Abstract:
An electronic equipment is provided with an antenna including a coil, a load, a power feeding unit for feeding power received by the antenna to the load, a communication unit for communicating with the outside world via the antenna, a switching circuit installed between the antenna and the communication unit, and a switching control unit for controlling ON/OFF of the switching circuit according to power to be received by the antenna.

Description:
TECHNICAL FIELD 
     This invention relates to an electronic device or a module, which comprises an antenna shared by communication and power reception in a non-contact electric power transmission. Furthermore, this invention relates to a system comprising the electronic device or the module. 
     BACKGROUND ART 
     One of systems with the electronic device of the type is, for example, disclosed in Patent Document 1. In a secondary device of Patent Document 1, one of a radio communication portion and a power reception portion is selectively coupled, by a switch, to an antenna consisting of a single coil. 
     PRIOR ART DOCUMENTS 
     Patent Document(s) 
     Patent Document 1: JP 2010-130835A 
     SUMMARY OF INVENTION 
     Technical Problem 
     The system of Patent Document 1 has a problem that a primary device cannot freely control timings of power transmission and communication. 
     It is therefore an object to provide an electronic device (secondary device) which has a structure allowing a primary device to freely control timings of power transmission and communication. 
     Solution to Problem 
     One aspect of the present invention provides an electronic device comprising: an antenna having a coil; a load; a power supply portion for supplying the load with an electric power received at the antenna; a communication portion for communicating with an outside of the communication portion through the antenna; a switch circuit provided between the antenna and the communication portion; and a switch controller for controlling, in response to an electric power received at the antenna, On state/Off state of the switch circuit. 
     Another aspect of the present invention provides a module comprising: an antenna; a power supply portion, coupled with a load, for supplying the load with an electric power received at the antenna; a communication portion for communicating with an outside of the communication portion through the antenna; a switch circuit provided between the antenna and the communication portion; and a switch controller for controlling, in response to an electric power received at the antenna, On state/Off state of the switch circuit. 
     Yet another aspect of the present invention provides a system comprising: the electronic device; and a primary device which includes a circuit for transmitting an electric power for the electronic device and another circuit for communicating with the electronic device. 
     Advantageous Effects of Invention 
     The present invention controls whether the communication portion is connected to the antenna or is disconnected from the antenna, on the basis of the electric power received at the antenna. Thus, the present invention enables the secondary device to substantially judge a power transmission period (power reception period) or a communication period on the basis of the received power. Therefore, the primary device can carry out power transmission and communication at any timings. 
     The present invention can prevent excess electric power from being supplied for the communication portion upon the power transmission. In other words, the present invention can properly protect the communication portion upon the power transmission. There is no need on redundant design of the communication portion in consideration of withstanding capability upon power reception, so that the communication portion with general structure can be used. 
     An appreciation of the objectives of the present invention and a more complete understanding of its structure may be had by studying the following description of the preferred embodiment and by referring to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram schematically showing a system which comprises a primary device and a secondary device (electronic device) in accordance with a first embodiment of the present invention. 
         FIG. 2  is a block diagram schematically showing the secondary device (electronic device) of  FIG. 1 . 
         FIG. 3  is a diagram showing a concrete circuit structure of a switch circuit of  FIG. 2 . 
         FIG. 4  is a diagram showing switch control of the secondary device (electronic device) of  FIG. 2 . 
         FIG. 5  is a diagram showing a modification of the switch circuit of  FIG. 3 . 
         FIG. 6  is a diagram showing another modification of the switch circuit of  FIG. 3 . 
         FIG. 7  is a diagram showing yet another modification of the switch circuit of  FIG. 3 . 
         FIG. 8  is a diagram showing still another modification of the switch circuit of  FIG. 3 . 
         FIG. 9  is a block diagram schematically showing a secondary device (electronic device) in accordance with a second embodiment of the present invention. 
         FIG. 10  is a block diagram schematically showing a secondary device (electronic device) in accordance with a third embodiment of the present invention. 
         FIG. 11  is a block diagram schematically showing a secondary device (electronic device) in accordance with a fourth embodiment of the present invention. 
