Circuit for converting high-precision voltage signal into current signal

Abstract

The utility model relates to the technical field of industrial control circuits, in particular to a circuit for converting a high-precision voltage signal into a current signal, which comprises a first operational amplifier and a second operational amplifier, and the in-phase input end of the first operational amplifier is connected with a VIN external input voltage through a second resistor; the inverting input end of the first operational amplifier is connected with the emitting electrode of the triode and the UOUT pin of the ninth resistor through the fourth resistor; the output end of the first operational amplifier is connected with the base electrode of the triode through a third resistor, and the collector electrode of the triode is connected with + 15V voltage; the UL pin of the ninth resistor is connected with an external load circuit interface and the non-inverting input end of the second operational amplifier, and the inverting input end of the second operational amplifier is connected with the output end of the second operational amplifier and is connected with the non-inverting input end of the first operational amplifier through a sixth resistor. The circuit can solve the problem of abnormal current output precision caused by temperature excursion in the existing circuit.

Description

Technical Field

[0001] This utility model relates to the field of industrial control circuit technology, and in particular to a circuit for converting high-precision voltage signals into current signals. Background Technology

[0002] In various sensor applications in industrial control, analog output signals are generally in the form of voltage. With the development of modern industrial equipment, the noise voltage present in industrial environments is increasing, making voltage signals highly susceptible to interference during signal transmission. In contrast, current noise in industrial environments is very low, thus having minimal impact on the transmission of 4-20mA current used in industrial applications. Stable and high-quality current signals play the following important roles:

[0003] 1. A stable and high-quality current signal can ensure that the controlled equipment can operate accurately according to the predetermined requirements.

[0004] 2. A stable and high-quality current signal can provide the stability and reliability required by the system.

[0005] 3. A stable and high-quality current source signal can reduce the impact of external interference on the system, thereby reducing errors and uncertainties.

[0006] 4. A stable and high-quality current signal can prevent damage to the system and equipment caused by excessively high or low voltage. It ensures that the system operates within a safe current range and provides appropriate protection mechanisms to prevent problems such as overload or overcurrent.

[0007] Therefore, a stable and high-quality current signal plays a crucial role in the field of industrial control.

[0008] like Figure 1 As shown, this circuit uses negative feedback to control the input voltage of the operational amplifier, thereby controlling the output current of the transistor, and the transistor operates in the amplification state.

[0009] In this design, the input signal of the second stage is the output signal of the transistor, and the output signal of the second stage is also derived from the transistor. In a transistor amplifier circuit, to ensure proper amplification of the input signal, a suitable DC bias voltage is usually applied between the base and emitter of the transistor. The magnitude and stability of the bias voltage have a significant impact on the performance of the amplifier circuit. Due to the characteristics of the transistor and the influence of the external environment, the bias voltage will drift with temperature changes. Specifically, when the transistor temperature rises, the bias voltage decreases due to the effect of temperature on the PN junction; conversely, when the temperature decreases, the bias voltage rises. This temperature drift of the bias voltage affects the operating stability of the transistor amplifier circuit and the accuracy of signal amplification. Therefore, in this circuit application, the temperature drift of the transistor will affect the accuracy of the current output.

[0010] Therefore, a new technical solution is urgently needed to solve the above-mentioned technical problems. Utility Model Content

[0011] The purpose of this invention is to overcome the problems of the prior art and provide a high-precision voltage signal to current signal conversion circuit to solve the technical problem of abnormal current output accuracy caused by temperature drift in existing circuits.

[0012] The above objectives are achieved through the following technical solutions:

[0013] A high-precision voltage signal to current signal conversion circuit includes a first operational amplifier and a second operational amplifier. The non-inverting input of the first operational amplifier is connected to an external input voltage VIN via a second resistor. The inverting input of the first operational amplifier is connected to the emitter of a transistor and the UOUT pin of a ninth resistor via a fourth resistor. The output of the first operational amplifier is connected to the base of the transistor via a third resistor, and the collector of the transistor is connected to a +15V voltage. The UL pin of the ninth resistor is connected to an external load circuit interface and the non-inverting input of the second operational amplifier. The inverting input of the second operational amplifier is connected to the output of the second operational amplifier and is connected to the non-inverting input of the first operational amplifier via a sixth resistor.

[0014] Furthermore, the transistor is a PNP type transistor.

[0015] Furthermore, a π-type filter is provided between the UL pin of the ninth resistor and the external load circuit interface.

[0016] Furthermore, the π-type filter includes a third capacitor connected to the UL pin of the ninth resistor, and an inductor connected in series with the third capacitor, the other end of which is connected to a fourth capacitor.

[0017] Furthermore, it also includes a reverse protection diode connected in parallel with the fourth capacitor.

[0018] Furthermore, the reverse protection diode is a Schottky diode.

[0019] Furthermore, a fuse is provided between the reverse protection diode and the external load circuit interface.

[0020] This invention provides a high-precision voltage signal to current signal conversion circuit that effectively avoids abnormal output accuracy caused by transistor temperature drift. This circuit is not only simple in structure, but its output current accuracy is only related to the accuracy of the sampling resistor and matching resistor, and is not affected by temperature drift, resulting in higher accuracy. Furthermore, it utilizes an operational amplifier to introduce feedback, achieving the conversion of high-precision input voltage into high-precision current. Attached Figure Description

[0021] Figure 1 This is a circuit diagram for converting a traditional voltage signal to a current signal.

