Distance sensing circuit, distance detection method, and non-contact distance sensor

Abstract

The application relates to a distance sensing circuit, a distance detection method, a non-contact distance sensor and a medical device. The distance sensing circuit comprises a first resonant circuit comprising a first capacitor and a coil, which is used for resonating under the action of an excitation signal; wherein during the resonating process, if a to-be-detected magnetic part is within the sensing range of the coil, the resonant frequency of the first resonant circuit changes; a processing module connected with the first resonant circuit is used for respectively acquiring a reference resonant frequency of the first resonant circuit when the coil is not affected by the to-be-detected magnetic part and a target resonant frequency of the first resonant circuit when the to-be-detected magnetic part is within the sensing range of the coil, and acquiring the distance between the coil and the to-be-detected magnetic part according to the reference resonant frequency and the target resonant frequency. The distance sensing circuit can measure the distance between the coil and the to-be-detected magnetic part.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of distance measurement technology, in particular to a distance sensing circuit, a distance detection method and a non-contact distance sensor. BACKGROUND

[0002] The distance sensor, also called displacement sensor, is a kind of sensor, mainly used for measuring the distance from an object.

[0003] At present, the distance sensor mainly adopts a laser ranging sensor. When the laser ranging sensor is in a working state, the light emitter of the laser ranging sensor emits a very thin laser beam to the object to be measured when working, and the light receiver receives the laser beam reflected by the object to be measured. The timer measures the time from the emission to the reception of the laser beam, and calculates the distance from the laser ranging sensor to the object to be measured. However, since the photoelectric sensor needs to emit and receive laser, the sensing range of the photoelectric sensor is greatly limited, and there is great limitation. SUMMARY

[0004] Therefore, it is necessary to provide a distance sensing circuit, a distance detection method, a non-contact distance sensor and a medical device.

[0005] In a first aspect, the present application provides a distance sensing circuit, comprising:

[0006] A first resonant circuit comprising a first capacitor and a coil, used for resonating under the action of an excitation signal; wherein during the resonating process, if the magnetic object to be measured is within the sensing range of the coil, the resonant frequency of the first resonant circuit changes;

[0007] A processing module connected with the first resonant circuit, used for acquiring a target resonant frequency of the first resonant circuit when the magnetic object to be measured is within the sensing range of the coil, and acquiring the distance between the coil and the magnetic object to be measured according to the reference resonant frequency and the target resonant frequency.

[0008] The distance sensing circuit described above, when the magnetic object to be measured is within the sensing range of the coil, the resonant frequency of the first resonant circuit changes when the coil and the first capacitor are resonating. The distance between the coil and the magnetic object can be acquired by measuring the change of the resonant frequency, i.e. the distance between the coil and the magnetic object to be measured can be acquired according to the reference resonant frequency and the target resonant frequency. The detection range of the distance sensing circuit is wide because the sensing range of the coil is wide. In addition, since the resonant frequency of the distance sensing circuit is only affected by the magnetic object, based on this characteristic, the interference of non-magnetic objects can be avoided, and the degree of environmental influence is small.

[0009] In one of the embodiments, the processing module is further configured to obtain a variation of inductance of the coil according to the reference resonant frequency and the target resonant frequency; obtain a variation of permeability of the magnetic object to be measured according to the variation of inductance; and obtain the distance between the coil and the magnetic object to be measured according to the variation of permeability.

[0010] In one of the embodiments, the first resonant circuit further comprises a switch module, wherein a first end of the switch module is connected to a positive pole of a power supply for providing the excitation signal and a first end of the first capacitor, a second end of the switch module is connected to a first end of the coil, a second end of the coil is connected to a second end of the first capacitor and a negative pole of the power supply, and a control end of the switch module is connected to an output end of the processing module, for entering a conducting state when receiving a conducting signal output by the processing module, wherein the processing module is configured to output the conducting signal when detecting that a voltage across the first capacitor reaches a preset value.

[0011] In one of the embodiments, the switch module comprises:

[0012] a silicon controlled element, a first end of the silicon controlled element serving as the first end of the switch module, a second end of the silicon controlled element serving as the second end of the switch module, and a control end of the silicon controlled element serving as the control end of the switch module, for entering a conducting state when receiving a conducting signal output by the processing module and a forward current flowing through the silicon controlled element, and entering an off state when the forward current is zero, wherein the forward current is a current flowing from the first end of the silicon controlled element to the second end of the silicon controlled element;

[0013] a diode, a positive pole of the diode being connected to the second end of the silicon controlled element, and a negative pole of the diode being connected to the first end of the silicon controlled element, for conducting when the silicon controlled element enters the off state, so as to pass a reverse current, wherein the reverse current is a current flowing from the positive pole of the diode to the negative pole of the diode.

