CN115406492A - Thermal diffusion type switch with protection circuit - Google Patents
Thermal diffusion type switch with protection circuit Download PDFInfo
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- CN115406492A CN115406492A CN202211216807.XA CN202211216807A CN115406492A CN 115406492 A CN115406492 A CN 115406492A CN 202211216807 A CN202211216807 A CN 202211216807A CN 115406492 A CN115406492 A CN 115406492A
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- 238000009792 diffusion process Methods 0.000 title claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 61
- 239000012530 fluid Substances 0.000 claims abstract description 38
- 230000003321 amplification Effects 0.000 claims description 22
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 22
- 239000003990 capacitor Substances 0.000 claims description 21
- 230000001105 regulatory effect Effects 0.000 claims description 10
- 230000000694 effects Effects 0.000 abstract description 5
- 230000017525 heat dissipation Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 6
- 230000000630 rising effect Effects 0.000 description 5
- 238000001816 cooling Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 239000000523 sample Substances 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/6888—Thermoelectric elements, e.g. thermocouples, thermopiles
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/696—Circuits therefor, e.g. constant-current flow meters
- G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
- G01F1/699—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters by control of a separate heating or cooling element
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
- H02H5/042—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature using temperature dependent resistors
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Nonlinear Science (AREA)
- Amplifiers (AREA)
Abstract
The invention relates to a thermal diffusion switch with a protection circuit, wherein a first temperature signal of fluid is acquired by a first temperature acquisition module to serve as a reference signal, a target area is heated by a heating module, and a second temperature signal of the target area is acquired by a second temperature acquisition module, wherein the faster the flow rate of the fluid is, the better the heat dissipation effect of the target area is, and the smaller the temperature difference between the first temperature signal and the second temperature signal is; therefore, the flow velocity of the fluid is measured by utilizing the corresponding relation between the temperature difference signal and the fluid velocity, and when the flow velocity is reduced to cause the value of the temperature difference signal to exceed the threshold value, the switch signal is output through the switch signal output module, so that the switch function based on the fluid flow is realized. Meanwhile, when the flow rate is reduced and the second temperature signal is increased to the temperature threshold value, the high-temperature cut-off module is used for generating a cut-off signal, so that the switch module is used for cutting off the heating module according to the cut-off signal, the temperature is prevented from continuously increasing, and the temperature limiting protection is carried out on the thermal diffusion switch.
Description
Technical Field
The invention belongs to the field of electronic switches, and particularly relates to a thermal diffusion type switch with a protection circuit.
Background
Thermal diffusion switches are solid state switches with no moving parts. It can be used for monitoring the flow state of various gases and liquids and the liquid level height state of the liquids. The thermal diffusion switch may provide a solid state or relay output. They are relatively compact and can be applied to a variety of pipe sizes. Full stainless steel construction, provides various technology connection sizes. Thermal diffusion switches may be used in general purpose and explosion-proof environments.
When the existing thermal diffusion switch is used for measuring the temperature of fluid, when the flow rate of the fluid is reduced, the thermal diffusion switch cannot effectively dissipate heat, so that the thermal diffusion switch is broken down or even damaged.
Disclosure of Invention
The invention provides a thermal diffusion switch with a protection circuit, which aims to solve the technical problem that the thermal diffusion switch cannot effectively dissipate heat when the flow speed of fluid is reduced in the prior art.
A thermal diffusion switch with a protection circuit comprises a first temperature acquisition module, a second temperature acquisition module, a heating module, a high-temperature cut-off module, a switch module and a switch signal output module;
the first temperature acquisition module is used for acquiring a first temperature signal of the fluid; the heating module is used for heating fluid in a target area, and the second temperature acquisition module is used for acquiring a second temperature signal of the fluid in the target area;
the output end of the second temperature acquisition module is connected with the input end of the high-temperature cut-off module, and the high-temperature cut-off module compares the second temperature signal with a preset temperature threshold value to generate a first comparison signal;
the output end of the high-temperature cut-off module is connected with the control end of the switch module, the switch module is connected with the heating module, and the switch module controls the starting and stopping state of the heating module according to the first comparison signal;
the first input end of the switching signal output module is connected with the first temperature acquisition module, and the second input end of the switching signal output module is connected with the second temperature acquisition module; the switch signal output module performs differential amplification on the first temperature signal value and the second temperature signal value to obtain a temperature difference signal; comparing the temperature difference signal with a preset temperature difference threshold value signal to obtain a second comparison signal; and outputs a switching signal according to the second comparison signal.
In an embodiment of the invention, the first temperature acquisition module comprises a first thermistor and a constant current driving circuit, the second temperature acquisition module comprises a second thermistor and a constant current driving circuit, and the heating module comprises a heating resistor and a constant current driving circuit;
the first thermistor and the second thermistor are connected with the heating resistor in parallel;
the input end of a constant current driving circuit in the first temperature acquisition module is connected with an external power supply, and the output end of the constant current driving circuit in the first temperature acquisition module is used for carrying out constant current driving on the first thermistor; the input end of a constant current driving circuit in the second temperature acquisition module is connected with an external power supply, and the output end of the constant current driving circuit in the second temperature acquisition module is used for carrying out constant current driving on the second thermistor; the input end of a constant current driving circuit in the heating module is connected with an external power supply, and the output end of the constant current driving circuit in the heating module is used for carrying out constant current driving on the heating resistor;
the input end of the high-temperature cut-off module is connected with one end of the second thermistor, and the output end of the high-temperature cut-off module is connected with the control end of the switch module.
