HK1119282B - Techniques for deactivating electronic article surveillance labels using energy recovery - Google Patents

Description

Techniques for deactivating electronic article surveillance tags using energy recovery

Background

Electronic Article Surveillance (EAS) systems are used to control inventory and prevent theft or unauthorized removal of items attached to EAS security tags from a controlled area. Such a system may include a transmitter and receiver to establish a surveillance zone (typically at the entrance and/or exit of a retail store) surrounding the controlled area. The anti-theft area is set up such that items to be taken from or brought into the controlled area must pass through the anti-theft area.

EAS security tags may be attached to an article such as an article, product, container, pallet, shipping container, or the like. The tag contains a marker or sensor adapted to interact with a first signal transmitted by an EAS system transmitter into the surveillance zone. This interaction establishes a second signal within the surveillance zone. The EAS system receiver receives the second signal. If an item with an EAS security tag attached passes through the surveillance zone, the EAS system recognizes the second signal as an unauthorized presence of the item within the controlled zone and may, for example, trigger an alarm in some cases. Once the item is purchased, the EAS security tag is deactivated so that an alarm is not activated when the tag passes through the surveillance zone.

Drawings

FIG. 1 shows a schematic diagram of a module according to one embodiment.

FIG. 2 shows a schematic diagram of a module according to one embodiment.

Fig. 3 illustrates waveforms according to one embodiment.

FIG. 4 shows a schematic diagram of a module according to one embodiment.

FIG. 5 illustrates waveforms according to one embodiment.

FIG. 6 illustrates a block diagram in accordance with one embodiment.

FIG. 7 shows a diagram in accordance with one embodiment.

FIG. 8 illustrates waveforms according to one embodiment.

FIG. 9 illustrates waveforms according to one embodiment.

FIG. 10 illustrates waveforms according to one embodiment.

FIG. 11 illustrates waveforms according to one embodiment.

FIG. 12 illustrates a diagram in accordance with one embodiment.

FIG. 13 shows a diagram in accordance with one embodiment.

FIG. 14 shows a diagram in accordance with one embodiment.

FIG. 15 shows a diagram in accordance with one embodiment.

FIG. 16 shows a block diagram in accordance with one embodiment.

FIG. 17 illustrates programming logic in accordance with one embodiment.

Detailed Description

The EAS tag comprises two strips of material: a resonator made of a magnetic material of high magnetic permeability exhibiting a magnetomechanical resonance phenomenon, and a bias element (biaselement) made of a hard magnetic material. The state of the biasing element sets the operating frequency of the tag. The functional tag contains a magnetized bias element. The tag is deactivated by demagnetizing the magnetic biasing element using a demagnetization module. The demagnetization process may include subjecting the biasing element to a strong Alternating Current (AC) magnetic field having a magnetic field strength sufficient to overcome a diamagnetic force of the biasing element of the tag for a first time period, and gradually reducing the magnetic field strength along a ring-down decay envelope to a point near zero over a second time period. The decay of the ring-down envelope over the second time period may be referred to as, for example, a ring-down decay rate. The demagnetization cycle is the time required for the entire demagnetization process to occur over the first and second time periods. Effective demagnetization requires the application of a sufficiently strong magnetic field to overcome the coercive force of the bias element material prior to reducing the magnetic field strength. Applying a magnetic field during the demagnetization cycle (especially during ring down decay) requires a certain amount of demagnetization energy. A portion of this energy is typically consumed and wasted.

The embodiments described herein provide recovery of a portion of the demagnetization energy that would normally be wasted. The recovered energy may typically be returned to the energy source or stored within the energy storage device and reused during a subsequent deactivation cycle. Embodiments provide an efficient deactivation coil and other module elements in the module, such as inductance (L), capacitor (C), and resistance (R). Embodiments provide techniques to control the ring down decay rate of a deactivated module to achieve optimal deactivation performance.

FIG. 1 illustrates one embodiment of a deactivation and energy recovery degausser module 100 (degausser) that includes a deactivation module 114 (deactivator) and an energy recovery module 112. Demagnetizer 100 may be implemented, for example, using multiple deactivators 114 and energy recovery modules 112 in a variety of combinations including a variety of configurations and topologies. In one equivalent embodiment, deactivator 114 may comprise an inductance-capacitor-resistance (LCR) resonant cavity module. Although inductive and capacitive elements of the LCR resonator may be explicitly provided, in one embodiment, the resistive elements may comprise lumped parasitic and lossy resistive characteristics of the LCR module. Deactivator 114 may include a deactivation ring-down decay module coupled to energy recovery module 112 through deactivation capacitor 108. In one embodiment, deactivator 114 may be coupled to energy recovery module 112 through energy coupler 115. In one embodiment, energy coupler 115 may be a capacitor. In one embodiment, energy coupler 115 may be an inductor. Thus, energy recovery module 112 may be inductively or capacitively coupled to deactivator 114. Capacitor 108 is typically charged by an energy source or storage device (not shown) prior to the beginning of the deactivation cycle. In one embodiment, deactivator 114 includes a deactivation antenna coil 102 (coil) coupled to a deactivation switch 106 (switch). In one embodiment, the coil 102 may comprise a coil comprising an air core or a magnetic core to generate a strong magnetic field within the space forming the deactivation zone in the vicinity of the coil 102. In one embodiment, switch 106 may comprise a triac, although other types of switches may be used. Deactivator 114 may also include a deactivation and energy recovery control module 104 (controller) coupled to switch 106. Controller 104 may be connected to switch 106 via connection 110 and may be connected to energy recovery module 112 via connection 118.

