A narrow pulse integrating position sensor analog front end circuit

Abstract

The application provides a narrow pulse integral positioning sensor analog front-end circuit, and belongs to the technical field of sensors.The narrow pulse integral positioning sensor analog front-end circuit comprises a long-wave sensor, a pulse sampling compensation circuit, a filter integration circuit, a thermal number conversion circuit, a phase generation circuit, a separable drive circuit and an infrared emitter, the input end of the long-wave sensor is connected with the pulse sampling compensation circuit, the output end of the pulse sampling compensation circuit is connected with the input end of the filter integration circuit, the thermal number conversion circuit is connected with the phase generation circuit and the filter integration circuit respectively, the output end of the phase generation circuit is connected with the separable drive circuit and the pulse sampling compensation circuit respectively, and the output end of the separable drive circuit is connected with the infrared emitter.The narrow pulse integral positioning sensor analog front-end circuit has the advantages of low cost, high efficiency, high precision and good practicability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sensor, in particular to a narrow pulse integral type positioning sensor analog front-end circuit. BACKGROUND

[0002] Infrared temperature measurement technology has been widely used in industry, automobile, household appliances and many other fields, but due to the high cost of detection materials, it is difficult to be widely used in consumer electronics and Internet of Things. The detection materials have thermocouples designed by MEMS process of silicon material, which has relatively low cost and poor measurement accuracy, and expensive materials such as vanadium oxide and germanium, which have high cost and high measurement accuracy. The cost of various technologies and materials is higher than that of pyroelectric, RGB image and other routes. In addition, since infrared imaging technology is an imaging technology, there is a privacy risk in some applications to a certain extent. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a narrow pulse integral type positioning sensor analog front-end circuit to solve the above technical problems.

[0004] The purpose of the present application can be realized by the following technical scheme: a narrow pulse integral type positioning sensor analog front-end circuit, comprising a long wave sensor, a pulse sampling compensation circuit, a filter integration circuit, a thermal number conversion circuit, a phase generating circuit, a separable driving circuit and an infrared emitter, the input end of the long wave sensor and the pulse sampling compensation circuit are connected, the output end of the pulse sampling compensation circuit and the input end of the filter integration circuit are connected, the thermal number conversion circuit is connected with the phase generating circuit and the filter integration circuit respectively, the output end of the phase generating circuit is connected with the separable driving circuit and the pulse sampling compensation circuit respectively, and the output end of the separable driving circuit is connected with the infrared emitter.

[0005] The principle of the present application is that the infrared emitter emits infrared signals outward, the infrared signals are reflected back after encountering the target object, the long wave sensor absorbs the reflected infrared signals and converts them into electrical signals, which are then sent to the pulse sampling compensation circuit, at the same time, the phase generating circuit sends signals of different phases to the pulse sampling compensation circuit, the pulse sampling compensation circuit mixes and modulates the two received signals, and then the signals after filtering and noise reduction are transmitted to the thermal number conversion circuit for conversion of heat and digital signals, so as to calculate the energy of the infrared light wave emitted by the target object itself, and thus obtain the heat dissipation of the target object, i.e. the temperature.

[0006] In the above narrow pulse integral type positioning sensor analog front-end circuit, the infrared signal emitted by the infrared emitter is an infrared narrow pulse signal.

[0007] In the narrow-pulse integration positioning sensor analog front-end circuit, the long-wave sensor is composed of a thermocouple MEMS device, including a plurality of series-connected thermocouples.

[0008] In the narrow-pulse integration positioning sensor analog front-end circuit, the long-wave sensor absorbs infrared wavelengths in the range of 5-15 um.

[0009] In the narrow-pulse integration positioning sensor analog front-end circuit, the pulse sampling compensation circuit includes switches D0 and D1 and a reference capacitor C, the switches D0 and D1 are in opposite states, the long-wave sensor is connected to the input side of the switches D0 and D1, respectively, the reference capacitor C is connected to the input side of the switch D1, the output side of the switches D0 and D1 is connected to the input side of the filter integration circuit, respectively, and the output end of the switch D0 is connected to the output end of the phase generation circuit and directly controlled or synchronized by the signal of the phase generation circuit.

