Direct current driving protection circuit of mid-infrared laser and design method thereof

Abstract

This invention relates to a DC drive protection circuit and its design method for a mid-infrared laser, belonging to the field of power supply drive protection technology. The core of this invention lies in achieving dual hardware protection for both laser voltage and current through three main modules. Key technical points include: a voltage protection module composed of comparator U1, operational amplifier U3, etc., integrating a voltage differential, hysteresis comparator, and adjustable potentiometer to monitor the voltage difference across the laser in real time and automatically cut off the power supply in case of overvoltage; a current protection module composed of comparator U5, etc., which limits the amplitude of the microcontroller's D / A signal through a hysteresis comparator and potentiometer to precisely control the current range; and a voltage-controlled constant current source module composed of operational amplifier U6, etc., generating a constant current to drive the laser. The voltage protection allows for flexible switching of the power supply based on the actual voltage difference, avoiding frequent false triggering; the current protection threshold is adjustable via a potentiometer to adapt to different laser specifications; and the constant current source ensures stable output. This improves the reliability and lifespan of the mid-infrared laser.

Description

Technical Field

[0001] This invention relates to the field of power supply drive protection technology, specifically to a DC drive protection circuit for a mid-infrared laser and its design method. Background Technology

[0002] The core advantages of mid-infrared lasers (2-20μm band) lie in their unique molecular spectral response, atmospheric transmission window, and absorption and penetration balance of water and organic matter. These characteristics make them irreplaceable in scenarios where near-infrared and visible lasers cannot cover. However, due to limitations in material properties, energy conversion mechanisms, and optical system design, their reliability is far lower than that of near-infrared or visible lasers. Furthermore, mid-infrared lasers place high demands on the current stability, voltage control accuracy, and fault response speed of the driving system; therefore, designing high-performance driving circuits and implementing multiple protection mechanisms is crucial.

[0003] Currently, most applications use traditional voltage-controlled constant current sources (VDCs) for control, adjusting the input voltage to control the laser current. Conventional LDs or LEDs do not have very strict requirements for current and voltage limits and signal fluctuations. Exceeding the nominal value within a certain range will not directly damage the device. Current and voltage protection and soft start are usually not considered in the design process. However, for mid-infrared lasers, they are extremely sensitive to fluctuations in pump current and voltage. Traditional VDC control methods often handle this in the program through software. This method has poor timeliness, relies entirely on program control, and cannot avoid the problem of abnormal input signals caused by program abnormalities. This may result in rapid current fluctuations or exceed the device's nominal current range. Furthermore, this method cannot cut off the power supply in time to protect the laser in case of power supply abnormalities.

[0004] To improve the reliability of mid-infrared laser drivers, it is essential to add current protection and voltage protection functions to circuits based on traditional voltage-controlled constant current sources. Summary of the Invention

[0005] To address the problems of the prior art, this invention provides a DC drive protection circuit for a mid-infrared laser and its design method.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: First aspect, a DC drive protection circuit for a mid-infrared laser, comprising a voltage protection module, a current protection module and a voltage-controlled constant current source module; The voltage protection module is connected to the laser and the power supply section to form a cut-off power supply circuit. The inverting input terminal of the current protection module is connected to the microcontroller, and the output terminal is connected to the voltage-controlled constant current source module. It is used to receive the D / A signal output by the microcontroller and limit the signal amplitude to drive the laser. The non-inverting input terminal of the voltage-controlled constant current source module is connected to the current protection module, and the constant current circuit part is connected to the laser to generate a constant output current to drive the laser. The voltage protection module includes a voltage comparison unit and a power switch circuit unit. The voltage comparison unit takes the voltage difference across the laser and the threshold adjustment voltage as input signals, compares the two input signals through a comparator to output a high or low level, and then controls the power switch circuit to turn on or off. The control signal of the power switch circuit unit comes from the comparator output and is used to control the MOSFET to realize the automatic switching of the power supply VCC. The current protection module is an open-collector type hysteresis output comparator circuit, including an input unit and an output unit: the input unit receives the D / A signal and threshold adjustment voltage signal output by the microcontroller, and the output unit compares the two input signals through a comparator to control the output voltage range; The voltage-controlled constant current source module is a current feedback closed-loop control circuit, including a current sampling resistor, an operational amplifier, and an N-channel enhancement-mode MOSFET with high gate charge. The voltage of the current sampling resistor is connected to the operational amplifier through the feedback circuit. The output of the operational amplifier controls the conduction state of the MOSFET to keep the laser circuit current constant.

