Autotransformer assisted resonated energy transfer circuit

Claim 2

In an electrical circuit for producing a magnetic field which circuit comprises a D.C. power source providing a predetermined amount of electrical energy, a resonant circuit comprising an inductive component in parallel with a resonating capacitor, a silicon controlled rectifier (SCR) and means for controllably switching the SCR to a conductive state to complete the circuit, the improvement wherein said inductive component is an autotransformer having a winding containing a total of at least 30 turns, having a primary portion containing between one-fifth and two-thirds of the total number of turns and having fewer turns than in a secondary portion, and wherein said primary portion is connected in series with said power source and said SCR, said SCR when switched to a conductive state permitting current to flow from the D.C. power source through said primary portion, thereby coupling electrical energy from said primary portion to said secondary portion, to transfer said electrical energy to said resonant circuit, a counter-EMF being developed due to reverse discharging of said resonating capacitor following transfer of said electrical energy to commutate the SCR, the electrical energy coupled from the primary portion to the secondary portion then being dissipated in oscillations in the resonant circuit.

Claim 3

An electrical circuit according to claim 1 wherein the total number of turns of said autotransformer is approximately 60, said primary portion of said autotransformer having approximately 20 turns, said secondary portion comprising the total number of turns, and said resonant circuit having a resonant frequency between 300 and 2,000 Hz.

Claim 4

An electrical circuit according to claim 1 wherein said D.C. power source comprises an electrolytic capacitor having a nominal capacitance of at least 300 uf and suitable for repeatedly storing charge at a potential of at least 450 VDC, and wherein switching of said SCR to a conducting state causes a predetermined amount of charge to be discharged from said electrolytic capacitor through said primary portion of the autotransformer means to induce a current in said secondary portion to generate a magnetic field having a peak intensity of at least 350 oersteds.

Claim 5

An electrical circuit according to claim 1, further comprising a diode connected in parallel with said primary portion of said autotransformer, wherein reverse oscillating currents in said resonant circuit are shorted out, thereby causing a unidirectional magnetic field to be produced by said resonant circuit.

Claim 6

An electrical circuit according to claim 1 wherein said switching means comprises manual control means for initiatiNg a signal pulse and switching means responsive to said signal pulse and coupled to said SCR for providing a trigger pulse to the gate of the SCR when a signal pulse is received.

Claim 7

An electrical circuit according to claim 5 wherein said switching means further comprises means for sensing the potential across said D.C. power source and for preventing said SCR from being switched to a conductive state unless said potential across said D.C. power source is in excess of a predetermined value.

Claim 8

In an anti-pilferage system utilizing ferromagnetic markers capable of producing a characteristic signal when subjected to a magnetic field of at least a predetermined peak intensity within an interrogation zone, an electrical circuit for producing a said magnetic field, which circuit comprises a D.C. power source providing a predetermined amount of electrical energy, a resonant circuit comprising an inductive component in parallel with a resonant capacitor, a silicon controlled rectifier (SCR) and means for controllably switching the SCR to a conductive state to complete the circuit, the improvement wherein said inductive component is an autotransformer having a winding containing a total of at least 30 turns, having a primary portion containing between one-fifth and two-thirds of the total number of turns and having fewer turns than in a secondary portion, and wherein said primary portion is connected in series with said power source and said SCR, said SCR when switched to a conductive state permitting current to flow from the D.C. power source through said primary portion, thereby coupling electrical energy from said primary portion to said secondary portion, to transfer said electrical energy to said resonant circuit, a counter-EMF being developed due to reverse discharging of said resonating capacitor following transfer of said electrical energy to commutate the SCR, the electrical energy coupled from the primary portion to the secondary portion then being dissipated in oscillations in the resonant circuit.

