Self-adaptive current output circuit

Abstract

The utility model provides a self-adaptive current output circuit. The self-adaptive current output circuit comprises a current control module, a wire system monitoring module and a current output protection module, the front end of the current control module is configured to be used for receiving PWM signals sent by the MCU, the tail end of the current control module is connected with the wire system monitoring module, the wire system monitoring module is connected with the MCU, one end of the current output protection module is connected with the current control module and the wire system monitoring module, and the other end of the current output protection module is connected with an external sensor; the MCU collects the voltage value of the output end of the wire system monitoring module, and outputs a two-wire system current signal or a three-wire system current signal through the current output protection module. The self-adaptive current output circuit provided by the utility model can automatically use a wiring mode of a user to transmit a corresponding current signal without setting of the user.

Description

Technical Field

[0001] This utility model belongs to the field of current output circuit technology, and in particular relates to an adaptive current output circuit. Background Technology

[0002] In industrial automation and control systems, the standardization of signal transmission is crucial for effective communication between devices. 4-20mA and 0-20mA are two commonly used current signal standards, widely used in signal transmission between sensors and actuators. The selection and use of these signals directly affect the system's performance, reliability, and maintenance costs.

[0003] The 4-20mA signal is a standard current signal, commonly used for sensor output. Its design philosophy is to use 4mA as the sensor's minimum value (e.g., zero point) and 20mA as the sensor's maximum value (e.g., full scale). The main advantages of this signal include: strong anti-interference capability; because the signal is current rather than voltage, it is less affected by cable length and resistance. Fault detection: If the signal is below 4mA, it usually indicates a sensor fault or disconnection, facilitating timely maintenance. The 0-20mA signal is also a current signal, with 0mA representing the sensor's minimum value and 20mA representing the maximum value. Its advantages include: ease of use: in some applications, 0mA can indicate the device's off state, making it easy to understand and operate.

[0004] Two-wire transmission uses only two wires for signal transmission: one for power supply and the other for signal transmission. Its advantages include: simplified wiring (requiring only two wires, reducing installation costs and complexity), and suitability for long-distance transmission (using current signals, suitable for long-distance transmission and reducing signal attenuation). Three-wire transmission uses three wires for signal transmission, typically two for power supply and signal transmission, and one for signal return. Its advantages include: improved accuracy (reducing signal errors caused by power supply voltage variations, ensuring signal accuracy), and suitability for complex systems (more common in applications requiring higher precision and stability). 4-20mA and 0-20mA signals play important roles in industrial control. The choice between two-wire and three-wire systems depends on specific application requirements and system complexity. Two-wire systems are suitable for simple, cost-sensitive applications, while three-wire systems are suitable for applications requiring higher precision and stability.

[0005] Currently available sensors are mostly single-output types, either two-wire 4~20mA or three-wire 0~20mA. They cannot simultaneously provide compatible output for both two-wire and three-wire systems. This causes great inconvenience to engineering designers, who need to select and purchase different types of sensors in advance to adapt to the actual application and field conditions. Utility Model Content

[0006] In view of this, the present invention aims to propose an adaptive current output circuit to solve the problem that the same sensor does not have compatible output for two-wire and three-wire systems, which causes great inconvenience to engineering designers.

[0007] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0008] This utility model provides an adaptive current output circuit, including a current control module, a wired monitoring module, and a current output protection module;

[0009] The front end of the current control module is configured to receive PWM signals from the MCU, and its end is connected to the wire monitoring module, which is connected to the MCU. One end of the current output protection module is connected to both the current control module and the wire monitoring module, and the other end is connected to an external sensor.

[0010] The MCU acquires the voltage value at the output terminal of the wired monitoring module and outputs a two-wire current signal or a three-wire current signal through the current output protection module.

[0011] Furthermore, the line monitoring module includes a first operational amplifier. The non-inverting input terminal of the first operational amplifier is grounded through a first resistor. The inverting input terminal of the first operational amplifier is connected to the terminal resistor of the current control module through a second resistor and to its output terminal through a third resistor. The output terminal of the first operational amplifier is grounded through two series resistors. The two series resistors are connected to the MCU through a line.

[0012] The power supply terminal of the first operational amplifier is connected to a power source, and its power supply terminal is also grounded through the first capacitor.

[0013] Furthermore, the output of the first operational amplifier is connected to a first switching transistor via a third resistor. The first end of the first switching transistor is connected to floating ground, and the second end of the first switching transistor is connected to analog ground.

[0014] Furthermore, the first switching transistor is an N-type MOSFET.

[0015] Furthermore, the current output protection module includes a fuse and a diode connected together. The fuse is connected to the terminal resistor of the current control module, and the cathode of the diode is connected to an external sensor.

[0016] Furthermore, the current control module includes a second operational amplifier, a third operational amplifier, and a second switching transistor;

[0017] The non-inverting input terminal of the second operational amplifier is connected to the output terminal of the third operational amplifier through a fourth resistor, the inverting input terminal of the second operational amplifier is grounded through a fifth resistor, and the output terminal of the second operational amplifier is connected to the first terminal of the transistor through a sixth resistor.

