CN105680296A - Temperature control circuit based on thermoelectric refrigerator - Google Patents
Temperature control circuit based on thermoelectric refrigerator Download PDFInfo
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- CN105680296A CN105680296A CN201610233111.6A CN201610233111A CN105680296A CN 105680296 A CN105680296 A CN 105680296A CN 201610233111 A CN201610233111 A CN 201610233111A CN 105680296 A CN105680296 A CN 105680296A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/02—Constructional details
- H01S3/04—Arrangements for thermal management
- H01S3/0405—Conductive cooling, e.g. by heat sinks or thermo-electric elements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B21/00—Machines, plants or systems, using electric or magnetic effects
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2321/00—Details of machines, plants or systems, using electric or magnetic effects
- F25B2321/003—Details of machines, plants or systems, using electric or magnetic effects by using thermionic electron cooling effects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
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- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Oscillators With Electromechanical Resonators (AREA)
Abstract
The invention discloses a temperature control circuit based on a thermoelectric refrigerator. The temperature control circuit comprises a TEC element, a thermistor, a TEC control unit, an MCU and a differential proportion circuit, wherein the thermistor is arranged on the surface of the TEC element and is connected with the differential proportion circuit; the TEC control unit converts a TEC temperature adjusting signal from the MCU into a voltage signal controlling the flow direction of a current; the TEC element carries out heat absorption or heat discharge according to the voltage signal from the TEC control unit; the differential proportion circuit carries out difference amplification on the difference between a collected thermistor voltage and a preset reference voltage, and a difference voltage is obtained; and the MCU obtains the sampling temperature of the thermistor at present according to the difference voltage of the differential proportion circuit and generates the TEC temperature adjusting signal according to the comparison result between the sampling temperature of the thermistor and a preset target temperature. According to the invention, the temperature is lowered, the circuit cost is controlled, and the utilization rate of an ADC is improved.
Description
The application is a divisional application of a Chinese invention patent application 201310434874.3 entitled "temperature control circuit based on thermoelectric cooler" filed on 09.18.2013.
Technical Field
The invention relates to the technical field of optical communication, in particular to a temperature control circuit based on a thermoelectric refrigerator.
Background
With the increasing demand of people for high bandwidth, in the field of optical communication, the transmission rate of an optical module is required to be higher and higher, and the volume is required to be smaller and smaller. An Electro-absorption modulated laser (EML) in an optical module has the characteristics of good spectral characteristics, high response speed, low power consumption and the like, and is widely applied to optical communication.
Since the center wavelength, output power, and the like of the EML laser are affected by the laser temperature, the temperature of the EML laser needs to be controlled to maintain the center wavelength and output power of the EML laser stable. Especially for the DWDM (dense optical multiplexing) application, the standard wavelength intervals are required to be 0.8nm and 0.4nm respectively at the most applied channel intervals of 100G and 50G. To ensure channel spacing, system manufacturers have proposed center wavelength stability requirements of 100G and 50G, typically plus or minus 20pm and plus or minus 10 pm. This stability requirement is very stringent, and therefore, the temperature of the EML laser needs to be tightly controlled.
In practical applications, a TEC (thermoelectric cooler, also called a semiconductor cooler) temperature control circuit is generally used to ensure that the operating temperature of the EML laser is constant. In the existing TEC temperature control method, a sampling circuit is generally constructed by an ADC (Analog-digital converter) in an MCU (micro control unit), the sampling circuit is powered by a preset reference voltage, the ADC samples a voltage value of a thermistor arranged in an EML laser according to a preset sampling period, and obtains a current resistance value of the thermistor according to a mapping relationship between a prestored thermistor resistance value and a thermistor voltage value, and then obtains a thermistor temperature corresponding to the current resistance value according to a prestored temperature-resistance characteristic relationship of the thermistor, compares the obtained thermistor temperature with a preset target temperature in the MCU, and generates a temperature closed-loop control signal according to a difference between the obtained thermistor temperature and the target temperature: when the acquired temperature of the thermistor is higher than the target temperature, sending a temperature closed-loop control signal containing the temperature reduction of the EML laser to the TEC element to enable the TEC element to absorb heat, so that the temperatures of the EML laser and the thermistor are reduced; when the acquired temperature of the thermistor is lower than the target temperature, sending a temperature closed-loop control signal containing the temperature rise of the EML laser to the TEC element to enable the TEC element to release heat, so that the temperatures of the EML laser and the thermistor are increased; and when the acquired temperature of the thermistor is equal to the target temperature, maintaining the current state of the TEC element unchanged. Therefore, the temperature of the EML laser can be guaranteed by controlling the TEC element to be heated or cooled in a closed loop mode, and the stability of the central wavelength, the output power and the like of the EML laser can be further guaranteed.
