Semiconductor laser temperature control system

Abstract

The utility model relates to a semiconductor laser temperature control system, and relates to the technical field of temperature control. Two sets of thermoelectric coolers and temperature sensors are packaged in a semiconductor laser, and a temperature acquisition signal processing module is used for acquiring signals of the temperature sensors in real time; the dual-channel analog-to-digital converter is used for converting the voltage analog signal into a voltage digital signal; the single chip microcomputer is used for converting the acquired voltage digital signal into a driving signal; the integrated digital PID calculation unit adjusts the temperature of the semiconductor laser; the dual-channel digital-to-analog converter is used for sending analog voltage signals to the two groups of TEC drivers; the TEC driver is used for applying driving current to the thermoelectric refrigerating unit. According to the integrated temperature control system of the dual-channel analog-to-digital converter and the dual-channel digital-to-analog converter, multi-channel temperature control can be realized in single equipment, the equipment cost is remarkably reduced, and the precision and the reliability of the system are improved at the same time.

Description

Technical Field

[0001] The utility model relates to the technical field of temperature control, in particular to a semiconductor laser temperature control system. Background Art

[0002] As an efficient light source, semiconductor lasers play a key role in many scientific and technological fields. Their performance, especially output power, wavelength stability and optical properties, is extremely sensitive to temperature. Temperature fluctuations may lead to degradation of laser performance, such as wavelength shift, output power attenuation and noise increase, thus affecting the performance and reliability of the entire system. Therefore, accurate temperature control is essential to maintain semiconductor lasers in optimal working conditions. Traditional temperature control solutions often have only a single temperature control loop, which is incapable of meeting the complex requirements of simultaneously controlling the temperature of the laser itself and other internal devices. For example, the utility model patent application "Semiconductor Laser Automatic Temperature Control System" with application number 201410480407.9 filed by Zhu Jun in 2014 uses a Wheatstone bridge and comparator circuit to achieve temperature control. These solutions usually rely on dispersed components and self-built bridge circuits, resulting in a large system size, high component consumption, and insufficient stability, making it difficult to achieve high-precision temperature control. When building a multi-channel independent temperature control system, the complexity and cost of the system double. Therefore, developing an integrated dual-channel temperature control system that can accurately control the temperature of the laser and its internal key components in a compact device has become an urgent need for the development of the industry.

[0003] With the continuous advancement of semiconductor technology, modern integrated circuit design enables a single mature chip to integrate functions that previously required multiple independent components to achieve, while ensuring high precision. Against the background of the growing demand for multi-channel temperature control, the traditional multi-device temperature control solution is not only bulky and costly, but also not conducive to the miniaturization and cost-effectiveness of semiconductor lasers.

[0004] Therefore, how to provide a semiconductor laser temperature control system has become a technical problem that technical personnel in this field urgently need to solve. Utility Model Content

[0005] The main purpose of the utility model is to provide a semiconductor laser temperature control system, which adopts an integrated temperature control system of a dual-channel analog-to-digital converter and a dual-channel digital-to-analog converter, can realize multi-channel temperature control in a single device, significantly reduce the equipment cost, and improve the accuracy and reliability of the system.

[0006] To achieve the above-mentioned purpose, the utility model provides a semiconductor laser temperature control system, comprising: a semiconductor laser, a temperature acquisition signal processing module, a dual-channel analog-to-digital converter, a single-chip microcomputer, an integrated digital PID calculation unit, a dual-channel digital-to-analog converter and a TEC driver; wherein, two groups of thermoelectric coolers and a temperature sensor are encapsulated inside the semiconductor laser, the temperature acquisition signal processing module is connected to the temperature sensor, and is used to collect the signal of the temperature sensor in real time and convert it into a voltage analog signal; the dual-channel analog-to-digital converter is connected to the temperature acquisition signal processing module, and is used to convert the voltage analog signal of the feedback temperature information into a voltage digital signal for processing by the single-chip microcomputer; the single-chip microcomputer is connected to the dual-channel analog-to-digital converter, and is used to convert the collected voltage digital signal into a drive signal; the integrated digital PID calculation unit is connected to the single-chip microcomputer to adjust the temperature of the semiconductor laser; the dual-channel digital-to-analog converter is connected to the integrated digital PID calculation unit, and is used to send the analog voltage signal to two groups of TEC drivers; the TEC driver is connected to the thermoelectric cooler, and is used to apply a drive current to the thermoelectric cooler.

