The present disclosure relates, in general, to an electric vehicle. In particular, the present disclosure relates to method and system for improving overall system efficiency of the electric vehicle by improving combined efficiency of DC-DC converter and auxiliary battery. With the present method and system, the DC-DC converter and the auxiliary battery run at maximum efficiency point so that overall efficiency of the auxiliary battery system having DC-DC converter and auxiliary battery can be increased to save more energy for traction of the electric vehicle to get maximum mileage.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present subject matter.
[0003] In electric vehicles, a traction battery pack is provided which is a primary energy source for providing energy for traction of vehicle. The traction battery pack has a battery string comprising of plurality of battery modules connected either in series or in parallel or in any combination with each other. A plurality of cells combined with each other to form a battery module and a plurality of battery modules combined with each other to form a battery pack or a traction battery pack. The traction battery pack generates a high voltage (HV) for traction of an electric motor for traction of the electric vehicle. The traction battery pack can be controlled by the electronic modules, such as electronic control unit (ECU) or vehicle control unit (VCU) from outside the traction battery pack, or can be controlled by electronic module, such as battery management system (BMS) from inside the traction battery pack. The electronic module operates passive protection devices to draw current from the traction battery pack.

These electronic modules are also responsible for implementing various battery state estimations, such as state of charge (SOC), state of health (SOH), state of function (SOF), state of power (SOP), etc.
[0004] The VCU controls charging, discharging of the traction battery pack along with activation and de-activation of DC-DC converter based on pre-stored instructions. The DC-DC converter converts high voltage from the traction battery pack into low voltage for charging the auxiliary battery and to power up auxiliary loads, such as headlamps, cabin lights, infotainment system, indicators, wipers, sound alert system, door locking system, auxiliary device charging. Simultaneously, the DC-DC converter supplies power to the auxiliary battery.
[0005] As known in the art that the DC-DC converter gives poor efficiency at lower output loads. Therefore, the existing technologies as claimed in the US patent US9315166B2 describes a method to improve efficiency of the DC-DC converter by switching off the converter in cycles and giving energy to the auxiliary loads from the auxiliary battery.
[0006] Technical disadvantage associated with the existing technologies is that switching between the DC-DC converter and the auxiliary battery is happening which resultantly effects the efficiency and performance of the auxiliary battery as well. As the auxiliary battery switching between charging and discharging mode happens frequently. Therefore, efficiency of the DC-DC converter is maintained at one hand and on the other hand efficiency of the auxiliary battery is decreased.
[0007] Accordingly, there is a need for method and system for improving overall efficiency of the system including the DC-DC converter and the auxiliary battery in the electric vehicle.
OBJECTS OF THE DISCLOSURE
[0008] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.

[0009] A general object of the present disclosure is to provide method and system for improving combined efficiency of a low voltage system including DC-DC converter and an auxiliary battery in electric vehicle.
[0010] An object of the present disclosure is to minimize overall losses of the low voltage system by supplying energy to auxiliary loads from auxiliary battery at lower load requirement and supplying energy to the auxiliary loads from the DC-DC converter at higher load requirements.
[0011] Another object of the present disclosure is to provide a method and a system that regularly monitors efficiency of the low voltage system and maintains efficiency of the low voltage system to a predefined threshold value.
[0012] These and other objects and advantages of the present disclosure will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY
[0013] This summary is provided to introduce concepts related to method and system for improving overall performance of low voltage system of an electric vehicle. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0014] The present disclosure relates to a method for improving overall efficiency of a low voltage system including a Direct Current (DC)-Direct Current (DC) converter and an auxiliary battery. The method comprising turning ON, by vehicle control unit (VCU), the DC-DC converter when required current load (Load) is more than a predefined current threshold (Ith) and state of charge (SOC) of the auxiliary battery is less than predefined threshold SOC value (SOCth); calculating, by an efficiency controller, efficiency (T|T) of the auxiliary system; increasing, by the efficiency controller, output current (lout) by a

