Pulse width modulation temperature detection circuit

Abstract

A pulse width modulation temperature detection circuit disclosed by the present invention comprises a main control chip, a temperature sampling circuit, a detection generation circuit and a conversion corresponding circuit, the detection generation circuit is connected with the temperature sampling circuit and the conversion corresponding circuit, and the temperature sampling circuit is used for converting a temperature signal into a voltage signal and inputting the voltage signal into the detection generation circuit. The detection generation circuit detects an input voltage amplitude and outputs a pulse width signal in a waveform period corresponding to a triangular wave to the conversion corresponding circuit according to a set square wave frequency, the conversion corresponding circuit generates a measuring range signal corresponding to the current temperature according to the pulse width and transmits the measuring range signal to the main control chip, and the main control chip confirms a temperature value according to the measuring range.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature measurement, in particular to a pulse width modulation temperature detection circuit. BACKGROUND

[0002] Publication No. CN118067262A discloses an isolation temperature detection circuit based on pulse width modulation, which can convert the analog voltage output by the temperature sampling circuit into a pulse width waveform through a pulse width conversion circuit and output to a coupling circuit for amplification, and complete detection after decoding by an analog-to-digital chip. However, the detection range includes the measurement interval and range of the thermosensitive element when the change rate is consistent. If only used in a certain temperature interval, the range cannot be adjusted, and the measurement range is still corresponding to the measurement interval when the rate is consistent, which reduces the temperature measurement accuracy. Therefore, a pulse width modulation temperature detection circuit is proposed, which can change the detection range and corresponding range according to the selected temperature interval. SUMMARY

[0003] In view of the above technical problems, the purpose of the present application is to provide a pulse width modulation temperature detection circuit, which comprises a main control chip, a temperature sampling circuit, a detection generation circuit, and a conversion corresponding circuit. The detection generation circuit is connected with the temperature sampling circuit and the conversion corresponding circuit. The temperature sampling circuit is used to convert the temperature signal into a voltage signal and input it to the detection generation circuit. The detection generation circuit detects the input voltage amplitude and outputs a pulse width signal in one waveform period of the corresponding triangular wave according to the set square wave frequency to the conversion corresponding circuit. The conversion corresponding circuit generates a range signal corresponding to the current temperature to the main control chip according to the pulse width. The main control chip confirms the temperature value according to the range.

[0004] Further, the detection generation circuit comprises a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first operational amplifier U1, a second operational amplifier U2, and a first capacitor C1. The output end of the first operational amplifier U1 is connected with one end of the third resistor R3 and one end of the fourth resistor R4. The inverting end of the first operational amplifier U1 is connected with the inverting end of the second operational amplifier U2, one end of the first capacitor C1, the other end of the third resistor R3, and one end of the fifth resistor R5. The non-inverting end of the second operational amplifier U2 is connected with the first input end IN1. The other end of the first capacitor C1, the other end of the fifth resistor R5, and the ground end are connected.

[0005] Further, the conversion corresponding circuit comprises a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a first field effect transistor Q1, a first diode D1, an inductor L1, and a second capacitor C2. One end of the tenth resistor R10 is connected with the power supply, one end of the first field effect transistor Q1 source and the seventh resistor R7, the other end of the tenth resistor R10 is connected, the first field effect transistor Q1 gate, the ninth resistor R9 one end and the detection generation circuit are connected, the first field effect transistor Q1 drain and the inductor L1 one end, the first diode D1 cathode are connected, the inductor L1 other end, the second capacitor C2 one end, the eighth resistor R8 one end and the first output end Out are connected, the seventh resistor R7 other end, the eighth resistor R8 other end, the ninth resistor R9 other end, the first diode D1 anode, the second capacitor C2 other end and the ground end are connected.

[0006] Further, the temperature sampling circuit comprises a sixth resistor R6 and a thermistor RT. One end of the sixth resistor R6 is connected with the power supply, the other end of the sixth resistor R6 and one end of the thermistor RT are connected with the detection generation circuit through the first input end IN1, and the other end of the thermistor RT is connected with the ground end.

[0007] Further, the detection generation circuit comprises a first resistor R1 and a second adjustable resistor R2. One end of the first resistor R1 is connected with the power supply, the other end of the first resistor R1 and one end of the second adjustable resistor R2, the first operational amplifier U1 noninverting terminal and the fourth resistor R4 other end are connected, and the other end of the second adjustable resistor R2 is connected with the ground end.

