Local temperature control module and application thereof

Abstract

The invention belongs to the related technical field of temperature control, and discloses a local temperature control module and application thereof, the local temperature control module comprises a temperature acquisition sub-module and a temperature control sub-module; the temperature acquisition sub-module acquires the temperature of a working environment through a 24-bit high-resolution ADC sampling and constant current source inversion method; and the temperature control sub-module is used for calculating the deviation between the temperature acquired by the temperature acquisition sub-module and the preset temperature, and calculating and outputting a PWM signal through a fuzzy PID algorithm to drive a semiconductor refrigerator TEC to heat or refrigerate the working environment, so that the environment temperature reaches a preset temperature value. The control precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to temperature control, and more specifically, relates to a local temperature control module and application thereof. Background Art

[0002] At present, the performance and parameters of many precision electronic components and optical devices are affected by changes in the working environment temperature, resulting in instability, namely temperature drift characteristics. For example, precision resistors, operational amplifier chips, and filter capacitors, etc. The circuit modules composed of these components that are easily affected by temperature changes and have unstable performance will bring uncertainty to the entire system product when working. If high-precision temperature control can be made in the local range where these components are located and their temperature drift can be suppressed to a low level, the accuracy and stability of the circuit modules and even the entire system product will be greatly improved.

[0003] In the prior art, the traditional temperature control method has limitations, which are mainly reflected in: the control accuracy is not high due to the low accuracy of the temperature acquisition link and the delay and lag of the control system; the system is a combined structure, the correlation between modules is relatively strong, the functional modules cannot work alone, and the integration is low; some only have heating modules, relying on natural heat dissipation, which is inefficient and not conducive to the implementation of temperature control algorithms. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a local temperature control module and application thereof, which aims to solve the problem of low control accuracy of the existing temperature control method.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present invention, a local temperature control module is provided, which includes a temperature acquisition submodule and a temperature control submodule; the temperature acquisition submodule acquires the temperature of the working environment through 24-bit high-resolution ADC sampling and a constant current source inversion method; the temperature control submodule is used to calculate the deviation between the temperature acquired by the temperature acquisition submodule and the preset temperature, and then calculates and outputs a PWM signal through a fuzzy PID algorithm to drive a semiconductor cooler TEC to heat or cool the working environment so that the ambient temperature reaches a preset temperature value.

[0006] Furthermore, the temperature acquisition submodule includes a constant current source circuit, a resistance ratio measurement circuit, a signal conditioning circuit and an A / D conversion circuit; the constant current source circuit is used to provide a 10uA constant current to the resistance ratio measurement circuit; the resistance ratio measurement circuit includes a standard resistor and an NTC thermistor, and the standard resistor and the NTC thermistor are connected in series; the signal conditioning circuit is used to gain amplify the voltage signal collected from the resistance ratio measurement circuit; the A / D conversion circuit is used to convert the analog voltage signal from the signal conditioning circuit into a digital signal and transmit it to the main control MCU of the temperature control submodule.

[0007] Furthermore, the constant current source circuit is a bidirectional constant current source, which uses a mechanical micro signal relay to control the switching current direction.

[0008] Furthermore, the constant current source circuit completely disconnects the current through a single-chip CMOS single-pole single-throw switch, sets a predetermined delay time, and after the delay ends, the mechanical micro-signal relay switches the current direction and then re-energizes through the switch chip.

[0009] Furthermore, the temperature acquisition submodule calculates the resistance ratio of the thermistor and the standard resistor using the four collected voltage data, determines the resistance value of the thermistor by the resistance value of the standard resistor, and determines the temperature of the measured working environment by the resistance-temperature conversion formula of the thermistor.

[0010] Furthermore, the temperature acquisition submodule also includes a mechanical micro-signal relay switching circuit, which is used to connect the ADC to both ends of the standard resistor and the thermistor, and switch the ADC to measure the standard resistor or the thermistor; it is also used to control the forward or reverse direction of the constant current source circuit, and pass the corresponding forward current or reverse current into the resistance ratio measurement circuit.

