Low-radiation acoustic-magnetic decoder

Abstract

The invention discloses a low-radiation acoustic magnetic decoder which comprises an alternating current power supply, a driving circuit and a first coil, the alternating current power supply is used for providing alternating current voltage, the first coil and the driving circuit are both connected with the alternating current power supply, and the first coil and the driving circuit are connected in series. The driving circuit controls the first coil and the AC power supply to form a closed loop based on the first control signal, generates an alternating current through the AC voltage and adjusts the peak value of the alternating current, and the first coil generates an alternating magnetic field based on the alternating current to inactivate the acoustic-magnetic EAS tag or mark. According to the low-radiation acoustic magnetic decoder disclosed by the invention, the alternating current power supply, the driving circuit and the first coil which are connected in series are formed, so that a tag or a mark can be inactivated by using an attenuation amplitude alternating magnetic field with a low inactivation frequency of 50Hz to 200Hz; and the exposure of the human body to the electromagnetic field is reduced to a level which conforms to increasingly strict human body electromagnetic field exposure limitation formulated by various supervision institutions, and the method has the characteristics of low emission and low radiation.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic article monitoring, and in particular relates to a low-radiation acoustic-magnetic decoder. Background Art

[0002] Electronic Article Surveillance (EAS) systems use reusable EAS tags or disposable EAS labels / tags to monitor merchandise. Reusable EAS tags are typically removed from merchandise before the customer leaves the store. Disposable tags or tags are typically attached to or placed inside the packaging with an adhesive; these tags remain on the merchandise and must be deactivated before the customer can remove them from the store.

[0003] EAS tags or labels can be deactivated using a deactivation device. According to a known technique for deactivating acoustomagnetic tags or labels, the magnetized element of the acoustomagnetic tag is demagnetized by exposing it to an alternating magnetic field with an initial amplitude greater than the coercive force of the element and then allowing the field to decay to zero. Once the element is demagnetized, the tag's resonant frequency deviates significantly from the predetermined interrogation signal frequency, and the tag's response amplitude to the interrogation signal is so low that it cannot be detected by a detection device.

[0004] Popular deactivation devices consist of an interrogation circuit that detects the presence of the tag or label to be deactivated. When the tag or label's presence is detected, a coil drive circuit is triggered, which uses a capacitor that is discharged through a deactivation coil to generate a decaying amplitude alternating deactivation signal that is applied to the deactivation coil. To ensure proper deactivation of the acoustomagnetic (AM) tag, the initial amplitude of the alternating magnetic field must be greater than the coercivity of the magnetized element of the AM tag or label.

[0005] Although the above-mentioned types of deactivation devices can be used satisfactorily for their intended purposes, they do not fully address the problem of human electromagnetic field exposure levels caused by attenuated amplitude alternating electromagnetic fields at a given electromagnetic field frequency. These types of deactivation devices typically use an inactivation electromagnetic field frequency of 800Hz to 3000Hz, and the coil drive voltage is as high as 200-500VDC. In some regions, regulatory agencies have established increasingly stringent human exposure limits for certain electrical equipment (including safety labels or marking deactivation devices). Some acoustomagnetic deactivation devices do not comply with the relevant electromagnetic field human exposure limits set by various regulatory agencies. Since it is undesirable to reduce the amplitude of the deactivation coil drive signal (i.e., the voltage of the energy storage device), reducing the frequency of the attenuated amplitude alternating electromagnetic field is a viable option because the human body's exposure level to electromagnetic fields is related to the frequency. According to the EN 50364:2010 standard, the human exposure limits (RMS) for alternating electromagnetic fields (B fields) are 6.25 microteslas (μT) at 3kHz and 100 microteslas (μT) at 50Hz. For example, an alternating demagnetizing electromagnetic field with a frequency of 3kHz and a strength of 10 microteslas (μT) would exceed the human exposure limit. However, human exposure to an alternating demagnetizing electromagnetic field with a frequency of 50Hz and a strength of 10 microteslas (μT) is safe.