predefined unit of the DC-DC converter; calculating, by the efficiency controller, efficiency (T|T+I) at increased current output current (lout) of the DC-DC converter; comparing, by the efficiency controller, the calculated efficiency (T|T+I) with the calculated efficiency (T|T) of the auxiliary system; and increasing, by the efficiency controller, output current (lout) when the calculated efficiency (T|T+I) is more than the calculated efficiency (T|T) of the auxiliary system.
[0015] In an aspect, the method includes calculating, by the efficiency controller, losses of the low voltage system by combining losses of the DC-DC converter and losses of the auxiliary battery.
[0016] In an aspect, the method includes decreasing, by the efficiency controller, output current (lout) by a predefined unit of the DC-DC converter when the calculated efficiency (T|T+I) is less than calculated efficiency (T|T) of the low voltage system.
[0017] In an aspect, the method includes comparing, by the efficiency controller, the calculated efficiency (T|T+I) at decreased current with the calculated efficiency (T|T) of the low voltage system and decreasing, by the efficiency controller, output current (lout) by a predefined unit of the DC-DC converter when the calculated efficiency (T|T+I) is more than calculated efficiency (T|T) of the low voltage system.
[0018] In an aspect, the method includes charging, by the VCU, the auxiliary battery when state of charge (SOC) of the auxiliary battery is less than threshold value of the state of charge (SOCth).
[0019] In an aspect, the method includes calculating, by the efficiency controller, efficiency (T|T) of the low voltage system when the auxiliary battery is in charging mode and receiving power from the DC-DC converter.
[0020] In an aspect, the method includes controlling, by the VCU, auxiliary loads when current output from the DC-DC converter is equal to highest predefined current (Wax) in order to achieve maximum efficiency of the overall system.

[0021] In another embodiment, the present subject matter relates to a vehicle controller unit (VCU) for improving overall efficiency of a low voltage system including a DC-DC converter and an auxiliary battery. The VCU comprising an efficiency controller including one or more processors coupled to a memory, and efficiency tracking unit. The efficiency controller is configured to calculate an efficiency (T|T) of the low voltage system and increase output current (lout) by a predefined unit of the DC-DC converter. The efficiency controller calculates an efficiency (T|T+I) of the low voltage system at increased output current (lout) and compare the calculated efficiency (T|T+I) of the low voltage system at increased output current (lout) with the efficiency (T|T). The efficiency controller increases the output current (lout) by a predefined unit of the DC-DC converter when the calculated efficiency (T|T+I) of the low voltage system at increased output current (lout) is more than the efficiency (T|T).
[0022] In an aspect, the VCU turns ON the DC-DC converter when required current load (Load) is more than a predefined current threshold (Ith) or state of charge (SOC) of the auxiliary battery (105) is less than predefined threshold SOC value (SOCth).
[0023] In an aspect, the efficiency controller decreases output current by a predefined unit of the DC-DC converter when the calculated efficiency (r|) of the low voltage system is more than predefined threshold efficiency (r|Th).
[0024] In an aspect, the efficiency controller compares the calculated efficiency (T|T+I) at decreased current with the calculated efficiency (T|T) of the low voltage system and decreases output current (lout) by a predefined unit of the DC-DC converter when the calculated efficiency (T|T+I) is more than calculated efficiency (T|T) of the low voltage system.
[0025] In an aspect, the efficiency controller calculates losses of the low voltage system by combining losses of the DC-DC converter and losses of the auxiliary battery.

[0026] In an aspect, the VCU charges the auxiliary battery when state of charge (SOC) of the auxiliary battery is less than threshold value of the state of charge (SOCth).
[0027] In an aspect, the efficiency controller calculates efficiency (r|) of the low voltage system when the auxiliary battery is in charging mode and receiving power from the DC-DC converter.
[0028] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0029] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0030] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0032] Fig. 1 illustrates an exemplary architecture of electric vehicle, in accordance with an embodiment of the present disclosure;

[0033] Fig. 2 illustrate the exemplary structure of a Vehicle Control Unit to achieve maximum efficiency of a low voltage system, in accordance with an embodiment of the present disclosure;
[0034] Fig. 3 illustrates efficiency graph of DC-DC converter and auxiliary battery with respect to output current, in accordance with an embodiment of the present disclosure;
[0035] Fig. 4 illustrates a method implemented in the VCU for operating DC-DC converter and auxiliary battery, in accordance with an embodiment of the present subject matter; and
[0036] Fig. 5 illustrates a method implemented in the VCU for obtaining maximum efficiency of low voltage system, in accordance with an embodiment of the present disclosure.
[0037] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in a computer-readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.
DETAILED DESCRIPTION
[0038] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.

