Description:FIELD OF THE INVENTION

[0001] The disclosure relates to an electric power supply device, and more particularly, an electric power supply device having a plurality of Switch Mode Rectifiers (SMRs) in series and parallel connection for charging an electric vehicle and a method of operation thereof.

BACKGROUND

[0002] Electric Vehicles (EVs) and Plug-In Hybrid Vehicles (PHEVs) are a category of vehicles that use electric energy to power the vehicle. Such vehicles have a battery bank that powers a prime mover of the EV or PHEV which is also charged using an electric charger. The electric charger can either be an onboard charger, i.e., a charger built into the vehicle, or an offboard charger, i.e., a charger outside the vehicle. The offboard chargers are generally installed in plural to form a charging station to provide a charging facility for multiple EVs, and PHEVs simultaneously.

[0003] One of the key limitations of the current charging station/ charger is that the current charging station/ charger is designed to output electricity as per the configuration of an EV and PHEV of a particular manufacturer. For instance, a charging unit adapted to charge an EV and PHEV from a particular manufacturer is not capable of charging another EV or PHEV from a different manufacturer. As a result, current charging stations/chargers are not capable of providing charging facilities for different kinds of EVs and PHEVs. One of the solutions to mitigate this issue is to install chargers of different throughput to cater to different kinds of EVs and PHEVs. However, such an arrangement is only effective as long as all the chargers are operational.

SUMMARY

[0004] This summary is provided to introduce a selection of concepts, in a simplified format, which is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.

[0005] The present disclosure relates to an electric power supply device that can provide direct current (DC) electric power at different DC voltage and DC current.

[0006] In an embodiment, the electric power supply device is disclosed that includes a plurality of Switch Mode Rectifiers (SMRs), each configured to receive an Alternating Current (AC) supply and output Direct Current (DC) power. The electric power supply device also includes a first connection port having a positive output terminal and a negative output terminal configured to connect to an electric load to provide output DC power of a predefined voltage and current thereto. In addition, the electric power supply device includes a plurality of switches configured to selectively establish an electric connection between at least one SMR of the plurality of SMRs and the first connection port in one of a series connection and/or a parallel connection. Further, the electric power supply device includes a control unit operably coupled to the plurality of SMRs and the plurality of switches. The control unit is configured to receive at least one parameter associated with an operation of the plurality of SMRs, and selectively operate the plurality of switches to configure the plurality of SMRs in a predefined mode to establish an electric connection between at least one SMR and the first connection port to produce the output DC power of the predefined voltage and current based on the received parameter.

[0007] In another embodiment, a method of operating an electric power supply device comprising a plurality of Switch Mode Rectifiers (SMRs) and a plurality of switches is disclosed. The method also includes receiving, by a control unit, a plurality of parameters associated with a user input and the plurality of SMRs. The method also includes determining a predefined voltage and a predefined current based on the user input. Further, the method includes selectively operating the plurality of switches to configure the plurality of SMRs in a predefined mode to establish an electric connection between at least one SMR and the first connection port to produce the output DC power of the predefined voltage and current based on the received plurality of parameters. Furthermore, the method includes monitoring, in real-time, the plurality of parameters of an SMR of the plurality of SMRs to determine a deviation between an operating condition of the SMR and an optimum condition thereof. Finally, the method includes operating the remaining SMRs of the plurality of SMRs to change one of the predefined modes and respective operating conditions to compensate for the deviation to maintain the predefined voltage and current.

[0008] According to the present disclosure, the control unit operates the switches to electrically connect the SMR’s output in either series or parallel connections to achieve the predefined power output. Further, the control unit monitors the health of each SMR in real-time and changes the predefined mode on the fly to maintain the predefined electric output. Such a capability not only ensures that the power supply device provides electric supply at different predefined voltages and currents but also ensures the longevity of the SMRs.

[0009] To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[00010] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[00011] Figure 1 illustrates a schematic of an electric power supply device having a pair of SMRs and a first connection port, according to an embodiment of the disclosure;
[00012] Figure 2 illustrates a schematic of an electric power supply device having a pair of SMRs, a first connection port and a second connection port, according to an embodiment of the disclosure;
[00013] Figure 3 illustrates a schematic of an electric power supply device having three SMRs and first/second connection ports, according to an embodiment of the disclosure;
[00014] Figure 4 illustrates an arrangement of the pair of SMRs in a parallel connection in a constant voltage mode, according to an embodiment of the disclosure;
[00015] Figure 5 illustrates an arrangement of the pair of SMRs in a series connection in the constant voltage mode, according to an embodiment of the disclosure;
[00016] Figure 6 illustrates an arrangement of the pair of SMRs in a parallel connection in a constant current mode, according to an embodiment of the disclosure;
[00017] Figure 7 illustrates an arrangement of the pair of SMRs in a series connection in the constant current mode, according to an embodiment of the disclosure;
[00018] Figure 8 illustrates a matrix indicating possible series and parallel connections of SMRs when the output voltage or output current is within a rated voltage and current of individual SMRs, according to an embodiment of the disclosure;
[00019] Figure 9 illustrates a matrix indicating possible series and parallel connections of SMRs when the output current is greater than a current of individual SMRs, according to an embodiment of the disclosure;
[00020] Figure 10 illustrates Table 1 which shows the states of four switches to enable the configuration of predefined modes in the electric power supply device shown in Figure 1, according to an embodiment of the disclosure;
[00021] Figure 11 illustrates Table 2 which shows the states of five switches to enable the configuration of predefined modes in the electric power supply device shown in Figure 2, according to an embodiment of the disclosure;
[00022] Figure 12 illustrates Table 3 which shows the states of six switches to enable the configuration of predefined modes in the electric power supply device shown in Figure 3, according to an embodiment of the disclosure;
[00023] Figure 13 illustrates a method of operating an electric power supply device having a plurality of switch mode rectifiers (SMRs) and a plurality of switches, according to an embodiment of the disclosure; and
[00024] Figure 14A-E illustrates a method of active load balancing technique of method in Figure 13, according to an embodiment of the disclosure.

