High-precision constant current source adjusting circuit and adjusting method

Abstract

The invention relates to a high-precision constant current source adjusting circuit and an adjusting method, and belongs to the technical field of constant current source circuits, the high-precision constant current source adjusting circuit comprises a low-precision current adjusting module and a high-precision current adjusting module which are connected in parallel, the low-precision current adjusting module comprises a first digital analog converter DAC1, a first operational amplifier U1A and a first NMOS tube Q1, rough adjustment of current is achieved, and the high-precision current adjusting module comprises a second digital analog converter DAC2, a second operational amplifier U1A and a second NMOS tube Q1; the high-precision current adjusting module comprises a second digital analog converter DAC2, a second operational amplifier U2A, a third operational amplifier U3A and a second NMOS tube Q2, and is used for compensating coarse adjustment current errors; the current is adjusted to be close to a target value through the low-precision current adjusting module, the compensation error is finely adjusted through the high-precision current adjusting module, current superposition is carried out, and the target current is obtained through segmented adjustment.

Description

Technical Field

[0001] The invention belongs to the technical field of constant current source circuits, and particularly relates to a high-precision constant current source circuit and an adjustment method. Background Art

[0002] A constant current source is a core module for realizing stable current output in an electronic system, and is widely used in fields such as LED driving, sensor excitation, battery charging, and precision measurement. Its core requirements are: the output current is not affected by the change of load impedance, has high temperature stability and anti-power supply fluctuation ability, and can adapt to different power and precision requirements. However, a simple combination such as a resistor-diode uses the fixed conduction voltage of the diode, which has problems of large temperature drift and low precision. The forward voltage drop of the diode is significantly affected by temperature, resulting in insufficient current stability. For example, the adjustment current corresponding to the unit step value of a traditional low-precision constant current source circuit is relatively large, and it is only suitable for coarse adjustment of larger currents. Taking the adjustment of a 0.1 mA current as an example, in a low-precision current adjustment module, when the maximum input value of the first digital-to-analog converter DAC1 is 4095 and its full-scale voltage is 3 V, the voltage corresponding to one digital step is 0.7 mV. Therefore, negative feedback and voltage reference technologies need to be introduced to improve performance. The negative feedback constant current source composed of an operational amplifier and a triode forms a closed-loop negative feedback through the operational amplifier. The sampling resistor detects the load current in real time, and after comparing it with the reference voltage, adjusts the conduction state of the triode to achieve current stability; the improved constant current source composed of an operational amplifier and a MOS transistor uses its voltage control characteristics and low gate current advantages to reduce the base current error.

[0003] In the prior art, a precision constant current source circuit with the publication number of CN113050742A includes a buck-boost power supply chip with buck-boost function, a power input filter capacitor, a voltage dividing resistor, a feedback circuit, a power output filter capacitor, a load, a microprocessor with an ADC module inside, and a digital potentiometer. The feedback circuit includes a sampling resistor and an operational amplifier. However, the linear adjustment and adjustment precision of this circuit depend on the resolution of the digital potentiometer, and the cooperation between the buck-boost power supply chip and the digital potentiometer to adjust the voltage involves multi-stage signal transmission, resulting in corresponding delays. In addition, the constant current source of this circuit is a single-channel closed-loop control, and the failure of the digital potentiometer or the sampling resistor will cause the system to fail. Summary of the Invention

[0004] The technical problem solved by the invention is: to overcome the defects existing in the prior art and provide a high-precision constant current source circuit and an adjustment method.