[0018] The non-inverting input terminal of the second operational amplifier is also grounded through a seventh resistor, and a second capacitor is connected in parallel across the two ends of the seventh resistor;

[0019] The inverting input of the second operational amplifier is also connected to the first resistor and the fuse respectively through an eighth resistor, and a second capacitor is connected in parallel across the two ends of the eighth resistor;

[0020] The non-inverting input of the third operational amplifier is connected to the MCU through a low-pass filter circuit, and the inverting input of the third operational amplifier is connected to its output.

[0021] The third terminal of the second switching transistor is connected to the first resistor, the eighth resistor, and the fuse through two series resistors, respectively. A Zener diode is also provided between the first terminal and the third terminal of the second switching transistor.

[0022] Furthermore, the second switching transistor is an NPN transistor.

[0023] Compared with the prior art, the adaptive current output circuit of this utility model has the following advantages:

[0024] The adaptive current output circuit described in this utility model employs a clever circuit design. By setting up a current control module, a wiring monitoring module, a current output protection module, and an MCU connected together, the MCU can determine whether the system is two-wire or three-wire and can automatically switch the corresponding circuit for current control. This control method does not require user settings and can automatically adapt to the user's wiring method and transmit the corresponding current signal. At the same time, it can effectively reduce engineering procurement costs, improve the redundancy of design errors for engineers, and reduce the probability of errors by on-site personnel. Attached Figure Description

[0025] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0026] Figure 1 This is a schematic diagram of an adaptive current output circuit according to an embodiment of the present invention. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Please see Figure 1 As shown, this embodiment provides an adaptive current output circuit, including a current control module, a line monitoring module, and a current output protection module;

[0030] The front end of the current control module is configured to receive PWM signals from the MCU (the MCU used in this embodiment is an HC32L196KCTA microcontroller), and its end is connected to the wire monitoring module. The wire monitoring module is connected to the MCU. One end of the current output protection module is connected to both the current control module and the wire monitoring module, and the other end is connected to an external sensor.

[0031] The MCU acquires the voltage value at the output of the wired monitoring module and outputs a two-wire or three-wire current signal through the current output protection module.

[0032] Specifically, in this embodiment, the present application employs a clever circuit design. By setting up a current control module, a wiring monitoring module, a current output protection module, and a microcontroller (MCU) connected together, the MCU can determine whether the system is two-wire or three-wire and can automatically switch the corresponding circuit for current control. This control method does not require user settings and can automatically adapt to the user's wiring method and transmit the corresponding current signal. At the same time, it can effectively reduce engineering procurement costs, improve the redundancy of design errors for engineers, and reduce the probability of errors by on-site personnel.

[0033] In some implementations, the wired monitoring module includes a first operational amplifier U10. The non-inverting input of the first operational amplifier U10 is grounded through a first resistor R78. The inverting input of the first operational amplifier U10 is connected to the terminal resistor R72 of the current control module through a second resistor R81 and to its output through a third resistor R83. The output of the first operational amplifier U10 is grounded through two series resistors (including R79 and R80). The two series resistors are connected to the PA01 / SEG22 pin of the MCU through a line.

[0034] The power supply terminal of the first operational amplifier U10 is connected to a 24V power supply, and its power supply terminal is also grounded through the first capacitor C66.

[0035] The output of the first operational amplifier U10 is also connected to the first switching transistor Q9 through the third resistor R82. The first switching transistor Q9 is an N-type MOS transistor. The drain of the first switching transistor Q9 is connected to the floating ground FGND, and the source of the first switching transistor Q9 is connected to the analog ground AGND.

[0036] Specifically, in this embodiment, the voltage amplitude at the lower end of resistor R72 can be determined according to the wiring method of the entire system. When the system is a three-wire wiring method, the lower end of resistor R72 is positive, and operational amplifier U10 will output 0V. After the microcontroller MCU collects this voltage, it can determine that it is a three-wire wiring method. When the system is a two-wire wiring method, the lower end of resistor R72 is negative, and operational amplifier U10 will output positive voltage. After the microcontroller MCU collects this voltage, it can determine that it is a two-wire wiring method. Based on the above method, the corresponding circuit can be switched autonomously for current control.

[0037] When the system is connected in a two-wire configuration, the operational amplifier U10 outputs a positive voltage, and the NMOS transistor Q9 is in the on state. At this time, the FGND and AGND of the NMOS transistor Q9 are grounded at the same point. When the system is connected in a three-wire configuration, the operational amplifier U10 outputs a 0V voltage, and the NMOS transistor is in the off state. At this time, the FGND and AGND of the NMOS transistor Q9 are not grounded at the same point.

[0038] In some implementations, the current output protection module includes a fuse F6 and a diode D16 connected together. The fuse F6 is connected to the terminal resistor R72 of the current control module, and the cathode of the diode D16 is connected to an external sensor.

