Large-current output voltage-controlled constant current source circuit

Abstract

The invention relates to a high-current output voltage-controlled constant current source circuit, which comprises a first operational amplifier, an output pin, a second operational amplifier and a sampling resistor unit, the in-phase input end of the first operational amplifier is connected to the positive electrode of an input power supply and is grounded through a first resistor, the inverted input end is connected to the output end through a second resistor, and the output end is further connected to the in-phase input end of the second operational amplifier through a third resistor; the in-phase input end of the second operational amplifier is also connected to the first end of the sampling resistor unit through a fifth resistor and is connected to the output pin through a load, and the inverted input end of the second operational amplifier is grounded through a fourth resistor and is connected to the second end of the sampling resistor unit and the output end of the second operational amplifier through a sixth resistor; the sampling resistor unit comprises a plurality of sampling resistors connected in parallel. Compared with the prior art, the method has the advantages of improving the output precision and the like.

Description

Technical Field

[0001] This invention relates to a constant current source for current sampling board testing, and more particularly to a high current output voltage-controlled constant current source circuit. Background Technology

[0002] In the field of railway communication, it is necessary to test current acquisition boards. During the testing process, a constant current source is required. However, traditional voltage-controlled constant current source solutions usually have some inherent drawbacks: For discrete component solutions: This involves using discrete components such as transistors, field-effect transistors, and operational amplifiers. This approach results in a large number of components, complex circuitry, and difficult debugging. Furthermore, its accuracy and stability heavily depend on individual component variations and temperature characteristics, making it difficult to achieve high precision.

[0003] For application-specific integrated circuit (ASIC) solutions: integrated voltage-controlled constant current source chips are used. Although they offer high integration, these chips are typically expensive, have a fixed output current range, lack flexibility, and are not readily available for specific current or voltage requirements.

[0004] Based on this, those skilled in the art generally tend to choose ordinary operational amplifier solutions. However, constant current sources built using ordinary operational amplifiers have limited output current capabilities and are difficult to directly drive loads requiring hundreds of mA. If current amplification is required, an external power transistor circuit needs to be added. For example, Chinese patent CN102723658A discloses a constant current source power supply circuit for lasers, mainly used in the field of tunable lasers. It can provide a highly stable laser power supply current. It includes a voltage-controlled input terminal, a voltage-controlled constant current source circuit, a current output terminal, and a positive feedback circuit. The positive feedback circuit includes a voltage follower, the input terminal of which is connected to the current output terminal, and the output terminal of which is connected to the non-inverting input terminal of the first operational amplifier. The control voltage is input from the voltage-controlled input terminal, and the voltage-controlled constant current source circuit controls the magnitude of the laser power supply current output from the current output terminal. When the control voltage changes abruptly, the power supply current smoothly transitions to the control voltage direction through the positive feedback circuit, controlling the voltage at the non-inverting input terminal of the first operational amplifier. Under the effect of the negative feedback speed of the voltage-controlled constant current source circuit being faster than the positive feedback speed, the power supply current smoothly changes to the current value set by the control voltage. In this existing technology, a field-effect transistor (FET) is used to increase the output current. On the one hand, the introduction of the FET will generate more heat and reduce linearity, both of which will lead to a decrease in overall accuracy. On the other hand, the sampling resistor on the output side uses a single resistor, so the heat dissipation efficiency is not high. As a result, heat generation will also occur, leading to a decrease in overall output accuracy. Summary of the Invention

[0005] The purpose of this invention is to provide a high-current output voltage-controlled constant current source circuit to solve the problems existing in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: A high-current output voltage-controlled constant current source circuit includes a first operational amplifier and an output pin for connecting to a current acquisition board under test, and also includes a second operational amplifier and a sampling resistor unit. The non-inverting input terminal of the first operational amplifier is connected to the positive terminal of the input power supply and grounded through the first resistor. The inverting input terminal is connected to the output terminal through the second resistor, and the output terminal is also connected to the non-inverting input terminal of the second operational amplifier through the third resistor. The non-inverting input of the second operational amplifier is also connected to the first terminal of the sampling resistor unit through the fifth resistor, and to the output pin through the load. The inverting input is grounded through the fourth resistor, and is connected to the second terminal of the sampling resistor unit and the output terminal of the second operational amplifier through the sixth resistor. The sampling resistor unit includes multiple sampling resistors connected in parallel.

