Capacitive proximity sensor
By implementing specific voltage control and acquisition stages in the capacitive sensor and calculating the average difference in capacitor voltage, the problem of false detection in humid environments is solved, and accurate detection of human presence is achieved in the presence of moisture.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- VTESCO TECH GMBH
- Filing Date
- 2022-05-10
- Publication Date
- 2026-07-14
AI Technical Summary
In wet or rainy conditions, capacitive sensors are prone to falsely detecting the presence of a human body, leading to inappropriate triggering of vehicle functions.
The system employs specific voltage control and acquisition phases, including initialization and first and second acquisition phases. It detects the presence of a human body by calculating the average voltage difference between the detection capacitor and the storage capacitor, thus eliminating moisture interference.
This effectively avoids the interference of moisture on the capacitive sensor, ensuring accurate detection of human presence in humid environments and preventing false triggering of vehicle functions.
Smart Images
Figure CN117296251B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of capacitive sensors, and more particularly to capacitive proximity sensors and methods of using such sensors. Background Technology
[0002] It is known to use capacitive sensors in motor vehicles to detect the presence of a person and trigger vehicle functions. For example, it is known to install a capacitive sensor in the handle of an opening component to detect the presence of a vehicle user's hand, thereby unlocking the opening component, or to install a capacitive sensor under the trunk of a vehicle to detect the passage of a foot, thereby opening it.
[0003] Such detection is possible because proximity to a human body increases the electrostatic field, thus increasing the capacitance of the capacitor. Therefore, in a known solution called a "Differential Capacitive Voltage Divider" (DC VD), the capacitive sensor includes electrodes connected to a detection circuit and a microcontroller. The detection circuit includes a capacitor and a switch, and the microcontroller enables control of the switch to perform measurements based on instructions stored in the microcontroller's memory.
[0004] The measurements are performed as a series of consecutive analog-to-digital conversions, for example, eight. The microcontroller performs the measurements as soon as it is available (i.e., when it is not processing instructions), so the time between two measurements is not predefined. In each measurement, the microcontroller periodically controls a switch to open and close to fill and then drain a detection capacitor into a storage capacitor, and then measures the voltage across the storage capacitor to determine its value. When no one is near the sensor, the value of the detection capacitor remains below a certain threshold for a predetermined number of consecutive measurements, for example, three. When someone is present, the value of the detection capacitor exceeds this threshold during the predetermined number of consecutive measurements.
[0005] However, in wet or rainy conditions, the detection capacitance value may exceed a threshold over a predetermined number of consecutive values. This can lead to the false detection of a person's presence, thereby inappropriately triggering certain vehicle functions, such as unlocking or opening components.
[0006] Therefore, it has been proven beneficial to at least partially remedy these shortcomings. Summary of the Invention
[0007] Therefore, the present invention relates to a capacitive proximity sensor, comprising a detection circuit, a DC voltage generator, and a microcontroller. The detection circuit includes a detection capacitor, a storage capacitor, and a switch. The microcontroller is configured to control the switch of the detection circuit. Notably, the microcontroller is configured to:
[0008] a) During the first initialization phase, the voltage applied across the detection capacitor is controlled to be equal to half the voltage delivered by the DC voltage generator.
[0009] b) During the first acquisition phase following the first initialization phase, which is repeated N times, where N is a natural number greater than or equal to 3, the following sub-steps are performed:
[0010] i) Control the discharge of the detection capacitor to reach a predefined first duration, then
[0011] ii) Control the detection capacitor to charge for the predefined first duration, then iii) Control the charge to transfer from the detection capacitor to the storage capacitor to obtain the voltage value across the storage capacitor via analog-to-digital conversion.
[0012] c) During the second initialization phase following the first acquisition phase, the voltage applied across the detection capacitor is controlled to be equal to half the voltage delivered by the DC voltage generator.
