A wireless CMOS temperature sensor based on wireless energy harvesting technology

Abstract

The application belongs to the technical field of sensors, and discloses a wireless CMOS temperature sensor based on wireless energy collection technology, which comprises a CMOS wireless energy collection circuit, a CMOS temperature sensor front-end circuit and a CMOS wireless signal transmitting circuit, the CMOS wireless energy collection circuit is used for collecting wireless energy and converting the wireless energy into a direct current voltage to supply power to the CMOS temperature sensor front-end circuit, the CMOS temperature sensor front-end circuit generates a signal with a frequency proportional to temperature and applies the signal on the CMOS wireless signal transmitting circuit, and temperature information is wirelessly transmitted in the form of backscattering. The circuit structure of the application is simple, the use of complex and high-power large-area modules such as an analog-to-digital conversion module ADC is avoided, the power consumption and area of the temperature sensor are reduced, and higher temperature resolution is realized.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, and in particular relates to a wireless CMOS temperature sensor based on wireless energy harvesting technology. Background Technology

[0002] Complementary metal-oxide-semiconductor (CMOS) temperature sensors are widely used in the field of biological temperature measurement, such as real-time body temperature monitoring of farmed animals, and human body temperature detection is also one of the early diagnostic criteria for diseases.

[0003] In CMOS temperature sensors, those based on bipolar junction transistors (BJTs) are widely used due to their stable temperature characteristics and high accuracy. Common BJT-based CMOS temperature sensors utilize the temperature characteristics of the BJT in the analog front-end circuit to convert the temperature into a current or voltage signal that is positively or negatively correlated with the temperature. The data is then read out through an analog-to-digital converter (ADC). However, this typically requires a large-area or high-power ADC module. Meanwhile, conventional CMOS temperature sensors directly utilize the difference between the base-emitter voltages of two bipolar junction transistors operating at different current densities. The current signal generated by applying a resistor changes very little with temperature, resulting in very low temperature resolution.

[0004] In addition, typical CMOS temperature sensors are powered by batteries, which limits the lifespan of the temperature sensor per use and increases the cost of using the temperature sensor. Summary of the Invention

[0005] The purpose of this invention is to provide a wireless CMOS temperature sensor based on wireless energy harvesting technology to solve the above-mentioned technical problems.

[0006] To solve the above-mentioned technical problems, the specific technical solution of the present invention for a wireless CMOS temperature sensor based on wireless energy harvesting technology is as follows: A wireless CMOS temperature sensor based on wireless energy harvesting technology includes a CMOS wireless energy harvesting circuit, a CMOS temperature sensing front-end circuit, and a CMOS wireless signal transmitting circuit. The CMOS wireless energy harvesting circuit is used to harvest wireless energy and convert it into DC voltage to power the CMOS temperature sensing front-end circuit. The CMOS temperature sensing front-end circuit generates a signal whose frequency is proportional to the temperature and applies it to the CMOS wireless signal transmitting circuit to wirelessly transmit the temperature information in a backscattering manner.

[0007] Furthermore, the CMOS wireless energy harvesting circuit includes an antenna, a CMOS differential input rectifier, and a low-dropout linear regulator; the CMOS temperature sensing front-end circuit includes a first bandgap reference, a second bandgap reference, a current subtraction circuit, an oscillator, and a low-dropout linear regulator; the CMOS wireless signal transmitting circuit includes an antenna and a backscatter switch; the two ends of the backscatter switch are respectively connected to the differential input terminals of the CMOS differential input rectifier, and the signal input terminal of the backscatter switch is connected to the output terminal of the oscillator; a pair of differential input terminals RFP and RFN of the CMOS differential input rectifier are connected to the two ends of the antenna; the output terminal VDC of the CMOS differential input rectifier is connected to the power supply terminals of the low-dropout linear regulator, the first bandgap reference, and the second bandgap reference; the low-dropout linear regulator is connected to the oscillator; the first bandgap reference and the second bandgap reference are connected to the current subtraction circuit; and the current subtraction circuit is connected to the oscillator.

