Overvoltage protection circuit, constant current source circuit and laser

Abstract

The invention discloses an overvoltage protection circuit, a constant current source circuit and a laser, and relates to the technical field of lasers, the overvoltage protection circuit comprises a main control circuit, the control end of the main control circuit is electrically connected with the feedback end of a stabilized power supply; the sampling end of the first voltage sampling circuit is electrically connected with the input end of the switching tube, and the output end of the first voltage sampling circuit is electrically connected with the signal receiving end of the main control circuit; the first voltage sampling circuit is used for sampling the voltage of the input end of the switching tube; the sampling end of the second voltage sampling circuit is electrically connected with the output end of the switching tube, and the output end of the second voltage sampling circuit is electrically connected with the signal receiving end of the main control circuit; the second voltage sampling circuit is used for sampling the voltage of the output end of the switching tube; the invention aims to solve the problem that when the output voltage of the stabilized voltage supply is too large, the current passing through the switching tube is too large, so that the heating power consumption of the switching tube is too large.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to an overvoltage protection circuit, a constant current source circuit, and a laser. Background Technology

[0002] Pulsed lasers are widely used in industrial processing, biomedicine, radar sensing, space exploration, and military research. Currently, common constant current sources typically consist of a DC-DC converter, an operational amplifier, and a sampling resistor as their basic topology.

[0003] A DC-DC converter is a regulated power supply. Due to the voltage uncertainty of the laser emitting component, the output voltage of the DC-DC converter must be set to a relatively high value to ensure that the laser emitting component can operate normally. Therefore, the excess voltage is entirely borne by the switching transistor and sampling resistor in the constant current source circuit. In some high-current fiber lasers or semiconductor lasers, the current amplitude is often very large, resulting in a very large current through the switching transistor. Since the switching transistor operates in the linear region, the excessive current amplitude will lead to very large heat dissipation of the switching transistor, and ordinary heat sinks cannot meet the requirements. Summary of the Invention

[0004] The main objective of this invention is to propose an overvoltage protection circuit, a constant current source circuit, and a laser, which aims to solve the problem that when the output voltage of the regulated power supply is too high, the current through the switching transistor becomes too high, resulting in excessive heat generation and power consumption of the switching transistor.

[0005] To achieve the above objectives, the present invention proposes an overvoltage protection circuit, the overvoltage protection circuit comprising:

[0006] The main control circuit, wherein the control terminal of the main control circuit is electrically connected to the feedback terminal of the regulated power supply;

[0007] A first voltage sampling circuit is used to sample the voltage at the input of the switching transistor. The sampling terminal of the first voltage sampling circuit is electrically connected to the input terminal of the switching transistor, and the output terminal of the first voltage sampling circuit is electrically connected to the signal receiving terminal of the main control circuit.

[0008] The second voltage sampling circuit has its sampling terminal electrically connected to the output terminal of the switching transistor, and its output terminal electrically connected to the signal receiving terminal of the main control circuit; the second voltage sampling circuit is used to sample the voltage at the output terminal of the switching transistor.

[0009] The main control circuit is used to calculate the difference between the voltage at the input terminal of the switching transistor and the voltage at the output terminal of the switching transistor, and compare the difference with a preset threshold. The main control circuit adjusts the voltage output of the regulated power supply according to the comparison result.

[0010] In one embodiment, the main control circuit includes:

[0011] The subtraction amplifier circuit has its first input terminal electrically connected to the output terminal of the first voltage sampling circuit, and its second input terminal electrically connected to the output terminal of the switching transistor. The subtraction amplifier circuit is used to calculate the difference between the voltage at the input terminal and the voltage at the output terminal of the switching transistor, amplify the corresponding difference signal according to a preset amplification factor, and output it to the feedback terminal of the regulated power supply.

[0012] In one embodiment, the subtraction amplifier circuit includes:

[0013] A first amplifier and a feedback resistor are provided. The non-inverting input of the first amplifier is electrically connected to the output of the first voltage sampling circuit, and the inverting input of the first amplifier is electrically connected to the output of the second voltage sampling circuit. The first end of the feedback resistor is electrically connected to the inverting input of the first amplifier, and the second end of the feedback resistor is electrically connected to the output of the first amplifier. The output of the first amplifier is also electrically connected to the feedback terminal of the regulated power supply.

