Patent Publication Number: US-2022234463-A1

Title: Charging apparatus and method of operating the same

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates to a charging apparatus, and more particularly to a bidirectional AC charging apparatus for use with electric vehicles and a method of operating the same. 
     Description of Related Art 
     The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art. 
     In recent years, due to the rising awareness of environmental protection, government agencies are actively promoting energy-saving and carbon-reducing policies, and therefore the electric vehicle (EV) industry, which can significantly reduce air pollution, has also developed vigorously. With the increasing popularity of electric vehicle applications, the charging technology of electric vehicles is getting more and more attention.  FIG. 1  illustrates a block diagram of a conventional charging apparatus for use with electric vehicles. The conventional charging apparatus  1 ′ is coupled to an AC power source  2 , for example an electrical grid provided by a power company, and is physically coupled to the electric vehicle  3  through a charging gun to charge the electric vehicle  3 . The conventional charging apparatus  1 ′ usually only provides power P 1  of the AC power source  2  to charge the electric vehicle  3  in a single current flow direction. During the charging process, a controller  16 ′ uses a communication unit  14  to communicate with the electric vehicle  3 , and controls a switch  20  to be turned on so as to establish a power transmission path for the charging current to flow. 
     However, due to the growing demand for electricity year by year, power companies are facing pressures to balance the supply and demand of the power grid. Along with the diversification of energy applications such as smart grid, renewable energy, and distributed enemy resources, the supply and demand of power electricity is no longer limited to the single-direction from power generation side to power consumption side. Therefore, power companies are trying to dispatch power more dynamically and flexibly based on the actual power demand, electricity cost, and the cost-effectiveness of power generation. Accordingly, the conventional single-direction EV charging method, from the AC power source  2  to the electric vehicle  3 , can no longer meet the above-mentioned energy applications and power dispatch requirements. 
     Therefore, the present disclosure provides a charging apparatus for use with an electric vehicle and a method of operating the same as a bidirectional power supply solution between the AC power source and the AC charging type electric vehicles according to the actual power dispatch requirements of the power system. 
     SUMMARY 
     In order to solve the above-mentioned problems, the charging apparatus is coupled to an AC power source and an electric vehicle. The charging apparatus includes a power transmission path, a switch, a first controller, a second controller, and a communication unit. One end of the power transmission path is coupled to the AC power source through a first connection port, and the other end of the power transmission path is coupled to the electric vehicle through a second connection port. The switch is disposed on the power transmission path. The first controller is coupled to the power transmission path and the switch. The second controller is coupled to the first controller and the AC power source. The communication unit is coupled to the first controller and the second connection port. When the second controller receives a first request from the AC power source, the second controller provides a first notification to the first controller, and the first controller communicates with the electric vehicle through the communication unit according to the first notification and controls the switch to be turned off. When the first controller receives a first EV notification from the electric vehicle, the first controller controls the switch to be turned on. 
     In order to solve the above-mentioned problems, the method of operating a charging apparatus includes steps of: (a) receiving, by a second controller, a first request from a power management system, (b) notifying, by the second controller, a first controller when the second controller receives the first request so that the first controller correspondingly uses a second signal to communicate with an electric vehicle through a communication unit, and controls a power transmission path to be not conducting, and (c) controlling, by the first controller, the power transmission path to be conducting when the first controller receives a first EV notification from the electric vehicle. 
     The main purpose and effect of the present invention are: the first controller determines whether the second controller receives the first request from the AC power source and whether the first controller receives the first EV notification to automatically control the switch to be turned on or turned off, so that the charging apparatus of the present invention can provide power bidirectionally based on the requests of the AC power source and the states of the electric vehicle. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the present disclosure as claimed. Other advantages and features of the present disclosure will be apparent from the following description, drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present disclosure can be more fully understood by reading the following detailed description of the embodiment, reference made to the accompanying drawing as follows: 
         FIG. 1  is a block diagram of an exemplary conventional charging apparatus. 
         FIG. 2  is a circuit block diagram of an exemplary charging apparatus according to the present disclosure. 
         FIG. 3  is a block diagram indicating how the operation modes of the charging apparatus are switched according to the present disclosure. 
         FIG. 4A  is a block diagram of an exemplary operation of the charging apparatus in a charging mode according to the present disclosure. 
         FIG. 4B  is a block diagram of an exemplary operation of the charging apparatus in a feeding mode according to the present disclosure. 
