Method and circuit for compensating thermal effect influence in passive temperature sensor chip

Abstract

The invention relates to a method and a circuit for compensating thermal effect influence in a passive temperature sensor chip. The invention belongs to the technical field of radio frequency identification, provides a complete compensation technology aiming at the influence of temperature difference caused by a thermal effect faced by a passive radio frequency identification temperature sensor tag chip product, and respectively takes a voltage quantity sample generated by discharged charges and a current quantity sample formed by the discharged charges as processing signals. Through the circuit implementation technology of analog-digital conversion module quantization and current comparator quantization and the implementation scheme of cooperation of hardware and software, the influence of temperature difference caused by a thermal effect is fundamentally solved, so that the measurement accuracy of a passive radio frequency identification temperature sensor tag is reliably guaranteed, and the measurement accuracy of the passive radio frequency identification temperature sensor tag is improved. And the batch yield is greatly improved, and the method has remarkable economic value.

Description

Technical Field

[0001] The present invention belongs to the field of radio frequency identification (RFID) technology, and specifically refers to a method for improving the temperature measurement accuracy of a temperature sensor by compensating for the influence of thermal effects in a passive temperature sensor chip in a passive radio frequency identification tag integrated with a temperature sensor, and a circuit for implementing the method. Background Art

[0002] With the development of intelligent Internet of Things, the combination of basic passive radio frequency identification technology and ultra-low power sensor technology has introduced new applications in the fields of animal husbandry, biopharmaceuticals and pet health. The ultra-low power temperature sensor is integrated into the RFID chip, which not only provides the ID number, but also sends the measured temperature information in the form of a digital code stream to the RFID data reader.

[0003] RFID temperature sensor tag chip is extended from the basic architecture of RFID required RF communication front end, logic control and storage module components to temperature measurement and analog-to-digital converter. Figure 1 The structural framework diagram is shown in the figure.

[0004] The dotted box contains an RFID temperature sensor tag chip, which only needs an external coil to work without an external battery. The left half of the dotted box is the RFID basic function part, and the right half of the dotted box is the extended temperature sensor part. The structure in the figure roughly shows the power supply connection between several functional modules inside the chip and the input and output relationship of the signal, and in particular, the signal transmission process of the digital code representing the temperature measurement is marked in the form of a thick arrow. As a passive RFID tag, the chip's external antenna obtains electromagnetic field energy of a specific frequency by resonating with the resonant circuit inside the chip. The energy is then processed by the rectifier circuit, converting the alternating current into a direct current that can be used as a power supply and output at the rectifier output end; the rectifier output power is further passed through a voltage regulator module to generate a more stable DC voltage, which is used as the power supply for other parts of the chip; the clock module extracts the incident electromagnetic field carrier signal frequency from the oscillation signal on the antenna and converts it into a synchronous clock signal required for the operation of the entire chip; the command demodulation module extracts the command and data sent from the reader to the tag from the amplitude modulation waveform on the antenna, converts it into a binary logic code and supplies it to the logic control module for further processing; the uplink modulation module is driven by the logic control module, and sends the digital code that the RFID tag chip wants to feedback to the reader device to the antenna in the form of amplitude modulation or frequency modulation, and completes the communication process with the reader through the air interface; in the above system architecture, the current leakage and limiting module mainly plays a role in protecting the devices inside the chip to prevent excessive energy on the antenna from generating high voltage and breaking down the internal semiconductor devices. When the energy is too high, the current discharge and limiting module provides a discharge channel to discharge the current to the ground, thereby reducing the amplitude of the oscillation signal on the antenna, thereby playing a protective role.

[0005] The leakage path in the leakage and limiting module is very distinctive for passive RFID tag chips. The leakage path circuit module is rarely used in other circuit systems. This is because the passive RFID tag chip is powered by external electromagnetic field energy, and the strength of the electromagnetic field is related to the distance of the tag chip relative to the reader device. Therefore, in different application scenarios, the energy level received by the tag chip is different and has a large difference. From the perspective of the limited withstand voltage characteristics of the internal devices of the chip, a reliable leakage path is essential, and the degree of opening of the leakage path is also a variable, which is adjustable according to the current field energy.

[0006] As a relatively independent part, the temperature measurement module is powered by the power supply of the aforementioned rectifier output, obtains electrical physical quantities that are linearly related to temperature, and then converts from analog to digital to obtain binary codes representing temperature information, and sends them to the card reader device through the modulation module and antenna. Unlike temperature sensing in the field of industrial control, sensors for measuring animal body temperature need to achieve an accuracy of within + / -0.1 degrees Celsius to meet the application of livestock breeding, biopharmaceutical research and development, and family pet health. This demand brings many challenges and technical innovation topics to RFID chip design. For example, patent technology CN109186790B, namely "A method for improving the measurement accuracy of semiconductor temperature sensors", solves the problem of accuracy from the perspective of measurement parameter calibration; patent technology CN109766980B, namely "A circuit and method for improving energy collection of passive radio frequency identification tags of temperature sensors", improves the energy collection of passive tags to obtain better performance in analog-to-digital conversion of temperature signals; patent technology CN102840925B, namely "A temperature measurement and calibration circuit, passive radio frequency identification tag and temperature measurement method", proposes a circuit implementation method for measuring and amplifying temperature physical quantities inside the chip; patent technology CN103837243B, namely "Time domain integrated temperature sensor", proposes a technology to eliminate the correlation between the quantization process from analog to digital conversion and the reader clock cycle parameters, thereby obtaining consistency in temperature measurement in batch sensor products, and so on.

