A new efficient partial power DC / DC converter topology for on-board electric vehicle (EV) fast charging

Abstract

Techniques for charging an electric vehicle (EV) battery are disclosed. In an example, a system includes an EV battery connected to a power source such that input power at a first power level is supplied to the EV battery. The system also includes a direct current (DC)-DC converter configured to convert the input power at the first power level into output power at a second power level. The second power level is less than the first power level. The DC-DC converter is connected with the power source and the EV battery.

Description

PATENT Attorney Docket No.097226-1513610 (009010WO) Client Ref. No.2022-047-02 A NEW EFFICIENT PARTIAL POWER DC / DC CONVERTER TOPOLOGY FOR ON-BOARD ELECTRIC VEHICLE (EV) FAST CHARGING CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No.63 / 666,424, filed July 1, 2024, the entire contents of which are hereby incorporated by reference for all purposes in its entirety. BACKGROUND OF THE INVENTION

[0002] On-board charging of electric vehicles (EVs) can be accomplished in two stages. In a first charging stage, a single-phase or three-phase alternating current (AC) voltage can beconverted into a direct current (DC) voltage ( ). The converted DC voltage ( ) can be largerthan a battery voltage ( ). Thus, a second charging stage, or DC-DC stage, can involvecharging the battery with an additional DC-DC converter. FIG. 1 is a diagram of a traditional on-board charger for an EV. Commercially available on-board chargers can use a full power processing converter at the DC-DC stage, which can require higher voltage and / or current rating for switches and diodes involved. Using a full power processing converter can restrict a power rating and charging speed for on-board chargers. Also, size, cost, and efficiency of any EV charger can depend on device rating and a number of power processing stages. BRIEF SUMMARY OF THE INVENTION

[0003] To be added as copy of claims when claims are approved. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG.1 is a diagram of a traditional on-board charger for an EV according to certain aspects of the present disclosure.

[0005] FIG.2A is a diagram of a Type-I step-down partial power processing (P3) DC-DC converter according to certain aspects of the present disclosure. KILPATRICK TOWNSEND 797813001

[0006] FIG.2B is a diagram of a Type-II step-down P3DC-DC converter according to certain aspects of the present disclosure.

[0007] FIG.3 is a diagram of a circuit configuration for a push-pull based P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0008] FIG.4 is a diagram depicting a control strategy for a push-pull based P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0009] FIG.5A is a diagram depicting circuit operation during a first mode of a switching cycle for a P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0010] FIG.5B is a diagram depicting circuit operation during a second mode of a switching cycle for a P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0011] FIG.5C is a diagram depicting circuit operation during a third mode of a switching cycle for a P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0012] FIG.5D is a diagram depicting circuit operation during a fourth mode of a switching cycle for a P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0013] FIG.6A and FIG.6B are an illustration of exemplary plots of steady state performance for a simulated P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0014] FIG.7A is an illustration of exemplary plots of dynamic performance measured by DC-link voltage variations for a simulated P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0015] FIG.7B is an illustration of exemplary plots of dynamic performance measured by load current variations for a simulated P3DC-DC converter for EV charging according to certain aspects of the present disclosure.

[0016] FIG.8 is a diagram of a circuit configuration for a push-pull based P3DC-DC converter for off-board EV charging according to certain aspects of the present disclosure. KILPATRICK TOWNSEND 797813001

[0017] FIG.9 is a flow chart of an exemplary process that can be implemented to charge an EV battery using a push-pull based P3DC-DC converter according to certain aspects of the present disclosure.

[0018] FIG.10 is a block diagram of a controller associated with a P3DC-DC converter according to certain aspects of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] Partial power processing (P3) with a phase shifted full bridge converter for voltage step up and step down can be incorporated in photovoltaic (PV) systems. Several topologies based on series connected P3converters are possible. A concept of P3at a DC-DC stage of EV charging may overcome issues of increased size and cost of converter electronic parts (e.g., diodes, switches, etc.). In such P3topologies, only a fraction of a total DC input power (or current) may be processed through power electronics of the P3converter. Thus, in P3configurations, ratings of incorporated semiconductor devices can be reduced significantly. The reduced ratings can achieve a higher power density due to a smaller footprint / compact size.

