Current-limiting protection circuit of continuous laser

Abstract

The utility model discloses a current-limiting protection circuit of a continuous laser, which relates to the technical field of circuit design, and is characterized in that an MCU (Microprogrammed Control Unit) controls a digital-to-analog converter to generate a required current-limiting voltage value through an SPI (Serial Peripheral Interface) bus, the maximum value of the voltage value is external reference source voltage, the current-limiting voltage value and a driven sawtooth signal value generate square waves through a comparator, and the square waves are output through a comparator. And the square wave signal is used as a control signal of the analog switch. A direct current level generated by the DAC is coupled to a comparator through an isolation buffer and a laser driving signal; the analog switch is used for switching to output a driving signal or a current-limiting protection signal through the output state of the comparator; an additional direct-current signal generator is not needed, the structure is simple, and the cost is low; and meanwhile, the limiting voltage point of the current limiting circuit is always loaded to the positive end of the comparator, the current limiting circuit is real-time and reliable, and the circuit protects the laser in real time under the condition of not changing the quality of a driving signal, so that the current limiting protection function is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit design, in particular to a current limiting protection circuit for a continuous laser. Background Art

[0002] In the laser control circuit, because the laser is expensive and has a high cost, its current limiting protection function must be done well in the process of driving the laser to emit light. At present, many current limiting protection circuits are designed with two PNP transistors. The emitter (E1) of a PNP transistor (Q1) is connected to the input voltage, and its collector (C1) is connected to the base (B2) of another PNP transistor (Q2) through a resistor, and the base (B1) of Q1 is directly connected to the emitter (E2) of Q2, and they are connected in series through several resistors. Among them, the resistor R1 is more critical. It plays a major role in current limiting when the circuit is working, and its current limiting formula is I=Vbe / R1. Among them: I: the maximum current value limited; Vbe: the voltage difference between the base and emitter of Q1; R1: represents the set resistance. Specifically, the maximum current flowing through the circuit is set by setting the resistance value of R1 (the circuit is as shown in the figure). Figure 1 shown).

[0003] The main working principle of this current limiting circuit is: in the default state, the base of Q2 is grounded at a low level, Q2 is turned on, and the mainstream path passes through R1 and Q2; when the current is too large, Q1 is turned on, and Q1's Vbe is the voltage drop on R1, which pulls up Q2's B pole, and Q2 is turned off. However, Q2 turning off will cause the mainstream path current to decrease. When the current is small, the voltage drop on R1 is small, and Q1's Vbe decreases accordingly. Q1 returns to the critical conduction state, and Q2 becomes the critical cut-off state again. After a period of dynamic balance, the output current is locked at a relatively fixed value.

[0004] This common implementation has the following disadvantages:

[0005] 1. This circuit uses resistors to set the current value, which has large errors and low precision, and it is difficult to control the design margin;

[0006] 2. The current limiting feedback speed of the circuit is low, and it completely relies on the dynamic adjustment of the two transistors, and the adjustment time cannot be guaranteed;

[0007] 3. It is not flexible enough, and the limited current cannot be changed in real time, and cannot cope with the recommended limit values ​​of different types of lasers. For this reason, we propose a current limiting protection circuit for continuous lasers. Utility Model Content

[0008] 1. Technical issues to be solved

[0009] In view of the deficiencies of the prior art, the utility model provides a current limiting protection circuit for a continuous laser, which solves the technical problems raised in the background technology.

[0010] (II) Technical solution

[0011] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0012] A current limiting protection circuit for a continuous laser, comprising:

[0013] The laser current limiting protection circuit is composed of analog-to-digital conversion chip, integrated operational amplifier, high-speed comparator and fast analog switch.

[0014] It includes an MCU circuit, a DAC circuit, a voltage-dividable buffer circuit, a current-limiting protection circuit, a comparator circuit, and an analog switch switching circuit;

[0015] MCU circuit, used to enable hardware SPI communication signals and control analog-to-digital conversion chips;

[0016] A reference source circuit is used to provide a reference voltage to the analog-to-digital conversion chip;

[0017] A DAC circuit, used for generating a voltage signal for limiting the laser current;

[0018] A current limiting buffer circuit is used to generate a voltage signal for limiting the laser current and to play an isolation buffer role;

[0019] A signal comparison circuit is used to compare the driving signal with the current limiting signal and output a signal to control the analog switch;

[0020] The signal simulation switch circuit is used to quickly switch the current limiting signal and the laser driving signal.

