A laser driving circuit

Abstract

This invention discloses a laser driving circuit. The circuit provides driving current to a laser output unit. The laser driving circuit includes a low-dropout linear regulator and a constant current source circuit. The low-dropout linear regulator, the laser output unit, and the constant current source circuit are connected in series to form a series circuit. The low-dropout linear regulator provides a stable voltage to the laser output unit, and the constant current source circuit stabilizes the current in the series circuit. This invention, by using a low-noise low-dropout linear regulator, provides a stable voltage to the laser output unit while reducing the impact of power supply noise on the driving current, thus enhancing the anti-interference capability of the laser driving circuit. By feeding back the output current of the laser output unit to the constant current source circuit, it enables a rapid response when the current changes, thereby ensuring the stability of the current in the series circuit and consequently guaranteeing the output stability of the laser output unit.

Description

Technical Field

[0001] This utility model relates to electronic circuit technology, and in particular to a laser driving circuit. Background Technology

[0002] In fields such as precision laser control, optical communication, and medical equipment, traditional laser drive circuits suffer from problems such as large temperature drift, slow response speed, and poor anti-interference capability, making it difficult to meet the requirements of high-precision applications. Therefore, there is an urgent need for a laser drive circuit that can achieve high stability, fast response, and easy integration. Utility Model Content

[0003] This invention provides a laser driving circuit that ensures the stability of the laser output wavelength and has the advantages of fast response speed and strong anti-interference ability.

[0004] This invention provides a laser driving circuit for supplying driving current to a laser output unit; the laser driving circuit includes a low-dropout linear regulator and a constant current source circuit.

[0005] The low-dropout linear regulator, the laser output unit, and the constant current source circuit are connected in series to form a series circuit.

[0006] The low-dropout linear regulator is used to provide a stable voltage to the laser output unit;

[0007] The constant current source circuit is used to stabilize the current in the series circuit.

[0008] Optionally, the constant current source circuit includes a first operational amplifier, a second operational amplifier, a power transistor, and a sampling resistor;

[0009] The first operational amplifier includes a first input terminal, a second input terminal, and a first output terminal;

[0010] The second operational amplifier includes a third input terminal, a fourth input terminal, and a second output terminal;

[0011] The power transistor includes a first terminal, a second terminal, and a control terminal;

[0012] The first input terminal is used to receive a first base current adjustment signal and a second current adjustment signal;

[0013] The second input terminal is used to receive the first current adjustment signal;

[0014] The first output terminal is electrically connected to the third input terminal, the fourth input terminal is electrically connected to the second terminal, and the second output terminal is electrically connected to the control terminal;

[0015] The first end is electrically connected to the laser output unit, and the second end is grounded through the sampling resistor.

[0016] Optionally, the constant current source circuit further includes a first filter circuit, a second filter circuit, a third filter circuit, and a fourth filter circuit;

[0017] The first operational amplifier further includes a first power supply terminal and a second power supply terminal, and the second operational amplifier further includes a third power supply terminal and a fourth power supply terminal;

[0018] The first power supply terminal is connected to the first power supply through the first filter circuit; the second power supply terminal is connected to the second power supply through the second filter circuit; the third power supply terminal is connected to the third power supply through the third filter circuit; and the fourth power supply terminal is connected to the fourth power supply through the fourth filter circuit.

[0019] The first power supply has the same voltage as the third power supply, the second power supply has the same voltage as the fourth power supply, and the first power supply has a different voltage from the second power supply.

[0020] Optionally, the first filter circuit, the second filter circuit, the third filter circuit, and the fourth filter circuit all include a first capacitor and a second capacitor connected in parallel, and the capacitance values ​​of the first capacitor and the second capacitor are different.

[0021] Optionally, the constant current source circuit further includes a voltage divider circuit connected in series between the first output terminal and the third input terminal.

[0022] Optionally, the voltage divider circuit includes a first resistor, a second resistor, and a third capacitor;

[0023] The first end of the first resistor is electrically connected to the first output terminal, the first end of the second resistor is grounded, and the first plate of the third capacitor is grounded; the second end of the first resistor, the second end of the second resistor, and the second plate of the third capacitor are electrically connected to each other and electrically connected to the third input terminal.