[0014] In one of the embodiments, the first resonant circuit further comprises a switch module, wherein a first end of the switch module is connected to a positive pole of a power supply for providing the excitation signal and a first end of the first capacitor, a second end of the switch module is connected to a negative pole of the power supply and a second end of the coil, a first end of the coil is connected to a second end of the first capacitor, and a control end of the switch module is connected to an output end of the processing module, for entering a conducting state when receiving a conducting signal output by the processing module, wherein the processing module is configured to output the conducting signal when detecting that a voltage across the first capacitor reaches a preset value.

[0015] In one of the embodiments, the switch module comprises:

[0016] a silicon controlled element, a first end of the silicon controlled element as a first end of the switch module, a second end of the silicon controlled element as a second end of the switch module, a control end of the silicon controlled element as a control end of the switch module, configured to enter a conducting state when a conducting signal output by the processing module is received and a forward current flowing through the silicon controlled element is positive, and enter an off state when the forward current is zero, wherein the forward current is a current flowing from the first end of the silicon controlled element to the second end of the silicon controlled element;

[0017] a diode, a positive pole of the diode connected with the second end of the silicon controlled element, a negative pole of the diode connected with the first end of the silicon controlled element, configured to conduct when the silicon controlled element enters the off state, so as to pass a reverse current, wherein the reverse current is a current flowing from the second end of the silicon controlled element to the first end of the silicon controlled element.

[0018] In one of the embodiments, the distance sensing circuit further comprises:

[0019] a second resonant circuit, a first end of the second resonant circuit connected with the first end of the silicon controlled element and the negative pole of the diode, a second end of the second resonant circuit connected with the second end of the silicon controlled element and the positive pole of the diode, configured to form a new resonant circuit with the first resonant circuit when the silicon controlled element and the diode are in the off state, to generate a new resonant frequency, the new resonant frequency used to distinguish the target resonant frequency.

[0020] In one of the embodiments, the second resonant circuit comprises:

[0021] a second capacitor, a first end of the second capacitor connected with the first end of the silicon controlled element and the negative pole of the diode;

[0022] a first resistor, a first end of the first resistor connected with a second end of the second capacitor, a second end of the first resistor connected with the second end of the silicon controlled element and the positive pole of the diode.

[0023] In a second aspect, the application provides a distance detection method, the method comprising:

[0024] obtaining a target resonant frequency in a resonant circuit when a coil of a to-be-detected magnetic part is in a sensing range of the coil;

[0025] obtaining a distance between the coil and the to-be-detected magnetic part according to a reference resonant frequency and the target resonant frequency.

[0026] The distance detection method can obtain the reference resonant frequency of the resonant circuit when the coil is not affected by the magnetic object to be detected and the target resonant frequency of the resonant circuit when the magnetic object to be detected is in the sensing range of the coil. The reference resonant frequency and the target resonant frequency can be used to determine the influence of the coil on the magnetic object to be detected. The influence of the coil on the magnetic object to be detected is related to the distance between the coil and the magnetic object to be detected. Therefore, the distance between the coil and the magnetic object to be detected can be obtained according to the reference resonant frequency and the target resonant frequency. In addition, the sensing range of the coil is wide, and the detection range of the distance sensing circuit is wide.

[0027] In one embodiment, obtaining the target resonant frequency of the resonant circuit when the magnetic object to be detected is in the sensing range of the coil includes:

[0028] Obtaining a sampling voltage across the first capacitor in the resonant circuit when the magnetic object to be detected is in the sensing range of the coil;

[0029] Obtaining the target resonant frequency according to the sampling voltage.

[0030] In one embodiment, obtaining the distance between the coil and the magnetic object to be detected according to the reference resonant frequency and the target resonant frequency includes:

[0031] Obtaining the inductance change of the coil according to the reference resonant frequency and the target resonant frequency;

[0032] Obtaining the permeability change of the magnetic object to be detected according to the inductance change;

[0033] Obtaining the distance between the coil and the magnetic object to be detected according to the permeability change.

[0034] In a third aspect, the present application provides a non-contact distance sensor, which includes an excitation module and a distance sensing circuit as described above. The output end of the excitation module is connected to the first end of the distance sensing circuit. The excitation module is used to output the excitation signal.

[0035] The advantages of the non-contact distance sensor over the prior art are basically the same as those of the distance sensing circuit over the prior art, and will not be repeated here.

[0036] In one embodiment, the excitation module includes:

[0037] A power supply for outputting the excitation signal;

[0038] A current limiting module arranged between the power supply and the distance sensing circuit, used to reduce the amplitude of the excitation signal.