[0006] The use of a low-frequency deactivation electromagnetic field can reduce human exposure to electromagnetic fields during the deactivation process, which is required by various regulatory agencies. From the perspective of human exposure to electromagnetic fields, it would be desirable to provide an acoustomagnetic EAS tag or marker deactivator that operates at a lower deactivation electromagnetic field frequency than currently popular deactivators.

[0007] Therefore, in response to the above technical problems, it is necessary to provide a low-radiation acoustic-magnetic decoder. Summary of the Invention

[0008] The object of the present invention is to provide a low-radiation acousto-magnetic decoder capable of generating a low-frequency deactivation electromagnetic field.

[0009] In order to achieve the above object, a specific embodiment of the present invention provides the following technical solutions:

[0010] A low-radiation acoustic magnetic decoder, comprising: an AC power supply, a drive circuit, and a first coil, wherein the AC power supply is used to provide an AC voltage, the first coil and the drive circuit are both connected to the AC power supply, and the first coil and the drive circuit are connected in series;

[0011] The driving circuit is used to control the first coil and the AC power supply to form a closed loop based on the first control signal, generate an alternating current based on the AC voltage, and adjust the peak value of the alternating current;

[0012] The first coil is used to generate an alternating magnetic field based on an alternating current to deactivate an acoustomagnetic EAS tag or label.

[0013] In one or more embodiments of the present invention, the driving circuit includes a switching unit and a resistance unit, wherein the switching unit is used to control the on-off connection between the resistance unit and the first coil based on a first control signal, and to control the total resistance value of the resistance units connected to the closed loop through the first control signal to adjust the peak value of the alternating current.

[0014] In one or more embodiments of the present invention, the switch unit includes a first switch unit and several second switch units, the first switch unit is connected between the AC power supply and the first coil, and the first switch unit is used to control the on and off between the first coil and the AC power supply based on a first control signal, the second switch unit is connected in series with the resistance unit and is connected between the AC power supply and the first coil, and the second switch unit is used to control the on and off between the AC power supply, the resistance unit and the first coil based on the first control signal.

[0015] In one or more embodiments of the present invention, the low-radiation acousto-magnetic decoder further includes a control circuit connected to the driving circuit, and the control circuit is configured to generate a first control signal.

[0016] In one or more embodiments of the present invention, the low-radiation acousto-magnetic decoder further includes a zero-crossing detection circuit, which is connected to the AC power supply and the drive circuit and is configured to generate a zero-crossing detection signal based on the AC voltage. The control circuit is configured to generate a first control signal based on the zero-crossing detection signal to adjust the peak value of the alternating current at the zero-crossing point of the AC voltage.

[0017] In one or more embodiments of the present invention, the low-radiation acoustomagnetic decoder further includes an interrogation circuit connected to the drive circuit and the control circuit, and a second coil connected to the interrogation circuit, wherein the interrogation circuit is configured to drive the second coil to generate a detection magnetic field for detecting the area to be detected and to generate a detection signal when an acoustomagnetic EAS tag or marker is detected, and the control circuit is configured to generate a first control signal based on the detection signal.

[0018] In one or more embodiments of the present invention, the first switching unit includes a first optocoupler isolator and a first bidirectional thyristor, the first bidirectional thyristor is connected in series between the AC power supply and the first coil, the first optocoupler isolator generates a first trigger signal based on a first control signal, and the first optocoupler isolator is connected to the control end of the first bidirectional thyristor to control the opening and closing of the first bidirectional thyristor based on the first trigger signal.

[0019] In one or more embodiments of the present invention, the second switching unit includes a second optocoupler isolator and a second bidirectional thyristor, the second bidirectional thyristor is connected in series in a branch where the AC power supply, the first coil and the resistance unit are located, the second optocoupler isolator generates a second trigger signal based on the first control signal, and the second optocoupler isolator is connected to the control end of the second bidirectional thyristor to control the opening and closing of the second bidirectional thyristor based on the second trigger signal.

[0020] In one or more embodiments of the present invention, the AC power supply includes a transformer, the transformer includes a secondary winding, a first end of the secondary winding is connected to the drive circuit, and a second end of the secondary winding is connected to the first coil.

[0021] In one or more embodiments of the present invention, the first coil and the second coil constitute a deactivation pad, and the first coil and the second coil are concentrically arranged.