[0024] Optionally, the laser driving circuit further includes a current detection circuit, which is electrically connected to the second terminal.

[0025] Optionally, the current detection circuit includes a third operational amplifier;

[0026] The third operational amplifier includes a fifth input terminal, a sixth input terminal, and a third output terminal;

[0027] The fifth input terminal is electrically connected to the second terminal, and the sixth input terminal is electrically connected to the third output terminal.

[0028] Optionally, the low-dropout linear regulator is an LT3045IMSE low-dropout linear regulator, and both the first operational amplifier and the second operational amplifier are AD797ARZ operational amplifiers.

[0029] Optionally, the low-dropout linear regulator further includes a current-limiting pin, which is connected in series with a current-limiting resistor and grounded.

[0030] The laser driving circuit provided by this invention uses a low-noise, low-dropout linear regulator to provide a stable voltage for the laser output unit while reducing the impact of power supply noise on the drive current, thus enhancing the anti-interference capability of the laser driving circuit. By feeding the output current of the laser output unit back to the constant current source circuit, it can respond quickly to changes in current, thereby ensuring the stability of the current in the series circuit and thus guaranteeing the output stability of the laser output unit. Simultaneously, the current of the laser output unit can be quickly adjusted, thereby changing the output laser wavelength. Attached Figure Description

[0031] Figure 1 A schematic diagram of a laser driving circuit provided in an embodiment of this utility model;

[0032] Figure 2 This is a schematic diagram of another laser driving circuit provided in an embodiment of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0034] Figure 1 A schematic diagram of a laser driving circuit provided in an embodiment of this utility model is shown below. Figure 1 As shown, the laser driving circuit 10 is used to provide driving current to the laser output unit 20; the laser driving circuit 10 includes a low-dropout linear regulator 30 and a constant current source circuit 40; the low-dropout linear regulator 30, the laser output unit 20 and the constant current source circuit 40 are connected in series to form a series circuit; the low-dropout linear regulator 30 is used to provide a stable voltage to the laser output unit 20; the constant current source circuit 40 is used to stabilize the current in the series circuit.

[0035] Specifically, the laser output unit 20 has different output wavelengths under different operating currents. The laser driving circuit 10 is used to provide driving current to the laser output unit 20. Therefore, when the laser driving circuit 10 controls the laser output unit 20 to output laser of a certain wavelength, it is necessary to ensure that the laser driving circuit 10 has high stability, thereby improving the output stability of the laser.

[0036] like Figure 1 As shown, the laser driving circuit 10 includes a low-dropout linear regulator 30 and a constant current source circuit 40. The low-dropout linear regulator 30 includes a voltage output terminal 301, which is electrically connected to the input terminal 201 of the laser output unit 20, and is used to provide a stable voltage to the laser output unit 20. Further, the low-dropout linear regulator 30 can be a low-noise power supply chip, which reduces the impact of power supply noise on the drive current when supplying power to the laser output unit 20. For example, the low-dropout linear regulator 30 can be an LT3045IMSE low-dropout linear regulator. In addition, filter capacitors of different capacitance values ​​can be added to the power supply terminal of the low-dropout linear regulator 30 to filter out high and low frequency noise in the power line, enhancing the anti-interference capability of the low-dropout linear regulator 30. For example, a 10μF capacitor and a 0.1μF capacitor can be connected in parallel.

[0037] In an optional embodiment, the low-dropout linear regulator 30 further includes a current-limiting pin, which is connected in series with a current-limiting resistor and grounded. The low-dropout linear regulator 30 limits the current that can flow through the laser output unit 20 through the current-limiting resistor, ensuring the safety of the laser output unit 20. Furthermore, the maximum current allowed to flow through the laser output unit 20 by the low-dropout linear regulator 30 can be changed by adjusting the resistance value of the current-limiting resistor. The low-dropout linear regulator 30 also includes a power monitoring pin, used to monitor whether the power supply voltage provided by the low-dropout linear regulator 30 to the laser output unit 20 is within the normal range. If it exceeds the normal range, the power monitoring pin shuts off the power supply voltage output, improving the safety of the laser output unit 20.