[00025] Further, skilled artisans will appreciate those elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

DETAILED DESCRIPTION OF FIGURES

[00026] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

[00027] For example, the term “some” as used herein may be understood as “none” or “one” or “more than one” or “all.” Therefore, the terms “none,” “one,” “more than one,” “more than one, but not all” or “all” would fall under the definition of “some.” It should be appreciated by a person skilled in the art that the terminology and structure employed herein is for describing, teaching, and illuminating some embodiments and their specific features and elements and therefore, should not be construed to limit, restrict, or reduce the spirit and scope of the present disclosure in any way.

[00028] For example, any terms used herein such as, “includes,” “comprises,” “has,” “consists,” and similar grammatical variants do not specify an exact limitation or restriction, and certainly do not exclude the possible addition of one or more features or elements, unless otherwise stated. Further, such terms must not be taken to exclude the possible removal of one or more of the listed features and elements, unless otherwise stated, for example, by using the limiting language including, but not limited to, “must comprise” or “needs to include.”

[00029] Whether or not a certain feature or element was limited to being used only once, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do not preclude there being none of that feature or element, unless otherwise specified by limiting language including, but not limited to, “there needs to be one or more...” or “one or more element is required.”

[00030] Unless otherwise defined, all terms and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by a person ordinarily skilled in the art.

[00031] Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements of the present disclosure. Some embodiments have been described for the purpose of explaining one or more of the potential ways in which the specific features and/or elements of the proposed disclosure fulfil the requirements of uniqueness, utility, and non-obviousness.

[00032] Use of the phrases and/or terms including, but not limited to, “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or other variants thereof do not necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or in the context of more than one embodiment, or in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

[00033] Any particular and all details set forth herein are used in the context of some embodiments and therefore should not necessarily be taken as limiting factors to the proposed disclosure.

[00034] Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[00035] Figure 1 illustrates a schematic of an electric power supply device (100) having a pair of Switch Mode Rectifiers (SMRs) (102, 104) and a first connection port 122, according to an embodiment of the present disclosure. The electric power supply device (100) may be used to provide electrical energy to an electric load. In one embodiment, the electric power supply device (100) may be referred to as an electric vehicle supply equipment (EVSE) (100) that supplies power to the electric load, such as a battery pack of the EV. The electric power supply device (100) is designed to provide direct current (DC) electric output at a range of voltage and current values. As a result, the electric power supply device (100) is capable of providing electric power to EVs with different configurations. For instance, the electric power supply device (100) can supply electric power at voltage values in a range of 30 Volts (V) to 110V and current values in a range of 0 Ampere (A) to 100A. In addition, the electric power supply device (100) is configured to operate in safe conditions in real-time.

[00036] The electric power supply device (100) may also include, but is not limited to, the pair of SMRs including a first SMR (102) and a second SMR (104), a plurality of switches including a first switch (106), a second switch (108), a third switch (110), and a fourth switch (112). In addition, the electric power supply device (100) also includes a control unit (114), a pair of sense and protection circuits (116, 118), a Switch Mode Power Supply (SMPS) 120, and a first connection port (122).

[00037] The first SMR (102) and the second SMR (104) are configured to receive an Alternating Current (AC) supply (124) and output DC power. The AC supply (124) may be a single-phase or a three-phase power supply that is supplied to both the first SMR (102) and the second SMR 104. The first SMR (102) and the second SMR (104) are configured to provide DC power at an output voltage and output current that can be varied. Further, each of the first SMR (102) and the second SMR (104) supplies the output DC power at a predefined voltage when connected in pre-defined configurations such as a single current mode, a Constant Current (CC) mode, a Constant Voltage (CV mode) which are detailed in the following paragraphs the specification. In one embodiment, the first SMR (102) and the second SMR (104) individually output DC electric power based on a requirement at the first connection port (122), wherein the first connection port (122) is adapted to allow a charger to electrically couple thereto extract DC electric power from the first connection port (122).

[00038] Although not shown, each SMR (102) and (104) may include various sensors that can sense the operating condition of the SMR (102) and (104). For instance, each SMR (102) and (104) may include a voltage sensor that senses the output voltage, a current sensor that senses the output current, and a temperature sensor that senses the operating temperature of the SMR (102) and (104). The sensor data may be used to configure the SMR (102) and (104) to provide the output voltage and current and also to monitor, in real-time, the output voltage and current. Real-time monitoring may be used to change the output voltage and current based on the operating condition.

[00039] In one embodiment, the first sense and protection unit (116) disposed between the first SMR (102) and the first switch 106, the fourth switch (112) and is adapted to protect the first SMR (102) from either reverse polarity power or short circuit. Similarly, the second sense and protection unit (118) is disposed between the second SMR (104) and the second switch (108) and is adapted to protect the second SMR (104) from reverse polarity and/or short circuit. Both the sense and protection units (116) and (118) may, in one embodiment, be circuit breakers or the like to protect the SMRs (102) and (104).

[00040] In one embodiment, the plurality of switches (106, 108, 110, and 112) are connected in a pre-defined manner for establishing an electric connection between at least one of the plurality of SMRs (102) and (104) and the first connection port (122) in a series connection and/or a parallel connection. The switches (106, 108, 110, and 112) may include the first switch (106), the second switch (108), the third switch (110), and the fourth switch (112). In one embodiment, the first switch (106) may have a first terminal (106A) connected to a positive terminal (102A) of the first SMR (102) and a second terminal (106B) is connected to the positive output terminal 122A of the first connection port (122).

[00041] Further, the second switch (108) has a first terminal 108A connected to a positive terminal (104A) of the second SMR (104) via the first sense and protection circuit (116) and a second terminal (108B) connected to a negative terminal 102B of the first SMR (102) and the first sense and protection circuit 116.