         FIG. 5A  is a flowchart of an exemplary method of setting operation modes of the charging apparatus according to the present disclosure. 
         FIG. 5B  is a flowchart of an exemplary method of providing a protection mechanism of the charging apparatus according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawing figures to describe the present disclosure in detail. It will be understood that the drawing figures and exemplified embodiments of present disclosure are not limited to the details thereof. 
     Please refer to  FIG. 2 , which shows a circuit block diagram of an exemplary charging apparatus according to the present disclosure. The charging apparatus  1  is coupled to an AC power source  2 , for example an electrical grid provided by a power company, and an electric vehicle  3  is coupled to the charging apparatus  1 . The charging apparatus  1  provides a power transmission path for charging the electric vehicle  3  from the AC power source  2 , or a power transmission path for feeding power to the AC power source  2  from the electric vehicle  3  according to demands of the electric vehicle  3  and the AC power source  2 . The electric vehicle  3  may be a vehicle propelled by electricity, such as an electric car or an electric scooter. The charging apparatus  1  includes a power transmission path  12 , a switch  20 , a communication unit  14 , a first controller  16 A, and a second controller  16 B. The switch  20  is disposed on the power transmission path  12 , and is used to be turned on to establish the power transmission path  12  or turned off to interrupt the power transmission path  12 . One end of the power transmission path  12  is coupled to the AC power source  2  through a power interface of a first connection port  1 A, and the other end of the power transmission path  12  is coupled to the electric vehicle  3  through a power interlace of the second connection port  1 B. Therefore, the power transmission path  12  can provide charging power transmission in a direction T 1  (from the first connection port  1 A to the second connection port  1 B) and provide feeding power transmission in a direction T 2  (from the second connection port  1 B to the first connection port  1 A). 
     The communication unit  14  is coupled to the first controller  16 A, and is coupled to the electric vehicle  3  through a communication interface of the second connection port  1 B. The communication unit  14  is used as a communication channel for information handshaking between the first controller  16 A and the electric vehicle  3  so as to exchange the information of each other&#39;s current status and power demand. After the electric vehicle  3  is physically coupled to the charging apparatus  1 , the first controller  16 A and the electric vehicle  3  exchange the information of each other&#39;s current status and power demand through the communication unit  14  so that the first controller  16 A controls the charging apparatus  1 , such as to provide a charging path or a power feeding path, according to the results of the handshaking communication with the electric vehicle  3 . The second controller  16 B is connected to an AC power source management system  2 A and the first controller  16 A, and the second controller  16 B may be a grid code controller. The second controller  16 B communicates with the AC power source management system  2 A to acquire the related information of the AC power source  2 , such as the voltage, the current, the frequency of the AC power source  2  and the power demand of the AC power source  2 . When the AC power source management system  2 A provides a first request RP, such as a power demand request, or a second request RS, such as a demand termination request, to the second controller  16 B according to the peak load demand, supply and demand balancing, or power quality management needs of the AC power source  2 , the second controller  16 B correspondingly provides a first notification to the first controller  16 A according to the first request RP, and provides a second notification to the first controller  16 A according to the second request RS. The first controller  16 A thus determines to turn on or turn off the switch  20  according to the received notifications. 
     Specifically, whether the power (current) flows from the AC power source  2  to the electric vehicle  3  or the power flows from the electric vehicle  3  to the AC power source  2  is controlled by turning on or turning off the switch  20  based on the power demand of the AC power source  2  and/or the power demand of the electric vehicle  3 , and such system behaviors are described as operation modes as follows. In one embodiment of the present disclosure, the operation modes include a charging mode and a feeding mode. In the charging mode, the power P 1  of the AC power source power  2  is transmitted in the direction T 1 , from the first connection port  1 A to the second connection port  1 B, through the power transmission path  12  when the switch  20  is turned on. In the feeding mode, feed power P 2  is transmitted in the direction T 2 , from the second connection port  1 B to the first connection port  1 A, through the power transmission path  12  when the switch  20  is turned on. Moreover, the operation modes further include a standby mode. In the standby mode, the power transmission path  12  is interrupted by turning off the switch  20  to cause no power transmission. In addition to the above-mentioned notification types, the first controller  16 A also selects the feeding mode, the charging mode, or the standby mode according to the results of the handshaking communication with the electric vehicle  3 . 
