POWER SUPPLY DEVICE AND POWER RECEIVING DEVICE WITH BILLING PROCESSING UNIT Technical Field [0001] The present disclosure relates to a power supply device, a power receiving device, a billing method, and a program. The present application builds upon concepts disclosed in prior applications by one or more of the inventors and/or the assignee, including the following: Japan Patent Ap plication No. 2012-028651, titled "OUTLET SYSTEM FOR CONTROLLING CHARGING USING IDENTIFICATION," filed February 13, 2012, and Japan Patent Application No. 2012-085362, filed April 4, 2012. The entire contents of each of the above-identified applications are hereby incorporated by reference. Background Art [0002] In recent years, devices capable of performing authentication on a device of a power supply target such as a power supply device for a vehicle, for example, an electric vehicle (EV), and selectively supplying the device of the power supply target with power according to an authentication result have been released. In addition, a technique of performing a billing process according to an amount of supplied electric power has been also developed. As a technique of performing billing for every local area network (LAN) on an amount of electric power supplied to LAN device, for example, there is a technique discussed in Patent Literature 1. Citation List Patent Literature [0003] PTL 1: JP 2006-13683 A Summary Technical Problem [0004] A device at a power reception side (hereinafter referred to as a "power receiving device") that receives electric power is connected with a device (for example, a device at a transmission side (hereinafter referred to as a "power supply device")) that supplies electric power via a power line in a wired manner, and receives electric power transmitted from the power supply device. Here, when a connection between a power supply device and a power receiving device via a power line is interrupted during transmission of electric power, for example, intentionally (for example, for power stealing) or unintentionally (for example, by accident), a user of the power supply device or a user of the power receiving device is likely to face a disadvantage in billing for the supply of electric power. For example, when electric power is transmitted after the user of the power receiving device pays the cost of the electric power that receives power (when prepayment is made for the cost of the electric power), if a connection is interrupted for reasons such as those mentioned above, it may be difficult for the power receiving device to receive electric power corresponding to the amount paid by the user of the power receiving device. Further, for example, when payment is made for the supplied electric power after supply to the power receiving device ends (when deferred payment is made for the cost of the electric power), when a connection is in terrupted for reasons such as those mentioned above, it may be difficult for the user of the power supply device to receive payment for the cost of the supplied electric power. [0005] In the present disclosure, a power supply device, a power receiving device, a billing method, and a program, which are new and improved and capable of reducing the dis advantage to a user in billing for supply of electric power. Solution to Problem [0006] According to an embodiment of the present disclosure, there is provided a power supply device including a billing information generating unit for generating billing in formation for an amount related to electric power transmitted by the power supply device; a billing processing unit for performing a billing process based on the billing information, wherein performing the billing process includes: performing commu nication with a second device, and determining a result of the billing process based on the communication; and a power control unit for selectively transmitting electric power based on the result of the billing process. [0007] In some embodiments, performing communication with the second device includes: transmitting a billing process command to the second device, and receiving a response signal from the second device, the response signal representing the result of the billing process, the second device being a power receiving device; and selectively transmitting the electric power comprises selectively transmitting the electric power to the power receiving device. [0008] According to another embodiment of the present disclosure, there is provided a billing method including generating billing information for an amount related to electric power transmitted by a power supply device; performing a billing process based on the billing information, wherein performing the billing process includes: performing communication with a second device, and determining a result of the billing process based on the communication; and selectively transmitting electric power based on the result of the billing process. [0009] In some embodiments, performing communication with the second device includes: transmitting a billing process command to the second device, and receiving a response signal from the second device, the response signal representing the result of the billing process, the second device being a power receiving device; and selectively transmitting the electric power comprises selectively transmitting the electric power to the power receiving device. [0010] According to another embodiment of the present disclosure, there is provided a power receiving device including a billing processing unit for: determining whether billing information has been received, the billing information being for an amount related to electric power received from a power supply device; and after it is de termined that the billing information has been received, performing a billing process; a power control unit for causing transmission of a response signal to the power supply device, the response signal being based on the billing process; and a notice control unit for providing notice regarding information related to the billing process. [001 1] According to another embodiment of the present disclosure, there is provided a billing method including determining whether billing information has been received, the billing information being for an amount related to electric power received from a power supply device; after it is determined that the billing information has been received, performing a billing process; transmitting a response signal to the power supply device, the response signal being based on the billing process; and providing notice regarding information related to the billing process. [Advantageous Effects] [0012] According to the present disclosure, it is possible to reduce the disadvantage to a user in billing for supply of electric power. Brief Description of Drawings [0013] [fig. l]Fig. 1 is a flowchart illustrating a first example of a process related to a billing method in a power supply device according to the present embodiment. [fig.2]Fig. 2 is a flowchart illustrating a second example of a process related to a billing method in a power supply device according to the present embodiment. [fig.3]Fig. 3 is a flowchart illustrating a second example of a process related to a billing method in a power supply device according to the present embodiment. [fig.4]Fig. 4 is a flowchart illustrating a second example of a process related to a billing method in a power supply device according to the present embodiment. [fig.5]Fig. 5 is a