[00042] Similarly, the third switch (110) has a first terminal 110A connected to the positive terminal (104A) of the second SMR (104) via the second sense and protection circuit (118) and a second terminal 110B connected to the positive output terminal (122A) of the first connection port (122). Further, the negative terminal (104B) of the second SMR (104) is connected to the negative terminal of the first connection port (122) via the second sense and protection circuit (118).

[00043] The fourth switch (112) has a first terminal 112A connected to a negative terminal (102B) of the first SMR (102) via the first sense and protection circuit (116) and a second terminal (112B) connected to the negative output terminal 122B of the first connection port (122).

[00044] In one embodiment, the control unit (114) is operably coupled to the plurality of SMRs and the plurality of switches. In an alternate embodiment, the control unit (114) may be connected to the SMRs and the switches via a Controller Area Network (CAN) interface (126). The control unit (114), in yet another embodiment, may be powered by the SMPS (120) and may also receive AC supply (124).

[00045] In operation, the control unit (114) may be configured to perform various tasks including, but not limited to receiving one or more parameters associated with an operation of the plurality of SMRs selectively operating the plurality of switches (106, 108, 110, and 112), to configure the plurality of SMRs (102) and (104) in a predefined mode to establish an electric connection between at least one SMR and the first connection port to produce the output DC power of the predefined voltage and current based on the received parameter. In addition, the control unit (114) may monitor, in real-time, the plurality of parameters of an SMR of the plurality of SMRs to determine a deviation between an operating condition of the SMR and an optimum condition thereof. Finally, the control unit (114) may operate the remaining SMRs of the plurality of SMRs (102) and (104) to change one of the predefined modes and respective operating conditions to compensate for the deviation to maintain the predefined voltage and current.

[00046] According to the present disclosure, the electric power supply device (100) may also include more than one connection port. An exemplary embodiment having an additional connection port is shown in Figure 2. Specifically, Figure 2 illustrates a schematic of an electric power supply device (200) having a pair of SMRs a first connection port (122) and a second connection port (202). In this illustration, most components of the electric power supply device (200) are the same as the electric power supply device (100) and hence are not repeated for the sake of brevity. The electric power supply device (200) may include the second connection port (202) that provides electric power.

[00047] Like the first connection port (122), the second connection port (202) has a positive output terminal and a negative output terminal adapted to connect to an additional electric load to provide DC power of the predefined voltage and current thereto. The electric power supply device (200), in order to connect the second connection port (202) to the SMRs, may also include a fifth switch (204) that has a first terminal (204A) connected to the positive terminal (104A) of the second SMR (104) and a second terminal (204B) connected to the positive terminal (202A) of the second connection port 202. Further, the negative terminal 104B of the second SMR (104) is connected to the negative terminal (202B) of the second connection port (202) via the second sense and protection circuit (118). In operation, the control unit (114) may additionally operate the fifth switch (204) to supply electric power to the second connection port (202).

[00048] There may also be a scenario where more than two SMRs are used to provide electric power to multiple connection ports. An exemplary embodiment of such a configuration is explained with respect to Figure 3. Specifically, Figure 3 illustrates a schematic of an electric power supply device (300) having three SMRs and first/second connection ports. Just like in the previous embodiment, the electric power supply device (300) has most of the components are same as in the electric power supply devices (100) and (200) and therefore not repeated for the sake of brevity. In this illustration, the electric power supply device (300) may include a third SMR (302), a sixth switch (304), and a third sense and protection unit (306). The third sense and protection unit (306) may be installed between the third SMR (302) and the sixth SMR (304). Further, the sixth SMR (304) may have a first terminal (304A) connected to a positive terminal (302A) of the third SMR (302) and a second terminal (304B) connected to the positive terminal of the second connection port (202). Further, the negative terminals (104B) and (302B) of each of the second SMR (104) and the third SMR (302) are connected to the negative terminal of the second connection port 202. In this embodiment as well, the control unit (114) may additionally operate the sixth switch (304) and the third SMR (302).

[00049] From the afore-mentioned description pertaining to the control unit (114), it is apparent that the control unit (114) operates the pre-defined switches which enable the operation of the SMRs in a plurality of modes such as the constant current (CC) mode, and constant voltage (CV) mode which are single output modes. In the single output mode, either the first SMR (102) or the second SMR (104) is connected to the first connection port (122), such that their respective output voltage and current are equal to the predefined voltage and current. Similarly, in the single output mode, the third SMR (302) is connected to the second connection port (202). Further, the CC mode and the CV mode are configured by setting voltage and current parameter of particular SMR (102, 104, 302) and either series or parallel connections are configured by operating the switches to connect the SMR in either a series connection or a parallel connection. Exemplary embodiments of each mode (i.e., CC mode and CV mode) in series and parallel connections are explained in Figures 4 to 7.

[00050] Referring now to Figure 4 which illustrates an arrangement (400) of the pair of SMRs in a parallel connection in the CV mode output, according to an embodiment of the present disclosure. In this illustration, one of the SMRs, for example, the second SMR (104) is configured in constant voltage mode, i.e., the second SMR (104) has a fixed and constant output voltage equal to the predefined voltage whereas the first SMR (102) is configured in constant current mode, i.e., the first SMR (102) has a fixed and constant output current. Thereafter, the control unit (114) may operate the switch in such a way that the positive terminal (104A) of the second SMR (104) is parallelly connected to the positive terminal 102A of the first SMR (102) and both the positive terminals (102A) and (104A) are connected to the positive output terminal (122A) of the first connection port (122). Similarly, the negative terminal (104B) of the second SMR (104) is parallelly connected to the negative terminal (102B) of the first SMR (102), and both the negative terminals 102B and 104B are connected to the negative output terminal (122B) of the first connection port (122). As a result, the predefined current becomes an aggregate of the output current of the first SMR (102) and the second SMR (104).

