Low-radiation acoustic magnetic decoder

Abstract

The utility model discloses a low emission acoustic magnetic decoder, include: alternating current source, drive circuit and first coil, alternating current source is used to provide alternating voltage, first coil and drive circuit all are connected with alternating current source, and first coil forms series connection with drive circuit, and drive circuit is based on first control signal control first coil and alternating current source form closed loop, and through alternating voltage generates the peak value of alternating current and adjusts alternating current, and first coil is based on alternating current and generates alternating magnetic field to deactivate acoustic magnetic EAS label or mark. The utility model discloses a low emission acoustic magnetic decoder, through forming the series connection of alternating current source, drive circuit and first coil, can use 50Hz to 200Hz's low deactivation frequency's attenuation amplitude alternating magnetic field to deactivate label or mark, in the deactivation process, reduce the exposure of human body to electromagnetic field to the level that conforms to the human body electromagnetic field exposure limit that each regulatory agency makes, increasingly strict, has low emission, low radiation's characteristics.

Description

Technical Field

[0001] This utility model belongs to the field of electronic article monitoring technology, specifically relating to a low-emission acousto-magnetic decoder. Background Technology

[0002] Electronic Article Surveillance (EAS) systems use reusable EAS tags or one-time EAS tags / markers to monitor merchandise. Reusable EAS tags are typically removed from merchandise before the customer leaves the store. One-time tags or marks are usually affixed to packaging with adhesive or placed inside packaging; these tags remain on the merchandise and must be deactivated before the customer takes them out of the store.

[0003] Deactivation devices can be used to deactivate EAS tags or markers. According to a known technique for deactivating acousto-magnetic tags or markers, the magnetizing element of the acousto-magnetic tag is demagnetized by exposing it to an alternating magnetic field with an initial amplitude greater than the coercivity of the magnetizing element, and then allowing the magnetic field to decay to zero. After demagnetization, the tag's resonant frequency deviates significantly from the predetermined interrogation signal frequency, and the tag or marker's response amplitude to the interrogation signal is too low for the detection device to detect it.

[0004] Modern deactivation devices include an interrogation circuit that detects the presence of a tag or marker to be deactivated. When the tag or marker is detected, a coil drive circuit is triggered. This circuit uses a capacitor that discharges through the deactivation coil to generate a decaying amplitude alternating deactivation signal applied to the deactivation coil. To ensure proper deactivation of the acousto-magnetic (AM) tag, the initial amplitude of the alternating magnetic field must be greater than the coercivity of the magnetizing element of the AM tag or marker.

[0005] While the aforementioned types of deactivation devices can be satisfactorily used for their intended purposes, they do not adequately address the issue of human electromagnetic field exposure levels caused by damped amplitude alternating electromagnetic fields at a given electromagnetic field frequency. These types of deactivation devices typically use deactivation electromagnetic field frequencies ranging from 800 Hz to 3000 Hz, and the coil drive voltage can reach 200-500 VDC. In some regions, regulatory agencies have imposed increasingly stringent human exposure limits for certain electrical devices, including safety tags or marking deactivation devices. Some acousto-magnetic deactivation devices do not comply with the relevant electromagnetic field human exposure limits set by various regulatory agencies. Since reducing the amplitude of the deactivation coil drive signal (i.e., the voltage of the energy storage device) is not desirable, reducing the frequency of the damped amplitude alternating electromagnetic field is a viable option, as human exposure to electromagnetic fields is frequency-dependent. According to EN 50364:2010, the human exposure limit (RMS) for alternating electromagnetic fields (B-fields) is 6.25 microtesla (μT) at 3 kHz and 100 microtesla (μT) at 50 Hz. For example, an alternating demagnetizing electromagnetic field with a frequency of 3 kHz and an intensity of 10 microtesla (μT) would exceed the human exposure limit, while human exposure to an alternating demagnetizing electromagnetic field with a frequency of 50 Hz and an intensity of 10 microtesla (μT) is safe.

[0006] Using low-frequency deactivation electromagnetic fields 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 order to address the aforementioned technical problems, it is necessary to provide a low-emissivity acousto-magnetic decoder. Utility Model Content

[0008] The purpose of this invention is to provide a low-emission acoustomagnetic decoder that can generate a low-frequency deactivation electromagnetic field.

[0009] To achieve the above objectives, the technical solution provided by a specific embodiment of this utility model is as follows:

[0010] A low-emission acousto-magnetic decoder includes: an AC power supply, a drive circuit, and a first coil. The AC power supply is used to provide AC voltage. The first coil and the drive circuit are both connected to the AC power supply. The first coil and the drive circuit are connected in series.

