CN107747954B

CN107747954B - Self-source sensor

Info

Publication number: CN107747954B
Application number: CN201710912260.XA
Authority: CN
Inventors: 刘杨
Original assignee: Suzhou Ripple Information Technology Co ltd
Current assignee: Suzhou Ripple Information Technology Co ltd
Priority date: 2017-09-29
Filing date: 2017-09-29
Publication date: 2020-05-05
Anticipated expiration: 2037-09-29
Also published as: CN107747954A

Abstract

The present disclosure relates to the field of microelectronic technologies, and in particular, to a self-powered sensor for use in a health monitoring system for a key part of a building, an airplane, an automobile, or the like. The self-source sensor comprises a floating gate field effect tube and a piezoelectric element; the piezoelectric element is connected to the source electrode of the floating gate field effect transistor; the piezoelectric material can inject and store generated electrons to a floating grid of the floating grid field effect tube under the condition of being excited by periodic deformation. Electrons generated by the periodic deformation of the piezoelectric element are stored in the chip, other power management modules are removed, and ultramicro power consumption and weak energy acquisition are achieved.

Description

Self-source sensor

Technical Field

The present disclosure relates to the field of microelectronic technologies, and in particular, to a self-powered sensor for use in a health monitoring system for key parts of buildings, airplanes, automobiles, and the like.

Background

For the interior of the key parts of buildings, airplanes, automobiles and the like, the space is often limited and the surrounding environment is severe, and the key parts need to be provided with sensors to monitor the running health conditions of the key parts. The traditional sensor needs a power supply or a battery for power supply, and a wiring module, an attached voltage management module and an energy buffer module, namely an analog-digital conversion and the like brought by the power supply or the battery for power supply, so that the traditional sensor cannot be arranged in a limited space such as an engine for long-term effective health monitoring.

Another type of sensor is a passive sensor, which does not have a power source of its own, and the sensor can be activated, read and transmitted by an external signal. The disadvantage is that the sensor cannot perform physical measurement in an unactuated state, so that the historical data cannot be recorded, which brings a limitation to the application of such sensors.

The technical difficulty that the technology for obtaining energy from the environment is very limited is that the design of the sensor needs to be designed with ultra-micro power consumption. Table 1 shows the energy that can be directly extracted from the movement of buildings and biomechanics.

TABLE 1

Disclosure of Invention

In view of the above, the present disclosure provides a self-powered sensor capable of continuously monitoring the fatigue level of an object without an external power supply.

A self-sourced sensor, comprising:

a floating gate field effect transistor and a piezoelectric element;

the piezoelectric element is connected to the source electrode of the floating gate field effect transistor;

the piezoelectric material can inject and store generated electrons to a floating grid of the floating grid field effect tube under the condition of being excited by periodic deformation.

Preferably, the material of the piezoelectric element is at least one of PZT and PVDF.

Preferably, the self-source sensor further includes:

the inverting input end of the operational amplifier is connected with the source electrode of the floating gate field effect tube, the non-inverting input end of the operational amplifier is connected with the reference voltage, and the output end of the operational amplifier is connected with the floating gate electrode of the floating gate field effect tube through the first capacitor.

Preferably, the output end of the operational amplifier is grounded through a switch, and the drain electrode of the floating gate field effect transistor is grounded.

Preferably, when the switch is in a closed state, the self-source sensor is in a reading mode; and when the switch is in an off state, the self-source sensor is in an injection mode.

Preferably, the floating gate of the floating gate field effect transistor is connected to a tunnel voltage through a second capacitor, and the tunnel voltage is used for clearing charges stored in the floating gate of the floating gate field effect transistor.

Preferably, the current injected by the piezoelectric element into the floating gate of the floating gate field effect transistor has a linear relationship with the source voltage input by the piezoelectric element.

The invention has the advantages that electrons generated by periodic deformation of the piezoelectric element are stored in the chip, other power management modules are eliminated, and ultramicro power consumption and weak energy acquisition are realized.

Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.

FIG. 1 illustrates a schematic diagram of a self-sourced sensor system on a chip, in accordance with an embodiment of the present invention;

FIG. 2 shows a schematic structural diagram of a self-sourced sensor of another embodiment of the invention;

FIG. 3 is a schematic structural diagram illustrating a self-sourced sensor in an injection mode according to another embodiment of the invention;

FIG. 4 is a schematic diagram of a self-sourced sensor in a read mode according to another embodiment of the invention;

FIG. 5 shows a schematic diagram of a self-sourced sensor of another embodiment of the invention;

FIG. 6 is a graph illustrating injection current values as a function of source voltage in a self-powered sensor system-on-chip according to another embodiment of the invention;

FIG. 7 shows a schematic diagram of a linear programmable FG voltage bias generator in a self-sourced sensor system on a chip according to another embodiment of the invention;

FIG. 8 shows test results of the operating range of a circuit in a self-sourced sensor system on a chip according to another embodiment of the invention;

FIG. 9 is a diagram illustrating the results of a circuit linearity index test developed in a system on a self-powered sensor chip according to another embodiment of the present invention;

FIG. 10 shows the results of testing of circuit INL according to another embodiment of the present invention;

FIG. 11 shows the DNL test results for a circuit according to another embodiment of the present invention.

