Voltage transmitting circuit of micro differential pressure transmitter

Abstract

The utility model provides a kind of voltage transmitting circuit's circuit of micro differential pressure transmitter, including control module, negative voltage generation module, reference voltage module and differential amplification module, negative voltage generation module is connected with external power supply, for converting positive power supply into negative power supply;Reference voltage module is connected with negative voltage generation module and external power supply respectively, and reference voltage module is used to generate reference voltage;The output end of the opposite phase input end of differential amplification module and reference voltage module is connected by the fourth resistance, and the same phase input end of differential amplification module is connected with the DAC output of control module;The eighth resistance is connected between the output end of differential amplification module and its opposite phase input end, and the output end of differential amplification module is connected with the control module.Cleverly utilize the negative power supply generated by charge pump, combined with the collaborative work of two-stage operational amplifier, under the premise of not significantly increasing cost, the true zero voltage output capability is realized, and the precision can reach millivolt level or even microvolt level.

Description

Technical Field

[0001] This utility model relates, and particularly to, a voltage transmission circuit for a differential pressure transmitter. Background Technology

[0002] In industrial control and precision measurement, voltage output transmitters (such as sensor signal conditioning circuits or DAC output circuits) often face a critical problem: when the theoretical output should be 0V, the actual output may have a small, fixed error (such as 0.005V or 0.008V), thus limiting the transmitter's accuracy and affecting the precision of the measurement results. This error originates from the op-amp's input offset voltage, power supply asymmetry, or the nonlinear characteristics of the device itself. Traditional solutions (such as using better operational amplifiers) may increase cost or complexity, while hardware adjustments (such as zero-point potentiometers) may introduce instability. Therefore, there is an urgent need for a low-cost, high-reliability hardware solution to completely eliminate zero-point error at the circuit design level to meet the requirements of high-precision applications. Utility Model Content

[0003] To address the aforementioned issues, the purpose of this invention is to provide a voltage transmission circuit for a differential pressure transmitter. By generating a negative power supply through a charge pump and combining it with the virtual short characteristic of the operational amplifier, the DAC output is adjusted to match the reference voltage, thereby enabling the differential amplifier module to output 0V and achieving true "zero output." This solves the problem of inaccurate accuracy when the theoretical output is 0V.

[0004] This utility model is achieved through the following technical solution:

[0005] A voltage transmission circuit for a differential pressure transmitter includes:

[0006] Control module;

[0007] A negative pressure generation module, which is connected to an external power supply, is used to convert positive power into negative power.

[0008] A reference voltage module is connected to the negative voltage generation module and an external power supply, and the reference voltage module is used to generate a reference voltage.

[0009] A differential amplifier module is provided, wherein the inverting input terminal of the differential amplifier module is connected to the output terminal of the reference voltage module through a fourth resistor, and the non-inverting input terminal of the differential amplifier module is connected to the DAC output of the control module; an eighth resistor is connected in series between the output terminal and the inverting input terminal of the differential amplifier module, and the output terminal of the differential amplifier module is connected to the control module.

[0010] Furthermore, the negative voltage generation module includes a charge pump chip and a capacitor bank connected to the charge pump chip. The power supply pin of the charge pump chip is connected to the external power supply, and the output terminal of the charge pump chip is connected to the reference voltage module. The capacitor bank includes a first capacitor connected between the power supply pin of the charge pump chip and ground, a second capacitor connected between the positive and negative capacitor pins of the charge pump chip, and a third capacitor connected between the output pin of the charge pump chip and ground.

[0011] Furthermore, the reference voltage module includes a first operational amplifier, a voltage divider component connected to the non-inverting input of the first operational amplifier, a positive power supply pin of the first operational amplifier connected to the external power supply, a negative power supply pin of the first operational amplifier connected to the output of the negative voltage generation module, an inverting input of the first operational amplifier connected to its output, and an output of the first operational amplifier connected to the fourth resistor.

[0012] Furthermore, the voltage divider assembly includes a fifth resistor and a fourteenth resistor connected in series, with the other end of the fourteenth resistor grounded and the other end of the fifth resistor connected to the external power supply; the common terminal of the fifth resistor and the fourteenth resistor is connected to the non-inverting input terminal of the first operational amplifier.

[0013] Furthermore, the positive and negative power supply pins of the first operational amplifier are grounded through capacitors.

[0014] Furthermore, the differential amplifier module includes a second operational amplifier, the inverting input of the second operational amplifier is connected to the fourth resistor, and the non-inverting input of the second operational amplifier is connected to the DAC output of the control module; the eighth resistor is connected in series between the inverting input of the second operational amplifier and its output.

[0015] Furthermore, a twelfth resistor is connected in series between the output terminal of the second operational amplifier and the eighth resistor, and the common terminal of the eighth resistor and the twelfth resistor is the output terminal of the voltage transmitter circuit.

[0016] Furthermore, a TVS diode is connected between the eighth resistor and the twelfth resistor, and the anode of the TVS diode is grounded.

