Patent Description:
<CIT> describes a field device whereby the device's additional information can be transmitted wirelessly without the need for battery replacement or external wiring. Further, a field device is described whereby the firmware of a wireless module in the field device can be developed at minimum cost and whereby it can be made easy to link the firmware to applications, such as an asset management system, on the host system side.

<CIT> describes a field device for use in an industrial process control or monitoring system with terminals configured to connect to a two-wire process control loop configured to carry data and to provide power. An RF circuitry in the field device is configured for radio frequency communication having variable power consumption.

<CIT> describes a field device for use in an industrial process control or monitoring system includes terminals configured to connect to a two-wire process control loop. The loop carries data and provides power to the field device.

In industrial settings, control systems are used to monitor and control inventories of industrial and chemical processes, and the like. Typically, the control system performs these functions using field devices distributed at key locations in the industrial process and coupled to control circuitry in a control room by a process control loop.

Typical industrial process field devices include device circuitry that enables the field device to perform conventional field device tasks such as process parameter monitoring and measurements using one or more sensors, and/or process control operations using one or more control elements. Exemplary sensors include pressure sensors, flow sensors, level sensors, temperature sensors, and other sensors used in industrial processes. Exemplary control elements include actuators, solenoids, valves, and other control elements.

The device circuitry of field devices may also include a controller that is used to control the sensors and/or control elements, and communicate with a process control room, or other circuitry, over a process control loop, such as a <NUM>-<NUM> mA process control loop. The process control loop may deliver a current that is regulated by the field device to indicate a sensed parameter value.

Many field devices are configured to be powered from the same two-wire process control loop used to transmit information. The two-wire process control loop may couple to a single field device or to multiple field devices ("multi-drop"). This limits the power that is available to the field device.

Process field devices may be configured to provide supplemental features beyond those typically provided by the device circuitry. Such supplemental features may include, for example, wireless data communications, flash writes, a display, or other supplemental features.

Powering such supplemental features using power provided over the two-wire process control loop requires circuitry that scavenges excess power that is not required to power the device circuitry or provide the desired current over the process control loop.

The present invention is directed to a field device for use in monitoring or controlling an industrial process according to claim <NUM>, and to a method of providing power to a field device according to claim <NUM>. Further advantageous embodiments are subject matter of the dependent claims. According to the invention, the field device includes first and second loop terminals configured to couple to a two-wire process control loop, device circuitry, a current regulator, a first shunt voltage regulator, supplemental circuitry, and a second shunt voltage regulator. The device circuitry is configured to monitor a process variable or control a control device, and is powered by power from the two-wire process control loop. The current regulator is in series with the first and second loop terminals and the device circuitry, and is configured to regulate a loop current flowing through the two-wire process control loop. The first shunt voltage regulator is connected in series with the current regulator and the first and second loop terminals, and in parallel with the device circuitry. The first shunt voltage regulator is configured to regulate a voltage across the device circuitry. The supplemental circuitry is connected in series with the first shunt voltage regulator and the second loop terminal, and is powered by power from the two-wire process control loop shunted through the first shunt voltage regulator. The second shunt voltage regulator is connected in series with the first shunt voltage regulator and the second loop terminal, and in parallel with the supplemental circuitry. The second shunt voltage regulator is configured to control a voltage across the supplemental circuitry.

According to the invention, the method of providing power to a field device for use in monitoring or controlling an industrial process, first and second loop terminals of the field device are coupled to a two-wire process control loop. Device circuitry of the field device is powered with power received from the two-wire process control loop. The device circuitry being configured to monitor a process variable sensor or control a control device. A loop current through the two-wire process control loop is regulated using a current regulator of the field device connected in series with the two-wire process control loop, the first and second loop terminals, and the device circuitry. A voltage across the device circuitry is regulated using a first shunt voltage regulator of the field device connected in series with the two-wire process control loop and the current regulator, and in parallel with the device circuitry. Supplemental circuitry connected in series with the first shunt voltage regulator and the second loop terminal is powered with power received from the two-wire process control loop shunted through the first shunt voltage regulator. A voltage across the supplemental circuitry is regulated using a second shunt voltage regulator of the field device connected in series with the first shunt voltage regulator and the second loop terminal, and in parallel with the supplemental circuitry.