[0007] Through the analysis of the existing technology, it is found that the passive radio frequency identification glass tube needs to receive electromagnetic field energy from the antenna through resonance when working. The strength of the received energy is related to the distance between the glass tube tag and the card reader device, that is, it is related to the strength of the electromagnetic field energy of the environment in which it is located. The alternating energy is converted into direct current to power the chip, and the excess part will flow into the substrate of the tag chip, that is, the ground wire, through the leakage channel in the form of discharge current. This part of the excess current is finally dissipated to the surrounding area of ​​the chip in the form of heat, which has a significant heating effect on the surrounding environment, thereby changing the ambient temperature that the temperature glass tube tag is measuring. For the requirements of precise measurement, the negative effects of this influencing factor cannot be ignored.

[0008] Existing communication systems, such as mobile phones and other mobile communication devices with RF transceiver functions, often have circuits that measure the incident RF signal power and make adaptive adjustments. This part of the circuit is often called an RSSI module in the prior art, that is, a Received Signal Strength Indicator module. In principle, this module in the prior art is without exception through direct measurement of the incident RF signal power, such as the signal generated by the voltage amplitude of the oscillation signal obtained by the antenna, and after a complex system communication channel compensation algorithm, a control voltage for controlling the variable gain amplifier is obtained to adjust the gain value in the receiving link to obtain a satisfactory receiving effect. This part of the circuit does not adopt or disclose the technology of sampling and quantizing the leakage path after the rectifier output of the RFID chip in the technology of this application. Summary of the invention

[0009] The present invention aims to provide a method and circuit for compensating the influence of thermal effects in a passive temperature sensor chip, sampling the physical quantity of the charge discharged by the radio frequency identification tag temperature sensor and quantizing it into a binary code, and then compensating the binary code, thereby improving the temperature measurement accuracy of the temperature sensor.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is a method for compensating for the influence of thermal effects in a passive temperature sensor chip, the method comprising the steps of obtaining electromagnetic field energy of a specific frequency by an external antenna of the chip through resonance with a resonant circuit inside the chip, the electromagnetic field energy being converted into a direct current by a rectifier circuit, a part of the direct current passing through a voltage stabilizing module to generate a more stable direct current voltage and inputting it into each module of the chip as a power supply, and another part of the direct current being discharged to a ground terminal through a discharge path module, the method further comprising the following steps: S1, sampling the physical quantity of the discharged charge flowing through the discharge path module, wherein the physical quantity of the discharged charge is a voltage quantity sample formed by the discharge current formed by the discharged charge flowing through a load branch after mirroring, or a current quantity sample obtained by mirroring the discharge current formed by the discharged charge in a series of proportions; S2, inputting the physical quantity of the sampled discharge charge into a quantization module for quantization processing; S3, inputting the binary code stream generated by the above quantization process into the algorithm module for algorithm processing; S4, according to the temperature difference value corresponding to the binary code stream obtained after the algorithm processing, the temperature difference value is subtracted from the temperature value measured by the temperature sensor, that is, the accurate temperature value after compensating for the influence of the thermal effect is obtained.

[0011] Furthermore, when the physical quantity of the discharged charge in step S1 is a voltage sample, the method of quantization processing in step S2 is to sample the discharge current formed by the discharged charge in proportion and mirror-copy it as a sample current, and then make the sample current flow through a load branch composed of a resistor string to obtain a voltage sample Vx, and the voltage sample Vx is input into the next-level N-bit quantization module for quantization processing, and the quantization module outputs an N-bit binary code stream that compensates for thermal effects.

[0012] Alternatively, when the physical quantity of the discharged charge in step S1 is a current sample, the quantization method in step S2 is to divide the sampled current sample into N M / 2 N Integer multiples of quantized currents are used to compare different quantized currents with N corresponding basic reference currents, thereby obtaining N-bit binary code streams for compensating for thermal effects in parallel.

[0013] The present invention also provides a circuit for compensating the influence of thermal effects in a passive temperature sensor chip, including a resonance and rectification circuit, wherein the output end of the rectification circuit is connected to a power supply voltage regulator module and a discharge current path module, wherein the power supply voltage regulator module is respectively connected to a clock module, a command demodulation module, an uplink modulation module, a logic control module, a storage array module, a temperature measurement module and an analog-to-digital conversion module, wherein the discharge current path module is connected to a discharge charge sampling module, wherein the output end of the discharge charge sampling module is connected to a quantization module, wherein the quantization module inputs the physical quantity of the discharge charge sampled by the discharge charge sampling module into the quantization module for quantization processing, and generates a binary code stream representing the temperature quantity, wherein the binary code stream is input into an algorithm module for algorithm processing, and a temperature difference corresponding to the binary code stream is obtained, and the temperature difference is subtracted from the temperature value measured by the temperature sensor, so as to obtain an accurate temperature value after compensating for the influence of thermal effects; The physical quantity of the discharged charge is either a voltage quantity sample formed by a discharge current formed by the discharged charge flowing through a load branch after being mirrored, or a current quantity sample obtained by mirroring the discharge current formed by the discharged charge in a series of proportions.

[0014] The technical solution for achieving the purpose of the present invention further includes that when the physical quantity of the discharged charge is a voltage quantity sample, the quantization module includes a first p-type MOS transistor PM1, a second p-type MOS transistor PM2, a first n-type MOS transistor NM1 and a resistive load branch, The gate and source of the first p-type MOS transistor PM1 and the second p-type MOS transistor PM2 are connected to each other, and the connected source is connected to the output end of the rectifier circuit. The gate of the first p-type MOS transistor PM1 and its drain are short-circuited to form a current mirror structure, and its drain is connected to the drain end of the first n-type MOS transistor NM1 to form a leakage path. The gate end of the first n-type MOS transistor NM1 is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge excess charge to the ground terminal. The drain of the second p-type MOS transistor PM2 outputs a current sample sampled in proportion and mirror-copied to the input end of the resistive load branch, and the voltage sample is converted by the resistive load.