[0007] In one specific implementation of the first aspect, in the voltage protection module, when the laser voltage difference is lower than a set threshold, the power supply VCC is turned on to supply power to the laser LD1; when the voltage difference exceeds the set threshold, the circuit cuts off the power supply to the laser LD1, and automatically restores the power supply after the voltage difference drops to a certain level.

[0008] In one specific implementation of the first aspect, in the current protection module, when the amplitude of the D / A signal output by the microcontroller is lower than a set threshold, the current protection module outputs a voltage signal with the same amplitude as the D / A signal; when the amplitude of the D / A signal is higher than the set threshold, the current protection module outputs a signal with an amplitude of 0.

[0009] In one specific implementation of the first aspect, in the voltage-controlled constant current source module, the two input terminals of the operational amplifier are respectively connected to the D / A signal and the voltage signal of the current sampling resistor, and the output of the operational amplifier controls the conduction state of the N-channel enhancement-mode MOSFET to achieve constant current control.

[0010] In one specific embodiment of the first aspect, the voltage protection module includes a comparator U1, an operational amplifier U3, MOSFETs Q1 and Q2, a buffer U2 and a buffer U4, resistors R1 and R2, adjustable resistors R3, R4, R5, R6, and R7, a laser LD1, a Zener diode D1, a reference voltage Vref, and a power supply VCC. The reference voltage Vref is connected to one end of the adjustable resistor R3, and the other end of R3 is grounded. The adjustment terminal of R3 and one end of resistor R1 are connected to the non-inverting input of comparator U1, the other end of resistor R1 is connected to the output of U1, and the inverting input of U1 is connected to the output of operational amplifier U3. The power supply VCC is connected to... The source of MOSFET Q1 is connected to the gate of Q1 and VCC via resistor R2, and the drain of Q1 is connected to the positive terminal of laser LD1. Resistor R4 is connected to VCC and the gate of MOSFET Q2, with the source of Q2 grounded and the drain of Q2 connected to the gate of Q1. The inverting input of operational amplifier U3 is connected to one end of resistors R6 and R7, with the other end of R6 connected to the output of U3. The non-inverting input of U3 is connected to one end of resistor R5, with the other end of R5 grounded. The input of buffer U2 is connected to the positive terminal of LD1, and its output is connected to the non-inverting input of U3. The input of buffer U4 is connected to the negative terminal of LD1, and its output is connected to the other end of resistor R7. The anode of Zener diode D1 is connected to the negative terminal of LD1, and its cathode is connected to the positive terminal of LD1.

[0011] In one specific embodiment of the first aspect, the specific circuit of the current protection module includes a comparator U5, whose non-inverting input terminal is connected to the center tap terminal of an adjustable potentiometer R10, one end of R10 is connected to the reference power supply Vref, and the other end is grounded; one end of resistor R8 is connected to the inverting input terminal of U5, and the other end is connected to the output terminal of U5; one end of resistor R11 is connected to the non-inverting input terminal of U5, and the other end is connected to the output terminal of U5.

[0012] In one specific implementation of the first aspect, in the specific circuit of the voltage-controlled constant current source module, the D / A signal output by the microcontroller is connected to the non-inverting input terminal of the operational amplifier U6 after passing through the current protection module; one end of the current sampling resistor R12 is connected to the inverting input terminal of U6, and the other end is grounded; a capacitor C1 is connected between the inverting input terminal and the output terminal of U6; the output terminal of U6 is connected to the gate of the N-channel enhancement-mode MOSFET Q3, the drain of Q3 is connected to the negative terminal of the laser LD1, the positive terminal of LD1 is connected to the power supply VCC after passing through the MOSFET Q1, and the source of Q3 is grounded after passing through the resistor R12.