[0020] In general, fast charging of a battery can be associated with a constant current (CC) charging mode, since CC mode can define a peak current that remains below a maximum value. The maximum value can be a maximum current value that the DC-DC converter can withstand and still operate normally. As long as the DC-DC converter can handle the peak current associated with CC mode, a voltage associated with the DC-DC converter can be a fraction of a battery voltage and the DC-DC converter can be connected in series with an input voltage. Two configurations can be consistent with CC mode and the DC-DC converter in series with the input voltage, each are shown in FIG.2A and FIG.2B.

[0021] FIG.2A is a diagram of a Type-I step-down P3DC-DC converter according to certain aspects of the present disclosure. The Type-I step-down P3DC-DC converter can also be referred to as an Input-Parallel Output-Series (IPOS) architecture. The Type-I converter architecture can include an AC-AC converter, the P3DC-DC converter (which can also be referred to as a partially rated DC-DC converter), and an EV battery. An input side of the AC- DC stage can be connected to a three-phase AC grid. An output side of the DC-DC converter can be connected to the EV battery. In an example, an on-board charger with the P3DC-DC converter is installed in an EV that also includes the EV battery. An output side of the AC-DC stage can be connected in parallel to an input side of the partially rated DC-DC converter. A KILPATRICK TOWNSEND 797813001first capacitance can be connected in parallel to the output side of the AC-DC stage and the input side of the partially rated DC-DC converter. For the Type-I converter, an input side or primary side of the DC-DC converter can be connected in parallel with an output DC link voltage of the AC-AC converter. At an output side or secondary side of the DC-DC converter, a component with a fraction of the battery voltage, , can be connected with the DC-DC converter secondary side.

[0022] FIG. 2B is a diagram of a Type-II step-down P3DC-DC converter according to certain aspects of the present disclosure. The Type-II converter can also be referred to as an Input-Series Output-Parallel ISOP architecture. The Type-II converter architecture can include an AC-AC converter, the P3DC-DC converter (which can also be referred to as a partially rated DC-DC converter), and an EV battery. An input side of the AC-DC stage can be connected to a three-phase AC grid. An output side of the DC-DC converter can be connected to the EV battery. In an example, an on-board charger with the P3DC-DC converter is installed in an EV that also includes the EV battery. An output side of the AC-DC stage can be connected in parallel to an input side of the partially rated DC-DC converter. A first capacitance can be connected in parallel to the output side of the AC-DC stage and the input side of the partially rated DC-DC converter. For the Type-II converter, a secondary side of the DC-DC converter can be connected in parallel to the battery voltage. However, on a primary side, a component with a fraction of the battery voltage, , can be connected with the DC-DC converter primary side. A path that includes the component with the fraction of the battery voltage can be a bypass connection for direct charging of the battery. Most of the battery charging current can flow through the bypass connection. While the charging current flows through the bypass connection, a transformer secondary may not supply power. Thus, only a portion of the battery power can be handled by the DC-DC converter in both the Type-I and Type-II converter configurations.

[0023] For a given converter voltage gain, a portion of power to be handled can be represented by a partial power ratio, , which can be defined as: (1) For the Type-I converter, the partial power ratio can be simplified to: KILPATRICK TOWNSEND 79781300111 (2)and for the Type-II converter, the partial power ratio becomes:1 (3)where is the converter voltage gain, and are the partial and DC-link powers, respectively. Thus, for given output and input voltages, independent of the battery voltage or an equivalent state of charge (SoC), the partial power ratio of the Type-II P3converter can always be lower than the partial power ratio of the Type-I P3converter. The portion of power handled by the DC-DC converter can always be lower for the Type-II converter, relative to Type-I. So, the converter rating for the Type-II converter can be significantly less than that of the Type-I converter.

