Laser temperature control circuit control method with multiple protection

Abstract

The invention discloses a laser temperature control circuit control method with multiple protection. The laser temperature control circuit control method comprises the steps that a microcontroller converts a set temperature into a set voltage signal and inputs the set voltage signal to a given port of a laser temperature control chip; the voltage of a thermistor in the laser is detected in real time through the protection module; and the detected voltage signal of the thermistor is used as a feedback signal, the set voltage signal is used as a given signal, and the temperature control of the laser is realized through a PID controller of the laser temperature control chip. The laser temperature control circuit with multiple protection can realize accurate and stable temperature control of the semiconductor laser, monitors the operation state of the laser, ensures safe operation of the laser, and has the characteristics of high precision and resolution, good stability and multiple protection.

Description

Technical Field

[0001] The present invention relates to the technical field of laser temperature control, and particularly relates to a control method for a laser temperature control circuit with multiple protections. Background Art

[0002] Tunable diode laser absorption spectroscopy is a spectroscopic measurement technology based on tunable diode lasers. This technology utilizes the unique narrow linewidth and the characteristic that the wavelength varies with the injection current of the diode laser to achieve precise measurement of single or several adjacent absorption lines of gas molecules. The accurate output of the wavelength of the diode laser is inseparable from the precise control of temperature and current. Therefore, it is first necessary to achieve precise and stable control of the laser temperature.

[0003] However, in the current laser temperature control process, due to the influence of characteristics such as device temperature drift, the temperature control accuracy is not high. Most existing systems use analog setting or low-resolution DAC adjustment, and cannot achieve high-resolution on-line temperature adjustment. Moreover, problems such as laser wire breakage and temperature runaway are not considered, and the laser protection measures are not perfect.

[0004] Therefore, how to achieve precise and stable control of the temperature inside the laser is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In order to solve the above technical problems, the present application proposes the following technical solutions:

[0006] An embodiment of the present application provides a control method for a laser temperature control circuit with multiple protections, including:

[0007] The microcontroller converts the set temperature into a set voltage signal and inputs it to the given port of the laser temperature control chip;

[0008] The protection module is used to detect the voltage of the thermistor inside the laser in real time;

[0009] Taking the detected voltage signal of the thermistor as the feedback signal and the set voltage signal as the given signal, the temperature control of the laser is realized through the PID controller of the laser temperature control chip.

[0010] In a possible implementation manner, the microcontroller converts the set temperature into a set voltage signal and inputs it to the given port of the laser temperature control chip, including:

[0011] After initializing the laser temperature control circuit, the microcontroller reads the temperature parameters stored in the internal memory;

[0012] According to the thermistor parameter table, the temperature parameter is converted into the voltage value corresponding to the temperature;

[0013] After inputting the binary digital quantity corresponding to the voltage value into a digital-to-analog converter through the SPI bus communication protocol for conversion into an analog voltage signal, the analog voltage signal is used as a set voltage signal and input to the given port of the laser temperature control chip.

[0014] In a possible implementation manner, the digital-to-analog conversion module uses an AD5683 chip. The VDD port of the AD5683 chip is electrically connected to the first end of the first decoupling capacitor, the first end of the second decoupling capacitor, and the RESET port of the AD5683 chip respectively. The VDD port of the AD5683 chip is electrically connected to the VDD power supply. The SDO port of the DAC chip is electrically connected to the SPI-DI port of the MCU. The SDI port, SYNC port, and SCLK port of the AD5683 chip are electrically connected to the SPI-CLK port, SPI-DQS port, and SPI-DO port of the MCU respectively. The VBEF port of the AD5683 chip is electrically connected to the first end of the third decoupling capacitor and the VREF power supply respectively. The VOUT port of the AD5683 chip is electrically connected to the FB+ given port of the laser temperature control chip. The FB+ given port of the laser temperature control chip is electrically connected to the first end of the first resistor and the first end of the fourth decoupling capacitor respectively. The second end of the first decoupling capacitor, the second end of the second decoupling capacitor, the second end of the third decoupling capacitor, the second end of the fourth decoupling capacitor, the second end of the first resistor, and the LDAC port and GND port of the DAC chip are grounded.

[0015] In a possible implementation manner, taking the detected voltage signal of the thermistor as a feedback signal and the set voltage signal as a given signal, the temperature control of the laser is realized through the PID controller of the laser temperature control chip, including:

[0016] Taking the difference between the set voltage signal and the thermistor voltage signal as an error signal and inputting it to the given input of the PID controller of the laser temperature control chip;

[0017] Determining the magnitude and direction of the current of the semiconductor cooler in the laser through the PID controller of the laser temperature control chip to realize the temperature control of the laser.

[0018] In a possible implementation manner, the determining the magnitude and direction of the current of the semiconductor cooler in the laser through the PID controller of the laser temperature control chip to realize the temperature control of the laser includes:

[0019] When the thermistor voltage is less than the set voltage, it is input to the internal PWM controller and gate controller of the chip through the CTLI port of the laser temperature control chip to drive the bridge circuit. The laser temperature control chip outputs a positive current, the semiconductor cooler cools, and the temperature decreases;

[0020] Or,

[0021] When the thermistor voltage is greater than the set voltage, it is input into the internal PWM controller and gate controller of the laser temperature control chip through the CTLI port, driving the bridge circuit. The laser temperature control chip outputs a reverse current, the semiconductor refrigerator generates heat, and the temperature rises.

