Power fault protection in a computer system having multiple power supplies

• US 6,202,171 B1
• Filed: 04/27/1995
• Issued: 03/13/2001
• Est. Priority Date: 05/09/1994
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Townsley, David B., Blanc, James J.
• Primary Examiner(s): LE, DIEU MINH T
• Application Number:
  US08/430,763
• Time in Patent Office: 2,147 Days
• Field of Search: 364/182.01, 364/182.12, 364/750, 369/948.4, 369/948.5, 369/949.4, 369/200, 363/41, 307/43, 307/44, 307/64, 307/65, 307/66, 713/300, 713/340
• US Class Current: 714/14
• 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: G06F 11/2015 Redundant power supplies power supply failure G06F1/30

Abstract

A power system fault handling mechanism for portable electronic devices having multiple power supplies. A safety-net circuit is triggered when a power fault condition is detected. The safety-net circuit is a diode-based bridging circuit which couples all available power supplies to the power load, yet avoids feeding power back from any of the supplies to one another. This ensures that the load continues to receive power after a fault condition occurs without interruption. A microcontroller may then implement a routine to switch to a working power supply so that the device may resume normal operation. The power system fault detection mechanism therefor allows for the switching between system power supplies without disrupting a running process.

Claims

1. A power fault protection system for an electronic device having a plurality of available power supplies of which only one of the plurality of available power supplies provides power to a load of the electronic device, the power fault protection system comprising:

a first power supply fault detection circuitry which detects a power system fault condition;

a power supply bridging circuitry, responsive to the first power supply fault detection circuitry, which couples the plurality of available power supplies together to collectively supply at least an operating voltage to the load of the electronic device when said power system fault condition exists; and

,

a power system fault recover logic circuitry, responsive to the first power supply fault detection circuitry, for recovering from the power system fault condition and selecting one of the plurality of available power supplies to provide the operating voltage to the load of the electronic device.

2. The power fault protection system of claim 1 wherein the power supply bridging circuitry comprises:

a plurality of power paths, each respectively coupled between one of the plurality of available power supplies and the load of the electronic device; and

a fault protection switch, responsive to the first power supply fault detection circuitry, to electrically connect each of the plurality of power paths to bridge the plurality of available power supplies in order to provide the operating voltage to the load of the electronic device when said power system fault condition exists.

3. The power fault protection system of claim 2 further comprising a plurality of diodes, each diode is respectively coupled within the plurality of power paths to ensure that power flows only away from each of the plurality of available power supplies.

4. The power fault protection system of claim 3 wherein the power fault detection circuitry comprises a comparator which compares the operating voltage being supplied to the load of the electronic device with a threshold voltage level, the comparator propagating a fault detection signal when the operating voltage being supplied falls below the threshold voltage level.

5. The power fault protection system of claim 1 wherein the power system fault recovery logic circuitry receives an applied logic voltage, the power fault protection system further comprising a second power supply fault detection circuitry which detects a power fault condition relating to the applied logic voltage.

6. The power fault protection system of claim 5 wherein the second power supply fault detection circuitry comprises a comparator which compares the applied logic voltage to a threshold voltage, the comparator propagating a second power fault detection signal when the applied logic voltage falls below the threshold voltage.

7. The power fault protection system of claim 6 further comprising a backup linear regulator which supplies power to the power system fault recovery logic circuitry during the power fault condition, the backup linear regulator is activated by the first power supply fault detection circuitry.

8. The power fault protection system of claim 1 wherein the plurality of available power supplies includes an AC adapter selectively utilized by activating a first switch, a first battery selectively utilized by activating a second switch, and a second battery selectively utilized by activating a third switch and the power supply bridging circuitry includes:

a first power path coupled between the AC adapter and the load of the electronic device, the first power path delivers power from the AC adapter to the load;

a second power path coupled between the first battery and the load and selectively coupled to the first power path;

a third power path coupled between the second battery and the load and selectively coupled to the first and second power paths; and

a fourth switch, coupled between the load and the first, second and third power paths, the fourth switch responsive to the first power supply fault detection circuitry, wherein when the fourth switch is on, each of the plurality of available power supplies is operatively coupled together to supply power to the load, further wherein, when the fourth switch is on, the first, second and third switches are off in response to the first power supply fault detection circuitry.

9. The power fault protection system of claim 8 wherein the power supply bridging circuitry further comprises:

a first diode implemented in the first power path and oriented to prevent power from flowing toward the AC adapter;

a second diode implemented in the second power path and oriented to prevent power from flowing toward the first battery; and

a third diode implemented in the third power path and oriented to prevent power from flowing toward the second battery.

10. The power fault protection system of claim 9 wherein the is power supply fault detection circuitry comprises a comparator which compares the operating voltage being supplied to the load of the electronic device with a threshold voltage level, the comparator propagating a fault detection signal when the operating voltage being supplied falls below the threshold voltage level.

11. The power fault protection system of claim 1 wherein the power system fault recovery logic circuitry receives an applied logic voltage, the power fault protection system further comprising a second power supply fault detection circuitry which detects a power fault condition relating to the applied logic voltage.

12. The power fault protection system of claim 11 wherein the second power supply fault detection circuitry comprises a second comparator which compares the applied logic voltage to a threshold voltage, the second comparator propagating a second power fault detection signal when the applied logic voltage falls below the threshold voltage.

13. The power fault protection system of claim 12 further comprising a backup linear regulator which supplies power to the power system fault recovery logic circuitry during the power fault condition, the backup linear regulator is activated by the first power supply fault detection circuitry.

14. A method of protecting an operating electronic device having a plurality of available power supplies from a fault condition, the method comprising the steps of:

comparing an operating voltage of the electronic device to a threshold voltage; and

bridging the plurality of available power supplies to collectively supply power to a load of the electronic device when the operating voltage drops below the threshold voltage and alternatively supplying power to a load of the electronic device from only one of the plurality of available power supplies during normal operations.

15. The method of claim 14 wherein the bridging step comprises the steps of:

decoupling each of the plurality of power supplies from the normal power paths to the load of the electronic device;

activating a fault condition power supply switch; and

providing power from each of the plurality of available power supplies to the load of the electronic device through an alternate combined power path when the operating voltage drops below the threshold voltage.

16. The method of claim 15 further comprising the step of initiating a fault recovery routine in a microcontroller implemented within the electronic device when the operating voltage drops below the threshold voltage.

17. The method of claim 16 further comprising the step of monitoring a voltage applied to the microcontroller.

18. The method of claim 17 further comprising the step of resetting the microcontroller when the voltage applied to the microcontroller falls below a second threshold voltage.