[0024] Certain aspects and examples of the present disclosure relate to a P3based DC-DC converter topology for charging EV batteries. The P3based DC-DC converter can be a Type- II converter and for simplicity can be referred to as a P3EV converter. The P3EV converter can be compatible with on-board chargers (e.g., on-board fast chargers) or off-board chargers with reduced cost and size on account of a reduction of voltage stress for switches on a primary side and a reduction in current stress for rectifier devices on a secondary side of a transformer. The P3EV converter can be powered by single phase AC, three phase AC, or DC power sources. The P3EV converter can facilitate ultrafast charging by a further extension of power in off-board charging systems. An efficiency of the P3EV converter can be higher than conventional EV converters due to lower losses in device and circuit components. For example, the P3EV converter can achieve an efficiency as high as 97% (simulated) without any soft switching used in circuit architecture. Most P3converters can be based on phase-shifted full bridge topologies that include four switches. The P3EV converter can involve a push-pull based P3topology that can operate with just two switches. Circuit architecture for the P3EV converter can include a bypass connection. In some examples, a majority of charging power can be supplied by the bypass connection. Charging via the bypass connection can enhance charging speed and can reduce a burden on the P3EV converter. Such a reduced burden can reduce voltage or current ratings of components included in the P3EV converter. A full power push- pull topology for EV fast charging can have a main limitation of a high device voltage stress((2 ), where is an input DC voltage. The P3 EV converter can significantly reduce theKILPATRICK TOWNSEND 797813001device voltage stress, converter size, and cost while increasing efficiency compared to fullpower converters. Specifically, device voltage stress in the P3 EV converter can be defined by:(4)where is the input DC voltage and is the battery voltage.

[0025] In the following description, various embodiments will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.

[0026] FIG. 3 is a diagram of a circuit configuration for a push-pull based P3DC-DC converter 302 (or P3EV converter) for EV charging according to certain aspects of the present disclosure. The circuit configuration can include an input DC voltage, , the P3DC-DC converter 302, and an EV battery. The EV battery can be represented by a battery voltage, , in parallel with a battery capacitance, . The P3DC-DC converter 302 can be a high frequency transformer. The P3DC-DC converter 302 can include a primary side 304 and a secondary side 306. The primary side 304 can be referred to as an input port and the secondary side 306 can be referred to as an output port.

[0027] The primary side 304 of the P3DC-DC converter 302 can include a first switch, and a second switch, . The first switch, and the second switch, can each be transistors, such as metal-oxide-semiconductor field effect transistors (MOSFETs) and each can have an on state and an off state. Although two switches are shown in FIG. 3, the primary side 304 can include any number of switches. The secondary side 306 of the P3DC-DC converter 302 can include rectifiers, such as rectifier , rectifier , rectifier , and rectifier . The rectifiers can be diodes.

[0028] The circuit configuration can also include a capacitor . A first terminal of the capacitor can be connected to a node 308 and a second end of the capacitor can be connected to a node 310. A fraction, , of the input voltage, , can drop across the capacitor . A first terminal 316 of the primary side 304 P3DC-DC converter 302 can be connected to node 308 and a second terminal 314 of the primary side 304 can be connected to node 310. A voltage across the primary side 304 of the P3DC-DC converter 302 can be less than the input voltage, , due to the voltage drop across the capacitor , so that the P3DC-DC converter KILPATRICK TOWNSEND 797813001302 can process less power than a nominal input power associated with the input DC voltage, . To control the P3EV converter, battery voltage and current can be measured and the measurements can be given to voltage and current proportional and integral (PI) controllers, respectively for CC and constant voltage (CV) charging modes.