[0013] In one specific implementation of the first aspect, the comparator in the current protection module is an open-collector output comparator, which can form a voltage follower with the input terminal when the output collector is open, thus preventing input signal distortion.

[0014] In one specific embodiment of the first aspect, the threshold calculation formula for the voltage protection module is: Wherein For reference voltage, This is the resistance value of the sliding rheostat. This represents the total resistance of the sliding rheostat. The threshold calculation formula for the current protection module is as follows: ,in For reference voltage, This is the resistance value of the sliding rheostat. This represents the total resistance of the sliding rheostat. The value of the sampling resistor; The relationship between the output current of the voltage-controlled constant current source module and the output of the microcontroller's D / A converter is as follows: ,in For laser current, The input signal voltage value. This is the resistance value of the sampling resistor.

[0015] Secondly, a design method for a DC drive protection circuit for a mid-infrared laser includes the following steps: S1. Select a high-precision, low-temperature-drift power sampling resistor with an accuracy of ≤1% and a temperature drift of ≤20ppm / ℃ to improve current control accuracy and reduce the impact of temperature drift. S2. Select a high-gain bandwidth operational amplifier with a gain and bandwidth ≥1MHz to reduce output ripple; S3. Select a high-precision, low-temperature drift voltage reference source chip with an accuracy of ≤0.1% and a temperature drift of ≤10ppm / ℃ to reduce the impact of input threshold offset. S4. Select an N-channel enhancement-type MOSFET with a gate threshold voltage of not more than 1.2V and a gate charge of not less than 1nC; S5. Set the current limiting protection threshold and adjust it according to the actual current range of the laser to ensure that the threshold does not exceed the maximum value of the laser current. S6. Set the power supply protection threshold and adjust it according to the actual voltage range of the laser to ensure that the threshold does not exceed the maximum value of the laser voltage. S7. After the threshold is set, connect the laser into the circuit loop to complete the configuration.

[0016] The beneficial effects of this invention are as follows: 1. This invention, through a pure hardware design of voltage and current protection modules, eliminates software dependence and directly achieves real-time monitoring and protection based on electronic components (such as comparators and MOSFETs). The voltage protection module monitors the voltage difference across the laser and automatically cuts off the power supply when it exceeds a set threshold; the current protection module limits the amplitude of the microcontroller's D / A signal to prevent current overload. This hardware circuit has a response speed in the microsecond range, far faster than software processing, avoiding malfunctions or delays caused by program abnormalities (such as microcontroller failures). "Reliable protection" is achieved through closed-loop feedback, ensuring timely power cut-off of the laser in case of overvoltage or overcurrent, significantly reducing the risk of damage. 2. This invention integrates adjustable potentiometers (such as adjustable resistor R3 in the voltage protection module and adjustable potentiometer R10 in the current protection module) into the voltage and current protection modules. Users can flexibly set the protection threshold by adjusting the center tap of the potentiometer. The voltage threshold calculation formula and the current threshold calculation formula are provided, where the reference voltage Vref and the resistance value are adjustable. This design allows the circuit to quickly adapt to mid-infrared lasers with different electrical specifications (such as voltage range 3-5V and current range 100-500mA) without modifying the circuit or software. 3. The comparator U1 in the voltage protection module adopts a hysteresis comparator design. Hysteresis characteristics are introduced through a positive feedback resistor (such as R1), ensuring the comparator output remains stable when fluctuating near the threshold. This avoids frequent power supply switching caused by power noise or small voltage changes. This design prevents frequent switching or false triggering of power supply protection, overcoming the shortcomings of traditional drivers that lack slow-start and surge buffering circuits. As a result, the laser power supply process is smoother, reducing the impact of switching stress on devices, improving overall system stability, and extending the laser's lifespan. 4. This invention employs carefully selected high-precision components, including high-precision, low-temperature-drift sampling resistors (accuracy ≤1%, temperature drift ≤20ppm / ℃), high-gain bandwidth operational amplifiers (bandwidth ≥1MHz), and high-precision voltage reference sources (accuracy ≤0.1%, temperature drift ≤10ppm / ℃). The voltage-controlled constant current source module utilizes these components to achieve precise current feedback control, with the output current and input voltage having the following relationship: This ensures a constant laser current, effectively reducing output ripple and temperature drift, avoiding the problem of "rapid current fluctuation" in traditional drives, and making the laser work more reliably. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of a traditional laser driving and protection method; Figure 2 This is a schematic block diagram of a DC drive protection circuit for a mid-infrared laser provided according to an embodiment of the present invention; Figure 3This is a schematic diagram of a DC drive protection circuit for a mid-infrared laser provided according to an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figures 1 to 3 shown.