In an embodiment of the present invention, the constant current driving circuit includes a first capacitor, a second capacitor, a third capacitor, a first operational amplifier, a first resistor, a second resistor, and a first triode;
the positive phase power supply end of the first operational amplifier is connected with an external power supply, and the negative phase power supply end of the first operational amplifier is grounded; the positive phase input end of the first operational amplifier is connected with an external second reference signal source, the positive phase input end of the first operational amplifier is grounded through the first capacitor, and the external power supply is grounded through the second capacitor;
the output end of the first operational amplifier is connected with the base electrode of the first triode after being connected with the first resistor in series; one end of the third capacitor is connected with the inverting input end of the first operational amplifier, and the other end of the third capacitor is connected with the output end of the first operational amplifier;
the collector of the first triode is connected with an external power supply, the emitter of the first triode is grounded through the second resistor, and the other end of the first thermistor is also directly connected with the inverting input end of the first operational amplifier;
the target resistor is arranged between an external power supply and the collector of the first triode, or the target resistor is arranged between the emitter of the first triode and the second resistor; the target resistor is one of the first thermistor, the second thermistor and the heating resistor.
In an embodiment of the present invention, the high temperature cutoff module includes a reference regulator sub-circuit, a second operational amplifier, a protection resistor, and a first diode;
the input end of the reference regulating sub-circuit is connected with an external first reference signal source, and the output end of the threshold regulating sub-circuit is connected with the positive phase input end of the second operational amplifier; the reference adjusting sub-circuit is used for adjusting the first reference signal;
the inverting input end of the second operational amplifier is connected with one end of the second thermistor, and the output end of the second operational amplifier is sequentially connected with the protection resistor, the first diode and the control end of the switch module;
the regulating sub-circuit is used for regulating a first reference signal sent by a first reference signal source to obtain a temperature threshold value;
the second operational amplifier is used for comparing the temperature threshold value with the second temperature signal to obtain a first comparison signal; when the second temperature signal is greater than the temperature threshold, the first comparison signal is at a low level, and when the second temperature signal is less than or equal to the temperature threshold, the first comparison signal is at a high level.
In an embodiment of the present invention, the reference adjusting sub-circuit includes a first voltage-dividing resistor and a second voltage-dividing resistor, one end of the first voltage-dividing resistor is connected to an external first reference signal source, and the other end of the first voltage-dividing resistor is connected to a non-inverting input terminal of the second operational amplifier; one end of the second voltage-dividing resistor is connected with the other end of the first voltage-dividing resistor, and the other end of the second voltage-dividing resistor is grounded.
In an embodiment of the present invention, the switching signal output module includes a differential amplifying circuit, a hysteresis comparing circuit, and an output circuit;
the first input end of the differential amplification circuit is connected with the first temperature acquisition module, the second input end of the differential amplification circuit is connected with the second temperature acquisition module, and the differential amplification circuit performs differential amplification on the first temperature signal value and the second temperature signal value to obtain a temperature difference signal;
a first input end of the hysteresis comparison circuit is connected with an output end of the differential amplification circuit, a second input end of the hysteresis comparison circuit is connected with a preset temperature difference threshold signal, and the hysteresis comparison circuit compares the temperature difference signal with the temperature difference threshold signal to obtain a second comparison signal;
the input end of the output circuit is connected with the second comparison signal, and the output circuit outputs a closing signal when the value of the temperature difference signal is greater than the value of the temperature difference threshold signal; and the output circuit outputs a starting signal when the value of the temperature difference signal is less than or equal to the value of the temperature difference threshold signal.
In an embodiment of the present invention, the differential amplifier circuit includes a third operational amplifier, a fourth operational amplifier, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor;
the positive phase input end of the third operational amplifier receives the first temperature signal through the third resistor, and the negative phase input end of the third operational amplifier is grounded through the fourth resistor; one end of the fifth resistor is connected with the inverting input end of the third operational amplifier, and the other end of the fifth resistor is connected with the output end of the third operational amplifier; the output end of the third operational amplifier is connected with the inverting input end of the fourth operational amplifier through the sixth resistor;
a positive phase input end of the fourth operational amplifier receives the second temperature signal through the seventh resistor, one end of the eighth resistor is connected with an inverted phase input end of the fourth operational amplifier, and the other end of the eighth resistor is connected with an output end of the fourth operational amplifier; and the output end of the fourth operational amplifier is used for outputting a temperature difference signal.
