CN210323908U - Low-impedance closed-loop temperature control circuit - Google Patents
Low-impedance closed-loop temperature control circuit Download PDFInfo
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- CN210323908U CN210323908U CN201921443272.3U CN201921443272U CN210323908U CN 210323908 U CN210323908 U CN 210323908U CN 201921443272 U CN201921443272 U CN 201921443272U CN 210323908 U CN210323908 U CN 210323908U
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Abstract
The utility model discloses a low impedance closed loop temperature control circuit, including power module, heating pin, switching element, microcontroller, constant current circuit and signal amplification circuit, power module's output is connected to switching element's one end, and microprocessor is connected to switching element's signal input part, and the one end of heating pin is connected to constant current circuit's output, and constant current circuit connects signal amplification circuit, and signal amplification circuit connects microcontroller, and power module's negative pole is connected to the other end of heating pin. The utility model discloses saved and set up sampling resistor, undertaken sampling resistor and heating element dual function by the heating pin, constant current module applys constant current for the heating pin when switching element disconnection, calculates the current temperature according to the both ends voltage of the heating pin that reads this moment, and the circuit is suitable for equally when even resistance is very low to efficiency is higher.
Description
Technical Field
The utility model relates to a temperature control technique especially relates to a low impedance closed loop temperature control circuit.
Background
At present, the most commonly adopted technical means for temperature measurement is to install a temperature sensor on a device to be measured, detect the working temperature of the device through the temperature sensor, and transmit the working temperature to a controller to process an output value. This detection method requires a temperature sensor.
Later, a new temperature detection mode is provided, which is to use a heating wire and a sampling resistor to collect the voltage of the heating wire and the sampling resistor and use the resistance value of the module to obtain the resistance value of the heating wire. Compared with the prior art, the temperature sensor is avoided, the cost and the use of components are saved, but the sampling resistor is relied on.
SUMMERY OF THE UTILITY MODEL
In order to overcome the defects of the prior art, the utility model aims to provide a low impedance closed loop temperature control circuit, which can solve the problem that the temperature must be set up by the prior art.
The purpose of the utility model is realized by adopting the following technical scheme:
a low-impedance closed-loop temperature control circuit comprises a power module, a heating pin, a switch element, a microcontroller, a constant current circuit and a signal amplification circuit, wherein one end of the switch element is connected with the output of the power module, the signal input end of the switch element is connected with the microprocessor, the output end of the constant current circuit is connected with one end of the heating pin, the constant current circuit is connected with the signal amplification circuit, the signal amplification circuit is connected with the microcontroller, and the other end of the heating pin is connected with the negative electrode of the power module.
Preferably, the switching element comprises a resistor R3 and a transistor Q1, one end of the resistor R3 is connected with the microprocessor, the other end of the resistor R3 is connected with the base of the transistor Q1, and the emitter and the collector of the transistor Q1 are connected with the constant current circuit.
Preferably, the constant current circuit includes a resistor R1, a resistor R2, a resistor R4, a resistor R6, a resistor R7, an operational amplifier U2A, and a transistor Q2, the heating pin is a resistor R5, one end of the resistor R1 is connected to a collector of the transistor Q1, an emitter of the transistor Q1 is connected to an emitter of the transistor Q2 through a resistor R2, the other end of the resistor R1 and one end of the resistor R6 are both connected to a non-inverting input terminal of the operational amplifier U2A, the other end of the resistor R6 is grounded, an inverting input terminal of the operational amplifier U2A is connected to an emitter of the transistor Q2 through a resistor R7, an output terminal of the operational amplifier U2A is connected to a base of the transistor Q4 through a resistor R4, a collector of the transistor Q4 is connected to one end of the resistor R4.
Preferably, the signal amplification circuit comprises a resistor R24, a resistor R22, a resistor R23 and an operational amplifier U2B, wherein one end of the resistor R24 is connected with one end of a resistor R5, one end of a resistor R24 is connected with the non-inverting input end of the operational amplifier U2B, one end of the resistor R22 is grounded, the other end of the resistor R22 and one end of the resistor R23 are both connected with the inverting input end of the operational amplifier U2B, and the inverting input end of the operational amplifier U2B and the other end of the resistor R23 are both connected with the microprocessor.