[0020] To address the inadequate protection issues caused by traditional voltage-controlled constant current source driving methods, this invention presents a DC drive protection circuit for mid-infrared lasers and its design method. The primary objective of this invention is to provide a DC drive protection circuit for a mid-infrared laser, comprising a voltage protection module, a current protection module, and a voltage-controlled constant current source module. The voltage protection module is connected to the laser and power supply to form a cut-off power supply circuit; The inverting input of the current protection module is connected to the microcontroller, and the output is connected to the voltage-controlled current source circuit. It is used to receive the D / A signal output by the microcontroller and limit the signal amplitude to drive the laser. The non-inverting input of the voltage-controlled constant current source module is connected to the current protection module, and the constant current circuit is connected to the laser to generate a constant output current to drive the laser. The voltage protection module includes a voltage comparison unit and a power switch circuit unit. The voltage comparison unit takes the voltage difference across the laser and the threshold adjustment voltage as input signals. The comparator compares the two input signals to output a high or low level, thereby controlling the power switch circuit to turn on or off. The control signal of the power switch circuit unit is the signal output by the comparator, which in turn controls the MOSFET to achieve automatic power on and off. The current protection module is an open-collector hysteresis output comparator circuit, including an input unit and an output unit. The input unit consists of a D / A signal output from the microcontroller and a threshold adjustment voltage signal. The output unit compares the two input signals through a comparator to control the range of the output voltage. The voltage-controlled constant current source module is a current feedback closed-loop control circuit, including a current sampling resistor, an operational amplifier, and an N-channel enhancement-mode MOSFET. The voltage of the current sampling resistor is connected to the operational amplifier through the feedback circuit. The output of the operational amplifier controls the conduction state of the MOSFET, thereby controlling the laser circuit current to remain constant. The voltage protection threshold Vth = Vref × R_sliding / R_total; where Vref is the reference voltage, R_sliding is the resistance value of the sliding rheostat, and R_total is the total resistance value of the sliding rheostat. The current protection threshold Ith = Vref × (Rslid / Rtotal) / R; where Vref is the reference voltage, Rslid is the resistance value of the sliding rheostat, Rtotal is the total resistance value of the sliding rheostat, and R is the resistance value of the sampling resistor. The relationship between the constant current source output and the microcontroller D / A output is: I=Vda / R, where I is the laser current, Vda is the input signal voltage value, and R is the sampling resistor value. The second objective of this invention is to provide a design method for a DC drive protection circuit for a mid-infrared laser, specifically comprising the following steps: S1. Select a high-precision, low-temperature-drift power-type sampling resistor to improve current control accuracy and reduce the impact of temperature drift; S2. Select a high-gain, high-bandwidth operational amplifier to reduce output ripple; S3. Select a high-precision, low-temperature-drift voltage reference source chip to reduce the impact of input threshold offset; S4. Select an N-channel enhancement-type MOSFET with a relatively large gate threshold voltage and gate charge. S5. The current limiting protection threshold should be set according to the actual current range of the laser, and the threshold should not exceed the maximum value of the laser current. S6. The power supply protection threshold should be set according to the actual voltage range of the laser, and the threshold should not exceed the maximum value of the laser voltage. S7. After the threshold is set, connect the laser to the circuit loop. The basic technical concept and implementation method of this invention are as follows: Based on traditional voltage-controlled constant current source modules for laser drivers, and addressing the sensitivity of mid-infrared lasers to voltage and current, a dual protection system for laser voltage and current was designed to prevent damage from overload. Its advantage lies in the fact that all protection methods are implemented in hardware circuitry, requiring no software intervention, thus improving the stability and reliability of the protection. Furthermore, by using carefully selected high-precision, low-temperature-drift sampling resistors and voltage reference sources, the current control accuracy is significantly improved. The use of a high-gain, bandwidth operational amplifier combined with a MOSFET soft-start circuit ensures smoother current and voltage changes acting on the laser, effectively preventing damage to the laser device due to current surges.

