Constant current source driver

Abstract

The application discloses a constant current source driver, comprising: a front stage processing unit for accessing an external control signal, filtering and amplitude adjusting the external control signal, and outputting a conditioned reference voltage signal; an error amplification unit for differentially amplifying the reference voltage signal and a feedback voltage signal, and outputting a driving signal, the error amplification unit being internally provided with an inner loop feedback subunit for reducing high frequency gain; an output and sampling unit for controlling the current flowing through a load according to the driving signal, and sampling the current to generate the feedback voltage signal; and a power supply unit for providing energy for the load. The application solves the problem that in a large power driving application scenario with large current and large power path parasitic parameters, a traditional linear negative feedback V-I conversion circuit is unstable and the output current oscillates due to the interference caused by large current and the existence of power path parasitic inductance and parasitic capacitance.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a constant current source driver. Background Technology

[0002] A constant current source driver is a power supply device that can provide a constant current to a load. It is widely used in driving devices with strong nonlinear current-voltage characteristics, such as light-emitting diodes and laser pump sources.

[0003] Currently, mainstream constant current drive solutions for the above application scenarios typically adopt, such as Figure 1 The circuit shown is a linear negative feedback VI converter. This circuit mainly consists of an operational amplifier U, a sixth resistor R6 (sampling resistor), and a MOSFET / transistor M, enabling constant current drive of the load. While this method is simple in structure, it is unsuitable for high-power drive applications with large current and parasitic parameters in the power path. The di / dt interference generated by the large current, as well as the parasitic inductance L and capacitance C of the power path, will make this linear negative feedback VI converter circuit unstable, prone to current oscillations, unable to meet constant current requirements, and in severe cases, may even burn out the circuit.

[0004] Therefore, how to effectively overcome the loop stability problem under high current and high parasitic parameter conditions, prevent current oscillation, and achieve safe and reliable driving of high-power loads while retaining the advantages of linear constant current drive output dynamic range, continuity, and high precision has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a constant current source driver that can solve the problem of instability of traditional linear negative feedback VI conversion circuits in high-power drive application scenarios with large current and large power path parasitic parameters.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is to provide a constant current source driver, comprising: The front-end processing unit is used to receive external control signals, filter and adjust the amplitude of the external control signals, and output a conditioned reference voltage signal. An error amplification unit is used to differentially amplify the reference voltage signal and the feedback voltage signal and output a drive signal. The error amplification unit is equipped with an inner loop feedback subunit for reducing high-frequency gain. An output and sampling unit is configured to control the current flowing through the load according to the drive signal, and sample the current to generate the feedback voltage signal; and A power supply unit is used to provide energy to the load.

[0007] Furthermore, the pre-processing unit includes a first resistor R1, a second resistor R2, and a first capacitor C1; the first end of the first resistor R1 serves as the input terminal of the pre-processing unit, connected to the external control signal, and the second end of the first resistor R1 serves as the output terminal of the pre-processing unit, electrically connected to the reference voltage signal input terminal of the error amplification unit; the first end of the second resistor R2 is electrically connected to the first end of the first resistor R1, and the second end of the second resistor R2 is grounded; the positive terminal of the first capacitor C1 is electrically connected between the second end of the first resistor R1 and the first end of the second resistor R2, and the negative terminal of the first capacitor C1 is grounded.

[0008] Furthermore, the error amplification unit also includes: An amplification subunit is used to differentially amplify the reference voltage signal and the feedback voltage signal, and output the drive signal; The first end of the inner loop feedback subunit is electrically connected to the feedback voltage signal input terminal of the amplification subunit, and the second end of the inner loop feedback subunit is electrically connected to the drive signal output terminal of the amplification subunit, which is used to reduce the high-frequency gain of the amplification subunit.

[0009] Furthermore, the amplification subunit includes an operational amplifier U1; the non-inverting input terminal of the operational amplifier U1 is electrically connected to the output terminal of the pre-processing unit, the inverting input terminal of the operational amplifier U1 is electrically connected to the feedback voltage signal output terminal of the output and sampling unit, and the output terminal of the operational amplifier U1 is electrically connected to the drive signal input terminal of the output and sampling unit.

[0010] Furthermore, the inner loop feedback subunit includes a third resistor R3 and a second capacitor C2; the first end of the third resistor R3 is electrically connected to the first end of the second capacitor C2 as the first end of the inner loop feedback subunit; the second end of the third resistor R3 is electrically connected to the second end of the second capacitor C2 as the second end of the inner loop feedback subunit.

