Dual-channel TEC temperature control circuit suitable for laser Doppler vibration measurement system

Abstract

The invention discloses a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system. The dual-channel TEC temperature control circuit comprises a power supply switch power supply circuit, a dual-semiconductor laser, a single-chip microcomputer, a dual-temperature acquisition circuit and a dual-TEC drive circuit. Wherein the double-semiconductor laser is used for outputting laser in a certain wavelength range; the single-chip microcomputer is used for adjusting the center temperature, the temperature control range and the like and setting output drive control voltage. The dual-temperature acquisition circuit is used for converting a temperature-sensitive resistor integrated in the dual-semiconductor laser into a proper voltage value and outputting the actual temperature of the dual-semiconductor laser; and the double-TEC driving circuit is used for controlling the TEC, and the magnitude and the direction of the current flowing through the TEC are adjusted by receiving a driving control signal, so that the heating and refrigeration of the TEC are controlled. The invention provides the dual-channel TEC temperature control circuit suitable for the laser Doppler vibration measurement system, the circuit and software configuration are simple, and the dual-channel TEC temperature control circuit can be suitable for any temperature control requirement of any semiconductor laser and is flexible in configuration.

Description

Technical Field

[0001] The invention relates to a semiconductor laser temperature control technology, and in particular to a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system. Background Art

[0002] Laser Doppler vibrometer system is an advanced measurement technology based on the principle of optical interference and Doppler effect, which is specially used for high-precision, non-contact vibration detection. The system emits a laser beam through a stable laser, and uses precision optical devices to accurately divide the laser into measurement light and reference light. When the measurement light is irradiated to the surface of the object to be measured, the tiny displacement caused by the vibration of the object will cause the frequency of the measurement light to produce a Doppler frequency shift. Through precise optical interference detection means, the system can capture the interference signal between the echo beam and the reference light, and accurately calculate the vibration speed and displacement of the object through complex signal processing algorithms. Due to the significant advantages of laser Doppler vibrometer system such as high precision and no additional mass influence, it has been widely used in mechanical vibration analysis, aerospace, precision manufacturing and other fields. In these fields, high-precision vibration measurement plays a vital role in ensuring product quality, optimizing mechanical performance and ensuring safe operation of equipment.

[0003] In the laser Doppler vibrometer system, the semiconductor laser is the core light source component, and the stability and accuracy of its performance have a decisive influence on the measurement accuracy and reliability of the entire system. In particular, the temperature stability of the laser is one of the key factors affecting its performance. Temperature changes will directly affect key parameters such as the laser's output wavelength, power, and spectral linewidth, thereby introducing measurement errors and affecting the measurement accuracy of the system. In order to meet the needs of different semiconductor lasers under different working conditions and adapt to the actual needs of different vibrometer systems, the temperature control circuit needs to have a flexible and adjustable temperature control range. By accurately adjusting the parameters of the temperature control circuit, accurate control of different lasers at different temperatures can be achieved to ensure that the laser always works in the best state, thereby improving the applicability and flexibility of the system.

[0004] Semiconductor lasers are usually composed of key components such as pump sources, gain media, thermistors, and thermoelectric coolers (TECs). Thermistors are used as temperature sensors to monitor the temperature of the laser in real time, while TECs adjust the current or voltage of the driver according to the feedback signal (resistance change) of the thermistor, thereby achieving temperature regulation of the laser. However, traditional TEC temperature control solutions have many shortcomings, such as poor linearization, fixed temperature control range, and difficulty in flexible adjustment through software. These defects limit its universality and versatility in practical applications.

[0005] At present, the mainstream TEC temperature control technology usually relies on the temperature-sensitive resistor integrated inside the laser to design the temperature acquisition circuit, and combines the PID control algorithm with the TEC drive circuit to achieve precise temperature control. However, the traditional temperature acquisition circuit is usually implemented with a simple voltage divider circuit, which has poor linearity performance, and the temperature control range and center temperature are often fixed, making it difficult to adapt to the needs of different lasers or different working environments. Without changing the hardware circuit, the traditional temperature acquisition circuit is difficult to flexibly adjust through software, which limits its flexibility and adaptability in practical applications.

