Universal analog circuit for heating, ventilation, and air conditioning (HVAC) field devices

Abstract

A heating, ventilation, and air conditioning (HVAC) field device (102) and a method for a heating, ventilation, and air conditioning (HVAC) field device are provided. The HVAC field device includes a controller (104) configured to generate an input voltage signal (202), a mode selector (108) to select a first mode or a second mode, and an analog circuit (106) including a first stage (112), a second stage (114), and a resistor (116). The first stage generates an intermediate current (204) based on the input voltage signal (202) and the selection of the first mode or the second mode, and the second stage generates an analog output signal (206) based on the intermediate current. The intermediate current is multiplied by a predefined ratio to define the analog output signal. The predefined ratio is associated with one or more of a plurality of resistors. The analog output signal is provided at a terminal (110).

Description

Technical Field

[0001] This invention relates to a method and apparatus for controlling the operation of a heating, ventilation, and air conditioning (HVAC) system. Specifically, this invention relates to a general-purpose analog circuit for HVAC field devices, used to configure the input / output (I / O) terminals of said HVAC field devices to provide current or voltage outputs. Background Technology

[0002] Significant progress has been made in industrial automation and building systems, including heating, ventilation, and air conditioning (HVAC), in recent years. Notably, crucial components of HVAC systems are field devices, including sensors and actuators. Traditionally, field devices have been designed with fixed configurations, supporting specific functions such as analog current output, analog voltage output, or digital signals. This fixed approach presents significant challenges. Limited configuration flexibility often forces users to select and install equipment based on specific needs, making system upgrades or adjustments cumbersome. Furthermore, producing multiple device variants to support different functions leads to increased costs and installation complexity. Compatibility issues also arise because traditional analog devices struggle to integrate seamlessly with modern digital communication protocols. Therefore, improvements to traditional circuit designs are needed to ensure compatibility with the various components of HVAC field devices. Summary of the Invention

[0003] The following overview is provided to facilitate understanding of certain innovative features unique to this disclosure and is not intended to be a comprehensive description. A full understanding of this disclosure can be obtained by viewing the entire specification, claims, drawings, and abstract as a whole.

[0004] This invention relates to a general-purpose I / O circuit for HVAC field devices. The general-purpose I / O circuit allows for selection of current or voltage output in the HVAC field device via software-configurable analog outputs. Through the low-complexity design of this general-purpose I / O circuit, this disclosure achieves both high-precision output signal accuracy and cost-effectiveness.

[0005] On one hand, an HVAC field device is described. The HVAC field device includes a controller configured to generate an input voltage signal. The HVAC field device also includes analog circuitry coupled to the controller. The controller is configured to provide the input voltage signal to the analog circuitry. The analog circuitry includes a first stage and a second stage coupled to the first stage. The analog circuitry also includes a plurality of resistors. Each of the plurality of resistors is coupled to at least one of the first stage or the second stage. Furthermore, the HVAC field device includes a mode selector coupled to the analog circuitry for selecting one of a first mode or a second mode. Additionally, the HVAC field device includes terminals coupled to the analog circuitry. The analog circuitry is configured to provide an analog output signal at the terminals. The first stage is configured to generate an intermediate current based on the input voltage signal and the selection of one of the first mode or the second mode. The second stage is configured to generate the analog output signal based on the intermediate current, such that the intermediate current is multiplied by a predefined ratio to define the analog output signal. The predefined ratio is associated with one or more of the plurality of resistors.

[0006] In one embodiment, the first mode is a current mode and the second mode is a voltage mode.

[0007] In one embodiment, the second stage is configured to implement a current multiplier configuration. The second stage includes a first amplifier circuit having a first positive terminal, a first negative terminal, and a first output terminal. The second stage further includes a first transistor circuit having a first control terminal, a first terminal, and a second terminal. The first control terminal is coupled to the first output terminal. The second stage further includes a first pair of resistors from the plurality of resistors, the first pair of resistors including a first resistor coupled to the first positive terminal and a second resistor coupled to the first terminal. The first resistor forms a first path for the intermediate current to flow to the first positive terminal. The second resistor forms a second path, in parallel with the first path, for the analog output signal to flow to the first terminal. Further, the second stage includes a feedback path between the first negative terminal and the first terminal. The feedback path can be configured to adjust a second voltage across the second path to be substantially equal to a first voltage across the first path.

[0008] In one embodiment, the gain factor of the analog circuit corresponds to the ratio of the value of the analog output signal to the value of the input voltage signal. In the first mode, the gain factor is associated with a first group of resistors among the plurality of resistors. In the second mode, the gain factor is associated with a second group of resistors among the plurality of resistors, and the first group and the second group of resistors are mutually exclusive. If the input voltage signal (which may be a pulse-width modulation (PWM) signal) is filtered, the value of the input voltage signal (e.g., amplitude or voltage level) can be considered as the average voltage level of the input voltage signal after low-pass filtering to smooth the signal. The gain factor may also include values ​​equal to or less than 1.

[0009] In one embodiment, the controller is coupled to the mode selector. The controller is configured to generate a mode selection signal to provide to the mode selector. The mode selection signal is associated with one of the first mode or the second mode.

[0010] In one embodiment, the analog circuit further includes feedback circuitry coupled to the mode selector, the feedback circuitry including a first feedback path associated with the first mode and a second feedback path associated with the second mode. The first feedback path is coupled to a current feedback resistor among the plurality of resistors such that a first voltage difference across the current feedback resistor is substantially equal to the value of the input voltage signal. The second feedback path is coupled to a first node between a second pair of resistors among the plurality of resistors such that a third voltage at the first node is substantially equal to the value of the input voltage signal. The mode selector is configurable to select either the first feedback path or the second feedback path based on the mode selection signal.

[0011] In one embodiment, the analog circuit is further configured to supply the controller with a first voltage output signal at the first node as an output voltage.

[0012] In one embodiment, the plurality of resistors includes a third pair of resistors connected in series, such that the third pair of resistors defines a second node therebetween. The analog circuit is further configured to use the third pair of resistors to generate a second voltage output signal at the second node based on the analog output signal. The analog circuit is further configured to supply the second voltage output signal to the controller as an output voltage.

[0013] In one embodiment, the controller further includes an analog-to-digital converter (ADC). The terminal is configured to be coupled to an external component. The controller is further configured to use the ADC to generate a digital signal based on the output voltage. The controller is further configured to determine status data associated with the external component based on the digital signal. The status data corresponds to at least one of fault data, connection data, or resistance data.

[0014] In one embodiment, the analog circuit can be dynamically configured to operate in either an input mode or an output mode, wherein in the input mode, an input signal from an external source is received at the terminal, and in the output mode, the analog output signal is supplied to the external component through the terminal.

[0015] In one embodiment, the analog circuitry may be configured to be coupled to a sensor to supply a predefined current through the terminals. The controller is further configured to use the ADC to generate a sensor signal based on the output voltage. The controller is further configured to determine sensor status data associated with the sensor based on the sensor signal. The sensor status data indicates sensor resistance data. The controller is preferably configured to determine temperature data associated with the sensor based on the sensor status data.

[0016] In one embodiment, the first stage is configured as a current sink. The first stage includes a second amplifier circuit having a second positive terminal, a second negative terminal, and a second output terminal, the second positive terminal being coupled to the controller to receive the input voltage signal, and the second negative terminal being coupled to the mode selector. The first stage also includes a second transistor circuit having a second control terminal, a third terminal, and a fourth terminal. The second control terminal is coupled to the second output terminal, the fourth terminal is coupled to the current feedback resistor, and the third terminal is coupled to the second stage.

[0017] In one embodiment, the controller is further configured to generate the mode selection signal based on one of the state data, the sensor state data, or user input.

[0018] In one embodiment, the analog circuit further includes a switchable pull-down load coupled to the terminal. The switchable pull-down load is configured to apply a pull-down bias based on selecting a second mode via the mode selector, such that the pull-down bias is applied to achieve a defined voltage at the terminal in the second mode. The switchable pull-down load is preferably implemented based on a current mirror configuration. The analog circuit further includes a switching circuit comprising a plurality of input nodes, an output node connected to the analog circuit, and a control input node coupled to the controller to receive a control signal. A first input node of the plurality of input nodes is connected to a first reference voltage, and a second input node of the plurality of input nodes is connected to a second reference voltage. The switching circuit is configured to switch between the first reference voltage and the second reference voltage based on the control signal. The analog circuit further includes a voltage buffer located between the terminal and one of the second pair of resistors or the third pair of resistors.

[0019] In one embodiment, the HVAC field device includes actuators and / or sensors. The actuator may include an electric motor for adjusting the position of an actuated component (e.g., a valve or damper). The sensor may include a pipe sensor, a conduit sensor, or a wall-mounted room sensor. In one embodiment, the HVAC field device may be hydraulically and / or mechanically connected to at least a portion (e.g., a port of a pipe, conduit, or valve and / or damper) of one or more fluid delivery loops of an HVAC system having fluid supply / return lines to regulate and / or measure parameters of one or more fluids flowing through it.

[0020] The HVAC field device may include an HVAC base block and an HVAC add-on block. The HVAC base block includes the actuator and / or the sensor, and the HVAC add-on block includes the analog circuitry to extend the functionality of the HVAC base block.

[0021] In one embodiment, the HVAC field device includes a digital communication interface that allows configuration of the analog circuitry and / or the controller via a computing device (particularly a mobile computing device). The communication interface may include communication circuitry, particularly near-field communication (NFC) circuitry. The HVAC field device is preferably configured to use electrical energy generated from NFC signals to transmit configuration parameters for configuring the analog circuitry and / or the controller.

[0022] On the other hand, a method is implemented using HVAC field equipment. The method includes generating an input voltage signal. The method further includes providing the input voltage signal to an analog circuit. The analog circuit includes a first stage, a second stage coupled to the first stage, and a plurality of resistors. Each of the plurality of resistors is coupled to at least one of the first stage or the second stage. The method further includes selecting one of a first mode or a second mode for operation of the analog circuit. The method further includes using the first stage to generate an intermediate current based on the input voltage signal and the selection of one of the first mode or the second mode. The method further includes using the second stage to generate an analog output signal such that the intermediate current is multiplied by a predefined ratio to define the analog output signal, the predefined ratio being associated with one or more of the plurality of resistors. The method further includes providing the analog output signal at a terminal associated with the analog circuit.

[0023] The foregoing description of the invention is merely illustrative and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, other aspects, embodiments, and features will become apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0024] After a general description of exemplary embodiments of the present invention, the invention will now be described with reference to the accompanying drawings, which are not necessarily drawn to scale, wherein: Figure 1 A block diagram of an HVAC field device according to an embodiment of the present disclosure is shown; Figure 2A and Figure 2B A block diagram of an HVAC field device according to an embodiment of the present disclosure is shown; Figure 3 An exemplary schematic diagram of the analog circuitry of an HVAC field device according to an embodiment of the present disclosure is shown; Figure 4 An exemplary schematic diagram of an analog circuit according to an embodiment of the present disclosure is shown; Figure 5 An exemplary schematic diagram of an analog circuit according to an embodiment of the present disclosure is shown; Figure 6 An exemplary schematic diagram of an analog circuit according to an embodiment of the present disclosure is shown; Figure 7 A perspective view of an additional module associated with an HVAC field device according to an embodiment of this disclosure is shown; Figure 8 A schematic diagram of a cover module for an analog circuit according to an embodiment of the present disclosure is shown; Figure 9A and Figure 9B An exemplary circuit diagram of an analog circuit of an HVAC field device according to an embodiment of the present disclosure is shown; and Figure 10 A flowchart illustrating a method for generating an analog output signal using analog circuitry, according to an example embodiment of the present disclosure, is shown. Detailed Implementation

[0025] Exemplary embodiments of an HVAC field device having general-purpose analog I / O circuitry are described in detail below with reference to the accompanying drawings. Furthermore, the exemplary embodiments described below can be modified in various ways without altering the essence of this disclosure.

[0026] For ease of explanation, numerous specific details are set forth in the following description to aid in a comprehensive understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be practiced without these specific details. In other instances, systems and methods are shown only as block diagrams to avoid obscuring the scope of this disclosure.

[0027] Some embodiments of this disclosure will be described more fully below with reference to the accompanying drawings, which illustrate some, but not all, of the embodiments of this disclosure. In fact, various embodiments of this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable this disclosure to meet applicable legal requirements. The same reference numerals throughout refer to the same elements. Furthermore, reference to “an embodiment” or “a particular embodiment” in this specification means that a specific feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this disclosure. The phrase “in one embodiment” appearing in different places throughout this specification does not necessarily refer to the same embodiment, and separate or alternative embodiments are not mutually exclusive of other embodiments. Further, the terms “an” and “a” do not imply a limitation of quantity herein, but rather indicate the presence of at least one of the referenced items. In addition, various features are described that may be present in some embodiments but not in others. Similarly, various requirements are described that may be required in some embodiments but not in others.

[0028] The embodiments described herein are for illustrative purposes only and many variations exist. It should be understood that various omissions and equivalent substitutions are contemplated, as long as circumstances permit or suitability permit, but are intended to cover this application or implementation without departing from the spirit or scope of this disclosure. Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered restrictive. Any headings used in this specification are for convenience only and have no legal effect or restrictive effect.

[0029] Figure 1 A block diagram 100 of an HVAC field device 102 according to an embodiment of the present disclosure is shown. Block diagram 100 includes the HVAC field device 102. The HVAC field device 102 includes a controller 104, analog circuitry 106, a mode selector 108, and terminals 110.

[0030] In one embodiment, an HVAC system is used to maintain an optimal indoor environment in residential, commercial, and industrial settings. In one example, the HVAC system may include a fluid loop comprising a pump, valves, a heat exchanger, and piping for interconnecting components of the fluid loop. The heat exchanger is used to heat or cool the room. The valves are equipped with actuators, such as electric motors, for opening and closing the valves, thereby controlling the flow rate of fluid through the fluid loop using different valve positions (or orifice sizes) corresponding to different valve opening degrees. Additionally, the pump can vary the flow rate through the fluid loop. Further, the HVAC system may also include air-based systems that utilize dampers, ductwork, and fans to regulate airflow.

[0031] The HVAC system may further include an optional building control system connected to valves or actuators. Those skilled in the art will understand that the HVAC system may include multiple fluid loops, each having one or more pumps, valves, heat exchangers, and additional heat exchangers, such as coolers and / or heaters.

[0032] Furthermore, HVAC systems may include multiple different sensors. For example, heat exchangers may be equipped with temperature sensors positioned at the inlet to measure the supply temperature of the fluid entering the heat exchanger, and positioned at the outlet to measure the return temperature of the fluid leaving the heat exchanger. Further, fluid loops may include flow sensors for measuring the flow rate (i.e., the velocity) of the fluid passing through valves or the fluid loop. For example, the flow sensor may be an ultrasonic flow sensor, an inductive magnetic flow sensor, or a heat flow sensor.

[0033] Furthermore, the HVAC equipment includes control devices, referred to as HVAC field devices 102 for controlling valves. Accordingly, HVAC field devices 102 regulate the flow rate of fluid through the valves and subsequently through the heat exchanger. Therefore, HVAC field devices 102 regulate the heat energy exchanged between the heat exchanger and its environment per unit time. HVAC field devices 102 are used to regulate temperature, humidity, air quality, and airflow in the indoor environment where the HVAC system is implemented, improving energy efficiency while ensuring comfort.