[0014] In one embodiment, the first voltage sampling circuit includes:

[0015] A first voltage divider circuit is provided, wherein a first terminal of the first voltage divider circuit is electrically connected to the input terminal of the switching transistor, and a second terminal of the first voltage divider circuit is electrically connected to the signal receiving terminal of the main control circuit; the main control circuit is used to determine the voltage at the input terminal of the switching transistor based on the voltage of the first voltage divider circuit.

[0016] The second voltage sampling circuit includes:

[0017] The second voltage divider circuit has its first terminal electrically connected to the output terminal of the switching transistor, and its output terminal grounded. The main control circuit is used to determine the voltage at the output terminal of the switching transistor based on the voltage of the second voltage divider circuit.

[0018] In one embodiment, the first voltage divider circuit includes:

[0019] A first resistor and a second resistor, wherein the first end of the first resistor is electrically connected to the input end of the switching transistor, the second end of the first resistor is electrically connected to the signal receiving end of the main control circuit and the second end of the second resistor, and the first end of the second resistor is grounded.

[0020] In one embodiment, the second voltage divider circuit includes:

[0021] The third resistor and the fourth resistor are connected in the following ways: the first end of the third resistor is electrically connected to the first end of the fourth resistor and the output end of the switching transistor; the second end of the fourth resistor is electrically connected to the signal receiving end of the main control circuit; and the second end of the third resistor is grounded.

[0022] In one embodiment, the plurality of resistors in the first voltage divider circuit and the plurality of resistors in the second voltage divider circuit are both adjustable resistors.

[0023] The present invention also proposes a constant current source circuit, including the overvoltage protection circuit described in any of the above claims.

[0024] The present invention also proposes a laser, including a laser emitting component and the constant current source circuit described above.

[0025] The technical solution of this invention employs a first voltage sampling circuit to acquire the input voltage of the switching transistor and a second voltage sampling circuit to acquire the output voltage of the switching transistor. The main control circuit calculates the difference between the input and output voltages of the switching transistor to obtain the switching transistor voltage. This difference is compared with a preset threshold, and the voltage output of the regulated power supply is adjusted according to the comparison result. If the difference is greater than the preset threshold, it indicates that the switching transistor voltage is too high, and the main control circuit controls the regulated power supply output voltage to decrease, thereby reducing the switching transistor voltage. With this configuration, the overvoltage protection circuit of this invention controls the regulated power supply output voltage to decrease when the switching transistor voltage is too high, thus avoiding the problem of excessive heat generation from the switching transistor. In practical applications, lasers equipped with the overvoltage protection circuit of this invention can monitor and control the voltage on the switching transistor in real time, preventing it from exceeding the safety threshold, thereby effectively protecting the laser from damage. Furthermore, because the switching transistor voltage is controllable, the heat generation and power consumption of the switching transistor are also controllable, reducing the need for a large heat sink for the laser. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a module according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the circuit structure of another embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the circuit structure of another embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the circuit structure of another embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the circuit structure of another embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the existing constant current source circuit.

[0033] Explanation of icon numbers:

[0034] 10. First voltage sampling circuit; 11. First voltage divider circuit; 20. Second voltage sampling circuit; 21. Second voltage divider circuit; 30. Main control circuit; 31. Subtraction amplifier circuit.

[0035] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0037] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0038] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0039] Figure 6 The circuit shown has certain defects. The DC-DC converter is a regulated power supply, and its output voltage Vdc = V laser + VNMOS +V RS Due to the voltage Vlaser uncertainty of the laser emitting component, the output voltage of the DC-DC converter must be set to a relatively high value to ensure the normal operation of the laser emitting component. Therefore, the excess voltage is entirely borne by the switching transistor and the sampling resistor Rs. In some high-current fiber lasers or semiconductor lasers, the current amplitude is often very large, resulting in a very large current in the MOSFET. At this time, since the switching transistor is operating in the linear region, the heat dissipation of the switching transistor is very large.