[0007] Furthermore, the temperature sensor adopts a thermistor with a negative temperature coefficient, and the resistance value decreases as the temperature rises.

[0008] Furthermore, the single chip microcomputer is integrated with a communication interface, allowing two-way data exchange and remote control with external devices, so that the user can independently set the temperature parameters of each temperature control channel, and has the function of uploading temperature control system status information to external devices.

[0009] Furthermore, the temperature acquisition signal processing module adopts a voltage comparator circuit design, and sets the temperature control center of the temperature control system by adjusting the resistance value of the comparison resistor, and sets the temperature control range by changing the feedback resistor.

[0010] Furthermore, the dual-channel analog-to-digital converter has at least 16-bit sampling accuracy, low noise, and a sampling rate of more than 1 MHz.

[0011] Furthermore, the dual-channel digital-to-analog converter has low power consumption, dual channels, and at least 16-bit precision buffered voltage output capability.

[0012] The beneficial effects of the utility model are:

[0013] (1) The utility model integrates a high-precision dual-channel analog-to-digital converter (ADC) and a dual-channel digital-to-analog converter (DAC), and combines it with an advanced integrated digital PID calculation unit, which not only realizes the accurate detection of the temperature of the laser and other internal devices, but also significantly improves the stability and long-term reliability of the system. This design enables the system to achieve high-precision temperature control better than ±0.01°C, meeting the stringent requirements of semiconductor lasers for temperature control accuracy.

[0014] (2) The utility model significantly simplifies the circuit design and greatly reduces the space occupied by components by adopting a multi-channel input and output analog chip and an integrated bridge-driven TEC driver. This innovative solution can independently and accurately control the temperature of a semiconductor laser and multiple key components inside it with only one device, reducing the complexity of the system, reducing costs and space occupation, and providing an economical and efficient solution for the temperature control of semiconductor lasers. In addition, the compactness and simplified design of the system also bring the advantages of easy maintenance and upgrading, further enhancing its feasibility and market competitiveness in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the system structure of the utility model;

[0016] Figure 2 This is the design diagram of the thermistor signal conversion analog voltage circuit in the utility model;

[0017] Figure 3 The characteristic curve of the relationship between the output voltage of the signal processing module and the temperature in the utility model;

[0018] Figure 4 This is the structure diagram of the dual-channel digital PID control algorithm of the utility model;

[0019] Figure 5 This is a temperature error diagram of the laser in the utility model after monitoring for 30 minutes. DETAILED DESCRIPTION

[0020] In order to achieve the above-mentioned purpose and effect, the technical means and structure adopted by the utility model are described in detail with reference to the accompanying drawings for the preferred embodiments of the utility model and their features and functions.

[0021] In view of the deficiencies of the prior art, the utility model provides an innovative semiconductor laser dual-channel temperature control system, aiming to solve the problems of low integration, insufficient temperature control accuracy and high cost of multi-channel temperature control in the prior art semiconductor laser temperature control system.

[0022] Traditional temperature control solutions are limited in terms of integration, accuracy and cost-effectiveness. This system has achieved independent and precise temperature control of semiconductor lasers and their internal key components, such as optical etalons, in a compact single device through a breakthrough design. This system significantly improves temperature control accuracy, reduces system complexity and overall cost, while reducing equipment footprint, providing a cost-effective solution for semiconductor laser temperature control.

[0023] The utility model proposes a semiconductor laser temperature control system, which adopts the design concept of miniaturization, low cost and high precision. Through the integrated dual-channel analog-to-digital converter (ADC) and dual-channel digital-to-analog converter (DAC), as well as advanced digital PID control algorithms, the system not only realizes the precise temperature control of the laser and other internal devices with temperature control requirements, but also greatly simplifies the circuit design, reduces the space occupied by components, and improves the stability and long-term reliability of the system. This innovative multi-channel temperature control solution not only meets the technical challenges of semiconductor lasers in high-precision temperature control, but also brings significant economic and practical value to related application fields.

[0024] like Figure 1-2 As shown, the utility model provides a semiconductor laser temperature control system, including: a semiconductor laser, a temperature acquisition signal processing module, a dual-channel analog-to-digital converter, a single-chip microcomputer, an integrated digital PID calculation unit, a dual-channel digital-to-analog converter and a TEC driver.

