Electronic lock

Abstract

An electronic lock system comprising a key (1) and a cylinder (2), a primary electronic circuit (4) mounted on the key (1) and including a primary microcontroller (A) and an electric power generator (8), a secondary electronic circuit (5) mounted on the cylinder (2) and including a secondary microcontroller (B), and a switching power supply for cyclic electrical energy transfer from the key (1) to the cylinder (2), where the switching power supply includes a primary electrical coil (L1) inserted in the primary electronic circuit (4), a secondary electrical coil (L2) inserted in the secondary electronic circuit (5), and a first electronic switch (M2) inserted in the primary electronic circuit (4), which can switch between an enabled state and a disabled state of the passing of electrical current through the primary electrical coil (L1), the primary microcontroller (A) being configured to generate by a clock signal the switching frequency determining the start of each cycle of electrical energy transfer, which aims to reach a maximum value of current intensity passing through the primary electrical coil (L1), and to synchronously transmit, at the switching frequency or its sub-multiple, a serial signal that selects the maximum current intensity passing through the primary electrical coil (L1) in each energy transfer cycle, for encoding data transmitted from the primary microcontroller (A) to the secondary microcontroller (B).

Description

[0001] ELECTRONIC LOCK

[0002] DESCRIPTION

[0003] The present invention relates to an electronic lock comprising a key and a cylinder equipped with a slot for the insertion of the key, and a method for bidirectional data transfer between the key and the cylinder when the key is inserted into the cylinder’s slot.

[0004] Electronic locks are known where the key features a primary electronic circuit comprising a primary microcontroller and an independent power source, typically a battery, and the cylinder includes a secondary electronic circuit comprising a secondary microcontroller and a power storage device, typically a capacitor.

[0005] In such electronic locks, a system for transferring electrical energy from the battery to the capacitor is generally provided. This system typically consists of a switching power supply that facilitates energy transfer through inductive coupling, which occurs between a primary electrical coil in the primary electronic circuit and a secondary electrical coil in the secondary electronic circuit when the key is inserted into the cylinder slot.

[0006] Furthermore, in such electronic locks, data exchange between the key and the cylinder typically occurs, as in the case of transponders with loose magnetic coupling, by amplitude modulation, often 100%, of the alternating magnetic field generated by the key to transmit data to the cylinder, and by varying the q- factor (quality factor) of the circuit, usually by short-circuiting the secondary coil, to transmit data from the cylinder to the key asynchronously.

[0007] The advantages of this system include circuit simplicity and low sensitivity to the coupling coefficient between the primary and secondary coils.

[0008] The disadvantages are the low communication speed, due to the need to integrate the carrier signal to significantly separate, usually by at least an order of magnitude, the modulated frequency from the carrier frequency, and the fact that to transmit, it is necessary to reduce the power transferred from the key to the cylinder by an average of 50% when transmitting from the key to the cylinder, and 75% from the cylinder to the key.

[0009] The technical task of the present invention is, therefore, to create an electronic lock of the aforementioned type that eliminates the technical drawbacks observed in the known art.

[0010] As part of this technical task, one objective of the invention is to create an electronic lock of the aforementioned type that can transmit at a higher speed and with less power reduction in both directions.

[0011] This technical task, as well as these and other objectives, according to the present invention, are achieved by providing an electronic lock system comprising a key, a cylinder with a slot for inserting the key, a primary electronic circuit mounted on the key and comprising a primary microcontroller and a power generator, a secondary electronic circuit mounted on the cylinder and comprising a secondary microcontroller, and a switching power supply for cyclic electrical energy transfer from the key to the cylinder, where said switching power supply includes a primary electrical coil inserted in the primary electronic circuit, a secondary electrical coil inserted in the secondary electronic circuit and inductively coupled to the primary coil when the key is inserted into the slot, and a first electronic switch in the primary electronic circuit that can switch between an enabled state and a disabled state, allowing or preventing electrical current from passing through the primary coil, characterized in that the primary microcontroller is configured to generate through a clock signal a switching frequency defining the moment of the beginning of each cycle of electric energy transfer, which includes achieving a maximum value of the intensity of said current passing through said primary coil, and synchronously transmitting, at the switching frequency or its sub-multiple, a serial signal for selecting said maximum value of the intensity of said current passing through said primary electrical coil in each energy transfer cycle for encoding data transmitted from said primary microcontroller to said secondary microcontroller. In a preferred embodiment of the invention, the secondary electronic circuit includes first signal analysis means at the terminals of the secondary coil, these first analysis means being configured to reconstruct the maximum current value passing through the primary coil during each energy transfer cycle when the first electronic switch is in the enabled state.

