Abstract:
A battery charging device, method and system are disclosed for wirelessly charging a battery. A transmitter can transmit an RF wireless power signal to a battery charging device, and a receiver within the battery charging device can receive the RF wireless power signal. The battery charging device can thereafter transfer the received RF wireless power signal to a battery receiving portion to charge the battery. In an embodiment, the RF wireless power signal is transferred at a frequency of about 13.56 MHz to overcome wave shadowing. A battery recharging feedback control circuit can optionally be applied in combination with the battery charging device and can monitor a power quantity of the RF wireless power signal.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to charging batteries with wireless power signals. In particular, the present invention relates to a device, method and system that wirelessly charges batteries with radio frequency (RF) signals. 
       BACKGROUND OF THE INVENTION 
       [0002]    Batteries have become an increasingly popular energy source for portable electronic devices, such as mobile phones, lap top computers, and digital cameras. Depending on the configuration, a single battery can power an electronic device for several hours without requiring the device to be plugged in to a wall receptacle or other power source. However, the power supplied by the battery is temporary by its very nature due to the electrochemical reaction that produces the electrical current. As a result, consumers are sometimes forced to throw away a battery after only a few uses. 
         [0003]    Efforts have been made to produce rechargeable batteries and battery recharging systems in order to avoid the waste and expense that conventional batteries offer. Current recharging systems include a cradle that holds the battery in place and that applies electrical energy to the battery in a manner that causes electron flow to reverse relative to the direction of electron flow during discharge. Power is therefore restored to the battery in the opposite manner that power was discharged from the battery. However, the conventional recharging systems require a contact-based recharging method, where the user must disassemble the batteries from the relevant device or from their container and insert the batteries into the cradle one by one. 
         [0004]    Wireless or “contactless” battery charging has achieved some developments in recent years due to the shortcomings of conventional contact-based battery charging systems. These contactless systems can be found in, for example, electronic toothbrushes, where the battery is recharged when the toothbrush is inserted into the cradle that holds it upright. Although there is contact between the plastic of the toothbrush and cradle, the battery itself does not contact the metallic recharging mechanism inside the cradle, and so this system is still considered “contactless.” A wireless consortium has even been established to standardize contactless recharging of batteries in the conventional fashion. However, conventional contactless recharging systems use magnetic fields to recharge the batteries, e.g. by using an induction coil provided within the cradle. Magnetic field recharging is incapable of charging a battery at larger distances, and is only adapted for close-range charging of a single, or very few, devices. 
         [0005]    Lithium-ion (Li-ion) batteries are a powerful and popular type of battery but include inherent safety drawbacks that require the batteries to be shipped partially discharged based on government regulations. Like all batteries, Li-ion batteries slowly discharge even when not in use, and if discharged below a certain threshold, will be permanently damaged. Electronics containing Li-ion batteries are thus susceptible to being purchased by a consumer with a battery that was shipped partially discharged (due to safety regulations), and where the battery is further discharged in a warehouse or on the shelf of the retailer while waiting to be purchased. 
         [0006]    Several attempts have been made to produce a sufficient long-range charging method using technology other than the conventional short-range magnetic recharging. For example, U.S. Pat. No. 7,288,918 to DiStefano uses longer-range radio frequency (RF) signals to transmit a power signal to a battery recharging circuit. DiStefano discloses a general block diagram configuration in which a power charger is operatively connected to a battery and receives a carrier frequency signal from a power transmitter to recharge the battery. The DiStefano system requires means for generating and transmitting a modulated signal with the modulation being one of frequency modulation, amplitude modulation and phase modulation. The relatively complex system of DiStefano further requires a power receiving circuit and an energy storing circuit for storing energy received from the power receiving circuit until sufficient energy is stored for transfer to a power charging circuit. The RF power signal is transmitted in a predetermined power and carrier frequency, and does not vary based on what is needed to charge the battery. Further, depending on the nature of the signal transmitted, power has to be stored and monitored/measured or sufficiency until such time as it is sufficient to be transferred to a charging circuit to charge a battery. DiStefano does not disclose any specific frequencies for the RF power signal, but only discusses the general idea of RF battery charging. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a non-complex system and method for directly charging batteries standing alone or within several devices at longer distances, and for example, for long-range recharging of Li-ion batteries for storage/shipment and use with electronic devices. The present disclosure describes a device, method and system for recharging a battery where multiple batteries can be charged at the same time. A contactless battery charging technology is disclosed where RF waves are transmitted to one or more batteries in a specific frequency, and can optionally be used in conjunction with a feedback system that varies the amount of power transmitted via the RF signal. 