In the case of reference voltage determination of the sampling circuit, the ADC samples thermistor voltages ranging between 0V and the reference voltage theoretically. However, in practical engineering applications, since the operating temperature of the EML laser is generally in a range, the EML laser is generally applied between 20 ℃ and 70 ℃, and according to the temperature-resistance characteristic relationship of the thermistor, when the temperature of the thermistor is 20 ℃, the corresponding resistance value of the thermistor is about thousands (K) ohms, and when the temperature of the thermistor is 70 ℃, the corresponding resistance value of the thermistor can reach tens of K. Therefore, in the conventional application environment, since the thermistor resistance value is also K level at the minimum, the minimum thermistor voltage sampled by the ADC is much larger than 0V, that is, in the conventional application environment, the thermistor voltage range sampled by the ADC is only a part of the thermistor voltage range theoretically sampled by the ADC, so that the thermistor voltage range theoretically sampled by the ADC is not utilized by 100%. Therefore, the temperature corresponding to the conventional application environment needs to be represented in a smaller voltage range, so that the actual sampling precision of the ADC is reduced, and the stable precision of the temperature of the laser is poor.
In order to improve the temperature stability and precision of the laser, the analog-to-digital conversion digit of the ADC is often required to be improved, so that the hardware design and production cost are increased; meanwhile, the stable precision of the temperature of the laser is improved by improving the analog-to-digital conversion digit of the ADC, and the situation that the voltage range of the thermistor sampled by the ADC theoretically is not utilized by 100% exists, so that the utilization rate of the ADC is low.
Disclosure of Invention
The embodiment of the invention provides a temperature control circuit based on a thermoelectric refrigerator, which reduces the cost of the temperature control circuit and improves the utilization rate of an ADC (analog to digital converter).
In order to achieve the above object, an embodiment of the present invention provides a temperature control circuit based on a thermoelectric refrigerator, including: the thermoelectric module comprises a TEC element, a thermistor, a TEC control unit, an MCU and a differential proportion circuit; the thermistor is arranged on the surface of the TEC element and connected with the differential proportional circuit; the differential proportional circuit is used for acquiring the voltage of the thermistor and differentially amplifying the difference value between the acquired voltage of the thermistor and a preset reference voltage to obtain a differential voltage; the MCU is used for receiving the differential voltage from the differential proportional circuit and determining a TEC temperature adjusting signal; the TEC control unit is used for converting the TEC temperature adjusting signal received by the MCU into a voltage signal for controlling the current flow direction; and the TEC element is used for absorbing or releasing heat according to the voltage signal from the TEC control unit.