[0021] like Figure 1As shown, traditional laser driving circuits mostly use a single voltage-controlled constant current source. This type of design is relatively simple, lacking inrush current suppression and circuits for slow start and surge buffering. The instantaneous inrush current generated when the system powers on or experiences a sudden load change can easily exceed the laser's safety threshold, leading to performance degradation or even direct damage to the device. Traditional design methods do not fully consider the high precision, high stability, and high reliability requirements of laser driving circuits, resulting in many technical defects. They cannot achieve high-precision closed-loop control of the laser drive, and they do not place much emphasis on component selection. They are inadequate in terms of control accuracy, current ripple, and impact mitigation. Moreover, relying solely on software limitations based on the microcontroller's D / A output for laser protection is not entirely reliable.

[0022] like Figure 2 As shown, addressing the problems of traditional laser driver circuits, this paper presents an optimized design focusing on laser driving accuracy, current input protection, and voltage input protection. A circuit system capable of providing comprehensive protection for the laser is conceived and designed, including protection against voltage across the laser terminals, protection against current flowing through the laser, and a more precise and stable current driving method. This system, through the integration of dual voltage and current protection with high-precision drive control, comprehensively covers the safety and performance requirements of the laser in scenarios such as startup, steady-state operation, operating condition switching, and external interference, achieving comprehensive protection for the laser while improving the stability of laser output power and extending device lifespan.

[0023] like Figure 3 As shown, the laser DC drive protection circuit designed in this paper uses a high-performance operational amplifier U6, MOSFET Q3, and sampling resistor R12 to form a voltage-controlled constant current source module, and adds gate current limiting resistor R9 to play a soft start role.

[0024] like Figure 3As shown, unlike traditional laser voltage protection methods that only use a parallel Zener diode, this design introduces a more reliable voltage protection measure. Addressing the issues of low voltage control accuracy and delayed response inherent in diodes, the improved voltage protection module employs a design combining a high-speed comparator U1 with a switching circuit composed of MOSFETs Q1 and Q2. This enables rapid overvoltage shutdown of the laser. Simultaneously, the high-speed comparator U1 uses a hysteresis comparison method to avoid frequent circuit switching near voltage thresholds or due to power supply noise. Mid-infrared lasers, due to their complex manufacturing process, are difficult to manufacture with consistent electrical parameters. Therefore, the voltage protection threshold can be adjusted by adjusting potentiometer R3. The potentiometer can be adjusted according to the specific conditions of different lasers. When the voltage difference across laser LD1 is lower than the voltage protection threshold, the power supply VCC is normally open; when the voltage difference across laser LD1 is higher than the voltage protection threshold, the comparator U1 output switches, thereby shutting off the laser's power supply VCC.

[0025] like Figure 3 As shown, to address the various problems of traditional laser driver circuits that rely on software-set current limits to control the laser drive current, this design introduces a laser drive current protection module based on a hysteresis comparator. The protection threshold for the laser drive current can be adjusted by adjusting potentiometer R10. When the D / A value output by the microcontroller is less than the set laser current threshold, comparator U5 is open-collector output, and the input of the voltage-controlled constant current source module follows the microcontroller's D / A output. When the microcontroller's D / A input is greater than the set laser current threshold, the output of comparator U5 is 0, thus causing the output of the voltage-controlled constant current source module to return to zero.