[0022] Figure 2 This is a circuit diagram of a high-precision voltage signal to current signal converter according to the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0024] like Figure 2 As shown, this solution provides a high-precision voltage signal to current signal conversion circuit, including a first operational amplifier U1A and a second operational amplifier U1B. The non-inverting input terminal of the first operational amplifier U1A is connected to the external input voltage VIN through a second resistor R2; the inverting input terminal of the first operational amplifier U1A is connected to the emitter of transistor Q1 and the UOUT pin of the ninth resistor R9 through a fourth resistor R4, for feeding back the voltage of the UOUT pin of the ninth resistor R9 to the inverting input terminal of the first operational amplifier U1A.

[0025] The output terminal of the first operational amplifier U1A is connected to the base of the transistor Q1 through the third resistor R3. The third resistor R3 is used for current limiting. The collector of the transistor Q1 is connected to a +15V voltage.

[0026] The UL pin of the ninth resistor R9 is connected to the external load circuit interface IOI and the non-inverting input of the second operational amplifier U1B. The inverting input of the second operational amplifier U1B is connected to the output of the second operational amplifier U1B, and is connected to the non-inverting input of the first operational amplifier U1A through the sixth resistor R6.

[0027] The negative input terminal of the first operational amplifier U1A is connected to -5V via a first resistor R1 and to analog ground via a first capacitor C1; the positive input terminal of the first operational amplifier U1A is connected to +15V via an eighth resistor R8 and to analog ground via a second capacitor C2. A seventh resistor R7 is provided between the inverting input terminal of the first operational amplifier U1A and the fourth resistor R4, and is grounded.

[0028] This circuit receives an input voltage signal of 0V to 2.5V, converts it into a current signal of 0 to 20mA, and then feeds it back to the operational amplifier through the ninth resistor R9 on the low side, which is used as a current sensor. This allows for precise current regulation.

[0029] The ninth resistor, R9, is the sampling resistor; the second resistor, R2, the fourth resistor, R4, the sixth resistor, R6, and the seventh resistor, R7, are matching resistors.

[0030] Specifically, in this embodiment, the voltage at the UL pin of the ninth resistor R9 is connected to the non-inverting input of the second operational amplifier U1B, and the inverting input of the second operational amplifier U1B is connected to its output. The sixth resistor R6 is then connected to form an operational amplifier follower circuit. This follower circuit ensures that the voltage at the UL pin of the ninth resistor R9 is equal to the voltage at the bottom of the pin of the sixth resistor R6, thereby making the signal more stable.

[0031] Furthermore, the output terminal of the second operational amplifier U1B is connected to the non-inverting input terminal of the first operational amplifier U1A through the sixth resistor R6, thereby sending the voltage of the UL pin of the ninth resistor R9 to the non-inverting input terminal of the first operational amplifier U1A.

[0032] When the external load changes, the voltage at pin UL of the ninth resistor R9 will change. Through the connection of the above circuit, the voltage at the non-inverting input of the first operational amplifier U1A will also change. At the same time, the voltage at the inverting input of the first operational amplifier U1A will change accordingly, causing the voltage at pin UOUT of the ninth resistor R9 to change as well. In this way, the circuit can maintain a constant output current when the external input voltage VIN is changed through dynamic adjustment.

[0033] It should be noted that the transistor Q1 described in this embodiment is a PNP type transistor.

[0034] This circuit incorporates a π-type filter between the UL pin of the ninth resistor R9 and the external load circuit interface IOI to filter out unwanted waveforms, resulting in a more stable and higher-quality signal. Specifically, the π-type filter includes a third capacitor C3 connected to the UL pin of the ninth resistor R9, and an inductor L1 connected in series with the third capacitor C3. The other end of the inductor L1 is connected to a fourth capacitor C4.

[0035] This circuit also includes a reverse protection diode D1 connected in parallel with the fourth capacitor C4, used to absorb external voltage spikes and ensure signal stability. The reverse protection diode D1 is a Schottky diode.

[0036] In addition, in this embodiment, a fuse FU1 is provided between the reverse protection diode D1 and the external load circuit interface IOI to protect the circuit.

[0037] The above description is only for illustrating the embodiments of this utility model and is not intended to limit this utility model. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A circuit for converting a high-precision voltage signal into a current signal, characterized in that The circuit comprises a first operational amplifier (U1A) and a second operational amplifier (U1B), the non-inverting input of the first operational amplifier (U1A) is connected with an external input voltage VIN through a second resistor (R2); the inverting input of the first operational amplifier (U1A) is connected with the emitter of a transistor (Q1) and the UOUT pin of a ninth resistor (R9) through a fourth resistor (R4); the output of the first operational amplifier (U1A) is connected with the base of the transistor (Q1) through a third resistor (R3), and the collector of the transistor (Q1) is connected with a +15V voltage; the UL pin of the ninth resistor (R9) is connected with an external load circuit interface (IOI) and the non-inverting input of the second operational amplifier (U1B), the inverting input of the second operational amplifier (U1B) is connected with the output of the second operational amplifier (U1B), and the non-inverting input of the first operational amplifier (U1A) is connected with the output of the second operational amplifier (U1B) through a sixth resistor (R6).

2. The circuit of claim 1, wherein, The transistor (Q1) is a PNP type transistor.

3. The circuit of claim 1, wherein, A π type filter is arranged between the UL pin of the ninth resistor (R9) and the external load circuit interface (IOI).

4. The circuit of claim 3, wherein, The π type filter comprises a third capacitor (C3) connected with the UL pin of the ninth resistor (R9), and an inductor (L1) connected with the third capacitor (C3) in series, and the other end of the inductor (L1) is connected with a fourth capacitor (C4).

5. The circuit of claim 4, wherein, A reverse protection diode (D1) is further connected with the fourth capacitor (C4) in parallel.

6. The circuit of claim 5, wherein, The reverse protection diode (D1) is a Schottky diode.

7. The circuit of claim 5, wherein, A fuse (FU1) is arranged between the reverse protection diode (D1) and the external load circuit interface (IOI).

Images