Automatic temperature control method for a distributed feedback laser

Abstract

This invention provides an automatic temperature control method for distributed feedback lasers, combining analog PID and digital PID control. The digital PID algorithm leverages its flexibility to find suitable proportional, integral, and derivative parameters, which are then applied to the analog PID. The analog PID temperature control method offers advantages such as high real-time performance, high reliability, and strong anti-interference capability. The digital temperature control algorithm, which is not limited to analog control, neural network control, and PID control, offers advantages such as adjustable parameters, flexible algorithms, and strong adaptability. Addressing the shortcomings of inconvenient parameter adjustment and poor flexibility in analog PID control, this invention combines analog PID and digital PID control, utilizing the flexibility of the digital PID algorithm to find suitable PID parameters, which are then transferred to the analog PID, resulting in high real-time performance, high reliability, and strong adaptability.

Description

Technical Field

[0001] This invention relates to the field of electrical components technology, and specifically to an automatic temperature control method for a distributed feedback laser. Background Technology

[0002] Most molecular gases exhibit fingerprint-like absorption spectra in the mid-infrared band. Tunable semiconductor laser absorption spectroscopy, employing wavelength modulation spectroscopy, aligns the laser's output center wavelength with the absorption peak of the gas being tested. By detecting the degree of absorption of the laser by the gas, non-contact, rapid, and non-destructive detection of gas concentration can be achieved.

[0003] Because the absorption spectrum of the gas being measured is generally very narrow, and the absorption coefficient varies greatly near the absorption peak, even a small change in the laser's output wavelength can have a significant impact on the gas concentration detection results. Besides the driving current, the laser's operating temperature is another factor that causes changes in the laser's output wavelength. Ambient temperature, airflow, and the temperature rise generated by the laser itself during operation can cause fluctuations in the laser's operating temperature and, conversely, slight changes in the driving current, thus leading to fluctuations in the laser's output wavelength. Therefore, to improve the accuracy of gas measurement, precise control of the laser's temperature is necessary.

[0004] In practical engineering applications, analog PID controllers are often used to achieve automatic temperature control of lasers. However, the proportional, integral, and derivative parameters of analog PID controllers are determined by resistors and capacitors, which has drawbacks such as inconvenient parameter adjustment. Therefore, PID parameters are often based on empirical values. When detecting multiple gases, different lasers are required, and these lasers operate at different powers and temperatures. Empirical PID values ​​often cannot meet the measurement requirements, exhibiting problems such as poor temperature stability and interference resistance, introducing additional errors into the detection results. Summary of the Invention

[0005] This invention addresses the problem that applying the same control strategy to different lasers can lead to slower laser temperature control response and increased overshoot. It provides an automatic temperature control method for distributed feedback lasers, which improves laser temperature stability, enhances anti-interference capabilities, and increases gas measurement accuracy.

[0006] This invention provides an automatic temperature control method for a distributed feedback laser, comprising the following steps: S1. Connect the TEC controller to the TEC, digital temperature controller, and analog PID controller. Connect both the digital temperature controller and analog PID controller to the NTC. Connect both the TEC and NTC to the laser. The NTC feeds back the laser temperature to the TEC controller and the analog PID controller in real time. The TEC controller uses the temperature control signal to control the voltage across the TEC and the direction and magnitude of the current flowing through it for cooling, heating, and power control. The digital temperature controller outputs a digital temperature control signal to the TEC controller, and the analog PID controller uses V... set The voltage value sets the expected laser temperature value, and after passing through the PID compensation network, the analog temperature control signal is output to the CTLI pin of the TEC controller. S2. Determine the optimal proportional, integral, and derivative parameters for temperature control speed, overshoot, and anti-interference balance of the digital temperature controller through simulation and experiment. S3. Change the resistance and capacitance values ​​of the analog PID controller to adjust the proportional, integral, and derivative parameters of the analog PID controller to the optimal proportional, integral, and derivative parameters, thereby transferring the optimal temperature control effect of the digital temperature controller to the analog PID controller. The S4 and TEC controllers perform automatic temperature control of the laser based on analog temperature control signals.

[0007] The automatic temperature control method for a distributed feedback laser according to the present invention, in a preferred embodiment, includes a digital temperature controller comprising an FPGA and a D / A converter and an A / D converter respectively connected to the FPGA; The output of the D / A converter is connected to the CTLI pin of the TEC controller to output a digital temperature control signal; The input of the A / D converter is connected to an operational amplifier and an NTC in sequence. The NTC is sampled and the output is sent to the FPGA.

[0008] The automatic temperature control method for a distributed feedback laser described in this invention, as a preferred embodiment, is as follows: when the CTLI pin voltage is greater than 1.5V, the TEC controller outputs a positive current, and the TEC cools; when the CTLI pin voltage is less than 1.5V, the TEC controller outputs a negative current, and the TEC heats up. The output current of the TEC controller is proportional to the voltage at the CTLI pin and the voltage difference of 1.5V.

