Delta-sigma temperature sensor with positive temperature coefficient reference voltage

Abstract

The invention provides a delta-sigma temperature sensor of positive temperature coefficient reference voltage, the delta-sigma temperature sensor is used for obtaining a temperature value according to an input voltage, a first temperature proportionality coefficient exists between the input voltage and the temperature, the delta-sigma temperature sensor comprises a reference voltage generating circuit, an integrating circuit and a quantizer, the reference voltage generating circuit is used for generating a positive temperature coefficient reference voltage and outputting the positive temperature coefficient reference voltage to the integrating circuit, the positive temperature coefficient reference voltage is in direct proportion to the temperature and has a second temperature proportionality coefficient, and the second temperature proportionality coefficient is smaller than the first temperature proportionality coefficient; the integrating circuit is used for amplifying and accumulating a difference value between the input voltage and the positive temperature coefficient reference voltage and outputting an integral output signal; the quantizer is configured to output a bitstream according to the integrated output signal.

Description

Technical Field

[0001] This application mainly relates to the technical field of battery management, and particularly relates to a delta-sigma temperature sensor with a positive temperature coefficient reference voltage. Background Art

[0002] In a battery management system (BMS), the battery temperature is an important parameter that needs to be measured in real time. With the increasingly strict national requirements for automobile emission standards, the market share of new energy vehicles has been increasing year by year in recent years. However, the occasional occurrence of new energy vehicle battery pack fire incidents has put forward higher requirements for the design of battery packs and battery management systems. It is necessary to monitor the temperature of power battery packs. When it is found that the battery pack temperature changes abnormally, such as exceeding the safety threshold, an alarm signal is sent for early warning to avoid danger. Therefore, temperature sensors are widely used in battery management chips. Integrated temperature sensors have the advantages of small size, low cost, and easy integration. However, for the detection of chip temperature, in some existing technologies, the characteristic that the voltage drop across a temperature diode decreases as the temperature rises is used to detect the temperature. Since the diode has a parasitic resistance, and this parasitic resistance varies with the process and cannot be accurately predicted. Therefore, there is a large deviation in detecting chip temperature using a temperature diode. In addition, the temperature measured by the temperature diode outputs a voltage signal, which cannot be directly read by digital signal processing circuits such as the CPU. Therefore, it is impossible to construct real-time battery temperature detection and protection based on the reference of the temperature diode. Digital temperature sensors based on sigma-delta ADCs have been widely used because they can output a data stream related to temperature and can be processed by MCU or ASIC circuits.

[0003] Figure 1 It is a digital temperature sensor based on a sigma-delta ADC. Among them, a bandgap reference circuit 110 independent of temperature is used to generate a reference voltage Vref, and this reference voltage Vref is input into the sigma-delta ADC 120. The traditional bandgap reference circuit uses the temperature coefficient of the base-emitter voltage Vbe of a bipolar transistor and the positive temperature coefficient of the difference between the base-emitter voltages of two bipolar transistors under different current densities to compensate each other, so that the output voltage has a very low temperature drift, so that the output voltage is almost independent of temperature and is a fixed value at different temperatures. However, this so-called fixed reference voltage is not completely constant. With the increasingly mature design of sigma-delta analog-to-digital converters, the error brought by the reference voltage has become the main factor restricting the improvement of the accuracy of temperature sensors. Therefore, a temperature sensor that can eliminate this error and improve the accuracy of temperature sensors is needed. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a Sigma-Delta temperature sensor that can eliminate the reference voltage drift error and has high precision.

[0005] To solve the above technical problem, this application provides a delta-sigma temperature sensor with a positive temperature coefficient reference voltage, which is used to obtain a temperature value according to an input voltage. There is a first temperature proportional coefficient between the input voltage and the temperature. The sensor includes a reference voltage generation circuit, an integration circuit, and a quantizer. Among them, the reference voltage generation circuit is used to generate a positive temperature coefficient reference voltage and output the positive temperature coefficient reference voltage to the integration circuit. The positive temperature coefficient reference voltage is proportional to the temperature and has a second temperature proportional coefficient, and the second temperature proportional coefficient is smaller than the first temperature proportional coefficient. The integration circuit is used to amplify and accumulate the difference between the input voltage and the positive temperature coefficient reference voltage and output an integration output signal. The quantizer is used to output a bit stream according to the integration output signal.