[0040] For example, suppose the output voltage of the DC-DC converter is 24V, i.e., Vdc = 24V, the maximum output current of the constant current source is 50A, and the voltage of the load laser emitting component (Laser) is 20V, i.e., V laser =20V, Rs is 0.01Ω, therefore the voltage V across the sampling resistor is... RS =0.5V, from which the voltage V of the switching transistor can be obtained. NMOS =Vdc-V Laser -V RS =24-20-0.5=3.5V, so the heat dissipation of the switching transistor at this time is P=U*I=3.5*50=175W. For the switching transistor, this heat dissipation is very large, and ordinary heat sinks cannot meet the requirements.

[0041] Therefore, the main objective of this invention is to propose an overvoltage protection circuit, a constant current source circuit, and a laser, which aims to solve the problem that when the output voltage of the regulated power supply is too high, the current through the switching transistor becomes too high, resulting in excessive heat generation and power consumption of the switching transistor.

[0042] refer to Figure 1-5 This invention proposes an overvoltage protection circuit, the overvoltage protection circuit comprising:

[0043] The main control circuit 30 is electrically connected to the feedback terminal of the regulated power supply.

[0044] A first voltage sampling circuit 10 is used to sample the voltage at the input terminal of the switching transistor. The sampling terminal of the first voltage sampling circuit 10 is electrically connected to the input terminal of the switching transistor, and the output terminal of the first voltage sampling circuit 10 is electrically connected to the signal receiving terminal of the main control circuit 30.

[0045] The second voltage sampling circuit 20 has its sampling terminal electrically connected to the output terminal of the switching transistor, and its output terminal electrically connected to the signal receiving terminal of the main control circuit 30; the second voltage sampling circuit 20 is used to sample the voltage at the output terminal of the switching transistor.

[0046] The main control circuit 30 is used to calculate the difference between the voltage at the input terminal of the switching transistor and the voltage at the output terminal of the switching transistor, and compare the difference with a preset threshold; the main control circuit 30 adjusts the voltage output of the regulated power supply according to the comparison result.

[0047] In this embodiment, the main control circuit 30 can be implemented using a main controller, such as an MCU (Microcontroller Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a SOC (System On Chip).

[0048] In this embodiment, the voltage sampling circuit can be implemented using one of the following: a voltage transformer, a Hall voltage sensor, or a resistive voltage divider sensor.

[0049] In this embodiment, the DAC signal (current amplitude signal) is generated by the controller and output to the controlled terminal of the switching transistor. Since the conduction degree of the switching transistor depends on the amplitude of the DAC signal, the current through the laser emitting component depends on the amplitude of the DAC signal. Thus, the user can adjust the amplitude of the DAC signal according to actual needs and adjust the current through the laser emitting component.

[0050] Specifically, the technical solution of this invention employs a first voltage sampling circuit 10 to collect the input voltage of the switching transistor, and a second voltage sampling circuit 20 to collect the output voltage of the switching transistor. The main control circuit 30 calculates the difference between the input and output voltages of the switching transistor to obtain the voltage of the switching transistor, compares the difference with a preset threshold, and adjusts the output voltage of the regulated power supply according to the comparison result. If the difference is greater than the preset threshold, it indicates that the voltage of the switching transistor is too high, and the main control circuit 30 controls the output voltage of the regulated power supply to decrease, thereby reducing the voltage of the switching transistor. With this configuration, the overvoltage protection circuit of this invention controls the output voltage of the regulated power supply to decrease when the voltage of the switching transistor is too high, thus avoiding the problem of excessive heat generation from the switching transistor. In practical applications, lasers equipped with the overvoltage protection circuit of this invention can monitor and control the voltage on the switching transistor in real time, preventing it from exceeding the safety threshold, thereby effectively protecting the laser from damage. Furthermore, since the voltage of the switching transistor is controllable, the heat generation and power consumption of the switching transistor are also controllable, so that the heat sink used in the laser does not need to be large.

[0051] In mass-produced constant current sources, because it's impossible to match the DC-DC converter and laser emitting components one-to-one, it's impossible to reduce the DC-DC output voltage to a suitable value and thus reduce the heat generated by the switching transistor. Therefore, the heatsink for the switching transistor must be made larger. With ever-increasing technological demands for smaller circuits and higher precision, traditional constant current source circuits struggle to meet these requirements.

[0052] Since the heat dissipation of the switching transistor of the laser with the overvoltage protection circuit of the present invention is controllable, the laser with the overvoltage protection circuit of the present invention does not need to be equipped with a large heat sink, so that the laser can be designed to be smaller. Thus, the laser with the present invention can be used in small devices with small size and high precision requirements, such as handheld measuring instruments and portable medical devices, thereby improving the portability and practicality of the devices.