[0011] The driving circuit is used to control the first coil to form a closed loop with the AC power supply based on the first control signal, and to 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 alternating current to deactivate acousto-magnetic EAS tags or markings.

[0013] In one or more embodiments of this utility model, the driving circuit includes a switching unit and a resistor unit. The switching unit is used to control the on / off connection between the resistor unit and the first coil based on a first control signal, and to control the total resistance value of the resistor unit 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 this utility model, the switching unit includes a first switching unit and a plurality of second switching units. The first switching unit is connected between the AC power supply and the first coil. The first switching unit is used to control the on / off connection between the first coil and the AC power supply based on a first control signal. The second switching unit is connected in series with the resistor unit and is connected between the AC power supply and the first coil. The second switching unit is used to control the on / off connection between the AC power supply, the resistor unit and the first coil based on the first control signal.

[0015] In one or more embodiments of the present invention, the low-emission acoustomagnetic decoder further includes a control circuit connected to the drive circuit, the control circuit being used to generate a first control signal.

[0016] In one or more embodiments of the present invention, the low-emission acoustomagnetic decoder further includes a zero-crossing detection circuit, which is connected to an AC power supply and a drive circuit, for generating a zero-crossing detection signal based on the AC voltage, and the control circuit for generating 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-emission acoustomagnetic decoder further includes an interrogation circuit connected to a driving circuit and a 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 tested and to generate a detection signal when an acoustomagnetic EAS tag or mark is detected. The control circuit is used 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. The first optocoupler isolator is connected to the control terminal 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 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 resistor unit are located. The second optocoupler generates a second trigger signal based on a first control signal. The second optocoupler is connected to the control terminal 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 this utility model, the AC power supply includes a transformer, the transformer includes a secondary winding, a first end of the secondary winding is connected to a drive circuit, and a second end is connected to a first coil.

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

[0022] Compared with the existing technology, which uses a higher deactivation magnetic field frequency in the range of 800Hz to 3000Hz and requires a voltage of up to 200-500V, the low-emission acoustomagnetic decoder of this invention, through a drive circuit, a first coil and an alternating power supply connected in series to form a closed loop, can generate a decaying amplitude alternating magnetic field with a low deactivation frequency of 50Hz to 200Hz to deactivate acoustomagnetic EAS tags or markers. During the deactivation process of acoustomagnetic EAS tags or markers, the human body's exposure to electromagnetic fields is reduced to a level that meets the increasingly stringent limits for human electromagnetic field exposure set by various regulatory agencies. It has the characteristics of low emissions and low radiation. Furthermore, the low-emission acoustomagnetic decoder of this invention can operate at a voltage of 50 to 80V, improving the safety of use.

[0023] The low-emission acoustomagnetic decoder of this invention can optimize the number of attenuated sine half-waves and attenuate low-frequency attenuated amplitude alternating magnetic fields more quickly without affecting the deactivation of acoustomagnetic EAS tags or markers, keeping the human exposure limit (RMS) exposure value of the deactivated electromagnetic field at the lowest possible level.

[0024] This invention relates to a low-emission acousto-magnetic decoder that can deactivate acousto-magnetic EAS tags or markers at a distance of at least 8 cm from the deactivation pad or deactivation coil, while still complying with the electromagnetic field exposure limits for humans set by various regulatory agencies, making it more convenient to use. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a block diagram illustrating the principle of a low-emission acoustomagnetic decoder in one embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the driving circuit of a low-emission acoustomagnetic decoder in one embodiment of the present invention;

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

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

[0030] Figure 5 This is a plan view showing the arrangement of the first and second coils in one embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this utility model, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

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

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

[0034] In the detailed description of this specification, reference is made to the accompanying drawings, which form a part thereof, wherein like reference numerals always denote like parts, and wherein exemplary embodiments are shown by way of example that may be implemented. It should be understood that other embodiments may be utilized, and structural or logical changes may be made, without departing from the scope of this application. Therefore, the following detailed description should not be considered limiting.

[0035] This utility model discloses a low-emission acoustomagnetic decoder, comprising: an AC power supply, a drive circuit, and a first coil. The AC power supply provides AC voltage, and both the first coil and the drive circuit are connected to the AC power supply, forming a series connection. The drive circuit controls the first coil to form a closed loop with the AC power supply based on a first control signal, and generates an alternating current through the AC voltage and adjusts the peak value of the alternating current. The first coil generates an alternating magnetic field based on the alternating current to deactivate acoustomagnetic EAS tags or markings.