[0006] In an embodiment of this application, the reference voltage generation circuit includes a first amplifier, a first transistor, a second transistor, a first MOS transistor, and a resistor unit. Among them, the bases and collectors of the first transistor and the second transistor are both connected to the reference ground. The emitter of the first transistor is connected to the first input terminal of the first amplifier. The emitter of the second transistor is connected to the second input terminal of the first amplifier. The output terminal of the first amplifier is connected to the gate of the first MOS transistor. The drain of the first MOS transistor is connected to one end of the resistor unit. The source of the first MOS transistor is connected to the power supply. The other end of the resistor unit is connected to the emitters of the first transistor and the second transistor. Among them, the drain of the first MOS transistor outputs the positive temperature coefficient reference voltage.

[0007] In an embodiment of this application, both the first transistor and the second transistor are bipolar transistors, and the ratio of the emitter area of the first transistor to the emitter area of the second transistor is 1:N, where N is a positive integer.

[0008] In an embodiment of this application, the resistor unit includes a first resistor, resistor A, resistor B, and resistor C. Among them, the first resistor is connected between the emitter of the second transistor and the second input terminal of the first amplifier. One end of resistor B is connected to the second input terminal of the first amplifier. The other end of resistor B is connected to one end of resistor C. The other end of resistor C is connected to the drain of the first MOS transistor. One end of resistor A is connected to the other end of resistor B. The other end of resistor A is connected to the emitter of the first transistor.

[0009] In an embodiment of the present application, the reference voltage generation circuit further includes a second MOS transistor. The gate of the second MOS transistor is connected to the gate of the first MOS transistor. The source of the second MOS transistor is connected to a power supply, and the drain of the second MOS transistor outputs the input voltage.

[0010] In an embodiment of the present application, the positive temperature coefficient reference voltage Vref is calculated using the following formula:

[0011]

[0012] V ref = V BE1 + I PTAT × (R A + 2R C )

[0013] where, I PTAT is the current corresponding to the input voltage, R1 represents the resistance value of the first resistor, R A represents the resistance value of resistor A, R C represents the resistance value of resistor C, q represents the electronic charge, k is the Boltzmann constant, T represents the absolute temperature, V BE1 represents the base-emitter voltage of the first transistor, and ΔV BE represents the difference between the base-emitter voltages of the first transistor and the second transistor.

[0014] In an embodiment of the present application, the quantizer includes a comparator. The first input terminal of the comparator is connected to the output terminal of the integration circuit, and the second input terminal of the comparator is connected to the positive temperature coefficient reference voltage.

[0015] In an embodiment of the present application, it further includes a DAC module. The DAC module includes a second resistor, a third resistor, and a switching element. Among them, one end of the third resistor is connected to the drain of the second MOS transistor and one end of the second resistor. The other end of the third resistor is connected to the reference ground. The other end of the second resistor is connected to one end of the switching element, and the other end of the switching element is connected to the reference ground. The output terminal of the comparator is connected to the other end of the switching element.

[0016] In an embodiment of the present application, the reference voltage generation circuit includes a constant current source, a Zener diode, a first voltage dividing resistor, and a second voltage dividing resistor. Among them, the Zener diode is connected in parallel with the series-connected first voltage dividing resistor and second voltage dividing resistor. The constant current source is connected to the cathode of the Zener diode, and the connection point of the first voltage dividing resistor and the second voltage dividing resistor outputs the positive temperature coefficient reference voltage.

[0017] In an embodiment of the present application, the reference voltage generation circuit further includes a charge pump. The Zener diode has a breakdown voltage, and the charge pump is used to boost the battery voltage above the breakdown voltage to drive the Zener diode.

[0018] Compared with the prior art, the present application uses a reference voltage generation circuit to provide a positive temperature coefficient reference voltage, which can reduce the error from the actual reference voltage, better predict the actual reference voltage in a large temperature range, improve the measurement accuracy of the temperature sensor, and also avoid the test time and cost spent on calibration at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are provided to further understand the present application, and they are incorporated into and constitute a part of this application. The drawings illustrate embodiments of the present application and, together with this specification, serve to explain the principles of the present application. In the drawings:

[0020] Figure 1 is a digital temperature sensor based on a sigma-delta ADC;

[0021] Figure 2 is a schematic diagram showing the relationship between the temperature and the reference voltage of a temperature sensor;

[0022] Figure 3 is a schematic diagram showing the result of predicting the reference voltage using the current calibration method;

[0023] Figure 4 is a delta-sigma temperature sensor with a positive temperature coefficient reference voltage according to Embodiment 1 of the present application;

[0024] Figure 5 is a delta-sigma temperature sensor with a positive temperature coefficient reference voltage according to Embodiment 2 of the present application;

[0025] Figure 6 is according to Figure 5 is a schematic diagram showing the relationship between the reference voltage and the temperature obtained from the temperature sensor according to Embodiment 2;

[0026] Figure 7 is a schematic diagram of the error after chip testing using the temperature sensor of Embodiment 2;

[0027] Figure 8 is a schematic diagram of the reference voltage generation circuit in a delta-sigma temperature sensor with a positive temperature coefficient reference voltage according to Embodiment 3 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative work, the present application can also be applied to other similar scenarios based on these drawings. Unless obvious from the language context or otherwise stated, the same reference numerals in the figures represent the same structure or operation.