[0039] In one embodiment, the current limiting module includes:

[0040] a second resistor, a first end of the second resistor being connected to a positive pole of the power supply, and a second end of the second resistor being connected to the first end of the distance sensing circuit;

[0041] a third resistor, a first end of the third resistor being connected to the second end of the distance sensing circuit, and a second end of the third resistor being connected to a negative pole of the power supply.

[0042] In a fourth aspect, the present application provides a medical device comprising the non-contact distance sensor as described above.

[0043] The advantages of the above medical device over the prior art are substantially the same as those of the above non-contact distance sensor over the prior art, and thus are not described here again. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only represent some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0045] Figure 1 a topological diagram of the distance sensing circuit in one embodiment;

[0046] Figure 2 a schematic diagram of the magnetic permeability of the coil being affected by the magnetic object to be measured;

[0047] Figure 3 a topological diagram of the distance sensing circuit in another embodiment;

[0048] Figure 4 a topological diagram of the distance sensing circuit in still another embodiment;

[0049] Figure 5 a schematic diagram of the first capacitor voltage waveform in one embodiment;

[0050] Figure 6 a schematic diagram of the current waveform in the first resonant circuit in one embodiment;

[0051] Figure 7 a topological diagram of the distance sensing circuit in still another embodiment;

[0052] Figure 8 a topological diagram of the distance sensing circuit in still another embodiment;

[0053] Figure 9 a topological diagram of the distance sensing circuit in still another embodiment;

[0054] Figure 10 A topology diagram of a distance sensing circuit in another embodiment;

[0055] Figure 11 A topology diagram of a distance sensing circuit in another embodiment;

[0056] Figure 12 A topology diagram of a distance sensing circuit in another embodiment;

[0057] Figure 13 A flowchart of a distance detection method in an embodiment;

[0058] Figure 14 and Figure 15 Internal circuit topology diagrams of a non-contact distance sensor in different embodiments.

[0059] Explanation of reference signs:

[0060] 1 - power supply, 2 - first resonant circuit, 21 - switch module, 3 - processing module, 4 - magnetic piece to be measured, 5 - second resonant circuit, 6 - current limiting module. DETAILED DESCRIPTION

[0061] In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the relevant drawings. The drawings show embodiments of the present application. However, the present application can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the specification of the present application is only for the purpose of describing specific embodiments of the present application, and is not intended to limit the present application.

[0063] It can be understood that the terms "first", "second" and the like used in the present application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first resistor can be referred to as the second resistor, and similarly, the second resistor can be referred to as the first resistor. The first resistor and the second resistor are both resistors, but they are not the same resistor.

[0064] It can be understood that "connection" in the following embodiments, if the circuits, modules, units and the like connected to each other have the transmission of electrical signals or data, should be understood as "electrical connection", "communication connection" and the like.

[0065] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", or the like, as used herein, specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. Also, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0066] In one embodiment, as shown in Figure 1 and Figure 2 The present application provides a distance sensing circuit, comprising: a first resonant circuit 2 and a processing module 3, the first resonant circuit 2 comprising a first capacitor C1 and a coil L, for resonating under the action of an excitation signal; wherein, during the resonance, if the magnetic object 4 to be measured is within the sensing range of the coil L, the resonant frequency of the first resonant circuit 2 changes; the processing module 3 is connected with the first resonant circuit 2, for acquiring the target resonant frequency of the coil L first resonant circuit 2 when the magnetic object 4 to be measured is within the sensing range of the coil L, and obtaining the distance between the coil L and the magnetic object 4 to be measured according to the reference resonant frequency and the target resonant frequency.

[0067] The power supply 1 outputs the excitation signal. The processing module 3 can include a single-chip microcomputer. The reference resonant frequency is the resonant frequency of the first resonant circuit when the coil is not affected by the magnetic object to be measured. The reference resonant frequency can be set by pre-input or measured in an environment without the influence of the magnetic object.

[0068] The above distance sensing circuit, when the magnetic object 4 to be measured is within the sensing range of the coil L, the resonant frequency of the first resonant circuit 2 changes when the coil L and the first capacitor C1 are resonating. The distance between the coil L and the magnetic object can be obtained by measuring the change of the resonant frequency, i.e. the distance between the coil L and the magnetic object 4 to be measured can be obtained according to the reference resonant frequency and the target resonant frequency. The detection range of this distance sensing circuit is wide because the sensing range of the coil L is wide. In addition, because the resonant frequency of the distance sensing circuit is only affected by the magnetic object, based on this characteristic, the interference of non-magnetic objects can be avoided, and the degree of environmental influence is small.

[0069] In one embodiment, the processing module 3 is further configured to obtain the inductance change amount of the coil L according to the reference resonant frequency and the target resonant frequency; obtain the magnetic permeability change amount of the magnetic object 4 to be measured according to the inductance change amount; and obtain the distance between the coil L and the magnetic object 4 to be measured according to the magnetic permeability change amount.