[0008] Further, the range detection circuit further comprises a third operational amplifier U3, a third triode Q3 and a buzzer LS1. One end of the buzzer LS1 is connected with the power supply, the other end of the buzzer LS1 is connected with the third triode Q3 collector, the third triode Q3 base is connected with the third operational amplifier U3 output end, the third operational amplifier U3 inverting terminal is connected with the conversion corresponding circuit through the first output end Out, and the third triode Q3 emitter is connected with the ground end.

[0009] Further, the range detection circuit further comprises an eleventh resistor R11 and a twelfth resistor R12. One end of the eleventh resistor R11 is connected with the power supply, the other end of the eleventh resistor R11 and one end of the twelfth resistor R12, the third operational amplifier U3 noninverting terminal are connected, and the other end of the twelfth resistor R12 is connected with the ground end.

[0010] Compared with the prior art, the present application has the following beneficial effects: The present application can convert the square wave into the equal frequency triangular wave signal first, convert the voltage signal of the detected thermistor feedback into the corresponding pulse width signal in one waveform period of the triangular wave signal, change the waveform voltage height or waveform width when adjusting the frequency, increase the signal corresponding range and detection range. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0013] Figure 2 The present invention provides a schematic diagram of the detection generation circuit, the conversion correspondence circuit, and the range detection circuit.

[0014] Figure 3 A schematic diagram of the temperature sampling circuit provided by the present invention. Detailed Implementation

[0015] To make the objectives and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection specifically claimed by the present invention.

[0016] This invention discloses a pulse width modulation (PWM) temperature detection circuit, characterized by comprising a main control chip, a temperature sampling circuit, a detection generation circuit, and a conversion-correspondence circuit. The detection generation circuit is connected to the temperature sampling circuit and the conversion-correspondence circuit. The temperature sampling circuit converts the temperature signal into a voltage signal and inputs it to the detection generation circuit. The detection generation circuit detects the input voltage amplitude and outputs a pulse width signal within one waveform period of a triangular wave according to a set square wave frequency to the conversion-correspondence circuit. The conversion-correspondence circuit generates a range signal corresponding to the current temperature according to the pulse width and sends it to the main control chip. The main control chip confirms the temperature value according to the range.

[0017] Specifically, the detection generation circuit includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first operational amplifier U1, a second operational amplifier U2, and a first capacitor C1; The output terminal of the first operational amplifier U1 is connected to one end of the third resistor R3 and one end of the fourth resistor R4. The inverting terminal of the first operational amplifier U1 and the inverting terminal of the second operational amplifier U2, one end of the first capacitor C1, the other end of the third resistor R3, and one end of the fifth resistor R5 are connected. The non-inverting terminal of the second operational amplifier U2 is connected to the first input terminal IN1. The other end of the first capacitor C1 and the other end of the fifth resistor R5 are connected to the ground terminal.

[0018] Specifically, the conversion corresponding circuit includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a first field effect tube Q1, a first diode D1, an inductor L1, and a second capacitor C2. One end of the tenth resistor R10 is connected with a power supply, a source of the first field effect tube Q1 is connected with one end of the seventh resistor R7 and the other end of the tenth resistor R10, a gate of the first field effect tube Q1 is connected with one end of the ninth resistor R9 and a detection generating circuit, a drain of the first field effect tube Q1 is connected with one end of the inductor L1 and a cathode of the first diode D1, the other end of the inductor L1, one end of the second capacitor C2, and one end of the eighth resistor R8 are connected with a first output terminal Out, the other end of the seventh resistor R7, the other end of the eighth resistor R8, the other end of the ninth resistor R9, an anode of the first diode D1, the other end of the second capacitor C2, and a ground terminal are connected.

[0019] Specifically, the temperature sampling circuit includes a sixth resistor R6 and a thermistor RT. One end of the sixth resistor R6 is connected with a power supply, the other end of the sixth resistor R6 and one end of the thermistor RT are connected with the detection generating circuit through a first input terminal IN1, and the other end of the thermistor RT is connected with a ground terminal.

[0020] Specifically, the detection generating circuit includes a first resistor R1 and a second adjustable resistor R2. One end of the first resistor R1 is connected with a power supply, the other end of the first resistor R1 and one end of the second adjustable resistor R2, a same-phase terminal of a first operational amplifier U1, and the other end of a fourth resistor R4 are connected, and the other end of the second adjustable resistor R2 is connected with a ground terminal.