[0029] As shown in the present application, unless the context clearly indicates an exception, words such as "a", "an", "one", and / or "the" are not specifically singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the clearly identified steps and elements, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0030] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the accompanying drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, such technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0031] In the description of the present application, it should be understood that the orientation or positional relationships indicated by orientation words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal", and "top, bottom" are usually based on the orientation or positional relationships shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description. Without contrary instructions, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as limiting the protection scope of the present application; the orientation words "inside, outside" refer to the inside and outside relative to the outline of each component itself.

[0032] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "upper" etc. may be used herein to describe the spatial positional relationship of one device or feature to other devices or features as shown in the figures. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, a device described as "above" or "over" other devices or structures will then be positioned "below" or "under" the other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the corresponding explanations will be made for the spatial relative descriptions used herein.

[0033] In addition, it should be noted that the use of terms such as "first", "second" etc. to define components is merely for the convenience of distinguishing the corresponding components. Without further declaration, the above terms have no special meanings, so they should not be construed as limiting the protection scope of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some of the terms mentioned in the specification of this application may be selected by the applicant according to his or her judgment, and their detailed meanings are described in the relevant parts of the description herein. In addition, it is required to understand this application not only through the actual terms used, but also through the meanings implied by each term.

[0034] The inventors of this application have found that Figure 1 the shown reference voltage Vref actually varies according to temperature. Figure 2 is the relationship between temperature and the reference voltage Vref obtained by the inventors of this application through experiments, where the horizontal axis is temperature temp in degrees Celsius and the vertical axis is the reference voltage Vref in volts. Obviously, the temperature shows a parabolic shape between -40 degrees and 85 degrees, not a linear relationship, let alone a fixed one. Figure 2 The error in the shown reference voltage varying with temperature has become the main factor restricting the improvement of the accuracy of the temperature sensor. Through research, the main sources of this error are: (1) the change in V caused by process fluctuations, V BE change, V BErepresent the base-emitter voltages of two bipolar transistors in the bandgap reference circuit; (2) the offset between two bipolar transistors Q1 and Q2 in the bandgap reference circuit and between related resistors; (3) the temperature coefficient of the reference voltage Vref still exists. Therefore, calibration techniques are required to ensure the accuracy of the temperature sensor and the consistency of sensor readings. Among them, the errors from sources (1) and (2) can be calibrated by measuring the correspondence between temperature and the output bitstream under normal temperature conditions. This application proposes a delta-sigma temperature sensor with a positive temperature coefficient reference voltage based on this source (3).

[0035] The general process of temperature sensor calibration is as follows:

[0036] The first step: Measure the reading (DTS R ) at normal temperature (around 20 degrees), and measure the reading (DTS H ) at high temperature (60 - 65 degrees).

[0037] The second step: Use the following formula to calculate the gain gain of the relationship between the temperature sensor output value and the ambient temperature:

[0038] gain = (DTS H - DTS R ) / (T H - T R );

[0039] Where, T H represents the high temperature, and T R represents the room temperature.

[0040] The third step: Use the following formula to calculate the offset offset of the relationship between the output value and the ambient temperature:

[0041] offset = DTS R - T R * gain;

[0042] After obtaining the two parameters of gain and offset, for any bitstream output by the ADC, it can be calibrated through the following formula as the final output:

[0043]

[0044] As can be seen from the above steps, under the conditions of the existing calibration method, since only the readings of the temperature sensor at normal temperature and high temperature are measured and used to calibrate any reading within the full temperature range, it is actually defaulted that each parameter inside the circuit is either independent of temperature or linearly related to temperature in order to perform accurate calibration through the readings at two points. However, Figure 2It is clearly shown that the actually obtained reference voltage value Vref is neither independent of temperature nor linearly related.