[0022] In a possible implementation, the laser temperature control chip uses MAX1978. The INOUT port of the MAX1978 is electrically connected to the first end of the second resistor and the CTLI port respectively. The INT- port of the MAX1978 is electrically connected to the first end of the first capacitor, the first end of the second capacitor, the first end of the third resistor, and the first end of the third capacitor respectively. The second end of the first capacitor is electrically connected to the second end of the second resistor. The second end of the second capacitor is electrically connected to the second end of the second resistor. The second end of the third resistor is electrically connected to the first end of the fourth resistor and the DIFOUT port of the MAX1978 respectively. The second end of the fourth resistor is electrically connected to the second end of the third capacitor. The BFB- port of the MAX1978 is electrically connected to the first end of the fifth resistor. The second end of the fifth resistor is electrically connected to the first end of the sixth resistor and the first end of the fourth capacitor respectively. The second end of the sixth resistor is electrically connected to the second end of the fourth capacitor and the AOUT port of the MAX1978 respectively. The AIN- port of the MAX1978 is electrically connected to the first end of the fourth capacitor. The OS1 port of the MAX1978 is electrically connected to the positive electrode of the thermoelectric cooler and the first end of the seventh resistor respectively. The OS2 port of the MAX1978 is electrically connected to the negative electrode of the thermoelectric cooler and the first end of the first inductor respectively. The CS port of the MAX1978 is electrically connected to the second end of the seventh resistor and the first end of the second inductor respectively. The LX1 port of the MAX1978 is electrically connected to the second end of the second inductor. The LX2 port of the MAX1978 is electrically connected to the second end of the first inductor. The REF port of the MAX1978 and the MAXV port of the MAX1978 are both electrically connected to the first end of the eighth resistor. The second end of the eighth resistor is electrically connected to the FB- port of the MAX1978 and the first end of the thermistor respectively. The MAXIN port of the MAX1978 and the MAXIP port of the MAX1978 are electrically connected to the MAXV port of the MAX1978 and the first end of the ninth resistor respectively. The second end of the ninth resistor is electrically connected to the first end of the tenth resistor and the AIN+ port of the MAX1978 respectively. The COMP port of the MAX1978 is electrically connected to the first end of the fifth capacitor. The FREQ port of the MAX1978, the second end of the thermistor, the second end of the tenth resistor, and the second end of the fifth capacitor are grounded.

[0023] In a possible implementation, the protection module can also monitor the over-temperature state inside the laser and the over-current state of the thermoelectric cooler in real time. Among them, the real-time monitoring of the over-temperature state inside the laser includes:

[0024] After the voltage of the thermistor inside the laser is obtained in real time through the protection module, the voltage is input to the MCU_AD1 port of the microcontroller;

[0025] Obtain the current temperature of the laser according to the thermistor parameter table, and compare the temperature with the upper limit temperature and the lower limit temperature stored inside the microcontroller;

[0026] When the current temperature of the laser exceeds the upper limit temperature range or the lower limit temperature range, the microcontroller pulls up the MCU_CTR1 port or the MCU_CTR2 port to control the laser temperature control chip and the laser current drive module to stop working.

[0027] In a possible implementation, the overcurrent state of the current of the semiconductor cooler inside the laser is monitored in real time, including:

[0028] Calculate the working current of the semiconductor cooler according to the set voltage and the current voltage of the semiconductor cooler. The calculation formula is:

[0029]

[0030] Among them, V ITEC is the current voltage of the semiconductor cooler, V REF is the set voltage, and R SENSE is the resistance value;

[0031] Compare the calculated real-time working current with the set current;

[0032] When the real-time working current is greater than the set current, the microcontroller controls the laser temperature control switch and the laser current drive switch to pull low to turn off the temperature control and current drive.

[0033] In a possible implementation, the protection module includes an acquisition sub-circuit and a protection sub-circuit. The first end of the NTC+ port of the acquisition sub-circuit is electrically connected to the first end of the thermistor inside the laser, and the first end of the NTC- port of the acquisition sub-circuit is electrically connected to the second end of the thermistor inside the laser. The second end of the NTC+ port of the acquisition sub-circuit is respectively electrically connected to the first end of the eleventh resistor, the FB- port of the laser temperature control chip, and the first input end of the first voltage follower. The second end of the eleventh resistor is electrically connected to the VBEF power supply. The second input end of the first voltage follower is respectively electrically connected to the output end of the first voltage follower and the MCU-AD1 port of the microcontroller. The second end of the NTC- port of the acquisition sub-circuit is grounded.