[0006] In response to the above problems, Ye Mao et al. proposed an improved solution in their study "Design of high-precision temperature control system for semiconductor lasers", 2024, 53(4): 20230713, which uses a digital potentiometer to achieve a variable temperature control zero point to improve the flexibility and adaptability of the temperature control circuit. However, this solution uses FPGA as the control core, the circuit structure is relatively complex, and it uses iterative and multi-objective optimization algorithms to calculate the temperature control zero point, and the software design is relatively cumbersome. Xing Suxia et al. proposed a method of manually changing the NTC series resistance value to change the temperature control resolution and center temperature in their study "Design of high-precision semiconductor laser drive control system", 2020, 43(17): 174-180.DOI: 10.19651 / j.cnki.emt.2004775. Although it improves the flexibility of the temperature control circuit to a certain extent, the debugging process is cumbersome and the applicability is poor. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that the center temperature and temperature control range of the existing TEC control circuit temperature acquisition circuit are fixed, and the temperature range and center temperature cannot be flexibly adjusted according to the different semiconductor lasers used and the different temperature control requirements, that is, the wavelength tuning range is not flexible and the universality of use is low. Therefore, the present invention provides a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, which does not require the replacement of hardware resistors, and the circuit and software configurations are relatively simple, and can be applied to any temperature control requirements of any semiconductor laser, so that each laser can achieve the expected range of wavelength tuning within the expected set temperature range, and the configuration is flexible.

[0008] To achieve the above object, the present invention provides a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, comprising a power supply switch circuit, a dual semiconductor laser, a single-chip microcomputer, a dual temperature acquisition circuit, and a dual TEC drive circuit; wherein,

[0009] The dual semiconductor laser is used to output lasers within a certain wavelength range, including thermistors and TEC devices; the single chip microcomputer is used to adjust the center temperature and temperature control range, perform digital PID calculations, read the internal temperature value of the dual semiconductor laser, and set the output drive control voltage; the dual temperature acquisition circuit is used to convert the internal integrated thermistor of the dual semiconductor laser into a suitable voltage value and output the actual temperature of the dual semiconductor laser; the dual TEC drive circuit is used to control TEC, and controls TEC heating and cooling by receiving the drive control signal to adjust the size and direction of the current flowing through TEC;

[0010] The temperature-sensitive circuit of the dual semiconductor laser is connected to the dual temperature acquisition circuit. After the resistance value is converted into voltage, it is connected to the DAC input through the operational amplifier output and input into the single-chip microcomputer for temperature data reading. The single-chip microcomputer performs digital PID processing on the two acquired temperature values ​​and calculates the corresponding output control parameters, which are output to the TEC drive circuit via ADC. By changing the TEC current, closed-loop control of the wavelengths of the two dual semiconductor lasers is achieved.

[0011] Furthermore, the single chip microcomputer includes a main control chip, a reset chip and a storage chip. The main control chip is connected to a four-channel digital potentiometer for controlling the central temperature and temperature control range of each of the dual TECs.

[0012] Furthermore, the temperature control range collected by the dual temperature collection circuit fluctuates, and the required temperature control range is set by storing the temperature-sensitive resistor value at the corresponding temperature in the single-chip microcomputer.

[0013] Furthermore, the dual temperature acquisition circuit sets the resistance value of the digital potentiometer according to the required temperature control accuracy and range, so that when the main control chip controls the ADC to collect temperature information, the low point of the range corresponds to the lowest control temperature, the midpoint corresponds to the center temperature, and the high point corresponds to the highest control temperature, that is, the voltage data collected by the ADC is linearly related to the current temperature.

