CN105784179A - Temperature detection circuit - Google Patents
Temperature detection circuit Download PDFInfo
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- CN105784179A CN105784179A CN201610152975.5A CN201610152975A CN105784179A CN 105784179 A CN105784179 A CN 105784179A CN 201610152975 A CN201610152975 A CN 201610152975A CN 105784179 A CN105784179 A CN 105784179A
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
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Abstract
The invention provides a temperature detection circuit. The temperature detection circuit comprises a temperature sensor circuit for generating a temperature voltage based on temperature change; a standard voltage circuit for receiving control of a control signal and outputting a discontinuous-change threshold voltage, wherein the threshold voltage is corresponding to the corresponding temperature; a comparison circuit for comparing the temperature voltage and the threshold voltage and converting the comparison result into digital signals; and a digital signal processor for processing the digital signals and sending the control signal to the standard voltage circuit, wherein the digital signal processor controls the standard voltage circuit to output the threshold voltage matched with the temperature voltage according to the digital signals. The thermistor temperature detection circuit is simple in structure, does not need an analog-to-digital converter and complex digital fitting signal processing, and can realize accurate temperature measurement through a comparator and a digital controller.
Description
Technical field
The present invention relates to testing circuit, particularly a kind of temperature sensing circuit.
Background technology
Critesistor, is the resistance of a kind of uniform temperature coefficient that changes with temperature rising resistance, has.Generally, negative tempperature coefficient thermistor, i.e. NTC thermistor, temperature measurement range can contain-40 degrees Celsius to 125 degrees Celsius；Semistor, i.e. PTC thermistor, temperature measurement range can contain-55 degrees Celsius to 315 degrees Celsius.The temperature detection range of critesistor can meet the demand of overwhelming majority application.So, adopt critesistor to carry out a kind of method that temperature detection is conventional detection temperature.
For critesistor, its resistance variation with temperature curve is not linear.For NTC thermistor, its resistance variation with temperature exponentially relation, expression formula is as follows:
Wherein, T0Represent room temperature, be generally 25 degrees Celsius, BT0/TRepresent temperature-sensitive constant during temperature T.If needing to adopt NTC thermistor to carry out temperature detection in a certain temperature range, it is necessary to the resistance of NTC thermistor is carried out join linearization.Generally, NTC thermistor is adopted to carry out the circuit of temperature detection as it is shown in figure 1, mainly include NTC thermistor 10 and voltage temperature change-over circuit 11, wherein, voltage temperature change-over circuit 11 includes zero-temperature coefficient electrical current source 110, analog-digital converter 111 and numeral fitted signal and processes 112.NTC thermistor is flow through in zero-temperature coefficient electrical current source can obtain the voltage of one and temperature correlation, and this magnitude of voltage is only relevant to the temperature coefficient of NTC thermistor.Quantization through analog-digital converter, it is possible to obtain a digital code relevant to NTC thermistor voltage.Digital code, after digital water transfer signal processing, obtains last temperature detection result.For digital water transfer signal processing, it is necessary to be previously obtained the curve that the resistance of NTC thermistor varies with temperature, the temperature corresponding to the voltage obtaining NTC thermistor thus can be precisely calculated.But the hardware spending of this voltage temperature testing circuit is very big, except analog-digital converter, digital water transfer signal processing circuit needs to adopt multiplication and the divider of multidigit.
Shown in Fig. 2 is another kind of NTC thermistor testing circuit.NTC thermistor and Rup serial chain are connected between power supply VCC and ground GND.The voltage expression of NTC point is:
Voltage temperature change-over circuit 20 mainly includes divider resistance R1 and R2, operational amplifier 200.NTC point is connected to the negative phase end of operational amplifier 200.If being only used for detecting a temperature spot, then the output low and high level of operational amplifier is it may determine that the temperature range of NTC thermistor.If detecting multiple temperature spot, then it have to be ensured that operational amplifier 200 is all operated in linear amplification region in whole temperature detection range, and its output needs to be undertaken quantifying and use digital signal processor to do linear fit by analog-digital converter, thus obtaining last detection temperature.The hardware spending of this method is equally very big.