[0034] In one embodiment, the HVAC field device 102 can enable real-time monitoring and adjustment of environmental conditions (such as temperature and humidity) in an indoor environment, reducing operating costs while ensuring occupant comfort. In one example, the HVAC field device 102 can be coupled to a building management system (BMS) installed within the building. Subsequently, the HVAC field device 102 can provide automation and efficiency in climate control within the building's indoor environment. When coupled or connected to sensors, actuators, controllers, or other field devices, the HVAC field device 102 may also be coupled to external components (such as loads).

[0035] However, sensors, actuators, controllers, or other field devices may operate in different modes. For example, some external components receive input in the form of current, while others receive input in the form of voltage. For instance, external components operating in current mode, i.e., current-controlled external components, may include actuators and sensors that respond to changes in current. Conversely, external components operating in voltage mode may include valves and controllers that respond to changes in voltage. Therefore, HVAC field device 102 needs to accommodate the various operational requirements of different types of external components. In other words, HVAC field device 102 needs to dynamically generate current or voltage outputs based on the type of external components connected to or controlled by it.

[0036] According to embodiments of this disclosure, HVAC field device 102 includes analog circuitry 106. Analog circuitry 106 configures terminals 110 of HVAC field device 102 as either current output terminals or voltage output terminals. The design or configuration of analog circuitry 106 provides accurate and stable output. Furthermore, analog circuitry 106 can be used in a variety of applications, such as for use in actuators and sensors. These sensors may include, for example, pipe sensors, tube sensors, and wall-mounted room sensors. Simultaneously, analog circuitry 106 can provide a setpoint via an analog interface to facilitate communication with actuators. Analog circuitry 106 allows actuators to send signals (e.g., feedback signals and sensor data) to other field devices, connect to passive sensors, and receive necessary sensor data (e.g., differential pressure signals) to control the actuator and its setpoint.

[0037] In sensor-related applications, analog circuitry is primarily used to provide analog measurement signals to other devices, such as field devices or controllers. Additionally, analog circuitry 106 is compatible with digital buses, allowing terminal 110 to be used as a digital I / O terminal. The circuit design of analog circuitry 106 can be adapted for use as a sub-circuit or component to form or design general-purpose I / O circuitry for HVAC field device 102 and other devices besides HVAC field device 102. Therefore, the implementation of analog circuitry 106 within HVAC field device 102 should not be construed as limiting.

[0038] In one example, analog circuit 106 can be used in a variety of applications, primarily focusing on signal input and signal output. This includes functions such as signal conditioning, where the circuit processes and modifies the input signal to ensure it is suitable for further use or analysis. Analog circuit 106 may include, but is not limited to, resistors, capacitors, inductors, diodes, transistors, and operational amplifiers. Analog circuit 106 is configured to receive an input signal at terminal 110, which may correspond to different types of inputs, including analog signals, digital signals, or resistive inputs. For example, analog signals may include input voltage signals ranging, for example, from 0 to 10 volts (V) DC or from 2 to 10 volts (V) DC, or input current signals ranging, for example, from 4 milliamps (mA) to 20 milliamps (mA). Additionally, analog circuit 106 may be configured to receive digital signals, including 24-volt DC signals. Analog circuit 106 is configured to interface with various sensors, such as 10 kΩ (kΩ) negative temperature coefficient (NTC) thermistors, 0-200 kΩ sensors, and multiple PT1000 or NI1000 resistance temperature detectors (RTDs) with resistance values ​​ranging from, for example, 500 to 2000 Ω. Furthermore, analog circuit 106 can be configured to generate output signals that can simultaneously include both analog and digital output signals.

[0039] The output signal may include, for example, an analog voltage signal ranging from 0 to 10V DC or a digital output signal corresponding to 24V DC. The output signal may also include, for example, an analog current signal ranging from 0 to 20mA or 4 to 20mA. Further, the analog circuit 106 may be configured to provide, for example, a 10V DC source-type digital output at terminal 110. The analog circuit 106 may further include a sinking 24V AC / DC output. This allows the HVAC field device 102 to effectively interface with a variety of external components while ensuring precise control of building interior environmental conditions.

[0040] In one embodiment, terminal 110 can serve as a connection point, facilitating, but not limited to, connection or coupling between a sensor, actuator, controller, or another field device. Terminal 110 of analog circuit 106 enables the transmission of electrical signals and power between analog circuit 106 and external components. In one embodiment, terminal 110 coupled to analog circuit 106 can correspond to screw terminals, barrier terminals, push-in terminal blocks, and pluggable terminals. Screw terminals provide a secure connection via a screw mechanism. In some cases, screw terminals can correspond to contacts on a printed circuit board (PCB), which can be connected using a connector. Terminal 110 used in this application can be based on the principles outlined in WO2023 / 088661A2 (Belimo Corporation), which describes an electrical connector for solderless connection to a printed circuit board (PCB). Barrier terminals prevent accidental short circuits. Push-in terminal blocks provide quick connection to analog circuit 106 and external components. Terminal 110 may include pluggable blocks, which allow easy connection and disconnection to external components for maintenance or inspection. Terminal 110 can be coupled to analog circuit 106 and provides connection between analog circuit 106 and external components.

[0041] In one embodiment, HVAC field device 102 may further include controller 104. Controller 104 may be configured to control one or more operations associated with one or more HVAC field devices, such as HVAC field device 102. In one example, controller 104 is configured to control the operation of HVAC field device 102. In one embodiment, controller 104 may include one or more processors, which may act as a central processing unit (CPU) that executes control algorithms and processes data from multiple sensors. In one embodiment, the one or more processors of controller 104 may range from simple microcontrollers and basic control circuitry (including simple application-specific integrated circuits (ASICs)) to more advanced embedded systems capable of running complex operating systems such as Linux. The one or more processors may directly affect the ability of controller 104 to process real-time analytics, enabling controller 104 to make precise adjustments based on external components and environmental conditions.

[0042] Furthermore, controller 104 also includes an analog-to-digital converter (ADC). The ADC is configurable to convert analog signals associated with the voltage at terminal 110 into digital data that controller 104 (i.e., the processor) can resolve. The voltage at terminal 110 is affected by interactions with attached external components at terminal 110. For example, when terminal 110 receives an input voltage or current, the analog signal may be related to a setpoint received from a field device or controller (such as a building management system (BMS)). Additionally, the ADC may detect the voltage on a digital bus line, measure the output voltage in a voltage output mode, or reflect the output voltage due to output current and (one or more) load resistance. Therefore, the ADC plays a crucial role in enabling the controller to effectively process various signals. This conversion is used to accurately monitor environmental conditions and make necessary adjustments to HVAC operation. For example, when a load (e.g., a temperature sensor) detects that the room temperature exceeds a set threshold, the ADC converts the analog signal into digital data, which the processor of controller 104 can analyze to determine whether to activate the cooling system or adjust airflow.

[0043] In addition, controller 104 may include one or more communication interfaces, such as UART, SPI, I2C, and Ethernet. Furthermore, controller 104 may support the MP bus for internal and external communication. Further, controller 104 may support wireless interfaces such as Near Field Communication (NFC), Bluetooth, and Wi-Fi. These one or more communication interfaces facilitate communication with sensors, actuators, and other devices within the HVAC system, enabling seamless integration and coordination of operations. Further details of controller 104 are described in conjunction with Figure 2.

[0044] HVAC field device 102 may further include a mode selector 108. Mode selector 108 selects between two input signals based on a mode selection signal and outputs a signal. The mode selection signal determines which input signal is delivered to the output. Mode selector 108 may correspond to a multiplexer (MUX) and may be implemented digitally or using hardware components such as, but not limited to, one or more MOSFETs. In a digital implementation, logic gates and flip-flops are used to control the selection of the input signal. Alternatively, MOSFETs may be used to switch different modes by controlling the voltage associated with them, thereby allowing or blocking the flow of current. Mode selector 108 may be configured to switch between a first mode and a second mode of analog circuitry 106 based on the mode selection signal. In one example, mode selector 108 may correspond to a 2:1 multiplexer (MUX). In one example, mode selector 108 may be coupled to multiple input signals and a single output line. Mode selector 108 may be digital circuitry that allows selection of one input signal from multiple input signals and routes the selected input signal to a single output line based on the mode selection signal. It should be noted that the first mode can correspond to the current mode, while the second mode can correspond to the voltage mode.

[0045] In operation, controller 104 is configured to generate input voltage signal 202. Analog circuitry 106 is coupled to controller 104. In one embodiment, the generated input voltage signal 202 is provided to analog circuitry 106. In one example, input voltage signal 202 corresponds to a pulse width modulation (PWM) signal. For example, an input voltage signal 202 of, for example, 3.3V, 10kHz is provided to analog circuitry 106. For example, the input voltage is determined by the duty cycle of the PWM signal, which reaches its maximum value of 3.3V when the duty cycle is 100%. In one example, controller 104 may be configured to use or control a PWM signal generator to generate input voltage signal 202 for analog circuitry 106. The PWM signal generator allows the controller to use simple general purpose input / output (GPIO) without the need for analog outputs or digital-to-analog converters (DACs).

[0046] Further, controller 104 is configured to provide an input voltage signal 202 to analog circuit 106. Analog circuit 106 includes a first stage 112, a second stage 114 coupled to the first stage 112, and a plurality of resistors 116. Further, each of the plurality of resistors 116 is coupled to the first stage 112 and / or the second stage 114. In one embodiment, analog circuit 106 includes an input terminal coupled to the first stage 112 for receiving the input voltage signal 202. In one embodiment, a group of resistors among the plurality of resistors 116 is coupled to the first stage 112 to facilitate the generation of an intermediate current. The arrangement and resistance values ​​of this group of resistors among the plurality of resistors 116 determine the gain of the transconductance amplifier of the first stage according to a selected mode. Based on the selection of this group of resistors among the plurality of resistors 116 and the mode, the gain of the transconductance amplifier of analog circuit 106 can vary. For example, in current mode, the gain of the transconductance amplifier is given by the first group of resistors among the plurality of resistors 116.

[0047] Further, analog circuit 106 is configured to select a first mode or a second mode for operation of analog circuit 106 based on a mode selection signal. In one embodiment, controller 104 is configured to generate a mode selection signal to enable mode selector 108 to select either the first mode or the second mode. Further, the mode selection signal is provided to analog circuit 106. Subsequently, analog circuit 106 processes input voltage signal 202 and generates an analog output signal based on the mode selection signal. In one embodiment, the first mode corresponds to a current mode, and the second mode corresponds to a voltage mode. In one example, when mode selector 108 selects a low-level (e.g., 0V) mode based on the mode selection signal, the mode of analog circuit 106 is selected as the first mode, i.e., analog circuit 106 is configured to generate a current-based analog output signal (current output signal I). OUT Conversely, when mode selector 108 selects a high-level (e.g., 3.3V) mode based on the mode selection signal, analog circuit 106 is selected in the second mode, i.e., analog circuit 106 is configured to generate a voltage-based analog output signal (voltage output signal V). OUT ).

[0048] Furthermore, the analog circuit 106 is configured to be based on the filtered input voltage signal V INThe selection of a first mode or a second mode is achieved using the first stage 112 to generate an intermediate current. In one example, the selection of the first mode or the second mode is based on a mode selection signal to generate the intermediate current. Specifically, the feedback of the first stage 112 is defined based on the mode selected according to the mode selection signal. In one embodiment, the first stage 112 corresponds to a transconductance stage. The first stage 112 is configured to generate an intermediate current in response to an input voltage signal received at an input terminal of the analog circuit 106. This allows for efficient conversion of the voltage input into a proportional current output, i.e., the intermediate current.

[0049] Furthermore, the second stage 114 is configured to generate an analog output signal (e.g., a voltage output signal V). OUT Or current output signal I OUT Specifically, the intermediate current received from the first stage 112 is multiplied by a predefined ratio to define the analog output signal. In one embodiment, the predefined ratio is associated with one or more resistors among the plurality of resistors 116. A second stage 114 is coupled to the first stage 112. Additionally, the second stage 114 is coupled to the plurality of resistors 116, forming a current multiplier configuration. In one embodiment, the second stage 114 of the analog circuit 106 is configured to generate the analog output signal by multiplying the intermediate current received from the first stage 112 by a predefined ratio associated with a first pair of resistors among the plurality of resistors 116. The predefined ratio associated with the first pair of resistors among the plurality of resistors 116 is independent of the selected mode (whether it is the first mode or the second mode). In one example, when the second stage 114 generates the analog output signal in the first mode (e.g., current mode), the gain factor of the analog circuit corresponds to the ratio of the value of the analog output signal 206 to the value of the input voltage signal 202. Specifically, in the first mode, the gain factor is associated with a first set of resistors among the plurality of resistors 116. In another example, when the second stage 114 generates an analog output signal in a second mode (e.g., voltage mode), the gain factor of the analog circuit corresponds to the ratio of the value of the analog output signal 206 to the value of the input voltage signal 202. Specifically, in the second mode, the gain factor is associated with a second group of resistors among a plurality of resistors 116. For example, the first group of resistors and the second group of resistors are mutually exclusive, i.e., they do not include resistors identical to those in the second group of resistors.

[0050] The arrangement of the second stage 114 and the first stage 112 allows for precise control of the analog output signal by adjusting the resistor values, thereby affecting the multiplication factor applied to the intermediate current. The integration of one or more resistors of the plurality of resistors 116 with the second stage 114 enables the analog circuit 106 to generate an analog output signal that accurately reflects the desired operating parameters (i.e., current operating mode or voltage operating mode). Furthermore, the first stage 112 and the second stage 114 are shared in both modes (i.e., current mode and voltage mode). Further details of the analog circuit 106 will be discussed in conjunction with... Figure 3 Describe it.

[0051] Furthermore, the HVAC field device 102 is configured to provide an analog output signal at terminal 110. Terminal 110 can be used as either an input or output terminal, thus providing flexibility to the HVAC field device 102. For example (and not limitingly), terminal 110 can be configured by software to either receive signals (i.e., operate as an input terminal) or transmit signals (i.e., operate as an output terminal). This dual functionality allows for efficient use of a limited number of pins, achieving greater flexibility without increasing the number of physical connections. Further, terminal 110 is coupled to analog circuitry 106. The analog circuitry 106 can be configured to provide an analog output signal at terminal 110. Terminal 110 can be connected to external components, such as loads, sensors, actuators, controllers, another field device, or other components that require an analog output signal to operate. The ability of analog circuitry 106 to output an analog output signal at terminal 110 ensures that the connected external component can receive the signal required for its function. By facilitating connection between analog circuitry 106 and loads, terminal 110 enhances the overall versatility and adaptability of the HVAC field device 102. Furthermore, the configuration of terminal 110 (i.e., input mode or output mode) allows for easy integration of different types of external components, such as, but not limited to, loads, sensors, actuators, field devices, and passive components, thereby ensuring that the HVAC field device 102 can respond to changing operating requirements. Further, analog output signals from analog circuitry 106 provide a means of communication between the HVAC system and its connected external components.

[0052] Figure 2A and Figure 2B Block diagrams 200A and 200B of an HVAC field device 102 according to an exemplary embodiment of the present invention are shown. Figure 2A and Figure 2B Combination Figure 1The components are described below. The HVAC field device 102 may include a controller 104, analog circuitry 106, a mode selector 108, and terminals 110. Further, the analog circuitry 106 may include a first stage 112, a second stage 114, an input terminal 208, and multiple resistors 116. Additionally, the HVAC field device 102 can be coupled to external components via terminals 110.