[0012] In a preferred embodiment of the invention, the secondary electronic circuit includes a component for modifying the resonant frequency of the inductively coupled circuit formed by the primary and secondary electronic circuits, and a second electronic switch configured to include or exclude this resonant frequency modification component.

[0013] In a preferred embodiment of the invention, the secondary microcontroller is configured to transmit a serial switching signal to said second electronic switch.

[0014] In a further preferred embodiment of the invention, the primary microcontroller includes second signal analysis means at the terminals of the primary coil, said second analysis means being configured to recognize said resonant frequency when said first electronic switch is in the disabled state.

[0015] In a preferred embodiment of the invention, said secondary electronic circuit includes third signal analysis means at the terminals of the secondary coil, said third analysis means being configured to reconstruct the clock synchronization signal when the first electronic switch is in the enabled state.

[0016] In a preferred embodiment of the invention, said secondary electronic circuit includes a storage capacitor for the electrical energy supplied by said secondary coil, and said secondary microcontroller is configured to acquire and analyze the voltage across said storage capacitor and to synchronously transmit, at the frequency of the reconstructed clock, a switching signal for said second electronic switch whenever the voltage across said storage capacitor reaches a threshold value.

[0017] In a preferred embodiment of the invention, the switching power supply is of the Fly-Back type. In the electronic lock, power transmission occurs using the inductively coupled primary and secondary coils.

[0018] Data exchange can take place either synchronously or asynchronously, with the first method being preferred when speed is a critical factor.

[0019] In the case of synchronous data exchange, the synchronization signal, meaning the clock signal generated by the primary microcontroller, is reconstructed on the cylinder side from the non-active portion of the voltage when the first electronic switch is in the enabled state.

[0020] Said synchronization signal defines the moment at which the signal across the primary coil contains information transmitted from the primary electronic circuit, with the signal level changing to indicate the transmission of a "one" or "zero" as a result of the change in maximum current intensity flowing through the primary coil.

[0021] The synchronization signal reconstructed by the secondary microcontroller defines the moment at which the secondary electronic circuit is modified by the inclusion of the resonant frequency modification component, so that, while the first electronic switch is in the disabled state, said second analysis means can determine whether the resonant frequency modification component is inserted or not.

[0022] Other features of the present invention are further defined in the subsequent claims.

[0023] Additional features and advantages of the invention will become more apparent from the description of a preferred but not exclusive embodiment of the electronic lock, presented for illustrative and non-limiting purposes in the accompanying drawings, in which:

[0024] Figure 1 schematically shows the key and the cylinder of the electronic lock;

[0025] Figure 2 shows the circuit diagram of the electronic lock;

[0026] Figure 3 schematically shows the data transfer method from the key to the cylinder.

[0027] With reference to the cited figures, the electronic lock comprises a key 1 and a cylinder 2 equipped with a slot 3 for the insertion of the key 1. The electronic lock also comprises a primary electronic circuit 4 mounted on the key 1 , a secondary electronic circuit 5 mounted on the cylinder 2, and a switching power supply for cyclic electrical energy transfer from the key 1 to the cylinder 2.

[0028] The primary electronic circuit 4 includes a primary microcontroller A, and similarly, the secondary electronic circuit 5 includes a secondary microcontroller B.

[0029] The switching power supply comprises a primary electrical coil LI inserted into the primary electronic circuit 4, and a secondary electrical coil L2 inserted into the secondary electronic circuit 5 and inductively coupled to the primary electrical coil LI when the key 1 is inserted into the slot 3 of the cylinder 2.

[0030] The switching power supply also includes an electronic switch M2 inserted into the primary electronic circuit 4 that can switch between an enabling state and a disabling state of the electrical current passing through the primary electrical coil LI.

[0031] The primary electrical coil LI can be incorporated into the blade of the key 1, and the secondary electrical coil L2 can be incorporated into the rotor of the cylinder 2 adjacent to the slot 3, so that when the key 1 is inserted into the slot 3, the primary electrical coil LI and the secondary electrical coil L2 are aligned with parallel or nearly parallel axes.

[0032] The primary microcontroller A is programmed to perform cyclic energy transfers from an independent power source 8 typically a battery, located in the primary electronic circuit 4, to an energy storage device, typically a capacitor C5, located in the secondary electronic circuit 5.

