CN105606239A - Temperature measurement circuit - Google Patents

Abstract

The invention provides a temperature measurement circuit comprising a temperature sensing circuit which outputs first and second voltages representing temperature change. The temperature sensing circuit comprises a bias current source which comprises first and second output ends outputting first and second currents respectively, and first and second MOS tubes which are configured to have a gate and a drain connected and grounded, wherein the source of the first MOS tube is connected with the first output end, and the source of the second MOS tube is connected with the second output end. The first voltage is the difference between the gate-source voltages of the first and second MOS tubes, and the second voltage is the gate-source voltage of the first or second MOS tube. The temperature measurement circuit of the invention is applicable to on-chip integration, has the characteristics of low power consumption and high precision, and can be applied to chip circuit systems with low power voltage.

Description

Temperature measuring circuit

Technical field

The present invention relates to a kind of temperature measuring circuit.

Background technology

At present, the market development of environmental monitoring, medical device and high-precision electronic device, to temperatureDegree measurement scheme has proposed low-power consumption, high accuracy, requirement easy of integration. For obtaining accurate temperatureDegree value, conventional scheme is to use high-accuracy temperature measuring device, but this method is not easy of integration, onlyBe applicable to the occasions such as laboratory measurement, can not be applicable to utilize RFID label to gather environment temperatureDeng emerging field.

Prior art, for example, in patent documentation CN102435336A, disclose and be applicable on sheetIntegrated temperature measuring circuit, is all to utilize conventional temperature-sensing element triode to carry out temperature survey,But the supply voltage of its requirement is higher, do not utilize system power dissipation. In addition, temperature in prior artThe A/D conversion accuracy of measuring circuit is too low, can not meet the demand of existing market.

Summary of the invention

For this reason, the invention provides a kind of temperature measuring circuit, comprise temperature sense circuit, itsOutput characterizes the first and second voltages of variations in temperature, and described temperature sense circuit comprises: biasingCurrent source, it comprises the first and second outputs of exporting respectively the first and second electric currents; FirstWith the second metal-oxide-semiconductor, be all configured to grid and be connected and ground connection with drain electrode, a described MOSThe source electrode of pipe connects described the first output, and the source electrode of described the second metal-oxide-semiconductor connects described the second outputEnd, wherein, described the first voltage is the gate source voltage of the described first or second metal-oxide-semiconductor, described inSecond voltage is the difference of the gate source voltage of described the first and second metal-oxide-semiconductors.

Further, described temperature measuring circuit also comprises analog to digital conversion circuit, for representingThe analog quantity of the ratio of described the first voltage and second voltage is converted into bit stream, and described modulus turnsChange circuit and comprise SARADC and Sigma-Delta modulator, wherein, described SARADCTransform the integer part of described analog quantity, described Sigma-Delta modulator transforms described analog quantityFractional part.

Further, described temperature measuring circuit also comprises digital processing circuit, to described bitStream carries out filtering and extracts and process to obtain measured temperature value and to store this temperature value.

Preferably, described the first and second metal-oxide-semiconductors are PMOS pipe.

Preferably, described the first electric current is 5～10 times of described the second electric current.

Preferably, described digital processing circuit comprises sinc³Digital filter is to carry out described filteringProcess with extracting.

Temperature measuring circuit of the present invention is applicable on sheet integrated, and utilizes diode connecting-typeThe characteristic of metal-oxide-semiconductor produces the voltage signal with temperature correlation, and it has the feature of low-power consumption, canBe applied to the chip circuit system of low supply voltage; Utilize SARADC and Sigma-Delta to adjustDevice processed combines and carries out analog-to-digital conversion, can reach existing market desired level.

Brief description of the drawings

Fig. 1 is the composition frame chart of temperature measuring circuit of the present invention;

Fig. 2 is the schematic diagram of an embodiment of temperature measuring circuit of the present invention.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, temperature measuring circuit of the present invention is done furtherDetailed description, but not as a limitation of the invention.

With reference to Fig. 1, it is the composition frame chart of temperature measuring circuit of the present invention. In this framework, temperatureDegree measuring circuit comprises temperature sense circuit 100, analog to digital conversion circuit 200 and digital processing circuit300。

Wherein, temperature sense circuit 100 is for exporting the first voltage V that characterizes variations in temperature₁WithTwo voltage V₂. This temperature sense circuit 100 comprises bias current sources 110, and it has output firstElectric current I₁The first output, and output the second electric current I₂The second output. Temperature sense circuit100 also comprise the first metal-oxide-semiconductor M₁With the second metal-oxide-semiconductor M₂, be all configured to diode connecting-type,I.e. two metal-oxide-semiconductor M₁And M₂Grid be connected and ground connection with drain electrode, and, a MOSPipe M₁Source electrode connect the first output, receive the first electric current I₁, the second metal-oxide-semiconductor M₂SourceThe utmost point connects the second output, receives the second electric current I₂. Temperature sense circuit 100 export firstVoltage V₁Be the first metal-oxide-semiconductor M₁Gate source voltage V_GS1Or the second metal-oxide-semiconductor M₂Gate source voltageV_GS2, the second voltage V of its output₂For M₁And M₂The difference of gate source voltage, as Fig. 2 instituteThe Δ V showing_GS。