[0039] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0041] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0043] Embodiments and/or implementations described herein relate to methods and systems of communication among communication devices over a common control network during reconfiguration of the communication devices.

[0044] Non-limiting Definitions
[0045] In the disclosure hereinafter, one or more terms are used to describe various aspects of the present disclosure. For a better understanding of the present disclosure, a few definitions are provided herein for better understanding of the present disclosure.
[0046] Vehicle Control Unit (VCU): A system which is any electronic system that manages a traction battery pack and based on load requirement draw current from the traction battery pack. The VCU manages all requirements from motor and other auxiliary loads.
[0047] Direct Current (DC)-Direct Current (DC) converter: A DC-DC
converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter.
[0048] Auxiliary Battery: It is a low voltage (voltage in between 7V to 24V) battery of any type such as VRLA, Li-ion, super capacitors, lead acid etc.
[0049] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0050] Technical objective of the present subject matter is to improve overall efficiency of low voltage system including a DC-DC converter and an auxiliary battery by minimizing overall losses of the low voltage system.
[0051] Reference is made to Fig. 1 which schematically shows an architecture of an electric vehicle in accordance with an embodiment of the present disclosure. The electric vehicle comprises a traction battery pack 100, a junction box 101, an inverter 102, a motor 103, a DC-DC converter 104, an auxiliary source or auxiliary battery 105, a plurality of auxiliary loads 106 and a Vehicle control unit

(VCU) 200. The traction battery 100 supplies high voltage to the inverter 102 through the junction box 101. The inverter 102 is provided to convert Direct Current (DC) to Alternating Current (AC) while provide current to motor 103 for traction and convert Alternating Current (AC) to Direct Current (DC) while charging of the traction battery pack 100. The VCU 200 controls complete system of the electric vehicle relating to charging, discharging, safety controls, and traction of vehicle by supplying required high voltage to the motor 103. The motor 103 is further coupled with a transmission system or drive train or power train for traction of the vehicle. The DC-DC converter 104 is coupled with the traction battery pack 100 through the junction box 101.
[0052] The DC-DC converter 104 supplies power to the plurality of auxiliary loads 106, for example, headlamps, cabin lights, infotainment system, indicators, wipers, sound alert system, door locking system, auxiliary device charging. All these auxiliary loads require low voltage power therefore the DC-DC converter 104 converts the high voltage, for example, more than 60V of the traction battery pack 100 into a low voltage, for example in range 7V to 24V. Further, working of DC-DC converter 104 is well known to a person skilled in the art therefore, detailed explanation of working of the DC-DC converter 104 is avoided. The DC-DC converter 104 is further coupled with the auxiliary battery 105. The auxiliary battery 105 receives low voltage power from the DC-DC converter 104 to charge up.
[0053] Referring to Fig. 3 showing efficiency graph between the output current and the DC-DC converter and auxiliary battery. As illustrated, the DC-DC converter 104 has poor efficiency at low output current and good efficiency at high output current requirements. Where the auxiliary battery 105 has good efficiency at low output current and poor efficiency at high output current. After a threshold value of output current (Ith), the DC-DC converter 104 shows good efficiency and the auxiliary battery 105 shows poor efficiency. Therefore, in the present embodiment, switching between the DC-DC converter 104 and the auxiliary battery 105 happens at the threshold value of output current (Ith).