[0022] Compared with the higher deactivation magnetic field frequencies in the range of 800Hz to 3000Hz and the required voltages of up to 200-500V in the prior art, the low-radiation acousto-magnetic decoder of the present invention generates an attenuated amplitude alternating magnetic field with a low deactivation frequency of 50Hz to 200Hz to deactivate the acousto-magnetic EAS tag or marker by connecting the drive circuit, the first coil, and the alternating power supply in series to form a closed loop. During the deactivation process of the acousto-magnetic EAS tag or marker, the human body's exposure to electromagnetic fields is reduced to a level that complies with the increasingly stringent human electromagnetic field exposure limits established by various regulatory agencies. It has the characteristics of low emissions and low radiation. In addition, the low-radiation acousto-magnetic decoder of the present invention can operate at a voltage of 50 to 80V, thereby improving its safety.

[0023] The low-radiation acousto-magnetic decoder of the present invention can optimize the number of attenuated sinusoidal half-waves without affecting the inactivation of acousto-magnetic EAS tags or labels, more quickly attenuate the low-frequency attenuated amplitude alternating magnetic field, and maintain the human exposure limit (RMS) exposure value of the inactivation electromagnetic field at the lowest possible level;

[0024] The low-radiation acousto-magnetic decoder of the present invention can deactivate acousto-magnetic EAS tags or labels at a distance of at least 8 cm from the deactivation pad or deactivation coil, while still complying with the human electromagnetic field exposure limits established by various regulatory agencies, and is more convenient to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a principle block diagram of a low-radiation acoustic magnetic decoder according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of a driving circuit for a low-radiation acoustic magnetic decoder according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of an alternating current waveform on a first coil in one embodiment of the present invention;

[0029] Figure 4 is a circuit diagram of a driving circuit in one embodiment of the present invention;

[0030] Figure 5 This is a plan view of the arrangement of the first coil and the second coil in one embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0032] The description uses the phrases "in this embodiment" or "in other embodiments" or "in some embodiments", which can each refer to one or more of the same or different embodiments. In addition, the terms "including", "comprising", "having", etc. used in relation to the embodiments of this application are synonymous.

[0033] The terms "coupled," "connected," or "connected" as used in this specification encompass both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as an electrically conductive medium, which may have parasitic inductance or capacitance. An indirect connection may also include a connection through other active or passive devices, such as switches, follower circuits, or other circuits or components, to achieve the same or similar functional objectives. Furthermore, in the present invention, terms such as "first" and "second" are primarily used to distinguish one technical feature from another and do not necessarily require or imply a specific relationship, quantity, or order between these technical features.

[0034] In the detailed description of the specification, reference is made to the accompanying drawings forming a part hereof, wherein like reference numerals designate like parts throughout, and wherein exemplary embodiments that may be implemented are shown by way of example. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present application. Therefore, the following detailed description should not be construed in a limiting sense.

[0035] The present invention discloses a low-radiation acousto-magnetic decoder, comprising an AC power supply, a drive circuit, and a first coil. The AC power supply is configured to provide an AC voltage. The first coil and the drive circuit are both connected to the AC power supply, with the first coil and the drive circuit connected in series. The drive circuit controls the first coil and the AC power supply to form a closed loop based on a first control signal, generates an alternating current from the AC voltage, and regulates the peak value of the alternating current. The first coil generates an alternating magnetic field based on the alternating current to inactivate an acousto-magnetic EAS tag or label.

[0036] The present invention can generate an attenuated amplitude alternating magnetic field with a low deactivation frequency of 50Hz to 200Hz to inactivate acoustomagnetic EAS tags or labels. During the deactivation process of the acoustomagnetic EAS tags or labels, the human body's exposure to electromagnetic fields is reduced to a level that complies with the increasingly stringent human electromagnetic field exposure limits established by various regulatory agencies. It has the characteristics of low emissions and low radiation. In addition, the low-radiation acoustomagnetic decoder of the present invention can operate at a voltage of 50 to 80V, thereby improving safety in use.