Preferably, the differential proportional circuit includes: the circuit comprises an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor and a second capacitor; wherein,
the non-inverting input end of the operational amplifier is respectively connected with one end of the fourth resistor and one end of the fifth resistor, the other end of the fifth resistor is grounded, and the other end of the fourth resistor is respectively connected with one end of the first resistor, one end of the first capacitor and one end of the thermistor;
applying a constant voltage to the other end of the first resistor and one end of the second resistor at the same time; the other end of the first capacitor and the other end of the thermistor are both grounded;
the inverting input end of the operational amplifier is respectively connected with one end of the sixth resistor and one end of the seventh resistor, wherein the other end of the seventh resistor is connected with the output end of the operational amplifier, the other end of the sixth resistor is connected with the other end of the second resistor and one end of the third resistor, and the other end of the third resistor is grounded;
applying a constant voltage to the other end of the first resistor and the other end of the second resistor at the same time; the other end of the first capacitor and the other end of the third resistor are both grounded;
the output end of the operational amplifier is connected with the input end of the MCU;
preferably, the differential proportional circuit further includes:
and one end of the second capacitor is connected with the output end of the operational amplifier, and the other end of the second capacitor is grounded.
Preferably, a ratio of the fourth resistance to the fifth resistance is equal to a ratio of the sixth resistance to the seventh resistance.
Preferably, the resistance of the fourth resistor is equal to the resistance of the sixth resistor, and the resistance of the fifth resistor is equal to the resistance of the seventh resistor.
Preferably, the constant voltage is divided by the second resistor and the third resistor, and the predetermined reference voltage is formed at a third node between the second resistor and the third resistor.
Preferably, the second capacitor is used for destroying the self-oscillation condition of the voltage feedback network and keeping the stable operation of the differential proportion circuit.
Preferably, the generating of the TEC temperature adjustment signal according to the comparison result specifically includes:
when the sampling temperature of the thermistor is higher than the target temperature, the MCU generates a TEC temperature adjusting signal which enables the TEC element to absorb heat and is represented by a positive level;
when the sampling temperature of the thermistor is lower than the target temperature, the MCU generates a TEC temperature adjusting signal expressed by a negative level, which enables the TEC element to release heat;
when the sampled temperature of the thermistor is equal to the target temperature, the MCU generates a TEC temperature adjustment signal represented by a zero level that causes the TEC element to maintain a current state.
Preferably, the converting the TEC temperature adjustment signal received from the MCU into a voltage signal for controlling a current flow direction includes:
when the received TEC temperature adjusting signal is represented by a positive level, the TEC control unit outputs a forward bias voltage signal for controlling the current flowing direction of the TEC element to be a forward direction to the TEC element;
when the received TEC temperature adjusting signal is represented by a negative level, the TEC control unit outputs a negative bias voltage signal for controlling the current flow direction of the TEC element to be negative to the TEC element;
when the received TEC temperature adjusting signal is represented by a zero level, the TEC control unit outputs a stable voltage signal for maintaining the current flowing direction of the TEC element to the TEC element.
Preferably, the absorbing or releasing heat according to the voltage signal from the TEC control unit is specifically:
when the voltage signal from the TEC control unit is a forward bias voltage signal, the current flow direction of the TEC element is in a forward direction, heat absorption is carried out, the thermistor is cooled, and the temperature of the thermistor is reduced;
when the voltage signal from the TEC control unit is a reverse bias voltage signal, the current flow direction of the TEC element is reverse, heat is released, the thermistor is heated, and the temperature of the thermistor is increased;
when the voltage signal from the TEC control unit is a stable voltage signal, the TEC element maintains the current flowing direction.
According to the technical scheme, the temperature control circuit based on the thermoelectric refrigerator provided by the embodiment of the invention considers the lower limit temperature of the EML laser in the conventional application environment during working, obtains the thermistor voltage collected by the ADC at the lower limit temperature in advance, and performs differential processing on the thermistor voltage value collected by the differential proportional circuit and the preset reference voltage by adding the differential proportional circuit, so that the voltage variation range of the thermistor subjected to differential processing can be enlarged to the whole voltage sampling interval of the ADC, 100% of the voltage sampling interval of the ADC is utilized, the sampling precision of the ADC is improved, and the utilization rate of the ADC is improved. Meanwhile, compared with the structure change caused by improving the analog-to-digital conversion digit of the ADC, the added differential proportional circuit has the advantage that the design and production cost can be relatively ignored, so that the cost of the temperature control circuit is effectively reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is to be understood that the drawings in the following description are merely exemplary of the invention and that other embodiments and drawings may be devised by those skilled in the art based on the exemplary embodiments shown in the drawings.