For example, controller 104 controls the timing of the deactivation ring-down decay period by controlling switch 106 via connection 110. In one embodiment, the controller 104 further includes a microprocessor 105 to provide a shaped ring down decay profile (profile) over the ring down decay period. During the deactivation process, the EAS tag is brought into a deactivation zone, for example, within the range of a strong magnetic field, and a strong AC magnetic field is applied to the EAS tag. For example, to deactivate an EAS tag, during deactivation, the controller 104 turns on the switch 106 and the energy stored in the capacitor 108 is transferred to the coil 102 in the form of a coil current 116. The current 116 generates a magnetic field to deactivate the EAS tag. Deactivator 114 controls switch 106 to begin the demagnetization process, and during the ring-down decay period, the strength of the AC magnetic field decreases as the energy initially contained within capacitor 108 is dissipated within the various resistive elements in the LCR resonant tank circuit. The equivalent LCR resonator module of deactivator 114 generates a strong and gradually decreasing AC magnetic field. Deactivator 114 charges capacitor 108 with a voltage before the deactivation cycle begins. When the deactivation cycle begins under the control of the controller 104, the switch 106 connects the charged capacitor 108 to the coil 102. The inductance of the coil 102 and the capacitor 108 form a resonant cavity module. If the lumped equivalent resistance within the cavity module is low enough, the LCR module will be under-damped and a decreasing AC current 116 flows through the coil 102. A current 116 flows through the windings of the coil 102 to generate a decreasing AC magnetic field in the deactivation zone. The deactivation cycle is complete when the current 116 and resulting magnetic field decay to a predetermined level. When capacitor 108 is fully recharged, deactivator 114 is ready for the next deactivation cycle.

The inductance of deactivator coil 102, the capacitance of resonant capacitor 108, and the charging voltage on capacitor 108 determine the peak voltage, current 116, and resonant frequency of the LCR module of deactivator 114 during a given deactivation cycle. Additionally, the size of deactivator coil 102, its winding structure, and core materials are design parameters that may determine the magnetic field strength and lossy resistive properties of the LCR module of deactivator 114, for example.

Proper deactivation of an EAS tag requires that the exponential decay or ring-down decay of the AC magnetic field envelope decrease at a predetermined rate within the deactivation zone. In one embodiment, the predetermined rate is limited to the following rate: at which the magnetic field does not decrease by more than 35% from one peak to the next peak of opposite phase, i.e. after half a resonance period. The faster ring-down decay rate is insufficient to deactivate the EAS tag. A slower ring-down decay rate is better suited for deactivating EAS tags that are stationary within the deactivation magnetic field. However, a very slow ring-down decay rate is undesirable because of the very long decay time required for the ring-down decay envelope to reach a very low near-zero value at the end of the deactivation cycle. The low resonant frequency deactivator 114 has a finite response time. Thus, a very slow ring-down decay is less desirable because if a fast moving EAS tag moves in and out of the deactivation zone while the deactivation field is still decaying, the tag cannot be properly deactivated. Thus, some embodiments described herein achieve ring down decay rates between 20% and 30%.

In general, the benefits obtained by forming the deactivator core antenna, such as coil 102 or other components, using high efficiency materials cannot be obtained in conventional deactivator antenna modules using conventional deactivator modules. Once a 20-30% ring down decay rate is achieved, it is not advantageous to increase the ring down decay rate. Since a rapid deactivation response is required as described above, a very slow ring-down decay rate is not used.

Embodiments requiring a very large deactivation distance also require a very large amount of energy to deactivate the EAS tag. Accordingly, deactivation capacitor 108 is required to have a very large energy storage capacity to generate a magnetic field of sufficiently high strength within deactivation coil 102 to increase the size of the deactivation zone. However, these embodiments are expensive and may be impractical due to the size of the power supply necessary to fully recharge deactivation capacitor 108 after each deactivation cycle.

Embodiments requiring high efficiency may be battery powered. However, battery life is greatly limited due to the need to fully charge capacitor 108 after each deactivation cycle. Embodiments with an effective deactivation coil 102 may not be useful for providing fast and effective EAS tag deactivation if they reduce the ring-down decay rate to less than 20-30%.

Embodiments may include high power modules to increase the power level of the power supply and use bulk capacitors to average the power supply requirements. Other embodiments include efficient modules to reduce the amount of energy stored within deactivator capacitor 108, increase the deactivation range, and increase battery life.

For example, the controller 104 controls the timing of the energy recovery process via connection 118. During the ring-down decay period, controller 104 controls or adjusts energy recovery module 112 to recover energy that would normally be wasted during the ring-down decay portion of the deactivation cycle. Various embodiments of energy recovery module 112 described herein may be used to recover energy from deactivator 114 during the resonant ring-down decay period of the deactivation cycle. Embodiments of energy recovery module 112 may recover energy via a direct, inductive, or capacitive coupling connection with deactivator 114. The recovered energy is delivered to a power source or an energy storage device, such as a battery or capacitor. The recovered energy may be used in subsequent deactivation cycles. Embodiments incorporating energy recovery module 112 improve the overall power efficiency of demagnetizer 100 by recovering energy that would otherwise be dissipated within deactivator 114 incorporating conventional circuitry.

Energy recovery module 112 enables embodiments of efficient demagnetizer 100 that would normally ring down at a rate well below the desired 20-30% ring down decay rate. Using energy recovery module 112, various embodiments provide a method of achieving a desired ring-down decay rate while efficiently recovering energy that would otherwise be dissipated. The recovered energy is then delivered to a power supply or energy storage module for use during a subsequent deactivation cycle, thereby improving the efficiency of demagnetizer 100. The high efficiency allows designers to reduce the power supply requirements of deactivator 114 and allows the use of high efficiency materials while maintaining a desirable ring-down decay envelope suitable for rapid and efficient deactivation.