[0017] Compared with the prior art, the technical solution of this utility model and its beneficial effects are as follows:

[0018] (1) This utility model integrates a control module, a negative voltage generation module, a reference voltage module, and a differential amplifier module. When the DAC output of the control module is 0, according to the virtual short principle of the differential amplifier module, the inverting input terminal of the differential amplifier module should also be 0V. The output of the reference voltage module 300 is V_ref, then the output of the differential amplifier module 400 is -(V_ref / R4)*R8, and this output is synchronously transmitted to the control module. The control module controls the DAC output V_ref to be consistent with the output voltage of the reference voltage module 300, so that the output terminal reaches 0V, thereby eliminating the fixed error when the output is 0V and realizing high-precision voltage output.

[0019] (2) This utility model uses a three-level hardware linkage of “negative power supply generation → negative reference voltage → differential compensation” to directly cancel the operational amplifier offset voltage in the differential amplifier module, and the theoretical zero-point output error approaches 0V.

[0020] (3) The design of the TVS tube and the twelfth resistor of the output current limiting resistor in this utility model prevents damage from overvoltage / overcurrent and adapts to complex interference in industrial environments. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of the voltage transmission circuit of a differential pressure transmitter provided in an embodiment of this utility model.

[0022] Illustration:

[0023] Control module-100; Negative voltage generation module-200; Reference voltage module-300; Differential amplifier module-400. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this utility model and are not intended to limit this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0025] See Figure 1A voltage transmission circuit for a differential pressure transmitter includes a control module 100, a negative voltage generation module 200, a reference voltage module 300, and a differential amplifier module 400. The negative voltage generation module 200 is connected to an external 24V power supply and is used to convert the positive power supply into a negative power supply -3V. The reference voltage module 300 is connected to both the negative voltage generation module 200 and the external 24V power supply. The reference voltage module 300 is used to generate a reference voltage; that is, after the reference voltage module is connected to both 24V and -3V, it outputs a fixed reference voltage. The inverting input terminal of the differential amplifier module 400 is connected to the output terminal of the reference voltage module 300 through a resistor R4, and the non-inverting input terminal of the differential amplifier module 400 is connected to the DAC output of the control module 100. A resistor R8 is connected in series between the output terminal and the inverting input terminal of the differential amplifier module 400, and the output terminal of the differential amplifier module 400 is connected to the control module 100.

[0026] When the DAC output of the control module is 0, according to the virtual short principle of the differential amplifier module, the inverting input of the differential amplifier module should also be 0V. Assuming the output of the reference voltage module 300 is V_ref, then the output of the differential amplifier module 400 is -(V_ref / R4)*R8. This output is synchronously transmitted to the control module. The control module controls the DAC output V_ref to match the output voltage of the reference voltage module 300, making the output terminal reach 0V, thereby eliminating the fixed error at 0V output and achieving high-precision voltage output.

[0027] The negative voltage generation module 200 includes a charge pump chip U9 and a capacitor bank connected to the charge pump chip U9. The power supply pin of the charge pump chip U9 is connected to an external 24V power supply, and the output terminal VOUT of the charge pump chip U9 is connected to the reference voltage module 300. The capacitor bank includes a capacitor C10 connected between the power supply pin V+ of the charge pump chip U9 and ground GND, a capacitor C8 connected between the positive and negative capacitor pins of the charge pump chip U9, and a capacitor C9 connected between the output pin VOUT of the charge pump chip U9 and ground GND. The charge pump chip U9 converts the positive power supply to a negative power supply, providing dual power supply for the reference voltage module. In this embodiment, the input is 24V and the output is -3V.

[0028] The reference voltage module 300 includes a first operational amplifier U4.1 and a voltage divider assembly connected to the non-inverting input of the first operational amplifier U4.1. The positive power supply pin of the first operational amplifier U4.1 is connected to an external 24V power supply, and the negative power supply pin of the first operational amplifier U4.1 is connected to the -3V output voltage of the negative voltage generation module. The inverting input of the first operational amplifier U4.1 is connected to its output, and the output of the first operational amplifier provides a fixed reference voltage that is transmitted to the differential amplifier module via a resistor R4. The positive and negative power supply pins of the first operational amplifier U4.1 are grounded through capacitors to eliminate high-frequency noise, prevent self-oscillation of the operational amplifier, and improve the purity of the reference voltage.

[0029] In this embodiment, the voltage divider assembly includes resistors R5 and R14 connected in series. One end of resistor R14 is grounded, and the other end of resistor R5 is connected to an external 24V power supply. The common terminal of resistors R5 and R14 is connected to the non-inverting input of the first operational amplifier U4.1. By dividing the voltage using resistors R5 and R14, and combining this with the operational amplifier follower circuit, a fixed reference voltage is generated. It can be understood that adjusting the resistance ratio of resistors R5 and R14 adjusts the value of the reference voltage.