[0015] Alternatively, when the physical quantity of the discharged charge is a current sample, the quantization module includes a mirror current source branch array, a second n-type MOS transistor NM2, a third n-type MOS transistor NM3, and an N-way current comparator. The mirror current source branch array is connected to the output end of the rectifier circuit to discharge the current I dump The mirror image is N branch currents I0, and I0=(M / 2 N )*I dump ,M<1,N n-type MOS tubes are connected in parallel between the output end of the rectifier circuit and the ground terminal to form an N-way current comparator. The drain end of the second n-type MOS transistor NM2 is connected to the output end of the rectifier circuit, and the gate end is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge the excess charge to the ground terminal. The drain terminal of the third n-type MOS transistor NM3 is connected to the reference current output terminal, the source terminal is grounded, and the gate and drain are connected to the bias voltage. unit The image is copied to the channel formed between the source and drain of the N n-type MOS tubes, and compared with the sampling current input at the drain end of the N n-type MOS tubes, and the sampling current is respectively taken as 2 of the branch current I0 0 times to 2 N-1 times, each n-type MOS tube respectively samples the current at its drain end and the reference current I at its gate end unit A comparison is performed, and a binary code is outputted according to the comparison result. The multiple binary codes outputted by the N current comparators respectively constitute an N-bit binary code stream representing the thermal effect generated by the leakage current of the temperature sensor itself.

[0016] Alternatively, when the physical quantity of the discharged charge is a current sample, the quantization module includes a mirror current source branch array, a second n-type MOS transistor NM2, a third n-type MOS transistor NM3, a fourth n-type MOS transistor NM4 and an N-way switch device group, The mirror current source branch array is connected to the output end of the rectifier circuit to discharge the current I dump The mirror image is N branch currents I0, and I0=(M / 2 N )*I dump , M<1, N switch device groups controlled by the counter are connected in parallel between the output end of the rectifier circuit and the drain end of the fourth n-type MOS tube NM4 to form a current comparator, The drain end of the second n-type MOS transistor NM2 is connected to the output end of the rectifier circuit, and the gate end is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge the excess charge to the ground terminal. The drain terminal of the third n-type MOS transistor NM3 is connected to the reference current output terminal, the source terminal is grounded, and the gate and drain are connected so that the reference current I unit A bias voltage is generated on the gate of the third n-type MOS transistor NM3, and the reference current I unit and compared with the sampling current inputted at the drain end of the fourth n-type MOS tube NM4, the sampling currents are respectively taken as 2 of the branch current I0. 0 times to 2 N-1 times, the counter controls the switch devices in the switch device group to turn on in sequence, and the sampling current and the reference current I unit The counter then switches different switch devices to conduct and outputs a binary code again. This process is repeated many times. The binary codes output multiple times form an N-bit binary code stream representing the thermal effect caused by the leakage of the temperature sensor itself.

[0017] The present invention proposes a complete compensation technology for the influence of temperature difference caused by thermal effect faced by passive radio frequency identification temperature sensor tag chip products. The voltage sample generated by the discharge charge and the current sample formed by the discharge charge are used as processing signals respectively. The circuit implementation technology of analog-to-digital conversion module quantization and current comparator quantization is implemented, and the implementation scheme of hardware and software collaboration is used to fundamentally solve the influence of temperature difference caused by thermal effect, so that the measurement accuracy of passive radio frequency identification temperature sensor tags is reliably guaranteed, the batch yield is greatly improved, and it has significant economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a structural block diagram of an existing RFID-based temperature sensor chip; Figure 2 It is a structural block diagram of the circuit for compensating the influence of thermal effect in the temperature sensor chip of the present invention; Figure 3This is a circuit structure diagram of Embodiment 1 of the present invention; Figure 4 This is a circuit structure diagram of Embodiment 2 of the present invention; Figure 5 This is a circuit structure diagram of Embodiment 3 of the present invention; Figure 6 This is a circuit structure diagram of Embodiment 4 of the present invention; Figure 7 This is a circuit structure diagram of embodiment 5 of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] like Figure 2 As shown, the method for compensating the influence of thermal effects in a passive temperature sensor chip of the present invention includes the steps of obtaining electromagnetic field energy of a specific frequency by an external antenna of the chip through resonance with a resonant circuit inside the chip, the electromagnetic field energy is converted into a direct current by a rectifier circuit, a part of the direct current passes through a voltage stabilizing module to generate a more stable direct current voltage and is input to each module of the chip as a power supply, and another part of the direct current is discharged to a ground terminal through a discharge path module, and the method also includes the following steps: S1, sampling the physical quantity of the discharged charge flowing through the discharge path module, wherein the physical quantity of the discharged charge is a voltage quantity sample formed by the discharge current formed by the discharged charge flowing through a load branch after mirroring, or a current quantity sample obtained by mirroring the discharge current formed by the discharged charge in a series of proportions; S2, inputting the physical quantity of the sampled discharge charge into a quantization module for quantization processing; S3, inputting the binary code stream generated by the above quantization process into the algorithm module for algorithm processing; S4, according to the temperature difference value corresponding to the binary code stream obtained after the algorithm processing, the temperature difference value is subtracted from the temperature value measured by the temperature sensor, that is, the accurate temperature value after compensating for the influence of the thermal effect is obtained.

[0021] This technology consists of three parts: the sampling part of the discharge charge, the quantization part and the temperature sensor algorithm processing. The sampling and quantization of the discharge charge are realized by the circuit inside the chip ( Figure 2The binary code generated by quantization can be digitally compensated inside the temperature sensor chip, that is, the temperature code corresponding to the binary code part representing the leakage current size is directly subtracted from the obtained temperature binary code using a fixed algorithm inside the chip; digital compensation can also be performed outside the temperature sensor chip ( Figure 2 The part outside the dotted box in the block diagram shown in the figure), that is, the binary code generated by quantization is sent to the temperature sensor reader together with the RFID code stream and the temperature data code stream. After the reader receives the signal and parses this part of the code, the processor of the reader makes corresponding adjustments in software and algorithm, that is, subtracts the temperature difference corresponding to the code from the original temperature data.