[0014] Furthermore, the dual temperature acquisition circuit includes an NTC1 temperature acquisition circuit and an NTC2 temperature acquisition circuit; both the NTC1 temperature acquisition circuit and the NTC2 temperature acquisition circuit include a specially designed amplifier component, a series of linearized resistor configurations and a temperature-sensitive resistor, wherein the rail-to-rail operational amplifier and the linearized resistors configured in series and parallel, as well as the temperature-sensitive resistor inside the TEC, together form a temperature-sensitive resistor linearization circuit with a specific structure;

[0015] It also includes a digital potentiometer, one end of the digital potentiometer R_DOP1 is connected to a specific reference voltage, and the other end is connected to the reverse input terminal of the operational amplifier; one end of the digital potentiometer R_DOP2 is connected to the reverse input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier; the series linear resistor R_DOWN is connected in series with the temperature-sensitive resistor R_NTC, and forms a parallel configuration with the parallel linear resistor R_PAR, one end of the two groups of resistors is connected to the reverse input terminal of the operational amplifier, and the other end is directly grounded; the positive input terminal of the operational amplifier is connected to another reference voltage, and its output is connected to an operational amplifier follower, and the output of the operational amplifier follower is connected to an input channel of the ADC, thereby realizing the collection and conversion of temperature signals.

[0016] Furthermore, in the thermistor linearization circuit of the temperature acquisition circuit, the resistance values ​​of the parallel linearization resistor R_PAR and the series linearization resistor R_DOWN are configured according to requirements, and appropriate resistance values ​​are selected to obtain the best linearity between the thermistor and the output voltage.

[0017] Furthermore, a digital potentiometer is set in the temperature sensitive resistor linearization circuit of the temperature acquisition circuit. Among them, R_NTC_SETTEMP is the resistance value of the thermistor when setting the center temperature of the temperature control. The center temperature is set according to actual needs. The dual-channel linearization circuit is exactly the same.

[0018] Furthermore, a digital potentiometer is set in the temperature sensitive resistor linearization circuit of the temperature acquisition circuit. in R_NTC_TOP is the resistance value of the thermistor at the highest temperature in the set temperature range; the temperature range is set according to actual needs, that is, R_NTC_TOP is adjusted, and the dual-channel linearization circuit is exactly the same.

[0019] Furthermore, the output voltage V_TEC_TEMP of the temperature acquisition circuit is in R_NTC is the thermistor resistance of the semiconductor laser at the current temperature, and the dual-channel temperature acquisition circuit is exactly the same.

[0020] Furthermore, according to the linear relationship between the thermistor and the output voltage in the temperature acquisition circuit, the output voltage corresponds to the temperature within the desired temperature control range one by one. According to the temperature characteristics of the semiconductor laser, after the main control chip sets the current stable temperature, the digital PID temperature control system controls the voltage value output to the drive circuit in real time according to the collected current temperature information, thereby adjusting the temperature of the semiconductor laser within the set temperature control range within the output voltage range of the DAC, and finally realizing the wavelength control and stabilization of the dual semiconductor laser.

[0021] Technical Effects

[0022] The present invention provides a dual-channel TEC temperature control circuit suitable for a laser Doppler vibrometer system. The circuit uses a single-chip microcomputer as the control core, and adjusts the series linear resistors and operational amplifier transimpedances in two temperature acquisition circuits respectively by accurately setting, calculating and controlling four digital potentiometers, thereby achieving the expected temperature control of two TECs (thermoelectric coolers). The temperature control circuit has the characteristic of adjustable center temperature control range, and can be flexibly adjusted according to different semiconductor lasers and any temperature control requirements to achieve any wavelength tuning range and control accuracy. In addition, the present invention also has the advantages of simple operation and strong applicability, and provides a stable and reliable temperature control solution for the laser Doppler vibrometer system.

