POWER SOURCE SWITCHOVER APPARATUS AND METHOD

• US 20090309552A1
• Filed: 08/18/2009
• Published: 12/17/2009
• Est. Priority Date: 11/23/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph H., Patel, Ronil
• Granted Patent: US 7,852,046 B2
• Time in Patent Office: Days
• US Class Current: 320/140
• 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. Such an apparatus may determine which of the first and second power supplies has a greater voltage, and may power a device from the power supply having the greater voltage or charge. A single boost converter may be 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 comparator operatively electrically connected to the first negative terminal, electrically connected to the second negative terminal, configured to compare a first voltage at the first negative terminal with a second voltage at the second negative terminal, and configured to generate an output based on such comparison; and

a single boost converter electrically connected to each of the first and second battery compartments, the boost converter operative to draw power from a one of the first and second battery compartments based on the output of the comparator.

2. The battery-switching apparatus of claim 1, wherein the comparator is operative to switch to one of the first and second battery compartments having a highest voltage based on the comparison in order to supply power to the boost converter.

3. The battery-switching apparatus of claim 1, 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 the 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 1, wherein:

the output of the comparator is electrically connected to a gate terminal of the first transistor and to a gate terminal of the second transistor;

the first negative terminal is electrically connected to a drain terminal of the first transistor; and

the second negative terminal is electrically connected to a drain terminal of the second transistor.

6. The battery-switching apparatus of claim 1, wherein:

the 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 to 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.

7. The battery-switching apparatus of claim 6, 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.

8. The battery-switching apparatus of claim 6, 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.

9. The battery-switching apparatus of claim 6, further comprising:

a third transistor electrically connected to the second transistor and to the third common node.

10. The battery-switching apparatus of claim 6, further comprising:

a first pullup resistor electrically connected between the first common node and the second common node; and

a second pullup resistor electrically connected between the first common node and the third common node.

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

the first pullup resistor is configured to establish a first defined voltage at the second common node when a battery is not installed in the first battery compartment; and

the second pullup resistor is configured to establish a second defined voltage at the third common node when a battery is not installed in the second battery compartment.

12. The battery-switching apparatus of claim 6, further comprising:

a capacitor electrically connected to the first common node and to a third transistor such that the capacitor and the third transistor are in series.

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

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

a voltage detector operatively connected to the output of the peak detector, the third transistor operatively connected to an output of the voltage detector.

14. The battery-switching apparatus of claim 13, wherein the voltage detector is configured to output a bias voltage to the third transistor once a voltage output from the peak detector reaches a predetermined threshold of the voltage detector.

15. The battery-switching apparatus of claim 14, wherein the bias voltage is invariant.

16. The battery-switching apparatus of claim 6, 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, the first capacitor operative to charge from a cell voltage of the first battery; 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, the second capacitor is operative to charge from a cell voltage of the second battery.

17. The battery-switching apparatus of claim 16, 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.

18. The battery-switching apparatus of claim 17, 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.

19. The battery-switching apparatus of claim 6, further comprising:

an output transistor electrically connected to an output of the boost converter; and

a third transistor operatively connected to the output transistor.

20. The battery-switching apparatus of claim 6, 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 and operatively connected to the third transistor.

21. The battery-switching apparatus of claim 20, wherein the voltage detector is configured to output a bias voltage to the third transistor once a voltage output from the peak detector reaches a predetermined threshold of the voltage detector.

22. The battery-switching apparatus of claim 21, wherein the bias voltage is invariant.

23. The battery-switching apparatus of claim 21, wherein:

the third transistor is operative to switch on the output transistor upon receipt of the bias voltage from the voltage detector;

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.

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

detecting a first voltage at a negative terminal of the first battery;

detecting a second voltage at a negative terminal of the second battery;

determining which one of the first battery and the second battery has a greater voltage based on the detected first and second voltages; and

in response to determining which one of the first battery and the second battery has a greater voltage, supplying power from the one of the first battery and the second battery having the greater voltage to a single boost converter.

25. The method of claim 24, wherein determining which one of the first battery and the second battery has a greater voltage based on the detected first and second voltages comprises comparing the detected first and second voltages.

26. The method of claim 24, further comprising:

detecting when a voltage of the one of the first battery and the second battery falls below the other of the first and second voltages;

in response to detecting when a voltage of the one of the first battery and the second battery falls below the other of the first and second voltages, disabling the one of the first battery and the second battery; and

further in response to detecting when a voltage of the one of the first battery and the second battery falls below the other of the first and second voltages, enabling the other of the first battery and the second battery.

27. The method of claim 24, wherein:

the single boost converter is electrically connected to both the first battery and second battery; and

the operation of supplying power from the one of the first battery and the second battery having the greater voltage comprises enabling the one of the first battery and the second battery and disabling the other of the first battery and the second battery.

28. The method of claim 27, wherein:

enabling the one of the first battery and the second battery comprises enabling a first transistor to enable the one of the first battery and the second battery; and

disabling the other of the first battery and the second battery comprises enabling a second transistor to disable a third transistor to disable the other of the first battery and the second battery.

29. The method of claim 27, wherein:

enabling the one of the first battery and the second battery comprises disabling a first transistor to enable a second transistor to enable the one of the first battery and the second battery; and

disabling the other of the first battery and the second battery comprises disabling a third transistor to disable the other of the first battery and the second battery.

30. The method of claim 24, further comprising:

charging a capacitor using an output voltage of the single boost converter;

comparing a voltage of the capacitor to a threshold voltage; and

when the voltage of the capacitor meets the threshold voltage, activating an output transistor connected to an output of the single boost converter; and

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

31. The method of claim 30, wherein outputting an output voltage comprises:

setting a desired output voltage; and

after activating the output transistor, charging an output capacitor to a voltage equal to the desired output voltage using a voltage output by the single boost converter.

32. The method of claim 30, wherein:

activating the output transistor comprises providing a bias voltage to a transistor operatively connected to the output transistor, the bias voltage enabling the transistor to enable the output transistor.

33. The method of claim 32, wherein the bias voltage is equal to the threshold voltage.