A reflux controlled semiconductor laser

Abstract

The present invention discloses a reflux-controlled semiconductor laser, characterized by comprising an MCU chip, a DAC digital-to-analog converter, a constant current circuit, an LD laser, a PD photodiode, a TIA module, and an ADC analog-to-digital converter. The MCU chip's input is connected to the ADC analog-to-digital converter's output and the output of an external host computer, the DAC digital-to-analog converter's input is connected to the MCU chip's output, the constant current circuit's input is connected to the DAC digital-to-analog converter's output, the LD laser's input is connected to the constant current circuit's output, the PD photodiode's input is connected to the LD laser's output, the TIA module's input is connected to the PD photodiode's output, and the ADC analog-to-digital converter's input is connected to the TIA module's output. The present invention achieves long-term, stable constant current control and temperature control through the rational design of the constant current circuit, temperature compensation module, and TIA module. The present invention uses the host computer to monitor the reflux control of the semiconductor laser throughout the entire process, making it convenient for users.

Description

Technical Field

[0001] The present invention relates to a semiconductor laser, in particular to a reflux controlled semiconductor laser. Background Art

[0002] In recent years, with the continuous development and promotion of laser technology, many traditional manufacturing industries have begun to adopt laser technology to improve processing quality and efficiency. Semiconductor lasers are extremely sensitive devices, and their drive often uses a combination of analog and digital circuits, utilizing technologies such as single-chip microcomputers, FPGAs, and DSPs to automatically control various indicators. With the continuous development and optimization of technology, the application fields of semiconductor lasers are becoming increasingly broad, and the performance requirements for semiconductor lasers are also becoming increasingly higher.

[0003] Laser performance is significantly affected by temperature, with fluctuations in temperature causing sudden changes in directivity, monochromaticity, and coherence. Therefore, lasers require high temperature accuracy, and most current technologies are not very accurate in temperature readings. Furthermore, the ability to output a constant-power optical signal is also a key indicator for evaluating laser performance. However, existing technologies have yet to achieve the design of a semiconductor laser that can output a constant-power optical signal and be temperature-controllable. Summary of the Invention

[0004] In view of this, an embodiment of the present invention provides a reflux controlled semiconductor laser.

[0005] The present invention provides a reflux-controlled semiconductor laser, comprising an MCU chip, a DAC digital-to-analog converter, a constant current circuit, an LD laser, a PD photodiode, a TIA module, and an ADC analog-to-digital converter; the input of the MCU chip is connected to the output of the ADC analog-to-digital converter and the output of an external host computer, the input of the DAC digital-to-analog converter is connected to the output of the MCU chip, the input of the constant current circuit is connected to the output of the DAC digital-to-analog converter, the input of the LD laser is connected to the output of the constant current circuit, the input of the PD photodiode is connected to the output of the LD laser, the input of the TIA module is connected to the output of the PD photodiode, and the input of the ADC analog-to-digital converter is connected to the output of the TIA module;

[0006] The MCU chip is used to receive instructions from the host computer, generate a first digital voltage signal and send it to the DAC digital-to-analog converter;

[0007] The DAC digital-to-analog converter is used to convert the first digital voltage signal into a first analog voltage signal;

[0008] The constant current circuit is used to generate a corresponding stable current value according to the analog voltage signal;

[0009] The LD laser is used to receive a stable current value and output an optical signal;

[0010] The PD photodiode is used to detect the optical power value of the optical signal output by the LD laser and generate a corresponding photocurrent signal according to the optical power value;

[0011] The TIA module generates a second analog voltage signal according to the photocurrent signal;

[0012] The ADC analog-to-digital converter converts the analog voltage signal into a second digital voltage signal and transmits it to the MCU chip. The MCU chip adjusts the output first digital voltage signal according to the second digital voltage signal.

[0013] Furthermore, the constant current circuit specifically includes an operational amplifier negative feedback loop and a low-side current detection circuit;

[0014] The operational amplifier negative feedback loop includes an operational amplifier U1B, resistors R1, R2, R3, R4, R5, R6, capacitors C1, C2, C3, C4, and a transistor Q1; the low-side circuit detection circuit includes an operational amplifier U1A, resistors R7, R8, R9, R10, R11, R12, and a capacitor C6, and the constant current circuit also includes a diode D1, a transistor Q2, and resistors R13 and R14;