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] like Figure 1 As shown, a low-radiation acousto-magnetic decoder includes an AC power supply, a drive circuit 10, a first coil L1, a zero-crossing detection circuit 40, a control circuit 20, an inquiry circuit 30 and a second coil L2.

[0039] In one embodiment, the AC power supply includes a transformer T, which includes a primary winding and a secondary winding. The primary winding of the transformer T receives AC power, while the first end of the secondary winding is connected to the drive circuit 10, and the second end is connected to the first coil L1. The transformer T is configured to reduce the voltage of the AC power to provide an AC voltage Vd, which serves as the operating power supply for the drive circuit 10.

[0040] The first coil L1 and the drive circuit 10 are both connected to an AC power supply. The first coil L1 and the drive circuit 10 are connected in series. The drive circuit 10 is used to control the first coil L1 and the AC power supply to form a closed loop based on a first control signal, generate an alternating current through an AC voltage Vd, and adjust the peak value of the alternating current based on the first control signal. The first coil L1 is used to generate a low-frequency attenuated amplitude alternating magnetic field based on the alternating current to inactivate the acoustomagnetic EAS tag or label.

[0041] In one embodiment, low frequency refers to a frequency range of 50 Hz to 200 Hz, and the low-frequency attenuated amplitude alternating magnetic field has the same frequency as the AC voltage Vd. For example, if the AC voltage Vd is 50 Hz or 60 Hz, the frequency of the low-frequency attenuated amplitude alternating magnetic field is also 50 Hz or 60 Hz, that is, the deactivation frequency is 50 Hz or 60 Hz.

[0042] The driving circuit 10 includes a switching unit and a resistance unit 13. The resistance unit 13 includes a plurality of resistance devices. The switching unit is used to control the on-off connection between the resistance unit 13 and the first coil L1 based on a first control signal, and to control the total resistance value of the resistance unit 13 connected to the closed loop through the first control signal to adjust the peak value of the alternating current.

[0043] It is understood that the low-frequency, attenuated-amplitude alternating magnetic field generated by the first coil L1 is the product of the number of turns of the first coil L1 and the coil current (i.e., the alternating current in this embodiment). This embodiment exposes the acoustomagnetic EAS tag or marker to an alternating magnetic field with an initial intensity greater than the coercive force of the acoustomagnetic EAS tag or marker. By gradually increasing the total resistance of the resistor unit 13 connected to the closed loop to gradually reduce the peak value of the alternating current, the low-frequency, attenuated-amplitude alternating magnetic field is regulated (i.e., the alternating magnetic field is attenuated to zero), thereby inactivating the acoustomagnetic EAS tag or marker.

[0044] like Figure 2 As shown, in one embodiment, the switch unit includes a first switch unit 11 and a plurality of second switch units 12. The first switch unit 11 is connected between the AC power source (i.e., the first end of the secondary winding of the transformer T) and the first coil L1. The first switch unit 11 is used to control the connection between the first coil L1 and the AC power source based on a first control signal CS0. The second switch unit 12 is connected in series with the resistor element in the resistor unit 13 and is connected between the AC power source and the first coil L1. The second switch unit is used to control the connection between the AC power source, the resistor unit 13, and the first coil L1 based on first control signals CS1 to CSN. It will be understood that in order to facilitate the distinction between the multiple second switch units 12, the second switch units K1 to KN are used below to represent the second switch units arranged in sequence, and the first switch unit K0 is the first switch unit 11.

[0045] Optionally, the number of the second switch units 12 corresponds to the number of resistors in the resistor unit 13, that is, the drive circuit 10 includes N second switch units (ie Figure 2 The second switch unit K1 to the second switch unit KN) and N resistor devices (ie Figure 2Furthermore, the resistance values ​​of the resistors R1 to RN increase sequentially, and under the control of the first control signals CS0 to CSN, the first switch unit K0 and the second switch units K1 to KN are turned on sequentially to generate an alternating current with a sinusoidal waveform of alternating attenuation amplitudes.