PTC thermistor is broadly divided into switching mode and slow change type two kinds.Wherein, switching mode PTC thermistor is in only small temperature range, and resistance rises suddenly several order of magnitude, and not dull in whole temperature range, therefore can only carry out temperature detection in finite temperature interval.In the temperature range that resistance value is monotone variation, the circuit of equally possible employing NTC thermistor detection temperature carries out the temperature detection of PTC thermistor.
Summary of the invention
The technical problem that present invention mainly solves is to provide temperature sensing circuit, the digital water transfer signal processing mode of analog-digital converter and complexity in temperature detection in replacement prior art.
For solving above-mentioned technical problem, the technical scheme that the present invention adopts is: providing a kind of temperature sensing circuit, described temperature sensing circuit includes:
Temperature sensor circuit, for being produced temperature voltage by temperature inversion；
Standard voltage circuit, is used for accepting control signal control, and exports the threshold voltage of discontinuous change, the corresponding corresponding temperature of described threshold voltage；
Comparison circuit, for comparing described temperature voltage and described threshold voltage and comparative result being converted to digital signal；
Digital signal processor, is used for processing described digital signal and sending control signal to described standard voltage circuit；
Described digital signal processor, according to described digital signal, controls the threshold voltage that the output of described standard voltage circuit matches with described temperature voltage.
Further, described temperature sensor circuit includes: critesistor, the first resistance and the second resistance, and described critesistor is first and the first resistance of connecting again after the second resistor coupled in parallel.
Further, described standard voltage circuit includes: divider resistance string and switch array, and described divider resistance string is in series by the divider resistance of multiple similar resistance, and described switch array is made up of multiple switches connected with divider resistance.
Further, described temperature sensing circuit also includes: being arranged on the voltage source between described temperature sensor circuit and standard voltage circuit, described temperature sensor circuit and standard voltage circuit have common ground connection.
Further, described comparison circuit includes: the first comparator, and an input of described first comparator is connected with switch array, and another input is connected with critesistor.
Further, the described digital signal processor digital signal according to the first comparator, judge when temperature voltage does not mate with current threshold voltage, described DSP CONTROL switch arrays have been turned on switching off, and control the switch of access failure in described switch array and in turn switch in order, stop after making temperature voltage again mate with threshold voltage.
Further, described comparison circuit includes: the first comparator and the second comparator.
Further, an input of described first comparator is connected with the switch being ordered as odd number in switch array, and another input of described first comparator is connected with critesistor.
Further, an input of described second comparator is connected with the switch being ordered as even number in switch array, and another input of described second comparator is connected with critesistor.
Further, the described digital signal processor digital signal according to the first comparator and the second comparator, judge when temperature voltage does not mate with present stage threshold voltage, described DSP CONTROL is opened the light and is had been turned on switching off in array, and control described switch array is positioned at the access failure switch having been turned on above and below switch and in turn switch in order, stopping after making temperature voltage again mate with threshold voltage.
The invention has the beneficial effects as follows: the thermistor temp testing circuit simple in construction that the present invention proposes, it is not necessary to analog-digital converter and complicated digital water transfer signal processing, adopt comparator and digitial controller to be namely capable of the accurate measurement to temperature.
Accompanying drawing explanation
Fig. 1 is a kind of NTC thermistor temperature sensing circuit figure in prior art；
Fig. 2 is another kind of NTC thermistor temperature sensing circuit figure in prior art；
Fig. 3 one embodiment of the present invention circuit diagram；
When Fig. 4 present invention adopts NTC thermistor detection temperature, the curve that TSNS voltage and comparator threshold vary with temperature；
Fig. 5 is present invention when adopting PTC thermistor detection temperature, the curve that TSNS voltage and comparator threshold vary with temperature；
Fig. 6 another embodiment of the present invention circuit diagram.