[0015] Among them, the sixth terminal of the operational amplifier U1B is connected to one end of the resistor R8 and one end of the resistor R6; the other end of the resistor R6 is connected to the capacitor C3; the two ends of the resistor R6 are connected in parallel with the capacitor C4; the seventh terminal of the operational amplifier U1B is connected to the other end of the capacitor C3, one end of the resistor R1, and one end of the resistor R5; the other end of the resistor R5 is connected in series with the capacitor C2 and then to ground; the other end of the resistor R1 is connected to the base of the transistor Q1 and one end of the resistor R3; the collector of the transistor Q1 is connected to one end of the diode D1 and the output LD_N; the other end of the diode D1 is connected to the digital power supply LD_VCC; the fifth terminal of the operational amplifier U1B is connected to one end of the resistor R4, one end of the capacitor C1, and one end of the resistor R2; the other end of the capacitor C1 is grounded; the other end of the resistor R4 is grounded; the other end of the resistor R2 is connected to the control signal input LD_CC_CTRL;

[0016] The first terminal of the operational amplifier U1A is connected to the other end of the resistor R8, one end of the resistor R12 and the sense current input LD_CURR_SENSE; the second terminal of the operational amplifier U1A is connected to the other end of the resistor R12 and one end of the resistor R11; the third terminal of the operational amplifier U1A is connected to one end of the resistor R7 and one end of the resistor R9; the fourth terminal of the operational amplifier U1A is grounded; the eighth terminal of the operational amplifier U1A is connected to the capacitor C6 and the analog power supply AVCC; the other end of the capacitor C6 is grounded; the other end of the resistor R7 is grounded; the other end of the transistor Q1 is connected to the other end of the resistor R3, the other end of the resistor R9 and one end of the resistor R10; the collector of the transistor Q2 is connected to the other end of the resistor R11 and the other end of the resistor R10; the emitter of the transistor Q2 is grounded and one end of the resistor R14; the base of the transistor Q2 is connected to the other end of the resistor R14 and one end of the resistor R13; the other end of the resistor R13 is connected to the switch signal LD_ON.

[0017] Furthermore, it also includes a temperature compensation module, which is connected to the MCU chip and the LD laser, including operational amplifiers OP1, OP2, resistors R19, R20, R21, R23, R26, R28, R29, R30, a thermistor NTC, and capacitors C13 and C14;

[0018] Among them, the negative input terminal of the operational amplifier OP1 is connected to one end of the resistor R23; the positive input terminal of the operational amplifier OP1 is connected to one end of the thermistor NTC and one end of the resistor R26; the other end of the resistor R26 is grounded; the other end of the thermistor NTC is connected to the reference voltage input VREFA; the output terminal of the operational amplifier OP1 is connected to the other end of the resistor R23 and one end of the resistor R19; the negative input terminal of the operational amplifier OP2 is connected to the other end of the resistor R19 and one end of the resistor R21; the other end of the resistor R21 is connected to the capacitor C14; the positive input terminal of the operational amplifier OP2 is connected to one end of the resistor R28 and one end of the resistor R20; the output terminal of the operational amplifier OP2 is connected to the other end of the capacitor C14 and the output OUT; the other end of the resistor R28 is connected to the MCU control voltage output terminal LD_TEMP_SET; the other end of the resistor R20 is connected to the capacitor C13, the other end of the capacitor C13 is connected to one end of the resistor R29 and one end of the resistor R30; the other end of the resistor R30 is grounded; the other end of the resistor R29 is connected to the reference voltage output VREF;

[0019] The thermistor NTC is integrated into the LD laser and is used to sense the temperature change of the LD laser; the resistance of the resistor R23 is 0Ω, and is used to form the operational amplifier OP1 into a voltage follower, and the operational amplifier OP2 into an integrator.

[0020] Furthermore, it also includes a TEC temperature control module; the TEC temperature control module is connected to the temperature compensation module and the MCU chip, and is used to control the operation of the temperature compensation module, specifically including the following steps:

[0021] Obtaining the resistance value of the thermistor NTC; the preset target temperature reference voltage is set by the host computer;

[0022] The resistance value of the thermistor NTC is converted into a temperature voltage signal LD_TEMP_SENSE through the operational amplifier OP1;

[0023] The temperature voltage signal LD_TEMP_SENSE is compared with a preset target temperature reference voltage to adjust the driving voltage value of the control voltage output terminal LD_TEMP_SET.

