A constant current driving circuit for semiconductor laser

Abstract

The present application discloses a semiconductor laser constant current drive circuit, comprising a microcontroller, a digital-to-analog conversion module, a current limiting protection circuit, and a negative feedback regulation circuit. The digital-to-analog conversion module utilizes an LTC2600 chip, and utilizes the characteristics of its operating voltage range to adjust the drive current within a range from milliamperes to amperes, making it applicable to a variety of semiconductor lasers and expanding the application range of the drive circuit. The digital-to-analog conversion module is used to output a voltage signal, which has higher accuracy and better stability than manual adjustment or PWM wave adjustment in the prior art. The current limiting protection circuit is used to clamp the voltage signal corresponding to the drive current. When the set value exceeds the voltage limit of the semiconductor laser, the final output drive current is clamped to the limit value, thereby achieving the purpose of protecting the circuit and the laser. The negative feedback regulation circuit of the present invention utilizes a linear compensation gain error method, which is applicable to different types of lasers and has high accuracy.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor laser control, and in particular relates to a semiconductor laser constant current drive circuit. Background Art

[0002] Semiconductor lasers have a streamlined structure, featuring small size, light weight, no need for high-voltage drivers, and direct modulation. They are widely used in fields such as communications, medical treatment, measurement, and precision machining. Consequently, the performance requirements for semiconductor lasers are becoming increasingly stringent. In addition to the performance of the laser device itself, the design of the corresponding drive circuit plays a crucial role in the laser field. Because semiconductor lasers are devices with extremely high quantum effects and high power density, under the same temperature conditions, the drive current injected during operation is an extremely important indicator of the output optical power and stability. Semiconductor lasers have poor tolerance to electrical shocks. Even slight changes in the drive current can cause changes in their optical power output, lasing wavelength, noise performance, and mode hops, which inevitably affect the normal operation and protection of the laser. Therefore, in practical applications, the performance of semiconductor laser drive circuits is highly demanding. Characteristics such as circuit current limiting protection, programmable control, a wide current adjustable range, and high precision have become key design targets for semiconductor laser constant current drive circuits.

[0003] Currently, the current regulation range of most semiconductor laser driver circuits is relatively small. For low-power driver circuits, it is generally in the milliampere range, while for high-power driver circuits, it can reach tens of amperes. However, in some specific situations, the drive current demand is between milliamperes and amperes, and there is no suitable driver circuit solution for this. Summary of the Invention

[0004] Based on this, the present invention aims to provide a constant current driving circuit for a semiconductor laser, which has a larger current adjustment range and overcomes the shortcomings of the above-mentioned prior art.

[0005] The present invention provides a constant current driving circuit for a semiconductor laser, comprising:

[0006] Microcontroller, digital-to-analog conversion module, current limiting protection circuit and negative feedback regulation circuit;

[0007] The output terminal of the microcontroller is connected to the input terminal of the digital-to-analog conversion module for transmitting the driving current setting value;

[0008] The output end of the digital-to-analog conversion module is connected to the input end of the current limiting protection circuit, and is used to convert the driving current setting value into a corresponding voltage signal;

[0009] The output end of the current limiting protection circuit is connected to the input end of the negative feedback regulation circuit, and is used to control the voltage signal not to exceed the voltage limit value of the controlled semiconductor laser;

[0010] The negative feedback regulation circuit is used to stabilize the driving current input to the semiconductor laser;

[0011] Wherein, the digital-to-analog conversion module adopts the LTC2600 chip.

[0012] Preferably, the current limiting protection circuit includes

[0013] a first operational amplifier, a second operational amplifier, a first diode, and a second diode;

[0014] The inverting input terminal of the first operational amplifier is connected to the output terminal of the digital-to-analog conversion module, and the non-inverting input terminal is connected to the first potentiometer, which is used to set the voltage limit value of the semiconductor laser;

[0015] The non-inverting input terminal of the second operational amplifier is connected to the output terminal of the digital-to-analog conversion module, the output terminal of the second operational amplifier is connected to the input terminal of the negative feedback regulation circuit, and the inverting input terminal and the output terminal of the second operational amplifier are connected through a resistor to form a voltage follower;

[0016] The first diode is forwardly connected between the non-inverting input terminal of the second operational amplifier and the inverting input terminal of the first operational amplifier;

[0017] The second diode is forwardly connected between the inverting input terminal and the output terminal of the first operational amplifier.