[0070] The inductance is determined by the cross-sectional area S, the total number of turns N, the length l, the magnetic permeability μ, etc. of the coil L. The inductance can be calculated by the following formula:

[0071] L = μ * N 2 S / l (1)

[0072] It can be understood that the capacitance and the coil L (the coil L can be regarded as an inductance) in the resonance control circuit together form a resonance. When a magnetic object is close to the coil L, the induced magnetic field will partially enter the magnetic material, and the magnetic permeability μ will increase, and the closer to the magnetic material, the greater the μ. According to formula (1), the inductance L of the coil L will also be larger. The formula for calculating the resonance frequency is as follows:

[0073]

[0074] Wherein, L in formula (2) is inductance, C is capacitance, and f is resonance frequency.

[0075] According to formula (2), the resonance frequency is related to the capacitance and the inductance, so the change of the inductance of the coil L will also change the resonance frequency. Since the capacitance of the first capacitor C1 can be considered to be constant, the inductance change amount of the coil L can be determined according to the reference resonance frequency and the target resonance frequency, and based on formula (1), the cross-sectional area S, the total number of turns N, and the length l of the coil L are fixed and can be obtained in advance, so the magnetic permeability change amount of the coil L can be obtained according to the inductance change amount, and the distance between the coil L and the magnetic object 4 can be determined according to the magnetic permeability change amount.

[0076] In the application, the magnetic permeability change amount-distance table can be established through multiple tests, and after the magnetic permeability change amount-distance table is stored in a specified position in advance, the distance between the coil L and the magnetic object can be obtained by searching the magnetic permeability change amount-distance table according to the magnetic permeability change amount obtained by the processing module 3. If there is no corresponding magnetic permeability change amount in the table, an interpolation algorithm can be used to determine the distance between the coil L and the magnetic object.

[0077] In one embodiment, as shown in Figure 3 The first resonance circuit 2 further comprises a switch module 21, wherein the first end of the switch module 21 is connected with the positive electrode of the power supply 1 for providing the excitation signal and the first end of the first capacitor C1, the second end of the switch module 21 is connected with the first end of the coil L, the second end of the coil L is connected with the second end of the first capacitor C1 and the negative electrode of the power supply 1, and the control end of the switch module 21 is connected with the output end of the processing module 3 for entering the conduction state when receiving the conduction signal output by the processing module 3, wherein the processing module 3 is used for outputting the conduction signal when detecting that the voltage across the first capacitor C1 reaches a preset value, that is, the processing module is used for measuring the voltage on the circuit and for controlling the switch module.

[0078] In the application, the first capacitor C1 can be fully charged in a certain time, and therefore, the processing module 3 can output the conduction signal when the charging time of the first capacitor C1 reaches the preset value.

[0079] The power supply 1 can be a program-controlled power supply 1, and the processing module 3 is connected to the control end of the power supply 1 to control the opening and closing of the power supply 1.

[0080] Specifically, when the switch module 21 is not in the conduction state, the power supply 1 charges the first capacitor C1, and when the first capacitor C1 is fully charged, the processing module 3 detects that the voltage across the first capacitor C1 reaches the preset value, and the processing module 3 outputs the conduction signal, and the switch module 21 enters the conduction state, and the first capacitor C1 is electrically connected to the coil L, and the first capacitor C1 and the coil L resonate. When the power supply 1 is a program-controlled power supply 1, the processing module 3 controls the program-controlled power supply 1 to be closed when the voltage across the first capacitor C1 reaches the preset value.

[0081] In one embodiment, as shown in Figure 4 The switch module 21 includes a silicon controlled element S1 and a diode D1. The first end of the silicon controlled element S1 is the first end of the switch module 21, the second end of the silicon controlled element S1 is the second end of the switch module 21, and the control end of the silicon controlled element S1 is the control end of the switch module 21, which is used to enter the conduction state when receiving the conduction signal output by the processing module 3 and the current flowing through the silicon controlled element S1 is a forward current, and is also used to enter the cut-off state when the forward current is zero, wherein the forward current is the current flowing from the first end of the silicon controlled element S1 to the second end of the silicon controlled element S1. The anode of the diode D1 is connected to the second end of the silicon controlled element S1, and the cathode of the diode D1 is connected to the first end of the silicon controlled element S1, which is used to conduct when the silicon controlled element S1 enters the cut-off state, so that the reverse current passes through, wherein the reverse current is the current flowing from the anode of the diode D1 to the cathode of the diode D1.