[0021] Specifically, the range detection circuit further includes a third operational amplifier U3, a third triode Q3, and a buzzer LS1. One end of the buzzer LS1 is connected with a power supply, the other end of the buzzer LS1 is connected with a collector of the third triode Q3, a base of the third triode Q3 is connected with an output terminal of the third operational amplifier U3, an inverting terminal of the third operational amplifier U3 is connected with the conversion corresponding circuit through a first output terminal Out, and an emitter of the third triode Q3 is connected with a ground terminal.

[0022] Specifically, the range detection circuit further includes an eleventh resistor R11 and a twelfth resistor R12. One end of the eleventh resistor R11 is connected with a power supply, the other end of the eleventh resistor R11 and one end of the twelfth resistor R12 are connected with a same-phase terminal of the third operational amplifier U3, and the other end of the twelfth resistor R12 is connected with a ground terminal.

[0023] The first resistor R1 and the second adjustable resistor R2 are used for setting a square wave frequency reference signal and feeding back to the non-inverting terminal of the first operational amplifier U1. The first operational amplifier U1, the fourth resistor R4 and the third resistor R3 generate a square wave signal and feed back to the first capacitor C1. The first capacitor C1 and the fifth resistor R5 convert the square wave into a constant frequency triangular wave signal, which is used for the pulse width signal in the conversion into a constant frequency period when the thermistor RT signal is input. In the initial state, the voltage signal at the connection end of the first resistor R1 and the second adjustable resistor R2 is integrated by the fourth resistor R4, the third resistor R3 and the first capacitor C1. The voltage drop at the connection end of the first resistor R1 and the second adjustable resistor R2 is followed by the voltage at the non-inverting terminal of the first operational amplifier U1 being lower than the voltage drop at the connection end of the first resistor R1 and the second adjustable resistor R2 input to the inverting terminal of the first operational amplifier U1. The voltage at the non-inverting terminal of the first operational amplifier U1 is output from the output terminal of the first operational amplifier U1. The signal output from the output terminal of the first operational amplifier U1 is fed back to the connection end of the first resistor R1 and the second adjustable resistor R2 through the fourth resistor R4 and the second adjustable resistor R2, so that the voltage at the connection end of the first resistor R1 and the second adjustable resistor R2 is pulled up. The other signal output from the output terminal of the first operational amplifier U1 is integrated by the third resistor R3 and the first capacitor C1, so that the voltage at the non-inverting terminal of the first operational amplifier U1 is higher than the voltage at the inverting terminal of the first operational amplifier U1. The first operational amplifier U1 is cut off. The voltage at the connection end of the first resistor R1 and the second adjustable resistor R2 is dropped again by the fourth resistor R4, the third resistor R3 and the first capacitor C1. The square wave at the output terminal of the first operational amplifier U1 is converted into a triangular wave signal at the connection end of the first capacitor C1. The signal is output as a pulse width reference signal when fed back to the inverting terminal of the second operational amplifier U2 as the non-inverting terminal input. The temperature signal is input to the non-inverting terminal of the second operational amplifier U2. The signal is obtained by the thermistor RT according to the temperature-dependent resistance. When the thermistor RT changes, the voltage at the non-inverting terminal of the second operational amplifier U2 is changed. When the voltage at the non-inverting terminal of the second operational amplifier U2 is higher than the voltage at the non-inverting terminal of the second operational amplifier U2, the triangular wave waveform point voltage at the inverting terminal of the second operational amplifier U2 is filtered out. The pulse width signal lower than the voltage at the inverting terminal of the second operational amplifier U2 is output from the output terminal of the second operational amplifier U2. The output terminal of the second operational amplifier U2 is connected to the gate of the first field effect transistor Q1. The tenth resistor R10 and the seventh resistor R7 are used for voltage division of the first field effect transistor Q1. The tenth resistor R10 and the seventh resistor R7 have the same resistance value. When the second operational amplifier U2 outputs, the voltage is the supply voltage of the second operational amplifier U2 minus the voltage drop. It is greater than the output of the second operational amplifier U2 minus the negative voltage conduction threshold between the gate and the source of the first field effect transistor Q1. When the pulse width signal output from the second operational amplifier U2 is high, the first field effect transistor Q1 is cut off. The inductor L1 is fed back through the eighth resistor R8, the first diode D1 and the inductor L1 closed loop. When the output of the second operational amplifier U2 is low, the first field effect transistor Q1 is turned on. The power supply signal at the connection end of the tenth resistor R10 and the seventh resistor R7 is filtered by the inductor L1 and the second capacitor C2 after energy storage, and is fed back to the output terminal Out.The first output Out outputs a direct current temperature voltage signal, and the signal corresponds to a waveform period. At this time, adjusting the knob of the second adjustable resistor R2 can change the frequency of the square wave output by the first operational amplifier U1. The smaller the frequency, the larger the waveform period, and the larger the angular wave voltage width. The greater the output range accuracy, the greater the frequency, the greater the waveform voltage height, and the greater the output voltage of the thermistor RT. The adjustment can be made according to the application. The first resistor R1 can also be replaced by an adjustable resistor. When a fault or parameter error causes the thermistor RT to change in a range exceeding the square wave frequency set by the first resistor R1 and the second adjustable resistor R2, the third operational amplifier U3 outputs, the eleventh resistor R11 and the twelfth resistor R12 divide the voltage amplitude to be lower than and close to the voltage at the ends of the tenth resistor R10 and the seventh resistor R7, removing the voltage drop of the first field effect transistor Q1. The second operational amplifier U2 outputs, and the third diode Q3 is turned on. The buzzer LS1 is connected through the third diode Q3 circuit to alarm.