[0053] In one example, in the output operating mode of analog circuit 106, analog circuit 106 can provide control signals, including setpoints, to external components coupled to HVAC field equipment 102 via terminal 110. These control signals affect the operation of the external components. Analog circuit 106 can also provide feedback signals to the external components. These external components may correspond to loads or passive sensors. Analog circuit 106 can provide the necessary bias current to passive sensors. The resistance change due to environmental variations can then be determined based on the change in output voltage.

[0054] In one embodiment, the external component coupled to terminal 110 may correspond to, but is not limited to, an actuator. The actuator may operate using current-mode or voltage-mode signals, which can be considered setpoint signals or control signals. For example, an HVAC actuator may include a motor assembly that adjusts the position of the actuated external component. The motor and its controller may be designed to receive either current-mode or voltage-mode signals. The current-mode signal may range from 4 to 20 mA. However, the voltage-mode signal may range from 0 to 10 volts. However, these specifications are merely examples and may vary depending on the specific application and design requirements. For example, selecting whether the external component operates in current-mode or voltage-mode may depend on factors such as the required accuracy and the type of signal input from the connected field device. In one embodiment, controller 104 is coupled to analog circuitry 106 via input terminal 208. Furthermore, controller 104 is coupled to terminal 110. Further, controller 104 is coupled to mode selector 108.

[0055] In one example, controller 104 is further configured to generate a mode selection signal. In one example, the mode selection signal is provided to mode selector 108, whereby mode selector 108 selects a first mode or a second mode of operation for analog circuitry 106. For this purpose, selection of the first or second mode by mode selector 108 causes selection of a first or second feedback path for analog circuitry 106. For example, if controller 104 generates a mode selection signal associated with the first mode, mode selector 108 is configured to select the first feedback path. Alternatively, if controller 104 generates a mode selection signal associated with the second mode, mode selector 108 is configured to select the second feedback path. Furthermore, the mode selection signal may correspond to a signal that determines the mode (e.g., current or voltage (mode)) of the analog output signal 206 generated by analog circuitry 106.

[0056] Controller 104 is configured to generate an input voltage signal 202. The input voltage signal 202 is provided to input terminal 208 of analog circuitry 106 for its operation. It should be noted that input terminal 208 is coupled to a first stage 112 (or a portion thereof). Subsequently, based on the input voltage signal 202, the first stage 112 is configured to generate an intermediate current 204. In one embodiment, the input voltage signal 202 may be a PWM signal. Further, the first stage 112 is coupled to a mode selector 108, which selects a feedback path for the first stage 112. It should be noted that the mode or feedback path selected based on the mode selection signal is also used to generate the intermediate current 204 in the first stage 112. In this regard, analog circuitry 106 is configured to adjust the voltage level associated with the selected feedback path to match the value of the input voltage signal 202. Based on the mode selection signal in the first stage 112, the selected feedback path is matched to the value of the input voltage signal 202.

[0057] Furthermore, the first stage 112 is coupled to the second stage 114. Therefore, the intermediate current 204 generated by the first stage 112 is provided to the input of the second stage 114. Furthermore, the second stage 114 is configured to generate an analog output signal 206 provided at terminal 110.

[0058] In one example, the second stage 114 is configured to implement a current multiplier configuration. This current multiplier configuration is configured to generate an analog output signal 206 at terminal 110. In one embodiment, the current multiplier configuration may include one or more resistors from a plurality of resistors 116. It should be noted that both the first stage 112 and the second stage 114 can be implemented using an operational amplifier and one or more transistors (e.g., field-effect transistors (FETs), bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), etc.).

[0059] A current multiplier configuration is an electronic circuit designed to generate an output current that is a multiple of the input current. Unlike a current mirror that replicates the input current, a current multiplier amplifies the input current through a specific gain factor, which can be set using resistors or other components. A current multiplier configuration may include multiple components arranged to control the gain via a feedback mechanism. Using a current multiplier configuration is particularly advantageous for amplifying small currents and enabling their use in circuits that require higher output currents.

[0060] In the second stage, one or more resistors, an operational amplifier, and one or more transistors may be configured to amplify the intermediate current 204 at a predefined ratio to output an analog output signal 206, such that the gain factor of the analog circuit 106 corresponds to a ratio defined by one or more of the plurality of resistors 116.

[0061] According to embodiments of this disclosure, the analog circuit 106 is well-suited for implementation using discrete components. This allows for flexibility in circuit design, enabling the use of individual components to achieve the desired functionality and performance, making it suitable for a variety of applications while ensuring efficient operation and ease of customization. Further, the current multiplier configuration is implemented using a first pair of resistors from a plurality of resistors 116. The first pair of resistors includes a first resistor and a second resistor. The first resistor forms a first path through which the intermediate current 204 flows, and the second resistor forms a second path in parallel with the first path. Furthermore, the second path causes the analog output signal 206 to flow through it. Further, the current multiplier configuration includes a feedback mechanism for adjusting the bias of the second stage 114. For example, the feedback mechanism may be configured to keep the voltage level across the first resistor equal to the voltage level across the second resistor.

[0062] In one embodiment, analog circuitry 106 is configured to generate analog output signal 206, allowing for multiple output modes to accommodate various operational requirements. At terminal 110, analog circuitry 106 can provide a 20mA digital output at 10V DC, which is crucial for reliably signaling devices requiring digital control signals. This configuration enables analog circuitry 106 to connect to and control external components, such as relays or indicators. Additionally, analog circuitry 106 provides a 24V AC / DC digital output, such as 50mA at 24V AC / DC. This configuration allows analog circuitry 106 to operate as a sinking output option. Subsequently, in the sinking output configuration, analog circuitry 106 is configured to control external components that operate on AC or require higher voltage levels for effective performance.

[0063] In some cases, analog circuit 106 is operated in various configurations. For example, analog circuit 106 can be configured to receive 0-10V DC analog input from various active sensors. Additionally, the input may include control or feedback signals from other field devices or controllers. Analog inputs can be used for direct voltage measurements from sensors to accurately monitor environmental conditions. This capability is crucial in HVAC systems, where accurate temperature and humidity readings are necessary for optimal system performance. Furthermore, analog circuit 106 can be configured to receive analog inputs in, for example, a range of 4mA to 20mA. Such an analog input range supports current loop signals commonly used in process control systems. This type of analog input ensures accurate data transmission over long distances, minimizing signal degradation and interference.

[0064] Furthermore, the analog circuit 106 can be configured to support resistive inputs, which may come from, for example, but not limited to, one or more temperature sensors (e.g., 10kΩ NTC (negative temperature coefficient) thermistors) whose resistance changes with temperature. Additionally, the analog circuit 106 can interface with PT1000 and NI1000 RTD (resistance temperature detectors) operating in a resistance range of, for example, 500Ω–2000Ω, thereby allowing for accurate temperature monitoring in various environments. Moreover, the analog circuit 106 can support 10kΩ thermistors, which are effective at measuring temperature changes over a wide temperature range.

[0065] Furthermore, the analog circuit 106, operating in a 24V DC digital input configuration, enables terminal 110 to receive digital signals from devices operating on AC or DC power. This allows the analog circuit 106 to be seamlessly integrated into existing systems and enhances the overall functionality of the HVAC field device 102. The design of the analog circuit 106 as a general-purpose I / O circuit significantly enhances its configurability and adaptability in HVAC applications. By allowing dynamic reconfiguration between different configurations of input and output modes, for example based on operational needs or user preferences, the HVAC field device 102 can maintain optimal performance of the HVAC system while reducing installation complexity and cost.

[0066] In one embodiment, controller 104 may include a processor, memory, I / O interfaces, and communication interfaces. The processor of controller 104 may be configured to perform one or more operations associated with HVAC field device 102. The processor may embody one or more of a variety of hardware processing devices, such as a coprocessor, microprocessor, digital signal processor (DSP), processing elements with or without an accompanying DSP, or various other processing circuitry including integrated circuits such as ASICs, FPGAs (Field-Programmable Gate Arrays), microcontroller units (MCUs), hardware accelerators, application-specific computer chips, etc. Therefore, in some embodiments, the processor may include one or more processing cores configured to execute independently. Multi-core processors can implement multiple processing within a single physical package. Additionally or alternatively, controller 104 may include one or more processors configured in series via a bus to implement independent instruction execution, pipelined, and / or multithreaded execution. Additionally or alternatively, the processor may include one or more processors capable of handling large workloads and computations to support big data analytics. In an exemplary embodiment, the processor may communicate with memory via a bus to transfer information between components of controller 104.

[0067] For example, when a processor executes software instructions, these instructions may specifically configure the processor to perform the algorithms and / or operations described herein when executing the instructions. However, in some cases, the processor may be a processor-specific device (e.g., a mobile terminal or fixed computing device) configured to further configure the processor by means of instructions for performing the algorithms and / or operations described herein, thereby employing embodiments of this disclosure. The processor may include, among other components, a clock, an arithmetic logic unit (ALU), and logic gates configured to support processor operation. The communication interface of controller 104 allows access to the network environment in which the HVAC field device 102 operates. This communication interface provides access to various features and data stored in controller 104.

[0068] In some exemplary embodiments, the I / O interface may include a display, and in some embodiments, it may also include a keyboard, mouse, touchscreen, touch area, softkeys, or other input / output mechanism. In one embodiment, controller 104 may include user interface circuitry configured to control at least some functions of one or more I / O interface elements (e.g., a display). A processor and / or I / O interface circuitry including the processor may be configured to control one or more operations of one or more I / O interface elements via computer program instructions (e.g., software and / or firmware) stored in processor-accessible memory.

[0069] In one embodiment, the I / O interface is specifically designed to enable communication with external I / O devices. This functionality allows for integration with various peripheral devices and components, thereby enhancing the overall performance of the analog circuit 106. For example, external I / O devices can be configured to interact directly with the controller 104, facilitating seamless data exchange and control. This interaction is crucial for applications requiring real-time monitoring, data acquisition, or control of external systems. By establishing a reliable communication link between the I / O interface and external devices, the controller 104 can effectively collect information, respond to inputs, and execute commands as needed.

[0070] The communication interface may include input and output interfaces for supporting communication with controller 104 or any other component with which controller 104 may communicate. The communication interface may be any device, such as a hardware or hardware-software combination of device or circuitry, configured to receive data from and / or transmit data to a communication device communicating with controller 104. In this regard, the communication interface may include, for example, a wired communication interface and / or a radio communication device for providing communication functionality to the controller of HVAC field device 102. Specifically, the communication interface includes one or more of the following: wired communication interfaces (e.g., USB, Ethernet, particularly Power over Ethernet (PoE), Single-Pair Ethernet (SPE), bus, particularly MP-Bus, BACnet, KNX, or Modbus interfaces), wide area network (WAN) communication circuits (e.g., GSM, LTE, 3G, 4G, or 5G mobile communication circuits), low-power WAN (e.g., Narrowband Internet of Things (NB-IoT), LoRa, LoRa WAN, Sigfox, or Long Term Evolution Class M1 (LTECatM1)), local area network (LAN) communication circuits (e.g., wireless LAN), short-range wireless communication circuits (e.g., Bluetooth, Bluetooth Low Energy (BLE), Ultra Wideband (UWB), Thread, and / or Zigbee), and / or near-field wireless communication circuits (e.g., RFID or Near Field Communication (NFC)). For example, the communication interface can enable the establishment of a connection between the HVAC field device 102 and the computing device running the building management system (BMS) directly or via gateway device 120 using a wired (e.g., bus connection) or wireless communication interface.

[0071] In one embodiment, the communication interface may include an antenna (or multiple antennas) and supporting hardware and / or software for enabling communication with a wireless communication network. Additionally, the communication interface may include circuitry for interacting with one or more antennas to induce signal transmission or process reception of signals received through one or more antennas. In some environments, the communication interface may alternatively or additionally support wired communication. Therefore, for example, the communication interface may include a communication modem and / or other hardware and / or software for supporting communication via cable, Digital Subscriber Line (DSL), Universal Serial Bus (USB), or other devices. In some embodiments, the communication interface may enable communication with a cloud-based network to implement deep learning.

[0072] Analog circuit 106 generates analog output signal 206, for example, to meet specific requirements of external components or user input connected to terminal 110. Analog circuit 106 is designed to provide accurate and stable output while remaining cost-effective due to its low complexity. Terminal 110 is configured to receive analog output signal 206 (e.g., voltage output V) from analog circuit 106. OUT Or current output I OUT This is used to provide output to external components, such as external off-chip circuitry. This allows the analog circuit 106 to efficiently interface with external components, such as actuators and sensors, including pipe sensors and wall-mounted room sensors.

[0073] In one embodiment, the HVAC field device 102 may include one or more terminals for various functions. For example, terminal 110 and input terminal 208 may correspond to the one or more terminals. Here, input terminal 208 is coupled to controller 104, enabling direct communication and control between controller 104 and analog circuitry 106. Furthermore, the one or more terminals may include terminals for connecting additional modules that can be used to enhance the functionality of the HVAC field device 102. Additional modules may be provided... Figure 8 Additional features or capabilities are further described below. The one or more terminals allow for easy upgrades and expansion of the HVAC field device 102 without significant redesign. Furthermore, the one or more terminals may include a reference terminal coupled to a reference voltage source. Further, the reference voltage source is configured to provide a reference voltage at the reference terminal, and the reference terminal provides a reference voltage to the analog circuit 106. In one embodiment, an input voltage signal, or a reference voltage for input to the analog circuit 106, may be generated by the analog circuit 106 or its sub-circuits using the reference voltage source 306.

[0074] refer to Figure 2BThe analog circuit 106 can be dynamically configured to operate in either an input mode or an output mode. In the input mode, it receives an input signal from an external source at terminal 110, and in the output mode, it supplies an analog output signal to an external component via terminal 110. The controller 104 is configured to generate a mode selection signal and then provide this mode selection signal to a mode selector 108. Further, the controller 104 is configured to generate an input mode control signal, which is provided to the input mode selector 210. For the input mode, the controller is configured to generate a mode selection signal to set the mode selector 108 to select a first mode. Further, the controller 104 is configured to generate an input mode control signal to select between a current input mode and a voltage input mode, thereby allowing the analog circuit 106 to operate in either a current input mode or a voltage input mode based on the specific requirements of the HVAC field device 102. In one embodiment, the input voltage signal 202 is set to 0 volts. In another embodiment, the controller 104 is configured to set the input voltage signal 202 to 0 volts.

[0075] Analog circuit 106 includes an input mode selection mechanism 212 that provides switching between a current input mode and a voltage input mode. An input mode control signal applied to input mode selector 210 is configured to select between a current input mode and a voltage input mode using input mode selection mechanism 212.

[0076] An input mode control signal, such as a high-level (HIGH) state signal, is provided to the input mode selector 210 to activate the current input mode using the input mode selection mechanism 212. To select the voltage input mode, an input mode control signal, such as a low-level (LOW) state signal, is provided to the input mode selector 210 to activate the voltage input mode using the input mode selection mechanism 212.

[0077] Therefore, the input mode selection mechanism 212, combined with the mode selector 210, serves as a crucial component in the analog circuit 106. This allows for seamless switching between current input and voltage input modes. This flexibility enhances the overall functionality of the analog circuit, making it suitable for a wide range of applications requiring precise control and monitoring of analog signals.

