Controllable output analog quantity transmission circuit for special transformer terminal

Abstract

The invention relates to the technical field of analog quantity transmission, and provides a controllable output analog quantity transmission circuit for a special transformer terminal, which comprises an adjustable reference voltage source generation circuit, a frequency-adjustable triangular wave generation circuit constructed by a hysteresis comparator, a PWM (Pulse Width Modulation) wave generation circuit with adjustable frequency and duty ratio, a 0-10V output circuit and a 4-20mA output circuit. The reference voltage source generating circuit outputs stable adjustable reference voltage, the triangular wave generating circuit generates triangular wave signals with adjustable frequency, and the PWM wave generating circuit generates PWM waveforms with adjustable frequency and duty ratio. The 0-10V output circuit converts the PWM wave signal into a 0-10V voltage analog quantity to be output, and the 4-20mA output circuit converts the PWM wave signal into a 4-20mA current analog quantity to be output. The circuit module completes analog quantity transmission together, has flexibility and expandability, and meets the requirements of different application scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of analog quantity transmission, and in particular to a controllable output analog quantity transmission circuit for a special transformer terminal. Background Art

[0002] There are currently two commonly used analog transmission methods for industrial instruments and meters, 4-20mA current loop transmission and 0-10V voltage analog transmission. Both analog transmission methods have longer transmission distances and stronger anti-interference performance that other industrial control methods do not have. This transmission method is widely used in the field of industrial instruments and meters for information collection and transmission, status monitoring and other links.

[0003] The existing analog quantity transmission implementation forms can be roughly divided into three categories: 1. Using a single-chip microcomputer with a DAC module or selecting a dedicated DAC module to realize voltage signal output, realizing 0-10V analog signal output by amplifying the signal operation, and realizing current signal output by converting the voltage signal into 4-20mA. This method is simple to implement, but it requires the use of expensive chips with DAC modules, which will greatly increase the cost of the collector or instrumentation. The other two analog quantity transmission methods are affected by the differences in chip batches and power supply quality, and the consistency of analog quantity transmission accuracy is poor; 2. Using a dedicated digital signal conversion chip to realize 4-20mA current output and 0-10V voltage analog output. This solution has a high implementation cost and the independent digital conversion chip has poor anti-interference performance. Additional anti-interference devices need to be added to the adapter collector and industrial instrumentation equipment, and the implementation form is complicated; 3. Based on the PWM waveform control of the single-chip microcomputer to realize 4-20mA current output and 0-10V voltage analog output, this method also requires the selection of an MCU with a PWM timer function, which is costly and complicated to implement.

[0004] In the prior art, the method of using a single-chip microcomputer with a DAC module or a dedicated DAC module to realize analog quantity transmission not only requires expensive chips, which greatly increases the cost of the collector and instruments, but also poses a challenge to cost control; although the use of a dedicated digital signal conversion chip can realize the function, the implementation cost is also high, and additional anti-interference devices are required, which increases the complexity of the circuit; at the same time, both the DAC module and the dedicated digital signal conversion chip have the problem of weak anti-interference performance, especially in a complex electromagnetic environment, which may affect the stability and accuracy of the transmission; in addition, due to differences in chip batches and power supply quality, the analog quantity transmission method using these technologies is difficult to maintain consistent transmission accuracy; the analog quantity transmission circuit in the prior art often lacks flexibility and scalability, and it is difficult to meet the needs of different application scenarios, and the scope of application is limited. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the present invention provides a controllable output analog quantity transmission circuit for a dedicated transformer terminal, which includes an adjustable reference voltage source generation circuit, an adjustable frequency triangle wave generation circuit constructed by a hysteresis comparator, an adjustable frequency and adjustable duty cycle PWM wave generation circuit, a 0-10V output analog quantity transmission circuit and a 4-20mA output analog quantity transmission circuit, wherein:

[0006] The adjustable reference voltage source generating circuit outputs a stable adjustable reference voltage OUT1, providing a stable voltage reference for subsequent circuits;

[0007] The frequency-adjustable triangle wave generating circuit constructed by the hysteresis comparator has power supply VCC and GND as inputs, and uses the hysteresis comparator to generate a frequency-adjustable triangle wave signal, and the output is a triangle wave signal OUT2;

[0008] The input of the PWM wave generating circuit with adjustable frequency and adjustable duty cycle is the output OUT1 of the reference voltage source generating circuit and the output OUT2 of the triangle wave generating circuit; the reference voltage and the triangle wave are compared by a comparator to generate a PWM waveform with adjustable frequency and adjustable duty cycle; the output is a PWM wave signal OUT3;

[0009] The input of the analog quantity transmission circuit with 0-10V output is the output OUT3 of the PWM wave generation circuit, which converts the PWM wave signal into a 0-10V voltage analog quantity output; the output is a 0-10V voltage signal OUT4;

[0010] The analog transmission circuit with 0-10V output uses the output of the PWM wave generation circuit as input, performs signal processing, and obtains a stable 0-10V voltage output;

[0011] The input of the analog transmission circuit of 4-20mA output is the output OUT3 of the PWM wave generation circuit, which converts the PWM wave signal into a 4-20mA current analog output; the output is a 4-20mA current signal OUT5;

[0012] The analog transmission circuit with 4-20mA output uses the output of the PWM wave generation circuit as input, and uses integrated operational amplifiers and switching MOS components for current conversion and control;

[0013] The above circuit modules jointly complete the analog quantity transmission, starting from the reference voltage source generation, through triangle wave generation, PWM wave generation, and finally converting into the required 0-10V voltage or 4-20mA current output.

