Technique for conveying overload conditions from an AC adapter to a load powered by the adapter

• US 6,950,950 B2
• Filed: 12/28/2001
• Issued: 09/27/2005
• Est. Priority Date: 12/28/2001
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Kok, James Mun Wai, Sawyers, Thomas P.
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US10/034,718
• Publication Number:
  US 20030126474A1
• Time in Patent Office: 1,369 Days
• Field of Search: 713300-340, 363/48
• US Class Current: 713/300
• 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
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence

Abstract

A constant voltage/constant power AC adapter converts AC voltage to DC voltage to provide power to a plurality of loads. The adapter'"'"'s output characteristic is approximately a constant voltage as long as the output current draw by the loads is less than a threshold (e.g. a safety threshold for the adapter). If, however, the power draw on the adapter is such that the output current exceeds the threshold, the adapter then decreases its output voltage to maintain the power draw at a safe level. One or more loads that draw power from the adapter may be adapted to detect a drop in the AC adapter'"'"'s output voltage. When such a voltage drop is detected, that information tells the load that too much current is being drawn from the adapter and that the load should throttle back (e.g., reducing battery charge current, CPU clock frequency, display brightness, etc.).

Claims

1. A computer system, comprising:

a CPU;

a battery subsystem;

an AC adapter coupled to said CPU and said battery subsystem, said adapter regulating its output voltage for variations in output current until said output current reaches a threshold above which said adapter regulates its output power to an approximately constant level;

wherein said adapter includes a transformer and a power control circuit coupled to a voltage feedback circuit, said voltage feedback circuit provides a feedback signal to the transformer to regulate the output voltage from the adapter, and said power control circuit causes said voltage feedback circuit to cause a reduction in the adapter'"'"'s output voltage when said output current exceeds said threshold;

wherein said power control circuit responds to changes in current more slowly than said voltage feedback circuit responds to changes in voltage.

2. A computer system, comprising:

a CPU;

a battery subsystem;

a means for regulating an AC adapter'"'"'s output voltage; and

a means for regulating an AC adapter'"'"'s output power when the adapter'"'"'s output current exceeds a threshold;

wherein said means for regulating an AC adapter'"'"'s output power responds to changes in output current more slowly than said means for regulating an AC adapter'"'"'s output voltage responds to changes in voltage.

3. An AC adapter, comprising:

an output voltage regulator which regulates the output voltage of said adapter to an approximately constant level if the adapter'"'"'s output current is below a threshold; and

a power regulator coupled to said output voltage regulator, said power regulator regulates the output power of said adapter when said output current exceeds said threshold;

wherein said adapter further includes a transformer and a power control circuit coupled to a voltage feedback circuit, and said voltage regulator provides a feedback signal to the transformer to cause the output voltage from the adapter to be a certain voltage, and said power control circuit causes said voltage feedback circuit to cause a reduction in the adapter'"'"'s output voltage when said output current exceeds said threshold;

wherein said power regulator responds to changes in current more slowly than said voltage regulator responds to changes in voltage.

4. An AC adapter, comprising:

a means for regulating an AC adapter'"'"'s output voltage; and

a means for regulating an AC adapter'"'"'s output power when the adapter'"'"'s output current exceeds a threshold;

wherein said means for regulating an AC adapter'"'"'s output power responds to changes in output current more slowly than said means for regulating an AC adapter'"'"'s output voltage responds to changes in voltage.