[0011] Furthermore, the output and sampling unit includes: A power output subunit is used to control the current flowing through the load according to the drive signal; The outer loop feedback subunit is used to sample the current flowing through the load to generate the feedback voltage signal.

[0012] Furthermore, the power output subunit includes a seventh resistor R7 and a switching transistor M1; the first end of the seventh resistor R7 is electrically connected to the output terminal of the operational amplifier U1 to receive a drive signal; the second end of the seventh resistor R7 is electrically connected to the gate of the switching transistor M1; the drain of the switching transistor M1 is electrically connected to the negative input terminal of the load, and the source of the switching transistor M1 is electrically connected to the sampling terminal of the outer loop feedback subunit.

[0013] Furthermore, the outer loop feedback subunit includes a sixth resistor R6 and a fifth resistor R5; the first end of the sixth resistor R6 serves as the sampling terminal of the outer loop feedback subunit and is electrically connected to the source of the switching transistor M1, and the second end of the sixth resistor R6 is grounded; the first end of the fifth resistor R5 is electrically connected to the source of the switching transistor M1, and the second end of the fifth resistor R5 is electrically connected to the inverting input terminal of the operational amplifier U1 to output a feedback voltage signal.

[0014] Furthermore, the power supply unit includes a power supply Vdc and a third capacitor C3; the positive terminal of the power supply Vdc is electrically connected to the positive input terminal of the load, and the negative terminal of the power supply Vdc is grounded; the positive terminal of the third capacitor C3 is electrically connected to the positive terminal of the power supply Vdc, and the negative terminal of the third capacitor C3 is grounded.

[0015] Furthermore, the third capacitor C3 is composed of multiple tantalum capacitors and ceramic plate capacitors connected in parallel.

[0016] The constant current source driver of the present invention has at least the following beneficial effects: (i) Based on the traditional linear negative feedback VI conversion circuit, an inner loop feedback sub-unit composed of the third resistor R3 and the second capacitor C2 is added to improve the performance of the operational amplifier, giving it low-pass characteristics, reducing high-frequency gain, increasing the stability of the outer loop feedback, and preventing the output current from oscillating. Through the combined effect of the inner loop feedback sub-unit and the outer loop feedback sub-unit, the high-frequency oscillation of the output current is effectively suppressed.

[0017] (ii) The front-end processing unit filters the control signal input from the front-end, filters out high-frequency interference on the transmission path of the front-end control signal, and uses the first resistor R1 and the second resistor R2 in series to divide the voltage for amplitude adjustment, so as to adjust the amplitude of the constant current of the subsequent stage, and ensure that the reference voltage signal sent to the error amplification unit is clean and stable.

[0018] (iii) This invention is applicable to high current and high power application scenarios. According to the application requirements, select the appropriate power level MOSFET and power sampling resistor, and maintain good heat dissipation. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a circuit diagram of a traditional linear negative feedback VI converter circuit.

[0020] Figure 2 This is a circuit diagram of one embodiment of the constant current source driver of the present invention.

[0021] Figure 3 This is a simulation circuit diagram for a traditional linear negative feedback VI conversion circuit.

[0022] Figure 4 The diagram shows the circuit simulation results of a traditional linear negative feedback VI converter circuit.

[0023] Figure 5 This is a test circuit diagram of a traditional linear negative feedback VI conversion circuit.

[0024] Figure 6 This is a simulation circuit diagram of the constant current source driver of the present invention.

[0025] Figure 7 The figure shows the simulation results of the constant current source driver of the present invention.

[0026] Figure 8 This is a test circuit diagram of the constant current source driver of the present invention. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] Please see Figure 2 The constant current source driver of the present invention includes a pre-processing unit 100, an error amplification unit 200, an output and sampling unit 300, and a power supply unit 400. The pre-processing unit 100 is used to receive an external control signal, filter and adjust the amplitude of the external control signal, and output a conditioned reference voltage signal. The error amplification unit 200 is used to differentially amplify the reference voltage signal and the feedback voltage signal, and output a drive signal. The error amplification unit 200 internally includes an inner loop feedback subunit 220 for reducing high-frequency gain. The output and sampling unit 300 is used to control the current flowing through the load 500 according to the drive signal, and samples the current to generate the feedback voltage signal. The power supply unit 400 is used to provide energy to the load 500. The inner loop feedback subunit 220 constitutes inner loop feedback, and the feedback voltage signal constitutes outer loop feedback. The inner loop feedback and the outer loop feedback together suppress high-frequency oscillation of the output current.