     After the electric vehicle  3  is physically coupled to the second connection port  1 B, the first controller  16 A communicates with the electric vehicle  3  with a first signal Sc 1  through the communication unit  14 . According to the standard of IEC 61851, which is an international standard for electric vehicle conductive charging systems, the first signal Sc 1  may be a PWM (pulse width modulation) signal with frequency of approximately 1 kHz. In addition to the default communication method of transmitting the first signal Sc 1  between the first controller  16 A and the electric vehicle  3 , if the second controller  16 B receives the first request RP from the AC power source management system  2 A and provides the first notification to the first controller  16 A, the communication method between the first controller  16 A and the electric vehicle  3  will be changed to transmitting a second signal Sc 2  different from the first signal Sc 1  in, such as but not limited to a signal with different pulse, packet, and/or frequency from the first signal Sc 1 . The first controller  16 A exchanges the related information of the first request RP (such as but not limited to the current power demand of the AC power source, the active power of the AC power source that needs to be compensation, or the frequency regulation demand) with the electric vehicle  3  through the second signal Sc 2 . After the information exchange of the first request RP between the first controller  16 A and the electric vehicle  3 , the first controller  16 A sets the operation mode to the standby mode to control the switch  20  to be turned off, thereby terminating any power transmission behavior. During the communication using the second signal Sc 2 , if the electric vehicle  3  determines that its own state and the state of its battery are not abnormal and the energy is sufficient to meet the first request RP, the electric vehicle  3  provides a first EV notification NB, which may instruct that the electric vehicle  3  allows to feed the stored electricity thereof to the AC power source  2 , to the first controller  16 A. 
     The first EV notification NB is provided to the first controller  16 A through the communication interface of the second connection port  1 B and the communication unit  14  so that the first controller  16 A determines that the electric vehicle  3  allows to feed the stored electricity thereof back to the AC power source  2 , and correspondingly set the operation mode to the feeding mode. Since the first controller  16 A communicates with the electric vehicle  3  using the PWM signal with frequency of 1 kHz in the charging mode, it&#39;s easier to implement signals with different frequencies from the first signal Sc 1  in the feeding mode. For example, in one embodiment of the present disclosure, the second signal Sc 2  with a higher frequency than the first signal Sc 1  is preferred. In order to be significantly distinguishable from the 1 kHz signal and easy to implement, the second signal Sc 2  is preferably a 10-kHz signal. On the contrary, after the electric vehicle  3  is physically coupled to second connection port  1 B, if the first controller  16 A does not receive the first request RP from the AC power source management system  2 A, it means that the feeding mode is not required. If the electric vehicle  3  has a charging demand and provides a ready-to-be-charged notification NA to the first controller  16 A, the first controller  16 A determines that the electric vehicle  3  is ready to receive energy, and sets the operation mode to the charging mode. 
     Please refer to  FIG. 3 , which shows a block diagram indicating how the operation modes of the charging apparatus are switched according to the present disclosure, and also refer to  FIG. 2 . In one embodiment, a standby mode SM is provided between a charging mode CM and a feeding mode BM. In the standby mode SM, the first controller  16 A controls the switch  20  to be turned off so that the power transmission path  12  is interrupted so as to prevent improper current flowing during the operation mode switching, which may cause damage to the charging apparatus  1 , the electric vehicle  3 , or the operator. For example, in the charging mode CM, the communication between the first controller  16 A and the electric vehicle  3  is performed with the first signal Sc 1 . If the second controller  16 B receives the first request RP from the AC power source management system  2 A, the second controller  16 B provides a first notification N 1  to the first controller  16 A. The first controller  16 A correspondingly stops using the first signal Sc 1  to communicate with the electric vehicle  3 , and instead changes to use the second signal Sc 2  to communicate with the electric vehicle  3  to exchange the related information of the first request RP with the electric vehicle  3 . After the information exchange of the first request RP between the first controller  16 A and the electric vehicle  3 , the first controller  16 A sets the operation mode to the standby mode SM and controls the switch  20  to be turned off so that the power transmission path  12  is interrupted (not conducting). When the first controller  16 A confirms that the power transmission path  12  is interrupted and the electric vehicle  3  provides the first EV notification NB (in the format of the second signal Sc 2 ) to the first controller  16 A, the first controller  16 A sets/changes the operation mode to the feeding mode BM to control the switch  20  to be turned on so that the feed power P 2  of the electric vehicle  3  is transmitted from the second connection port  1 B to the first connection port  1 A through the power transmission path  12  to be supplied to the AC power source  2 . 