[0036] This invention can generate a decaying amplitude alternating magnetic field with a low deactivation frequency of 50Hz to 200Hz to deactivate acoustomagnetic EAS tags or markers. During the deactivation process of acoustomagnetic EAS tags or markers, the human body's exposure to electromagnetic fields is reduced to a level that meets the increasingly stringent limits on human electromagnetic field exposure set by various regulatory agencies. It features low emissions and low radiation. Furthermore, the low-emission acoustomagnetic decoder of this invention can operate at a voltage of 50 to 80V, 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-emission acoustomagnetic 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 interrogation circuit 30, and a second coil L2.

[0039] In one embodiment, the AC power supply includes a transformer T, which comprises a primary winding and a secondary winding. The primary winding of the transformer T receives AC power, and 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 used to step down the AC power to provide an AC voltage Vd, which serves as the operating power supply for the drive circuit 10.

[0040] Both the first coil L1 and the drive circuit 10 are connected to the 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 to form a closed loop with the AC power supply based on the first control signal, and to generate an alternating current through the 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 decaying amplitude alternating magnetic field based on the alternating current to deactivate the acoustomagnetic EAS tag or mark.

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

[0042] The driving circuit 10 includes a switching unit and a resistor unit 13. The resistor unit 13 includes several resistor devices. The switching unit is used to control the on / off connection between the resistor unit 13 and the first coil L1 based on a first control signal, and to control the total resistance of the resistor 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 decaying 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). In this embodiment, the acousto-magnetic EAS tag or marker is exposed to an alternating magnetic field with an initial intensity greater than the coercivity of the acousto-magnetic EAS tag or marker. By gradually increasing the total resistance of the resistor unit 13 connected to the closed loop, the peak value of the alternating current is gradually reduced, thereby achieving the adjustment of the low-frequency decaying amplitude alternating magnetic field (even if the alternating magnetic field decays to zero), so as to deactivate the acousto-magnetic EAS tag or marker.

[0044] like Figure 2As shown, in one embodiment, the switching unit includes a first switching unit 11 and several second switching units 12. The first switching unit 11 is connected between the AC power supply (i.e., the first end of the secondary winding of transformer T) and the first coil L1. The first switching unit 11 is used to control the on / off connection between the first coil L1 and the AC power supply based on a first control signal CS0. The second switching units 12 are connected in series with the resistors in the resistor unit 13 and are connected between the AC power supply and the first coil L1. The second switching units are used to control the on / off connection between the AC power supply, the resistor unit 13, and the first coil L1 based on the first control signals CS1 to CSN. It can be understood that, for ease of distinguishing multiple second switching units 12, the second switching units are referred to as second switching units K1 to second switching units KN respectively, and the first switching unit K0 is the first switching unit 11.

[0045] Optionally, the number of second switching units 12 corresponds to the number of resistive devices in the resistor unit 13, that is, the driving circuit 10 includes N second switching units (i.e., Figure 2 The second switching unit K1 to the second switching unit KN shown) and N resistive devices (i.e. Figure 2 The resistors R1 to RN are shown. Further, the resistance values ​​of resistors R1 to RN increase sequentially. Under the control of the first control signal CS0 to the first control signal CSN, the first switch unit K0 and the second switch units K1 to the second switch units KN are turned on sequentially to generate an alternating current with alternating attenuation amplitude sinusoidal waveform.

[0046] Specifically, the first control signal CS0 turns on the first switching unit K0 at the zero-crossing point of the AC voltage Vd, forming a closed loop between the first coil L1 and the AC power supply. According to Ohm's law, 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. At this time, the total impedance of the closed loop includes the impedance value of the first coil L1 and the on-resistance of the switching unit (which is the same as the on-resistance of the first switching unit K0).

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

[0048] At the subsequent zero-crossing point, the first switching unit K0 and the second switching unit K1 are turned off, and the first control signal CS2 causes the second switching unit K2 to turn 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 alternating current flowing through the first coil L1 is further reduced at this time.

[0049] This process continues until the second switching 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, resistor RN (RN>R(N-1)) and AC power supply form a closed loop. At this time, the alternating current of the closed loop has a low peak value to ensure that the acoustomagnetic EAS tag or marker can be fully deactivated, and the response amplitude of the acoustomagnetic EAS tag or marker to the detection signal is very low, so it cannot be detected by the detection device.