[0005] The technical solution adopted by the invention is as follows:

[0006] The high-precision constant current source adjustment circuit described in the invention includes:

[0007] Low-precision current regulation module, the low-precision current regulation module is connected to a first digital-to-analog converter DAC1, the low-precision current regulation module includes a first operational amplifier U1A, and the first digital-to-analog converter DAC1 is connected to the non-inverting input terminal of the first operational amplifier U1A;

[0008] High-precision current regulation module, the high-precision current regulation module is connected to a second digital-to-analog converter DAC2, the high-precision current regulation module includes a second operational amplifier U2A, and the second digital-to-analog converter DAC2 is connected to the non-inverting input terminal of the second operational amplifier U2A;

[0009] Current superposition module, the current superposition module is connected to the output terminal of the low-precision current regulation module and the output terminal of the high-precision current regulation module;

[0010] Feedback regulation module, the feedback regulation module includes a fifth operational amplifier U5A, a photodiode PD and a resistor R11. The output terminal of the fifth operational amplifier U5A is connected to the inverting input terminal of the second operational amplifier U2A in the high-precision current regulation module. The non-inverting input terminal of the fifth operational amplifier U5A is grounded. The inverting input terminal of the fifth operational amplifier U5A is connected to one end of the photodiode PD, the other end of the photodiode PD is grounded, and the resistor R11 is connected between the output terminal of the fifth operational amplifier U5A and the photodiode PD;

[0011] Microcontroller, the microcontroller is electrically connected to the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2.

[0012] The low-precision current regulation module further includes a resistor R1, a resistor R2, a resistor R3 and a first NMOS transistor Q1. The output terminal of the first operational amplifier U1A is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the gate of the first NMOS transistor Q1, the source of the first NMOS transistor Q1 is connected to one end of the resistor R3, the other end of the resistor R3 is grounded, the inverting input terminal of the first operational amplifier U1A is connected to one end of the resistor R2, and the other end of the resistor R2 is connected between the source of the first NMOS transistor Q1 and the resistor R3.

[0013] The high-precision current regulation module further includes a resistor R4, a resistor R5 and a second NMOS transistor Q2. The output terminal of the second operational amplifier U2A is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the gate of the second NMOS transistor Q2, the source of the second NMOS transistor Q2 is connected to one end of the resistor R5, and the other end of the resistor R5 is grounded.

[0014] The high-precision current regulation module further includes a third operational amplifier U3A, a resistor R6, a resistor R7, and a resistor R8. The non-inverting input terminal of the third operational amplifier U3A is connected between the source of the second NMOS transistor Q2 and the resistor R5. The inverting input terminal of the third operational amplifier U3A is connected to one end of the resistor R7, and the other end of the resistor R7 is grounded. One end of the resistor R6 is connected between the inverting input terminal of the third operational amplifier U3A and the resistor R7. The other end of the resistor R6 and the output terminal of the third operational amplifier U3A are both connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the inverting input terminal of the second operational amplifier U2A.

[0015] The high-precision current regulation module increases the operational amplifier module in parallel and adjusts the connection relationship to improve the current regulation accuracy.

[0016] The operational amplifier module includes a resistor R9, a resistor R10, and a fourth operational amplifier U4A. The non-inverting input terminal of the fourth operational amplifier U4A is connected to the resistor R6 and the output terminal of the third operational amplifier U3A. The inverting input terminal of the fourth operational amplifier U4A is connected to one end of the resistor R10, and the other end of the resistor R10 is grounded. One end of the resistor R9 is connected between the inverting input terminal of the fourth operational amplifier U4A and the resistor R10. The other end of the resistor R9 and the output terminal of the fourth operational amplifier U4A are connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the inverting input terminal of the second operational amplifier U2A.

[0017] The high-precision constant current source regulation method according to the present invention, based on a high-precision constant current source regulation circuit, includes the following steps:

[0018] S1: Coarse current adjustment. The first digital-to-analog converter DAC1 outputs an initial voltage to drive the low-precision current regulation module to adjust the output current to be close to the target value.

[0019] S2: Fine current adjustment. The second digital-to-analog converter DAC2 outputs a correction voltage to drive the high-precision current regulation module to compensate for the remaining error, so that the output current reaches the target value.

[0020] S3: Current superposition. The output current of the low-precision current regulation module and the output current of the high-precision current regulation module are superposed to obtain the final output current of the high-precision constant current source.

[0021] S4: Dynamic calibration. The feedback signal of the load current is collected in real time, and the output voltages of the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2 are adjusted according to whether the detected current deviation exceeds the threshold.