     On the contrary, in the feeding mode BM, the communication between the first controller  16 A and the electric vehicle  3  is performed with the second signal Sc 2 . If the second controller  16 B receives the second request RS, such as a request to terminate the power feeding demand, from the AC power source management system  2 A (and then the second controller  16 B provides a second notification N 2  to the first controller  16 A), or if the first controller  16 A receives a second EV notification NS (in the format of the second signal Sc 2 ) from the electric vehicle  3  due to internal events of the electric vehicle  3  (such as but not limited to electric vehicle system failure, battery failure, or insufficient battery power), the first controller  16 A correspondingly stops using the second signal Sc 2  to communicate with the electric vehicle  3 , and sets the operation mode to the standby mode SM and controls the switch  20  to be turned off so that the power transmission path  12  is interrupted (not conducting). After the first controller  16 A confirms that the power transmission path  12  is interrupted, the first controller  16 A changes to use the first signal Sc 1  to communicate with the electric vehicle  3 . When the first controller  16 A confirms that the electric vehicle  3  provides the ready-to-be-charged notification NA (in the format of the first signal Sc 1 ) to the first controller  16 A, the first controller  16 A sets/changes the operation mode to the charging mode CM to control the switch  20  to be turned on so that the power P 1  of the AC power source  2  is transmitted from the first connection port  1 A to the second connection port  1 B through the power transmission path  12  to be supplied to the electric vehicle  3 . 
     Therefore, the communication between the first controller  16 A and the electric vehicle  3  is performed with different types of signals according to different requests from the AC power source management system  2 A, so that the first controller  16 A can automatically switch the operation mode between the feeding mode BM, the charging mode CM, or the standby mode SM, therefore solving the issue of the conventional technology in  FIG. 1  that it only provides single-direction charging. Accordingly, the charging apparatus of the present disclosure can achieve bidirectional power supply according to the power demand of the AC power source  2  or the electric vehicle  3 . 
     Please refer to  FIG. 2  again, the charging apparatus  1  further includes a detection circuit  18 . The detection circuit  18  is coupled to the power transmission path  12  and the first controller  16 A. The detection circuit  18  detects the AC power of the power transmission path  12  to generate a power information signal Sp. The first controller  16 A determines to control the switch  20  to be turned on or turned off so that the power transmission path  12  is conducting or not conducting according to the power information signal Sp. Specifically, the detection circuit  18  includes a plurality of detection units, such as a first voltage detection unit  182 , a current detection unit  184 , a frequency detection unit  186 , a residual current detection unit  188 , and a second voltage detection unit  190  for detecting power parameters of the power transmission path  12 . The detection units  182 - 190  are respectively coupled to the first controller  16 A. 
     The first voltage detection unit  182  detects a voltage of a first path between the first connection port  1 A and the switch  20 , and generates a first voltage signal Sv 1 . The second voltage detection unit  190  detects a voltage of a second path between the switch  20  and the second connection port  1 B, and generates a second voltage signal Sv 2 . When the switch  20  is not turned on, the first voltage signal Sv 1  is corresponding to a voltage at the AC power source side and the second voltage signal Sv 2  is corresponding to a voltage at the electric vehicle side. The current detection unit  184  detects a current of the power transmission path  12 , and generates a current signal Si. The frequency detection unit  186  detects an AC frequency of a voltage and that of a current of the power transmission path  12 , and generates a frequency signal Sf. The residual current detection unit  188  detects a residual current of the power transmission path  12 , and generates a residual current signal Sir. The power information signal Sp includes at least the first voltage signal Sv 1 , the second voltage signal Sv 2 , the current signal Si, the frequency signal Sf, and the residual current signal Sir. The first controller  16 A determines to turn on or turn off the switch  20  so that the power transmission path  12  is conducting or not conducting according to the above-mentioned signals. The first controller  16 A can determine whether an over voltage (OV) event, an under voltage (UV) event, an over current (OC) event, an over frequency (OF) event, or an under frequency (UF) event of the power transmission path  12  occurs according to the first voltage signal Sv 1 , the second voltage signal Sv 2 , the current signal Si, and the frequency signal Sf, and determine whether a current leakage event of the power transmission path  12  (between a ground end N) occurs according to the residual current signal Sir. If the above-mentioned abnormalities do not occur, the first controller  16 A controls the switch  20  to be turned on so that the power transmission path  12  is conducting. On the contrary, when any one of the abnormalities occurs, the first controller  16 A controls the switch  20  to be turned off so that the power transmission path  12  is not conducting. In particular, the switch  20  may be a switch component allowing bidirectional current flow when turned on, a switch with two transistors connected in series, or a relay. 