[0013] d) During the second acquisition phase following the second initialization phase, which is repeated N times, the following sub-steps are executed:
[0014] i) Control the detection capacitor to charge for a predefined second duration, then
[0015] ii) Control the discharge of the detection capacitor for the predefined second duration, and then iii) control the transfer of charge from the storage capacitor to the detection capacitor to obtain the voltage value across the storage capacitor via analog-to-digital conversion, and
[0016] e) Determine the value of the detection parameter equal to the difference between the first mean and the second mean, wherein the first mean is defined as the average of the voltage values obtained at the end of each repetition in the first acquisition phase, and wherein the second mean is defined as the average of the voltage values at the end of each repetition in the second acquisition phase, and
[0017] f) Compare the difference between the determined first mean and the determined second mean with the predefined detection threshold.
[0018] The disclosure of this invention and the description of the accompanying drawings mention a detection capacitor and a storage capacitor. Those skilled in the art will understand that the detection capacitor and the storage capacitor can be referred to in an equivalent manner. Similarly, the value of capacitance and the capacitance of a capacitor can be referred to in an equivalent manner.
[0019] It can be implicitly understood that, in this invention, when no one is present near the sensor, the value of the storage capacitor Cext is equal to the value of the detection capacitor Ce. This is a conventional characteristic of storage capacitors in the field of this invention. Throughout the text, it is assumed that no one is near the sensor when there is no one within a radius of 50 cm or even 20 cm around the sensor.
[0020] In other words, in step b), the detection capacitor is controlled to discharge for a duration equal to a predefined first duration, and then the detection capacitor is controlled to charge for a duration equal to the same defined first duration.
[0021] Similarly, in step d), the detection capacitor is controlled to charge for a duration equal to a predefined second duration, and then the detection capacitor is controlled to discharge for a duration equal to the same defined second duration.
[0022] In step b), the sub-steps are advantageously performed one after another. Similarly, in step d), the sub-steps are advantageously performed one after another.
[0023] Therefore, the sensor and microcontroller enable the determination of a person's presence, and the presence of moisture in the sensor's surrounding environment does not interfere with the measurements performed by the sensor. In fact, the first and second acquisition phases eliminate the influence of water presence on the detection measurements performed by the microcontroller.
[0024] Advantageously, step f) includes detecting the presence of a person when the difference between the determined first mean and the determined second mean is greater than a predefined detection threshold. In other words, step f) then includes providing information about the presence of an individual when the difference is greater than the predefined detection threshold. Thus, the sensor according to the invention enables the performance of measurements for detecting the presence of a person in the vicinity.
[0025] The present invention also relates to vehicles including the sensors and microcontrollers described above.
[0026] Therefore, when the sensor is installed in, for example, the handle of a vehicle's opening mechanism, the sensor and microcontroller enable the prevention of false detections due to moisture in the vehicle's surrounding environment.
[0027] Finally, the present invention also relates to a method implemented by a microcontroller of a sensor as described above, the notable feature of which is that it includes:
[0028] a) First initialization phase, wherein a voltage is applied across the detection capacitor, the value of which is equal to half the voltage delivered by the DC voltage generator.
[0029] b) The first acquisition phase following the first initialization phase, which is repeated N times, where N is a natural number greater than or equal to 3, includes the following sub-steps:
[0030] i) Control the discharge of the detection capacitor to reach a predefined first duration, then
[0031] ii) Control the detection capacitor to charge for the predefined first duration, then
[0032] iii) Control the transfer of charge from the detection capacitor to the storage capacitor so as to obtain the voltage value across the storage capacitor through analog-to-digital conversion.
[0033] c) A second initialization phase following the first acquisition phase, wherein a voltage is applied across the detection capacitor, the value of which is equal to half the voltage delivered by the DC voltage generator.
[0034] d) The second acquisition phase following the second initialization phase, which is repeated N times, includes the following sub-steps:
[0035] i) Control the detection capacitor to charge for a predefined second duration.