[0034] In a possible implementation, the MCU_INT1 port of the microcontroller is electrically connected to the first end of the twelfth resistor in the protection sub-circuit and the collector of the first triode in the protection sub-circuit. The base of the first triode in the protection sub-circuit is electrically connected to the port of the laser temperature control chip. The second end of the twelfth resistor in the protection sub-circuit is electrically connected to the VDD power supply. The MCU_INT2 port of the microcontroller is electrically connected to the first end of the thirteenth resistor in the protection sub-circuit and the collector of the second triode in the protection sub-circuit. The base of the second triode in the protection sub-circuit is electrically connected to the port of the laser temperature control chip. The second end of the thirteenth resistor in the protection sub-circuit is electrically connected to the VDD power supply. The MCU_CTR1 port of the microcontroller is electrically connected to the first end of the fourteenth resistor in the protection sub-circuit. The second end of the fourteenth resistor in the protection sub-circuit is electrically connected to the first end of the fifteenth resistor in the protection sub-circuit and the gate of the first MOS transistor in the protection sub-circuit. The drain of the first MOS transistor in the protection sub-circuit is electrically connected to the VDD power supply and the second end of the fifteenth resistor in the protection sub-circuit. The source of the first MOS transistor in the protection sub-circuit is electrically connected to the port of the laser temperature control chip. The MCU_CTR2 port of the microcontroller is electrically connected to the first end of the sixteenth resistor in the protection sub-circuit. The second end of the sixteenth resistor in the protection sub-circuit is electrically connected to the first end of the seventeenth resistor in the protection sub-circuit and the gate of the second MOS transistor in the protection sub-circuit. The drain of the second MOS transistor in the protection sub-circuit is electrically connected to the VDD power supply and the second end of the seventeenth resistor in the protection sub-circuit. The source of the second MOS transistor in the protection sub-circuit is electrically connected to the port of the laser current drive. The MCU-AD2 port of the microcontroller is electrically connected to the output end of the second voltage follower. The first input end of the second voltage follower is electrically connected to the output end of the second voltage follower. The second input end of the second voltage follower is electrically connected to the VITEC port of the laser temperature control chip. The emitters of the first triode and the second triode in the protection sub-circuit are grounded.

[0035] Compared with the prior art, the beneficial effects of the present application are as follows:

[0036] The laser temperature control circuit with multiple protections adopted in the present application can achieve precise and stable temperature control of the semiconductor laser, monitor the operating state of the laser at the same time, ensure the safe operation of the laser, and has the characteristics of high precision and resolution, good stability, and multiple protections. Description of the Drawings

[0037] Figure 1 Schematic diagram of the process of a laser temperature control circuit control method with multiple protections provided by an embodiment of the present application;

[0038] Figure 2 Schematic diagram of the circuit of a laser temperature control circuit with multiple protections provided by an embodiment of the present application;

[0039] Figure 3 Schematic diagram of the circuit of the digital-to-analog conversion module provided by an embodiment of the present application;

[0040] Figure 4 Schematic diagram of the circuit of the protection module provided by an embodiment of the present application;

[0041] Figure 5 Schematic diagram of the circuit of the laser temperature control chip provided by an embodiment of the present application. Detailed implementation manners

[0042] The following elaborates on this solution in combination with the accompanying drawings and the detailed implementation manners.

[0043] Figure 1 Schematic diagram of the process of a laser temperature control circuit control method with multiple protections provided by an embodiment of the present application. Refer to Figure 1 , a laser temperature control circuit control method with multiple protections in this embodiment includes:

[0044] S101, the microcontroller converts the set temperature into a set voltage signal and inputs it to the given port of the laser temperature control chip.

[0045] Refer to Figure 2 , the laser temperature control circuit with multiple protections in this embodiment includes a microcontroller 1, a digital-to-analog conversion module 2, a laser temperature control chip 3, and a protection module 4. Among them, the microcontroller 1 is electrically connected to the digital-to-analog conversion module 2 to control the digital-to-analog conversion module 2 to output a temperature setting voltage. The digital-to-analog conversion module 2 is electrically connected to the laser temperature control chip 3 to output the temperature given voltage to the FB- port of the laser temperature control chip 3. The current output end of the laser temperature control chip 3 is electrically connected to both ends of the thermoelectric cooler inside the semiconductor laser to control the thermoelectric cooler to refrigerate or heat. The temperature feedback pin of the laser temperature control chip 3 is electrically connected to one end of the thermistor inside the semiconductor laser to obtain the real-time temperature of the laser. The protection module 4 is simultaneously electrically connected to the microcontroller 1 and the laser temperature control chip 3. The protection module inputs the thermistor feedback voltage to the internal analog-to-digital converter of the microcontroller after processing, and at the same time inputs the temperature control switch output signal of the microcontroller to the shutdown pin of the laser temperature control chip after conversion, and at the same time inputs the temperature out-of-control output of the laser temperature control chip to the external interrupt pin of the microcontroller.