[0038] Furthermore, the constant current source circuit 40 includes an input terminal 401 and a ground terminal 402, wherein the input terminal 401 is electrically connected to the output terminal 202 of the laser output unit 20, and the ground terminal 402 is grounded. When the low-dropout linear regulator 30 supplies power to the laser output unit 20, and the laser output unit 20 outputs laser light of a certain wavelength, in order to ensure a stable current in the laser output unit 20, the output terminal 202 of the laser output unit 20 is electrically connected to the input terminal 401 of the constant current source circuit 40. This allows the constant current source circuit 40 to monitor the current flowing through the laser output unit 20 and to respond quickly when the current changes, thereby ensuring the stability of the current in the series circuit. In addition, when the laser output unit 20 needs to change the wavelength of the output laser, the constant current source circuit 40 can also be used to change the current in the series circuit, thereby achieving rapid adjustment of the laser's output wavelength.

[0039] This embodiment of the invention uses a low-noise, low-dropout linear regulator to provide a stable voltage for the laser output unit while reducing the impact of power supply noise on the drive current, thus enhancing the anti-interference capability of the laser drive circuit. By feeding the output current of the laser output unit back to the constant current source circuit, it can respond quickly to changes in current, thereby ensuring the stability of the current in the series circuit and thus guaranteeing the output stability of the laser output unit. Simultaneously, the current of the laser output unit can be quickly adjusted, thereby changing the output laser wavelength.

[0040] Optionally, Figure 2 A schematic diagram of another laser driving circuit provided in an embodiment of this utility model is shown below. Figure 2 As shown, the constant current source circuit 40 includes a first operational amplifier 41, a second operational amplifier 42, a power transistor 43, and a sampling resistor R404. The first operational amplifier 41 includes a first input terminal 411, a second input terminal 412, and a first output terminal 413. The second operational amplifier 42 includes a third input terminal 421, a fourth input terminal 422, and a second output terminal 423. The power transistor 43 includes a first terminal 431, a second terminal 432, and a control terminal 433. The first input terminal 411 is used to receive a first basic current adjustment signal and a second current adjustment signal. The second input terminal 412 is used to receive the first current adjustment signal. The first output terminal 413 is electrically connected to the third input terminal 421, the fourth input terminal 422 is electrically connected to the second terminal 432, and the second output terminal 423 is electrically connected to the control terminal 433. The first terminal 431 is electrically connected to the laser output unit 20, and the second terminal 432 is grounded through the sampling resistor 44.

[0041] Specifically, refer to Figure 2The constant current source circuit 40 includes a first operational amplifier 41, a second operational amplifier 42, a power transistor 43, and a sampling resistor R404. The first operational amplifier 41 includes a first input terminal 411, a second input terminal 412, and a first output terminal 413. The first input terminal 411 is used to receive a first base current adjustment signal and a second current adjustment signal, and the second input terminal 412 is used to receive the first current adjustment signal. The first base current adjustment signal is used to provide a base current for the laser output unit 20, and the first current adjustment signal and the second current adjustment signal are used to adjust the current flowing through the laser output unit 20.

[0042] When the user changes the second current adjustment signal and the first current adjustment signal input to the first input terminal 411 and the second input terminal 412, the current flowing through the laser output unit 20 can be quickly adjusted. Simultaneously, the phase of the current flowing through the laser output unit 20 can be controlled to be in phase or out of phase with the second and first current adjustment signals. Specifically, the relationship between the first output terminal 413 (Vout1) of the first operational amplifier 41 and the first input terminal 411 (Vin1) and the second input terminal 412 (Vin2) can be expressed as Vout1∝(Vin1-Vin2). Therefore, when the user inputs the second current adjustment signal to the first input terminal 411, a current in phase with the second current adjustment signal can be obtained; when the user inputs the first current adjustment signal to the second input terminal 412, a current out of phase with the first current adjustment signal can be obtained. For example, refer to... Figure 2 The first basic current regulation signal can be provided by a fixed voltage of 1V through resistor R414.

