Power source switchover apparatus and method

• US 20070114968A1
• Filed: 11/23/2005
• Published: 05/24/2007
• Est. Priority Date: 11/23/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph, Patel, Ronil
• Granted Patent: US 7,598,711 B2
• Time in Patent Office: Days
• US Class Current: 320/103
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

An apparatus for switching from a first power supply to a second power supply. The embodiment may detect the charge or voltage of both the first and second power supply, and power a device from the power supply having the greatest voltage or charge. A single boost converter is used regardless of which power supply is providing power.

Claims

1. A battery-switching apparatus for switching between at least a first battery and a second battery, comprising:

a first battery compartment having a first positive terminal and a first negative terminal;

a second battery compartment having a second positive terminal and a second negative terminal;

a single boost converter connected to each of the first and second battery compartments;

wherein

the boost converter is operative to draw power from a one of the first and second battery compartments having the highest voltage.

2. The battery-switching apparatus of claim 1, further comprising:

a comparator electrically connected to each of the first and second battery compartments;

wherein

the comparator is operative to switch to the one of the first and second battery compartments having the highest voltage in order to supply power to the boost converter.

3. The battery-switching apparatus of claim 2, further comprising:

a first transistor operatively connected to the comparator; and

a second transistor operatively connected to the comparator;

wherein

the first and second transistors switch states according to an output of the comparator.

4. The battery-switching apparatus of claim 3, wherein:

the first and second transistors are each electrically connected to the output of the comparator; and

the first transistor switches off when the second transistor switches on.

5. The battery-switching apparatus of claim 4, wherein:

a positive terminal of the first battery compartment is connected directly to a first common node;

the positive terminal of the second battery compartment is connected directly to the first common node;

the negative terminal of the first battery compartment is connected a first input of the comparator through a second common node; and

the negative terminal of the second battery compartment is connected to a second input of the comparator through a third common node.

6. The battery-switching apparatus of claim 5, wherein:

a voltage at the second common node exceeds a voltage at the third common node when a cell voltage of a first battery in the first battery compartment exceeds a cell voltage of a second battery in the second battery compartment.

7. The battery-switching apparatus of claim 5, wherein:

a voltage at the third common node exceeds a voltage at the second common node when a cell voltage of the second battery exceeds a cell voltage of the first battery.

8. The battery-switching apparatus of claim 5, further comprising:

a first capacitor electrically connected to the second common node at a first side and electrically connected to a ground at a second side; and

a second capacitor electrically connected to the third common node at a first side and electrically connected to the ground at a second side.

9. The battery-switching apparatus of claim 8, wherein:

the first capacitor is operative to charge from a cell voltage of the first battery; and

the second capacitor is operative to charge from a cell voltage of the second battery.

10. The battery-switching apparatus of claim 9, wherein:

as the first capacitor charges, a voltage of the second common node rises; and

as the second capacitor charges, a voltage of the third common node rises.

11. The battery-switching apparatus of claim 10, wherein:

as the cell voltage of the first battery drops, the charge of the first capacitor drops and the voltage of the second common node drops; and

as the cell voltage of the second battery drops, the charge of the second capacitor drops and the voltage of the third common node drops.

12. The battery-switching apparatus of claim 1, further comprising an output transistor operatively connected to an output of the boost converter.

13. The battery-switching apparatus of claim 12, further comprising:

a peak detector operatively connected to the output of the boost converter; and

a voltage detector operatively connected to the output of the peak detector.

14. The battery-switching apparatus of claim 13, wherein:

the output transistor is operative to switch on when the voltage detector outputs a voltage above a voltage threshold;

an output voltage at an output node is zero until the output transistor switches on; and

the output voltage at the output node exceeds zero after the output transistor switches on.

15. The battery-switching apparatus of claim 1, wherein the boost converter is operative to draw power from the one of the first and second battery compartments having the highest voltage until the voltages of both the first and second battery compartments are below 0.9 volts.

16. The battery-switching apparatus of claim 1, wherein the output of the boost converter supplies a bias voltage for operation of at least one transistor operatively connected thereto.

17. A method for switching between at least a first battery and a second battery, comprising:

detecting a first voltage across the first battery;

detecting a second voltage across the second battery;

determining which of the first voltage and second voltage is greatest; and

in response to determining which of the first voltage and second voltage is greatest, supplying power from the greatest voltage to a single boost converter.

18. The method of claim 17, wherein the single boost converter is electrically connected to both the first battery and second battery.

19. The method of claim 18, wherein the operation of supplying power from the greatest voltage to a single boost converter comprises disabling the one of the first and second voltages not supplying power to the single boost converter.

20. The method of claim 19, wherein at least one transistor is used to disable the one of the first and second voltage not supplying power to the single boost converter.

21. The method of claim 20, further comprising:

detecting a bias voltage;

in the event the bias voltage exceeds a threshold, activating an output transistor; and

in response to activating the output transistor, outputting an output voltage.

22. The method of claim 19, further comprising:

charging a peak detector capacitor from an output of the boost converter; and

once the peak detector capacitor is fully charged, detecting the bias voltage.

23. The method of claim 19, wherein the operation of determining which of the first voltage and second voltage is greatest is executed by a comparator.

24. The method of claim 23, further comprising:

in the event the first voltage is greatest, enabling a first capacitor and disabling a second capacitor; and

in the event the second voltage is greatest, disabling the first capacitor and enabling the second capacitor.

25. The method of claim 24, wherein the operation of disabling the second capacitor comprises:

enabling a third capacitor; and

employing an output of the third capacitor to disable the second capacitor.

26. The method of claim 25, further comprising the operation of charging an output capacitor from the output voltage after activating the output transistor.

27. The method of claim 20, further comprising:

detecting when the greatest voltage falls below the one of the first and second voltages that is not the greatest voltage;

in response to detecting when the greatest voltage falls below the one of the first and second voltages that is not the greatest voltage, disabling the one of the first and second voltages corresponding to the greatest voltage; and

further in response to detecting when the greatest voltage falls below the one of the first and second voltages that is not the greatest voltage, enabling the one of the first and second voltages not corresponding to the greatest voltage.