Low-cost closed-loop analog quantity output module

Abstract

The utility model discloses a low-cost closed-loop analog quantity output module, which relates to the field of analog quantity output modules and comprises a single chip microcomputer, a low-pass filter circuit, a voltage regulation amplifying circuit, a voltage and current conversion circuit and a feedback circuit. The low-pass filter circuit is used for filtering an input signal output by a single chip microcomputer and transmitting the input signal to the voltage regulation amplification circuit and the voltage-current conversion circuit, the voltage regulation amplification circuit outputs a voltage output signal according to the filtered signal, and the voltage-current conversion circuit outputs a current output signal according to the filtered signal. The feedback circuit is used for collecting a voltage output signal and a current output signal, and the single-chip microcomputer is used for adjusting an input signal according to the voltage output signal and the current output signal. The analog quantity output module has the advantages of low cost, high precision, strong anti-interference capability and the like.

Description

Technical Field

[0001] This utility model relates to the field of analog output modules, and in particular to a low-cost closed-loop analog output module. Background Technology

[0002] In the field of industrial automation, continuous control of physical quantities (such as temperature, pressure, flow rate, and speed) is a core requirement. Analog signals, with their characteristics of continuous variation, high resolution, and direct drive of actuators, have become a key carrier for achieving precise regulation. Typical scenarios include:

[0003] Process control: For example, the temperature of a chemical reactor needs to be maintained with an accuracy of ±0.5℃;

[0004] Motion control: such as servo motor positioning, requires micron-level accuracy and millisecond-level response;

[0005] Energy management: For example, the output current of a photovoltaic inverter needs to smoothly track the maximum power point.

[0006] Such scenarios require signals to have high precision, anti-interference, and dynamic response capabilities, while discrete digital signals (such as switching signals) cannot meet the requirements, making analog signals an irreplaceable solution.

[0007] To convert digital control commands into analog signals that can be executed by industrial equipment, analog output modules (AO modules) have emerged. These modules achieve seamless connection between PLC systems and field devices through standardized interfaces (such as 4-20mA, 0-10V), becoming the "nerve endings" in the industrial control chain.

[0008] Most mainstream analog output modules currently employ an open-loop design based on a DAC (digital-to-analog converter). Please refer to [reference needed]. Figure 1 Current analog output modules use a DAC to convert the digital signal output by the microcontroller into an analog signal, and then amplify and filter the analog signal before outputting it.

[0009] While the resolution and conversion rate of modern DACs are constantly improving, the procurement cost of high-precision DACs (such as 16-bit and above) is relatively high, and they require sophisticated peripheral circuitry (such as reference voltage sources and low-noise operational amplifiers), further increasing hardware costs. If a low-cost DAC solution is adopted, issues such as nonlinearity error and temperature drift (such as ±10ppm / ℃) will directly degrade the output accuracy, creating a dilemma of "performance-cost" trade-offs.

[0010] In addition, the open-loop system design also has some significant drawbacks, especially in terms of accuracy, stability, and anti-interference capability, including:

[0011] Insufficient accuracy: Open-loop output relies on initial calibration and cannot compensate for DAC errors, op-amp offset and load fluctuations in real time. During long-term operation, it is prone to cumulative errors due to device aging or changes in ambient temperature and humidity.

[0012] Poor stability: Sudden changes in external load impedance (such as actuator short circuit / open circuit) or power fluctuations can cause the output voltage / current to deviate from the set value, and the system cannot adjust adaptively, which may lead to control failure.

[0013] Weak anti-interference capability: Electromagnetic interference (EMI) and grounding loop noise commonly found in industrial environments can be directly coupled to the analog signal chain. The open-loop architecture lacks a feedback mechanism to suppress interference, resulting in output signal distortion (such as jitter in 4-20mA signals).