In an embodiment of the invention, the hysteresis comparing circuit includes a fifth operational amplifier, a ninth resistor, a tenth resistor, and a varistor;
the inverting input end of the fifth operational amplifier is connected with an external first reference signal source through the rheostat, the non-inverting input end of the fifth operational amplifier is connected with the output end of the differential amplification circuit through the ninth resistor, one end of the tenth resistor is connected with the non-inverting input end of the fifth operational amplifier, and the other end of the tenth resistor is connected with the output end of the fifth operational amplifier;
the rheostat is used for adjusting the value of the reference signal output by the first reference signal source to obtain a temperature difference threshold signal; the fifth operational amplifier is used for comparing the value of the temperature difference signal with the value of the temperature difference threshold value signal to generate a second comparison signal; when the value of the temperature difference signal is greater than that of the temperature difference threshold signal, the second comparison signal is at a high level; and when the value of the temperature difference signal is smaller than or equal to the value of the temperature difference threshold signal, the second comparison signal is at a low level.
In an embodiment of the present invention, the output circuit includes an eleventh resistor, a twelfth resistor, a second triode, a relay, a second diode, and a third diode;
the base electrode of the second triode is connected with the output end of the hysteresis comparison circuit through the second diode and the eleventh resistor which are sequentially connected in series, and the base electrode of the second triode is grounded through the twelfth resistor;
and the collector of the second triode is connected with the anode of the third diode and one side of the control end of the relay, the cathode of the third diode and the other side of the control end of the relay are connected with an external power supply, and the emitter of the second triode is grounded.
In an embodiment of the present invention, the thermal diffusion switch further includes an alarm module, and the alarm module is connected to the relay; the alarm module is used for giving an alarm according to the switch signal.
The invention provides a thermal diffusion switch with a protection circuit, which has the following beneficial effects: the device comprises a first temperature acquisition module, a second temperature acquisition module, a heating module, a high-temperature cutting module, a switch module and a switch signal output module, wherein the first temperature acquisition module is used for acquiring a first temperature signal of fluid; the heating module is used for heating the fluid in the target area, and the second temperature acquisition module is used for acquiring a second temperature signal of the fluid in the target area; the high-temperature cut-off module is used for generating a cut-off signal when the value of the second temperature signal exceeds a preset temperature threshold value; the switch module is used for switching off the heating module according to the switching-off signal; the switching signal output module is used for calculating a temperature difference value between the first temperature signal value and the second temperature signal value to obtain a temperature difference signal, and generating a switching signal when the value of the temperature difference signal exceeds a preset temperature difference threshold value. According to the invention, a first temperature signal of fluid is acquired by a first temperature acquisition module to serve as a reference signal, then a target area is heated by a heating module, and a second temperature signal of the target area is acquired by a second temperature acquisition module, wherein the faster the flow speed of the fluid is, the better the heat dissipation effect of the target area is, and the smaller the temperature difference between the first temperature signal and the second temperature signal is; therefore, the flow velocity of the fluid is measured by utilizing the corresponding relation between the temperature difference signal and the fluid velocity, and when the flow velocity is reduced and the value of the temperature difference signal exceeds a threshold value, the switch signal is output through the switch signal output module, so that the switch function based on the fluid flow is realized. Meanwhile, when the flow rate is reduced and the second temperature signal is increased to the temperature threshold value, the high-temperature cut-off module is used for generating a cut-off signal, so that the switch module is used for cutting off the heating module according to the cut-off signal, the temperature is prevented from continuously increasing, and the temperature limiting protection is carried out on the thermal diffusion switch.
Drawings
FIG. 1 is a schematic diagram of an exemplary thermal diffusion switch with a protection circuit, in accordance with an embodiment of the present invention;
fig. 2 is a circuit diagram of an exemplary constant current driving circuit in an embodiment of the present invention;
fig. 3 is a circuit diagram of an exemplary constant current driving circuit and high temperature cutoff module in an embodiment of the invention;
FIG. 4 is a circuit diagram of an exemplary differential amplifier circuit in an embodiment of the present invention;
FIG. 5 is a circuit diagram of an exemplary hysteretic comparison circuit in an embodiment of the invention;
FIG. 6 is a circuit diagram of an exemplary output circuit and alarm module in an embodiment of the present invention.
Detailed Description
The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
In the following description, numerous details are set forth to provide a more thorough explanation of embodiments of the present invention, however, it will be apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details.
As shown in fig. 1, the thermal diffusion switch with a protection circuit provided in the present invention includes a first temperature acquisition module, a second temperature acquisition module, a heating module, a high temperature cutoff module, a switch module, and a switch signal output module; the switch module comprises a control end and a controller end; the switching signal output module comprises a first input end, a second input end and an output end;
specifically, the first temperature acquisition module comprises a first thermistor RW and a constant current driving circuit (constant current driving 1); the second temperature acquisition module comprises a second thermistor RW and a constant current drive circuit (constant current drive 2); the heating module comprises a heating resistor RA and a constant current driving circuit (constant current drive 3), and the switch module is a triode Q5;
the first temperature acquisition module is used for acquiring a first temperature signal VW of the fluid; the heating module is used for heating the fluid in the target area, and the second temperature acquisition module is used for acquiring a second temperature signal VS of the fluid in the target area;
the output end of the second temperature acquisition module is connected with the input end of the high-temperature cut-off module, and the high-temperature cut-off module compares the second temperature signal VS with a preset temperature threshold value to generate a first comparison signal;
the output end of the high-temperature cut-off module is connected with the control end of the switch module Q5, the controlled end of the switch module Q5 is connected with the heating module, and the switch module Q5 controls the starting and stopping state of the heating module according to the first comparison signal;
the first input end of the switching signal output module is connected with the first temperature acquisition module, and the second input end of the switching signal output module is connected with the second temperature acquisition module; the switch signal output module performs differential amplification on the first temperature signal value and the second temperature signal value to obtain a temperature difference signal; comparing the temperature difference signal with a preset temperature difference threshold signal to obtain a second comparison signal; and outputs a switching signal according to the second comparison signal.