[0078] Exemplary modes of analog circuit 106 are shown in Table T1. Table T1 Table T1 provides a detailed overview of one or more modes of analog circuit 106, listing the corresponding mode selection and input mode control signals, the applied input voltage signal level, the bias current generated for resistance or temperature measurement, and the measurement / input range. Based on specific application requirements (e.g., current and voltage input / output modes, temperature measurement, and resistance measurement), Table T1 serves as a reference for configuring the analog circuit. Table T1 includes selection signals (mode selection signal and input mode control signal) that define the function of the analog circuit based on mode selector 108 and input mode selector 210. Depending on the selected mode, different input voltage levels (Vin) are applied after filtering to ensure compatibility with the corresponding measurement or output range. In one embodiment, in current output mode, a low-level (LOW) signal is applied to the mode selection signal and the input mode control signal, and analog circuit 106 applies an input voltage level (Vin) of 0.6V to 3V after filtering. in The current input mode operates by generating an output current in the range of 4 to 20 mA, which is commonly used for long-distance signal transmission in industrial automation. Similarly, the voltage output mode is activated by setting the mode selection signal to high and the input mode control signal to low. This mode allows input voltages from 0 to 2.5 V, resulting in an output voltage in the range of 0 to 10 V, which is widely used for interfacing with voltage-sensitive components. For input signal processing, the current input mode configures analog circuit 106 to accept an input current of 4 to 20 mA when the mode selection signal is low and the input mode control signal is high. In voltage input mode, both the mode selection signal and the input mode selection signal are set to low, allowing an input voltage range of 0 to 10 V. These modes are crucial for processing analog signals from a variety of sensors and field devices. Table T1 further describes the PT1000 temperature measurement mode, in which both the mode selection signal and the input mode control signal are applied at a low level (LOW), while the input voltage signal 202 is applied to terminal 208 to generate a filtered input voltage V of 93.75mV. in (V) in_bias_pt1000 This voltage will generate a maximum bias current of 0.625mA (I0). bias max In this example, the temperature measurement range extends from 50°C to 160°C, and the resistance value ranges from 800 ohms at -50°C to 1600 ohms at 160°C. Additionally, a resistance measurement mode is outlined, in which different voltage biases are applied depending on the resistance value. For example, a 10kΩ resistor corresponds to a V0 of 21mV. in_bias and 141µA of I in The 680Ω resistor has a Vo of 81mV. in_bias and 542µA of I inIn this example, the resistance measurement range is 680Ω to 200kΩ, a range suitable for applications such as temperature measurement based on NTC thermistors. The applied voltage bias and corresponding bias current can be pulse-modulated to reduce the average current and prevent self-heating of the resistive element. For example, for the PT1000 sensor, the average bias current needs to be below 300μA.

[0079] Figure 3 An exemplary schematic diagram 300 is shown of the analog circuitry 106 of an HVAC field device 102 according to an embodiment of the present disclosure. Figure 3 Combination Figure 1 , Figure 2A and Figure 2B The components are described.

[0080] In one embodiment, controller 104 is configured to generate an input voltage signal 202. Further, controller 104 is configured to provide the input voltage signal 202 to analog circuit 106 via input terminal 208. For example, the input voltage signal 202 may be a pulse width modulation (PWM) signal. In another embodiment, controller 104 is configured to control the duty cycle of the input voltage signal 202 (e.g., the duty cycle of a PWM signal). In one example, controller 104 is configured to adjust the output voltage and current supplied to an external component connected to terminal 110 by changing the duty cycle of the input voltage signal 202. By way of example and not limitation, controller 104 utilizes an internal timer and registers to generate a square wave signal that alternates between a high-level (HIGH) state and a low-level (LOW) state. The high-level state may correspond to, but is not limited to, 3.3V, and the low-level state may correspond to, but is not limited to, 0V. Furthermore, by adjusting the proportion of time the input voltage signal 202 remains in the high-level state during each cycle, controller 104 can modulate the filtered input voltage supplied to analog circuit 106. For example, a 75% duty cycle means that the PWM signal is high for three-quarters of each cycle, resulting in a filtered input voltage that is 75% of the high-level state voltage. Conversely, a 25% duty cycle indicates a lower average input voltage supplied to the analog circuit 106.

[0081] In one embodiment, although not shown, the HVAC field device 102 may include a PWM signal generator. This PWM signal generator is configured to generate an input voltage signal 202. The PWM signal generator can control the supply of the input voltage signal 202 to analog circuitry 106. In this configuration, the PWM signal generator rapidly switches between an ON and OFF state. The ratio of the ON time to the total cycle time determines the generated effective average voltage, which is the analog voltage generated from the digital input.

[0082] In another embodiment, although not shown, the HVAC field device 102 (specifically, controller 104) includes a digital-to-analog converter (DAC). In this regard, controller 104 is configured to use the DAC instead of a PWM signal generator to generate the input voltage signal 202. For example, the DAC is configured to receive digital signals from controller 104. The DAC is configured to convert the digital signals into analog signals corresponding to the input voltage signal 202, which are then provided to analog circuitry 106.

[0083] In one embodiment, analog circuitry 106 may be powered by a single power supply to output analog output signal 206 while maintaining high accuracy. This power supply may be regulated or unregulated. In one example, the single power supply may form or correspond to a reference voltage supply 306. Analog circuitry 106 is designed to ensure the generation of analog signals with high accuracy, and the gain is determined by a combination of multiple resistors 116. This configuration enables effective signal conditioning and amplification, thereby ensuring that the output meets the specifications required for a variety of applications.

[0084] Furthermore, analog circuit 106 includes a low-pass filter 302 coupled to input terminal 208 of first stage 112. This low-pass filter 302 is an electronic circuit configured to allow signal components with frequencies below the cutoff frequency to pass through, while attenuating (i.e., reducing) signal components with frequencies above the cutoff frequency in the input voltage signal 202. In one example, low-pass filter 302 may be configured to filter a PWM signal received from controller 104 at input terminal 208. Additionally, low-pass filter 302 is configured to output a signal with a frequency below the cutoff frequency and provide this signal to first stage 112 of analog circuit 106.

[0085] In one embodiment, the low-pass filter 302 can be implemented using various methods, including passive components such as one or more resistors and one or more capacitors. In one example, the low-pass filter 302 is implemented using resistor R4, 310 (hereinafter referred to as resistor 310) and capacitor C1, 312 (hereinafter referred to as capacitor 312). The cutoff frequency can be adjusted based on the selection of the resistance value of resistor 310 and the capacitance value of capacitor 312.

[0086] In another embodiment, the low-pass filter 302 can be implemented using active components (e.g., but not limited to operational amplifiers or transistors).

[0087] In one embodiment, resistor 310 has a resistance of 10 kΩ and capacitor 312 has a capacitance of 1 microfarad (µF). The input voltage signal 202 received by input terminal 208 is a 3.3V PWM signal with a frequency of 20 kHz. In this case, the cutoff frequency of low-pass filter 302 can be configured according to the resistance value associated with resistor 310 and the capacitance value associated with capacitor 312.

[0088] In one example, the predetermined cutoff frequency of a resistor-capacitor (RC) circuit can be calculated based on the following formula: , Among them, F c =Pre-determined cutoff frequency, R = the resistance value associated with the resistor, and C = the capacitance value associated with the capacitor.

[0089] It is important to note that the low-pass filter 302 is configured to convert the PWM signal into a filtered input voltage signal Vin. By smoothing the inherent rapid fluctuations in the PWM signal, the low-pass filter 302 ensures that only the desired low-frequency components are allowed to pass through, while effectively eliminating high-frequency noise.

[0090] In one embodiment, the input terminal 208 (denoted as node A) of analog circuit 106 may be coupled to resistor 310 and capacitor 312. For example, the output of low-pass filter 302 is coupled to first stage 112. In one example, first stage 112 is configured to be based on the filtered input voltage signal V received from low-pass filter 302. IN The intermediate current 204 is generated by the mode selected by the mode selector 108.

[0091] In one embodiment, the first stage 112 is configured as a current sink. Furthermore, the first stage 112 includes a second amplifier circuit 314 having a second positive terminal coupled to the controller 104 to receive the input voltage signal 202, a second negative terminal coupled to the mode selector 108, and a second output terminal. For example, the second amplifier circuit 314 corresponds to operational amplifier U1. It should be noted that in some cases, the second positive terminal is coupled to the controller 104 via a low-pass filter 302 to receive the input voltage signal 202.

[0092] Furthermore, the first stage 112 includes a second transistor circuit 316. According to this example, the second transistor circuit 316 is implemented using a MOSFET, but this implementation should not be construed as limiting. In other embodiments, the second transistor circuit 316 may be implemented using a FET, BJT, Darlington transistor, etc. The second transistor circuit may have a second control terminal, a third terminal, and a fourth terminal. According to this example, the second control terminal may correspond to the gate terminal of the MOSFET, the third terminal may correspond to the drain terminal of the MOSFET, and the fourth terminal may correspond to the source terminal of the MOSFET. The second control terminal (or gate terminal) is coupled to the second output terminal of the second amplifier circuit 314. Furthermore, the fourth terminal (or source terminal) of the second transistor circuit 316 is coupled to the current feedback resistor R3318, and the third terminal (or drain terminal) of the second transistor circuit 316 is coupled to the second stage 114.

[0093] In one embodiment, the filtered input voltage signal V IN This can be applied to the second positive terminal of the second amplifier circuit 314. The second positive terminal corresponds to the non-inverting input terminal (labeled "+"), and is coupled to the output of the low-pass filter 302 to receive the filtered input voltage signal V from the low-pass filter 302. IN In one example, the second negative terminal is coupled to mode selector 108. For example, the second negative terminal may correspond to the inverting input (labeled "-"). Furthermore, the second amplifier circuit 314 may receive a positive supply voltage V. CC and negative power supply voltage V GND In one case, the negative power supply voltage V GND Grounding. However, it is conceivable to use any suitable positive supply voltage V as needed. CC and negative power supply voltage V GND In some cases, the second amplifier circuit 314 can be configured to generate an output voltage at the second output terminal that maintains the voltage level at the second positive terminal equal to the voltage level at the second negative terminal. Furthermore, the second output terminal is coupled to the second transistor circuit 316.

[0094] In one embodiment, the second negative terminal of the second amplifier circuit 314 is coupled to a mode selector 108. The mode selector 108 is configured to select or switch between a first feedback path and a second feedback path based on a mode selection signal. For example, when the mode selector 108 selects the first mode, thereby selecting the first feedback path, the second negative terminal of the second amplifier circuit 314 is coupled to node B between the fourth terminal of the second transistor circuit 316 and the current feedback resistor 318. Conversely, when the mode selector 108 selects the second mode, thereby selecting the second feedback path, the second negative terminal of the second amplifier circuit 314 is coupled to a first node as shown at node G. When the mode selector 108 switches from the second mode (voltage mode) to selecting the first mode (current mode), the second amplifier circuit 314 is configured to make the voltage level at node B equal to the voltage level at the second positive terminal of the second amplifier circuit 314 (i.e., the filtered input voltage signal V). IN The voltage level at node G is kept equal to the voltage level at the second positive terminal of the second amplifier circuit 314. Conversely, when the mode selector 108 switches from the first mode (current mode) to the second mode (voltage mode), the second amplifier circuit 314 is configured to keep the voltage level at node G equal to the voltage level at the second positive terminal of the second amplifier circuit 314. Furthermore, [the following is a continuation of the previous sentence, which is incomplete and requires further context]. Figure 4 Provide details.

[0095] Continuing on, the third terminal of the second transistor circuit 316 of the first stage 112 is coupled to the second stage 114 of the analog circuit 106. In one embodiment, the second stage 114 is configured to implement a current multiplier configuration 304. The second stage 114 includes a first amplifier circuit 326 having a first positive terminal, a first negative terminal, and a first output terminal. The second stage 114 includes a first transistor circuit 328 having a first control terminal, a first terminal, and a second terminal. The first control terminal is coupled to the first output terminal of the first amplifier circuit 326. In one embodiment, the first amplifier circuit 326 corresponds to an operational amplifier (op-amp). In this case, the first positive terminal corresponds to the non-inverting terminal (labeled "+") of the operational amplifier, and the first negative terminal corresponds to the inverting terminal (labeled "-"). Furthermore, the first transistor circuit 328 corresponds to a MOSFET. For example, the control terminal corresponds to the gate terminal of the MOSFET, the first terminal corresponds to the source terminal of the MOSFET, and the second terminal corresponds to the drain terminal of the MOSFET. The first control terminal (i.e., the gate terminal) is coupled to the first output terminal of the first amplifier circuit 326.

[0096] In one example, the first positive terminal (i.e., the non-inverting terminal) of the first amplifier circuit 326 is coupled to the third terminal (i.e., the drain terminal of the MOSFET of the first stage 112) of the second transistor circuit 316. Furthermore, the first negative terminal (i.e., the inverting terminal) of the first amplifier circuit 326 is coupled to a feedback path associated with the first terminal (i.e., the source terminal) of the first transistor circuit 328. Additionally, the first amplifier circuit 326 can receive a positive supply voltage V. CC and negative power supply voltage V GND .

[0097] Furthermore, the second stage 114 includes a first pair of resistors among a plurality of resistors 116. The first pair of resistors may include a first resistor 322, R1 coupled to a first positive terminal. For example, the first resistor 322 is coupled to the first stage 112 at a third terminal (or drain terminal) of the second transistor circuit 316, and coupled to the second stage at a first positive terminal of the first amplifier circuit 326. The first pair of resistors may also include a second resistor 324, R2 coupled to a first terminal of the first transistor circuit 328.

[0098] Analog circuit 106 can be connected to a reference voltage power supply 306. The reference voltage power supply 306 can provide a reference voltage to analog circuit 106 to power components such as the first amplifier circuit 326, the first transistor circuit 328, the second amplifier circuit 314, and the second transistor circuit 316. In one embodiment, a first resistor 322 and a second resistor 324 are coupled to the reference voltage power supply 306 via a first terminal 320. In one example, the reference voltage power supply 306 is configured to provide a stable and accurate voltage signal in the form of a reference voltage. To configure the reference voltage power supply 306, a voltage regulator or a dedicated reference integrated circuit (IC) can be used. For example, a Zener diode can be used to regulate the voltage in analog circuit 106. These components are designed to maintain a constant output voltage regardless of changes in the reference voltage power supply 306, temperature, or load conditions. For example, a reference voltage power supply set to 15V will ensure that the output voltage remains at 15V with minimal fluctuation.

[0099] The current multiplier configuration 304, implemented using the second stage 114, defines a first path and a second path. Specifically, the first resistor 322 forms a first path for the intermediate current 204 to flow to the first positive terminal. The intermediate current flows via the first positive terminal to ground, for example, from point D to point B or to ground. On the other hand, the second resistor 324 forms a second path in parallel with the first path for the analog output signal 206 to flow to the first terminal (e.g., from point D to point E). For example, the current from the first terminal 320 is the sum of the currents flowing through the first path and the second path. Therefore, the analog output signal 206 generated by the current multiplier configuration 304 depends on the ratio of the resistance value associated with the first resistor 322 to the resistance value associated with the second resistor 324, thereby enabling precise control of the output characteristics of the analog output signal 206 based on these resistance values. For example, this allows for high accuracy of the output signal, with an accuracy of less than 0.1%, over a temperature range of, for example, 0°C to 50°C.

[0100] The second stage 114 also includes a feedback path between the first negative terminal of the first amplifier circuit 326 and the first terminal of the first transistor circuit 328. Preferably, the feedback path is configured to adjust the first voltage across the first path to be substantially equal to the second voltage across the second path. For example, the first resistor 322 forms a path for the intermediate current 204 to flow to the non-inverting terminal of the operational amplifier. The second resistor 324 forms a second path, connected in parallel with the first path, for the analog output signal 206 to flow to the source terminal of the MOSFET.