[0043] Further, refer to Figure 2 The second operational amplifier 42 includes a third input terminal 421, a fourth input terminal 422, and a second output terminal 423. The first output terminal 413 of the first operational amplifier 41 is electrically connected to the third input terminal 421. In an optional embodiment, since the voltage value output by the first output terminal 413 may be relatively large, the constant current source circuit 40 further includes a voltage divider circuit 45, which is connected in series between the first output terminal 413 and the third input terminal 421. (Continue to refer to...) Figure 2The voltage divider circuit 45 includes a first resistor R401, a second resistor R400, and a third capacitor C402. The first terminal of the first resistor R401 is electrically connected to the first output terminal 413, the first terminal of the second resistor R400 is grounded, and the first plate of the third capacitor C402 is grounded. The second terminals of the first resistor R401, the second terminal of the second resistor R400, and the second plate of the third capacitor C402 are electrically connected to each other and to the third input terminal 421. Specifically, the resistance values ​​of the first resistor R401, the second resistor R400, and the first output terminal 413 (Vout1) determine the input voltage (Vin3) of the third input terminal 421, which can be specifically expressed as follows: Therefore, the voltage input to the third input terminal 421 of the second operational amplifier 42 can be precisely controlled by the voltage divider circuit 45. The third capacitor 453 is located between the third input terminal 421 and ground, and is used to filter out noise interference input to the third input terminal 421.

[0044] Similarly, the relationship between the third input terminal 421 (Vin3), the fourth input terminal 422 (Vin4), and the second output terminal 423 (Vout2) of the second operational amplifier 42 can be expressed as Vout2∝(Vin3-Vin4). Therefore, when the user changes the first current adjustment signal and the second current adjustment signal, the voltage of the second output terminal 423 of the second operational amplifier 42 will also change accordingly.

[0045] Furthermore, the power transistor 43 includes a first terminal 431, a second terminal 432, and a control terminal 433. The control terminal 433 is electrically connected to the second output terminal 423 of the second operational amplifier 42. The second terminal 432 is grounded through a sampling resistor R404. When the first current adjustment signal and the second current adjustment signal are changed, the voltage of the second output terminal 423 increases, which in turn causes the voltage between the control terminal 433 and the second terminal 432 of the power transistor 43 to exceed the turn-on threshold of the power transistor 43, thereby turning on the power transistor 43. Furthermore, when the power transistor 43 is turned on, the conduction current (Id) flowing through the power transistor 43 is determined by the voltage (Vgs) between the control terminal 433 and the second terminal 432, which can be approximately expressed as Id∝Vgs. Therefore, when the conduction current (Id) flowing through the power transistor 43 increases, the conduction current (Id) can be reduced by decreasing the voltage (Vgs) between the control terminal 433 and the second terminal 432. For example, power transistor 43 can be an IGLT65R025D2.

[0046] Further reference Figure 2The first terminal 431 of the power transistor 43 is electrically connected to the laser output unit 20. Specifically, the voltage output terminal 301 of the low-dropout linear regulator 30 is electrically connected to the input terminal 201 of the laser output unit 20, and the output terminal 202 of the laser output unit 20 is electrically connected to the first terminal 431 of the power transistor 43. When the power transistor 43 is turned on, the low-dropout linear regulator 30 provides current to the laser output unit 20, and this current value is the on-state current (Id) of the power transistor 43. Therefore, when the on-state current (Id) changes, the output wavelength of the laser output unit 20 also changes.

[0047] Furthermore, in order to monitor the current value flowing through the laser output unit 20, the constant current source circuit 40 also includes a sampling resistor R404, which is connected between the second terminal 432 of the power transistor 43 and ground. Therefore, when the resistance value of the sampling resistor R404 is constant, if the conduction current (Id) of the power transistor 43 increases, the voltage (Vs) of the second terminal 432 of the power transistor 43 will also increase accordingly.

[0048] Furthermore, the fourth input terminal 422 (Vin4) of the second operational amplifier 42 is electrically connected to the second terminal 432 of the power transistor 43. Therefore, when the voltage (Vs) at the second terminal 432 of the power transistor 43 increases, the voltage at the fourth input terminal 422 (Vin4) also increases. When the first current adjustment signal and the second current adjustment signal are not changed, the voltage at the second output terminal 423 of the second operational amplifier 42 will change in the opposite direction. That is, when the fourth input terminal 422 (Vin4) increases, the voltage at the second output terminal 423 decreases. This ultimately leads to a decrease in the voltage between the control terminal 433 and the second terminal 432 of the power transistor 43, thereby controlling the decrease in the conduction current (Id) of the power transistor 43. In this way, the output current feedback control of the laser output unit 10 is realized, improving the output stability of the laser output unit 10.