         FIG. 12  is a block diagram schematically showing a secondary device (electronic device) in accordance with a fifth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     [First Embodiment] 
     With reference to  FIG. 1 , a system according to a first embodiment of the present invention comprises a primary device  10  and a secondary device (electronic device)  20 . 
     As shown in  FIG. 1 , the primary device  10  generally comprises a communication/power-transmission circuit  12  and an antenna  14 . The communication/power-transmission circuit  12  is capable of selectively controlling communication and power transmission freely. The communication/power-transmission circuit  12  communicates with the secondary device  20  through the antenna  14  upon communication, while transmitting an electric power to the secondary device  20  through the antenna  14  upon power transmission. For example, the communication/power-transmission circuit  12  comprises a circuit for communication, a circuit for power transmission and a control portion, wherein the circuit for communication includes a communication portion and a matching circuit for communication, the circuit for power transmission includes a power transmission portion and a matching circuit for power transmission, and the control portion controls at least the communication portion and the power transmission portion. In general, the antenna  14  is formed by a coil (coil antenna). The coil forming the antenna  14  may be separated for the circuit for communication and the circuit for power transmission. Namely, two or more coils may be used therefor. The coil forming the antenna  14  may be shared by the circuit for communication and the circuit for power transmission. Namely, only one coil may be used therefor. 
     In this embodiment, a frequency of an electric power wave used in electric power transmission and another frequency of a carrier wave used in communication belongs to 13.56 MHz bands and are equal to each other. An antenna power of an electric wave transmitted upon electric power transmission is 5 W or more, while another antenna power upon communication is 1 W or less. Namely, an antenna power of an electric wave transmitted upon electric power transmission is larger than another antenna power upon communication. Although a carrier wave frequency upon electric power transmission and another carrier wave frequency upon communication may be different from each other, it is preferable that both carrier wave frequencies are equal to each other, taking it into consideration that a use of a single antenna is efficiently shared by communication and electric power transmission in the secondary device  20  with simple control as explained afterwards. 
     As shown in  FIG. 1 , the secondary device  20  according to the present embodiment comprises a module  22  and a load  24  coupled to the module  22 . Specifically, the load  24  of the present embodiment is a battery. Generally, the module  22  has a function to communicate with the primary device  10  and another function to receive an electric power from the primary device  10  to supply it for the load  24  (i.e., to put a battery on charge). In this embodiment, it is assumed that the load  24  be coupled to the module  22  by using a connector or the like upon fabrication of the secondary device  20 . However, the present invention is not limited thereto. For example, the secondary device  20  may be fabricated by coupling the load  24  directly to a circuit board on which a function similar to the function of the module  22  is installed. 
     As shown in  FIG. 2 , the module  22  of the secondary device  20  according to the present embodiment comprises an antenna  30 , a power supply portion  40 , a switch circuit  50 , a communication portion  60 , and a switch controller  70 , wherein the antenna  30  has a coil  32 , the power supply portion  40  is connected to the antenna  30  and the load  24 , the switch circuit  50  is connected to the antenna  30 , the communication portion  60  is connected to the switch circuit  50 , and the switch controller  70  is connected to the power supply portion  40  and the switch circuit  50 . For example, the actual secondary device  20  is provided with a matching circuit for electric power supply and so prior to the power supply portion  40  and another matching circuit for communication and so on prior to the switch circuit  50 . However, those are omitted for the sake of better understanding of the present embodiment. 
     The antenna  30  is for supplying the power supply portion  40  with an alternating power which is an electric power transmitted from the primary device  10  through magnetic coupling. The antenna  30  is also used to communicate with the primary device  10 . Namely, the use of the antenna  30  according to the present embodiment is shared by electric power transmission and communication. 
     The power supply portion  40  is for supplying the load  24  with an electric power received at the antenna  30 . For example, the power supply portion  40  comprises a rectifier and a DC/DC (direct current/direct current) converter, wherein the rectifier rectifies a received electric power of the antenna  30  to produce a rectification signal, and the DC/DC converter carries out DC/DC conversion on the rectification signal to supply the load  24  with the converted as a supply signal. 