[0014] In applications such as motor drives and precision instrument control, the accuracy and stability defects of open-loop systems can trigger a chain reaction. For example, in chemical process control, drift in the analog output of valve opening can lead to uncontrolled flow; noise interference in the current output of medical equipment can threaten patient safety. Therefore, there is an urgent need to design a low-cost analog output module with a closed-loop design. Utility Model Content

[0015] To address the aforementioned problems and technical requirements, the applicant has proposed a low-cost closed-loop analog output module. The technical solution of this utility model is as follows:

[0016] A low-cost closed-loop analog output module includes a microcontroller, a low-pass filter circuit, a voltage adjustment and amplification circuit, a voltage-to-current conversion circuit, and a feedback circuit.

[0017] The microcontroller is connected to the low-pass filter circuit and the feedback circuit. The low-pass filter circuit is connected to the voltage adjustment amplifier circuit and the voltage-to-current conversion circuit. The voltage adjustment amplifier circuit and the voltage-to-current conversion circuit are connected to the feedback circuit.

[0018] The low-pass filter circuit is used to filter the input signal output by the microcontroller and transmit it to the voltage adjustment amplifier circuit and the voltage-to-current conversion circuit. The voltage adjustment amplifier circuit outputs a voltage output signal according to the filtered signal, and the voltage-to-current conversion circuit outputs a current output signal according to the filtered signal. The feedback circuit is used to collect the voltage output signal and the current output signal, and the microcontroller is used to adjust the input signal according to the voltage output signal and the current output signal.

[0019] A further technical solution is that the low-pass filter circuit includes resistors R1 and R2, capacitor C1 and capacitor C2, wherein...

[0020] One end of resistor R1 is connected to the microcontroller, and the other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C1. The other end of capacitor C1 is grounded, and the other end of resistor R2 is grounded through capacitor C2.

[0021] A further technical solution is that the voltage adjustment and amplification circuit includes resistors R3, R5, and R6, an operational amplifier U2, a capacitor C3, and a switching transistor Q1, wherein...

[0022] The inverting input terminal of the operational amplifier U2 is grounded through resistor R5, and the inverting input terminal of the operational amplifier U2 is connected to the output terminal of the operational amplifier U2 through resistor R3. The capacitor C3 is connected in parallel with the resistor R3.

[0023] The output terminal of the operational amplifier U2 is connected to the second electrode of the switching transistor Q1. The third electrode of the switching transistor Q1 is connected to the power supply voltage VCC through resistor R6. The first electrode of the switching transistor Q1 is connected to the voltage output terminal and the output terminal of the operational amplifier U2.

[0024] A further technical solution is that the voltage-to-current conversion circuit includes resistor R4, resistor R7, operational amplifier U3, capacitor C4, and switching transistor Q2, wherein,

[0025] The inverting input terminal of the operational amplifier U3 is grounded through resistor R7, and the inverting input terminal of the operational amplifier U3 is connected to the first electrode of the switching transistor Q2 through resistor R4. The capacitor C4 is connected in parallel with the resistor R4.

[0026] The output terminal of the operational amplifier U3 is connected to the second electrode of the switching transistor Q2, the third electrode of the switching transistor Q2 is connected to the power supply terminal of the operational amplifier U3 and connected to the power supply voltage VCC, and the first electrode of the switching transistor Q2 is connected to the first current output terminal.

[0027] A further technical solution includes a drive enhancement circuit, wherein the low-pass filter circuit is connected to the voltage adjustment amplifier circuit and the voltage-current conversion circuit through the drive enhancement circuit.

[0028] The drive enhancement circuit includes an operational amplifier U1. The other end of the resistor R2 is connected to the non-inverting input terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is connected to the non-inverting input terminals of the operational amplifier U2 and the operational amplifier U3. The inverting input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1.

[0029] A further technical solution includes a current sampling circuit, which includes resistor R8 and resistor R9.

[0030] One end of resistor R8 is connected to the second current output terminal, the other end of resistor R8 is connected to one end of resistor R9, and the other end of resistor R9 is grounded.

[0031] A further technical solution is that the switching transistors Q1 and Q2 are triodes.

[0032] A further technical solution is that the voltage output terminal is grounded through capacitor C5, the voltage output terminal is connected to the positive terminal of diode D1 and the negative terminal of diode D2, the negative terminal of diode D1 is connected to the power supply voltage VCC, and the positive terminal of diode D2 is grounded.