[0029] Additionally, the circuit configuration can include a bypass connector 320. The bypass connector 320 can be a link between node 308 and node 312. In certain examples or modes of operation, the bypass connector 320 can form a bypass connection together with the capacitor and an inductor . The bypass connection can be used to charge the EV battery using, for example, a bypass current .

[0030] FIG. 4 is a diagram depicting a control strategy for a push-pull based P3DC-DC converter for EV charging according to certain aspects of the present disclosure. When a stateof charge (SoC) is less than 90% ( 90%), the battery can be charged in CC mode and areference of battery current can be determined by the voltage PI controller. For 90%, battery charging can be switched to CV mode and the reference of the battery current can be determined by a charging power given by a battery management system (BMS) and battery voltage. Further, a pulse generated by the current PI controller can be sent to switch and, after a delay of less than a half cycle, switch can be turned on. Thus, based on a switching sequence generation, the P3EV converter can operate in four different modes over a single switching cycle. Operating principles of the P3EV converter during each of the four modes are explained in the description of FIGs.5A-5D below.

[0031] MODE I

[0032] FIG. 5A is a diagram depicting circuit operation during a first mode of a switching cycle for a P3DC-DC converter (or P3EV converter) for EV charging according to certain aspects of the present disclosure. During this first mode, switch of a primary side of the P3DC-DC converter may be the only switch on. A currentcan flow through a lower half of the primary side. Voltages,and can appear across the primary and secondary sides of the P3DC-DC converter, respectively. Thus, rectifiers and of the secondary side can be on. The P3EV converter can supply battery current (via ) in this first mode.

[0033] MODE II

[0034] FIG.5B is a diagram depicting circuit operation during a second mode of a switching cycle for a P3DC-DC converter (or P3EV converter) for EV charging according to certain KILPATRICK TOWNSEND 797813001aspects of the present disclosure. During the second mode, both switches, and , of a primary side of the P3DC-DC converter can be turned on. Currents, and , can flow through both an upper and lower half of the primary side. Voltages and can cancel each other out. No voltage may be induced on a secondary side of the P3DC-DC converter. Rectifiers may be off during this second mode and no current may flow on the secondary side. Thus, the battery can be charged directly from the DC-link using a non-zero bypass current, , in a bypass connection.

[0035] MODE III

[0036] FIG. 5C is a diagram depicting circuit operation during a third mode of a switching cycle for a P3DC-DC converter (or P3EV converter) for EV charging according to certain aspects of the present disclosure. During this third mode, switch of a primary side of the P3DC-DC converter may be the only switch on. Current can flow through an upper half of the primary side. Voltages, and can appear across the primary and secondary sides of the P3DC-DC converter, respectively. Thus, rectifiers and of the secondary side can be on. The P3EV converter can supply battery current (via ) in this third mode.

[0037] MODE IV

[0038] FIG.5D is a diagram depicting circuit operation during a fourth mode of a switching cycle for a P3DC-DC converter (or P3EV converter) for EV charging according to certain aspects of the present disclosure. Both switches and of a primary side of the P3DC- DC converter can be in an off state. Thus, no voltage can be induced in a secondary side of the of the P3DC-DC converter. The P3DC-DC converter may not supply any power in this mode. Rectifiersof the secondary side can be off during this mode. Thus, the battery can be charged directly from the DC-link using a non-zero bypass current, , in a bypass connection.

[0039] EXAMPLES

[0040] Performance of a P3EV converter with a 10 kW design can be demonstrated using a MATLAB / Simulink environment under steady state as well as dynamic conditions. In the following examples, a DC-link voltage is varied from 420-450 Volts (V). A selected battery voltage range, for these examples, is between 320-390 V with a nominal rating of 350V, 100 Ampere-hours (Ah). KILPATRICK TOWNSEND 797813001

[0041] FIG. 6A and FIG. 6B are an illustration of exemplary plots of steady state performance for a simulated P3DC-DC converter for EV charging according to certain aspects of the present disclosure. The simulated P3DC-DC converter is rated at a DC input voltage, of 450V and battery voltage, , is 380V at a 60% SoC. Since the DC-DC converter processes a portion of the battery power, switchesand observe a switch voltage stress of 70V, which is equivalent to . Here, is the P3DC-DC converter voltage, which is a fraction of the battery voltage, . Thus, the switch voltage of the P3EV converter is reducedto 140V (e.g., 2 ) compared to a conventional push-pull converter switch voltage of 900V(e.g., 2 ).