Fig. 1 is a schematic structural diagram of a temperature control circuit based on a thermoelectric refrigerator according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a differential proportional circuit according to an embodiment of the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The existing TEC temperature control method cannot utilize the voltage range of the thermistor theoretically sampled by the ADC by 100%, so that the actual sampling precision of the ADC is reduced, and the temperature stability precision of the laser is poor. In order to improve the stable accuracy of the laser temperature, the analog-to-digital conversion bit number of the ADC is often required to be increased to improve the sampling accuracy, but the design cost is increased and wasted.
Based on the defects of the existing TEC temperature control method, the invention considers the lower limit temperature of the EML laser in the working process in the conventional application environment, obtains the thermistor voltage collected by the ADC in advance under the lower limit temperature, and performs differential processing on the thermistor voltage value collected by the differential proportional circuit and the preset reference voltage by adding a differential proportional circuit, so that the voltage variation range of the thermistor subjected to differential processing can be amplified to the whole voltage sampling interval of the ADC, the voltage sampling interval of the ADC is 100% utilized, the sampling precision of the ADC is improved, and the utilization rate of the ADC is improved. Meanwhile, compared with the structure change caused by improving the analog-to-digital conversion digit of the ADC, the added differential proportional circuit has the advantage that the design and production cost can be relatively ignored, so that the cost of the temperature control circuit is effectively reduced.
Fig. 1 is a schematic structural diagram of a temperature control circuit based on a thermoelectric refrigerator according to an embodiment of the present invention. The thermoelectric cooler temperature control circuit includes: thermoelectric refrigerator TEC element 10, thermistor 20, micro control unit MCU30, TEC control unit 40, and differential proportional circuit 50; wherein,
the TEC element 10, the thermistor 20 and the EML laser form a laser assembly, and the thermistor 20 and the EML laser are both arranged on the surface of the TEC element 10; the input end of the MCU30 is connected with the output end of the differential proportional circuit 50, and the output end is connected with the input end of the TEC control unit 40; the output end of the TEC control unit 40 is connected with the TEC element 10; the input of the differential proportional circuit 50 is connected to the thermistor 20.
The differential proportional circuit 50 is used for acquiring the voltage of the thermistor 20 and differentially amplifying the difference value between the acquired thermistor voltage and a preset reference voltage to obtain a differential voltage;
in the embodiment of the present invention, the preset reference voltage may be a voltage value on the thermistor, which is acquired correspondingly to a lower limit temperature of the EML laser during operation in a conventional application environment under the condition of the same temperature control parameter. In practical application, the preset reference voltage may also be a voltage value on the thermistor acquired by the upper limit temperature of the EML laser during operation under the same condition as the temperature control parameter in the conventional application environment. In this way, the differential voltage obtained through differential amplification can tend to zero, so that the whole voltage sampling interval can be covered, and the voltage sampling interval can be utilized by 100%.
The MCU30 is used for receiving the differential voltage from the differential proportional circuit 50 and obtaining the thermistor voltage corresponding to the received differential voltage according to the mapping relation between the thermistor voltage and the differential voltage stored in advance; according to the obtained thermistor voltage, combining a pre-stored mapping relation between the thermistor resistance value and the thermistor voltage to obtain a thermistor resistance value corresponding to the obtained thermistor voltage; obtaining the current sampling temperature of the thermistor corresponding to the obtained thermistor resistance value according to the temperature-resistance characteristic of the thermistor; comparing the sampling temperature of the thermistor with a preset target temperature, generating a TEC temperature adjustment signal according to the comparison result, and outputting the TEC temperature adjustment signal to a TEC control unit 40 through a DAC (Digital-analog converter) channel;
the TEC control unit 40 is configured to convert the TEC temperature adjustment signal received from the MCU30 into a voltage signal for controlling a current flow direction, and output the voltage signal to the TEC element 10;
in the embodiment of the present invention, if the TEC temperature adjustment signal is represented by a positive level, it indicates that the current flow direction of the TEC element 10 needs to be controlled to be a positive direction, so that the TEC element 10 absorbs heat to refrigerate the EML laser; if the TEC temperature adjustment signal is represented by a negative level, it indicates that the current flow direction of the TEC element 10 needs to be controlled to be reverse, so that the TEC element 10 generates heat to heat the EML laser; if the TEC temperature adjustment signal is represented by a zero level, it indicates that the current flow of the TEC element 10 needs to be maintained.
