Self-adaptive high-precision constant current source circuit

Abstract

The invention relates to the technical field of constant current sources, in particular to a self-adaptive high-precision constant current source circuit. The controller comprises a controller adaptive calculation unit, an operational amplifier circuit, a feedback circuit and a sampling resistor, the feedback circuit comprises a first-stage negative feedback circuit, a first-stage positive feedback circuit and a second-stage negative feedback circuit, the controller adaptive calculation unit comprises a gear shifting circuit, and the gear shifting circuit, the operational amplifier circuit and the sampling resistor are sequentially connected. The sampling resistor is connected with a power output end, two ends of the first-stage negative feedback loop and the first-stage positive feedback loop are respectively connected with an input end of the operational amplifier circuit and an output end of the sampling resistor, and two ends of the second-stage negative feedback loop are respectively connected with an input end and an output end of the operational amplifier circuit. The first-stage negative feedback loop or the first-stage positive feedback loop feeds back the output voltage, and the second-stage negative feedback loop feeds back the output voltage of the operational amplifier. According to the invention, the output current can be calibrated automatically, and the output current is high in gear resolution and high in precision.

Description

Technical Field

[0001] The invention relates to the technical field of constant current sources, and in particular to an adaptive high-precision constant current source circuit. Background Art

[0002] In industrial control field applications, current can not only be used as a standard for analog signal transmission, but also often as a drive control signal for sensors, solid-state switches, valve limiters or other output actuators. The reason is that the current signal is suitable for long-distance transmission, is not affected by the distributed resistance of the transmission line, has no attenuation, has strong anti-interference, and can effectively ensure the accuracy of signal transmission. The constant current source circuit with a power of hundreds of milliwatts generally includes an amplifier-driven transistor circuit and an integrated current chip circuit. Among them, the output current of the amplifier-driven transistor circuit is difficult to be completely linear with the input voltage; although the integrated current chip has high output accuracy, it requires an external current limiting circuit, especially when the circuit is too complicated in a multi-channel configuration and occupies a large area of ​​the printed circuit board. When current is used as a drive control signal for industrial applications, hundreds of milliwatts of power are often required, and some scenarios such as sensor drive control signals have high precision requirements. Summary of the invention

[0003] The invention provides an adaptive high-precision constant current source circuit, aiming to solve the problems existing in the existing hundred-milliwatt-level power constant current source circuit.

[0004] The present invention provides an adaptive high-precision constant current source circuit, comprising a controller adaptive calculation unit, an operational amplifier circuit, a feedback loop, and a sampling resistor. The feedback circuit comprises one or more combinations of a first-level negative feedback loop, a first-level positive feedback loop, and a second-level negative feedback loop. The controller adaptive calculation unit comprises a gear adjustment circuit. The gear adjustment circuit, the operational amplifier circuit, and the sampling resistor are connected in sequence. The sampling resistor is connected to a power supply output end. The two ends of the first-level negative feedback loop and the first-level positive feedback loop are respectively connected to the input end of the operational amplifier circuit and the output end of the sampling resistor. The two ends of the second-level negative feedback loop are respectively connected to the input end and the output end of the operational amplifier circuit. The first-level negative feedback loop or the first-level positive feedback loop feeds back the output voltage, and the second-level negative feedback loop feeds back the output voltage of the operational amplifier.

[0005] As a further improvement of the present invention, when the feedback circuit consists of a first-stage negative feedback loop and a first-stage positive feedback loop, the first-stage negative feedback loop is composed of a resistor R3, the first-stage positive feedback loop is composed of a second-stage operational amplifier A2 and a feedback resistor R4, the operational amplifier circuit includes a first-stage operational amplifier A1, a resistor R1, and a resistor R2, the output end of the gear adjustment circuit is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the non-inverting input end of the first-stage operational amplifier A1, the inverting input end of the first-stage operational amplifier A1 is grounded after passing through the resistor R1, and the output end of the first-stage operational amplifier A1 is connected to the sampling resistor R S One end of the sampling resistor R S The other end of the resistor R3 is connected to the power supply output end and the non-inverting input end of the second stage operational amplifier A2, and the two ends of the resistor R3 are connected to the sampling resistor R S and the inverting input terminal of the first stage operational amplifier A1, the output terminal and the inverting input terminal of the second stage operational amplifier A2 are both connected to one end of a resistor R4, and the other end of the resistor R4 is connected to the non-inverting input terminal of the first stage operational amplifier A1;