[0026] In summary, this example, through the combined use of a high-performance operational amplifier and comparator, along with an adjustable threshold potentiometer, improves the reliability and protection capabilities of the laser DC drive circuit. It constructs an adjustable threshold laser drive circuit with dual protection against voltage and current, effectively protecting the laser from overload damage. Furthermore, this example can also be applied to other DC drive circuits that are highly sensitive to current and voltage.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A DC drive protection circuit for a mid-infrared laser, characterized in that: Includes voltage protection module, current protection module and voltage-controlled constant current source module; The voltage protection module is connected to the laser and the power supply section to form a cut-off power supply circuit. The inverting input terminal of the current protection module is connected to the microcontroller, and the output terminal is connected to the voltage-controlled constant current source module. It is used to receive the D / A signal output by the microcontroller and limit the signal amplitude to drive the laser. The non-inverting input terminal of the voltage-controlled constant current source module is connected to the current protection module, and the constant current circuit part is connected to the laser to generate a constant output current to drive the laser. The voltage protection module includes a voltage comparison unit and a power switch circuit unit. The voltage comparison unit takes the voltage difference across the laser and the threshold adjustment voltage as input signals, compares the two input signals through a comparator to output a high or low level, and then controls the power switch circuit to turn on or off. The control signal of the power switch circuit unit comes from the comparator output and is used to control the MOSFET to realize the automatic switching of the power supply VCC. The current protection module is an open-collector type hysteresis output comparator circuit, including an input unit and an output unit: the input unit receives the D / A signal and threshold adjustment voltage signal output by the microcontroller, and the output unit compares the two input signals through a comparator to control the output voltage range; The voltage-controlled constant current source module is a current feedback closed-loop control circuit, including a current sampling resistor, an operational amplifier, and an N-channel enhancement-mode MOSFET with high gate charge. The voltage of the current sampling resistor is connected to the operational amplifier through the feedback circuit. The output of the operational amplifier controls the conduction state of the MOSFET to keep the laser circuit current constant.

2. The DC drive protection circuit for a mid-infrared laser according to claim 1, characterized in that: In the voltage protection module, when the voltage difference of the laser is lower than the set threshold, the power supply VCC is turned on to supply power to the laser LD1; when the voltage difference exceeds the set threshold, the circuit cuts off the power supply to the laser LD1, and automatically restores the power supply after the voltage difference drops to a certain level.

3. The DC drive protection circuit for a mid-infrared laser according to claim 1, characterized in that: In the current protection module, when the amplitude of the D / A signal output by the microcontroller is lower than the set threshold, the current protection module outputs a voltage signal with the same amplitude as the D / A signal; when the amplitude of the D / A signal is higher than the set threshold, the current protection module outputs a signal with an amplitude of 0.

4. The DC drive protection circuit for a mid-infrared laser according to claim 1, characterized in that: In the voltage-controlled constant current source module, the two input terminals of the operational amplifier are connected to the D / A signal and the voltage signal of the current sampling resistor, respectively. The output of the operational amplifier controls the conduction state of the N-channel enhancement-mode MOSFET to achieve constant current control.