As shown in Figure 2, the first metal-oxide-semiconductor M₁With the second metal-oxide-semiconductor M₂Be preferably PMOS pipe,The first electric current I₁It is the second electric current I₂M doubly, be preferably 5～10 times. Thus, temperature sense electricityRoad 100 use are biased in the PMOS pipe of the diode connecting-type under different current densities, respond toExtraneous temperature, can obtain the first voltage V₁, i.e. negative temperature coefficient voltage V_GS(V_GS1Or V_GS2)，By changing the first electric current I₁With the second electric current I₂Current ratio, can regulate second voltage V₂,Positive temperature coefficient voltage Δ V_GS, more just can carry out temperature survey by subsequent conditioning circuit.

Due to the gate source voltage V of metal-oxide-semiconductor under normal temperature_GSApproximate 0.3V, and conventional temperature-sensitive unitThe base-emitter voltage V of part triode_BEApproximate 0.7V, visible, the V of metal-oxide-semiconductor_GSThan threeThe V of utmost point pipe_BEMuch lower, therefore it can be operated under lower supply voltage. With prior artCompare, this temperature sense circuit 100 utilizes metal-oxide-semiconductor to carry out temperature-sensitive, is simplifying circuit designMeanwhile, reduced the power consumption of system. Meanwhile, because it can be operated in lower supply voltageUnder, therefore, its range of application is wider.

The the first voltage V being exported by temperature sense circuit 100₁(be negative temperature coefficient voltage V_GS)With second voltage V₂(be positive temperature coefficient voltage Δ V_GS) principle that obtains measured temperature value retouchesState as follows. By positive temperature coefficient voltage Δ V_GSWith negative temperature coefficient voltage V_GS, one-tenth zero temperature capable of being combinedDegree coefficient voltages V_REF. And zero-temperature coefficient voltage V_REF＝V_GS+α·ΔV_GS, wherein, α is constant,Value 14～18.

Then, can obtain and the positively related coefficient r of temperature according to following formula (1):

$r=\frac{\mathrm{\α}\·\mathrm{\Δ}{V}_{\mathrm{GS}}}{\mathrm{\α}\·\mathrm{\Δ}{V}_{\mathrm{GS}}+V_{\mathrm{GS}}}=\frac{\mathrm{\α}}{\mathrm{\α}+\frac{V_{\mathrm{GS}}}{\mathrm{\Δ}{V}_{\mathrm{GS}}}},$ Formula (1)

Wherein, α is a constant, and value is 14～18,For temperature sense circuit 100 is exportedThe first voltage V₁(be negative temperature coefficient voltage V_GS) and second voltage V₂(be positive temperature coefficientVoltage Δ V_GS) ratio.

Finally, determine the principle of straight line according to two points, can obtain with temperature positively relatedCoefficient r is to the mapping relations of temperature value Temp, that is:

Temp=A*r-B, formula (2)

Wherein, A=580～620, B=260～280.

In order to improve the first voltage V₁With second voltage V₂The digitized precision of ratio, thisBright temperature measuring circuit also comprises analog to digital conversion circuit 200, for comprising the electricity of temperature informationPress the analog quantity of signal to be converted into the bit stream that data bit width is 1 bit. Wherein, comprise temperatureThe analog quantity of the voltage signal of information is the first voltage V₁With second voltage V₂Ratio, i.e. negative temperatureCoefficient voltages V_GSWith positive temperature coefficient voltage Δ V_GSRatio

To analog quantityWhile carrying out digitlization, integer part and fractional part are carried out respectivelyConversion. Analog quantity can be decomposed, that is:

$\frac{V_{\mathrm{GS}}}{\mathrm{\Δ}{V}_{\mathrm{GS}}}=n+\mathrm{\μ},$ Formula (3)

Wherein n is integer part, and μ is fractional part.

Analog to digital conversion circuit 200 comprises SAR (successive approximation register type) ADC (simulation numberWord converter) 210 and Sigma-Delta modulator 220, wherein, described SARADC210The integer part n of converts analog amount, described Sigma-Delta modulator 220 transforms described simulationThe fractional part μ of amount.

With reference to Fig. 2, the analog-digital conversion process of analog to digital conversion circuit 200 is described.

First, complete thick conversion with SARADC (being preferably the SARADC of 5 bits) 210,By V_GSΔ V with integral multiple_GSMake comparisons, thereby obtain integer part n, and be stored in registerIn.

