Delay Circuit With Reset Feature

• US 20110060926A1
• Filed: 01/22/2008
• Published: 03/10/2011
• Est. Priority Date: 01/22/2008
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Clegg, Joseph A., Squibb, George F., Brooks, Robert C., Wright, Robert S.
• Granted Patent: US 8,464,078 B2
• Time in Patent Office: Days
• US Class Current: 713/300
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C

Abstract

A system comprises an AC/DC adapter having a connector. The system also comprises a portable computer that receives said connector. The portable computer comprising a delay circuit coupled to a power transistor that is coupled in parallel with a resistor. The delay circuit causes the power transistor to activate following a time delay after current from the adapter begins to flow through the resistor. As a result of a user beginning to remove the connector from the portable computer, a control transistor is activated to reset the delay circuit.

Claims

1. A system, comprising:

an AC/DC adapter having a connector; and

a portable computer that receives said connector, said portable computer comprising a delay circuit coupled to a power transistor coupled in parallel with a resistor, said delay circuit causes said power transistor to activate following a time delay after current from said adapter begins to flow through said resistor;

wherein, as a result of a user beginning to remove said connector from said portable computer, a control transistor is activated to reset said delay circuit.

2. The system of claim 1 further wherein, upon activation of the power switch by the delay circuit, current bypasses said resistor and flows through said power transistor instead.

3. The system of claim 1 wherein said delay circuit receives an adapter identification signal from said AC/DC adapter, said adapter identification signal encoding information about said adapter, and said adapter identification signal also used to control said delay circuit.

4. The system of claim 3 wherein said connector comprises a first pin containing said adapter identification signal and a second pin containing a DC voltage to power said portable computer, and upon beginning to remove said connector from said portable computer, said first pin disconnects before said second pin disconnects.

5. The system of claim 4 wherein said delay circuit resets during removal of said connector in a time period between disconnection of said first pin and said second pin.

6. The system of claim 4 wherein said delay circuit comprises a control transistor that is activated based on said adapter identification signal.

7. The system of claim 6 wherein said adapter identification signal causes said control transistor to activate during said time period to cause charge to be discharged from a capacitor in said delay circuit through said control transistor to thereby reset said delay circuit.

8. A system, comprising:

means for delaying activation of a power transistor coupled in parallel with a resistor to control current flow from an AC/DC adapter; and

means for resetting the means for delaying using a signal from said AC/DC adapter.

9. The system of claim 8 wherein said means for resetting comprises a pin in an electrical plug that is shorter than another pin in said electrical plug carrying DC voltage.

10. The system of claim 9 wherein said signal comprises a signal that designates a type associated with said AC/DC adapter.

11. The system of claim 8 wherein said means for delaying comprises a comparator whose output controls said power transistor.

12. A system, comprising:

a chassis having a receptacle that receives a connector from an AC adapter, said portable computer comprising a delay circuit coupled to a power transistor in parallel with a resistor, said delay circuit causes said power transistor to activate following a time delay after current from said adapter begins to flow through said resistor;

wherein, as a result of a user beginning to remove said connector from said portable computer, a control transistor is activated to reset said delay circuit.

13. The system of claim 12 wherein, upon a user beginning to remove said connector, a first pin in said connector disconnects while power and ground pins in said connector remain connected thereby continuing to provide power to said system.

14. The system of claim 13 wherein a signal associated with said first pin causes said control transistor to be activated.

15. The system of claim 14 wherein said signal comprises an adapter identification signal that encodes information about said AC adapter.

16. The system of claim 12 wherein said delay circuit resets in a time period that is less than the time delay.