5. The DC drive protection circuit for a mid-infrared laser according to claim 2, characterized in that: The specific circuit of the voltage protection module includes a comparator U1, an operational amplifier U3, MOSFETs Q1 and Q2, buffers U2 and U4, resistors R1 and R2, adjustable resistors R3, R4, R5, R6, and R7, a laser LD1, a Zener diode D1, a reference voltage Vref, and a power supply VCC. The reference voltage Vref is connected to one end of the adjustable resistor R3, and the other end of R3 is grounded. The adjustment terminal of R3 and one end of resistor R1 are connected to the non-inverting input of comparator U1, the other end of resistor R1 is connected to the output of U1, and the inverting input of U1 is connected to the output of operational amplifier U3. The power supply VCC is connected to the source of MOSFET Q1. Resistor R2 is connected to the gate of Q1 and VCC respectively, and the drain of Q1 is connected to the positive terminal of laser LD1; resistor R4 is connected to VCC and the gate of MOSFET Q2 respectively, the source of Q2 is grounded, and the drain of Q2 is connected to the gate of Q1; the inverting input of operational amplifier U3 is connected to one end of resistors R6 and R7, the other end of R6 is connected to the output of U3, and the non-inverting input of U3 is connected to one end of resistor R5, the other end of R5 is grounded; the input of buffer U2 is connected to the positive terminal of LD1, and the output is connected to the non-inverting input of U3; the input of buffer U4 is connected to the negative terminal of LD1, and the output is connected to the other end of resistor R7; the anode of Zener diode D1 is connected to the negative terminal of LD1, and the cathode is connected to the positive terminal of LD1.

6. The DC drive protection circuit for a mid-infrared laser according to claim 3, characterized in that: The specific circuit of the current protection module includes a comparator U5, whose non-inverting input is connected to the middle tap of an adjustable potentiometer R10. One end of R10 is connected to the reference power supply Vref, and the other end is grounded. One end of resistor R8 is connected to the inverting input of U5, and the other end is connected to the output of U5. One end of resistor R11 is connected to the non-inverting input of U5, and the other end is connected to the output of U5.

7. The DC drive protection circuit for a mid-infrared laser according to claim 4, characterized in that: In the specific circuit of the voltage-controlled constant current source module, the D / A signal output by the microcontroller is connected to the non-inverting input of the operational amplifier U6 after passing through the current protection module; one end of the current sampling resistor R12 is connected to the inverting input of U6, and the other end is grounded; a capacitor C1 is connected between the inverting input and output of U6; the output of U6 is connected to the gate of the N-channel enhancement-mode MOSFET Q3; the drain of Q3 is connected to the negative terminal of the laser LD1; the positive terminal of LD1 is connected to the power supply VCC after passing through the MOSFET Q1; and the source of Q3 is grounded after passing through the resistor R12.

8. The DC drive protection circuit for a mid-infrared laser according to claim 3, characterized in that: The comparator in the current protection module is an open-collector output comparator. When its output collector is open, it can form a voltage follower with the input terminal to prevent input signal distortion.

9. The DC drive protection circuit for a mid-infrared laser according to claim 2, characterized in that: The threshold calculation formula for the voltage protection module is as follows: Wherein For reference voltage, This is the resistance value of the sliding rheostat. This represents the total resistance of the sliding rheostat. The threshold calculation formula for the current protection module is as follows: ,in For reference voltage, This is the resistance value of the sliding rheostat. This represents the total resistance of the sliding rheostat. The value of the sampling resistor; The relationship between the output current of the voltage-controlled constant current source module and the output of the microcontroller's D / A converter is as follows: ,in For laser current, The input signal voltage value. This is the resistance value of the sampling resistor.

10. A design method for a DC drive protection circuit for a mid-infrared laser, characterized in that... This includes the following steps: S1. Select a high-precision, low-temperature-drift power sampling resistor with an accuracy of ≤1% and a temperature drift of ≤20ppm / ℃ to improve current control accuracy and reduce the impact of temperature drift. S2. Select a high-gain bandwidth operational amplifier with a gain and bandwidth ≥1MHz to reduce output ripple; S3. Select a high-precision, low-temperature drift voltage reference source chip with an accuracy of ≤0.1% and a temperature drift of ≤10ppm / ℃ to reduce the impact of input threshold offset. S4. Select an N-channel enhancement-type MOSFET with a gate threshold voltage of not more than 1.2V and a gate charge of not less than 1nC; S5. Set the current limiting protection threshold and adjust it according to the actual current range of the laser to ensure that the threshold does not exceed the maximum value of the laser current. S6. Set the power supply protection threshold and adjust it according to the actual voltage range of the laser to ensure that the threshold does not exceed the maximum value of the laser voltage. S7. After the threshold is set, connect the laser into the circuit loop to complete the configuration.

Images