[0022] Whether it is processed inside the RFID temperature sensor tag, or sent back to the read-write device with the temperature measurement data, and further processed by the processor software on the read-write device, an algorithm module is required. The processing algorithm in the algorithm module establishes a functional relationship between the binary code representing the leakage flow size and the actual temperature difference, or establishes a corresponding relationship in the form of a lookup table. The functional relationship and the corresponding relationship presented by the lookup table depend on the actual measurement and calibration results, as well as the specific heat capacity parameter value of the material of the environment around the specific glass tube, so the specific expression of the function or the corresponding relationship of the lookup table is not within the scope of the specific specification of the present application technology, so it will not be further elaborated and discussed here.

[0023] Depend on Figure 2 As shown, the method for compensating for the influence of thermal effects described in the present invention starts from the discharge path. The main purpose of the discharge path itself is to discharge the excess field energy to the ground in the form of current, so that the voltage across the RFID tag antenna under strong field conditions will not be too high to break down the transistor device with a limited withstand voltage limit that is directly connected to the tag antenna inside the chip. The discharge path is controlled by a discharge control switch signal. When the field energy is too high and reaches the discharge threshold, the switch signal controls the discharge path to be turned on so that the current can be discharged to the ground terminal; when the field energy is not enough to reach the discharge threshold, the switch signal controls the discharge path to be disconnected to save the acquired energy.

[0024] The discharge path is connected to the discharge charge sampling module of the next level by a sampling control signal, which is used to ensure that there is a good linear relationship between the sampling result and the current of the discharge path, that is, a constant proportional relationship. Because the current passing through the discharge path may be very large, from the perspective of power consumption and linearity, the subsequent signal processing circuit is obviously not suitable for processing excessively large signals, so the sampling control signal here mainly plays the role of linear sampling, such as obtaining a sample equivalent to one tenth or even one hundredth of the discharge charge for subsequent processing. In short, the physical quantity of the sampled discharge charge is a voltage quantity sample formed by the discharge current formed by the discharge charge flowing through a load branch after mirroring, or a current quantity sample obtained by copying the discharge current formed by the discharge charge according to a series of proportional mirror images.

[0025] The sampled voltage quantity sample or current quantity sample is subjected to a quantization process to obtain an N-bit digital output, that is, when the physical quantity of the discharged charge in step S1 is a voltage quantity sample, the quantization processing method in step S2 is to proportionally sample the discharge current formed by the discharged charge and mirror-copy it as a sample current, and then make the sample current flow through a load branch composed of a resistor string to obtain a voltage quantity sample Vx, and the voltage quantity sample Vx is input into the next-level N-bit quantization module for quantization processing, and the quantization module outputs an N-bit binary code stream for compensating thermal effects; When the physical quantity of the discharged charge in step S1 is a current sample, the quantization method in step S2 is to divide the sampled current sample into N M / 2 N Integer multiples of quantized currents are used to compare different quantized currents with N corresponding basic reference currents, thereby obtaining N-bit binary code streams for compensating for thermal effects in parallel.

[0026] The above quantization process can be completed by a typical N-bit analog-to-digital converter ADC, or by other forms of more simplified quantization circuit modules. Obviously, for the overall performance requirements of the RFID tag chip, no matter which implementation method is used, low power consumption is an inevitable performance requirement. The design of low-power analog-to-digital converters is a separate and huge research field, which will not be further described here. From the spirit of the present application technology, any form of ADC quantization is optional.

[0027] Therefore, the N-bit digital code obtained by the quantization module is an objective measure of the discharged charge, and further objectively reflects the additional heat caused by the discharged charge. Relying on the existing communication method of RFID, the reader and writer can obtain the N-bit digital code reflecting the thermal effect of the temperature glass tube tag. Different N-bit numbers represent different precisions for sampling and quantifying the thermal effect. Obviously, the more N-bit numbers, the higher the precision. However, the higher the complexity of the circuit, the higher the power consumption. Therefore, the determination of the N value depends on a comprehensive system-level consideration. Because the material and internal environment of the glass tube package have been determined after packaging, after obtaining the N-bit digital code, a temperature difference corresponding to the code can be determined based on the empirical value, so as to subtract the difference from the final calculated sensor output temperature value. Such empirical values ​​can be stored in the code inside the chip or the reader and writer using a simple lookup table, or stored in the storage medium inside the chip or the reader and writer for updating at any time. Because the N-bit digital code obtained by the present application technology has nothing to do with the linearity of analog-to-digital conversion, but only with the thermal effect at the time of measurement; it is obviously reasonable to subtract the N-bit digital code from the temperature measurement value as a temperature difference. Therefore, after this compensation operation, the passive temperature sensor glass tube tag has a more accurate temperature measurement effect.

[0028] The present invention also provides a circuit for implementing the method for compensating the thermal effect in the passive temperature sensor chip, such as Figure 2 As shown, it includes a resonance and rectification circuit, the output end of the rectification circuit is connected to a power supply voltage regulator module and a discharge current path module, the power supply voltage regulator module is respectively connected to a clock module, a command demodulation module, an uplink modulation module and a logic control module, a storage array module, a temperature measurement module and an analog-to-digital conversion module, the discharge current path module is connected to a discharge charge sampling module, the output end of the discharge charge sampling module is connected to a quantization module, the quantization module inputs the physical quantity of the discharge charge sampled by the discharge charge sampling module into the quantization module for quantization processing, generates a binary code stream representing the temperature quantity, the binary code stream is input into the algorithm module for algorithm processing, obtains the temperature difference corresponding to the binary code stream, and subtracts the temperature difference from the temperature value measured by the temperature sensor, that is, obtains the accurate temperature value after compensating for the influence of thermal effect; The physical quantity of the discharged charge is either a voltage quantity sample formed by a discharge current formed by the discharged charge flowing through a load branch after being mirrored, or a current quantity sample obtained by mirroring the discharge current formed by the discharged charge in a series of proportions.