[0011] Furthermore, when the mechanical micro signal relay switching circuit is in the first working state, a forward current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the standard resistor;

[0012] When the mechanical micro signal relay switching circuit is in the second working state, a forward current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the thermistor;

[0013] When the mechanical micro signal relay switching circuit is in the third working state, a reverse current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the standard resistor;

[0014] When the mechanical micro signal relay switching circuit is in the fourth working state, a reverse current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the thermistor.

[0015] Furthermore, the temperature acquisition submodule calculates the resistance ratio of the thermistor and the standard resistor using the four collected voltage data, and then determines the resistance value of the thermistor by the resistance value of the standard resistor. The corresponding calculation formula is:

[0016]

[0017] Where RT is the thermistor resistance, RS is the standard resistor resistance, and U RT1 U is the voltage across the thermistor collected by the ADC when the forward current is passed. RT2 U is the voltage across the thermistor collected by the ADC when the reverse current is passed. RS1 U is the voltage across the standard resistor collected by the ADC when the forward current is passed. RS2 It is the voltage across the standard resistor collected by the ADC when reverse current is passed.

[0018] Furthermore, the temperature control submodule includes a fuzzy PID controller, an STM32 single-chip microcomputer, a TEC driver chip and a TEC semiconductor refrigerator. The STM32 single-chip microcomputer serves as the main control MCU of the temperature control submodule. The temperature acquisition submodule is used to acquire the temperature of the temperature-controlled object and transmit the acquired temperature information to the main control MCU of the temperature control submodule. The main control MCU calculates the error e and the error change rate ec between the current temperature value and the set temperature value according to the received temperature data, and uses the error e and the error change rate ec as inputs of the fuzzy PID controller; the fuzzy PID controller is used to control the STM32 single-chip microcomputer to output a corresponding PWM duty cycle signal to the TEC driver chip after processing the received data. The TEC driver chip is used to output a temperature control signal to the TEC semiconductor refrigerator. The TEC semiconductor refrigerator is used to heat or cool the temperature-controlled object.

[0019] The present invention also provides an application of the local temperature control module as described above in electronic components and / or optical devices.

[0020] In general, compared with the prior art, the local temperature control module and its application provided by the present invention have the following beneficial effects:

[0021] 1. The temperature of the working environment is collected by 24-bit high-resolution ADC sampling and constant current source reversal method. In the process of constant current source reversal, the transient voltage impact problem is taken into consideration and suppressed, which can effectively reduce the impact, give full play to the output performance of the precision constant current source, and the temperature collection accuracy is high.

[0022] 2. The fuzzy PID algorithm is combined with the pulse width modulation signal (PWM signal) of STM32, and the bidirectional precision temperature control of heating and cooling is realized through the high-performance isolated half-bridge gate driver, which can achieve high-precision temperature control effects for precision electronic components, optical devices and other objects.

[0023] 3. The present invention adopts an independent module design, which is divided into a high-precision temperature acquisition submodule and a high-precision temperature control submodule. The two submodules realize independent functions, have high integration, low cost, small size and compact structure.

[0024] 4. The constant current source circuit adopts the "break before make" method. The current is completely disconnected through a single-chip CMOS single-pole single-throw switch (ADG802). A certain delay time (millisecond level) is set. After the delay ends, the mechanical micro-signal relay switches the current direction and then the power is turned on again through the switch chip. At this time, the current is already in the reverse state, so the transient impact generated when the current direction is switched can be reduced or avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic block diagram of the overall principle of a local temperature control module provided by the present invention;

[0026] Figure 2 It is a system flow chart of the local temperature control module provided by the present invention;

[0027] Figure 3 It is an algorithm flow chart of the temperature control method according to the present invention;

[0028] Figure 4 It is a principle diagram of a constant current source circuit involved in the present invention;

[0029] Figure 5 (a) and (b) are respectively the application principle diagrams of the TEC drive circuit involved in the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of 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. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] In order to solve the problems of low temperature acquisition accuracy, low control accuracy, low integration, and incomplete cooling or heating functions in the existing temperature control technology, the present invention provides a high-precision local temperature control module, which has high acquisition accuracy, high control accuracy and high integration, and has low cost, small size and compact structure.

