery receiving any additional available power.

19. A power supply circuit comprising:

means for measuring the voltage drop across a battery charge controller providing power to a portable device and the input of a semiconductor switch in parallel;

means for controlling the current output of said battery charge controller; and

means for responding to the voltage drop across said battery charge controller by modulating said semiconductor switch to reduce the quantity of current supplied to said rechargeable battery when said voltage drop is too great;

whereby the total power dissipated by said battery charge controller is controlled, said portable device receiving the power it needs to operate and said rechargeable battery receiving any additional available power.