[00051] For example, the EV requests a predefined voltage and current of 50V 70A respectively in CV mode. In one embodiment, each SMR can deliver 58V at 55A. Further, the control unit (114) may configure the second SMR (104) in CV mode to match the requested predefined voltage 50V. The first SMR (102) in CC mode clamps its output voltage to the same 50V. Thereafter, the control unit (114) sets the first SMR’s output current as half or any portion of the requested predefined current. The remaining current is supplied by the second SMR (104) in CV mode. In one embodiment, any SMR (102) and (104) may be configured in CC mode or CV mode and in case of more than two SMRs, such as shown in Figure 3, at least one SMR needs to be configured in CV mode.

[00052] Referring now to Figure 5 that illustrates an arrangement (500) of the pair of SMRs in a series connection in the CV mode output, according to an embodiment of the disclosure. In this illustration, the control unit (114) configures both SMRs in CV mode. In addition, the control unit (114) operates the switches in such a way that the positive terminal (104A) is connected to the negative terminal (102B) of the first SMR (102). Further, the negative terminal (104B) of the second SMR (104) is connected to the negative output terminal (122B) of the first connection port (122) and the positive terminal (102A) of the first SMR (102) is connected to the positive output terminal (122A) of the first connection port (122). As a result, the predefined current is equal to the output current of the first SMR (102) and the second SMR (104).

[00053] For example, the EV requests a predefined voltage and current of 80V at 50A respectively in CV mode. In one embodiment, each SMR delivers 58V at 55A. The control unit (114) may split the voltage between the first SMR (102) and the second SMR (104) in any portion of the requested voltage so that the first SMR (102) and the second SMR (104) are able to deliver 80V at 50A as single CV output.

[00054] Referring to Figure 6 that illustrates an arrangement (600) of the pair of SMR in a parallel connection in the CC mode output, according to an embodiment of the disclosure. In this illustration, the control unit (114) configures both, the first SMR (102) and the second SMR (104) in CC mode. In addition, the control unit (114) may operate the switches (102) and (104) in such a way that the positive terminal (104A) of the second SMR (104) is parallelly connected to the positive terminal (102A) of the first SMR (102) and both the positive terminals (102A) and (104A) are connected to the positive output terminal (122A) of the first connection port (122). Similarly, the negative terminal (104B) of the second SMR (104) is parallelly connected to the negative terminal (102B) of the first SMR (102) and both the negative terminals (102B) and (104B) are connected to the negative output terminal (122B) of the first connection port (122). As a result, the predefined current is an aggregate of the output current of the first SMR (102) and the second SMR (104) and the predefined voltage is equal to the output voltages of the first SMR (102) and the second SMR (104).

[00055] For example, the EV requests a predefined voltage and current of 50V 70A respectively in CC mode output. In one embodiment, each SMR can deliver 58V at 55A. Further, the control unit (114) may configure both the first SMR (102) and the second SMR (104) in CC mode. Thereafter, the control unit (114) may split the current between the first SMR (102) and the second SMR (104). The output voltage for each of the first SMR (102) and the second SMR (104) is equal to the requested predefined voltage.

[00056] Referring now to Figure 7 which illustrates an arrangement (700) of the pair of SMR in a series connection in the CC mode output, according to an embodiment of the disclosure. In this illustration, one of the SMRs, for example, the second SMR (104) is configured in CV mode whereas the first SMR (102) is configured in CC mode. Thereafter, the control unit (114) operates the switches (106, 108, 110, 112) in such a way that the positive terminal (104A) is connected to the negative terminal (102B) of the first SMR (102). Further, the negative terminal (104B) of the second SMR (104) is connected to the negative output terminal (122B) of the first connection port (122) and the positive terminal (102A) of the first SMR (102) is connected to the positive output terminal (122A) of the first connection port 122. As a result, the predefined voltage is equal to an aggregate of the output voltage of the first SMR (102) and the second SMR (104) and the predefined current is equal to the output current of each of the first SMR (102) and the second SMR (104).

[00057] For example, the EV requests a predefined voltage and current of 80V 50A respectively in CC mode output and each SMR can deliver 58V at 55A. Further, the control unit (114) may configure the second SMR (104) in CV mode to the output voltage at 50V. The first SMR (102) in CC mode is configured to output voltage remaining voltage, i.e., 30V from the requested voltage, and the first SMR (102) is configured for the maximum current 55A.

[00058] The aforementioned modes are summarized in Figure 8 which illustrates a matrix (800) indicating possible series and parallel connections of SMRs (102, 104, 302) when the output voltage or output current is within a rated voltage and current of individual SMRs (102, 104, 302), according to an embodiment of the disclosure. The matrix (800) may include a horizontal axis that indicates possible configurations to achieve CC or CV mode in series connection whereas a vertical axis indicates possible configurations to achieve CC or CV mode in parallel connection. In order to achieve CC mode output in series connection, one SMR represented by a block (802) is configured in the CC mode and rest of SMRs represented by the blocks (804) are configured in CV mode. Furthermore, in order to achieve CV mode output in series connection, all the SMRs represented by blocks (802) and (804) are configured in CV mode.

[00059] On the other hand, in order to achieve CC mode output in parallel connection, all the SMRs represented by blocks (802) and (806) are configured in CC mode and in order to achieve CV mode output in parallel connection, the SMR represented by the block (802) is configured in CV mode and remaining SMRs represented by the blocks (806) are configured in CC mode.

[00060] Figure 9 illustrates a matrix (900) indicating possible series and parallel connections of SMRs (102, 104, 302) when the output voltage and current is greater than a current of individual SMRs (102, 104, 302), according to an embodiment of the disclosure. In such a scenario, multiple SMRs (102, 104, 302) are connected in series/parallel connections to forms modules (902) and (904) and the modules (902) and (904) are then connected in series or parallel connection to provide the output voltage and current. The horizontal and vertical axes of the matrix (900) are identical to the matrix (800) in Figure 8 and hence are not repeated here.

[00061] In order to achieve CC mode output in series connection, each of the modules (902) and (904) are configured in such a way that the SMR (102, 104, 302) represented by a block (906) is set in CC mode and remaining SMR (102, 104, 302) represented by blocks (908) are configured in CV mode to achieve the high output voltage. Thereafter, both the modules (902) and (904) are connected in parallel connection to achieve the high output current.