[0032] The local temperature control module includes a temperature acquisition submodule and a temperature control submodule, and the temperature acquisition submodule and the temperature control submodule are respectively a high-precision temperature acquisition submodule and a high-precision temperature control submodule.

[0033] The temperature acquisition submodule collects the working environment temperature through the NTC thermistor four-wire ratio measurement method and 24-bit high-resolution ADC. Among them, the temperature acquisition submodule includes a constant current source circuit, a resistance ratio measurement circuit, a signal conditioning circuit and an A / D conversion circuit. The constant current source circuit is used to provide a 10uA constant current to the resistance ratio measurement circuit. The resistance ratio measurement circuit includes a standard resistor and an NTC thermistor, the standard resistor and the NTC thermistor are connected in series, the temperature drift of the resistance value of the standard resistor is extremely small, and the resistance value hardly changes with temperature. The resistance value of the NTC thermistor changes with temperature. The signal conditioning circuit is used to gain amplify the voltage signal collected from the resistance ratio measurement circuit, and the gain multiple is 10 times. The A / D conversion circuit is used to convert the analog voltage signal from the signal conditioning circuit into a digital signal and transmit it to the main control MCU of the temperature control submodule.

[0034] The constant current source circuit is a bidirectional constant current source, which uses a mechanical micro signal relay to control the switching current direction. When the micro signal relay controls the current direction to change suddenly, it will inevitably cause the circuit to generate transient voltage shocks, resulting in voltage spikes, affecting the acquisition accuracy. In order to reduce the shock, the "break before make" method is adopted. The constant current source circuit completely disconnects the current through a single-chip CMOS single-pole single-throw switch (ADG802), sets a certain delay time (millisecond level), and after the delay ends, the mechanical micro signal relay switches the current direction, and then re-energizes through the switch chip. At this time, the current is already in the reverse state, so the transient shock generated when the current direction is switched can be reduced or avoided.

[0035] The specific steps of the temperature acquisition submodule for collecting data are as follows: first, a forward current is passed through the two ends of the resistor, and a high-resolution analog-to-digital converter ADC is used to collect the voltage across the two ends of the standard resistor, and the ADC is used to collect the voltage across the thermistor after a 20ms delay. After the switch chip ADG802 disconnects the current after a 5ms delay, the mechanical micro-signal relay switches the current direction, and then a reverse current is passed through the two ends of the resistor, and the ADC is used to collect the voltage across the two ends of the standard resistor, and the ADC is used to collect the voltage across the two ends of the thermistor after a 20ms delay; the entire acquisition module collects a total of four voltage data.

[0036] The temperature acquisition submodule calculates the resistance ratio of the thermistor and the standard resistor using the four collected voltage data, then determines the resistance value of the thermistor by the resistance value of the standard resistor (10KΩ), and determines the temperature of the measured working environment by the resistance-temperature conversion formula of the thermistor.

[0037] Among them, the forward current and the reverse current correspond to the forward and reverse directions of the current generated by the constant current source circuit, respectively. In another embodiment, the temperature acquisition submodule further includes a mechanical micro-signal relay switching circuit, which is used to connect the ADC to both ends of the standard resistor and the thermistor, and switch the ADC to measure the standard resistor or thermistor; and is also used to control the forward or reverse direction of the constant current source circuit, and pass the corresponding forward current or reverse current into the resistance ratio measurement circuit.

[0038] When the mechanical micro signal relay switching circuit is in the first working state, a forward current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the standard resistor;

[0039] When the mechanical micro signal relay switching circuit is in the second working state, a forward current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the thermistor;

[0040] When the mechanical micro signal relay switching circuit is in the third working state, a reverse current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the standard resistor;

[0041] When the mechanical micro signal relay switching circuit is in the fourth working state, a reverse current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the thermistor.

