Abstract:
This invention relates to a cost effective and long-awaited apparatus and method for making a battery charging unit wherein the apparatus and method solution used induction to eliminate the requirement to constantly remove rechargeable batteries from their particular units in order to recharge them. This invention further relates to a cost-effective and long-awaited apparatus and method wherein the apparatus and method solution uses induction to eliminate the requirement to electrically or mechanically connect the charged device to a battery charging unit in order to recharge the battery.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   There are no cross-references related to this application. 
   FIELD OF THE INVENTION  
   The present invention relates to solid state technologies and more particularly to a charging circuit (i.e. power transmitter circuit) that uses induction to provide power transfer between a power transmitter such as a charging base and a power receiving device (i.e. eliminating the use of wires). Relevant potential applications for the present invention include any small portable hand-held device that uses standard sized batteries, but not limited to, calculators, cameras, mp3 players, CD players, GPS units, hand-held electronic instruments, hand-held medical instruments etc., or any device that requires batteries to be taken out for replacement or for recharging. 
   BACKGROUND OF THE INVENTION 
   Many hand-held devices use either non-rechargeable (primary) or rechargeable (secondary) cells for drawing power. Common cell sizes are AAA, AA, C, D, and the like. Using rechargeable cells is a preferable on-going cost savings option for the user and provides a positive environmental impact. However, one drawback of using rechargeable batteries is the constant requirement placed on the user to periodically remove the cells and place them in a charger, or to plug in a specific cell charger to the particular device used. 
   “Trickle charging” in the context of rechargeable batteries is well-known in the art as charging a battery at a rate close to its self-discharge rate. All rechargeable batteries slowly discharge themselves over a period of perhaps many hundreds of hours. “Trickle charging” keeps a battery ‘topped up’. If a battery has a capacity C, then it may perhaps be allowed to be charged at a rate C/8 which means that it reaches full charge in 8 hours. That would be a typical charge rate. “Trickle charging” would be at a rate of perhaps C/100 or lower (i.e. to charge it from fully discharged at the trickle rate it would take 100 hours or more). 
   Wireless recharging of batteries is a known technology, used widely, for example in battery operated electric toothbrushes. In these the toothbrush is rested on a recharging base when no in use, the base containing the primary coil of a transformer. The secondary coil of the transformer is in the handle of the toothbrush. Power is coupled magnetically to charge the cells in the toothbrush. This is a very purpose specific application as it operates with a closely coupled transformer at relatively low frequency. 
   SUMMARY OF THE INVENTION  
   The present invention provides an apparatus and method to allow batteries that use this invention to be inductively charged or re-charged while allowing the batteries to remain situated within their power receiving device. The present invention further eliminates the requirement for power transmitter to be electrically or mechanically connected to the power receiving device. The batteries of the present invention are subject to a wireless charging capability provided by an apparatus and method well known in the art and described herein, utilizing another well-known technology to signal charging completion. Such wireless-charged batteries would remain inside power receiving device, and by being placed in the induced field of power transmitter (i.e. a charging unit), would couple energy from the power transmitter. 
   The present invention describes a generally applicable means to permit the user to keep the cells charged at a trickle charge rate without the need to remove the cells for recharging or to plug the secondary cell power receiving device into a cell charger. 
   Further, the present invention extends the concept of wireless recharging at a trickle charge rate to general purpose rechargeable batteries. 
   The present invention is differentiated from the technique in common use in electric toothbrushes which use a relatively large mutual inductance afforded by the physical arrangement of the primary and secondary coils. By arranging the primary coil and secondary coil to operate at much higher frequency (e.g. of the order of 1 MHz), and by adding a capacitor to make these inductors resonant at that frequency, the primary coil and secondary coil can be made much smaller, and with fewer turns. 
   An aspect of an embodiment of the present invention comprises a modified version of a standard AA (or other sized) battery. 
   A further aspect of an embodiment of the present invention is to provide a cost effective and long-awaited apparatus and method for making a wireless battery charging unit wherein the apparatus and method solution uses induction to eliminate the requirement to constantly remove rechargeable batteries from their particular units in order to recharge them. 
   A further aspect of an embodiment of the present invention is to provide a cost-effective and long-awaited apparatus and method wherein the apparatus and method solution uses induction to eliminate the requirement to electrically or mechanically connect the power receiving device to a power transmitter (i.e. battery charging unit) in order to recharge the battery. 
   A further aspect of an embodiment the present invention avoids using a large mutual inductance, but instead uses coils of lower inductance by using a capacitor in parallel in the receiver and in series in the transmitter, though resonance capabilities of the present invention is not limited to these design features. 
   Additional aspects, objectives, features and aims of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a side view of a rechargeable battery, in accordance with the embodiments of the present invention. 
       FIG. 2  illustrates a rechargeable battery in accordance with the embodiments of the present invention. 
       FIG. 3  illustrates a top and side portion of a rechargeable battery in accordance with the embodiments of the present invention. 
       FIG. 4  illustrates a power receiving and rectification circuit that inductively receives power from the transmitter illustrated in  FIG. 5  in accordance with the embodiments of the present invention. 