FIG. 2 illustrates a schematic diagram of one embodiment of an LCR equivalent module 200. In one embodiment, LCR equivalent module 200 of demagnetizer 100 includes an inductive element 202(L) representing the inductance of coil 202 and other stray or parasitic inductances, and a capacitive element 206(C) representing the capacitance of deactivation capacitor 108, switch 106, and other stray or parasitic capacitances. Embodiments typically do not include discrete resistive elements within the module. Instead, resistive element 204(R) is formed by the Equivalent Series Resistance (ESR) of capacitor 108, the ESR of deactivation switch 106, the winding resistance of coil 102, and other losses (e.g., magnetic material losses when a magnetic core is used within coil 102). During the deactivation ring-down decay period, elements 202(L), 204(R), and 206(C) form a series LCR module. Various embodiments include an energy recovery module 112 directly or indirectly connected to the deactivator ring-down decay module.

FIG. 3 illustrates at 300 the voltage waveform of deactivation capacitor 108 from the time deactivation switch 106 is turned on, with the ring-down decay voltage of capacitor 108 shown on vertical axis 302 and time shown on horizontal axis 304. Fig. 3 shows two curves. Plot 306 is the ring-down decay voltage of capacitor 108, and plots 308A, 308B are the positive and negative envelopes of the ring-down decay voltage. Graphs 306 and 308A, B illustrate the ring-down decay voltage and decay envelope waveforms of deactivation capacitor 108 without the effect of energy recovery module 112. For example, curve 306 shows the voltage waveform across deactivation capacitor 108, which deactivation capacitor 108 is not loaded with energy recovery module 112 across, and thus is not energy recovered. Curve 308A, B of the deactivator ring down decay voltage waveform of curve 306 includes a positive portion 308A and a negative portion 308B. Equation (1) below describes the activity of the voltage waveform of deactivation capacitor 108 within deactivator 114 as a function of time (t). Equation (5) defines the ring-down decay envelope of curves 308A, 308B. It should be noted that equation (5) is the first term of equation (1) and defines the exponential decay rate of the sinusoidal waveform deactivator voltage of curve 306.

V_cap＝V_init·e^-α·t·cos(ω_d·t) (1)

Wherein, V_initIs the initial voltage on deactivation capacitor 108, and:

V_env＝±V_init·e^-α·t (5)

FIG. 4 shows a schematic diagram of one embodiment of an LCR equivalent module 400 of the demagnetizer 100 shown in FIG. 1, which includes energy recovery module 112 in parallel with capacitive element 206 (C). The equivalent module 400 also includes an inductive element 202(L) and a resistive element 204 (R). The energy recovery module 112 may be represented by an equivalent load 402 (Re). In one embodiment, the energy recovery module 112 may present a constant parallel load 402 to the deactivation capacitor 206. However, the parallel loads 402 may be controlled using a control module such that the amount of energy extracted from the module 400 during the deactivation ring-down decay period varies as a function of time. As will be explained in more detail below. For example, the voltage across the deactivation capacitor 206 may be approximated according to equation (6). The energy recovery module 112 can efficiently transfer the extracted energy back to the energy source or energy storage module described below to save energy.

V_cap＝V_init·e^-α·t·cos(ω_d·t) (6)

Wherein, V_initIs the initial voltage on the deactivation capacitor 206, and:

equations (7) - (8) are rewritten in accordance with "Principles of Solid-State Power conversion", Ralph E.Tarter, 1985, Howard W.Sams, pgs.33-36.

FIG. 5 illustrates at 500 the voltage waveform across deactivation capacitor 108 from the time deactivation switch 106 is turned on, with the voltage of capacitor 108 shown on vertical axis 302 and time shown on horizontal axis 304. Fig. 5 shows three curves. As previously described, curve 306 is the ring down decay voltage of capacitor 108 without energy recovery, and curve 308A, B is the decay envelope, while curve 502 is the capacitor ring down decay voltage affected by energy recovery module 112. For comparison, curves 306 and 308A, B show the deactivation capacitor 108 ring-down decay voltage and decay envelope waveform without the energy recovery effect of energy recovery module 112, while curve 502 is the ring-down decay voltage of capacitor 108 affected by the load of energy recovery module 112 at its two ends. FIG. 5 illustrates that deactivating a ring down decay module, such as deactivator 104, the energy contained therein may be extracted by energy recovery module 112 such that the ring down decay voltage of capacitor 108 of demagnetizer 100 decays much faster than the natural ring down decay voltage following an envelope such as that shown within curve 308A, B.