[0054] Referring to Fig. 2, the VCU 200 comprises an efficiency controller 208 for improving efficiency of the low voltage system 107 including the DC-DC converter 104 and the auxiliary battery 105. The VCU 200 controls switching ON and OFF of the DC-DC controller 104.
[0055] The VCU 200 includes a processor(s) 202, an interface(s) 204, and a memory 206.
[0056] The processor(s) 202 may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, logic circuitries, and/or any devices that manipulate data based on operational instructions.
[0057] Among other capabilities, the one or more processor(s) 202 are configured to fetch and execute computer-readable instructions and one or more routines stored in the memory 206. The memory 206 may store one or more computer-readable instructions or routines, which may be fetched and executed to implement maintain maximum efficiency of the low voltage system 107. The memory 206 may include any non-transitory storage device including, for example, volatile memory such as RAM, or non-volatile memory such as EPROM, flash memory, and the like.
[0058] The interface(s) 204 may include a variety of interfaces, for example, interfaces for data input and output devices referred to as I/O devices, storage devices, and the like. The interface(s) 204 may facilitate communication of the VCU 200 and an efficiency controller 208 with various devices coupled to the VCU 200. The interface(s) 204 may also provide a communication pathway for one or more components of the VCU 200. Examples of such components include, but are not limited to, an efficiency controller 208 and data 210.
[0059] The efficiency controller 208 may be implemented as a combination of hardware and programming (for example, programmable instructions) to implement one or more functionalities of the efficiency controller 208. In examples described herein, such combinations of hardware and programming may

be implemented in several different ways. For example, the programming for the efficiency controller 208 may be processor-executable instructions stored on a non-transitory machine-readable storage medium and the hardware for the efficiency controller 208 may include a processing resource (for example, one or more processors), to execute such instructions. In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, implement the efficiency controller 208. In such examples, the VCU 200 may include the machine-readable storage medium storing the instructions and the processing resource to execute the instructions or the machine-readable storage medium may be separate but accessible to the VCU 200 and the processing resource. In other examples, the efficiency controller 208 may be implemented by electronic circuitry. In another embodiment, the efficiency controller 208 may be implemented as a standalone device as micro¬controller having all instructions stored in a memory or look-up tables coupled with the low voltage system 107 to improve efficiency.
[0060] The efficiency controller 208 may include other unit(s) which may implement functionalities that supplement applications or functions performed by the VCU 200 or the processing unit(s) 202.
[0061] Further, the data 210 may include data that is either stored or generated as a result of functionalities implemented by any of the components of the efficiency controller 208. In some aspects, the data 210 may be stored in the memory 206 in the form of various data structures, for example, look-up tables. Additionally, data 210 can be organized using data models, such as relational or hierarchical data models. The data 210 may store data, including temporary data and temporary files, generated by the efficiency controller 208 for performing the various functions of the VCU 200.
[0062] In operation, the efficiency controller 208 compares state of charge (SOC) of the auxiliary battery 105 with a predefined threshold value of SOC (SOCth) as stored in the memory 206. When the SOC of the auxiliary battery 105 is more than the predefined threshold value (SOCth), the efficiency controller 208

compares current requirement (Iioad) from the plurality of auxiliary loads 106 with the predefined threshold value of current requirement (Ith) as stored in the memory 206. The threshold values may be stored in the look-up tables or any other predefined data structure in the memory 206 for efficient execution. When the current requirement (Iioad) is less than the predefined threshold value of current requirement (Ith), the efficiency controller 208 keeps the DC-DC converter 104 in OFF mode and supplies required power from the auxiliary battery 105 to the plurality of auxiliary loads 106.
[0063] When the SOC of the auxiliary battery 105 is less than the predefined threshold value (SOCth), the efficiency controller 208 turn ON the DC-DC converter 104 to charge the auxiliary battery 105 along with supplying power to the plurality of auxiliary loads 106.
[0064] When the DC-DC controller 104 is running to convert high voltage to low voltage for charging the auxiliary battery 105, or supplying power to the plurality of auxiliary loads 106 or charging the auxiliary battery and supplying power to the plurality of auxiliary loads 106 both, the efficiency controller 208 calculates efficiency of the low voltage system 107.
[0065] To calculate the efficiency of the low voltage system 107, the efficiency controller 208 calculates energy losses in the DC-DC converter 104 by using inputs and output electrical parameters and energy losses in the auxiliary battery 105. The efficiency controller 208 calculates energy losses in the DC-DC converter 104 using below mentioned in equation 1.
DC-DC power loss = input power - output power
DC-DC energy loss = DC-DC power loss * time (e.g. lOsec)
Input power = input voltage * input current
Output power = output voltage * output current
For example, input voltage = 300V, input current = 5A, output voltage = 15V, output current = 90A