[0006] The first stage operational amplifier A1 and the second stage operational amplifier A2 form a common phase adder, and the sampling resistor R S The output voltage is output to the non-inverting input terminal of the first stage amplifier A1 after passing through the non-inverting input terminal of the second stage amplifier A2 to maintain the sampling resistor R S The voltage across both ends is constant.

[0007] As a further improvement of the present invention, the power supply output terminal includes an equivalent load R L , the sampling resistor R S The other end is connected to an equivalent load R L One end of the equivalent load R L The other end is grounded.

[0008] As a further improvement of the present invention, when the feedback circuit is composed of a first-stage negative feedback loop and a second-stage negative feedback loop, it also includes a proportional circuit formed by a second-stage operational amplifier A2 and its peripheral resistors, and the first-stage negative feedback loop is composed of a feedback resistor R F The second stage negative feedback loop consists of capacitor C F The operational amplifier circuit includes a first-stage operational amplifier A1, the in-phase input terminal of the first-stage operational amplifier A1 is connected to the gear adjustment circuit, and the output terminals of the first-stage operational amplifier A1 are respectively connected to the sampling resistors R S One end of the proportional circuit, the non-inverting input end, the sampling resistor R S The other end is connected to the power supply output and the inverting input of the proportional circuit respectively, and the output of the proportional circuit is connected to the feedback resistor R F One end of the feedback resistor R FThe other end is connected to the inverting input terminal of the first stage op amp A1, the capacitor C F The two ends of are respectively connected to the output terminal and the inverting input terminal of the first stage operational amplifier A1;

[0009] The output voltage of the first stage operational amplifier A1 is passed through the capacitor C F feedback, the output voltage of the second stage op amp A2 passes through the feedback resistor R F For loopback, the sampling resistor R S The output voltage is regulated by the second stage op amp A2 and then passes through the feedback resistor R F Output to the inverting input of the first stage op amp A1 to maintain the sampling resistor R S The voltage across both ends is constant.

[0010] As a further improvement of the present invention, the adaptive high-precision constant current source circuit also includes a sampling circuit, which is connected to both ends of the sampling resistor. The controller adaptive calculation unit also includes a control unit, which is respectively connected to the gear adjustment circuit and the sampling circuit. The sampling circuit samples the voltage at both ends of the sampling resistor, performs signal conditioning and analog-to-digital conversion, and then sends the sampling value to the controller adaptive calculation unit to obtain the current output current data, and fine-tune the gear position through the gear adjustment circuit after real-time calculation.

[0011] As a further improvement of the present invention, the controller adaptive calculation unit obtains the current output current data, and in the process of fine-tuning the gear position through the gear adjustment circuit after real-time calculation, the controller adaptive calculation unit calibrates and adaptively adjusts the output accuracy of the constant current source circuit through internal software, and the execution process includes:

[0012] After initializing the relevant parameters, check whether the calibration flag is set; if the calibration flag is set, it means that factory calibration is required at this time, then the software automatically sets the output gear according to the circuit range, reads the current value of the current sampling position after stabilization, obtains the data of each gear, calculates the calibration coefficient and saves it; if the calibration flag is not set, it means that the saved calibration coefficient can be read normally at this time, the gear can be calibrated, and the output can be carried out normally after the communication interface instruction; when the communication interface instruction is received, first determine whether it is a calibration instruction, if so, set the calibration flag; if not, determine whether the circuit configuration output needs to be carried out normally, if this judgment condition is met, then output the gear, read the current sampling position current value, and judge with the corresponding pre-stored data whether it meets the expectations, if it meets the expectations, return to the main program; if it does not meet the expectations, then determine the difference between the sampling value and the expectations, step the gear and output the gear, and read the current sampling value, repeat several times until it meets the expectations, then it means that the gear adjustment meets the requirements and can return to the main program normally.

