CONTROL CIRCUIT OF AN ELECTRONIC ACCESS CONTROL SYSTEM WITH A TRANSPONDER DETECTOR AND METHOD FOR READ A TRANSPONDER

Description

[0001] The invention relates to a control circuit of an electronic access control system with a transponder detector for signals from a transponder, in particular an RFID transponder, with a main antenna and with a detection antenna for detecting the transponder located within communication range, wherein in a first operating mode one is designed to supply the main antenna with electrical current to generate an electromagnetic field and in a second operating mode to communicate with the transponder via the main antenna. Furthermore, the invention relates to a method for reading a transponder, in particular an RFID transponder, with the control circuit, wherein a main antenna is supplied with current and a control device detects the change in an amplitude at a detection antenna.

[0002] A transponder detector is known, for example, from EP 1 840 790 B1. This transponder detector generates detection sequence signals and thus detects transponders within communication range. If no transponder is detected, the generation of detection sequence signals continues continuously. If a transponder is detected, communication is established with it. However, this requires a high energy consumption.

[0003] The detection of a transponder and the start of communication is generally referred to as "wake up" because the control circuit is transferred from a sleep mode in which detection sequence signals are generated to an operating mode in which communication with the transponder is generated.

[0004] The well-known transponder detector operates with multiple carrier frequencies. The two antennas each function as a transmitter and receiver. Due to the dual function of both antennas and the use of multiple carrier frequencies, the transponder detector requires a high amount of energy and has a very complex design.

[0005] However, high energy consumption and an unnecessarily complex design must be avoided when such a transponder detector is used in an electronic locking device, such as a lock cylinder. These locking devices usually only have a battery as an energy storage device with limited capacity and also offer very little installation space.

[0006] From EP 3 300 039 A1, an electronic access control system for a building is disclosed in which a control unit operates an access control component either in a fully operational mode or in a standby mode. This access control system comprises a radio network with multiple network nodes.

[0007] US patent 2014 / 0038516 A1 discloses antenna structures for near-field communication. A first antenna coil is connected to electronics, while a second antenna coil is not electronically connected to any other component. The second antenna coil serves as a resonator for the first antenna coil.

[0008] The invention is based on the problem of creating a control circuit with a transponder detector that is as simple as possible and has particularly low energy consumption. Furthermore, a particularly simple method for reading the transponder is to be created.

[0009] This problem is solved according to the invention by magnetically coupling the main antenna and the detection antenna and electrically isolating them from each other, and by designing the control device to detect attenuation of the voltage at the detection antenna, and by evaluating a signal from the detection antenna in the first operating mode and detecting sufficient attenuation of the voltage at the detection antenna by the control device in order to switch to the second operating mode.

[0010] This design enables the transponder detector and main antenna to communicate bidirectionally with the transponder. Since the detection antenna is only magnetically coupled to the main antenna, it experiences attenuation when a transponder is within range. This attenuation is detected by the control unit, which then switches from the first operating mode to the second, enabling communication with the transponder via the main antenna. Thanks to this invention, the antenna circuitry is particularly simple. The control circuit also has very low energy consumption, making it especially suitable for use in locking systems with limited energy storage capacity. The fact that the control unit is designed to detect the voltage attenuation at the detection antenna further simplifies the design of the transponder detector.The signal from the detection antenna is evaluated during the polling process, i.e., in the first operating mode. When the signal strength reaches a sufficient level, which corresponds to adequate attenuation of the antenna voltage, the control unit detects the signal and switches to the second operating mode. This allows an attempt to communicate with the detected transponder.

[0011] According to another advantageous embodiment of the invention, the magnetic coupling with simultaneous electrical separation of the main antenna from the detection antenna is particularly simple if the main antenna and the detection antenna enclose each other or are arranged on a common core. This design makes the transponder detector particularly simple.

