Abstract:
A wireless charger and a method allow the wireless charger to have enhanced portability and a smaller footprint when not performing the charging function. The wireless charger includes a charging circuit providing power on one or more power lines, a housing for the wireless charger, and a flexible platform that includes a charging surface with two or more contact electrodes. The flexible platform may be unfolded or unrolled for charging a mobile device, and folded up or rolled up to achieve a smaller footprint, when not performing a charging operation. The wireless charger may further includes a data communication circuit for data communication between a power-line network and the mobile device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to chargers for mobile devices. In particular, the present invention relates to chargers for mobile devices having a flexible charging platform that can be folded or rolled up for greater compactness and portability. 
         [0003]    2. Discussion of the Related Art 
         [0004]    Most portable computing devices (e.g., cellular or smart telephones, notebook computable and tablet computers) require frequent recharging, as a relatively small battery size is often key to device compactness and weight. As many such devices can provide only one or two days of useful service between recharging, chargers are also required to be compact and portable, so that a traveler who needs to be away for more than one or two days may be able to bring the charger along. 
         [0005]    Generally speaking, there are two types of chargers for mobile devices on the market. The first type requires a cable to connect the mobile device to the charger. The cable designs for this type of chargers are often customized or proprietary, so that a user carrying multiple mobile devices may have to carry multiple chargers. Furthermore, plugging and unplugging the cable to and from the mobile device cause wear and tear on both the connector on the cable and the corresponding connector on the mobile device. As a result, a second type of chargers has appeared. This second type of chargers does not require a cable between the charger and the mobile device. (In this detailed description, a charger that does not require a cable to connect to a mobile device is referred to as a “wireless charger”). Instead, charging is achieved by induction using a changing magnetic field. Efficiency in inductive charging, however, is very low, so that a significant amount of heat is often generated because of the inductive loss. Inductive chargers are also typically bulky and costly. 
       SUMMARY 
       [0006]    According to one embodiment of the present invention, a wireless charger and a method allow the wireless charger to have enhanced portability and smaller footprint when not performing the charging function. The wireless charger includes (a) an interface to an external power source; (b) a charging circuit coupled to receive power from the external power source through the interface, the charging circuit providing power on one or more power lines; (c) an energy storage device (e.g., a battery) coupled to the charging circuit and the charging power lines; (d) a housing for the wireless charger for housing the charging circuit and the energy storage device; and (e) a flexible platform including a charging surface with two or more contact electrodes, wherein the flexible platform has a first physical configuration, in which charging surface is exposed for coupling charging electrodes of a mobile device, and a second physical configuration, in which the flexible platform has a smaller footprint relative to the first physical configuration. 
         [0007]    In one embodiment, in the second physical configuration, the flexible platform is rolled up or wrapped around a cylindrical housing. A light source and an on-off switch controlling the light source may be mounted on opposite ends of the cylindrical housing. The interface to the external power source may also be mounted on one end of the cylindrical housing. 
         [0008]    In one embodiment, the charging circuit may include a polarity detection circuit that determines the polarities of the contact electrodes when a mobile device is in contact with the charging surface, and wherein the charging circuit couples the charging power lines to the contact electrodes in accordance with the polarities determined. The charging circuit may also include an identification circuit which identifies parameters of a battery in the mobile device. The charging circuit may also include an effectiveness circuit which monitors progress of a charging operation. The charging circuit may also include detection and handling circuits for one or more exceptional conditions, such as over-current, over-voltage, over-charged, or high temperature. 
         [0009]    According to one embodiment of the present invention, the wireless charger further includes a data communication circuit for data communication between a power-line network and the mobile device. Data communication on the power lines may be based on analog signals. The data communication circuit may include a first data circuit that is AC-coupled to the power lines to mediate data signals between the wireless charger and the power-line network. AC-coupling may be achieved by blocking capacitors. The first data circuit includes an analog front end circuit that converts data signals from the wireless charger to analog form and data signals from the power-line network to digital form. In like manner, the wireless charger further includes a second data circuit AC-coupled to the power lines to mediate data signals between the wireless charger and the mobile device. 
         [0010]    The present invention is better understood upon consideration of the detailed description below in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIGS. 1(   a ) and  1 ( b ) show wireless charger  100  in unrolled and rolled up configurations, respectively, according to one embodiment of the present invention. 
           [0012]      FIG. 2  shows wireless charger  200  including connector  4  for connecting to an external power source, according to one embodiment of the present invention. 
           [0013]      FIG. 3(   a ) shows wireless charger  300  having contact electrodes  301  and  302  provided on charging surface  3 , in accordance with one embodiment of the present invention. 
           [0014]      FIG. 3(   b ) shows wireless charger  350  having contact electrodes  301  and  302  provided on charging surface  3 , in accordance with one embodiment of the present invention. 