[0024] Furthermore, the TIA module includes a feedback capacitor C F , feedback resistor R F and an operational amplifier OP-AMP; the negative input terminal of the operational amplifier OP-AMP is connected to the output terminal of the PD photodiode, the feedback capacitor C F One end of the feedback resistor R F The positive input terminal of the operational amplifier OP-AMP is connected to the input terminal of the PD photodiode and the reference voltage V REF The power supply terminals of the operational amplifier OP-AMP are connected to the power input V CC and V EE The output terminal of the operational amplifier OP-AMP is connected to the feedback capacitor C F The other end of the feedback resistor RF and the second analog voltage signal V OUT .

[0025] Furthermore, the MCU chip adjusts the output first digital voltage signal according to the second digital voltage signal, specifically through a PID module, including the following steps:

[0026] Performing proportional operation, integral operation and differential operation on the second digital voltage signal to obtain a proportional result, an integral result and a differential result;

[0027] Add the proportional result, the integral result and the differential result to obtain the regulated digital voltage value;

[0028] The MCU chip adjusts the first digital voltage signal according to the adjusted digital voltage value.

[0029] Furthermore, the method further comprises the following steps:

[0030] Determine whether a mutation occurs in the second digital voltage signal received by the MCU chip; the mutation refers to a difference between the second digital voltage signal received at this moment and the second digital voltage signal at the previous moment being greater than a preset voltage threshold; the preset voltage threshold is set by the host computer;

[0031] When the second digital voltage signal suddenly changes, the PID module stops working.

[0032] Furthermore, the MCU chip establishes communication transmission with the host computer through a serial port DMA mode.

[0033] Embodiments of the present invention have the following beneficial effects: A reflux-controlled semiconductor laser of the present invention achieves long-term stable constant current control and temperature control through a rational design of a constant current circuit, a temperature compensation module, and a TIA module, and achieves constant-power optical signal output based on the constant current. The present invention utilizes a host computer to monitor the reflux control of the semiconductor laser throughout the process, enabling visual operation of the semiconductor laser and facilitating user use.

[0034] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] Figure 1 This is a basic data structure diagram of a reflux controlled semiconductor laser of the present invention;

[0037] Figure 2 This is an overall structural diagram of a constant current circuit in a reflux controlled semiconductor laser of the present invention;

[0038] Figure 3 It is a partial enlarged view of a negative feedback loop in a constant current circuit of a reflux-controlled semiconductor laser according to the present invention;

[0039] Figure 4 It is a partial enlarged view of a low-side current detection circuit in a constant current circuit of a reflux-controlled semiconductor laser of the present invention;

[0040] Figure 5 This is a diagram of the overall circuit structure of a TEC temperature control module in a reflux controlled semiconductor laser of the present invention;

[0041] Figure 6This is a schematic diagram of the maximum TEC voltage limit of a TEC temperature control module in a reflux controlled semiconductor laser of the present invention;

[0042] Figure 7 This is a schematic diagram of the maximum TEC current limit of a TEC temperature control module in a reflux controlled semiconductor laser of the present invention;

[0043] Figure 8 This is a diagram showing the overall structure of a temperature compensation module in a reflux controlled semiconductor laser according to the present invention;

[0044] Figure 9 This is a schematic diagram of a TIA module in a reflux controlled semiconductor laser of the present invention;

[0045] Figure 10 This is a schematic diagram of the calculation flow of the PID module in the MCU chip of the reflux control semiconductor laser of the present invention.

[0046] Figure 11 The present invention is a schematic diagram of the control process of the host computer in a reflux controlled semiconductor laser. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0048] like Figure 1 As shown, an embodiment of the present invention provides a reflux controlled semiconductor laser, including an MCU chip, a DAC digital-to-analog converter, a constant current circuit, an LD laser, a PD photodiode, a TIA module and an ADC analog-to-digital converter; the input of the MCU chip is connected to the output of the ADC analog-to-digital converter and the output of an external host computer, the input of the DAC digital-to-analog converter is connected to the output of the MCU chip, the input of the constant current circuit is connected to the output of the DAC digital-to-analog converter, the input of the LD laser is connected to the output of the constant current circuit, the input of the PD photodiode is connected to the output of the LD laser, the input of the TIA module is connected to the output of the PD photodiode, and the input of the ADC analog-to-digital converter is connected to the output of the TIA module.