The TEC element 10 absorbs or radiates heat according to the voltage signal from the TEC control unit 40, and thus, the EML laser and the thermistor 20 provided on the surface of the TEC element 10 can be cooled or heated. When the TEC element 10 absorbs heat, the EML laser and the thermistor 20 are cooled; when the TEC elements 10 release heat, the EML laser and the thermistor 20 are heated.
In the embodiment of the invention, the MCU30 can be a single chip microcomputer, a microprocessor, a CPU, an FPGA and the like.
In the embodiment of the present invention, the TEC element and the TEC control unit both adopt a structure commonly used in existing TEC temperature control circuits, which are well known to those skilled in the art and will not be described herein again.
FIG. 2 is a schematic diagram of a differential proportional circuit according to an embodiment of the present invention. As shown in fig. 2, the differential proportional circuit 50 includes: operational amplifier Q1A first resistor R1A second resistor R2A third resistor R3A fourth resistor R4A fifth resistor R5A sixth resistor R6A seventh resistor R7A first capacitor C1A second capacitor C2。
Operational amplifier Q1With the non-inverting input terminal '+' respectively connected with the fourth resistor R4One end of (1), a fifth resistor R5Is connected to one end of, wherein a fifth resistor R5The other end of which is grounded, a fourth resistor R4The other end of the first resistor R is respectively connected with the first resistor R1One terminal of (1), a first capacitor C1And one end of the thermistor 20.
Operational amplifier Q1Respectively with the sixth resistor R6One end of (1), a seventh resistor R7Is connected to one end of, wherein, a seventh resistor R7And the other end of (1) and an operational amplifier Q1Is connected to the output terminal "OUT", a sixth resistor R6The other end of the first resistor is respectively connected with a second resistor R2One terminal of (1), a third resistor R3Is connected to one end of a third resistor R3And the other end of the same is grounded.
At the first resistor R1And the other end of the second resistor R2While the other end is simultaneously applied with a constant voltage VREF(ii) a A first capacitor C1The other end of (2) and the other end of the thermistor 20 are both grounded;
operational amplifier Q1Respectively with the second capacitor C2One end of the MCU30 is connected with the input end of the MCU 30; second capacitor C2And the other end of the same is grounded.
In the embodiment of the present invention, the differential ratio circuit 50 passes through the first resistor R1A first capacitor C1And a constant voltage VREFAt the first resistance R1A first junction with the first capacitorAt point, the sampled voltage V of the thermistor 20 in the laser assembly is acquired in real timei；
Sampling voltage V at thermistoriThrough a fourth resistor R4And a fifth resistor R5After voltage division, the voltage at the second node between the fourth resistor and the fifth resistor is input to the operational amplifier Q1The non-inverting input of "+";
constant voltage VREFThrough a second resistor R1A third resistor R2After voltage division, a preset reference voltage V is formed at a third junction between the second resistor and the third resistorthers_refWherein a reference voltage V is presetthers_refCan be expressed as: vthers_ref=R3/(R2+R3)×VREF；
At a predetermined reference voltage Vthers_refVia a sixth resistor R6And a seventh resistor R7After the voltage feedback network is formed, the voltage at the fourth node between the sixth resistor and the seventh resistor is input into the operational amplifier Q1Is provided with an inverting input "-".
