POWER SUPPLY CIRCUIT

• US 20090218997A1
• Filed: 02/29/2008
• Published: 09/03/2009
• Est. Priority Date: 02/29/2008
• Status: Abandoned Application

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: O'Brien, Richard A., Lee, John Chiang-Yung, Hey, George M.
• Application Number:
  US12/040,397
• Publication Number:
  US 20090218997A1
• Time in Patent Office: Days
• US Class Current: 323/273
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence

Abstract

In one embodiment, a current limiter is configured to limit current drawn from a main power supply to a maximum value. A load device is coupled with an output of the current limiter. The load device is configured to periodically draw a first current during operation. The maximum value is below a value of the first current. A charge storage device is coupled with the load device. The charge storage device is configured to supply additional current to the load device to satisfy the first current value. A linear voltage regulator is coupled between the charge storage device and the load device.

Claims

1. A circuit comprising:

a current limiter configured to limit current drawn from a main power supply to a maximum value;

a load device coupled with an output of the current limiter, the load device configured to periodically draw a first current during operation, wherein the maximum value is below a value of the first current;

a charge storage device coupled with the load device, the charge storage device configured to supply additional current to the load device to satisfy the first current value; and

a linear voltage regulator coupled between the charge storage device and the load device.

2. The circuit of claim 1, wherein the load device is configured to periodically draw a second current between the periodic drawing of the first current, and wherein the first current value is higher than a value of the second current.

3. The circuit of claim 1, wherein the first current corresponds to intermittent high power intervals, each of the high power intervals having a duration of at least about one millisecond.

4. The circuit of claim 3, wherein each of the high power intervals corresponds to a transmission of data.

5. The circuit of claim 1, wherein the load device comprises a modem.

6. The circuit of claim 1, wherein the maximum value is at most about 1 Amperes.

7. The circuit of claim 1, wherein the additional current is at least about 1.5 Amperes.

8. A circuit comprising:

a current limiter having an input and an output, the input of the current limiter configured to couple with a main power supply;

a diode coupled with the input of the current limiter;

a capacitor coupled with the output of the current limiter; and

a low dropout voltage regulator coupled with the capacitor and the output of the current limiter,

wherein an output of the low dropout voltage regulator is configured to supply a substantially noise free power to a load device.

9. The circuit of claim 8, wherein a current limit value of the current limiter is variable.

10. The circuit of claim 8, wherein an output voltage of the low dropout voltage regulator is about 3.3 direct current volts, and wherein a voltage provided by the main power supply is at least about 5 direct current volts.

11. The circuit of claim 8, wherein the capacitor is configured to supply additional current to compensate for a limited current set by the current limiter.

12. The circuit of claim 8, wherein the capacitor has a capacitance of at least about 33 milliFarads.

13. The circuit of claim 8, wherein the diode comprises a Schottky diode.

14. An apparatus comprising:

a host device;

a plurality of modules configured to couple with the host device, each of the plurality of modules comprising;

a current limiter configured to limit power from the host device;

a data communication device coupled with an output of the current limiter, the data communication device configured to periodically draw a first power;

a capacitor coupled with the data communication device, the capacitor configured to store power from the host device and supplement the current limiter to satisfy a value of the first power; and

a linear voltage regulator coupled between the capacitor and the data communication device, the linear voltage regulator configured to step down a voltage.

15. The apparatus of claim 14, wherein the host device comprises a router.

16. The apparatus of claim 14, wherein each of the data communication devices of each of the plurality of modules comprises a wireless GSM modem.

17. A method comprising:

operating a load device, the load device periodically drawing a first current during operation;

limiting a current drawn from a main power source to a limited current value, the limited current value being below a value of the first current;

supplying additional current from a capacitor to satisfy a desired current during the operation of the load device; and

supplying a substantially constant and substantially noise free voltage to the load device.

18. The method of claim 17, wherein the periodic drawing of the first current corresponds to periodic power bursts for transmission of data.

19. The method of claim 18, wherein the load device draws at most about 5 Watts from the main power source during each of the periodic power bursts.

20. A method comprising:

providing a current limiter having an input and an output, the input of the current limiter configured to couple with a main power supply;

coupling a capacitor with the output of the current limiter;

coupling a linear voltage regulator with the capacitor and the output of the current limiter; and

coupling a load device with an output of the linear voltage regulator, the output of the linear voltage regulator configured to provide a supply power to the load device.

21. The method of claim 20, further comprising:

coupling a diode with the input of the current limiter.