[0042] The temperature acquisition submodule calculates the resistance ratio of the thermistor and the standard resistor using the four collected voltage data, and then determines the resistance value of the thermistor by the resistance value of the standard resistor (10KΩ). The corresponding calculation formula is:

[0043]

[0044] Where RT is the thermistor resistance, RS is the standard resistor resistance, and U RT1 U is the voltage across the thermistor collected by the ADC when the forward current is passed. RT2 U is the voltage across the thermistor collected by the ADC when the reverse current is passed. RS1 U is the voltage across the standard resistor collected by the ADC when the forward current is passed. RS2 It is the voltage across the standard resistor collected by the ADC when reverse current is passed.

[0045] The temperature control submodule is used to calculate the deviation between the temperature collected by the temperature collection submodule and the preset temperature, and then calculate and output a PWM signal through a fuzzy PID algorithm to drive the semiconductor cooler TEC to heat or cool the working environment so that the ambient temperature reaches the preset temperature value.

[0046] The temperature control submodule includes a fuzzy PID controller, an STM32 single-chip microcomputer, a TEC driver chip and a TEC semiconductor refrigerator, and the STM32 single-chip microcomputer serves as the main control MCU of the temperature control submodule.

[0047] After the temperature acquisition submodule acquires the temperature of the temperature-controlled object, the collected temperature information is transmitted to the main control MCU of the temperature control submodule. The main control MCU calculates the error e and the error change rate ec between the current temperature value and the set temperature value according to the received temperature data, and uses the error e and the error change rate ec as the input of the fuzzy PID controller.

[0048] The main actuator of the temperature control submodule is the TEC semiconductor refrigerator. The fuzzy PID controller is used to process the received data and then control the STM32 microcontroller to output the corresponding PWM duty cycle signal to the TEC driver chip. The TEC driver chip outputs a temperature control signal to the TEC semiconductor refrigerator, and the TEC semiconductor refrigerator heats or cools the temperature control object.

[0049] The TEC driver chip is the ADUM4221-2 chip, which is an isolated half-bridge gate driver, a dual-channel gate driver with adjustable dead time, high drive strength and low latency to achieve optimal performance; the ADUM4221-2 chip is used to provide forward or reverse current to the TEC semiconductor cooler to achieve heating or cooling.

[0050] In one embodiment, see Figure 1The local temperature control module provided in this implementation is mainly composed of a temperature acquisition submodule and a temperature control submodule. The communication interface of the local temperature control module communicates with the outside world through a signal isolation RS-485 interface transceiver, and the communication protocol is the Modbus-RTU protocol. The semiconductor refrigeration chip is connected to the module through the temperature control element interface. The MCU inside the module outputs PWM waves with different duty cycles through the temperature control PID algorithm. The PWM signal is used as the input of the isolated half-bridge gate driver to control the output power and current direction of the driver, and drive the semiconductor to perform heating or cooling with different powers.

[0051] See also Figure 2 , the specific steps of temperature control are:

[0052] (1) Connect the temperature sensor, and the high-precision temperature acquisition submodule starts to collect resistance values ​​and stores the collected resistance values ​​in the MCU register.

[0053] (2) Multiple resistance values ​​are collected within a specified time interval (such as 3 seconds) to obtain n resistance value data, and then a filtering algorithm is used to process the sampled resistance values ​​to obtain a resistance value that is closer to the actual value.

[0054] (3) Use the TR formula calibrated by the temperature sensor at the factory to calculate the current measured temperature value.

[0055] (4) Calculate the deviation e between the current measured temperature value and the preset temperature value and the deviation change rate ec as the input of the fuzzy PID controller.

[0056] (5) After obtaining the deviation value e and the deviation change rate ec, the fuzzy PID controller starts to use the adaptive fuzzy PID algorithm, outputs the controller parameters, and controls the MCU to output a PWM wave with a corresponding duty cycle.