[0022] S1 includes the following specific steps:

[0023] S11: Compare the first reference voltage output by the first digital-to-analog converter DAC1 with the feedback voltage of the low-precision current regulation module through the first operational amplifier U1A;

[0024] S12: Adjust the conduction state of the first NMOS transistor Q1;

[0025] S13: Adjust the output current of the low-precision current regulation module to stepwise approach the target current value according to a preset precision.

[0026] S2 includes the following specific steps:

[0027] S21: Compare the second reference voltage output by the second digital-to-analog converter DAC2 with the feedback voltage of the high-precision current regulation module through the second operational amplifier U2A;

[0028] S22: Add the third operational amplifier U3A to form a multi-stage negative feedback;

[0029] S23: Adjust the conduction state of the second NMOS transistor Q2;

[0030] S24: Make the output current of the high-precision current regulation module stepwise compensate for the deviation of the low-precision current regulation module with higher precision.

[0031] S4 includes the following specific steps:

[0032] S41: Current deviation detection, the photodiode PD monitors the load current in real time and converts the current change on the load into a voltage signal to reflect the deviation between the actual output current and the target value;

[0033] S42: Signal amplification processing, the inverting input terminal of the fifth operational amplifier U5A receives the voltage signal of the photodiode PD;

[0034] S43: Closed-loop compensation control, the output correction signal of the fifth operational amplifier U5A is sent to the inverting input terminal of the second operational amplifier U2A, and then the gate voltage of the second NMOS transistor Q2 is adjusted, thereby controlling the output current of the high-precision module and compensating for the remaining error of the low-precision module;

[0035] S44: Dynamic calibration and optimization, continuously collect the voltage signal of the photodiode PD, dynamically adjust the output voltage of the second digital-to-analog converter DAC2, optimize the compensation amount, and the multi-stage feedback network composed of the third operational amplifier U3A and the fourth operational amplifier U4A suppresses temperature drift and power supply noise.

[0036] The present invention has the following beneficial effects:

[0037] 1. The low-precision current regulation module achieves rapid coarse adjustment, shortening the adjustment time. The high-precision current regulation module achieves fine-tuning compensation, effectively improving the output current accuracy of the constant current source. The parallel connection of the low-precision current regulation module and the high-precision current regulation module enables them to work independently, enhancing the reliability and stability of the circuit.

[0038] 2. The third operational amplifier U3A and the fourth operational amplifier U4A can form a multi-stage feedback loop. By combining with a resistor network to optimize the gain distribution, it can effectively suppress temperature drift and power supply fluctuations.

[0039] 3. The microcontroller monitors the current deviation of the load in real time and dynamically adjusts the output voltages of the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2, which can effectively control the error and meet the operating requirements in complex environments.

[0040] 5. The first NMOS transistor Q1 and the second NMOS transistor Q2 respectively achieve rapid approximation to the target value and precise compensation through gate voltage regulation, and improve the overall regulation efficiency through segmented regulation.

[0041] 6. The current superposition module superposes the output currents of the output terminals of the low-precision current regulation module and the high-precision current regulation module, effectively avoiding multi-stage signal transmission delay and having a fast response. Description of the Drawings

[0042] Figure 1 is the schematic diagram of the traditional low-precision constant current source circuit;

[0043] Figure 2 is the electrical connection block diagram of the present invention;

[0044] Figure 3 is the schematic diagram of the circuit of the present invention;

[0045] Figure 4 is the schematic diagram of the circuit of the added operational amplifier module of the present invention;

[0046] Figure 5 is the schematic diagram of the circuit of the added feedback regulation module of the present invention;

[0047] Figure 6 is the schematic diagram of the steps of the adjustment method of the present invention;

[0048] Figure 7 is the schematic diagram of the current coarse adjustment step;

[0049] Figure 8 is the schematic diagram of the current fine adjustment step;

[0050] Figure 9 is the schematic diagram of the feedback regulation step. Detailed Embodiments

[0051] Example 1:

[0052] As Figures 1 to 5 shown, the high-precision constant current source adjustment circuit of the present invention includes:

[0053] A low-precision current adjustment module, the low-precision current adjustment module is connected to a first digital-to-analog converter DAC1. The low-precision current adjustment module includes a first operational amplifier U1A, and the first digital-to-analog converter DAC1 is connected to the non-inverting input terminal of the first operational amplifier U1A;

[0054] A high-precision current adjustment module, the high-precision current adjustment module is connected to a second digital-to-analog converter DAC2. The high-precision current adjustment module includes a second operational amplifier U2A, and the second digital-to-analog converter DAC2 is connected to the non-inverting input terminal of the second operational amplifier U2A;

[0055] A current superposition module, the current superposition module is connected to the output terminals of the low-precision current adjustment module and the high-precision current adjustment module;

[0056] A feedback adjustment module, the feedback adjustment module includes a fifth operational amplifier U5A, a photodiode PD, and a resistor R11. The output terminal of the fifth operational amplifier U5A is connected to the inverting input terminal of the second operational amplifier U2A in the high-precision current adjustment module. The non-inverting input terminal of the fifth operational amplifier U5A is grounded. The inverting input terminal of the fifth operational amplifier U5A is connected to one end of the photodiode PD, the other end of the photodiode PD is grounded, and the resistor R11 is connected between the output terminal of the fifth operational amplifier U5A and the photodiode PD;

[0057] A microcontroller, the microcontroller is electrically connected to the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2.

[0058] The low-precision current adjustment module further includes a resistor R1, a resistor R2, a resistor R3, and a first NMOS transistor Q1. The output terminal of the first operational amplifier U1A is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the gate of the first NMOS transistor Q1, the source of the first NMOS transistor Q1 is connected to one end of the resistor R3, the other end of the resistor R3 is grounded, the inverting input terminal of the first operational amplifier U1A is connected to one end of the resistor R2, and the other end of the resistor R2 is connected between the source of the first NMOS transistor Q1 and the resistor R3.

[0059] The high-precision current adjustment module further includes a resistor R4, a resistor R5, and a second NMOS transistor Q2. The output terminal of the second operational amplifier U2A is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the gate of the second NMOS transistor Q2, the source of the second NMOS transistor Q2 is connected to one end of the resistor R5, and the other end of the resistor R5 is grounded.

[0060] The high-precision current regulation module further includes a third operational amplifier U3A, a resistor R6, a resistor R7, and a resistor R8. The non-inverting input terminal of the third operational amplifier U3A is connected between the source of the second NMOS transistor Q2 and the resistor R5. The inverting input terminal of the third operational amplifier U3A is connected to one end of the resistor R7, and the other end of the resistor R7 is grounded. One end of the resistor R6 is connected between the inverting input terminal of the third operational amplifier U3A and the resistor R7. The other end of the resistor R6 and the output terminal of the third operational amplifier U3A are both connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the inverting input terminal of the second operational amplifier U2A.

[0061] The high-precision current regulation module increases the operational amplifier modules in parallel and adjusts the connection relationship to improve the current regulation accuracy.

[0062] The operational amplifier module includes a resistor R9, a resistor R10, and a fourth operational amplifier U4A. The non-inverting input terminal of the fourth operational amplifier U4A is connected to the resistor R6 and the output terminal of the third operational amplifier U3A. The inverting input terminal of the fourth operational amplifier U4A is connected to one end of the resistor R10, and the other end of the resistor R10 is grounded. One end of the resistor R9 is connected between the inverting input terminal of the fourth operational amplifier U4A and the resistor R10. The other end of the resistor R9 and the output terminal of the fourth operational amplifier U4A are connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the inverting input terminal of the second operational amplifier U2A.

[0063] Specifically, the high-precision constant current source regulation circuit of the present invention is controlled by two digital-to-analog converters, mainly composed of a digital-to-analog converter, an operational amplifier, an NMOS transistor, and several resistors, and includes a low-precision regulation circuit and a high-precision regulation circuit connected in parallel.