[0021] Furthermore, the above technical solution is improved to also include a driving signal circuit for generating the laser, and the laser driving signal or the current limiting protection signal enters the subsequent driving circuit of the laser.

[0022] Preferably, the MCU controls the digital-to-analog converter through the SPI bus to generate the required current-limiting voltage value, and the maximum value of the voltage value is the external reference source voltage. Since the output driving capability of the digital-to-analog converter is limited, a current-limiting buffer circuit is required in the later stage to improve the load capacity, so that the buffered current-limiting voltage signal and the laser sawtooth driving signal enter the comparator at the same time to compare the output, and the output is a high and low ±5V square wave signal. The current-limiting voltage value and the driving sawtooth signal value are passed through the comparator to generate a square wave, and the square wave signal is used as the control signal of the analog switch. If the voltage at a certain point of the laser sawtooth voltage is greater than the current-limiting voltage signal, the comparator outputs a high level, and the comparator outputs a high level to control the analog switch to switch to the current-limiting voltage signal, thereby limiting the current; otherwise, the analog switch always outputs the laser-driven sawtooth signal.

[0023] Preferably, the MCU controls the DAC chip through a 3-wire SPI to generate a certain analog voltage signal, which is the current-limiting voltage signal used. The current-limiting voltage signal generated by the DAC chip passes through a filter buffer circuit composed of an integrated operational amplifier and enters one end of the comparator circuit.

[0024] Preferably, the laser driving signal is sent to the other end of the high-speed comparator for comparison. If the driving signal voltage is less than the current limiting voltage of the filter buffer, the comparator outputs the laser driving signal; if the driving signal voltage is greater than the current limiting voltage of the filter buffer, the comparator outputs a current limiting protection signal.

[0025] Preferably, if the laser driving signal voltage is less than the current limiting voltage of the filter buffer and the control end outputs a low level, the signal output by the comparator enters the control end of the multi-channel analog multiplexing switch, and the sawtooth signal of the laser driving circuit is selected to promote the normal operation of the laser; if the laser driving signal voltage is greater than the current limiting voltage of the filter buffer and the control end outputs a high level, the signal output by the comparator enters the control end of the multi-channel analog multiplexing switch, and the DC signal of the current limiting protection circuit is selected to promote the laser current limiting to the maximum value.

[0026] Preferably, the MCU adopts STM32F767I GT6, the core is a 32-bit Cortex-M7 CPU, its FLASH is 1M, SRAM is 512K; there are 6 groups of configurable SPI communication channels, and the CS, SCK, and MOSI of the SPI 1 of the single-chip microcomputer are respectively connected to the 9-pin SYNC, 10-pin SCLK, and 11-pin Di n of the DAC chip; thereby realizing the communication between the MCU and the DAC chip to generate a low-level current-limiting voltage signal.

[0027] Preferably, the reference source circuit uses REF50xxx voltage comparator to form a feedback loop, and the voltage reference source is REF50XX, which is a product series with low noise, low drift and extremely high precision voltage reference. These references support both current sinking and current sourcing, and have excellent linear regulation and load regulation, making REF5025 very suitable for high-precision data acquisition systems.

[0028] Preferably, the DAC circuit is composed of a DAC85xxx chip. The DAC85XX is a low-power, voltage-output, four-channel, 16-bit digital-to-analog converter (DAC). This device is a monolithic device that provides excellent linearity and greatly reduces harmful code-to-code transient voltages (glitch pulses). The DAC8564 uses a multi-purpose 3-wire serial port that can run at a clock rate of up to 50MHz. The external reference source is 2.5V. The DAC8564 can generate a current limiting protection voltage with a resolution of 0.03815mV, thereby ensuring the high accuracy of the current limiting voltage.