[0053] refer to Figure 2 In one embodiment of the present invention, the main control circuit 30 includes:

[0054] The subtraction amplifier circuit 31 has its first input terminal electrically connected to the output terminal of the first voltage sampling circuit 10, and its second input terminal electrically connected to the output terminal of the switching transistor. The controlled terminal of the subtraction amplifier circuit is used to receive control signals sent by an external terminal. The subtraction amplifier circuit 31 is used to calculate the difference between the voltage at the input terminal and the voltage at the output terminal of the switching transistor, and after processing the difference according to the control signal, output it to the feedback terminal of the regulated power supply.

[0055] In this embodiment, the subtraction amplifier circuit 31 is composed of at least one operational amplifier. The subtraction amplifier circuit 31 calculates the difference between the voltages at its two input terminals, adjusts the difference according to a control signal sent from an external terminal, and outputs the result to the feedback terminal of the regulated power supply. This configuration allows the user to adjust the output difference of the subtraction amplifier circuit according to actual conditions, thereby adjusting the voltage and heat dissipation of the switching transistor, achieving controllable voltage and heat dissipation of the switching transistor. For example, if the withstand voltage of the actual switching transistor (e.g., 10V) is less than the preset upper voltage threshold of the regulated power supply (e.g., 15V), then when the voltage of the switching transistor is too high, the regulated power supply cannot control its output voltage to decrease because the received voltage of 10V is less than the upper voltage threshold of 15V. However, in this invention, the user can adjust the output difference of the subtraction amplifier circuit by setting a corresponding control signal through a host computer, increasing the withstand voltage of the switching transistor to be equal to the preset voltage threshold of the regulated power supply. This allows the regulated power supply to promptly control the reduction of its output voltage when the voltage of the switching transistor is too high.

[0056] Furthermore, the subtraction amplifier circuit 31 includes:

[0057] A first amplifier U1 and a feedback resistor Rf are connected. The non-inverting input of the first amplifier U1 is electrically connected to the output of the first voltage sampling circuit 10, and the inverting input of the first amplifier U1 is electrically connected to the output of the second voltage sampling circuit 20. The first end of the feedback resistor Rf is electrically connected to the inverting input of the first amplifier U1, and the second end of the feedback resistor Rf is electrically connected to the output of the first amplifier U1. The output of the first amplifier U1 is also electrically connected to the feedback terminal of the regulated power supply. The feedback resistor is an adjustable resistor.

[0058] In this embodiment, the feedback resistor Rf can be a digital potentiometer, the effective resistance of which can be adjusted by outputting a corresponding control signal; or it can be a mechanical adjustable resistor, the resistance of which can be changed by manually rotating the adjustment knob.

[0059] In this embodiment, adjusting the value of the feedback resistor Rf adjusts the output difference of the first amplifier U1. With this configuration, when the voltage withstand capability of the actual application's switching transistor is less than the preset voltage threshold of the regulated power supply, adjusting the value of the feedback resistor Rf increases the output difference of the first amplifier U1 to match the preset voltage threshold of the regulated power supply. Thus, since the output difference to the regulated power supply is controllable, the voltage and heat dissipation of the switching transistor are controllable. The user can adjust the value of the feedback resistor Rf according to the ambient temperature. For example, when the ambient temperature is high, the heat dissipation threshold of the switching transistor decreases, and the voltage withstand capability of the switching transistor also decreases. By adjusting the value of the feedback resistor Rf, the output difference of the first amplifier U1 can be adjusted so that the switching transistor can reach the preset voltage threshold set by the regulated power supply even when the withstand voltage decreases. This achieves controllable heat dissipation of the switching transistor, eliminating the need for a large heat sink in lasers using the overvoltage protection circuit of this invention.

[0060] In one embodiment of the present invention, the first voltage sampling circuit 10 includes:

[0061] A first voltage divider circuit 11 has a first terminal electrically connected to the input terminal of the switching transistor, and a second terminal electrically connected to the signal receiving terminal of the main control circuit 30. The main control circuit 30 is used to determine the voltage at the input terminal of the switching transistor based on the voltage of the first voltage divider circuit 11.