Embodiments of the present disclosure are described more fully hereinafter with reference to the accompanying drawings. Elements that are identified using the same or similar reference characters refer to the same or similar elements. Some elements may not be shown in each of the figures in order to simplify the illustrations.

The various embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

<FIG> is a simplified diagram of an example of an industrial process control or measurement system <NUM>, in accordance with embodiments of the present disclosure. The system <NUM> may be used in the processing of a material (e.g., process medium) to transform the material from a less valuable state into more valuable and useful products, such as petroleum, chemicals, paper, food, etc. For example, the system <NUM> may be used in an oil refinery that performs industrial processes that can process crude oil into gasoline, fuel oil, and other petrochemicals.

The system <NUM> includes a field device <NUM> having a housing <NUM> that may be coupled to an industrial process, which may be contained in a pipe <NUM>, through a process coupling <NUM>. The device <NUM> is illustrated as including one or more process interface elements <NUM>. If the field device <NUM> is configured as a process variable transmitter, the process interface element <NUM> may comprise a process variable sensor for measuring a parameter of the process. Examples of the process variable sensor include a pressure sensor for measuring a pressure of the process, a flow sensor for measuring a flow rate of the process, a temperature sensor for measuring a temperature of the process, a level sensor for measuring a level of the process, or another process variable sensor. If the field device <NUM> is configured as a process variable controller, the process interface element <NUM> can be configured as a control element for controlling an aspect of the process, such as a valve, an actuator to control a position of a valve, a solenoid, a heating element, or another control element.

Communications between a control unit <NUM>, which may be remotely located from the field device in a control room <NUM>, and the field device <NUM> may be performed over a process control loop <NUM>, in accordance with conventional analog and/or digital communication protocols. In some embodiments, the process control loop <NUM> includes a two-wire process control loop, such as a <NUM>-<NUM> milliamp process control loop, in which a process variable or a control signal may be represented by a level of a loop current I flowing through the process control loop <NUM>. Exemplary digital communication protocols include the modulation of digital signals onto the analog current level of the two-wire control loop <NUM>, such as in accordance with the HART® communication standard. Other purely digital techniques may also be employed including FieldBus and Profibus communication protocols.

<FIG> is a simplified block diagram showing circuitry of a field device <NUM>, in accordance with embodiments of the present disclosure. Field device <NUM> includes device circuitry <NUM>, supplemental circuitry <NUM> and power supply circuitry <NUM>. The power supply circuitry <NUM> controls electrical power to the device circuitry <NUM> and the supplemental circuitry <NUM>, that is received over the two-wire process control loop <NUM>. The power delivered over the two-wire process control loop <NUM> may be generated by a power source located in the control room <NUM> (<FIG>), for example.

The device circuitry <NUM> generally includes conventional circuitry for performing primary operations of the field device <NUM>, such as sensing or measuring a process variable and/or controlling a process using the one or more process interface elements <NUM>. Thus, the device circuitry <NUM> may include process interface elements <NUM> in the form of one or more process variable sensors for sensing the process variable of an industrial process when the field device <NUM> is configured as a process variable transmitter. Alternatively, the device circuitry <NUM> may include process interface elements <NUM> in the form of one or more control elements for controlling an industrial process when the field device <NUM> is configured as a process controller. The device circuitry <NUM> may also include measurement circuitry <NUM> for processing signals from the one or more process variable sensors, and/or control circuitry for controlling the one or more control elements.

The device circuitry <NUM> may also include communications circuitry <NUM> for controlling communications over the two-wire process control loop <NUM>. Thus, the communications circuitry <NUM> may be used to represent a process variable value using the level of the loop current I, and/or communicate data using a modulated signal on the loop current I, for example.

The device circuitry <NUM> also includes a controller <NUM>, which represents one or more processors that control components of the field device <NUM> to perform one or more functions described herein in response to the execution of instructions, which may be stored locally in memory of the field device <NUM> or in memory that is remote from the field device, such as in the control unit <NUM>. Examples of these functions include performing a process variable measurement using the one or more process interface elements <NUM>, performing a process control function using the one or more process interface elements <NUM>, communicating with the control unit <NUM> over the two-wire process control loop <NUM> using the communications circuitry <NUM>, and/or other conventional field device functions. Additionally, the controller <NUM> may communicate with the supplemental circuitry as indicated by arrow <NUM>. The communications <NUM> may include control signals from the controller <NUM> to the supplemental circuitry <NUM>, data communication between the controller <NUM> and the supplemental circuitry <NUM>, and/or other communications.