[0049] When it is necessary to change the output wavelength of the laser output unit 10, it is only necessary to change the first current adjustment signal and the second current adjustment signal, so that the output voltage of the first output terminal 413 of the first operational amplifier 41 increases or decreases, thereby increasing or decreasing the voltage of the second output terminal 423 of the second operational amplifier 42, which in turn increases or decreases the voltage between the control terminal 433 and the second terminal 432 of the power transistor 43, ultimately increasing or decreasing the current flowing through the laser output unit 10. For example, the first operational amplifier 41 and the second operational amplifier 42 can be AD797ARZ.

[0050] Optionally, the constant current source circuit 40 further includes a first filter circuit 46, a second filter circuit 47, a third filter circuit 48, and a fourth filter circuit 49; the first operational amplifier 41 further includes a first power supply terminal 414 and a second power supply terminal 415, and the second operational amplifier 42 further includes a third power supply terminal 424 and a fourth power supply terminal 425; the first power supply terminal 414 is connected to the first power supply through the first filter circuit 46; the second power supply terminal 415 is connected to the second power supply through the second filter circuit 47; the third power supply terminal 424 is connected to the third power supply through the third filter circuit 48; and the fourth power supply terminal 425 is connected to the fourth power supply through the fourth filter circuit 49; the voltages of the first power supply and the third power supply are the same, the voltages of the second power supply and the fourth power supply are the same, and the voltages of the first power supply and the second power supply are different.

[0051] Specifically, the first power supply and the second power supply power the first operational amplifier 41 and the second operational amplifier 42. To ensure that the first operational amplifier 41 and the second operational amplifier 42 can operate normally, the difference between the first power supply and the second power supply should be within the allowable power supply range of the first operational amplifier 41 and the second operational amplifier 42. Furthermore, in an optional embodiment, refer to... Figure 2 The first filter circuit 46, the second filter circuit 47, the third filter circuit 48, and the fourth filter circuit 49 all include a first capacitor and a second capacitor connected in parallel. The first capacitor can be C408, C407, C403, or C401 as shown in the figure, and the second capacitor can be C409, C406, C404, or C400 as shown in the figure. The first capacitor and the second capacitor have different capacitance values, which can filter out both high-frequency and low-frequency noise on the power line and ensure the stability of the power supply.

[0052] Optionally, continue to refer to Figure 2 The laser drive circuit 10 also includes a current detection circuit 50, which is electrically connected to the second terminal 432. Referring to the above, when the current of the laser output unit 20 changes, since the resistance of the sampling resistor R404 is fixed, the voltage at the second terminal 432 of the power transistor 43 will change accordingly, and thus the current detection circuit 50 can identify the current change of the laser output unit 20.

[0053] In an optional embodiment, the current detection circuit 50 includes a third operational amplifier 51; the third operational amplifier 51 includes a fifth input terminal 511, a sixth input terminal 512 and a third output terminal 513; the fifth input terminal 511 is electrically connected to the second terminal 432, and the sixth input terminal 512 is electrically connected to the third output terminal 513.

[0054] Specifically, when the current of the laser output unit 20 changes, causing a change in the voltage at the second terminal 432 of the power transistor 43, the voltage at the fifth input terminal 511 of the third operational amplifier 51 also changes. Electrically connecting the sixth input terminal 512 of the third operational amplifier 51 to the third output terminal 513 achieves a voltage following function, meaning the voltage at the third output terminal 513 is equal to the voltage at the fifth input terminal 511. Therefore, the third output terminal 513 can be connected to a monitoring device such as a controller to determine whether the current in the laser output unit 10 is normal. For example, the third operational amplifier 51 can be an OPA320AIDBVR.

[0055] In an optional embodiment, the constant current source circuit 40 further includes a loop compensation circuit 60 to improve the stability of the current feedback loop. The loop compensation circuit 60 includes a third resistor R402, a fourth resistor R403, and a fourth capacitor C405. The first terminal of the third resistor R402 is connected to the second output terminal 423, and the second terminal of the third resistor R402 is connected to the control terminal 433. The first plate of the fourth capacitor C405 is connected to the first terminal of the third resistor R402, and the second plate of the fourth capacitor C405 is connected to the first terminal of the fourth resistor R403. The second terminal of the fourth resistor R403 is connected to the second terminal 432 of the power transistor 43.