Accompanying drawing illustrates: 10, NTC thermistor；11, voltage temperature change-over circuit；110, zero-temperature coefficient electrical current source；111, analog-digital converter；112, digital water transfer signal processing circuit；20, voltage temperature change-over circuit；200, operational amplifier；201, digital signal processing circuit；30, thermistor network；31, voltage temperature change-over circuit；310, divider resistance string；311, switch arrays；312, comparator circuit；313, digital signal processor；The curve that when 40, adopting NTC thermistor to detect temperature, TSNS voltage varies with temperature；41, the curve that comparator threshold THR_TH varies with temperature；42, the curve that comparator threshold THR_TH_HYS varies with temperature；The curve that when 50, adopting PTC thermistor to detect temperature, TSNS voltage varies with temperature；51, the curve that comparator threshold THR_TH varies with temperature；52, the curve that comparator threshold THR_TH_HYS varies with temperature；60, thermistor network；61, voltage temperature change-over circuit；610, divider resistance string；611, switch arrays；612, comparator circuit；613, Digital Signal Processing electrical equipment.
Detailed description of the invention
For the ease of understanding the present invention, below in conjunction with the drawings and specific embodiments, the present invention will be described in more detail.It should be noted that be expressed " being fixed on " another element when element, it can directly on another element or can there is one or more element placed in the middle therebetween.When an element is expressed " connection " another element, it can be directly to another element or can there is one or more element placed in the middle therebetween.Term " vertical ", " level ", "left", "right" and similar statement that this specification uses are for illustrative purposes only.
Unless otherwise defined, all of technology that this specification uses is identical with the implication that the those skilled in the art belonging to the present invention are generally understood that with scientific terminology.The term used in the description of the invention in this specification is intended merely to the purpose describing specific embodiment, is not intended to the restriction present invention.The term "and/or" that this specification uses includes the arbitrary and all of combination of one or more relevant Listed Items.
Embodiment 1
Refer to Fig. 3, a kind of temperature sensing circuit, including: thermistor network 30 and voltage temperature change-over circuit 31, wherein, thermistor network 30 includes: temperature sensor circuit, and temperature sensor circuit produces temperature voltage based on temperature inversion.Voltage temperature change-over circuit 31 includes: standard voltage circuit, comparison circuit and digital signal processor.Standard voltage circuit accepts control signal and controls to export the threshold voltage of discontinuous change, and the corresponding corresponding temperature of threshold voltage, namely each threshold voltage represents a concrete temperature.Comparison circuit is for comparing described temperature voltage and described threshold voltage and comparative result being converted to digital signal.Digital signal processor, according to digital signal, controls the threshold voltage that standard voltage circuit output matches with temperature voltage.
Temperature sensor circuit is made up of critesistor parallel resistance Rpall series resistance Rup again, and it act as the resistance value that linearisation critesistor varies with temperature.Temperature sensor circuit is connected between the voltage source VDD of voltage temperature change-over circuit 31 and ground GND, and being wherein carried in the voltage on critesistor is TSNS.TSNS is an input signal of comparison circuit 312.
Standard voltage circuit includes: divider resistance string 310 and switch array 311, and divider resistance string 310 is in series by the unit resistance matched each other, the threshold voltage that the TSNS voltage for producing to produce with thermistor network compares.nullDivider resistance string is respectively connected with after each divider resistance a switch，In measurement process, only partial switch is closed，It is carried in the voltage on divider resistance，Depend on the distance of turn on-switch distance voltage source VDD，The voltage got due to each divider resistance of standard voltage circuit all represents a clear and definite temperature value，The voltage being carried on divider resistance is called threshold voltage，Therefore in standard voltage circuit, connect a road voltage dividing resistance circuit every time，By the temperature voltage that the voltage connecting a road in this bleeder circuit detects with temperature sensor circuit is compared，Just can learn the temperature value represented by temperature voltage，Illustrate，If the road voltage connected in standard voltage circuit is 3V，Represented temperature is 50 degrees Celsius，If the output voltage TSNS of temperature voltage circuit is also 3V，Then can determine that the temperature represented by temperature voltage circuit is 50 degrees Celsius.