[0023] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system according to a preferred embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of a single chip microcomputer and its peripheral circuits of a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system in a preferred embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of a dual temperature acquisition circuit of a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system in a preferred embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of a dual TEC driving circuit of a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system in a preferred embodiment of the present invention;

[0028] Figure 5 It is a preferred embodiment of the present invention, a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, the fixed controlled TEC center temperature is 25°C, and the corresponding temperature acquisition circuit output voltage versus temperature curve when the temperature control range is set differently;

[0029] Figure 6 A preferred embodiment of the present invention is a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, in which the fixed controlled TEC temperature control range is 5°C, and a curve diagram of the output voltage of the corresponding temperature acquisition circuit versus temperature when the center temperature is set differently. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] In the following description, specific details such as specific internal procedures and techniques are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0032] like Figure 1 As shown, the embodiment of the present invention provides a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, including a power supply switch circuit, a dual semiconductor laser, a single-chip microcomputer, a dual temperature acquisition circuit, and a dual TEC drive circuit; wherein,

[0033] The dual semiconductor laser is used to output lasers with a certain wavelength range, including thermistors and TEC devices; the single-chip microcomputer is used to adjust the center temperature and temperature control range, digital PID operation, read the internal temperature value of the dual semiconductor laser, and set the output drive control voltage; the dual temperature acquisition circuit is used to convert the integrated thermistor of the dual semiconductor laser into a suitable voltage value and output the actual temperature of the dual semiconductor laser; the dual TEC drive circuit is used to control the TEC, and the magnitude and direction of the current flowing through the TEC are adjusted by receiving the drive control signal to achieve the control of TEC heating and cooling; the temperature-sensitive circuit of the dual semiconductor laser is connected to the dual temperature acquisition circuit, and the resistance value is converted into voltage and then connected to the DAC input through the op amp output, and then input to the single-chip microcomputer for temperature data reading; the single-chip microcomputer performs digital PID processing on the two temperature values ​​obtained, and then calculates the corresponding output control parameters, which are output to the TEC drive circuit through the ADC, and the closed-loop control of the wavelength of the two dual semiconductor lasers is achieved by changing the TEC current. The laser Doppler vibration measurement system is a vibration measurement method for obtaining target displacement and velocity. In order to determine the target velocity, it is necessary to measure the Doppler shift when the wavelength is known. Therefore, it is necessary to control the wavelengths of the two lasers, that is, to control the temperatures of the two lasers to measure the Doppler shift.

[0034] Among them, the semiconductor laser used to output laser light of a certain wavelength integrates a negative temperature coefficient thermistor and a TEC device with a nominal resistance of 10KΩ@25℃ and a B value of 3950K@25℃.

[0035] The single chip microcomputer includes a main control chip, a reset chip and a storage chip. The main control chip is connected to a four-channel digital potentiometer to control the center temperature and temperature control range of the dual TEC. Figure 2 As shown, the main control chip is the single-chip microcomputer U8. U8 communicates with the four-channel digital potentiometer through SPI (serial peripheral interface) to adjust the resistance of each channel; U8 communicates with the external ADC and DAC through SPI to collect two-channel temperature data and set the output heating or cooling instructions; U8 receives external instructions through the serial port to set the current center temperature, temperature control range and preset temperature control value; U8, as the main control chip, uses digital PID combined with temperature information input to perform actual temperature control calculations. U10 is a non-volatile memory that stores the resistance information of the temperature-sensitive resistor at various temperatures and the relevant parameters of the digital PID. U11 is a watchdog chip to ensure that the reset operation can be started through a certain voltage value to eliminate the impact of transient interference on the single-chip microcomputer.

[0036] The temperature control range collected by the dual temperature acquisition circuit fluctuates. The required temperature control range is set by storing the temperature-sensitive resistor value at the corresponding temperature in the single-chip microcomputer.

[0037] Furthermore, the dual temperature acquisition circuit sets the resistance value of the digital potentiometer according to the required temperature control accuracy and range, so that when the main control chip controls the ADC to collect temperature information, the low point of the range corresponds to the lowest control temperature, the midpoint corresponds to the center temperature, and the high point corresponds to the highest control temperature, that is, the voltage data collected by the ADC is linearly related to the current temperature.