[0025] A semiconductor laser, which is internally encapsulated with two sets of thermoelectric coolers and a temperature sensor. The thermoelectric cooler is used to independently control the temperature of different areas inside the semiconductor laser tube shell; the temperature sensor is installed at the key thermal node position to monitor the temperature in real time and provide accurate temperature feedback to the single-chip microcomputer;

[0026] The temperature acquisition signal processing module is used to collect the temperature sensor signal in real time and accurately convert it into an adaptive voltage analog signal;

[0027] Dual-channel analog-to-digital converter, with two voltage sampling channels, used to convert the voltage analog signal of feedback temperature information into a voltage digital signal for processing by the microcontroller;

[0028] A single chip microcomputer, configured with a temperature control algorithm, is used to process the collected voltage digital signal and generate control instructions to achieve real-time temperature adjustment and manage the operation of the temperature control system;

[0029] Integrated digital PID calculation unit calculates the correction value according to the deviation between the actual detected temperature and the set temperature, and sends the correction value to the dual-channel digital-to-analog converter to achieve precise adjustment and stable control of the semiconductor laser temperature;

[0030] A dual-channel digital-to-analog converter with two voltage output channels is used to convert the correction amount into an analog voltage signal and send it to two sets of TEC drivers respectively;

[0031] The TEC driver applies a corresponding driving current to the thermoelectric cooler according to the voltage signal sent by the dual-channel digital-to-analog converter, and determines the direction of the output driving current according to the comparison result between the voltage signal and the reference voltage.

[0032] Further optimization, the temperature sensor uses a thermistor with a negative temperature coefficient, and the resistance value decreases as the temperature rises.

[0033] Further optimization, the single-chip microcomputer is integrated with a communication interface, allowing two-way data exchange and remote control with external devices, so that users can independently set the temperature parameters of each temperature control channel, and have the function of uploading temperature control system status information to external devices. The single-chip microcomputer adopts STMicroelectronics' ARM core product G070RBT6, which has a hardware SPI communication interface, 59 GPIO ports, and 128KB program storage capacity. This type of single-chip microcomputer is inexpensive and its performance meets the needs of dual-channel temperature control and calculation. At the same time, it also supports domestic single-chip microcomputers such as GigaDevice GD32 series as alternatives. The single-chip microcomputer integrates a UART or I2C communication interface, which can upload system status information such as the temperature detected by the thermistor, the current and voltage of the TEC, and the set PID parameters to the host computer through the communication interface, and the user can also issue control instructions.

[0034] like Figure 2 As shown, the temperature acquisition signal processing module adopts a voltage comparator circuit design, which sets the temperature control center of the temperature control system by adjusting the resistance of the comparison resistor, and sets the temperature control range by changing the feedback resistor. The temperature acquisition signal processing module accurately converts the resistance change of the NTC into a linear voltage output. Figure 2 As shown in the figure, the module adopts a voltage comparator circuit design, in which the voltage divider resistors R1 and R2 have the same resistance value, which is used to provide a stable reference voltage neutral point. Resistor R4 is an NTC thermistor, and its nominal resistance is 10kΩ at room temperature of 25℃. In order to adapt to different working environment temperature ranges, a compensation resistor R5 is introduced, and its resistance value is accurately calculated to adjust the temperature control center point of the temperature control system and optimize the linear relationship between voltage and temperature. The resistance value of the matching resistor R3 is equal to the sum of R4 and R5 to ensure the balance of the circuit. The feedback resistor R6 of the operational amplifier determines the amplitude of the output terminal of the operational amplifier. By adjusting the resistance value of R6, the temperature control range of the temperature control system can be set, and at the same time, the output voltage can be ensured to be within the input range of the analog-to-digital converter.

[0035] In the selection of operational amplifiers, the utility model example uses the OPA2376 dual-channel precision operational amplifier produced by Texas Instruments. The operational amplifier has an extremely low offset voltage, which enables it to maintain a very small deviation when converting the resistance change of the NTC thermistor into a voltage, thereby ensuring that the detected temperature obtained by calculation has higher accuracy and less distortion.

[0036] like Figure 3 As shown, the temperature control system of this embodiment sets the temperature control center to 35°C, the temperature control range is 15-55°C, and the corresponding voltage output range is 0-2.5V. It can be seen from the figure that the temperature feedback from the thermistor can be basically converted into voltage linearly. Using a 16-bit precision analog-to-digital converter, the temperature acquisition signal processing module can achieve a resolution of 0.0006°C.