[0033] The first current output terminal is connected to the positive terminal of diode D3 and the negative terminal of diode D4. The negative terminal of diode D3 is connected to the power supply voltage VCC, and the positive terminal of diode D4 is grounded.

[0034] A further technical solution is that the feedback circuit includes a current feedback circuit and a voltage feedback circuit, wherein,

[0035] The current feedback circuit includes capacitors C8, C9, C10, and C11, resistors R13, R14, R15, and R16, and operational amplifier U4.

[0036] The second current output terminal is connected to the non-inverting input terminal of the operational amplifier U4 through resistor R14, the inverting input terminal of the operational amplifier U4 is grounded through resistor R13, one end of the capacitor C9 is connected to the second current output terminal, and the other end of the capacitor C9 is grounded.

[0037] The non-inverting input terminal of the operational amplifier U4 is grounded through resistor R15, and capacitor C10 is connected in parallel with resistor R15. The inverting input terminal of the operational amplifier U4 is connected to the output terminal of the operational amplifier U4 through resistor R16, and capacitor C8 is connected in parallel with resistor R16. The output terminal of the operational amplifier U4 is grounded through capacitor C11, and the output terminal of the operational amplifier U4 is connected to the microcontroller.

[0038] A further technical solution is that the voltage feedback circuit includes resistors R10, R11, and R12, capacitors C6 and C7, and operational amplifier U5, wherein...

[0039] The voltage output terminal is connected to the non-inverting input terminal of operational amplifier U5 through resistor R10. The non-inverting input terminal of operational amplifier U5 is grounded through capacitor C6. The inverting input terminal of operational amplifier U5 is connected to the output terminal of operational amplifier U5. The output terminal of operational amplifier U5 is connected to one end of resistor R11 and resistor R12, one end of capacitor C7, and the microcontroller through resistor R11. The other end of resistor R12 and capacitor C7 is grounded.

[0040] The beneficial technical effects of this utility model are:

[0041] The low-cost closed-loop analog output module provided by this invention can actively adjust the output of the analog signal according to the feedback signal, and has the following advantages:

[0042] 1) Dynamic error compensation: Errors caused by nonlinearity of PWM signal (input signal), attenuation of filter circuit, load changes, etc. can be corrected through real-time feedback.

[0043] 2) Resistance to temperature drift and aging: It can automatically calibrate device parameter drift (such as resistance value change) and reduce long-term operating errors.

[0044] 3) Suppress external noise: After detecting the output deviation caused by interference, the duty cycle of the PWM signal (input signal) can be quickly adjusted in a closed loop to restore the output signal to the target value.

[0045] 4) Handling sudden load changes: When the load impedance changes (such as when the motor is stalled), the duty cycle of the PWM signal (input signal) can be automatically adjusted to maintain the stability of the output voltage / current.

[0046] 5) Simplify the calibration process: Reduce manual debugging costs in the production process through closed-loop automatic calibration.

[0047] Furthermore, this analog output module eliminates the need for a DAC chip, requiring only basic components such as resistors, capacitors, and operational amplifiers, significantly reducing manufacturing costs. Moreover, the method of adjusting the PWM signal duty cycle to obtain an equivalent analog voltage eliminates the need for digital-to-analog conversion, improving the signal's noise immunity and making it suitable for long-distance signal transmission. The entire module can be modularly designed, with miniaturized and standardized internal functional circuit modules, facilitating configuration, replacement, and maintenance. In summary, this invention improves the control accuracy of analog signal output, effectively solving the problems of low accuracy, poor stability, and weak anti-interference capabilities of analog modules in practical applications, and can adapt to more applications requiring high precision and high reliability. Attached Figure Description

[0048] Figure 1 This is a structural block diagram of a traditional open-loop analog output module provided by this utility model.

[0049] Figure 2 This is a structural block diagram of one embodiment of the closed-loop analog output module provided by this utility model.

[0050] Figure 3 This is a circuit schematic diagram of one embodiment of the low-pass filter circuit, drive enhancement circuit, voltage adjustment and amplification circuit, voltage-current conversion circuit and current sampling circuit provided by this utility model.

[0051] Figure 4 This is a circuit diagram of one embodiment of the current feedback circuit provided by this utility model.