[0029] Figure 2In the dotted box, the chip circuit part related to the compensation of thermal effect is mainly composed of the following parts: discharge path, discharge charge sampling circuit, and circuit for quantifying the discharge charge sample; the rest of the circuit parts of the RFID temperature measurement tag in the dotted box, namely the RFID communication part, the temperature physical quantity measurement part PTAT, the analog-digital conversion module ADC and the storage Memory circuit are all existing parts of the RFID temperature measurement tag chip itself, and are not within the scope of the present invention. It should be pointed out that the thermal effect compensation code generated by this technology can be regarded as a part of the temperature sensor measurement parameters, that is, a new parameter expanded on the basis of the A, B, Alpha and X parameters described in the patent technology CN109186790B "A method for improving the measurement accuracy of semiconductor temperature sensors", which is completely consistent with the interaction mode and other parameters of the rest of the circuit parts of the RFID temperature measurement tag, that is, whether to write to a certain memory address or send it as a temperature data code stream together with other parameters can be determined by the configuration, etc., and no further detailed description will be given here. Naturally, when the thermal effect compensation code needs to be processed inside the RFID temperature sensor tag, the algorithm module needs to be set in the temperature sensor chip. If the compensation code is sent back to the read-write device along with the temperature measurement data and further processed by the processor software on the read-write device, the algorithm module needs to be set in the temperature sensor read-write device.

[0030] When the physical quantity of the discharged charge is a voltage quantity sample, the quantization module includes a first p-type MOS transistor PM1, a second p-type MOS transistor PM2, a first n-type MOS transistor NM1 and a resistive load branch. The gate and source of the first p-type MOS transistor PM1 and the second p-type MOS transistor PM2 are connected to each other, and the connected source is connected to the output end of the rectifier circuit. The gate of the first p-type MOS transistor PM1 and its drain are short-circuited to form a current mirror structure, and its drain is connected to the drain end of the first n-type MOS transistor NM1 to form a leakage path. The gate end of the first n-type MOS transistor NM1 is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge excess charge to the ground terminal. The drain of the second p-type MOS transistor PM2 outputs a current sample sampled in proportion and mirror-copied to the input end of the resistive load branch, and the voltage sample is converted by the resistive load.

[0031] Figure 3: is a circuit structure diagram of an embodiment of the present invention. In this embodiment, the resistive load branch is a plurality of resistors connected in series, and one end of the last resistor connected in series is grounded. Two input ends of an N-bit analog-to-digital converter are connected to two nodes among the plurality of resistors, and the voltage Vx at the two node ends is sampled. The sampled voltage samples are input into an N-bit analog-to-digital conversion module for quantization processing, and an N-bit binary code stream representing the thermal effect caused by the leakage of the temperature sensor itself is output.

[0032] The drain of the second p-type MOS transistor PM2 outputs the current sample sampled in proportion and mirror-copied to the input end of the resistive load branch, and the resistive load converts the current sample into a voltage sample. Specifically, for example, the discharge current I dump After the second p-type MOS transistor PM2 is sampled proportionally and mirrored, I0 = M*I is obtained on the mirror branch. dump , M<1 discharge current sample. The discharge current sample I0 flows through the branch composed of the resistor string, and the voltage Vx is sampled at two nodes in the resistor string. The sampled voltage sample Vx is input to the next level N-bit ADC for quantization processing. The ADC outputs the data code (Bit N-1 , Bit N-2 , …, Bit1, Bit0) to the algorithm module inside the chip for processing, or sent by the RFID tag antenna. The temperature sensor read-write device obtains the data and processes it in the form of software code to give a specific temperature value after compensation.

[0033] The advantage of this embodiment is that it has a very clear signal processing concept, a relatively clear architectural division, and is easy to implement. On the other hand, if a low-power successive approximation register ADC is used, the N-bit digital code conversion requires at least N clock cycles, so the implementation technology will have a certain delay, and too long a delay will affect the application experience of on-site temperature measurement, or lead to an increase in the communication burden.

[0034] For example, if the ADC is set to 8 bits and the discharge current I dump When the discharge current I dumpWhen it is less than 20nA, the discharge path is in the cut-off state, the discharge current sample I0 on the mirror branch is 0, and the voltage Vx between the two nodes in the resistor string is 0. At this time, the binary code stream output by the ADC is 00000000. When the rectifier current at the antenna end increases, the discharge current I dump When it is greater than 20nA, the discharge current sample I0 on the mirror branch is greater than 0, the voltage Vx is greater than 0, and the binary code stream output by the ADC ranges from 00000001 to 11111111. The binary code stream is input to the algorithm module in the temperature sensor chip, or the algorithm module in the read-write device. The algorithm module converts the binary code stream into the corresponding temperature difference through a functional relationship established between the binary code stream and the actual temperature difference, or by looking up the corresponding relationship in the form of a table, and subtracts the temperature difference from the temperature value measured by the temperature sensor, and finally obtains the accurate temperature value after thermal effect compensation.