[0029] The pre-processing unit 100 includes a first resistor R1, a second resistor R2, and a first capacitor C1. The first end of the first resistor R1 serves as the input terminal of the pre-processing unit 100, receiving the external control signal. The second end of the first resistor R1 serves as the output terminal of the pre-processing unit 100, electrically connected to the reference voltage signal input terminal of the error amplification unit 200. The first end of the second resistor R2 is electrically connected to the first end of the first resistor R1, and the second end of the second resistor R2 is grounded. The positive terminal of the first capacitor C1 is electrically connected between the second end of the first resistor R1 and the first end of the second resistor R2, and the negative terminal of the first capacitor C1 is grounded. The external control signal is typically an analog voltage signal generated by the pre-amplifier DAC module. The voltage divider network formed by the first resistor R1 and the second resistor R2 allows for amplitude adjustment of the input external control signal to match the processing range of the subsequent circuitry. The first capacitor C1 filters high-frequency interference coupled along the transmission path of the external control signal, ensuring that the reference voltage signal sent to the error amplification unit 200 is clean and stable. For example, the resistance values ​​of the first resistor R1 and the second resistor R2 are both 27KΩ, and the capacitance value of the first capacitor C1 is 100pF.

[0030] The error amplification unit 200 includes an amplification subunit 210 and an inner loop feedback subunit 220. The amplification subunit 210 is used to differentially amplify the reference voltage signal and the feedback voltage signal, and output the drive signal. The first terminal of the inner loop feedback subunit 220 is electrically connected to the feedback voltage signal input terminal of the amplification subunit 210, and the second terminal of the inner loop feedback subunit 220 is electrically connected to the drive signal output terminal of the amplification subunit 210, which is used to reduce the high-frequency gain of the amplification subunit 210.

[0031] In this embodiment, the amplification subunit 210 includes an operational amplifier U1. The non-inverting input of the operational amplifier U1 is electrically connected to the output of the pre-processing unit 100 to receive the reference voltage signal. The inverting input of the operational amplifier U1 is electrically connected to the feedback voltage signal output of the output and sampling unit 300 to receive the feedback voltage signal. The output of the operational amplifier U1 is electrically connected to the drive signal input of the output and sampling unit 300 to output a drive signal. The operational amplifier U1 is preferably a voltage-type high-speed rail-to-rail operational amplifier to ensure sufficient drive capability and response speed. For example, the operational amplifier U1 can be implemented using an operational amplifier of model SX8042MF.

[0032] The inner loop feedback subunit 220 includes a third resistor R3 and a second capacitor C2. The first end of the third resistor R3 is electrically connected to the first end of the second capacitor C2, serving as the first terminal of the inner loop feedback subunit 220, and is electrically connected to the inverting input terminal of the operational amplifier U1. The second end of the third resistor R3 is electrically connected to the second end of the second capacitor C2, serving as the second terminal of the inner loop feedback subunit 220, and is electrically connected to the output terminal of the operational amplifier U1.

[0033] The third resistor R3 and the second capacitor C2 constitute the local frequency compensation network of the operational amplifier U1, enabling the error amplification unit 200 to have low-pass filtering characteristics to reduce high-frequency gain. The values ​​of the third resistor R3 and the second capacitor C2 determine the corner frequency of the inner loop feedback. In this embodiment, the resistance of the third resistor R3 is 27KΩ, and the capacitance of the second capacitor C2 is 2200pF. When a high-frequency interference signal (such as interference caused by a large current) appears, the capacitive reactance of the second capacitor C2 decreases sharply, drawing the high-frequency component directly back from the output of the operational amplifier U1 to the inverting input, thereby significantly compressing the amplification capability of the operational amplifier U1 for high-frequency signals. This allows the operational amplifier to ignore high-frequency interference and only amplify DC and low-frequency control signals normally. It should be understood that the specific values ​​of the third resistor R3 and the second capacitor C2 can be appropriately adjusted according to the frequency characteristics of the interference signal in the actual application scenario, and are not limited to the specific values ​​mentioned above.