[0024] It will be obvious to a person skilled in the art that, as the application is not limited to the details of the exemplary embodiments described above, it can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and range of the equivalent elements of the claims are intended to be embraced by the application. Any mark in the claims should not be considered as limiting the claims involved.

Claims

1. A pulse width modulation temperature sensing circuit, characterized by, Including master control chip, temperature sampling circuit, detection generation circuit, conversion corresponding circuit, detection generation circuit and temperature sampling circuit, conversion corresponding circuit are connected, temperature sampling circuit is used to convert temperature signal into voltage signal input to detection generation circuit, detection generation circuit detects input voltage amplitude, and according to the set square wave frequency, output corresponding triangle wave in one waveform period Pulse width signal to conversion corresponding circuit, conversion corresponding circuit generates range signal corresponding to current temperature to master control chip according to pulse width, and master control chip confirms temperature value according to range.

2. The pulse width modulated temperature sensing circuit of claim 1, wherein, The detection generation circuit comprises a third resistor, a fourth resistor, a fifth resistor, a first operational amplifier, a second operational amplifier and a first capacitor. The output end of the first operational amplifier is connected with one end of the third resistor and one end of the fourth resistor, the inverting terminal of the first operational amplifier is connected with the inverting terminal of the second operational amplifier, one end of the first capacitor, the other end of the third resistor and one end of the fifth resistor, the non-inverting terminal of the second operational amplifier is connected with the first input end, the other end of the first capacitor, the other end of the fifth resistor and the ground terminal are connected.

3. The pulse width modulated temperature sensing circuit of claim 1, wherein, The conversion corresponding circuit comprises a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first field effect transistor, a first diode, an inductor and a second capacitor. One end of the tenth resistor is connected with the power supply, the source of the first field effect transistor is connected with one end of the seventh resistor and the other end of the tenth resistor, the gate of the first field effect transistor and one end of the ninth resistor are connected with the detection generation circuit, the drain of the first field effect transistor is connected with one end of the inductor and the cathode of the first diode, the other end of the inductor, one end of the second capacitor and one end of the eighth resistor are connected with the first output end, the other end of the seventh resistor, the other end of the eighth resistor, the other end of the ninth resistor, the anode of the first diode, the other end of the second capacitor and the ground terminal are connected.

4. The pulse width modulated temperature sensing circuit of claim 1, wherein, The temperature sampling circuit comprises a sixth resistor and a thermistor. One end of the sixth resistor is connected with the power supply, the other end of the sixth resistor and one end of the thermistor are connected with the detection generation circuit through the first input end, and the other end of the thermistor is connected with the ground terminal.

5. The pulse width modulated temperature sensing circuit of claim 2, wherein, The detection generation circuit comprises a first resistor and a second adjustable resistor. One end of the first resistor is connected with the power supply, the other end of the first resistor, one end of the second adjustable resistor, the non-inverting terminal of the first operational amplifier and the other end of the fourth resistor are connected, and the other end of the second adjustable resistor is connected with the ground terminal.

6. The pulse width modulated temperature sensing circuit of claim 1, wherein, The range detection circuit further comprises an eleventh resistor and a twelfth resistor. One end of the eleventh resistor is connected with the power supply, the other end of the eleventh resistor and one end of the twelfth resistor are connected with the non-inverting terminal of the third operational amplifier, and the other end of the twelfth resistor is connected with the ground terminal.

7. The pulse width modulated temperature sensing circuit of claim 6, wherein, ​ ​

Images