FIG. 6 illustrates a block diagram of one embodiment of a deactivation and energy recovery demagnetization module 600 (demagnetizer). In one embodiment, demagnetizer 600 includes deactivator 601, rectifier 604, energy recovery module 112, and energy module 606, which contains an energy source or energy storage device, for example. Deactivator 601 includes a coil 102 connected to a switch 106, which is in turn connected to a capacitor 108. The deactivation and energy recovery control module 602 (controller) may control the deactivation function via a connection 610 with the switch 106 and may control the energy recovery function via a connection 612 with the energy recovery module 112. Control module 602 (controller) controls the voltage decay waveform across deactivation capacitor 108. In one embodiment, controller 602 may also include microprocessor 105 to provide a shaped ring down decay profile over the ring down decay period. In one embodiment, energy recovery module 112 may be connected across deactivation capacitor 108. Other embodiments may provide energy recovery module 112 connected across coil 102 (not shown) or to degausser 600 via a capacitor or inductive coupling (not shown). In one embodiment, rectifier 604 may be disposed between deactivation capacitor 108 and energy recovery module 112. The rectifier 604 may be a full-wave or half-wave rectifier 604. Rectifier 604 rectifies the voltage of deactivation capacitor 108. The rectified voltage is then provided to the input of the energy recovery module 112, for example at input 614. Energy recovery module 112 converts the recovered energy and provides it to energy module 606 via output 616. In one embodiment, energy module 606 may be, for example, a battery or other device that generates electrical power, for example. In one embodiment, energy module 606 may be, for example, a capacitor, a rechargeable battery, or other energy storage device, so that the recovered energy may be stored for later use.

The embodiment of energy recovery module 112 varies depending on the desired characteristics of energy module 606. In general, embodiments of energy recovery module 112 may include, for example, a switch and an inductive element, such as an inductor or a transformer, to effect this conversion. In one embodiment, the switch may comprise a high frequency switch and the inductive element may comprise a high frequency inductive element. Embodiments of the energy recovery module 112 may, for example, include switching regulators of various topologies to achieve the energy recovery function. The selection of a particular topology depends on input/output characteristics, such as the expected input voltage of deactivation capacitor 108, the output voltage provided to energy module 606, the loading effect of energy recovery module 112, and the operating power level of energy recovery module 112.

For example, fig. 7, 13, 14 and 15 show some illustrations of topologies of switching regulators/converters (regulators) suitable for implementing the energy recovery module 112. These topologies may include, for example, isolated flyback regulators, boost (boost) regulators, buck (buck) regulators, and single-ended primary inductance regulators (SEPICs). Although each of these topologies may be suitable for various combinations of voltage and power levels, they do not represent an exhaustive list of topologies that may be used to implement energy recovery module 112 in accordance with embodiments described herein. Although configurations of various topologies are described herein, examples of the operation of these various topologies will be described with reference to an isolated flyback topology such as that shown in FIG. 7.

Fig. 7 illustrates one embodiment of the energy recovery module 112 incorporating an isolated flyback regulator 700 topology. The isolated flyback regulator 700 may include a coupled inductor 702, the inductor 702 including, for example, a primary winding 704 and a secondary winding 706. In one aspect, the primary winding 704 is connected to the rectifier 604 at an input 614. On the other hand, the primary winding is connected to a switch 708. In one embodiment, switch 708 may be, for example, a high frequency switch. Secondary winding 706 is connected to a series diode 10, which in turn is connected to a parallel capacitor 712. The voltage across the capacitor 712 is provided to the energy module 606 via the output 616. E.g. V from rectifier 604_in615 are received at an input 614 and provided to the primary winding 704. When switch 708 is on for a predetermined period of time, it provides a return path to ground, and V_in615 causing a current I_inFlowing in the direction indicated by arrow 714. Switch 708 is controlled by controller 602 at frequency f_sThe pulses generated and provided to switch 708 via line 612 are turned on or modulated for a predetermined period of time. Thus, the controller 602 controls the current I in the coupling inductor 702_inThe conversion of (1). Energy is stored within the coupling inductor 702 when the switch 708 is turned on. When the switch 708 is opened, the current I_outIs released into the capacitor 712. Thus, current I_inIs "converted" into a current I_out. Energy recovery current I flowing in the direction indicated by arrow 720_outIs provided to a series diode 710 and charges a capacitor 712 to a voltage V_cap719. Output capacitor voltage V_cap719 is provided to the energy module 606 via connection 616. Thus, energy recovery module 112 converts I provided to coupled inductor 702 at input 614 under the control of controller 602 and switch 708_inAnd supplies this energy to the energy module 606 via connection 616. Capacitor voltage V_cap719 to supply or charge an energy module 606, which may include a battery, rechargeable battery, capacitor, or other source of electrical energy or energy storage device.

In one embodiment, the on-time t of switch 708_onCan be defined by equation (10) as follows:

wherein, t_onIs the on time of switch 708; l is_pIs a voltage transformationThe inductance of the primary winding 704 of the machine 702; f. of_sIs the switching frequency of the flyback regulator 700 controlled by the controller 602; and R is_loadIs the average resistive load that flyback regulator 700 places on deactivation capacitor 108.

Those skilled in the art will appreciate that equation (10) assumes a constant switching frequency (f) from controller 602_s) And constant switch 708 on time (t)_on) The flyback regulator 700 presents a constant average load to the deactivation capacitor 108. Inductance (L) of primary winding 704_p) May be suitably selected to accommodate the maximum voltage across deactivation capacitor 108 and the switching frequency of deactivator 601 (e.g., the switching frequency applied to switch 106 via connection 610). Thus, flyback regulator 700 may, for example, operate in a discontinuous mode at a fixed frequency and a fixed duty cycle (duty cycle) to present a constant average resistive load to deactivator 601.