[0008] Furthermore, the second bandgap reference includes three PMOS current mirrors, an operational amplifier, a resistor R, and two sets of transistors operating at different current densities. The source of the first PMOS current mirror is connected to the power supply VDC of the bandgap reference, and its drain is connected to the emitter of the transistor operating at unit current density. The source of the second PMOS current mirror is connected to the power supply VDC of the bandgap reference, and its drain is connected to a resistor R. The other end of the resistor R is connected to the emitters of n transistors connected in parallel. Simultaneously, the gates of the first and second PMOS current mirrors are connected together to the output of the operational amplifier. The drains of the first and second PMOS current mirrors are connected to the non-inverting and inverting inputs of the operational amplifier, respectively. The bases and collectors of all transistors are grounded. The third PMOS current mirror replicates the current across the resistor R and outputs it. .

[0009] Furthermore, the first bandgap reference consists of four common-source cascode current mirrors, an operational amplifier, four resistors, and a pair of transistors with a ratio of 1:n. In the first common-source cascode current mirror, the drain of the lower-layer PMOS is connected to resistor R1 and the emitter of one transistor, with the other end of resistor R1, the base, and the collector of the transistor all grounded. In the second common-source cascode current mirror, the drain of the lower-layer PMOS is connected to resistors R2 and R3, with the other end of resistor R2 connected to the emitter of n parallel transistors, the other end of resistor R3 grounded, and the base and collector of the n parallel transistors grounded. The third common-source cascode current mirror is used to convert the current from the first two current mirrors. The fourth common-source cascode current mirror uses the drain resistor R4 of the lower-level PMOS transistor, which is also connected to the junction as a reference voltage for the bandgap. At the output point, the other end of resistor R4 is grounded; the inverting and non-inverting inputs of the operational amplifier are connected to one side of resistor R2 and the emitter of a transistor of number 1, respectively; the output of the operational amplifier is connected to the gate of the upper PMOS transistor in the common-source cascode current mirror.

[0010] Furthermore, the current subtraction circuit includes NMOS1, NMOS2, NMOS3, and NMOS4. Current flows to the drain of NMOS1, and the gate of NMOS1 is connected to the drain. The gate of NMOS2 is connected to the gate of NMOS1. The ratio of the number of NMOS2 to the number of NMOS1 is p:1. The drains of NMOS2 and NMOS3 are connected to the input, the gate of NMOS3 is connected to the drain, and the gate of NMOS4 is connected to the gate of NMOS3. The ratio of the number of NMOS4 to NMOS3 is 1:1. The substrates and sources of all NMOS4 are grounded. After being replicated and amplified by a set of PMOS current mirrors, it is fed into the oscillator.

[0011] Furthermore, the oscillator circuit is composed of M-stage inverters connected end-to-end, where M is an odd number ≥ 3. The sources of the PMOS transistors in all inverters are connected together, and then connected to the generator. The drain of the current mirror, the substrate of all PMOS in the inverter is connected to the power supply of the oscillator, that is, the output VDD of the low dropout linear regulator, the source and substrate of all NMOS in the inverter are grounded, and the position where the drains of PMOS and NMOS in any stage of the inverter are connected can be used as the output terminal of the oscillator.

[0012] Furthermore, the backscatter switch is composed of two NMOS transistors. The sources of both NMOS transistors are grounded, and their drains are respectively connected to the RFP and RFN terminals of the CMOS differential input rectifier. The gates of the two NMOS transistors are connected to the output terminal of the oscillator, and the substrates of both NMOS transistors are grounded.

[0013] Furthermore, CMOS differential input rectifiers and low dropout linear regulators use a common CMOS structure.

[0014] The wireless CMOS temperature sensor based on wireless energy harvesting technology of the present invention has the following advantages: The present invention uses an antenna and a rectifier to wirelessly power the CMOS temperature sensor, uses a backscatter switch to achieve wireless transmission of temperature information, and uses two sets of bandgap references to amplify the temperature-proportional current change with temperature, thus giving the temperature signal higher resolution. At the same time, the circuit structure is simple, avoiding the use of complex and high-power, large-area modules such as analog-to-digital converters (ADCs), reducing the power consumption and area of ​​the temperature sensor, while achieving higher temperature resolution. Attached Figure Description

[0015] Figure 1 This is a system architecture diagram of the present invention; Figure 2 This is a circuit schematic diagram of an embodiment of the present invention. Detailed Implementation

[0016] To better understand the purpose, structure, and function of this invention, the following detailed description of a wireless CMOS temperature sensor based on wireless energy harvesting technology is provided in conjunction with the accompanying drawings.