[0062] The second voltage sampling circuit 20 includes:

[0063] The second voltage divider circuit 21 has its first terminal electrically connected to the output terminal of the switching transistor, and its output terminal grounded. The main control circuit 30 is used to determine the voltage at the output terminal of the switching transistor based on the voltage of the second voltage divider circuit 21.

[0064] In this embodiment, the voltage divider circuit consists of at least two resistors, as shown in the reference. Figure 3 The circuit shown includes the following components: the first voltage divider circuit 11.

[0065] A first resistor R1 and a second resistor R2 are connected. The first end of the first resistor R1 is electrically connected to the input end of the switching transistor. The second end of the first resistor R1 is electrically connected to the signal receiving end of the main control circuit 30 and the second end of the second resistor R2. The first end of the second resistor R2 is grounded.

[0066] The second voltage divider circuit 21 includes:

[0067] The third resistor R3 and the fourth resistor R4 are connected in the following ways: the first end of the third resistor R3 is electrically connected to the first end of the fourth resistor R4 and the output end of the switching transistor, the second end of the fourth resistor R4 is electrically connected to the signal receiving end of the main control circuit 30, and the third resistor R3 is grounded.

[0068] In this embodiment, the first voltage divider circuit 11 and the second voltage divider circuit 21 distribute the collected voltage to different voltage divider points according to the resistance ratio. The voltage received by the main control circuit 30 depends on the resistance values ​​of the first voltage divider circuit 11 and the second voltage divider circuit 21. That is, the difference output by the main control circuit 30 depends on the resistance values ​​of the first voltage divider circuit 11 and the second voltage divider circuit 21. The larger the resistance of the first voltage divider circuit 11 and the smaller the resistance of the second voltage divider circuit 21, the larger the difference output by the main control circuit 30. Conversely, the smaller the resistance of the first voltage divider circuit 11 and the smaller the resistance of the second voltage divider circuit 21, the larger the difference output by the main control circuit 30. The larger the resistance value, the smaller the output difference of the main control circuit 30. With this setting, in practical applications, the user can adjust the resistance values ​​of the first voltage divider circuit 11 and the second voltage divider circuit 21 according to the actual situation, such as the voltage withstand value of the switching transistor in the actual application, and adjust the output difference of the main control circuit 30. For example, when the voltage withstand value of the switching transistor is less than the preset voltage threshold of the regulated power supply, the output difference of the main control circuit can be increased by increasing the resistance value of the first voltage divider circuit or decreasing the resistance value of the second voltage divider circuit, so that the voltage withstand value of the switching transistor after amplification is equal to the preset voltage threshold of the regulated power supply. Thus, since the output voltage difference to the regulated power supply is controllable, the heat dissipation of the switching transistor is also controllable. Users can adjust the resistance values ​​of the first voltage divider circuit 11 and the second voltage divider circuit 21 according to the ambient temperature. For example, when the ambient temperature is high, the heat dissipation threshold of the switching transistor decreases, and the voltage that the switching transistor can withstand also decreases. By adjusting the resistance values ​​of the first voltage divider circuit 11 and the second voltage divider circuit 21, the output voltage difference is increased, so that even when the voltage that the switching transistor can withstand decreases, it can still reach the preset voltage threshold set by the regulated power supply after amplification. This makes the heat dissipation of the switching transistor controllable, so that lasers using the overvoltage protection circuit of this invention do not need to be equipped with large heat sinks.

[0069] refer to Figure 4 In one embodiment of the present invention, the overvoltage protection circuit further includes:

[0070] An operational amplifier and a fifth resistor R5, wherein the first end of the fifth resistor R5 is electrically connected to the output terminal of the switching transistor, and the second end of the fifth resistor R5 is grounded;

[0071] The non-inverting input of the operational amplifier is connected to a current amplitude signal, the inverting input of the operational amplifier is electrically connected to the first end of the first resistor, and the output of the operational amplifier is electrically connected to the controlled end of the switching transistor.

