EP1280170A1 - Switch with inductive coupling - Google Patents

Abstract

The contact state detector (SW) method has a secondary coil (L2) magnetically coupled to a primary coil (L1). The primary and secondary coils are tuned resonance circuits. The primary circuit detects the sinusoidal wave setting and passes it to the electronic circuit (E). The electronic circuit detects the variations in the sinusoidal wave phase, thus determining the contact state.

Description

The present invention relates to an electronic device and a method for detecting the state of a contact placed in the circuit of a secondary coil and magnetically coupled to a coil of a primary circuit to which the detection circuit is connected.

The applications of this type of inductive coupling are extremely numerous and varied, including door opening systems, chests, rags, etc. in the automotive field, an example more particularly highlighted in the following description for to facilitate understanding.

Currently, in most cases, vehicles equipped with electronically controlled opening systems have switches mounted on their traditional openings such as doors and / or removable windows. These switches are external to the body, so as to be activated from the outside by a user of the vehicle to allow the power supply of the electric unlocking device of the opening.

An electrical connection must be established between the mobile opening and the fixed main passenger compartment of the vehicle, which travels in particular through the bodywork and the joints connecting the latter to each opening.

This electrical connection can take various forms, depending on the structure of the opening. For example, when the latter consists of a window, it is in most cases by metallized tracks deposited on the glass, and cooperating with specific connectors.

In all cases, however, there is a physical connection between the mobile part constituting the opening and the fixed part of the vehicle to which it is attached, a link which concentrates the problems of this structure. In devices that work to date, leakage problems are thus commonly manifest, especially at the connectors on said physical link, or at the control buttons of the power supply of the electronic unlocking device of the opening.

One of the weak links of the electrical connections between the buttons or control members on the one hand and the unlocking electronics on the other hand is moreover constituted by adjacent connectors of the mechanical joints. In addition, in the case of a circuit attached to a window, the metallized tracks traced on the glass are sensitive to scratches, which can deteriorate and render the electrical circuit inoperative.

The present invention overcomes these drawbacks, and proposes a switching device without electrical connection or mechanical connection between the button or the switch and the release control circuit of the opening. In the aforementioned automotive application, this device comprises a contact connected to a coil and mounted directly on the opening, constituting an electrically insulated and mechanically independent medium.

The electronic device of the invention, which comprises a so-called primary coil magnetically coupled to the aforementioned secondary one, the circuit of which is permanently supplied with at least one alternating signal, is essentially characterized in that the circuits of the primary and secondary coils are tuned resonant circuits, an intermediate sinusoidal signal taken from the primary circuit being sent into an electronic processing circuit provided for detecting the phase variations of said intermediate signal reflecting the state of the contact.

In fact, the inductively coupled primary and secondary coils form a transformer whose operation depends on the positioning of one with respect to the other. For the record, if the primary coil is excited by an alternating electric signal, it emits a magnetic field in the secondary coil. By closing the contact located in the circuit of the secondary coil, it creates conversely a magnetic field variation that will oppose the field emitted by the primary coil. This effect is reflected in the primary coil by a change in current because the impedance of the primary coil changes depending on the state of contact, due to the existence of mutual induction.

The advantage of this structure is to allow the removal of any electrical connection between a mobile part and a fixed part, in particular because it allows mechanical independence between the two coils. It is indeed possible to provide a device in which the primary coil is fixed on the frame or a fixed part of the vehicle, while the secondary coil is secured to the opening. Thus, when the latter is closed, the two coils are coupled and allow the transmission of the contact information by magnetic coupling. When the unlocking device is activated, the opening of the opening separates the two coils and breaks the magnetic connection between them.

The coupling of the coils can also be improved using a ferrite core disposed between them, or by equipping each coil of such a core. It then becomes possible to increase the coupling distance.

More specifically, the resonant circuit of the primary coil consists of a capacitor in series with said coil, the free ends of these two components being supplied by alternating voltages in phase opposition of frequency close to the resonant frequency of the primary circuit. , the intermediate signal sinusoidal pace being then taken between them.

The primary circuit is therefore a conventional LC series resonant circuit, whose power mode makes it possible to know the value of the phase shift, close to the quadrature, of the signal taken between the two components.

The resonant circuit of the secondary coil consists of a capacitor placed in parallel with the secondary coil, the contact being connected in parallel with said components.

Closing the contact, for example a push button located in the circuit of the secondary coil, is to short circuit thereof, resulting in the occurrence of a sudden change in magnetic field.