Comparator circuit 312 is by the first comparator and the second comparator, the negative input end of the first comparator is connected with the switch being ordered as odd number in switch array from lower to upper, the positive input terminal of the first comparator is connected with critesistor, the negative input end of the second comparator is connected with the switch being ordered as even number number in switch array from lower to upper, the positive input terminal of the second comparator is connected with critesistor, and the negative input end of comparator is connected with standard voltage circuit.First comparator is for detecting TSNS and temperature voltage threshold value THR_TH<i>relation, wherein 0≤i≤N-1, output signal is COMP_THR；Second comparator is for detecting TSNS and sluggish temperature voltage threshold value THR_TH_HYS<i>relation, wherein 0≤i≤N-1, output signal is COMP_THR_HYS.Owing to comparator circuit 312 having two comparators, two negative input ends of two comparators are connected in switch array to be ordered as from lower to upper the switch of odd and even number, so when digital signal processor discover temperature voltage change time, the switch above and below present stage coupling cock can be controlled connect simultaneously, namely detection variations in temperature is to rise or decline simultaneously, it is possible to quickly update variations in temperature.
Digital signal processor, the digital signal processor 313 selection signal THR_TH_SEL<N-1:0 according to current switch>, THR_TH_HYS_SEL<N-1:0>and output signal COMP_THR, the COMP_THR_HYS of comparator determine the temperature of current critesistor and next switch selection signal THR_TH_SEL<N-1:0>and THR_TH_HYS_SEL<N-1:0>value.
Thermistor network and voltage temperature change-over circuit are all connected between power vd D and ground GND, and therefore TSNS magnitude of voltage can represent with the percentage ratio of vdd voltage.The matching precision of divider resistance is higher, and therefore the precision of voltage temperature change-over circuit is also significantly high.For different critesistor, it is necessary to the percentage ratio P to vdd voltage of the TSNS magnitude of voltage corresponding to the temperature T of detectionTFor,
Wherein, RNTC(T) resistance of critesistor, R when temperature is T is representedpallRepresent the resistance in parallel with critesistor, RupRepresent the resistance connected with critesistor.The temperature T that can detect as required and critesistor resistance temperature curve, calculate and obtain PTValue, then pass through switch selection signal THR_TH_SEL<N-1:0>and THR_TH_HYS_SEL<N-1:0>, obtaining TSNS voltage from divider resistance string needs the threshold value that compares.
Illustrating, for adopting NTC thermistor to carry out the circuit of temperature detection, Fig. 4 shows TSNS voltage and the threshold value THR_TH of the first comparator, the curve that the threshold value THR_TH_HYS of the second comparator varies with temperature.When temperature changes from low to high, the resistance of NTC thermistor can change from high to low, and the voltage of TSNS also can change from high to low.When temperature is less than T<0>time, THR_TH_SEL<0>it is 1, other position is 0, and the threshold value THR_TH of the first comparator is THR_TH<0>；THR_TH_HYS_SEL<0>it is 1, other position is 0, and the threshold value THR_TH_HYS of the second comparator is THR_TH_HYS<0>.Temperature rises and exceeds T<0>time, the output signal COMP_THR of the first comparator overturns from high to low, now digital signal processor switches threshold value THR_TH to the THR_TH<1 of the first comparator>, i.e. THR_TH_SEL<1>it is 1, other position is 0, the output signal COMP_THR of the first comparator is because the switching of THR_TH overturns from low to high, and the threshold value THR_TH_HYS of the second comparator is maintained at THR_TH_HYS<0>.When temperature continues to rise, and exceed T<1>time, the output signal COMP_THR of the first comparator overturns from high to low, now digital signal processor switches threshold value THR_TH to the THR_TH<2 of the first comparator>, i.e. THR_TH_SEL<2>it is 1, other position is 0, and the output signal COMP_THR of the first comparator is because the switching of THR_TH overturns from low to high；Switch threshold value THR_TH_HYS to the THR_TH_HYS<1 of the second comparator>, i.e. THR_TH_HYS_SEL<1>it is 1, other position is 0.If temperature exceeds T<0>after begin to decline, and it is reduced to T_HYS<0>below, the output COMP_THR_HYS of the second comparator overturns from low to high, now digital signal processor switches threshold value THR_TH to the THR_TH<0 of the first comparator>, i.e. THR_TH_SEL<0>it is 1, other position is 0, and the threshold value THR_TH_HYS of the second comparator keeps THR_TH_HYS<0>.