[0013] As a further improvement of the present invention, the adaptive high-precision constant current source circuit also includes a filtering circuit, which includes a filtering resistor R1 and a filtering capacitor C1, wherein the two ends of the filtering resistor R1 are respectively connected to the gear adjustment circuit and the in-phase input end of the first-stage operational amplifier A1, and the two ends of the filtering capacitor C1 are respectively connected to the filtering resistor R1 and ground.

[0014] As a further improvement of the present invention, the proportional circuit includes a second-stage operational amplifier A2, a resistor R 21 , R 22 , R 23 , R 24 , capacitor C 21 , C 22 , the resistor R 21 In series with the inverting input terminal of the second stage op amp A2, the resistor R 22 In series with the non-inverting input terminal of the second stage op amp A2, the resistor R 23 , capacitor C 22 The resistor R 24 One end of the resistor R is connected to the non-inverting input terminal of the second stage op amp A2. 24 The other end of the capacitor C 21 With resistor R 24 in parallel.

[0015] As a further improvement of the present invention, the power supply output terminal includes an equivalent load R L , equivalent load capacitance C L , the sampling resistor R S The other end is connected to an equivalent load R L One end of the equivalent load R L The other end is grounded, and the equivalent load capacitance C L With equivalent load R L in parallel.

[0016] The beneficial effects of the present invention are: the parameters can be automatically adjusted according to changes in system parameters or external environment, so as to automatically calibrate the output current, and the output current gear resolution is high and the precision is high, so it is suitable for application scenarios that require high-precision current drive in industrial control. The adaptability of the present invention is reflected in that it only needs to be calibrated once before leaving the factory, and the output current is sampled during normal operation, so as to automatically adjust the closed-loop output current, and no manual calibration and intervention are required. The constant current source circuit of the present invention realizes the output of hundreds of milliwatts of power by the signal operational amplifier circuit. Not only is the circuit simple, but also good gear resolution and DC precision are guaranteed. The feedback loop of the present invention ensures DC precision and loop stability, maintains a constant voltage across the sampling resistor, and thus keeps the constant current source output constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The block diagram of the self-adaptive adjustable high-precision constant current source multi-feedback topology circuit of the present invention;

[0018] Figure 2 A circuit diagram of a common-phase adder circuit in an embodiment of the present invention for realizing output adjustable constant current drive;

[0019] Figure 3 The circuit diagram of an adjustable constant current source with multiple negative feedback topologies in an embodiment of the present invention is as follows;

[0020] Figure 4 A circuit diagram of an adjustable high-precision constant current source with adaptability in an embodiment of the present invention;

[0021] Figure 5 In the embodiment of the present invention Figure 4 Flowchart of the output accuracy adaptive control procedure of the constant current source circuit. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0023] The invention relates to a hundred milliwatt level constant current source circuit, in particular to an adaptive adjustable high-precision constant current source circuit, the output power of which can reach the hundred milliwatt level.

[0024] like Figure 1 As shown, an adaptive high-precision constant current source circuit of the present invention includes a controller adaptive calculation unit, an operational amplifier circuit, a feedback loop, and a sampling resistor. The feedback circuit includes one or more combinations of a first-level negative feedback loop, a first-level positive feedback loop, and a second-level negative feedback loop. The controller adaptive calculation unit includes a gear adjustment circuit. The gear adjustment circuit, the operational amplifier circuit, and the sampling resistor are connected in sequence. The sampling resistor is connected to the power supply output end. The two ends of the first-level negative feedback loop and the first-level positive feedback loop are respectively connected to the input end of the operational amplifier circuit and the output end of the sampling resistor. The two ends of the second-level negative feedback loop are respectively connected to the input end and the output end of the operational amplifier circuit. The first-level negative feedback loop or the first-level positive feedback loop feeds back the output voltage, and the second-level negative feedback loop feeds back the output voltage of the operational amplifier.