[0045] Figure 3 It is a schematic diagram of the result of predicting the reference voltage by using the current calibration method. As Figure 3 shown, the parabolic curve therein is the "actual" reference voltage "Vref_T", and the virtual straight line therein is the reference voltage "Vref_F" after "error". Specifically, at low temperature (taking -40°C as an example), the actual reference voltage value Vref_T is the lowest value in the full temperature range. However, according to the existing calibration method, which is based on a linear relationship, when calibrating the sensor readings at low temperature, it is predicted by the extension line of the reference voltage values at normal temperature and high temperature in the low temperature direction. Then, the obtained reference voltage value Vref_F is the maximum value in the full temperature range. It can be seen that this reference voltage value is completely inconsistent with the actual low temperature reference voltage value, resulting in a large error still existing after the sensor is calibrated. Based on such a result, in order to obtain accurate values in the low temperature range, it is often necessary to add some test points at low temperature, and the test at each temperature point means higher test cost and time cost.

[0046] This result also shows that if the designed temperature characteristic of the reference voltage is no longer parabolic but follows the Figure 3 shape of the extension line therein, then the error of the sensor caused by the reference voltage can be eliminated. Based on this idea, the present application uses a linear reference voltage generation circuit to replace the parabolic bandgap reference circuit, so as to improve the calibration accuracy of the temperature sensor, especially at low temperature, on the premise of maintaining the existing calibration method and not adding additional measured temperature points.

[0047] Figure 4 It is a delta-sigma temperature sensor with a positive temperature coefficient reference voltage in Embodiment 1 of the present application. In the following text of the present application, the "delta-sigma temperature sensor" is abbreviated as the "temperature sensor". Refer to Figure 4 . The temperature sensor 400 of this embodiment includes a reference voltage generation circuit 410, an integration circuit 420, and a quantizer 430. Among them, the reference voltage generation circuit 410 is used to generate a positive temperature coefficient reference voltage Vref and output the positive temperature coefficient reference voltage Vref to the integration circuit 420. It should be noted that Vref here is different from Vref described above, only using the same label. The positive temperature coefficient reference voltage Vref is a reference voltage proportional to temperature. As Figure 4, where the input voltage V1 is a temperature-sensitive voltage for representing the voltage signal of the temperature of the object to be measured. For example, in a battery management circuit, it can be achieved by collecting the voltage on an integrated diode in an integrated circuit process. When the temperature sensor 400 is used to detect temperature, the voltage of the integrated diode can reflect the temperature of the battery electrode to be detected.

[0048] The integrating circuit 420 is used to amplify and accumulate the difference between the input voltage V1 and the positive temperature coefficient reference voltage Vref and output an integration output signal Vi. The quantizer 430 outputs a bit stream Bs according to the integration output signal Vi. The duty cycle of the bit stream Bs is used to obtain the temperature value corresponding to the input voltage V1. The duty cycle represents the ratio of the time occupied by the pulse to the total time within a continuous working time period. The temperature sensor 400 of the present application can convert the temperature value into an output duty cycle, that is, the duty cycle can be used to calculate the temperature value corresponding to the input voltage subsequently.

[0049] Specifically, in the present application, it is assumed that there is a first temperature proportionality coefficient between the input voltage V1 and the temperature, and the positive temperature coefficient reference voltage Vref has a second temperature proportionality coefficient, and the second temperature proportionality coefficient is less than the first temperature proportionality coefficient. In this way, it can be realized that the duty cycle of the bit stream is proportional to V1, and V1 is proportional to the temperature, so as to realize that the output duty cycle is proportional to the temperature. It should be noted that both the first temperature proportionality coefficient and the second temperature proportionality coefficient are positive numbers, representing the change rate of the voltage with respect to the temperature. If the input voltage V1 is inversely proportional to the temperature, the voltage V1 can be converted to be proportional to the temperature through a conversion circuit. In practice, the first temperature proportionality coefficient is significantly greater than the second temperature proportionality coefficient.

[0050] In some embodiments, the 1-bit bit stream Bs signal output by the temperature sensor of the present application can be sent to the FPGA for processing, the duty cycle of the bit stream Bs within a period of time can be obtained, and then the data is transmitted to the processor through the interface of the FPGA, and the temperature value can be obtained. The processor is, for example, a personal computer, a mobile terminal, etc. with a processor such as a CPU or an MCU.

[0051] The present application does not limit the specific circuit structure of the reference voltage generation circuit 410, as long as it is a circuit that can generate a qualified reference voltage Vref with a positive temperature coefficient, it belongs to the scope protected by the present application.

[0052] According to Figure 4 the temperature sensor 400 shown, since the reference voltage Vref with a positive temperature coefficient is adopted, as described above, by using the current calibration process to calibrate the temperature sensor 400, the error caused by the reference voltage can be eliminated, and without adding additional temperature measurement points, the accuracy of the temperature sensor can be improved.