           [0015]      FIGS. 4(   a ) and  4 ( b ) show wireless chargers  400  and  450 , respectively, in accordance with one embodiment of the present invention; each wireless charger having two electrodes A and B, but arranged in orthogonal directions. 
           [0016]      FIGS. 5(   a ) and  5 ( b ) shows wireless chargers  500  and  550  having more than two contact electrodes arranged different patterns on charging surface  3 , in accordance with one embodiment of the present invention. 
           [0017]      FIGS. 6(   a ) and  6 ( b ) show wireless chargers  600  and  650 , respectively, each providing light source  7 , in accordance with one embodiment of the present invention. 
           [0018]      FIG. 7(   a ) is block diagram showing circuit  700  in a wireless charger, which implements an interface (“receiver”) to an external power source, in accordance with one embodiment of the present invention. 
           [0019]      FIG. 7(   b ) shows circuit  750  of the wireless charger, which implements an interface to the mobile device to be charged (“transmitter”), in accordance with one embodiment of the present invention. 
           [0020]      FIG. 8  is a block diagram of circuit  800  implementing charger interface and control circuit  704   a,  in accordance with one embodiment of the present invention. 
           [0021]      FIG. 9  shows circuit  900  which implements AFE  707  of  FIG. 7(   a ). 
           [0022]      FIG. 10  shows interface circuit  1000  between the mobile device and the wireless charger, in accordance with one embodiment of the present invention. 
       
    
    
       [0023]    To facilitate cross-referencing among the figures, like elements are assigned like reference numerals. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The present invention provides a wireless charger having a flexible charging platform that can be folded or rolled up to make more compact and to enhance portability. In addition, according to one embodiment of the present invention, the wireless charger also provides data communication capability to allow the mobile device to maintain data communication operations while charging. 
         [0025]      FIG. 1(   a ) shows wireless charger  100 , according to one embodiment of the present invention. As shown in  FIG. 1(   a ), wireless charger  100  includes cylindrical housing  1  and flexible charging platform  2 , which includes charging surface  3  where the electrodes for charging the mobile device are provided. Flexible platform  2  and charging surface  3  are preferably formed out of a flexible material that allows charging platform  2  to be rolled up or wrapped around cylindrical housing  1  in a folded or rolled-up configuration, such as shown in  FIG. 1(   b ). In wireless charger  100 , charging surface  3  is configured with contact electrodes for contacting charging electrodes of a mobile device. Suitable charging electrodes of the mobile device are typically embedded in a back cover or provided at suitable locations on a planar surface of its housing. This arrangement allows the mobile device to be charged by simply placing the mobile device on the charging surface of the charger. Examples of wireless chargers and mobile devices with such charging arrangements are described, for example, in co-pending U.S. patent applications (“Co-pending Patent Applications”), (i) U.S. patent application Ser. No. 13/734,610, entitled “Wireless Charger Circuit and Method,” filed on Jan. 4, 2013, and (ii) U.S. patent application ser. No. 13/594,673, entitled “Wireless Battery Charger For Mobile Devices and Method Thereof”, filed on Aug. 24, 2012. The Co-pending Patent Applications are hereby incorporated by reference in its entirety. The Co-pending Patent Applications describe, for example, a wireless charger which automatically detects the polarities of the mobile device&#39;s charging electrodes through the contact electrodes provided on a charging surface, once the mobile device is placed on the charging surface. In that wireless charger, a user need not be concerned about aligning the polarities of the charging electrodes of the mobile device with the polarities of the contact electrodes of the wireless charger. With a wireless charger, wear and tear damage to the charging connector of a mobile device due to frequent plugging and unplugging a charging cable is avoided. When not being used for charging a mobile device, charging surface  3  may be used as a mouse pad. 
         [0026]      FIG. 2  shows wireless charger  200  including connector  4  for connecting to an external power source, according to one embodiment of the present invention. As shown in  FIG. 2 , connector  4  is provided at one end of cylindrical housing  1 . Connector  4  may be an industry standard Universal Serial Bus (USB) connector, or any suitable power connector to a power adapter. The external power source may be an external computational device (a desktop or notebook computer) or a power adapter drawing power from wall socket or a car battery. Wireless charger  200  includes a charging circuit (not shown, but described in conjunction with respect to  FIGS. 7(   a ) and  8  below) that charges internal energy storage device  5  (e.g., a lithium ion battery). Power from the external power source charges internal storage device  5 . When a mobile device is placed on charging surface  3 , power for charging the mobile device may be provided by internal energy storage device  5 , when wireless charger  200  is not connected to an external power source. However, when wireless charger  200  is connected to an external power source, the external power source, internal energy storage device  5 , or both, may provide power to charge the mobile device. The placement of connector  4  at one end of cylindrical housing  1  ensures that internal power device  5  may be charged even when wireless charger  200  is in a rolled up configuration. 