[0046] In this embodiment, after initializing the laser temperature control circuit, the microcontroller reads the temperature parameters stored in the internal memory, converts the temperature parameters into the voltage value corresponding to the temperature according to the 10 kΩ negative temperature coefficient thermistor parameter table, and inputs the binary digital quantity corresponding to the voltage value to the digital-to-analog converter through the SPI bus communication protocol. After the digital-to-analog converter converts the digital quantity into an analog voltage signal, the analog voltage signal is used as the set voltage signal and input to the given port FB+ of the laser temperature control chip. When the reference changes slightly, the actual given voltage will also change accordingly, which can offset the temperature drift caused by this change and play a role in temperature compensation. See Figure 3 , in this embodiment, the digital-to-analog conversion module uses an AD5683 chip. The VDD port of the AD5683 chip is electrically connected to the first end of the first decoupling capacitor C1, the first end of the second decoupling capacitor C2, and the RESET port of the AD5683 chip respectively. The VDD port of the AD5683 chip is electrically connected to the VDD power supply. The SDO port of the DAC chip is electrically connected to the SPI-DI port of the MCU. The SDI port, SYNC port, and SCLK port of the AD5683 chip are electrically connected to the SPI-CLK port, SPI-DQS port, and SPI-DO port of the MCU respectively. The VBEF port of the AD5683 chip is electrically connected to the first end of the third decoupling capacitor C3 and the VREF power supply respectively. The VOUT port of the AD5683 chip is electrically connected to the given port FB+ of the laser temperature control chip. The given port FB+ of the laser temperature control chip is electrically connected to the first end of the first resistor R1 and the first end of the fourth decoupling capacitor C4 respectively. The second end of the first decoupling capacitor C1, the second end of the second decoupling capacitor C2, the second end of the third decoupling capacitor C3, the second end of the fourth decoupling capacitor C4, the second end of the first resistor R1, and the LDAC port and GND port of the DAC chip are grounded. In this embodiment, the first resistor R1 uses a precision adjustable potentiometer, which is used to realize manual temperature adjustment and is generally not soldered, serving as a selectable soldering device for external adjustment.

[0047] S102, the protection module is used to detect the voltage of the thermistor inside the laser in real time.

[0048] , in this embodiment, the protection module integrates a total of 4 detection items and 2 protection measures, including real-time temperature monitoring, real-time TEC current monitoring, temperature over-upper limit monitoring, temperature over-lower limit monitoring, temperature control shutdown protection, and laser current shutdown protection. See Figure 4, the protection module includes an acquisition sub - circuit and a protection sub - circuit. The first end of the NTC + port of the acquisition sub - circuit is electrically connected to the first end of the thermistor inside the laser. The first end of the NTC - port of the acquisition sub - circuit is electrically connected to the second end of the thermistor inside the laser. The second end of the NTC + port of the acquisition sub - circuit is respectively electrically connected to the first end of the eleventh resistor R4, the FB - port of the laser temperature control chip, and the first input terminal of the first voltage follower U2.1. The second end of the eleventh resistor R4 is electrically connected to the VBEF power supply. The second input terminal of the first voltage follower U2.1 is respectively electrically connected to the output terminal of the first voltage follower U2.1 and the MCU - AD1 port of the micro - controller. The second end of the NTC - port of the acquisition sub - circuit is grounded. The MCU_INT1 port of the micro - controller is respectively electrically connected to the first end of the twelfth resistor R7 in the protection sub - circuit and the collector of the first triode Q3 in the protection sub - circuit. The base of the first triode Q3 in the protection sub - circuit is electrically connected to the port of the laser temperature control chip. The second end of the twelfth resistor R7 in the protection sub - circuit is electrically connected to the VDD power supply. The MCU_INT2 port of the micro - controller is respectively electrically connected to the first end of the thirteenth resistor R8 in the protection sub - circuit and the collector of the second triode Q4 in the protection sub - circuit. The base of the second triode Q4 in the protection sub - circuit is electrically connected to the port of the laser temperature control chip. The second end of the thirteenth resistor R8 in the protection sub - circuit is electrically connected to the VDD power supply. The MCU_CTR1 port of the micro - controller is electrically connected to the first end of the fourteenth resistor R2 in the protection sub - circuit. The second end of the fourteenth resistor R2 in the protection sub - circuit is respectively electrically connected to the first end of the fifteenth resistor R3 in the protection sub - circuit and the gate of the first MOS transistor Q1 in the protection sub - circuit. The drain of the first MOS transistor Q1 in the protection sub - circuit is respectively electrically connected to the VDD power supply and the second end of the fifteenth resistor R3 in the protection sub - circuit. The source of the first MOS transistor Q1 in the protection sub - circuit is electrically connected to the port of the laser temperature control chip. The MCU_CTR2 port of the micro - controller is electrically connected to the first end of the sixteenth resistor R5 in the protection sub - circuit. The second end of the sixteenth resistor R5 in the protection sub - circuit is respectively electrically connected to the first end of the seventeenth resistor R6 in the protection sub - circuit and the gate of the second MOS transistor Q2 in the protection sub - circuit. The drain of the second MOS transistor Q2 in the protection sub - circuit is respectively electrically connected to the VDD power supply and the second end of the seventeenth resistor R6 in the protection sub - circuit. The source of the second MOS transistor Q2 in the protection sub - circuit is electrically connected to the The ports are electrically connected. The MCU-AD2 port of the microcontroller is electrically connected to the output terminal of the second voltage follower U2.2. The first input terminal of the second voltage follower U2.2 is electrically connected to the output terminal of the second voltage follower U2.2. The second input terminal of the second voltage follower U2.2 is electrically connected to the VITEC port of the laser temperature control chip. The emitters of the first triode Q3 and the second triode Q4 in the protection sub-circuit are grounded. The two ends of NTC+ and NTC- are connected to the thermistor inside the laser. FB- is connected to the temperature feedback pin of the laser temperature control chip. After passing through the voltage follower formed by the operational amplifier U9.1, it is input into the internal ADC channel MCU_AD1 of the MCU. The ADC converts the voltage analog signal into a digital signal. The program calculates the resistance value of the thermistor at the current temperature through this voltage value and calls the internal stored temperature-resistance value look-up table to perform look-up, so as to obtain the current temperature. The operational amplifier U9.2 forms a voltage follower. The input is connected to the VITEC pin of the laser temperature control chip, and the output is connected to the internal ADC channel MCU_AD2 of the MCU. The ADC converts the voltage analog signal into a digital signal, and then calculates the current TEC working current through a formula.