[0064] Specifically, taking the digital-to-analog converter of model AD9764 as an example, the resolution of this digital-to-analog converter is 12 bits, that is, the input digital value ranges from 0 to 4095, a total of 4096 discrete levels. When the input digital value is the maximum value 4095, the analog voltage of the AD9764 is the full-scale voltage.

[0065] Specifically, taking the regulation of a 0.1 mA current as an example, on the low-precision current regulation module, the first digital-to-analog converter DAC1 inputs the maximum value 4095, and its full-scale voltage is 3V. Then the voltage corresponding to one digital step is 0.7 mV. Substitute it into the following formula:

[0066] V R3 =V DAC1

[0067] I R3 =V R3 / R3

[0068] ΔI R3 = ΔV DAC1 / R3

[0069] Where: V R3 is the voltage value across resistor R3, V DAC1 is the output voltage value of the first digital-to-analog converter, I R3 is the current value across resistor R3, R3 is the resistance value of resistor R3, ΔV DAC1 is the output voltage change value of the first digital-to-analog converter, ΔI R3 is the current change value across resistor R3. The resistance value of resistor R3 is set to 10 Ω, so the current corresponding to one digital step is 0.07 mA. Therefore, it is obviously impossible to adjust to 0.1 mA only by the low-precision adjustment circuit.

[0070] Specifically, on the high-precision current adjustment module, the second digital-to-analog converter DAC2 inputs a maximum value of 4095, and its full-scale voltage is 3 V. Then the voltage corresponding to one digital step is 0.7 mV. Substitute it into the following formula:

[0071] V R5 = V DAC2 (R7 / (R6 + R7))

[0072] I R5 = V R5 / R5

[0073] ΔI R5 = ΔV R5 / R5

[0074] Where, V R5 is the voltage value across resistor R5, V DAC2 is the output voltage value of the second digital-to-analog converter DAC2, R5, R6, and R7 are the resistance values of resistor R5, resistor R6, and resistor R7 respectively, IR5 is the current value across resistor R5, ΔI R5 is the current change value across resistor R5, ΔV R5 is the voltage change value across resistor R5. The resistance values of resistor R5, resistor R6, and resistor R7 are set to 10 Ω, 9000 Ω, and 1000 Ω respectively. Then the current corresponding to one digital step is 0.007 mA, significantly improving the adjustment current accuracy.

[0075] Specifically, by adjusting the output voltage values of the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2, the output current values of the low-precision current adjustment module and the high-precision current adjustment module are adjusted in segments and current superposition is performed. By the method of coarse adjustment first and then fine adjustment, the current accuracy of the constant current source is increased several times.

[0076] Example 2:

[0077] As Figures 6 to 9 shown, the high-precision constant current source regulation method of the present invention is based on a high-precision constant current source regulation circuit and includes the following steps:

[0078] S1: Coarse current adjustment. The first digital-to-analog converter DAC1 outputs an initial voltage to drive the low-precision current adjustment module to adjust the output current to be close to the target value;

[0079] S2: Fine current adjustment. The second digital-to-analog converter DAC2 outputs a correction voltage to drive the high-precision current adjustment module to compensate for the remaining error, so that the output current reaches the target value;

[0080] S3: Current superposition. The output current of the low-precision current adjustment module and the output current of the high-precision current adjustment module are superposed to obtain the final output current of the high-precision constant current source;

[0081] S4: Dynamic calibration. The feedback signal of the load current is collected in real time, and the output voltages of the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2 are adjusted according to whether the detected current deviation exceeds the threshold.

[0082] S1 includes the following specific steps:

[0083] S11: Compare the first reference voltage output by the first digital-to-analog converter DAC1 with the feedback voltage of the low-precision current adjustment module through the first operational amplifier U1A;

[0084] S12: Adjust the conduction state of the first NMOS transistor Q1;

[0085] S13: Adjust until the output current of the low-precision current adjustment module steps towards the target current value according to the preset precision.