The specific principle of the embodiment is as follows:
the thermal diffusion switch with the protection circuit in the embodiment comprises two probes, wherein one probe internally encapsulates the heating module and the second temperature acquisition module, and the other probe encapsulates the first temperature acquisition module. When the temperature sensor is used, the two probes are immersed into fluid to be measured, and first temperature information acquired by the first temperature acquisition module is a reference signal. And the constant power is used for heating the heating module and simultaneously transferring heat to the second temperature acquisition module. This creates a temperature difference between the two temperature acquisition modules. As the flow rate of the fluid increases, there is a cooling effect as the fluid moves past the heated second temperature acquisition module. The greater the flow, the more cooling. The temperature difference between the two temperature acquisition modules decreased, indicating an increase in flow rate. When the velocity of flow descends, the cooling is less, and this results in the difference in temperature to increase, and when the difference in temperature increased to preset difference in temperature threshold value, production switching signal, switching signal can be used for reporting to the police.
Meanwhile, if the flow rate is reduced and the cooling is less, the heating module is used for continuously heating the second temperature acquisition module in the target area at constant power, and heat can be accumulated in the second temperature acquisition module; therefore, if the second temperature signal VS acquired by the second temperature acquisition module rises to the temperature threshold, the high-temperature cutoff module generates a cutoff signal, and the cutoff signal drives the switch module Q5 to cut off the heating module, so that the temperature of the second temperature acquisition module is prevented from further rising, and the thermal diffusion switch is protected from overheating. In a similar way, when the fluid is at a high flow rate, the heating resistor is in a low-temperature state, and the circuit is normally driven.
In one embodiment of the present invention, the first temperature acquisition module includes a first thermistor RW and a constant current driving circuit, the second temperature acquisition module includes a second thermistor RS and a constant current driving circuit, and the heating module includes a heating resistor RA and a constant current driving circuit; the control end of the switch module Q5 is a base electrode, and the controlled end of the switch module Q5 is a collector electrode and an emitter electrode;
the first thermistor RW and the second thermistor RS are connected in parallel with the heating resistor RA;
the input end of a constant current driving circuit in the first temperature acquisition module is connected with an external power supply VCC, and the output end of the constant current driving circuit in the first temperature acquisition module is used for carrying out constant current driving on a first thermistor RW; the input end of a constant current driving circuit in the second temperature acquisition module is connected with an external power supply VCC, and the output end of the constant current driving circuit in the second temperature acquisition module is used for carrying out constant current driving on the second thermistor RS; the input end of a constant current driving circuit in the heating module is connected with an external power supply VCC, and the output end of the constant current driving circuit in the heating module is used for carrying out constant current driving on a heating resistor RA;
the input end of the high-temperature cut-off module is connected with one end of the second thermistor RS, and the output end of the high-temperature cut-off module is connected with the control end of the switch module Q5.
In this embodiment, the first thermistor RW and the second thermistor RS are positive-resistance-coefficient thermistors or negative-resistance-coefficient thermistors, taking a positive-resistance-coefficient thermistor as an example; the first thermistor RW and the second thermistor RS are connected in parallel and are both driven by a constant current driving circuit, so that when the flow rate of the fluid decreases, the temperature and the resistance of the second thermistor RS continuously increase, and thus the value of the current flowing through the second thermistor RS decreases (the second temperature signal is the current signal flowing through the second thermistor RS, and the larger the current value is, the smaller the temperature is); the high-temperature cutting-off module generates a cutting-off signal according to the decreased current signal, so that the triode Q5 is controlled to cut off the constant current driving circuit (the constant current drive 3), and the heating resistor RA stops working; the temperature of the second thermistor RS is prevented from rising continuously.
