Soft start with active reset

• US 8,327,165 B2
• Filed: 01/21/2010
• Issued: 12/04/2012
• Est. Priority Date: 01/21/2010
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Clegg, Joseph Alexander, Hijazi, Mohammed K., Wood, Merle J. III
• Primary Examiner(s): Lee, Thomas
• Assistant Examiner(s): SNYDER, SCOTT ELDER
• Application Number:
  US12/691,351
• Publication Number:
  US 20110179292A1
• Time in Patent Office: 1,048 Days
• Field of Search: 713/300
• US Class Current: 713/300
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C

Abstract

A power supply input circuit includes an input node configured to removeably couple to an electrical source. A solid state switch is coupled between the input node and a capacitive load. An RC soft start circuit is coupled to the input node and the switch. The soft start circuit has a capacitor that causes the switch to increasingly pass electrical power from the source to the load as the capacitor charges from the source. An active reset circuit is coupled to the soft start circuit. The reset circuit is configured to detect when the source is removed from the input node and in response to the source being removed from the input node, the reset circuit discharges the capacitor to reset the soft start circuit.

Claims

1. A power supply input circuit comprising:

an input node configured to removeably couple to a plurality of electrical power sources including a wireless electrical power source;

a solid state switch coupled between the input node and a capacitive load that is coupled to a power rail, wherein the capacitive load is sized to permit the wireless electrical power source to power a load coupled to the power rail;

an RC soft start circuit coupled to the solid state switch, the RC soft start circuit having a capacitor that causes the solid state switch to increasingly pass electrical power from one of the plurality of the electrical power sources to the capacitive load as the capacitor charges from the one of the plurality of the electrical power sources; and

an active reset circuit coupled to the RC soft start circuit, the active reset circuit configured to detect when the one of the plurality of the electrical power sources is decoupled from the input node and, in response, discharges the capacitor to actively reset the soft start circuit.

2. The power supply input circuit of claim 1, wherein the capacitive load is sized at approximately 10,000 micro Farads.

3. The power supply input circuit of claim 2, wherein the plurality of electrical power sources includes a battery electrical power source and a wired electrical power source.

4. The power supply input circuit of claim 1, wherein the capacitor is discharged in less than 30 milliseconds using the active reset circuit.

5. The power supply input circuit of claim 1, wherein the active reset circuit includes a transistor that passes charge from the capacitor to discharge the capacitor.

6. The power supply input circuit of claim 5, wherein a comparator device drives the transistor.

7. The power supply input circuit of claim 1, wherein the solid state switch is a MOSFET solid state switch.

8. An information handling system (IHS) comprising:

a processor;

a memory device coupled to the processor; and

a power supply input circuit coupled to the processor and the memory device, the power supply input circuit comprising;

an input node configured to removeably couple to a plurality of electrical power sources including a wireless electrical power source;

a solid state switch coupled between the input node and a capacitive load that is coupled to the processor and the memory device, wherein the capacitive load is sized to permit the wireless electrical power source to power the processor and the memory device;

an RC soft start circuit coupled to the solid state switch, the RC soft start circuit having a capacitor that causes the solid state switch to increasingly pass electrical power from one of the plurality of the electrical power sources to the capacitive load as the capacitor charges from the one of the plurality of the electrical power sources; and

an active reset circuit coupled to the RC soft start circuit, the active reset circuit configured to detect when the one of the plurality of the electrical power sources is decoupled from the input node and, in response, discharges the capacitor to actively reset the soft start circuit.

9. The IHS of claim 8, wherein the capacitive load is sized at approximately 10,000 micro Farads.

10. The IHS of claim 9, wherein the plurality of electrical sources includes a battery electrical power source and a wired electrical power source.

11. The IHS of claim 8, wherein the capacitor is discharged in less than 30 milliseconds using the active reset circuit.

12. The IHS of claim 8, wherein the active reset circuit includes a transistor that passes charge from the capacitor to discharge the capacitor.

13. The IHS of claim 12, wherein a comparator device drives the transistor.

14. The IHS of claim 8, wherein the solid state switch is a MOSFET solid state switch.

15. A method comprising:

providing a solid state switch between an input node and a capacitive load that is coupled to a power rail, wherein the capacitive load is sized to permit a wireless electrical power source to power a load coupled to the power rail;

receiving power by an RC soft start circuit from one of a plurality of electrical power sources coupled to the input node, wherein the RC soft start circuit causes the switch to increasingly pass power from the one of the plurality of electrical power sources to the capacitive load; and

detecting when the one of the plurality of electrical power sources is decoupled from the input node and, in response, actively resetting the RC soft start circuit.

16. The method of claim 15,

wherein the capacitive load is sized at approximately 10,000 micro Farads.

17. The method of claim 16,

wherein the plurality of electrical power sources to include a battery electrical power source and a wired electrical power source.

18. The method of claim 15, wherein the actively resetting the RC soft start circuit is performed in less than 30 milliseconds.

19. The method of claim 15,

wherein the actively resetting the RC soft start circuit includes discharging a capacitor in the RC soft start circuit using a transistor.

20. The method of claim 19, further comprising:

driving the transistor using a comparator device.