         [0008]    In particular, the present disclosure describes a simple, inexpensive system and method for battery recharging, including a transmitter that transmits a radio frequency (RF) wireless power signal at one of the Radio Frequency Identification (RFID) frequencies, including one of a frequency of about 125K Hz, about 13.56 MHz, or about 915 MHz (individually referred to herein as “an RFID Frequency”). The system and method of the disclosure further includes an RF transmitter that transmits a wireless RF power signal or signals and an RF signal receiving device and a battery recharging receiving device that is connected to the positive and negative terminals of a cell or battery to electrically transfer power to the battery to charge the battery. With the RF receiver, battery charging receiver, and battery receiving portion implemented as part of a battery “pack,” each battery has its own, low cost, receiver adapted to receive the RF wireless power signal and each battery pack is adapted to electrically transfer the received power to its respective battery to charge the battery within range of the RF wireless power signal. 
         [0009]    Also disclosed is a battery charging method including the steps of receiving an RF wireless signal transmitted at an RFID frequency, conveying the RF wireless power signal to a battery receiving portion, and charging a battery positioned within the battery receiving portion with the RF wireless signal. With the receiver and battery receiving portion implemented as part of a battery “pack,” each battery is provided with its own, low cost, receiver adapted to receive the RF wireless power signal and each battery pack is configured to electrically communicate power to the respective battery to charge the battery within range of the RF wireless power signal. 
         [0010]    In addition, the present application discloses a battery charging feedback system including a main transceiver adapted to transmit an RF wireless power signal, the main transceiver further including a power adjusting circuit adapted to adjust a power quantity of an RF wireless power signal to be transmitted, and a secondary transceiver adapted to receive the RF wireless power signal and determine the power quantity of the RF wireless power signal, and transmit information indicating the determined power quantity to the main transceiver. 
         [0011]    The present disclosure avoids the complicated modulation schemes of known systems, and provides a simple and inexpensive charging system for charging batteries/packs in transit or as they sit on a shelf waiting to be sold or deployed in an electronic device. The system and method according to the invention may be transmitting constantly at a constant, high power to charge batteries in storage or with a feedback mechanism it may be monitoring and regulating transmission as a function of external considerations such as battery charge state or storage facility considerations including time of day, presence and proximity of humans in the facility or electrical demand resource management considerations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For the purpose of facilitating an understanding of the subject matter sought to be protected, there is illustrated in the accompanying drawing embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
           [0013]    The detailed description particularly refers to the accompanying figures in which: 
           [0014]      FIG. 1  is a block diagram of one embodiment of the present invention. 
           [0015]      FIG. 2  is a general schematic diagram of the battery charging device. 
           [0016]      FIG. 3  is a more detailed schematic circuit diagram of the battery charging device. 
           [0017]      FIG. 4  is a schematic diagram of a battery charging feedback system. 
           [0018]      FIG. 5  is a flowchart illustrating one embodiment of the battery charging system with a feedback mechanism. 
           [0019]      FIG. 6  is a flowchart illustrating a second embodiment of the feedback mechanism of the battery charging system. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    While this invention is applicable to embodiments in many different forms, there is shown in the drawings and will herein be described in detail an illustrative embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiments illustrated. 
         [0021]      FIG. 1  illustrates a general block diagram of the battery charging system  100  according to the present application. As shown, the battery charging system  100  includes a transmitter  105  that is adapted to transmit an RF wireless power signal to a battery charging device  110 . A battery receiving portion  115  is in functional communication with the battery charging device  110  and is adapted to hold a battery  120  and apply charge to the battery  120 . 
         [0022]    The transmitter  105  can be any device or combination of devices that is/are capable of transmitting an RF wireless power signal to the receiver  110 . The transmitter  105  can also be a transceiver capable of receiving wireless communication from the battery charging device  110 . In one embodiment, the transmitter  105  transmits the RF wireless power signal at one of the Radio Frequency Identification (RFID) frequencies, including one of a frequency of about 125K Hz, about 13.56 MHz, or about 915 MHz (individually referred to herein as “an RFID Frequency”). In a preferred implementation, the transmitter transmits at approximately 13.56 MHz, the same frequency as many currently implemented radio frequency identification (RFID) signals. The inventor of the present application has determined that the 13.56 MHz transmission frequency allows for greater power levels to be transmitted and at greater distances between the transmitter  105  and the battery charging device  110 . In addition, it was determined that the 13.56 MHz transmission frequency is more forgiving to so-called “wave shadowing,” i.e. where a front battery will “shadow” the signal from a rear battery. It was discovered that 13.56 MHz waves bend around the front battery and permit greater coverage of the RF charging system. 
         [0023]    The battery charging device  110  can be a combination of electrical components that are capable of receiving the RF wireless power signal transmitted by the transmitter  105 , and applying the received RF signal to the battery  120  to charge the battery  120 . In one embodiment, the battery charging device  110  is an electronic circuit implemented as part of a battery pack, as discussed below in more detail with reference to  FIGS. 2 and 3 . 