As shown in fig. 2, in an embodiment of the present invention, the constant current driving circuit includes a first capacitor C7, a second capacitor C1, a third capacitor C17, a first operational amplifier U2A, a first resistor R11, a second resistor R15, and a first transistor Q1;
the positive phase power supply end of the first operational amplifier U2A is connected with an external power supply VCC, and the negative phase power supply end of the first operational amplifier U2A is grounded; the positive phase input end of the first operational amplifier U2A is connected with an external second reference signal source VREF2, the positive phase input end of the first operational amplifier U2A is grounded through a first capacitor C7, and an external power supply VCC is grounded through a second capacitor C1;
the output end of the first operational amplifier U2A is connected with the base electrode of the first triode Q1 after being connected with the first resistor R11 in series; one end of the third capacitor C17 is connected with the inverting input end of the first operational amplifier U2A, and the other end of the third capacitor C17 is connected with the output end of the first operational amplifier U2A;
the collector of the first triode Q1 is connected with an external power supply VCC, the emitter of the first triode Q1 is grounded through a second resistor R15, and the other end of the first thermistor RW is also directly connected with the inverting input end of the first operational amplifier U2A;
the target resistor is arranged between an external power supply VCC and a collector of the first triode Q1, or the target resistor is arranged between an emitter of the first triode Q1 and the second resistor R15; the target resistor is one of the first thermistor RW, the second thermistor RS, and the heating resistor RA.
In this embodiment, the non-inverting input terminal of the first operational amplifier U2A is externally connected to a second reference signal source VREF2, according to the virtual short and virtual disconnection characteristic of the first operational amplifier U2A, the voltage at the inverting input terminal of the first operational amplifier U2A is also VREF2, so that the voltage at the node P7 is VREF2, the voltage at one end of the second resistor R15 is VREF2, and the other end of the second resistor R15 is grounded, so that the current passing through the second resistor R15 is constant VREF2/R15, and further the current passing through a target resistor (such as the second thermistor RS) connected in series with the second resistor R15 is also VREF2/R15, thereby implementing constant current driving.
As shown in fig. 3, the heating resistor RA is constant-current driven by another constant-current driving circuit, and is disposed between the external power source VCC and the collector of the transistor Q2.
As shown in fig. 3, in an embodiment of the present invention, the high temperature shutdown module includes a reference regulator sub-circuit, a second operational amplifier U6B, a protection resistor R8, and a first diode D4;
the input end of the reference regulating sub-circuit is connected with an external first reference signal source VREF1, and the output end of the threshold regulating sub-circuit is connected with the positive phase input end of a second operational amplifier U6B; the reference adjusting sub-circuit is used for adjusting the first reference signal;
the inverting input end of a second operational amplifier U6B is connected with one end of a second thermistor RS, and the output end of the second operational amplifier U6B is sequentially connected with a protective resistor R8, a first diode D4 and the control end of a switch module Q5;
the adjusting sub-circuit is used for adjusting a first reference signal sent by a first reference signal source to obtain a temperature threshold value;
the second operational amplifier U6B is used for comparing the temperature threshold value with the second temperature signal to obtain a first comparison signal; when the second temperature signal is greater than the temperature threshold, the first comparison signal is at a low level, and when the second temperature signal is less than or equal to the temperature threshold, the first comparison signal is at a high level. The switch module is a triode Q5 which is opened when the base is at high level and closed when the base is at low level.
In this embodiment, the adjusted first reference signal is a temperature threshold signal, the second operational amplifier U6B is used as a comparator to compare the temperature threshold signal with the second temperature signal VS, so as to determine whether the value of the second temperature signal VS exceeds the temperature threshold, and when the second temperature signal VS is greater than the adjusted first reference signal, a shutdown signal is output.
In an embodiment of the present invention, the reference adjusting sub-circuit includes a first voltage-dividing resistor R29 and a second voltage-dividing resistor R28, one end of the first voltage-dividing resistor R29 is connected to an external first reference signal source VREF1, and the other end of the first voltage-dividing resistor R29 is connected to a non-inverting input terminal of the second operational amplifier U6B; one end of the second voltage-dividing resistor R28 is connected to the other end of the first voltage-dividing resistor R29, and the other end of the second voltage-dividing resistor R28 is grounded.
In the embodiment, the first reference signal is adjusted by adopting a voltage division principle, namely, the temperature threshold value is adjusted;
in an embodiment of the present invention, the switching signal output module includes a differential amplifying circuit, a hysteresis comparing circuit, and an output circuit;
a first input end of the differential amplification circuit is connected with the first temperature acquisition module, a second input end of the differential amplification circuit is connected with the second temperature acquisition module, and the differential amplification circuit performs differential amplification on the first temperature signal value and the second temperature signal value to obtain a temperature difference signal;
a first input end of the hysteresis comparison circuit is connected with an output end of the differential amplification circuit, a second input end of the hysteresis comparison circuit is connected with a preset temperature difference threshold signal, and the hysteresis comparison circuit compares the temperature difference signal with the temperature difference threshold signal to obtain a second comparison signal;
the input end of the output circuit is connected with the second comparison signal, and the output circuit outputs a closing signal when the value of the temperature difference signal is greater than the value of the temperature difference threshold signal; the output circuit outputs a start signal when the value of the temperature difference signal is smaller than or equal to the value of the temperature difference threshold signal.