When temperature is higher than T<i>, wherein 0 < i < N-1, the output signal COMP_THR of the first comparator overturns from high to low, now digital signal processor switches threshold value THR_TH to the THR_TH<i+1 of the first comparator>, i.e. THR_TH_SEL<i+1>it is 1, other position is 0, and the output signal COMP_THR of the first comparator is because the switching of THR_TH overturns from low to high；Switch threshold value THR_TH_HYS to the THR_TH_HYS<i of the second comparator>, i.e. THR_TH_HYS_SEL<i>it is 1, other position is 0.When temperature continues to rise, and exceed T<i+1>time, the output signal COMP_THR of the first comparator overturns from high to low, digital signal processor switches threshold value THR_TH to the THR_TH<i+2 of the first comparator>, i.e. THR_TH_SEL<i+2>it is 1, other position is 0, and the output signal COMP_THR of the first comparator is because the switching of THR_TH overturns from low to high；Switch threshold value THR_TH_HYS to the THR_TH_HYS<i+1 of the second comparator>, i.e. THR_TH_HYS_SEL<i+1>it is 1, other position is 0.If temperature exceeds T<i>after begin to decline, and it is reduced to T_HYS<i>below, the output signal COMP_THR_HYS of the second comparator overturns from low to high, and digital signal processor switches threshold value THR_TH to the THR_TH<i of the first comparator>, i.e. THR_TH_SEL<i>it is 1, other position is 0；Switch threshold value THR_TH_HYS to the THR_TH_HYS<i-1 of the second comparator>, i.e. THR_TH_HYS_SEL<i-1>it is 1, other position is 0, and the output signal COMP_THR_HYS of the second comparator is because the switching of THR_TH_HYS overturns from high to low.
Digital signal processor selects signal THR_TH_SEL<N-1:0 according to current comparator threshold>and THR_TH_HYS_SEL<N-1:0>temperature range residing for NTC thermistor can be obtained.As THR_TH_SEL<i>=1 and THR_TH_HYS_SEL<i-1>=1 time, the temperature T that NTC thermistor detects is between T_HYS<i-1>and T<i>between, wherein 0 < i < N-1.As THR_TH_SEL<0>=1 and THR_TH_HYS_SEL<0>=1 time, the temperature T that NTC thermistor detects is lower than T<0>.As THR_TH_SEL<N-1>=1 and THR_TH_HYS_SEL<N-1>=1 time, the temperature T that NTC thermistor detects be higher than T<N-1>.