[0010] In the narrow-pulse integration positioning sensor analog front-end circuit, a reset switch RST is provided between the switch D0 and the long-wave sensor and between the switch D1 and the reference capacitor C, respectively.

[0011] In the narrow-pulse integration positioning sensor analog front-end circuit, the switches D0 and D1 are MOS switches.

[0012] In the narrow-pulse integration positioning sensor analog front-end circuit, the filter integration circuit includes capacitors CA and CB, the input side of the capacitor CA is connected to the output side of the switch D0, and the input side of the capacitor CB is connected to the output side of the switch D1.

[0013] In the narrow-pulse integration positioning sensor analog front-end circuit, the capacitors CA and CB have the same theoretical capacitance or the capacitance is infinitely close in reality.

[0014] In the narrow-pulse integration positioning sensor analog front-end circuit, the phase generation circuit is a clock circuit for generating four phase signals with a phase difference of 90°.

[0015] Compared with the prior art, the narrow-pulse integration positioning sensor analog front-end circuit has the following advantages: it can be applied to many application scenarios, has strong applicability and good practicability; it can find the target object closest to the reference object in space through lens scanning or array, and lock the target temperature source through temperature difference comparison without thermal imaging and privacy issues; in addition, it has the advantages of low cost, high efficiency and high precision. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of a narrow pulse integrating positioning sensor analog front-end circuit of an embodiment.

[0017] Figure 2 is a connection diagram of a pulse sampling compensation circuit and a filter integration circuit of an embodiment.

[0018] Figure 3 is a schematic diagram of four phase signals generated by a phase generation circuit of an embodiment.

[0019] Figure 4 is a filter principle schematic diagram of a filter integration circuit of an embodiment.

[0020] Figure 5 is a schematic diagram of the relationship between the four phases after integration by a filter integration circuit of an embodiment.

[0021] In the figure, 1 is a long wave sensor; 2 is a pulse sampling compensation circuit; 3 is a filter integration circuit; 4 is a thermal number conversion circuit; 5 is a phase generation circuit; 6 is a separable driving circuit; and 7 is an infrared emitter. DETAILED DESCRIPTION

[0022] Embodiments of the present application are described in detail below with reference to the attached drawings, wherein like or similar elements are denoted by the same or similar reference signs throughout the drawings. The embodiments described below are examples and are intended to explain the present application, and should not be understood as limiting the present application.

[0023] In addition, the terms "first", "second", etc. are used only for the purpose of description, and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0024] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "linking", "fixing", etc. should be understood in a broad sense, for example, can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] As Figure 1As shown, the present invention provides a narrow pulse integral type positioning sensor analog front-end circuit, which includes a long-wavelength sensor 1, a pulse sampling compensation circuit 2, a filtering integration circuit 3, a thermal conversion circuit 4, a phase generation circuit 5, a separable drive circuit 6, and an infrared emitter 7. The long-wavelength sensor 1 is connected to the input terminal of the pulse sampling compensation circuit 2, the output terminal of the pulse sampling compensation circuit 2 is connected to the input terminal of the filtering integration circuit 3, the thermal conversion circuit 4 is connected to the phase generation circuit 5 and the filtering integration circuit 3 respectively, the output terminal of the phase generation circuit 5 is connected to the separable drive circuit 6 and the pulse sampling compensation circuit 2 respectively, and the output terminal of the separable drive circuit 6 is connected to the infrared emitter 7.

[0026] In this embodiment, the infrared signal emitted by the infrared emitter 7 is a narrow-pulse infrared signal, typically within 10 ns. The narrow pulse reduces the influence of ambient noise, thus avoiding the impact of abundant far-infrared radiation from the air and surrounding environment on the results. The long-wavelength sensor 1 is composed of a thermopile MEMS device, including several thermocouples connected in series. The infrared wavelength range absorbed by the long-wavelength sensor 1 is 5 μm to 15 μm.