[0036] ii) Control the discharge of the detection capacitor to reach the predefined second duration.
[0037] iii) Control the transfer of charge from the storage capacitor to the detection capacitor so as to obtain the voltage value across the detection capacitor through analog-to-digital conversion.
[0038] e) Determine the value of the detection parameter equal to the difference between the first mean and the second mean, wherein the first mean is defined as the average of the voltage values obtained at the end of each repetition in the first acquisition phase, and wherein the second mean is defined as the average of the voltage values at the end of each repetition in the second acquisition phase, and
[0039] f) Compare between the following two: the difference between the determined first mean and the determined second mean, and the predefined detection threshold.
[0040] In other words, in step b), the detection capacitor is controlled to discharge for a duration equal to a predefined first duration, and then the detection capacitor is controlled to charge for a duration equal to the same defined first duration.
[0041] Similarly, in step d), the detection capacitor is controlled to charge for a duration equal to a predefined second duration, and then the detection capacitor is controlled to discharge for a duration equal to the same defined second duration.
[0042] In step b), the sub-steps are advantageously performed one after another. Similarly, in step d), the sub-steps are advantageously performed one after another.
[0043] Advantageously, step f) includes detecting the presence of a person when the difference between the determined first mean and the determined second mean is greater than a predefined detection threshold. In other words, step f) then includes providing information about the presence of an individual when the difference is greater than the predefined detection threshold. Thus, the method according to the invention forms a method for detecting the presence of a person near a sensor as described above.
[0044] The present invention also relates to a computer program product, notably comprising a set of program code instructions that, when executed by one or more processors, configure the one or more processors to implement the methods described above. The one or more processors pertain to a microcontroller for a sensor according to the present invention. Attached Figure Description
[0045] Other features and advantages of the invention will become more apparent from the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:
[0046] Figure 1 The sensor and microcontroller according to the present invention are illustrated schematically.
[0047] Figure 2 A method for detecting the presence of a person according to the present invention is shown.
[0048] Figure 3 It is shown in accordance with Figure 2 The method detects the voltage change across the capacitor and the voltage change across the capacitor of the water equivalent model during the first initialization phase.
[0049] Figure 4 It is shown in accordance with Figure 2 The method detects the voltage change across the capacitor and the voltage change across the capacitor of the water equivalent model during the second initialization phase. Detailed Implementation
[0050] The sensor according to the invention is a capacitive proximity sensor, designed to be installed in a motor vehicle to detect the presence of a person near the sensor for the purpose of performing vehicle functions. In particular, the sensor can be installed in the door handle or near the trunk of a motor vehicle to detect the presence of a user, thereby enabling the unlocking of the vehicle's opening mechanism.
[0051] Figure 1 An example of the electronic circuitry of a sensor 1 according to the present invention is shown. The sensor 1 includes a detection circuit 10 and a microcontroller 20.
[0052] In this example, the detection circuit 10 is a DCVD type circuit.
[0053] The detection circuit 10 includes a first electrode connected to a printed circuit board, which includes a capacitor (labeled Ce) called the "detection capacitor" and a capacitor (labeled Cext) called the "storage capacitor". A first switch T1 is positioned between the positive terminal of the voltage generator Vcc and the first terminal of the detection capacitor Ce. A second switch T2 is positioned between the first terminal of the detection capacitor Ce and the first terminal of the storage capacitor Cext. The second terminals of both the detection capacitor Ce and the storage capacitor Cext, as well as the negative terminal of the voltage generator Vcc, are grounded M. A third switch T3 is connected between the first and second terminals of the storage capacitor Cext, i.e., in parallel with the storage capacitor Cext.
[0054] The fourth switch T4 is connected to the power supply voltage generator Vcc on one side and to the first terminal of the storage capacitor Cext on the other side. The fifth switch T5 is connected to the first terminal of the sensing capacitor on one side and to the second terminal of the sensing capacitor Ce on the other side.