[00062] As mentioned before, the control unit (114) operates the switches to configure the SMRs (102, 104, and 302) in the aforementioned modes. The control unit (114), in one embodiment, may toggle the switches ON/OFF to achieve the series or parallel connections for each of the CV and CC modes. An exemplary state of switches is explained with respect to the following tables.

[00063] Figure 10 illustrates Table 1 which shows the states of four switches (106, 108, 110, and 112) to form predefined modes in the electric power supply device 100, according to an embodiment of the disclosure. In the illustrated table, the switches (106, 108, 110, and 112) are operated by the control unit (144) in the OFF/ON state. In order to form a series connection, the first switch (106) and second switch (108) are switched ON while the fourth switch (112) and the third switch (110) are switched OFF. On the other hand, in order to form a parallel connection, the first switch (106), the fourth switch (112), and the third switch (110) are switched ON and the second switch (108) is switched OFF. Further, to connect the first SMR (102) to the first connection port (122), the first switch (106) and the fourth switch (112) are switched ON while the second switch (108) and the third switch (110) are switched OFF. Furthermore, to connect the second SMR (104) to the first connection port 122, the first switch 106, the second switch (108), and the fourth switch (112) is switched OFF and the third switch (110) is switched ON.

[00064] Referring now to Figure 11 illustrates Table 2 which shows the states of five switches (106, 108, 110, 112, and 204) to form the predefined modes in the electric power supply device 200 shown in Figure 2. In the first column of Table 2, the configuration ‘Series H1, H2 OFF’ indicates a series electric connection between the first SMR (102), and the second SMR with the first connection port (122). Further, in this configuration, the first switch (106) and the second switch (108) are switched ON and the rest of the switches, namely the third switch 110, the fourth switch 112, and the fifth switch (204) are switched OFF. Further, the configuration ‘H1 ON, H2 OFF’ indicates that the first SMR (102) and the second SMR (104) are parallelly connected to the first connection port 122. Specifically, in this configuration, the first switch (106) and the fourth switch (112) are switched ON whereas the second switch 108, the third switch 110, and the fifth switch (204) are switched OFF. On the other hand, the configuration ‘H2 ON, H1 OFF’ indicates that the second SMR (104) alone is connected to the first connection port (122). In this configuration, the first switch (106), the second switch (108), the fourth switch (112), and the fifth switch (204) are switched OFF whereas the second switch (108) is switched ON.

[00065] Furthermore, the configuration ‘H1 ON, H2 ON’ indicates that the second SMR (104) is in CV mode and is connected with the first SMR (102) to connect parallelly to the first connection port (122). Specifically, in this configuration, the first switch (106), the third switch (110), and the fourth switch (112) are switched ON whereas the second switch (108), and the fifth switch (204) are switched OFF. Finally, the configuration ‘Parallel H1, H2 OFF’ indicates that the first SMR (102) is connected to the first connection port (122) and the second SMR (104) is connected to the second connection port (202). In this configuration, the first switch (106) and the fourth switch (112) are switched ON to connect the first SMR (102) to the first connection port (122). Similarly, the fifth switch (204) is switched on to connect the second SMR (104) to the second connection port (202) whereas the second switch (108), and the third switch (110) are switched OFF to disconnect the second SMR (104) from the first SMR (102) and the first connection port (122).

[00066] Figure 12 illustrates Table 3 which shows the states of six switches (106, 108, 110, 112, 204, and 304), to form predefined modes in the electric power supply device (300). In Table 3, the first five configurations, namely ‘Series H1, H2 OFF’, ‘H1 ON, H2 OFF’, ‘H2 ON, H1 OFF’, ‘H1 ON, H2 ON’, and ‘Parallel H1, H2 OFF’ are the same as mentioned in Table 2 including the state of switches (106, 108, 110, 112, and 204) and hence are not repeated for brevity. Further, in each of the aforementioned configurations, the sixth switch 302 is switched OFF.

[00067] Additional functions in Table 3 include a function ‘Parallel H2, H1 OFF’ which indicates that the first SMR (102) is disconnected from the first connection port (122) and the second SMR (102) is connected to the first connection port (122). Further, the third SMR (302) is connected to the second connection port (202). Specifically, in this configuration, the first switch (106), the second switch (108), the fourth switch (112), and the fifth switch (204) are switched OFF whereas the third switch (108) and the sixth switch (304) are switched ON.

[00068] Further, a configuration ‘Parallel H1, H2 ON’ indicates that the first SMR (102) is connected to the first connection port (122) and the second SMR (106) along with the third SMR (302) are connected parallelly to the second connection port 202. Specifically, in this configuration, the first switch 106, the fourth switch 112, the fifth switch 204, and the sixth switch (304) are switched ON whereas the second switch 108, and the third switch (110) are switched OFF. The next configuration ‘Parallel H2, H1 ON’ indicates that the first SMR (102) along with the second SMR (104) are parallelly connected to the first connection port 122, and the second SMR (104) along with the third SMR (302) is connected to the second connection port (202). Specifically, in this configuration, the first switch (106), the third switch (110), the fourth switch (112), and the sixth switch (302) are switched ON whereas the second switch (108) and the fifth switch (204) are switched OFF.

[00069] Finally, the next function ‘Series H1, H2 ON’ indicates that the first SMR (102) and the second SMR (104) are connected in series to the first connection port 122, and the third SMR (302) is connected to the second connection port 204. Specifically, in this configuration, the first switch (102), the second switch (104), and the sixth switch (304) are switched ON whereas the third switch (110), the fourth switch (204), and the fifth switch (204) are switched OFF.

[00070] Referring to Figure 13, the present disclosure also relates to a method (1300) for operating the electric power supply devices (100, 200, and 300), according to an embodiment of the disclosure. The order in which the method steps are described below is not intended to be construed as a limitation, and any number of the described method steps may be combined in any appropriate order to execute the method or an alternative method. Additionally, individual steps may be deleted from the method without departing from the scope of the subject matter described herein.