[0052] Figure 5 This is a circuit diagram of one embodiment of the voltage feedback circuit provided by this utility model. Detailed Implementation

[0053] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0054] This invention provides a low-cost closed-loop analog output module, such as... Figure 2 As shown, a low-cost closed-loop analog output module is characterized by comprising a microcontroller, a low-pass filter circuit, a voltage adjustment and amplification circuit, a voltage-to-current conversion circuit, and a feedback circuit.

[0055] The microcontroller is connected to the low-pass filter circuit and the feedback circuit. The low-pass filter circuit is connected to the voltage adjustment amplifier circuit and the voltage-to-current conversion circuit. The voltage adjustment amplifier circuit and the voltage-to-current conversion circuit are connected to the feedback circuit.

[0056] The low-pass filter circuit is used to filter the input signal output by the microcontroller and transmit it to the voltage adjustment amplifier circuit and the voltage-to-current conversion circuit. The voltage adjustment amplifier circuit outputs a voltage output signal according to the filtered signal, and the voltage-to-current conversion circuit outputs a current output signal according to the filtered signal. The feedback circuit is used to collect the voltage output signal and the current output signal, and the microcontroller is used to adjust the input signal according to the voltage output signal and the current output signal.

[0057] Specifically, the input signal is a PWM (Pulse Width Modulation) signal. When the PWM signal passes through a low-pass filter circuit, the low-pass filter circuit filters out the high-frequency components of the signal, retaining the DC component, thereby generating a smooth analog voltage. The analog voltage is amplified by a voltage adjustment and amplification circuit to generate a voltage output signal. The analog voltage is then amplified by a voltage-to-current conversion circuit and converted into a current output signal. The voltage output signal and the current output signal are the analog signals output by the analog output module. In this embodiment, the frequency of the PWM signal can be 10kHz to reduce the ripple after filtering and improve the response speed.

[0058] The analog voltage is proportional to the duty cycle of the PWM signal. Therefore, the microcontroller can control the magnitude of the analog voltage output by the low-pass filter circuit by controlling the duty cycle of the PWM signal, thereby controlling the magnitude of the voltage and current output signals. Specifically, the voltage and current output signals are acquired by the feedback circuit and fed back to the ADC (Analog-to-Digital Converter) module in the microcontroller. The microcontroller dynamically adjusts the duty cycle of the PWM signal based on the voltage and current output signals, forming a closed-loop feedback control to compensate for errors caused by filter circuit attenuation, load changes, external noise, temperature drift, etc., and maintain the stability of the voltage and current output signals.

[0059] The feedback signals (voltage feedback signal and current feedback signal) collected by the feedback circuit are input to the ADC module of the microcontroller. The ADC module converts them into digital signals (digital voltage signal and digital current signal), which are then processed by the microcontroller. This data processing includes noise reduction and filtering to reduce noise interference in the feedback signal. Noise reduction and filtering algorithms commonly used by those skilled in the art can be employed. The microcontroller calculates the magnitude of the actual output signal (voltage output signal and current output signal) based on the converted and denoised feedback signal, and calculates the output deviation between the target value and the actual output signal. Specifically, it calculates the voltage output deviation based on the voltage output signal and the target voltage value, and the current output deviation based on the current output signal and the target current value. Then, based on the voltage output deviation and the current output deviation, a dynamic correction algorithm is used to adjust the duty cycle of the PWM signal. For example, when the voltage output deviation and / or current output deviation exceed the corresponding threshold, the duty cycle of the PWM signal can be adjusted by a dynamic correction algorithm. The dynamic correction algorithm adjusts the duty cycle of the PWM signal by a small amount each time and verifies the adjustment effect based on the feedback signal to avoid sudden changes in the actual output. The specific form of the dynamic correction algorithm can be consistent with the prior art.

[0060] Furthermore, the low-pass filter circuit is specifically a second-order RC low-pass filter circuit, such as... Figure 3As shown, the low-pass filter circuit includes resistor R1, resistor R2, capacitor C1, and capacitor C2. One end of resistor R1 is connected to the microcontroller, and the PWM signal is input to the low-pass filter circuit through one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C1. The other end of capacitor C1 is grounded, and the other end of resistor R2 is grounded through capacitor C2.