Illustrating by way of further example, for adopting PTC thermistor to carry out the circuit of temperature detection, Fig. 5 shows TSNS voltage and the threshold value THR_TH of the first comparator, the curve that the threshold value THR_TH_HYS of the second comparator varies with temperature.When temperature changes from low to high, the resistance of PTC thermistor can change from low to high, and the voltage of TSNS also can change from low to high.When temperature is less than T_HYS<N-1>time, THR_TH_SEL<N-1>it is 1, other position is 0, and the threshold value THR_TH of the first comparator is THR_TH<N-1>；THR_TH_HYS_SEL<N-1>it is 1, other position is 0, and the threshold value THR_TH_HYS of the second comparator is THR_TH_HYS<N-1>.Temperature rises and exceeds T_HYS<N-1>time, the output signal COMP_THR_HYS of the second comparator overturns from low to high, now digital signal processor switches threshold value THR_TH_HYS to the THR_TH_HYS<N-2 of the second comparator>, i.e. THR_TH_HYS_SEL<N-2>it is 1, other position is 0, the output signal COMP_THR_HYS of the second comparator is because the switching of THR_TH_HYS overturns from high to low, and the threshold value THR_TH of the first comparator is maintained at THR_TH<N-1>.When temperature continues to rise, and exceed T_HYS<N-2>time, the output signal COMP_THR_HYS of the second comparator overturns from low to high, now digital signal processor switches threshold value THR_TH_HYS to the THR_TH_HYS<N-3 of the second comparator>, i.e. THR_TH_HYS_SEL<N-3>it is 1, other position is 0, and the output signal COMP_THR_HYS of the second comparator is because the switching of THR_TH_HYS overturns from high to low；Switch threshold value THR_TH to the THR_TH<N-2 of the first comparator>, i.e. THR_TH_SEL<N-2>it is 1, other position is 0.If temperature exceeds T_HYS<N-1>after begin to decline, and it is reduced to T<N-1>below, the output COMP_THR of the first comparator overturns from high to low, now digital signal processor switches threshold value THR_TH_HYS to the THR_TH_HYS<N-1 of the second comparator>, i.e. THR_TH_HYS_SEL<N-1>it is 1, other position is 0, and the threshold value THR_TH of the first comparator keeps THR_TH<N-1>.
When temperature is higher than T_HYS<i>, wherein 0 < i < N-1, the output signal COMP_THR_HYS of the second comparator overturns from low to high, now digital signal processor switches threshold value THR_TH_HYS to the THR_TH_HYS<i-1 of the second comparator>, i.e. THR_TH_HYS_SEL<i-1>it is 1, other position is 0, and the output signal COMP_THR_HYS of the second comparator is because the switching of THR_TH_HYS overturns from high to low；Switch threshold value THR_TH to the THR_TH<i of the first comparator>, i.e. THR_TH_SEL<i>it is 1, other position is 0.When temperature continues to rise, and exceed T_HYS<i-1>time, the output signal COMP_THR_HYS of the second comparator overturns from low to high, digital signal processor switches threshold value THR_TH_HYS to the THR_TH_HYS<i-2 of the second comparator>, i.e. THR_TH_HYS_SEL<i-2>it is 1, other position is 0, and the output signal COMP_THR_HYS of the second comparator is because the switching of THR_TH_HYS overturns from high to low；Switch threshold value THR_TH to the THR_TH<i-1 of the first comparator>, i.e. THR_TH_SEL<i-1>it is 1, other position is 0.If temperature exceeds T_HYS<i>after begin to decline, and it is reduced to T<i>below, the output signal COMP_THR of the first comparator overturns from high to low, digital signal processor switches threshold value THR_TH_HYS to the THR_TH_HYS<i of the second comparator>, i.e. THR_TH_HYS_SEL<i>it is 1, other position is 0；Switch threshold value THR_TH to the THR_TH<i+1 of the first comparator>, i.e. THR_TH_SEL<i+1>it is 1, other position is 0, and the output signal COMP_THR of the first comparator is because the switching of THR_TH overturns from low to high.
Digital signal processor selects signal THR_TH_SEL<N-1:0 according to current comparator threshold>and THR_TH_HYS_SEL<N-1:0>temperature range residing for PTC thermistor can be obtained.As THR_TH_SEL<i+1>=1 and THR_TH_HYS_SEL<i>=1 time, the temperature T that PTC thermistor detects is between T_HYS<i>and T<i+1>between, wherein 0 < i < N-1.As THR_TH_SEL<0>=1 and THR_TH_HYS_SEL<0>=1 time, the temperature T that PTC thermistor detects be higher than T<0>.As THR_TH_SEL<N-1>=1 and THR_TH_HYS_SEL<N-1>=1 time, the temperature T that PTC thermistor detects is lower than T<N-1>.