[0101] In one embodiment, analog circuit 106 may further include diode 330. In one example, the second terminal of the first transistor circuit 328 is coupled to diode D1, 330. Subsequently, analog output signal 206 passes through diode 330. Diode 330 acts as a protective component, allowing current to flow in one direction while preventing any potential reverse current that could interfere with the operation of analog circuit 106. Figure 6 Further details of the analog circuitry are provided. Diode 330 allows analog circuitry 106 to use terminal 110 as an input terminal. Furthermore, diode 330 is coupled to terminal 110, facilitating the transmission of analog output signal 206 to connected external components.

[0102] In one embodiment, controller 104 is configured to provide a mode selection signal to mode selector 108, for example, via terminal 308. Mode selector 108 is configured to select an operating mode of analog circuitry 106 based on the mode selection signal. This mode can be selected from a first mode (i.e., current mode) or a second mode (i.e., voltage mode). Specifically, analog circuitry 106 may include feedback circuitry coupled to mode selector 108. This feedback circuitry includes a first feedback path associated with the first mode and a second feedback path associated with the second mode. The mode selection via mode selector 108 can then be based on the selection of either the first or second feedback path according to the mode selection signal. In other words, mode selector 108 can be configured to select either the first or second feedback path based on the mode selection signal.

[0103] In one example, mode selector 108 may correspond to a multiplexer that can be configured to switch between a first feedback path or a second feedback path.

[0104] The first feedback path is established between node B and the second negative terminal of the second amplifier circuit 314. It is important to note that node B is located at the junction or contact between the fourth terminal (or source terminal) of the second transistor circuit 316 and the current feedback resistor 318. Therefore, the first feedback path is coupled to the current feedback resistor 318 such that the first voltage difference across the current feedback resistor is substantially equal to the value of the input voltage signal 202.

[0105] Furthermore, a second feedback path is established between node G and the second negative terminal of the second amplifier circuit 314. It is important to note that node G is located at the first node between the second pair of resistors 332 of the plurality of resistors 116. Subsequently, the second feedback path is coupled to the first node between the second pair of resistors 332. For this purpose, the third voltage at the first node is substantially equal to the value of the input voltage signal 202. In one example, the second pair of resistors 332 includes resistors R5, 336 and resistors R6, 338. Resistors 336 and 338 in the second pair of resistors 332 are connected in series to define the first node between them. For this purpose, the feedback circuit ensures, based on the mode selection signal, that the voltage level associated with either the first or second feedback path is equal to the filtered input voltage level V. in match.

[0106] In one example, the second pair of resistors 332 may be implemented as a voltage divider circuit or configuration at the second terminal of the first transistor circuit 328. The second pair of resistors 332 is coupled to terminal 110, for example, at node F. By utilizing the voltage divider circuit, the voltage to the second pair of resistors 332 can be scaled down to a desired level. This is particularly useful for interfacing with other external components that require specific voltage levels for optimal performance. For example, the voltage to the second pair of resistors 332 may correspond to analog output signal 206. Subsequently, the second pair of resistors 332 can scale down the analog output signal 206 to obtain and output the desired voltage level at the first node. In one example, the controller 104 is coupled to the first node via terminal 334, for example, at node G. Furthermore, the analog circuit 106 is configured to supply a first voltage output signal to the controller 104 via the first node. For example, the first voltage output signal is provided to the controller 104 as an output voltage. For example, this output voltage is a scaled-down value of the analog output signal 206 provided to the controller 104.

[0107] According to an embodiment of this disclosure, resistors R5, 336 are connected between node F and node G, specifically between terminal 110 (a general-purpose I / O terminal that can be coupled to external components) and terminal 334 (the terminal where controller 104 can be coupled). Furthermore, resistor R6, 338 is grounded. It should be noted that mode selector 108 is coupled to node G (i.e., terminal 334) to select the second feedback path. In one embodiment, resistors R5, 336 are omitted and short-circuited. In this case, the first voltage signal provided to controller 104 is equal to the voltage of the output signal.

[0108] In one example, analog circuit 106 is coupled to an external component, for example, via terminal 110. In one embodiment, an MP bus is connected to analog circuit 106. An absolute voltage level is detected when the voltage level at terminal 110 is high (i.e., greater than a predetermined value).

[0109] In one example, controller 104 is configured to detect changes in the voltage level at its output to detect the presence of the MP bus. In some cases, it may not be necessary to detect voltage changes to detect the presence of the MP bus.

[0110] In one embodiment, in current mode, controller 104 is configured to directly detect the resistance of an external component based on the output current and the voltage level at terminal 110, the output current being a function of input voltage signal 202. In one example, the resistance of the external component can be determined based on a digital signal generated by an ADC (not shown) connected to terminal 334.

[0111] In some cases, a short circuit can be detected in current mode by sensing the output voltage and comparing the detected output voltage to a threshold (e.g., 0.2V). In one example, an open circuit can be detected based on the output voltage, for instance, if the output voltage is greater than another threshold (e.g., 11V).

[0112] Furthermore, in voltage mode, a short circuit can be detected if the output voltage does not reach the expected output voltage, because, as described below, the output current is limited to, for example, 23mA. Additionally, in voltage mode, the presence of a bus can be detected using absolute values.

[0113] Based on an assessment of the output voltage under load conditions, controller 104 can be configured to, for example, control certain operations of HVAC field device 102 or the HVAC system. The controller is configured to determine status data associated with external components, such as loads, digital buses, sensors, actuators, or any other component of HVAC field device 102. Furthermore, the status data may correspond to, but is not limited to, fault data, connection data, or resistance data.

[0114] Fault data can indicate a malfunction in an external component and / or a failure in the connection to that component, such as a short circuit at terminal 110 in voltage mode, or when the load resistor of an external component is determined to be below a threshold. In one example, a short circuit can be detected when the output voltage does not reach a predetermined threshold because the output current would saturate if the threshold is not reached. Furthermore, a fault is identified and reported if the output voltage under load conditions does not meet expectations or is outside the expected range. In this case, terminal 110 may be disabled, thereby stopping the supply of the analog output signal 206 to the external component. In one example, terminal 110 can be disabled by switching the mode of analog circuit 106 to current mode and setting the input voltage signal 202 or the PWM signal to 0 volts.

[0115] Connection data can indicate a valid connection to an external component, thereby enabling the identification of the presence of an external component connected to terminal 110 and / or the type of external component. Furthermore, resistance data can indicate the resistance value of an external component (e.g., a resistive sensor).

[0116] In one embodiment, controller 104 includes an analog-to-digital converter (ADC). In one example, controller 104 uses the ADC to measure the output voltage. Controller 104 is configured to generate a digital signal based on a first voltage output signal at a first node or a second voltage output signal at a second node when an external component is connected to terminal 110. Status data can be determined based on this digital signal.

[0117] In one embodiment, controller 104 is configured to generate a mode selection signal based on status data, sensor status data, or user input. When controller 104 analyzes the status data, it can determine the most appropriate mode to improve the operation of HVAC field equipment 102. For example, if the status data indicates fault data associated with a failure or malfunction, controller 104 can generate a mode selection signal corresponding to a current mode for the safe operation of analog circuitry 106 and to prevent further problems.

[0118] Therefore, the analog circuit can be dynamically configured to operate in input mode to receive input signals from an external source at terminal 110, or in output mode to supply analog output signals 206 to external components via terminal 110. In one example, the analog circuit 106 has the ability to be dynamically configured to operate in two different modes (i.e., input mode and output mode). This versatility is crucial for applications requiring flexible signal processing and control. In input mode, the analog circuit 106 is configured to receive input signals from an external source at terminal 110. This mode is suitable for applications where field devices need to monitor or analyze signals from external sources (e.g., sensors). When operating in input mode, the analog circuit can process or convert the input signal into a format suitable for further analysis or digital conversion. These signals can be used to monitor environmental conditions, detect anomalies, or facilitate user interaction.

[0119] Conversely, in output mode, analog circuitry 106 is configured to supply analog output signals 206 to external components via terminal 110. Output mode is employed in applications where analog circuitry 106 needs to drive external components (e.g., actuators, motors, valves, pumps, or other devices requiring specific analog signals for their operation). This mode ensures that appropriate signals are generated for the operation of these external devices. By supplying analog output signals 206, analog circuitry 106 provides signals that affect the performance of connected external devices, thereby enabling various functions, such as setting position setpoints for valve or damper actuators, speed setpoints for pumps, flow or differential pressure setpoints for flow or pressure regulation systems (e.g., variable air volume (VAV) control units and electronic pressure-independent valves (EPIV)), or temperature setpoints for heating or cooling systems. Furthermore, the analog circuitry can also provide signals representing measured values ​​(e.g., ambient air temperature or CO2 concentration levels) and feedback values ​​from control loops.

[0120] In one embodiment, analog circuitry 106 may be configured to be coupled to a passive sensor to supply a predetermined current through terminal 110. Controller 104 is also configured to generate a sensor signal based on the output voltage using an ADC. Controller 104 generates the sensor signal based on the output voltage from the sensor using an ADC. It converts the analog voltage level generated by the sensor into a digital format that the controller can interpret and analyze. The resulting sensor signal quantitatively reflects the sensor's output, which is affected by various environmental factors such as temperature or pressure.

[0121] During operation, the current multiplier configuration 304 is configured to multiply the intermediate current 204 by a predefined ratio to generate an analog output signal 206. In one embodiment, the first amplifier circuit 326 operates as a voltage follower, thereby outputting a voltage at a first terminal of node E that tracks the voltage at node C, which corresponds to the voltage at the positive terminal. As a result, the analog circuit 106, including the first amplifier circuit 326 and the first transistor circuit 328, adjusts the second voltage across the second path to be substantially equal to the first voltage across the first path. The reference voltage supply 306 is coupled to a first resistor 322 and a second resistor 324 via a first terminal 320. The first positive terminal of the first amplifier circuit 326 is coupled at node C to a third terminal of the second transistor circuit 316 and the first resistor 322. Furthermore, the first negative terminal is coupled at node E to a first terminal of the first transistor circuit 328 and the second resistor 324. The connection between the first negative terminal and node E can form a feedback path between the first negative terminal and the first terminal. The feedback path is configured to adjust the second voltage across the second path to be substantially equal to the first voltage across the first path. For this purpose, the current multiplier configuration 304 is configured such that the second voltage at node E is kept equal to the first voltage at node C. This arrangement results in a parallel connection between the first resistor 322 and the second resistor 324 due to the first amplifier circuit 326.

[0122] In one example, if the voltage difference across the first resistor 322 is equal to the voltage difference across the second resistor 324, and if the intermediate current 204 is I1, then the current I2 flowing through the second resistor 324 can be calculated using Ohm's law. In one example, the first voltage at node C can be determined as: V=I 1 R 1 (1), And if the first voltage and the second voltage are equal, then we can conclude that: I 1 R 1=I 2 R 2 (2).

[0123] Based on this relationship, we can deduce that: .

[0124] Equation 3 shows that the current I2 corresponding to the analog output signal 206 can be calculated based on the ratio of the resistance values ​​associated with the first resistor 322 and the second resistor 324. The multiplier configuration effectively scales the intermediate current 204 according to the resistance ratio, thereby generating the analog output signal 206 that reflects the desired operating parameters.

[0125] In one example, controller 104 is further configured to determine sensor status data associated with the sensor based on the sensor signal. The sensor status data represents sensor resistance data. Once the sensor signal is generated, the controller is able to determine the sensor status data associated with the sensor. This status data includes information about the sensor resistance, which can indicate the sensor's operating status. By analyzing the resistance data, controller 104 can assess whether the sensor is operating normally or whether any problems need to be addressed. Furthermore, controller 104 can determine sensor readings based on the sensor data. In some cases, based on this reading, controller 104 can be configured to control the operation of certain external components of the HVAC field device 102.

[0126] In one example, controller 104 is configured to determine temperature data associated with the sensor based on sensor state data. Controller 104 uses the sensor state data to derive temperature data that can be measured by the sensor. In this case, the sensor can be an RTD (Resistant Temperature Detector). By analyzing the resistance data in conjunction with the known temperature characteristics of the sensor element, controller 104 is able to accurately determine the temperature range. This includes not only the ambient temperature but also the temperature of various fluids (e.g., water or air).

[0127] Figure 4 This is an exemplary schematic diagram 400 of an analog circuit 106 according to an embodiment of the present disclosure. The analog circuit 106 may include a Zener diode D2, 402 and a switchable pull-down load 406.

[0128] A Zener diode 402 is coupled between the output terminal of the second amplifier circuit 314 and ground. The Zener diode 402 acts as a protective component in the analog circuit 106. The Zener diode 402 prevents excessive current by limiting the voltage applied to the gate terminal of the MOSFET. In one example, during normal operation, the output from the second amplifier circuit 314 controls the voltage at the second control terminal of the second transistor circuit 316. This can cause an intermediate current 204 to flow from the third terminal (or drain terminal) of the second transistor circuit 316 to the fourth terminal (or source terminal). However, during transient voltage spikes, the voltage at the second control terminal of the second transistor circuit 316 may exceed a safe threshold, posing a risk of damage to the second transistor circuit 316 and other circuit components of the analog circuit 106. The Zener diode 402 addresses this problem by clamping the voltage at the second control terminal when it exceeds the breakdown voltage of the Zener diode. The breakdown voltage can be set to a value that ensures the safe operation of the second transistor circuit 316. By limiting the voltage at the second control terminal, the Zener diode 402 effectively limits the maximum current that the second transistor circuit 316 can absorb, thereby ensuring that the circuit operates safely and reliably under varying load conditions.

[0129] In one embodiment, the Zener diode 402 protects the MOSFET and also defines the maximum output current I. out_max Zener diode 402 is selected such that when I2 exceeds a predetermined current limit I... out_max At that time, the gate-source voltage (V) is obtained by subtracting the voltage drop (I1*R3) across the current feedback resistor 318 from the gate voltage. GS The voltage will be lower than or close to the MOSFET's threshold voltage (V). th Typically, this means that the breakdown voltage of a Zener diode is close to I. out_max *R3*R2 / R1+V th Therefore, for example in voltage mode, current limiting can be achieved using one or more of the multiple resistors 116, thereby limiting the analog output signal 206 to less than 25mA in the event of a short circuit.

[0130] In one embodiment, mode selector 108 may correspond to a 2:1 multiplexer. Mode selector 108 is configured to select a first mode or a second mode based on a mode selection signal. In one example, the mode selection signal may be generated by controller 104. This mode selection signal is provided at terminal 308 of analog circuit 106. Furthermore, the mode selection signal is provided to mode selector 108 to configure a first feedback path 404A or a second feedback path 404B. In one example, the mode selection signal may serve as a selection signal for a 2:1 multiplexer. Based on this selection signal, mode selector 108 is configured to select either the first feedback path 404A or the second feedback path 404B.

[0131] In one embodiment, the mode selection signal is associated with a first mode, which is defined as a current mode. In this case, analog circuit 106 is configured to output analog output signal 206 as a current signal varying in the range of, for example, 0mA to 20mA, based on input voltage signal 202 at input terminal 208. Controller 104 is configured to generate a mode selection signal of 0V, which is provided to mode selector 108 via a selection line. Upon receiving the mode selection signal as low (LOW), mode selector 108 is configured to select first feedback path 404A. First feedback path 404A is coupled at node B to the fourth terminal of second transistor circuit 316 and current feedback resistor 318. After switching to first feedback path 404A, second amplifier circuit 314 is configured to force the voltage level at node B to be equal to the voltage level at the second positive terminal (i.e., non-inverting terminal) of second amplifier circuit 314. The second positive terminal of second amplifier circuit 314 is coupled at node A to the output terminal of low-pass filter 302. For example, if the output voltage of the low-pass filter 302 is V in Then the second amplifier circuit 314 is configured to keep the voltage level at node B equal to V. in Furthermore, the voltage difference across the current feedback resistor 318 causes the intermediate current 204 to flow. The intermediate current 204 is calculated using Ohm's law as follows: V=IR, Where V = the voltage difference across the current feedback resistor 318, I = the current flowing through the current feedback resistor 318, and R = the resistance value associated with the current feedback resistor 318.