As shown in fig. 4, in an embodiment of the present invention, the differential amplifier circuit includes a third operational amplifier U2C, a fourth operational amplifier U2D, a third resistor R25, a fourth resistor Rs2, a fifth resistor Rf2, a sixth resistor Rs1, a seventh resistor R20, and an eighth resistor Rf1;
the non-inverting input terminal of the third operational amplifier U2C receives the first temperature signal VW through the third resistor R25, and the inverting input terminal of the third operational amplifier U2C is grounded through the fourth resistor Rs 2; one end of the fifth resistor Rf2 is connected to the inverting input terminal of the third operational amplifier U2C, and the other end of the fifth resistor Rf2 is connected to the output terminal of the third operational amplifier U2C; the output end of the third operational amplifier U2C is connected with the inverting input end of the fourth operational amplifier U2D through a sixth resistor Rs 1;
a positive phase input end of the fourth operational amplifier U2D receives the second temperature signal VS through the seventh resistor R20, one end of the eighth resistor Rf1 is connected to an inverted phase input end of the fourth operational amplifier U2D, and the other end of the eighth resistor Rf1 is connected to an output end of the fourth operational amplifier U2D; and the output end of the fourth operational amplifier U2D is used for outputting a temperature difference signal.
In this embodiment, a differential amplification circuit is constructed by using the third operational amplifier U2C and the fourth operational amplifier U2D, and the first temperature signal and the second temperature signal are differentially amplified to obtain a temperature difference signal capable of reflecting a flow rate.
As shown in fig. 5, in an embodiment of the invention, the hysteresis comparison circuit includes a fifth operational amplifier U6A, a ninth resistor R21, a tenth resistor R22, and a varistor R18;
an inverting input end of the fifth operational amplifier U6A is connected to an external first reference signal source VREF1 through a rheostat R18, a non-inverting input end of the fifth operational amplifier U6A is connected to an output end of the differential amplification circuit through a ninth resistor R21, one end of a tenth resistor R22 is connected to the non-inverting input end of the fifth operational amplifier U6A, and the other end of the tenth resistor R22 is connected to an output end of the fifth operational amplifier U6A;
the rheostat R18 is used for adjusting the value of the reference signal output by the first reference signal source VREF1 to obtain a temperature difference threshold signal; the fifth operational amplifier U6A is used for comparing the value of the temperature difference signal with the value of the temperature difference threshold signal to generate a second comparison signal; when the value of the temperature difference signal is greater than that of the temperature difference threshold signal, the second comparison signal is at a high level; and when the value of the temperature difference signal is less than or equal to the value of the temperature difference threshold signal, the second comparison signal is at a low level.
In this embodiment, the rheostat is used to adjust the input reference signal to obtain a temperature difference threshold, the hysteresis comparison circuit compares the value of the temperature difference signal with the temperature difference threshold through the fifth operational amplifier U6A, and when the value of the temperature difference signal is greater than the temperature difference threshold, it indicates that the flow rate is slow, and the temperature of the second thermal sensor RS is in a continuous rising stage.
As shown in fig. 6, in an embodiment of the present invention, the output circuit includes an eleventh resistor R19, a twelfth resistor R26, a second transistor Q4, a relay K1, a second diode D3, and a third diode D1; the relay K1 comprises a control end and a controlled end;
the base electrode of the second triode Q4 is connected with the output end of the hysteresis comparison circuit through a second diode D3 and an eleventh resistor R19 which are sequentially connected in series, and the base electrode of the second triode Q4 is grounded through a twelfth resistor R26;
the collector of the second triode Q4 is connected with the anode of the third diode D1 and one side of the control end of the relay K1, the cathode of the third diode D1 and the other side of the control end of the relay K1 are connected with an external power supply VCC, and the emitter of the second triode Q4 is grounded.
In this embodiment, the switching function of the thermal diffusion switch is mainly embodied by the relay K1, and the relay K1 is driven after the second comparison signal is amplified by the triode, so as to realize the switching function. When the second comparison signal is at a high level, the second triode Q4 is turned on, the relay K1 is in a first state (for example, turned on), and when the second comparison signal is at a low level, the second triode Q4 is turned off, and the relay K1 is in a second state (for example, turned off).
In an embodiment of the invention, the thermal diffusion switch further comprises an alarm module SX3, and the alarm module SX3 is connected with the relay; and the alarm module SX3 is used for alarming according to the switch signal.
In this embodiment, the switching function of the relay K1 is used to turn on/off the alarm module, and when the value of the temperature difference signal is greater than the temperature difference threshold, it indicates that the flow rate is slow, and the temperature of the second thermal sensor RS is in a continuous rising stage; at the moment, the alarm module SX3 is opened through the relay K1 to realize the alarm function.