The supplemental circuitry <NUM> generally includes circuitry for one or more devices that are used to perform secondary functions that are generally not essential to the process variable measurement or process control functions performed by the device circuitry <NUM>. Examples of the supplemental circuitry include a display <NUM>, a display controller <NUM> for displaying information on a display, a wireless communications module <NUM> for providing wireless communications, a flash memory writer <NUM> for writing data to flash memory, a power storage module <NUM>, and/or other circuitry that may supplement the conventional field device operations performed by the device circuitry <NUM>.

The display <NUM> may be integrated or connected to the field device <NUM>, and may be an LCD display or another suitable display. The display controller <NUM> may be used to drive the display of information on the display <NUM> or another display that is connected to the field device <NUM>. The wireless communications module <NUM> may be used to provide wireless communication capability to the field device <NUM>, or to expand the wireless communication capability of the field device <NUM>. For example, the wireless communications module <NUM> may facilitate wireless communications in accordance with a wireless communication protocol, such as WirelessHARTO (IEC <NUM>) or ISA <NUM>. 11a (IEC <NUM>), Bluetooth, WiFi, LoRa, Sigfox, BLE, or another wireless protocol that is not provided by the device circuitry <NUM>, such as by the communications circuitry <NUM>. The flash memory writer <NUM> may be used to write data to flash memory that is connected to the field device <NUM>.

Due to the important functions provided by the device circuitry <NUM>, it is critical for the power supply circuitry <NUM> to first serve the power needs of the device circuitry <NUM>. Power for the supplemental circuitry <NUM> may be scavenged from the excess power that remains after providing the required power (e.g., an operating voltage) to the device circuitry <NUM> and the power required to generate the desired loop current I over the two-wire process control loop <NUM>.

The power storage module <NUM> may be used to store the excess power that is not used by the device circuitry <NUM>. The power stored by the power storage module <NUM> may be used by components of the field device <NUM>, such as components of the supplemental circuitry <NUM>. Examples of the power storage module <NUM> include a bulk capacitor, a battery, or another suitable power storage component.

The supplemental circuitry <NUM> may also include user-accessible terminals 141A and 141B for accessing power for powering an external device, as shown in <FIG>. The terminals 141A and 141B may receive power from the power storage module <NUM>, or another suitable component of the supplemental circuitry <NUM>.

<FIG> and <FIG> are schematic diagrams of a field device <NUM> that includes power supply circuitry <NUM> in accordance with the prior art. The power supply circuitry <NUM> includes loop terminals <NUM> and <NUM> that are used to couple to the two-wire process control loop <NUM>, a current regulator <NUM>, and a shunt voltage regulator <NUM>. The current regulator <NUM> is in series with the process control loop <NUM> and the loop terminals <NUM> and <NUM>, and controls the loop current I in response to a current control signal <NUM> from the device circuitry <NUM> (e.g., the communications circuitry) using conventional techniques, such as using feedback from a sense resistor that is in series with the loop current I, for example. The current control signal <NUM> may direct the current regulator <NUM> to set the loop current I to a value that represents a process variable sensed by a process variable sensor <NUM> (<FIG>).

The shunt voltage regulator <NUM> receives a current ISH and controls a voltage VDC that powers the device circuitry <NUM>. The voltage VDC may be set by the shunt voltage regulator <NUM> in response to a voltage control signal <NUM> from the device circuitry <NUM>, such as from the controller <NUM> (<FIG>).

In <FIG>, the supplemental circuitry <NUM> is connected in series with the process control loop <NUM>, the loop terminals <NUM> and <NUM>, and in stack with the device circuitry <NUM>. This configuration of the power supply circuit <NUM> allows the supplemental circuit <NUM> to be powered by the loop current I. A current IDC is supplied to the device circuitry, where IDC=I-ISH. This configuration forces the device circuitry <NUM> to work on different voltage levels, complicates the control circuit, and increases the minimum requirements for the lift-off voltage of the field device <NUM>.