[0053] Figure 5 is the delta-sigma temperature sensor with a positive temperature coefficient reference voltage in the second embodiment of the present application. Refer to Figure 5 As shown, in this embodiment, the temperature sensor 500 includes a reference voltage generation circuit 510. The reference voltage generation circuit 510 specifically includes a first amplifier OA1, a first transistor Q1, a second transistor Q2, a first MOS transistor J1, and a resistor unit 511. Among them, the bases b and collectors c of the first transistor Q1 and the second transistor Q2 are both connected to the reference ground refgnd. The emitter e of the first transistor Q1 is connected to the first input terminal 512 of the first amplifier OA1. The emitter e of the second transistor Q2 is connected to the second input terminal 513 of the first amplifier OA1. The output terminal 514 of the first amplifier OA1 is connected to the gate g of the first MOS transistor J1. The drain d of the first MOS transistor J1 is connected to one end of the resistor unit 511. The source s of the first MOS transistor J1 is connected to the power supply VDD. The other end of the resistor unit 511 is connected to the emitters e of the first transistor Q1 and the second transistor Q2. Among them, the drain d of the first MOS transistor J1 outputs the positive temperature coefficient reference voltage Vref.

[0054] In some embodiments, as Figure 5 shown, the first transistor Q1 and the second transistor Q2 are both bipolar transistors, and the ratio of the emitter area of the first transistor Q1 to the emitter area of the second transistor Q2 is 1:N, where N is a positive integer.

[0055] According to the reference voltage generation circuit 510, a Vref with a positive temperature coefficient can be generated. Among them, the resistor unit 511 is a resistor network composed of multiple resistors connected in series and / or in parallel. The present application does not limit the specific structure of the resistor unit 511.

[0056] Furthermore, in some embodiments, as Figure 5 shown, the resistor unit 511 includes a first resistor R1, a resistor A, a resistor B, and a resistor C. Among them, the first resistor R1 is connected between the emitter e of the second transistor Q2 and the second input terminal 513 of the first amplifier OA1. One end of the resistor B is connected to the second input terminal 513 of the first amplifier OA1. The other end of the resistor B is connected to one end of the resistor C. The other end of the resistor C is connected to the drain d of the first MOS transistor J1. One end of the resistor A is connected to the other end of the resistor B. The other end of the resistor A is connected to the emitter e of the first transistor Q1.

[0057] By setting the connection mode of the resistors in the resistor unit 511 and the resistance values of each resistor, the magnitude of the positive temperature coefficient reference voltage Vref can be adjusted according to the actual situation.

[0058] In some embodiments, the reference voltage generation circuit 510 further includes a second MOS transistor J2. The gate g of the second MOS transistor J2 is connected to the gate g of the first MOS transistor J1, and correspondingly, is connected to the output terminal 514 of the first amplifier OA1. The source s of the second MOS transistor J2 is connected to the power supply VDD, and the drain d of the second MOS transistor J2 outputs an input voltage V1. This input voltage V1 is a temperature-sensitive voltage that is positively correlated with temperature, so it is used as the input voltage V1. As Figure 5 , in this embodiment, the integration circuit 520 includes a second amplifier OA2 and a capacitor C1, which is a common integration circuit structure. The output terminal of the integration circuit 520 is fed back to the drain d of the second MOS transistor J2, thereby feedback affecting the input voltage V1.

[0059] As Figure 5 shown, the quantizer X includes a single-ended input device connected to the negative terminal of the capacitor C1, and outputs a 0 / 1 bit stream according to the integration output signal of the integration circuit 520.

[0060] Furthermore, the quantizer X includes a differential input device, which is a comparator 530. The first input terminal 531 of the comparator 530 is connected to the output terminal of the integration circuit 520, and the second input terminal 532 of the comparator 530 is connected to a positive temperature coefficient reference voltage Vref. Among them, as Figure 5 shown, the first input terminal 531 can be a negative input terminal, and the second input terminal 532 can be a positive input terminal.

[0061] The temperature sensor further includes a DAC module 540. The output terminal of the quantizer X is connected to the DAC module 540.

[0062] In some embodiments, the DAC module 540 includes a switched-mode current source. The DAC module 540 is connected to the input voltage V1. When the bit stream signal Bs output by the comparator 530 is 1, the switched-mode current source is turned on, making the integration output signal of the integration circuit 520 smaller, so that Bs flips to 0. When the bit stream signal BS is 0, the switched-mode current source is turned off, making the integration output signal of the integration circuit 520 larger, so that Bs flips to 1.