[0057] (6) The PWM wave controls the isolated half-bridge gate driver to drive the TEC to perform temperature control operations, and the TEC performs heating or cooling accordingly.

[0058] (7) Return to step (1) and re-obtain the measured temperature value after the temperature control operation is performed until the working environment temperature is constantly controlled to fluctuate within a high-precision range allowed by the preset temperature.

[0059] See also Figure 3The temperature acquisition submodule acquires and detects the temperature value change of the controlled object. The MCU calculates the deviation value e and the deviation change rate ec between the current temperature value and the preset temperature value, and uses them as two inputs of the fuzzy PID controller. After a series of processes such as fuzzification, fuzzy reasoning, and clarification, the fuzzy PID controller outputs the adjustment values ​​ΔKp, ΔKi, and ΔKd of the PID control parameters. The final PID control parameter values ​​Kp, Ki, and Kd are the sum of the initial values ​​and the adjustment values. Finally, the PWM duty cycle output by the MCU timer is adjusted accordingly to change the size and direction of the output current of the TEC driver chip.

[0060] Fuzzy rules are the core of realizing adaptive adjustment of fuzzy PID controller parameters. The design of fuzzy rules of this module is based on the experience of simulation and experiment. The basic principle is that when the deviation value e is large, a larger proportional coefficient Kp and a smaller integral coefficient Ki are taken to ensure the module response speed and control overshoot; when the deviation value e is small, a larger integral coefficient Ki is taken to reduce the steady-state error of the module; when the deviation change rate ec is large, a smaller differential coefficient Kd is taken to reduce the module's sensitivity to temperature change disturbances.

[0061] See also Figure 4 , a high-precision 10μA constant current source is designed by combining instrument amplifier INA818 with op amp. INA818 is a precision instrument amplifier with low power consumption and high common-mode rejection ratio, which is suitable for amplifying small signals without distortion. In the circuit, according to the principle of "virtual short and virtual break" of op amp, the load resistor R load The current flowing through is:

[0062]

[0063] A mechanical miniature signal relay is used to switch the current direction of the constant current source, and the switch chip ADG802 is connected in series before the load current output. The purpose is to reduce the transient voltage impact on the components when the current direction of the constant current source changes suddenly, so as to prevent the impact on the acquisition accuracy. The specific usage process is: after forward acquisition of resistance, STM32 controls the Cur_switch pin to a high level to disconnect the current. After a delay of 5ms, STM32 controls the Cur_rev pin to a high level, the relay is activated, and the current is reversed. Then STM32 controls the Cur_switch pin to a low level, and then reversely acquires the resistance value.

[0064] See also Figure 5The PC6 and PC7 pins of the STM32 main control chip output PWM signals through the timer. The output PWM-TEC1 and PWM-TEC2 control signals pass through the isolation circuit inside the ADUM4221-2 chip to control the on / off state and on / off duration of the four internal CMOS tubes, thereby realizing the power size and current direction of the TEC drive, and realizing heating and cooling with different powers. The driving voltage of TEC is 5V, and the power is provided by the DC-DC isolation module DC converter.

[0065] The present invention also provides an application of the local temperature control module as described above in electronic components and / or optical devices, where the electronic components and / or optical devices use the local temperature control module to control their own temperatures.

[0066] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A local temperature control module, characterized in that: The local temperature control module includes a temperature acquisition submodule and a temperature control submodule; the temperature acquisition submodule acquires the temperature of the working environment through 24-bit high-resolution ADC sampling and constant current source reverse method; the temperature control submodule is used to calculate the deviation between the temperature acquired by the temperature acquisition submodule and the preset temperature, and then calculates and outputs a PWM signal through a fuzzy PID algorithm to drive the semiconductor cooler TEC to heat or cool the working environment so that the ambient temperature reaches the preset temperature value.