[0033] The battery 8 powers all active components of the primary electronic circuit 4, including the primary microcontroller A, through an input port VCCA.

[0034] The primary microcontroller A has a digital serial output port, labeled "clock out A," through which it transmits a clock signal, the switching frequency determining the start of each cycle of electrical energy transfer, which involves achieving a maximum value kia, kib of the current ILI passing through the primary electrical coil LI . The start of each energy transfer cycle corresponds to the moment at which electrical current begins to flow through the primary electrical coil LI.

[0035] The primary microcontroller A also transmits, from a digital serial output port labeled “serial out A,” a signal synchronously at the switching frequency or at a sub-multiple of it, selecting a maximum current value Lia or Lib of the current ILI passing through the primary electrical coil LI during each energy transfer cycle to encode data transmitted from the primary microcontroller A to the secondary microcontroller B.

[0036] In practice, during data transmission from the key to the cylinder, the primary microcontroller A, for each energy transfer cycle or groups of cycles, at a time interval ti defined by the clock signal, selects between two distinct current values, ILI a and Lib, for the maximum current intensity Li.

[0037] Selecting the lower value Lib corresponds to transmitting a “zero,” while selecting the higher value Lia corresponds to transmitting a “one.”

[0038] The switching power supply can be of the Fly-Back type.

[0039] In this case, the Fly-Back includes a Flip-Flop Al and a voltage comparator Ul, and the electronic switch M2 is formed by a MOSFET controlled by the Flip-Flop Al.

[0040] The voltage comparator Ul compares the current voltage across a resistor R14, through which the current flowing through the primary electrical coil LI passes, with a reference voltage in order to switch the MOSFET M2 from a conducting state to a blocking state when the current voltage across resistor R14 exceeds the reference voltage.

[0041] The energy transfer cycle proceeds as follows.

[0042] The primary microcontroller A sends a clock signal that sets the Flip-Flop Al.

[0043] When set, the Flip-Flop Al sends a signal from its Q output that causes the MOSFET M2 to switch from the blocking state to the conducting state.

[0044] The electrical current supplied by the battery 8 flows in sequence through the primary electrical coil LI, the MOSFET M2, and the resistor R14. Resistor R14 has one terminal connected to ground and the other connected to the inverting input of the voltage comparator Ul, while its non-inverting input is maintained at said maximum reference voltage, which is determined by a voltage present at an analog output port labeled “analog out A" of the primary microcontroller A and mediated by a voltage divider consisting of resistors R15, R16, R17, and a capacitor filter C8.

[0045] As the current flowing through the coil LI gradually increases, the voltage across resistor R14 increases proportionally.

[0046] When the voltage at the inverting input of comparator Ul exceeds the maximum reference voltage at the non-inverting input of comparator Ul, comparator Ul resets Flip-Flop Al by sending a signal to a CLR input of Flip-Flop Al.

[0047] As a result of the reset, Flip-Flop Al not only sends a signal from its Q output that switches MOSFET M2 from the conducting state to the blocking state but also sends a signal from its Q- output that is detected by the primary microcontroller A via a digital serial input port labeled “digital in A."

[0048] When MOSFET M2 switches from the conducting state to the blocking state, current flow through the primary electrical coil LI stops, and current begins to flow through the secondary electrical coil L2.

[0049] The electrical current flowing through the secondary coil L2 charges capacitor C5 via diode D6. Essentially, while MOSFET M2 is in the conducting state, energy is stored in the magnetic field formed by the primary electrical coil LI and secondary coil L2, while once MOSFET M2 switches from the conducting state to the blocking state, the energy stored in the magnetic field is transferred to capacitor C5 and then to a load R6.

[0050] The secondary electronic circuit 5 includes first signal analysis means at the terminals of the secondary coil L2. These first analysis means are configured to reconstruct the maximum value Ina or Lib of the current ILI passing through the primary electrical coil LI during each energy transfer cycle when the first electronic switch M2 is in the enabled state.

[0051] The first analysis means include a comparator U4, specifically a voltage comparator, connected to the secondary microcontroller B.

[0052] Comparator U4 captures the peak voltage across the secondary coil L2 and compares it with a reference voltage.

[0053] If the captured peak voltage exceeds the reference voltage, comparator U4 sends a “one” signal to a digital serial input port of the secondary microcontroller B, labeled “serial in B” “one” signal identifying the maximum current value Ina reached in the primary coil LI ; instead, if the captured peak voltage is lower than the reference voltage, comparator U4 sends a “zero” signal to the digital serial input port of the secondary microcontroller B, labeled “serial in B”, “zero” signal identifying the minimum current value Inb of the current ILI of reached in the primary coil LI .