[0132] The intermediate current 204 flowing through the current feedback resistor 318 can be calculated using Ohm's law. In one embodiment, the intermediate current 204 flowing through the current feedback resistor 318 flows from the third terminal to the fourth terminal of the second transistor circuit 316 because the current at the second control terminal of the second transistor circuit 316 is zero. For example, if the resistance value associated with the current feedback resistor 318 is set to 2kΩ, and at the second positive terminal (V... in If a 3V input signal is applied at the current feedback resistor 318, the current flowing through the current feedback resistor 318 can be calculated to be 1.5mA. This calculation shows that under these conditions, an intermediate current 204 of approximately 1.5mA flows through the current feedback resistor 318.

[0133] In one embodiment, the first amplifier circuit 326 is configured to maintain the voltage level at node E equal to the voltage level at node C. Therefore, the voltage across the second resistor 324 is equal to the voltage across the first resistor 322. In one example, the resistance associated with the first resistor 322 is 1 kΩ, and the resistance associated with the second resistor 324 is 75 Ω. For example, if the intermediate current 204 is 1.5 mA, then the voltage across the first resistor 322 and the voltage across the second resistor 324 are both 1.5 V. Therefore, the current multiplier configuration 304 is configured to generate a current output signal equal to the following value: , Here, I1 represents the intermediate current 204 flowing through the first resistor 322, while the current output signal I2 represents the analog output signal 206 in current mode. The predefined ratio of the resistance values ​​of resistor R1 to R2 determines the scale of the intermediate current 204 to generate the output current I2.

[0134] In the example, an intermediate current I1 of 1.5mA causes a current I2 of 20mA to flow through the second resistor 324. Assuming the current at the first control terminal of the first transistor circuit 328 is zero, the entire 20mA current flows through the diode 330 and into the external component coupled to terminal 110. This configuration ensures that the output current I2 is effectively delivered to the external component. The ability of the first amplifier circuit 326 to maintain the voltage level across the first resistor 322 and the voltage level across the second resistor 324 equal is crucial for achieving precise current control within the analog circuit 106.

[0135] Furthermore, it is important to note that the current flowing through the second pair of resistors 332 is negligible. In one example, the second pair of resistors 332 can function as a voltage divider circuit. The second pair of resistors 332 may include resistors 336 and 338, which are used to measure the output voltage. In one example, the maximum input resistance of the external component coupled to terminal 110 in current mode is specified as 500 ohms. This configuration allows the HVAC field device 102 to operate efficiently under varying load conditions. Conversely, the minimum input resistance of the external component can be 0 ohms, which is equivalent to a short circuit. This design accommodates a maximum output current I2 of 22mA, which is achieved when the input voltage signal 202 is set to 3.3V, at which point this 3.3V serves as the reference voltage for the HVAC field device 102.

[0136] For example, considering a resistance of 10 ohms associated with an external component, this configuration would produce a voltage drop of 200 millivolts with an output current I2 of 20mA. Specifically, low resistance may occur in current mode. This characteristic can be used to implement cable short-circuit detection. By monitoring the voltage drop (in mA) across the resistance of the external component, the controller 104 of the HVAC field device 102 can identify conditions indicating a short circuit, thereby improving safety and reliability. If the output voltage level for a predetermined test current (e.g., 20mA) is lower than a predetermined minimum voltage level (e.g., 200mV), the controller 104 can identify conditions indicating a short circuit. By ensuring that the HVAC field device 102 can handle both maximum and minimum load conditions while providing accurate current output, this design improves overall performance and adaptability.

[0137] In one embodiment, the analog circuit 106 has the advantage of using local feedback in current mode, which utilizes the voltage across resistor R3 318 to measure the intermediate current 204. This design ensures that the output current depends only on the resistance values ​​of the first pair of resistors (i.e., resistors R1, 322, R2, 324, and the current feedback resistor R3, 318). Therefore, as long as the output voltage is within compliance range, the output current is independent of the reference voltage supply 306 and the output common-mode voltage.

[0138] In one embodiment, when the mode selection signal is associated with a first mode, the analog circuit 106 is configured to use the analog output signal 206 as a current output signal I. OUTOutput. Furthermore, the second stage 114 is configured to generate an analog output signal 206 such that the intermediate current 204 is multiplied by a predefined ratio to define the analog output signal 206. In one example, the predefined ratio is associated with a first pair of resistors among a plurality of resistors 116, wherein the first pair of resistors may include a first resistor 322 and a second resistor 324. In one example, the value of the analog circuit at the input voltage signal 202 is compared with the current output signal I. OUT The gain factor between the values ​​of the analog output signal 206 and the first group of resistors (116) is associated with the first group of resistors. Furthermore, the first group of resistors may include a first resistor 322, a second resistor 324, and a current feedback resistor 318. The gain may correspond to the ratio of the product of the first resistor 322 to the product of the current feedback resistor 318 and the second resistor 324, i.e., .

[0139] Furthermore, controller 104 is configured to determine the voltage level of analog output signal 206. If the voltage level of analog output signal 206 is higher than a predetermined threshold, controller 104 is configured to generate an error message and disable analog output signal 206 by setting the input voltage to 0V. In one example, controller 104 may determine whether the output voltage level of the voltage output signal is lower than a minimum voltage level (which is, for example, 0.2V for a predetermined test current (e.g., 20mA)). When the output voltage level is lower than the minimum voltage level, a short circuit can be detected. In this case, controller 104 is configured to generate an error message and / or disable analog output signal 206 by setting the input voltage to 0V.

[0140] In another embodiment, when the mode selection signal is associated with a second mode corresponding to a voltage mode, the analog circuit 106 is configured to output an analog output signal 206 as a voltage output signal V varying in the range of, for example, 0 to 10V, based on the input voltage signal 202 at input terminal 208. OUT Output. Controller 104 is configured to provide a high-level (HIGH) or 3.3V mode selection signal to mode selector 108. When this mode selection signal is received from controller 104, mode selector 108 is configured to select the second feedback path 404B.

[0141] In the second feedback path 404B, mode selector 108 is coupled at node G to the first node defined by the second pair of resistors 332. Furthermore, the second amplifier circuit 314 is configured to maintain the voltage level at node G equal to the voltage level at the second positive terminal of the second amplifier circuit 314. In one example, the voltage difference across resistor 338 is equal to the voltage level at the second positive terminal, i.e., V in The current flowing through resistor 338 is equal to V.in / R6. The analog output signal 206 at terminal 110 can be equal to the voltage difference V across resistors R5, 336 and R6, 338. out This voltage difference can be calculated using Ohm's law. Since the current flowing through resistor 338 (R6) must also flow through resistor 336 (R5), the voltage difference (voltage output signal, V) is... OUT It can be calculated using the following formula: V out =I*(R) 5 +R 6 ）， Substitute into I=V in / R6 value , Among them, V in = The voltage at the second positive terminal of the second amplifier circuit 314, R5 = the resistance value associated with resistor 336, and R6 = the resistance value associated with resistor 338.

[0142] The ratio of the sum of the resistances of resistors R5 and R6 to the resistance of resistor R6 (expressed as (R5 + R6) / R6) defines the gain factor in voltage mode. The gain factor is associated with a second group of resistors among the plurality of resistors 116, which includes resistors 336 and 338. In one example, if the resistance values ​​associated with resistors 336 and 338 are 30 kΩ and 10 kΩ respectively, the gain factor corresponds to the filtered input voltage V. in and analog output signal 206 (i.e., voltage output signal V) OUT The ratio between ) . The gain factor in voltage mode can correspond to 4. In one example, a filtered input voltage V of 3.3 volts is provided. in Analog circuit 106 generates an analog output signal 206 of 13.2 volts.

[0143] In another embodiment, analog circuitry 106 is configured to detect whether a digital bus is connected to terminal 110. For example, controller 104 may be configured to determine the connection status of the digital bus by interpreting a digital signal received from a first voltage signal at node G. An analog-to-digital converter (ADC) within controller 104 is designed to recognize changes in voltage levels exceeding a predetermined threshold. For example, the predetermined threshold is set to be greater than the maximum analog output voltage or greater than the output voltage at the maximum input voltage, e.g., 13.2V. Once it is determined that the digital bus is connected to analog circuitry 106, controller 104 is configured to generate a mode selection signal. This mode selection signal causes analog circuitry 106 to switch to either a first mode or a current mode. In this case, controller 104 generates the mode selection signal; furthermore, mode selector 108 is configured to select the first mode based on the mode selection signal; and further still, controller 104 is configured to set input voltage signal 202 to 0V.

[0144] In one embodiment, analog circuitry 106 further includes a switchable pull-down load R7, 406 coupled to terminal 110 and switch 408. Controller 104 is configured to activate switchable pull-down load 406 based on a mode selection signal, particularly when the mode selection signal corresponds to a second mode (i.e., voltage mode). In one example, switch 408 is configured to connect switchable pull-down load 406 to ground when the mode selection signal corresponds to the second mode. If controller 104 provides a 3.3V mode selection signal, switchable pull-down load 406 is grounded. In one example, switchable pull-down load 406 may be configured to apply a pull-down bias to maintain a defined voltage level at terminal 110. Furthermore, switch 408 is connected to ground potential to ensure that the voltage at node F remains at a specified low level when no valid signal is applied at terminal 110. For example, activation of switchable pull-down load 406 is based on the selection of a second mode by the mode selector. A pull-down bias is applied to obtain a defined voltage at terminal 110 in voltage mode.

[0145] When the analog circuit 106 is not actively driving the analog output signal 206, the voltage level can be stabilized at a known reference point by establishing a ground connection and switching the pull-down load 406. This prevents undefined states from occurring, which could cause malfunctions in the HVAC field equipment 102.

[0146] In one example, the switchable pull-down load 406 can be implemented using a resistor or one or more transistors selected based on the required current consumption and the characteristics of the analog circuit 106. The resistance value associated with the switchable pull-down load 406 can be low enough to provide an effective path to ground, while the resistance value must be high enough to limit power consumption during the active state.

[0147] The switchable pull-down load 406 is configured to connect to the reference ground potential, thereby effectively pulling the voltage at node F down to a predetermined low level.

[0148] In an alternative embodiment, the switchable pull-down load 406 is implemented based on a current mirror configuration. When activated, the current mirror configuration generates a load-sinking bias current that, unlike the current drawn through a resistor pull-down configuration, remains substantially constant over a wide output voltage range. Figure 9A and Figure 9B The current mirror pull-down configuration is described in more detail.

[0149] Figure 5 This is an exemplary schematic diagram 500 of an analog circuit 106 according to an embodiment of the present disclosure. The analog circuit 106 may include voltage buffers U3, 502 for providing impedance transformation. Furthermore, the analog circuit 106 may include a third pair of resistors 506. The third pair of resistors 506 is connected in series to define a second node therebetween.

[0150] In one embodiment, voltage buffer 502 is positioned between terminal 110 and either the second pair of resistors 332 or the third pair of resistors 506. The primary purpose of the voltage buffer is to provide high input impedance, which offers several advantages. In current output mode, the output current (I2) is entirely transferred to external components, while the current flowing through the voltage divider is negligible, ensuring that the output current accurately follows the input signal due to the high input impedance of the voltage buffer. In voltage input mode, the high input impedance minimizes the load effect on the source, preventing it from outputting current exceeding the ideal value. Furthermore, in current input mode, the input impedance is determined solely by the shunt resistor (e.g., 500 ohms) used to convert the input current to voltage, and is unaffected by the resistance of the voltage divider.

[0151] In one embodiment, voltage buffer 502 may be a voltage buffer amplifier that includes an operational amplifier. This voltage buffer amplifier employs a stage with unity voltage gain, does not experience phase or polarity reversal, and acts as an ideal circuit with extremely high input impedance and low output impedance.

[0152] The output voltage of voltage buffer 502 can be equal to the input signal of voltage buffer 502 (e.g., analog output signal 206). When the output voltage of voltage buffer 502 is equal to the input signal of voltage buffer 502 (e.g., analog output signal 206), voltage buffer 502 can be designed as a unity-gain voltage buffer. The design of voltage buffer 502 can include an operational amplifier as a core component. This operational amplifier can be a high-gain differential amplifier with two inputs (one inverting input and one non-inverting input) and one output. The non-inverting input terminal can be coupled to the output of diode 330, while the inverting input terminal can receive the output signal of voltage buffer 502 as input. The output of voltage buffer 502 is connected at node J and can be adjusted to a voltage level to eliminate any voltage difference between the inverting and non-inverting input terminals of voltage buffer 502 due to the high open-loop gain of the operational amplifier.

[0153] The output signal of voltage buffer 502 can be coupled to a voltage divider circuit implemented using multiple resistors 116, thereby providing the signal required for further processing. The output of the voltage divider circuit can be connected, for example, via an ADC to a voltage feedback path or controller 104.

[0154] In one embodiment, analog circuit 106 may include a third pair of resistors 506 among a plurality of resistors 116. The third pair of resistors 506 includes resistor R. 10 506A and resistor R 11 506B. A third pair of resistors 506 are connected in series, thereby defining a second node therebetween. Furthermore, the third pair of resistors 506 is connected in parallel with the second pair of resistors 332. Additionally, the analog circuit 106 is configured to generate a second voltage output signal using the third pair of resistors 506 and based on the analog output signal 206. The second voltage output signal is generated at the second node. The analog circuit 106 is further configured to supply this second voltage output signal as an output voltage to the controller 104. Details associated with the analysis of the output voltage corresponding to this second voltage output signal will be discussed in conjunction with, for example... Figure 3 Provide a detailed description.

[0155] In one embodiment, the second pair of resistors 332 includes resistors R8, 504A and R9, 504B. In one embodiment, resistor 504A is similar to resistor 336, and resistor 504B is similar to resistor 338. In one embodiment, resistor 504A is coupled to the output of voltage buffer 502 at node J. Furthermore, resistor 504A is connected in series with resistor 504B, such that resistors 504A and 504B define a first node between them at node H. In one embodiment, mode selector 108 is coupled to the second pair of resistors 332 at the first node. For example, the connection between node H and mode selector 108 defines a second feedback path 404B. Furthermore, analog circuit 106 is configured to generate a first voltage output signal at the first node using the second pair of resistors 332 based on analog output signal 206. Furthermore, analog circuit 106 is configured to supply the first voltage output signal to the second feedback path 404B based on the selection of the second feedback path 404B by mode selector 108. In one embodiment, if the controller 104 is configured to generate a mode selection signal associated with the second mode, the analog circuit 106 is configured to adjust the voltage level associated with the second feedback path 404B to match the value of the input voltage signal 202.

[0156] The second voltage divider allows for different voltage ratios to be selected for the two output voltage signals, which can be customized to fit the second voltage to the ADC signal range. For example, the scaling factor at the first output can be 1:4, while the scaling factor at the second output can be 1:5. This flexibility in voltage scaling helps improve signal accuracy and overall system performance.