[0029] Preferably, the current limiting circuit is composed of an OPA2xxx integrated circuit, and the current limiting buffer circuit is composed of a two-stage operational amplifier. The voltage signal of the current limiting protection generated by the DAC set by the MCU is connected to the 3rd pin of the operational amplifier U24A through a first-order RC filter, and is followed by the output through pins 2 and 6. The purpose of this stage is to improve the load capacity of the voltage signal of the current limiting protection. The output end of pin 1 of U24A continues to output and follow through two voltage-dividing resistors and capacitor filtering. Resistors R125 and R129 can be selectively welded, and the purpose is to modify the voltage signal value of the current limiting protection by hardware. Similarly, if the DAC output voltage is too low, R131 and R132 can also be welded to achieve signal amplification, so that the circuit design can better meet the current limiting voltage required for the project to be adjusted. The first-order cutoff frequency of the circuit can be calculated as Fc=1 / (2πRC), and the cutoff frequency of the currently designed first-order filter is 159Hz.

[0030] Preferably, the signal comparison circuit uses an AD86xxx voltage comparator to form a feedback loop, and the comparator circuit simply uses a dedicated high-speed comparator chip AD86XX. The op amp pin 7 of the above-mentioned U24B enters the front-end resistor R132 through R128 and then enters the pin 2 of the comparator U25. R134 is connected to the laser drive signal (driving the laser to emit light) and is connected to the pin 3 of U25 through R134. When the voltage of pin 2 of U25 is higher than the voltage of its pin 3, the voltage of pin 2 is output, otherwise the voltage of pin 3 is output.

[0031] Preferably, the analog switch circuit is composed of an ADG7xxx multiplexer switch. Whether the switching of the analog switch is a current limiting protection signal or a signal that effectively drives the laser depends entirely on the control signal. The control signal is pin 1 of U26. Whether the level of this pin is high or low depends on the output of the comparator. When the comparator output is a high level, the switch is switched to pin 6, that is, the current limiting protection signal is started. Conversely, a low level is switched to pin 4, that is, the laser driving signal. The level of control pin 1 is obtained by comparing the current limiting protection signal with the normal driving signal. If the driving signal value voltage is greater than the current limiting signal voltage value, the current limiting protection signal is output, thereby protecting the laser well.

[0032] (III) Beneficial effects

[0033] 1. The DC level generated by the DAC is coupled to the comparator through the isolation buffer and the laser drive signal; the analog switch switches the output drive signal or the current limiting protection signal through the output state of the comparator; no additional DC signal generator is required, the structure is simple and the cost is low; at the same time, the limiting voltage point of the current limiting circuit is always loaded with the positive end of the comparator, which is real-time and reliable. The circuit protects the laser in real time without changing the quality of the drive signal, thereby achieving the current limiting protection function.

[0034] 2. The circuit has high control accuracy and small temperature drift, and can accurately output milliampere-level limiting current. The circuit has high control speed, good real-time performance, flexibility and convenience, and can achieve control of any current limiting value, which can reduce system interference and improve the reliability of system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above description is only an overview of the technical solution of the utility model. In order to more clearly understand the technical means of the utility model and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the utility model in conjunction with the accompanying drawings.

[0036] Figure 1 This is a prior art circuit diagram of a current limiting protection circuit for a continuous laser of the utility model;

[0037] Figure 2 This is a circuit structure block diagram of a current limiting protection circuit for a continuous laser of the utility model;

[0038] Figure 3 This is a reference source circuit diagram of a current limiting protection circuit for a continuous laser of the utility model;

[0039] Figure 4 This is a circuit diagram of a digital-to-analog conversion circuit of a current limiting protection circuit for a continuous laser of the utility model;

[0040] Figure 5A circuit diagram of a current limiting buffer circuit of a current limiting protection circuit for a continuous laser according to the utility model;

[0041] Figure 6 A circuit diagram of a comparator circuit of a current limiting protection circuit for a continuous laser according to the utility model;

[0042] Figure 7 The utility model discloses a circuit diagram of an analog switch switching circuit of a current limiting protection circuit of a continuous laser. DETAILED DESCRIPTION

[0043] The embodiment of the present application solves the problem of low sensitivity in the prior art by providing a current limiting protection circuit for a continuous laser. The DC level generated by a DAC is coupled to a comparator through an isolation buffer and a laser drive signal; an analog switch switches the output drive signal or the current limiting protection signal according to the output state of the comparator; no additional DC signal generator is required, thereby reducing errors and improving accuracy.

[0044] Example 1

[0045] The technical solution in the embodiment of the present application is to solve the above-mentioned problem of large error, and the overall idea is as follows:

[0046] In view of the problems existing in the prior art, the utility model provides a current limiting protection circuit for a continuous laser, abandoning the traditional current limiting circuit composed of two diodes. The laser current limiting protection circuit is composed of an analog-to-digital conversion chip, an integrated operational amplifier, a high-speed comparator, and a fast analog switch.