Circuit supply voltage VCCIs an operational amplifier Q1Providing a circuit voltage; second capacitor C2For breaking the resistor R6And a seventh resistor R7The self-oscillation condition of the formed voltage feedback network keeps the stable work of the differential ratio circuit.
Alternatively, embodiments of the present invention may not include the second capacitor C2. In this case, the operational amplifier Q1Is connected to an input of the MCU 30.
In the embodiment of the invention, how to utilize the second capacitor C2The implementation of self-oscillation conditions that disrupt the voltage feedback network is well known in the art and will not be described further herein.
In the embodiment of the invention, the thermistor samples the voltage ViAnd a preset reference voltage Vthers_refVia an operational amplifier Q1Difference processing is carried out to obtain a difference voltage Vtemp(ii) a According to the principle of differential proportional circuits, the differential voltage VtempCan be expressed as: vtemp=Vi×（R5/(R4+R5)×((R6+R7)/R6)－Vthers_ref×R7/R6From an operational amplifier Q1The output of the 'OUT' output terminal;
in the embodiment of the present invention, a ratio of the fourth resistor to the fifth resistor is equal to a ratio of the sixth resistor to the seventh resistor, that is: r4/R5=R6/R7For convenience of calculation, in practical application, the fourth resistor R is made4And the sixth resistor R6Are equal, the fifth resistor R5And the seventh resistor R7Are equal, so that the differential voltage Vtemp=R7/R6×（Vi－Vthers_ref）。
In the embodiment of the invention, the ADC sampling channel of the MCU30 is selected from the operational amplifier Q of the differential proportional circuit 501The 'OUT' output terminal receives the differential voltage and according to the mapping relation between the thermistor voltage and the differential voltage stored in advance: vtemp=Vi×（R5/(R4+R5)×((R6+R7)/R6)－Vthers_ref×R7/R6Obtaining thermistor sampling voltage V corresponding to the differential voltagei(ii) a According to the obtained thermistor sampling voltage ViAnd obtaining the sampling voltage V of the thermistor by combining the prestored mapping relation between the resistance value of the thermistor and the voltage of the thermistoriThe current resistance value of the corresponding thermistor; then obtaining a thermistor temperature value corresponding to the obtained current resistance value of the thermistor, namely the sampling temperature of the thermistor according to the temperature-resistance characteristic of the thermistor; comparing the obtained sampling temperature of the thermistor with a preset target temperature, and generating a TEC temperature adjusting signal according to the difference value between the obtained sampling temperature of the thermistor and the target temperature；
In an embodiment of the present invention, when the obtained sampling temperature of the thermistor is higher than the target temperature, the MCU30 generates a TEC temperature adjustment signal represented by a positive level that causes the TEC elements 10 to absorb heat; when the resulting sampled temperature of the thermistor is below the target temperature, the MCU30 generates a TEC temperature adjustment signal, represented by a negative level, that causes the TEC elements 10 to emit heat; when the resulting sampled temperature of the thermistor is equal to the target temperature, the MCU30 generates a TEC temperature adjustment signal, represented by a zero level, that changes to 0 to maintain the TEC elements 10 in the current state.
The TEC control unit 40 converts the TEC temperature adjustment signal received from the MCU30 into a voltage signal that controls the flow of current;
in the embodiment of the present invention, when the received TEC temperature adjustment signal is represented by a positive level, the TEC control unit 40 outputs a forward bias voltage signal to the TEC element 10, where the forward bias voltage signal controls the current flow direction of the TEC element 10 to be a forward direction; when the TEC temperature adjustment signal is represented by a negative level, the TEC control unit 40 outputs a reverse bias voltage signal that controls a current flow direction of the TEC element 10 to be negative to the TEC element 10; when the TEC temperature adjustment signal is represented by a zero level, the TEC control unit 40 outputs a steady voltage signal to the TEC elements 10 to maintain the current flow direction of the TEC elements.