flowchart illustrating a second example of a process related to a billing method in a power supply device according to the present embodiment [fig.6]Fig. 6 is an explanatory diagram for describing an example of wireless commu nication according to the present embodiment. [fig.7]Fig. 7 is an explanatory diagram illustrating an example of a configuration for implementing wireless communication performed between a power supply device according to the present embodiment and a power receiving device according to the present embodiment. [fig.8]Fig. 8 is an explanatory diagram for describing an example of a power line com munication according to the present embodiment. [fig.9]Fig. 9 is an explanatory diagram illustrating an example of a configuration of a power line communication unit arranged in a power supply device according to the present embodiment. [fig. 10] Fig. 10 is an explanatory diagram illustrating another example of a power line communication unit arranged in a power supply device according to the present em bodiment. [fig. 1l]Fig. 11 is an explanatory diagram illustrating an example of a configuration of a first filter arranged in a power supply device according to the present embodiment [fig. 12] Fig. 12 is an explanatory diagram illustrating an example of a configuration of a second filter arranged in a power supply device according to the present embodiment. [fig.l3]Fig. 13 is an explanatory diagram illustrating an example of a configuration of a power line communication unit arranged in a power receiving device according to the present embodiment. [fig. 14] Fig. 14 is an explanatory diagram illustrating another example of a con figuration of a power line communication unit arranged in a power receiving device according to the present embodiment. [fig.l5]Fig. 15 is an explanatory diagram illustrating an example of a configuration of a power supply device according to the present embodiment. [fig.l6]Fig. 16 is a flowchart illustrating an example of a process related to a billing method in a power receiving device according to the present embodiment. [fig.l7]Fig. 17 is an explanatory diagram illustrating an example of a configuration of a power receiving device according to the present embodiment. Description of Embodiments [0014] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. [0015] Further, the description will proceed in the following order. 1. Billing Method According to Present Embodiment 2. Communication According to Present Embodiment 3. Power Supply Device According to Present Embodiment 4. Power Receiving Device According to Present Embodiment 5. Program According to Present Embodiment [0016] (Billing Method According to Present Embodiment) Before configurations of the power supply device according to the present embodiment and the power receiving device according to the present embodiment are described, first, the billing method according to the present embodiment will be described. In the following, the billing method according to the present embodiment will be described in connection with an example in which a process related to the billing method according to the present embodiment is performed by the power supply device according to the present embodiment. A process related to the billing method according to the present embodiment in the power receiving device according to the present embodiment will be described later. [0017] As described above, when a connection between a power supply device and a power receiving device via a power line is disconnected during transmission of electric power for a certain reason, the user of the power supply device and the user of the power receiving device are likely to face disadvantages in billing for supply of electric power. [0018] In this regard, the power supply device according to the present embodiment generates billing information representing the cost of electric power supplied to an external device (which corresponds to the power receiving device and which may be hereinafter referred to as an "external connection device") connected by a power line in a wired manner for each predetermined amount related to electric power transmitted to the power line (a billing information generating process). Here, for example, data rep resenting the price or data representing a value equivalent to currency may be used as the billing information according to the present embodiment. The billing information according to the present embodiment may further include, for example, identification information (which will be described later) representing a billing target device (an external connection device). [0019] Further, the power supply device according to the present embodiment performs a billing process based on the generated billing information (a billing process). Then, the power supply device according to the present embodiment selectively transmits electric power to the external connection device based on the result of the billing process (a power control process). [0020] (1) Billing Information Generating Process For example, the power supply device according to the present embodiment detects an amount related to electric power transmitted to the external connection device, and determines whether or not the detected amount related to electric power satisfies a set condition based on the detected amount related to electric power. Then, when it is de termined that the detected amount related to electric power satisfies the set condition, the power supply device according to the present embodiment determines that the detected amount related to electric power has reached a predetermined amount of transmitted electric power, and generates billing information corresponding to electric power supplied to the external connection device. [0021] Here, for example, at least one or two or more of an amount of a power supply time to the external connection device, an amount of electric power supplied to the external connection device, and the cost of an amount of electric power supplied to the external connection device may be used as an amount related to transmitted electric power according to the present embodiment. [0022] Here, when the power supply time to the external connection device is used as an amount related to transmitted electric power, the power supply device according to the present embodiment determines that a detected amount related to electric power has satisfied a set condition, for example, each time a predetermined time (an example of the set condition) elapses after power supply to the external connection device (transmission of electric power to the external connection device) starts. Here, for example, the predetermined time may be a fixed time interval which is set in advance or may be a variable time interval which can be changed by the user of the power supply device according to the present embodiment. Further, for example, the prede termined time may be randomly set. [0023] Further, when an amount of electric power supplied to the external connection device is used as an amount related to transmitted electric power, the power supply device according to the present embodiment determines that a detected amount related to electric power has satisfied a set condition, for example, each time a predetermined amount of electric power (an example of the set condition) is supplied after power supply to the external connection device starts. Here, for example, the predetermined amount of electric power may be a