FIG. 8 illustrates at 800 the make signal and energy recovery current I of switch 708_inThe relationship between, wherein the switch 708 on signal and the energy recovery current I are shown on the vertical axis 810_inAnd time is shown on the horizontal axis 812. Fig. 8 shows two curves. Curve 802 is the switch 708 on signal and curve 804 is the corresponding energy recovery current I_in. Curve 802 shows the switching period T of switch 708_s(i.e., switching frequency f)_s＝1/T_s) And corresponding on-time t of switch 708_on. In one embodiment, switch 708 is on for time t_onMay remain constant for the duration of the entire ring-down decay period. Curve 804 shows the recovery current I_inPeriod T of signal_s ¹. As shown, the current I is recovered_inPeriod T of signal_s ¹Tracking the on-time T of switch 708_s。

FIG. 9 illustrates at 900 the electricity V of deactivation capacitor 108 after passing through, for example, rectifier 604_in615, and the resulting high frequency energy recovery current I_inWith rectified deactivation capacitance shown on vertical axis 910Voltage V of device 108_in615 and the resulting high frequency energy recovery current I_inAnd time is shown on the horizontal axis 912. Fig. 9 shows four curves. Curve 902 is the rectified voltage V of capacitor 108_in615, curve 904 is the high frequency energy recovery current I_inCurve 906 is V_in615 and curve 908 is the high frequency energy recovery current I_inThe decay envelope of (a). Rectified capacitor voltage V_in615 curve 902 and high frequency energy recovery current I_inCurve 904 is the waveform generated by a demagnetizer 600 implemented with an energy recovery module 112, the module 112 containing a constant switching frequency (f)_s) And a constant switch 708 on time (t)_on) The flyback regulator 700 of operation. Curve 902 is the resulting rectified input voltage V provided to the primary winding 704_in615 and curve 904 is the resulting high frequency energy recovery current I flowing through the primary winding 704_in. At a constant switching frequency (f)_s) And a constant switch 708 on time (t)_on) Flyback regulator 700, operating during the ring-down decay period T portion of the deactivation cycle, provides a constant resistive load to deactivation capacitor 108. Rectified electricity V from deactivation capacitor 108_in615 are provided to the input 614 of the flyback regulator 700 and for a time t when the switch 708 is on_onGenerating a resulting energy recovery current I_in. The high frequency energy recovery current I flowing in the primary winding 704 is shown in curve 908_inFollows the rectified deactivation capacitor voltage V shown in curve 906 throughout the ring-down decay period T (e.g., approximately 0.02 seconds as shown at 900)_in615.

FIG. 10 illustrates at 1000 the rectified capacitor 108 voltage V shown within curve 902 of FIG. 9_in615 for the first quarter of the deactivated ring-down decay period T and the current waveform I of flyback regulator 700 operating in discontinuous mode_inWherein the rectified voltage V of deactivation capacitor 108 is shown on vertical axis 1004_in615 and the resulting high frequency energy recovery current I_inAnd the horizontal axisTime is shown at 1006. Fig. 10 shows two curves. Curve 902 is the rectified voltage V of capacitor 108_in615 and curve 904 is the high frequency energy recovery current I_in。

The embodiments described above with reference to fig. 7-10 represent one example of the topology of isolated flyback regulator 700 of energy recovery module 112, which energy recovery module 112 acts as a constant resistive load for deactivation capacitor 108, for example, throughout the duration of the ring-down decay period T of deactivator 601. However, other embodiments may provide microprocessor 105 to provide a ring-down decay profile having a shape over ring-down decay period T to further improve deactivation performance. In one embodiment, microprocessor 105 may be used to control the shape of the ring-down decay profile over the separated portion of the deactivated ring-down decay period. For example, embodiments under the control of microprocessor 105 may provide an adjustable duty cycle for ring-down decay period T instead of a fixed duty cycle. Microprocessor 105 may be used to vary a ring down decay envelope, such as shown within curve 908 of fig. 9, during different portions of ring down decay period T. For example, the microprocessor 105 may be used to control the ring-down decay rate such that it remains a slow ring-down decay rate during a first portion (e.g., the first few cycles) of the deactivation cycle, and then increases the ring-down decay to a faster rate during a second portion (e.g., near the end) of the deactivation cycle. Referring to fig. 1 and 6, the controllers 104 and 602, respectively, may include the microprocessor 105 or may be controlled by the microprocessor 105 to control ring-down decay during different portions of the deactivation period T. In one embodiment, deactivator 114, 601 may include microprocessor 105 or may be controlled by microprocessor 105 to decay at a slow ring-down decay rate during the first few cycles of deactivation period T and then decay at a fast ring-down decay rate during deactivation period T.

FIG. 11 illustrates, at 1100, a voltage V of deactivation capacitor 108 after rectification_in615, and the resulting high frequency energy recovery current I_inHaving a topology used to include an isolated flyback modulator 700The microprocessor 105 of the energy recovery module 112 controls a shaped ring down decay profile. In one embodiment, energy recovery module 112 may be operated as a variable resistive load with respect to deactivation capacitor 108 throughout the duration of ring-down decay period T of deactivator 601. Microprocessor 105 may be used to control the variable load characteristics of energy recovery module 112 over multiple time periods (e.g., T1, T2, etc.) throughout the duration of ring-down decay period T. In one embodiment, for example, the load characteristics of energy recovery module 112 may be adjusted to affect the shape of the ring down envelope. The rectified voltage V of deactivation capacitor 108 is shown on vertical axis 1112_in615 and the resulting high frequency energy recovery current I_inAnd time is shown on the horizontal axis 1114. Fig. 11 shows five curves. Curve 1102 is the low energy recovery period T₁Rectified capacitor voltage V during 1116_in615. Curve 1104 is the high energy recovery period T₂Rectified capacitor voltage V during 1118_in615. Curve 1106 is at T₂During which an energy recovery current I is available for recovery_in. Curve 1110 is rectified V_in615 Voltage during time period T₁Upper decay rate envelope. Curve 1112 is the time period T₂Rectified V of_in615 decay rate envelope. FIG. 11 illustrates one example of a microprocessor controlled ring-down decay profile having a shape in which the load (e.g., resistance) presented to deactivation capacitor 108 by energy recovery module 112 (e.g., input impedance of flyback regulator 700) is adjusted by a microprocessor within controller 602 at different times during the deactivation ring-down decay period.