[0082] Specifically, in the initial state, the silicon controlled element S1 and the diode D1 are both in the cut-off state, the power supply 1 charges the first capacitor C1, and when the capacitor C1 is fully charged, the capacitor voltage reaches the maximum value, the processing module 3 outputs the conduction signal, the silicon controlled element S1 is turned on, and the first capacitor C1 and the coil L enter the LC resonance (the initial time is recorded as t0). Wherein, as shown in Figure 5 and Figure 6As shown, from t0 to t1: the first capacitor C1 discharges to the coil L in the positive direction through S1, the energy of the first capacitor C1 is transferred to the coil L, at this time, the positive current I on the circuit increases, and the voltage U_c1 across the first capacitor C1 decreases. From t1 to t2: due to the fact that the current on the coil L cannot be abruptly changed, the freewheeling continues; the energy on the coil L will be reversely transferred to the capacitor, the current I decreases, and the voltage U_c1 of the capacitor reversely increases, at t2, the reverse voltage U_c1 is the largest, the positive current is zero, and the thyristor S1 enters the cutoff state. From t2 to t3: the capacitor C1 discharges to the coil L in the reverse direction through the diode, at this time, the current I on the circuit reversely increases, at t3, the reverse current reaches the highest peak, and the energy is completely transferred from the capacitor C1 to the coil L. From t3 to t4: the coil L freewheels, the energy is transferred from L to C1, which causes the voltage of C1 to positively increase, at t4, the voltage of C1 is the highest. After t4, due to the unidirectional conduction characteristic of the diode D1 and the fact that the thyristor S1 is in the cutoff state, the first capacitor C1 cannot continue to discharge to the coil L through the diode D1 or the thyristor S1 after t4. From t0 to t4, one period of resonance is counted, which is T (the resonance frequency f = 1 / T).

[0083] In another embodiment, as shown in Figure 7 The first resonant circuit 2 further includes: a switch module 21, a first end of the switch module 21 is connected with a positive pole of the power supply 1 for providing an excitation signal and a first end of the first capacitor C1, a second end of the switch module 21 is connected with a negative pole of the power supply 1 and a second end of the coil L, a second end of the first capacitor C1 is connected with a first end of the coil L, and a control end of the switch module 21 is connected with an output end of the processing module 3, for entering a conduction state when receiving a conduction signal output by the processing module 3.

[0084] In the conduction state of the switch module 21, the first capacitor C1 and the coil L resonate, and through the above connection mode, the voltage across the power supply 1 body is the same as the voltage across the switch module 21, so that during the LC resonance, the voltage across the power supply 1 body is low, the power supply 1 body is less disturbed by external voltage stress, and is more secure. Therefore, in a high-voltage application environment, the circuit with the above connection mode can be used.

[0085] In one embodiment, as shown in Figure 8As shown, the switching module 21 includes a silicon controlled rectifier (SCR) element S1 and a diode D1. The first terminal of the SCR element S1 serves as the first terminal of the switching module 21, the second terminal of the SCR element S1 serves as the second terminal of the switching module 21, and the control terminal of the SCR element S1 serves as the control terminal of the switching module 21. It is used to enter a conducting state when a conduction signal is received from the processing module 3 and the current flowing through the SCR element S1 is a forward current, and also to enter a cut-off state when the forward current is zero. The forward current is the current flowing from the first terminal of the SCR element S1 to the second terminal of the SCR element S1. The anode of the diode D1 is connected to the second terminal of the SCR element S1, and the cathode of the diode D1 is connected to the first terminal of the SCR element S1. It is used to conduct when the SCR element S1 enters the cut-off state to allow reverse current to pass through. The reverse current is the current flowing from the anode of the diode D1 to the cathode of the diode D1.

[0086] Similarly, as Figure 5 and Figure 6 As shown, from t0 to t1: the first capacitor C1 discharges forward through S1 to the coil L, transferring energy from C1 to L. At this time, the forward current I increases, and the voltage U_c1 across C1 decreases. From t1 to t2: Since the current in coil L cannot change abruptly, it continues to flow. Energy in coil L flows back into the capacitor, reducing current I and increasing the capacitor voltage U_c1 in the reverse direction. At t2, U_c1 reaches its maximum in the reverse direction, and the forward current is zero, causing S1 to enter the cutoff state. From t2 to t3: capacitor C1 discharges in the reverse direction to the coil L through the diode. The current I increases in the reverse direction, reaching its peak at t3, with all energy transferred from C1 to L. From t3 to t4: the coil L continues to flow, and energy flows from L into C1, causing the voltage of C1 to rise in the forward direction. The voltage of C1 reaches its highest point at t4. During the resonance process, since the voltage across the thyristor S1 and the diode D1 is 0V, the voltage across the main body of power supply 1 remains 0V during the LC resonance period. Therefore, power supply 1 is not subjected to external voltage stress and is relatively safe.