[0027] Specifically, such as Figure 2 As shown, the pulse sampling compensation circuit 2 includes switches D0 and D1, and a reference capacitor C. Switches D0 and D1 are both MOS switches. The switching states of switches D0 and D1 are opposite. The long-wavelength sensor 1 is connected to the input sides of both switches D0 and D1. The reference capacitor C is connected to the input side of switch D1. The output sides of switches D0 and D1 are connected to the input sides of the filter integration circuit 3. Switch D0 is connected to the output terminal of the phase generation circuit 5 and is directly controlled or synchronized by the signal from the phase generation circuit 5. A reset switch RST is provided between switch D0 and the long-wavelength sensor 1, and between switch D1 and the reference capacitor C, respectively.

[0028] The filter integrator circuit 3 includes capacitors CA and CB. Theoretically, capacitors CA and CB have the same capacitance value, or in practice, their capacitance values ​​are infinitely close. The input side of capacitor CA is connected to the output side of switch D0, and the input side of capacitor CB is connected to the output side of switch D1. Using this filter integrator circuit 3, the capacitors can filter out high-frequency noise, and the difference in capacitance can eliminate common-mode noise. Figure 4 As shown, common-mode noise interferes with both CA and CB, and a clean potential difference can be obtained through the difference.

[0029] Before the detection process is carried out, the infrared thermopile is first made to obtain a reference voltage using a standard temperature source or reference object. The specific process is as follows: close switch D1 and open D0, and the reference capacitor obtains the reference voltage of the reference object; then open switch D1 and close switch D0, and the circuit starts to work; close reset switch Rst to initialize capacitors CA and CB, and then open Rst.

[0030] like Figure 3 As shown, the phase generation circuit 5 is a clock circuit capable of generating any clock signal. In this embodiment, it sequentially generates four phase signals of 0°, 180°, 90°, and 270°, each 90° out of phase. Then, switching and sampling are performed using D0 and a completely reversed D1. First, the reflected signal is integrated with the 0° phase-shifted C1 signal over a fixed time. Then, the reflected signal is sequentially mixed and integrated with the phase-shifted signals C2, C3, and C4 at 180°, 90°, and 270° respectively.

[0031] After integrating phase shifts of 0°, 180°, 90°, and 270° respectively, the charge signals of Q1, Q2, Q3, and Q4 are transmitted to the thermal conversion circuit 4 (TDC). The TDC receives the integrated charge from the two capacitors of the filtering and integrating circuit 3, and then calculates the difference between the capacitor charges to eliminate circuit noise and obtain a cleaner modulated signal of the integrated charge. The relationship between each phase and the system cooling time is as follows: Figure 5 As shown.

[0032] To mathematically recover the phase from the returned modulated signal, convolution calculations will be used. a ( t )and b ( t The convolution of is defined as:

[0033] The following is from the reflected signal r ( t Obtain phase information from ) φ The measurement process models the reflected signal as a simple harmonic function and demodulates the signal... d ( t The model is a cosine signal. The convolution function can then be simplified to a simple cosine expression with a phase delay.

[0034] in a Represents the signal amplitude. φ Represents phase difference, ω Represents frequency, T Represents a cycle;

[0035] Then, the correlation function is sampled within one period with equal step sizes, for example, by changing the illumination phase in 90-degree step sizes. This correlation function will then produce four distinct terms:

[0036] The convolution parameters become:

[0037] All these terms can be combined to calculate the phase:

[0038] To achieve the above mathematical transformation, the light source signal is modulated sequentially at the light source end using four signals with a 90° phase difference.

[0039] Furthermore, the reflected light source is filtered sequentially by the filter integration circuit 3 before the signal is transmitted to the thermal conversion circuit 4 for signal demodulation.