Detailed Description

Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers can indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present disclosure may be practiced without some of these specific details. In some instances, methods, means, elements and circuits that are well known to those skilled in the art have not been described in detail so as not to obscure the present disclosure.

FIG. 1 illustrates a schematic diagram of a self-sourced sensor system on a chip, in accordance with an embodiment of the present invention. As shown in fig. 1, the self-sourced sensor system on chip includes: the linear PFG array 11 comprises a plurality of self-source sensors, each self-source sensor comprises a floating gate field effect tube and a piezoelectric element connected with a source electrode of the floating gate field effect tube, wherein the piezoelectric element can inject and store generated electrons into a floating gate of the floating gate field effect tube under the condition of being subjected to periodic deformation excitation;

and the digital control circuit 13 is connected with the linear PFG array 11 and used for reading the detection data of the respective source sensor from the linear PFG array.

In one possible implementation, the digital control circuit 13 includes a digital processor 21, a power supply reset 22, a ring oscillator 23, an injection charge pump 24, and a tunnel charge pump 25;

the digital processor 21 is respectively connected with a power supply restorer 22, a ring oscillator 23, an injection charge pump 24 and a tunnel charge pump 25;

the ring oscillator 23 is further connected to an injection charge pump 24 and a tunnel charge pump 25, respectively;

the power supply resetter 22 is used for initializing the content of the digital processor;

the digital processor 21 is used for activating the tunnel charge pump 25 when an applied voltage is input to generate an input voltage to drive a reading circuit of the self-source sensor;

the tunnel charge pump 25 is further configured to generate a tunnel voltage, and the tunnel voltage is used for resetting stored charges of the floating gate field effect transistor;

the ring oscillator 23 is connected to the digital processor 21, the injection charge pump 24 and the tunnel charge pump 25, respectively, and is configured to control the digital processor 21, the injection charge pump 24 and the tunnel charge pump 25.

In a possible implementation manner, the self-sourced sensor system on chip further includes:

an event detector 15 connected to the floating gate of each floating gate field effect transistor in the linear PFG array; the event detector 15 is also connected to the reference source 12.

and a protection circuit 17 provided between the piezoelectric element and the event detector for protecting against overvoltage or overcurrent.

In a possible implementation manner, in the self-sourced sensor system on chip, a level conversion module 19 is arranged between the digital control circuit 13 and the linear PFG array 11.

Referring to fig. 2, in a possible implementation manner, the self-sourced sensor further includes:

an operational amplifier A having an inverting input terminal (-) and a floating gate field effect transistor M_fgThe non-inverting input terminal (+) of the operational amplifier A is connected with a reference voltage V_refThe output end of the operational amplifier A passes through a first capacitor C_fgConnecting floating gate field effect transistor M_fgThe floating gate of (1).

In a possible implementation, the output of the operational amplifier a is further connected to the output of the operational amplifier a via a switch S_pGrounded, the floating gate field effect transistor M_fgIs grounded.

In a possible implementation, the switch S_pIn the closed state, the self-sourced sensor is in the read mode, see fig. 4; the switch is in the off state and the self-sourced sensor is in the injection mode, see fig. 3.

In one possible implementation, as shown in FIG. 7, the floating gate FET M_fgIs passed through a second capacitor C_tunConnecting tunnel voltage V_tunAnd the tunnel voltage is used for clearing the charges stored in the floating gate of the floating gate field effect tube.

In one possible implementation, as shown in fig. 5, the current injected by the piezoelectric element into the floating gate of the floating gate field effect transistor has a linear relationship with the source voltage input by the piezoelectric element.

Referring to fig. 1, the System On Chip (SOC) of the present disclosure is mainly composed of two main parts: the linear PFG injection unit array (linear PFG array for short) is used for controlling the electron injection of the piezoelectric material; and a digital controller module (namely a digital control circuit) for realizing control and reading. The system mainly has two working modes: in the injection or programming mode (energy in the environment is collected and stored in the chip) and in the reading mode (information stored in the chip is read), in the present disclosure, the material of the piezoelectric element may be at least one of PZT (lead zirconate titanate binary system piezoelectric ceramic) and PVDF (polyvinylidene fluoride).