[0157] Figure 6 This is an exemplary schematic diagram 600 of an analog circuit 106 according to an embodiment of this disclosure. (The diagram will be combined with...) Figure 1 , Figure 2A , Figure 2B , Figure 3 , Figure 4 and Figure 5 Components Figure 6 Describe it.

[0158] In one embodiment, analog circuit 106 may be configured to operate not only in output mode to provide an analog output signal to an external component coupled via terminal 110, but also in input mode to receive an input signal from an external source at terminal 110. In input mode, analog circuit 106 may also be configured to operate in both current input mode and voltage input mode.

[0159] Diode 330 allows analog circuit 106 to use terminal 110 as an input terminal. Analog circuit 106 further includes a voltage conversion resistor 610 and an input selection switch 612 corresponding to a reference. Figure 2B The input mode selector 210 is described. In one embodiment, in current input mode, input selection switch 612 is configured to establish a current path between terminal 110 and GND (ground) via voltage conversion resistor 610. For example, input selection switch 612 may close when a control signal such as a high level (HIGH) (e.g., a 3.3V signal) is applied at terminal 614. In this case, current input mode is enabled, and an input current (e.g., 20mA) applied to terminal 110 flows through the 500Ω voltage conversion resistor 610, thereby generating a voltage (e.g., 10V) at node F, which can also be obtained at node G by the ADC. Conversely, when input voltage mode (e.g., a 0V signal) is selected, input selection switch 612 closes. The voltage at node F (e.g., 10V) can be obtained at node G by the ADC.

[0160] It is important to note that when the input mode is activated, the voltage input signal must be set to 0V, and current mode must be selected for two reasons: First, to prevent analog circuit 106 from compensating for the voltage caused by the input signal at terminal 110, which is the voltage intended for measurement; second, to disable the pull-down load (although...). Figure 6 (not shown in the image), thereby increasing the input impedance for signals input at terminal 110.

[0161] In a specific embodiment, the voltage conversion resistor 610 is a precision resistor, preferably a 500Ω resistor.

[0162] In a specific embodiment, controller 104 is configured to calibrate the output current using voltage-to-voltage conversion resistor 610 and accordingly determine the gain factor in current mode. In this embodiment, controller 104 is configured to, in current output mode, temporarily apply an input current enable signal (e.g., a 3.3V signal) at terminal 614 at input selection switch 612 for a given output current setpoint and corresponding voltage input signal, and then establish a parallel connection between voltage-to-voltage conversion resistor 610 and the load resistor (i.e., the resistance of the resistance temperature sensor). The parallel connection causes a voltage drop at terminal 110, and a corresponding voltage drop at node F, which can be obtained at node G via an ADC. This voltage drop can be used to calibrate the voltage input signal in current mode, and accordingly to determine the gain factor, so that the output current delivered in current mode corresponds to the expected value. In this specific embodiment, calibration is performed repeatedly. This is particularly useful when controller 104 is configured to use a resistance temperature sensor to measure temperature. In another embodiment, when the parallel connection is activated, at least one second current setpoint different from the first setpoint is applied for calibrating the output current and determining the gain factor.

[0163] In one embodiment, the HVAC field device 102 may include several advanced features to ensure reliable and safe operation under various conditions. Analog circuitry 106 is designed to be compatible with a digital bus via a high-impedance output, thereby minimizing current consumption and ensuring accurate signal transmission. Employing a precision voltage reference (e.g., a first reference voltage at the first node of the switching circuit with an initial accuracy of 0.1%) helps improve measurement stability and accuracy. In one embodiment, 0.1% or 25ppm resistors are used for critical components to ensure minimal drift and high accuracy.

[0164] Furthermore, the output circuitry is robust enough to withstand ±40 volts continuously without limitation. This resilience is achieved by selecting, for example, a diode 330, such that it can withstand up to 40V when a positive voltage is applied to the output, while the output transistor (e.g., the first transistor circuit 328) can withstand voltages higher than 40V under negative conditions. In some cases, additional protection can be provided by a 40V ESD (electrostatic discharge) diode.

[0165] In one embodiment, in voltage mode, the load resistor for external components can be completely omitted (open circuit), while in current mode, the output may be short-circuited without limitation without compromising system integrity. This flexibility enables safe operation in various scenarios while ensuring critical safety measures are in place to protect analog circuitry 106, HVAC field device 102, and external components connected to HVAC field device 102.

[0166] In one embodiment, an additional digital output is provided. In a specific embodiment, a current-sinking output is provided. The current-sinking output includes a switch, a terminal 606 for connecting to a power supply, and another terminal 604 for outputting a digital signal. Terminal 602 is coupled to switch 608. Furthermore, switch 608 is coupled to terminal 606 for connecting to a power supply. For example, the power supply can be a 24V DC or 24V AC power supply. However, other power supplies can also be connected.

[0167] In one example, analog circuit 106 may include one or more current sink outputs to allow selective activation or deactivation of external components, or to provide digital signals to external components.

[0168] Figure 7 A perspective view 700 shows an additional module associated with HVAC field device 102 according to an embodiment of this disclosure. (To be combined with...) Figure 1 , Figure 2A , Figure 2B , Figure 3 , Figure 4 , Figure 5 and Figure 6 Components Figure 7 Describe it.

[0169] HVAC field device 102 includes multiple stacked modules. The multiple stacked modules include a base module 702 and an add-on module 710. The base module 702 includes a housing 704, a motor and / or sensor, a connection interface 708, and electronic circuitry connected to the motor and / or sensor. The HVAC field device further includes one or more external electrical interfaces 706, 722. One or more external electrical interfaces 706, 722 may be included in the base module 702 and / or the add-on module. The motor is arranged within the housing 704 of the base module 702 to drive actuated components. In one example, if the electronic circuitry is connected to the motor, the electronic circuitry is configured to generate control signals for controlling the motor to implement one or more HVAC control functions.

[0170] According to embodiments of this disclosure, the sensor is located within the housing 704 of the base module 702. Furthermore, the sensor is coupled to electronic circuitry. The sensor of the base module 702 is configured to measure parameters of the HVAC system, particularly environmental parameters of the environment in which the HVAC system or HVAC field device 102 is located, such as the temperature and / or humidity of the indoor environment of a building controlled by the HVAC system, and / or the particulate matter (PM) and / or carbon dioxide (CO2) levels of the environment controlled by the HVAC system. Alternatively or additionally, the sensor of the base module 702 is provided for measuring operating parameters of various components of the HVAC system, such as the actuation position of actuated components and / or the operating state of the HVAC field device 102 and / or other parameters of the HVAC system (e.g., flow rate or differential pressure at the location of liquid in a fluid delivery system).

[0171] To meet the need for providing a variety of HVAC equipment in numerous different configurations without manufacturing a specific type of HVAC field equipment for every possible combination of functions and / or parameters, HVAC field equipment can be assembled by attaching an add-on module 710 to the connection interface 708 of the base module 702. The add-on module 710 can extend the functionality of the base module 702. However, to provide functionality not supported by either the base module 702 or the installed add-on module 710, an additional second connection interface can be added to the base module 702 to accommodate the second add-on module, thereby enabling additional functionality.

[0172] The add-on module 710 includes a housing 714, at least one circuit board 716, a first-type connection interface 718, a second-type connection interface 712, and optional one or more external electrical interfaces 722. As a mating component to the first-type connection interface 708 of the base module 702, the second-type connection interface 712 of the add-on module 710 is disposed on the bottom side of the housing 714. The first-type connection interface 708 of the base module 702 and the second-type connection interface 712 of the add-on module 710 are configured to be mechanically and electrically connected to each other.

[0173] The first type of connection interface 718 of the add-on module 710 is disposed on the first top side of the housing 714. By disposing of the complementary first type of connection interface 718 and the second type of connection interface 712 on the parallel and opposite sides of the housing 714 of the add-on module 710, multiple add-on modules can be stacked while maintaining a constant footprint / cross-section of the formed HVAC field device 102.

[0174] The one or more additional modules can implement one or more functional expansion devices. At least one board 716 of the additional module may include analog circuitry 106 and a controller 104 for providing software-configurable analog output terminals, thereby enabling selection of a current output mode or a voltage output mode in HVAC field equipment. In another preferred embodiment, at least one board includes software-configurable analog circuitry 106 for providing software-configurable input / output terminals, allowing the controller 104 to select a current output mode, a voltage output mode, a current input mode, a voltage input mode, or a resistance measurement input mode based on status data, sensor status data, or user input. This enables flexible interface connections with various HVAC system components.

[0175] The at least one circuit board 716 may include more than one analog circuit. It may include other processing devices, such as microcontrollers or application-specific integrated circuits (ASICs), for providing additional computing power to the HVAC field device 102. The controller 104 and / or processing devices may implement controller devices for advanced motor control or signal processing and / or for implementing HVAC control functions. One or more additional modules may also include communication devices implemented via the circuit board, including wired communication interfaces and / or radio communication devices for providing communication functions to the HVAC field device 102, as described above. Figure 1 The communication interface can be used for mode selection of the analog circuit 106 via a computing device, input by the user.

[0176] In a specific embodiment, the electronic circuitry of the base module 702 includes analog circuitry 106. This is particularly advantageous if no additional modules are provided.

[0177] In one example, if the input mode is selected, various signals can be received within the actuator using analog circuitry 106, such as analog position setpoints from an external controller (e.g., a building management system or field equipment) or measurements from sensors. Electronic circuitry (preferably interacting with a processor on board 716), if present, is configured to generate control signals for controlling the motor based on the received signals, thereby enabling one or more HVAC control functions.

[0178] In addition, analog circuitry 106 can be connected to passive sensors and receive digital signals. The electronic circuitry and / or processor on the circuit board can use the received signals to control the motor. If an output mode is selected, analog circuitry 106 can also output signals to other field devices (e.g., feedback signals indicating actuator position or internal control variables).

[0179] In another example, if the field device includes sensors, the analog circuit 106 is configured to output analog signals representing operating parameters of the HVAC system (e.g., temperature and / or humidity), or signals representing operating parameters of individual components of the HVAC system. The sensor signals are typically digitally preprocessed by the circuitry of the base module 702 and / or the processor of the board 716.

[0180] In one example, an external electrical interface 706 is located at the base module 702 and at the analog circuitry 106 on the circuit board 716 of the add-on module 710. The external electrical interface 706 of the base module 702 is electrically connected to the analog circuitry 106 on the circuit board 716 of the add-on module 710 via a connection interface between the base module 702 and the add-on module 710. This allows the analog circuitry 106 to be connected to external components, such as loads, sensors, actuators, or other field devices, via the external connection interface 706 of the base module 702. In another example, an external electrical interface 722 is located at the add-on module 710. The external electrical interface 722 is electrically connected to the analog circuitry 106 and allows the analog circuitry 106 to be connected to external components via a corresponding connector 724. The corresponding connector may include a direct connector (e.g., a RAST connector) to enable a direct, solderless connection to the terminals 110 of the analog circuitry on the circuit board 716. In another example, analog circuitry 106 is located at base module 702, and external electrical interface 706 at base module 702 is electrically connected to analog circuitry 106, thereby allowing analog circuitry 106 to be connected to external components. The modules of HVAC field device 102 are configured to be powered by an external power source, for example, by using one of external connection interfaces 706 or 722.

[0181] To prevent connection interfaces from being exposed when modules are stacked, a cover module is provided. This cover module may include a housing and a second type of connection interface. To cover the first type of connection interface of the outermost add-on module, the cover module is stacked on top of the outermost add-on module, thereby mechanically and preferably also electrically connecting the second type of connection interface of the cover module to the first type of connection interface of the outermost add-on module. The term "outermost" should be understood as an HVAC equipment block having exposed (i.e., not covered by the corresponding connection interface of another add-on module to which it is attached) connection interfaces.

[0182] Subsequently, the cover module may accommodate or include a circuit board. This circuit board may include a controller 104 and / or analog circuitry 106. The cover module may further include a human-machine interface (HID). The circuit board may be electrically connected via a connection interface to the electronic circuitry of one or more of the additional modules and / or the electronic circuitry 106 of the base module 702. Specifically, the HID may be connected to the controller 104, which in turn is further connected to the analog circuitry 106. In one example, the HID is configured to display status data. The status data may indicate connection data, which indicates the connection status of external components. In some cases, the HID may display connection parameters of the HVAC field device 102. Including the HID as part of the cover module is advantageous because, after the HVAC field device 102 is assembled, the cover module is the outermost block and provides access to the HID. The HID is configured to control and / or display one or more of the operating parameters of the HVAC field device 102 (or one or more HVAC device blocks comprising it) and / or the operating parameters of the HVAC system measured by sensors.

[0183] Figure 8 A schematic diagram of the cover module 800 of the analog circuit 106 of an HVAC field device 102 according to an embodiment of the present disclosure is shown. (To be combined with...) Figure 1 , Figure 2A , Figure 2B , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 Components Figure 8 Describe it.

[0184] In one embodiment, the HVAC field device 102 may include a cover module 800 designed to protect and support various internal components. Analog circuitry 106 may be implemented on a printed circuit board (PCB), which serves as the basis for the circuitry's functionality. The controller 104 may also be implemented on a PCB. The cover module 800 provides isolation protection for the PCB of the analog circuitry 106, shielding it from external environmental influences and ensuring stable operation under various conditions. The cover module 800 is designed to house or rivet the PCB of the analog circuitry 106 in the correct position, preventing movement that could disrupt connections or functionality. Furthermore, the cover module 800 may incorporate a configurable snap-fit ​​structure for seamless attachment to the HVAC field device 102. This feature enhances installation flexibility and facilitates assembly and disassembly when maintenance or upgrades are required. The analog circuitry 106 may be connected to other components of the HVAC field device 102 (e.g., external components) via one or more terminals, either immediately upon cover attachment or prior to attachment to the housings 704, 714 of the base module 702 or additional modules.

[0185] Figure 9A and Figure 9B Exemplary circuit diagrams 900A and 900B are shown respectively, illustrating the analog circuitry 106 of an HVAC field device 102 according to embodiments of this disclosure. (The last sentence appears to be incomplete and possibly refers to a separate topic.) Figure 1 , Figure 2A , Figure 2B , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 Components Figure 9A Describe it.

[0186] refer to Figure 9A and Figure 9B The analog circuit 106 includes a switching circuit 902 and a two-stage PWM low-pass filter 904. The switching circuit 902 includes multiple input nodes, an output node connected to the two-stage PWM low-pass filter 904, and a control input node coupled to the controller 104 via an input terminal 208 to receive an input voltage signal 202 as a control signal. A first input node of the multiple input nodes is connected to a first reference voltage, and a second input node of the multiple input nodes is connected to a second reference voltage. The switching circuit 902 is configured to switch between the first reference voltage and the second reference voltage based on the control signal. In one example, the first reference voltage may correspond to a 3.3V reference voltage, while the second reference voltage is grounded. The switching circuit 902 is configured to switch between the first reference voltage and the second reference voltage based on the control signal.

[0187] In one example, if the amplitude of the input voltage signal 202 received from the controller 104 (i.e., the input voltage signal 202 in Figure 2) fluctuates due to power supply instability, or if the input voltage signal 202 is noisy, the switching circuit 902 can still generate an accurate PWM signal.

[0188] In one embodiment, the switching circuit 902 may correspond to a multiplexer. A control input node may correspond to a select line of the multiplexer. The control input node selects which of a plurality of input nodes will output at the output node. For example, the control input node is coupled to a controller 104. The controller 104 is configured to provide control signals to the control input node of the switching circuit 902.