[0087] In one embodiment, such as Figure 9 and Figure 10 As shown, the distance sensing circuit further includes a second resonant circuit 5. The first end of the second resonant circuit 5 is connected to the first end of the thyristor element S1 and the negative terminal of the diode D1. The second end of the second resonant circuit 5 is connected to the second end of the thyristor element S1 and the positive terminal of the diode D1. When the thyristor element S1 and the diode D1 are in the off state, it is used to form a new resonant circuit with the first resonant circuit 2 to generate a new resonant frequency. The new resonant frequency is used to distinguish the target resonant frequency.

[0088] It can be understood that after the time t4, the thyristor S1 and the diode D1 are in the off state, the second resonant circuit 5 and the first resonant circuit 2 jointly form a new resonant circuit, and a new resonant frequency is generated, and the new resonant frequency is obviously different from the target resonant frequency, so that the processing module 3 can distinguish the target resonant frequency, and effectively exclude the non-expected waveform after t4.

[0089] In one embodiment, as shown in Figure 11 and Figure 12 , the second resonant circuit 5 includes a second capacitor C2 and a first resistor R1. The first end of the second capacitor C2 is connected with the first end of the thyristor S1 and the negative electrode of the diode D1; the first end of the first resistor R1 is connected with the second end of the second capacitor C2, and the second end of the first resistor R1 is connected with the second end of the thyristor S1 and the positive electrode of the diode D1.

[0090] Specifically, after the time t4, the thyristor S1 is opened, and the diode D1 is reversely cut off. At this time, the first capacitor C1, the second capacitor C2, the first resistor R1 and the coil L constitute a new resonant circuit. Since the whole formed by the first capacitor C1 and the second capacitor C2 in series resonates with the coil L, and the capacitance of the whole formed by the first capacitor C1 and the second capacitor C2 in series changes, according to formula (2), the resonant frequency of the new resonant circuit at this time is different from the target resonant frequency, and the target resonant frequency can be distinguished, the accuracy of the target resonant frequency is ensured, and the accuracy of the distance between the coil L and the to-be-measured magnetic piece 4 obtained is improved. In addition, since the second resonant circuit 5 includes the first resistor R1, the electric energy is consumed through the first resistor R1, and the voltage in C1 is quickly released, so that the next distance measurement process can be quickly entered.

[0091] Exemplarily, the capacitance of the second capacitor C2 can be far less than the capacitance of the first capacitor C1. Since the capacitance of the second capacitor C2 is far less than the first capacitor C1, the series capacitance of the first capacitor C1 and the second C2 can be equivalent to C2. After the time t4, the voltage waveform obtained by the processing module 3 will be distorted, the processing module 3 can identify the distortion point, and then obtain a single LC resonant waveform, ensure the accuracy of the target resonant frequency, and improve the accuracy of the distance between the coil L and the to-be-measured magnetic piece 4 obtained.

[0092] In one embodiment, as shown in Figure 13 , the present application also provides a distance detection method, which comprises:

[0093] S1301: obtaining a target resonant frequency in a resonant circuit when a to-be-measured magnetic piece is in a sensing range of a coil.

[0094] Wherein, the reference resonance frequency is the resonance frequency of the first resonance circuit when the coil is not affected by the magnetic object to be measured. The reference resonance frequency can be set by pre-input or measured in an environment without the influence of the magnetic object.

[0095] S1302: Obtain the distance between the coil and the magnetic object to be measured according to the reference resonance frequency and the target resonance frequency.

[0096] The above distance detection method obtains the reference resonance frequency of the resonance circuit when the coil L is not affected by the magnetic object to be measured 4, and the target resonance frequency in the resonance circuit when the magnetic object to be measured 4 is in the sensing range of the coil L. According to the reference resonance frequency and the target resonance frequency, it can be determined that the coil L is affected by the magnetic object to be measured 4, and the distance between the coil L and the magnetic object to be measured 4 is related to the influence of the coil L on the magnetic object to be measured 4. Therefore, the distance between the coil L and the magnetic object to be measured 4 can be obtained according to the reference resonance frequency and the target resonance frequency. In addition, since the sensing range of the coil L is wide, the detection range of the distance sensing circuit is wide.

[0097] In one embodiment, obtaining the target resonance frequency in the resonance circuit when the magnetic object to be measured is in the sensing range of the coil includes: obtaining a sampling voltage across the first capacitor C1 in the resonance circuit when the magnetic object to be measured is in the sensing range of the coil; and obtaining the target resonance frequency according to the sampling voltage.

[0098] As shown in Figure 5 , the resonance period T can be obtained according to the waveform of the sampling voltage, and then the target resonance frequency (target resonance frequency f = 1 / T) is obtained.

