# US 2018/0024620 A1 · Communications system using hybrid common mode choke and kelvin sensing of voltage

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- Number: US 2018/0024620 A1
- Document ID: US20180024620A1
- Status: Published application
- Kind: A1
- Application number: 15/653,058
- Filed: 2017-07-18
- Published: 2018-01-25
- Earliest claimed: 2016-07-25
- Assignees: Linear Technology Corporation
- Applicants: Linear Technology Corporation
- Inventors: Andrew J. Gardner
- Web page: https://patentgrep.com/patent/US20180024620A1

## CPC

- G06F 1/3296: by lowering the supply or operating voltage
- G06F 1/3287: by switching off individual functional units in the computer system
- H04B 3/548: {the power on the line being DC (arrangements for feeding power H04L12/10; extracting feeding power from signals H04L25/02)}
- H04B 3/56: Circuits for coupling, blocking, or by-passing of signals
- H04L 12/10: Current supply arrangements
- H04L 12/40045: {Details regarding the feeding of energy to the node from the bus}
- H04L 25/0266: {Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling}
- H04L 25/0276: {Arrangements for coupling common mode signals}
- H04L 25/0282: {Provision for current-mode coupling}
- H04L 25/0298: {Arrangement for terminating transmission lines}
- H04B 2203/547: via DC power distribution
- H04B 2203/5483: using coupling circuits
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

In a communications system that conducts differential data via a pair of wires, AC common mode noise is undesirably coupled to the wires in a noisy environment. A hybrid common mode choke (HCMC) attenuates the AC common mode noise while passing the differential data to a PHY. The HCMC includes a CMC (windings with the same polarity) and a differential mode choke (windings with opposite polarities). The CMC attenuates the AC common mode noise, and the DMC passes the attenuated AC common mode noise to termination circuity to eliminate it. Also disclosed is a technique for Kelvin sensing the DC voltage at the pair of wires, in a PoDL system, by detecting the voltage on wires that do not carry DC current, so as to provide a more accurate measurement.

## Claims

### Claim 1

A Power over Data Lines (PoDL) system and voltage measurement system comprising:
a pair of wires carrying differential data and a DC voltage;
Power Sourcing Equipment (PSE) providing the DC voltage to the pair of wires via a DC-coupling circuit;
a common mode choke (CMC) coupled between the pair of wires and a transceiver, the CMC comprising a first transformer with two windings having the same polarity, wherein the CMC attenuates AC common mode signals on the pair of wires and substantially passes the differential data;
termination circuitry coupled between the CMC and the pair of wires, the termination circuitry comprising a first resistor coupled to a first of the wires, wherein the first resistor is coupled to ground via a first capacitor, the termination circuity further comprising a second resistor coupled to a second of the wires, wherein the second resistor is coupled to ground via a second capacitor;
a first conductor coupled to a first node between the first resistor and the first capacitor;
a second conductor couple to a second node between the second resistor and the second capacitor; and
the first conductor and the second conductor being coupled to a voltage sensor for detecting the DC voltage applied to the pair of wires.

### Claim 2 (depends on 1)

The system of claim 1 further comprising power sourcing equipment (PSE) coupling a DC voltage to the pair of wires, the PSE being coupled between the CMC and the transceiver via DC-coupling circuitry.

### Claim 3 (depends on 2)

The system of claim 2 wherein the DC-coupling circuitry comprises one or more inductors.

### Claim 4 (depends on 2)

The system of claim 2 wherein the DC-coupling circuitry comprises a differential mode choke (DMC) coupled between the CMC and the transceiver, the DMC comprising a second transformer with two windings having opposite polarities, wherein the DMC substantially passes the AC common mode signals that pass through the CMC from the pair of wires.

### Claim 5 (depends on 4)

The system of claim 4 wherein the DMC applies the AC common mode signals to AC termination circuitry to further attenuate the AC common mode signals prior to being received by the transceiver.

### Claim 6 (depends on 5)

The system of claim 5 wherein the voltage sensor is located within the PSE.

### Claim 7 (depends on 1)

The system of claim 1 wherein the voltage sensor comprises an analog-to-digital converter.

### Claim 8 (depends on 1)

The system of claim 1 wherein the first conductor and the second conductor provide a Kelvin connector to the pair of wires for detecting the DC voltage applied to the pair of wires.

### Claim 9 (depends on 1)

The system of claim 1 further comprising power sourcing equipment (PSE) coupling a DC voltage to the pair of wires, the PSE being coupled to the pair of wires via DC-coupling circuitry.

### Claim 10 (depends on 9)

The system of claim 9 wherein the DC-coupling circuitry comprises one or more inductors.

### Claim 11 (depends on 9)

The system of claim 9 wherein the DC-coupling circuitry comprises a differential mode choke (DMC) coupled between the PSE and the pair of wires, the DMC comprising a second transformer with two windings having opposite polarities.

### Claim 12 (depends on 11)

The system of claim 11 wherein the DC voltage is not coupled to the pair of wires through the CMC.