[0007] The positive input terminal of the first operational amplifier is connected to the positive terminal of the first power supply and to one end of the first capacitor and the second capacitor. The other ends of the first capacitor and the second capacitor are both grounded. The negative input terminal of the first operational amplifier is connected to the negative terminal of the first power supply and to one end of the third and fourth capacitors, the other ends of the third and fourth capacitors being grounded.

[0008] The positive input terminal of the second operational amplifier is connected to the positive terminal of the second power supply and to one end of the fifth and sixth capacitors, the other ends of the fifth and sixth capacitors being grounded; The negative input terminal of the second operational amplifier is connected to the negative terminal of the second power supply and to one end of the seventh and eighth capacitors, the other ends of the seventh and eighth capacitors being grounded.

[0009] All sampling resistors in the sampling resistor unit have the same resistance value.

[0010] The resistance values ​​of the third resistor and the fourth resistor are equal.

[0011] The fifth and sixth resistors have the same resistance value.

[0012] The resistance values ​​of the third resistor and the fifth resistor are equal.

[0013] The resistance of the first resistor is ten times that of the second resistor.

[0014] The rated current of the second operational amplifier is greater than the rated current of the first operational amplifier.

[0015] The resistance value of the voltage sampling resistor of the first power supply is equal to the resistance value of the fifth resistor.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. By designing a two-stage operational amplifier for amplification without using a field-effect transistor (FET), the problems of high heat generation and poor linearity caused by FET can be solved. On the other hand, the sampling resistor unit includes multiple parallel sampling resistors, and the spacing between the multiple sampling resistors is set as large as possible, which can improve the heat dissipation effect and ultimately improve the current control accuracy and anti-interference capability.

[0017] 2. A precision feedback control loop based on differential input is adopted, which realizes high-precision linear control of the output current and has strong anti-interference ability.

[0018] 3. Using multiple precision resistors (Rs1-Rs4) in parallel as current sampling units effectively improves the power processing capability and thermal stability of the sampling network, avoiding the decrease in accuracy caused by heat generation in a single resistor.

[0019] 4. Using resistor R3 for coupling between the two operational amplifiers provides good impedance matching and signal isolation, improving the independence and stability of the operation of the preceding and following stages. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; Where: R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; RL, load; Rs1 to Rs4 are sampling resistors; C1, first capacitor; C2, second capacitor; C3, third capacitor; C4, fourth capacitor; C5, fifth capacitor; C6, sixth capacitor; C7, seventh capacitor; C8, eighth capacitor; Vin, input power supply; Vout, output pin; U1, first operational amplifier; U2, second operational amplifier. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "proximal," "distal," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Physical quantities in formulas, unless otherwise specified, should be understood as basic quantities in the International System of Units (SI), or derived quantities derived from basic quantities through mathematical operations such as multiplication, division, differentiation, or integration.

[0024] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] A high-current output voltage-controlled constant current source circuit, such as Figure 1 As shown, it includes a first operational amplifier U1 and an output pin Vout for connecting to the current acquisition board under test, and also includes a second operational amplifier U2 and a sampling resistor unit; The non-inverting input terminal of the first operational amplifier U1 is connected to the positive terminal of the input power supply Vin and grounded through the first resistor R1. The inverting input terminal is connected to the output terminal through the second resistor R2, and the output terminal is also connected to the non-inverting input terminal of the second operational amplifier U2 through the third resistor R3. The non-inverting input of the second operational amplifier U2 is also connected to the first terminal of the sampling resistor unit through the fifth resistor R5, and to the output pin Vout through the load RL. The inverting input is grounded through the fourth resistor R4, and is connected to the second terminal of the sampling resistor unit and the output terminal of the second operational amplifier U2 through the sixth resistor R6. The sampling resistor unit consists of multiple sampling resistors connected in parallel.

[0027] By designing a two-stage operational amplifier for amplification without using a field-effect transistor (FET), the problems of high heat generation and poor linearity caused by FET can be solved. On the other hand, the sampling resistor unit includes multiple parallel sampling resistors, which are spaced as far apart as possible to improve heat dissipation. Ultimately, this can improve current control accuracy and anti-interference capability.