According to particular embodiments, deactivating the change in the ring-down decay envelope may, for example, improve deactivation performance. When the effective load resistance of the energy recovery module 112 is driven from the time period T₁The "Low energy recovery mode" during 1116 is adjusted to a time period T₂In "high energy recovery mode" during 1118, a deactivation capacitor voltage V is generated_in615 and energy recovery current I_in. This allows, for example, a ring-down decay rate from within the time period T₁OnEnvelope 1110 changes to time period T₂Upper envelope 1112. As shown in curve 1106, the respective recovery current I_inThe decay rate of (a) is correspondingly changed. As previously described, the effective load resistance of energy recovery module 112 may be a controlled microprocessor that may be housed within controller 104, 602, or may be integrally formed with energy recovery module 112.

Fig. 12 illustrates at 1200 the energy recovery percentage versus the ring down decay rate percentage for some coil configurations of flyback regulator 700 having an average efficiency of 85%. The energy recovery percentage is shown on the vertical axis 1212 and the ring down decay rate percentage is shown on the horizontal axis 1214. For example, different energy recovery levels may be achieved for different embodiments of energy recovery module 112. Fig. 12 provides the energy recovery rate of the ring-down decay module 114 coupled to or connected to the energy recovery module 112 configured as the topology of the isolated flyback regulator 700. Other topologies will use similar high frequency switching techniques but may result in slightly different waveforms. Fig. 12 shows five curves. Curve 1202 is a range of 20-30% ring-down decay rates. Curve 1204 is the plot for deactivator 114, 601 with a 5% natural ring-down decay rate efficiency. Curve 1206 is the plot for deactivator 114, 601 with a 10% natural ring-down decay rate efficiency. Curve 1208 is the plot for deactivator 114, 601 with a 15% natural ring down decay rate efficiency. Plot 1210 is the plot of deactivator 114, 601 with a 20% natural ring-down decay rate efficiency. For example, the efficiency of various embodiments may range from a 5% natural ring down decay rate as shown in curve 1204, to a 10% natural ring down decay rate as shown in curve 1206, to a 15% natural ring down decay rate as shown in curve 1208, to a 20% natural ring down decay rate as shown in curve 1210. For example, simulations using an energy recovery module 112 of the flyback regulator 700 type with an average efficiency of 85% may be used to predict estimates of the amount of energy recovered from the deactivators 114, 601 under different operating conditions. In one embodiment, the simulation may be performed using a flyback regulator 700 connected to the deactivation capacitor 108. Additionally, in this example analysis, the equivalent load associated with the flyback regulator 700 remains constant throughout the ring-down decay period. To generate the curve shown in fig. 12, the energy recovery load was varied to provide an estimate of the percent energy recovery and resulting ring-down decay rate.

Table 1 shows the estimated energy recovery for various embodiments including various ring down decay rates and deactivator 114, 601 efficiencies for ring down decay rates between 20% and 35%. As shown in the table, embodiments of deactivators 114, 601 that exhibit very high efficiencies may provide very high energy savings of between 60% and 70%. Even embodiments of deactivators 114, 601 that exhibit lower efficiencies may still achieve 20% -30% energy savings. For example, for a target ring-down decay rate of 30% and a natural ring-down decay rate of 10%, the estimated energy recovery is 59%.

TABLE 1

Fig. 13 illustrates one embodiment of an energy recovery module 112 including a regulator 1300 arranged in a boost topology. In one embodiment, the regulator 1300 may include an inductor 1302 having one end connected to, for example, the input 614 and the capacitor 108. In one embodiment, for example, inductor 1302 may be a high frequency power inductor. The other end of the inductor 1302 is connected in series with one end of the diode 710. The other end of the diode 710 is connected to a parallel capacitor 712. The capacitor 712 may be connected to the energy module 606 via an output 616. As previously explained with reference to fig. 6, the voltage of the capacitor 108 may be rectified by the rectifier 604. For example, V_in615 may be rectified before being provided at the input 614 to the input of the inductor 1302. Switch 708 is connected to the junction of inductor 1302 and diode 710. When the switch 708 is turned on for a period of time t_on(fig. 8), it provides a conductive path 716 to ground. Controller602 controls or modulates a switch 708. The controller 602 generates a frequency f_sPulse 802 (fig. 8). Pulse 802 is provided to connection 612 to control switch 708 to control rectified V_in615. Thus, at the on-time t_onPeriod, V_in615 resulting in an energy recovery current I_inThe pulse flows through the high frequency power inductor 1302 in the direction indicated by arrow 1304. Thus, during the entire deactivation cycle, switch 708 is turned on at frequency f_sOperate so that a plurality of energy recovery currents I_inThe pulse flows in the direction shown by arrow 1304, flows through diode 710 and charges capacitor 712. As a result, the voltage V_cap720 are stored in the capacitor 712 and provided to the energy module 606 via connection 616 for recovery. Capacitor voltage V_cap720 charge the energy module 606, which may comprise a battery, a rechargeable battery, a capacitor, or other electrical energy source or energy storage device. Thus, regulator 1300 converts the rectified V provided at input 614 under the control of controller 602 and switch 708_in615 and deliver the energy to the energy module 606 via connection 616.