[0047] like Figure 2 As shown, in order to achieve the above purpose, the technical solution adopted by the utility model is: a current limiting protection circuit for a continuous laser, including an MCU circuit, a DAC circuit and a voltage-dividable buffer circuit, a current limiting protection circuit, a comparator circuit and an analog switch switching circuit;

[0048] MCU controls the digital-to-analog converter through the SPI bus to generate the required current-limiting voltage value. The maximum value of this voltage value is the external reference source voltage. Because the output driving capability of the digital-to-analog converter is limited, the subsequent stage needs a current-limiting buffer circuit to improve the load capacity. The buffered current-limiting voltage signal and the laser sawtooth drive signal enter the comparator at the same time to compare the output. The output is a high and low ±5V square wave signal. The current-limiting voltage value and the driven sawtooth signal value are passed through the comparator to generate a square wave. The square wave signal is used as the control signal of the analog switch. If the voltage at a certain point of the laser sawtooth voltage is greater than the current-limiting voltage signal, the comparator outputs a high level to control the analog switch to switch to the current-limiting voltage signal, thereby limiting the current; otherwise, the analog switch always outputs the sawtooth signal driven by the laser.

[0049] The MCU circuit is used to enable the hardware SPI communication signal and control the analog-to-digital conversion chip;

[0050] The reference source circuit is used to provide a reference voltage to the analog-to-digital conversion chip;

[0051] The DAC circuit is used to generate a voltage signal for limiting the laser current;

[0052] The current limiting buffer circuit is used to generate a voltage signal to limit the laser current and play an isolation buffer role.

[0053] The signal comparison circuit is used to compare the driving signal with the current limiting signal and output a signal to control the analog switch.

[0054] The signal simulation switch circuit is used for rapidly switching the current limiting signal and the laser driving signal.

[0055] Furthermore, the above technical solution is improved to also include a driving signal circuit for generating the laser, and the laser driving signal or the current limiting protection signal enters the subsequent driving circuit of the laser.

[0056] The specific process is as follows:

[0057] 1. MCU controls the DAC chip through the 3-wire SPI to generate a certain analog voltage signal, which is the current-limiting voltage signal used. The current-limiting voltage signal generated by the DAC chip enters one end of the comparator circuit through the filter buffer circuit composed of the integrated operational amplifier.

[0058] 2. The laser driving signal is sent to the other end of the high-speed comparator for comparison. If the driving signal voltage is less than the current limiting voltage of the filter buffer, the comparator outputs the laser driving signal; if the driving signal voltage is greater than the current limiting voltage of the filter buffer, the comparator outputs the current limiting protection signal.

[0059] 3. If the laser driving signal voltage is less than the current limiting voltage of the filter buffer and the control end outputs a low level, the signal output by the comparator enters the control end of the multi-channel analog multiplexing switch, and the sawtooth signal of the laser driving circuit is selected to promote the normal operation of the laser; if the laser driving signal voltage is greater than the current limiting voltage of the filter buffer and the control end outputs a high level, the signal output by the comparator enters the control end of the multi-channel analog multiplexing switch, and the DC signal of the current limiting protection circuit is selected to promote the laser current limiting to the maximum value.

[0060] like Figure 3As shown in the figure, the reference source circuit uses REF50xxx voltage comparator to form a feedback loop. The voltage reference source is REF50XX, which is a product series with low noise, low drift and extremely high precision voltage reference. These references support both current sinking and current sourcing, and have excellent linear regulation and load regulation, making REF5025 very suitable for high-precision data acquisition systems.

[0061] like Figure 4 As shown in the figure, the DAC circuit is composed of DAC85xxx chips. DAC85XX is a low-power, voltage-output, four-channel, 16-bit digital-to-analog converter (DAC). This device is a monolithic device that provides excellent linearity and greatly reduces harmful code-to-code transient voltages (glitch pulses). DAC8564 uses a multi-purpose 3-wire serial port that can run at a clock rate of up to 50MHz. The external reference source is 2.5V. The DAC8564 can generate a current-limiting protection voltage with a resolution of 0.03815mV, thereby ensuring the high accuracy of the current-limiting voltage.