[0086] S2 includes the following specific steps:

[0087] S21: Compare the second reference voltage output by the second digital-to-analog converter DAC2 with the feedback voltage of the high-precision current adjustment module through the second operational amplifier U2A;

[0088] S22: Add the third operational amplifier U3A to form a multi-stage negative feedback;

[0089] S23: Adjust the conduction state of the second NMOS transistor Q2;

[0090] S24: Make the output current of the high-precision current adjustment module step to compensate for the deviation of the low-precision current adjustment module with higher precision.

[0091] S4 includes the following specific steps:

[0092] S41: Current deviation detection. The photodiode PD monitors the load current in real time and converts the current change on the load into a voltage signal to reflect the deviation between the actual output current and the target value.

[0093] S42: Signal amplification processing. The inverting input terminal of the fifth operational amplifier U5A receives the voltage signal from the photodiode PD.

[0094] S43: Closed-loop compensation control. The output correction signal of the fifth operational amplifier U5A is sent to the inverting input terminal of the second operational amplifier U2A, thereby adjusting the gate voltage of the second NMOS transistor Q2, and thus controlling the output current of the high-precision module to compensate for the remaining error of the low-precision module.

[0095] S44: Dynamic calibration optimization. Continuously collect the voltage signal of the photodiode PD, dynamically adjust the output voltage of the second digital-to-analog converter DAC2, optimize the compensation amount, and the multi-stage feedback network composed of the third operational amplifier U3A and the fourth operational amplifier U4A suppresses temperature drift and power supply noise.

[0096] Specifically, the initial voltage is output by the first digital-to-analog converter DAC1 to drive the low-precision current regulation module, and the output current is adjusted to be close to the target value. The first operational amplifier U1A receives the first reference voltage output by the first digital-to-analog converter DAC1 and compares it with the feedback voltage of the low-precision current regulation module. The feedback voltage is sampled from the source of the first NMOS transistor Q1 through the resistor R2; according to the comparison result, the gate voltage of the first NMOS transistor Q1 is adjusted, and the conduction state of the first NMOS transistor Q1 is controlled through the resistor R1, so that the current at the source of the first NMOS transistor Q1 steps towards the target current value according to the preset precision.

[0097] Specifically, the correction voltage is output by the second digital-to-analog converter DAC2 to drive the high-precision current regulation module to compensate for the error after rough adjustment. The second operational amplifier U2A receives the second reference voltage output by the second digital-to-analog converter DAC2 and compares it with the feedback voltage of the high-precision current regulation module. The feedback voltage is sampled from the source of the second NMOS transistor Q2 through the resistor R5, and the voltage at the inverting input terminal of the second operational amplifier U2A is dynamically adjusted through the feedback network composed of the third operational amplifier U3A, the resistor R6, the resistor R7, and the resistor R8; according to the feedback result, the conduction state of the second NMOS transistor Q2 is adjusted, so that the current at the source of the second NMOS transistor Q2 steps with higher precision to compensate for the deviation of the low-precision current regulation module.

[0098] Specifically, the output current of the low-precision current regulation module and the output current of the high-precision current regulation module are connected in parallel and superimposed through the current superimposing module to obtain the final output current of the high-precision constant current source.

[0099] Specifically, the microcontroller collects the feedback signal of the load current in real time, calculates the deviation between the current output current and the target value, and adjusts the output voltages of the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2 again according to the comparison result between the deviation and the preset threshold. The current rough adjustment and current fine adjustment are repeated. If the deviation is within the preset threshold range, the current output is maintained.

[0100] Specifically, a feedback adjustment module is added to the circuit. The feedback adjustment module includes a photodiode PD. Taking the output light of 10 dB as an example, the photodiode PD is connected to a 99:1 splitter for the output light, and 1% of it is connected to the photodiode PD. Substitute it into the following formula:

[0101] A = 10 Lg(B)

[0102] Where A is the optical power in dB, and B is also the optical power in mW. It can be seen that 10 dB corresponds to 10 mW, so 1% of the light corresponds to 0.1 mW. The photoelectric efficiency of the photodiode PD is 1 A / W, so the photodiode PD can generate 0.1 mA of current.