[0017] like Figure 1 As shown, a wireless CMOS temperature sensor based on wireless energy harvesting technology includes a CMOS wireless energy harvesting circuit, a CMOS temperature sensing front-end circuit, and a CMOS wireless signal transmitting circuit. The CMOS wireless energy harvesting circuit harvests wireless energy and converts it into a DC voltage to power the CMOS temperature sensing front-end circuit. The CMOS temperature sensing front-end circuit generates a signal whose frequency is proportional to the temperature and applies it to the CMOS wireless signal transmitting circuit, wirelessly transmitting the temperature information in a backscattering manner.

[0018] The CMOS wireless energy harvesting circuit includes an antenna, a CMOS differential input rectifier, and a low-dropout linear regulator. The CMOS temperature sensing front-end circuit includes a first bandgap reference, a second bandgap reference, a current subtraction circuit, an oscillator, and a low-dropout linear regulator. The CMOS wireless signal transmitting circuit includes an antenna and a backscatter switch. The two ends of the backscatter switch are connected to the differential input terminals of the CMOS differential input rectifier, and the signal input terminal of the backscatter switch is connected to the output terminal of the oscillator. The pair of differential input terminals RFP and RFN of the CMOS differential input rectifier are connected to the two ends of the antenna. The output terminal VDC of the CMOS differential input rectifier is connected to the power supply terminals of the low-dropout linear regulator, the first bandgap reference, and the second bandgap reference. The low-dropout linear regulator is connected to the oscillator. The first and second bandgap references are connected to the current subtraction circuit, which is connected to the oscillator. After an external wireless signal is received, the antenna collects the wireless energy and converts the differential AC voltage signals RFP and RFN into a DC voltage VDC that can be used to power the low-dropout linear regulator, the first bandgap reference, and the second bandgap reference via a CMOS differential input rectifier. The first bandgap reference generates a temperature-independent current. The second bandgap reference generates a current proportional to temperature. Then, a current that is independent of temperature is amplified by p times using a current subtraction circuit to obtain... Subtracting these two from each other, we get (This value needs to be greater than 0 at any temperature). Originally The change with temperature is relatively small, so it can be reduced by subtracting... The invariants in the current result in the final current. The change in current with temperature increases significantly. Then, this current path... After being copied and amplified, the signal is fed into an oscillator, which outputs an oscillation signal DATA whose frequency is proportional to the temperature.

[0019] like Figure 2 As shown, the core of the second bandgap reference consists of three PMOS current mirrors, an operational amplifier, a resistor R, and two sets of transistors operating at different current densities. The source of the first PMOS current mirror is connected to the bandgap reference's power supply VDC, and its drain is connected to the emitter of a transistor operating at unit current density. The source of the second PMOS current mirror is also connected to the bandgap reference's power supply VDC, and its drain is connected to a resistor R. The other end of resistor R is connected to the emitters of n transistors connected in parallel. The gates of both current mirrors are connected together to the output of the operational amplifier, and the drains of the two current mirrors are connected to the non-inverting and inverting inputs of the operational amplifier, respectively. The currents of the first and second current mirrors are the same. A 1:1 / n transistor operating current density is achieved by connecting one transistor to one current mirror and the other to n transistors connected in parallel. The base and collector of all transistors are grounded. In this way, the difference in base-emitter voltage between the two bipolar junction transistors operating at different current densities is proportional to temperature. The current is applied across resistor R and converted into a temperature-proportional current. This current is then replicated through a third PMOS current mirror to obtain another temperature-proportional current. .

[0020] The first bandgap reference consists of four cascode PMOS current mirrors, an operational amplifier, four resistors, and a pair of transistors with a ratio of 1:n. In the first cascode current mirror, the drain of the lower PMOS is connected to resistor R1 and the emitter of one transistor. The other end of resistor R1, the base of the transistor, and the collector of the transistor are all grounded. In the second cascode current mirror, the drain of the lower PMOS is connected to resistors R2 and R3. The other end of resistor R2 is connected to the emitters of n parallel transistors, the other end of resistor R3 is grounded, and the bases and collectors of the n parallel transistors are grounded. The third cascode current mirror is used to convert the current from the first two current mirrors... The fourth common-source cascode current mirror uses the drain resistor R4 of the lower-level PMOS transistor, which is also connected to the junction as a reference voltage for the bandgap. At the output point, the other end of resistor R4 is grounded. The non-inverting and inverting inputs of the operational amplifier are connected to one side of resistor R2 and the emitter of a single transistor, respectively. The output of the operational amplifier is connected to the gate of the upper-layer PMOS transistor in the cascode current mirror. When it is operating, the voltage at the non-inverting and inverting inputs of the operational amplifier is equal, which is equal to the voltage of the single transistor. Therefore, the voltage across resistor R2... This generates a current that is proportional to the temperature, flowing from across resistor R3. A current inversely proportional to temperature is generated. The sum of these two currents is then replicated across resistor R4 via a fourth common-source cascode current mirror, generating a temperature-independent reference voltage. Since the temperature coefficient of the resistor itself is very small, the current copied to R4 can also be considered as a temperature-independent current. This current is then copied through the third common-source cascode current mirror before being output.