[0034] The output and sampling unit 300 includes a power output subunit 310 and an outer loop feedback subunit 320. The power output subunit 310 is used to control the current flowing through the load 500 according to the drive signal. The outer loop feedback subunit 320 is used to sample the current flowing through the load 500 to generate the feedback voltage signal.

[0035] The power output subunit 310 includes a seventh resistor R7 and a switching transistor M1. The first end of the seventh resistor R7 is electrically connected to the output of the operational amplifier U1 to receive a drive signal; the second end of the seventh resistor R7 is electrically connected to the gate of the switching transistor M1. The drain of the switching transistor M1 is electrically connected to the negative input terminal of the load 500, and the source of the switching transistor M1 is electrically connected to the sampling terminal of the outer loop feedback subunit 320. The seventh resistor R7 serves as the gate resistor of the switching transistor M1, used to limit the drive current and prevent high-frequency oscillation at the gate of the switching transistor M1. In this embodiment, the switching transistor M1 is an N-channel MOSFET, selected in a high-power package (such as TO-247) with good heat dissipation. Due to the parameter dispersion of multiple MOSFETs and the influence of parasitic parameters in the layout traces, the stability of the feedback loop will be reduced, resulting in the inability to achieve a constant current effect. Therefore, the switching transistor M1 is preferably a single power MOSFET. For example, the switching transistor M1 can be implemented using a CSW20N011-J type MOSFET, and the resistance value of the seventh resistor R7 is 36Ω.

[0036] The outer loop feedback subunit 320 includes a sixth resistor R6 and a fifth resistor R5. The first end of the sixth resistor R6 serves as the sampling terminal of the outer loop feedback subunit 320 and is electrically connected to the source of the switching transistor M1. The second end of the sixth resistor R6 is grounded. The first end of the fifth resistor R5 is electrically connected to the source of the switching transistor M1, and the second end of the fifth resistor R5 is electrically connected to the inverting input terminal of the operational amplifier U1.

[0037] The sixth resistor R6 serves as a sampling resistor, converting the current flowing through the load 500 into a sampling voltage. The fifth resistor R5 serves as a voltage divider resistor, transmitting the sampling voltage to the inverting input of the operational amplifier U1 to form the feedback voltage signal. In this embodiment, the fifth resistor R5 is a general-purpose surface mount resistor, and the sixth resistor R6 is a power resistor. The power consumption of the sixth resistor R6 is calculated based on the required constant current. Multiple power resistors can be connected in parallel to reduce the power consumption of a single power resistor. For example, the resistance of the fifth resistor R5 is 27KΩ, and the resistance of the sixth resistor R6 is 70mΩ, composed of 14 1Ω power resistors connected in parallel. Using multiple power resistors in parallel can, on the one hand, distribute power consumption and reduce the thermal stress of a single resistor; on the other hand, it can reduce the equivalent series inductance, minimizing the adverse effects of parasitic parameters in the sampling circuit on loop stability.

[0038] The power supply unit 400 includes a power supply Vdc and a third capacitor C3. The positive terminal of the power supply Vdc is electrically connected to the positive input terminal of the load 500, and the negative terminal of the power supply Vdc is grounded. The positive terminal of the third capacitor C3 is electrically connected to the positive terminal of the power supply Vdc, and the negative terminal of the third capacitor C3 is grounded. The power supply Vdc can be a DC / DC module, a battery, or other power supply device, used to provide energy to the load 500. The third capacitor C3 serves as a supporting capacitor, and its capacitance is typically very large, reaching approximately 5000μF to 15000μF, to compensate for the insufficient transient output capability of the power supply Vdc. In this embodiment, the capacitance of the third capacitor C3 is 10000μF, and it is composed of multiple tantalum capacitors and ceramic plate capacitors connected in parallel. The positive terminals of all capacitors are connected to the positive terminal of the power supply Vdc, and the negative terminals are connected to ground. Among them, the tantalum capacitors play a major role in energy storage, and the ceramic plate capacitors compensate for the weak transient output capability of the tantalum capacitors. The load 500 is an object requiring constant current drive, and can be a resistive load or a diode-type load. Its positive input terminal is electrically connected to the positive terminal of the power supply Vdc and the positive terminal of the third capacitor C3, and its negative input terminal is electrically connected to the drain of the switching transistor M1. For example, the load 500 is a 1Ω power resistor.