     Please refer to  FIG. 2  again, the charging apparatus  1  further includes an auxiliary power circuit  30 . The auxiliary power circuit  30  is coupled to internal loads inside the charging apparatus  1 , such as but not limited to the first controller  16 A, the communication unit  14 , the switch  20 , and other peripheral circuits or electronic components that require auxiliary power to operate. The auxiliary power circuit  30  includes a first conversion circuit  30 A and a second conversion circuit  30 B. The first conversion circuit  30 A and the second conversion circuit  30 B are suitable for a three-phase power system or a single-phase power system. In one embodiment, the first conversion circuit  30 A is coupled to power lines of two phases of the power transmission path  12 , and the coupling position thereof is preferably closer to the first connection port  1 A. The first conversion circuit  30 A may by a conventional AC-to-DC conversion circuit, for example but not limited to a flyback conversion circuit, a forward conversion circuit, and so on. The first conversion circuit  30 A converts the voltage of the power transmission path  12  into an auxiliary power voltage Vcc for the internal loads, and the auxiliary power voltage Vcc may be +15 volts, +12 volts, +5 volts, and/or +3 volts. The second conversion circuit  30 B is coupled to power lines of two phases of the power transmission path  12 , and the coupling position thereof is preferably closer to the second connection port  1 B. The second conversion circuit  30 B may by a conventional AC-to-DC conversion circuit for converting the voltage of the power transmission path  12  into the auxiliary power voltage Vcc for the internal loads. The output ends of the second conversion circuit  30 B are connected with the output ends of the first conversion circuit  30 A in parallel. 
     One feature of the charging apparatus  1  is that the auxiliary power voltage Vcc can be provided/supplied by the first conversion circuit  30 A and/or by the second conversion circuit  30 B in different operation modes. In the charging mode CM, since the switch  20  is turned on, the voltage of the power P 1  of AC power source  2  may be converted into the auxiliary power voltage Vcc by the first conversion circuit  30 A or the second conversion circuit  30 B so that the first controller  16 A can work and stably provide the control of charging mode CM for the charging apparatus  1 . Similarly, in the feeding mode BM, since the switch  20  is turned on, the voltage of the feed power P 2  may be converted into the auxiliary power voltage Vcc by the first conversion circuit  30 A or the second conversion circuit  30 B. However, in the standby mode SM, since the switch  20  is turned off, only the AC power source  2  or the electric vehicle  3  can provide power. Therefore, whether the power is provided by the AC power source  2  or the electric vehicle  3 , the auxiliary power circuit  30  can convert the power into the auxiliary power voltage Vcc. Assuming that if only the first conversion circuit  30 A exists in the charging apparatus  1 , in a situation that the first controller  16 A is operating in the charging mode CM but the AC power source  2  happens to fail, or a situation that the first controller  16 A is operating in the standby mode SM, which means the switch  20  is not turned on yet, but the AC power source  2  fails, the first conversion circuit  30 A will not be able to supply power to the first controller  16 A due to the loss of the AC power source  2 , so that the charging apparatus  1  will fail, and vice versa. Therefore, the second conversion circuit  30 B is additionally used to ensure that once one of the AC power source  2  and the electric vehicle  3  fails, the first controller  16 A can be successfully supplied the auxiliary power Vcc by the other power source. 
     Please refer to  FIG. 4A  and  FIG. 4B , which respectively show block diagrams of the controller operating in the charging mode and in the feeding mode according to the present disclosure, and also refer to  FIG. 2  to  FIG. 3 . In  FIG. 4A , after the electric vehicle  3  is physically coupled to the second connection port  1 B, the first controller  16 A communicates with the electric vehicle  3  through the communication unit  14  using the first signal Sc 1 . When the first controller  16 A receives the ready-to-be-charged notification NA provided by the electric vehicle  3  according to the results of the handshaking communication, the first controller  16 A operates in the charging mode CM. Afterward, the first controller  16 A controls the switch  20  of the charging apparatus  1  to be turned on so that the power P 1  provided by the AC power source  2  is transmitted in the direction T 1  to the electric vehicle  3  through the first connection port  1 A, the switch  20 , and the second connection port  1 B. 