The TEC element 10 absorbs or releases heat according to a voltage signal from the TEC control unit 40, thereby cooling or heating the EML laser and the thermistor 20.
In the embodiment of the invention, when the received voltage signal is a forward bias voltage signal, the current flow direction of the TEC element 10 is forward, heat absorption is performed, the EML laser and the thermistor 20 are cooled, and the temperatures of the EML laser and the thermistor 20 are reduced; when the received voltage signal is a reverse bias voltage, the current flow direction of the TEC element 10 is reversed, heat is released, the EML laser and the thermistor 20 are heated, and the temperatures of the EML laser and the thermistor 20 are increased; when the received voltage signal is a steady voltage signal, the TEC elements 10 maintain the current flow direction.
In practice, the operational amplifier Q in the differential ratio circuit 50 is defined1Set magnification a = R7/R6Then the differential voltage V outputted from the differential proportional circuit 50tempCan be expressed as: vtemp=A×（Vi－Vthers_ref). In practical conventional applications, EML lasers typically operate between 20 ℃ and 70 ℃. The thermistor 20 is generally operated in a range of several K to ten-odd K according to the temperature-resistance characteristic of the thermistor, and thus, it is assumed that the thermistor first sampling voltage V1The second sampling voltage V of the thermistor corresponds to the lower limit resistance value of the thermistor when the EML laser works at the lower limit temperature2When the EML laser works at the upper limit temperature and the upper limit resistance value of the thermistor corresponds to, the thermistor samples the voltage ViValue range of V1To V2Thus, the differential voltage V outputted from the differential proportional circuit 50tempValue range of Vtemp1=A×（V1－Vthers_ref) To Vtemp2=A×（V2－Vthers_ref) In the meantime.
In practical applications, in the case of reference voltage determination of the ADC sampling channel in the MCU30, the voltage sampling range of the ADC entire sampling interval is 0V to the reference voltage. Therefore, the preset reference voltage V in the differential proportional circuit is adjustedthers_ref（Vthers_ref=R3/(R2+R3)×VREF) The set ratio corresponds to the thermistor first sampling voltage V1Slightly smaller, ensure Vtemp1Close to 0V, Vtemp2The reference voltage of the ADC sampling channel in the MCU30 is close, so that the voltage variation range of the thermistor subjected to differential processing of ADC sampling can be amplified to the whole sampling interval of the ADC, the ADC channel is 100% utilized, the utilization rate of the ADC channel is improved, the sampling precision of the ADC in a unit is improved, and the stability precision of the temperature of the EML laser is improved. Meanwhile, compared with the structure change caused by improving the analog-to-digital conversion digit of the ADC, the added differential proportional circuit has the advantage that the design and production cost can be relatively ignored, so that the temperature control is effectively reducedManufacturing circuit cost.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also encompasses these modifications and variations.
Claims (10)
1. A thermoelectric cooler based temperature control circuit comprising: TEC component, thermistor and TEC the control unit, its characterized in that still includes: the MCU and the differential proportional circuit; wherein,
the thermistor is arranged on the surface of the TEC element and connected with the differential proportion circuit;
the differential proportional circuit is used for acquiring the voltage of the thermistor and differentially amplifying the difference value between the acquired voltage of the thermistor and a preset reference voltage to obtain a differential voltage;
the MCU is used for receiving the differential voltage from the differential proportional circuit and determining a TEC temperature adjusting signal;
the TEC control unit is used for converting the TEC temperature adjusting signal received by the MCU into a voltage signal for controlling the current flow direction;
and the TEC element is used for absorbing or releasing heat according to the voltage signal from the TEC control unit.
