Patent Application
20090146502
The systems and methods relate generally to the field of process control systems. More specifically, the disclosed systems and methods relate to field devices powered at least partly by process control loops.
Conventional process control systems generally include basic components for sensing, measuring, evaluating, and adjusting or otherwise controlling a variety of process variables. Additionally, common systems include components that provide means for communicating information about process control variables between sensing, measuring, or adjusting components and evaluation components. One such system for communicating information is a two-wire system that creates a loop that physically connects a sensing, measuring, evaluating, or adjusting device to a controller.
Sensing, measuring, evaluating, and/or adjusting devices in industrial production environments are generally referred to as field devices. Field devices commonly sense or monitor one or more process control variables such as temperature, pressure, or rate of fluid flow, among others. Many of these field devices can communicate information about the sensed or monitored variable to a process controller by regulating electrical current on the two-wire system. The controller in this type of environment can sense the electrical current, such as by using a current sense resistor, and translate the sensed magnitude of the current, as well as any sensed change of the current, into information about the sensed or monitored control variable. Many common field devices can receive information from the controller and effect changes or adjustments to the sensed or monitored control.
Two methods of communicating information using a multi-wire loop system include analog signaling methods, such as communicating information via an analog current signal, and digital signaling methods that can communicate information as a frequency shift keyed carrier signal which can be superimposed on, and coexist with, an analog signaling method on the multi-wire loop. One digital signaling method is the Highway Addressable Remote Transducer (“HART”) communications protocol from the HART® Communication Foundation. As referred to herein, HART refers to any past or present version of the HART protocol, including Wireless HART, variants of such versions, as well as any future version that may be created so long as those future versions are compatible or can be modified to be compatible with the systems and methods disclosed herein.
According to one embodiment, a power management circuit can comprise a power regulator and a wireless communication device. The power regulator is configured to maintain a voltage level at an input and includes an input and an output. The input is configured to receive a current signal communicated between a power supply and a field device. The output is configured to deliver charging power. The wireless communication device is in electrical communication with the power regulator and is configured to receive the charging power to power the wireless communication device. The charging power is generated from the voltage level at the input and the current signal. The charging power also changes in response to a change in the current signal.
A process control system comprises a field device, a power supply, and a power management circuit. The power supply is in electrical communication with the field device. The power supply is configured to transmit a current signal to the field device. The field device is configured to regulate the current signal. The power management circuit is in electrical communication with each of the field device and the power supply. The power management circuit comprises a power regulator and a wireless communication device. The power regulator is configured to maintain a voltage level at an input. The power regulator includes an input and an output. The input is configured to receive the current signal. The output is configured to deliver charging power. The wireless communication device is in electrical communication with the power regulator and is configured to receive the charging power to power the wireless communication device. The charging power is generated from the voltage level at the input and the current signal. The charging power changes in response to a change in the current signal.
A method for managing power for a wireless communication device comprises receiving a current signal at an input, the current signal being transmitted between a power supply and a field device. The method further comprises regulating a voltage level at the input and generating charging power from the voltage level at the input and the current signal, wherein the charging power changes in response to a change in the current signal. The method yet further comprises delivering the charging power to an electrical storage device and delivering the charging power from the electrical storage device to a wireless communication device.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the same will be better understood from the following description taken in conjunction with the accompanying drawings in which:
Most components and methods disclosed are described with reference to the drawings. In drawings, like reference numbers are used to refer to like elements throughout the drawings. In the following description, to aid in explanation, a number of specific details are provided to promote understanding of the disclosed subject matter. It may be evident, however, that certain of these specific details can be omitted or combined with others in a specific implementation. In other instances, certain structures and devices are shown in block diagram form in order to facilitate description. Further, it should be noted that although specific examples presented can include or reference specific components, a specific implementation of the components and methods disclosed and described is not necessarily limited to those specific examples and can be employed in other contexts as well. Those of ordinary skill in the art will readily recognize that the disclosed and described components and methods can be used to create other components and execute other methods in a wide variety of ways.