[0061] The voltage adjustment and amplification circuit includes a first non-inverting amplifier composed of resistors R3, R5, and R6, operational amplifier U2, and capacitor C3, as well as a switching transistor Q1. The inverting input terminal of operational amplifier U2 is grounded through resistor R5, and the inverting input terminal of operational amplifier U2 is connected to the output terminal of operational amplifier U2 through resistor R3. The capacitor C3 is connected in parallel with resistor R3. The output terminal of operational amplifier U2 is connected to the second electrode of switching transistor Q1, and the third electrode of switching transistor Q1 is connected to the power supply voltage VCC through resistor R6. The first electrode of switching transistor Q1 is connected to the voltage output terminal (V1) and the output terminal of operational amplifier U2. The voltage output terminal is used to output a voltage output signal.

[0062] The voltage-to-current conversion circuit includes a second non-inverting amplifier composed of resistors R4 and R7, operational amplifier U3, and capacitor C4, as well as a switching transistor Q2. The inverting input terminal of operational amplifier U3 is grounded through resistor R7, and the inverting input terminal of operational amplifier U3 is connected to the first electrode of switching transistor Q2 through resistor R4. Capacitor C4 is connected in parallel with resistor R4. The output terminal of operational amplifier U3 is connected to the second electrode of switching transistor Q2, the third electrode of switching transistor Q2 is connected to the power supply terminal of operational amplifier U3 and connected to the power supply voltage VCC, and the first electrode of switching transistor Q2 is connected to the voltage-to-current conversion circuit.

[0063] In this embodiment, both switching transistors Q1 and Q2 are NPN transistors. For each transistor, the first electrode is the emitter, the second electrode is the base, and the third electrode is the collector. The power supply voltage VCC is 15V, and the ground terminal of the operational amplifier U3 is connected to a 5V negative voltage.

[0064] The first non-inverting amplifier and the second non-inverting amplifier have the same amplification factor. The analog voltage amplified by the second non-inverting amplifier is converted into a current output signal by the switching transistor Q2. In specific implementation, the load is connected between the first current output terminal (I1+) and the second current output terminal (I1-). The current output signal flows from the first current output terminal to the second current output terminal through the load.

[0065] Furthermore, a drive enhancement circuit is provided between the low-pass filter circuit, the voltage adjustment amplifier circuit, and the voltage-to-current conversion circuit. This drive enhancement circuit includes a voltage follower formed by operational amplifier U1 to improve the driving capability (output current capability) of the analog output module. The other end of resistor R2 is connected to the non-inverting input terminal of operational amplifier U1. The output terminal of operational amplifier U1 is connected to the non-inverting input terminals of operational amplifiers U2 and U3, and the inverting input terminal of operational amplifier U1 is connected to its output terminal. The power supply terminal of operational amplifier U1 is connected to a 5V power supply, and its ground terminal is grounded.

[0066] Furthermore, the analog output module also includes a current sampling circuit, which includes resistors R8 and R9. One end of resistor R8 is connected to the second current output terminal, and the other end of resistor R8 is connected to one end of resistor R9, with the other end of resistor R9 grounded. Both resistors R8 and R9 are sampling resistors used to sample the current output signal.

[0067] Furthermore, the voltage output terminal is grounded through capacitor C5, and is connected to the anode of diode D1 and the cathode of diode D2. The cathode of diode D1 is connected to the power supply voltage VCC, and the anode of diode D2 is grounded. The first current output terminal is connected to the anode of diode D3 and the cathode of diode D4. The cathode of diode D3 is connected to the power supply voltage VCC, and the anode of diode D4 is grounded.