[0046] Specifically, the first control signal CS0 turns on the first switch unit K0 at the zero-crossing point of the AC voltage Vd, forming a closed loop with the first coil L1 and the AC power source. Ohm's law states that the peak value of the alternating current flowing through the first coil L1 is determined by the AC voltage Vd and the total impedance of the closed loop. Without changing the AC voltage Vd, the peak value of the alternating current flowing through the first coil L1 decreases as the total impedance of the closed loop increases. In this case, the total impedance of the closed loop comprises the impedance of the first coil L1 and the on-resistance of the switch unit (the on-resistance of the switch unit in this case is the on-resistance of the first switch unit K0).

[0047] At the next zero-crossing point of the AC voltage Vd, the first switch unit K0 turns off, and the first control signal CS1 turns on the second switch unit K1 at the zero-crossing point of the AC voltage Vd. The first coil L1, resistor R1, and the AC power supply form a closed loop. Similarly, the peak value of the AC current flowing through the first coil L1 is determined by the AC voltage Vd and the total impedance of the closed loop. At this point, the total impedance of the closed loop includes the impedance of the first coil L1, the on-resistance of the switch unit, and the resistance of resistor R1. Compared to the previous zero-crossing point, the total impedance of the closed loop increases, thereby reducing the peak value of the AC current. It should be noted that the on-resistance of the switch unit at this point can be understood as the on-resistance of the second switch unit K1. Since the first and second switch units have similar structures, the difference in on-resistance between them is negligible and will not be further discussed.

[0048] At the subsequent zero-crossing point, the first switch unit K0 and the second switch unit K1 are turned off, and the first control signal CS2 causes the second switch unit K2 to be turned on at the zero-crossing point of the AC voltage Vd. The first coil L1, the resistor R2 (R2>R1) and the AC power supply form a closed loop. Similarly, it can be seen that the peak value of the AC current flowing through the first coil L1 is further reduced at this time.

[0049] And so on, until the second switch unit KN is turned on at the zero-crossing point of the AC voltage Vd by the first control signal CSN, the first coil L1, the resistor RN (RN>R(N-1)) and the AC power supply form a closed loop. At this time, the alternating current in the closed loop has a low peak value to ensure that the acoustomagnetic EAS tag or mark can be fully inactivated, and the response amplitude of the acoustomagnetic EAS tag or mark to the detection signal is very low and cannot be detected by the detection device.

[0050] Figure 3The figure shows the waveform of the alternating current on the first coil L1 when the first coil L1 generates a low-frequency, attenuated-amplitude alternating magnetic field. The low-frequency, attenuated-amplitude alternating magnetic field has alternating polarity with decreasing peak amplitude within each period Tc (20ms), the number of sinusoidal half waves with attenuated peak values ​​is between 10 and 16, and the total attenuation period is 100 to 160 milliseconds.

[0051] It can be understood that compared to the prior art, the present invention optimizes the number of attenuated sinusoidal half-waves without affecting the inactivation of the acoustomagnetic EAS tag or label, thereby more quickly attenuating the low-frequency, attenuated-amplitude alternating magnetic field and maintaining the human exposure limit (RMS) of the deactivation electromagnetic field at a minimum. In one embodiment, the low-frequency, attenuated-amplitude alternating magnetic field decays to near zero after approximately 120 milliseconds.

[0052] The control circuit 20 is connected to the drive circuit 10 and is configured to generate a first control signal. Furthermore, in one embodiment, the control circuit includes a processor. The control circuit 20 controls the switch unit via the first control signal, thereby controlling the order in which resistors R1 to RN in the resistor unit 13 are connected to the closed loop, and controlling the total resistance of the resistor units 13 connected to the closed loop, so as to generate a sinusoidal alternating current with a decaying amplitude of X sinusoidal half-waves in the closed loop. The alternating current attenuates its peak value in the first coil L1, thereby ensuring that the acousto-magnetic EAS tag or marker is fully inactivated, so that the acousto-magnetic EAS tag or marker's response amplitude to the detection signal is so low that it cannot be detected by the detection device.

[0053] It is understood that to limit the number of required resistors (R1-RN) and second switch units (K1-KN), multiple second switch units can be simultaneously turned on at the same zero-crossing point to reduce the peak value of the alternating current. Furthermore, the alternating current with an alternating sinusoidal waveform of attenuated amplitude can be generated by various drive circuits 10 and is not limited to the drive circuit 10 shown in this embodiment.