According to one possibility, the resonant frequency of the secondary coil circuit is set at about half the resonant frequency of the primary coil circuit.

The resonant circuits allow stable frequency operation, which will be seen in the following text that it is controlled by the electronic processing circuit. The frequency differences, as well as the location of the signal sampling point in the primary circuit, are chosen to allow an optimal evaluation of the phase variation induced in the primary circuit by the change in the secondary circuit during the closing of the circuit. contact. The double resonant circuit also has the function of increasing the detection sensitivity of the opening / closing of the contact.

Preferably, the resonance frequencies of the primary and secondary circuits are between 1 kHz and 1000 kHz.

More specifically, the electronic processing circuit comprises an initial comparator of the phase of the intermediate signal and a supply signal of the primary circuit, said initial comparator delivering a signal marking their phase shift, sent to a window comparator comparing it to two stored and adjustable reference values, the output signal of the window comparator being fed to an analyzer stage delivering an active level signal to the output of said circuit when the button is closed, or a reference value recalibration signal in case malfunction of the circuit.

The principle is based on a double comparison, knowing that the terms of the comparison are each time related to the operating conditions of the device, and adjustable if the internal tests indicate that their value is no longer compatible with proper operation from the whole.

More specifically, the power supply signal generator of the primary circuit is connected to an initialization circuit allowing, on power up, the adjustment of said signal as a function of the signal from the initial comparator to which it is connected.

This adjustment is made possible by the knowledge of the main operating parameters of the primary circuit. The supply signal must be close to the resonance frequency of the latter, and the frequency of the signal taken between the components of the latter has a phase shift with the supply frequency which is therefore known.

The initialization circuit is further connected to the output of the analyzer stage emitting a recalibration signal.

Such an emission occurs when the analyzer stage indicates that the offset between the resonant frequency of the primary circuit and the frequency of the intermediate signal is lower than the lowest threshold value.

The other output of the analyzer stage, emitting an active signal in the event of closure of the contact, is in turn connected to an integrating filter, to which is connected a directly usable output of the processing circuit.

This integrator makes it possible to validate the information of the signal after a certain number of cycles has repeated it. It acts in particular as a contact debounce filter, by quantifying the number of periods during which the comparator has detected an active state.

Optionally, this integrating filter may be followed by a delay stage providing a delayed output to the processing circuit, which makes it possible to deliver a pulse of fixed duration at the instant of closure of the contact.

Given the temporal nature of the measurement, exclusively related to the phase of the different signals, the analysis circuit described above, that is to say the one which is in charge of the electronic processing of the signals, is preferably based on logical components or on a microprocessor.

This temporal character of the measurement also induces peculiarities at the input of the intermediate signal in the electronic processing circuit. Thus, the initial comparator of this circuit may be preceded by a diode clipping device, which may be associated with a fronts detector circuit.

This internal clipping device makes it possible to take the phase information on the oscillating circuit of the primary coil independently of its amplitude.

In addition, a resistance greater than 10,000 Ω is placed between the intermediate signal sampling point and the input of said processing circuit.

Here again, since the amplitude has no value as regards the signal processing, it is not necessary to treat or even to keep what belongs to this information. This high resistance essentially allows to keep only the "component" phase of the signal. In fact, the phase variations only depend on the impedance of the circuit, and no longer on the amplitude variations caused by the variations of this same impedance and the amplitude of the input signal.

The idea underlying the invention is in summary that by eliminating the amplitude factor of the measurement, the phase variations arising from the changes in the contact state of the secondary circuit can be analyzed in the time domain, each oscillation cycle of the oscillating signal delivered by the power generator, in a way very accurate and very reliable with the aid of logic circuits, or even a microprocessor.

The resonance of the primary circuit and the secondary circuit also eliminates primary current detection. The impedance of the primary circuit capacitor remains constant regardless of whether the button is open or closed. Only the impedance of the primary coil and the coefficient of mutual induction associated with it vary according to the state of the contact.

Finally, the invention also relates to a method for detecting the state of a contact placed in the circuit of a secondary coil inductively coupled to a primary coil, the circuits of said coils each comprising a capacitor to constitute tuned resonant oscillating circuits. , said method being very generally characterized by measuring the variation of the phase of an intermediate signal taken between the coil and the capacitor of the primary circuit.

In order to correspond to the device of the invention, this method is particularly characterized in that the phase of said intermediate signal is compared with the phase of a signal supplying said circuit, the measured offset being then compared with two respective upper and lower threshold values. lower whose upper and lower crossing respectively means the closure of the contact and a drift of the phase requiring recalibration of said threshold values, the maintenance in the range signifying that said contact is open.