[0039] Specifically, in this embodiment, IOUT- serves as the current output pin, connected to an external sensor. When the signal is determined to be two-wire, the IOUT- pin is connected to the negative power supply, outputting a two-wire 4~20mA signal; when the signal is determined to be three-wire, the IOUT- pin is connected to the signal line, outputting a 0~20mA signal.

[0040] In some implementations, the current control module includes a second operational amplifier U9A, a third operational amplifier U9B, and a second switching transistor Q8;

[0041] The non-inverting input of the second operational amplifier U9A is connected to the output of the third operational amplifier U9B through the fourth resistor R66. The inverting input of the second operational amplifier U9A is grounded through the fifth resistor R64. The output of the second operational amplifier U9A is connected to the first terminal of the transistor Q8 through the sixth resistor R63.

[0042] The non-inverting input of the second operational amplifier U9A is also grounded through the seventh resistor R71, and the second capacitor C64 is connected in parallel across the two ends of the seventh resistor R71.

[0043] The inverting input of the second operational amplifier U9A is also connected to the first resistor R81 and the fuse F6 through the eighth resistor R73. The second capacitor C65 is connected in parallel across the eight resistor R73.

[0044] The non-inverting input of the third operational amplifier U9B is connected to the PA04 / SEG19 pin of the MCU through a low-pass filter circuit (composed of R67, R68, R69, C62, and C63), and the inverting input of the third operational amplifier U9B is connected to its output.

[0045] The second switching transistor Q8 is an NPN transistor. The emitter of the second switching transistor Q8 is connected to the first resistor R81, the eighth resistor R73 and the fuse F6 through two series resistors (including R70 and R72). A Zener diode DZ1 is also provided between the base and the emitter of the second switching transistor Q8 (the anode of the Zener diode DZ1 is connected to resistors R70 and R71, and the cathode is connected to the base).

[0046] Specifically, in this embodiment, IDA_OUT is a digital PWM waveform signal sent by the MCU. After low-pass filtering by R67, C62, R68, and C63, the digital signal sent by the MCU can be converted into an analog signal. Combined with the voltage follower of operational amplifier U9B, a voltage control is performed on pin 3 of operational amplifier U91A. By sampling the current of R72, the sampled voltage is fed back to the non-inverting and inverting inputs of operational amplifier U91A through R71 and R73. At this time, operational amplifier U91A controls the current required for stable output of transistor Q8.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model.

[0048] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An adaptive current output circuit, characterized in that: It includes a current control module, a wired monitoring module, and a current output protection module; The front end of the current control module is configured to receive PWM signals from the MCU, and its end is connected to the wire monitoring module, which is connected to the MCU. One end of the current output protection module is connected to both the current control module and the wire monitoring module, and the other end is connected to an external sensor. The MCU acquires the voltage value at the output terminal of the wired monitoring module and outputs a two-wire current signal or a three-wire current signal through the current output protection module. The line monitoring module includes a first operational amplifier. The non-inverting input terminal of the first operational amplifier is grounded through a first resistor. The inverting input terminal of the first operational amplifier is connected to the terminal resistor of the current control module through a second resistor and to its output terminal through a third resistor. The output terminal of the first operational amplifier is grounded through two series resistors. The two series resistors are connected to the MCU through a line.

2. The adaptive current output circuit according to claim 1, characterized in that: The power supply terminal of the first operational amplifier is connected to a power source, and its power supply terminal is also grounded through the first capacitor.

3. The adaptive current output circuit according to claim 1, characterized in that: The output of the first operational amplifier is also connected to a first switching transistor via a third resistor. The first end of the first switching transistor is connected to floating ground, and the second end of the first switching transistor is connected to analog ground.

4. The adaptive current output circuit according to claim 3, characterized in that: The first switching transistor is an N-type MOSFET.

5. The adaptive current output circuit according to claim 1, characterized in that: The current output protection module includes a fuse and a diode connected together. The fuse is connected to the terminal resistor of the current control module, and the cathode of the diode is connected to an external sensor.

6. The adaptive current output circuit according to claim 5, characterized in that: The current control module includes a second operational amplifier, a third operational amplifier, and a second switching transistor; The non-inverting input terminal of the second operational amplifier is connected to the output terminal of the third operational amplifier through a fourth resistor, the inverting input terminal of the second operational amplifier is grounded through a fifth resistor, and the output terminal of the second operational amplifier is connected to the first terminal of the second switching transistor through a sixth resistor. The non-inverting input terminal of the second operational amplifier is also grounded through a seventh resistor, and a second capacitor is connected in parallel across the two ends of the seventh resistor; The inverting input of the second operational amplifier is also connected to the first resistor and the fuse respectively through an eighth resistor, and a second capacitor is connected in parallel across the two ends of the eighth resistor; The non-inverting input of the third operational amplifier is connected to the MCU through a low-pass filter circuit, and the inverting input of the third operational amplifier is connected to its output. The third terminal of the second switching transistor is connected to the first resistor, the eighth resistor, and the fuse through two series resistors, respectively. A Zener diode is also provided between the first terminal and the third terminal of the second switching transistor.

7. The adaptive current output circuit according to claim 6, characterized in that: The second switching transistor is an NPN transistor.

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