[0055] The first terminal of the storage capacitor Cext is electrically connected to the microcontroller 20.
[0056] The microcontroller 20 implements an analog-to-digital converter (ADC), which enables the quantization of the voltage stored in the storage capacitor Cext.
[0057] The microcontroller 20 is configured to control the switches T1, T2, T3, T4, and T5 of the detection circuit 10 to periodically charge the detection capacitor Ce and then discharge it into the storage capacitor Cext, and to measure the voltage across the storage capacitor Cext in order to detect whether a person is near the sensor 1.
[0058] In addition, the presence of water or moisture in the vehicle's surrounding environment when the vehicle is in a wet environment, especially when it is raining, is electronically modeled using capacitor Cw and resistor Rw. Capacitor Cw and resistor Rw are connected in series with each other and are bypassed together with detection capacitor Ce.
[0059] Implementation
[0060] refer to Figure 2 An embodiment of the method for detecting the presence of a person according to the present invention, implemented by the microcontroller 20, will now be described.
[0061] Before implementing this method, the second switch T2, the third switch T3, and the fifth switch T5 are closed, and the first switch T1 and the fourth switch T4 are open.
[0062] The method first includes a first initialization phase, Pinit1.
[0063] refer to Figure 3 The first initialization phase, Pinit1, is defined between the initial time t0 and the first time t1, and the first time t1 is defined after the initial time t0.
[0064] The first initialization phase, Pinit1, includes: a sub-step controlling the discharge of the detection capacitor Ce for a predefined time period, followed by a sub-step controlling the charging of the detection capacitor Ce for the same time period, and then a sub-step controlling the transfer of charge from the detection capacitor Ce to the storage capacitor Cext. Thus, in the absence of anyone near the sensor, the voltage applied across the detection capacitor Ce should be equal to half the voltage delivered by the DC voltage generator Vcc. The same voltage is also applied across the capacitor Cw of the water equivalent model. The predefined time period is approximately 10 microseconds.
[0065] More specifically, during the controlled discharge sub-step, the microcontroller 20 controls the second switch T2 to open for a predefined time period. The predefined time period is approximately 10 microseconds. The third switch T3 and the fifth switch T5 are closed, and the first switch T1 and the fourth switch T4 are open.
[0066] During the controlled charging sub-step, the microcontroller 20 controls the first switch T1 to close for a predefined time period and controls the fifth switch T5 to open for a predefined time period (the second switch T2 and the fourth switch T4 are already open and the third switch T3 is already closed). This allows the voltage generator Vcc to charge the sensing capacitor Ce.
[0067] During the sub-step of controlling the transfer of charge from the detection capacitor Ce to the storage capacitor Cext, the microcontroller 20 controls the first switch T1 and the third switch T3 to open and controls the second switch T2 to close (the fourth and fifth switches T4 and T5 are open), which allows the charge to be transferred from the detection capacitor Ce to the storage capacitor Cext through current conduction.
[0068] It can be implicitly understood that the characteristic that the voltage across the sensing capacitor is equal to half the voltage delivered by the DC voltage generator Vcc when no one is near the sensor is obtained by means of:
[0069] - The aforementioned steps of discharging the detection capacitor Ce, charging the detection capacitor Ce, and transferring charge between the two capacitors by connecting them in series and grounding (see the previous paragraph); and
[0070] - When no one is near the sensor, the capacitances Ce and Cext take the same value.
[0071] Following the first initialization phase Pinit1, the method includes a first acquisition phase P1, which includes: a sub-step E11 of controlling the discharge of the detection capacitor Ce for a predefined duration d1, followed by a sub-step E12 of controlling the charging of the detection capacitor Ce for the predefined duration d1, followed by a sub-step E13 of controlling the transfer of charge from the detection capacitor Ce to the storage capacitor Cext, so as to obtain the voltage value across the storage capacitor Cext by analog-to-digital conversion.