[0014] Furthermore, the adjustable reference voltage source generating circuit includes a sliding rheostat RX1, a transistor QU1, resistors R1 and R2, an electrolytic capacitor E1, a reference voltage output signal OUT1, and power supplies VCC and GND; the connection relationship is that the sliding rheostat RX1-2 is connected to the resistor R1 and the transistor QU1-b, the other end of R1 is connected to VCC, the resistor R2 is connected to VCC, the other end of R2 is connected to QU2-e, the electrolytic capacitor E1, and the reference voltage output signal OUT1, and the other ends of RX1-3, QU1-c, and E1 are connected to GND; the impedance value of the sliding rheostat RX1 can be adjusted to obtain different base voltages of the transistor QU1, thereby obtaining different emitter voltages of the transistor QU1, that is, obtaining different reference voltage sources OUT1; and the establishment time of the reference voltage is adjusted by adjusting the size of the electrolytic capacitor E1 on the reference voltage source.

[0015] Furthermore, the frequency-adjustable triangular wave generating circuit constructed by the hysteresis comparator includes a sliding rheostat RX2, a comparator N1B, resistors R3, R4, R5, R6, capacitors C1, C2, a triangular wave output signal OUT2, and power supplies VCC and GND; the connection relationship is that the resistor R3 is connected to the power supply VCC, and the other end is connected to the resistor R4, the capacitor C1, the comparator N1B-5, and the resistor R5, the other end of the resistor R4 and the other end of the capacitor C1 are connected to GND, and the other end of the resistor R5 is connected to N1B-7, the resistor R6, the sliding rheostat RX2- 2. The other end of resistor R6 is connected to VCC, RX2-3 is connected to capacitor C2, N1B-6, and triangular wave output signal OUT2, and the other end of C2 is connected to GND; the following parameters can be adjusted to adjust the frequency of the output triangular wave OUT2, and adjust the VCC voltage value. When VCC increases, the frequency of triangular wave OUT2 increases; adjust the resistance value of sliding rheostat RX2, such as reducing the resistance value of RX2, to increase the frequency of triangular wave OUT2; adjust the capacitance value of capacitor C2, such as reducing the capacitance value of C2, to increase the frequency of triangular wave OUT2.

[0016] Furthermore, a PWM wave generating circuit with adjustable frequency and adjustable duty cycle includes a reference voltage output signal OUT1, a triangular wave output signal OUT2, a comparator N1A, resistors R7, R8, R9, capacitors C3, C4, a PWM wave output signal OUT3, and power supplies VCC and GND; the connection relationship is that the reference voltage output signal OUT1 is connected to resistor R7, the other end of R7 is connected to comparator N1A-3, the triangular wave output signal OUT2 is connected to resistor R8, the other end of R8 is connected to comparator N1A-2, N1A-1 is connected to resistor R9, PWM wave output signal OUT3, the other end of R9, capacitor C3, capacitor C4, N1A-8 are connected to power supply VCC, and the other ends of C3, C4, N1A-4 are connected to GND; the adjustable reference voltage source OUT1 and the triangular wave output signal OUT2 with adjustable frequency are input into the comparator N1A, and a PWM output signal OUT3 with adjustable frequency and duty cycle can be obtained.

[0017] Further, the analog quantity transmission circuit of 0-10V output includes PWM wave output signal OUT3, operational amplifier N2A, diode VD1, voltage regulator VD2, resistors R10, R11, capacitors C5, C6, C7, C8, C9, 0-10V output signal OUT4, power supply VCC, GND; its connection relationship is that PWM wave output signal OUT3 is connected to resistor R10, the other end of R10 is connected to capacitor C5, resistor R11, the other end of R11 is connected to capacitor C6, operational amplifier N2A-3, operational amplifier N2A-2 is connected to operational amplifier N2A-1, diode VD1 positive electrode, voltage regulator VD2 negative electrode, capacitor C9, 0-10V output signal OUT4, N2A-8, capacitor C7, capacitor C8, negative electrode of VD1 is connected to power supply VCC, C5, C6, C 7. Connect the positive poles of C8, C9, N2A-4 and VD2 to GND; adjust the resistors R10 and R11, and the capacitors C5 and C6 to adjust the second-order RC passive low-pass filter depth of the PWM wave output signal OUT3; adjust the frequency and duty cycle of the PWM wave output signal OUT3 to adjust the value of the 0-10V output signal OUT4. For example, if the frequency of the PWM wave output signal OUT3 is gradually increased, the value of the 0-10V output signal OUT4 will gradually decrease. For example, if the duty cycle of the PWM wave output signal OUT3 is gradually increased, the value of the 0-10V output signal OUT4 will gradually decrease. Add diode VD1 to the interface to clamp the interface input continuous voltage value that damages the device. Add TVS tube VD2 and capacitor C9 to the interface to resist static electricity and other electromagnetic interference resistance test shocks.