[0030] Continue reading Figure 1 The differential amplifier module 400 includes a second operational amplifier U4.2. The inverting input of the second operational amplifier U4.2 is connected to resistor R4, and the non-inverting input of the second operational amplifier U4.2 is connected to the DAC output of the control module 100. Resistor R8 is connected in series between the inverting input and the output of the second operational amplifier U4.2. The reference voltage is connected to the inverting input of the second operational amplifier U4.2 through resistor R4, and the output of the second operational amplifier U4.2 is fed back to the inverting input through resistor R8, forming negative feedback. When the DAC output of the control module is 0V, utilizing the virtual short characteristic of the second operational amplifier U4.2 (the voltages at pins 5 and 6 are equal), the DAC output voltage is adjusted to match the output voltage at pin 1 of operational amplifier U4.1, so that the output (V) reaches 0V. Vout = R8 * (V DAC -Vref) / R4, Vout is the output value of the voltage transmitter circuit, and Vref is the output voltage of the first operational amplifier U4.1. DAC =Vref, Vout equals 0. The second operational amplifier U4.2 constitutes an adjustable gain differential amplifier, and the amplification factor is set by the ratio of resistors R4 and R8. At the same time, hardware-level zero-point compensation is achieved using a reference voltage.

[0031] A resistor R12 is connected in series between the output of the second operational amplifier U4.2 and resistor R8. The common terminal of resistors R8 and R12 is the output terminal of the voltage transmitter circuit. Resistor R12 serves as output current limiting protection, preventing damage to the operational amplifier due to short circuits or overloads, and improving circuit robustness. A TVS diode U15 is also connected between resistors R8 and R12 to clamp the output voltage, preventing transient overvoltages (such as ESD) from damaging the downstream circuitry and enhancing anti-interference capabilities.

[0032] The foregoing description illustrates and describes preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the present invention through the foregoing teachings or related technical or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A voltage transmission circuit for a differential pressure transmitter, characterized in that, include: Control module; A negative pressure generation module, which is connected to an external power supply, is used to convert positive power into negative power. A reference voltage module is connected to the negative voltage generation module and an external power supply, and the reference voltage module is used to generate a reference voltage. A differential amplifier module is provided, wherein the inverting input terminal of the differential amplifier module is connected to the output terminal of the reference voltage module through a fourth resistor, and the non-inverting input terminal of the differential amplifier module is connected to the DAC output of the control module; an eighth resistor is connected in series between the output terminal and the inverting input terminal of the differential amplifier module, and the output terminal of the differential amplifier module is connected to the control module.

2. The voltage transmission circuit of a differential pressure transmitter according to claim 1, characterized in that, The negative voltage generation module includes a charge pump chip and a capacitor bank connected to the charge pump chip. The power supply pin of the charge pump chip is connected to the external power supply, and the output terminal of the charge pump chip is connected to the reference voltage module. The capacitor bank includes a first capacitor connected between the power supply pin of the charge pump chip and ground, a second capacitor connected between the positive and negative capacitor pins of the charge pump chip, and a third capacitor connected between the output pin of the charge pump chip and ground.

3. The voltage transmission circuit of a differential pressure transmitter according to claim 1, characterized in that, The reference voltage module includes a first operational amplifier and a voltage divider component connected to the non-inverting input of the first operational amplifier. The positive power supply pin of the first operational amplifier is connected to the external power supply, and the negative power supply pin of the first operational amplifier is connected to the output of the negative voltage generation module. The inverting input of the first operational amplifier is connected to its output, and the output of the first operational amplifier is connected to the fourth resistor.

4. The voltage transmission circuit of a differential pressure transmitter according to claim 3, characterized in that, The voltage divider assembly includes a fifth resistor and a fourteenth resistor connected in series. The other end of the fourteenth resistor is grounded, and the other end of the fifth resistor is connected to the external power supply. The common terminal of the fifth resistor and the fourteenth resistor is connected to the non-inverting input terminal of the first operational amplifier.

5. The voltage transmission circuit of a differential pressure transmitter according to claim 3, characterized in that, The positive and negative power supply pins of the first operational amplifier are grounded through capacitors.

6. The voltage transmission circuit of a differential pressure transmitter according to claim 1, characterized in that, The differential amplifier module includes a second operational amplifier, the inverting input of which is connected to the fourth resistor, and the non-inverting input of which is connected to the DAC output of the control module; the eighth resistor is connected in series between the inverting input and the output of the second operational amplifier.

7. The voltage transmission circuit of a differential pressure transmitter according to claim 6, characterized in that, A twelfth resistor is connected in series between the output terminal of the second operational amplifier and the eighth resistor, and the common terminal of the eighth resistor and the twelfth resistor is the output terminal of the voltage transmitter circuit.

8. The voltage transmission circuit of a differential pressure transmitter according to claim 7, characterized in that, A TVS diode is also connected between the eighth resistor and the twelfth resistor, and the anode of the TVS diode is grounded.

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