Granted Patent B2

US 12,592,559 · App. 18/084,068 · Granted Mar 31, 2026

Inventors: Yevgeny Yurevich Korolev (Maple Grove, MN); William Michael Mansfield (Niwot, CO); Xiong Gao (Gothenburg, SE)

Assignee: ROSEMOUNT INC.

H02H9/02

Abstract

Claims (71)

1 . A current limiting circuit for limiting a current through a pair of terminals powered from a 2-wire Advanced Physical Layer (APL) spur, the current limiting circuit comprising:

a current source connected to one of the terminals and configured to source a current conducted through the terminals having an amplitude that is at a current source threshold;

a first current limiter connected to the current source and configured to limit the amplitude below a first threshold; and

a second current limiter connected to the first current limiter and configured to limit the amplitude below a second threshold,

wherein:

the current source includes a pass transistor through which the current travels;

the current travels through first and second terminals of the pass transistor; and

the amplitude of the current is based on a voltage at a third terminal of the pass transistor, which is disconnected from the first and second terminals.

2 . The current limiting circuit of claim 1 , wherein the first and second thresholds are greater than the current source threshold.

3 . The current limiting circuit of claim 1 , further comprising a current sensor configured to output a feedback signal that is indicative of the amplitude to the current source, the first current limiter and the second current limiter.

4 . The current limiting circuit of claim 3 , wherein the current sensor comprises a sense resistor and the feedback signal comprises a voltage.

5 . The current limiting circuit of claim 3 , wherein:

the current source includes a control circuit;

the first current limiter and the second current limiter each comprise:

a control circuit; and

a pass transistor, having first, second and third terminals,

wherein:

the current travels through the first and second terminals; and

the amplitude of the current is based on a voltage at the third terminal, which is connected to the first terminal through a resistor; and

each control circuit uses the feedback signal to control the voltage at the third terminal, which controls the passage of the current through the corresponding pass transistor.

6 . A field device for an industrial process comprising:

a pair of terminals configured to receive power from a 2-wire Advanced Physical Layer (APL) spur;

a current limiting circuit configured to limit a current through the terminals comprising:

a current source connected to one of the terminals and configured to source a current conducted through the terminals having an amplitude that is at a current source threshold;

a first current limiter connected to the current source and configured to limit the amplitude below a first threshold; and

a second current limiter connected to the first current limiter and configured to receive the current from the first current limiter and limit the amplitude below a second threshold; and

field device circuitry connected to the second current limiter and powered using the current,

wherein:

the current source includes a pass transistor through which the current travels; and

an emitter of the pass transistor is disconnected from a base of the transistor.

7 . The field device of claim 6 , wherein the field device circuitry comprises an active component selected from the group consisting of a sensor configured to sense a process parameter, and a control device configured to control a process of the industrial process.

8 . The field device of claim 7 , including APL PHY circuitry configured to communicate through the pair of terminals in accordance with an Ethernet protocol.

9 . The field device of claim 6 , wherein the first and second thresholds are greater than the current source threshold.

10 . The field device of claim 6 , wherein the current limiting circuit comprises a current sensor configured to output a feedback signal that is indicative of the amplitude to the current source, the first current limiter and the second current limiter.

11 . The field device of claim 10 , wherein the current sensor comprises a sense resistor and the feedback signal comprises a voltage.

12 . The field device of claim 10 , wherein;

the current source includes a control circuit;

the first current limiter and the second current limiter each comprise:

a control circuit; and

a pass transistor, having first, second and third terminals,

wherein:

the current travels through the first and second terminals; and

the amplitude of the current is based on a voltage at the third terminal, which is connected to the first terminal through a resistor; and

each control circuit uses the feedback signal to control the voltage at the third terminal, which controls the passage of the current through the corresponding pass transistor.

13 . A method of controlling a current in a field device, which includes a pair of terminals, field device circuitry and a current limiting circuit that includes a current source connected to one of the terminals, a first current limiter connected to the current source, and a second current limiter connected to the first current limiter and the field device circuitry, the method comprising:

receiving power from a 2-wire Advanced Physical Layer (APL) spur at the pair of terminals;

sourcing a current conducted through the terminals using the current source, which limits an amplitude of the current to a current source threshold;

receiving the current from the current source at the first current limiter;

limiting the amplitude of the current below a first threshold using the first current limiter;

receiving the current from the first current limiter at the second current limiter;

limiting the amplitude of the current below a second threshold using the second current limiter; and

powering field device circuitry using the current,

wherein:

the current source includes a pass transistor through which the current travels;

the current travels through first and second terminals of the pass transistor; and

the amplitude of the current is based on a voltage at a third terminal of the pass transistor, which is disconnected from the first and second terminals.

14 . The method of claim 13 , wherein the first and second thresholds are greater than the current source threshold.

15 . The method of claim 13 , further comprising:

generating a feedback signal that is indicative of the amplitude using a current sensor; and

controlling the current source, the first current limiter and the second current limiter using the feedback signal.

16 . The method of claim 15 , wherein the current sensor comprises a sense resistor and the feedback signal comprises a voltage.

17 . The method of claim 15 , wherein:

the current source includes a control circuit;

the first current limiter and the second current limiter each comprise:

a control circuit; and

a pass transistor, having first, second and third terminals,

wherein:

the current travels through the first and second terminals; and

the amplitude of the current is based on a voltage at the third terminal, which is connected to the first terminal through a resistor; and

each control circuit uses the feedback signal to control the voltage at the third terminal, which controls the passage of the current through the corresponding pass transistor.

18 . The method of claim 13 , wherein the field device circuitry comprises an active component selected from the group consisting of a sensor configured to sense a process parameter, and a control device configured to control a process of the industrial process, and APL PHY circuitry configured to communicate through the pair of terminals in accordance with an Ethernet protocol.

Assignments (1)

Continuity (1)

References Cited (151)