[0072] In this embodiment, due to the virtual short characteristic of the operational amplifier, the voltage at its inverting input is equal to the voltage at its non-inverting input. Since the non-inverting input of the operational amplifier receives the DAC signal, and the inverting input is electrically connected to the fifth resistor, the current I through the fifth resistor is equal to the quotient of the voltage VDAC of the current amplitude signal and the resistance value R5 of the fifth resistor, i.e., I = VDAC / R5. Because the laser emitting component, the switching transistor, and the fifth resistor are connected in series, the current through the fifth resistor R5 is equal to the current through the laser emitting component. The current through the laser emitting component can be adjusted by adjusting the value of VDAC. This configuration typically includes a negative feedback mechanism within the operational amplifier, which helps reduce nonlinear distortion and noise in the current amplitude signal, ensuring that the current I through the fifth resistor R5 (i.e., I = VDAC / R5) is strictly proportional to the voltage value VDAC of the DAC signal, thereby improving the accuracy of the current through the laser emitting component. However, existing constant current source circuits may not be able to control the current accurately due to factors such as the nonlinear relationship between the gate voltage and the source voltage, the gate capacitance effect, and the threshold voltage of the switching transistor itself, since the current amplitude signal is connected to the controlled terminal of the switching transistor.

[0073] It is understood that in this embodiment, the fifth resistor R5 and the third resistor R3 mentioned above can be the same resistor, while the operational amplifier and the subtraction amplifier circuit 31 are not the same operational amplifier.

[0074] In summary, for reference Figure 5 In the circuit described above, the first resistor R1 and the second resistor R2 are used to divide the input voltage of the switching transistor, and the third resistor R3 and the fourth resistor R4 are used to divide the output voltage of the switching transistor. The first amplifier U1 calculates the difference between the two voltage division values ​​and amplifies the difference according to a preset amplification factor, which is fed back to the regulated power supply. The amplification factor depends on the resistance value of the feedback resistor. When the difference received by the regulated power supply is greater than the preset value, the regulated power supply will reduce its own output voltage, thereby reducing the voltage difference between the input and output terminals of the switching transistor to below 1.5V. In this way, the voltage of the switching transistor will be controlled below 1.5V, and the heat dissipation of the switching transistor is P≤U*I=1. 5*50=75W. This heat dissipation will not affect the normal operation of the N-channel MOSSET, thus avoiding the problem of excessive voltage to the switching transistor causing excessive heat dissipation. This allows the laser equipped with the overvoltage protection circuit of this invention to be heat-dissipated without the need for a large heat sink. The difference depends on the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, and the feedback resistor Rf. Users can change the resistance values ​​of these resistors according to actual applications (e.g., by using different types of switching transistors) to adjust the output difference, ensuring that the laser equipped with the overvoltage protection circuit of this invention can maintain a good working state under various conditions.

[0075] Furthermore, due to the virtual short characteristic of operational amplifiers, the voltage at their inverting input is equal to the voltage at their non-inverting input. Since the non-inverting input receives the DAC signal and the inverting input is electrically connected to the third resistor R3, the current I through the third resistor R3 is equal to the quotient of the voltage VDAC of the current amplitude signal and the resistance R3, i.e., I = VDAC / R3. Because the laser emitting component, the switching transistor, and the third resistor R3 are connected in series, the current through the third resistor R3 is equal to the current through the laser emitting component. This configuration, where the operational amplifier typically includes a negative feedback mechanism, helps reduce nonlinear distortion and noise in the current amplitude signal. It ensures that the current I (i.e., I = VDAC / R3) through the laser emitting component and the third resistor R3 is strictly proportional to the DAC signal voltage VDAC, making the current through the laser emitting component a constant current. This guarantees that the intensity of the laser emitted by the laser emitting component remains stable at a preset value.

[0076] The present invention also proposes a constant current source circuit, including the overvoltage protection circuit described above.

[0077] It is worth noting that since the constant current source circuit of the present invention is based on the overvoltage protection circuit described above, the embodiments of the constant current source circuit of the present invention include all the technical solutions of all the embodiments of the overvoltage protection circuit described above, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0078] The present invention also proposes a laser, including a laser emitting assembly and a constant current source circuit as described above.