[0035] Figure 4 : is a circuit structure diagram of the second embodiment of the present invention, which is a further limitation of the first embodiment. In this embodiment, the resistive load branch is a plurality of resistors connected in series, and both ends of the plurality of resistors connected in series are respectively connected to a switch device group controlled by a counter, and a plurality of switch devices in the switch device group are in a parallel structure, one end of each switch device is connected between two adjacent resistors, and the other ends of the switch devices are connected to each other and connected through a main switch S comp Connected to the first input of the comparator, the second input of the comparator is connected to the reference voltage output, the counter controls the switch devices in the switch device group to turn on in sequence, samples the voltage of the resistor corresponding to the switch device, and outputs the sampled voltage sample to the first input of the comparator, compares it with the reference voltage signal input at the second input of the comparator, outputs a binary code, and the counter switches two different switch devices to turn on, outputs a binary code again, and repeats this process, the binary codes output multiple times form an N-bit binary code stream representing the thermal effect generated by the leakage of the temperature sensor itself. Similarly, the binary code stream is input into the algorithm module inside the chip, or the algorithm module of the read-write device for algorithm processing, to obtain the temperature difference corresponding to the binary code stream, and the temperature difference is subtracted from the temperature value measured by the temperature sensor, that is, the accurate temperature value after compensating for the thermal effect is obtained.

[0036] This embodiment is a single-bit voltage comparator quantization technology. The difference from the above-mentioned embodiment 1 is that the voltage Vx between two resistors is sampled in the embodiment 1, and the counter in this embodiment cyclically controls the sampling switch devices S0, ..., S N-2 ,S N-1The switches are turned on in sequence, so the voltage of the resistor corresponding to the switch device is sampled, so that the signal input to the input end of the single-bit voltage comparator is a voltage sample of different proportions, which is compared with the reference voltage input to the second input end of the comparator. Therefore, the single-bit output B i The binary code is exactly the thermometer code representing the magnitude of the discharge voltage. Repeatedly, the counter cyclically controls the switch device to conduct and the binary code output multiple times constitutes an N-bit binary code stream representing the thermal effect generated by the temperature sensor's own discharge current.

[0037] When the physical quantity of the discharged charge is a current sample, the quantization module uses Figure 5 and Figure 6 The circuit structure diagram of the third embodiment of the present invention is shown in FIG. 1 . In this embodiment, the quantization module includes a mirror current source branch array, a second n-type MOS transistor NM2, a third n-type MOS transistor NM3, and an N-way current comparator. The mirror current source branch array is connected to the output end of the rectifier circuit to discharge the current I dump The mirror image is N branch currents I0, and I0=(M / 2 N )*I dump ,M<1,N n-type MOS tubes are connected in parallel between the output end of the rectifier circuit and the ground terminal to form an N-way current comparator. The drain end of the second n-type MOS transistor NM2 is connected to the output end of the rectifier circuit, and the gate end is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge the excess charge to the ground terminal. The drain terminal of the third n-type MOS transistor NM3 is connected to the reference current output terminal, the source terminal is grounded, and the gate and drain are connected to the bias voltage. unit The image is copied to the channel formed between the source and drain of the N n-type MOS tubes, and compared with the sampling current input at the drain end of the N n-type MOS tubes, and the sampling current is respectively taken as 2 of the branch current I0 0 times to 2 N-1 times, each n-type MOS tube respectively samples the current at its drain end and the reference current I at its gate end unit A comparison is performed, and a binary code is outputted according to the comparison result. The multiple binary codes outputted by the N current comparators respectively constitute an N-bit binary code stream representing the thermal effect generated by the leakage current of the temperature sensor itself.

[0038] The mirror current source branch array uses multiple MOS tubes with the same channel length and proportional channel width to be connected into a mirror structure, so as to discharge the current I dumpAccording to a certain ratio, N different integer multiples of branch current I0 are mirrored, I0=(M / 2 N )*I dump , M<1, that is, from the perspective of low power consumption, only a part of the discharge current samples are taken for quantification, and the sampling current of each branch is taken as 2 of the branch current I0 0 times to 2 N-1 times to correspond to different current quantization intervals; on the other hand, the reference current I unit It is the reference current value set by the quantization system, which is given by the reference current part of the RFID temperature measurement tag chip. The reference current I unit Under the action of the bias voltage, the current is mirrored to the channel formed between the source and drain of the N n-type MOS tubes. Thus, the N branches of the two sets of mirror current sources are connected respectively, and each branch constitutes a current comparator. The sampling current and reference current I of each branch unit The current is synchronously input to the two input terminals of the current comparator composed of the n-type MOS tube, and a binary code is outputted according to the comparison result. The multiple binary codes outputted by the N current comparators constitute an N-bit binary code stream representing the thermal effect generated by the leakage current of the temperature sensor itself.

[0039] Specifically, for any current comparator of the i-th (i = 0, 1, …, N-1) branch, if the sampling current I0*2 i > I unit , then Bit i The output logic level is high. Otherwise, if I0*2 i < I unit , then Bit i The output logic level is low. Therefore, when the current discharge control switch is turned on, the discharge current I dump When the excess charge is discharged to the ground through the discharge path, a portion of the sample M*I dump , M<1 is sampled and quantized into M*I dump / 2 N The digital code with units of 1 and 2 is a digital code. Obviously, the digital code for the quantized output here must be the encoding method of the thermometer code in the logic design. The characteristics of the encoding method of the thermometer code can be simply summarized as "in the thermometer code arrangement from low to high, the low logic bit always precedes the high logic bit", and its behavior is like a mercury thermometer, hence the name.

[0040] The difference from the above-mentioned first and second embodiments is that a single analog-to-digital converter ADC is replaced by a multi-bit parallel processing current comparator in this embodiment.