[0009] The automatic temperature control method for a distributed feedback laser described in this invention, as a preferred embodiment, uses a digital temperature controller based on an MCU to control the laser temperature through fuzzy control, neural network control, PID control, analog PID algorithm, and neural network PID algorithm.

[0010] In the automatic temperature control method for a distributed feedback laser described in this invention, as a preferred embodiment, an NTC is connected in series with a resistor R1 and then connected to a reference source. The resistance value R0 of the NTC at 25°C is the same as that of the resistor R1. The relationship between the resistance value R0 and the temperature is obtained through the RT curve.

[0011] In the automatic temperature control method for a distributed feedback laser described in this invention, as a preferred embodiment, both R0 and R1 are 10kΩ, the accuracy of resistor R1 is 0.1%, and the B value of NTC is 3930.

[0012] The automatic temperature control method for a distributed feedback laser described in this invention, in a preferred embodiment, includes an operational amplifier U1, capacitor C1, and capacitor C2 all connected to the CTL1 port of the TEC controller; resistors R2, C3, and R3 connected sequentially to the other end of capacitor C1; resistor R4 connected in parallel with capacitor C3 and resistor R3; resistor R5 connected to both resistors R4 and R3; operational amplifier U2; and resistor R6 and operational amplifier U3 connected sequentially to the negative input terminal of operational amplifier U2. The positive input terminal of operational amplifier U1 is connected to a reference voltage. VREF The negative input terminal is connected to capacitor C2, resistor R2, capacitor C3 and resistor R4 respectively, and the output terminal is connected to CTL1 port; The positive input terminal of operational amplifier U2 is connected between resistor R1 and NTC, the negative input terminal is connected to resistors R5 and R6, and the output terminal is connected to resistors R3, R4, and R5. The positive input terminal of operational amplifier U3 is V set The negative input terminal is connected between the output terminal and resistor R6.

[0013] The automatic temperature control method for a distributed feedback laser described in this invention, as a preferred embodiment, includes a PID compensation network comprising a variable resistance resistor and a variable capacitance capacitor.

[0014] The automatic temperature control method for a distributed feedback laser described in this invention, preferably uses a distributed feedback laser.

[0015] This invention relates to wavelength modulation spectroscopy in optical sensing technology.

[0016] This invention provides an automatic temperature control method for a distributed feedback laser, including a TEC (Transmission Controlled Temperature Regulator), an NTC (Natural Temperature Regulator), a TEC controller, an analog PID controller, and a digital temperature controller. The TEC utilizes the Peltier effect of semiconductor materials; when current flows through it, one end absorbs heat and the other releases heat, enabling precise temperature control of the laser. The resistance of the NTC changes with temperature, and the current temperature of the laser can be calculated and monitored in real time using an RT (Rapid Reduction) curve. The TEC controller controls the cooling, heating, and power of the TEC by controlling the voltage across the TEC and the direction and magnitude of the current flowing through it. The analog PID controller is the key control network of the temperature control system, achieving continuous temperature control based on hardware circuitry. The digital controller, based on an MCU (Microcontroller Unit), uses algorithms such as analog control, neural network control, and PID control to achieve laser temperature control.

[0017] This invention addresses the shortcomings of analog PID control, such as inconvenient parameter adjustment and poor flexibility. It combines analog PID and digital PID control, utilizing the flexibility of digital PID algorithms to find suitable proportional, integral, and derivative parameters, which are then applied to analog PID. This approach offers advantages such as high real-time performance, high reliability, and strong adaptability.

[0018] The present invention has the following advantages: (1) The present invention adopts the temperature control method of analog PID, which has the advantages of high real-time performance, high reliability and strong anti-interference ability.

[0019] (2) The present invention adopts a digital temperature control algorithm, which is not limited to analog control, neural network control and PID control, and has the advantages of adjustable parameters, flexible algorithm and strong adaptability.

[0020] (3) In view of the disadvantages of inconvenient adjustment and poor flexibility of analog PID control parameters, this invention combines analog PID and digital PID control, uses the flexibility of digital PID algorithm to find suitable PID parameters, and then transplants them into analog PID. It has the advantages of high real-time performance, high reliability and strong adaptability. Attached Figure Description

[0021] Figure 1 A flowchart of an automatic temperature control method for a distributed feedback laser; Figure 2 This is a schematic diagram of the system architecture for an automatic temperature control method for a distributed feedback laser.