[0072] The predefined duration d1 is approximately 10 microseconds.
[0073] More specifically, during the sub-step E11 of controlling the discharge, the microcontroller 20 controls the second switch T2 to open and the third switch T3 and the fifth switch T5 to close for a predefined duration d1 from the first time t1 to the second time t2. The first switch T1 and the fourth switch T4 are open.
[0074] refer to Figure 3 During step E11, the voltage Vce across capacitor Ce is detected to decrease until it reaches zero. Furthermore, the voltage Vw across capacitor Cw in the electronic equivalent model of water also decreases.
[0075] More specifically, the voltage Vw at the second time t2 is equal to the following voltage:
[0076]
[0077] Where, σ 水 The time constant corresponding to water.
[0078] During the sub-step E12 of controlling the charging, the microcontroller 20 controls the first switch T1 to close and the fifth switch T5 to open for a predefined duration d1 from the second time t2 to the third time t3 (the second switch T2 and the fourth switch T4 are already open, and the third switch T3 is already closed). This enables the voltage generator Vcc to charge the sensing capacitor Ce.
[0079] Therefore, the voltage Vce across the sensing capacitor Ce increases to the voltage provided by the voltage generator Vcc. Furthermore, the voltage Vw across the capacitor Cw in the electronic equivalent model of water also increases. More specifically, the value of the voltage Vw at the third time t3 is equal to the following voltage:
[0080]
[0081]
[0082]
[0083] Therefore, at the third time t3, since d1 < σ水 Therefore, the voltage Vw(t3) is almost equal to Vcc / 2. In other words, when no one is near the sensor, the voltage Vw is again equal to the voltage applied to capacitor Cw during the first initialization phase Pinit1, which is half the voltage delivered by the DC voltage generator Vcc. In fact, since the sub-steps E11 for controlling discharge and E12 for controlling charging have equal durations, the equivalent model of water's capacitor Cw discharges as much as it charges. Therefore, capacitor Cw does not affect the voltage value of the detection capacitor Ce.
[0084] During sub-step E13, in which charge is transferred from the detection capacitor Ce to the storage capacitor Cext, the microcontroller 20 controls the first switch T1 and the third switch T3 to open and controls the second switch T2 to close (the fourth and fifth switches T4 and T5 are open), which allows charge to be transferred from the detection capacitor Ce to the storage capacitor Cext by current conduction.
[0085] At the end of each sub-step E13 of the control transfer, the microcontroller 20 obtains the voltage value across the storage capacitor Cext by performing analog-to-digital conversion. In other words, the voltage across the storage capacitor Cext is then determined, for example, by performing analog-to-digital conversion in the microcontroller 20.
[0086] Furthermore, the first acquisition phase P1 is repeated N times, where N is a natural number greater than or equal to 3. Preferably, the first acquisition phase P1 is executed four times.
[0087] refer to Figure 2 After the last repetition of the first acquisition phase P1, the method includes a second initialization step Pinit2.
[0088] refer to Figure 4 The second initialization phase, Pinit2, is defined between time t4 and time t5, with time t5 defined after time t4. Pinit2 includes: a sub-step controlling the charging of the detection capacitor Ce for a predefined second time period; a sub-step controlling the discharging of the detection capacitor Ce for the same predefined second time period; and a sub-step controlling the transfer of charge from the storage capacitor Cext to the detection capacitor Ce. Thus, when the value of the detection capacitor Ce equals the value of the storage capacitor Cext (in the absence of anyone near the sensor), the voltage applied across the detection capacitor Ce should be equal to half the voltage delivered by the DC voltage generator Vcc. The same voltage is then applied across the capacitor Cw of the water's equivalent model. The predefined second time period is approximately 10 microseconds and is specifically equal to the value of the first time period.