[0068] Furthermore, the feedback circuit includes a current feedback circuit and a voltage feedback circuit, wherein, as... Figure 4 As shown, the current feedback circuit includes capacitors C8, C9, C10, and C11, resistors R13, R14, R15, and R16, and operational amplifier U4. The second current output terminal is connected to the non-inverting input terminal of operational amplifier U4 via resistor R14, and the inverting input terminal of operational amplifier U4 is grounded via resistor R13. One end of capacitor C9 is connected to the second current output terminal, and the other end of capacitor C9 is grounded. The non-inverting input terminal of operational amplifier U4 is grounded via resistor R15, and capacitor C10 is connected in parallel with resistor R15. The inverting input terminal of operational amplifier U4 is connected to the output terminal of operational amplifier U4 via resistor R16, and capacitor C8 is connected in parallel with resistor R16. The output terminal of operational amplifier U4 is grounded via capacitor C11, and the output terminal of operational amplifier U4 is connected to a microcontroller, specifically to the current sampling pin A-I1 of the microcontroller.

[0069] The current feedback circuit is specifically a differential amplifier circuit, which collects and amplifies the voltage across resistors R8 and R9. The microcontroller can determine the magnitude of the current output signal based on the amplification factor of the differential amplifier circuit and the resistance values ​​of resistors R8 and R9.

[0070] Furthermore, such as Figure 5 As shown, the voltage feedback circuit includes resistors R10, R11, and R12, capacitors C6 and C7, and operational amplifier U5. The voltage output terminal is connected to the non-inverting input terminal of operational amplifier U5 via resistor R10. The non-inverting input terminal of operational amplifier U5 is grounded via capacitor C6. The inverting input terminal of operational amplifier U5 is connected to its output terminal. The output terminal of operational amplifier U5 is connected to one end of resistor R11 and resistor R12, one end of capacitor C7, and the microcontroller, specifically to the microcontroller's voltage sampling pins A-V1. The other ends of resistor R12 and capacitor C7 are grounded. The voltage feedback circuit acquires and amplifies the voltage output signal from the first amplification circuit. The microcontroller can determine the magnitude of the voltage output signal based on the amplification factor of the voltage feedback circuit.

[0071] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. A feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. References to terms such as "an embodiment / mode" indicate that a specific feature, structure, or characteristic in connection with that embodiment / mode is included in at least one embodiment / mode of this application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode.

[0072] Those skilled in the art should understand that the above embodiments are merely for clearly illustrating this disclosure and are not intended to limit the scope of this disclosure. Other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of this utility model should be considered to be included within the protection scope of this utility model.

Claims

1. A low-cost closed-loop analog output module, characterized in that, It includes a microcontroller, a low-pass filter circuit, a voltage regulation and amplification circuit, a voltage-to-current conversion circuit, and a feedback circuit; The microcontroller is connected to the low-pass filter circuit and the feedback circuit. The low-pass filter circuit is connected to the voltage adjustment and amplification circuit and the voltage-to-current conversion circuit. The voltage adjustment and amplification circuit and the voltage-to-current conversion circuit are connected to the feedback circuit. The low-pass filter circuit is used to filter the input signal output by the microcontroller and transmit it to the voltage adjustment amplifier circuit and the voltage-to-current conversion circuit. The voltage adjustment amplifier circuit outputs a voltage output signal according to the filtered signal, and the voltage-to-current conversion circuit outputs a current output signal according to the filtered signal. The feedback circuit is used to collect the voltage output signal and the current output signal, and the microcontroller is used to adjust the input signal according to the voltage output signal and the current output signal.

2. The low-cost closed-loop analog output module according to claim 1, characterized in that, The low-pass filter circuit includes resistor R1, resistor R2, capacitor C1, and capacitor C2, wherein... One end of resistor R1 is connected to the microcontroller, and the other end of resistor R1 is connected to one end of resistor R2 and one end of capacitor C1. The other end of capacitor C1 is grounded, and the other end of resistor R2 is grounded through capacitor C2.

3. The low-cost closed-loop analog output module according to claim 2, characterized in that, The voltage adjustment and amplification circuit includes resistors R3, R5, and R6, operational amplifier U2, capacitor C3, and switching transistor Q1. The inverting input terminal of the operational amplifier U2 is grounded through resistor R5, and the inverting input terminal of the operational amplifier U2 is connected to the output terminal of the operational amplifier U2 through resistor R3. The capacitor C3 is connected in parallel with the resistor R3. The output terminal of the operational amplifier U2 is connected to the second electrode of the switching transistor Q1. The third electrode of the switching transistor Q1 is connected to the power supply voltage VCC through resistor R6. The first electrode of the switching transistor Q1 is connected to the voltage output terminal and the output terminal of the operational amplifier U2.