[0049]

[0050] In the formula, V ITEC is the current voltage of the thermoelectric cooler, V REF is the set voltage, R SENSE is the resistance value of R10 in the figure. Q3 and Q4 respectively form two-level converters. The inputs are respectively connected to the temperature over-limit alarm output OT and the temperature under-limit alarm output UT of the laser temperature control chip. The outputs MCU_INT1 and MCU_INT2 are respectively connected to the external interrupt pins of the MCU. When the temperature exceeds the limit, the pins are pulled low, triggering the change of the MCU pin level interrupt. Q1 and Q2 and the resistors R2, R3, R5, and R6 form a switching circuit. The inputs MCU_CTR1 and MCU_CTR2 are respectively connected to the GPIO of the MCU, and the outputs are respectively connected to the shutdown pin SHDN of the laser temperature control chip and the shutdown pin LDSD of the laser current drive. When working normally, the MCU outputs a low level to MCU_CTR1 and MCU_CTR2, and the laser temperature control and current drive work normally. When the MCU detects out-of-control temperature, over-limit current, and over-limit temperature, the MCU outputs a high level to MCU_CTR1 and MCU_CTR2, and the laser temperature control and current drive are shut down, thus protecting the laser.

[0051] S103, use the detected voltage signal of the thermistor as the feedback signal, the set voltage signal as the given signal, and realize the temperature control of the laser through the PID controller of the laser temperature control chip.

[0052] In this embodiment, the difference between the set voltage signal and the thermistor voltage signal is used as the error signal and input to the given input of the PID controller of the laser temperature control chip. The magnitude and direction of the current of the semiconductor cooler in the laser are determined by the PID controller of the laser temperature control chip to achieve the temperature control of the laser. When the thermistor voltage is less than the set voltage, it is input to the internal PWM controller and gate controller of the chip through the CTLI port in the laser temperature control chip to drive the bridge circuit. The laser temperature control chip outputs a forward current, and the semiconductor cooler cools down the temperature. Or, when the thermistor voltage is greater than the set voltage, it is input to the internal PWM controller and gate controller of the chip through the CTLI port in the laser temperature control chip to drive the bridge circuit. The laser temperature control chip outputs a reverse current, and the semiconductor cooler heats up the temperature.

[0053] See Figure 5, in this embodiment, the laser temperature control chip uses MAX1978. The INTOUT port of the MAX1978 is electrically connected to the first end of the second resistor R9 and the CTLI port respectively. The INT- port of the MAX1978 is electrically connected to the first end of the first capacitor C6, the first end of the second capacitor C5, the first end of the third resistor R11, and the first end of the third capacitor C4 respectively. The second end of the first capacitor C6 is electrically connected to the second end of the second resistor R9. The second end of the second capacitor C5 is electrically connected to the second end of the second resistor R9. The second end of the third resistor R11 is electrically connected to the first end of the fourth resistor R14 and the DIFOUT port of the MAX1978 respectively. The second end of the fourth resistor R14 is electrically connected to the second end of the third capacitor C4. The BFB- port of the MAX1978 is electrically connected to the first end of the fifth resistor R17. The second end of the fifth resistor R17 is electrically connected to the first end of the sixth resistor R16 and the first end of the fourth capacitor C7 respectively. The second end of the sixth resistor R16 is electrically connected to the second end of the fourth capacitor C7 and the AOUT port of the MAX1978 respectively. The AIN- port of the MAX1978 is electrically connected to the first end of the fourth capacitor C7. The OS1 port of the MAX1978 is electrically connected to the positive pole of the thermoelectric cooler and the first end of the seventh resistor R10 respectively. The OS2 port of the MAX1978 is electrically connected to the negative pole of the thermoelectric cooler and the first end of the first inductor L2 respectively. The CS port of the MAX1978 is electrically connected to the second end of the seventh resistor R10 and the first end of the second inductor L1 respectively. The LX1 port of the MAX1978 is electrically connected to the second end of the second inductor L1. The LX2 port of the MAX1978 is electrically connected to the second end of the first inductor L2. The REF port of the MAX1978 and the MAXV port of the MAX1978 are both electrically connected to the first end of the eighth resistor R12. The second end of the eighth resistor R12 is electrically connected to the FB- port of the MAX1978 and the first end of the thermistor respectively. The MAXIN port of the MAX1978 and the MAXIP port of the MAX1978 are electrically connected to the MAXV port of the MAX1978 and the first end of the ninth resistor R15 respectively. The second end of the ninth resistor R15 is electrically connected to the first end of the tenth resistor R18 and the AIN+ port of the MAX1978 respectively. The COMP port of the MAX1978 is electrically connected to the first end of the fifth capacitor C8. The FREQ port of the MAX1978, the second end of the thermistor, the second end of the tenth resistor R18, and the second end of the fifth capacitor C8 are grounded.