[0089] More specifically, during the sub-step of controlling charging, the microcontroller 20 controls the first switch T1 and the fourth switch T4 to close and controls the second switch T2 to open (the third switch T3 and the fifth switch T5 to open) during the second time period.
[0090] During the sub-step of controlling the discharge, the microcontroller 20 controls the first switch T1 to open (the second switch T2 and the third switch T3 have already been opened) and controls the fifth switch T5 to close (the fourth switch T4 has already been closed) during the second time period.
[0091] During the sub-step of controlling the transfer of charge from the storage capacitor Cext to the detection capacitor Ce, the microcontroller 20 controls the fourth switch T4 and the fifth switch T5 to open and controls the second switch T2 to close (the first switch T1 and the third switch T3 are open).
[0092] It can be implicitly understood that the characteristic that the voltage across the sensing capacitor is equal to half the voltage delivered by the DC voltage generator Vcc when no one is near the sensor is obtained by means of:
[0093] - The aforementioned steps of charging the detection capacitor Ce, discharging the detection capacitor Ce, and transferring charge between the two capacitors by connecting them in series and grounding (see the previous paragraph); and
[0094] - When no one is near the sensor, the capacitances Ce and Cext take the same value.
[0095] Following the second initialization phase Pinit2, the method includes a second acquisition phase P2, which includes: a sub-step E21 of controlling the detection capacitor Ce to charge for a predefined second duration d2, followed by a sub-step E22 of controlling the detection capacitor Ce to discharge while simultaneously charging the storage capacitor Cext for a predefined second duration d2, followed by a sub-step E23 of controlling the charge to transfer from the storage capacitor Cext to the detection capacitor Ce, so as to obtain the voltage value across the storage capacitor Cext through analog-to-digital conversion.
[0096] The predefined second duration d2 is approximately 10 microseconds. Preferably, the second duration d2 is equal to the first duration d1.
[0097] More specifically, during the sub-step E21 of controlling charging, the microcontroller 20 controls the first switch T1 and the fourth switch T4 to close and controls the second switch T2 to open (the third switch T3 and the fifth switch T5 to open) during a predefined second duration d2 from the fifth time t5 to the sixth time t6.
[0098] During step E21, the voltage Vce across capacitor Ce is increased until it equals the voltage supplied by voltage generator Vcc. Furthermore, the voltage Vw across capacitor Cw in the electronic equivalent model of water also increases as capacitor Cw is charged.
[0099] More specifically, the voltage Vw at the sixth time t6 is equal to the following voltage:
[0100]
[0101] During the sub-step E22 of controlling the discharge, the microcontroller 20 controls the first switch T1 to open (the second switch T2 and the third switch T3 have already been opened) and controls the fifth switch T5 to close (the fourth switch T4 has already been closed) during a predefined second duration d2 from the sixth time t6 to the seventh time t7.
[0102] During step E22, the voltage Vce across capacitor Ce is detected to decrease until it reaches zero. Furthermore, the voltage Vw across capacitor Cw in the electronic equivalent model of water also decreases.
[0103] More specifically, the voltage Vw at the seventh time t7 is equal to the following voltage:
[0104]
[0105]
[0106]
[0107] Therefore, at the seventh time t7, since d2 < σ 水 Therefore, the voltage Vw(t7) is almost equal to Vcc / 2. In other words, when no one is near the sensor, the voltage Vw is again equal to the voltage applied to capacitor Cw during the second initialization phase Pinit2, which is half the voltage delivered by the DC voltage generator Vcc. In fact, since the sub-steps E21 for controlling charging and E22 for controlling discharging have equal durations, the equivalent model of water's capacitor Cw charges and discharges as much. Therefore, capacitor Cw does not affect the voltage value of the detection capacitor Ce.
[0108] During sub-step E23, in which the charge is transferred from the storage capacitor Cext to the detection capacitor Ce, the microcontroller 20 controls the fourth switch T4 and the fifth switch T5 to open and controls the second switch T2 to close (the first switch T1 and the third switch T3 are open) so as to discharge the storage capacitor Cext into the detection capacitor Ce.