Compared with the prior art, the beneficial effects of the utility model reside in that:
the utility model discloses saved and set up sampling resistor, undertaken sampling resistor and heating element dual function by the heating pin, constant current module applys constant current for the heating pin when switching element disconnection, calculates the current temperature according to the both ends voltage of the heating pin that reads this moment, and the circuit is suitable for equally when even resistance is very low to efficiency is higher.
Drawings
Fig. 1 is a block diagram of a low impedance closed loop temperature control circuit according to the present invention;
fig. 2 is a circuit structure diagram of the constant current circuit of the present invention;
fig. 3 is a circuit diagram of the signal amplification circuit of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings and specific embodiments:
as shown in fig. 1, the utility model provides a low impedance closed loop temperature control circuit, including power module, the needle that generates heat, switching element, microcontroller, constant current circuit and signal amplification circuit, power module's output is connected to switching element's one end, microprocessor is connected to switching element's signal input part, the one end of the needle that generates heat is connected to constant current circuit's output, constant current circuit connects signal amplification circuit, signal amplification circuit connects microcontroller, power module's negative pole is connected to the other end of the needle that generates heat, also be the power negative pole that just shows of fig. 1.
The utility model discloses a circuit structure's theory of operation does: the microprocessor outputs PWM control signals to control the on-off of an MOS tube of the switching element so as to heat the heating needle, meanwhile, when the MOS tube is switched off, the microprocessor controls the constant current circuit to work, the constant current circuit applies a constant current (for example, 25mA) to the heating needle, the microprocessor reads the amplified voltage at the two ends of the heating needle, and the current temperature is indirectly calculated through the read voltage value. And comparing the difference between the current temperature and the actual temperature to adjust the PWM so as to realize closed-loop control. Because the sampling resistor is not arranged, the heating resistor is applicable when the resistance of the heating needle is very low, the efficiency is higher, the resistance value of the heating wire which is originally adopted must be more than several times of the resistance value of the sampling resistor to be normally used, otherwise, the efficiency is low, and the problem of heating of the sampling resistor is overcome.
Further, as shown in fig. 2, the switching element includes a resistor R3 and a transistor Q1, one end of the resistor R3 is connected to the microprocessor, the other end of the resistor R3 is connected to the base of the transistor Q1, and the emitter and the collector of the transistor Q1 are connected to the constant current circuit. The constant current circuit comprises a resistor R1, a resistor R2, a resistor R4, a resistor R6, a resistor R7, an operational amplifier U2A and a triode Q2, a heating pin is a resistor R5, one end of the resistor R1 is connected with a collector of a triode Q1, an emitter of the triode Q1 is connected with an emitter of a triode Q2 through a resistor R2, the other end of the resistor R1 and one end of the resistor R6 are both connected with a non-inverting input end of an operational amplifier U2A, the other end of the resistor R6 is grounded, an inverting input end of the operational amplifier U2A is connected with an emitter of a triode Q2 through a resistor R7, an output end of the operational amplifier U2A is connected with a base of a triode Q4 through a resistor R4, a collector of the triode Q4 is connected with one end of the resistor R36.
The resistor R2 is a current-limiting resistor of the constant current circuit, the resistor R1 and the resistor R6 are used for adjusting the voltage of the V1 end, the voltage of the V1 end is determined by the ratio of the resistor R1 to the resistor R6, the current of the resistor R5 is approximately equal to (Vcc-V1-0.3)/R2, wherein 0.3 is the approximate voltage drop of Q1. When the resistance of R5 is reduced, the current of the loop 1 is increased, the voltage of V1 is reduced, the voltage of V2 is higher than the voltage of V1, when the voltage of V2 is higher than the voltage of V1, the output voltage of pin 1 of U2A is increased, the current of a Q2 base is reduced, finally, the current of the loop 1 is reduced, the set current value is returned, and the constant current effect is achieved. When the resistance of R5 becomes larger, the current of the loop 1 becomes smaller, the voltage of V1 becomes larger, the voltage of V2 is lower than the voltage of V1, when the voltage of V2 is lower than the voltage of V1, the output voltage of pin 1 of U2A becomes smaller, the base current of Q2 becomes larger, finally the current of the loop 1 becomes larger, the set current value returns, and the constant current effect is achieved.