[0054] like Figure 4 As shown, in one embodiment, the first switch unit 11 includes a first optocoupler OP1, a first bidirectional thyristor ES0, a first matching resistor R8A, and a second matching resistor R9A. The first optocoupler OP1 generates a first trigger signal based on a first control signal CS0. The first optocoupler OP1 is connected to the control terminal of the first bidirectional thyristor ES0 to control the on and off of the first bidirectional thyristor ES0 based on the first trigger signal. It will be understood that when the first bidirectional thyristor ES0 is turned on, the alternating power supply, the first coil L1, and the drive circuit 10 are connected in series to form a closed loop.

[0055] Specifically, the first bidirectional thyristor ES0 is connected in series between the AC power supply and the first coil L1, the first end of the first matching resistor R8A is connected to the 3.3V power supply, and the second end is connected to pin 1 of the first optocoupler isolator OP1, pin 2 of the first optocoupler isolator OP1 receives the first control signal CS0, pin 3 of the first optocoupler isolator OP1 is connected to the control end of the first bidirectional thyristor ES0, pin 4 of the first optocoupler isolator OP1 is connected to the first end of the second matching resistor R9A, the first end of the first bidirectional thyristor ES0 is connected to the second end of the second matching resistor R9A and the first end of the secondary winding of the transformer T (i.e., the AC power supply), and the second end of the first bidirectional thyristor ES0 is connected to the first end of the first coil L1.

[0056] The second switch unit 12 includes a second optocoupler OP2, a second bidirectional thyristor ES1, a third matching resistor R8B, and a fourth matching resistor R9B. The second bidirectional thyristor ES1 is connected in series in the branch where the AC power supply, the first coil L1, and the resistor unit 13 are located. The second optocoupler OP2 generates a second trigger signal based on the first control signal CS1. The second optocoupler OP2 is connected to the control terminal of the second bidirectional thyristor ES1 to control the opening and closing of the second bidirectional thyristor ES1 based on the second trigger signal. It can be understood that when the second bidirectional thyristor ES1 is turned on, the AC power supply, the first coil L1, and the drive circuit 10 are connected in series to form a closed loop.

[0057] Specifically, the first end of the third matching resistor R8B is connected to a 3.3V power supply, the second end is connected to pin 1 of the second optocoupler isolator OP2, pin 2 of the second optocoupler isolator OP2 receives the first control signal CS1, pin 3 of the second optocoupler isolator OP2 is connected to the control end of the second bidirectional thyristor ES1, pin 4 of the second optocoupler isolator OP2 is connected to the first end of the fourth matching resistor R9B, the first end of the second bidirectional thyristor ES1 is connected to the second end of the fourth matching resistor R9B and the first end of the secondary winding of the transformer T (i.e., the alternating power supply), the second end of the second bidirectional thyristor ES1 is connected to the first end of the resistor R1, and the second end of the resistor R1 is connected to the first end of the first coil L1.

[0058] It should be noted that Figure 4The illustrated driving circuit 10 includes a plurality of second switch units 12 arranged in parallel and a plurality of corresponding resistor devices. For example, in this embodiment, another second switch unit 12 includes a second optocoupler OP3, a second bidirectional thyristor ES2, a third matching resistor R8C, and a fourth matching resistor R9C. In this embodiment, another second switch unit 12 includes a second optocoupler OP4, a second bidirectional thyristor ES3, a third matching resistor R8D, and a fourth matching resistor R9D, and so on. OP2 to OP8 are all second optocouplers, R8B to R8H are all third matching resistors, and R9B to R9H are all fourth matching resistors. The resistor unit 13 includes resistors R1 to R7. The connection relationships thereof are the same as those in the second switch unit 12 described above and are not further described here.

[0059] like Figure 1 As shown, the zero-crossing detection circuit 40 is connected to the control circuit 20 and the AC power supply and is configured to generate a zero-crossing detection signal based on the AC voltage Vd. The control circuit 20 generates a first control signal based on the zero-crossing detection signal to control the total resistance of the resistor units connected to the closed loop at the zero-crossing point of the AC current to adjust the peak value of the AC current.