[0056] This embodiment of the invention, through the use of a first operational amplifier, a second operational amplifier, a power transistor, and a sampling resistor, automatically adjusts the current value of the laser output unit in the opposite direction when the current changes, ensuring a constant output current for the laser output unit. Simultaneously, a current detection circuit is added, enabling timely monitoring of current changes in the laser output unit, thus improving the safety of the laser drive circuit. The use of a low-dropout linear regulator, a constant current source circuit, and a layout of multiple modules for the laser output unit facilitates future expansion to multi-channel laser systems.

[0057] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A laser driving circuit, characterized in that, The laser driving circuit is used to provide drive current to the laser output unit; the laser driving circuit includes a low dropout linear regulator and a constant current source circuit. The low-dropout linear regulator, the laser output unit, and the constant current source circuit are connected in series to form a series circuit. The low-dropout linear regulator is used to provide a stable voltage to the laser output unit; The constant current source circuit is used to stabilize the current in the series circuit.

2. The laser driving circuit according to claim 1, characterized in that, The constant current source circuit includes a first operational amplifier, a second operational amplifier, a power transistor, and a sampling resistor; The first operational amplifier includes a first input terminal, a second input terminal, and a first output terminal; The second operational amplifier includes a third input terminal, a fourth input terminal, and a second output terminal; The power transistor includes a first terminal, a second terminal, and a control terminal; The first input terminal is used to receive a first base current adjustment signal and a second current adjustment signal; The second input terminal is used to receive the first current adjustment signal; The first output terminal is electrically connected to the third input terminal, the fourth input terminal is electrically connected to the second terminal, and the second output terminal is electrically connected to the control terminal; The first end is electrically connected to the laser output unit, and the second end is grounded through the sampling resistor.

3. The laser driving circuit according to claim 2, characterized in that, The constant current source circuit further includes a first filter circuit, a second filter circuit, a third filter circuit, and a fourth filter circuit; The first operational amplifier further includes a first power supply terminal and a second power supply terminal, and the second operational amplifier further includes a third power supply terminal and a fourth power supply terminal; The first power supply terminal is connected to the first power supply through the first filter circuit; the second power supply terminal is connected to the second power supply through the second filter circuit; the third power supply terminal is connected to the third power supply through the third filter circuit; and the fourth power supply terminal is connected to the fourth power supply through the fourth filter circuit. The first power supply has the same voltage as the third power supply, the second power supply has the same voltage as the fourth power supply, and the first power supply has a different voltage from the second power supply.

4. The laser driving circuit according to claim 3, characterized in that, The first filter circuit, the second filter circuit, the third filter circuit, and the fourth filter circuit all include a first capacitor and a second capacitor connected in parallel, and the capacitance values ​​of the first capacitor and the second capacitor are different.

5. The laser driving circuit according to claim 2, characterized in that, The constant current source circuit also includes a voltage divider circuit, which is connected in series between the first output terminal and the third input terminal.

6. The laser driving circuit according to claim 5, characterized in that, The voltage divider circuit includes a first resistor, a second resistor, and a third capacitor; The first end of the first resistor is electrically connected to the first output terminal, the first end of the second resistor is grounded, and the first plate of the third capacitor is grounded; the second end of the first resistor, the second end of the second resistor, and the second plate of the third capacitor are electrically connected to each other and electrically connected to the third input terminal.

7. The laser driving circuit according to claim 2, characterized in that, The laser driving circuit further includes a current detection circuit, which is electrically connected to the second terminal.

8. The laser driving circuit according to claim 7, characterized in that, The current detection circuit includes a third operational amplifier; The third operational amplifier includes a fifth input terminal, a sixth input terminal, and a third output terminal; The fifth input terminal is electrically connected to the second terminal, and the sixth input terminal is electrically connected to the third output terminal.

9. The laser driving circuit according to claim 2, characterized in that, The low-dropout linear regulator is an LT3045IMSE low-dropout linear regulator, and both the first and second operational amplifiers are AD797ARZ operational amplifiers.

10. The laser driving circuit according to claim 9, characterized in that, The low-dropout linear regulator also includes a current-limiting pin, which is connected in series with a current-limiting resistor and grounded.

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