Fig. 14 illustrates one embodiment of the energy recovery module 112 including a regulator 1400 arranged in a buck topology. In one embodiment, switch 708 may be connected between input 614 and one end of inductor 1302. A diode 1402 may be connected to the junction of the switch 708 and the inductor 1302. The other end of the diode 1402 is connected to ground 716. The other end of the inductor 1302 may be connected to a parallel capacitor 712. The capacitor 712 may be connected to the energy module 606 via an output 616. When the switch 708 is on for a period of time t_on(fig. 8) the switch provides a conductive path between the input 614 and the inductor 1302. The controller 602 controls the operation of the switch 708. The controller 602 generates a frequency f_sPulse 802 (fig. 8). These pulses 802 are provided to a connection 612 to control a switch 708 to control the rectified V_in615. Thus, at the on-time t_onDuring the period, V after rectification_in615 resulting in an energy recovery current I_inThe pulse flows through the inductor in the direction indicated by arrow 14041302. Thus, during the entire deactivation cycle, switch 708 is turned on at frequency f_sOperate so that a plurality of energies recover I_inThe current pulse flows in the direction shown by arrow 1404 and charges capacitor 712. As mentioned above, the voltage V_cap720 are stored in the capacitor 712 and provided to the energy module 606 via connection 616 for recovery. Capacitor voltage V_cap720 charge the energy module 606, which may comprise a battery, a rechargeable battery, a capacitor, or other electrical energy source or energy storage device. Thus, regulator 1400 switches from V under the control of controller 602 and switch 708_in615 and deliver the energy to the energy module 606 via connection 616.

Fig. 15 illustrates one embodiment of the energy recovery module 112 including a regulator 1500 arranged in a SEPIC topology. In one embodiment, the regulator 1300 may include a first high frequency power inductor 1302 having one end connected to, for example, the input terminal 614. This end of the first high frequency power inductor 1302 may be connected to the capacitor 108. The other end of the first high frequency power inductor 1302 may be connected to an input of the switch 708. At this connection, the first high-frequency power inductor 1302 is also connected in series with one end of the capacitor 1502. The other end of the capacitor 1502 may be connected to one end of the diode 7102 and one end of the second high frequency power inductor 1504. The other end of the second high frequency power inductor 1504 may be connected to ground 716. The other end of the diode 710 may be connected to a capacitor 712, which capacitor 712 is connected to the energy module 606 via an output 616. As previously explained with reference to FIG. 6, in one embodiment, the voltage across the capacitor 108 may be rectified, for example, by the rectifier 604, and the rectified V_in615 may be input to the high frequency power inductor 1302 at the input 614. When the switch 708 is turned on for a period of time t_on(fig. 8), it provides a conductive path 716 to ground. The controller 602 controls the operation of the switch 708 and generates a frequency f_sPulse (fig. 8). These pulses 802 are provided to a connection 612 to control a switch 708 to control the rectified V_in615. At switch 708 on time t_onDuring the period, energy recovery current I_inThe pulse flows in the direction shown by arrow 1504, couples through capacitor 1502 and diode 710, and charges capacitor 712. The resulting voltage V across capacitor 712_capIs provided to the energy module 606 via connection 616. Capacitor voltage V_capThe energy module 606, which may comprise a battery, capacitor, or other electrical energy source or energy storage device, is charged. Thus, the regulator module 1500 converts the rectified V provided at the input 614 as controlled by the activation and energy recovery controller 602 and the switch 708_in615 and deliver the energy to the energy module 606 via connection 616.

Fig. 16 shows a block diagram of one embodiment of a deactivation and energy recovery module including a charging module 1600. The deactivation, energy recovery, and charging module 1600 includes a deactivation module 1601 and further includes an energy recovery module 112 arranged in any of the topologies previously described in connection with fig. 7, 13, 14, and 15 (e.g., flyback, boost, buck, and SEPIC). The deactivation module 1601 may include a coil 102 connected to a switch 106, which switch 106 may in turn be connected to a deactivation capacitor 108. A deactivation capacitor charging module 1604 (charging module) may be connected to the charging switch 1606 and the energy module 606. The module 1600 may also include a charging loop 1610 connecting the energy module 606 to a charging module 1604, and a charging switch 1606. For example, charge loop 1610 provides a conductive path for charging deactivation capacitor 108 from energy module 606. An output of the charging switch 1606 is connected to the capacitor 108, and an input of the charging switch 1606 is connected to the charging module 1604. The charge switch 1606 may be controlled by a deactivation, energy recovery and charge control module 1602 (controller) via a connection 1611. In operation, when the controller 1602 turns the charge switch 1606 on, the charging module 1604 charges the deactivation capacitor 108. In one embodiment, for example, energy for charging deactivation capacitor 108 may be provided by energy module 606.

The controller 1602 may control the deactivation and energy recovery functions of the deactivation module 1601. In one embodiment, the controller 1602 may also control the operation of the switch 106 via connection 610. As previously described, by adjusting switch 106, controller 1602 controls the voltage waveform across deactivation capacitor 108 so that the ring-down decay voltage meets a predetermined characteristic. In one embodiment, module 1600 also includes an energy and recovery module 112 connected to deactivation capacitor 108. For example, other embodiments may provide energy recovery module 112 connected across coil 102 (not shown) or to module 1600 via capacitive or inductive coupling (not shown). Controller 1602 also controls the operation of energy recovery module 112 via connection 1612. In one embodiment, rectifier 604 may be located between deactivation capacitor 108 and energy recovery module 112. For example, the rectifier 604 may be a full-wave or half-wave rectifier. Various embodiments and techniques of the energy recovery module 112 may be adapted to function with, for example, a full-wave or half-wave rectifier 604, or operate without the rectifier 604. In embodiments including rectifier 604, the voltage across deactivation capacitor 108 is rectified by rectifier 604. The rectified voltage is then provided to the input of the energy recovery module 112 at input 614, for example. The energy recovery module 112 then, for example, converts the energy within the rectified input voltage and provides it to the energy module 606 via the output 616. In one embodiment, energy module 606 may be, for example, a battery, or other device that generates electrical power. In one embodiment, energy module 606 may be a rechargeable battery, capacitor, or other energy storage device, so that the recovered energy may be stored for later use during the deactivation cycle. In operation, under control of the controller 1602 via connection 1612, the charge switch 1606 is turned on and completes the charge loop 1610. While the charge switch 1606 is in the on state, the charging module 1604 charges the capacitor 108 with the charging energy provided by the energy module 606.