[0018] Preferably, the negative feedback regulation circuit includes

[0019] The third op amp, the fourth op amp and the field effect transistor;

[0020] The non-inverting input terminal of the third operational amplifier is connected to the output terminal of the current limiting protection circuit, the inverting input terminal is connected to the output terminal of the fourth operational amplifier, and the output terminal is connected to the gate of the field effect transistor;

[0021] The non-inverting input terminal of the fourth operational amplifier is connected to the source of the field effect tube, a second potentiometer is connected between the inverting input terminal and the common ground, and is connected to the output terminal via a resistor, for adjusting the voltage amplification gain;

[0022] The drain of the field effect tube is connected to the cathode of the semiconductor laser and is used to output a driving current to the semiconductor laser.

[0023] Preferably, the non-inverting input terminal of the third operational amplifier is connected to the output terminal of the second operational amplifier.

[0024] Preferably, a sampling resistor is further connected between the source of the field effect tube and the common ground.

[0025] Preferably, the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier are all operational amplifiers of model OP07C.

[0026] Preferably, the above-mentioned constant current driving circuit further includes a reference voltage source circuit for providing a reference voltage for the digital-to-analog conversion module.

[0027] Preferably, the reference voltage source circuit uses the REF5025 chip.

[0028] Preferably, the microcontroller is connected to the digital-to-analog conversion module using SPI communication.

[0029] Preferably, the microcontroller is an MSP430F149 chip.

[0030] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0031] The present invention discloses a semiconductor laser constant current drive circuit. The LTC2600 chip is used as a digital-to-analog conversion module to output a voltage signal corresponding to a set value of a drive current. The characteristic of the operating voltage range of the LTC2600 chip is utilized to adjust the drive current within a range from milliamperes to amperes, making the circuit applicable to various semiconductor lasers and expanding the application range of the drive circuit. The digital-to-analog conversion module is used to output the voltage signal, which has higher precision and better stability than manual adjustment or PWM wave adjustment in the prior art. A current limiting protection circuit is used to clamp the voltage signal corresponding to the drive current. When the set value exceeds the voltage limit value of the semiconductor laser, the final output drive current is clamped to the limit value, thereby achieving the purpose of protecting the circuit and the laser. The negative feedback regulation circuit of the present invention adopts a linear gain error compensation method, is applicable to lasers of different models, and has higher precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0033] Figure 1 A structural block diagram of a constant current drive circuit according to an embodiment of the present invention

[0034] Figure 2 Schematic diagram of a digital-to-analog conversion module according to an embodiment of the present invention

[0035] Figure 3 Schematic diagram of a current limiting protection circuit according to an embodiment of the present invention

[0036] Figure 4 Schematic diagram of a negative feedback regulation circuit according to an embodiment of the present invention DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] See Figures 1 to 4 , this embodiment provides a semiconductor laser constant current driving circuit, such as Figure 1 As shown, the driving circuit includes

[0039] Microcontroller, digital-to-analog conversion module, current limiting protection circuit and negative feedback regulation circuit;

[0040] The microcontroller sets the driving current setting value through a program, and its output terminal is connected to the input terminal;

[0041] A digital-to-analog conversion module, used to convert the digital signal of the drive current setting value from the microcontroller into a corresponding voltage analog signal, the output end of which is connected to the input end of the current limiting protection circuit;

[0042] The current limiting protection circuit is used to control the voltage signal corresponding to the driving current setting value not to exceed the limit value of the controlled semiconductor laser, and its output end is connected to the input end of the negative feedback regulation circuit;

[0043] Negative feedback regulation circuit, used to stabilize the driving current input to the semiconductor laser;