fixed amount of electric power which is set in advance or may be a variable amount of electric power which can be changed by the user of the power supply device according to the present embodiment. Further, the pre determined amount of electric power may be randomly set. [0024] Further, when the cost of an amount of electric power supplied to the external connection device is used as an amount related to transmitted electric power, the power supply device according to the present embodiment determines that a detected amount related to electric power has satisfied the set condition, for example, each time the price corresponding to electric power supplied after power supply to the external connection device starts reaches a predetermined amount (an example of the set condition). Here, for example, the predetermined amount is a fixed amount which is set in advance or may be a variable amount which can be changed by the user of the power supply device according to the present embodiment. Further, the predetermined amount may be randomly set. [0025] Further, when two or more amounts are used as an amount related to transmitted electric power, for example, the power supply device according to the present embodiment determines whether or not the detected amount related to electric power has satisfied a combination condition in which a plurality of conditions are combined. Here, for example, an AND condition or an OR condition may be used as the com bination condition according to the present embodiment, but the combination condition according to the present embodiment is not limited to this example. For example, a condition in which a priority or a weight is set to the condition configuring the com bination condition may be used as the combination condition according to the present embodiment. [0026] The billing information generating process in the power supply device according to the present embodiment is not limited to the above examples. For example, when it is detected that a connection with the external connection device via the power line is dis connected, the power supply device according to the present embodiment may generate billing information corresponding to electric power supplied to the external connection device at a detection point in time (an example of the exceptional process). Further, for example, when a disturbance signal is detected in communication with the external connection device, the power supply device according to the present embodiment may generate billing information corresponding to electric power supplied to the external connection device at a detection point in time (another example of an exceptional process). [0027] Further, for example, the power supply device according to the present embodiment may change the cost of an amount of electric power supplied to the external connection device based on a status of power supply to the external connection device and generate the billing information. For example, a process of changing the cost of an amount of electric power supplied to the external connection device when electric power is supplied to the external connection device at a normal power supply speed (hereinafter, referred to as "on normal mode") and when electric power is supplied to the external connection device at a higher power supply speed (hereinafter, referred to as "on fast mode" or "on higher speed mode") and generating the billing information may be used as the process of generating the billing information based on the status of power supply to the external connection device. In other words, for example, the power supply device according to the present embodiment may generate the billing in formation that indicates a cost corresponding to the power supply mode being set selected from a plurality of levels of power supply speed (one or more power supply modes, for example, the normal mode or fast mode (higher speed mode) mentioned above. [0028] Note that the process of generating billing information based on a status of power supply to the external connection device is not limited to the above examples. For example, the power supply device according to the present embodiment may generate the billing information corresponding to the amount of electric power supplied to the external connection device based on the total amount of electric power supplied to the external connection device. By generating the billing information corresponding to the total amount of electric power supplied to the external connection device, the power supply device according to the present embodiment may change the cost of the amount of the electric power supplied to the external connection device, for example, and generate the billing information. Here, as process for changing the cost based on the total amount of electric power supplied to the external connection device, for example, there may be a process to reduce the cost of electric power (for example, unit price such as a cost per kWh, and so on) as the amount of electric power supplied to the external connection device is increased. [0029] Further, the power supply device according to the present embodiment may generate the billing information corresponding to price information (data) of electric power indicated by the price information indicating price of acquired electric power. By generating the billing information based on the acquired price information, the power supply device according to the present embodiment may generate the billing in formation on which price on real time is reflected. Here, the power supply device according to the present embodiment, for example, acquires price information from an external device such as a server, and generates the billing information based on price of electric power indicated by the acquired price information and the amount of electric power supplied to the external connection device. Note that a method for acquiring price information according to the present embodiment is not limited to the above. For example, the power supply device according to the present embodiment may receive the price information packetized to be transmitted to the power line, and acquire the price information. [0030] (2) Billing Process The power supply device according to the present embodiment performs the billing process based on the billing information generated in the process (1) (the billing in formation generating process). [003 1] (2- 1) First Billing Process For example, the power supply device according to the present embodiment performs communication with the external connection device and performs billing on the external connection device. [0032] More specifically, the power supply device according to the present embodiment transmits a billing process command causing a value corresponding to the cost rep resented by the billing information to be subtracted from an electronic value (currency or data having a value equivalent to currency) to the external connection device. For example, data including data representing processing content and data representing a value of an electronic value to be subtracted may be used as the billing process command according to the present embodiment. The billing process command according to the present embodiment is not limited to this example. For example, the billing process command according to the present embodiment may be data rep resenting a process (a process of moving an electronic value) of transmitting an electronic value corresponding