[00071] It will be appreciated that the modules, processes, systems, and devices described above can be implemented in hardware, hardware programmed by software, software instruction stored on a non-transitory computer readable medium or a combination of the above. Embodiments of the methods, processes, modules, devices, and systems (or their sub-components or modules), may be implemented on a general-purpose computer, a special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit element, an ASIC or other integrated circuit, a digital signal processor, a hardwired electronic or logic circuit such as a discrete element circuit, a programmed logic circuit such as a programmable logic device (PLD), programmable logic array (PLA), field-programmable gate array (FPGA), programmable array logic (PAL) device, or the like. In general, any process capable of implementing the functions or steps described herein can be used to implement embodiments of the methods, systems, or computer program products (software program stored on a non-transitory computer readable medium.

[00072] Furthermore, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program product may be readily implemented, fully or partially, in software using, for example, object or object-oriented software development environments that provide portable source code that can be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program product can be implemented partially or fully in hardware using, for example, standard logic circuits or a very-large-scale integration (VLSI) design. Other hardware or software can be used to implement embodiments depending on the speed and/or efficiency requirements of the systems, the particular function, and/or particular software or hardware system, microprocessor, or microcomputer being utilized.

[00073] In one embodiment, the method (13 00) may be performed partially or completely by the control unit (114) shown in Figures 1 to 3. The method (1300) comprises the steps of receiving a plurality of parameters associated with a user input and the plurality of SMRs (102) and (104) at the control unit (114) in step (1302). Upon receipt of the parameters pertaining to the user input and the plurality of SMRs (102) and (104), the control unit (114) determines a predefined voltage and a predefined current based on the user input in step (1304). Thereafter, in step (1306), the control unit (114), may selectively operate the plurality of switches (106, 108, 110, 112) to configure the plurality of SMRs (102) and (104) in a predefined mode to establish an electric connection between at least one SMR (102) and (104) and the first connection port (122) to produce the output DC power of the predefined voltage and current based on the received plurality of parameters.

[00074] In step (1308), while the electric power is being supplied to the first connection port (122), the control unit (114), may monitor, in real-time, the plurality of parameters of an SMR of the plurality of SMRs (102) and (104) to determine a deviation between an operating condition of the SMR and an optimum condition thereof. The deviation may be, in one embodiment, a change in the operating temperature of one or more SMRs (102) and (104). The control unit (114), as a part of monitoring the received plurality of parameters, may compare the temperature of an SMR of the plurality of SMRs (102) and (104) with a corresponding optimum temperature to determine if the SMR is operating at an elevated operating condition of the SMR.

[00075] Subsequently, in step (1310), the control unit (114) may operate the remaining SMRs of the plurality of SMRs (102) and (104) to change either the predefined mode or respective operating conditions to compensate for the deviation to maintain the predefined voltage and current. In one embodiment, operating the plurality of SMRs (102) and (104) may include changing respective operating conditions to compensate for the deviation caused by the increase in temperature. The afore mentioned active load-balancing technique aims to provide a wide range of uninterrupted electric power while ensuring the longevity of the SMRs (102) and (104).

[00076] Specifically, Figure 14 A-E illustrates a method (1400) of the active load balancing technique of the method in Figure 10, according to an embodiment of the disclosure. The method 1400 comprises the steps of connecting the EV to the first connection port (122) of the electric power supply device 100 in step (1402). Thereafter, in step (1404), the control unit (114) authenticates the EV and thereafter receives the user inputs from a throttle body of the EV In one embodiment, the user input includes the predefined voltage and current limits that are communicated to the control unit (114). This also includes completing the authentication process. At step (1406), the control unit (114), based on the voltage and current requirement of the EV, configures the SMRs (102) and (104) to operate in any one of the four configurations namely, ‘A’, ‘B’, ‘C’, and ‘D’ Each configuration is explained with respect to Figures 11B, 11C, 11D, and 11E.

[00077] Referring to Figure 14B, the control unit (114), at step (1408), determines that the EV requirement is only for one SMR. Accordingly, the control unit (114) may activate one of the SMRs, either the first SMR (102) or the second SMR 104. In step (1410), the selection of SMR is performed which is based on the operating condition and usage history of the SMRs present. The operation condition and usage history are also termed Mean Time To Repair (MTTR), and Mean Time Between Failure (MTBF). The SMR selection is done so that each SMR is used in such a way that the operating load is balanced and improves the life of the SMRs. Once the selection is made, for example, the first SMR (102), the control unit (114) operates the switches to connect the first SMR (102) to the first connection port (122) to initiate the charging session. In an embodiment, the control unit (114) may switch ON the first switch (106) and the second switch (108) and switch OFF the third switch (110) and the fourth switch (112).

[00078] In step (1412), the control unit (114), during the charging session, checks if the pre-defined parameters associated with the deration of the selected SMR such as but not limited to temperature, increases above a pre-defined threshold, and as a result, the control unit (114) limits the operation of the SMR for the purpose of protecting the SMR. Accordingly, the control unit (114) switches ON a different SMR and distributes the load between two/ multiple SMRs. In step (1414), the control unit (114), in order to keep the power delivery efficiency high, checks if the heated SMR is not overheating. In case the efficiency decreases due to the overheated SMRs running at lower power output, the control unit (114) gradually turns OFF the heated SMR and operates the newly turned-on SMR as the sole charger.