[0054] In this embodiment, in the laser temperature control chip circuit, R13 and U3 TEC are the thermistor and the thermoelectric cooler integrated inside the semiconductor laser. The positive and negative terminals of U3 are respectively connected to OS1 and OS2 of the laser temperature control chip. R12 is a 10 kΩ high-precision resistor, which forms a voltage division circuit with R13. The two ends of R13 are respectively connected to FB- and GND of the laser temperature control chip to form temperature feedback. At the same time, one end of the negative temperature coefficient thermistor is also connected to the temperature monitoring input FB- of the protection module. The temperature setting pin FB+ of the laser temperature control chip is connected to the analog output pin of the digital-to-analog conversion module. The REF pin of the laser temperature control module is connected to the system reference voltage VREF1 to provide the only reference voltage for the system. L1 and L2 are power inductors. R16, R17, C8, R15 and R18 form a thermistor voltage monitor. R9, R11, R14, C5, C6, C7 form an external PID controller to achieve fast following and precise control of the target temperature and the set temperature, and the control accuracy reaches 0.001 °C.

[0055] The working process of this circuit is as follows. After power-on, the system initializes first. The microcontroller reads the temperature parameters stored in the internal memory, and then converts the temperature parameters into the voltage value corresponding to this temperature according to the 10kΩ negative temperature coefficient thermistor parameter table. Then, the binary digital quantity corresponding to this voltage value is sent to the digital-to-analog conversion module through SPI. The digital-to-analog conversion module converts the digital quantity into an analog voltage and inputs the analog voltage to the temperature setting pin (FB+) of the laser temperature control chip 3. Then, the microcontroller 1 sets the MCU_CTR1 pin to zero, the P-type MOS transistor conducts, and the enable pin of the laser temperature control chip 3 is pulled high to start working. The thermistor 6 (R13) inside the semiconductor laser samples the laser temperature in real time, and after voltage division, it is input to the feedback input FB- of the temperature control chip, forming an error with the temperature setting voltage FB+ and inputting it to the PID controller of the temperature control chip 3. The output of the controller is input to the internal PWM controller and gate driver through the CRLI pin to control the internal bridge circuit, thereby controlling the direction and magnitude of the current. When the temperature deviation is positive, the output current is positive, and the semiconductor refrigerator cools down, and the temperature decreases. When the temperature deviation is negative, the output current is negative, and the semiconductor refrigerator heats up, and the temperature increases. At the same time, the PID controller will control the magnitude of the output current according to the magnitude of the temperature deviation, so that the actual temperature of the laser quickly reaches the set temperature. At the same time, the protection module 4 also samples the voltage of the thermistor 6 in real time, and inputs the voltage value to the MCU_AD1 pin of the microcontroller 1, converts it into a digital quantity, obtains the current laser temperature by looking up the table after calculation, and compares the temperature with the upper limit temperature and lower limit temperature stored inside the microcontroller 1 in real time. When it exceeds this range, the MCU_CTR1 and MCU_CTR2 are pulled high, the P-type MOS transistor is turned off, and the enable pin of the laser temperature control chip 3 is set to zero to stop working, thus avoiding the laser temperature getting out of control and burning out. When the current of the semiconductor refrigerator is overcurrent, the MCU compares the current of the semiconductor refrigerator with the set current through calculation. When the real-time current is greater than the set current, the MCU controls the laser temperature control switch and the laser current drive switch to pull low, turning off the temperature control and current drive, and completing the overcurrent protection process of the semiconductor refrigerator current. When the temperature control cannot be stabilized for a long time, or the stable error is large, it is determined that the temperature is out of control. At this time, the MCU controls the laser temperature control switch and the laser current drive switch to pull low, turning off the temperature control and current drive, and completing the temperature out-of-control protection process.

[0056] In the embodiments of this application, "a plurality of" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent the situation where A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0057] It should be noted that in this text, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0058] As described above, the foregoing is only a specific embodiment of the present application. Any person skilled in the art within the technical scope disclosed in the present application can easily conceive of changes or substitutions, which should all be covered within the protection scope of the present application. The protection scope of the present application shall be subject to the protection scope of the said claims.