         [0024]    The battery receiving portion  115  can be any of various structures capable of holding or interacting with a battery, in the case of a battery pack containing functionality in addition to the basic battery function, and applying charge to the battery. For example, the battery receiving portion  115  can be a cradle, container, two-pronged assembly, or any other structure that can electrically connect the battery charging device  110  to the battery  120 . In a preferred embodiment, the battery receiving portion  115  includes a positive and negative terminal as part of the battery pack to facilitate the flow of electrons into the battery  120 . 
         [0025]      FIG. 2  illustrates a more detailed configuration of the battery charging device  110 . As shown, the battery charging device includes a receiver  125  coupled to a rectifier circuit  130 , which is in functional communication with a battery charging capacitor  135 . As discussed above, a battery  120  is coupled to the battery charging device  110  via a battery receiving portion  115 . In a battery pack implementation, the battery charging device is configured as miniature components in the pack, so that the battery and battery charging device are effectively a fully integrated, unitary entity. 
         [0026]    The receiver  125  can be any device that is capable of receiving an RF wireless power signal. In one embodiment, the receiver  125  is an antenna, such as a tag antenna, that is coupled to the rectifier circuit  130  and that is capable of receiving the signal transmitted from the transmitter  105 . The receiver  125  is connected to the rectifier circuit  130  so that the received alternating current (AC) signal can be converted to a direct current (DC) signal, and optionally transmitted to the battery charging capacitor  135 . Once received by the battery charging capacitor  135 , charge can by transmitted to the battery  120  when the stored charge of the battery charging capacitor  135  overcomes the electrostatic potential of the battery charging capacitor  135  to thereby allow current to flow into the battery  120  connected to the battery receiving portion  115 . 
         [0027]      FIG. 3  illustrates a more detailed schematic circuit diagram of the battery charging device  110  according to the present application. As shown, the battery charging device  110  includes a receiver  125  connected in parallel to a first capacitor  140 , which can be an adjustable capacitor. The RF power signal received by the receiver  125  can be transmitted through the first capacitor  140  and into a circuit that includes a second capacitor  145 , a first transistor  150  and a second transistor  155 . Connected in parallel to the antenna  125  is a Zener diode  160  that protects the overall circuitry if the transmitted voltage is above a predetermined threshold, for example, 14V. The battery charging device  110  can further include a resistor  165  and a third capacitor  170 , and prior to the power signal reaching the battery charging capacitor  135 , a voltage regulator  175  can be included to manage the voltage that is eventually supplied to the battery  120 . 
         [0028]    As discussed above, the Zener diode  160  protects the overall circuitry of the battery charging device  110 . Optionally, the Zener diode  160  can be omitted from the battery charging device  110  and at least one of the first transistor  150  or the second transistor  155  can maintain a higher breakdown voltage. The circuit as described, or alternatives thereto with substantially similar functionality, can be implemented in a very small scale Application Specific Integrated Circuit (ASIC) or semiconductor die. The receiver die can be attached to the tag antenna significantly reducing package size and cost. 
         [0029]      FIG. 4  illustrates an optional battery charging feedback system  400  according to the present application. The feedback system  400  works in conjunction with a main transceiver  405  to wirelessly power one or more batteries  410  positioned within a battery holder  415 . In addition, one or more secondary transceivers  420  are provided at the far ends of the generated field of signals provided by the main transceiver  405 . A power adjusting circuit  425  can be positioned in functional communication with the main transceiver  405  and can be adapted to increase or decrease the power of the RF wireless signal transmitted by the main transceiver  405 . The battery holder  415  can be any device or structure that is capable of holding one or more batteries to allow wireless RF charging of the batteries. In an embodiment, the battery holder  415  includes a plurality of openings that are configured to receive a battery  410  in a fashion that spaces apart the batteries  410  approximately one inch from one another from the back of one battery to the front of the battery behind it. The present inventor discovered that vertically spacing the batteries  410  at least approximately one inch apart from one another helped avoid wave shadowing and allowed all of the batteries  410  to be more sufficiently charged. Positioning the batteries  410  side by side was permissible, so long as the vertical spacing of the batteries  410  was at least approximately one inch so as to space the receivers  125  of the battery charging device  110  connected to the batteries  410 . In this embodiment, the cells  410  can be coupled to or positioned directly behind the battery charging device  110  to achieve the preferred positional arrangement. In implementing the invention as described in the context of battery shipping and storage, the battery holder  415  may be a dedicated package/carton for shipping a plurality of batteries. 