In one embodiment, as illustrated in
In order to communicate the amount of current to the controller 112, in one embodiment, the controller 112 can include a current sense resistor 118 which can operate to sense the loop current provided through the control loop wires 108, 110. However, it will be appreciated that the controller 112 can sense loop current or other variable in any of a variety of suitable alternative configurations. Additionally or alternatively, the process control system 100 can include digital signaling components (not shown) to facilitate the communication of information as a carrier signal on the control loop wires 108, 110. In one embodiment, the field device 102 can include HART communication components, such as wireless HART communication components. However, the process control system can include components for any of a variety of suitable alternative communication protocols such as, for example, ISA SP100 and Fieldbus among others.
It will be appreciated however, that in some embodiments, the controller 112 may not support digital signaling methods such as, for example, when digital signaling equipment is not present on the controller 112 or during failure of digital signaling equipment. Therefore, in one embodiment, as illustrated in
Conventionally, the wireless adapter device 220 can be powered by dedicated power sources such as, for example, a separate wired power circuit, a battery, or a solar power cell, among others. However, installation and maintenance of a wireless adapter device powered by these dedicated power sources can be costly and time consuming. Therefore, as illustrated in
It will be appreciated that the wireless communication device 224 can consume more power than is instantaneously provided by the insertion power. Accordingly, the power management circuit 222 can store electrical power in order to power the wireless communication device 224. In one embodiment, the power management circuit 222 can include an electrical storage element configured to store insertion power and deliver the stored insertion power to the wireless communication device 224 as needed. Although the electrical storage device is illustrated in
The power management circuit 222 can power the wireless communication device 224 and charge the electrical storage device from loop current. In particular, loop current can be provided through the power management circuit 222 and can induce an insertion voltage drop across nodes L1P and L1N. It will be appreciated that the power available from the loop current to power the wireless communication device 224 and charge the electrical storage device (e.g., insertion power) is generally the multiplicative product of a magnitude of the loop current provided through the power management circuit 222 and the insertion voltage drop.
It will be appreciated that the insertion voltage drop induced by the flow of current through the power management circuit can provide an additional voltage drop to the process control system 200. When the wireless adapter device 220 is connected between nodes L1P and L1N, the magnitude of the insertion drop voltage should be such, that when the insertion drop voltage is combined with the other voltage losses in the process control system 200, the power supply voltage is not exceeded. For example, the combined voltage losses across the process control wires 208a, 208b, 210a, 210b, the wireless adapter device 220, the field device 202, and the current sense resistor 218 should be maintained at or below the power supply voltage.
It will be appreciated that the power supply voltage and corresponding voltage losses can vary for different process control system configurations. Conventionally, the insertion voltage drop on a power management circuit is permanently set at a low level (e.g., about 1 Volt DC (“VDC”)) in order to ensure compatibility with various process control system configurations. However, if these conventional power management circuits are provided on a process control system with low cumulative voltage losses, insertion power can be lost. For example, if the power supply 214 can supply about a 5 VDC voltage, and the combined voltage losses of a process control system (ignoring the insertion voltage drop) total about 2 VDC, the process control system can accept an insertion voltage drop of up to about 3 VDC. However, if the insertion voltage drop of the conventional power management circuit has been set at about 1 VDC, the insertion power will be comparatively less than a conventional management circuit having an insertion voltage drop of about 3 VDC. Therefore, the power management circuit 222 can be configured to control the insertion voltage drop (e.g., stabilize, regulate) to maximize the insertion power for any of a variety of process control system configurations.
It will be appreciated that the insertion voltage drop of a conventional power management circuit can be controlled with a current shunt provided in parallel with the power management circuit. The current shunt can control the insertion voltage drop by balancing the loop current with a combination of current consumption in the power management circuit plus the current consumption in the current shunt (e.g., a current divider circuit). As the loop current changes with a process variable, the current shunt can regulate the current flow through each of the shunt and the power management circuit, to maintain a constant insertion voltage drop. It will be appreciated however, that any current that flows through the current shunt may not be available to the power management circuit to power the wireless adapter device, and thus can be wasted power.
The power management circuit 222, however, can be configured to control the insertion voltage drop while allowing full loop current (less the miniscule current consumed by the other circuits) to flow to the power management circuit 222 (e.g., to power the wireless adapter device 220). In one embodiment, the power management circuit 222 can include a voltage converter 228 having an input 230 and an output 232. The input 230 is configured to receive loop current from node L1P and the output 232 is configured to deliver insertion power derived from the loop current.