[0109] At the end of each sub-step E23 of the control transfer, the microcontroller 20 then determines the voltage across the storage capacitor Cext by performing analog-to-digital conversion.
[0110] Furthermore, the second acquisition phase P2 is repeated N times, where N is a natural number greater than or equal to 3. Preferably, the second acquisition phase P2 is performed four times.
[0111] Once the first acquisition phase P1 and the second acquisition phase P2 have been executed, the method includes a step P3 of calculating detection parameters. During this step, the microcontroller 20 determines the difference between a first mean and a second mean, the first mean being equal to the mean of the voltage values obtained at the end of each repetition of the first acquisition phase P1, and the second mean being equal to the mean of the voltage values obtained at the end of each repetition of the second acquisition phase P2.
[0112] After calculating step P3, the microcontroller 20 analyzes the difference between the determined first mean and the determined second mean, where the first mean increases when a user is present near sensor 1, and the determined second mean decreases when a user is present near sensor 1. The method then includes a step P4 comparing the difference between the determined first mean and the determined second mean with a predefined detection threshold. Step P4 advantageously includes providing information about the presence or absence of a human operator near sensor 1 (human presence detection) when the difference between the determined first mean and the determined second mean is greater than the predefined detection threshold.
[0113] Therefore, the method implemented by the microcontroller 20 enables the prevention of interference from the presence of moisture in the environment surrounding the sensor 1 with the measurements performed by the sensor 1, in particular by eliminating the capacitance Cw of the equivalent model to the capacitance of the storage capacitor Cext or the detection capacitor Ce and thus the effect on the measurements performed by the microcontroller 20.
Claims
1. A capacitive proximity sensor (1), comprising: - The detection circuit (10) includes a measuring electrode forming a detection capacitor (Ce), a storage capacitor (Cext), and switches (T1, T2, T3, T4, T5), wherein, when no one is present near the sensor, the value of the storage capacitor (Cext) is equal to the value of the detection capacitor (Ce). - A DC voltage generator (Vcc) that can be connected to a sense capacitor (Ce) and / or a storage capacitor (Cext), and - A microcontroller (20) configured to control switches (T1, T2, T3, T4, T5) of a detection circuit (10), wherein a first switch (T1) connects a detection capacitor (Ce) to a DC voltage generator (Vcc), a second switch connects the detection capacitor (Ce) and a storage capacitor (Cext) in series, a third switch (T3) short-circuits the storage capacitor (Cext), a fourth switch (T4) connects the storage capacitor (Cext) to the DC voltage generator (Vcc), and a fifth switch (T5) short-circuits the detection capacitor (Ce), characterized in that the microcontroller (20) is configured as follows: a) During the first initialization phase (Pinit1), a control switch is used to transfer charge between the detection capacitor (Ce) and the storage capacitor (Cext), such that the detection capacitor (Ce)... The voltage across the two terminals is equal to the voltage across the storage capacitor (Cext), and in the absence of anyone near the sensor, it is equal to half the voltage delivered by the DC voltage generator (Vcc). b) The first acquisition phase (P1) following the first initialization phase (Pinit1) During this period, the first acquisition phase (P1) is repeated N times, where N is a natural number greater than or equal to 3, and the following sub-steps are executed: i) Control the discharge of the detection capacitor (Ce) to reach a predefined first duration (d1), then ii) Control the detection capacitor (Ce) to charge for the predefined first duration (d1), then iii) Controlling the transfer of charge from the detection capacitor (Ce) to the storage capacitor (Cext), Then, the voltage across the storage capacitor (Cext) is measured using analog-to-digital conversion. c) The second initialization phase (Pinit2) following the first acquisition phase (P1). During this period, the control switch causes the charge to move between the detection capacitor (Ce) and the storage capacitor (Cext). The voltage across the sensing capacitor (Ce) is transferred to the storage capacitor (Cext), making the voltage across