[0025] The present invention is a circuit that can realize the output of a hundred milliwatt power of a signal operational amplifier circuit, which is a multi-feedback topology. The circuit mainly includes a controller adaptive calculation unit, an operational amplifier circuit, a feedback loop, a sampling resistor and a sampling circuit. The controller adaptive calculation unit includes command input parsing and adaptive calculation of the sampling value and output gear. The feedback loop includes a first-level negative feedback loop or a first-level positive feedback loop and a second-level negative feedback loop, and the main purpose is to maintain a constant voltage across the sampling resistor, so that the output of the constant current source is constant. The first-level negative feedback loop or the first-level positive feedback loop feeds back the output voltage, thereby ensuring the accuracy of the input end of the first-level operational amplifier A1 in the operational amplifier circuit, thereby maintaining the DC accuracy of the output. The second-level negative feedback loop feeds back the output of the operational amplifier, thereby maintaining loop stability. The adaptive control program can adapt to changes in load or other parameters, automatically adjust parameters and close the loop output current, and the circuit is simple and can meet the design requirements of high-precision output current.

[0026] Embodiment 1:

[0027] Depend on Figure 1 The adaptive adjustable high-precision constant current source circuit in the embodiment can be used to obtain a specific implementation method, such as Figure 2 As shown, when the feedback circuit consists of a first-stage negative feedback loop and a first-stage positive feedback loop, the first-stage negative feedback loop is composed of a resistor R3, the first-stage positive feedback loop is composed of a second-stage operational amplifier A2 and a feedback resistor R4, the operational amplifier circuit includes a first-stage operational amplifier A1, a resistor R1, and a resistor R2, the output end of the gear adjustment circuit is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the non-inverting input end of the first-stage operational amplifier A1, the inverting input end of the first-stage operational amplifier A1 is grounded after passing through the resistor R1, and the output end of the first-stage operational amplifier A1 is connected to the sampling resistor R S One end of the sampling resistor R S The other end of the resistor R3 is connected to the power supply output and the in-phase input of the second-stage operational amplifier A2, and the two ends of the resistor R3 are connected to the sampling resistor R S One end of the resistor R4 is connected to the inverting input end of the first-stage operational amplifier A1, the output end and the inverting input end of the second-stage operational amplifier A2 are both connected to one end of the resistor R4, and the other end of the resistor R4 is connected to the non-inverting input end of the first-stage operational amplifier A1. The first-stage operational amplifier A1 and the second-stage operational amplifier A2 form a non-inverting adder.

[0028] The power supply output includes an equivalent load R L , sampling resistor R S The other end is connected to an equivalent load R L One end of the equivalent load R L The other end is grounded.

[0029] This embodiment is a common-phase adder circuit that realizes output adjustable constant current drive, in which a follower circuit is used as a first-stage positive feedback circuit, and a resistor is used to form a first-stage negative feedback circuit. Figure 2 Medium output voltage V OUT After being followed by the second stage op amp A2, it reaches the non-inverting input terminal of the first stage op amp A1 to maintain the sampling resistor R S The voltage at both ends is constant, so that the output of the constant current source is constant. For the first-stage op amp A1, it is a local negative feedback circuit, which still meets the conditions of virtual short and virtual break, so that the first-stage op amp A1 and the second-stage op amp A2 form a common-phase adder. V1 is the input of the gear adjustment circuit, and R4 is the negative feedback resistor of the first-stage op amp A1. The formula is as follows:

[0030] R1=R2=R3=R4 (1)

[0031]

[0032] V4=2V3=V1+V7 (3)