Embodiment 2
Refer to Fig. 6, a kind of temperature sensing circuit, including: thermistor network 60 and voltage temperature change-over circuit 61, wherein, thermistor network 60 includes: temperature sensor circuit, and temperature sensor circuit produces temperature voltage based on temperature inversion.Voltage temperature change-over circuit 61 includes: standard voltage circuit, comparison circuit and digital signal processor.Standard voltage circuit accepts control signal and controls to export the threshold voltage of discontinuous change, and the corresponding corresponding temperature of threshold voltage, namely each threshold voltage represents a concrete temperature.Comparison circuit is for comparing described temperature voltage and described threshold voltage and comparative result being converted to digital signal.Digital signal processor, according to digital signal, controls the threshold voltage that standard voltage circuit output matches with temperature voltage.
Temperature sensor circuit is made up of critesistor parallel resistance Rpall series resistance Rup again, and it act as the resistance value that linearisation critesistor varies with temperature.Temperature sensor circuit is connected between the voltage source VDD of voltage temperature change-over circuit 61 and ground GND, and being wherein carried in the voltage on critesistor is TSNS.TSNS is an input signal of comparison circuit 612.
Standard voltage circuit includes: divider resistance string 610 and switch array 611, and divider resistance string 610 is in series by the unit resistance matched each other, the threshold voltage that the TSNS voltage for producing to produce with thermistor network compares.nullDivider resistance string is respectively connected with after each divider resistance a switch，In measurement process, only partial switch is closed，It is carried in the voltage on divider resistance，Depend on the distance of turn on-switch distance voltage source VDD，The voltage got due to each divider resistance of standard voltage circuit all represents a clear and definite temperature value，The voltage being carried on divider resistance is called threshold voltage，Therefore in standard voltage circuit, connect a road voltage dividing resistance circuit every time，By the temperature voltage that the voltage connecting a road in this bleeder circuit detects with temperature sensor circuit is compared，Just can learn the temperature value represented by temperature voltage，Illustrate，If the road voltage connected in standard voltage circuit is 3V，Represented temperature is 50 degrees Celsius，If the output voltage TSNS of temperature voltage circuit is also 3V，Then can determine that the temperature represented by temperature voltage circuit is 50 degrees Celsius.
Comparator circuit 612 is made up of a comparator, the negative input end of comparator is connected with standard voltage circuit, the positive input terminal of comparator is connected with temperature sensor circuit, as shown in Figure 6, comparator is for detecting TSNS and temperature voltage threshold value THR_TH<i>relation, wherein 0 < i < N-1, output signal is COMP_THR.Owing to comparator circuit 612 having a comparator, so when digital signal processor initialized controlling switch by the fixed cycle, namely in turn switching on switch from top to bottom or from down to up, until matching the threshold voltage mated with temperature voltage.
Digital signal processor 613, the digital signal processor 613 selection signal THR_TH_SEL<N-1:0 according to switch>, THR_TH_HYS_SEL<N-1:0>and the signal COMP_THR that exports of comparator determine the temperature of current critesistor.
Thermistor network and voltage temperature change-over circuit are all connected between power vd D and ground GND, and therefore TSNS magnitude of voltage can represent with the percentage ratio of vdd voltage.The matching precision of divider resistance is higher, and therefore the precision of voltage temperature change-over circuit is also significantly high.For different critesistor, it is necessary to the percentage ratio P to vdd voltage of the TSNS magnitude of voltage corresponding to the temperature T of detectionTFor:
Wherein, RNTC(T) resistance of critesistor, R when temperature is T is representedpallRepresent the resistance in parallel with critesistor, RupRepresent the resistance connected with critesistor.The temperature T that can detect as required and critesistor resistance temperature curve, calculate and obtain PTValue, then pass through switch selection signal THR_TH_SEL<N-1:0>and THR_TH_HYS_SEL<N-1:0>, obtaining TSNS voltage from divider resistance string needs the threshold value that compares.