[0038] The dual temperature acquisition circuit includes an NTC1 temperature acquisition circuit and an NTC2 temperature acquisition circuit; both the NTC1 temperature acquisition circuit and the NTC2 temperature acquisition circuit include a specially designed amplifier component, a series of linearized resistor configurations and a temperature-sensitive resistor, wherein the rail-to-rail operational amplifier and the linearized resistors configured in series and parallel, as well as the temperature-sensitive resistor inside the TEC, together form a temperature-sensitive resistor linearization circuit with a specific structure;

[0039] It also includes a digital potentiometer, one end of the digital potentiometer R_DOP1 is connected to a specific reference voltage, and the other end is connected to the reverse input terminal of the operational amplifier; one end of the digital potentiometer R_DOP2 is connected to the reverse input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier; the series linear resistor R_DOWN is connected in series with the temperature-sensitive resistor R_NTC, and forms a parallel configuration with the parallel linear resistor R_PAR, one end of the two groups of resistors is connected to the reverse input terminal of the operational amplifier, and the other end is directly grounded; the positive input terminal of the operational amplifier is connected to another reference voltage, and its output is connected to an operational amplifier follower, and the output of the operational amplifier follower is connected to an input channel of the ADC, thereby realizing the collection and conversion of temperature signals.

[0040] In the thermistor linearization circuit of the temperature acquisition circuit, the resistance values ​​of the parallel linearization resistor R_PAR and the series linearization resistor R_DOWN are configured according to requirements, and the appropriate resistance values ​​are selected to obtain the best linearity between the thermistor and the output voltage.

[0041] In the temperature sensing resistor linearization circuit of the temperature acquisition circuit, set the digital potentiometer Among them, R_NTC_SETTEMP is the resistance value of the thermistor when setting the center temperature of the temperature control. The center temperature is set according to actual needs. The dual-channel linearization circuit is exactly the same.

[0042] In the temperature sensing resistor linearization circuit of the temperature acquisition circuit, set the digital potentiometer in R_NTC_TOP is the resistance value of the thermistor at the highest temperature in the set temperature range; the temperature range is set according to actual needs, that is, R_NTC_TOP is adjusted, and the dual-channel linearization circuit is exactly the same.

[0043] The output voltage V_TEC_TEMP of the temperature acquisition circuit is in R_NTC is the thermistor resistance of the semiconductor laser at the current temperature, and the dual-channel temperature acquisition circuit is exactly the same.

[0044] In this embodiment, it is assumed that an 8-bit, 100KΩ four-channel digital potentiometer is selected, the series linear resistor R_DOWN is 5KΩ, the parallel linear resistor R_PAR is 1MΩ, and the reference voltage is 2.5V. Set the center temperature to 25℃ and the temperature control range to 20~30℃. First, according to Calculate and set the digital potentiometer's center temperature corresponding resistance value R_DOP1 to 14.84375K. The current linearized thermistor value is calculated to be 12.890625K, and the digital potentiometer's op amp transresistance R_DOP2 is set to 98.046875K.

[0045] Therefore, the output voltage V_TEC_TEMP of the temperature acquisition circuit can be obtained as follows: in

[0046] The actual temperature control range is about 19.6℃~30℃, and the center temperature is about 24.85℃. The temperature control resolution using a 16-bit ADC is 0.00016℃ / 1LSB.

[0047] According to the linear relationship between the thermistor and the output voltage in the temperature acquisition circuit, the output voltage corresponds to the temperature within the desired temperature control range. According to the temperature characteristics of the semiconductor laser, after the main control chip sets the current stable temperature, the digital PID temperature control system controls the voltage value output to the drive circuit in real time according to the collected current temperature information, thereby adjusting the temperature of the semiconductor laser within the set temperature control range within the output voltage range of the DAC, and finally realizing the wavelength control and stabilization of the dual semiconductor laser.