In summary, the invention provides a thermal diffusion switch with a protection circuit, which is provided with a first temperature acquisition module, a second temperature acquisition module, a heating module, a high temperature cut-off module, a switch module Q5 and a switch signal output module, wherein the first temperature acquisition module is used for acquiring a first temperature signal VW of a fluid; the heating module is used for heating the fluid in the target area, and the second temperature acquisition module is used for acquiring a second temperature signal VS of the fluid in the target area; the high-temperature cut-off module is used for generating a cut-off signal when the value of the second temperature signal VS exceeds a preset temperature threshold; the switch module Q5 is used for switching off the heating module according to the switching-off signal; the switching signal output module is used for calculating a temperature difference value between a first temperature signal VW value and a second temperature signal VS value to obtain a temperature difference signal, and generating a switching signal when the temperature difference signal exceeds a preset temperature difference threshold value. According to the invention, a first temperature signal VW of fluid collected by a first temperature collection module is used as a reference signal, then a target area is heated by a heating module, and a second temperature signal VS of the target area is collected by a second temperature collection module, wherein the faster the flow rate of the fluid is, the better the heat dissipation effect of the target area is, and the smaller the temperature difference between the first temperature signal VW and the second temperature signal VS is; therefore, the flow velocity of the fluid is measured by utilizing the corresponding relation between the temperature difference signal and the fluid velocity, and when the flow velocity is reduced to cause the value of the temperature difference signal to exceed the threshold value, the switch signal is output through the switch signal output module, so that the switch function based on the fluid flow is realized. Meanwhile, when the flow rate decreases and the second temperature signal VS rises to the temperature threshold, the high-temperature cutoff module is used for generating a cutoff signal, so that the switch module Q5 is used for cutting off the heating module according to the cutoff signal, the temperature is prevented from continuously rising, and the thermal diffusion switch is subjected to temperature limitation protection.
In the embodiments described above, although the present invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those skilled in the art in light of the foregoing description. The embodiments of the invention are intended to embrace all such alternatives, modifications and variances that fall within the broad scope of the appended claims.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A thermal diffusion switch with a protection circuit is characterized by comprising a first temperature acquisition module, a second temperature acquisition module, a heating module, a high-temperature cut-off module, a switch module and a switch signal output module;
the first temperature acquisition module is used for acquiring a first temperature signal of the fluid; the heating module is used for heating the fluid in the target area, and the second temperature acquisition module is used for acquiring a second temperature signal of the fluid in the target area;
the output end of the second temperature acquisition module is connected with the input end of the high-temperature cut-off module, and the high-temperature cut-off module compares the second temperature signal with a preset temperature threshold value to generate a first comparison signal;
the output end of the high-temperature cut-off module is connected with the control end of the switch module, the switch module is connected with the heating module, and the switch module controls the starting and stopping state of the heating module according to the first comparison signal;
the first input end of the switch signal output module is connected with the first temperature acquisition module, and the second input end of the switch signal output module is connected with the second temperature acquisition module; the switch signal output module performs differential amplification on the first temperature signal value and the second temperature signal value to obtain a temperature difference signal; comparing the temperature difference signal with a preset temperature difference threshold value signal to obtain a second comparison signal; and outputs a switching signal according to the second comparison signal.
2. The thermal diffusion switch with the protection circuit according to claim 1, wherein the first temperature acquisition module comprises a first thermistor and a constant current driving circuit, the second temperature acquisition module comprises a second thermistor and a constant current driving circuit, and the heating module comprises a heating resistor and a constant current driving circuit;
the first thermistor and the second thermistor are connected with the heating resistor in parallel;
the input end of a constant current driving circuit in the first temperature acquisition module is connected with an external power supply, and the output end of the constant current driving circuit in the first temperature acquisition module is used for carrying out constant current driving on the first thermistor; the input end of a constant current driving circuit in the second temperature acquisition module is connected with an external power supply, and the output end of the constant current driving circuit in the second temperature acquisition module is used for carrying out constant current driving on the second thermistor; the input end of the constant current driving circuit in the heating module is connected with an external power supply, and the output end of the constant current driving circuit in the heating module is used for carrying out constant current driving on the heating resistor;
the input end of the high-temperature cut-off module is connected with one end of the second thermistor, and the output end of the high-temperature cut-off module is connected with the control end of the switch module.
3. The thermal diffusion switch with the protection circuit according to claim 2, wherein the constant current driving circuit comprises a first capacitor, a second capacitor, a third capacitor, a first operational amplifier, a first resistor, a second resistor, and a first triode;
the positive phase power supply end of the first operational amplifier is connected with an external power supply, and the negative phase power supply end of the first operational amplifier is grounded; the positive phase input end of the first operational amplifier is connected with an external second reference signal source, the positive phase input end of the first operational amplifier is grounded through the first capacitor, and the external power supply is grounded through the second capacitor;
the output end of the first operational amplifier is connected with the base electrode of the first triode after being connected with the first resistor in series; one end of the third capacitor is connected with the inverting input end of the first operational amplifier, and the other end of the third capacitor is connected with the output end of the first operational amplifier;
the collector of the first triode is connected with an external power supply, the emitter of the first triode is grounded through the second resistor, and the other end of the first thermistor is also directly connected with the inverting input end of the first operational amplifier;
the target resistor is arranged between an external power supply and the collector of the first triode, or the target resistor is arranged between the emitter of the first triode and the second resistor; the target resistor is one of the first thermistor, the second thermistor and the heating resistor.