In some conventional configurations, voltage converters, such as voltage converter 228, can maintain a consistent voltage level at the output 232 by varying the power transferred from the input 230. Generally, this conventional voltage regulator configuration is suitable where there is ample power provided at the input 230 (e.g., to satisfy the power demands of a circuit electrically connected to the output 232 of the voltage regulator). However, when the current and power provided at the input 230 is limited, as is the case with the loop current, and the demand on the output is significant, as is the case with the electrical storage device, this common voltage converter configuration may quickly transfer too much power to the output 232 thereby reducing the insertion voltage drop at input 230.
The voltage converter 228, therefore, can be configured as a power converter whereby the insertion power can be balanced with the power transferred into the electrical storage device to maintain the insertion voltage drop at the input 230 at a controlled value. In one embodiment, to facilitate the configuration of the voltage converter 228 as a power converter, the insertion voltage drop can be compared with a fixed reference voltage to regulate the insertion voltage drop to a fixed value. For example, as illustrated in
In such a configuration, the voltage converter 228 can overcome some of the shortcomings of using a current shunt in a power management circuit. For example, the insertion power (less the miniscule power consumed by the other circuits) generated from the insertion voltage drop and the loop current can be delivered to the output 232 of the voltage converter 228 (e.g., charging power). In addition, the delivery power can response to a change in the loop current for a greater range of loop current magnitudes. For example, when the loop current changes (e.g., when a control process variable changes) the power management circuit 222 can dynamically adjust to allow for the additional loop current. This additional loop current, when multiplied by the insertion voltage drop, can provide more insertion power than can be provided with a conventional power management circuit. For example, if a 20 mA loop current is generated by the power supply 214 and provided to a conventional power management circuit, the current shunt would only allow a portion of the loop current to flow through the conventional power management circuit. If the insertion voltage drop is controlled to about 1 VDC and the current shunt is configured to allow 50% loop current through the conventional power management circuit, the insertion power will be about 10 mW. However, if a 20 mA loop current is generated by the power supply 214 and provided to the power management circuit 222, the entire loop current would flow through the power management circuit 222. If the insertion voltage drop is controlled to about 1 VDC, the insertion power would be about 20 mW.
As illustrated in
The power management circuit 222 can be configured to define a variable setpoint to vary the insertion voltage drop. By varying the insertion voltage drop, the insertion power made available to the power management circuit 222 can be changed. In certain embodiments, where a range of insertion voltage drop values may be appropriate, the insertion voltage drop can be increased to a maximum value (in light of the other cumulative voltage losses of the process control system 200) to provide increased insertion power to the power management circuit 222. Increasing this insertion power may improve the rate at which the electrical storage component stores power and how much total average power can be available to operate the wireless communication device 224.
It will be appreciated that the variable setpoint can defined in any of a variety of configurations. In one embodiment, a variable scalar circuit can be provided in communication with the feedback circuit. In such an embodiment, the variable scalar circuit can be configured to facilitate selective control of the insertion voltage drop. For example, as illustrated in
It will be appreciated that during charging of the electrical storage device and prior to the electrical storage device reaching capacity, the power delivered from the output 232 of the voltage converter 228 (less the miniscule power consumed by the other circuits) can be provided to charge the supercapacitor 226. However, as the supercapacitor 226 reaches maximum capacity, the voltage across the supercapacitor 226 can continue to rise beyond proper operating limits of the power management circuit 222. Rather than shunting current and power away from the power management circuit 222 with a current shunt, a voltage shunting circuit can be provided in communication with the supercapacitor 226. The voltage shunting circuit can be configured to prevent an over-voltage condition within the supercapacitor 226. In one embodiment, as illustrated in
It will be appreciated to power various components of the power management circuit 222, a stable voltage can be provided from the insertion voltage drop. In one embodiment, as illustrated in
The power management circuit 222 can provide fast deployment that allows the application of loop currents in excess of the loop current normal operating ranges (e.g., about 3.5-20 mA, up to about 130 mA). This fast deployment can allow a user installing wireless adapter device 220 to rapidly charge the electrical storage device to provide minimal delay after installation to power the wireless communication device 224. To facilitate this fast deployment, the power management circuit 222 includes a fast deployment circuit configured to sense a magnitude of the loop current, and when the magnitude of the loop current reaches a threshold value, maintain the voltage level at the input at an elevated level to facilitate a substantial increase in the charging power delivered to the electrical storage element. In one embodiment, the power management circuit 222 can include a sense resistor 248 and a loop current amplifier 250. The microcontroller 247 can monitor the loop current across the sense resistor 248 and compare it with a threshold value. When the magnitude of the loop current exceeds the threshold value, the microcontroller 247 can define a setpoint for maximum insertion voltage with using the variable scaler 242, and the power management circuit can then receive maximum insertion power. In one embodiment, the microcontroller can compare the loop current against a threshold value of 25 mA. When the loop current exceeds 25 mA for a period of time the variable scaler 242 can be set to provide a maximum insertion voltage drop.