[0040] Furthermore, the thermal-to-digital conversion circuit 4 transmits the demodulated phase signal to the digital processing circuit;

[0041] Furthermore, the digital processing circuit calculates the phase difference. φ back, φ / 2π is the integration time, therefore the temperature change value is:

[0042] The principle of this invention is as follows: Infrared emitter 7 emits infrared signals outward, and the emitted narrow pulses in the far-infrared band hit the target object and are reflected back. The reflected infrared pulses contain the emitted energy, the reflected energy, and the ambient noise energy. Long-wavelength sensor 1 absorbs the reflected infrared signals and converts them into electrical signals, which are then sent to pulse sampling compensation circuit 2. At the same time, phase generation circuit 5 sends phase signals of 0°, 180°, 90°, and 270° to pulse sampling compensation circuit 2. Pulse sampling compensation circuit 2 mixes and modulates the two received signals, and then the filtered and noise-reduced signals are transmitted to thermal-to-digital conversion circuit 4 for conversion of heat and digital signals. The energy of the infrared light waves emitted by the target object itself is calculated, thereby obtaining the heat dissipation of the target object, i.e., its temperature.

[0043] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A narrow pulse integrating position sensor analog front end circuit, comprising: The long wave sensor (1), the pulse sampling compensation circuit (2), the filter integration circuit (3), the thermal number conversion circuit (4), the phase generating circuit (5), the separable drive circuit (6) and the infrared emitter (7) are connected, the input end of the long wave sensor (1) is connected with the pulse sampling compensation circuit (2), the output end of the pulse sampling compensation circuit (2) is connected with the input end of the filter integration circuit (3), the thermal number conversion circuit (4) is connected with the phase generating circuit (5) and the filter integration circuit (3) respectively, the output end of the phase generating circuit (5) is connected with the separable drive circuit (6) and the pulse sampling compensation circuit (2) respectively, the output end of the separable drive circuit (6) is connected with the infrared emitter (7), the pulse sampling compensation circuit (2) comprises the switch D0, the switch D1 and the reference capacitor C, the switch state of the switch D0 and the switch D1 is opposite, the input side of the long wave sensor (1) is connected with the switch D0 and the switch D1 respectively, the input side of the reference capacitor C is connected with the switch D1, the output side of the switch D0 and the switch D1 is connected with the input side of the filter integration circuit (3) respectively, the output end of the switch D0 is connected with the phase generating circuit (5) and is directly controlled or synchronized by the signal of the phase generating circuit (5), the phase generating circuit (5) is a clock circuit for generating four phase signals with a phase difference of 90°.

2. The narrow pulse integrating position sensor analog front end circuit of claim 1, wherein, The infrared signal emitted by the infrared emitter (7) is an infrared narrow pulse signal.

3. The narrow pulse integrating position sensor analog front-end circuit according to claim 1 or 2, characterized in that, The long wave sensor (1) is composed of a thermoelectric pile MEMS device and comprises a plurality of series-connected thermocouples.

4. The narrow pulse integrating position sensor analog front end circuit of claim 3, wherein, The infrared wavelength range absorbed by the long wave sensor (1) is 5-15 μm.

5. The narrow pulse integrating position sensor analog front-end circuit of claim 1 or 2, wherein, A reset switch RST is arranged between the switch D0 and the long wave sensor (1) and between the switch D1 and the reference capacitor C respectively.

6. The narrow pulse integrating position sensor analog front end circuit of claim 5, wherein, The switch D0 and the switch D1 are MOS switches.

7. The narrow pulse integrating position sensor analog front-end circuit of claim 1 or 2, wherein, The filter integration circuit (3) comprises a capacitor CA and a capacitor CB, the input side of the capacitor CA is connected with the output side of the switch D0, and the input side of the capacitor CB is connected with the output side of the switch D1.

8. The narrow pulse integrating position sensor analog front end circuit of claim 7, wherein, The capacitor CA and the capacitor CB have the same theoretical capacitance or the capacitance is infinitely close in reality.

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