Power distribution with digital current control

• US 6,841,979 B2
• Filed: 05/17/2002
• Issued: 01/11/2005
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: PowerDsine Limited (Microchip Technology Incorporated)
• Inventors: Ferentz, Alon, Korcharz, Dror, Barnea, Nadav, Pincu, David, Elkayam, Shimon, Berson, Yuval
• Primary Examiner(s): Patel, Rajnikant B
• Application Number:
  US10/151,649
• Publication Number:
  US 20020196004A1
• Time in Patent Office: 970 Days
• Field of Search: 323/282, 323/285, 323/284, 361/93.8, 361/103, 361/58, 361/64, 307/64, 307/65, 307/66
• US Class Current: 323/282
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16
• CPC Class Codes: H02J 1/04 Constant-current supply systems
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 1/0093 wherein the output is created by adding a regulated voltage to or subtracting it from an unregulated input
• CPC Class Codes: H02M 1/143 using compensating arrangements for reducing noise from the supply in transmission systems H04B15/005
• CPC Class Codes: H02M 1/4208 Arrangements for improving power factor of AC input
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 3/1557 Single ended primary inductor converters [SEPIC]
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

Power distribution apparatus, for controlling supply of a current from an electrical power source to at least one load, includes a current sensor, which is coupled to provide an indication of a magnitude of the current flowing to the at least one load. A current limiter is adapted, responsive to the indication, to apply a pulse width modulation to the current drawn from the source so as to maintain the magnitude of the current flowing to the at least one load within a predetermined limit.

Claims

1. Power distribution apparatus, for controlling supply of a current from an electrical power source to at least one load, the apparatus comprising:

a current limiter, which is coupled to controllably reduce a magnitude of the current supplied to the at least one load;

a current sensor, which is coupled to provide an indication of a magnitude of the current flowing to the at least one load; and

a controller, adapted to;

a) set said current limiter to operate at first and second settings, said second setting being different from said first setting, and to determine, using said current sensor, first and second magnitudes of the current at said first and second settings, respectively;

b) determine an estimated current limiting characteristic based on said first and second magnitudes;

c) set said current limiter to a third setting; and

d) receive said indication from the current sensor of a third magnitude of the current at said third setting,

said controller being adapted, responsive to said indication, to determine whether said third magnitude of the current at said third setting exceeds a predetermined maximum and if so, to select a target setting of said current limiter responsive to said estimated current limiting characteristic, so as to reduce the magnitude of the current to less than said predetermined maximum.

2. Apparatus according to claim 1, wherein said controller is adapted to determine, using said current sensor, a new magnitude of the current at said target setting of the current limiter, and to adjust the setting of the current limiter responsive to said new magnitude until said new current magnitude converges to a predetermined range.

3. Apparatus according to claim 2, wherein said controller is adapted to use said new magnitude of the current determined at said target setting to revise said estimated current limiting characteristic, and to select a new target setting of said current limiter based on said revised estimated current limiting characteristic.

4. Apparatus according to claim 1, wherein said controller is adapted to determine, using said current sensor, the magnitude of the current at said target setting, and to restore said third setting of said current limiter if the current is below a predetermined minimum.

6. Apparatus according to claim 1, wherein the current limiter comprises a variable-impedance device, and wherein the first and second settings correspond respectively to first and second impedance settings.

7. Apparatus according to claim 6, wherein said variable-impedance device comprises a transistor, the apparatus further comprising a digital/analog converter coupled to receive said first and second impedance settings from said controller and, responsive thereto, to apply respective first and second gate voltages to said transistor.

8. Apparatus according to claim 1, wherein the current limiter comprises a pulse width modulator, which is coupled to apply pulse width modulation to the current supplied to the at least one load, and wherein the first and second settings correspond respectively to first and second duty cycles of the pulse width modulation.

9. Apparatus according to claim 1, wherein said controller is adapted to determine fitting parameters so as to fit a curve to said first and second magnitudes as a function of said first and second settings, said estimated current limiting characteristic being a function of said fitting parameters.

10. Apparatus according to claim 1, wherein the at least one load comprises a plurality of loads, and

wherein said current limiter comprises a plurality of current limiters, respectively coupled to reduce the magnitudes of the respective currents, and

wherein said controller comprises a single digital processor, which is adapted to estimate respective current limiting characteristics for two or more of said plurality of current limiters.

11. Apparatus according to claim 10, wherein the current sensor comprises a single current sensing device, which is coupled to sample the respective currents supplied to the plurality of the loads so as to provide the magnitudes of the respective currents to the digital processor.

12. Apparatus according to claim 1, wherein the electrical power source is coupled to supply the current to said plurality of loads over a local area network (LAN).