to the value corresponding to the cost represented by the billing information to the external connection device. [0033] The external connection device that has received the billing process command performs processing, for example, on an electronic value stored in the external connection device or an electronic value stored in an external device capable of performing communication with the external connection device based on the billing process command. Then, the external connection device transmits a response signal representing a processing result based on the billing process command to the power supply device according to the present embodiment. Here, for example, an electronic value that the external connection device uses as a target of the processing based on the billing process command may be an electronic value which is stored in the external connection device or the external device capable of performing communication with the external connection device in advance or may be a newly charged electronic value. [0034] Here, for example, a signal representing that the process based on the billing process command has been completed normally (subtraction of an electronic value, that is, billing is completed) or a signal representing that the process based on the billing process command has not been completed normally (billing has not been completed) may be used as the response signal transmitted from the external connection device. Further, a signal representing that subtraction of an electronic value has not been performed or a signal representing that subtraction of an electronic value has been partially performed and including an electronic value that has not been subjected to subtraction of an electronic value may be used as the signal representing that the process based on the billing process command has not been completed normally. [0035] The power supply device according to the present embodiment determines whether or not the billing process has been completed normally based on the response signal to the received billing process command. By determining whether or not the billing process has been completed normally based on the received response signal, for example, the power supply device according to the present embodiment can determine whether or not billing has been completed normally, billing has not been performed at all, or billing has been partially performed. [0036] The first billing process in the power supply device according to the present em bodiment is not limited to the above example. For example, when it is determined that the billing process has not been completed normally based on the response signal, the power supply device according to the present embodiment may notify the user of the external connection device of the fact that the billing process has not been completed normally, a deficient amount of money, a charge request of an electronic value corre sponding to a deficient amount of money, or the like. The power supply device according to the present embodiment causes a notice to be given to the user of the external connection device, for example, using a visual notice method using a letter or an image or an acoustical notice method using a sound (including music or a beep sound; the same applies hereinafter). Here, an example of a target that is caused to give a notice by the power supply device according to the present embodiment includes an external device such as a display unit (which will be described later) arranged in its own device (the power supply device according to the present embodiment), an external display device, or an external connection device. [0037] (2-2) Second Billing Process For example, the power supply device according to the present embodiment performs communication with an external billing processing device capable of performing billing (for example, post-usage billing performed after power reception) for the user of the external connection device, and causes the external billing processing device to perform billing for the user of the external connection device. In other words, the second billing process according to the present embodiment corresponds to an indirect billing process that causes the external billing processing device to perform a sub stantive billing process, whereas the first billing process according to the present em bodiment is a direct billing process on the external connection device. Here, a server corresponding to a credit card owned by the user of the external connection device, a server corresponding to an account owned by the user of the external connection device, or the like may be used as the external billing processing device according to the present embodiment. [0038] For example, the power supply device according to the present embodiment performs communication with the external billing processing device based on information set before supply of electric power to the external connection device starts. For example, information representing the external billing processing device or information specifying the user of the external connection device may be used as the set in formation according to the present embodiment. Here, for example, an Internet protocol (IP) address or a selection number selected by the user from a list in which an IP address is associated with a selection number may be used as the information rep resenting the external billing processing device according to the present embodiment. Further, a credit card number or an account number may be used as the information specifying the user of the external connection device according to the present em bodiment. For example, the power supply device according to the present embodiment starts supply of electric power to the external connection device after it is confirmed that communication with the external billing processing device is performed based on the set information according to the present embodiment. [0039] More specifically, for example, the power supply device according to the present em bodiment transmits the billing information generated in the process (1) (the billing in formation generating process) to the external billing processing device as the billing process. Here, for example, the power supply device according to the present em bodiment transmits the generated billing information to the external billing processing device each time the billing information is generated, but the second billing process in the power supply device according to the present embodiment is not limited to this example. For example, the power supply device according to the present embodiment may add up the cost represented by the billing information corresponding to the same external connection device when a predetermined time arrives or at predetermined time intervals, and cause the billing information representing the added value to be transmitted to the external billing processing device. [0040] For example, the power supply device according to the present embodiment de termines whether or not the billing process has been completed normally based on the communication result with the external billing processing device. For example, when communication with the external billing processing device has been performed and the response signal representing that the billing information is received normally has been received, the power supply device according to the present embodiment determines that the process based on the billing process