[0103] Specifically, through the current rough adjustment step, assuming that the target current of 180 mA corresponds to the optical power of 10 dB, first perform point calibration. Set a calibration point for every 10 mA difference in the target current. In the range from zero current to the target current, the power and current are linearly related, and then perform interval calibration.

[0104] Specifically, assuming that the target power is 10 dB, when the low-precision current adjustment module has adjusted the power to 9.9 dB, to obtain the target power of 10 dB, it is necessary to intervene in the high-power current adjustment module and the feedback adjustment module. According to the formula:

[0105] V U5A = IPD * 20000

[0106] Where V U5A is the output voltage of the fifth operational amplifier U5A.

[0107] Specifically, the optical power of 10 dB corresponds to the current of 0.1 mA of the photodiode, so the output voltage of the fifth operational amplifier U5A is 2V. Thus, the output voltage of the second digital-to-analog converter is set to 2V. When the power is small, the current of the high-precision current adjustment module continues to increase, and the circuit reaches a stable state when the current feedback value of the photodiode PD reaches the target value.

[0108] Specifically, assuming that the target power is 10 dB, when the low-precision current adjustment module has adjusted the power to be greater than the target power, the high-precision current adjustment module is stopped from working. At this time, it is necessary to reduce the current value of the low-precision current adjustment module. When ensuring that the actual power is less than the target power, the high-precision current adjustment module is started for fine current adjustment.

Claims

1. A high-precision constant current source regulation circuit, characterized in that, Comprising: A low-precision current regulation module, the low-precision current regulation module is connected to a first digital-to-analog converter DAC1, the low-precision current regulation module includes a first operational amplifier U1A, and the first digital-to-analog converter DAC1 is connected to the non-inverting input terminal of the first operational amplifier U1A; A high-precision current regulation module, the high-precision current regulation module is connected to a second digital-to-analog converter DAC2, the high-precision current regulation module includes a second operational amplifier U2A, and the second digital-to-analog converter DAC2 is connected to the non-inverting input terminal of the second operational amplifier U2A; A current superposition module, the current superposition module is connected to the output terminal of the low-precision current regulation module and the output terminal of the high-precision current regulation module; A feedback regulation module, the feedback regulation module includes a fifth operational amplifier U5A, a photodiode PD and a resistor R11, the output terminal of the fifth operational amplifier U5A is connected to the inverting input terminal of the second operational amplifier U2A in the high-precision current regulation module, the non-inverting input terminal of the fifth operational amplifier U5A is grounded, the inverting input terminal of the fifth operational amplifier U5A is connected to one end of the photodiode PD, the other end of the photodiode PD is grounded, and the resistor R11 is connected between the output terminal of the fifth operational amplifier U5A and the photodiode PD; A microcontroller, the microcontroller is electrically connected to the first digital-to-analog converter DAC1 and the second digital-to-analog converter DAC2.

2. The high-precision constant current source adjustment circuit according to claim 1, wherein The low-precision current regulation module further includes a resistor R1, a resistor R2, a resistor R3 and a first NMOS transistor Q1, the output terminal of the first operational amplifier U1A is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the gate of the first NMOS transistor Q1, the source of the first NMOS transistor Q1 is connected to one end of the resistor R3, the other end of the resistor R3 is grounded, the inverting input terminal of the first operational amplifier U1A is connected to one end of the resistor R2, and the other end of the resistor R2 is connected between the source of the first NMOS transistor Q1 and the resistor R3.

3. The high-precision constant current source adjustment circuit according to claim 2, wherein The high-precision current regulation module further includes a resistor R4, a resistor R5 and a second NMOS transistor Q2, the output terminal of the second operational amplifier U2A is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the gate of the second NMOS transistor Q2, the source of the second NMOS transistor Q2 is connected to one end of the resistor R5, and the other end of the resistor R5 is grounded.