[0042] Since the transformer supplies current may only during modes when at least one switch is on, a voltage only develops only during modes I and III. Most of the battery current is supplied during a bypass connection, thus, a current is observed to be almost equal to a rated battery current (e.g., 22 Amps). Current processed by the transformer and converter is very low, so a secondary rectifier can be of low current rating (e.g., is observed to be only 3 Amps). Thus, ratings of switches and diodes (e.g., between 200V to 900V voltage ratings for switches, between 3A to 25A current ratings for diodes) included in the P3EV converter can be significantly reduced compared to ratings of similar components included in a regular full power processed DC-DC converter.

[0043] FIG. 7A is an illustration of exemplary plots of dynamic performance measured by DC-link voltage variations for a simulated P3DC-DC converter for EV charging according to certain aspects of the present disclosure. The dynamic performance of the P3EV converter is verified under a variation in DC-link voltage from 450V-420V at 0.8 seconds and 420V- 450V at 1.8 seconds. Battery voltage rises (e.g., a slight change for 100 Ah) as a charging current of 23A is maintained during CC charging. However, for a decrease or increase in DC- link voltage, DC-link current observes a corresponding rise and dip, at 0.85 seconds and 1.85 seconds, respectively. Performance of the P3EV converter is further verified by a change in battery voltage from 350-320V and vice versa at 2.5 seconds and 3.5 seconds. Battery current remains constant at 23A. However, the DC-link current displays a change from 23A to 22A to maintain a power balance for the P3EV converter.

[0044] FIG. 7B is an illustration of exemplary plots of dynamic performance measured by load current variations for a simulated P3DC-DC converter for EV charging according to certain aspects of the present disclosure. To verify efficacy of the P3EV converter, a variation KILPATRICK TOWNSEND 797813001in load current is introduced from 23A-15A at 4.05 seconds and from 15A-23A at 4.6 seconds. The simulated P3DC-DC converter is rated at a DC input voltage, of 450V and battery voltage, , is 380V at a 60% SoC. As confirmed in FIG.7B, the P3EV converter can sustain these changes in load (or battery current). The DC-link current is seen to vary from 15A- 23A and 23A-15A following an overall power profile for the EV charger.

[0045] FIG. 8 is a diagram of a circuit configuration for a push-pull based P3DC-DC converter for EV off-board charging according to certain aspects of the present disclosure. The circuit configuration can include a three phase AC grid power source, low frequency(LF) isolation, an electromagnetic interference (EMI) filter, an AC-DC stage, and an off-board charger. The off-board charger can include an isolated (partial rated) DC-DC stage and an EV battery. The isolated DC-DC stage can be cost effective in comparison to interleaved and phase-shifted full bridge LLC converters.

[0046] FIG. 9 is a flowchart of an example of a process 900 that can be implemented to charge an EV battery using a push-pull based P3DC-DC converter according to some aspects of the present disclosure. Operations of processes may be performed by software, firmware, hardware, or a combination thereof. The operations of the process 900 start at block 910.