command has been completed normally. For example, when communication with the external billing processing device has not been performed or when the response signal representing that the billing information is received normally has not been received, the power supply device according to the present embodiment determines that the process based on the billing process command has not been completed normally. [0041] By determining whether or not the billing process has been completed normally based on the communication result with the external billing processing device, for example, the power supply device according to the present embodiment can determine whether or not billing has been completed normally. [0042] (2-3) Third Billing Process The billing process in the power supply device according to the present embodiment is limited to neither the first billing process nor the second billing process. For example, the power supply device according to the present embodiment may perform a process in which the first billing process (the direct billing process on the external connection device) is combined with the second billing process (the indirect billing process on the external connection device). [0043] More specifically, for example, the power supply device according to the present em bodiment first performs the direct billing process on the external connection device through the same process as the first billing process. Further, when it is determined that the billing process has been completed normally based on the response signal to the received billing process command, the power supply device according to the present embodiment does not perform the same process as the second billing process. [0044] Further, when it is determined that the billing process has not been completed normally based on the response signal to the received billing process command, the power supply device according to the present embodiment performs the same process as the second billing process. [0045] Here, when it is determined that billing has not been performed at all based on the response signal to the received billing process command, for example, the power supply device according to the present embodiment transmits the billing information generated in the process (1) (the billing information generating process) to the external billing processing device. Further, when it is determined that billing has been partially performed based on the response signal to the received billing process command, new billing information corresponding to part of the cost represented by the billing in formation generated in the process (1) (the billing information generating process) is transmitted to the external billing processing device. For example, the power supply device according to the present embodiment generates the new billing information based on an electronic value which has not been subjected to subtraction of an electronic value, which is included in the received response signal. [0046] For example, the power supply device according to the present embodiment prefer entially performs the first billing process, and performs the process in which the first billing process is combined with the second billing process as the third billing process. [0047] The third billing process according to the present embodiment is not limited to this example. For example, the power supply device according to the present embodiment may selectively perform the first billing process (the direct billing process on the external connection device) and the second billing process (the indirect billing process on the external connection device) based on a set billing process setting. Here, for example, the billing process setting according to the present embodiment is set in advance, and reset based on a user operation by the user of the power supply device according to the present embodiment. [0048] The power supply device according to the present embodiment performs, for example, any one of the first billing process to the third billing process as the billing process based on the billing information generated in the process (1) (the billing in formation generating process). The billing process in the power supply device according to the present embodiment is not limited to the first billing process to the third billing process. For example, when the power supply device according to the present embodiment has a function of the external billing processing device according to the second billing process, the power supply device according to the present em bodiment may perform billing (for example, a process related to withdrawal of an amount of money corresponding to the cost represented by the billing information) based on the billing information on the account owned by the user of the external connection device. [0049] (3) Power Control Process The power supply device according to the present embodiment selectively transmits electric power to the external connection device based on the result of the process (2) (the billing process). Further, when no external device (power receiving device) is connected by a power line in a wired manner, the power supply device according to the present embodiment does not transmit electric power. [0050] More specifically, for example, when it is determined that billing has been completed normally in the process (2) (the billing process), the power supply device according to the present embodiment causes a power supply unit (which will be described later) capable of selectively supplying electric power to enter the power suppliable state. Thus, when it is determined that billing has been completed normally in the process (2) (the billing process), electric power is continuously transmitted to the external connection device. [0051] However, when it is determined that billing has not been completed normally in the process (2) (the billing process), the power supply device according to the present em bodiment does not cause a power supply unit (which will be described later) capable of selectively supplying electric power to enter the power suppliable state. Thus, when it is determined that billing has not been completed normally in the process (2) (the billing process), electric power is not transmitted to the external connection device. [0052] The power control process in the power supply device according to the present em bodiment is not limited to the above example. For example, the power supply device according to the present embodiment may perform authentication on the external connection device (an authentication process) and selectively transmit electric power to the external connection device based on the result of the process (2) (the billing process) and the authentication result. [0053] More specifically, the power supply device according to the present embodiment performs communication with the external connection device, acquires the identi fication information representing the external connection device from the external connection device, and performs authentication on the external connection device based on the acquired identification information. Here, the identification information according to the present embodiment refers to information which can be used to identify the external connection device. For example, data representing an identi fication number specific to the external connection device, data representing the type of external connection device (data representing, for example, a