[0028] In this embodiment, the positive input terminal of the first operational amplifier U1 is connected to the positive terminal of the first power supply and to one end of the first capacitor C1 and the second capacitor C2. The other ends of the first capacitor C1 and the second capacitor C2 are both grounded. The negative input terminal of the first operational amplifier U1 is connected to the negative terminal of the first power supply, and is also connected to one end of the third capacitor C3 and the fourth capacitor C4. The other ends of the third capacitor C3 and the fourth capacitor C4 are both grounded.

[0029] In this embodiment, the positive input terminal of the second operational amplifier U2 is connected to the positive terminal of the second power supply and to one end of the fifth capacitor C5 and the sixth capacitor C6. The other ends of the fifth capacitor C5 and the sixth capacitor C6 are both grounded. The negative input terminal of the second operational amplifier U2 is connected to the negative terminal of the second power supply, and is connected to one end of the seventh capacitor C7 and the eighth capacitor C8. The other ends of the seventh capacitor C7 and the eighth capacitor C8 are both grounded.

[0030] In addition, all sampling resistors in the sampling resistor unit have the same resistance value, and the resistance values ​​of the third resistor R3 and the fourth resistor R4 are equal.

[0031] In this embodiment, the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 are also equal.

[0032] Generally, the resistance values ​​of the third resistor R3 and the fifth resistor R5 are equal, and the resistance value of the first resistor R1 is ten times that of the second resistor R2.

[0033] The rated current of the second operational amplifier U2 is greater than the rated current of the first operational amplifier U1.

[0034] In addition, in this embodiment, the first operational amplifier U1 is a high-voltage operational amplifier, which can be an OPA445, and the second operational amplifier U2 is a high-current power operational amplifier, which can be an OPA547F. In the first operational amplifier U1, the non-inverting input terminal of the first operational amplifier U1 is also grounded through a first resistor R1R1 to provide an input bias current path and enhance stability. The resistance value of resistor R1 is 10KΩ.

[0035] In this embodiment, a second resistor R2R2 with a resistance of 1kΩ is connected between the inverting input terminal and the output terminal of the first operational amplifier U1 to form a gain-adjustable non-inverting amplifier or buffer. The first operational amplifier U1 is powered by both positive and negative power supplies.

[0036] In this embodiment, the output terminal of the first operational amplifier U1 is connected to the non-inverting input terminal of the second operational amplifier U2 through a third resistor R3R3.

[0037] The inverting input of the second operational amplifier U2 is grounded through a fourth resistor R4R4, and simultaneously connected to its output through a sixth resistor R6R6. Together with the fourth resistor R4R4, they set the closed-loop gain of the second operational amplifier U2. The non-inverting input of the second operational amplifier U2 is also connected to the sampling point (i.e., the connection point between the subsequent sampling resistor network and the load RLRL) through a fifth resistor R5R5.

[0038] The output of the second operational amplifier U2 is connected to a precision sampling resistor consisting of four parallel resistors. In this embodiment, the resistance of each sampling resistor is 24Ω, and the sampling point is the connection point between the sampling resistor unit and the load RL.

[0039] This circuit uses a clever dual op-amp architecture and feedback network to control the current I flowing through the load RL. out It is strictly linearly related to the control voltage Vin. Its core equation is I... out = Vin / Rs, where Rs is the total equivalent resistance of the parallel sampling resistors.

[0040] The work process is as follows: 1. First-stage op-amp: The input voltage Vin is initially amplified or buffered by the first op-amp and its peripheral second resistor R2. Its output voltage is sent to the second stage via the third resistor R3.

[0041] 2. Second-stage operational amplifier: U2 and its external resistors R4, R5, and R6 form a differential amplifier or summator circuit. It processes two signals simultaneously: the output signal from U1 and the voltage feedback signal from the sampling point. The output of U2 drives the sampling resistor network and the load RL.

[0042] 3. Constant Current Establishment: The entire system forms a negative feedback closed loop. When the load changes, causing the output current I... out When the value deviates from the setpoint, the voltage at the sampling point changes accordingly. This change is fed back to U2 through R5, compared and amplified with the signal input through R3, thereby driving U2 to adjust its output voltage, ultimately forcing I... out The system returns to stability, achieving constant current output. By carefully matching the values ​​of resistors R3, R4, R5, and R6, the current expression can be simplified, and control accuracy can be improved.

[0043] Role division: 1. For U1, as a high-precision, high-input-impedance preamplifier, it ensures that the control voltage Vin is accurately received and processed.