[00079] Back to Figure 14A, in case the requirement from the EV warrants a high charging current, the method proceeds to configuration ‘B’ which is elaborated with respect to Figure 14C. Referring to Figure 14C now, the control unit (114), in step (1416), determines if the EV current requirement is high, the control unit (114) switches ON multiple SMRs (102) and (104) in parallel connection. Based on that, the control unit 114, in step (1418), sets the limit on the voltage. Thereafter, in step (1420), the control unit (114) decides the number of SMRs (102) and (104) to be turned ON based on the current requirement of EV and the current delivering capability of each SMR. Further, in step (1422), the control unit (114) checks if the current demand from EV increases or decreases during the session. In step (1424), the control unit (114) determines if the number of SMRs (102) and (104) connected to the first connection port (122) can be increased or decreased to meet the pre-defined requirement. The control unit (114), in block (1426), may switch ON the first switch (106), the third switch (110), and the fourth switch (112) and switch OFF the second switch (108). In step (1428), in a case when the control unit (114) determines that during the change in demand of current, the control unit (114) decreases the current output from the heated-up SMR and reroutes the current to other SMRs which are working at a better efficiency, giving the other SMR to cool down and then balancing of power can happen again.

[00080] On the other hand, subsequent to step (1420), the control unit (114) checks if one of the SMRs has heated up more than the permitted limit as per the efficiency data available with the control unit (114) in step (1430). Thereafter, in step (1432), the control unit (114) turns OFF that SMR and turns ON a new SMR to ensure maximum efficiency. Also, the control unit (114), in step (14 34), checks if the input AC voltage is low or system temperature is rising or the efficiency of the electric power supply device (100) decreases, the control unit (114) can add SMRs in parallel and decrease the load on the derated or lower efficiency SMRs. Finally, in step (1436), the control unit (114) may reduce the SMR Temperature and let the SMR cool down without losing out on maximum power output with the highest possible efficiency.

[00081] Back to Figure 14A, in case the requirement from the EV warrants a high charging voltage at constant current, the method proceeds to configuration ‘C’ which is elaborated with respect to Figure 14D. Referring to Figure 14D now, the control unit (114), at step (1438), determines if the EV requirement is of high voltage. Thereafter, at step (1440), the control unit (114) turns ON multiple SMRs in series connection keeping one SMR in CC mode while other SMR(s) in CV mode. At step (1442), the control unit (114) sets the number of SMRs (102) and (104) based on the voltage requirement of the EV. Further, at step (1444), the control unit (114) decides the output voltage distribution among the SMRs (102) and (104), and the SMRs (102) and (104) are set to output different CV voltages based on efficiency data present to control unit (114). At step (14 46), the control unit sets (114) the voltage of each SMR running in CV mode to get the highest efficiency. At step (1448), the control unit (114) sets the current output to the CC mode SMR and changes the mode based on EV request. At step (1450), the control unit (114), with an increase in voltage of the battery as charging happens, balances the CV voltage of each SMR dynamically throughout the session to maintain the highest efficiency.

[00082] On the other hand, at step (1452) subsequent to step (1446), the control unit (114) determines if the initial voltage of the EV is less but the highest voltage limit is high and accordingly, the control unit (114) starts with a minimum number of SMRs to meet the initial voltage output requirement based on EV load voltage. Thereafter, in step (1144), as battery charges and voltage increase, the control unit (114) turns ON more SMRs in CV mode in a series configuration and therefore provide, an increased voltage requirement of EV. Finally, in step (1456), the control unit (114) turns ON the new SMR, for instance, the second SMR (104), and sets the CV voltage of each SMR based on the voltage efficiency of each SMR to get the highest efficiency for the electric power supply device (100).

[00083] Back to Figure 14A, in case the requirement from the EV warrants higher charging voltage and current than the predefined voltage and current of single SMR 102, 104, the method proceeds to configuration ‘D’ which is elaborated with respect to Figure 14E. Referring to Figure 14E now, the control unit (114), in step (1458), determines if both voltage and current requirements are higher than that of a single SMR. Accordingly, in step (1460, the control unit (114) sets up the SMRs (102) and (104) in a series configuration to form one CC mode output module to achieve the required voltage. In step (1462), the control unit (114) then configures similar CC mode modules in parallel to each other to reach the current requirement (CC mode output). Finally, at step (1464), the control unit monitors the current, voltage and temperature of all the SMRs and makes decisions to get the best efficiency possible.

[00084] According to this disclosure, the electric power supply device (100) provides a variable supply of electric power based on the requirement of the EV thereby making the electric power supply device (100) compatible with a wide range of different EVs and PHEVs. Moreover, the control unit (114) also performs real-time monitoring of internal components thereby ensuring the best efficiency and longevity.

[00085] While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.
, Claims:1. An electric power supply device, comprising:
a plurality of Switch Mode Rectifiers (SMRs) (102, 104, 302), each configured to receive an Alternating Current (AC) supply (124) and output Direct Current (DC) power;
a first connection port (122) having a positive output terminal (122A) and a negative output terminal (122B) configured to connect to an electric load to provide output DC power of a predefined voltage and current thereto;
a plurality of switches (106, 108, 110, 112, 202, 304) configured to selectively establish an electric connection between at least one SMR (102, 104, 302) of the plurality of SMRs (102, 104, 302) and the first connection port (122) in one of in a series connection and/or a parallel connection; and
a control unit (114) operably coupled to the plurality of SMRs (102, 104, 302) and the plurality of switches (106, 108, 110, 112), wherein the control unit (114) is configured to:
receive at least one parameter associated with an operation of the plurality of SMRs (102, 104, 302) (102, 104, 302), and
selectively operate the plurality of switches (106, 108, 110, 112) to configure the plurality of SMR (102, 104, 302) in a predefined mode to establish an electric connection between at least one SMR (102, 104, 302) and the first connection port (122) to produce the output DC power of the predefined voltage and current based on the received parameter.

2. The electric power supply device (100, 200, 300) as claimed in claim 1, wherein the electric power supply device (100, 200, 300) is an electric vehicle supply equipment (EVSE), and the electric load is a battery pack of the electric vehicle (EV).

3. The electric power supply device (100, 200, 300) as claimed in claim 1, a plurality of protection and sense units electrically connected to the plurality of SMRs (102, 104, 302) and configured to protect the plurality of SMRs (102, 104, 302) from one of reverse polarity and short circuit.