[0060] It is understood that the zero-crossing detection circuit 40 is well known in the prior art and will not be described in detail herein. Any known or unknown zero-crossing detection circuit 40 may be used herein without limitation.

[0061] like Figure 1 As shown, in one embodiment, the interrogation circuit 30 is connected to the drive circuit 10 and the control circuit 20, and the second coil L2 is connected to the interrogation circuit 30. The interrogation circuit 30 is configured to drive the second coil L2 to generate a detection magnetic field to detect the test area 50 and generate a detection signal when an acoustomagnetic EAS tag or marker is detected. The control circuit 20 is configured to generate a first control signal based on the detection signal. It should be noted that after the acoustomagnetic EAS tag or marker is deactivated, its resonant frequency will significantly deviate from the predetermined detection signal frequency, and the acoustomagnetic EAS tag or marker's response amplitude to the detection signal will be too low to be detected by the interrogation circuit 30.

[0062] Specifically, the interrogation circuit 30 is used to drive the second coil L2 to generate a 58 kHz detection magnetic field to detect whether an acousto-magnetic EAS tag or marker is within the detection magnetic field. Upon detecting an acousto-magnetic EAS tag or marker, a detection signal is generated. Based on the detection signal, the control circuit 20 generates first control signals CS0 to CSN at the zero-crossing point of the alternating voltage to sequentially activate the first switch unit K0 and the second switch units K1 to KN, thereby generating an alternating current with a sinusoidal waveform of alternating attenuated amplitudes. Furthermore, after a preset time, the second coil L2 is re-driven to repeat the detection. If an undeactivated anti-theft tag or marker is still present, the detection signal continues to be generated. If, after a predetermined number of attempts, the acousto-magnetic EAS tag or marker remains undeactivated or has been verified as deactivated, the control circuit 20 initiates an appropriate warning signal.

[0063] It can be understood that the range and direction of the attenuated amplitude alternating magnetic field generated by the first coil L1 and the detection magnetic field formed by the second coil L2 are roughly matched.

[0064] It will be appreciated that the interrogation circuit 30 is well known in the art and will not be described in detail herein, and any known or unknown interrogation circuit 30, tag or marker detector may be used herein without limitation.

[0065] like Figure 5 As shown, in other alternative embodiments, the first coil L1 and the second coil L2 constitute a deactivation pad, the first coil L1 and the second coil L2 are concentrically arranged, the first coil L1 is located outside the second coil L2, and the first coil L1 and the second coil L2 are parallel or coplanar.

[0066] In other alternative embodiments, only one coil may be provided to serve as both the first coil L1 and the second coil L2 , and the coil is connected to the interrogation circuit 30 and the drive circuit 10 .

[0067] like Figure 1 As shown, the low-radiation acoustic magnetic decoder in one embodiment further includes an AC-DC conversion circuit 60, which is connected to the second end of the secondary winding of the transformer T and the tap of the secondary winding of the transformer T for realizing conversion between AC and DC.

[0068] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0069] Compared with the higher deactivation magnetic field frequency in the range of 800Hz to 3000Hz and the required voltage of up to 200-500V in the prior art, the low-radiation acousto-magnetic decoder of the present invention, through a drive circuit, a first coil and an alternating power supply connected in series to form a closed loop, can generate an attenuated amplitude alternating magnetic field with a low deactivation frequency of 50Hz to 200Hz to deactivate the acousto-magnetic EAS tag or label. During the deactivation process of the acousto-magnetic EAS tag or label, the human body's exposure to the electromagnetic field is reduced to a level that complies with the increasingly stringent human electromagnetic field exposure limits established by various regulatory agencies. It has the characteristics of low emissions and low radiation. In addition, the low-radiation acousto-magnetic decoder of the present invention can operate at a voltage of 50 to 80V, thereby improving safety in use.

[0070] The low-radiation acousto-magnetic decoder of the present invention can optimize the control of the number of attenuated sinusoidal half waves without affecting the inactivation of the acousto-magnetic EAS tag or marker, more quickly attenuate the low-frequency attenuated amplitude alternating magnetic field, and maintain the human exposure limit (RMS) exposure value of the inactivation electromagnetic field at the lowest possible level.