[0033] V1=V4-V7 (4)

[0034] V OUT =V5=V6=V7 (5)

[0035] V1=V4-V OUT (6)

[0036] I2≈0(7) so R S The voltage across the two ends is equal to V1, and

[0037]

[0038] The output current comes from the first-stage operational amplifier A1. For this constant current source circuit, V1 can only be given by a precise reference source. The hardware filtering method after the controller MCU sends the PWM wave cannot be used, because this will cause the peripheral circuit structure of the first-stage operational amplifier A1 to be asymmetric, and RC filtering will cause a voltage drop on R.

[0039] Embodiment 2:

[0040] like Figure 3 As shown, when the feedback circuit consists of a first-stage negative feedback loop and a second-stage negative feedback loop, it also includes a proportional circuit formed by the second-stage operational amplifier A2 and its peripheral resistors. The first-stage negative feedback loop consists of a feedback resistor R F The second stage negative feedback loop consists of capacitor C F The operational amplifier circuit includes a first-stage operational amplifier A1, the in-phase input terminal of the first-stage operational amplifier A1 is connected to the gear adjustment circuit, and the output terminals of the first-stage operational amplifier A1 are respectively connected to the sampling resistors R SOne end of the proportional circuit, the non-inverting input end, the sampling resistor R S The other end is connected to the power supply output and the inverting input of the proportional circuit, and the output of the proportional circuit is connected to the feedback resistor R F One end of the feedback resistor R F The other end is connected to the inverting input of the first stage op amp A1, and the capacitor C F The two ends are respectively connected to the output terminal and the inverting input terminal of the first stage operational amplifier A1.

[0041] The adaptive high-precision constant current source circuit also includes a filtering circuit, which includes a filtering resistor R1 and a filtering capacitor C1. The two ends of the filtering resistor R1 are respectively connected to the gear adjustment circuit and the in-phase input terminal of the first-stage operational amplifier A1, and the two ends of the filtering capacitor C1 are respectively connected to the filtering resistor R1 and ground.

[0042] The proportional circuit includes the second stage op amp A2, resistor R 21 , R 22 , R 23 , R 24 , capacitor C 21 , C 22 , resistor R 21 Connected in series to the inverting input of the second stage op amp A2, the resistor R 22 Connected in series to the non-inverting input of the second-stage op amp A2, the resistor R 23 , capacitor C 22 Respectively connected in parallel to the output and inverting input of the second-stage operational amplifier A2, resistor R 24 One end is connected to the non-inverting input terminal of the second stage op amp A2, and the resistor R 24 The other end of the capacitor C 21 With resistor R 24 in parallel.

[0043] The power supply output includes an equivalent load R L , equivalent load capacitance C L , sampling resistor R S The other end is connected to an equivalent load R L One end of the equivalent load R L The other end is grounded, and the equivalent load capacitance C L With equivalent load R L in parallel.

[0044] This embodiment Figure 2 Based on the scheme, the first-stage positive feedback circuit is cancelled and the second-stage negative feedback circuit is added, and the following is obtained: Figure 3 The adjustable constant current source circuit with multiple negative feedback topology shown in the figure has the function of multi-stage negative feedback circuit to pass capacitor C when the capacitive impedance of the load is relatively large. FFeedback the output of the first stage op amp A1 to maintain loop stability. The output voltage V4 of the second stage op amp A2 is fed back through the feedback resistor R F The second stage op amp A2 and its peripheral resistors form a proportional circuit, the ratio can be doubled or increased as needed within the op amp power supply range and output capacity. Output voltage V OUT After being conditioned by the second stage op amp A2, it is then fed back by the negative feedback resistor R F To the inverting input of the first stage op amp A1, to maintain the sampling resistor R S The voltage at both ends is constant, so that the output of the constant current source is constant. At the same time, in general precision applications, the controller MCU can be selected to send PWM waves and then perform hardware filtering. In high precision applications, the MCU can be selected to control the DAC to adjust the gear and then perform filtering, which does not affect the circuit structure.