         [0027]      FIG. 3(   a ) shows wireless charger  300  having contact electrodes  301  and  302  provided on charging surface  3 , in accordance with one embodiment of the present invention. As shown in  FIG. 3(   a ), contact electrodes  301  and  302  have relatively large surface areas to contact the charging electrodes of a mobile device. Contact electrodes  301  and  302  may each be provided, for example, by a conductive polymeric or plastic material or a conductive rubber material, so as to maintain the flexibility of charging platform  2 . Conductive polymeric or plastic materials or conductive rubber materials are polymeric, plastic or rubber substrates in which conducting particles or wires are embedded. Alternatively, flexible conductive materials based on grapheme or carbon nanotubes may also be used. Some of these materials have the advantage of providing transparent electrodes, which may render charging surface  3  more esthetically pleasing. Contact electrodes  301  and  302  may be roughened or magnetized to provide a better hold of the mobile device, especially during motion. This roughening allows wireless charger  300  to charge a mobile device in a moving vehicle, drawing power from a car generator or a battery, for example. 
         [0028]      FIG. 3(   b ) shows wireless charger  350  having contact electrodes  301  and  302  provided on charging surface  3 , in accordance with one embodiment of the present invention. Unlike wireless charger  300  of  FIG. 3(   a ), which provides contact electrodes  301  and  302  of large surface areas, wireless charger  350  provides contact electrodes  301  and  302  as conductive strips of suitable smaller extents. As described below, a wireless charger of the present invention may support data communication operations. Conductive strip contact electrodes, such as contact electrodes  301  and  302  of  FIG. 3(   b ) may be desirable, as the smaller surface area signal avoids signal attenuation, power dissipation and noise. 
         [0029]    Additional configurations of contact electrodes are shown in  FIGS. 4(   a ),  4 ( b ),  5 ( a ) and  5 ( b ).  FIGS. 4(   a ) and  4 ( b ) show wireless chargers  400  and  450 , respectively, in accordance with one embodiment of the present invention; each wireless charger having two electrodes A and B, but arranged in orthogonal directions. Electrodes A and B are provided in  FIGS. 4(   a ) and  4 ( b ) to perform the contact electrode functions of contact electrodes  301  and  302  described above. Wireless chargers  400  and  450  of  FIGS. 4(   a ) and  4 ( b ) may also include a light source powered by internal energy storage device  5  in cylindrical housing  1 , so that these chargers can also serve as a portable light source (e.g., a flashlight) suitable for mobile use.  FIGS. 5(   a ) and  5 ( b ) show wireless chargers  500  and  550  having more than two contact electrodes arranged in different patterns on charging surface  3 , in accordance with one embodiment of the present invention. As discussed in the Co-pending Pending Applications, having numerous contact electrodes in various arrangements accommodate mobile devices of different sizes and allow charging of numerous mobile devices placed in different orientations simultaneously.  FIGS. 5(   a ) and  5 ( b ) show that wireless chargers  500  and  550  each include circuit board  8  which provides the charging circuit, a control circuit for controlling charging operations, data communication circuits and other circuits. 
         [0030]      FIGS. 6(   a ) and  6 ( b ) show wireless chargers  600  and  650 , respectively, each providing light source  7 , in accordance with one embodiment of the present invention. Light source  7  may include, for example, an incandescent bulb, fluorescent bulb or tube, or an LED bulb, as desired. Light source  7  and its corresponding on-off switch  6  may be placed, for example, on opposite ends of cylindrical housing  1 . Placing on-off switch  6  on one end of cylindrical housing  1  allows light source  7  to provide light even when flexible charging platform  2  is extended for charging a mobile device.  FIG. 6(   b ) shows, in addition, connector  4  for connecting to an external power source being provided on the on-off-switch assembly. As a portable device with energy storage, wireless chargers of the present invention are particularly suitable to serve also as light sources for outdoor use, such as at a camp site, at a construction work site or any harsh work environment exposed to the elements. 
         [0031]      FIG. 7(   a ) is block diagram showing circuit  700  of the wireless charger, which implements an interface to an external power source (“receiver”) in a wireless charger, in accordance with one embodiment of the present invention. The wireless charger implemented by circuit  700  supports data communication between the mobile device to be charged and a power-line network residing on the power lines of the external power source. As shown in  FIG. 7 , circuit  700  receives power line  701  and ground reference  702  from an external power source. Circuit  700  includes (i) charging circuit  704  which includes charging interface and control circuit  704   a  and charger circuit  704   b,  and (ii) data communication circuit  705 , which includes blocking capacitors  706   a  and  706   b,  analog front end (AFE)  707 , digital circuit  708 , and data interface  709  which connects to the mobile device to be charge through charging electrodes  301  and  302  of the wireless charger. 