[0054] In detail, resistors R20 and R21 form the divider that adjusts the input voltage to the working voltage of comparator U3, which extracts the clock signal and sends it to the microcontroller B via the "clock in B" port.

[0055] Resistors R22 and R23 form the divider that adjusts the input voltage to the working voltage of comparator U4, which extracts the data signal and sends it to the microcontroller B via the "serial in B" port.

[0056] The secondary electronic circuit 5 also includes a component Cl for modifying the resonant frequency of the inductively coupled circuit formed by the primary electronic circuit 4 and the secondary electronic circuit 5, and a second electronic switch Ml configured to include or exclude the component Cl for modifying the resonant frequency. The second electronic switch Ml is composed of a second MOSFET. The secondary microcontroller B is configured to transmit a switching signal for the second electronic switch Ml via a digital serial output port labeled "serial out B".

[0057] The component Cl for modifying the resonant frequency consists of a capacitor placed in parallel with the secondary coil L2.

[0058] The primary microcontroller A includes second signal analysis means at the terminals of the primary electrical coil LI .

[0059] These second analysis means are configured to detect the resonant frequency when the first electronic switch M2 is in the disabled state. The second analysis means include a comparator U2, specifically a voltage comparator, connected to the primary microcontroller A through its digital serial input port labeled "serial in A".

[0060] The secondary electronic circuit 5 also includes third signal analysis means at the terminals of the secondary electrical coil L2.

[0061] These third analysis means are configured to reconstruct the clock synchronization signal when the first electronic switch M2 is in the enabled state.

[0062] The third analysis means include a comparator U3, specifically a voltage comparator, connected to the secondary microcontroller B.

[0063] Comparator U3 detects the zero crossing of the voltage at the terminals of the secondary coil L2 and sends the data to a digital serial input port of the secondary microcontroller B, labeled "clock in B" allowing the secondary microcontroller B to reconstruct the clock signal generated by the primary microcontroller A.

[0064] In detail, resistors R20 and R21 form the divider that adjusts the input voltage to the working voltage of comparator U3, which extracts the clock signal and sends it to microcontroller B via the "clock in B" port. The secondary microcontroller B is configured to acquire and analyze the voltage at the terminals of the storage capacitor C5 and, synchronously with the reconstructed clock frequency, transmit, via the digital serial output port labeled "serial out B," a switching signal for the second switch Ml whenever the voltage at the terminals of storage capacitor C5 reaches a threshold voltage, read by the secondary microcontroller B through an analog input port labeled "analog in B." Specifically, the secondary microcontroller B engages capacitor Cl whenever the voltage at the terminals of storage capacitor C5 reaches the threshold voltage.

[0065] In practice, the switching signal changes the state of the MOSFET Ml, which, in turn, either excludes or includes capacitor Cl in parallel with the secondary coil L2.

[0066] When included, capacitor Cl changes the resonant frequency of the inductively coupled circuit through coils LI and L2, and this, in turn, affects the signal at the terminals of the primary electrical coil LI when MOSFET M2 is in the disabled state, as the voltage supplied by battery 8 is present across the primary coil LI when in the enabled state.

[0067] Therefore, when MOSFET M2 is in the disabled state, a voltage is recorded across a resistor R19, placed in series with the primary coil LI and upstream of a diode D4, the average value of this voltage, acquired through a capacitor C7, is taken from the midpoint of a voltage divider formed by resistors R11 and R12 and communicated to one input of comparator U2, while to the other input is communicated the instantaneous value of this voltage, acquired through a resistor R13 located upstream of diode D4 and in series with resistor R19.

[0068] This voltage oscillates at a lower frequency when capacitor Cl is engaged, and as a result, the amplitude of this oscillation decreases.

[0069] Comparator U2 discriminates whether the instantaneous value of this voltage is greater or less than its average value, with one case corresponding to the exclusion of capacitor Cl and the other corresponding to its inclusion. Comparator U2 then transmits this information to the primary microcontroller A via the digital serial input port "serial in A".

[0070] In detail, resistors R9, RIO, and capacitor C6 form a low-pass filter that eliminates high-frequency and undesirable components of the signal. This filter can also be implemented in other ways, such as through a DSP circuit.

[0071] The electronic lock is thus capable of highly efficient and effective bidirectional data exchange between the key and the cylinder.