4. The electric power supply device (100, 200, 300) as claimed in claim 1, wherein the control unit (114) is configured to regulate an output voltage and an output current of each of the plurality of SMRs (102, 104, 302).

5. The electric power supply device (100, 200, 300) as claimed in claim 1, wherein the predefined mode is a single output mode, and wherein in the single output mode, an SMR (102, 104, 302) out of the plurality of SMRs (102, 104, 302) is electrically connected to the output terminals (122A, 122B) using the plurality of switches (106, 108, 110, 112, 202, 304).

6. The electric power supply device (100, 200, 300) as claimed in one of claim 1, wherein the predefined mode is a constant current mode, and wherein in the constant current mode:
in a series SMR (102, 104, 302) connection, the predefined voltage is equal to an aggregate of the output voltage of each of the plurality of SMRs (102, 104, 302) and the predefined current is equal to the output current of each of the plurality of SMRs (102, 104, 302); and
in a parallel SMR (102, 104, 302) connection, the predefined current is an aggregate of the output current of the plurality of SMRs (102, 104, 302), and the predefined voltage is equal to the output voltage of each of the plurality of SMRs (102, 104, 302).

7. The electric power supply device (100, 200, 300) as claimed in one of claim 1, wherein the predefined mode is a constant voltage mode, and wherein in the constant voltage mode:
in a series SMR (102, 104, 302) connection, the predefined current is equal to the output current of each of the plurality of SMR (102, 104, 302), and the predefined voltage is an aggregate of the output voltage of the plurality of SMR (102, 104, 302); and
in a parallel SMR (102, 104, 302) connection, a SMR (102, 104, 302) of the plurality of SMR (102, 104, 302) is configured to output the predefined voltage and the predefined current is an aggregate of the output current of the plurality of SMR (102, 104, 302).

8. The electric power supply device (100, 200, 300) as claimed in claim 1, wherein the control unit (114) is configured to:
monitor a temperature of an SMR (102, 104, 302) of the plurality of SMRs (102, 104, 302) to determine a deviation between an operating condition of the SMR (102, 104, 302) and an optimum condition thereof; and
operate remaining SMRs (102, 104, 302) of the plurality of SMRs (102, 104, 302) to change respective operating conditions to compensate the deviation to maintain the predefined voltage and current at the first connection port (122).

9. A method of operating an electric power supply device (100, 200, 300) having a plurality of switch mode rectifiers (SMRs (102, 104, 302)) and a plurality of switches (106, 108, 110, 112), comprising:
receiving (1002), by a control unit (114), a user input and a plurality of parameters associated with the plurality of SMRs (102, 104, 302);
determining (1004), by a control unit (114), a predefined voltage and a predefined current based on the user input;
selectively (1006), by a control unit (114), operate the plurality of switches (106, 108, 110, 112) to configure the plurality of SMRs (102, 104, 302) in a predefined mode to establish an electric connection between at least one SMR (102, 104, 302) and the first connection port (122) to produce the output DC power of the predefined voltage and current based on the received plurality of parameters;
monitoring (1008), by the control unit in real-time, the plurality of parameters of an SMR (102, 104, 302) of the plurality of SMRs (102, 104, 302) to determine a deviation between an operating condition of the SMR (102, 104, 302) and an optimum condition thereof; and
operating (1010), by the control unit (114), remaining SMRs (102, 104, 302) of the plurality of SMRs (102, 104, 302) to change one of the predefined mode and respective operating conditions to compensate the deviation to maintain the predefined voltage and current.

10. The method (1000) as claimed in claim 9, wherein monitoring the received plurality of parameters comprises:
comparing a temperature of an SMR (102, 104, 302) of the plurality of SMRs (102, 104, 302) with a corresponding optimum temperature to determine if the SMR (102, 104, 302) is operating at an elevated operating condition of the SMR (102, 104, 302).

11. The method (1000) as claimed in claim 9, wherein the received plurality of parameters is at least one a temperature of the SMR, an output voltage, and an output current of the SMR (102, 104, 302).

12. The method (1000) as claimed in claim 9, wherein the electric power supply device (100, 200, 300) is an electric vehicle supply equipment (EVSE), and the electric load is a battery pack of the electric vehicle (EV).

13. The method (1000) as claimed in claim 9, wherein the control unit (114) is configured to regulate an output voltage and an output current of each of the plurality of SMRs (102, 104, 302).

14. The method (1000) as claimed in one of claim 9, a plurality of protection and sense units disposed electrically connected to the plurality of SMRs (102, 104, 302) and configured to protect the plurality of SMRs (102, 104, 302) from one of reverse polarity and short circuit.

15. The method (1000) as claimed in claim 9, wherein the predefined mode is a single output mode, and wherein in the single output mode, an SMR (102, 104, 302) out of the plurality of SMRs (102, 104, 302) is electrically connected to the output terminals.

16. The method (1000) as claimed in one of claim 9, wherein the predefined mode is a constant current mode, and wherein in the constant current mode:
in a series SMR (102, 104, 302) connection, the predefined voltage is equal to the sum of the output voltages of each of the plurality of SMRs (102, 104, 302) and the predefined current is equal to the output current of each of the plurality of SMRs (102, 104, 302); and
in a parallel SMR (102, 104, 302) connection, the predefined current is an aggregate of the output current of the plurality of SMRs (102, 104, 302) and the predefined voltage is equal to the output voltage of each of the plurality of SMRs (102, 104, 302).

17. The method (1000) as claimed in one of claim 9, wherein the predefined mode is a constant voltage mode, and wherein in the constant voltage mode:
in a series SMR (102, 104, 302) connection, the predefined current is equal to the output current of each of the plurality of SMR (102, 104, 302), and the predefined voltage is an aggregate of the output voltage of the plurality of SMR; and
in a parallel SMR (102, 104, 302) connection, an SMR (102, 104, 302) of the plurality of SMR (102, 104, 302) is configured to output the predefined voltage and the predefined current is an aggregate of the output current of the plurality of SMR.