[0048] like Figure 4 As shown, the driving circuit consists of an H-bridge, a current sampling and comparison circuit and an inverter. The H-bridge consists of two N-channel MOS tubes and two P-channel MOS tubes. The source of the two PMOS is connected to the TEC drive voltage, which is generated by a switching power supply. The drain is connected to the drain of the two NMOS respectively, and the other gates are connected to the voltage divider resistors respectively. Selecting a MOS with appropriate specifications and packaging, it is necessary to ensure that the threshold voltage Vth of NMOS and PMOS is strictly symmetrical about 0V. By setting the appropriate voltage divider resistance values ​​of R32, R33, R35, R36 and R54, R55, R56, and R57, it is possible to satisfy that under any circumstances, the two MOS tubes on one diagonal of the H-bridge are turned on and the two MOS tubes on the other diagonal are turned off, so that the H-bridge circuit can operate normally. The current sampling and comparison circuit consists of a sampling resistor, a comparator and an integrator. The resistance value and amplification factor of the sampling resistor must meet R SAM*A=1. The following is an example of the use of the present invention: the resistance of the current sampling resistor is set to 50mΩ, and R59, R58 and R37, R38 in the comparator are set to 1KΩ and 20KΩ respectively, that is, the amplification factor is set to 20 times accordingly. When a certain current flows through the sampling resistor, the comparator converts the current into a voltage difference and compares it with the midpoint of the DAC range 2.5V, and its output is connected to the reverse input end of the integrator. The positive input end of the integrator is connected to the DAC output voltage, and 0~5V corresponds linearly to the currently set temperature control range. When the comparator output is not equal to the DAC output voltage, the output voltage of the integrator changes accordingly until the comparator output is equal to the DAC output voltage, which indicates that the current temperature of the TEC is the same as the preset temperature value. The output voltage of the integrator can only control the opening and closing of the half-bridge MOS, so it is necessary to add an inverting circuit to control the opening and closing of the other half-bridge MOS, and the opening and closing states of the left and right half-bridges are mirrored. Select NMOS and PMOS with a threshold voltage of ±3V, and set the voltage divider resistors to 100K and 75K. The amplification factor of the inverter circuit needs to be matched according to the voltage loaded by the op amp. The forward input terminal of the inverter circuit is connected to half of the voltage loaded by the op amp, so that the reverse input voltage and the output voltage of the inverter are symmetrical about the midpoint. The op amp power supply voltage is loaded to 9V, that is, the forward input terminal of the inverter is loaded with a 4.5V reference voltage. The DAC output control voltage, the integrator control voltage, the inverter output voltage and the comparator output voltage are all linearly related and correspond one to one. As a result, the drive circuit can control the output voltage of the DAC through the MCU, accurately control the direction and size of the current flowing through the TEC, thereby achieving the effect of temperature control.

[0049] In the present invention, the curve of the output voltage of the temperature acquisition circuit with a central temperature of 25°C as a function of temperature is as follows: Figure 5 As shown. By changing the transresistance value of the digital potentiometer through the MCU, the temperature control range can be flexibly changed. Set the 16-bit DAC output half-scale 32767, that is, when the output is 2.5V, the TEC temperature will be stable at 25℃. When the DAC outputs 0-65535, the corresponding voltage range is 0-5V. Set the temperature-sensitive resistor divider value to 14.844K. Set the transresistance of the op amp to 98.0479K, 173.047K and 267.1875K respectively, which can achieve a temperature adjustment range of 10℃, 5℃ and 2.5℃ respectively.