[0049] The MCU chip is used to receive instructions from the host computer, generate a first digital voltage signal and send it to the DAC digital-to-analog converter;

[0050] The DAC digital-to-analog converter is used to convert the first digital voltage signal into a first analog voltage signal;

[0051] The constant current circuit is used to generate a corresponding stable current value according to the analog voltage signal;

[0052] LD laser is used to receive stable current value and output optical signal;

[0053] The PD photodiode is used to detect the optical power value of the optical signal output by the LD laser and generate a corresponding photocurrent signal according to the optical power value;

[0054] The TIA module generates a second analog voltage signal according to the photocurrent signal;

[0055] The ADC analog-to-digital converter converts the analog voltage signal into a second digital voltage signal and transmits it to the MCU chip. The MCU chip adjusts the output first digital voltage signal according to the second digital voltage signal.

[0056] The semiconductor laser of this embodiment achieves the following effects: A host computer sends a command, and after receiving the command, the MCU chip uses the second digital voltage signal obtained by the first sampling after setting the current as the target value. This signal is continuously adjusted and maintained in conjunction with the temperature compensation module, so that the first digital voltage signal output by the circuit maintains this value. The output first digital voltage signal then passes through the DAC digital-to-analog converter, converting the first digital voltage signal into a first analog voltage signal. This signal is then converted into a stable current value through a constant current circuit, and then sent to the LD laser. The PD photodiode detects the optical power value of the output optical signal and generates a photocurrent signal. The TIA module generates a second analog voltage signal based on the photocurrent signal and sends it to the ADC analog-to-digital converter. The ADC converts the second analog voltage signal into a second digital voltage signal, which is then fed back to the MCU chip.

[0057] The core of this embodiment is to design corresponding constant current circuit, temperature control circuit, TIA module, MCU chip and host computer for semiconductor laser.

[0058] The overall circuit diagram of the constant current circuit is as follows Figure 2 As shown in the figure, the constant current circuit specifically includes an op amp negative feedback loop and a low-side current detection circuit. In the constant current circuit design, the first digital voltage signal transmitted by the MCU chip is converted from digital to analog via a DAC (digital-to-analog converter). After conversion, it is converted into a stable current value by the constant current circuit. This stable current value changes in real time with the input first analog voltage signal. Therefore, the performance of the constant current circuit is affected by the DAC (digital-to-analog converter). The higher the signal conversion accuracy of the DAC (digital-to-analog converter), the more accurate the constant current setting of the constant current circuit.

[0059] like Figure 3 、 Figure 4As shown, the op amp negative feedback loop includes an operational amplifier U1B, resistors R1, R2, R3, R4, R5, R6, capacitors C1, C2, C3, C4, and transistor Q1; the low-side circuit detection circuit includes an operational amplifier U1A, resistors R7, R8, R9, R10, R11, R12, and capacitor C6, and the constant current circuit also includes a diode D1, transistor Q2, and resistors R13 and R14.

[0060] Among them, the sixth terminal of the operational amplifier U1B is connected to one end of the resistor R8 and one end of the resistor R6; the other end of the resistor R6 is connected to the capacitor C3; the two ends of the resistor R6 are connected in parallel with the capacitor C4; the seventh terminal of the operational amplifier U1B is connected to the other end of the capacitor C3, one end of the resistor R1, and one end of the resistor R5; the other end of the resistor R5 is connected in series with the capacitor C2 and then to ground; the other end of the resistor R1 is connected to the base of the transistor Q1 and one end of the resistor R3; the collector of the transistor Q1 is connected to one end of the diode D1 and the output LD_N; the other end of the diode D1 is connected to the digital power supply LD_VCC; the fifth terminal of the operational amplifier U1B is connected to one end of the resistor R4, one end of the capacitor C1, and one end of the resistor R2; the other end of the capacitor C1 is grounded; the other end of the resistor R4 is grounded; the other end of the resistor R2 is connected to the control signal input LD_CC_CTRL;

[0061] The first terminal of the operational amplifier U1A is connected to the other end of the resistor R8, one end of the resistor R12 and the sense current input LD_CURR_SENSE; the second terminal of the operational amplifier U1A is connected to the other end of the resistor R12 and one end of the resistor R11; the third terminal of the operational amplifier U1A is connected to one end of the resistor R7 and one end of the resistor R9; the fourth terminal of the operational amplifier U1A is grounded; the eighth terminal of the operational amplifier U1A is connected to the capacitor C6 and the analog power supply AVCC; the other end of the capacitor C6 is grounded; the other end of the resistor R7 is grounded; the other end of the transistor Q1 is connected to the other end of the resistor R3, the other end of the resistor R9 and one end of the resistor R10; the collector of the transistor Q2 is connected to the other end of the resistor R11 and the other end of the resistor R10; the emitter of the transistor Q2 is grounded and one end of the resistor R14; the base of the transistor Q2 is connected to the other end of the resistor R14 and one end of the resistor R13; the other end of the resistor R13 is connected to the switch signal LD_ON.