4. The low-cost closed-loop analog output module according to claim 3, characterized in that, The voltage-to-current conversion circuit includes resistor R4, resistor R7, operational amplifier U3, capacitor C4, and switching transistor Q2. The inverting input terminal of the operational amplifier U3 is grounded through resistor R7, and the inverting input terminal of the operational amplifier U3 is connected to the first electrode of the switching transistor Q2 through resistor R4. The capacitor C4 is connected in parallel with resistor R4. The output terminal of the operational amplifier U3 is connected to the second electrode of the switching transistor Q2, the third electrode of the switching transistor Q2 is connected to the power supply terminal of the operational amplifier U3 and connected to the power supply voltage VCC, and the first electrode of the switching transistor Q2 is connected to the first current output terminal.

5. The low-cost closed-loop analog output module according to claim 4, characterized in that, It also includes a drive enhancement circuit, wherein the low-pass filter circuit is connected to the voltage adjustment amplifier circuit and the voltage-current conversion circuit through the drive enhancement circuit; The drive enhancement circuit includes an operational amplifier U1. The other end of the resistor R2 is connected to the non-inverting input terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is connected to the non-inverting input terminals of the operational amplifier U2 and the operational amplifier U3. The inverting input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1.

6. The low-cost closed-loop analog output module according to claim 4, characterized in that, It also includes a current sampling circuit, which includes resistor R8 and resistor R9; One end of resistor R8 is connected to the second current output terminal, the other end of resistor R8 is connected to one end of resistor R9, and the other end of resistor R9 is grounded.

7. The low-cost closed-loop analog output module according to claim 4, characterized in that, The switching transistors Q1 and Q2 are bipolar transistors.

8. The low-cost closed-loop analog output module according to claim 6, characterized in that, The voltage output terminal is grounded through capacitor C5. The voltage output terminal is connected to the positive terminal of diode D1 and the negative terminal of diode D2. The negative terminal of diode D1 is connected to the power supply voltage VCC, and the positive terminal of diode D2 is grounded. The first current output terminal is connected to the positive terminal of diode D3 and the negative terminal of diode D4. The negative terminal of diode D3 is connected to the power supply voltage VCC, and the positive terminal of diode D4 is grounded.

9. The low-cost closed-loop analog output module according to claim 6, characterized in that, The feedback circuit includes a current feedback circuit and a voltage feedback circuit, wherein... The current feedback circuit includes capacitors C8, C9, C10, and C11, resistors R13, R14, R15, and R16, and operational amplifier U4. The second current output terminal is connected to the non-inverting input terminal of the operational amplifier U4 through resistor R14, the inverting input terminal of the operational amplifier U4 is grounded through resistor R13, one end of the capacitor C9 is connected to the second current output terminal, and the other end of the capacitor C9 is grounded. The non-inverting input terminal of the operational amplifier U4 is grounded through resistor R15, and capacitor C10 is connected in parallel with resistor R15. The inverting input terminal of the operational amplifier U4 is connected to the output terminal of the operational amplifier U4 through resistor R16, and capacitor C8 is connected in parallel with resistor R16. The output terminal of the operational amplifier U4 is grounded through capacitor C11, and the output terminal of the operational amplifier U4 is connected to the microcontroller.

10. The low-cost closed-loop analog output module according to claim 9, characterized in that, The voltage feedback circuit includes resistors R10, R11, and R12, capacitors C6 and C7, and operational amplifier U5. The voltage output terminal is connected to the non-inverting input terminal of operational amplifier U5 through resistor R10. The non-inverting input terminal of operational amplifier U5 is grounded through capacitor C6. The inverting input terminal of operational amplifier U5 is connected to the output terminal of operational amplifier U5. The output terminal of operational amplifier U5 is connected to one end of resistor R11 and resistor R12, one end of capacitor C7, and the microcontroller through resistor R11. The other end of resistor R12 and capacitor C7 is grounded.

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