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

[0051] Understandably, compared to existing technologies, this invention optimizes the number of attenuated sine half-waves without affecting the deactivation of acousto-magnetic EAS tags or markers. This allows for faster attenuation of the low-frequency attenuated amplitude alternating magnetic field, keeping the human exposure limit (RMS) exposure value of the deactivated electromagnetic field as low as possible. In one embodiment, the low-frequency attenuated amplitude alternating magnetic field attenuates to near zero after approximately 120 ms.

[0052] The control circuit 20 is connected to the drive circuit 10. The control circuit 20 is used to generate a first control signal. Further, in one embodiment, the control circuit includes a processor. The control circuit 20 controls the switching unit through the first control signal, thereby controlling the order in which the resistors R1 to RN in the resistor unit 13 are connected to the closed loop, and controlling the total resistance value of the resistor unit 13 connected to the closed loop, so that a sinusoidal alternating current with a decaying amplitude of X sinusoidal half-waves is generated in the closed loop. The peak value of the alternating current is attenuated in the first coil L1 to ensure that the acousto-magnetic EAS tag or marker is sufficiently deactivated, so that the response amplitude of the acousto-magnetic EAS tag or marker to the detection signal is so low that it cannot be detected by the detection device.

[0053] It is understood that, in order to limit the required number of resistors (R1~RN) and second switching units (K1~KN), multiple second switching units can be turned on simultaneously at the same zero-crossing point to reduce the peak value of the alternating current. Furthermore, the alternating current with alternating sinusoidal waveforms of alternating attenuation amplitude can be generated by different 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 switching unit 11 includes a first optocoupler OP1, a first bidirectional thyristor ESO, 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 ESO to control the opening and closing of the first bidirectional thyristor ESO based on the first trigger signal. It can be understood that when the first bidirectional thyristor ESO 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 ESO 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 OP1. Pin 2 of the first optocoupler OP1 receives the first control signal CS0. Pin 3 of the first optocoupler OP1 is connected to the control terminal of the first bidirectional thyristor ESO. Pin 4 of the first optocoupler OP1 is connected to the first end of the second matching resistor R9A. The first end of the first bidirectional thyristor ESO 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). The second end of the first bidirectional thyristor ESO is connected to the first end of the first coil L1.

[0056] The second switching 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 containing the AC power supply, the first coil L1, and the resistor unit 13. 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 form a closed loop in series.

[0057] Specifically, the first end of the third matching resistor R8B is connected to the 3.3V power supply, the second end is connected to pin 1 of the second optocoupler OP2, pin 2 of the second optocoupler OP2 receives the first control signal CS1, pin 3 of the second optocoupler OP2 is connected to the control terminal of the second bidirectional thyristor ES1, pin 4 of the second optocoupler 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 4 The driving circuit 10 shown includes multiple second switching units 12 arranged in parallel and multiple corresponding resistors. For example, in this embodiment, another second switching 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 switching 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, and their connection relationships are the same as those in the second switching units 12 described above, which will not be repeated 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 used 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 unit connected to the closed loop at the zero-crossing point of the alternating current to adjust the peak value of the alternating current.

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

[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. The second coil L2 is connected to the interrogation circuit 30. The interrogation circuit 30 is used to drive the second coil L2 to generate a detection magnetic field to detect the area 50 under test and to generate a detection signal when an acousto-magnetic EAS tag or marker is detected. The control circuit 20 is used to generate a first control signal based on the detection signal. It should be noted that after the acousto-magnetic EAS tag or marker is deactivated, the resonant frequency of the acousto-magnetic EAS tag or marker will deviate significantly from the predetermined detection signal frequency. The response amplitude of the acousto-magnetic EAS tag or marker to the detection signal is too low, so that the interrogation circuit 30 cannot detect it.

[0062] Specifically, the interrogation circuit 30 drives the second coil L2 to generate a 58kHz detection magnetic field to detect whether an acousto-magnetic EAS tag or mark is within the detection magnetic field. When an acousto-magnetic EAS tag or mark is detected, 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 turn on the first switching unit K0 and the second switching units K1 to KN, thereby generating an alternating current with alternating attenuation amplitudes of a sinusoidal waveform. Further, after a preset time, the second coil L2 is re-driven for repeated detection. If an inactive anti-theft tag or mark is still present, a detection signal continues to be generated. If, after a predetermined number of attempts, the acousto-magnetic EAS tag or mark is still not deactivated or has been verified as deactivated, the control circuit 20 will activate an appropriate warning signal.

[0063] It is understandable that the range and direction of the decaying amplitude alternating magnetic field generated by the first coil L1 are roughly matched with the detection magnetic field formed by the second coil L2.