[0012] According to another advantageous embodiment of the invention, further simplification of the transponder detector is achieved by connecting the control unit to the main antenna via a digital interface and to the detection antenna via an analog interface. In the first operating mode, the main antenna can be easily supplied with detection signals via the digital interface in a so-called polling process, and in the second operating mode, the data from the transponder can be read out. The attenuation caused by the transponder within the reception range at the detection antenna can be easily measured via the analog interface. This allows the control unit to switch from the first to the second operating mode.

[0013] According to another advantageous embodiment of the invention, a constant power supply to the main antenna in the first operating mode can be easily avoided if the control device for powering the main antenna is designed to operate at intervals. This results in particularly low energy consumption for the transponder detector.

[0014] According to another advantageous embodiment of the invention, the voltage signal of the detection antenna during the detection of a transponder can be amplified if the detection antenna is coupled to at least one amplitude amplification module. Such an amplitude amplification module thus functions as a voltage multiplier. This makes the detection antenna significantly more sensitive to voltage changes or attenuation during the polling process. Due to the increased sensitivity, the polling process can be carried out at considerably lower field energies, which contributes to a reduction in energy consumption. Furthermore, transponders with particularly low coupling factors can also be detected.

[0015] According to another advantageous embodiment of the invention, further increasing the voltage signal is achieved by connecting several amplitude amplification modules in series.

[0016] According to another advantageous embodiment of the invention, the amplitude amplification module is particularly simple in design if the amplitude amplification module comprises a Delon circuit or a Villard circuit.

[0017] According to another advantageous embodiment of the invention, the sensitivity of the detection antenna is further increased if the detection antenna has a higher number of turns than the main antenna. For example, doubling the number of turns doubles the sensitivity.

[0018] According to another advantageous embodiment of the invention, the structural complexity and susceptibility to errors of the transponder detector can be kept particularly low if the carrier frequency for excitation of the main antenna is the same in both operating modes. This design avoids the need for the main antenna and the transponder to be designed for different frequencies. Preferably, the carrier frequency is 13.56 MHz.

[0019] According to an advantageous embodiment of the invention, reliable detection of various transponders with a wide range of resonant frequencies and coupling factors can be ensured by connecting a switchable matching network downstream of the main antenna. This matching network is tuned to a frequency above the carrier frequency and has two switching states, wherein the matching network exhibits a lower impedance in a first switching state than in a second switching state. The matching network, which is typically connected downstream of RFID antennas, is usually composed of coils, capacitors, and resistors and is generally tuned to a fixed frequency corresponding to the carrier frequency. The matching network adapts the voltage signal output and input at the antenna to the system's requirements and, for example, filters out unwanted harmonics of a signal that would complicate processing.

[0020] The two switching states are preferably each assigned to one of the two operating modes, with the first switching state assigned to the first operating mode and the second switching state to the second operating mode. The reduced impedance in the first switching state can be achieved, for example, by switching off capacitors in the matching network. By assigning the first switching state to the first operating mode, the matching network exhibits a lower impedance when generating an electromagnetic field for detecting potential communication partners. Thus, a stronger field can be generated with the same current. This allows transponders with lower coupling factors to be detected more reliably.Furthermore, the inventive design also enables the detection of transponders with a resonant frequency that deviates significantly from the carrier frequency, resulting in lower attenuation at the carrier frequency and thus a weaker detection signal. Such deviations in the resonant frequency of transponders can occur, for example, due to environmental factors (e.g., in a metallic environment).

[0021] The control circuit can be used in many areas. Due to its small size and low energy consumption, the transponder detector can be easily integrated into locking systems, provided the control unit is connected to an electronic locking mechanism and that the locking mechanism is connected to an energy storage device. This allows the transponder detector to be used in lock cylinders, which are typically very small and controlled by electronic passive transponders. Such lock cylinders contain the locking mechanism, a battery or cell as an energy storage device, and the control circuit for activating the locking mechanism.