The thermistor temp testing circuit simple in construction that the present invention proposes, it is not necessary to analog-digital converter and complicated digital water transfer signal processing, the substitute is divider resistance string, switch arrays, two voltage comparators and simple digital signal processor.Except realizing circuit and be simple, the present invention can realize higher temperature detecting precision simultaneously.
It should be noted that, the description of the present invention and accompanying drawing thereof give the preferred embodiment of the present invention, but, the present invention can be realized by many different forms, it is not limited to the embodiment described by this specification, these embodiments are not as the extra restriction to present invention, it is provided that the purpose of these embodiments is to make the understanding to the disclosure more thorough comprehensively.Further, above-mentioned each technical characteristic continues to be mutually combined, and forms various embodiments not enumerated above, is accordingly to be regarded as the scope that description of the present invention is recorded；Further, for those of ordinary skills, it is possible to improved according to the above description or convert, and all these improve and conversion all should belong to the protection domain of claims of the present invention.
Claims (10)
1. a temperature sensing circuit, it is characterised in that described temperature sensing circuit includes:
Temperature sensor circuit, for being produced temperature voltage by temperature inversion；
Standard voltage circuit, is used for accepting control signal control, and exports the threshold voltage of discontinuous change, the corresponding corresponding temperature of described threshold voltage；
Comparison circuit, for comparing described temperature voltage and described threshold voltage and comparative result being converted to digital signal；
Digital signal processor, is used for processing described digital signal and sending control signal to described standard voltage circuit；
Described digital signal processor, according to described digital signal, controls the threshold voltage that the output of described standard voltage circuit matches with described temperature voltage.
2. temperature sensing circuit according to claim 1, it is characterised in that described temperature sensor circuit includes: critesistor, the first resistance and the second resistance, described critesistor is first and the first resistance of connecting again after the second resistor coupled in parallel.
3. temperature sensing circuit according to claim 2, it is characterized in that, described standard voltage circuit includes: divider resistance string and switch array, and described divider resistance string is in series by the divider resistance of multiple similar resistance, and described switch array is made up of multiple switches connected with divider resistance.
4. temperature sensing circuit according to claim 3, it is characterized in that, described temperature sensing circuit also includes: being arranged on the voltage source between described temperature sensor circuit and standard voltage circuit, described temperature sensor circuit and standard voltage circuit have common ground connection.
5. temperature sensing circuit according to claim 4, it is characterised in that described comparison circuit includes: the first comparator, and an input of described first comparator is connected with switch array, and another input is connected with critesistor.
6. temperature sensing circuit according to claim 4, it is characterized in that, the described digital signal processor digital signal according to the first comparator, judge when temperature voltage does not mate with current threshold voltage, described DSP CONTROL switch arrays have been turned on switching off, and control the switch of access failure in described switch array and in turn switch in order, stop after making temperature voltage again mate with threshold voltage.
7. temperature sensing circuit according to claim 4, it is characterised in that described comparison circuit includes: the first comparator and the second comparator.
8. temperature sensing circuit according to claim 7 a, it is characterised in that input of described first comparator is connected with the switch being ordered as odd number in switch array, and another input of described first comparator is connected with critesistor.
9. temperature sensing circuit according to claim 8 a, it is characterised in that input of described second comparator is connected with the switch being ordered as even number in switch array, and another input of described second comparator is connected with critesistor.
10. temperature sensing circuit according to claim 9, it is characterized in that, the described digital signal processor digital signal according to the first comparator and the second comparator, judge when temperature voltage does not mate with present stage threshold voltage, described DSP CONTROL is opened the light and is had been turned on switching off in array, and control described switch array is positioned at the access failure switch having been turned on above and below switch and in turn switch in order, stopping after making temperature voltage again mate with threshold voltage.
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