[0099] In one embodiment, obtaining the distance between the coil and the magnetic object to be measured according to the reference resonance frequency and the target resonance frequency includes: obtaining the inductance change amount of the coil according to the reference resonance frequency and the target resonance frequency; obtaining the magnetic permeability change amount of the magnetic object to be measured according to the inductance change amount; and obtaining the distance between the coil and the magnetic object to be measured according to the magnetic permeability change amount.

[0100] Wherein, the inductance is determined by the cross-sectional area S of the coil L, the total number of turns N, the length l, the magnetic permeability μ, etc. The inductance can be calculated by the following formula:

[0101] L = μ * N 2 * / l (1)

[0102] It can be understood that the capacitor in the resonance control circuit and the coil L (the coil L can be regarded as inductance) together form a resonance. When a magnetic object is close to the coil L, the induced magnetic field will partially enter the magnetic material, and the magnetic permeability μ will increase. The closer to the magnetic material, the larger the μ. According to formula (1), the inductance L of the coil L will also be larger. The calculation formula of the resonance frequency is as follows:

[0103]

[0104] Wherein, L in formula (2) is inductance, C is capacitance, and f is resonance frequency.

[0105] According to formula (2), the resonance frequency is related to the capacitance and the inductance, and the resonance frequency will change when the inductance of the coil L changes. Since the capacitance of the first capacitor C1 can be considered unchanged, the inductance change of the coil L can be determined according to the reference resonance frequency and the target resonance frequency. According to formula (1), the cross-sectional area S, the total number of turns N, and the length l of the coil L are fixed and can be obtained in advance. Therefore, the permeability change of the coil L can be obtained according to the inductance change, and the distance of the coil L from the magnetic object can be determined according to the permeability change and the permeability change-distance table.

[0106] In one embodiment, the present application also provides a non-contact distance sensor, comprising an excitation module and a distance sensing circuit as described above, the output end of the excitation module is connected with the first end of the distance sensing circuit, and the excitation module is used to output an excitation signal.

[0107] The advantages of the above-mentioned non-contact distance sensor over the prior art are generally the same as those of the above-mentioned distance sensing circuit over the prior art, and will not be repeated here.

[0108] In one embodiment, the excitation module comprises: a power supply 1 for outputting an excitation signal; and a current limiting module 6 arranged between the power supply 1 and the distance sensing circuit, for reducing the amplitude of the excitation signal.

[0109] In one embodiment, as shown in Figure 14 and Figure 15 the current limiting module 6 comprises: a second resistor R2, the second resistor R2 is connected with the positive pole of the power supply 1, and the second end of the second resistor R2 is connected with the first end of the distance sensing circuit; and a third resistor R3, the first end of the third resistor R3 is connected with the second end of the distance sensing circuit, and the second end of the third resistor R3 is connected with the negative pole of the power supply 1.

[0110] Wherein, the size of the second resistor R2 and the third resistor R3 can be determined according to the desired charging time (the expected charging time of the first capacitor C1).

[0111] In application, the current limiting module 6 can only include one resistor, or can include three or more resistors, as long as the amplitude of the excitation signal (the charging current of the first capacitor C1 by the power supply 1) can be reduced to the desired value through the current limiting module 6.

[0112] In one embodiment, the present application also provides a medical device comprising a non-contact distance sensor as described in the above embodiments.

[0113] The medical device can be a medical device for a blood oxygenation system. The advantages of the medical device over the prior art are substantially the same as those of the non-contact distance sensor over the prior art, and will not be described here.

[0114] In the description of the present specification, the description referring to the terms "some embodiments", "other embodiments", "ideal embodiments", and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0115] The technical features of the above-described embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered as falling within the scope of the present specification.

[0116] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A distance sensing circuit, characterized by, The method comprises the following steps: A first resonant circuit comprising a first capacitor and a coil is used to resonate under the action of an excitation signal; wherein, during the resonance, if the magnetic object to be measured is within the sensing range of the coil, the resonant frequency of the first resonant circuit changes; A processing module is connected to the first resonant circuit, used to obtain the target resonant frequency of the first resonant circuit when the magnetic object to be measured is within the sensing range of the coil, and to obtain the distance between the coil and the magnetic object to be measured according to the reference resonant frequency and the target resonant frequency; The first resonant circuit further comprises a switch module, wherein the first end of the switch module is connected to the positive pole of a power supply for providing the excitation signal and the first end of the first capacitor, the second end of the switch module is connected to the first end of the coil, the second end of the coil is connected to the second end of the first capacitor and the negative pole of the power supply, and the control end of the switch module is connected to the output end of the processing module, used to enter the conduction state when receiving the conduction signal output by the processing module, wherein the processing module is used to output the conduction signal when detecting that the voltage across the first capacitor reaches a preset value; or The first resonant circuit further comprises a switch module, wherein the first end of the switch module is connected to the positive pole of a power supply for providing the excitation signal and the first end of the first capacitor, the second end of the switch module is connected to the negative pole of the power supply and the second end of the coil, the second end of the first capacitor is connected to the first end of the coil, and the control end of the switch module is connected to the output end of the processing module, used to enter the conduction state when receiving the conduction signal output by the processing module, wherein the processing module is used to output the conduction signal when detecting that the voltage across the first capacitor reaches a preset value.