[0072] The electronic lock, as conceived, is subject to numerous modifications and variations, all of which fall within the scope of the inventive concept; furthermore, all details can be replaced by technically equivalent elements.

[0073] In practice, the materials used and the dimensions may vary depending on needs and current technology.

Claims

CLAIMS1. Electronic lock system comprising a key (1), a cylinder (2) provided with a slot (3) for the insertion of the key (1), a primary electronic circuit (4) mounted on the key (1) and comprising a primary microcontroller (A) and an electric power generator (8), a secondary electronic circuit (5) mounted on the cylinder (2) and comprising a secondary microcontroller (B), and a switching power supply for cyclically transferring electric energy from the key (1) to the cylinder (2), wherein said switching power supply comprises a primary electrical coil (LI) inserted in the primary electronic circuit (4), a secondary electrical coil (L2) inserted in said secondary electronic circuit (5) and inductively coupled to said primary electrical coil (LI) when said key (1) is inserted into said slot (3), and a first electronic switch (M2) inserted in the primary electronic circuit (4) and switchable between a state of enabling and a state of disabling the passage of electric current through the primary electrical coil (LI), characterized in that said primary microcontroller (A) is configured to generate, through a clock signal, a switching frequency defining the moment of the beginning of each cycle of electric energy transfer, which includes achieving a maximum value of the intensity of said current passing through said primary electrical coil (LI), and to synchronously transmit, at the switching frequency or one of its submultiples, a serial signal for selecting said maximum value of the intensity of said current passing through said primary electrical coil (LI) in each cycle of energy transfer for encoding data transmitted from said primary microcontroller (A) to said secondary microcontroller (B).

2. Electronic lock system according to the preceding claim, characterized in that said first electronic switch (M2) is formed by a first Mosfet.

3. Electronic lock system according to any preceding claim, characterized in that said secondary electronic circuit (5) comprises first means for analyzing the signal at the ends of the secondary electrical coil (L2), said first means being configured for the reconstruction of the maximum value(In a, Lib) of the intensity of said current (ILI) passing through said primary electrical coil (LI) in each cycle of energy transfer when said first electronic switch (M2) is in the enabled state.

4. Electronic lock system according to the preceding claim, characterized in that said first means of analysis comprise a comparator (U4) connected to said secondary microcontroller (B).

5. Electronic lock system according to any preceding claim, characterized in that said secondary electronic circuit (5) comprises a component (Cl) for modifying the resonance frequency of the inductively coupled circuit formed by the primary electronic circuit (4) and the secondary electronic circuit (5), and a second electronic switch (Ml) configured to include or exclude said component (Cl) for modifying the resonance frequency.

6. Electronic lock system according to the preceding claim, characterized in that said second microcontroller (B) is configured to transmit a serial signal for switching said second electronic switch (Ml).

7. Electronic lock system according to any claims 5 and 6, characterized in that said component (Cl) for modifying the resonance frequency is a capacitor.

8. Electronic lock system according to any claim from 5 to 7, characterized in that said second electronic switch (Ml) is formed by a second Mosfet.

9. Electronic lock system according to any claim from 5 to 8, characterized in that said primary microcontroller (A) comprises second means for analyzing the signal at the ends of the primary electrical coil (LI), said second means being configured for recognizing said resonance frequency when said first electronic switch (M2) is in the disabled state.

10. Electronic lock system according to the preceding claim, characterized in that said second means of analysis comprise a comparator (U2) connected to said primary microcontroller (A).

11. Electronic lock system according to any preceding claim, characterized in that said secondary electronic circuit (5) comprises third means for analyzing the signal at the ends of the secondaryelectrical coil (L2), said third means being configured for the reconstruction of the clock synchronization signal when said first electronic switch (M2) is in the enabled state.

12. Electronic lock system according to the preceding claim, characterized in that said third means of analysis comprise a comparator (U3) connected to said secondary microcontroller (B).

513. Electronic lock system according to any claim from 9 to 12, characterized in that said secondary electronic circuit (5) comprises a capacitor (C5) for accumulating the electric energy supplied by said secondary coil (L2), and said second microcontroller (B) is configured to acquire and analyze the voltage across said accumulation capacitor (C5) and to synchronously transmit, at the reconstructed clock frequency, a switching signal of said second electronic switch (Ml) whenever0 the voltage across said accumulation capacitor (C5) reaches a threshold value.

14. Electronic lock system according to any preceding claim, characterized in that said switching power supply is of the Fly-Back type.

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