[0189] Furthermore, the PWM low-pass filter 904 can convert the PWM signal at the output of the switching circuit 902 into a smooth voltage signal with reduced ripple (e.g., less than 1 millivolt). In one embodiment, both the first stage 112 and the second stage 114 of the analog circuit 106 can be implemented using bipolar Darlington transistors. For example, the first transistor circuit 916 of the second stage 114 may include or be composed of a first Darlington transistor, while the second transistor circuit 912 of the first stage 112 may include or be composed of a second Darlington transistor. The use of bipolar Darlington transistors is advantageous because they provide high current gain, which is crucial for effective signal amplification in the analog circuit 106. This configuration allows for improved performance while maintaining a compact design. Furthermore, the use of bipolar Darlington transistors helps reduce the overall cost associated with the analog circuit 106. Additionally, the inherent characteristics of bipolar Darlington transistors (e.g., their ability to handle higher currents and voltages) contribute to the robustness and reliability of the analog circuit 106. For example, in some cases, transistor circuits 912 and 916 can be implemented using MOSFETs instead of Darlington transistors.

[0190] Furthermore, the first stage 112 and the second stage 114 of the analog circuit 106 are shared in two modes (i.e., current mode and voltage mode) to generate the desired analog output signal.

[0191] In one embodiment, analog circuit 106 includes a current-limiting function to improve safety and reliability. Key components such as current-sensing resistors, operational amplifiers, Zener diodes, and transistors work together to monitor and regulate current flow. Specifically, in voltage mode, the current is limited to less than 25mA to prevent potential short-circuit conditions. This ensures that the circuit continues to operate without damage under fault conditions. In current mode, the output voltage is limited in the event of an open circuit.

[0192] Analog circuit 106 includes a switchable pull-down load 906 comprising a current mirror configuration, which includes an input transistor and an output transistor. The base and collector of the input transistor are coupled to terminal 308 via an input resistor Rin, which is also coupled to mode selector 108. In this example, the pull-down load is configured to be activated when the mode select signal is provided at a high level (HIGH) (e.g., 3.3V at terminal 308), thereby generating a reference current I through the input resistor. ref The base (or gate) voltage of the input transistor is mirrored to the base (or gate) of the second transistor, thereby ensuring that the output transistor conducts a similar current. (As shown in the example, according to...) Figure 5 The current drawn down by the load through the resistor is different from that of the load, which absorbs a bias current that remains essentially constant over a wide output voltage range.

[0193] In one embodiment, a ground terminal 908 is incorporated to provide a stable ground connection to the analog circuit 106. The ground terminal 908 establishes a common return path for current, thereby allowing the various components within the analog circuit 106 to operate normally.

[0194] In one embodiment, a Zener diode is used to generate a reference voltage signal (V). ref A Zener diode is used to provide a stable voltage reference. Using a Zener diode generates an accurate reference voltage, which is crucial for maintaining the stability and accuracy of analog circuits. In this case, a reference voltage with an accuracy of 0.1% is used to enhance the overall stability of analog circuit 106. In some cases, analog circuit 106 is powered by a single supply (even an unregulated one) while still maintaining high accuracy defined by multiple resistors 116.

[0195] In one example, a Zener diode generates a first reference voltage and / or a second reference voltage. In one example, the first reference voltage is 0V and the second reference voltage is 3V. The stability of the reference voltage signal is crucial in applications requiring precise voltage levels for signal processing, amplification, or other functions.

[0196] In addition, an artificial bias is introduced by a resistor 914 connected between the first negative input terminal of the first amplifier circuit 326 and GND, so that the output current is always 0mA when the input voltage is always 0 volts.

[0197] refer to Figure 9BTerminal 614 is connected to a low-pass filter, which is further connected to an input selection switch 612. In one embodiment, the controller 104 may be configured to provide a control signal at terminal 614, which is then provided to the low-pass filter. The low-pass filter ensures that any fluctuations in the control signal received from the controller are smoothed, thereby contributing to improved stability and accuracy of the voltage conversion process. Additionally, the control signal is provided to the input selection switch 612. The input selection switch 612 is configured to connect the voltage conversion resistor 610 to ground based on the control signal. When the controller 104 sends a control signal to the input selection switch 612 via terminal 614, a current input mode is activated. In this mode, an input current (e.g., 20mA) applied to terminal 110 flows through the voltage conversion resistor 610, which has a resistance of 500Ω. As a result, this configuration produces a voltage of approximately 10V at node F. Further details are provided in conjunction with… Figure 6 It has been described.

[0198] Although not shown, analog circuit 106 can be implemented using discrete components. In other words, the electronic subcircuit can consist of a set of individual electronic components instead of using integrated circuits (ICs), which form all electronic components on a single silicon chip.

[0199] Figure 10 This is a flowchart 1000 of a method for generating an analog output signal 206 using analog circuit 106 according to an embodiment of the present disclosure. (The last sentence appears to be incomplete and possibly refers to a separate topic.) Figure 1 , Figure 2A , Figure 2B , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9A and Figure 9B Components Figure 10 Provide a description. (See reference.) Figure 10 The diagram illustrates flowchart 1000. The operations of the exemplary flowchart can be performed by HVAC field device 102. The operation of flowchart 1000 can begin from step 1002.

[0200] In step 1002, an input voltage signal 202 is generated. In one embodiment, the controller 104 of the HVAC field device 102 is configured to generate the input voltage signal 202. In one example, the input voltage signal 202 may correspond to a PWM signal generated using switching circuitry and / or a digital-to-analog converter (DAC).

[0201] In step 1004, an input voltage signal 202 is provided to the analog circuit 106. In one embodiment, an input terminal 208 is coupled to a first stage 112 of the analog circuit 106. The input voltage signal 202 is provided to the input terminal 208 of the analog circuit 106. In one example, the analog circuit 106 may be configured to receive the input voltage signal 202 at the input terminal 208. Furthermore, the analog circuit 106 includes a first stage 112, a second stage 114 coupled to the first stage 112, and a plurality of resistors 116, each of which is coupled to at least one of the first stage 112 and the second stage 114, providing a mode selection signal to the analog circuit 106.

[0202] In step 1006, one of a first mode or a second mode is selected. In one embodiment, the HVAC field device 102 is configured to select either a first mode or a second mode for the operation of the analog circuit 106. For example, the controller 104 is configured to generate a mode selection signal. The mode selection signal is associated with one of the first mode or the second mode. For example, the first mode may correspond to a current mode, and the second mode may correspond to a voltage mode. In one example, in the first mode, the controller 104 can generate the mode selection signal by providing a 0V signal. Conversely, in the second mode, the controller 104 is configured to generate the mode selection signal by providing a 3.3V signal.

[0203] In step 1008, an intermediate current is generated based on the input voltage signal 202 and the selection of a first mode or a second mode. In one embodiment, the first stage 112 of the analog circuit 106 is configured to generate an intermediate current 204 based on the input voltage signal 202 and one of the selected first mode and second mode.

[0204] In step 1010, a second stage 114 is used to generate an analog output signal 206. In one embodiment, the HVAC field device 102 is configured to generate the analog output signal 206 based on an intermediate current 204, such that the intermediate current 204 is multiplied by a predefined ratio to define the analog output signal 206. In another embodiment, the second stage 114 is configured to generate the analog output signal 206 such that the intermediate current 204 is multiplied by a predefined ratio to define the analog output signal 206. The predefined ratio is associated with a first pair of resistors, namely R1 / R2, which includes a first resistor R1, 322 and a second resistor R2, 324.

[0205] In one example, in the first mode, the gain factor of the analog circuit corresponds to the ratio of the value of the analog output signal 206 to the value of the input voltage signal 202. In the first mode, the gain factor is associated with a first group of resistors among a plurality of resistors 116. Furthermore, the first group of resistors includes a first resistor R1, 322, a second resistor R2, 324, and a current feedback resistor R3, 318. Here, the gain factor corresponds to the ratio of the product of the first resistor and the second and third resistors, i.e., R1 / R3*R2. The transconductance gain of the first stage corresponds to the reciprocal of the resistance value of the third resistor, 1 / R3, and the predefined ratio R1 / R2 of the second stage.

[0206] In another example, the gain factor in the second mode is associated with a second group of resistors among a plurality of resistors 116. Furthermore, the second group of resistors includes resistors R5, 336 and R6, 338. Here, the gain factor corresponds to the ratio of the sum of resistors R5 and R6 to resistor R6, i.e., (R5 + R6) / R6. The second group of resistors, including resistors R5 and R6, is independent of the first group of resistors, including R1, R2, and R3. Due to the direct feedback of the third voltage, the gain factor associated with the second mode is independent of the predefined ratio of the second mode.

[0207] In step 1012, an analog output signal 206 is provided at terminal 110. In one embodiment, the HVAC field device 102 is configured to provide an analog output signal 206 at an input / output (I / O) terminal (i.e., terminal 110). In one example, a second stage 114 may be configured to provide an analog output signal 206 at terminal 110. Furthermore, external components are coupled to the analog circuitry 106 at terminal 110.

[0208] Therefore, each block of flowchart 1000 supports both combinations of various devices for performing a specified function and combinations of various operations for performing a specified function.

[0209] In one embodiment, the HVAC field device 102 may include means for performing each of the operations described above. In this regard, according to an example embodiment, examples of means for performing the operations may include, for example, devices or circuitry for executing instructions or performing methods for processing information as described above.

[0210] Many modifications and other embodiments of the present invention will be apparent to those skilled in the art upon reference to the teachings provided in the foregoing description and accompanying drawings. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, and that various modifications and other embodiments should be included within the scope defined by the appended claims. Furthermore, although exemplary embodiments have been described in the foregoing description and accompanying drawings in the context of certain exemplary combinations of reactants and / or functions, it should be understood that alternative embodiments may provide different combinations of reactants and / or functions without departing from the scope defined by the appended claims. In this regard, for example, the present invention covers other combinations of reactants and / or functions beyond those explicitly described above, which may be outlined in some of the appended claims. Although specific terminology is used herein, it is for general and descriptive purposes only and not for limitation.

Claims

1. A heating, ventilation, and air conditioning (HVAC) field device, comprising: Controller; An analog circuit coupled to the controller, the analog circuit being configured to receive an input voltage signal, and the analog circuit comprising: Level 1 The second stage, which is coupled to the first stage, and A plurality of resistors, wherein each of the plurality of resistors is coupled to at least one of the first stage or the second stage; A mode selector, coupled to the analog circuit, is configured to select one of a first mode or a second mode; and Terminals, which are coupled to the analog circuit, wherein, The first stage is configured to generate an intermediate current based on the input voltage signal and the selection of either the first mode or the second mode. The second-level configuration generates an analog output signal by multiplying the intermediate current by a predefined ratio, wherein the predefined ratio is associated with one or more of the plurality of resistors, and The terminal is configured to receive the analog output signal from the analog circuit.

2. The HVAC field device according to claim 1, wherein, The first mode is a current mode and the second mode is a voltage mode.

3. The HVAC field device according to claim 1, wherein, The gain factor of the analog circuit is associated with a first set of resistors in the first mode and with a second set of resistors in the second mode, wherein the first set of resistors and the second set of resistors do not contain each other.

4. The HVAC field device according to claim 1, wherein, The analog circuit further includes a feedback circuit coupled to the mode selector, the feedback circuit including a first feedback path associated with the first mode and a second feedback path associated with the second mode, and The mode selector is configured to select either the first feedback path or the second feedback path based on the selection of either the first mode or the second mode.

5. The HVAC field device according to claim 1, wherein, The analog circuit is dynamically configured to operate in (i) an input mode, such that the analog circuit is configured to receive an input signal from an external component via the terminal, or in (ii) an output mode, such that the analog circuit is configured to supply the analog output signal to an external component via the terminal.

6. The HVAC field device according to claim 5, wherein, The external component is a passive sensor. The analog circuit is configured to supply bias current to the passive sensor through the terminal, and The controller is further configured to determine resistance data associated with the passive sensor and to determine temperature data based on the determined resistance data.

7. The HVAC field device according to claim 6, wherein, The controller is further configured to pulse-modulate the bias current supplied to the passive sensor to reduce the average current and prevent the passive sensor from self-heating.

8. The HVAC field device according to claim 1, wherein, The second-stage configuration is a current multiplier configuration and includes a first amplifier circuit and a first transistor circuit.

9. The HVAC field device according to claim 8, wherein, The second level further includes: The first resistor of the plurality of resistors is coupled to the positive terminal of the first amplifier circuit to form a first path for the intermediate current. The second resistor of the plurality of resistors is coupled to a terminal of the first transistor circuit to form a second path in parallel with the first path for the analog output signal. The feedback path is configured to keep the voltage across the second path substantially equal to the voltage across the first path.

10. The HVAC field device according to claim 1, wherein, The first stage is configured as a current sink and includes a second amplifier circuit and a second transistor circuit.

11. The HVAC field device according to claim 1, wherein, The controller further includes an analog-to-digital converter (ADC), and the controller is further configured to: A digital signal is generated using the ADC based on the voltage at the terminal; and Status data is determined based on the digital signal, wherein the status data corresponds to at least one of fault data, connection data, or resistance data.

12. The HVAC field device according to claim 11, wherein, The controller is configured to automatically generate a mode selection signal based on determined state data or user input, and supply the mode selection signal to the mode selector.

13. The HVAC field device according to claim 11, wherein, The controller is configured to determine whether a digital bus exists at the terminal when the digital signal indicates a voltage level exceeding a predefined threshold, and wherein the controller is further configured to generate a mode selection signal to select the first mode in response to the determination of the existence of the digital bus.

14. The HVAC field device according to claim 1, wherein, The plurality of resistors includes a second pair of resistors connected in series to define a first node therebetween, and wherein the analog circuit is further configured to supply a first voltage output signal from the first node to the controller.

15. The HVAC field device according to claim 14, wherein, The plurality of resistors further includes a third pair of resistors connected in series to define a second node therebetween, and wherein the analog circuit is further configured to generate a second voltage output signal at the second node and supply the second voltage output signal to the controller.

16. The HVAC field device of claim 1, further comprising a switching circuit having a first input node connected to a first reference voltage and a second input node connected to a second reference voltage, wherein, The switching circuit is configured to generate the input voltage signal by switching between the first reference voltage and the second reference voltage based on a control signal received from the controller.

17. The HVAC field device of claim 1, further comprising at least one voltage divider circuit and a voltage buffer located between the terminal and the at least one voltage divider circuit, wherein, The voltage buffer is configured to provide a high input impedance to the at least one voltage divider circuit.

18. The HVAC field device according to claim 1, wherein, The analog circuit further includes a switchable pull-down load coupled to the terminal, wherein the switchable pull-down load is configured to apply a pull-down bias based on the selection of the second mode by the mode selector.

19. The HVAC field device according to claim 1, wherein, The analog circuit further includes a voltage conversion resistor, and the controller is further configured to perform a calibration procedure in the first mode in such a way that: Temporarily activate the input current mode to connect the voltage conversion resistor in parallel with an external component coupled to the terminal; Measure the voltage drop across the parallel connection; and The input voltage signal is adjusted based on the measured voltage drop to calibrate the analog output signal.

20. A method for use in a heating, ventilation, and air conditioning (HVAC) field device, the method comprising: Generate input voltage signal; The input voltage signal is provided to the analog circuit; Select one of the first mode or the second mode for the operation of the analog circuit; An intermediate current is generated based on the input voltage signal and the selection of one of the first mode or the second mode; An analog output signal is generated based on the intermediate current by multiplying the intermediate current by a predefined ratio, wherein the predefined ratio is associated with one or more resistors among a plurality of resistors; and Provide the analog output signal.

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