4. The thermal diffusion switch with the protection circuit according to claim 2, wherein the high temperature cutoff module comprises a reference regulator sub-circuit, a second operational amplifier, a protection resistor and a first diode;
the input end of the reference regulating sub-circuit is connected with an external first reference signal source, and the output end of the threshold regulating sub-circuit is connected with the positive phase input end of the second operational amplifier; the reference adjusting sub-circuit is used for adjusting the first reference signal;
the inverting input end of the second operational amplifier is connected with one end of the second thermistor, and the output end of the second operational amplifier is sequentially connected with the protection resistor, the first diode and the control end of the switch module;
the regulating sub-circuit is used for regulating a first reference signal sent by a first reference signal source to obtain a temperature threshold value;
the second operational amplifier is used for comparing the temperature threshold value with the second temperature signal to obtain a first comparison signal; when the second temperature signal is greater than the temperature threshold, the first comparison signal is at a low level, and when the second temperature signal is less than or equal to the temperature threshold, the first comparison signal is at a high level.
5. The thermal spread switch with protection circuit of claim 4, wherein the reference regulator sub-circuit comprises a first voltage-dividing resistor and a second voltage-dividing resistor, one end of the first voltage-dividing resistor is connected to a first external reference signal source, and the other end of the first voltage-dividing resistor is connected to the non-inverting input terminal of the second operational amplifier; one end of the second voltage-dividing resistor is connected with the other end of the first voltage-dividing resistor, and the other end of the second voltage-dividing resistor is grounded.
6. The thermal diffusion switch with the protection circuit according to claim 1, wherein the switching signal output module comprises a differential amplifying circuit, a hysteresis comparing circuit and an output circuit;
the first input end of the differential amplification circuit is connected with the first temperature acquisition module, the second input end of the differential amplification circuit is connected with the second temperature acquisition module, and the differential amplification circuit performs differential amplification on the first temperature signal value and the second temperature signal value to obtain a temperature difference signal;
a first input end of the hysteresis comparison circuit is connected with an output end of the differential amplification circuit, a second input end of the hysteresis comparison circuit is connected with a preset temperature difference threshold signal, and the hysteresis comparison circuit compares the temperature difference signal with the temperature difference threshold signal to obtain a second comparison signal;
the input end of the output circuit is connected with the second comparison signal, and the output circuit outputs a closing signal when the value of the temperature difference signal is greater than the value of the temperature difference threshold signal; and the output circuit outputs a starting signal when the value of the temperature difference signal is less than or equal to the value of the temperature difference threshold signal.
7. The thermal diffusion switch with the protection circuit according to claim 6, wherein the differential amplifier circuit comprises a third operational amplifier, a fourth operational amplifier, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor;
the positive phase input end of the third operational amplifier receives the first temperature signal through the third resistor, and the negative phase input end of the third operational amplifier is grounded through the fourth resistor; one end of the fifth resistor is connected with the inverting input end of the third operational amplifier, and the other end of the fifth resistor is connected with the output end of the third operational amplifier; the output end of the third operational amplifier is connected with the inverting input end of the fourth operational amplifier through the sixth resistor;
a positive phase input end of the fourth operational amplifier receives the second temperature signal through the seventh resistor, one end of the eighth resistor is connected with an inverted phase input end of the fourth operational amplifier, and the other end of the eighth resistor is connected with an output end of the fourth operational amplifier; and the output end of the fourth operational amplifier is used for outputting a temperature difference signal.
8. The thermal spread switch with protection circuit of claim 6, wherein the hysteresis comparator circuit comprises a fifth operational amplifier, a ninth resistor, a tenth resistor, a varistor;
the inverting input end of the fifth operational amplifier is connected with an external first reference signal source through the rheostat, the non-inverting input end of the fifth operational amplifier is connected with the output end of the differential amplification circuit through the ninth resistor, one end of the tenth resistor is connected with the non-inverting input end of the fifth operational amplifier, and the other end of the tenth resistor is connected with the output end of the fifth operational amplifier;
the rheostat is used for adjusting the value of the reference signal output by the first reference signal source to obtain a temperature difference threshold signal; the fifth operational amplifier is used for comparing the value of the temperature difference signal with the value of the temperature difference threshold signal to generate a second comparison signal; when the value of the temperature difference signal is greater than that of the temperature difference threshold signal, the second comparison signal is at a high level; and when the value of the temperature difference signal is less than or equal to the value of the temperature difference threshold signal, the second comparison signal is at a low level.
9. The thermal diffusion switch with the protection circuit according to claim 6, wherein the output circuit comprises an eleventh resistor, a twelfth resistor, a second triode, a relay, a second diode, and a third diode;
the base electrode of the second triode is connected with the output end of the hysteresis comparison circuit through the second diode and the eleventh resistor which are sequentially connected in series, and the base electrode of the second triode is grounded through the twelfth resistor;
the collector of the second triode is connected with the anode of the third diode and one side of the control end of the relay, the cathode of the third diode and the other side of the control end of the relay are connected with an external power supply, and the emitter of the second triode is grounded.
10. The thermal diffusion switch with the protection circuit according to claim 9, further comprising an alarm module, wherein the alarm module is connected to the relay; the alarm module is used for giving an alarm according to the switch signal.
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| CN202211216807.XA CN115406492A (en) | 2022-09-30 | 2022-09-30 | Thermal diffusion type switch with protection circuit |
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| CN202211216807.XA CN115406492A (en) | 2022-09-30 | 2022-09-30 | Thermal diffusion type switch with protection circuit |
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