4. The high-precision constant current source regulation circuit according to claim 3, characterized in that The high-precision current regulation module further includes a third operational amplifier U3A, a resistor R6, a resistor R7, and a resistor R8. The non-inverting input terminal of the third operational amplifier U3A is connected between the source of the second NMOS transistor Q2 and the resistor R5. The inverting input terminal of the third operational amplifier U3A is connected to one end of the resistor R7, and the other end of the resistor R7 is grounded. One end of the resistor R6 is connected between the inverting input terminal of the third operational amplifier U3A and the resistor R7. The other end of the resistor R6 and the output terminal of the third operational amplifier U3A are both connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the inverting input terminal of the second operational amplifier U2A.

5. The high-precision constant current source regulation circuit according to claim 4, wherein The high-precision current regulation module improves the current regulation accuracy by adding operational amplifier modules in parallel and adjusting the connection relationship.

6. The high-precision constant current source regulation circuit according to claim 5, characterized in that, The operational amplifier module includes a resistor R9, a resistor R10, and a fourth operational amplifier U4A. The non-inverting input terminal of the fourth operational amplifier U4A is connected to the resistor R6 and the output terminal of the third operational amplifier U3A. The inverting input terminal of the fourth operational amplifier U4A is connected to one end of the resistor R10, and the other end of the resistor R10 is grounded. One end of the resistor R9 is connected between the inverting input terminal of the fourth operational amplifier U4A and the resistor R10. The other end of the resistor R9 and the output terminal of the fourth operational amplifier U4A are connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the inverting input terminal of the second operational amplifier U2A.

7. A method for adjusting a high-precision constant current source, characterized in that, Based on the high-precision constant current source regulation circuit according to any one of claims 1-6, the following steps are included: S1: Coarse current adjustment. The first digital-to-analog converter DAC1 outputs an initial voltage to drive the low-precision current regulation module to adjust the output current to be close to the target value. S2: Fine current adjustment. The second digital-to-analog converter DAC2 outputs a correction voltage to drive the high-precision current regulation module to compensate for the remaining error, so that the output current reaches the target value. S3: Current superposition. The output current of the low-precision current regulation module and the output current of the high-precision current regulation module are superposed to obtain the final output current of the high-precision constant current source. S4: Feedback regulation. Continuously collect the voltage signal of the photodiode PD to determine the compensation amount, and adjust the second digital-to-analog converter DAC2 for optimized compensation.

8. The high-precision constant current source regulation method according to claim 7, wherein The S1 includes the following specific steps: S11: Compare the first reference voltage output by the first digital-to-analog converter DAC1 with the feedback voltage of the low-precision current regulation module through the first operational amplifier U1A. S12: Adjust the conduction state of the first NMOS transistor Q1. S13: Adjust until the output current of the low-precision current regulation module steps towards the target current value according to the preset accuracy.

9. The high-precision constant current source regulation method according to claim 8, characterized in that, The S2 includes the following specific steps: S21: Compare the second reference voltage output by the second digital-to-analog converter DAC2 with the feedback voltage of the high-precision current regulation module through the second operational amplifier U2A. S22: Add a third operational amplifier U3A to form a multi-stage negative feedback. S23: Adjust the conduction state of the second NMOS transistor Q2. S24: Make the output current of the high-precision current regulation module compensate for the deviation of the low-precision current regulation module with a higher-precision step.

10. The high-precision constant current source regulation method according to claim 9, wherein The said S4 includes the following specific steps: S41: Current deviation detection. The photodiode PD monitors the load current in real time and converts the current change on the load into a voltage signal to reflect the deviation between the actual output current and the target value. S42: Signal amplification processing. The inverting input terminal of the fifth operational amplifier U5A receives the voltage signal of the photodiode PD. S43: Closed-loop compensation control. The output correction signal of the fifth operational amplifier U5A is sent to the inverting input terminal of the second operational amplifier U2A, and then the gate voltage of the second NMOS transistor Q2 is adjusted, thereby controlling the output current of the high-precision module to compensate for the remaining error of the low-precision module. S44: Dynamic calibration optimization. Continuously collect the voltage signal of the photodiode PD, dynamically adjust the output voltage of the second digital-to-analog converter DAC2, optimize the compensation amount, and the multi-stage feedback network composed of the third operational amplifier U3A and the fourth operational amplifier U4A suppresses the temperature drift and power supply noise.

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