[0047] At block 910, the process 900 involves charging, during a first mode of a switching cycle, the EV battery. The P3DC-DC converter can include a primary side and a secondary side. An example of the P3DC-DC converter can be P3DC-DC converter 302 from FIG. 3. The primary side can include a first switch and a second switch. Each of the switches can have an ‘On’ state and an ‘Off’ state. For example, the switches can be MOSFETs and a state of each switch can be determined based on a gate voltage or a channel current of each MOSFET. A controller associated with the P3DC-DC converter can control states of the switches and thus can cause the P3DC-DC converter to undergo switching cycles. The secondary side can include rectifiers, such as four rectifiers. Each of the rectifiers can be diodes. Architecture associated with the P3DC-DC converter can include a bypass connection. In some examples the bypass connection can include a bypass connector, such as bypass connector 320 of FIG. 3. Under some conditions, the bypass connection can be used to charge the EV battery.

[0048] During the first mode of the switching cycle, the controller can turn the first switch on (e.g., in an ‘On’ state), while the second switch is off (e.g., in an ‘Off’ state). A current (e.g., of FIG.5A) can flow through a lower half of the primary side. Voltages, (e.g., and from FIG.5A) can appear across the primary and secondary sides of the P3DC-DC converter. KILPATRICK TOWNSEND 797813001Two rectifiers . . , and of FIG. 5A) of the secondary side can be on. The P3 EVconverter can supply battery current (via, for example, of FIG.5A) to charge the EV battery in this first mode.

[0049] At block 920, the process 900 involves charging, during a second mode of the switching cycle, the EV battery. During the second mode, both switches of the primary side of the P3EV converter, such as and of FIG.3, can be turned on. Currents, (e.g., and of FIG. 5B), can flow through both an upper and lower half of the primary side. Voltages (e.g., and of FIG. 5B) can cancel each other out. No voltage may be induced on a secondary side of the P3DC-DC converter. The rectifiers of the secondary side (e.g.,of FIG. 5B) may be off during this second mode and no current may flow on the secondary side. Thus, the EV battery can be charged using a non-zero bypass current, (e.g., of FIG. 5B), in the bypass connection.

[0050] At block 930, the process 900 involves charging, during a third mode of the switching cycle, the EV battery. During the third mode, the controller associated with the P3DC-DC may turn off the first switch, while leaving the second switch (e.g., of FIG. 5C) in the ‘On’ state. Current (e.g., from FIG. 5C) can flow through an upper half of the primary side. Voltages, (e.g., and from FIG. 5C) can appear across the primary and secondary sides of the P3DC-DC converte. Thus, rectifiers (e.g., and of FIG. 5C) of the secondary side can be on. The P3EV converter can supply battery current (via, for example current of FIG. 5C) in this third mode.

[0051] At block 940, the process 900 involves charging, during a fourth mode of the switching cycle, the EV battery. The controller associated with the P3DC-DC converter can place both switches (e.g., and from FIG. 5D) in an off state. Thus, no voltage can be induced in a secondary side of the of the P3DC-DC converter. The P3DC-DC converter may not supply any power in this mode. Rectifiers (e.g., of FIG.5D) of the secondary side can be off during this mode. Thus, the EV battery can be charged directly using a non-zero bypass current, (e.g., from FIG.5D), in the bypass connection.

[0052] In some examples, the EV battery can be charged by CC charging during each mode of the switching cycle. The controller associated with the P3DC-DC converter can monitor a SoC for the EV battery. When the SoC of the EV battery exceeds 90%, the controller can cause the EV battery to be charged using CV charging instead of CC charging. KILPATRICK TOWNSEND 797813001

[0053] FIG.10 is a block diagram of a controller 1000 associated with a P3DC-DC converter according to certain aspects of the present disclosure. P3DC-DC converter 302 of FIG. 3 can be an example of the P3DC-DC converter. As shown, the controller 1000 includes a processor 1002 communicatively coupled to memory 1004. The processor 1002 can include one processing device or multiple processing devices. Non-limiting examples of the processor 1002 include a Field-Programmable Gate Array (FPGA), an application specific integrated circuit (ASIC), a microprocessor, or any combination of these. The processor 1002 can execute instructions 1010 stored in the memory 1004 to perform operations, such as the operations of process 900 from FIG. 9. In some examples, the instructions 1010 can include processor- specific instructions generated by a compiler or an interpreter from code written in any suitable computer-programming language, such as C, C++, C#, Python, or Java.