[0018] Further, the analog quantity transmission circuit of 4-20mA output includes PWM wave output signal OUT3, operational amplifiers N2B and N3A, NMOS tube VT1, PMOS tube VT2, inductor L1, fuse RT1, 4-20mA output signal OUT5, resistors R12, R13, R14, R15, R16, R17, capacitors C10, C11, C12, C13, power supplies VCC and GND; its connection relationship is that the PWM wave output signal OUT3 is connected to resistor R12, the other end of R12 is connected to resistor R13 and operational amplifier N2B-5, operational amplifier N2B-6 is connected to NMOS tube VT1-s and resistor R16, N2B-7 is connected to resistor R14, the other end of R14 is connected to VT1-g, VT1-d is connected to resistor R15 and operational amplifier N3A-3, the other end of R15 and resistor R17 are connected to VCC, and the other end of R17 is connected to N3A-2 and PMOS tube VT2 -s, N3A-1 is connected to VT2-g, VT2-d is connected to capacitor C12 and inductor L1, the other end of L1 is connected to capacitor C13 and fuse RT1, the other end of RT1 is connected to 4-20mA output signal OUT5, N3A-4, capacitor C10, and capacitor C11 are connected to VCC, and the other end of R13, the other end of R16, the other end of C10, the other end of C10, the other end of C12, and the other end of C13 are connected to GND; the frequency and duty cycle of the PWM wave output signal OUT3 can be adjusted to adjust the value of the 4-20mA output signal OUT5. For example, if the frequency of the PWM wave output signal OUT3 is gradually increased, the value of the 4-20mA output signal OUT5 will gradually increase. For example, if the duty cycle of the PWM wave output signal OUT3 is gradually increased, the value of the 4-20mA output signal OUT5 will gradually increase. Inductor L1 and fuse RT1 are added to the interface to prevent short circuit and overcurrent in the line.

[0019] The beneficial effects achieved by the present invention are:

[0020] The present invention achieves low cost, high precision, strong anti-interference performance, good flexibility and scalability by adopting discrete devices to build circuits, modular design and careful parameter adjustment mechanism, and provides an effective solution for cost control and performance improvement of collectors and traditional instruments. Specifically:

[0021] The present invention adopts discrete devices to build the circuit, abandoning the expensive DAC module or dedicated digital signal conversion chip widely used in traditional solutions, which directly reduces the hardware cost. This cost optimization strategy enables the technical solution to achieve significant results in cost control in the production of collectors and traditional instruments.

[0022] The entire circuit of the present invention is divided into five modules: an adjustable reference voltage source generation circuit, a triangle wave generation circuit, a PWM wave generation circuit, a 0-10V output circuit and a 4-20mA output circuit. The function of each module is clear, and this modular design is not only convenient for debugging and maintenance of the circuit, but also makes the overall structure of the circuit more concise and clear. The modular design also makes the circuit easy to expand and upgrade functions, which provides convenience for future technology iterations and product upgrades. At the same time, the use of discrete devices rather than complex chips to build the circuit further simplifies the implementation form, and through the circuit structure and parameter adjustment mechanism, the accuracy of analog transmission is effectively controlled, reducing the transmission error that may be caused by differences in chip batches and power supply quality. At the same time, since the use of expensive chips with different performance is avoided, the entire circuit can maintain consistency in transmission accuracy, thereby improving the stability and reliability of the system.

[0023] The circuit interface adopts a variety of anti-electromagnetic interference designs, and designs components such as diodes, voltage regulators, inductors and fuses, which effectively improves the stability of the circuit in complex electromagnetic environments. At the same time, the circuit of the present invention has good flexibility and scalability. The PWM wave generation circuit supports adjustable frequency and duty cycle, so that the circuit can adapt to different working scenarios and needs, and can be applied to various industrial instruments and acquisition terminals to meet the needs of different application environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a block diagram of the overall architecture of the present invention.

[0025] Figure 2 Generate a circuit block diagram for an adjustable voltage reference.

[0026] Figure 3 Block diagram of the frequency-adjustable triangle wave generation circuit built for the hysteresis comparator.

[0027] Figure 4 The circuit structure diagram for generating PWM wave with adjustable frequency and adjustable duty cycle.

[0028] Figure 5 This is the structure diagram of the analog transmission circuit with 0-10V output.