     In  FIG. 4B , after the electric vehicle  3  is physically coupled to the second connection port  1 B, the first controller  16 A communicates with the electric vehicle  3  through the communication unit  14  using the first signal Sc 1 . The second controller  16 B is coupled to the AC power source management system  2 A, and acquires the related information of the AC power source  2 , such as but not limited to voltage, current, frequency, and power demand, from the AC power source management system  2 A. When the second controller  16 B receives the first request RP provided by the AC power source management system  2 A, and provides the first notification N 1  to the first controller  16 A according to the first request RP, the first controller  16 A correspondingly stops using the first signal Sc 1  to communicate with the electric vehicle  3 , and instead changes to use the second signal Sc 2  to communicate with the electric vehicle  3  so as to exchange the related information of the first request RP with the electric vehicle  3 . After the information exchange of the first request RP between the first controller  16 A and the electric vehicle  3 , the first controller  16 A sets the operation mode to the standby mode SM to control the switch  20  to be turned off so that the power transmission path  12  is not conducting. If the first controller  16 A receives the first EV notification NB provided by the electric vehicle  3  through the communication unit  14 , the first controller  16 A sets/changes the operation mode to the feeding mode BM. In particular, the first EV notification NB and the second EV notification NS are used in the format of the second signal Sc 2 . Afterward, the first controller  16 A determines the optimal timing of turning on the switch  20  according to the current AC power source information provided by the second controller  16 B. Alternatively, the first controller  16 A provides the current AC power source information to the electric vehicle  3 , and the electric vehicle  3  determines the voltage and phase of the feed power P 2  according to the AC power source information. After the electric vehicle  3  outputs the feed power P 2  and notifies the first controller  16 A, the first controller  16 A controls the switch  20  to be turned on so that the feed power P 2  provided by the electric vehicle  3  is transmitted in the direction T 2  to the AC power source  2  through the second connection port  1 B, the switch  20 , and the first connection port  1 A. If the first signal Sc 1  and the second signal Sc 2  are different types of signals, different signal transmission lines can be used to respectively transmit these two signals, as shown in  FIG. 4B . If the first signal Sc 1  and the second signal Sc 2  are the same type of signals, for example both are PWM signals with difference only in frequency, the same signal transmission line can be used to transmit the two signals. In particular, the use of the transmission line(s) may be adjusted according to actual needs. 
     Please refer to  FIG. 5A , which shows a flowchart of an exemplary method of setting operation modes of the charging apparatus according to the present disclosure, and also refer to  FIG. 2  to  FIG. 4B . The method of operating the charging apparatus  1  includes the following steps. First, a second controller receives a first request (S 100 ). The second controller  16 B is connected to an AC power source management system  2 A and a first controller  16 A. The second controller  16 B communicates with the AC power source management system  2 A to acquire the related information of the AC power source  2 , such as but not limited to the status and the power demand of the AC power source  2 . Afterward, when the second controller receives the first request, for example a power demand request, provided by the AC power source management system, the second controller notifies the first controller so that the first controller correspondingly changes to use a second signal to communicate with the electric vehicle through a communication unit, and controls the power transmission path to be not conducting (S 120 ). When the AC power source management system  2 A provides the first request RP to the second controller  16 B according to the demand of current supply and demand balance of the AC power source  2 , the second controller  16 B provides a first notification to the first controller  16 A according to the first request RP. After the first controller  16 A receives the first notification, the first controller  16 A changes to use a second signal Sc 2  different from a first signal Sc 1 , such as but not limited to a signal with different pulse, package, and/or frequency from the first signal Sc 1 , to communicate with electric vehicle  3 . After the information exchange of the first request RP between the first controller  16 A and the electric vehicle  3 , the first controller  16 A controls the switch  20  of the power transmission path  12  to be turned off so that the power transmission path  12  is not conducting. 