[0050] In the present invention, the curve of the output voltage of the temperature acquisition circuit with a temperature control range of 5°C as a function of temperature is shown in FIG. Figure 6As shown. By changing the thermistor divider resistance value of the digital potentiometer and the transresistance value of the op amp through the MCU, the center temperature can be flexibly changed. Set the 16-bit DAC output half-scale 32767, that is, when the output is 2.5V, the TEC temperature will stabilize at the preset center temperature. When the DAC outputs 0 to 65535, the corresponding voltage range is 0 to 5V. Set the thermistor divider resistance value to 16.0156K, 14.844K and 13.672K respectively. Set the transresistance of the op amp to 202.7344K, 173.047K and 225.781K respectively, and the center temperature can be set to 22.5℃, 25℃ and 27.5℃ respectively.

[0051] The invention provides a dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, and designs a power supply switch power supply circuit, a dual semiconductor laser, a single-chip microcomputer and its peripheral circuit, a dual temperature acquisition circuit, and a dual TEC drive circuit; after determining the center temperature and the temperature range, the system uses an MCU to calculate and control the resistance of four digital potentiometers, sets different NTC series voltage divider resistors and operational amplifier transresistances for different semiconductor lasers, obtains two voltage values ​​corresponding to the two temperatures after being processed by the temperature acquisition circuit, and inputs the voltage data into the MCU through AD acquisition. The current expected stable temperature is set, and the MCU calculates the voltage value output at each moment according to the offset between the current and expected stable temperatures of a single TEC through a digital PID algorithm. The output voltage is converted into the corresponding amplitude and direction current value flowing through the TEC through an H-bridge drive circuit, that is, the drive circuit can control the voltage magnitude and positive and negative of the voltage at both ends of the TEC through the output voltage to control the magnitude and direction of the current flowing through the TEC, thereby controlling the heating or cooling of the TEC device, thereby realizing the target temperature control of different lasers in different temperature ranges, and the temperature of the two semiconductor lasers is read in real time by the MCU through two ADC channels. The present invention does not require the replacement of hardware resistors, and the circuit and software configurations are relatively simple, and can be applied to any temperature control requirements of any semiconductor laser. Each laser can achieve wavelength tuning within the expected range within the expected set temperature range, and the configuration is flexible. When the temperature control accuracy is high, the digital potentiometer can be controlled to increase the transimpedance of the operational amplifier to improve the resolution. When the temperature control range is wide, the digital potentiometer can be controlled to reduce the transimpedance of the operational amplifier to increase the temperature control range. Since the center temperature is variable, the expected control temperature can be adjusted to a small range close to the center temperature, which helps to overcome the temperature control nonlinearity phenomenon that the actual temperature at both ends often deviates from the set temperature in traditional digital PID.

[0052] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system, characterized in that: It includes a power switch circuit, a dual semiconductor laser, a single chip microcomputer, a dual temperature acquisition circuit, and a dual TEC drive circuit; among which, The dual semiconductor laser is used to output laser light within a certain wavelength range, and includes a temperature-sensitive resistor and a TEC device; the single-chip microcomputer is used to adjust the central temperature and the temperature control range, perform digital PID calculations, read the internal temperature value of the dual semiconductor laser, and set the output drive control voltage; the dual temperature acquisition circuit is used to convert the temperature-sensitive resistor integrated inside the dual semiconductor laser into a suitable voltage value, and output the actual temperature of the dual semiconductor laser; the dual TEC drive circuit is used to control the TEC, and controls the heating and cooling of the TEC by adjusting the magnitude and direction of the current flowing through the TEC through receiving a drive control signal; The temperature-sensitive circuit of the dual semiconductor laser is connected to the dual temperature acquisition circuit, and the resistance value is converted into voltage and then connected to the DAC input end through the operational amplifier output, and then input into the single-chip microcomputer for temperature data reading; the single-chip microcomputer performs digital PID processing on the two acquired temperature values, calculates the corresponding output control parameters, and outputs them to the TEC drive circuit via ADC, and realizes closed-loop control of the wavelengths of the two dual semiconductor lasers by changing the TEC current.

2. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 1, characterized in that: The single chip microcomputer comprises a main control chip, a reset chip and a storage chip. The main control chip is connected to a four-channel digital potentiometer for controlling the central temperature and the temperature control range of each of the dual TECs.

3. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 1, characterized in that: The temperature control range collected by the dual temperature collection circuit fluctuates. The required temperature control range is set by storing the temperature-sensitive resistor value at the corresponding temperature in the single-chip microcomputer.

4. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 1, characterized in that: The dual temperature acquisition circuit sets the resistance value of the digital potentiometer according to the required temperature control accuracy and range, so that when the main control chip controls the ADC to collect temperature information, the low point of the range corresponds to the lowest control temperature, the midpoint corresponds to the center temperature, and the high point corresponds to the highest control temperature, that is, the voltage data collected by the ADC is linearly related to the current temperature.

5. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 1, characterized in that: The dual temperature acquisition circuit includes an NTC1 temperature acquisition circuit and an NTC2 temperature acquisition circuit; the NTC1 temperature acquisition circuit and the NTC2 temperature acquisition circuit both include a specially designed amplifier component, a series of linearized resistor configurations and a temperature-sensitive resistor, wherein the rail-to-rail operational amplifier and the linearized resistors configured in series and parallel, and the temperature-sensitive resistor inside the TEC together form a temperature-sensitive resistor linearization circuit with a specific structure; It also includes a digital potentiometer, one end of the digital potentiometer R_DOP1 is connected to a specific reference voltage, and the other end is connected to the reverse input terminal of the operational amplifier; one end of the digital potentiometer R_DOP2 is connected to the reverse input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier; the series linear resistor R_DOWN is connected in series with the temperature-sensitive resistor R_NTC, and forms a parallel configuration with the parallel linear resistor R_PAR, one end of the two groups of resistors is connected to the reverse input terminal of the operational amplifier, and the other end is directly grounded; the positive input terminal of the operational amplifier is connected to another reference voltage, and its output is connected to an operational amplifier follower, and the output of the operational amplifier follower is connected to an input channel of the ADC, thereby realizing the collection and conversion of temperature signals.

6. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 5, characterized in that: In the thermistor linearization circuit of the temperature acquisition circuit, the resistance values ​​of the parallel linearization resistor R_PAR and the series linearization resistor R_DOWN are configured according to requirements, and the appropriate resistance values ​​are selected to obtain the best linearity between the thermistor and the output voltage.

7. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 5, characterized in that: In the temperature sensing resistor linearization circuit of the temperature acquisition circuit, set the digital potentiometer Wherein R_NTC_SETTEMP is the resistance value of the thermistor when setting the center temperature of the temperature control, wherein the center temperature is set according to actual needs, and the dual-channel linearization circuit is exactly the same.

8. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 5, characterized in that: In the temperature sensing resistor linearization circuit of the temperature acquisition circuit, set the digital potentiometer in R_NTC_TOP is the resistance value of the thermistor at the highest temperature in the set temperature range; the temperature range is set according to actual needs, that is, R_NTC_TOP is adjusted, and the dual-channel linearization circuit is exactly the same.

9. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 5, characterized in that: The output voltage V_TEC_TEMP of the temperature acquisition circuit is in R_NTC is the resistance value of the thermistor of the semiconductor laser at the current temperature, and the dual-channel temperature acquisition circuit is exactly the same.

10. A dual-channel TEC temperature control circuit suitable for a laser Doppler vibration measurement system as claimed in claim 9, characterized in that: According to the linear relationship between the thermistor and the output voltage in the temperature acquisition circuit, the output voltage corresponds to the temperature within the desired temperature control range. According to the temperature characteristics of the semiconductor laser, after the main control chip sets the current stable temperature, the digital PID temperature control system controls the voltage value output to the drive circuit in real time according to the collected current temperature information, thereby adjusting the temperature of the semiconductor laser within the set temperature control range within the output voltage range of the DAC, and finally realizing the wavelength control and stabilization of the dual semiconductor laser.

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