The function of the various components of the electronic processing circuit is highlighted by the methodological nature of the method.

In fact, the supply signal (s) of the primary circuit are adjusted, at the time of power-up, to obtain a frequency close to the resonant frequency of the primary circuit.

Preferably, said adjustment is performed using a signal from the comparison of the offset between the intermediate signal and the supply signal or signals.

• la figure 1 représente schématiquement le circuit électrique du couplage inductif, le circuit primaire étant relié à une unité de traitement électronique ;
• la figure 2 comporte un schéma logique du fonctionnement du circuit électronique de traitement ; et
• la figure 3 montre schématiquement l'application de l'invention à un haillon de véhicule automobile.

The invention will now be described in more detail, with reference to the figures, for which:

• FIG. 1 diagrammatically represents the electrical circuit of the inductive coupling, the primary circuit being connected to an electronic processing unit;
• Figure 2 comprises a logic diagram of the operation of the electronic processing circuit; and
• Figure 3 schematically shows the application of the invention to a motor vehicle rag.

With reference to FIG. 1, the secondary circuit is composed of a coil (L2), arranged in parallel with a capacitor (C2), and a contact of the pushbutton type referenced (SW). The coil (L2) is electromagnetically coupled to the coil (L1) of the primary circuit, which is arranged in series with a capacitor (C1). The primary circuit is powered by two outputs (S1 and S2) whose voltages are in phase opposition. The frequency of these supplies substantially corresponds to the resonant frequency of the primary circuit, which is approximately double the resonant frequency of the secondary circuit. The components are chosen for this purpose.

An alternating sinusoidal signal is taken between the coil (L1) and the capacitor (C1). Given the structure of the circuit, this signal is in phase quadrature with respect to the voltage of the outputs (S1 and S2). A high resistance (Ri), preferably greater than 10,000 Ω, is arranged between the sampling point of said intermediate signal and its input into the electronic processing circuit (E). As stated before, this resistance plays an important role in suppressing the amplitude factor in the measurement. A clipping device (D) located at the input of the circuit (E) allows the surplus to minimize the aspects of the signal related to the amplitude.

The precise operation of the electronic processing circuit (E) is shown in FIG. 2. Downstream of the clipping device (D) is an edge detector circuit (14) which produces an output pulse at each rising or falling edge of the signal coming from the resistor (Ri), that is to say coming from the point common to the resonant circuit L1C1.

The output of the edge detector circuit (14) is connected to one of the inputs of a phase comparator (15), the other input of which is connected to the generator supplying the primary circuit, the operation of which will be seen in more detail hereinafter in the text. The digital quantity obtained at the output of the phase comparator (15) corresponds to the temporary offset between the signal of the generator (13) and the signal of the point common to the circuit L1C1. This digital quantity constitutes a signal used to fulfill several functions in the circuit (E). Firstly, it adjusts the frequency of the voltages emitted by the power generator (13) after powering up the circuit (E).

sont utilisées respectivement pour l'alimentation d'une des bornes de la bobine (L1) et d'une des bornes du condensateur (C1). Le changement d'état de la bascule est obtenu via un compteur binaire (12) dont la capacité de comptage est d'au moins 8 bits, et qui est relié à un oscillateur (10) basé sur un quartz ou un résonateur céramique (11) qui garantissent la stabilité de la base de temps à moyen terme. Le compteur est réglé de telle manière qu'il fournisse à chaque cycle un signal de dépassement C_V de périodicité égale à la moitié du signal délivré sur le circuit résonant primaire L1C1.This generator (13) is simply a flip-flop, whose two outputs Q and $\overline{\mathit{\text{Q}}}$

are respectively used for supplying one of the terminals of the coil (L1) and one of the terminals of the capacitor (C1). The change of state of the flip-flop is obtained via a binary counter (12) whose counting capacity is at least 8 bits, and which is connected to an oscillator (10) based on a quartz or a ceramic resonator (11). ) which guarantee the stability of the time base in the medium term. The counter is set in such a way that it provides each cycle with an excess signal C _V of periodicity equal to half the signal delivered on the primary resonant circuit L1C1.

The flip-flop (13) guarantees the provision of a signal perfectly symmetrical in duration at each change of state on the outputs S1 and S2, which therefore convey signals in phase opposition.