[0054] The memory 1004 can include one memory device or multiple memory devices. The memory 1004 can be non-volatile and may include any type of memory device that retains stored information when powered off. Non-limiting examples of the memory 1004 include electrically erasable and programmable read-only memory (EEPROM), flash memory, or any other type of non-volatile memory. At least some of the memory 1004 can include a non- transitory computer-readable medium from which the processor 1002 can read instructions 1010. The non-transitory computer-readable medium can include electronic, optical, magnetic, or other storage devices capable of providing the processor 1002 with the instructions 1010 or other program code. Non-limiting examples of the non-transitory computer-readable medium include magnetic disk(s), memory chip(s), RAM, an ASIC, or any other medium from which a computer processor can read instructions 1010.

[0055] The memory 1004 can further include a SoC of an EV battery 1012. The processor 1002 of the controller 1000 can control states of switches of the P3DC-DC converter and can cause P3DC-DC converter to undergo switching cycles. For example, the processor 1002 can initiate a first mode of the switching cycle by causing a first switch of the P3DC-DC converter to be in an ‘On’ state while a second switch is in an ‘Off’ state. The processor can cause the first switch to be in the ‘On’ state, for example, by sending a voltage pulse to a gate of the first switch. The processor 1002 can initiate a second mode of the switching cycle by causing the second switch of the P3DC-DC converter to be in an ‘On’ state while maintaining the ‘On’ state for the first switch. The processor 1002 can initiate a third mode of the switching cycle by causing the first switch of the P3DC-DC converter to be in an ‘Off’ state while the second switch is still in the ‘On’ state. The processor 1002 can initiate a fourth mode of the switching KILPATRICK TOWNSEND 797813001cycle by causing both the first and second switch to be in an ‘Off’ state. The processor 1002 can cause the P3DC-DC converter to switch from CC charging to CV charging and vice versa. For example, when the SoC of the EV battery 1012 exceeds 90%, the processor 1002 can cause the P3DC-DC converter to switch from CC charging to CV charging.

[0056] While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations, and / or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art. Indeed, the methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.

[0057] Conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain examples include, while other examples do not include, certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more examples or that one or more examples necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular example.

[0058] Disjunctive language such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is otherwise understood within the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain examples require at least one of X, at least one of Y, or at least one of Z to each be present.

[0059] Use herein of the word “or” is intended to cover inclusive and exclusive OR conditions. In other words, A or B or C includes any or all of the following alternative KILPATRICK TOWNSEND 797813001combinations as appropriate for a particular usage: A alone; B alone; C alone; A and B only; A and C only; B and C only; and all three of A and B and C.

[0060] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the disclosed examples (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. The use of “adapted to” or “configured to” herein is meant as open and inclusive language that does not foreclose devices adapted to or configured to perform additional tasks or steps. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Additionally, the use of “based on” is meant to be open and inclusive, in that a process, step, calculation, or other action “based on” one or more recited conditions or values may, in practice, be based on additional conditions or values beyond those recited. Similarly, the use of “based at least in part on” is meant to be open and inclusive, in that a process, step, calculation, or other action “based at least in part on” one or more recited conditions or values may, in practice, be based on additional conditions or values beyond those recited. Headings, lists, and numbering included herein are for ease of explanation only and are not meant to be limiting.

[0061] The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and sub- combinations are intended to fall within the scope of the present disclosure. In addition, certain method or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate. For example, described blocks or states may be performed in an order other than that specifically disclosed, or multiple blocks or states may be combined in a single block or state. The example blocks or states may be performed in serial, in parallel, or in some other manner. Blocks or states may KILPATRICK TOWNSEND 797813001be added to or removed from the disclosed examples. Similarly, the example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed examples.