the sensing capacitor equal to the voltage across the storage capacitor (Cext). The voltage across the terminals, and in the absence of anyone near the sensor, is equal to half the voltage delivered by the DC voltage generator (Vcc). d) The second acquisition phase (P2) following the second initialization phase (Pinit2) During this period, the second acquisition phase (P2) is repeated N times, executing the following sub-steps: i) Control the detection capacitor (Ce) to charge for a predefined second duration (d2), then ii) Control the discharge of the detection capacitor (Ce) to reach the predefined second duration (d2), then iii) Controlling the transfer of charge from the storage capacitor (Cext) to the detection capacitor (Ce), Then, the voltage across the storage capacitor (Cext) is measured using analog-to-digital conversion. e) Determine the value of the detection parameter equal to the difference between the first mean and the second mean, wherein the first mean is defined as the average of the voltage values measured at the end of each repetition in the first acquisition phase (P1), and wherein the second mean is defined as the average of the voltage values measured at the end of each repetition in the second acquisition phase (P2), and f) Compare the difference between the determined first mean and the determined second mean with the predefined detection threshold.
2. The sensor (1) according to the preceding claim, wherein, The value of the sensing capacitor (Ce) is equal to the value of the storage capacitor (Cext).
3. A vehicle comprising the sensor (1) and microcontroller (20) as described in the preceding claims.
4. A method implemented by a microcontroller (20) of a sensor according to any one of claims 1 to 3, characterized in that, The method includes: a) First initialization phase (Pinit1), wherein a control switch is used to transfer charge between the detection capacitor (Ce) and the storage capacitor (Cext), such that the voltage across the detection capacitor (Ce) is equal to the voltage across the storage capacitor (Cext), and, in the absence of anyone near the sensor, is equal to half the voltage delivered by the DC voltage generator (Vcc). b) The first acquisition phase (P1) following the first initialization phase (Pinit1), which is repeated N times, where N is a natural number greater than or equal to 3, includes the following sub-steps: i) Control the discharge of the detection capacitor (Ce) (E11) to reach a predefined first duration (d1), then ii) Control the detection capacitor to charge (E12) until the predefined first duration (d1), then iii) Controlling the transfer of charge from the detection capacitor (Ce) (E13) to the storage capacitor (Cext), Then, the voltage across the storage capacitor (Cext) is measured using analog-to-digital conversion. c) In the second initialization phase (Pinit2) following the first acquisition phase (P1), a control switch is used to transfer charge between the detection capacitor (Ce) and the storage capacitor (Cext), such that the voltage across the detection capacitor (Ce) is equal to the voltage across the storage capacitor (Cext), and, in the absence of anyone near the sensor, is equal to half the voltage delivered by the DC voltage generator (Vcc). d) The second acquisition phase (P2) following the second initialization phase (Pinit2), which is repeated N times, includes the following sub-steps: i) Control the charging of the detection capacitor (E21) to reach a predefined second duration (d2), Then ii) Control the discharge of the detection capacitor (E22) to reach the predefined second duration (d2), then iii) Controlling the transfer of charge from the storage capacitor (Cext) (E23) to the detection capacitor (Ce), Then, the voltage across the capacitor is measured using an analog-to-digital converter. e) Determine the value of the detection parameter equal to the difference between the first mean and the second mean, wherein the first mean is defined as the average of the voltage values measured at the end of each repetition in the first acquisition phase (P1), and wherein the second mean is defined as the average of the voltage values measured at the end of each repetition in the second acquisition phase (P2), and f) Compare between the following two: the difference between the determined first mean and the determined second mean, and the predefined detection threshold.
5. A computer program product, characterized in that, It includes a set of program code instructions that, when executed by one or more processors, configure the one or more processors to implement the method according to claim 4.