       FIG. 5  illustrates a power transmission circuit that transmits power to the circuit illustrated in  FIG. 4  which is coupled inductively to it in accordance with the embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION  
   An embodiment of the present invention comprises a modified version of a standard AA (or other sized) battery. In this embodiment of the present invention, the reverse side of the label on the rechargeable cell is printed with a pattern of lines using conductive ink. Conductive inks are well-known. The pattern on the self adhesive label is shown at  FIG. 1 . Dimensions shown in  FIG. 1  are for an “AA” sized battery which is typically 14 mm in diameter and 48 mm high. However, additional sized batteries may be used and the size of the adhesive label would be adjusted accordingly. The conductive ink pattern is overlaid with an insulating layer, then with the pressure sensitive adhesive that holds the label onto the cell once assembled. Three apertures  10 ,  11  and  12  are provided in the insulating layer and the adhesive layer. 
   The label, as shown in  FIGS. 1 ,  2 , and  3  comprises four layers, and is made from a material that is well-known to one of ordinary skill in the art. The label comprises a first base layer of insulating material, which will provide the outer sheath for the battery when assembled. Next a pattern is printed in a second layer of conductive ink, shown as elements  13  in  FIG. 1 . A third layer of insulating material is laminated over the second layer and has apertures  11  and  12  cut in it to expose said conductive ink elements. This top insulating layer is coated with a forth layer which is a pressure sensitive adhesive to hold the label onto the battery, and to fix together the overlap of the label where aperture  11  (folded back at fold line  15 ) is brought into opposition to aperture  12 , as shown in  FIG. 1 . 
   The label is rolled onto the cell, so that the diagonal conductors  13  make contact at the overlap through aperture  12  in the insulating layer. The edge with aperture  11  is folded back along line  15  to present the conductive ink lines in opposition to those exposed through aperture  12 . This design technique results in a coil of conductive ink ‘wiring’ round the cell, with the two ends of the coil brought to the top of the cell at tab  14 . 
   The significance of the aforementioned design technique is that in arranging the conductive ink pattern and the apertures described, the action of rolling the label onto the cell (which is a typical part of the manufacturing process for such a cell) results in the creation of a coil of conductive ink round the cell, said coil being the receiver of charging power as shown in  FIG. 4 . Clearly, a similar result may be achieved by winding a coil of insulating wire round the cell. However, a design technique winding a coil of insulated wire would be an expensive operation and not achievable with current battery manufacturing equipment. Making a coil using conductive inks patterns, apertures, and labels in the way described in the present invention may be achieved with current battery labeling equipment. 
   As shown in  FIG. 3 , assembled on tab  14  are a small capacitor  16  chosen to make the coil resonant at the desired frequency, and a Schottky diode  17  to rectify the voltage induced in the resonant coil. The output voltage from the rectified coil is connected to the cell through the apertures  10  and  12  (shown in  FIG. 1 ) onto the metal casing of the cell at the positive top part of the cell and negative bottom part of the cell. 
   In another embodiment of the present invention,  FIG. 4  illustrates a power receiving and rectification circuit that inductively receives power from the transmitter in  FIG. 5  (described herein), then rectifies it by means of the Schottky diode and uses the resultant d.c. current to charge the cell. More specifically, the circuit shown in  FIG. 4  comprises a receiving coil  19  and a parallel capacitor  16  which the capacitor&#39;s value is chosen to make the parallel circuit resonate at the frequency of the power transmission circuit shown in  FIG. 5 . In this regard, the receiver is made more efficient by arranging it to be resonant at the frequency of the transmitter. Thus, when the receiving circuit (embodied on the label of the battery) is in close proximity to the transmitting circuit of  FIG. 5 , an alternating voltage will be induced in the coil  19 . This voltage is rectified by the Schottky diode  17  to provide a charging voltage for the cell  18 . A Schottky diode is chosen in the preferred embodiment (though not essential to carrying out the present invention) since it has a lower forward voltage drop than other types of diodes so it will be more efficient at permitting charging current to flow. 
   In another embodiment of the invention,  FIG. 5  illustrates an example of a power transmission circuit that transmits power to the circuit in  FIG. 4  (described herein) and which is coupled inductively to the circuit in  FIG. 4  (i.e.  FIG. 5  is the circuit for the device that performs the charging of the batteries). More specifically,  FIG. 5  illustrates a driving circuit comprising elements  20 ,  21 ,  22  and  23 , such that oscillator  20  drives a pair of transistors  21  and  22  in anti-phase by the use of a phase inverter  23  and a series resonant tuned circuit comprising inductor  25  and capacitor  26 . These elements are all powered by a d.c. power source  24  which is applied such that power source  24  is supplied to the driver transistors at the common point of which drives the series resonant transmitter circuit comprising inductor coil  25  and capacitor  26 . 
   In another embodiment of the present invention, the inductor  25  may comprise a small number of circular turns of sufficient diameter to allow them to cover an area of approximately 18 to 20 square inches (i.e. a coil of a diameter for example between 4 and 5 inches). This design manifests itself as a suitably flat coil, and could easily be molded into a mat or into the base of a tray made of insulating material. Devices containing wireless rechargeable batteries to be charged could be placed onto the mat or into the base of a tray allowing energy would flow from the charging circuit to the wireless battery charged circuit by electromagnetic induction. 
   In operation, the wireless charging circuit may be built into a mat or the base of a tray, and hand-held devices with wireless rechargeable batteries in them may be placed on the mat or tray when they are not in use. While the charged devices are in close proximity to the wireless recharging circuit, the cells will be trickle charged. 
   The apparatus and method of this invention has been described with respect to individual charged devices. However, it is contemplated that the apparatus and method of wireless charging may be employed with a plurality of charged devices per wireless charging circuit. 
   While particular embodiments of the present invention have been described herein for the purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.