[0062] In this embodiment, when the operational amplifier negative feedback loop is in a deep negative feedback state, the steady-state formula of the loop can be obtained by virtual short and virtual break, and U LD CC CTRL It reflects the size of the stable current set in the host computer. From this, it can be seen that the LD working current is exactly equal to the current set by the host computer, which means that the host computer has realized the function of real-time monitoring and adjustment of the LD working current.

[0063] Since the stability of semiconductor laser characteristics (wavelength, average optical power, efficiency, extinction ratio, etc.) depends on the temperature of the laser, as long as the temperature drifts, the wavelength of the semiconductor laser will change and the conversion efficiency will decrease.

[0064] To control the temperature of a semiconductor laser, a loop consisting of an NTC thermistor, a temperature compensation module, and a TEC temperature control module is required. The thermistor's resistance changes proportionally with temperature (either inversely or directly, depending on the type of TC thermistor, N). When configured as a voltage divider, it can be used to convert temperature into a voltage. The TEC temperature control module compares this feedback voltage with a reference voltage representing the target temperature and then controls the current flowing through the TEC temperature control module, thereby adjusting the amount of heat transferred by the TEC temperature control module.

[0065] TEC temperature control module specific circuit reference Figure 5 The TEC temperature control module is connected to the temperature compensation module and the MCU chip to control the operation of the temperature compensation module. Specifically, the following steps are included:

[0066] Obtain the resistance value of the thermistor NTC; preset the target temperature reference voltage through the host computer;

[0067] The resistance value of the thermistor NTC is converted into a temperature voltage signal LD_TEMP_SENSE through the operational amplifier OP1;

[0068] The temperature voltage signal LD_TEMP_SENSE is compared with a preset target temperature reference voltage to adjust the driving voltage value of the control voltage output terminal LD_TEMP_SET.

[0069] To ensure laser temperature stability, this embodiment integrates an NTC thermistor and a TEC hotspot cooler into the LD laser. The NTC thermistor's resistance changes proportionally with temperature. This property is used to convert temperature into a voltage. The TEC controller then compares this voltage with a target temperature reference voltage and adjusts the amount of heat transferred by the TEC (heating or cooling) by controlling the current flowing through the TEC. The TEC controller reads the feedback voltage from the NTC thermistor and provides a drive voltage to the TEC. An MCU chip monitors and controls the thermal loop.

[0070] In this embodiment, the TEC temperature control module uses the ADN8834 chip for temperature control. In particular, a voltage limiter and / or a voltage limiter can be applied to the VLIM / SD pin to set the maximum voltage across the TEC temperature control module and the current flowing through the TEC temperature control module to protect the TEC temperature control module. The circuit structure of the voltage limiter is shown in FIG. Figure 6 shown. Figure 6 Medium V LIMC Indicates the cooling limit, V LIMHIndicates the heating limit, the two values ​​can be asymmetric.

[0071] The circuit structure of the voltage limiter is as follows Figure 7 As shown in the figure, the current flowing through the TEC temperature control module is set by the resistor divider. When the ADN8834 drives the TEC temperature control module to run in the cooling direction, the internal current sink circuit connected to ILIM will generate a current of about 40μA to obtain a larger cooling current.

[0072] Temperature Compensation Module Reference Figure 8 In this embodiment, the temperature compensation module is connected to the TEC temperature control module and the NTC chip, including operational amplifiers OP1 and OP2, resistors R19, R20, R21, R23, R26, R28, R29, and R30, a thermistor NTC, and capacitors C13 and C14;

[0073] Among them, the negative input terminal of the operational amplifier OP1 is connected to one end of the resistor R23; the positive input terminal of the operational amplifier OP1 is connected to one end of the thermistor NTC and one end of the resistor R26; the other end of the resistor R26 is grounded; the other end of the thermistor NTC is connected to the reference voltage input VREFA; the output terminal of the operational amplifier OP1 is connected to the other end of the resistor R23 and one end of the resistor R19; the negative input terminal of the operational amplifier OP2 is connected to the other end of the resistor R19 and one end of the resistor R21; the other end of the resistor R21 is connected to the capacitor C14; the positive input terminal of the operational amplifier OP2 is connected to one end of the resistor R28 and one end of the resistor R20; the output terminal of the operational amplifier OP2 is connected to the other end of the capacitor C14 and the output OUT; the other end of the resistor R28 is connected to the MCU control voltage output terminal LD_TEMP_SET; the other end of the resistor R20 is connected to the capacitor C13, the other end of the capacitor C13 is connected to one end of the resistor R29 and one end of the resistor R30; the other end of the resistor R30 is grounded; the other end of the resistor R29 is connected to the reference voltage output VREF;