[0022] Figure label: 1. TEC controller; 2. TEC; 3. Digital PID controller; 31. FPGA; 32. D / A converter; 33. A / D converter; 4. Analog PID controller; 5. NTC. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] Example 1 like Figure 1 , Figure 2 As shown, an automatic temperature control method for a distributed feedback laser includes the following steps: S1. Connect TEC controller 1 to TEC2, digital temperature controller 3, and analog PID controller 4. Connect both digital temperature controller 3 and analog PID controller 4 to NTC5. Connect both TEC2 and NTC5 to the laser. S2. Determine the optimal proportional, integral, and derivative parameters for the temperature control speed, overshoot, and anti-interference balance of the digital temperature controller 3 through simulation and experimentation. S3. Change the resistance and capacitance values ​​of the analog PID controller 4 to adjust the proportional, integral, and derivative parameters of the analog PID controller 4 to the optimal proportional, integral, and derivative parameters, thereby transferring the optimal temperature control effect of the digital temperature controller 3 to the analog PID controller 4. S4, TEC controller 1 performs automatic temperature control of the laser based on analog temperature control signals.

[0025] TEC2 utilizes the Peltier effect of semiconductor materials; when current flows through it, one end of TEC2 absorbs heat and the other end releases heat, enabling precise temperature control of the laser. The resistance of NTC5 changes with temperature, and the current temperature of the laser can be calculated and monitored in real time using the RT curve. TEC controller 1 controls the cooling, heating, and power of TEC2 by controlling the voltage across TEC2 and the direction and magnitude of the current flowing through it. Analog PID controller 4 is the key control network of the temperature control system, achieving continuous temperature control based on hardware circuitry. Digital temperature controller 3, based on an MCU, uses algorithms such as analog control, neural network control, and PID control to achieve laser temperature control.

[0026] The analog PID controller 4 includes a reference source, a high-precision operational amplifier, resistors, and capacitors.

[0027] The digital temperature controller 3 includes an MCU, an A / D converter, and a D / A converter.

[0028] The digital temperature controller 3 can employ fuzzy control, neural network control, PID control, as well as analog PID and neural network PID algorithms.

[0029] When a positive current is applied to the TEC2, its surface is cooled; when a negative current is applied, its surface is heated. The power of cooling or heating increases with the increase of the current.

[0030] The NTC5 is a negative temperature coefficient thermistor, whose resistance decreases as temperature increases. The relationship between resistance and temperature can be calculated using the RT curve. The analog PID controller 4 and the digital temperature controller 3 use the same NTC5 to monitor the real-time temperature of the laser surface.

[0031] The TEC controller 1 includes a reference source, amplifier, MOSFET driver, and MOSFETs, and the driving modes include linear drive and PWM switching drive.

[0032] Figure 1 This is an architecture diagram of an automatic temperature control system for a distributed feedback laser according to the present invention.

[0033] like Figure 2 This is an example diagram of the present invention.

[0034] exist Figure 2 In the specific implementation shown, the JMAX1978 serves as the linear drive TEC controller 1, providing a TEC drive capability of ±4.3V maximum output voltage and ±3A maximum output current. When the voltage at the CTLI pin of TEC controller 1 is greater than 1.5V, TEC controller 1 outputs a positive current, cooling TEC2; when the voltage at the CTLI pin is less than 1.5V, TEC controller 1 outputs a negative current, heating TEC2. Furthermore, the output current of TEC controller 1 is proportional to the voltage difference between the CTLI pin voltage and 1.5V. TEC2 is integrated into the laser, with a maximum input voltage of 1.45V, a maximum input current of 0.8A, and a maximum temperature difference of 67℃ under no-load conditions. NTC5 is also integrated into the laser, connected in series with a 10kΩ resistor R1 (0.1% precision) to the reference source. At 25℃, R0=10kΩ and B=3930 for NTC5. An analog PID controller 4 is composed of the reference source, a high-precision operational amplifier, resistors, and capacitors, and is controlled by V... setThe voltage value sets the expected temperature value, which is then output to the CTLI pin of TEC controller 1 after passing through a PID compensation network to control TEC2 for cooling or heating. Digital temperature controller 3, composed of FPGA 31, 12-bit A / D converter 33, 12-bit D / A converter 32, and operational amplifier, uses A / D converter 33 to sample the voltage on NTC5 at a 10kHz sampling rate as feedback. The PID control algorithm is implemented in FPGA 31 and output to the CTLI pin of TEC controller 1 via D / A converter 32. Through simulation and multiple experimental verifications, it was determined that when the proportional, integral, and derivative parameters of the digital PID controller are 120, 10, and 5 respectively, the set temperature can be reached quickly while minimizing overshoot and exhibiting strong anti-interference capability across the entire temperature range. Finally, by changing the values ​​of the resistor and capacitor in analog PID controller 4, the proportional, integral, and derivative parameters of analog PID controller 4 are adjusted to match those of the digital PID controller, enabling the analog PID controller to achieve a temperature control effect similar to that of the digital PID controller.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An automatic temperature control method for a distributed feedback laser, characterized in that: Includes the following steps: S1. Connect the TEC controller (1) to the TEC (2), the digital temperature controller (3), and the analog PID controller (4). Connect the digital temperature controller (3) and the analog PID controller (4) to the NTC (5). Connect the TEC (2) and the NTC (5) to the laser. The NTC (5) feeds back the laser temperature to the TEC controller (1) and the analog PID controller (4) in real time. The TEC controller (1) controls the voltage across the TEC (2) and the direction and magnitude of the current flowing through the TEC (2) according to the temperature control signal to perform cooling control, heating control and power control of the TEC (2). The digital temperature controller (3) outputs a digital temperature control signal to the TEC controller (1). The analog PID controller (4) controls the laser temperature through V... set The voltage value sets the expected value of the laser temperature, and after passing through the PID compensation network, the analog temperature control signal is output to the CTLI pin of the TEC controller (1); S2. Determine the optimal proportional parameter, optimal integral parameter and optimal derivative parameter of the digital temperature controller (3) for temperature control speed, overshoot, and anti-interference balance through simulation and experiment. S3. Change the resistance and capacitance values ​​of the analog PID controller (4) to adjust the proportional, integral, and derivative parameters of the analog PID controller (4) to the optimal proportional, integral, and derivative parameters, thereby transferring the optimal temperature control effect of the digital temperature controller (3) to the analog PID controller (4). S4. The TEC controller (1) performs automatic temperature control of the laser based on the analog temperature control signal.