     The switch circuit  50  is provided between the antenna  30  and the communication portion  60 . The switch circuit  50  is for connecting between the antenna  30  and the communication portion  60  (On state) or for disconnecting the communication portion  60  from the antenna  30  (Off state) under control of the switch controller  70  as described later. 
     With reference to  FIG. 3 , the switch circuit  50  of the present embodiment comprises switches (unilateral switches)  52  and additional switches  54  and Zener diodes ZD, wherein the switches  52  are provided on two lines connected between the antenna  30  and the communication portion  60 , respectively, the additional switches  54  are provided between a ground and the respective lines, and the Zener diodes ZD and the additional switches  54  are connected in parallel. Each of the switches  52  and the additional switches  54  according to the present embodiment is made of an Nch FET (field effect transistor). The drain of the FET forming the switch  52  is connected to one end of the coil  32  of the antenna  30 , the source thereof is connected to the communication portion  60 , and the gate thereof is connected to the switch controller  70 . The drain of the FET forming the additional switch  54  is connected to a corresponding one of the lines, the source thereof is connected to the ground, and the gate thereof is connected to the switch controller  70 . Each Zener diode ZD has a cathode connected to a corresponding one of the lines and an anode connected to the ground. 
     By using the switch circuit  50  with the aforementioned structure, it is possible that the antenna  30  and the communication portion  60  are connected, i.e., in the On state, when the switches  52  are turned on and the additional switches  54  are turned off, while the communication portion  60  is surely disconnected from the antenna  30 , i.e., in the Off state, when the switches  52  are turned off and the additional switches  54  are turned on. In addition, because the Zener diodes ZD are provided, an input voltage to the communication portion  60  is prevented from exceeding a certain level even upon switching of the switch circuit  50 , i.e., even upon transition from the On state to the Off state. As understood from the aforementioned matter, the Zener diodes ZD serve to add, to the switch circuit  50 , an input protection function of the communication portion  60  as another function than the switching function. In other words, the Zener diodes ZD serve as an input protection portion that protects an input of the communication portion  60  in the switch circuit  50 . The Zener diodes ZD may be omitted if the communication portion  60  itself has a structure tolerant to a temporal excess voltage. 
     With reference to  FIG. 2  again, the communication portion  60  is for communicating with, i.e., transmitting into/ receiving from, the primary device  10  through the antenna  30  when the switch circuit  50  is in the On state. 
     The switch controller  70  is for controlling, in response to the received electric power of the antenna  30 , the state of the switch circuit  50 , i.e., whether the switch circuit  50  is in the On state or in the Off state. As described above, in this embodiment, an antenna power of an electric power wave transmitted from the primary device  10  upon electric power transmission is greater than another antenna power upon communication. Therefore, on the basis of the level of the received electric power of the antenna  30 , the secondary device  20  can determine to take an electric power transmission mode when the electric level is high or to take a communication mode when the electric level is low. Specifically, as understood from  FIGS. 2 and 6 , the switch controller  70  determines, on the basis of the rectification signal received from the power supply portion  40 , to let the switch circuit  50  take the Off state, i.e., electric power transmission mode, to disconnect the communication portion  60  from the antenna  30  if the received electric power level is high, or to let the switch circuit  50  take the On state, i.e., communication mode, to connect between the antenna  30  and the communication portion  60  so that the communication portion  60  carries out radio communication with the antenna  30 , if the received electric power level is low. A threshold value used to carry out level judgment of the received electric power is properly set by a system. For example, the threshold value may be a single value or may have hysteresis which has a threshold value for transition from high received electric power to low received electric power and another threshold value for transition from low received electric power to high received electric power, both threshold values being different from each other. 
     The present embodiment switches the electric power transmission mode and the communication mode in response to the level of the received electric power so that the primary device can freely control whether it carries out electric power transmission or communication. 