[0021] The current subtraction circuit includes NMOS1, NMOS2, NMOS3, and NMOS4. Current flows into the drain of NMOS1, and the gate of NMOS1 is connected to the drain. The gate of NMOS2 is connected to the gate of NMOS1. The ratio of the number of NMOS2 to the number of NMOS1 is p:1. Therefore, looking into the drain of NMOS2... It is magnified by p times. Input the drains of NMOS2 and NMOS3, because the current flowing into NMOS2 is... Therefore, the magnitude of the current input to the drain of NMOS3 is The gate of NMOS3 is connected to its drain, while the gate of NMOS4 is connected to the gate of NMOS3. The ratio of the number of NMOS4 and NMOS4 is 1:1. Therefore... It is copied 1:1, then replicated and amplified by a set of PMOS current mirrors before being fed into the oscillator. The substrates and sources of all NMOS transistors in the current subtraction circuit are grounded.

[0022] The oscillator circuit consists of M stages of inverters (M being an odd number ≥ 3) connected end to end. The sources of the PMOS transistors in all inverters are connected together, and then connected to the generator. The drain of the current mirror is connected to the oscillator's power supply, i.e., the output VDD of the low-dropout linear regulator, on the substrate of all PMOS transistors in the inverters. The source and substrate of the NMOS transistors in all inverters are grounded. The connection point between the drains of the PMOS and NMOS transistors in any stage of the inverter can serve as the output terminal of the oscillator.

[0023] The backscatter switch consists of two NMOS transistors. The sources of both NMOS transistors are grounded, and their drains are connected to the RFP and RFN terminals of the CMOS differential input rectifier, respectively. The gates of the two NMOS transistors are connected to the output of the oscillator, and the substrates of both NMOS transistors are grounded.

[0024] CMOS differential input rectifiers and low dropout linear regulators use a common CMOS structure.

[0025] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A wireless CMOS temperature sensor based on wireless energy harvesting technology, comprising a CMOS wireless energy harvesting circuit, a CMOS temperature sensing front-end circuit, and a CMOS wireless signal transmitting circuit, characterized in that, The CMOS wireless energy harvesting circuit is used to harvest wireless energy and convert it into DC voltage to power the CMOS temperature sensing front-end circuit. The CMOS wireless energy harvesting circuit includes an antenna, a CMOS differential input rectifier, and a low-dropout linear regulator. The CMOS temperature sensing front-end circuit includes a first bandgap reference, a second bandgap reference, a current subtraction circuit, an oscillator, and a low-dropout linear regulator. The CMOS wireless signal transmitting circuit includes an antenna and a backscatter switch. The two ends of the backscatter switch are respectively connected to the differential input terminals of the CMOS differential input rectifier, and the signal input terminal of the backscatter switch is connected to the output terminal of the oscillator. A pair of differential input terminals RFP and RFN of the CMOS differential input rectifier are connected to the two ends of the antenna. The output terminal VDC of the CMOS differential input rectifier is connected to the power supply terminals of the low-dropout linear regulator, the first bandgap reference, and the second bandgap reference. The low-dropout linear regulator is connected to the oscillator. The first bandgap reference and the second bandgap reference are connected to the current subtraction circuit, and the current subtraction circuit is connected to the oscillator. The CMOS temperature sensing front-end circuit utilizes a first bandgap reference, a second bandgap reference, and a current subtraction circuit. The first bandgap reference circuit generates a temperature-independent current, while the second bandgap reference circuit generates a temperature-proportional current. The current subtraction circuit amplifies the temperature-independent current by a factor of p to obtain the desired temperature sensor. Subtracting these two from each other, we get This results in the final current. As the temperature change increases significantly, the current-controlled oscillator generates an oscillation signal with a frequency proportional to the temperature, which is applied to the CMOS wireless signal transmitting circuit to wirelessly transmit the temperature information in a backscattering manner.