[0044] It also includes a reference voltage source circuit for providing a stable reference voltage for the digital-to-analog conversion module to ensure the accuracy of the output voltage analog signal;

[0045] like Figure 2 As shown, the digital-to-analog conversion module U3 adopts the LTC2600 chip, the reference voltage source circuit U2 adopts the REF5025 chip, and the microcontroller U1 uses the MSP430F149 chip of the MSP430 series, which communicates with the digital-to-analog conversion module through the SPI protocol. The SPI protocol communication can be achieved through the three pins SCK, SDI, and SDO, so that the digital-to-analog conversion module converts the driving current setting value set by the microcontroller into the corresponding voltage analog signal, that is, the driving current setting value and the voltage analog signal have a one-to-one mapping relationship.

[0046] Current limiting protection circuit such as Figure 3As shown, it includes two OP07C operational amplifiers, namely the first operational amplifier U4 and the second operational amplifier U5, and also includes a first diode D1 and a second diode D2; when the driving current setting value does not exceed the current limit value of the laser, the current limiting protection circuit does not work, and the driving current is output according to the set value; when the limit value is exceeded, the current limiting protection circuit clamps the output to the limit value, so that the driving current is output according to the current limit value of the laser.

[0047] The inverting input terminal of U4 is connected to the output terminal LDIS of the digital-to-analog conversion module U3 through the resistor R2, and the non-inverting input terminal is connected to the first potentiometer R4, which is used to set the voltage limit value of the semiconductor laser;

[0048] The non-inverting input terminal of U5 is connected to the output terminal LDIS of the digital-to-analog conversion module U3 through the resistor R2, and its output terminal is connected to the input terminal of the negative feedback regulation circuit. The inverting input terminal and the output terminal of U5 are connected through the resistor R5 to form a voltage follower;

[0049] The first diode D1 is forward connected between the non-inverting input terminal of U5 and the inverting input terminal of U4;

[0050] The second diode D2 is forwardly connected between the inverting input terminal and the output terminal of U4 via the resistor R3.

[0051] When the current limiting protection circuit is working, R4 is adjusted to set the voltage limit value of the controlled laser. When the voltage analog signal is less than the limit value, U4 outputs a positive voltage, diode D2 is in the off state, and U5, as a voltage follower, outputs the voltage analog signal corresponding to the drive current set value. When the set value is exceeded, U4 outputs a negative voltage, diode D2 is turned on, U4 negative feedback is established, and the output is the limit value. Then, U5 follows and obtains the laser's limit voltage, and the drive current is clamped to achieve overcurrent protection. Capacitors C5, C10, and C11 are used to filter and reduce noise and ripple in the circuit.

[0052] It should be understood that the signal transmitted in the circuit is a voltage signal, so adjusting R4 is essentially adjusting the voltage divider, converting the current limit value of the laser into a corresponding voltage value for current limiting control.

[0053] Negative feedback regulation circuit such as Figure 4 As shown, it includes two operational amplifiers of model OP07C, namely the third operational amplifier U6 and the fourth operational amplifier U7, and also includes a field effect transistor Q1;

[0054] The non-inverting input terminal of U6 is connected to the output terminal of the current limiting protection circuit, that is, the output terminal of U5, the inverting input terminal is connected to the output terminal of U7, and the output terminal is connected to the gate of the field effect transistor Q1;

[0055] The non-inverting input terminal of U7 is connected to the source of Q1, a second potentiometer R8 is connected between the inverting input terminal and the common ground, and is connected to the output terminal through a resistor R10 for adjusting the voltage amplification gain;

[0056] The drain of Q1 is connected to the cathode of the semiconductor laser D3 for outputting a driving current to D3.

[0057] A sampling resistor R7 is also connected between Q1 and the common ground, so that the driving current of D3 is converted into a corresponding voltage value, and U7 samples the voltage through the sampling resistor R7 to achieve negative feedback.