     In this embodiment, the secondary device  20  changes the switch circuit  50  in the Off state to disconnect the communication portion  60  from the antenna  30  when being in the electric power transmission mode, so that the communication portion  60  can be protected from a high electric power transmitted from the primary device  10 . Therefore, the communication portion  60  can has a general structure with no consideration of high electric power tolerance. 
     As apparent from the above-described embodiment, the switch circuit  50  is provided only between the antenna  30  and the communication portion  60  but not between the antenna  30  and the power supply portion  40 . In other words, the secondary device  20  of the present embodiment includes the switch circuit  50  that disconnects the communication portion  60  from the antenna  30  under the electric power transmission mode, while including a structure that always connects between the power supply portion  40  and the antenna  30 . As mentioned above, the power supply portion  40  of the present embodiment is connected to the antenna  30  even under the communication mode. Therefore, a circuit size of the switch circuit  50  can be made small, and the control of the switch circuit  50  becomes easy. In addition, the communication portion  60  can be supplied with an electric power by using the received electric power even upon the communication mode. 
     The switch circuit  50  is not limited to the above-mentioned one but may be another one which can switch On/Off connection between the antenna  30  and the communication portion  60  under the control of the switch controller  70 . For example, in the switch circuit  50  illustrated in  FIG. 3 , the switches (unilateral switches)  52  are provided on the respective lines. However, as the switch circuit  50 ′ shown in  FIG. 5 , a bilateral switch  56  may be provided on one of the lines. The switch circuit  50 ′ shown in  FIG. 5  has the Zener diode ZD connected between the ground and the line on which the bilateral switch  56  is provided for input protection of the communication portion  60 . However, as the switch circuit  50 ″ shown in  FIG. 6 , the Zener diode ZD can be omitted. For either the switch circuit  50 ′ of  FIG. 5  or the switch circuit  50 ″ of  FIG. 6 , the switch controller  70  controls the switch circuit  50 ′ or the switch circuit  50 ″ to change it to the On state under the communication mode by turning the bilateral switch  56  on and turning the additional switch  54  off. Under the electric power transmission mode, the switch controller  70  controls the switch circuit  50 ′ or the switch circuit  50 ″ to change it to the Off state under the electric power transmission mode by turning the bilateral switch  56  off and turning the additional switch  54  on. 
     Furthermore, although the input protection portion protecting the input of the communication portion  60  in the aforementioned switch circuit  50  is formed of the Zener diodes, the present invention is not limited thereto. For example, the switch circuit  50 - 1  shown in  FIG. 7  comprises an input protection portion  55 - 1  formed of diodes. Anodes of the diodes forming the input protection portion  55 - 1  are connected to the lines, respectively. Cathodes of the diodes are connected to the ground. With this structure, if voltages equal to or more than the forward voltages Vf of the diodes are applied to the respective lines, the diodes are turned on so that the communication portion  60  is protected. As the switch circuit  50 - 2  shown in  FIG. 8 , an input protection portion  55 - 2  may be formed by connecting a plurality of diodes in series. As illustrated in the drawing, anodes of the diodes forming one ends of the in-series connected diodes are connected to the lines, respectively, while cathodes of the diodes forming the other ends of the in-series connected diodes are connected to the ground. If the input protection portion  55 - 2  is formed of the diodes same as each other, the operating voltage of the input protection portion  55 - 2  becomes a voltage determined by multiplying a forward voltage Vf of the diode by the number of the diodes (in-series number). If the input protection portion  55 - 2  is formed of the diodes which are of plural types, the operating voltage of the input protection portion  55 - 2  becomes a voltage determined by summing all forward voltages Vf of all diodes. Thus, if the input protection portion  55 - 2  is formed of the plurality of diodes, the operating voltage of the input protection portion  55 - 2  can be set strictly. If voltages applied to the lines are equal to or more than the thus set operating voltage, currents flow into the input protection portion  55 - 2  so that the communication portion  60  is protected. Consequently, even if the spread due to the angle of view of the imaging device  8  is taken into consideration, the field of view F of the imaging device  8  becomes a maximum of about 120 mm. 