13. Apparatus according to claim 12, wherein the current limiter and the current sensor are coupled to the LAN an a mid-span configuration.

14. Apparatus according to claim 12, wherein the current limiter and the current sensor are coupled to the LAN together with a switching hub in an end-span configuration.

28. Apparatus according to claim 1, wherein said controller is adapted to set said current limiter to a plurality of first and second settings at a plurality of temperatures of said current limiter, and to determine a plurality of estimated current limiting characteristics as a function of temperature.

29. Apparatus according to claim 28, wherein said target setting is selected responsive to one of said plurality of estimated current limiting characteristics, said one of said plurality of estimated current limiting characteristics being selected as a function of the temperature of the current limiter.

5. Apparatus according to claim wherein 4, the controller is adapted to determine the magnitude of the current at the target setting after a predetermined delay, and to control the current limiter so as to shut off the current to the at least one load if the current has not dropped below the predetermined minimum.

15. A method for controlling supply of power to at least one load, comprising:

supplying a current to the at least one load through a current limiter;

setting said current limiter to a first setting and a second setting, said second setting being different from said first setting;

sampling the current to determine first and second magnitudes thereof at said first and second settings, respectively, of said current limiter;

estimating a current limiting characteristic based on said first and second magnitudes;

setting said current limiter to a third setting;

sampling the current to determine whether the magnitude of the current at said third setting exceeds a predetermined maximum; and

if said magnitude of the current at said third setting exceeds said predetermined maximum,

selecting a target setting of said current limiter responsive to said estimated current limiting characteristic, so as to reduce the magnitude of the current to less than said predetermined maximum.

16. A method according to claim 15, and comprising sampling the current at said target setting to determine a new magnitude of the current, and adjusting the setting of said current limiter responsive to said new magnitude until the sampled current converges to a predetermined range.

17. A method according to claim 16, wherein adjusting the setting comprises using the new magnitude of the current determined at the target setting to revise the estimated current limiting characteristic, and selecting a new target setting of the current limiter based on the revised estimated characteristic.

18. A method according to claim 15, and comprising sampling the current at said target setting, and restoring said third setting of the current limiter if the current is below a predetermined minimum.

19. A method according to claim 18, wherein sampling the current comprises sampling the current alter a predetermined delay, and comprising shutting off the current to the load if the current has not dropped below the predetermined minimum.

20. A method according to claim 15, wherein said current limiter comprises a variable-impedance device, and wherein said first and second settings correspond respectively to first and second impedance settings.

21. A method according to claim 20, wherein the variable-impedance device comprises a transistor, and wherein the first and second impedance settings correspond respectively to first and second gate voltages applied to the transistor.

22. A method according to claim 15, wherein said current limiter comprises a pulse width modulator, which is coupled to apply pulse width modulation to the current supplied to the load, and wherein said first and second settings correspond respectively to first and second duty cycles of said pulse width modulation.

23. A method according to claim 15, wherein estimating said current limiting characteristic comprises determining fitting parameters so as to fit a curve to said first and second magnitudes as a function of said first and second settings.

24. A method according to claim 15, wherein supplying the current comprises supplying respective currents to a plurality of loads through respective current limiters, and wherein estimating said current limiting characteristic comprises using a single digital processor to estimate respective current limiting characteristics for two or more of said current limiters.

25. A method according to claim 24, wherein sampling the current comprises sampling the respective currents supplied to the plurality of the loads using a single current sensing device to determine and provide the magnitudes of the respective currents to the digital processor.

26. A method according to claim 15, wherein said supplying a current comprises supplying a current to the at least one load over a local area network (LAN).

30. A method according to claim 15, wherein said setting of said current limiter to a first and second setting is accomplished at a plurality of temperatures, and further comprising estimating a plurality of current limiting characteristics as a function of said respective temperatures.

31. A method according to claim 30, further comprising obtaining a temperature indication of said current limiter;

wherein said selecting a target setting accomplished responsive to said estimated current limiting characteristic selected from said plurality of current limiting characteristics, said selected estimated current limiting characteristic being selected responsive to said obtained temperature indication.

27. A method for controlling supply of power to at least one load, comprising:

supplying a current to the at least one load through a current limiter at an initial setting of the current limiter;

sampling the current to determine whether an initial magnitude of the current exceeds a predetermined maximum;

if the current exceeds the predetermined maximum,

sampling the current to determine first and second magnitudes thereof at first and second settings, respectively, of the current limiter, at which first and second settings the current passed by the current limiter is less than the current at the initial setting;

estimating a current limiting characteristic based on the first and second magnitudes; and

selecting a target setting of the current limiter responsive to the estimated current limiting characteristic, so as to reduce the magnitude of the current to less than the predetermined maximum.