[0079] It is worth noting that since the laser of the present invention is based on the constant current source circuit described above, the embodiments of the laser of the present invention include all the technical solutions of all the embodiments of the constant current source circuit described above, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0080] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An overvoltage protection circuit, characterized in that, The overvoltage protection circuit includes: The main control circuit, wherein the control terminal of the main control circuit is electrically connected to the feedback terminal of the regulated power supply; A first voltage sampling circuit is used to sample the voltage at the input of the switching transistor. The sampling terminal of the first voltage sampling circuit is electrically connected to the input terminal of the switching transistor, and the output terminal of the first voltage sampling circuit is electrically connected to the signal receiving terminal of the main control circuit. The second voltage sampling circuit has its sampling terminal electrically connected to the output terminal of the switching transistor, and its output terminal electrically connected to the signal receiving terminal of the main control circuit; the second voltage sampling circuit is used to sample the voltage at the output terminal of the switching transistor. The main control circuit is used to calculate the difference between the voltage at the input terminal of the switching transistor and the voltage at the output terminal of the switching transistor, and compare the difference with a preset threshold. The main control circuit adjusts the voltage output of the regulated power supply according to the comparison result.

2. The overvoltage protection circuit as described in claim 1, characterized in that, The main control circuit includes: The subtraction amplifier circuit has its first input terminal electrically connected to the output terminal of the first voltage sampling circuit, and its second input terminal electrically connected to the output terminal of the switching transistor. The controlled terminal of the subtraction amplifier circuit is used to receive control signals sent by an external terminal. The subtraction amplifier circuit is used to calculate the difference between the voltage at the input terminal and the voltage at the output terminal of the switching transistor, and after processing the difference according to the control signal, output it to the feedback terminal of the regulated power supply.

3. The overvoltage protection circuit as described in claim 2, characterized in that, The subtraction amplifier circuit includes: A first amplifier and a feedback resistor are provided. The non-inverting input of the first amplifier is electrically connected to the output of the first voltage sampling circuit, and the inverting input of the first amplifier is electrically connected to the output of the second voltage sampling circuit. The first end of the feedback resistor is electrically connected to the inverting input of the first amplifier, and the second end of the feedback resistor is electrically connected to the output of the first amplifier. The output of the first amplifier is also electrically connected to the feedback terminal of the regulated power supply. The feedback resistor is an adjustable resistor.

4. The overvoltage protection circuit as described in claim 1, characterized in that, The first voltage sampling circuit includes: A first voltage divider circuit is provided, wherein a first terminal of the first voltage divider circuit is electrically connected to the input terminal of the switching transistor, and a second terminal of the first voltage divider circuit is electrically connected to the signal receiving terminal of the main control circuit; the main control circuit is used to determine the voltage at the input terminal of the switching transistor based on the voltage of the first voltage divider circuit. The second voltage sampling circuit includes: The second voltage divider circuit has its first terminal electrically connected to the output terminal of the switching transistor, and its output terminal grounded. The main control circuit is used to determine the voltage at the output terminal of the switching transistor based on the voltage of the second voltage divider circuit.

5. The overvoltage protection circuit as described in claim 4, characterized in that, The first voltage divider circuit includes: A first resistor and a second resistor, wherein the first end of the first resistor is electrically connected to the input end of the switching transistor, the second end of the first resistor is electrically connected to the signal receiving end of the main control circuit and the second end of the second resistor, and the first end of the second resistor is grounded.

6. The overvoltage protection circuit as described in claim 4, characterized in that, The second voltage divider circuit includes: The third resistor and the fourth resistor are connected in the following ways: the first end of the third resistor is electrically connected to the first end of the fourth resistor and the output end of the switching transistor; the second end of the fourth resistor is electrically connected to the signal receiving end of the main control circuit; and the second end of the third resistor is grounded.

7. The overvoltage protection circuit as described in any one of claims 4 to 6, characterized in that, Both the resistors in the first voltage divider circuit and the resistors in the second voltage divider circuit are adjustable resistors.

8. The overvoltage protection circuit as described in claim 1, characterized in that, The overvoltage protection circuit also includes: An operational amplifier and a fifth resistor, wherein the first end of the fifth resistor is electrically connected to the output terminal of the switching transistor, and the second end of the fifth resistor is grounded; The non-inverting input of the operational amplifier is connected to a current amplitude signal, the inverting input of the operational amplifier is electrically connected to the first end of the first resistor, and the output of the operational amplifier is electrically connected to the controlled end of the switching transistor.

9. A constant current source circuit, characterized in that, Includes the overvoltage protection circuit as described in any one of claims 1 to 8.

10. A laser, characterized in that, It includes a laser emitting component and a constant current source circuit as described in claim 9.

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