Power Loss = (300*5) - (15*90) = 1500 - 1350 = 150W
Energy loss in 10 sec = 150W * 10s = 1500Ws
[0066] The efficiency controller 208 calculates energy losses of the auxiliary battery 105 using current and internal losses as values in equation 2.
P = I2R
Where I is current of auxiliary battery and R is internal resistance of the auxiliary battery 105.
For example, I = 50A and R = lOmQ.
Power loss = 50*50*0.01 = 25W
Energy loss in 10 sec = 25W * 10s = 250Ws
[0067] Upon calculating energy losses of the DC-DC converter 104 and the auxiliary battery 105, the efficiency controller 208 calculates losses of the low voltage system 107 by adding energy losses of the DC-DC converter 104 and the auxiliary battery 105 using equation 3.
Total losses of the Low voltage system ratio = {(losses in DC-DC converter) + (losses in auxiliary battery)}/ total energy supplied to auxiliary load
Total energy supplied to auxiliary load = auxiliary voltage * Load current *Time (10 sec)
Energy supplied to auxiliary load = 15 * 90* 10s = 13500Ws equation 4
Total energy loss = 1500Ws + 250Ws = 1750Ws, So, Total losses of the low voltage system ratio = 1750Ws/ 13500Ws = 0.13
[0068] The efficiency controller 208 calculates efficiency of the low voltage system 107 using the total losses in the low voltage system 107 using equation 5.
T|T = 1 - Total losses of the Low voltage system ratio equation 5
T|T= 1-0.13 =0.87

[0069] The efficiency controller 208 increases the output current (lout) from the DC-DC converter 104 by a predefined unit as stored in the memory. For example, the output current (lout) is increased by 1A. The efficiency controller 208 calculates the efficiency (T|T+I) of the low voltage system 107 at the increased output current (Lut+IA).
[0070] Upon calculating the efficiency (T|T+I) at increased output current, the efficiency controller 208 compares the calculated efficiency (T|T+I) with previously calculated efficiency (T|T). If the efficiency (T|T+I) is more than the calculated efficiency (T|T), the efficiency controller 208 keeps on increasing the output current (lout) with the predefined unit to keep the efficiency (T|T) of the low voltage system 107 at maximum level.
[0071] When load current is more than the Ith and less than current value at which DC-DC converter is at maximum efficiency. At that point, by increasing the DC-DC current beyond the load current start charging the battery with low current. So, DC-DC converter achieves better efficiency with a minimal loss in battery due to low current.
[0072] When the calculated efficiency (T|T+I) is less than the previously calculated efficiency (T|T) of the low voltage system 107, the efficiency controller 208 decreases the output current (lout) by a predefined unit as stored in the memory. For example, the predefined unit is 1A. The efficiency controller 208 calculates the efficiency (T|T+I) of the low voltage system 107 at the decreased output current (lout -1A).
[0073] Upon calculating the efficiency (T|T+I) at decreased output current, the efficiency controller 208 compares the calculated efficiency (T|T+I) with previously calculated efficiency (T|T). If the efficiency (T|T+I) is more than the calculated efficiency (T|T), the efficiency controller 208 keeps on decreasing the output current (lout) with the predefined unit to keep the efficiency (T|T) of the low voltage system 107 at maximum level in all situations.

[0074] When load current is more than current value at which DC-DC converter is at maximum efficiency. At that point, by decreasing the DC-DC current below the load current starts discharging the battery with low current. So, DC-DC converter achieves better efficiency with a minimal loss in battery due to low current.
[0075] In the present embodiment, the efficiency (T|T) of the low voltage system 107 is dynamic which keeps on changing based on the conditions and load requirement of the plurality of auxiliary loads 106.
[0076] Fig. 4 illustrates a method implemented in the VCU 200 for operating DC-DC converter 104 and auxiliary battery 105 in the low voltage system 107, in accordance with an embodiment of the present subject matter. The order in which the method 400 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any appropriate order to carry out the method 400 or an alternative method. Additionally, individual blocks may be deleted from the method 400 without departing from the scope of the subject matter described herein.
[0077] At step 401, the method 400 includes comparing state of charge (SOC) of the auxiliary battery 105 with threshold value of the state of charge (SOCth) of the auxiliary battery 105. When the SOC of the auxiliary battery 105 is more than the predefined threshold value of the state of charge (SOCth), the method proceeds to step 403. When the SOC of the auxiliary battery 105 is less than the predefined threshold value of the state of charge (SOCth), the method proceeds to step 402.
[0078] At step 402, the method 400 includes turning ON the DC-DC converter 104 by the VCU 200 to supply power to the plurality of auxiliary loads or both the plurality of auxiliary loads and auxiliary battery.
[0079] At step 403, the method includes comparing the current requirement (Iioad) of the plurality of auxiliary loads 106 with predefined threshold value of the current (Ith). When the current requirement (Iioad) of the plurality of auxiliary loads