[0063] In Figure 5In the illustrated embodiment, the DAC module 540 includes a second resistor R2, a third resistor R3, and a switching element 541. One end of the third resistor R3 is connected to the drain d of the second MOS transistor J2 and one end of the second resistor R2. The other end of the third resistor R3 is connected to the reference ground refgnd. The other end of the second resistor R2 is connected to one end of the switching element 541. The other end of the switching element 541 is connected to the reference ground refgnd. The output end of the comparator 530 is connected to the other end of the switching element 541. In some embodiments, the switching element 541 is, for example, an NMOS transistor. In this case, the first input terminal 531 of the comparator 530 serving as the quantizer X is set as the negative terminal, and the second input terminal 532 is set as the positive terminal. As Figure 5 shown, when the bitstream signal Bs is 1, the switching element 541 is turned on, causing the integration output signal of the integration circuit 520 to become smaller, thereby causing Bs to flip to 0; when the bitstream signal BS is 0, the switching element 541 is turned off, causing the integration output signal of the integration circuit 520 to become larger, thereby causing Bs to flip to 1. In this way, a continuous 01 bitstream is formed. In other embodiments, the switching element 541 is, for example, a PMOS transistor. In this case, the polarity of the X1 output needs to be modified. The first input terminal 531 of the comparator 530 serving as the quantizer X is set as the positive terminal, and the second input terminal 532 is set as the negative terminal. Then, when the bitstream signal Bs is 1, the switching element 541 is turned off, causing the integration output signal of the integration circuit 520 to become smaller, thereby causing Bs to flip to 0; when the bitstream signal BS is 0, the switching element 541 is turned on, causing the integration output signal of the integration circuit 520 to become larger, thereby causing Bs to flip to 1.

[0064] According to Figure 5 the reference voltage generation circuit 510 shown, the positive temperature coefficient reference voltage Vref can be calculated using the following formula:

[0065]

[0066] V ref =V BE1 +I PTAT ×(R A +2R C ) (2)

[0067] where, I PTAT is the current corresponding to the input voltage V1, R1 represents the resistance value of the first resistor, R A represents the resistance value of resistor A, R C represents the resistance value of resistor C, q represents the electron charge, k is the Boltzmann constant, T represents the absolute temperature, V BE1 represents the base-emitter voltage of the first transistor Q1, and ΔV BE represents the difference between the base-emitter voltages of the first transistor Q1 and the second transistor Q1.

[0068] As Figure 5 , I PTAT is the current flowing from the drain d of the second MOS transistor J2 to the second resistor R2 and the third resistor R3. According to the principle of the bandgap reference circuit, I PTAT is proportional to the absolute temperature (PTAT, Proportional To Absolute Temperature). In this embodiment, R A is equal to R B . Therefore, based on the circuit principle, the above equations (1) and (2) are obtained, and the obtained positive temperature coefficient reference voltage Vref has a linear characteristic proportional to the temperature.

[0069] According to the above equation (2), by adjusting the magnitude of Rc, a positive temperature coefficient reference voltage Vref with different temperature coefficients can be created.

[0070] Figure 6 is a schematic diagram of the relationship between the reference voltage and the temperature obtained from the temperature sensor 500 according to Embodiment 2 shown in Figure 5 . As shown in Figure 6 , the horizontal axis is the temperature temp, with the unit of degree Celsius, and the vertical axis is the positive temperature coefficient reference voltage Vref, with the unit of V. Obviously, the positive temperature coefficient reference voltage Vref has a linear positive correlation with the temperature. In this way, by only measuring the temperatures of two points and extending the line fitted through these two points, as shown by the dashed line in Figure 6 , the reference voltage Vref within other temperature ranges can be accurately predicted, greatly reducing the error after calibration.

[0071] The inventor of the present application uses the temperature sensor 500 shown in Figure 5 to perform chip testing, and calibrates the temperature of the tested chip through the test values at 27°C and 60°C. The final performance is as shown in Figure 7 . Figure 7 In Figure 7 , the horizontal axis is the temperature and the vertical axis is the error. Figure 3 shows the error results of temperature detection for 11 chips within the temperature range from -40°C to 12°C, and the errors are all within ±1°C. While the error range of the original temperature sensor shown in

[0072] Figure 3 is within ±3°C. Using the temperature sensor 500 of the present application significantly improves the accuracy of temperature measurement.

[0072] For the reference voltage generation circuit used in the temperature sensor of the present application to generate a positive temperature coefficient reference voltage, there can also be other implementation manners. Another example is given below.