[0041] Figure 7This is a circuit structure diagram of the fourth embodiment of the present invention. This embodiment is the same as the third embodiment above, and is aimed at the physical quantity of the discharged charge being a current quantity sample. In this embodiment, The quantization module includes a mirror current source branch array, a second n-type MOS transistor NM2, a third n-type MOS transistor NM3, a fourth n-type MOS transistor NM4 and an N-way switch device group. The mirror current source branch array is connected to the output end of the rectifier circuit to discharge the current I dump The mirror image is N branch currents I0, and I0=(M / 2 N )*I dump , M<1, N switch device groups controlled by the counter are connected in parallel between the output end of the rectifier circuit and the drain end of the fourth n-type MOS tube NM4 to form a current comparator, The drain end of the second n-type MOS transistor NM2 is connected to the output end of the rectifier circuit, and the gate end is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge the excess charge to the ground terminal. The drain terminal of the third n-type MOS transistor NM3 is connected to the reference current output terminal, the source terminal is grounded, and the gate and drain are connected so that the reference current I unit A bias voltage is generated on the gate of the third n-type MOS transistor NM3, and the reference current I unit and compared with the sampling current inputted at the drain end of the fourth n-type MOS tube NM4, the sampling currents are respectively taken as 2 of the branch current I0. 0 times to 2 N-1 times, the counter controls the switch devices in the switch device group to turn on in sequence, and the sampling current and the reference current I unit The counter then switches different switch devices to conduct and outputs a binary code again. This process is repeated many times. The binary codes output multiple times form an N-bit binary code stream representing the thermal effect caused by the leakage of the temperature sensor itself.

[0042] This embodiment is a single-bit current comparator quantization technology. The difference from the above-mentioned embodiment 3 is that the embodiment 3 sets a current comparator in each branch to compare the sampled current and the reference current, and outputs them in sequence to generate a multi-bit binary code stream. This embodiment is a counter cyclically controlling the sampling switch devices S0, ..., S N-2 ,S N-1 The single-bit current comparator input signals are current samples of different proportions, which are compared with the reference current input to the comparator gate. iThe binary code is exactly the thermometer code representing the magnitude of the discharge current. Repeatedly, the counter cyclically controls the switch device to conduct and the binary code output multiple times constitutes an N-bit binary code stream representing the thermal effect generated by the temperature sensor's own discharge current.

[0043] The technology of the present invention discloses that in the process of quantizing the temperature physical quantity from analog to digital, a glass tube type passive radio frequency identification temperature sensor temperature measuring chip samples the physical quantity of the discharge charge at the output end of the rectifier circuit of the temperature sensor temperature measuring chip, and quantifies the sample to obtain a binary code representing the size of the discharge current. After further processing, the temperature measured by the temperature sensor temperature measuring chip is compensated with the above binary code representing the size of the discharge current, thereby obtaining a more realistic temperature measurement result, fundamentally solving the influence of the temperature difference caused by the thermal effect, making the measurement accuracy of the passive radio frequency identification temperature sensor tag reliably guaranteed, greatly improving the batch yield, and having significant economic value.

Claims

1. A method for compensating for the influence of thermal effects in a passive temperature sensor chip, the method comprising the steps of obtaining electromagnetic field energy of a specific frequency by an external antenna of the chip through resonance with a resonant circuit inside the chip, the electromagnetic field energy being converted into a direct current by a rectifier circuit, a part of the direct current passing through a voltage stabilizing module to generate a more stable direct current voltage and inputting it into each module of the chip as a power supply, and another part of the direct current being discharged to a ground terminal through a discharge path module, characterized in that: The method further comprises the following steps: S1, sampling the physical quantity of the discharged charge flowing through the discharge path module, wherein the physical quantity of the discharged charge is a voltage quantity sample formed by the discharge current formed by the discharged charge flowing through a load branch after mirroring, or a current quantity sample obtained by mirroring the discharge current formed by the discharged charge in a series of proportions; S2, inputting the physical quantity of the sampled discharge charge into a quantization module for quantization processing; S3, inputting the binary code stream generated by the above quantization process into the algorithm module for algorithm processing; S4, according to the temperature difference value corresponding to the binary code stream obtained after the algorithm processing, the temperature difference value is subtracted from the temperature value measured by the temperature sensor, that is, the accurate temperature value after compensating for the influence of the thermal effect is obtained.

2. The method according to claim 1, characterized in that When the physical quantity of the discharged charge in step S1 is a voltage sample, the method of quantization processing in step S2 is to sample the discharge current formed by the discharged charge in proportion and mirror-copy it as a sample current, and then make the sample current flow through a load branch composed of a resistor string to obtain a voltage sample Vx, and the voltage sample Vx is input into the next-level N-bit quantization module for quantization processing, and the quantization module outputs an N-bit binary code stream for compensating thermal effects.

3. The method according to claim 1, characterized in that When the physical quantity of the discharged charge in step S1 is a current sample, the quantization method in step S2 is to divide the sampled current sample into N M / 2 N Integer multiples of quantized currents are used to compare different quantized currents with N corresponding basic reference currents, thereby obtaining N-bit binary code streams for compensating for thermal effects in parallel.

4. A circuit for implementing the method of claim 1, comprising a resonance and rectification circuit, wherein the output end of the rectification circuit is connected to a power supply voltage regulator module and a discharge path module, wherein the power supply voltage regulator module is respectively connected to a clock module, a command demodulation module, an uplink modulation module and a logic control module, a storage array module, a temperature measurement module and an analog-to-digital conversion module, wherein: The discharge path module is connected to the discharge charge sampling module, and the output end of the discharge charge sampling module is connected to the quantization module. The quantization module inputs the physical quantity of the discharge charge sampled by the discharge charge sampling module into the quantization module for quantization processing, generates a binary code stream representing the temperature quantity, and the binary code stream is input into the algorithm module for algorithm processing to obtain the temperature difference corresponding to the binary code stream, and the temperature difference is subtracted from the temperature value measured by the temperature sensor, that is, the accurate temperature value after compensating for the influence of thermal effect is obtained; The physical quantity of the discharged charge is either a voltage quantity sample formed by a discharge current formed by the discharged charge flowing through a load branch after being mirrored, or a current quantity sample obtained by mirroring the discharge current formed by the discharged charge in a series of proportions.