     [Second Embodiment] 
     With reference to  FIGS. 2 and 9 , a secondary device (electronic device)  20   a  according to a second embodiment of the present invention is a modification of the secondary device  20  according to the aforementioned first embodiment. Therefore, in  FIG. 9 , components similar to the components of  FIG. 2  are depicted with reference numerals same as those of  FIG. 2 ; explanations thereabout are omitted. Hereinafter, explanation will be mainly directed to its difference from the first embodiment. 
     As shown in  FIG. 9 , a module  22   a  of the secondary device  20   a  of the present embodiment comprises a supplemental rectifier  80  connected to both ends of the coil  32  of the antenna  30 . A switch controller  70   a  of the present embodiment controls the switch circuit  50  not based on the rectification signal output from the power supply portion  40  but based on an output of the supplemental rectifier  80 , so that the switch circuit  50  is in the Off state under the electric power transmission mode while is in the On state under the communication mode. 
     In the secondary device  20   a  of the present embodiment, the switch controller  70   a  controls the switch circuit  50  only on the basis of the output of the supplemental rectifier  80 . The switch controller  70   a  may control the switch circuit  50  on the basis of both the output of the power supply portion  40  (rectification signal) and the output of the supplemental rectifier  80 . 
     The switch circuit  50  is not limited to the structure shown in  FIG. 3  but may be another structure if it can connect/disconnect between the antenna  30  and the communication portion  60  under the control of the switch controller  70   a.    
     [Third Embodiment] 
     With reference to  FIGS. 2 and 10 , a secondary device (electronic device)  20   b  according to a third embodiment of the present invention is a modification of the secondary device  20  according to the aforementioned first embodiment. Therefore, in FIG.  10 , components similar to the components of  FIG. 2  are depicted with reference numerals same as those of  FIG. 2 ; explanations thereabout are omitted. Hereinafter, explanation will be mainly directed to its difference from the first embodiment. 
     As shown in  FIG. 10 , a module  22   b  of the secondary device  20   b  of the present embodiment comprises a supplemental antenna  90  having a supplemental coil  92  and a supplemental rectifier  80  connected to both ends of the supplemental coil  92 . A switch controller  70   b  of the present embodiment controls the switch circuit  50  on the basis of the electric power received at the supplemental antenna  90  and rectified at the supplemental rectifier  80 , so that the switch circuit  50  is in the Off state under the electric power transmission mode while is in the On state under the communication mode. 
     The switch circuit  50  is not limited to the structure shown in  FIG. 3  but may be another structure if it can connect/disconnect between the antenna  30  and the communication portion  60  under the control of the switch controller  70   b.    
     [Fourth Embodiment] 
     With reference to  FIGS. 10 and 11 , a secondary device (electronic device)  20   c  according to a fourth embodiment of the present invention is a modification of the secondary device  20   b  according to the aforementioned third embodiment. Therefore, in  FIG. 11 , components similar to the components of  FIG. 10  are depicted with reference numerals same as those of  FIG. 10 ; explanations thereabout are omitted. Hereinafter, explanation will be mainly directed to its difference from the third embodiment. 
     As shown in  FIG. 11 , a switch controller  70   c  of a module  22   c  of the secondary device  20   c  of the present embodiment controls the switch circuit  50  on the basis of not only the output of the supplemental rectifier  80  but also the output of the power supply portion  40  (rectification signal) and the output of the supplemental rectifier  80 . The system preferably sets how the switch controller  70   c  uses two outputs, i.e., the output of the supplemental rectifier  80  and the output of the power supply portion  40 . For example, the switch controller  70   c  may control the switch circuit  50  so that the state of the switch circuit  50  is changed if any one of the output of the supplemental rectifier  80  and the output of the power supply portion  40  exceeds a predetermined threshold value. Or, the switch controller  70   c  may control the switch circuit  50  so that the state of the switch circuit  50  is changed only if both the output of the supplemental rectifier  80  and the output of the power supply portion  40  exceed a predetermined threshold value. The threshold values used for judgments of the outputs of the supplemental rectifier  80  and the power supply portion  40  may be different from each other. 