The output of the phase comparator circuit (15) is sent to an initialization circuit (16) which adjusts, at the time of power-up, the counting capacity of the counter (12) to obtain a signal from the latch. a frequency approaching as close as possible the natural resonance frequency of the circuit L1 C1 associated by inductive coupling to the circuit L2C2.

• un état de repos tant que la phase issue du comparateur (15) est comprise entre les niveaux de référence haut et bas. Cet état de repos correspond à l'état d'ouverture du contact (SW) ;
• un état actif tant que la phase issue du comparateur (15) est supérieure au niveau de référence haut. Cet état actif correspond à la fermeture du contact (SW) dans le circuit secondaire ;
• un état de recalibration tant que la phase issue du comparateur (15) est inférieure au niveau de référence bas. Cet état de recalibration correspond à une dérive de la phase qui a lieu pendant l'état de repos ou est due à un processus erroné de fonctionnement.

When this condition is fulfilled, the intermediate signal is close to the phase quadrature with the available power signals at S1 and S2. The result of their comparison by the comparator (15) is therefore predictable and adjustable. This result is also sent to a digital window comparator (17), which compares it with two reference levels up and down, stored at two different locations referenced respectively (18) and (19). Their storage takes place at the time of power-up, from the value read by the phase comparator (15), just after the adjustment phase of the periodicity of the counter (12). The output of the comparator (17) can take three distinct states:

• a state of rest as long as the phase coming from the comparator (15) lies between the high and low reference levels. This state of rest corresponds to the state of opening of the contact (SW);
• an active state as long as the phase coming from the comparator (15) is greater than the high reference level. This active state corresponds to the closing of the contact (SW) in the secondary circuit;
• a recalibration state as long as the phase coming from the comparator (15) is lower than the low reference level. This state of recalibration corresponds to a drift of the phase which takes place during the state of rest or is due to an erroneous process of operation.

The state of the signal from the comparator (17) is analyzed by an analyzer stage (20), responsible for recalibrating the high and low reference levels, and for delivering an active state when the contact (SW) is closed.

This stage is thus connected on the one hand to the initialization circuit (16), whose functions include adjustments and recalibrations, and on the other hand via another of its outputs, to an integrating filter (21) whose output is activated only after a certain amount of active states of valid measurement cycles has been measured. The integrable quantity can be parameterized from 2 to 250 cycles of oscillation of the generator (13).

The output signal of the integrating filter (21) can be directly operated via a direct output (23).

Alternatively, the output of the integrating filter (21) can be connected to a delay circuit (22), a delayed signal then being available at the output (24) of the processing circuit (E). This delay serves in particular to emit a pulse signal of fixed duration as soon as the contact (SW) is closed in the secondary circuit.

The circuit (E) comprises according to a possibility a certain number of logic components based on synchronous or asynchronous elementary circuits. Alternatively, it may consist of a microprocessor or microcontroller, an essentially logical processing being made possible by the temporal nature of the measurement.

However, it is also possible to make it using discrete analog components.

One of the advantages of the circuit of the invention is that it allows a constant self-monitoring of the reliability of the measurements, as well as an adaptation of the supply frequencies and the threshold values according to the actual operating parameters, including the primary circuit.

With reference to FIG. 3, the circuit of the invention can be applied, in the automotive field, to the detection of the opening of a solid contact of a mobile part such as a rag (1). essentially consisting of a glazed surface which pivots with respect to a frame (2) of the vehicle frame.

The contact (3) is in the circuit of the secondary coil (4), also attached to the hanger (1), while the primary coil (5) is fixed to the frame, as is the electronic circuit (6) for processing and the lock (7) electrically controlled.

The coils (4, 5) are arranged such that when the rag (1) is closed, they are in an electromagnetic coupling situation. As already indicated, this coupling can be improved by means of a ferrite core fixed on the side of one or other of the coils (4, 5), or by means of two cores each equipping a coil ( 4, 5).

The invention has been described by means of a particular example of a circuit which can not be considered as limiting. On the contrary, it encompasses the variants of shape and configuration that are within the reach of those skilled in the art.