[0062] like Figure 5 As shown, the current limiting circuit is composed of OPA2xxx integrated circuit, and the current limiting buffer circuit is composed of two stages of operational amplifiers. The voltage signal of the current limiting protection generated by the DAC set by the MCU is connected to the 3rd pin of the operational amplifier U24A through the first-order RC filter, and is followed by the output through the 2nd and 6th pins. The purpose of this stage is to improve the load capacity of the voltage signal of the current limiting protection. The 1st pin output end of U24A continues to output and follow through two voltage-dividing resistors and capacitor filtering. Resistors R125 and R129 can be selectively welded, and the purpose is to modify the voltage signal value of the current limiting protection by hardware. Similarly, if the DAC output voltage is too low, R131 and R132 can also be welded to achieve signal amplification, so that the circuit design can better meet the current limiting voltage required by the project for adjustment. The first-order cutoff frequency of the circuit can be calculated as Fc=1 / (2πRC). The cutoff frequency of the current-limiting first-order filter is currently designed to be 159Hz.

[0063] like Figure 6 As shown, the signal comparison circuit uses AD86xxx voltage comparator to form a feedback loop. The comparator circuit simply uses a dedicated high-speed comparator chip AD86XX. The operational amplifier pin 7 of the above-mentioned U24B enters the front-end resistor R132 through R128 and then enters the pin 2 of the comparator U25. R134 is connected to the laser drive signal (driving the laser to emit light) and is connected to the pin 3 of U25 through R134. When the voltage of pin 2 of U25 is higher than the voltage of its pin 3, the voltage of pin 2 is output, otherwise the voltage of pin 3 is output.

[0064] like Figure 7As shown, the analog switch circuit is composed of ADG7xxx multiplexer switch. Whether the analog switch switches the current limiting protection signal or the signal that effectively drives the laser depends entirely on the control signal. The control signal is pin 1 of U26. Whether the level of this pin is high or low depends on the output of the comparator. When the comparator output is high, the switch is switched to pin 6, which starts the current limiting protection signal. Otherwise, the low level is switched to pin 4, which is the laser driving signal. The level of control pin 1 is obtained by comparing the current limiting protection signal with the normal driving signal. If the driving signal value voltage is greater than the current limiting signal voltage value, the current limiting protection signal is output, thereby protecting the laser well.

[0065] Beneficial effects of the utility model:

[0066] The DC level generated by the DAC is coupled to the comparator through the isolation buffer and the laser driving signal; the analog switch switches the output driving signal or the current limiting protection signal through the output state of the comparator; no additional DC signal generator is required, the structure is simple and the cost is low; at the same time, the limiting voltage point of the current limiting circuit is always loaded with the positive end of the comparator, which is real-time and reliable. The circuit protects the laser in real time without changing the quality of the driving signal, thereby achieving the current limiting protection function.

[0067] The circuit has high control accuracy and small temperature drift, and can accurately output milliampere-level limiting current. The circuit has high control speed, good real-time performance, flexibility and convenience, and can achieve control of any current limiting value, which can reduce system interference and improve the reliability of system operation.

[0068] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. A current limiting protection circuit for a continuous laser, characterized in that: The current limiting protection circuit includes an MCU circuit, a DAC circuit, a voltage divider buffer circuit, a current limiting protection circuit, a comparator circuit and an analog switch switching circuit. MCU controls the digital-to-analog converter through the SPI bus to generate the required current-limiting voltage value. The maximum value of this voltage value is the external reference source voltage. The current-limiting voltage value and the driven sawtooth signal value are passed through the comparator to generate a square wave, and the square wave signal is used as the control signal of the analog switch. If the voltage at a certain point of the laser sawtooth voltage is greater than the current-limiting voltage signal, the comparator outputs a high level, and the comparator outputs a high level to control the analog switch to switch to the current-limiting voltage signal, thereby limiting the current; otherwise, the analog switch always outputs the sawtooth signal driven by the laser; The MCU circuit is used to enable the hardware SPI communication signal and control the analog-to-digital conversion chip; A reference source circuit is used to provide a reference voltage to the analog-to-digital conversion chip; The DAC circuit is used to generate a voltage signal for limiting the laser current; A current limiting buffer circuit is used to generate a voltage signal for limiting the laser current and to play an isolation buffer role; A signal comparison circuit is used to compare the driving signal with the current limiting signal and output a signal to control the analog switch; The signal simulation switch circuit is used to quickly switch the current limiting signal and the laser driving signal. This circuit also includes a driving signal circuit for generating the laser, and the laser driving signal or the current limiting protection signal enters the post-driving circuit of the laser.

2. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The MCU controls the DAC chip through a 3-wire SPI to generate a certain analog voltage signal, which is the current-limiting voltage signal used. The current-limiting voltage signal generated by the DAC chip passes through a filter buffer circuit composed of an integrated operational amplifier and enters one end of the comparator circuit.

3. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The laser driving signal is sent to the other end of the high-speed comparator for comparison. If the driving signal voltage is less than the current limiting voltage of the filter buffer, the comparator outputs the laser driving signal; if the driving signal voltage is greater than the current limiting voltage of the filter buffer, the comparator outputs the current limiting protection signal.

4. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: If the voltage of the laser driving signal is less than the current limiting voltage of the filter buffer and the control end outputs a low level, the signal output by the comparator enters the control end of the multi-channel analog multiplexing switch, and the sawtooth signal of the laser driving circuit is selected to promote the normal operation of the laser; if the voltage of the laser driving signal is greater than the current limiting voltage of the filter buffer and the control end outputs a high level, the signal output by the comparator enters the control end of the multi-channel analog multiplexing switch, and the DC signal of the current limiting protection circuit is selected to promote the laser current limiting to be at the maximum value.

5. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The MCU adopts STM32F767IGT6, the core is a 32-bit Cortex-M7 CPU, its FLASH is 1M, SRAM is 512K; there are 6 groups of configurable SPI communication channels, and the CS, SCK, and MOSI of the SPI1 of the microcontroller are respectively connected to the 9-pin SYNC, 10-pin SCLK, and 11-pin Din of the DAC chip, so as to realize the communication between the MCU and the DAC chip to generate a low-level current-limiting voltage signal.

6. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The reference source circuit uses REF5025 voltage comparator to form a feedback loop. These references support both current sinking and current sourcing.

7. A current limiting protection circuit for a continuous wave laser as claimed in claim 1, characterized in that: The DAC circuit is composed of a DAC8564 chip. The DAC8564 uses a multi-purpose 3-wire serial port that can run at a clock rate of up to 50MHz. The external reference source is 2.5V. The DAC8564 can generate a current limiting protection voltage with a resolution of 0.03815mV.

8. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The current limiting circuit is composed of integrated circuits. The current limiting buffer circuit is composed of two-stage operational amplifiers. The voltage signal of the current limiting protection generated by the DAC set by the MCU is connected to the 3rd pin of the operational amplifier U24A through the first-order RC filter, and then output through the 2nd and 6th pins. The 1st pin output of U24A continues to output and follow through two voltage-dividing resistors and capacitor filtering. Resistors R125 and R129 can be selectively welded. Similarly, if the DAC output voltage is too low, R131 and R132 can be welded to achieve signal amplification. The first-order cutoff frequency of the circuit is calculated to be Fc=1 / (2πRC). The cutoff frequency of the current designed first-order filter is 159Hz.

9. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The signal comparison circuit uses a voltage comparator to form a feedback loop. The comparator circuit simply uses a dedicated high-speed comparator chip. The op amp pin 7 of the above-mentioned U24B enters the front-end resistor R132 through R128 and then enters the pin 2 of the comparator U25. R134 is connected to the laser drive signal, which is connected to the pin 3 of U25 through R134. When the voltage of pin 2 of U25 is higher than the voltage of its pin 3, the voltage of pin 2 is output, otherwise the voltage of pin 3 is output.

10. A current limiting protection circuit for a continuous laser as claimed in claim 1, characterized in that: The analog switch circuit is composed of a multiplexed switch. The switching of the analog switch is a current limiting protection signal or a signal that effectively drives the laser. The control signal is pin 1 of U26. Whether the level of this pin is high or low depends on the output of the comparator. When the comparator output is a high level, the switch is turned to pin 6, that is, the current limiting protection signal is started. Conversely, the low level is turned to pin 4, which is the laser driving signal. The level of control pin 1 is obtained by comparing the current limiting protection signal with the normal driving signal. If the driving signal value voltage is greater than the current limiting signal voltage value, the current limiting protection signal is output.

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