Abstract:
A wireless charger is disclosed. The charger contains a coil with a plurality of taps, thereby facilitating charging according to different frequencies and standards. Detection of the standard appropriate to a particular receiver may be accomplished by modulation of the power carrier or via low power modalities, including NFC or Bluetooth.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to wireless charging pads and methods for their use. More particularly, it relates generally to wireless charging pads utilizing a single coil with multiple taps. 
     BACKGROUND OF THE INVENTION 
     Many equipments or devices, including, for example, mobile phones and electronic equipment, to name but a few, contain rechargeable batteries. An increasingly popular method of recharging such rechargeable batteries is wireless or inductive charging. An example of the use of wireless charging is provided in U.S. Pat. No. 8,212,518. It is common to refer to the charging apparatus as the “transmitter” or “charging pad” or “pad” and to the device or equipment being charged as the “receiver”. 
     Unfortunately, there are different standards and procedures for charging electronic equipment or devices. Consequently, effective charging can only be accomplished when the electronic equipment or device is matched with a charger that charges according to the standard or procedures specified by the maker of the equipment or device. For example, various standards may differ in the principles of power transfer, frequencies used, presence of device detection and communication protocols. 
     SUMMARY OF THE INVENTION 
     Illustrative embodiments of the invention include an apparatus for wirelessly charging a receiver including a coil having one or more taps; each of the taps being connected to a transmitter; and a controller capable of directing the transmitter to provide charging energy via that portion of the coil energized via a selected tap. Other embodiments include having each tap connected to a respective transmitter. Another embodiment includes a switch connected between each tap and its respective transmitter. Further embodiments include a controller connected to control each transmitter and open and close the switches. Additional embodiments include an NFC element connected to one of the taps. The NFC element may be a tag or may be an element capable of both transmitting and receiving signals. Furthermore, in other embodiments, the controller may be capable of directing at least one transmitter to transmit a modulated signal on its power carrier. Such modulation may, illustratively be FSK or ASK. 
     In another embodiment there is an apparatus for wirelessly charging a receiver which includes: a coil with a plurality of taps, each of the taps defining a respective portion of the coil; a plurality of switches, each of the switches being connected to a respective tap; a plurality of transmitters, each of said transmitters being connectable to a respective tap by closing the respective switch; a controller adapted to; (i) close a selected switch; (ii) choose a respective transmitter and cause the transmitter to transmit charging energy through the selected switch and thereby energize a respective portion of the coil; cause the respective transmitter to generate a modulated communication signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing showing an illustrative embodiment of the present invention; 
         FIG. 2  is a schematic drawing showing another illustrative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  illustrates a single charging coil with multiple taps. The multiple taps facilitate charging according to a variety of standards and also facilitate communication between the coil (which is located in the pad) and the receiver so that charging according to the appropriate standard may be accomplished. 
     Reference numeral  11  denotes the pad. A single coil  13  is located within the pad. Taps  15  and  17  are provided at appropriate locations on coil  13 . Switches  19 ,  21 , and  23  (which may be transistors, relays, or other types of switches) facilitate the energization of either the entire coil  13 , or portions of coil  13  as will be described in further detail. 
     For example, closing switch  19 , (while allowing other switches  21  and  23  remain open) enables coil segments  25 ,  27 , and  29  together to be energized, via transmitter  33 . Alternatively, switches  19  and  23  may be left open and switch  21  closed, thereby energizing only coil segments  27  and  29 , via transmitter  35 . 
     By way of example, it may be assumed that closing of switch  19  and resultant energization of coil segments  25 ,  27 , and  29  (i.e. entire coil  13 ) is required to effect charging according to a particular wireless charging standard, i.e. “Standard X”. It may be further assumed that closing of switch  21  (and leaving switches  19  and  23  open) and the resultant energization of coil segments  27  and  29  together is required to effect charging according to another wireless charging standard, i.e. “Standard Y”. Charging according to additional standards may be accomplished by adding additional taps and switches. 
     For example, closing of switch  23 , while allowing switches  19  and  21  to remain open causes energization of coil segment  29  may be used to effect charging according to another wireless charging standard, i.e. “Standard Z”. Alternative embodiments may include a coil with more taps and transmitters and switches. One may detect which standard is required by a particular receiver by following an iterative process further described below that involves detection of the presence of a receiver, followed by an attempt at communication (either by modulation on a power carrier or by low power communication via NFC) and then, if communication is established, charging via energization of the appropriate coil segment(s) (or the entire coil, if appropriate). 
     Controller  37  may control the operation of transmitters  31 ,  33  and  35 . Controller  37  may also be configured to open and close switches  19 ,  21 , and  23 . 