[0073] Figure 8It is a schematic diagram of a reference voltage generation circuit in a delta-sigma temperature sensor with a positive temperature coefficient reference voltage according to Embodiment 3 of the present application. Figure 8 It shows a reference voltage generation circuit 800, which is different from Figure 5 the reference voltage generation circuit 510 in

[0074] Specifically, the reference voltage generation circuit 800 of this embodiment includes a constant current source 810, a Zener diode D1, a first voltage dividing resistor R11, and a second voltage dividing resistor R12. The first voltage dividing resistor R11 and the second voltage dividing resistor R12 are connected in series, and the Zener diode D1 is connected in parallel with the series-connected first voltage dividing resistor R11 and second voltage dividing resistor R12. The constant current source 810 is connected to the cathode of the Zener diode D1, and the connection point of the first voltage dividing resistor R11 and the second voltage dividing resistor R12 outputs a positive temperature coefficient reference voltage Vref. Among them, the Zener diode D1 is a semiconductor device with a positive temperature coefficient. When it breaks down, it can generate a stable voltage approximately equal to its breakdown voltage and having a positive temperature coefficient. Exemplarily, let the breakdown voltage be equal to 6V. Then when the current provided by the current source 810 makes the voltage at the cathode end of the Zener diode D1 greater than 6V, D1 breaks down, generating a voltage of about 6V. After being divided by the first voltage dividing resistor R11 and the second voltage dividing resistor R12, a positive temperature coefficient reference voltage Vref of about 1.2V and having a positive temperature coefficient can be generated. Exemplarily, its temperature coefficient is about 0.4mV / ℃.

[0075] It can be understood that, as shown in Figure 4 the output end of the reference voltage generation circuit 800 is connected to the integration circuit 420, so as to form a temperature sensor of another embodiment, which will not be elaborated here.

[0076] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation to the present application. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to the present application. Such modifications, improvements, and corrections are proposed in the present application, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of the present application.

[0077] Meanwhile, the present application uses specific terms to describe the embodiments of the present application. For example, "an embodiment", "one embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that the "an embodiment" or "one embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the present application can be appropriately combined.

[0078] Some aspects of the present application can be executed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above-mentioned hardware or software can all be referred to as "data blocks", "modules", "engines", "units", "components", or "systems". The processor can be one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or a combination thereof. In addition, aspects of the present application may be embodied as a computer product located in one or more computer-readable media, which includes computer-readable program codes. For example, the computer-readable media may include, but are not limited to, magnetic storage devices (such as hard disks, floppy disks, magnetic tapes...), optical discs (such as compact discs CD, digital versatile discs DVD...), smart cards, and flash memory devices (such as cards, sticks, key drives...).

[0079] The computer-readable media may contain a propagated data signal containing computer program codes, such as on a baseband or as part of a carrier wave. This propagated signal may have various forms of representation, including electromagnetic form, optical form, etc., or a suitable combination of forms. The computer-readable media can be any computer-readable media other than computer-readable storage media, which can be connected to an instruction execution system, device, or equipment to implement communication, propagation, or transmission for use of the program. The program codes located on the computer-readable media can be propagated through any suitable media, including radio, cable, fiber optic cable, radio frequency signal, or similar media, or any combination of the above media.

[0080] Similarly, it should be noted that, in order to simplify the description of the present application and thus help the understanding of one or more embodiments of the invention, in the foregoing description of the embodiments of the present application, sometimes multiple features are grouped into one embodiment, drawing, or description thereof. However, this disclosure method does not mean that the features required by the subject matter of the present application are more than those mentioned in the claims. In fact, the features of the embodiment are less than all the features of the single embodiment disclosed above.

[0081] In some embodiments, numbers are used to describe components and the quantity of attributes. It should be understood that such numbers used in the description of embodiments are modified by the modifiers "about", "approximate" or "substantially" in some examples. Unless otherwise stated, "about", "approximate" or "substantially" indicate that the said numbers allow a variation of ±20%. Accordingly, in some embodiments, the numerical parameters used in this application are all approximate values, and such approximate values may change according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining the general number of digits. Although the numerical ranges and parameters used in some embodiments of this application to confirm the breadth of their scope are approximate values, in specific embodiments, the setting of such numerical values is as precise as possible within the feasible range.

[0082] Although this application has been described with reference to current specific embodiments, those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the spirit of this application, they will fall within the scope of the claims of this application.