FIG. 17 illustrates a logic flow diagram that represents a check-out and/or exit process in accordance with one embodiment. In one embodiment, FIG. 17 illustrates programming logic 1700. Programming logic 1700 may be representative of the operations executed by one or more structures described herein, such as systems 100, 200, 400, 600, 700, 1300, 1400, 1500, and 1600. The operation of the above-described system and associated programming logic may be better understood as an example, as shown in diagram 1700.

Thus, in block 1710, the system containing the deactivator generates a deactivation magnetic field during a first deactivation period. At block 1720, a portion of the energy used to generate the deactivation magnetic field that would normally be dissipated within the deactivation circuit is recovered. At block 1730, a portion of the recovered energy is stored for later use. As explained earlier, recovering a portion of the energy comprises, for example, receiving a first voltage signal portion of the portion of energy to be recovered and converting the first voltage signal to a second voltage signal at a predetermined rate. The second voltage signal is then stored in an energy module. At block 1740, the stored recovered energy is provided back to the deactivator to form a magnetic field during the second deactivation period.

Numerous specific details have been set forth herein to provide a thorough understanding of the embodiments. However, it will be understood by those skilled in the art that the embodiments may be practiced without these specific details. In other instances, well-known operations, components, and modules have been described in detail so as not to obscure the embodiments. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.

It should also be noted that any reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

Some embodiments may be described using the expression "coupled" and "connected" along with their derivatives. It should be understood that these terms may not be synonymous with one another. For example, some embodiments may be described using the term "connected" to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may be described using the term "coupled" to indicate that two or more elements are in direct physical or electrical contact. The term "coupled," however, also means that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.

While certain features of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.

Claims (19)

1. An apparatus for deactivating an Electronic Article Surveillance (EAS) tag, comprising:

a deactivator for deactivating an Electronic Article Surveillance (EAS) tag having a deactivation antenna coil and a capacitor for storing energy, the deactivator for converting the stored energy to an alternating current over a deactivation period, the alternating current generating a deactivation magnetic field when driven through the deactivation antenna coil during the deactivation period, the alternating current defining a ring down envelope during the deactivation period; and

an energy recovery module having an electrical impedance, the energy recovery module coupled to the deactivator to recover a portion of the energy converted to the alternating current during a portion of the deactivation cycle based on the impedance,

wherein the deactivator includes: a controller for generating a signal having a frequency and a duty cycle for controlling the impedance of the energy recovery module.

2. The apparatus of claim 1, wherein the energy recovery module is coupled to the deactivated antenna coil.

3. The apparatus of claim 1, wherein the energy recovery module is coupled to the capacitor.

4. The apparatus of claim 1, wherein the energy recovery module is coupled to the deactivator by an energy coupling capacitor.

5. The apparatus of claim 1, wherein the energy recovery module is coupled to the deactivator by an energy coupling inductor.

6. The apparatus of claim 1, further comprising a rectifier coupled between the deactivator and the energy recovery module, the rectifier to rectify the voltage of the capacitor.

7. The apparatus of claim 1, further comprising an energy module coupled to the energy recovery module, the energy module to store the portion of energy recovered by the energy recovery module.

8. The apparatus of claim 1, wherein the energy recovery module comprises a switch coupled to the controller, the switch receiving the signal to activate the switch over an on period of the duty cycle and deactivate the switch over an off period of the duty cycle.

9. The apparatus of claim 8, wherein the frequency remains constant during the deactivation period.

10. The apparatus of claim 8, wherein the frequency is variable during the deactivation period.

11. The apparatus of claim 8, wherein the duty cycle remains constant during the deactivation cycle.

12. The apparatus of claim 8, wherein the duty cycle is variable during the deactivation cycle.

13. The apparatus of claim 1, wherein the signal changes the impedance of the energy recovery module at different times during the deactivation cycle to change the ring down envelope.

14. The apparatus of claim 1, wherein the controller comprises a processor for generating the signal.

15. A method for deactivating an Electronic Article Surveillance (EAS) tag, comprising:

generating, by the deactivator, a deactivation magnetic field during the deactivation period using energy stored in the energy storage device; and

recovering, by an energy recovery module, a portion of the energy used to generate the deactivation magnetic field, the energy defining a ring-down envelope,

wherein the step of generating a deactivation magnetic field during a deactivation cycle comprises: a signal having a frequency and a duty cycle is generated for controlling an impedance of the energy recovery module.

16. The method of claim 15, further comprising:

storing the recovered portion of the energy.

17. The method of claim 15, wherein the step of recovering a portion of the energy comprises:

providing the stored recovered energy to the deactivator to generate the magnetic field during a second deactivation period.

18. The method of claim 15, further comprising: rectifying the energy.

19. The method of claim 15, further comprising:

changing the ring down envelope during the deactivation period.