[0039] This invention, based on the traditional linear negative feedback VI conversion circuit, adds a third resistor R3 and a second capacitor C2 to give the operational amplifier low-pass characteristics and reduce high-frequency gain, thereby achieving stable constant current output under high current and high parasitic parameter conditions. Its working principle can be explained through the following transfer function derivation.

[0040] like Figure 1 As shown, the electrical relationship of a traditional linear negative feedback VI converter circuit is:

[0041]

[0042]

[0043] in, This represents the input voltage at the non-inverting input terminal of the operational amplifier. This represents the feedback voltage at the inverting input of the operational amplifier. This indicates the open-loop gain of the operational amplifier. This represents the output voltage of the operational amplifier. Indicates the output current. This represents the transconductance of the MOSFET. It can be seen that the output current... and input voltage It is a linear proportional relationship.

[0044] However, in practical applications, the power path contains non-negligible parasitic inductance and capacitance, which will generate interference voltage superimposed on the sixth resistor R6 (i.e., the sampling resistor) or the -input terminal of the operational amplifier. Let the interference voltage be... Then we have:

[0045]

[0046] From the above equation, it can be seen that the change in output current caused by the interference voltage is: The sixth resistor R6 is usually in the mΩ range. As long as the interference voltage is a few mV, it may cause the output current to fluctuate by several A. Moreover, the interference voltage has high frequency characteristics, which will eventually cause the output current to fluctuate and fail to achieve the effect of constant current.

[0047] according to Figure 3 The simulation of the circuit diagram shown is performed, and the simulation results are as follows: Figure 4 As shown, the feedback voltage and output current of the sixth resistor fluctuate. A circuit was built based on this circuit for testing, and the measured results are shown in the figure below. Figure 5 As shown, the measured output current is in an oscillating state and cannot achieve a constant current effect.

[0048] The output current of the dual-feedback architecture of this invention is derived as follows:

[0049] The third resistor R3 is connected in parallel with the second capacitor C2, and its equivalent impedance is .

[0050] replace When frequency When it approaches infinity, the output current The high-frequency response is:

[0051] Interference voltage It is a high-frequency characteristic signal, which can be seen in the high-frequency band, interference voltage Due to the presence of the inner loop feedback subunit 220, the output current It is no longer affected by it, and is only controlled by the input voltage. .

[0052] When frequency When it approaches 0, the output current The low-frequency response is:

[0053] Interference voltage It is a high-frequency characteristic signal, and its amplitude in the low-frequency range approaches 0. When the frequency approaches 0, the interference voltage also approaches 0, that is, the DC component is 0. Therefore, at this time, the output current is only controlled by the input voltage. .

[0054] according to Figure 6 The circuit diagram of the constant current source driver of the present invention shown is simulated, and the simulation results are as follows: Figure 7 As shown, after adding the inner loop feedback subunit 220, the output current no longer oscillates, and the waveform is stable. Compared with the traditional linear negative feedback VI conversion circuit, the stability is significantly improved. Figure 8 This is a test circuit diagram of the constant current source driver of the present invention. Under the input pulse signal (amplitude 0.5V / frequency 200Hz / pulse width 100μs), the output pulse current amplitude is 4.5A (2A / div). It can be seen that the output current is completely controlled by the input control voltage and is no longer affected by parasitic parameters, which verifies the effectiveness of the present invention in suppressing parasitic parameter interference in the power path.

[0055] This invention's constant current source driver, based on a traditional linear negative feedback VI converter circuit, adds an inner-loop feedback sub-unit consisting of a third resistor R3 and a second capacitor C2. This improves the operational amplifier's performance, giving it low-pass characteristics, reducing high-frequency gain, increasing the stability of the outer-loop feedback, and preventing output current oscillations. The combined effect of the inner and outer-loop feedback sub-units effectively suppresses high-frequency oscillations in the output current. The pre-processing unit filters the control signal input from the pre-stage, removing high-frequency interference along the transmission path. It also uses a series voltage divider with the first resistor R1 and the second resistor R2 to adjust the amplitude of the subsequent constant current, ensuring a clean and stable reference voltage signal sent to the error amplifier unit. This invention is applicable to high-current, high-power applications. Depending on the application requirements, appropriate power ratings of MOSFETs and power sampling resistors can be selected, while maintaining good heat dissipation.