[0058] The working principle of the negative feedback regulation circuit is: the voltage signal output by U5 is loaded into the non-inverting input terminal of U6, U7 samples the voltage corresponding to the driving current through R7, and realizes a voltage amplification of 10 times through resistors R8, R9, and R10. The voltage amplification factor of U7 is calculated as follows: The amplified voltage is output to the inverting input terminal of U6, forming a negative feedback regulation to stabilize the driving current output to the laser D3.

[0059] Due to the error caused by the resistance value itself and the influence of factors such as the trace resistance of the circuit PCB board in actual application, the semiconductor laser current accuracy requirement is relatively high. In order to reduce the impact of these factors on the laser drive circuit, the potentiometer R8 is selected to adjust the amplification gain according to the actual situation. This linear compensation method reduces the error and effectively improves the accuracy of the drive current. It is suitable for semiconductor lasers in different working environments.

[0060] The circuit also uses a method of connecting bypass capacitors with smaller capacitance and electrolytic capacitors with larger capacitance in parallel, such as C14 in parallel with C15, C16 in parallel with C17, and C18 in parallel with C19. This can not only avoid electrostatic shock, but also limit the transient change of the semiconductor laser voltage, and filter and reduce the noise and ripple of the current flowing through the laser.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A semiconductor laser constant current drive circuit, comprising a microcontroller, a digital-to-analog conversion module, a current limiting protection circuit and a negative feedback regulation circuit, characterized in that: The output end of the microcontroller is connected to the input end of the digital-to-analog conversion module for transmitting the driving current setting value, and the digital-to-analog conversion module adopts the LTC2600 chip; The output end of the digital-to-analog conversion module is connected to the input end of the current limiting protection circuit, and is used to convert the driving current setting value into a corresponding voltage signal; The output end of the current limiting protection circuit is connected to the input end of the negative feedback regulation circuit, and is used to control the voltage signal not to exceed the voltage limit value of the controlled semiconductor laser; The negative feedback regulation circuit is used to stabilize the driving current input to the semiconductor laser; The semiconductor laser constant current driving circuit further comprises a reference voltage source circuit, and the reference voltage source circuit is used to provide a reference voltage for the digital-to-analog conversion module; The current limiting protection circuit includes a first operational amplifier, a second operational amplifier, a first diode, and a second diode; the inverting input terminal of the first operational amplifier is connected to the output terminal of the digital-to-analog conversion module, and the non-inverting input terminal is connected to the first potentiometer, for setting the voltage limit value of the semiconductor laser; the non-inverting input terminal of the second operational amplifier is connected to the output terminal of the digital-to-analog conversion module, and the output terminal is connected to the input terminal of the negative feedback regulation circuit, and the inverting input terminal and output terminal of the second operational amplifier are connected through a resistor to form a voltage follower; the first diode is forward connected between the non-inverting input terminal of the second operational amplifier and the inverting input terminal of the first operational amplifier; the second diode is forward connected between the inverting input terminal and the output terminal of the first operational amplifier; The negative feedback regulation circuit includes a third operational amplifier, a fourth operational amplifier, and a field-effect transistor; the non-inverting input terminal of the third operational amplifier is connected to the output terminal of the second operational amplifier, the inverting input terminal of the third operational amplifier is connected to the output terminal of the fourth operational amplifier, and the output terminal is connected to the gate of the field-effect transistor; the non-inverting input terminal of the fourth operational amplifier is connected to the source of the field-effect transistor, a second potentiometer is connected between the inverting input terminal and a common ground, and the fourth operational amplifier is connected to the output terminal via a resistor for adjusting the voltage amplification gain; the drain of the field-effect transistor is connected to the cathode of the semiconductor laser for outputting a driving current to the semiconductor laser, and a sampling resistor is connected between the field-effect transistor and the common ground.

2. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier are all operational amplifiers of model OP07C.

3. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The reference voltage source circuit uses the REF5025 chip.

4. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The microcontroller is connected to the digital-to-analog conversion module using the SPI protocol for communication.

5. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The microcontroller is an MSP430F149 chip.

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