[0045] R 21 =R 22 =R b (9)

[0046] R 23 =R 24 =R c (10)

[0047] C 21 =C 22 =C a (11)

[0048]

[0049] I OUT =I1-I4 (14)

[0050] Substituting (9) to (12) into (13), we obtain:

[0051]

[0052] Due to R b , R c Generally, kilo-ohm resistors are selected, so I4≈0, I5≈0, then:

[0053] V4≈V2≈V1(16)

[0054]

[0055] From (14) to (17), we have

[0056]

[0057] Embodiment three:

[0058] On the basis of the second embodiment, in the case where the robustness and output accuracy need to be further improved, the sampling resistor R S High-precision and low-temperature drift resistors are required, and the sampling resistor R S The voltage at both ends is sampled, and after signal conditioning and analog-to-digital conversion, the value is sent to the adaptive calculation unit controller to obtain the current output current I OUT Data, specific implementation such as Figure 4 As shown, the adaptive high-precision constant current source circuit also includes a sampling circuit, which includes a signal conditioning circuit, an analog-to-digital conversion circuit, etc. The sampling circuit is connected to both ends of the sampling resistor, and the controller adaptive calculation unit also includes a control unit MCU. The control unit MCU is respectively connected to the gear adjustment circuit and the sampling circuit. The sampling circuit samples the voltage at both ends of the sampling resistor, performs signal conditioning, and analog-to-digital conversion, and then sends the sampled value to the controller adaptive calculation unit to obtain the current output current data. After real-time calculation, the gear is fine-tuned through the gear adjustment circuit to compensate for the error between the output current demand and the actual output current. This process only needs to be calibrated once at the factory, and no manual calibration and intervention are required during the subsequent working process, which improves the adaptability to changes in system parameters or external environmental parameters, improves the robustness of the circuit, and has good gear resolution.

[0059] like Figure 5 As shown in the embodiment Figure 4 Based on the above, a program flow chart of a method for further calibrating and adaptively adjusting the circuit output accuracy through software is provided.

[0060] like Figure 5 As shown, the controller adaptive calculation unit obtains the current output current data, and after real-time calculation, fine-tunes the gear position through the gear adjustment circuit. The controller adaptive calculation unit calibrates and adaptively adjusts the output accuracy of the constant current source circuit through internal software. The execution process includes:

[0061] After the main program initializes the relevant parameters, including ADC parameters, DAC parameters, PWM frequency and duty cycle parameters, communication interface parameters, etc., it queries whether the calibration flag is set. If the calibration flag is set, it means that factory calibration is required at this time. The software automatically sets the output gear according to the circuit range, that is, sets the DAC / configures the PWM frequency and duty cycle, and reads the current value (ADC code value) of the current sampling position after stabilization, thereby obtaining the data of each gear, and calculates and saves the calibration coefficient, which can be stored in a non-volatile storage medium. If the calibration flag is not set, it means that the saved calibration coefficient can be read normally at this time, the gear can be calibrated, that is, the DAC code value / PWM duty cycle can be calibrated, and the output can be performed normally after the communication interface instruction. When the communication interface instruction is received, first determine whether it is a calibration instruction. If so, set the calibration flag and enable the communication reception interrupt; if not, determine whether the circuit configuration output needs to be performed normally, that is, determine whether to update the DAC code value / PWM duty cycle. If this judgment condition is met, output the gear, that is, output the DAC code value / PWM duty cycle, and then read the current sampling position current value (ADC code value), and judge with the corresponding pre-stored data (ADC code value) whether it meets the expectations. If so, enable the communication reception interrupt and return to the main program; if not, determine the difference between the sampling value (ADC code value) and the expectation, step the gear and output the gear, that is, output the DAC code value / PWM duty cycle, and then read the current sampling value (ADC code value). Repeat several times until it meets the expectations, which means that the gear adjustment meets the requirements and can return to the main program normally. The MCU fine-tunes the gear after real-time calculation to compensate for the output current demand and the actual output current I OUT The output accuracy adaptive control program of the constant current source circuit can improve the stability and responsiveness of the constant current source circuit, has strong robustness to system and environmental noise and interference, and has good adaptability to system changes.

