# US 7,613,936 B2 · Dual-mode detection of powered device in power over ethernet system

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- Number: US 7,613,936 B2
- Document ID: US7613936B2
- Status: Granted
- Kind: B2
- Application number: 11/252,624
- Filed: 2005-10-19
- Published: 2006-07-27
- Granted: 2009-11-03
- Earliest claimed: 2005-01-25
- Assignees: Linear Technology Corporation
- Inventors: John Arthur Stineman, Jr.; Jeffrey Lynn Heath
- Web page: https://patentgrep.com/patent/US7613936B2

## CPC

- H04L 49/351: for local area network [LAN], e.g. Ethernet switches
- H04L 12/10: Current supply arrangements
- H02H 3/12: responsive to underload or no-load {(for motors H02H7/0827)}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)

## Abstract

Novel circuitry and methodology for detecting a Powered Device (PD) in a system for providing power to the PD. PD detection circuitry detects the PD in a first mode by providing detection current to probe the PD, and in a second mode by providing detection voltage to probe the PD. A control circuit determines that the PD is a valid device if the PD is detected both in the first mode and in the second mode.

## Claims

### Claim 1

A system for providing power to a powered device (PD), comprising:
PD detection circuitry for detecting the PD in a first mode by providing detection current to probe the PD, and in a second mode by providing detection voltage to probe the PD, and
a control circuit for determining that the PD is a valid device if the PD is detected both in the first mode and in the second mode.

### Claim 2 (depends on 1)

The system of claim 1, wherein the PD detection circuitry is configured for determining voltage produced in response to the detection current in the first mode, and for determining current produced in response to the detection voltage in the second mode.

### Claim 3 (depends on 1)

The system of claim 1, wherein the PD detection circuitry comprises a force-current detection circuit for operating in the first mode and a force-voltage detection circuit for operating in the second mode.

### Claim 4 (depends on 1)

The system of claim 1, wherein the PD detection circuitry is configured to determine prescribed resistance in the PD in the first mode and in the second mode.

### Claim 5 (depends on 1)

The system of claim 1, wherein the PD detection circuitry is configured to detect the PD sequentially in the first mode and in the second mode.

### Claim 6 (depends on 5)

The system of claim 5, wherein the PD detection circuitry is controlled to detect the PD in the first mode before detecting the PD in the second mode.

### Claim 7 (depends on 1)

The system of claim 1, wherein the control circuit is configured to control the PD detection circuitry to operate in the first and second modes.

### Claim 8

A Power Sourcing Equipment (PSE) in a Power over Ethernet (PoE) system, comprising:
a powered device (PD) detection source for detecting a PD in a force-current mode and a force-voltage mode, and
a control circuit for validating the PD if the PD is detected in both the force-current mode and the force-voltage mode.

### Claim 9 (depends on 8)

The PSE of claim 8, wherein the PD detection source comprises a force-current detection circuit for producing detection current to probe the PD in the force-current mode, and the force-voltage detection circuit for producing detection voltage to probe the PD in the force-voltage mode.

### Claim 10 (depends on 9)

The PSE of claim 9, wherein the force-current detection circuit is configured for determining voltage produced in response to the detection current, and the force-voltage detection circuit is configured for determining current produced in response to the detection voltage.

### Claim 11 (depends on 8)

The PSE of claim 8, wherein the PD detection source is configured to determine signature resistance in the force-current mode and the force-voltage mode.

### Claim 12 (depends on 8)

The PSE of claim 8, wherein the PD detection source is configured to detect the PD sequentially in the force-current mode and the force-voltage mode.

### Claim 13 (depends on 8)

The PSE of claim 8, wherein the PD detection source is configured to detect the PD in the force-current mode before detecting the PD in the force-voltage mode.

### Claim 14 (depends on 8)

The PSE of claim 8, wherein the control circuit is configured for controlling the PD detection source to operate in the force-current mode and the force-voltage mode.

### Claim 15

A method of detecting a powered device (PD), comprising the steps of:
determining a prescribed parameter of the PD in a force-current mode,
determining the prescribed parameter of the PD in a force-voltage mode, and
validating the PD if the prescribed parameter of the PD is found to be valid in both the force-current mode and the force-voltage mode.

### Claim 16 (depends on 15)

The method of claim 15, wherein the prescribed parameter of the PD includes prescribed resistance in the PD.

### Claim 17 (depends on 15)

The method of claim 15, wherein the force-current mode and the force-voltage mode are carried out sequentially.

### Claim 18 (depends on 15)

The method of claim 15, wherein the force-current mode is carried out before the force-voltage mode.

### Claim 19 (depends on 15)

The method of claim 15, wherein the force-voltage mode is carried out by probing the PD with test voltage of a prescribed value.

### Claim 20 (depends on 19)

The method of claim 19, wherein the force-current mode is carried out by probing the PD with test current corresponding to the test voltage of the prescribed value.