[0029] Figure 6 The structure diagram of the analog transmission circuit with 4-20mA output DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. In addition, the forms of the various structures recorded in the following embodiments are merely illustrative, and the present invention is not limited to the various structures recorded in the following embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0031] Reference Figure 1-Figure 6 The present invention provides a controllable output analog quantity transmission circuit for a dedicated transformer terminal, which includes an adjustable reference voltage source generation circuit, an adjustable frequency triangle wave generation circuit constructed by a hysteresis comparator, an adjustable frequency and adjustable duty cycle PWM wave generation circuit, a 0-10V output analog quantity transmission circuit and a 4-20mA output analog quantity transmission circuit, wherein:

[0032] The adjustable reference voltage source generating circuit outputs a stable adjustable reference voltage OUT1, providing a stable voltage reference for subsequent circuits;

[0033] The frequency-adjustable triangle wave generating circuit constructed by the hysteresis comparator has power supply VCC and GND as inputs, and uses the hysteresis comparator to generate a frequency-adjustable triangle wave signal, and the output is a triangle wave signal OUT2;

[0034] The input of the PWM wave generating circuit with adjustable frequency and adjustable duty cycle is the output OUT1 of the reference voltage source generating circuit and the output OUT2 of the triangle wave generating circuit; the reference voltage and the triangle wave are compared by a comparator to generate a PWM waveform with adjustable frequency and adjustable duty cycle; the output is a PWM wave signal OUT3;

[0035] The input of the analog quantity transmission circuit with 0-10V output is the output OUT3 of the PWM wave generation circuit, which converts the PWM wave signal into a 0-10V voltage analog quantity output; the output is a 0-10V voltage signal OUT4;

[0036] The analog transmission circuit with 0-10V output uses the output of the PWM wave generation circuit as input, performs signal processing, and obtains a stable 0-10V voltage output;

[0037] The input of the analog transmission circuit of 4-20mA output is the output OUT3 of the PWM wave generation circuit, which converts the PWM wave signal into a 4-20mA current analog output; the output is a 4-20mA current signal OUT5;

[0038] The analog transmission circuit with 4-20mA output uses the output of the PWM wave generation circuit as input, and uses integrated operational amplifiers and switching MOS components for current conversion and control;

[0039] The above circuit modules jointly complete the analog quantity transmission, starting from the reference voltage source generation, through triangle wave generation, PWM wave generation, and finally converting into the required 0-10V voltage or 4-20mA current output.

[0040] The adjustable reference voltage source generating circuit includes a sliding rheostat RX1, a transistor QU1, resistors R1 and R2, an electrolytic capacitor E1, a reference voltage output signal OUT1, and power supplies VCC and GND; the connection relationship is that the sliding rheostat RX1-2 is connected to the resistor R1 and the transistor QU1-b, the other end of R1 is connected to VCC, the resistor R2 is connected to VCC, the other end of R2 is connected to QU2-e, the electrolytic capacitor E1, and the reference voltage output signal OUT1, and the other ends of RX1-3, QU1-c, and E1 are connected to GND; the impedance value of the sliding rheostat RX1 can be adjusted to obtain different base voltages of the transistor QU1, thereby obtaining different emitter voltages of the transistor QU1, that is, obtaining different reference voltage sources OUT1; and the establishment time of the reference voltage is adjusted by adjusting the size of the electrolytic capacitor E1 on the reference voltage source.

[0041] The frequency-adjustable triangular wave generating circuit constructed by the hysteresis comparator includes a sliding rheostat RX2, a comparator N1B, resistors R3, R4, R5, R6, capacitors C1, C2, a triangular wave output signal OUT2, and power supplies VCC and GND; its connection relationship is that the resistor R3 is connected to the power supply VCC, and the other end is connected to the resistor R4, the capacitor C1, the comparator N1B-5, and the resistor R5, the other end of the resistor R4 and the other end of the capacitor C1 are connected to GND, the other end of the resistor R5 is connected to N1B-7, the resistor R6, and the sliding rheostat RX2-2, The other end of resistor R6 is connected to VCC, RX2-3 is connected to capacitor C2, N1B-6, and triangular wave output signal OUT2, and the other end of C2 is connected to GND; the following parameters can be adjusted to adjust the frequency of the output triangular wave OUT2, and adjust the VCC voltage value. When VCC increases, the frequency of triangular wave OUT2 increases; adjust the resistance value of sliding rheostat RX2, such as reducing the resistance value of RX2, to increase the frequency of triangular wave OUT2; adjust the capacitance value of capacitor C2, such as reducing the capacitance value of C2, to increase the frequency of triangular wave OUT2.

[0042] The PWM wave generating circuit with adjustable frequency and adjustable duty cycle includes a reference voltage output signal OUT1, a triangular wave output signal OUT2, a comparator N1A, resistors R7, R8, R9, capacitors C3, C4, a PWM wave output signal OUT3, and power supplies VCC and GND; its connection relationship is that the reference voltage output signal OUT1 is connected to resistor R7, and the other end of R7 is connected to comparator N1A-3, the triangular wave output signal OUT2 is connected to resistor R8, and the other end of R8 is connected to comparator N1A-2, N1A-1 is connected to resistor R9, PWM wave output signal OUT3, the other end of R9, capacitor C3, capacitor C4, and N1A-8 are connected to power supply VCC, and the other ends of C3, C4, and N1A-4 are connected to GND; the adjustable reference voltage source OUT1 and the triangular wave output signal OUT2 with adjustable frequency are input into the comparator N1A, and the PWM output signal OUT3 with adjustable frequency and duty cycle can be obtained.