[0037] Further optimization, the dual-channel analog-to-digital converter has at least 16-bit sampling accuracy, low noise, and a sampling rate of more than 1MHz. The dual-channel analog-to-digital converter uses the AD7616 chip of ADI, which has 16 voltage input channels, all channels can achieve 16-bit resolution without missing codes, and the conversion speed is up to 1MSPS. This can ensure the accuracy of temperature acquisition and can quickly respond to temperature changes, so that the temperature control system can quickly and accurately control the temperature of the semiconductor laser to the set value. In addition, the redundant input channels provide convenience for the expansion of more temperature control channels in the future.

[0038] In order to meet the application of lasers and other devices in different scenarios, the control range of the temperature control circuit must be large enough. At the same time, in order to achieve fast response of TEC and improve the temperature control accuracy, TI's DAC80502 analog-to-digital conversion chip was selected to generate the voltage signal calculated by the PID control algorithm. The chip has a 16-bit resolution, a dual-channel output voltage range of 0-2.5V, a full-scale voltage settling time of less than 5us, and an integral linearity of 1LSB, with the advantages of high precision and high speed. The voltage signal output by the digital-to-analog conversion circuit controls the TEC driver and changes the current flowing through the two ends of the TEC.

[0039] In order to accurately control the temperature of the semiconductor laser, a TEC is encapsulated inside the semiconductor laser, which is a semiconductor device that can both cool and heat. By adjusting the direction and size of the current flowing through the TEC, the cooling or heating power of the TEC can be controlled, thereby adjusting the temperature of the semiconductor laser. In order to effectively drive the TEC and ensure the precise control of the laser temperature, the embodiment of the utility model uses the ADN8834 thermoelectric cooler controller chip of ADI as the TEC driver. The chip integrates a low on-resistance MOSFET, builds an efficient H-bridge circuit, and uses a single inductor to output linear power. This design enables the chip to provide a maximum current output of up to 1.5A in a smaller volume. In addition, the chip has the maximum output current and maximum output voltage limiting functions. The current and voltage output of the circuit can be limited by configuring resistors to prevent the temperature of the TEC from being too high or too low to damage the semiconductor laser.

[0040] Further optimized, the dual-channel digital-to-analog converter has low power consumption, dual channels, and at least 16-bit precision buffered voltage output capability.

[0041] Further optimization, in order to achieve precise temperature control of semiconductor lasers and their optical standards, a digital PID calculation unit is programmed in the single-chip microcomputer to drive a dual temperature control loop. The integrated digital PID calculation unit includes a software control algorithm implemented in the single-chip microcomputer, which can collect the error between the actual temperature feedback of the thermistor and the set temperature within a set time period, and calculate the voltage value applied to the TEC driver by each output channel of the DAC in the next cycle according to the preset proportional, integral and differential coefficients, thereby correcting the actual temperature. Specifically, the calculation unit performs PID calculation on the deviation between the collected actual temperature and the set temperature, and outputs the calculation result to the TEC driver through a digital-to-analog converter to achieve the purpose of temperature control. The PID algorithm formula can be expressed as: U(t)=K P ·E T +K I ∑E t +K D (E T -E T-1 ), where E is the temperature error of a certain sampling period, and Kp, Ki, and Kd are the proportional, integral, and differential coefficients, respectively. In order to reduce the problem of long stabilization time caused by overshoot of the control system, the limit of the integral term is introduced into the control algorithm to limit the maximum and minimum values ​​of the integral term, thereby enhancing the stability of the system.

[0042] The algorithm structure is as follows Figure 4 As shown in the figure, the temperature stability target of the dual-channel temperature control is set first. In each temperature control cycle, the microcontroller reads the actual temperature value from the thermistor near the laser and the optical standard through the dual-channel ADC. The difference between the actual temperature and the set temperature, i.e. the error ET , substitute the set proportional coefficient, integral coefficient and differential coefficient for PID operation, and obtain the voltage values ​​output by the dual-channel DAC in the next cycle. Subsequently, the microcontroller transmits the calculated voltage value to the DAC80502 chip through the SPI communication interface, and the latter establishes the corresponding voltage output. These output voltages are then used to control each TEC driver ADN8834, adjust the direction and size of its output current, and accurately control the cooling or heating power of the TEC, so as to achieve constant temperature control of the laser and its optical standard.

[0043] The integrated digital PID calculation unit also includes an adaptive adjustment algorithm, which can automatically adjust the temperature control parameters according to the working state of the laser and environmental changes.