When the system is in the read mode, the applied voltage V_ddD(1.8V) for powering the digital part of the digital control circuit 13 and activating the tunnel charge pump, with an applied voltage V_ddaThe analog part of the digital control circuit 13 is powered to drive the read circuit of the sensor. The tunnel charge pump is also used to generate a tunnel voltage V_TunFor clearing the charge of the floating gate memory. The power reset function POR is used to initialize the contents of the digital counter. The present disclosure employs a digital processor for controlling hot electron injection and reading. The ring oscillator generates a clock signal for the entire system, controlling the digital processor, the injection charge pump and the tunnel charge pump. An isolation diode is used to isolate the read mode from the injection (or programming) mode, preventing the read mode current from being introduced into the piezoelectric material. The protection circuit is a high voltage/overcurrent protection circuit for protecting other circuits from being damaged by high voltage (or overcurrent) caused by the piezoelectric material.

Thus, as shown in fig. 2, a linear PFG circuit (i.e., a linear PFG array) controls the injection of electrons from the piezoelectric material into the transistors. The desired effect is electron injection and V of the piezoelectric material into the transistor_progThe voltage is linear. This is achieved byBy measuring V_progThe magnitude of the voltage of (a) is obtained as a deformation of the piezoelectric element.

V_progHow to achieve a 13-bit high accuracy linear PFG (piezoelectric floating gate field effect transistor) circuit has been measured.

The core circuit of the linear PFG array works according to the following principle:

in a floating gate field effect transistor (also referred to as a silicon gate transistor, a PMOS transistor, etc.), impact ionization hot electron injection current I_injDependent on the source current I of the transistor_sSource drain voltage V_sdAnd gate to drain voltage V_gdThe relationship between them can be represented by the following function:

I_inj＝f(I_s,V_sd,V_gd) (1)

this is an arbitrary function and the exact mathematical function is currently temporarily unknown. Many previous experimental models suggest a rough function, as the following impact ionization hot electron injection model has proven to hold for all regions of operation of the transistor:

wherein α, λ, β, δ and the injection voltage V_injAre variables of the model, and the parameter values for the measurement data α, λ, β, δ are related to the kind of floating gate transistor.

In the linear injection technique proposed by the present disclosure, the factors affecting the injection current, such as the injection current I_injSource drain voltage V_sdAnd gate to drain voltage V_gdAre all kept constant, so that according to function (1), the injection current I_injAnd remain constant.

Referring to FIG. 3, switch S_POpen, the circuit is in the injection mode, activate the operational amplifier A and the floating gate field effect transistor M_fgAnd forming a negative feedback loop. The source current is maintained at I_ref(reference current) to ensure the source-gate voltage V_sgAnd remains constant during the implant. By regulating the output voltage V of the operational amplifier A_cgThe operational amplifier A ensures the source and drainVoltage V_sdAnd remain constant. Therefore, the injection current also remains constant according to function (1). Setting duration of injection to I_refThereby ensuring a fixed amount of charge injection into the floating gate field effect transistor.

Referring to FIG. 4, in the read mode, the switch S_PClosed, connected to V_cgVoltage and a reference potential (here the reference potential is voltage ground). Floating gate voltage V of PMOS transistor_fgIs formed by injected charges and a capacitor C_fgAnd (6) determining. By considering the influence of the finite gain of the operational amplifier a and the small signal parameter obtained by the measurement, the formula of the linear injection can be derived. Injection current I in FIG. 3 according to function (1)_injThe calculated function (without taking thermal noise into account) is:

I_inj＝f(I_ref,V_s,V_fg) (3)

V_sand V_progAll represent floating gate field effect transistor M_fgThe source voltage of (1).

By increased source voltage deltav and increased floating gate voltage deltav_fgThe function can be linearized as:

wherein, from the source end point of view,

representing the injected transconductance parameter, considered from the floating gate transistor end,

the injected transconductance parameter is represented. Assuming a constant reference current, a small signal analysis of the PMOS transistor current yields:

ΔI_ref＝(g_m+g_d)ΔV_s-g_mΔV_fg＝0 (5)

wherein the content of the first and second substances,

is a transconductance small signalParameter, V_gRepresenting the gate voltage. If the PMOS transistor is in the saturation region, if g_m＞＞g_d，ΔV_S≈ΔV_fg。V_tun、V_s、V_dAnd V_bRespectively representing the tunnel voltage, source voltage, drain voltage and bulk voltage of the floating gate field effect transistor, C_tun、C_s、C_dAnd C_bRespectively representing the corresponding capacitances (parasitic and non-parasitic), C_fgThe floating gate capacitance of the floating gate field effect transistor is represented, and the capacitance is coupled in the voltages, so that the electric quantity stored in the floating gate is represented as:

Q＝C_fg(V_fg-V_cg)+C_tun(V_fg-V_tun)+C_s(V_fg-V_s)+C_d(V_fg-V_d)+C_b(V_fg-V_b) (6)

due to the feedback of FIG. 3, except V_fgExcept that all the node voltages are kept at a constant potential, the change of the electric quantity Δ Q can be simplified as follows:

ΔQ＝ΔV_fgC_T(7)

wherein, C_T＝(C_fg+C_tun+C_s+C_d+C_b) Is the total capacitance associated with the floating gate. If the gain of the operational amplifier is set to A_VThen the feedback loop ensures that:

therefore, the temperature of the molten metal is controlled,

wherein, when the gain is infinite, V_sIs constant. (9) The charge variation Δ Q and the injection current in the equation can be expressed as:

ΔQ＝-I_injΔt (10)

applying equations (8) to (10) to equation (4) and letting Δ t → 0, a first order differential equation can be obtained as follows:

thereby deriving

Equation (12) shows that the finite gain of the operational amplifier causes a time dependence of the injected current, which causes errors in the writing of the floating gate voltage. Due to the duration of the injection being t_pThe error introduced by the implant can be calculated as:

figure 6 shows the measured injection current when the source voltage is varied and the other parameters are not. According to the measured data, the small signal parameter G is obtained when the reference current is between 45nA and 90nA_sAnd G_fgBetween 0.149 and 2.316fS is expected, so an amplifier with a small signal gain of 40dB should achieve linearity of at least 16 bits according to (13). However, when electrons are injected into the floating gate capacitor, the degree of accuracy of the injection is also affected by thermal noise. The error can be approximately expressed as

Wherein C is_TIs the total capacitance (including parasitic capacitance) of the floating gate, K is the boltzian maturity, and T is the temperature. In this study, C_T100fF, therefore V_n200 μ V. We will show in the measured data that thermal noise has less of an impact on the accuracy of the linear programming technique proposed herein.

Using the injection principles presented herein, we implement a linearly programmable floating gate voltage bias generator. The circuit is shown in fig. 7, and the adopted process is the 0.5-mu mCMOS standard process.

(1) Output range of the circuit

Experiment one, the linear output range of the voltage offset generator was measured. Use ofBefore the injection of the pulse, the supply voltage is raised to 6.5V, and the switch S is turned on_PUsing FN tunneling, V_sIs set to be higher than 4.3V. By means of a digitally-controlled switch S_PAnd use of V_refAnd I_refThe different combinations of (a) and (b) control the rate of injection. After each injection cycle, Vs is measured using an external analog-to-digital converter. FIG. 8 shows the measurement results, V_refWhen the voltage is 4.9V, I_ref50nA and fit into an ideal linear model. Fig. 9 shows the calculated resolution in the interval 4.1V to 0.1V. Considering that the voltage of lsb (lestsignitiant bit) in dnl (differential nonlinearity) is less than 0.4mV, it is equivalent to 13.4 bits of resolution.

(2) Programming (injection) resolution

The following set of experiments investigated the programming resolution of the voltage offset generator. First, FN tunneling is used to set the output voltage to 3 to 4V. I is_refSet to 50nA, tp to 50ms, adjust only V_refTo control the implantation rate. For different V_refThe change in the output voltage is recorded after each injection period until the drop in the output voltage reaches 1V. In order to eliminate the influence of measurement noise, a large filter capacitor is adopted in a buffer area in the experiment. Although this disclosure fails to eliminate the 1/f noise introduced by the feedback amplifier and FG transistor (floating gate field effect transistor), experimental results show that the effect of 1/f noise is negligible compared to thermal noise. Fig. 10 and 11 are test results of circuits INL (integral nonlinearity) and DNL (Differential nonlinearity), showing that the circuit resolution can achieve 13.4 bit precision.

Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A self-sourced sensor, comprising:

a floating gate field effect transistor and a piezoelectric element;

the piezoelectric element can inject and store generated electrons to a floating grid of the floating grid field effect tube under the condition of being excited by periodic deformation;

2. The self-sourced sensor of claim 1, wherein: the material of the piezoelectric element is at least one of PZT and PVDF.

3. The self-sourced sensor of claim 1, wherein: the output end of the operational amplifier is grounded through a switch, and the drain electrode of the floating gate field effect transistor is grounded.

4. The self-sourced sensor of claim 3, wherein: when the switch is in a closed state, the self-source sensor is in a reading mode; and when the switch is in an off state, the self-source sensor is in an injection mode.

5. The self-sourced sensor of claim 4, wherein: and the floating gate of the floating gate field effect tube is connected with a tunnel voltage through a second capacitor, and the tunnel voltage is used for clearing the charges stored in the floating gate of the floating gate field effect tube.

6. The self-sourced sensor of any one of claims 1 to 5, wherein: the current injected by the piezoelectric element to the floating gate of the floating gate field effect tube has a linear relation with the source voltage input by the piezoelectric element.