[0043] The analog quantity transmission circuit with 0-10V output includes PWM wave output signal OUT3, operational amplifier N2A, diode VD1, voltage regulator VD2, resistors R10, R11, capacitors C5, C6, C7, C8, C9, 0-10V output signal OUT4, power supply VCC, GND; its connection relationship is that the PWM wave output signal OUT3 is connected to resistor R10, the other end of R10 is connected to capacitor C5, resistor R11, the other end of R11 is connected to capacitor C6, operational amplifier N2A-3, operational amplifier N2A-2 is connected to operational amplifier N2A-1, diode VD1 positive electrode, voltage regulator VD2 negative electrode, capacitor C9, 0-10V output signal OUT4, N2A-8, capacitor C7, capacitor C8, VD1 negative electrode is connected to power supply VCC, C5, C6, C7, The positive poles of C8, C9, N2A-4 and VD2 are connected to GND; the second-order RC passive low-pass filter depth of the PWM wave output signal OUT3 can be adjusted by adjusting the resistors R10 and R11, and the capacitors C5 and C6; the value of the 0-10V output signal OUT4 can be adjusted by adjusting the frequency and duty cycle of the PWM wave output signal OUT3. For example, if the frequency of the PWM wave output signal OUT3 is gradually increased, the value of the 0-10V output signal OUT4 will gradually decrease; for example, if the duty cycle of the PWM wave output signal OUT3 is gradually increased, the value of the 0-10V output signal OUT4 will gradually decrease; a diode VD1 is added to the interface to clamp the interface input continuous voltage value that damages the device; an interface TVS tube VD2 and capacitor C9 are added to resist static electricity and other electromagnetic interference test shocks.

[0044] The analog quantity transmission circuit of 4-20mA output includes PWM wave output signal OUT3, operational amplifiers N2B and N3A, NMOS tube VT1, PMOS tube VT2, inductor L1, fuse RT1, 4-20mA output signal OUT5, resistors R12, R13, R14, R15, R16, R17, capacitors C10, C11, C12, C13, power supplies VCC and GND; its connection relationship is that the PWM wave output signal OUT3 is connected to resistor R12, the other end of R12 is connected to resistor R13 and operational amplifier N2B-5, operational amplifier N2B-6 is connected to NMOS tube VT1-s and resistor R16, N2B-7 is connected to resistor R14, the other end of R14 is connected to VT1-g, VT1-d is connected to resistor R15 and operational amplifier N3A-3, the other end of R15 and resistor R17 are connected to VCC, and the other end of R17 is connected to N3A-2 and PMOS tube VT2-s , N3A-1 is connected to VT2-g, VT2-d is connected to capacitor C12 and inductor L1, the other end of L1 is connected to capacitor C13 and fuse RT1, the other end of RT1 is connected to 4-20mA output signal OUT5, N3A-4, capacitor C10, and capacitor C11 are connected to VCC, the other end of R13, the other end of R16, the other end of C10, the other end of C10, the other end of C12, and the other end of C13 are connected to GND; the frequency and duty cycle of the PWM wave output signal OUT3 can be adjusted to adjust the value of the 4-20mA output signal OUT5. For example, if the frequency of the PWM wave output signal OUT3 is gradually increased, the value of the 4-20mA output signal OUT5 will gradually increase. For example, if the duty cycle of the PWM wave output signal OUT3 is gradually increased, the value of the 4-20mA output signal OUT5 will gradually increase; the interface adds inductor L1 and fuse RT1 to prevent the line from short-circuiting and overcurrent.

[0045] The working process of a controllable output analog quantity transmission circuit for a dedicated transformer terminal of the present invention is as follows:

[0046] 1. Reference voltage source generation; the workflow of the entire circuit starts with the reference voltage source generation.

[0047] Components and connections: Components include sliding rheostat RX1, transistor QU1, resistors R1, R2 and electrolytic capacitor E1.

[0048] Pin 2 of the sliding rheostat RX1 is connected to the resistor R1 and the base of the transistor QU1 (b), and the other end of R1 is connected to the power supply VCC. Resistor R2 is connected to VCC, and the other end is connected to the emitter of the transistor QU1 (e), the electrolytic capacitor E1 and the reference voltage output signal OUT1. Pin 3 of the sliding rheostat RX1, the collector of the transistor QU1 (c) and the other end of the electrolytic capacitor E1 are connected to GND.

[0049] By adjusting the impedance value of the sliding rheostat RX1, the base voltage of the transistor QU1 can be changed, and then its emitter voltage (i.e., the reference voltage source OUT1) can be adjusted. The electrolytic capacitor E1 is used to adjust the reference voltage build-up time to ensure output stability. A stable and adjustable reference voltage OUT1 is output to provide a voltage reference for subsequent circuits.