manufacturer or a model number), power waveform data representing a power waveform when the external connection device is used (when the external connection device is driven), or the like may be used as the identification information according to the present em bodiment. The identification information according to the present embodiment is not limited to the above examples as long as information which can be used to identify the external connection device is used. [0054] Here, for example, when communication with the external connection device is not performed or when the identification information is not acquired from the external connection device, the power supply device according to the present embodiment de termines that the external connection device is not the external device of the power supply target. [0055] Further, when the identification information is not acquired from the external connection device by communication with the external connection device, the power supply device according to the present embodiment performs authentication based on the identification information For example, the power supply device according to the present embodiment performs authentication on the external connection device based on whether or not identification information corresponding to the identification in formation acquired from the external connection device remains stored in a database recording identification information representing the external device of the power supply target. Here, the database may be stored in a recording medium such as a storage unit (which will be described later) arranged in the power supply device according to the present embodiment, or the power supply device according to the present embodiment may acquire the database from an external device such as a server. For example, the power supply device according to the present embodiment may acquire the identification information from the external connection device before supply of electric power to the external connection device starts, record the acquired identification information in the database, and then start supply of electric power to the external connection device. [0056] For example, the power supply device according to the present embodiment de termines that the external connection device is the external device of the power supply target when authentication has been performed normally, but determines that the external connection device is not the external device of the power supply target when authentication has not been performed normally. [0057] For example, when it is determined that billing has been performed normally in the process (2) (the billing process) and it is determined that the external connection device is the external device of the power supply target, the power supply device according to the present embodiment causes the power supply unit (which will be described later) capable of selectively supplying electric power to enter the power suppliable state. Thus, in this case, electric power can be continuously transmitted to the external connection device. [0058] However, for example, when it is determined that billing has not been performed normally in the process (2) (the billing process) and it is determined that the external connection device is not the external device of the power supply target, the power supply device according to the present embodiment does not cause the power supply unit (which will be described later) capable of selectively supplying electric power to enter the power suppliable state. Thus, in this case, electric power is not transmitted to the external connection device. [0059] For example, the power supply device according to the present embodiment performs the process (1) (the billing information generating process) to the process (3) (the power control process) as the process related to the billing method according to the present embodiment. [0060] Here, the power supply device according to the present embodiment generates the billing information for each predetermined amount related to transmitted electric power in the process (1) (the billing information generating process), and performs the billing process based on the generated billing information in the process (2) (the billing process). Further, the power supply device according to the present embodiment se lectively transmits electric power to the external connection device based on the result of the process (2) (the billing process) in the process (3) (the power control process). [0061] As described above, the power supply device according to the present embodiment does not perform billing on electric power continuously supplied to the external connection device once in advance or later but performs billing based on the billing in formation which is generated for each predetermined amount related to transmitted electric power. Thus, even when a connection between the power supply device according to the present embodiment and the power receiving device according to the present embodiment (the external connection device) via the power line is interrupted during transmission of electric power for a certain reason, it is possible to prevent the situation in which electric power corresponding to the cost paid by the user of the power receiving device is not received by the power receiving device. Further, even when a connection between the power supply device according to the present em bodiment and the power receiving device according to the present embodiment (the external connection device) via the power line is interrupted during transmission of electric power for a certain reason, the cost of supplied electric power which is not received by the user of the power supply device can be reduced to be smaller than when billing on supplied electric power is performed once later. [0062] Thus, for example, processes from the process (1) (the billing information generating process) to the process (3) (the power control process) are performed as the process related to the billing method according to the present embodiment, and thus the power supply device according to the present embodiment can reduce the disadvantage to the user in billing for supply of electric power. [0063] The process related to the billing method in the power supply device according to the present embodiment is not limited to the above example. For example, when it is detected that a connection with the external connection device via the power line is in terrupted, the power supply device according to the present embodiment may perform the process (1) (the billing information generating process) at a detection point in time, and perform the process (2) (the billing process) based on the billing information in the second billing process. Here, for example, the power supply device according to the present embodiment detects that a connection with the external connection device via the power line is interrupted based on the fact that transmission of electric power has not been performed or a change in the connection state of the external device in the connecting unit (which will be described later). [0064] Further, the power supply device according to the present embodiment, for example, may cause various information related to the billing methods, such as information on supply power on the power supply mode configurable (or the power supply mode being set), information on prices of electric power at each time (for example, unit price