     The switch circuit  50  is not limited to the structure shown in  FIG. 3  but may be another structure if it can connect/disconnect between the antenna  30  and the communication portion  60  under the control of the switch controller  70   c.    
     [Fifth Embodiment] 
     With reference to  FIGS. 2 and 12 , a secondary device (electronic device)  20   d  according to a fifth embodiment of the present invention is a modification of the secondary device  20  according to the aforementioned first embodiment. Therefore, in  FIG. 12 , components similar to the components of  FIG. 2  are depicted with reference numerals same as those of  FIG. 2 ; explanations thereabout are omitted. Hereinafter, explanation will be mainly directed to its difference from the first embodiment. 
     As shown in  FIG. 12 , a module  22   d  of the secondary device  20   d  according to the present embodiment further comprises a DC/DC converter  100 , a level detector  110 , an LDO (Low Drop Output) regulator  120  and a supply circuit  130 , wherein the DC/DC converter  100  is connected to the power supply portion  40 , the level detector  110  is connected to the power supply portion  40 , the LDO regulator  120  is connected to the level detector  110 , and the supply circuit  130  is connected to the DC/DC converter  100  and the LDO regulator  120  and is also connected to the communication portion  60 . 
     The DC/DC converter  100  receives the rectification signal from the power supply portion  40  and produces a first direct current signal to input the first direct current signal into the supply circuit  130 . The level detector  110  receives the rectification signal and, if a level of the electric power received at the antenna  30  is lower than a predetermined level, inputs the rectification signal as a low electric power signal into the LDO regulator  120 . When receiving the low electric power signal from the level detector  110 , the LDO regulator  120  produces a second direct current signal to input the second direct current signal into the supply circuit  130 . The supply circuit  130  comprises a first diode D 1  and a second diode D 2 , wherein an anode of the first diode D 1  is connected to the DC/DC converter  100  while a cathode of the first diode D 1  is connected to the communication portion  60 , and an anode of the second diode D 2  is connected to the LDO regulator  120  while a cathode of the second diode D 2  is connected to the communication portion  60 . In other words, the first direct current signal is input into the anode of the first diode D 1 , while the second direct current signal is input into the anode of the second diode D 2 . The supply circuit  130  uses the first diode D 1  and the second diode. D 2  connected in Wired-OR configuration and supply the communication portion  60  with a higher one of the first direct current signal and the second direct current signal. 
     The above-described structure enables that the electric power received at the antenna  30  is efficiently supplied to the communication portion  60 . 
     The above-described present invention is applicable to an electronic device such as a mobile phone or a digital camera which has a non-contact battery-charging function. Also, it is applicable to a system including the same. 
     The present application is based on Japanese patent applications of JP2010-289054 and JP2011-155646 filed before the Japan Patent Office on Dec. 27, 2010 and Jul. 14, 2011, respectively, the contents of which are incorporated herein by reference. 
     While there has been described what is believed to be the preferred embodiment of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such embodiments that fall within the true scope of the invention. 
     REFERENCE SIGNS LIST 
       10  Primary Device 
       12  Communication/Power-Transmission Circuit 
       14  Antenna 
       20 ,  20   a ,  20   b ,  20   c ,  20   d  Secondary Device (Electronic Device) 
       22 ,  22   a ,  22   b ,  22   c ,  22   d  Module 
       24  Load 
       30  Antenna 
       32  Coil 
       40  Power Supply Portion 
       50 ,  50 ′,  50 ″ Switch Circuit 
       52  Switch (Unilateral Switch) 
       54  Additional Switch 
     ZD Zener Diode 
       56  Bilateral Switch 
       60  Communication Portion 
       70 ,  70   a ,  70   b ,  70   c  Switch Controller 
       80  Supplemental Rectifier 
       90  Supplemental Antenna 
       92  Supplemental Coil 
       100  DC/DC Converter (DC/DC) 
       110  Level Detector 
       120  LDO Regulator (LDO) 
       130  Supply Circuit 
     D 1  First Diode 
     D 2  Second Diode