[0062] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. KILPATRICK TOWNSEND 797813001

Claims

WHAT IS CLAIMED IS:

1. A system for charging an electric vehicle (EV) battery, the system comprising: the EV battery connected to a power source such that input power at a first power level is supplied to the EV battery; and a direct current (DC)-DC converter configured to convert the input power at the first power level into output power at a second power level, wherein the second power level is less than the first power level, and wherein the DC-DC converter is connected with the power source and the EV battery.

2. The system of claim 1, further comprising: a current Proportional Integral (PI) controller configured to implement a constant current (CC) charging mode and receive a first sensed value for a current in the EV battery; and a voltage PI controller configured to implement a constant voltage (CV) charging mode and receive a second sensed value for a voltage across the EV battery, wherein the DC-DC converter is operated in one of the CC charging mode and the CV charging mode based on the first sensed value and the second sensed value.

3. The system of claim 2, wherein the DC-DC converter is configured to switch from the CC charging mode to the CV charging mode when a state of charge (SoC) for the EV battery exceeds 90%.

4. The system of claim 1, wherein the system further comprises: a first switch in a primary side of the DC-DC converter; a second switch in the primary side of the DC-DC converter; and a plurality of rectifiers in a secondary side of the DC-DC converter, wherein the DC-DC converter is configured to convert the input power into the output power by at least controlling an operation of at least one of the first switch, the second switch, or the plurality of rectifiers.

5. The system of claim 4, wherein the plurality of rectifiers comprises a current rating less than 3 Amps. KILPATRICK TOWNSEND 7978130016. The system of claim 4, wherein the two switches comprise a voltage rating comprising a difference between an input DC voltage for the DC-DC converter and a voltage across the EV battery.

7. The system of claim 4, further comprising: a bypass connection configured to provide a power charge to the EV battery.

8. The system of claim 7, wherein the bypass connection is formed by a capacitor, an inductor, and a bypass connector that forms a link between the capacitor and the inductor.

9. The system of claim 7, wherein the DC-DC converter is further configured to charge the EV battery based on a multi-mode switching cycle.

10. The system of claim 9, wherein the multi-mode switching cycle comprises: at least one mode wherein charging current is provided to the EV battery from the DC-DC converter; at least a different mode wherein the charging current is provided by the bypass connection.

11. The system of claim 1, wherein the DC-DC converter is configured to charge the EV battery as part of an off-board charging system.

12. A method for charging an EV battery, the method comprising: charging, during at least one mode of a switching cycle for a direct current (DC)-DC converter, the EV battery using the DC-DC converter, wherein the DC-DC converter converts input power at a first power level into output power at a second power level that is less than the first power level; charging, during at least one different mode of the switching cycle, the EV battery using a bypass connection.

13. The method of claim 12, wherein the bypass connection is formed at least in part by a capacitor connected to an input port of the DC-DC converter. KILPATRICK TOWNSEND 79781300114. The method of claim 12, wherein charging, during a first mode, the EV battery comprises switching on a first switch of the DC-DC converter.

15. The method of claim 12, wherein charging, during a second mode, the EV battery comprises switching on a second switch of the DC-DC converter.

16. The method of claim 12, wherein charging, during a third mode, the EV battery comprises switching off a first switch of the DC-DC converter.

17. The method of claim 12, wherein charging, during a third mode, the EV battery comprises switching off a second switch of the DC-DC converter.

18. The method of claim 12, further comprising switching from a constant current (CC) charging mode to a constant voltage (CV) charging mode when a state of charge (SoC) for the EV battery exceeds 90%.

19. The method of claim 12, wherein a plurality of rectifiers of the DC-DC converter comprises a current rating less than 3 Amps.

20. The method of claim 12. wherein two switches of the DC-DC converter comprise a voltage rating comprising a difference between an input DC voltage for the DC-DC converter and a voltage across the EV battery. KILPATRICK TOWNSEND 797813001

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