[0022] The second problem, namely the creation of a particularly simple method for reading the transponder, is solved according to the invention by the control unit detecting attenuation of the voltage at the detection antenna and switching from a first to a second operating mode when the attenuation is sufficient. The switch from the second operating mode to the first operating mode occurs after a predetermined time interval or after the communication with the transponder is completed. This design defines a termination criterion that ends communication or a communication attempt with the transponder. Upon occurrence of this termination criterion, the system switches back to the polling process described above.

[0023] The invention allows for numerous embodiments. To further illustrate its basic principle, several of these are shown in the drawing and described below. This shows in Fig. 1 schematically a control circuit with an electronic locking device, Fig. 2 schematically another embodiment of a control circuit, Fig. 3 schematically another embodiment of a control circuit, Fig. 4 an embodiment of a magnetic coupling of two antennas of the control circuit, Fig. 5 a Villard circuit of the control circuit, Fig. 6 a Delon bridge circuit, Fig. 7 a Delon multiplier, Fig. 8 a method for reading a transponder with the control circuit.

[0024] Figure 1Figure 1 shows a control circuit 1 of an electronic access control system with a transponder detector 2 for the signals of a transponder 3. The access control system has an exemplary locking cylinder 4 with an energy storage device 5 and a locking mechanism 6. The transponder 3 has a transponder chip 7 and an antenna 8 and is designed as an electronic key for controlling the locking mechanism 6 of the locking cylinder 4. The control circuit 1 has an evaluation unit 9 for evaluating the signals of the transponder 3 and is, in practice, structurally integrated into the locking cylinder 4.

[0025] The transponder detector 2 has a main antenna 10 and a detection antenna 11, which are magnetically coupled to each other. The main antenna 10 is bidirectionally connected to a control unit 13 via a digital interface 12. The detection antenna 11 is connected to the control unit 13 via an analog interface 14.

[0026] Figure 2 shows another embodiment of a control circuit 101, which differs from the Figure 1This embodiment differs in that an amplitude amplification module 115 is arranged between a detection antenna 111 and a control unit 113, and that a switchable matching network 112 is arranged between the main antenna 110 and the control unit 113. The amplitude amplification module 115 increases the voltage signal of the detection antenna 111. The matching network 112 has two switching states with different impedances and is switched when the control circuit 1 switches between its two operating modes. Otherwise, this embodiment is like the one described in Figure 1 built.

[0027] Figure 3 shows a further embodiment of a control circuit 201, which differs from that of Figure 2 only differs in that several amplitude amplification modules 215 are arranged one after the other. Otherwise, this embodiment is like the one from Figure 2The amplitude amplification modules 215 can be interconnected to form a multiplier 216.

[0028] Figure 4 shows an embodiment of a magnetic coupling of the main antenna 10 and the detection antenna 11 of the control circuit 1 from the Figures 1 to 3 It can be seen that the detection antenna 11 and the main antenna 10 surround each other. The detection antenna 11 and the main antenna 10 can also be arranged on a common core (not shown). In an embodiment not shown, the detection antenna 11 has a higher number of turns than the main antenna 10.

[0029] Figure 5 shows a Villard circuit 17, which is used in the amplitude amplification module 115 in the Figure 2 and 3shown control circuits 101 and is connected to the detection antenna 111. C represents a capacitor and D a diode. The voltage output from the Villard circuit 17 is labeled UA.

[0030] Figure 6 shows a bridge circuit according to Delon 18, which is used as an amplitude gain module 115 in the Figure 2 and 3 The control circuits shown in section 101 can be used. The symbol designations correspond to those in Figure 5 described, where several capacitors C i and diodes D i (i= 1, 2) are used.

[0031] Figure 7 shows a multiplier according to Delon 19, which is used for several amplitude amplification modules 215 as a multiplier 216 according to the control circuit 201. Figure 3 can be used and connected to the detection antenna 211.