In <FIG>, the supplemental circuitry <NUM> is in parallel with the device circuitry <NUM> and the shunt voltage regulator <NUM>. Here, the current Ic (IC=I-ISH) is shared by the device circuitry <NUM>, which receives the current IDC, and the supplemental circuitry <NUM>, which receives the current Isc. This configuration requires monitoring of the power consumption of the supplemental circuit <NUM> to prevent underpowering the operation of the device circuitry <NUM> and disrupting its critical performance of the primary objectives of the field device <NUM>. This monitoring of the power consumption may be provided using control signals <NUM> and <NUM> from the device circuitry <NUM> to the current regulator <NUM> and the shunt voltage regulator <NUM>, and a control or feedback signal <NUM> from the supplemental circuitry <NUM> to the current regulator, for example. Additionally, this configuration of the power supply circuitry <NUM> may result in greater power loss than the configuration of <FIG>.

<FIG> is a schematic diagram of a field device <NUM> that includes power supply circuitry <NUM> in accordance with embodiments of the present disclosure. The power supply circuitry <NUM> includes loop terminals <NUM> and <NUM>, a current regulator <NUM>, a shunt voltage regulator <NUM>, and a shunt voltage regulator <NUM>. The current regulator <NUM> is positioned in series with the process control loop <NUM>, the loop terminals <NUM> and <NUM> and the device circuitry <NUM>. The current regulator <NUM> may operate in accordance with conventional current regulators, such as the current regulator <NUM> of <FIG> or <FIG>, and may control the loop current I in response to a current control signal <NUM> from the device circuitry (e.g., the communications circuitry <NUM> or the controller <NUM>) using conventional techniques, such as using feedback from a sense resistor that is in series with the loop current I, for example. The current control signal <NUM> may direct the current regulator <NUM> to set the loop current I to a value that represents a process variable sensed by a sensor <NUM> (<FIG>).

The shunt voltage regulator <NUM> is connected in series with the current regulator <NUM> and the two-wire process control loop, and in parallel with the device circuitry <NUM>. The voltage regulator <NUM> receives a current ISH and controls a voltage VDC that drives the current IDC (I=IDC+ISH) and powers the device circuitry <NUM>. The voltage VDC is set by the shunt voltage regulator <NUM> in response to a voltage control signal <NUM> from the device circuitry <NUM>, such as from the controller <NUM> (<FIG>), in accordance with conventional techniques.

The shunt voltage regulator <NUM> and the supplemental circuitry <NUM> are connected in series to the shunt voltage regulator <NUM>, arranged in parallel between the shunt voltage regulator <NUM> and ground or common corresponding to the loop terminal <NUM>. The shunt voltage regulator <NUM> and the supplemental circuitry <NUM> are powered by power from the two-wire process control loop <NUM> that is shunted through the shunt voltage regulator <NUM>. The shunt voltage regulator <NUM> receives a current ISH1 and controls a voltage Vsc that drives a current ISH2 (ISH2 = ISH - ISH1) and powers the supplemental circuitry <NUM>. For the field device <NUM> to operate in a stable manner, the voltage Vsc across the device circuitry <NUM> must generally be less than the voltage VDC across the supplemental circuitry <NUM>.

As indicated in <FIG>, the shunt voltage regulator <NUM> may comprise a Zener diode <NUM> or other suitable circuitry. The voltage Vsc may correspond to the reverse breakdown voltage of the diode <NUM>.

In some embodiments, the power supply circuitry <NUM> does not require additional diagnostics of power consumption or connection to the device circuitry <NUM> over the conventional power supply circuitry <NUM> (<FIG>). Rather, the supplemental circuitry <NUM> simply consumes all the needed power from the power shunted through the shunt voltage regulator <NUM>, and the excess power is fed to the process control loop <NUM>. Power may be consumed by the supplemental circuitry <NUM> without disruption to the loop current I or the operation of the device circuitry <NUM>, even in the case of a short circuit through the supplemental circuitry <NUM>.

In some embodiments, the field device <NUM> include output terminals <NUM> and <NUM> that are coupled to the power supply circuitry <NUM>, as shown in <FIG>. In one embodiment, the output terminals <NUM> and <NUM> are user accessible terminals that may be accessed through the housing <NUM> and connected to an external device (e.g., computing device). The output terminal <NUM> may be coupled to the voltage Vsc and the output terminal <NUM> may be coupled to electrical common or ground corresponding to the loop terminal <NUM>, as shown in <FIG>. In some embodiments, the voltage difference between the output terminals <NUM> and <NUM> may represent a process variable measurement sensed by a process variable sensor <NUM>.