[0050] 2. Triangle wave generation: After the reference voltage is generated, the triangle wave generation stage begins.

[0051] Components and connections: Components include sliding rheostat RX2, comparator N1B, resistors R3, R4, R5, R6 and capacitors C1 and C2. Resistor R3 is connected to VCC, and the other end is connected to resistor R4, capacitor C1, pin 5 of comparator N1B and resistor R5. The other end of resistor R4 and capacitor C1 is connected to GND. The other end of resistor R5 is connected to pin 7 of comparator N1B, resistor R6 and pin 2 of sliding rheostat RX2. The other end of resistor R6 is connected to VCC, and pin 3 of sliding rheostat RX2 is connected to capacitor C2, pin 6 of comparator N1B and triangle wave output signal OUT2. The other end of capacitor C2 is connected to GND.

[0052] A triangular wave signal with adjustable frequency is generated by using a hysteresis comparator. The frequency of the output triangular wave OUT2 can be changed by adjusting the VCC voltage value, the resistance value of the sliding resistor RX2, and the capacitance value of the capacitor C2. The triangular wave signal OUT2 with adjustable frequency is output.

[0053] 3. PWM wave generation; after the triangle wave is generated, it enters the PWM wave generation stage.

[0054] Components and connections: Components include comparator N1A, resistors R7, R8, R9, and capacitors C3 and C4. The reference voltage output signal OUT1 is connected to resistor R7, and the other end is connected to pin 3 of comparator N1A. The triangle wave output signal OUT2 is connected to resistor R8, and the other end is connected to pin 2 of comparator N1A. Pin 1 of comparator N1A is connected to resistor R9 and PWM wave output signal OUT3. The other end of resistor R9, capacitor C3, capacitor C4, and pin 8 of comparator N1A are connected to VCC. Capacitors C3, C4, and pin 4 of comparator N1A are connected to GND.

[0055] The reference voltage OUT1 is compared with the triangular wave signal OUT2 by the comparator N1A to generate a PWM waveform with adjustable frequency and adjustable duty cycle, and output a PWM wave signal OUT3 with adjustable frequency and adjustable duty cycle.

[0056] 4.0-10V voltage output conversion; PWM wave signal enters the 0-10V voltage output conversion module.

[0057] Components and connections: Components include op amp N2A, diode VD1, voltage regulator VD2, resistors R10, R11, and capacitors C5, C6, C7, C8, and C9. The PWM wave output signal OUT3 is connected to resistor R10, and the other end is connected to capacitor C5 and resistor R11. The other end of resistor R11 is connected to capacitor C6 and pin 3 of op amp N2A. Pin 2 of op amp N2A is connected to pin 1 of op amp N2A, the positive electrode of diode VD1, the negative electrode of voltage regulator VD2, capacitor C9, and 0-10V output signal OUT4. Pin 8 of op amp N2A, capacitor C7, capacitor C8, and the negative electrode of diode VD1 are connected to VCC. Capacitors C5, C6, C7, C8, C9, pin 4 of op amp N2A, and the positive electrode of voltage regulator VD2 are connected to GND.

[0058] Convert the PWM wave signal OUT3 into a 0-10V voltage analog output. By adjusting the values ​​of resistors R10, R11 and capacitors C5, C6, the depth of the second-order RC passive low-pass filter can be changed, thereby affecting the output voltage. Diode VD1 and voltage regulator VD2 provide interface protection to prevent voltage from damaging the device. Output a stable 0-10V voltage signal OUT4.

[0059] 5.4-20mA current output conversion; PWM wave signal enters the 4-20mA current output conversion module at the same time.

[0060] Components and connections: Components include op amps N2B, N3A, NMOS tube VT1, PMOS tube VT2, inductor L1, fuse RT1, resistors R12, R13, R14, R15, R16, R17 and capacitors C10, C11, C12, C13. The PWM wave output signal OUT3 is connected to resistor R12, and the other end is connected to resistor R13 and pin 5 of op amp N2B. Pin 6 of op amp N2B is connected to the source (s) of NMOS tube VT1 and resistor R16. Pin 7 of op amp N2B is connected to resistor R14, and the other end is connected to the gate (g) of NMOS tube VT1. The drain (d) of NMOS tube VT1 is connected to resistor R15 and pin 3 of op amp N3A. The other end of resistor R15, resistor R17 and VCC are connected to pin 2 of op amp N3A and the source (s) of PMOS tube VT2. Pin 1 of op amp N3A is connected to the gate (g) of PMOS tube VT2. The drain (d) of PMOS tube VT2 is connected to capacitor C12 and inductor L1. The other end of inductor L1 is connected to capacitor C13 and fuse RT1, and the other end of fuse RT1 is connected to 4-20mA output signal OUT5. Pin 4 of op amp N3A, capacitor C10, and capacitor C11 are connected to VCC. The other end of resistor R13, the other end of resistor R16, the other end of capacitor C10, the other end of capacitor C12, and the other end of capacitor C13 are connected to GND.