[0062] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. An adaptive high-precision constant current source circuit, characterized in that: It includes a controller adaptive calculation unit, an operational amplifier circuit, a feedback loop, and a sampling resistor. The feedback circuit includes one or more combinations of a first-level negative feedback loop, a first-level positive feedback loop, and a second-level negative feedback loop. The controller adaptive calculation unit includes a gear adjustment circuit. The gear adjustment circuit, the operational amplifier circuit, and the sampling resistor are connected in sequence. The sampling resistor is connected to the power supply output end. The two ends of the first-level negative feedback loop and the first-level positive feedback loop are respectively connected to the input end of the operational amplifier circuit and the output end of the sampling resistor. The two ends of the second-level negative feedback loop are respectively connected to the input end and the output end of the operational amplifier circuit. The first-level negative feedback loop or the first-level positive feedback loop feeds back the output voltage, and the second-level negative feedback loop feeds back the output voltage of the operational amplifier.

2. The adaptive high-precision constant current source circuit according to claim 1, characterized in that: When the feedback circuit consists of a first-stage negative feedback loop and a first-stage positive feedback loop, the first-stage negative feedback loop consists of a resistor R 3, the first stage positive feedback loop is composed of the second stage op amp A2 and feedback resistor R 4, the operational amplifier circuit includes a first-stage operational amplifier A1, a resistor R 1. Resistance R 2. The output end of the gear adjustment circuit is connected to a resistor R 2, the resistor R The other end of 2 is connected to the non-inverting input of the first stage op amp A1, and the inverting input of the first stage op amp A1 is connected to the inverting input of the first stage op amp A1 through a resistor R 1 is then grounded, and the output of the first stage op amp A1 is connected to the sampling resistor R S One end of the sampling resistor R S The other end of the resistor is connected to the power supply output and the non-inverting input of the second stage operational amplifier A2. R Connect the two ends of 3 to the sampling resistor R S The output and inverting input of the first stage op amp A1 are connected to the feedback resistor. R 4, the feedback resistor R The other end of 4 is connected to the non-inverting input of the first stage operational amplifier A1; The first stage operational amplifier A1 and the second stage operational amplifier A2 form a common phase adder, and the sampling resistor R S The output voltage is output to the non-inverting input terminal of the first stage amplifier A1 after passing through the non-inverting input terminal of the second stage amplifier A2 to maintain the sampling resistor R S The voltage across both ends is constant.

3. The adaptive high-precision constant current source circuit according to claim 2, characterized in that: The power supply output terminal includes an equivalent load R L , the sampling resistor R S The other end is connected to an equivalent load R L One end of the equivalent load R L The other end is grounded.

4. The adaptive high-precision constant current source circuit according to claim 1, characterized in that: When the feedback circuit is composed of a first-stage negative feedback loop and a second-stage negative feedback loop, it also includes a proportional circuit formed by a second-stage operational amplifier A2 and its peripheral resistors. The first-stage negative feedback loop is composed of a feedback resistor R F The second stage negative feedback loop consists of capacitor C F The operational amplifier circuit includes a first-stage operational amplifier A1, the in-phase input terminal of the first-stage operational amplifier A1 is connected to the gear adjustment circuit, and the output terminals of the first-stage operational amplifier A1 are respectively connected to the sampling resistors R S One end of the proportional circuit, the non-inverting input end, the sampling resistor R S The other end is connected to the power supply output and the inverting input of the proportional circuit respectively, and the output of the proportional circuit is connected to the feedback resistor R F One end of the feedback resistor R F The other end of the capacitor is connected to the inverting input terminal of the first stage op amp A1. C F The two ends of are respectively connected to the output terminal and the inverting input terminal of the first stage operational amplifier A1; The output voltage of the first stage operational amplifier A1 is passed through the capacitor C F feedback, the output voltage of the second stage op amp A2 passes through the feedback resistor R F To loop back, the sampling resistor R S The output voltage is regulated by the second stage op amp A2 and then passed through the feedback resistor R F Output to the inverting input of the first stage op amp A1 to maintain the sampling resistor R S The voltage across both ends is constant.