Some embodiments of the present disclosure are directed to a method of providing power to a field device <NUM>. <FIG> is a flowchart illustrating embodiments of one example of the method with reference to the power supply circuitry shown in <FIG>.

At <NUM>, the first and second loop terminals <NUM> and <NUM> of the power supply circuitry <NUM> are coupled to the two-wire process control loop <NUM>. At <NUM>, device circuitry <NUM> of the field device <NUM> is powered with power received from the two-wire process control loop <NUM>.

At <NUM> of the method, a loop current I flowing through the two-wire process control loop is regulated using a current regulator <NUM> of the field device <NUM> that is connected in series with the two-wire process control loop <NUM>, the first and second loop terminals <NUM> and <NUM>, and the device circuitry <NUM>. This regulation of the loop current I may be in response to a control signal <NUM> from the device circuitry <NUM>, such as the communications circuit <NUM> or the controller <NUM> (<FIG>) of the device circuitry <NUM>. Additionally, the loop current I may be set to a level (e.g., <NUM>-<NUM> mA) in response to the control signal <NUM> that represents a process variable of an industrial process measured using a process variable sensor <NUM> (<FIG>), such as a pressure sensor, a temperature sensor, a flow sensor, and a level sensor.

A voltage VDC across the device circuitry <NUM> is regulated at <NUM> using the shunt voltage regulator <NUM> (first shunt voltage regulator) of the field device <NUM> that is connected in series with the two-wire process control loop <NUM> and the current regulator <NUM>, and in parallel with the device circuitry <NUM>, as shown in <FIG>. The voltage VDC may be controlled in response to a control signal <NUM> from the device circuitry <NUM>, such as the controller <NUM>.

At <NUM> of the method, the supplemental circuitry <NUM>, which is connected in series with the shunt voltage regulator <NUM> and the second loop terminal <NUM>, is powered with power received from the two-wire process control loop <NUM> that is shunted through the shunt voltage regulator <NUM>.

At <NUM>, a voltage Vsc across the supplemental circuitry <NUM> is regulated using the shunt voltage regulator <NUM> (second shunt voltage regulator) of the field device <NUM> that is connected in series with the shunt voltage regulator <NUM> and the second loop terminal <NUM>, and in parallel with the supplemental circuitry <NUM>. The voltage Vsc is used to power the supplemental circuitry <NUM>.

In some embodiments, the voltage Vsc and the current ISH2 are used to power components of the supplemental circuitry, such as a display <NUM>, a display controller <NUM> for displaying information on a display, a wireless communications module <NUM> for providing wireless communications, a flash memory writer <NUM> for writing data to flash memory, and/or a power storage module <NUM> for storing electrical energy, which are shown in <FIG>.

Claim 1:
A field device (<NUM>) for use in monitoring or controlling an industrial process comprising:
first and second loop terminals (<NUM>, <NUM>) configured to couple to a two-wire process control loop;
device circuitry (<NUM>) configured to monitor a process variable or control a control device, the device circuitry (<NUM>) powered by power from the two-wire process control loop;
a current regulator (<NUM>) in series with the first and second loop terminals (<NUM>, <NUM>) and the device circuitry (<NUM>), the current regulator (<NUM>) configured to regulate a loop current flowing through the two-wire process control loop and the first and second loop terminals (<NUM>, <NUM>);
a first shunt voltage regulator (<NUM>) connected in series with the current regulator (<NUM>) and the first and second loop terminals (<NUM>, <NUM>), and in parallel with the device circuitry (<NUM>), the first shunt voltage regulator (<NUM>) configured to regulate a first voltage across the device circuitry (<NUM>) and
to power the device circuitry (<NUM>), wherein the first shunt voltage regulator (<NUM>) is coupled to the device circuitry (<NUM>) which is configured to provide a voltage control signal (<NUM>) for controlling the first voltage;
supplemental circuitry connected (<NUM>) in series with the first shunt voltage regulator (<NUM>) and the second loop terminal (<NUM>), and powered by power from the two-wire process control loop shunted through the first shunt voltage regulator (<NUM>); and
a second shunt voltage regulator (<NUM>) connected in series with the first shunt voltage regulator (<NUM>) and the second loop terminal (<NUM>), and in parallel with the supplemental circuitry (<NUM>), the second shunt voltage regulator (<NUM>) configured to control a second voltage across the supplemental circuitry (<NUM>), and to power the supplemental circuitry (<NUM>) through the second voltage.