Power regulator for a contactless credit card system
First Claim
1. In a receptor for a computerized transaction card containing microcomputer means, a power transfer coil, and a power transfer ferromagnetic member adapted, when said card is in said receptor, to flux link said coil with a transformer primary means in said receptor for transfer of energy from said receptor to said microcomputer means to provide therefor both operating power and a clock signal transmitted to said coil from said receptor, an improvement comprising:
- a power amplification circuit adapted to drive the transformed primary means in response to an oscillator signal of predetermined frequency, the transformer primary means being connected to a variable voltage source;
means for measuring current flow in the transformer primary and for providing an output signal (Ia) representing an averaged magnitude of same;
said microcomputer means being responsve to values of Pthresh, Iq, Vn and C.F., stored in memory means, for performing the calculations;
space="preserve" listing-type="equation">P.sub.card =(I.sub.a -I.sub.q)×
V.sub.n ×
C.F. where;
Iq =quiescent current flow in the transformer primaryVn =magnitude of voltage sourceC.F.=correction factorPthresh =threshold power level for the transaction card and increasing said variable voltage source until Pcard exceeds Pthresh.
1 Assignment
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Accused Products
Abstract
A power transfer arrangement provides regulated power transfer from a station to a contactless portable data card without the need for regulation circuitry on the card itself. The station includes a primary coil for magnetically coupling power to a secondary coil, located on the card, when the data card is brought into close association with the station. The arrangment includes a microprocessor, a power amplifier including the primary coil, a variable voltage source and apparatus for measuring current flow in the primary coil. When the portable data card is not in close association with the station, the microprocessor causes the variable voltage source to provide a sequence of stepped voltages. Quiescent current flow is measured at each step and stored in memory. When the portable data card is brought into close association with the station, the microprocessor causes the variable voltage source to provide a sequence of stepped voltages. Active current flow is measured at each step and stored in memory. Power delivered to the data card is calculated as the difference between active and quiescent currents--multiplied by the magnitude of the variable voltage source. The sequence of active current measurements continues until the calculated value of power delivered to the data card exceeds a predetermined threshold power, at which time the data card is receiving a precise, predetermined amount of power.
52 Citations
12 Claims
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1. In a receptor for a computerized transaction card containing microcomputer means, a power transfer coil, and a power transfer ferromagnetic member adapted, when said card is in said receptor, to flux link said coil with a transformer primary means in said receptor for transfer of energy from said receptor to said microcomputer means to provide therefor both operating power and a clock signal transmitted to said coil from said receptor, an improvement comprising:
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a power amplification circuit adapted to drive the transformed primary means in response to an oscillator signal of predetermined frequency, the transformer primary means being connected to a variable voltage source; means for measuring current flow in the transformer primary and for providing an output signal (Ia) representing an averaged magnitude of same;
said microcomputer means being responsve to values of Pthresh, Iq, Vn and C.F., stored in memory means, for performing the calculations;
space="preserve" listing-type="equation">P.sub.card =(I.sub.a -I.sub.q)×
V.sub.n ×
C.F.where; Iq =quiescent current flow in the transformer primary Vn =magnitude of voltage source C.F.=correction factor Pthresh =threshold power level for the transaction card and increasing said variable voltage source until Pcard exceeds Pthresh.
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2. A method for magnetically coupling a threshold amount of power across a dielectric interface from a primary coil in a station apparatus to a secondary coil embedded in a movable electronic transaction card, the primary coil being a circuit element in a power amplifier connected to a variable voltage source;
- comprising the steps of;
i. storing a predetermined value of quiescent current flow (Iq,n) in the primary coil at each of n voltage source levels; ii. measuring the magnitude of current flow (Ia,n) in the primary coil at a particular voltge source level (Vn); iii. calculating the quantity;
space="preserve" listing-type="equation">P.sub.card =[I.sub.an -I.sub.q,n ]×
V.sub.n ×
Kwhere;
K is a predetermined scaling factoriv. terminating the process when Pcard exceeds the threshold amount of power; and v. increasing the voltage source level and repeating the steps starting at step ii. - View Dependent Claims (3)
- comprising the steps of;
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4. Improved apparatus for supplying an alternating current signal to a portable electronic transaction card wherein the apparatus includes a first coil for coupling the alternating current signal to a second coil located on the card, and further includes a sensor that provides first and second sensor voltages in response to the presence and abence of the card in the apparatus, the improvement comprising:
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a first semiconductor device, interconnected to a variable voltage source through the first coil, for amplifying the alternating current signal; means responsive to the current flowing through the first coil, for providing a digital signal reflecting the magnitude of said flowing current; and microprocessor means, including memory and stored instructions, responsive to the digital signal representing the magnitude of the flowing current and responsive to the sensor voltges, for controlling the magnitude of the variable voltage source. - View Dependent Claims (5, 6)
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7. Apparatus for magnetically coupling an AC power signal from a primary coil to a movable secondary coil across a dielectric interface, the primary coil being connected to a voltage source and driven by an amplifier, the apparatus including means for sensing when the movable secondary coil is in close association with the apparatus, the apparatus further including:
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means for determining the difference in power delivered to the primary coil, between the condition that the second coil is in close association with the apparatus and the condition that it is not; and means for varying the magnitude of the AC power signal in accordance with the difference in power.
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8. A power transfer arrangement for magnetically coupling a predetermined amount of electrical power from an amplifier to a load impedance across a contactless interface, said amplifier including a primary coil connected to a variable voltage source, the arrangement comprising:
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means for detecting the condition that the load impedance is in close physical proximity to the contactless interface and for providing an indication of same; means for determining differential current flow through the primary coil between the condition that the load impedance is in close physical proximity to the contactless interface and the condition that it is not; means responsive to said differential current and to the magnitude of the voltage source for determining the amount of power being delivered to the load impedance; and means for increasing the magnitude of the voltage source during the condition that the load impdeance is in close physical proximity to the contactless interface until the delivered power is substantially equal to said predetermined amount of electrical power. - View Dependent Claims (9)
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10. Apparatus for magnetically coupling AC power from a primary coil to a movable secondary coil across a dielectric interface, the primary coil being connected to a voltage source and driven by an amplifier, the apparatus including means for sensing when the movable secondary coil is in close association with the apparatus, the apparatus further including:
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means for varying the magnitude of the voltage source connected to the primary coil; means for measuring active current flowing in the primary coil at various magnitudes of the voltage source when the secondary coil is in close association with the apparatus; means for measuring quiescent current flowing in the primary coil at said various magnitudes of the voltage source when the secondary coil is not in close association with the apparatus; means responsive to the difference between the measured active and quiescent currents at said various magnitudes of the voltage source for calculating delivered power; and means for increasing the magnitude of the voltage source when the secondary coil is in close association with the apparatus until the delivered exceeds a predetermined threshold. - View Dependent Claims (11, 12)
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Specification