     Communication between the receiver and the pad may be accomplished via various forms of modulation at various carrier frequencies. For example, controller  37  may be programmed to provide charging using “Standard X” by utilizing energy transmitted from transmitter  33  via closure of switch  19 . Standard X may require energy transmission via a first frequency, illustratively between 100 and 200 kHz. Controller  37  may cause transmitter  33  to transmit an initial low energy burst at the first frequency. Communication with the receiver may be accomplished via, for example, ASK modulation on the first frequency carrier. Presence of the receiver may be detected through load detection (i.e. impedance change). The receiver may be configured to harvest some of the transmitted energy to enable it to reply, also perhaps via ASK modulation on the first frequency carrier. In the event that the ASK modulated reply indicates that the receiver is compliant with Standard X, controller  37  directs transmitter  33  to transmit at higher power at the first frequency to accomplish charging of the receiver. 
     Should there be no response to the ASK modulated signal transmitted by the pad, an attempt may be made to determine if the receiver is compatible with charging at another standard, for example, “Standard Y”. The above procedure—or a similar procedure—may be performed again. Controller  37  may open switch  19  and close switch  21 . Controller  37  may direct transmitter  35  to attempt to establish communication at a second frequency (which may, illustratively be between 100 and 300 kHz), utilizing, perhaps another type of modulation, illustratively, FSK on the carrier. Presence of the receiver may again be confirmed by load detection (i.e. impedance change). (The same type of modulation may also be used in other embodiments.) If the receiver&#39;s charging requirements are compatible with Standard Y, it will harvest some of the initial burst of energy to reply via FSK at the same carrier frequency. In the event that communication indicates that the receiver is compatible with Standard Y charging, controller  37  may direct transmitter  35  to transmit at higher power at the second frequency to accomplish charging of the receiver according to Standard Y. A similar process may be followed to determine if charging should proceed according to Standard Z. 
     A charging pad may, in other embodiments, be configured to provide communication regarding the appropriate charging standard by utilizing various modulation techniques on the carrier and also using low power communication channels, such as NFC. 
     Another embodiment of the invention is disclosed in  FIG. 2 . Reference numeral  211  denotes a pad. A single coil  213  is located within the pad. Taps  215  and  217  are provided at appropriate locations on coil  213 . Switches  219  and  221  (which may be transistors, relays, or other types of switches) facilitate energization of the entire coil  213  or portions or coil  213  as will be described in further detail. 
     Controller  241  controls switches  219  and  221  and is capable of opening one and closing the other as desired. Reference numerals  233  and  235  denote transmitters capable of providing charging energy according to the requirements of different standards. 
     In operation, controller may close switch  219 , while leaving switch  221  open, thereby permitting transmitter  233  to transmit energy via entire coil  213 . Alternatively, controller may close switch  221 , while leaving switch  219  open, thereby permitting transmitter  235  to transmit energy via combined coil segments  227  and  229 . 
     Communication between controller  241  and the receiver is accomplished by NFC element  237  which utilizes coil segment  229  to tune to the NFC carrier, i.e. 13.56 MHz. NFC element may be (i) an NFC passive tag or (ii) an NFC transceiver (which is capable of performing as reader/writer in peer to peer or card emulation modes). In operation, either the receiver or pad  211  may initiate communication. (In embodiments in which pad  211  initiates communication, NFC element  237  is capable of transmitting.) After communication via NFC is established, information concerning the appropriate charging standard is transmitted via NFC element  237  to controller  241  which then selects the appropriate transmitter, i.e.  233  or  235  and closes the associated switch, i.e.  219  or  221  to begin charging 
     Various exemplary embodiments are described in reference to specific illustrative examples. The illustrative examples are selected to assist a person of ordinary skill in the art to form a clear understanding of, and to practice the various embodiments. However, the scope of systems, structures and devices that may be constructed to have one or more of the embodiments, and the scope of methods that may be implemented according to one or more of the embodiments, are in no way confined to the specific illustrative examples that have been presented. On the contrary, as will be readily recognized by persons of ordinary skill in the relevant arts based on this description, many other configurations, arrangements, and methods according to the various embodiments may be implemented. 
     To the extent positional designations such as top, bottom, upper, lower have been used in describing this invention, it will be appreciated that those designations are given with reference to the corresponding drawings, and that if the orientation of the device changes during manufacturing or operation, other positional relationships may apply instead. As described above, those positional relationships are described for clarity, not limitation. 
     The present invention has been described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto, but rather, is set forth only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, for illustrative purposes, the size of various elements may be exaggerated and not drawn to a particular scale. It is intended that this invention encompasses inconsequential variations in the relevant tolerances and properties of components and modes of operation thereof. Imperfect practice of the invention is intended to be covered. 
     Where the term “comprising” is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun, e.g. “a” “an” or “the”, this includes a plural of that noun unless something otherwise is specifically stated. Hence, the term “comprising” should not be interpreted as being restricted to the items listed thereafter; it does not exclude other elements or steps, and so the scope of the expression “a device comprising items A and B” should not be limited to devices consisting only of components A and B. This expression signifies that, with respect to the present invention, the only relevant components of the device are A and B.