[0061] Convert the PWM wave signal OUT3 to a 4-20mA current analog output. By adjusting the frequency and duty cycle of the PWM wave, the output current can be controlled. Inductor L1 and fuse RT1 provide line protection to prevent short circuit and overcurrent. Output 4-20mA current signal OUT5.

[0062] The entire circuit of the present invention realizes accurate conversion from PWM wave to analog signal through reference voltage source generation, triangle wave generation, PWM wave generation and subsequent 0-10V voltage and 4-20mA current output conversion module. Each module has a specific function, and the stability and accuracy of the circuit are ensured through parameter adjustment and component selection, and is suitable for various industrial instruments and acquisition terminals.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A controllable output analog quantity transmission circuit for a dedicated transformer terminal, characterized in that: It includes an adjustable reference voltage source generation circuit, an adjustable frequency triangle wave generation circuit built by a hysteresis comparator, an adjustable frequency and duty cycle PWM wave generation circuit, a 0-10V output analog quantity transmission circuit and a 4-20mA output analog quantity transmission circuit, wherein: The adjustable reference voltage source generating circuit outputs a stable adjustable reference voltage OUT1, providing a stable voltage reference for subsequent circuits; The frequency-adjustable triangle wave generating circuit constructed by the hysteresis comparator has power supply VCC and GND as inputs, and uses the hysteresis comparator to generate a frequency-adjustable triangle wave signal, and the output is a triangle wave signal OUT2; The input of the PWM wave generating circuit with adjustable frequency and adjustable duty cycle is the output OUT1 of the reference voltage source generating circuit and the output OUT2 of the triangle wave generating circuit; the reference voltage and the triangle wave are compared by a comparator to generate a PWM waveform with adjustable frequency and adjustable duty cycle; the output is a PWM wave signal OUT3; The input of the analog quantity transmission circuit with 0-10V output is the output OUT3 of the PWM wave generation circuit, which converts the PWM wave signal into a 0-10V voltage analog quantity output; the output is a 0-10V voltage signal OUT4; The analog transmission circuit with 0-10V output uses the output of the PWM wave generation circuit as input, performs signal processing, and obtains a stable 0-10V voltage output; The input of the analog transmission circuit of 4-20mA output is the output OUT3 of the PWM wave generation circuit, which converts the PWM wave signal into a 4-20mA current analog output; the output is a 4-20mA current signal OUT5; The analog transmission circuit with 4-20mA output uses the output of the PWM wave generation circuit as input, and uses integrated operational amplifiers and switching MOS components for current conversion and control; The above circuit modules jointly complete the analog quantity transmission, starting from the reference voltage source generation, through triangle wave generation, PWM wave generation, and finally converting into the required 0-10V voltage or 4-20mA current output.

2. The controllable output analog quantity transmission circuit for a dedicated transformer terminal according to claim 1, characterized in that: An adjustable reference voltage source generating circuit comprises a sliding rheostat RX1, a transistor QU1, resistors R1 and R2, an electrolytic capacitor E1, a reference voltage output signal OUT1, and power supplies VCC and GND; the connection relationship is as follows: the sliding rheostat RX1-2 is connected to the resistor R1 and the transistor QU1-b, the other end of R1 is connected to VCC, the resistor R2 is connected to VCC, the other end of R2 is connected to QU2-e, the electrolytic capacitor E1, and the reference voltage output signal OUT1, and the other ends of RX1-3, QU1-c, and E1 are connected to GND; the impedance value of the sliding rheostat RX1 can be adjusted to obtain different base voltages of the transistor QU1, thereby obtaining different emitter voltages of the transistor QU1, that is, obtaining different reference voltage sources OUT1; and the establishment time of the reference voltage can be adjusted by adjusting the size of the electrolytic capacitor E1 on the reference voltage source.

3. The controllable output analog quantity transmission circuit for a dedicated transformer terminal according to claim 1, characterized in that: The frequency-adjustable triangle wave generating circuit constructed by the hysteresis comparator includes a sliding rheostat RX2, a comparator N1B, resistors R3, R4, R5, R6, capacitors C1, C2, a triangle wave output signal OUT2, and power supplies VCC and GND; its connection relationship is that the resistor R3 is connected to the power supply VCC, and the other end is connected to the resistor R4, the capacitor C1, the comparator N1B-5, and the resistor R5, the other end of the resistor R4 and the other end of the capacitor C1 are connected to GND, the other end of the resistor R5 is connected to N1B-7, the resistor R6, and the sliding rheostat RX2-2, The other end of resistor R6 is connected to VCC, RX2-3 is connected to capacitor C2, N1B-6, and triangular wave output signal OUT2, and the other end of C2 is connected to GND; the following parameters can be adjusted to adjust the frequency of the output triangular wave OUT2, and adjust the VCC voltage value. When VCC increases, the frequency of triangular wave OUT2 increases; adjust the resistance value of sliding rheostat RX2, such as reducing the resistance value of RX2, to increase the frequency of triangular wave OUT2; adjust the capacitance value of capacitor C2, such as reducing the capacitance value of C2, to increase the frequency of triangular wave OUT2.