2. The distance sensing circuit of claim 1, wherein, The processing module is further used to obtain the inductance change amount of the coil according to the reference resonant frequency and the target resonant frequency, to obtain the permeability change amount of the magnetic object to be measured according to the inductance change amount, and to obtain the distance between the coil and the magnetic object to be measured according to the permeability change amount.

3. The distance sensing circuit of claim 1, wherein, The switch module comprises: A silicon controlled element, the first end of the silicon controlled element serving as the first end of the switch module, the second end of the silicon controlled element serving as the second end of the switch module, and the control end of the silicon controlled element serving as the control end of the switch module, used to enter the conduction state when receiving the conduction signal output by the processing module and the current flowing through the silicon controlled element is a forward current, and used to enter the cutoff state when the forward current is zero, wherein the forward current is the current flowing from the first end of the silicon controlled element to the second end of the silicon controlled element; A diode, the positive pole of the diode being connected to the second end of the silicon controlled element, and the negative pole of the diode being connected to the first end of the silicon controlled element, used to conduct when the silicon controlled element enters the cutoff state to allow a reverse current to pass through, wherein the reverse current is the current flowing from the positive pole of the diode to the negative pole of the diode.

4. The distance sensing circuit of claim 3, wherein, The distance sensing circuit further comprises: A second resonant circuit, a first end of the second resonant circuit being connected with the first end of the thyristor and the negative pole of the diode, a second end of the second resonant circuit being connected with the second end of the thyristor and the positive pole of the diode, for forming a new resonant circuit with the first resonant circuit when the thyristor and the diode are in the off state, and generating a new resonant frequency, the new resonant frequency being used for distinguishing the target resonant frequency.

5. The distance sensing circuit of claim 4, wherein, The second resonant circuit comprises: A second capacitor, a first end of the second capacitor being connected with the first end of the thyristor and the negative pole of the diode; A first resistor, a first end of the first resistor being connected with a second end of the second capacitor, a second end of the first resistor being connected with the second end of the thyristor and the positive pole of the diode.

6. A distance detection method characterized by, The method applied to the processing module in the distance sensing circuit according to any one of claims 1 to 5, the method comprising: Obtaining a target resonant frequency in the resonant circuit when the to-be-detected magnetic piece is in the sensing range of the coil; Obtaining the distance between the coil and the to-be-detected magnetic piece according to the reference resonant frequency and the target resonant frequency.

7. The distance detection method according to claim 6, characterized by, The method of obtaining the target resonant frequency in the resonant circuit when the to-be-detected magnetic piece is in the sensing range of the coil comprises: Obtaining a sampling voltage between the first capacitor and the second capacitor in the resonant circuit when the to-be-detected magnetic piece is in the sensing range of the coil; Obtaining the target resonant frequency according to the sampling voltage.

8. The distance detection method according to claim 7, characterized by, The method of obtaining the distance between the coil and the to-be-detected magnetic piece according to the reference resonant frequency and the target resonant frequency comprises: Obtaining a change amount of inductance of the coil according to the reference resonant frequency and the target resonant frequency; Obtaining a change amount of magnetic permeability of the to-be-detected magnetic piece according to the change amount of inductance; Obtaining the distance between the coil and the to-be-detected magnetic piece according to the change amount of magnetic permeability.

9. A non-contact distance sensor characterized by, The distance sensing circuit according to any one of claims 1 to 5, and an excitation module, an output end of the excitation module being connected with a first end of the distance sensing circuit, the excitation module being used for outputting the excitation signal.

10. The non-contact distance sensor of claim 9, wherein, The excitation module comprises: A power supply, used for outputting the excitation signal; A current limiting module, arranged between the power supply and the distance sensing circuit, used for reducing the amplitude of the excitation signal.

11. The non-contact distance sensor of claim 10, wherein, The current limiting module comprises: A second resistor, connected with a positive pole of the power supply, a second end of the second resistor being connected with the first end of the distance sensing circuit; A third resistor, a first end of the third resistor being connected with a second end of the distance sensing circuit, a second end of the third resistor being connected with a negative pole of the power supply.

12. A medical device, characterized by The non-contact distance sensor according to any one of claims 9 to 11.

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