As shown in fig. 3, the signal amplifying circuit includes a resistor R24, a resistor R22, a resistor R23, and an operational amplifier U2B, wherein one end of the resistor R24 is connected to one end of the resistor R5, one end of the resistor R24 is connected to the non-inverting input terminal of the operational amplifier U2B, one end of the resistor R22 is grounded, the other ends of the resistor R22 and the resistor R23 are both connected to the inverting input terminal of the operational amplifier U2B, and the inverting input terminal of the operational amplifier U2B and the other end of the resistor R23 are both connected to the microprocessor.
V3 is the voltage of the heating element (i.e. the heating needle or the heating wire), V4 is the amplified voltage, the amplification factor of the voltage is determined by the ratio of R22 to R23, V4 is (1+ R23/R22) × V3, because the main purpose of the constant current module is to calculate the resistance of the heating element, the current setting value is generally small, and is in milliampere level, so the voltage of V3 is generally small, which is not beneficial to the reading process of the microprocessor, so the reading process is given to the microprocessor after the amplification.
Various other modifications and changes may be made by those skilled in the art based on the above-described technical solutions and concepts, and all such modifications and changes are intended to fall within the scope of the claims.
Claims (4)
1. A low-impedance closed-loop temperature control circuit is characterized by comprising a power module, a heating pin, a switch element, a microcontroller, a constant current circuit and a signal amplification circuit, wherein one end of the switch element is connected with the output of the power module, the signal input end of the switch element is connected with the microprocessor, the output end of the constant current circuit is connected with one end of the heating pin, the constant current circuit is connected with the signal amplification circuit, the signal amplification circuit is connected with the microcontroller, and the other end of the heating pin is connected with the negative electrode of the power module.
2. The low impedance closed loop temperature control circuit of claim 1, wherein said switching element comprises a resistor R3 and a transistor Q1, one terminal of the resistor R3 is connected to the microprocessor, the other terminal of the resistor R3 is connected to the base of the transistor Q1, and the emitter and collector of the transistor Q1 are connected to the constant current circuit.
3. The low impedance closed loop temperature control circuit of claim 2, wherein the constant current circuit comprises a resistor R1, a resistor R2, a resistor R4, a resistor R6, a resistor R7, an operational amplifier U2A, a transistor Q2, a heating pin is a resistor R5, one end of the resistor R1 is connected to a collector of a transistor Q1, an emitter of the transistor Q1 is connected to an emitter of a transistor Q2 through a resistor R2, the other end of the resistor R1 and one end of the resistor R6 are both connected to a non-inverting input terminal of an operational amplifier U2A, the other end of the resistor R6 is grounded, an inverting input terminal of the operational amplifier U2A is connected to an emitter of a transistor Q2 through a resistor R7, an output terminal of the operational amplifier U2A is connected to a base of a transistor Q4 through a resistor R4, a collector of the transistor Q4 is connected to one end of the resistor R4, and the other.
4. The low impedance closed loop temperature control circuit of claim 3, wherein said signal amplification circuit comprises a resistor R24, a resistor R22, a resistor R23 and an operational amplifier U2B, wherein one end of the resistor R24 is connected to one end of a resistor R5, one end of a resistor R24 is connected to the non-inverting input of the operational amplifier U2B, one end of the resistor R22 is grounded, the other end of the resistor R22 and one end of the resistor R23 are both connected to the inverting input of the operational amplifier U2B, and the inverting input of the operational amplifier U2B and the other end of the resistor R23 are both connected to the microprocessor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921443272.3U CN210323908U (en) | 2019-08-29 | 2019-08-29 | Low-impedance closed-loop temperature control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921443272.3U CN210323908U (en) | 2019-08-29 | 2019-08-29 | Low-impedance closed-loop temperature control circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN210323908U true CN210323908U (en) | 2020-04-14 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201921443272.3U Active CN210323908U (en) | 2019-08-29 | 2019-08-29 | Low-impedance closed-loop temperature control circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN210323908U (en) |
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2019
- 2019-08-29 CN CN201921443272.3U patent/CN210323908U/en active Active
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