2. The thermoelectric chiller based temperature control circuit of claim 1, wherein the differential proportional circuit comprises: the circuit comprises an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor and a second capacitor; wherein,
the non-inverting input end of the operational amplifier is respectively connected with one end of the fourth resistor and one end of the fifth resistor, the other end of the fifth resistor is grounded, and the other end of the fourth resistor is respectively connected with one end of the first resistor, one end of the first capacitor and one end of the thermistor;
applying a constant voltage to the other end of the first resistor and one end of the second resistor at the same time; the other end of the first capacitor and the other end of the thermistor are both grounded;
the inverting input end of the operational amplifier is respectively connected with one end of the sixth resistor and one end of the seventh resistor, wherein the other end of the seventh resistor is connected with the output end of the operational amplifier, the other end of the sixth resistor is connected with the other end of the second resistor and one end of the third resistor, and the other end of the third resistor is grounded; the sixth resistor and the seventh resistor form a voltage feedback network;
and the output end of the operational amplifier is connected with the input end of the MCU.
3. The thermoelectric chiller based temperature control circuit of claim 2, wherein the differential proportional circuit further comprises:
and one end of the second capacitor is connected with the output end of the operational amplifier, and the other end of the second capacitor is grounded.
4. The thermoelectric cooler-based temperature control circuit according to claim 2 or 3, wherein a ratio of the fourth resistance to the fifth resistance is equal to a ratio of the sixth resistance to the seventh resistance.
5. The thermoelectric cooler-based temperature control circuit according to claim 4, wherein the fourth resistor has a resistance equal to that of the sixth resistor, and the fifth resistor has a resistance equal to that of the seventh resistor.
6. The thermoelectric cooler-based temperature control circuit according to claim 2,
the constant voltage is divided by the second resistor and the third resistor, and the preset reference voltage is formed at a third junction between the second resistor and the third resistor.
7. The thermoelectric chiller based temperature control circuit of claim 2, wherein the second capacitor is configured to break a self-oscillating condition of the voltage feedback network, maintaining stable operation of the differential proportional circuit.
8. The thermoelectric chiller based temperature control circuit of claim 1, wherein the MCU is specifically configured to:
according to the received differential voltage of the differential proportional circuit, determining the sampling temperature of the thermistor; wherein,
when the sampling temperature is higher than the target temperature, the MCU generates a TEC temperature adjusting signal expressed by a positive level, which enables the TEC element to absorb heat;
when the sampling temperature is lower than the target temperature, the MCU generates a TEC temperature adjustment signal expressed by a negative level, which enables the TEC element to release heat;
when the sampled temperature is equal to the target temperature, the MCU generates a TEC temperature adjustment signal represented by a zero level that causes the TEC element to maintain a current state.
9. The thermoelectric cooler-based temperature control circuit according to claim 8, wherein the TEC temperature adjustment signal received from the MCU is converted into a voltage signal for controlling a current flow direction, specifically:
when the received TEC temperature adjusting signal is represented by a positive level, the TEC control unit outputs a forward bias voltage signal for controlling the current flowing direction of the TEC element to be a forward direction to the TEC element;
when the received TEC temperature adjusting signal is represented by a negative level, the TEC control unit outputs a negative bias voltage signal for controlling the current flow direction of the TEC element to be negative to the TEC element;
when the received TEC temperature adjusting signal is represented by a zero level, the TEC control unit outputs a stable voltage signal for maintaining the current flowing direction of the TEC element to the TEC element.
10. The thermoelectric chiller based temperature control circuit of claim 8, wherein the MCU is specifically configured to:
obtaining thermistor voltage corresponding to the received differential voltage according to a mapping relation between the prestored thermistor voltage and the differential voltage; acquiring a thermistor resistance value corresponding to the thermistor voltage according to the thermistor voltage by combining a prestored mapping relation between the thermistor resistance value and the thermistor voltage; then according to the temperature-resistance characteristic of the thermistor, obtaining a sampling temperature corresponding to the resistance value of the thermistor; and comparing the sampling temperature with a preset target temperature, and generating a TEC temperature adjusting signal according to the comparison result.
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| CN115085817A (en) * | 2021-03-10 | 2022-09-20 | 青岛海信宽带多媒体技术有限公司 | Optical module and optical module TEC power-off protection method |
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Application publication date: 20160615 |