The power management circuit 222 can include over-current protection. This over current protection can limit the amount of insertion power when an excessive amount of loop current is being provided to the power management circuit. To facilitate over-current protection the power management circuit 222 can include an over current protection circuit configured to sense the magnitude of the loop current and, when the magnitude of the loop current reaches an over-current threshold value, disable the power regulator. In one embodiment, over current protection circuit can include the sense resistor 248 and the loop current amplifier 250. The positive input and negative input of the loop current amplifier 250 can be electrically connected on opposite sides of the sense resistor 248 to monitor the magnitude of the loop current. If the loop current exceeds a maximum threshold, the output of the loop current amplifier can provide a signal to shut down the power regulator thereby limiting the insertion power provided to the power management circuit 222. In one embodiment, the loop current amplifier 250 can compare the loop current against about a 130 mA threshold. When the loop current exceeds 130 mA, the loop current amplifier 250 can provide a signal to shut down the power regulator.
The power management circuit 222 can include a power save capability. The power management circuit can monitor the loop current (e.g., through sense resistor 248). If the magnitude of the loop current is reduced to a negligible amount, the power management circuit 222 can power down all significant power consuming circuits to preserve the power stored in the electrical storage device. When the loop current regains a particular magnitude (e.g., greater than a negligible amount), the power management circuit 222 can return power to the circuits that were previously shut down. If a process control system has a power outage, this function can help ensure that the wireless adapter device 220 will be immediately available with the electrical storage device at capacity when power returns. If a user has pre-charged the wireless adapter device 220 (e.g., in a lab), this feature can ensure that the wireless adapter device 220 will be fully powered and immediately available to begin radio communications when it is installed on a process control system.
The power management circuit 222 can include an instant-on function, whereby an auxiliary power is established to power the internal control circuitry before the electrical storage element charges up.
The power management circuit 222 can include dynamic radio duty cycle management. In particular, the power management circuit 222 can inform a wireless communication network of the insertion power available to power the wireless communication device 224. Accordingly, the wireless communication network can dynamically configure a maximum radio duty cycle to match the insertion power available to power the wireless communication device 224. When the insertion power is elevated, a duty cycle can be increased to achieve faster update rates for changing process variables. However, when the insertion power is depleted, the duty cycle can be reduced to ensure that the power demand by the wireless communication network does not exhaust the storage capacity of the electrical storage device thereby causing an ultimately loss of radio communication until the electrical storage device can be recharged.
What has been described above includes illustrative examples of certain components and methods. It is, of course, not possible to describe every conceivable combination of components or methodologies, but one of ordinary skill in the art will recognize that many further combinations and permutations are possible.
In particular and in regard to the various functions performed by the above described components, devices, circuits, systems and the like, the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (for example, a functional equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the examples provided. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired or advantageous for any given or particular application.
The foregoing description of embodiments and examples has been presented for purposes of illustration and description. It is not intended to be exhaustive or limiting to the forms described. Numerous modifications are possible in light of the above teachings. Some of those modifications have been discussed and others will be understood by those skilled in the art. The embodiments were chosen and described for illustration of various embodiments. The scope is, of course, not limited to the examples or embodiments set forth herein, but can be employed in any number of applications and equivalent devices by those of ordinary skill in the art. Rather it is hereby intended the scope be defined by the claims appended hereto.
The present application claims priority of U.S. Provisional Application Ser. No. 60/937,396, filed Jun. 26, 2007, U.S. Provisional Application Ser. No. 60/937,397, filed Jun. 26, 2007, U.S. Provisional Application Ser. No. 61/012,262 filed Dec. 7, 2007, the entire disclosures of which are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60937396 | Jun 2007 | US | |
| 60937397 | Jun 2007 | US | |
| 61012262 | Dec 2007 | US |