Then, Sigma-Delta modulator 220 completes essence conversion, when comparator output firstFor example, when state (being output as 1), Sigma-Delta modulator 220 integration V_GS-(n+1)·ΔV_GS，For example, in the time that comparator is exported the second state (being output as 0), integration V_GS-n·ΔV_GS. Work oneAfter the section time, according to principle of charge conservation, that is:

(1-μ)·(V_GS-n·ΔV_GS)+u·(V_GS-(n+1)·ΔV_GS)=0, formula (4)

Can obtain the value of fractional part according to following formula (5):

$\mathrm{\μ}=\frac{V_{\mathrm{GS}}}{\mathrm{\Δ}{V}_{\mathrm{GS}}}-n,$ Formula (5)

Wherein, integer part n is converted to by SARADC210.

Thus, analog to digital conversion circuit 200 has obtainedInteger part n and fractional part μDigitized value, has obtainedOutputed to digital processing circuit 300. Numeral placeReason circuit 300 comprises sinc³Digital filter, for analog to digital conversion circuit 200 is exported 1The bit stream of bit extracts and filtering processing, becomes data signal, the position of this data signalWide can according to precision need select, for example, selecting data bit wide is 12 bits. These are 12 years oldThe data of bit can obtain in formula (1) and (2) positively related with temperature divided by 4096Coefficient r, thus the temperature value Temp that will measure obtained. This temperature value Temp obtaining is passableBe stored in memory, and can be directly read by digital communication interface by external entity.

The analog to digital conversion circuit 200 of temperature measuring circuit of the present invention, adopts SARADC210The framework combining with Sigma-Delta modulator 220, forms at a high speed and high-precision modulus turnsParallel operation. Due to integer and fractional part are quantized respectively, ensureing that quantification is high-precision sameTime, to the required precision of Sigma-Delta modulator 220 reduce (for example, do not need to adopt asThe disclosed double precision Sigma-Delta modulator of patent documentation CN102435336A, also can reachTo the precise digitization higher than the document). Due to the precision to Sigma-Delta modulator 220Require to reduce, its over-sampling rate does not need too highly, and therefore its working time shortens greatly, fromAnd reduce the average power consumption of system; Also to the demand of amplifier output voltage swing and sampling capacitance simultaneouslyReduce, can reduce further system power dissipation.

Temperature measuring circuit of the present invention is applicable on sheet integrated, and utilizes diode connecting-typeThe characteristic of metal-oxide-semiconductor produces the voltage signal with temperature correlation, and it has the feature of low-power consumption, canBe applied to the chip circuit system of low supply voltage; Utilize SARADC and Sigma-Delta to adjustDevice processed combines and carries out analog-to-digital conversion, can reach existing market desired level.

Above detailed description of the invention is only illustrative embodiments of the present invention, can not be used for limitingThe present invention, protection scope of the present invention is defined by the claims. Those skilled in the art canIn essence of the present invention and protection domain, the present invention is made various amendments or is equal to replacement,These amendments or be equal to replacement and also should be considered as dropping in protection scope of the present invention.

Claims (6)

1. a temperature measuring circuit, comprises temperature sense circuit, and its output characterizes variations in temperatureThe first and second voltages, described temperature sense circuit comprises:

Bias current sources, it comprises first and second outputs of exporting respectively the first and second electric currentsEnd;

The first and second metal-oxide-semiconductors, are all configured to grid and are connected and ground connection with drain electrode, and describedThe source electrode of one metal-oxide-semiconductor connects described the first output, described in the source electrode of described the second metal-oxide-semiconductor connectsThe second output, wherein,

Described the first voltage is the gate source voltage of the described first or second metal-oxide-semiconductor, described the second electricityPress the difference for the gate source voltage of described the first and second metal-oxide-semiconductors.

2. temperature measuring circuit according to claim 1, is characterized in that, described temperatureMeasuring circuit also comprises analog to digital conversion circuit, for representing described the first voltage and second voltageThe analog quantity of ratio be converted into bit stream, analog-digital conversion circuit as described comprise SARADC andSigma-Delta modulator, wherein, described SARADC transforms the integer portion of described analog quantityPoint, described Sigma-Delta modulator transforms the fractional part of described analog quantity.

3. temperature measuring circuit according to claim 2, is characterized in that, described temperatureMeasuring circuit also comprises digital processing circuit, to described bit stream carry out filtering and extract process withObtain measured temperature value and store this temperature value.

4. temperature measuring circuit according to claim 1, is characterized in that, described firstBe PMOS pipe with the second metal-oxide-semiconductor.

5. temperature measuring circuit according to claim 1, is characterized in that, described firstElectric current is 5～10 times of described the second electric current.

6. temperature measuring circuit according to claim 3, is characterized in that, described numeralTreatment circuit comprises sinc³Digital filter is to carry out described filtering and to extract and process.