Claims (18)

Electronic device for detecting the state of a contact (SW) placed in the circuit of a secondary coil (L2) magnetically coupled to a primary coil (L1) whose circuit is continuously supplied with at least one alternating signal, characterized in that the circuits of the primary (L1) and secondary (L2) coils are tuned resonant circuits, an intermediate sinusoidal signal taken from the primary circuit being sent to an electronic processing circuit (E) provided for detecting the phase variations of said intermediate signal reflecting the state of said contact (SW). Electronic device for detecting the state of a contact (SW) according to the preceding claim, characterized in that the resonant circuit of the primary coil (L1) consists of a capacitor (C1) in series with said coil (L1 ), the free ends of these two components being fed by alternating voltages in opposite phase of frequency close to the resonant frequency of the primary circuit, the intermediate signal of sinusoidal pace being taken between them. Electronic device for detecting the state of a contact (SW) as claimed in one of the preceding claims, characterized in that the resonant circuit of the secondary coil (L2) consists of a capacitor (C2) placed in parallel with the secondary coil (L2), the contact (SW) being connected in parallel with said components. Electronic device for detecting the state of a contact (SW) according to the preceding claim, characterized in that the resonant frequency of the circuit of the secondary coil (L2) is set at about half the resonance frequency of the circuit of the primary coil (L1). An electronic device for detecting the state of a contact (SW) according to any one of claims 2 to 4, characterized in that said resonance frequencies are between 1 kHz and 1000 kHz. Electronic device for detecting the state of a contact (SW) according to any one of the preceding claims, characterized in that the electronic processing circuit comprises an initial comparator (15) of the phase of the intermediate signal and a signal of the generator (13) supplying the primary circuit, said initial comparator (15) delivering a signal marking their phase shift, sent to a window comparator (17) comparing it with two adjustable reference values (18, 19) adjustable, the output signal from the window comparator (17) being fed to an analyzer stage (20) delivering on a first output an active level signal to the output (23) of the processing circuit (E) in the event of contact closure (SW) and, on a second output, a signal to recalibrate the reference values in case of malfunction. Electronic device for detecting the state of a contact (SW) according to the preceding claim, characterized in that the supply signal generator (13) of the primary circuit is connected to an initialization circuit (16) allowing, upon power-up, adjusting said signal according to the signal from the initial comparator (15) to which it is connected. Electronic device for detecting the state of a contact (SW) according to the preceding claim, characterized in that the initialization circuit (16) is connected to the output of the analyzer stage (20) emitting a recalibration signal . Electronic device for detecting the state of a contact (SW) according to one of claims 7 and 8, characterized in that the primary circuit supply signal generator comprises a flip-flop (13) whose outputs Q , $\overline{\mathit{\text{Q}}}$

are respectively connected to the coil (L1) and to the capacitor (C1), the state change signal being produced by a counter (12) whose counting pulses come from a stabilized oscillator (10). Electronic device for detecting the state of a contact (SW) according to one of Claims 6 to 9, characterized in that the output of the analyzer stage (20) emits an active signal in the event of contact closure. (SW) is connected to an integrating filter (21), to which is connected a directly usable output (23) of the processing circuit (E). Electronic device for detecting the state of a contact (SW) according to the preceding claim, characterized in that the integrating filter (21) is followed by a delay stage (22) providing a delayed output (24) to the circuit treatment (E). An electronic device for detecting the state of a contact (SW) according to any one of claims 6 to 11, characterized in that the processing circuit (E) is based on logic components or on a microprocessor. Electronic device for detecting the state of a contact (SW) according to one of Claims 6 to 12, characterized in that the comparator (15) is preceded by a diode clipping device (D) followed by a fringe detector circuit (14). Electronic device for detecting the state of a contact (SW) according to one of the preceding claims, characterized in that a resistor (Ri) with a value greater than 10,000 Ω is placed between the sampling point of the intermediate signal and the input of the electronic processing circuit (E). A method for detecting the state of a contact (SW) placed in the circuit of a secondary coil (L2) inductively coupled to a primary coil (L1), the circuits of said coils (L1, L2) each having a capacitor ( C1, C2) to constitute tuned resonant oscillating circuits, characterized by measuring the variation of the phase of an intermediate signal taken between the coil (L1) and the capacitor (C1) of the primary circuit. A method for detecting the state of a contact (SW) according to the preceding claim, characterized in that the phase of said intermediate signal is compared to the phase of a signal supplying said primary circuit, the measured offset being then compared to two upper and lower threshold values whose crossing respectively means the closure of the contact (SW) and a drift of the phase requiring a recalibration of said threshold values, maintaining in the range meaning that said contact (SW) is open. A method for detecting the state of a contact (SW) according to the preceding claim, characterized in that the supply of the primary circuit is adjusted at the moment of power-up to obtain a frequency close to the resonance frequency of the circuit primary. A method for detecting the state of a contact (SW) according to the preceding claim, characterized in that said adjustment is made with the aid of a signal resulting from the comparison of the offset between the intermediate signal and a signal of food.

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