per [kWh], and so on), information on discount adopted for the total amount of electric power supplied, to be noticed (notice control process). The power supply device according to the present embodiment, for example, causes a device (such as a display device, an audio output device such as a speaker, and so on) related to notice arranged in the supply device according to the present embodiment, and/or an external device such as an external connection device or device regarding external notice, to make a notice on various information related to the billing method. For example, when notifying the external connection device, the power supply device according to the present embodiment causes the external connection device to make a notice on various information related to the billing method by transmitting control data that controls notice using the later-described communication according to the present embodiment. Here, the control data that controls notice according to the present embodiment includes, for example, a notice command that executes notice. Further, the control data that controls notices according to the present embodiment may further include, for example, data indicating contents of the notice (for example, image data, audio data, and so on). [0065] Hereinafter, an example of process related to the billing method of the power supply device according to the present embodiment will be described in more detail. [0066] 1. First Example of a Process Related to a Billing Method Fig. 1 is a flowchart illustrating a first example of the process related to the billing method in the power supply device according to the present embodiment. Here, the process of steps S102 and S104 illustrated in Fig. 1 corresponds to the process (1) (the billing information generating process), and the process of steps S106 and S108 i l lustrated in Fig. 1 corresponds to the process (2) (the billing process). Further, the process of steps S100 and SI 10 illustrated in Fig. 1 corresponds to the process (3) (the power control process). Further, Fig. 1 illustrates an example of a process after transmission of electric power to the external connection device starts. [0067] The power supply device according to the present embodiment transmits electric power to the external connection device (S100). Here, the power supply device according to the present embodiment detects an amount related to electric power transmitted to the external connection device. For example, at least one or two or more amount of the power supply time to the external connection device, an amount of electric power supplied to the external connection device, and the cost of an amount of electric power supplied to the external connection device may be used as an amount related to transmitted electric power detected by the power supply device according to the present embodiment. [0068] The power supply device according to the present embodiment determines whether or not an amount related to electric power has satisfied a set condition (S102). Here, for example, when the detected amount related to electric power has satisfied the set condition, the power supply device according to the present embodiment determines that an amount related to electric power has satisfied the set condition. Further, when the detected amount related to electric power has not satisfied the set condition, the power supply device according to the present embodiment determines that an amount related to electric power has not satisfied the set condition. [0069] Here, when it is determined in step SI02 that an amount related to electric power has not satisfied the set condition, the power supply device according to the present em bodiment repeats the process starting from step S100. [0070] However, when it is determined in step SI02 that an amount related to electric power has satisfied the set condition, the power supply device according to the present em bodiment generates the billing information corresponding to electric power supplied to the external connection device (S104). Here, for example, the billing information generated in step S104 is data representing an amount of money or a price equivalent to a currency serving as the cost of electric power supplied to the external connection device after transmission of electric power to the external connection device starts (first time) or after previous billing information is generated (after first time). [0071] Here, when the billing information is generated in step S104, the power supply device according to the present embodiment performs the billing process (S106). Then, the power supply device according to the present embodiment determines whether or not the billing process has been completed normally (S108). Here, in steps S106 and S108, for example, the power supply device according to the present embodiment performs any one of the first billing process to the third billing process. [0072] Here, when it is determined in step S108 that the billing process has been completed normally, the power supply device according to the present embodiment repeats the process starting from step S100. [0073] Further, when it is determined in step S108 that the billing process has not been completed normally, the power supply device according to the present embodiment does not transmit electric power to the external connection device (SI 10). [0074] For example, the power supply device according to the present embodiment performs the first example of a process illustrated in Fig. 1 as the process related to the billing method. [0075] The first example of process related to the billing method in the power supply device according to the present embodiment is not limited to the process illustrated in Fig. 1. For example, when it is detected that a connection with the external connection device via the power line is interrupted, the power supply device according to the present em bodiment may perform the process starting form step SI04 at a detection point in time (an example of the exceptional process). Further, for example, when the disturbance signal is detected in communication with the external connection device, the power supply device according to the present embodiment may perform the process starting from step SI04 at a detection point in time (another example of the exceptional process). [0076] 2. Second Example of Process Related to Billing Method FIG. 2 is a flowchart illustrating a second example of a process related to a billing method in a power supply device according to the present embodiment. Here, processes of step S202 to S208 shown in FIG. 2 correspond to the above (1) process (billing information generation process), while processes of step S210 to S212 shown in FIG. 2 corresponds to the above (2) process (billing process). Further, processes of steps S200 and S214 shown in FIG. 2 correspond to the above (3) process (power control unit). In addition, FIG. 2 illustrates an example after the power transmission has been started to the external connection device. [0077] The power supply device according to the present embodiment transmits electric power to the external connection device same as step S100 shown in FIG. 1 (S200). [0078] The power supply device according to the present embodiment determines whether or not an amount related to electric power satisfies a condition being set (S202) same as step SI02 shown in FIG. 1. When it is not determined that the amount related to the electric power does