[0074] In this embodiment, the negative input terminal of operational amplifier OP1 and its output terminal are short-circuited via 0Ω resistor R23 to form a voltage follower, which transmits the voltage value fed back by the NTC thermistor to the integrator formed by operational amplifier OP2. The voltage follower of operational amplifier OP1 is a buffer stage. Its positive input terminal IN1P presents a high-impedance state to the NTC voltage divider circuit, and its output terminal OUT1 presents a low-impedance state to the subsequent circuit, acting as a constant voltage source, thereby isolating the previous and subsequent circuits. This prevents any impact on the NTC voltage divider value. Operational amplifier OP2 forms an integrator. LD_TEMP_SET is the output terminal for the MCU chip control voltage, and LD_TEMP_SENSE is used by the MCU to monitor temperature data.

[0075] The circuit structure of the TIA module is as follows Figure 9As shown. The TIA module includes feedback capacitor C F , feedback resistor R F And operational amplifier OP-AMP; the negative input terminal of operational amplifier OP-AMP is connected to the output terminal of PD photodiode and feedback capacitor C F One end of the feedback resistor R F One end of the operational amplifier OP-AMP; the positive input end is connected to the input end of the PD photodiode and the reference voltage V REF ; The power supply terminals of the operational amplifier OP-AMP are connected to the power input V CC and V EE ; The output of the operational amplifier OP-AMP is connected to the feedback capacitor C F The other end of the feedback resistor RF and the second analog voltage signal V OUT .

[0076] The circuit of the TIA module in this embodiment consists of a feedback capacitor C F , feedback resistor R F This circuit is composed of a front-end amplifier (OP-AMP) for the PD photodiode in a semiconductor laser. It converts the photocurrent signal from the PD photodiode into a second analog voltage signal. This is achieved by using a transimpedance across the operational amplifier. The converted voltage is then connected to a DAC (digital-to-analog converter). The MCU chip reads the converted second digital voltage signal and uses it as a feedback signal for reflux control.

[0077] In this embodiment, the MCU chip adjusts the output first digital voltage signal according to the second digital voltage signal, specifically through the PID module, such as Figure 10 As shown, the following steps are included:

[0078] Performing proportional operation, integral operation and differential operation on the second digital voltage signal to obtain a proportional result, an integral result and a differential result;

[0079] Add the proportional result, the integral result and the differential result to obtain the regulated digital voltage value;

[0080] The MCU chip adjusts the first digital voltage signal according to the adjusted digital voltage value.

[0081] In this embodiment, the adjustment amplitude of the first digital voltage signal by the MCU chip is determined by the PID module. Each time the feedback of the second digital voltage signal is received, the current voltage value is read and the second digital voltage signals of the previous two times are recorded. Through the calculation of the PID module, the adjustment of the first digital voltage signal that needs to be set can be obtained, so that the power value of the LD laser can be adjusted and stabilized.

[0082] In particular, to protect the LD laser, the adjustment of the first digital voltage signal in this embodiment further includes the following steps:

[0083] Determine whether a mutation occurs in the second digital voltage signal received by the MCU chip; a mutation means that the difference between the second digital voltage signal received at this moment and the second digital voltage signal at the previous moment is greater than a preset voltage threshold; the preset voltage threshold is set by the host computer;

[0084] When the second digital voltage signal suddenly changes, the PID module stops working.

[0085] In this embodiment, the MCU chip and the host computer establish communication transmission through the serial port DMA method. The control process of the host computer to the MCU chip is as follows: Figure 11 The host computer can customize the sending and receiving instructions to achieve the following functions:

[0086] 1. Set current: used to control the actual output stable current value of the constant current circuit;

[0087] 2. Set the maximum current: used to control the upper limit of the output current value of the constant current circuit;

[0088] 3. Set the output mode: used to control the start / stop of the PID module code in the MCU chip;

[0089] 4. Set the input feedback source: used to control the readback channel of the TIA module receiving the photocurrent, select the feedback source (PD1 / PD2, etc.)

[0090] 5. Dynamically adjust PID parameters: modify the parameters of the PID module in the MCU chip

[0091] 6. Real-time display of the second digital voltage signal, temperature, set current, etc.