2. The local temperature control module according to claim 1, characterized in that: The temperature acquisition submodule includes a constant current source circuit, a resistance ratio measurement circuit, a signal conditioning circuit and an A / D conversion circuit; the constant current source circuit is used to provide a 10uA constant current to the resistance ratio measurement circuit; the resistance ratio measurement circuit includes a standard resistor and an NTC thermistor, and the standard resistor and the NTC thermistor are connected in series; the signal conditioning circuit is used to gain amplify the voltage signal collected from the resistance ratio measurement circuit; the A / D conversion circuit is used to convert the analog voltage signal from the signal conditioning circuit into a digital signal and transmit it to the main control MCU of the temperature control submodule.

3. The local temperature control module according to claim 2, characterized in that: The constant current source circuit is a bidirectional constant current source, which uses a mechanical micro signal relay to control the switching current direction.

4. The local temperature control module according to claim 3, characterized in that: The constant current source circuit completely disconnects the current through a single-chip CMOS single-pole single-throw switch, sets a predetermined delay time, and after the delay ends, the mechanical micro-signal relay switches the current direction and then re-energizes through the switch chip.

5. The local temperature control module according to claim 2, characterized in that: The temperature acquisition submodule calculates the resistance ratio of the thermistor and the standard resistor using the four collected voltage data, determines the resistance value of the thermistor by the resistance value of the standard resistor, and determines the temperature of the measured working environment by the resistance-temperature conversion formula of the thermistor.

6. The local temperature control module according to claim 1, characterized in that: The temperature acquisition submodule also includes a mechanical micro-signal relay switching circuit, which is used to connect the ADC to both ends of the standard resistor and the thermistor, and switch the ADC to measure the standard resistor or the thermistor; it is also used to control the forward or reverse direction of the constant current source circuit, and pass the corresponding forward current or reverse current into the resistance ratio measurement circuit.

7. The local temperature control module according to claim 6, characterized in that: When the mechanical micro signal relay switching circuit is in the first working state, a forward current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the standard resistor; When the mechanical micro signal relay switching circuit is in the second working state, a forward current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the thermistor; When the mechanical micro signal relay switching circuit is in the third working state, a reverse current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the standard resistor; When the mechanical micro signal relay switching circuit is in the fourth working state, a reverse current flows into the standard resistor and the thermistor, and the ADC collects the voltage across the thermistor.

8. The local temperature control module according to claim 7, characterized in that: The temperature acquisition submodule calculates the resistance ratio of the thermistor and the standard resistor using the four collected voltage data, and then determines the resistance value of the thermistor by the resistance value of the standard resistor. The corresponding calculation formula is: Where RT is the thermistor resistance, RS is the standard resistor resistance, and U RT1 U is the voltage across the thermistor collected by the ADC when the forward current is passed. RT2 U is the voltage across the thermistor collected by the ADC when the reverse current is passed. RS1 U is the voltage across the standard resistor collected by the ADC when the forward current is passed. RS2 It is the voltage across the standard resistor collected by the ADC when reverse current is passed.

9. The local temperature control module according to any one of claims 1 to 8, characterized in that: The temperature control submodule includes a fuzzy PID controller, an STM32 single-chip microcomputer, a TEC driver chip and a TEC semiconductor refrigerator. The STM32 single-chip microcomputer serves as the main control MCU of the temperature control submodule. The temperature acquisition submodule is used to acquire the temperature of the temperature-controlled object and transmit the acquired temperature information to the main control MCU of the temperature control submodule. The main control MCU calculates the error e and the error change rate ec between the current temperature value and the set temperature value according to the received temperature data, and uses the error e and the error change rate ec as the input of the fuzzy PID controller; the fuzzy PID controller is used to control the STM32 single-chip microcomputer to output a corresponding PWM duty cycle signal to the TEC driver chip after processing the received data. The TEC driver chip is used to output a temperature control signal to the TEC semiconductor refrigerator. The TEC semiconductor refrigerator is used to heat or cool the temperature-controlled object.

10. Application of the local temperature control module according to any one of claims 1 to 9 in electronic components and / or optical devices.

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