[0064] It is understood that the interrogation circuit 30 is well known in the prior art and therefore will not be described in detail herein. Any known or unknown interrogation circuit 30, tag or marker detector may be used herein without restriction.

[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 this coil is connected to the interrogation circuit 30 and the drive circuit 10.

[0067] like Figure 1 As shown, in one embodiment, the low-emission acoustomagnetic decoder also 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 the conversion between AC and DC.

[0068] As can be seen from the above technical solutions, this utility model has the following beneficial effects:

[0069] Compared to existing technologies with higher deactivation magnetic field frequencies in the 800Hz to 3000Hz range and required voltages as high as 200-500V, the low-emission acoustomagnetic decoder of this invention, through a drive circuit, a first coil, and an alternating power supply connected in series to form a closed loop, can generate a decaying amplitude alternating magnetic field with a low deactivation frequency of 50Hz to 200Hz to deactivate acoustomagnetic EAS tags or markers. During the deactivation process of acoustomagnetic EAS tags or markers, the human body's exposure to electromagnetic fields is reduced to a level that meets the increasingly stringent limits for human electromagnetic field exposure set by various regulatory agencies. It features low emissions and low radiation, and the low-emission acoustomagnetic decoder of this invention can operate at a voltage of 50 to 80V, improving safety in use.

[0070] This invention's low-emission acoustomagnetic decoder can optimize the control of the number of attenuated sine half-waves without affecting the deactivation of acoustomagnetic EAS tags or markers, and attenuate low-frequency attenuated amplitude alternating magnetic fields more quickly, keeping the human exposure limit (RMS) exposure value of the deactivated electromagnetic field at the lowest possible level.

[0071] This invention relates to a low-emission acousto-magnetic decoder that can deactivate acousto-magnetic EAS tags or markers at a distance of at least 8 cm from the deactivation pad or deactivation coil, while still complying with the electromagnetic field exposure limits for humans set by various regulatory agencies, making it more convenient to use.

[0072] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A low-emissivity acousto-magnetic decoder, characterized in that, include: The AC power supply, the drive circuit, and the first coil are provided. The AC power supply is used to provide AC voltage. The first coil and the drive circuit are both connected to the AC power supply. The first coil and the drive circuit are connected in series. The driving circuit is used to control the first coil to form a closed loop with the AC power supply based on the first control signal, and to generate an alternating current based on the AC voltage and adjust the peak value of the alternating current. The first coil is used to generate an alternating magnetic field based on alternating current to deactivate acousto-magnetic EAS tags or markings.

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

3. The low-emissivity acousto-magnetic decoder according to claim 2, characterized in that, The switching unit includes a first switching unit and several second switching units. The first switching unit is connected between the AC power supply and the first coil. The first switching unit is used to control the connection and disconnection between the first coil and the AC power supply based on a first control signal. The second switching units are connected in series with the resistor unit and are connected between the AC power supply and the first coil. The second switching units are used to control the connection and disconnection between the AC power supply, the resistor unit and the first coil based on the first control signal.

4. The low-emissivity acousto-magnetic decoder according to claim 1, characterized in that, The low-emission acoustomagnetic decoder also includes a control circuit connected to the drive circuit, the control circuit being used to generate a first control signal.

5. The low-emissivity acousto-magnetic decoder according to claim 4, characterized in that, The low-emission acoustomagnetic decoder also includes a zero-crossing detection circuit, which is connected to an AC power supply and a drive circuit. The zero-crossing detection circuit 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-emissivity acousto-magnetic decoder according to claim 4, characterized in that, The low-emission acoustomagnetic decoder also includes an interrogation circuit connected to the driving 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 tested and to generate a detection signal when an acoustomagnetic EAS tag or mark is detected. The control circuit is used to generate a first control signal based on the detection signal.

7. The low-emissivity acousto-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. The first optocoupler isolator is connected to the control terminal 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-emissivity acousto-magnetic decoder according to claim 3, characterized in that, The second switching unit includes a second optocoupler 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 resistor unit are located. The second optocoupler generates a second trigger signal based on a first control signal. The second optocoupler is connected to the control terminal 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-emissivity acousto-magnetic decoder according to claim 1, characterized in that, The AC power supply includes a transformer, which includes a secondary winding. The first end of the secondary winding is connected to the drive circuit, and the second end is connected to the first coil.

10. The low-emissivity acousto-magnetic decoder according to claim 6, characterized in that, The first coil and the second coil form a deactivation pad, and the first coil and the second coil are arranged concentrically.

Images