[0092] In some optional embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided in an exemplary manner for the purpose of providing a more comprehensive understanding of the technology. The disclosed method is not limited to the operation and logic flow presented herein. Optional embodiments are contemplated in which the order of the various operations is changed and the sub-operations described as a part of a larger operation are performed independently.

[0093] Furthermore, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise indicated, one or more of the functions and / or features described may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in separate physical devices or software modules. It will also be understood that a detailed discussion of the actual implementation of each module is not necessary for understanding the present invention. More specifically, given the properties, functions, and internal relationships of the various functional modules in the devices disclosed herein, the actual implementation of the module will be understood within the ordinary skill of an engineer. Therefore, a person skilled in the art using ordinary skill will be able to implement the present invention set forth in the claims without undue experimentation. It will also be understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.

[0094] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0095] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

[0096] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A reflux controlled semiconductor laser, characterized in that: It includes an MCU chip, a DAC digital-to-analog converter, a constant current circuit, an LD laser, a PD photodiode, a TIA module and an ADC analog-to-digital converter; the input of the MCU chip is connected to the output of the ADC analog-to-digital converter and the output of an external host computer, the input of the DAC digital-to-analog converter is connected to the output of the MCU chip, the input of the constant current circuit is connected to the output of the DAC digital-to-analog converter, the input of the LD laser is connected to the output of the constant current circuit, the input of the PD photodiode is connected to the output of the LD laser, the input of the TIA module is connected to the output of the PD photodiode, and the input of the ADC analog-to-digital converter is connected to the output of the TIA module; The MCU chip is used to receive instructions from the host computer, generate a first digital voltage signal and send it to the DAC digital-to-analog converter; The DAC digital-to-analog converter is used to convert the first digital voltage signal into a first analog voltage signal; The constant current circuit is used to generate a corresponding stable current value according to the analog voltage signal; The LD laser is used to receive a stable current value and output an optical signal; The PD photodiode is used to detect the optical power value of the optical signal output by the LD laser and generate a corresponding photocurrent signal according to the optical power value; The TIA module generates a second analog voltage signal according to the photocurrent signal; The ADC analog-to-digital converter converts the second analog voltage signal into a second digital voltage signal and transmits the second digital voltage signal to the MCU chip, and the MCU chip adjusts the output first digital voltage signal according to the second digital voltage signal; The TIA module includes a feedback capacitor C F , feedback resistor R F and an operational amplifier OP-AMP; the negative input terminal of the operational amplifier OP-AMP is connected to the output terminal of the PD photodiode, the feedback capacitor C F One end of the feedback resistor R F The positive input terminal of the operational amplifier OP-AMP is connected to the input terminal of the PD photodiode and the reference voltage V REF The power supply terminals of the operational amplifier OP-AMP are connected to the power input V CC and V EE The output terminal of the operational amplifier OP-AMP is connected to the feedback capacitor C F The other end of the feedback resistor R F The other end and the second analog voltage signal V OUT .

2. A reflux controlled semiconductor laser according to claim 1, characterized in that: The constant current circuit specifically includes an operational amplifier negative feedback loop and a low-side current detection circuit; The operational amplifier negative feedback loop includes an operational amplifier U1B, resistors R1, R2, R3, R4, R5, R6, capacitors C1, C2, C3, C4, and a transistor Q1; the low-side current detection circuit includes an operational amplifier U1A, resistors R7, R8, R9, R10, R11, R12, and a capacitor C6, and the constant current circuit also includes a diode D1, a transistor Q2, and resistors R13 and R14; Among them, the sixth terminal of the operational amplifier U1 B is connected to one end of the resistor R8 and one end of the resistor R6; the other end of the resistor R6 is connected to the capacitor C3; the two ends of the resistor R6 are connected in parallel with the capacitor C4; the seventh terminal of the operational amplifier U1 B is connected to the other end of the capacitor C3, one end of the resistor R1, and one end of the resistor R5; the other end of the resistor R5 is connected in series with the capacitor C2 and then to ground; the other end of the resistor R1 is connected to the base of the transistor Q1 and one end of the resistor R3; the collector of the transistor Q1 is connected to one end of the diode D1 and the output LD_N; the other end of the diode D1 is connected to the digital power supply LD_VCC; the fifth terminal of the operational amplifier U1 B is connected to one end of the resistor R4, one end of the capacitor C1, and one end of the resistor R2; the other end of the capacitor C1 is grounded; the other end of the resistor R4 is grounded; the other end of the resistor R2 is connected to the control signal input LD_CC_CTRL; The first terminal of the operational amplifier U1A is connected to the other end of the resistor R8, one end of the resistor R12 and the sense current input LD_CURR_SENSE; the second terminal of the operational amplifier U1A is connected to the other end of the resistor R12 and one end of the resistor R11; the third terminal of the operational amplifier U1A is connected to one end of the resistor R7 and one end of the resistor R9; the fourth terminal of the operational amplifier U1A is grounded; the eighth terminal of the operational amplifier U1A is connected to the capacitor C6 and the analog power supply AVCC; the other end of the capacitor C6 is grounded; the other end of the resistor R7 is grounded; the other end of the transistor Q1 is connected to the other end of the resistor R3, the other end of the resistor R9 and one end of the resistor R10; the collector of the transistor Q2 is connected to the other end of the resistor R11 and the other end of the resistor R10; the emitter of the transistor Q2 is grounded and one end of the resistor R14; the base of the transistor Q2 is connected to the other end of the resistor R14 and one end of the resistor R13; the other end of the resistor R13 is connected to the switch signal LD_ON.