not satisfy the condition being set in step S202, the power supply device according to the present embodiment repeats the process starting from step S200. [0079] Further, when it is determined that an amount related to electric power satisfies a condition being set in step 202, the power supply device according to the present em bodiment determines whether or not the power supply mode related to the power supply speed is the fast mode (higher speed mode, which is one example of the power supply mode) (S204). Here, the power supply mode according to the present em bodiment may be set, for example, based on a user's setting operation, or the like prior to starting transmission of electric power to the external connection device. [0080] When it is determined as to be the fast mode in step 204, the power supply device according to the present embodiment generates billing information corresponding to the fast mode (S206). The power supply device according to the present embodiment, for example, specifies a price of electric power corresponding to the fast mode based on data indicating a price of electric power corresponding to the fast mode (for example, an unit price such as a price per [kWh]), and generates the billing information corresponding to the fast mode. [008 1] Here, data representing a price of electric power corresponding to the fast mode is stored in a storage unit (later described) which the power supply device according to the present embodiment, or an external recording medium removably mounted in the power supply device according to the present embodiment, and the power supply device according to the present embodiment reads the data representing the price of electric power corresponding to the fast mode from the storage unit (later described) or the like to acquire the data representing the price of electric power corresponding to the fast mode. Note that, a method of acquiring the data representing the price of electric power corresponding to the fast mode is not limited to the method described above. For example, the power supply device according to the present embodiment may acquire the data representing the price of electric power corresponding to the fast mode by communicating with an external device, such as a server. [0082] When it is not determined to be a fast mode in step 204, the power supply device according to the present embodiment generates billing information corresponding to a normal mode (one example of the power supply mode) (S208). The power supply device according to the present embodiment, same as the above step S206, for example, specifies a price of electric power corresponding to the normal mode based on data indicating a price of electric power corresponding to the normal mode (for example, an unit price such as a price per [kWh]), and generates the billing information corresponding to the normal mode. [0083] When the billing information is generated in the process of step S206 or step S208, the power supply device according to the present embodiment performs the billing process, same as step S106 shown in Fig. 1 (S210). Then the power supply device according to the present embodiment determines whether the billing process has normally completed (S212). [0084] When the billing process is determined to have been normally completed in step S212, the power supply device according to the present embodiment repeats the processes starting from step S200. [0085] Further, when the billing process is not determined to have been normally completed in step S212, the power supply device according to the present embodiment does not allow an external connection device to transmit electric power (S214). [0086] The power supply device according to the present embodiment performs processing shown in Fig. 2, for example, as a process related to the second example of the billing method. [0087] Note that the process related to the billing method for the power supply device according to the present embodiment is not limited to the process shown in Fig. 2. In Fig. 2, an example shows that the power supply device according to the present em bodiment generates billing information corresponding to one power supply mode being set from the two power supply modes, fast mode or normal mode, however, the power supply device according to the present embodiment may generate the billing in formation corresponding to one power supply mode being set from three or more power supply modes. [0088] 3. Third Modified Example of Process Related to Billing Method FIG. 3 is a flowchart illustrating a third example of a process related to a billing method in a power supply device according to the present embodiment. Here, processes of step S302 to S312 shown in FIG. 3 correspond to the above (1) process (billing information generation process), while processes of steps S314 and S316 shown in FIG. 3 corresponds to the above (2) process (billing process). Further, processes of steps S300 and S318 shown in FIG. 3 correspond to the above (3) process (power control unit). In addition, FIG. 3 illustrates an example after the power transmission has been started to the external connection device. [0089] The power supply device according to the present embodiment transmits electric power to the external connection device same as step S100 shown in FIG. 1 (S300). [0090] The power supply device according to the present embodiment determines whether or not an amount related to electric power has satisfied a set condition, same as step SI02 shown in Fig. 1 (S302). When it is not determined that the amount related to electric power has satisfied a set condition in step S302, the power supply device according to the present embodiment repeats the process starting from step S300. [0091] Further, when it is determined that the amount related to electric power has satisfied a set condition in step S302, the power supply device according to the present em bodiment determines whether cumulated power supply which is total amount of electric power supplied to the external connection device is equal to or less than a pre determined value a (or, whether the cumulated power supply is less than the prede termined value a, and so on) (S304). Here, the predetermined value a (a[kWh], for example) may be a fixed value which has been set already, or may be a variable which is variable based on a user's operation or the like. [0092] When it is determined that the cumulated power supply is equal to or less than the predetermined value a in step S304, the power supply device according to the present embodiment generates billing information Pa which corresponds to the predetermined value a (S306). The power supply device according to the present embodiment, same as step S206 shown in Fig.2, for example, generates billing information corresponding to the predetermined value a by specifying a price of electric power corresponding to the predetermined value a based on data representing the price of electric power corre sponding to the predetermined value a (for example, an unit prices such as a price per [kWh]). [0093] Further, when it is not determined that the cumulated in step S304, the cumulated power supply is equal to or less than the predetermined value a in step S304, the power supply device according to the present embodiment determines whether the cumulated power supply which is the total amount of electric power supplied to the external connection device is equal to or less than a predetermined value b (where a