         [0030]    In the feedback system  400 , the secondary transceivers  420  can measure or sense the RF signal generated by the main transceiver  405  and communicate with the main transceiver  405  and/or the power adjusting circuit  425  to change the power transmitted via the RF wireless power signal. The secondary transceivers  420  can be self powered by, for example, batteries of their own or a simple wall socket power source, or can be powered by the RF wireless power signal and contain a battery charging device  110  similar to that discussed above. Alternatively, the secondary transceivers  420  need not have a dedicated battery charging device  110 , but can receive and process the RF power signal without the use of a battery or specific charging circuit. 
         [0031]    As illustrated in  FIGS. 5 and 6 , the battery charging feedback system  400  can operate in a variety of ways to ensure that the power supplied by the main transceiver  405  is utilized efficiently. As illustrated in  FIG. 5 , the process begins and proceeds to S 505  where the RF wireless power signal is received at the secondary transceiver  420 . The secondary transceiver  420  can then detect the strength of the received signal S 510  and communicate information indicating a strength of the signal back to the main transceiver  405 . Once the signal is received by the main transceiver  405 , it can be determined whether the signal strength is above a predetermined threshold S 520 , and thus whether the signal strength of the primary transmitter needs to be increased S 525  by the power adjusting circuit in order to efficiently transmit the RF wireless power signal. 
         [0032]    Using the method of  FIG. 5 , the battery charging feedback system  400  can efficiently transmit power signals to the battery  410 , and the secondary transceivers  420  can relay information relating to the strength of the received signal back to the main transceiver  405  to adjust the transmitted power level so that excessive or inadequate power quantities are not transmitted via the RF wireless signals. 
         [0033]    In yet another embodiment, a wireless charging feedback system is shown in  FIG. 6  where the power adjusting circuit  425  increases signal strength in the absence of secondary transceivers  420  communicating back to the main transceiver  405 . In this manner, if the main transceiver  405  does not receive a signal indicating that the RF wireless power signal has been successfully transmitted to the secondary transceiver  420 , the main transceiver  405  knows that the signal strength is inadequate. 
         [0034]    In particular, the process begins and proceeds to S 605  where the RF wireless signal is transmitted from the main transceiver  405  to the batteries  410  and towards the secondary transceiver  420 . At step S 610 , it is determined whether the RF wireless signal has been received by the secondary transceiver  420  to determine whether the signal strength needs to be adjusted. If the secondary transceiver  420  does not provide a “signal received” signal within a predetermined amount of time, the main transmitter  405  will determine that the power of the RF wireless power signal is insufficient and that the power adjusting circuit  425  should increase the power of the primary transmitter, as shown in S 615 . However, if the signal has been received by the secondary transceiver  420 , the process proceeds to S 620 , and the signal is not increased. Optionally, the secondary transceiver  420  can then transmit a signal to the main transceiver  405  that the RF signal has been received S 625  at the adjusted power level. 
         [0035]    The methods referenced above with respect to  FIGS. 5 and 6  discuss the main transceiver  405  and the secondary transceivers  420  as transceivers that communicate information relating to the power level of the RF wireless signal. However, the main transceiver  405  and the secondary transceiver  420  can communicate other information, for example, information relating to a cell, temperature, current, capacity, voltage, time, serial number, model number, or other battery charging or management parameters and component number of the battery that is being charged. Additionally, it is possible to place the wireless transceiver circuitry that exists in the second transceiver  420  in each of the battery packs  410  themselves. In this arrangement, the battery packs themselves can communicate directly to the main transmitter, or any host, information relating to a charging status, cell, temperature, current, capacity, voltage, time, serial number, model number, or other battery charging or management parameters and component number of the batter that is being charged, as well as other information. Other information can be communicated between the main transceiver  405 , secondary transceiver  420 , and battery charging device  110 , as needed. 
         [0036]    As discussed above, the battery charging device  110  can be either attached to or integral with the battery  120  to which it supplies power. Further, a single battery charging device  110  can charge multiple batteries, or multiple battery charging devices  110  can charge a single battery, as needed. 
         [0037]    The above configuration has also been discussed with the battery charging device  110  being dedicated to one battery  120  independent of the container in which it is held, and with the transmitter  105  being remote from the batteries by a relatively large distance. However, the transmitter  105  can be provided in a reusable storage box to charge batteries within the box. Alternatively, the transmitter  105  can rest on a table or surface, or under a table or surface, and send a power signal across the table top or drawer to charge battery packs lying elsewhere. Alternatively, the transmitter  105  can be fixed to a single position, or movable about a position, within a warehouse or another facility that stores electronic devices with batteries. 
         [0038]    The matter set forth in the foregoing description and accompanying drawings and examples is offered by way of illustration only and not as a limitation. More particular embodiments have been shown and described, and it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of Applicant&#39;s contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper prospective based on the prior art.