         [0032]      FIG. 8  is a block diagram of circuit  800  implementing charger interface and control circuit  704   a,  in accordance with one embodiment of the present invention. As shown in  FIG. 8 , circuit  800  include polarity detection and control circuit  801 , battery identification and charging control unit  802 , charging effectiveness and control unit  803 , over-current protection unit  804 , over-voltage protection unit  805 , over-charged protection unit  807  and temperature control unit  806 . Polarity detection and control unit  801  detects the polarities of the charging electrodes of the mobile device through contact electrodes  301  and  302 . The detected polarity is then used to configure the switches that connect charger circuit  704   b  to contact electrodes  301  and  302 , so that the mobile device may be charged properly. Battery identification and charging control unit  802  tries to determine if the battery in the mobile device to be charged is one for which a predetermined charging program exists. If so, battery identification and charging control unit  802  runs the predetermined charging program to control charging by charger circuit  704   b.  Battery identification and charging control unit  802  may also determine the values of battery parameters, such as capacity, charging current limits, charging voltages, and battery chemistry or technology (e.g., a lithium ion battery). Charging effectiveness and control circuit  803  monitors the progress of the charging process, reporting any exceptional condition and terminating the charging process, if appropriate. Exceptional conditions include over-current, over-voltage, over-charged and exceptional high temperature. These exceptional conditions are detected and handled, respectively, by over-current protection unit  804 , over-voltage protection unit  805  and temperature control unit  806 . 
         [0033]    Returning to  FIG. 7(   a ), data communication over the power-line network is achieved by modulated high frequency data signal riding on the DC voltage across power line  701  and ground reference  702 . As shown in  FIG. 7 , blocking capacitors  706   a  and  706   b  pass the high frequency data signal to and from data communication circuit  705 . AFE  707  converts an analog data signal from the power-line network into a digital signal for digital circuit  708 . In the opposite direction, a digital signal from digital circuit  708  is injected by AFE  707  into the power-line network through power line  701 .  FIG. 9  shows circuit  900  which implements AFE  707  of  FIG. 7(   a ). A data signal received from the power-line network is first filtered (e.g., down-converted) in filter  901 . Programmable gain amplifier (PGA)  903  scales the filtered signal to an appropriate voltage range. The amplified signal is then digitized by an analog-to-digital converter (ADC)  904  for digital circuit  708 . In the opposite direction, a data signal from digital circuit  708  is first received into digital circuit  902 , and converted to digital form by digital-to-analog converter (DAC)  905  into an analog signal. After proper filtering (e.g., up-converted) in filter  906 , the analog signal is attenuated in power amplifier  907  to become a signal of appropriate amplitude range for injection through blocking capacitor  706   b  into the power-line network. Typically, this amplitude range for data in the power-line network is significantly less than the DC voltage of the power lines. 
         [0034]      FIG. 7(   b ) shows circuit  750  of the wireless charger, which implements an interface to the mobile device to be charged (“transmitter”), in accordance with one embodiment of the present invention. As shown in  FIG. 7(   b ), under control of polarity detection and control circuit  801 , auto-switch circuit  751  connects power line  701  and ground reference  702  properly to contact electrodes  301  and  302  to provide proper polarities for charging the mobile device. Data communication between the wireless charger and the mobile device is handled by digital circuit  708  through AFE  753 , which receives and transmits analog signals of the appropriate amplitude range through blocking capacitors  752   a  and  752   b  from and to power line  701 , respectively. AFE  753  may be implemented in substantially the same manner as AFE circuit  900  of  FIG. 9 . 
         [0035]    As discussed in the Co-pending Patent Applications, for a mobile device to be charged by the wireless charger of the present invention, an interface circuit may be required. Such interface circuit may be provided, for example, in a back cover for the mobile device. Charging electrodes may be provided on the back cover to make connection with contact electrodes  301  and  302 . One example of such an interface circuit is illustrated by  FIG. 10 , which shows interface circuit  1000 . As shown in  FIG. 10 , charging electrodes  1004  and  1005  carry power line  701  and ground reference  702 , which are coupled with proper polarities to contact electrodes  301  and  302 ) from the wireless charger. Blocking capacitors  1006   a  and  1006   b  pass the data communication signals to and from power line  701 . The digital communication signals are provided by digital circuit  1002  through AFE  1001  and may be implemented in substantially the same manner as AFE circuit  900  of  FIG. 9 . Digital circuit  1002 , in turn, handles data communication signals to and from the mobile device through interface  1003 , which also provides the charging signals to the mobile device. Interface  1003  may be, for example, an interface connector, which may be an adapter to a proprietary connector to the mobile device. 
         [0036]    The above detailed description is provided to illustrate specific embodiments of the present invention and is not intended to be limiting. Numerous modifications and variations within the scope of the present invention are possible. The present invention is set forth in the accompanying claims.