4. A controllable output analog quantity transmission circuit for a dedicated transformer terminal as claimed in claim 1, characterized in that: The PWM wave generating circuit with adjustable frequency and adjustable duty cycle includes a reference voltage output signal OUT1, a triangular wave output signal OUT2, a comparator N1A, resistors R7, R8, R9, capacitors C3, C4, a PWM wave output signal OUT3, and power supplies VCC and GND; its connection relationship is that the reference voltage output signal OUT1 is connected to resistor R7, and the other end of R7 is connected to comparator N1A-3, the triangular wave output signal OUT2 is connected to resistor R8, and the other end of R8 is connected to comparator N1A-2, N1A-1 is connected to resistor R9, PWM wave output signal OUT3, the other end of R9, capacitor C3, capacitor C4, and N1A-8 are connected to power supply VCC, and the other ends of C3, C4, and N1A-4 are connected to GND; the adjustable reference voltage source OUT1 and the triangular wave output signal OUT2 with adjustable frequency are input into the comparator N1A, and the PWM output signal OUT3 with adjustable frequency and duty cycle can be obtained.

5. A controllable output analog quantity transmission circuit for a dedicated transformer terminal as claimed in claim 1, characterized in that: The analog quantity transmission circuit with 0-10V output includes a PWM wave output signal OUT3, an operational amplifier N2A, a diode VD1, a voltage regulator VD2, resistors R10 and R11, capacitors C5, C6, C7, C8 and C9, a 0-10V output signal OUT4, and power supplies VCC and GND; the connection relationship is that the PWM wave output signal OUT3 is connected to the resistor R10, the other end of R10 is connected to the capacitor C5 and the resistor R11, the other end of R11 is connected to the capacitor C6 and the operational amplifier N2A-3, the operational amplifier N2A-2 is connected to the operational amplifier N2A-1, the positive electrode of the diode VD1, the negative electrode of the voltage regulator VD2, the capacitor C9, the 0-10V output signal OUT4, the N2A-8, the capacitor C7, the capacitor C8, the negative electrode of VD1 is connected to the power supply VCC, and C5, C6 and C7 , C8, C9, N2A-4, VD2 positive pole connected to GND; adjust the resistors R10, R11, capacitors C5, C6 can adjust the second-order RC passive low-pass filter depth of the PWM wave output signal OUT3; adjust the frequency and duty cycle of the PWM wave output signal OUT3 to adjust the value of the 0-10V output signal OUT4, for example, adjust the frequency of the PWM wave output signal OUT3 to gradually increase, the value of the 0-10V output signal OUT4 will gradually decrease, for example, adjust the duty cycle of the PWM wave output signal OUT3 to gradually increase, the value of the 0-10V output signal OUT4 will gradually decrease; add diode VD1 to the interface, clamp the interface input continuous voltage value to damage the device, add interface TVS tube VD2 and capacitor C9, anti-static and other electromagnetic immunity test shock.

6. A controllable output analog quantity transmission circuit for a dedicated transformer terminal as claimed in claim 1, characterized in that: The analog quantity transmission circuit of 4-20mA output includes PWM wave output signal OUT3, operational amplifiers N2B and N3A, NMOS tube VT1, PMOS tube VT2, inductor L1, fuse RT1, 4-20mA output signal OUT5, resistors R12, R13, R14, R15, R16, R17, capacitors C10, C11, C12, C13, power supplies VCC and GND; its connection relationship is that the PWM wave output signal OUT3 is connected to resistor R12, the other end of R12 is connected to resistor R13 and operational amplifier N2B-5, operational amplifier N2B-6 is connected to NMOS tube VT1-s and resistor R16, N2B-7 is connected to resistor R14, the other end of R14 is connected to VT1-g, VT1-d is connected to resistor R15 and operational amplifier N3A-3, the other end of R15 and resistor R17 are connected to VCC, and the other end of R17 is connected to N3A-2 and PMOS tube VT2-s , N3A-1 is connected to VT2-g, VT2-d is connected to capacitor C12 and inductor L1, the other end of L1 is connected to capacitor C13 and fuse RT1, the other end of RT1 is connected to 4-20mA output signal OUT5, N3A-4, capacitor C10, and capacitor C11 are connected to VCC, the other end of R13, the other end of R16, the other end of C10, the other end of C10, the other end of C12, and the other end of C13 are connected to GND; the frequency and duty cycle of the PWM wave output signal OUT3 can be adjusted to adjust the value of the 4-20mA output signal OUT5. For example, if the frequency of the PWM wave output signal OUT3 is gradually increased, the value of the 4-20mA output signal OUT5 will gradually increase. For example, if the duty cycle of the PWM wave output signal OUT3 is gradually increased, the value of the 4-20mA output signal OUT5 will gradually increase; the interface adds inductor L1 and fuse RT1 to prevent the line from short-circuiting and overcurrent.

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