Current-Monitoring Apparatus

• US 20140097828A1
• Filed: 09/30/2013
• Published: 04/10/2014
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Geirnaert, Koen, Janssens, Johan, Gouwy, Christophe, Sevenhans, Joannes Mathilda Josephus, BERTIN, Jacques J., Van Roeyen, Stevan, Hout-Marchand, Alexis
• Granted Patent: US 9,322,851 B2
• Time in Patent Office: Days
• US Class Current: 324/132
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A local area networking apparatus comprises a power stage for connecting to a network cable for carrying power and data. The power stage comprises a main current flow path which includes a switch comprising at least one transistor positioned in the main current flow path and a current monitoring apparatus for monitoring current flow in the main current flow path, and wherein the current monitoring apparatus comprises a sensor which is not placed in series with the main current flow path. The current monitoring apparatus can comprise a current mirroring stage which is arranged to mirror current flowing in the main current flow path to a monitoring current flow path. The switch can be implemented as a set of switches.

Claims

1. A power supply apparatus for connecting to a cable which carries power and data, the power supply apparatus comprising:

a main current flow path which includes a switch comprising at least one transistor positioned in the main current flow path; and

a current monitoring apparatus for monitoring current flow in the main current flow path, wherein the current monitoring apparatus comprises a sensor which is not placed in series with the main current flow path.

2. The power supply apparatus according to claim 1, wherein the current monitoring apparatus comprises a current mirroring stage arranged to mirror current flowing in the main current flow path to a monitoring current flow path.

3. The power supply apparatus according to claim 2, wherein the current mirroring, stage comprises:

a mirror transistor positioned in the monitoring current flow path; and

a voltage setting stage arranged to set voltages at each side of the mirror transistor equal to a corresponding voltage at a respective side of the switch, or to set voltages between terminals of the mirror transistor equal to voltages across corresponding terminals of the switch.

4. The power supply apparatus according to claim 3, wherein the voltage setting stage comprises a cascode current mirror circuit configured to copy a voltage on the transistor of the switch and to force the voltage on the current mirroring stage.

5. The power supply apparatus according to claim 4, further comprising a circuit to compensate the monitoring current flow for errors introduced by a current contributed by the cascade current mirror circuit.

6. The power supply apparatus according to claim 3, the voltage setting, stage comprises a cascode current mirror circuit configured to copy a voltage on the transistor of the switch and to force the voltage on the current mirroring stage, wherein a cascode transistor of the cascode current mirror circuit is driven by an output of a common gate differential structure.

7. The power supply apparatus according to claim 3, wherein the switch comprises a plurality of transistors arranged in parallel with one another and wherein the voltage setting stage is arranged to set the voltage at a first side of the mirror transistor equal to a function of voltages at individual ones of the plurality of transistors and is further arranged to set the voltage at a second side of the mirror transistor equal to a function of the voltages at individual ones of the plurality of transistors.

8. The power supply apparatus according to claim 7, wherein the voltage setting stage is arranged to set the voltage equal to a function of the voltages at a sub-set of the plurality of transistors.

9. The power supply apparatus according to claim 7, wherein the voltage setting stage is arranged to set the voltage equal to a function of the voltages at all of the plurality of transistors.

10. The power supply apparatus according to claim 7, wherein the function is an average value of the voltages at individual ones of the transistors.

11. The power supply apparatus according to claim 7, wherein the voltage setting stage comprises a network of sense resistors which connects to respective ones of the transistors.

12. The power supply apparatus according to claim 3, wherein the voltage setting stage comprises an operational amplifier and a source follower transistor positioned in series with the mirror transistor, the operational amplifier having a non-inverting input connected to a first side of the switch, an output connected to the gate of the source follower transistor and an inverting input connected to a source of the source follower transistor.

13. The power supply apparatus according to claim 1, wherein the voltage setting stage comprises an operational amplifier having a non-inverting input connected to a second side of the switch, an output connected to a source of the mirror transistor and an inverting input connected to the source of the mirror transistor.

14. The power supply apparatus according to claim 1, further comprising a detector for measuring an amount of current flowing in the monitoring current path.

15. The power supply apparatus according to claim 14, further comprising:

a temperature sensor for sensing operating temperature of the apparatus; and

a storage of calibration data and control logic arranged to adjust the measured current according to the calibration data.

16. The power supply apparatus according to claim 15, wherein the calibration data comprises measurement data obtained during a production test, which represents values for at least one measured quantity at two different operating temperatures.

17. The power supply apparatus according to claim 16, wherein the calibration data comprises a correspondence between a value of a test current and a value of a measured current at, at least, two values of test current, at two different operating temperatures.

18. The power supply apparatus according to claim 15, wherein the detector is an analog-to-digital converter and the calibration data includes data for at least one of:

gain and offset of the converter with varying temperature.

19. The power supply apparatus according to claim 1 in the form of a Power Sourcing Equipment (PSE) or a Powered Device (PD) for use in a Power over Ethernet (POE) system.

20. A power supply apparatus for connecting to cable, which carries power and data, the power supply apparatus comprising:

a main current flow path which includes a switch positioned in the main current flow path; and

a current monitoring apparatus for monitoring current flow in the main current flow path, wherein the current monitoring apparatus includes a current mirror.