[0056] The above description merely illustrates preferred embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A constant current source driver, characterized in that, include: The front-end processing unit is used to receive external control signals, filter and adjust the amplitude of the external control signals, and output a conditioned reference voltage signal. An error amplification unit is used to differentially amplify the reference voltage signal and the feedback voltage signal and output a drive signal. The error amplification unit is equipped with an inner loop feedback subunit for reducing high-frequency gain. An output and sampling unit is configured to control the current flowing through the load according to the drive signal, and sample the current to generate the feedback voltage signal; and A power supply unit is used to provide energy to the load.

2. The constant current source driver as described in claim 1, characterized in that: The pre-processing unit includes a first resistor R1, a second resistor R2, and a first capacitor C1. The first end of the first resistor R1 serves as the input terminal of the pre-processing unit, connected to the external control signal. The second end of the first resistor R1 serves as the output terminal of the pre-processing unit and is electrically connected to the reference voltage signal input terminal of the error amplification unit. The first end of the second resistor R2 is electrically connected to the first end of the first resistor R1, and the second end of the second resistor R2 is grounded. The positive terminal of the first capacitor C1 is electrically connected between the second end of the first resistor R1 and the first end of the second resistor R2, and the negative terminal of the first capacitor C1 is grounded.

3. The constant current source driver as described in claim 1, characterized in that, The error amplification unit further includes: An amplification subunit is used to differentially amplify the reference voltage signal and the feedback voltage signal, and output the drive signal; The first end of the inner loop feedback subunit is electrically connected to the feedback voltage signal input terminal of the amplification subunit, and the second end of the inner loop feedback subunit is electrically connected to the drive signal output terminal of the amplification subunit, which is used to reduce the high-frequency gain of the amplification subunit.

4. The constant current source driver as described in claim 3, characterized in that: The amplification subunit includes an operational amplifier U1; the non-inverting input terminal of the operational amplifier U1 is electrically connected to the output terminal of the pre-processing unit, the inverting input terminal of the operational amplifier U1 is electrically connected to the feedback voltage signal output terminal of the output and sampling unit, and the output terminal of the operational amplifier U1 is electrically connected to the drive signal input terminal of the output and sampling unit.

5. The constant current source driver as described in claim 4, characterized in that: The inner loop feedback subunit includes a third resistor R3 and a second capacitor C2; the first end of the third resistor R3 is electrically connected to the first end of the second capacitor C2 as the first end of the inner loop feedback subunit; the second end of the third resistor R3 is electrically connected to the second end of the second capacitor C2 as the second end of the inner loop feedback subunit.

6. The constant current source driver as described in claim 4, characterized in that, The output and sampling unit includes: A power output subunit is used to control the current flowing through the load according to the drive signal; The outer loop feedback subunit is used to sample the current flowing through the load to generate the feedback voltage signal.

7. The constant current source driver as described in claim 6, characterized in that: The power output subunit includes a seventh resistor R7 and a switching transistor M1; the first end of the seventh resistor R7 is electrically connected to the output terminal of the operational amplifier U1 to receive a drive signal; the second end of the seventh resistor R7 is electrically connected to the gate of the switching transistor M1; the drain of the switching transistor M1 is electrically connected to the negative input terminal of the load, and the source of the switching transistor M1 is electrically connected to the sampling terminal of the outer loop feedback subunit.

8. The constant current source driver as described in claim 7, characterized in that: The outer loop feedback subunit includes a sixth resistor R6 and a fifth resistor R5; the first end of the sixth resistor R6 serves as the sampling terminal of the outer loop feedback subunit and is electrically connected to the source of the switching transistor M1, and the second end of the sixth resistor R6 is grounded; the first end of the fifth resistor R5 is electrically connected to the source of the switching transistor M1, and the second end of the fifth resistor R5 is electrically connected to the inverting input terminal of the operational amplifier U1 to output a feedback voltage signal.

9. The constant current source driver as described in claim 1, characterized in that: The power supply unit includes a power supply Vdc and a third capacitor C3; the positive terminal of the power supply Vdc is electrically connected to the positive input terminal of the load, and the negative terminal of the power supply Vdc is grounded; the positive terminal of the third capacitor C3 is electrically connected to the positive terminal of the power supply Vdc, and the negative terminal of the third capacitor C3 is grounded.

10. The constant current source driver as described in claim 9, characterized in that: The third capacitor C3 is composed of multiple tantalum capacitors and ceramic plate capacitors connected in parallel.

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