[0044] like Figure 5 As shown in the figure, when the ambient temperature is 25℃, the laser temperature control is set at 40℃. After the temperature control system reaches a stable state, the temperature read by the microcontroller is sent to the host computer through the serial port, and the actual temperature fluctuation of the laser when the system turns on the temperature control is recorded. The test results show that within a 30-minute detection period, the temperature fluctuation of the laser is less than ±0.005℃, which meets the technical requirements of the semiconductor laser dual-path temperature control system of the utility model.

[0045] The utility model integrates a high-precision dual-channel analog-to-digital converter (ADC) and a dual-channel digital-to-analog converter (DAC), and combines it with an advanced integrated digital PID calculation unit, which not only realizes the accurate detection of the temperature of the laser and other internal devices, but also significantly improves the stability and long-term reliability of the system. This design enables the system to achieve high-precision temperature control better than ±0.01°C, meeting the strict requirements of semiconductor lasers for temperature control accuracy. The utility model significantly simplifies the circuit design and greatly reduces the space occupied by components by adopting an analog chip with multi-channel input and output and a TEC driver with integrated bridge drive. This innovative solution only requires one device to independently and accurately control the temperature of a semiconductor laser and multiple key components inside it, reducing the complexity of the system, reducing costs and space occupancy, and providing a cost-effective solution for the temperature control of semiconductor lasers. The system has a variety of protection mechanisms, including thermistor short circuit or open circuit protection, over-temperature protection, TEC overcurrent and short circuit protection, and the system state exceeds the threshold to trigger the protection to shut down the TEC driver output to ensure the safe operation of the system. The modular design of the system combines redundancy and multiple protection mechanisms to enhance the safety and reliability of the system. In addition, the compactness and simplified design of the system also bring the advantages of easy maintenance and upgrading, further enhancing its feasibility and market competitiveness in practical applications. With its simple structure and efficient performance, the temperature control system is particularly suitable for semiconductor laser application scenarios with multi-channel temperature control requirements and extremely high temperature control accuracy requirements.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A semiconductor laser temperature control system, characterized in that: include: Semiconductor laser, temperature acquisition signal processing module, dual-channel analog-to-digital converter, single-chip microcomputer, integrated digital PID calculation unit, dual-channel digital-to-analog converter and TEC driver; wherein, two groups of thermoelectric coolers and temperature sensors are encapsulated inside the semiconductor laser, the temperature acquisition signal processing module is connected to the temperature sensor, and is used to collect the signal of the temperature sensor in real time and convert it into a voltage analog signal; the dual-channel analog-to-digital converter is connected to the temperature acquisition signal processing module, and is used to convert the voltage analog signal of the feedback temperature information into a voltage digital signal for processing by the single-chip microcomputer; the single-chip microcomputer is connected to the dual-channel analog-to-digital converter, and is used to convert the collected voltage digital signal into a drive signal; the integrated digital PID calculation unit is connected to the single-chip microcomputer to adjust the temperature of the semiconductor laser; the dual-channel digital-to-analog converter is connected to the integrated digital PID calculation unit, and is used to send the analog voltage signal to two groups of TEC drivers; The TEC driver is connected to the thermoelectric cooler and is used to apply a driving current to the thermoelectric cooler.

2. A semiconductor laser temperature control system as claimed in claim 1, characterized in that: The temperature sensor adopts a thermistor with a negative temperature coefficient, and the resistance value decreases as the temperature rises.

3. A semiconductor laser temperature control system as claimed in claim 1, characterized in that: The single chip microcomputer is integrated with a communication interface, allowing two-way data exchange and remote control with external devices, being able to independently set the temperature parameters of each temperature control channel, and having the function of uploading temperature control system status information to external devices.

4. A semiconductor laser temperature control system as claimed in claim 1, characterized in that: The temperature acquisition signal processing module adopts a voltage comparator circuit design, and sets the temperature control center of the temperature control system by adjusting the resistance value of the comparison resistor, and sets the temperature control range by changing the feedback resistor.

5. A semiconductor laser temperature control system as claimed in claim 1, characterized in that: The dual-channel analog-to-digital converter has at least 16-bit sampling accuracy, low noise, and a sampling rate of more than 1 MHz.

6. A semiconductor laser temperature control system as claimed in claim 1 or 5, characterized in that: The dual-channel digital-to-analog converter has low power consumption, dual channels, and at least 16-bit precision buffered voltage output capability.

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