5. The adaptive high-precision constant current source circuit according to claim 4, characterized in that: It also includes a sampling circuit, which is connected to the two ends of the sampling resistor. The controller adaptive calculation unit also includes a control unit, which is respectively connected to the gear adjustment circuit and the sampling circuit. The sampling circuit samples the voltage at both ends of the sampling resistor, performs signal conditioning, and analog-to-digital conversion, and then sends the sampling value to the controller adaptive calculation unit to obtain the current output current data, and fine-tune the gear position through the gear adjustment circuit after real-time calculation.

6. The adaptive high-precision constant current source circuit according to claim 5, characterized in that: The controller adaptive calculation unit obtains the current output current data, and performs fine-tuning of the gear position through the gear adjustment circuit after real-time calculation. The execution process of the controller adaptive calculation unit calibrating and adaptively adjusting the output accuracy of the constant current source circuit through internal software includes: After initializing the relevant parameters, check whether the calibration flag is set; if the calibration flag is set, it means that factory calibration is required at this time, then the software automatically sets the output gear according to the circuit range, reads the current value of the current sampling position after stabilization, obtains the data of each gear, calculates the calibration coefficient and saves it; if the calibration flag is not set, it means that the saved calibration coefficient can be read normally at this time, the gear can be calibrated, and the output can be carried out normally after the communication interface instruction; when the communication interface instruction is received, first determine whether it is a calibration instruction, if so, set the calibration flag; if not, determine whether the circuit configuration output needs to be carried out normally, if this judgment condition is met, then output the gear, read the current sampling position current value, and judge with the corresponding pre-stored data whether it meets the expectations, if it meets the expectations, return to the main program; if it does not meet the expectations, then determine the difference between the sampling value and the expectations, step the gear and output the gear, and read the current sampling value, repeat several times until it meets the expectations, then it means that the gear adjustment meets the requirements and can return to the main program normally.

7. The adaptive high-precision constant current source circuit according to any one of claims 4 to 6, characterized in that: Also includes a filter circuit, the filter circuit includes a filter resistor R 1. Filter capacitor C 1. The filter resistor R The two ends of 1 are connected to the gear adjustment circuit and the in-phase input terminal of the first stage operational amplifier A1 respectively. The filter capacitor C Connect filter resistors to both ends of 1 R 1 and ground.

8. The adaptive high-precision constant current source circuit according to any one of claims 4 to 6, characterized in that: The proportional circuit includes a second-stage operational amplifier A2, a resistor R 21 , R 22 , R 23 , R 24 ,capacitance C 21 , C 22 , the resistor R 21 In series with the inverting input terminal of the second stage op amp A2, the resistor R 22 The resistor is connected in series to the non-inverting input terminal of the second stage op amp A2. R 23 ,capacitance C 22 are connected in parallel to the output terminal and the inverting input terminal of the second stage operational amplifier A2, the resistor R 24 One end of the resistor is connected to the non-inverting input terminal of the second stage op amp A2. R 24 The other end of the capacitor is grounded. C 21 With resistance R 24 in parallel.

9. The adaptive high-precision constant current source circuit according to any one of claims 4 to 6, characterized in that: The power supply output terminal includes an equivalent load R L , equivalent load capacitance C L , the sampling resistor R S The other end is connected to an equivalent load R L One end of the equivalent load R L The other end is grounded, and the equivalent load capacitance C L With equivalent load R L in parallel.

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