106 is more than predefined threshold value of the current (Ith), the method 400 proceeds to step 405. When the current requirement (Iioad) of the plurality of auxiliary loads 106 is less than predefined threshold value of the current (Ith), the method 400 proceeds to step 404.
[0080] At step 404, the method 400 includes turning OFF the DC-DC converter 104 by the VCU 200.
[0081] At step 405, the method 400 includes turning ON the DC-DC converter 104 by the VCU 200 to supply power to the plurality of auxiliary loads or both the plurality of auxiliary loads and auxiliary battery.
[0082] At step 406, the method 400 includes calculating efficiency of the low voltage system 107.
[0083] At step 407, the method 400 includes supplying power to the auxiliary battery 105 from the DC-DC converter 104.
[0084] At step 408, the method 400 includes determining whether the auxiliary battery 105 is in charging mode or not. When the auxiliary battery is in charging mode, the method proceeds to step 409 to calculate the efficiency of the low voltage system 107. When the auxiliary battery 107 is not in charging mode, the method proceeds to step 410.
[0085] At step 410, the method 400 includes determining whether the DC-DC converter 104 is generating maximum current or not. When the DC-DC converter 104 is generating maximum current, the method proceeds to step 411. When the DC-DC converter is not generating maximum current, the method proceeds to back to step 407 to keep the auxiliary battery in charging mode by varying the output voltage of DC-DC converter.
[0086] At step 411, the method 400 includes controlling the plurality of auxiliary loads. Any one of the plurality of auxiliary loads is switched OFF or allowed to run in low performance mode to reduce output current requirement load on the DC-DC converter 104.

[0087] Fig. 5 illustrates a method implemented in the VCU for obtaining maximum efficiency of low voltage system, in accordance with an embodiment of the present disclosure. Further, the VCU 200 activates the efficiency controller 208 to track the efficiency of the low voltage system only when the DC-DC converter 104 is ON mode.
[0088] At step 501, the method 500 includes calculating losses of DC-DC converter 104 by using inputs and output electrical parameters of the DC-DC converter 104. The losses of the DC-DC converter are calculated only when the DC-DC converter is in ON Mode.
[0089] At step 502, the method includes calculating losses of the auxiliary battery 105 by using current and internal resistance. The losses of the auxiliary battery 105 are calculated only when the DC-DC converter is in ON Mode.
[0090] At step 503, the method includes calculating the low voltage system losses ratio by adding losses of the DC-DC converter 104 and losses of the auxiliary battery 105 and dividing by total energy supplied to the plurality of auxiliary loads 106 or both, auxiliary loads 106 and auxiliary source 105.
[0091] At step 504, the method includes calculating the low voltage system efficiency by subtracting the low voltage system losses ratio from 1.
[0092] At step 505, the method includes increasing output current (lout) from the DC-DC converter 104 by a predefined unit as stored in the memory. For example, the output current (lout) is increased by 1A. The efficiency controller 208 calculates the efficiency (T|T+I) of the low voltage system 107 at the increased output current (Lut+IA).
[0093] At step 506, the method includes calculating the efficiency (T|T+I) at increased output current. The efficiency controller 208 compares the calculated efficiency (T|T+I) with previously calculated efficiency (T|T). If the efficiency (T|T+I) is more than the calculated efficiency (T|T), the efficiency controller 208 keeps on increasing the output current (lout) with the predefined unit to keep the efficiency (T|T) of the low voltage system 107 at maximum level.