Claims

1. A delta-sigma temperature sensor with a positive temperature coefficient reference voltage for obtaining a temperature value based on an input voltage, where there is a first temperature proportionality coefficient between the input voltage and the temperature, characterized in that, It includes a reference voltage generation circuit, an integration circuit, and a quantizer. Among them, the reference voltage generation circuit is used to generate a positive temperature coefficient reference voltage and output the positive temperature coefficient reference voltage to the integration circuit. Among them, the positive temperature coefficient reference voltage is proportional to temperature and has a second temperature proportional coefficient, and the second temperature proportional coefficient is less than the first temperature proportional coefficient; the integration circuit is used to amplify and accumulate the difference between the input voltage and the positive temperature coefficient reference voltage and output an integration output signal; the quantizer is used to output a bit stream according to the integration output signal.

2. The delta-sigma temperature sensor according to claim 1, characterized in that The reference voltage generation circuit includes a first amplifier, a first transistor, a second transistor, a first MOS transistor, and a resistor unit. Among them, the bases and collectors of the first transistor and the second transistor are both connected to the reference ground. The emitter of the first transistor is connected to the first input end of the first amplifier. The emitter of the second transistor is connected to the second input end of the first amplifier. The output end of the first amplifier is connected to the gate of the first MOS transistor. The drain of the first MOS transistor is connected to one end of the resistor unit. The source of the first MOS transistor is connected to the power supply. The other end of the resistor unit is connected to the emitters of the first transistor and the second transistor. Among them, the drain of the first MOS transistor outputs the positive temperature coefficient reference voltage.

3. The delta-sigma temperature sensor according to claim 2, characterized in that, The first transistor and the second transistor are both bipolar transistors, and the ratio of the emitter area of the first transistor to the emitter area of the second transistor is 1:N, where N is a positive integer.

4. The delta-sigma temperature sensor according to claim 3, wherein, The resistor unit includes a first resistor, resistor A, resistor B, and resistor C. Among them, the first resistor is connected between the emitter of the second transistor and the second input end of the first amplifier. One end of resistor B is connected to the second input end of the first amplifier. The other end of resistor B is connected to one end of resistor C. The other end of resistor C is connected to the drain of the first MOS transistor. One end of resistor A is connected to the other end of resistor B. The other end of resistor A is connected to the emitter of the first transistor.

5. The delta-sigma temperature sensor according to claim 4, wherein The reference voltage generation circuit further includes a second MOS transistor. The gate of the second MOS transistor is connected to the gate of the first MOS transistor. The source of the second MOS transistor is connected to the power supply. The drain of the second MOS transistor outputs the input voltage.

6. The delta-sigma temperature sensor according to claim 5, wherein, The following formula is used to calculate the positive temperature coefficient reference voltage Vref: V ref = V BE1 + I PTAT × (R A + 2R C ) Among them, I PTAT is the current corresponding to the input voltage, R1 represents the resistance value of the first resistor, R A represents the resistance value of resistor A, R C represents the resistance value of resistor C, q represents the electron charge, k is the Boltzmann constant, T represents the absolute temperature, V BE1 represents the base-emitter voltage of the first transistor, ΔV BE represents the difference between the base-emitter voltages of the first transistor and the second transistor.

7. The delta-sigma temperature sensor according to claim 1, wherein, The quantizer includes a comparator. The first input end of the comparator is connected to the output end of the integration circuit. The second input end of the comparator is connected to the positive temperature coefficient reference voltage.

8. The delta-sigma temperature sensor according to claim 7, wherein, It further includes a DAC module, and the DAC module includes a second resistor, a third resistor, and a switching element. Among them, one end of the third resistor is connected to the drain of the second MOS transistor and one end of the second resistor, the other end of the third resistor is connected to the reference ground, the other end of the second resistor is connected to one end of the switching element, the other end of the switching element is connected to the reference ground, and the output end of the comparator is connected to the other end of the switching element.

9. The delta-sigma temperature sensor according to claim 1, characterized in that, The reference voltage generation circuit includes a constant current source, a Zener diode, a first voltage dividing resistor, and a second voltage dividing resistor. Among them, the Zener diode is connected in parallel with the series-connected first voltage dividing resistor and second voltage dividing resistor, the constant current source is connected to the cathode of the Zener diode, and the connection point of the first voltage dividing resistor and the second voltage dividing resistor outputs the positive temperature coefficient reference voltage.

10. The delta-sigma temperature sensor according to claim 9, wherein The reference voltage generation circuit further includes a charge pump. The Zener diode has a breakdown voltage, and the charge pump is used to boost the battery voltage above the breakdown voltage to drive the Zener diode.

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