2. The wireless CMOS temperature sensor based on wireless energy harvesting technology according to claim 1, characterized in that, The second bandgap reference includes three PMOS current mirrors, an operational amplifier, a resistor R, and two sets of transistors operating at different current densities. The source of the first PMOS current mirror is connected to the bandgap reference's power supply VDC, and its drain is connected to the emitter of a transistor operating at unit current density. The source of the second PMOS current mirror is connected to the bandgap reference's power supply VDC, and its drain is connected to a resistor R. The other end of resistor R is connected to the emitters of n transistors connected in parallel. The gates of the first and second PMOS current mirrors are connected together to the output of the operational amplifier. The drains of the first and second PMOS current mirrors are connected to the non-inverting and inverting inputs of the operational amplifier, respectively. The bases and collectors of all transistors are grounded. The third PMOS current mirror replicates the current across resistor R and outputs it. .

3. The wireless CMOS temperature sensor based on wireless energy harvesting technology according to claim 2, characterized in that, The first bandgap reference consists of four common-source cascode current mirrors, an operational amplifier, four resistors, and a pair of transistors with a ratio of 1:n. In the first common-source cascode current mirror, the drain of the lower-layer PMOS is connected to resistor R1 and the emitter of one transistor. The other end of resistor R1, the base of the transistor, and the collector are all grounded. In the second common-source cascode current mirror, the drain of the lower-layer PMOS is connected to resistors R2 and R3. The other end of resistor R2 is connected to the emitter of n parallel transistors, the other end of resistor R3 is grounded, and the base and collector of the n parallel transistors are grounded. The third common-source cascode current mirror is used to convert the current from the first two current mirrors. The fourth common-source cascode current mirror uses the drain resistor R4 of the lower-level PMOS transistor, which is also connected to the junction as a reference voltage for the bandgap. At the output point, the other end of resistor R4 is grounded; the inverting and non-inverting inputs of the operational amplifier are connected to one side of resistor R2 and the emitter of a transistor of number 1, respectively; the output of the operational amplifier is connected to the gate of the upper PMOS transistor in the common-source cascode current mirror.

4. The wireless CMOS temperature sensor based on wireless energy harvesting technology according to claim 3, characterized in that, The current subtraction circuit includes NMOS1, NMOS2, NMOS3, and NMOS4. Current flows to the drain of NMOS1, and the gate of NMOS1 is connected to the drain. The gate of NMOS2 is connected to the gate of NMOS1. The ratio of the number of NMOS2 to the number of NMOS1 is p:

1. The drains of NMOS2 and NMOS3 are connected to the input, the gate of NMOS3 is connected to the drain, and the gate of NMOS4 is connected to the gate of NMOS3. The ratio of the number of NMOS4 to NMOS3 is 1:

1. The substrates and sources of all NMOS4 are grounded. After being replicated and amplified by a set of PMOS current mirrors, it is fed into the oscillator.

5. The wireless CMOS temperature sensor based on wireless energy harvesting technology according to claim 4, characterized in that, The oscillator circuit consists of M-stage inverters connected end-to-end, where M is an odd number ≥ 3. The sources of the PMOS transistors in all inverters are connected together, and then connected to the generator. The drain of the current mirror, the substrate of all PMOS in the inverter is connected to the power supply of the oscillator, that is, the output VDD of the low dropout linear regulator, the source and substrate of all NMOS in the inverter are grounded, and the position where the drains of PMOS and NMOS in any stage of the inverter are connected can be used as the output terminal of the oscillator.

6. The wireless CMOS temperature sensor based on wireless energy harvesting technology according to claim 1, characterized in that, The backscatter switch is composed of two NMOS transistors. The sources of both NMOS transistors are grounded, and their drains are connected to the RFP and RFN terminals of the CMOS differential input rectifier, respectively. The gates of the two NMOS transistors are connected to the output terminal of the oscillator, and the substrates of both NMOS transistors are grounded.

7. The wireless CMOS temperature sensor based on wireless energy harvesting technology according to claim 1, characterized in that, The CMOS differential input rectifier and low dropout linear regulator use a common CMOS structure.

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