Claims

1. A laser temperature control circuit control method with multiple protections, characterized in that: include: The microcontroller converts the set temperature into a set voltage signal and inputs it into a given port of the laser temperature control chip; The voltage of the thermistor inside the laser is detected in real time through the protection module; The detected voltage signal of the thermistor is used as a feedback signal, and the voltage signal is set as a given signal, and the temperature control of the laser is realized through the PID controller of the laser temperature control chip.

2. The laser temperature control circuit control method with multiple protections according to claim 1 is characterized in that: The microcontroller converts the set temperature into a set voltage signal and inputs it into a given port of the laser temperature control chip, including: After initializing the laser temperature control circuit, the microcontroller is used to read the temperature parameters stored in the internal memory; Convert the temperature parameter into a voltage value corresponding to the temperature according to a thermistor parameter table; After the binary digital quantity corresponding to the voltage value is input into the digital-to-analog converter through the SPI bus communication protocol to be converted into an analog voltage signal, the analog voltage signal is used as a set voltage signal and input into a given port of the laser temperature control chip.

3. The laser temperature control circuit control method with multiple protections according to claim 1 is characterized in that: The digital-to-analog conversion module adopts an AD5683 chip, the VDD port of the AD5683 chip is electrically connected to the first end of the first decoupling capacitor, the first end of the second decoupling capacitor and the RESET port of the AD5683 chip respectively, the VDD port of the AD5683 chip is electrically connected to the VDD power supply, the SDO port of the DAC chip is electrically connected to the SPI-DI port of the MCU, the SDI port, the SYNC port and the SCLK port of the AD5683 chip are electrically connected to the SPI-CLK port, the SPI-DQS port and the SPI-DO port of the MCU respectively, The VBEF port of the AD5683 chip is electrically connected to the first end of the third decoupling capacitor and the VREF power supply, respectively; the VOUT port of the AD5683 chip is electrically connected to the FB+ given port of the laser temperature control chip; the FB+ given port of the laser temperature control chip is electrically connected to the first end of the first resistor and the first end of the fourth decoupling capacitor, respectively; the second end of the first decoupling capacitor, the second end of the second decoupling capacitor, the second end of the third decoupling capacitor, the second end of the fourth decoupling capacitor, the second end of the first resistor, and the LDAC port and GND port of the DAC chip are grounded.

4. The laser temperature control circuit control method with multiple protections according to claim 1, characterized in that: The detected voltage signal of the thermistor is used as a feedback signal, the voltage signal is set as a given signal, and the temperature control of the laser is realized by a PID controller of a laser temperature control chip, including: The difference between the set voltage signal and the thermistor voltage signal is input as an error signal to the given input of the PID controller of the laser temperature control chip; The PID controller of the laser temperature control chip determines the size and direction of the current of the semiconductor cooler in the laser to achieve temperature control of the laser.

5. The laser temperature control circuit control method with multiple protections according to claim 4 is characterized in that: The PID controller of the laser temperature control chip determines the magnitude and direction of the current of the semiconductor refrigerator in the laser to achieve the temperature control of the laser, including: When the thermistor voltage is less than the set voltage, it is input to the chip's internal PWM controller and gate controller through the CTLI port in the laser temperature control chip, driving the bridge circuit, the laser temperature control chip outputs a forward current, the semiconductor refrigerator cools, and the temperature drops; or, When the thermistor voltage is greater than the set voltage, it is input into the chip's internal PWM controller and gate controller through the CTLI port in the laser temperature control chip, driving the bridge circuit. The laser temperature control chip outputs a reverse current, the semiconductor cooler heats up, and the temperature rises.

6. The laser temperature control circuit control method with multiple protections according to claim 4 or 5, characterized in that: The laser temperature control chip adopts MAX1978, the INTOUT port of the MAX1978 is electrically connected to the first end of the second resistor and the CTLI port respectively, the INT- port of the MAX1978 is electrically connected to the first end of the first capacitor, the first end of the second capacitor, the first end of the third resistor and the first end of the third capacitor respectively, the second end of the first capacitor is electrically connected to the second end of the second resistor, the second end of the second capacitor is electrically connected to the second end of the second resistor, the second end of the third resistor is electrically connected to the first end of the fourth resistor and the DIFOUT port of the MAX1978 respectively, the second end of the fourth resistor is electrically connected to the second end of the third capacitor, the BFB- port of the MAX1978 is electrically connected to the first end of the fifth resistor, the second end of the fifth resistor is electrically connected to the first end of the sixth resistor and the first end of the fourth capacitor respectively, the second end of the sixth resistor is electrically connected to the second end of the fourth capacitor and the AOUT port of the MAX1978 respectively, the AIN- port of the MAX1978 is electrically connected to the first end of the fourth capacitor, the OS1 port of the MAX1978 is electrically connected to the positive electrode of the semiconductor refrigeration plate and the first end of the seventh resistor respectively, the The OS2 port of MAX1978 is electrically connected to the negative electrode of the semiconductor refrigeration plate and the first end of the first inductor respectively, the CS port of the MAX1978 is electrically connected to the second end of the seventh resistor and the first end of the second inductor respectively, the LX1 port of the MAX1978 is electrically connected to the second end of the second inductor, the LX2 port of the MAX1978 is electrically connected to the second end of the first inductor, the REF port of the MAX1978 and the MAXV port of the MAX1978 are both electrically connected to the first end of the eighth resistor, and the second end of the eighth resistor is electrically connected to the The FB- port is electrically connected to a first end of the thermistor, the MAXIN port of the MAX1978 and the MAXIP port of the MAX1978 are electrically connected to the MAXV port of the MAX1978 and the first end of a ninth resistor, respectively, the second end of the ninth resistor is electrically connected to the first end of the tenth resistor and the AIN+ port of the MAX1978, respectively, the COMP port of the MAX1978 is electrically connected to a first end of a fifth capacitor, and the FREQ port of the MAX1978, the second end of the thermistor, the second end of the tenth resistor, and the second end of the fifth capacitor are grounded.