Claim 9

In an anti-pilferage system utilizing ferromagnetic markers capable of producing a characteristic signal when subjected to a magnetic field of at least a predetermined peak intensity within an interrogation zone, an electrical circuit for producing a said magnetic field, which circuit comprises a D.C. power source providing a predetermined amount of electrical energy, a resonant circuit comprising an inductive component in parallel with a resonant capacitor, a silicon controlled rectifier (SCR) and means for controllably switching the SCR to a conductive state to complete the circuit, the improvement wherein said inductive component is an autotransformer having a winding containing a total of at least 30 turns, having a primary portion containing between one-fifth and two-thirds of the total number of turns and having fewer turns than in a secondary portion, and wherein said primary portion is connected in series with said power source and said SCR, said SCR when switched to a conductive state permitting current to flow from the D.C. power source through said primary portion, thereby coupling electrical energy from said primary portion to said secondary portion, to transfer said electrical energy to said resonant circuit, a counter-EMF being developed due to reverse discharging of said resonating capacitor following transfer of said electrical energy to commutate the SCR, the electrical energy coupled from the primary portion to the secondary portion then being dissipated in oscillations in the resonant circuit.

Claim 10

In an anti-pilferage system utilizing ferromagnetic markers capable of producing a characteristic signal when subjected to a magnetic field of at least a predetermined peak intensity within an interrogation zone, said markers being further capable of becoming desensitized to prevent the production of said characteristic signal when subjected to said magnetic field, a resensitizing device for restoring said markers to a state wherein said characteristic signals are produced when said markers are subjected to said magnetic field, an electrical circuit for producing a said magnetic field, which circuit comprises a D.C. power source providing a predetermined amount of electrical energy, a resonant circuit comprising an inductive component in parallel with a resonating capacitor, a silicon controlled rectifier (SCR) and means controllably switching the SCR to a conductive state to complete the circuit, the improvement wherein said inductive component is an autotransformer having a winding containing a total of at least 30 turns, having a primary portion containing between one-fifth and two-thirds of the total number of turns and having fewer turns than in a secondary portion, and wherein said primary portion is connected in series with said power source and said SCR, said SCR when switched to a conductive state permitting current to flow from the D.C. power source through said primary portion, thereby coupling electrical energy from said primary portion to said secondary portion, to transfer said electrical energy to said resonant circuit, a counter-EMF being developed due to reverse discharging of said resonating capacitor following transfer of said electrical energy to commutate the SCR, the electrical energy coupled from the primary portion to the secondary portion then being dissipated in oscillations in the resonant circuit.

Claim 11

In an anti-pilferage system utilizing ferromagnetic markers capable of producing a characteristic signal when subjected to a magnetic field of at least a predetermined peak intensity within an interrogation zone, said markers being further capable of becoming desensitized to prevent the production of said characteristic signal when subjected to said magnetic field, a resensitizing device for restoring said markers to a state wherein said characteristic signals are produced when said markers are subjected to said magnetic field, an electrical circuit for producing a said magnetic field, which circuit comprises a D.C. power source providing a predetermined amount of electrical energy, a resonant circuit comprising an inductive component in parallel with a resonating capacitor, a silicon controlled rectifier (SCR) and means controllably switching the SCR to a conductive state to complete the circuit, the improvement wherein said inductive component is an autotransformer having a winding containing a total of at least 30 turns, having a primary portion containing between one-fifth and two-thirds of the total number of turns and having fewer turns than in a secondary portion, and wherein said primary portion is connected in series with said power source and said SCR, said SCR when switched to a conductive state permitting current to flow from the D.C. power source through said primary portion, thereby coupling electrical energy from said primary portion to said secondary portion, to transfer said electrical energy to said resonant circuit, a counter-EMF being developed due to reverse discharging of said resonating capacitor following transfer of said electrical energy to commutate the SCR, the electrical energy coupled from the primary portion to the secondary portion then being dissipated in oscillations in the resonant circuit.

Claim 12

In an anti-pilferage system according to claim 8 wherein the improvement to said elEctrical circuit includes means for desensitizing said markers, said desensitizing means comprising a diode connected in parallel with said primary portion of said autotransformer, wherein reverse oscillating currents in said resonant circuit are shorted out, thereby causing a unidirectional magnetic field to be produced by said resonant circuit.