[0032] Figure 8shows a method for reading the transponder 3 of the control circuit 1 according to the Figures 1 to 3In a first operating mode, which characterizes the ground state S1 of the control circuit 1, a detection signal is cyclically transmitted from the main antenna 10 at long intervals during a polling process S2. The control unit 1 detects, in step S3, any attenuation of the antenna voltage of the detection antenna 11 by the transponder 3 located within communication range. If this attenuation is detected, a communication attempt S5 with the transponder 3 is initiated in a second operating mode in step S4. In step S6, the data from the transponder 3 is read, and access authorization for the locking cylinder 4 is requested. In step S7, the locking mechanism 6 is activated, thereby unlocking the locking cylinder 4.If the communication attempt fails in step S5, if a transponder 3 is not detected in step S3, if there is no access authorization in step S6, or after a specified time period has elapsed in step S7, the system switches back to the first operating mode and the procedure is restarted.

Claims

1. Control circuit (1, 101, 201) of an electronic access control system comprising a transponder detector (2) for signals from a transponder (3), in particular an RFID transponder, comprising a main antenna (10, 110) and comprising a detection antenna (11, 111, 211) for detecting the transponder (3) located within communication range, a control device (13, 113) being designed in a first operating mode to supply the main antenna (10, 110) with electrical current to generate an electromagnetic field and in a second operating mode to communicate with the transponder (3) via the main antenna (10), characterized in that the main antenna (10, 110) and the detection antenna (11, 111, 211) are magnetically coupled to one another and electrically separated from one another, and in that the control device (13, 113) is designed to measure a damping of the voltage at the detection antenna (11, 111, 211), and in that a signal from the detection antenna (11, 111, 211) is evaluated in the first operating mode and, when the voltage at the detection antenna (11, 111, 211) is sufficiently damped, is measured by the control device (13, 113) in order to change to the second operating mode.

2. Control circuit according to claim 1, characterized in that the main antenna (10, 110) and the detection antenna (11, 111, 211) surround each other or are arranged on a common core.

3. Control circuit according to either claim 1 or claim 2, characterized in that the control device (13, 113) is connected to the main antenna (10, 110) via a digital interface (12) and to the detection antenna (11, 111, 211) via an analog interface (14).

4. Control circuit according to at least one of claims 1 to 3, characterized in that the control device (13, 113) is designed to energize the main antenna (10) at intervals.

5. Control circuit according to at least one of claims 1 to 4, characterized in that the detection antenna (111, 211) is coupled to at least one amplitude amplification module (115, 215).

6. Control circuit according to claim 5, characterized in that a plurality of amplitude amplification modules (215) are connected in series.

7. Control circuit according to at least one of claims 5 and 6, characterized in that the amplitude amplification module (115) has a Greinacher circuit (18) or a cascade circuit (17).

8. Control circuit according to at least one of claims 1 to 7, characterized in that the detection antenna (11, 111, 211) has a higher number of turns than the main antenna (10, 110).

9. Control circuit according to at least one of claims 1 to 7, characterized in that the carrier frequency for exciting the main antenna (10, 110) is the same in both operating modes.

10. Control circuit according to at least one of claims 1 to 9, characterized in that a switchable matching network (112) is connected downstream of the main antenna (110), which network is tuned to a resonance frequency above the carrier frequency and which has two switching states, the matching network (112) having a lower impedance in a first switching state than in a second switching state.

11. Control circuit according to at least one of claims 1 to 10, characterized in that the control device (13, 113) is connected to an electronic locking mechanism (6) and in that the locking mechanism (6) is connected to an energy store (5).

12. Method for reading out a transponder (3), in particular an RFID transponder, having the control circuit (1, 101, 201) according to any of the preceding claims, a main antenna (10, 110) being energized and a control device (13, 113) measuring the change in an amplitude, characterized in that the control device (13, 113) measures a damping of the voltage at the detection antenna (11, 111, 211) and, when the voltage at the detection antenna (11, 111, 211) is sufficiently damped, changes from a first to the second operating mode, and in that the change from the second operating mode to the first operating mode takes place after a predetermined period of time or after completion of communication with the transponder.