3. The reflux controlled semiconductor laser according to claim 1, characterized in that: It also includes a temperature compensation module, which is connected to the MCU chip and the LD laser, including operational amplifiers OP1, OP2, resistors R19, R20, R21, R23, R26, R28, R29, R30, a thermistor NTC, and capacitors C13 and C14; Among them, the negative input terminal of the operational amplifier OP1 is connected to one end of the resistor R23; the positive input terminal of the operational amplifier OP1 is connected to one end of the thermistor NTC and one end of the resistor R26; the other end of the resistor R26 is grounded; the other end of the thermistor NTC is connected to the reference voltage input VREFA; the output terminal of the operational amplifier OP1 is connected to the other end of the resistor R23 and one end of the resistor R19; the negative input terminal of the operational amplifier OP2 is connected to the other end of the resistor R19 and one end of the resistor R21; the other end of the resistor R21 is connected to the capacitor C14; the positive input terminal of the operational amplifier OP2 is connected to one end of the resistor R28 and one end of the resistor R20; the output terminal of the operational amplifier OP2 is connected to the other end of the capacitor C14 and the output OUT; the other end of the resistor R28 is connected to the MCU control voltage output terminal LD_TEMP_SET; the other end of the resistor R20 is connected to the capacitor C13, the other end of the capacitor C13 is connected to one end of the resistor R29 and one end of the resistor R30; the other end of the resistor R30 is grounded; the other end of the resistor R29 is connected to the reference voltage output VREF; The thermistor NTC is integrated into the LD laser and is used to sense the temperature change of the LD laser; the resistance of the resistor R23 is 0Ω, and is used to form the operational amplifier OP1 into a voltage follower, and the operational amplifier OP2 into an integrator.

4. The reflux controlled semiconductor laser according to claim 3, characterized in that: It also includes a TEC temperature control module; the TEC temperature control module is connected to the temperature compensation module and the MCU chip, and is used to control the operation of the temperature compensation module, specifically including the following steps: Get the resistance value of the thermistor NTC; The resistance value of the thermistor NTC is converted into a temperature voltage signal LD_TEMP_SENSE through the operational amplifier OP1; The temperature voltage signal LD_TEMP_SENSE is compared with a preset target temperature reference voltage to adjust the driving voltage value of the control voltage output terminal LD_TEMP_SET; the preset target temperature reference voltage is set by a host computer.

5. The reflux controlled semiconductor laser according to claim 1, characterized in that: The MCU chip adjusts the output first digital voltage signal according to the second digital voltage signal, specifically through a PID module, including the following steps: Performing proportional operation, integral operation and differential operation on the second digital voltage signal to obtain a proportional result, an integral result and a differential result; Add the proportional result, the integral result and the differential result to obtain the regulated digital voltage value; The MCU chip adjusts the first digital voltage signal according to the adjusted digital voltage value.

6. The reflux controlled semiconductor laser according to claim 5, characterized in that: The following steps are also included: Determine whether a mutation occurs in the second digital voltage signal received by the MCU chip; the mutation refers to a difference between the second digital voltage signal received at this moment and the second digital voltage signal at the previous moment being greater than a preset voltage threshold; the preset voltage threshold is set by the host computer; When the second digital voltage signal suddenly changes, the PID module stops working.

7. The reflux controlled semiconductor laser according to claim 1, characterized in that: The MCU chip establishes communication transmission with the host computer through the serial port DMA mode.

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