Load current dependent reduction of charge battery current

• US 20090267571A1
• Filed: 05/02/2008
• Published: 10/29/2009
• Est. Priority Date: 04/29/2008
• Status: Active Grant

• Current Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Wolf, Christian, Lloyd, David, Clowes, Anthony
• Granted Patent: US 7,746,036 B2
• Time in Patent Office: Days
• US Class Current: 320/162
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence

Abstract

Circuits and methods to charge batteries of a portable device simultaneously with supplying power to the device for its operation, using a power source with limited maximum current, as e.g. an USB port, have been achieved. The system invented relies upon digital control only. No direct sensing of the current required for the operation of the portable device is required. The control takes care that the sum of the charging current and of the current to run the portable device does not exceed the maximum allowable current of the power source. The current required to run the portable device has precedence over the charging current.

Claims

1. A method to charge batteries of portable devices simultaneously with supplying power to these devices for their operations is comprising the following steps:

(1) providing a DC power source, a supply regulator, one or more rechargeable batteries, a battery charger controlled by a digital control unit, a voltage comparator, and a capacitor;

(2) setting charge current to charge batteries to a predefined default current level;

(3) delaying process flow for a defined time interval;

(4) checking if voltage at inputs of said portable device and of said battery charger is lower than a defined threshold voltage, and, if positive, go to step (5) else go to step (7);

(5) checking, if said charge current is zero, and if positive, go to step (3) else go to step (6);

(6) decreasing said charge current and go then to step (3);

(7) checking if said charge current is smaller than said predefined default current level, and if positive, go to step (8), else go to step (3); and

(8) increasing said charge current and go then to step (3).

2. The method of claim 1 wherein said delay time has an order of magnitude of 100 μ

sec.

3. The method of claim 1 wherein said DC power source has a maximum allowable current limit.

4. The method of claim 3 wherein said DC power source is a universal serial bus (USB) port.

5. The method of claim 3 wherein said DC power source is a Firewire/IEEE1394 port.

6. The method of claim 3 wherein said DC power source is a current limited wall brick.

7. The method of claim 3 wherein said supply regulator does allow a maximum output current, which is slightly lower than said maximum allowable current limit of said DC power source.

8. The method of claim 1 wherein said digital control performs said check if said charge current is zero and sends the result to said digital control unit.

9. The method of claim 1 wherein said digital control performs said check if said charge current is smaller than said predefined default current level and sends the result to said digital control unit.

10. The method of claim 1 wherein said supply regulator, one or more rechargeable batteries, the battery charger, the digital control unit, and the voltage comparator are integrated in said portable device.

11. The method of claim 1 wherein said supply regulator is a linear regulator.

12. The method of claim 1 wherein said supply regulator is a switched regulator.

13. The method of claim 1 wherein said digital control controls the battery charger in a way that the current required for the operation of the portable device has precedence over the charging current of the batteries.

14. A system to charge batteries of a portable device simultaneously with supplying power to the device for its operation is comprising:

a rechargeable battery,

a DC power source connected at its output to a supply regulator;

said supply regulator regulating its output voltage and limiting its output current just below the maximum allowable output current of said DC power supply, wherein the output of the supply regulator is supplying the operation of the portable device and its voltage corresponds to the supply voltage level required the portable device, and the output is further connected to the power input of a battery charger, charging said rechargeable battery, to a first terminal of a capacitor, and to a first input of a voltage comparator;

said capacitor having its second terminal connected to ground;

said battery charger, charging with its, output said rechargeable battery, having its operation controlled by a digital controller;

said digital controller wherein an input is connected to an output of said voltage comparator and the output is connected to said battery charger; and

said voltage comparator having a reference voltage as a second input comparing said reference voltage with the output voltage of said supply regulator.

15. The system of claim 14 wherein said DC power source has a maximum allowable current limit.

16. The system of claim 15 wherein said DC power source is a universal serial bus (USB) port.

17. The system of claim 15 wherein said DC power source is a Firewire/IEEE1394 port.

18. The system of claim 15 wherein said DC power source is a current limited wall brick.

19. The system of claim 14 wherein said supply regulator, one or more rechargeable batteries, the battery charger, the digital control unit, the capacitor, and the voltage comparator are integrated in said portable device.

20. The system of claim 14 wherein a system capacitance replaces said capacitor.

21. The system of claim 14 wherein said supply regulator allows a maximum output current, which is slightly lower than said maximum allowable current limit of said DC power source.

22. The system of claim 14 wherein said supply regulator is a linear regulator.

23. The system of claim 14 wherein said supply regulator is a switched regulator.

24. The system of claim 14 wherein more than one rechargeable battery is deployed.

25. The system of claim 14 wherein said digital control controls the battery charger in a way that the current required for the operation of the portable device has precedence over the charging current of the batteries.