[0071] The low-radiation acousto-magnetic decoder of the present invention can deactivate acousto-magnetic EAS tags or labels at a distance of at least 8 cm from the deactivation pad or deactivation coil, while still complying with the human electromagnetic field exposure limits established by various regulatory agencies, and is more convenient to use.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0073] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A low-radiation acoustic magnetic decoder, characterized in that: include: An AC power supply, a drive circuit, and a first coil, wherein the AC power supply is used to provide an AC voltage, the first coil and the drive circuit are both connected to the AC power supply, and the first coil and the drive circuit are connected in series; The driving circuit is configured to control the first coil and the AC power supply to form a closed loop based on a first control signal, generate an alternating current based on the AC voltage, and adjust a peak value of the alternating current; The first coil is used to generate an alternating magnetic field based on an alternating current to deactivate an acoustomagnetic EAS tag or label.

2. The low-radiation acoustic magnetic decoder according to claim 1, characterized in that: The driving circuit includes a switch unit and a resistance unit. The switch unit is used to control the on-off between the resistance unit and the first coil based on a first control signal, and to control the total resistance of the resistance units connected to the closed loop through the first control signal to adjust the peak value of the alternating current.

3. The low-radiation acoustic magnetic decoder according to claim 2, characterized in that: The switch unit includes a first switch unit and several second switch units. The first switch unit is connected between the AC power supply and the first coil. The first switch unit is used to control the on / off between the first coil and the AC power supply based on a first control signal. The second switch unit is connected in series with the resistance unit and connected between the AC power supply and the first coil. The second switch unit is used to control the on / off between the AC power supply, the resistance unit and the first coil based on the first control signal.

4. The low-radiation acoustic magnetic decoder according to claim 1, characterized in that The low-radiation acoustic magnetic decoder further includes a control circuit connected to the drive circuit, and the control circuit is used to generate a first control signal.

5. The low-radiation acoustic magnetic decoder according to claim 4, characterized in that: The low-radiation acousto-magnetic decoder also includes a zero-crossing detection circuit, which is connected to the AC power supply and the drive circuit and is used to generate a zero-crossing detection signal based on the AC voltage. The control circuit is used to generate a first control signal based on the zero-crossing detection signal to adjust the peak value of the alternating current at the zero-crossing point of the AC voltage.

6. The low-radiation acoustic magnetic decoder according to claim 4, characterized in that: The low-radiation acousto-magnetic decoder also includes an interrogation circuit connected to the drive circuit and the control circuit, and a second coil connected to the interrogation circuit. The interrogation circuit is used to drive the second coil to generate a detection magnetic field to detect the area to be detected and generate a detection signal when an acousto-magnetic EAS tag or marker is detected. The control circuit is used to generate a first control signal based on the detection signal.

7. The low-radiation acoustic magnetic decoder according to claim 3, characterized in that: The first switching unit includes a first optocoupler isolator and a first bidirectional thyristor, the first bidirectional thyristor is connected in series between the AC power supply and the first coil, the first optocoupler isolator generates a first trigger signal based on a first control signal, and the first optocoupler isolator is connected to the control end of the first bidirectional thyristor to control the opening and closing of the first bidirectional thyristor based on the first trigger signal.

8. The low-radiation acoustic magnetic decoder according to claim 3, characterized in that: The second switching unit includes a second optocoupler isolator and a second bidirectional thyristor, the second bidirectional thyristor is connected in series in the branch where the AC power supply, the first coil and the resistance unit are located, the second optocoupler isolator generates a second trigger signal based on the first control signal, and the second optocoupler isolator is connected to the control end of the second bidirectional thyristor to control the opening and closing of the second bidirectional thyristor based on the second trigger signal.

9. The low-radiation acoustic magnetic decoder according to claim 1, characterized in that: The AC power supply includes a transformer, and the transformer includes a secondary winding. A first end of the secondary winding is connected to the drive circuit, and a second end of the secondary winding is connected to the first coil.

10. The low-radiation acoustic magnetic decoder according to claim 6, characterized in that: The first coil and the second coil constitute a deactivation pad, and the first coil and the second coil are concentrically arranged.

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