7. The laser temperature control circuit control method with multiple protections according to claim 1, characterized in that: The protection module can also monitor the over-limit temperature state in the laser and the over-current state of the semiconductor refrigerator in real time, wherein the over-limit temperature state in the laser is monitored in real time, including: The voltage of the thermistor inside the laser is acquired in real time through the protection module and then input into the MCU_AD1 port of the microcontroller; Obtain the current temperature of the laser according to the thermistor parameter table, and compare the temperature with the upper and lower temperature limits stored in the microcontroller; When the current temperature of the laser exceeds the upper temperature range or the lower temperature range, the microcontroller pulls up the MCU_CTR1 port or the MCU_CTR2 port to control the laser temperature control chip and the laser current drive module to stop working.

8. The laser temperature control circuit control method with multiple protections according to claim 7, characterized in that: Real-time monitoring of the current overcurrent status of the semiconductor cooler in the laser, including: The working current of the semiconductor refrigerator is calculated according to the set voltage and the current voltage of the semiconductor refrigerator. The calculation formula is: Among them, V ITEC is the current voltage of the semiconductor cooler, V REF is the set voltage, R SENSE is the resistance value; Compare the calculated real-time operating current with the set current; When the real-time working current is greater than the set current, the microcontroller controls the laser temperature control switch and the laser current drive switch to be pulled low, turning off the temperature control and current drive.

9. The laser temperature control circuit control method with multiple protections according to claim 4 or 7, characterized in that: The protection module includes a collection subcircuit and a protection subcircuit, the first end of the NTC+ port of the collection subcircuit is electrically connected to the first end of the thermistor inside the laser, the first end of the NTC- port of the collection subcircuit is electrically connected to the second end of the thermistor inside the laser, the second end of the NTC+ port of the collection subcircuit is electrically connected to the first end of the eleventh resistor, the FB- port of the laser temperature control chip and the first input end of the first voltage follower respectively, the second end of the eleventh resistor is electrically connected to the VBEF power supply, the second input end of the first voltage follower is electrically connected to the output end of the first voltage follower and the MCU-AD1 port of the microcontroller respectively, and the second end of the NTC- port of the collection subcircuit is grounded.

10. The laser temperature control circuit control method with multiple protections according to claim 9, characterized in that: The MCU_INT1 port of the microcontroller is electrically connected to the first end of the twelfth resistor in the protection subcircuit and the collector of the first transistor in the protection subcircuit respectively, and the base of the first transistor in the protection subcircuit is electrically connected to the base of the laser temperature control chip. The first terminal of the 13th resistor in the protection subcircuit is electrically connected to the VDD power supply, the MCU_INT2 port of the microcontroller is electrically connected to the first terminal of the 13th resistor in the protection subcircuit and the collector of the second triode in the protection subcircuit, and the base of the second triode in the protection subcircuit is electrically connected to the base of the laser temperature control chip. The MCU_CTR1 port of the microcontroller is electrically connected to the first end of the 14th resistor in the protection subcircuit, the second end of the 14th resistor in the protection subcircuit is electrically connected to the first end of the 15th resistor in the protection subcircuit and the gate of the first MOS tube in the protection subcircuit, the drain of the first MOS tube in the protection subcircuit is electrically connected to the VDD power supply and the second end of the 15th resistor in the protection subcircuit, and the source of the first MOS tube in the protection subcircuit is electrically connected to the laser temperature control chip. The MCU_CTR2 port of the microcontroller is electrically connected to the first end of the sixteenth resistor in the protection subcircuit, the second end of the sixteenth resistor in the protection subcircuit is electrically connected to the first end of the seventeenth resistor in the protection subcircuit and the gate of the second MOS tube in the protection subcircuit, the drain of the second MOS tube in the protection subcircuit is electrically connected to the VDD power supply and the second end of the seventeenth resistor in the protection subcircuit, and the source of the second MOS tube in the protection subcircuit is electrically connected to the laser current drive. The ports are electrically connected, the MCU-AD2 port of the microcontroller is electrically connected to the output end of the second voltage follower, the first input end of the second voltage follower is electrically connected to the output end of the second voltage follower, the second input end of the second voltage follower is electrically connected to the VITEC port of the laser temperature control chip, and the emitter of the first transistor in the protection subcircuit and the emitter of the second transistor in the protection subcircuit are grounded.

Images