2. The automatic temperature control method for a distributed feedback laser according to claim 1, characterized in that: The digital temperature controller (3) includes an FPGA (31) and a D / A converter (32) and an A / D converter (33) respectively connected to the FPGA (31). The output terminal of the D / A converter (32) is connected to the CTLI pin of the TEC controller (1) to output the digital temperature control signal; The input terminal of the A / D converter (33) is connected to the operational amplifier and the NTC (5) in sequence, and the NTC (5) is sampled and output to the FPGA (31).

3. The automatic temperature control method for a distributed feedback laser according to claim 1, characterized in that: When the CTLI pin voltage is greater than 1.5V, the TEC controller (1) outputs a positive current and the TEC (2) cools; when the CTLI pin voltage is less than 1.5V, the TEC controller (1) outputs a negative current and the TEC (2) heats up. The magnitude of the output current of the TEC controller (1) is proportional to the voltage of the CTLI pin and the voltage difference of 1.5V.

4. The automatic temperature control method for a distributed feedback laser according to claim 1, characterized in that: The digital temperature controller (3) is based on an MCU and uses fuzzy control, neural network control, PID control, analog PID algorithm and neural network PID algorithm to control the temperature of the laser.

5. The automatic temperature control method for a distributed feedback laser according to claim 1, characterized in that: The NTC (5) is connected in series with the resistor R1 and then connected to the reference source. The resistance R0 of the NTC (5) at 25℃ is the same as that of the resistor R1. The relationship between the resistance R0 and the temperature is obtained through the RT curve.

6. The automatic temperature control method for a distributed feedback laser according to claim 5, characterized in that: Both R0 and R1 are 10kΩ, the accuracy of resistor R1 is 0.1%, and the B value of the NTC (5) is 3930.

7. The automatic temperature control method for a distributed feedback laser according to claim 5, characterized in that: The PID compensation network includes an operational amplifier U1, a capacitor C1, a capacitor C2 connected to the CTL1 port of the TEC controller (1), a resistor R2, a capacitor C3, a resistor R3 connected in sequence to the other end of the capacitor C1, a resistor R4 connected in parallel with the capacitor C3 and the resistor R3, a resistor R5 connected to both the resistor R4 and the resistor R3, an operational amplifier U2, and a resistor R6 and an operational amplifier U3 connected in sequence to the negative input terminal of the operational amplifier U2. The positive input terminal of operational amplifier U1 is connected to a reference voltage. VREF The negative input terminal is connected to capacitor C2, resistor R2, capacitor C3 and resistor R4 respectively, and the output terminal is connected to CTL1 port; The positive input terminal of the operational amplifier U2 is connected between resistor R1 and the NTC (5), the negative input terminal is connected to resistors R5 and R6, and the output terminal is connected to resistors R3, R4 and R5. The positive input terminal of operational amplifier U3 is V set The negative input terminal is connected between the output terminal and resistor R6.

8. The automatic temperature control method for a distributed feedback laser according to claim 7, characterized in that: The PID compensation network includes a variable resistance resistor and a variable capacitance capacitor.

9. The automatic temperature control method for a distributed feedback laser according to claim 1, characterized in that: The laser is a distributed feedback laser.

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