     Afterward, when first controller receives a first EV notification provided by the electric vehicle, the first controller controls the power transmission path to be conducting (S 140 ). During the communication between the first controller  16 A and the electric vehicle  3  using the second signal Sc 2 , if the electric vehicle  3  determines that its own state and the state of its battery are not abnormal and the energy stored in its battery is sufficient to meet the first request, the electric vehicle  3  provides a first EV notification NB to the first controller  16 A to instruct that the electric vehicle  3  allows to feed the stored electricity thereof to the AC power source  2 . The first EV notification NB is provided to the first controller  16 A through a communication interface of the second connection port  1 B and the communication unit  14  so that the first controller  16 A determines that the electric vehicle  3  allows to feed the stored electricity thereof back to the AC power source  2 , and the operation mode is set to a feeding mode. In the feeding mode, the switch  20  of the power transmission path  12  is turned on so that the power transmission path  20  is conducting to provide a path to transmit power from the electric vehicle  3  back to the AC power source  2 . 
     Afterward, in the feeding mode, when the second controller receives a second request provided by the AC power source management system, the second controller notifies the first controller so that the first controller correspondingly changes to use the first signal to communicate with the electric vehicle through the communication unit, and the first controller controls the power transmission path to be not conducting (S 160 ). Alternatively, in the feeding mode, when the first controller receives a second EV notification provided by the electric vehicle, the first controller correspondingly changes to use the first signal to communicate with the electric vehicle through the communication unit, and the first controller controls the power transmission path to be not conducting (S 180 ). In the step (S 140 ), in the feeding mode BM, the communication between the first controller  16 A and the electric vehicle  3  is performed with the second signal Sc 2 . If the second controller  16 B receives the second request RS, such as a demand termination request, provided by the AC power source management system  2 A, or the first controller  16 A receives the second EV notification NS provided by the electric vehicle  3  instructing that the electric vehicle  3  wants to stop feeding power, the first controller  16 A changes from using the second signal Sc 2  to the first signal Sc 1  to communicate with the electric vehicle  3  and enters the standby mode SM, and controls the switch  20  of the power transmission path  12  to be turned off so that the power transmission path  12  is not conducting. 
     Finally, in the standby mode, when the first controller receives a allow charging notification provided from the electric vehicle, the first controller operates in a charging mode that the power of the AC power source is transmitted to the electric vehicle through the power transmission path (S 200 ). After the step (S 160 ) and the step (S 180 ), when the first controller  16 A enters the standby mode and confirms that the power transmission path  12  is not conducting, the first controller  16 A continuously communicates with the electric vehicle  3  through the first signal Sc 1 . After the electric vehicle  3  provides the ready-to-be-charged notification NA, the first controller  16 A sets/changes the operation mode to the charging mode CM to control the switch  20  to be turned on so that the power P 1  of the AC power source  2  is transmitted from the first connection port  1 A to the second connection port  1 B through the power transmission path  12  to be supplied to the electric vehicle  3 . 
     Please refer to  FIG. 5B , which shows a flowchart of an exemplary method of providing a protection mechanism of the charging apparatus according to the present disclosure, and also refer to  FIG. 2  to  FIG. 5A . In the step (S 100 ) to the step (S 200 ), a protection mechanism of the charging apparatus  1  is provided. The method of providing the protection mechanism includes the following steps. First, the power of the power transmission path is detected for generating a power information signal (S 300 ). A detection circuit  18  includes a plurality of detection units, such as a first voltage detection unit  182 , a current detection unit  184 , a frequency detection unit  186 , a residual current detection unit  188 , and a second voltage detection unit  190  for detecting power parameters of the power transmission path  12 . The detection circuit  18  detects the power parameters of the power transmission path  12  to generate a power information signal Sp. The power information signal Sp includes at least the first voltage signal Sv 1 , the second voltage signal Sv 2 , the current signal Si, the frequency signal Sf, and the residual current signal Sir. Afterward, the first controller controls the power transmission path to be conducting or not conducting according to the power information signal (S 320 ). The first controller  16 A can determine whether an overvoltage (OV) event, an under voltage (UV) event, an over current (OC) event, an over frequency (OF) event, or an under frequency (UF) event of the power transmission path  12  occurs according to the first voltage signal Sv 1 , the second voltage signal Sv 2 , the current signal Si, and the frequency signal Sf, and determine whether a current leakage event of the power transmission path  12  (between a ground end N) occurs according to the residual current signal Sir. If the above-mentioned abnormalities do not occur, the first controller  16 A controls the switch  20  to be turned on so that the power transmission path  12  is conducting. On the contrary, if any one of the abnormalities occurs, the first controller  16 A controls the switch  20  to be turned off so that the power transmission path  12  is not conducting. 
     Although the present disclosure has been described with reference to the preferred embodiment thereof, it will be understood that the present disclosure is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the present disclosure as defined in the appended claims.