[0044] 2. For U2: As the core of power drive, it provides a large output current and uses its internal protection circuit to ensure system safety.

[0045] 3. For sampling resistors: The output current is converted into a voltage signal for feedback. The parallel structure helps to distribute power, improve reliability, and reduce the effects of thermal drift. This application innovatively adopts a cascaded structure of high-voltage precision operational amplifier (OPA445) and high-current power operational amplifier (OPA547F), and designs a feedback loop containing a specific resistor network (R3, R4, R5, R6) and a parallel precision sampling resistor network, which together constitute a voltage-controlled constant current source with a simple structure, high precision, strong driving capability and stability.

[0046] Thanks to the high precision of the OPA445, its deep negative feedback design, and the low temperature drift characteristics brought by the parallel sampling resistor, the output current accuracy and stability are excellent.

[0047] The OPA547F can provide up to 500mA of output current, and the output current can be linearly adjusted by changing Vin.

[0048] The core circuit consists of two integrated circuits and a small number of precision resistors, eliminating the need for complex discrete component current amplification or compensation circuits, thus reducing cost and design complexity.

[0049] The OPA547F's built-in protection functions and the shunt heat dissipation design of the parallel sampling resistor together ensure the system's high reliability under conditions such as overload or short circuit.

[0050] The parallel design of sampling resistors significantly reduces the power dissipation of individual resistors, reduces temperature rise, and thus reduces measurement errors caused by temperature changes.

[0051] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A large current output voltage controlled constant current source circuit comprising a first operational amplifier and an output pin for connecting a current collection board under test, characterized in that, The second operational amplifier and the sampling resistor unit are further included. The non-inverting input terminal of the first operational amplifier is connected to the positive pole of an input power supply and grounded through a first resistor, the inverting input terminal is connected to the output terminal through a second resistor, and the output terminal is further connected to the non-inverting input terminal of the second operational amplifier through a third resistor. The non-inverting input terminal of the second operational amplifier is further connected to the first end of the sampling resistor unit through a fifth resistor and to the output pin through a load, the inverting input terminal is grounded through a fourth resistor and connected to the second end of the sampling resistor unit and the output terminal of the second operational amplifier through a sixth resistor. The sampling resistor unit comprises a plurality of parallel sampling resistors.

2. A large current output voltage controlled constant current source circuit according to claim 1, characterized in that, The positive pole input terminal of the first operational amplifier is connected to the positive pole of a first power supply and to one end of a first capacitor and a second capacitor, and the other ends of the first capacitor and the second capacitor are grounded. The negative pole input terminal of the first operational amplifier is connected to the negative pole of the first power supply and to one end of a third capacitor and a fourth capacitor, and the other ends of the third capacitor and the fourth capacitor are grounded.

3. The large current output voltage controlled constant current source circuit according to claim 1, wherein, The positive pole input terminal of the second operational amplifier is connected to the positive pole of a second power supply and to one end of a fifth capacitor and a sixth capacitor, and the other ends of the fifth capacitor and the sixth capacitor are grounded. The negative pole input terminal of the second operational amplifier is connected to the negative pole of the second power supply and to one end of a seventh capacitor and an eighth capacitor, and the other ends of the seventh capacitor and the eighth capacitor are grounded.

4. The large current output voltage controlled constant current source circuit of claim 1, wherein, The resistance values of all the sampling resistors in the sampling resistor unit are equal.

5. The large current output voltage controlled constant current source circuit of claim 1, wherein, The resistance values of the third resistor and the fourth resistor are equal.

6. A large current output voltage controlled constant current source circuit according to claim 1, wherein, The resistance values of the fifth resistor and the sixth resistor are equal.

7. A large current output voltage controlled constant current source circuit as claimed in claim 5 or 6, characterized in that, The resistance values of the third resistor and the fifth resistor are equal.

8. The large current output voltage controlled constant current source circuit of claim 1, wherein, The resistance value of the first resistor is ten times that of the second resistor.

9. The large current output voltage controlled constant current source circuit of claim 1, wherein, The rated current of the second operational amplifier is greater than that of the first operational amplifier.

10. The large current output voltage controlled constant current source circuit according to claim 2, wherein, The resistance value of the voltage sampling resistor of the first power supply is equal to that of the fifth resistor.

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