5. The circuit according to claim 4, characterized in that The algorithm module is arranged in the temperature sensor chip, or in the temperature sensor reading and writing device.

6. The circuit according to claim 4, characterized in that When the physical quantity of the discharged charge is a voltage quantity sample, the quantization module includes a first p-type MOS transistor PM1, a second p-type MOS transistor PM2, a first n-type MOS transistor NM1 and a resistive load branch. The gate and source of the first p-type MOS transistor PM1 and the second p-type MOS transistor PM2 are connected to each other, and the connected source is connected to the output end of the rectifier circuit. The gate of the first p-type MOS transistor PM1 and its drain are short-circuited to form a current mirror structure, and its drain is connected to the drain end of the first n-type MOS transistor NM1 to form a leakage path. The gate end of the first n-type MOS transistor NM1 is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge excess charge to the ground terminal. The drain of the second p-type MOS transistor PM2 outputs a current sample sampled in proportion and mirror-copied to the input end of the resistive load branch, and the voltage sample is converted by the resistive load.

7. The circuit according to claim 6, characterized in that The resistive load branch is a plurality of resistors connected in series, and one end of the last resistor connected in series is grounded. The two input ends of the N-bit analog-to-digital converter are connected to two nodes among the plurality of resistors, and the voltage Vx at the two node ends is sampled. The sampled voltage samples are input into the N-bit analog-to-digital conversion module for quantization processing, and an N-bit binary code stream representing the thermal effect caused by the leakage of the temperature sensor itself is output.

8. The circuit according to claim 6, characterized in that The resistive load branch is a plurality of resistors connected in series, and both ends of the plurality of resistors connected in series are respectively connected to a switch device group controlled by a counter, and a plurality of switch devices in the switch device group are in a parallel structure, one end of each switch device is connected between two adjacent resistors, and the other ends of the switch devices are connected to each other through a main switch S comp The counter is connected to the first input terminal of the comparator, and the second input terminal of the comparator is connected to the reference voltage output terminal. The counter controls the switching devices in the switching device group to be turned on in sequence, samples the voltage of the resistor corresponding to the switching device, and outputs the sampled voltage sample to the first input terminal of the comparator, compares it with the reference voltage signal input at the second input terminal of the comparator, outputs a binary code, and then switches two different switching devices to be turned on, and outputs a binary code again. This is repeated, and the binary codes output multiple times constitute an N-bit binary code stream representing the thermal effect caused by the leakage of the temperature sensor itself.

9. The circuit according to claim 4, characterized in that When the physical quantity of the discharged charge is a current quantity sample, the quantization module includes a mirror current source branch array, a second n-type MOS transistor NM2, a third n-type MOS transistor NM3, and an N-way current comparator. The mirror current source branch array is connected to the output end of the rectifier circuit to discharge the current I dump The mirror image is N branch currents I0, and I0=(M / 2 N )*I dump ,M<1,N n-type MOS tubes are connected in parallel between the output end of the rectifier circuit and the ground terminal to form an N-way current comparator. The drain end of the second n-type MOS transistor NM2 is connected to the output end of the rectifier circuit, and the gate end is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge the excess charge to the ground terminal. The drain terminal of the third n-type MOS transistor NM3 is connected to the reference current output terminal, the source terminal is grounded, and the gate and drain are connected to the bias voltage. unit The image is copied to the channel formed between the source and drain of the N n-type MOS tubes, and compared with the sampling current input at the drain end of the N n-type MOS tubes, and the sampling current is respectively taken as 2 of the branch current I0 0 times to 2 N-1 times, each n-type MOS tube respectively samples the current at its drain end and the reference current I at its gate end unit A comparison is performed, and a binary code is outputted respectively according to the comparison result. The multiple binary codes outputted by the N current comparators respectively constitute an N-bit binary code stream representing the thermal effect generated by the leakage current of the temperature sensor itself.

10. The circuit according to claim 4, characterized in that When the physical quantity of the discharged charge is a current quantity sample, the quantization module includes a mirror current source branch array, a second n-type MOS transistor NM2, a third n-type MOS transistor NM3, a fourth n-type MOS transistor NM4 and an N-way switch device group, The mirror current source branch array is connected to the output end of the rectifier circuit to discharge the current I dump The mirror image is N branch currents I0, and I0=(M / 2 N )*I dump , M<1, N switch device groups controlled by the counter are connected in parallel between the output end of the rectifier circuit and the drain end of the fourth n-type MOS tube NM4 to form a current comparator, The drain end of the second n-type MOS transistor NM2 is connected to the output end of the rectifier circuit, and the gate end is connected to the output end of the leakage control switch signal unit. Under the control of the leakage control switch signal, the leakage path is turned on to discharge the excess charge to the ground terminal. The drain terminal of the third n-type MOS transistor NM3 is connected to the reference current output terminal, the source terminal is grounded, and the gate and drain are connected so that the reference current I unit A bias voltage is generated on the gate of the third n-type MOS transistor NM3, and the reference current I unit and compared with the sampling current inputted at the drain end of the fourth n-type MOS tube NM4, the sampling currents are respectively taken as 2 of the branch current I0. 0 times to 2 N-1 times, the counter controls the switch devices in the switch device group to turn on in sequence, and the sampling current and the reference current I unit The counter then switches different switch devices to conduct and outputs a binary code again. This process is repeated many times. The binary codes output multiple times form an N-bit binary code stream representing the thermal effect caused by the leakage of the temperature sensor itself.

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