[0094] At step 507, the method includes decreasing the output current (lout) by a predefined unit as stored in the memory when the calculated efficiency (T|T+I) is less than the previously calculated efficiency (T|T) of the low voltage system 107. For example, the predefined unit is 1A. The efficiency controller 208 calculates the efficiency (T|T+I) of the low voltage system 107 at the decreased output current
(lout -1A).
[0095] At step 508, the method includes comparing the calculated efficiency (T|T+I) with previously calculated efficiency (T|T) upon calculating the efficiency (T|T+I) at decreased output current. If the efficiency (T|T+I) is more than the calculated efficiency (T|T), the efficiency controller 208 keeps on decreasing the output current (lout) with the predefined unit to keep the efficiency (T|T) of the low voltage system 107 at maximum level in all situations.
[0096] The above description does not provide specific details of the manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art can choose suitable manufacturing and design details.
[0097] It should be understood, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as apparent from the discussion herein, it is appreciated that throughout the description, discussions utilizing terms such as "receiving," or "setting," or "transmitting," or the like, refer to the action and processes of an electronic control unit, or similar electronic device, that manipulates and transforms data represented as physical (electronic) quantities within the control unit's registers and memories into other data similarly represented as physical quantities within the control unit memories or registers or other such information storage, transmission or display devices.
[0098] Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It

will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0099] It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
[00100] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

We claim:

1. A method (400, 500) for improving overall efficiency of a low voltage
system (107) including a direct current (DC) to direct current (DC)
converter (104) and an auxiliary battery (105), the method (500)
comprising:
turning ON (402, 404), by vehicle control unit (VCU) (300), the DC-DC converter (104) when required current load (Iioad) is more than a predefined current threshold (Ith) and state of charge (SOC) of the auxiliary battery (105) is less than predefined threshold SOC value (SOCth);
calculating (409, 504), by an efficiency controller (208), efficiency (T|T) of the low voltage system (107);
increasing (505), by the efficiency controller (208), output current (lout) by a predefined unit of the DC-DC converter (104);
calculating (505), by the efficiency controller (208), efficiency (T|T+I) at increased current output current (lout) of the DC-DC converter (104);
comparing (506), by the efficiency controller (208), the calculated efficiency (T|T+I) with the calculated efficiency (T|T) of the low voltage system (107); and
increasing (505), by the efficiency controller (208), output current (lout) when the calculated efficiency (T|T+I) is more than the calculated efficiency (T|T) of the low voltage system (107).
2. The method (400, 500) as claimed in claim 1, wherein the method (400,
500) comprise:
calculating (503), by the efficiency controller (300), losses of the low voltage system (107) by combining losses of the DC-DC converter (104) and losses of the auxiliary battery (105).
3. The method (400, 500) as claimed in claim 1, wherein the method (400,
500) comprises:
decreasing (507), by the efficiency controller (208), output current (lout) by a predefined unit of the DC-DC converter (104) when the

calculated efficiency (T|T+I) is less than calculated efficiency (T|T) of the low voltage system (107).
4. The method (400, 500) as claimed in claim 3, wherein the method (400,
500) comprises:
comparing (508), by the efficiency controller (208), the calculated efficiency (T|T+I) at decreased current with the calculated efficiency (T|T) of the low voltage system (107);
decreasing (507), by the efficiency controller (208), output current (lout) by a predefined unit of the DC-DC converter (104) when the calculated efficiency (T|T+I) is more than calculated efficiency (T|T) of the low voltage system (107).
5. The method (400, 500) as claimed in claim 1, wherein the method (400,
500) comprises:
charging (407), by the VCU (300), the auxiliary battery (105) when state of charge (SOC) of the auxiliary battery (105) is less than threshold value of the state of charge (SOCth).
6. The method (400, 500) as claimed in claim 1, wherein the method
comprises:
calculating (409, 504), by the efficiency controller (208), efficiency (T|T) of the low voltage system (107) when the auxiliary battery (105) is in charging mode and receiving power from the DC-DC converter (104).
7. The method (400, 500) as claimed in claim 1, wherein the method (400,
500) comprises:
controlling (411), by the VCU (300), auxiliary loads when current output from the DC-DC converter (104) is equal to highest predefined current (Imax).
8. A vehicle controller unit (VCU) (200) for improving overall efficiency of
a low voltage system (107) including a DC-DC converter (104) and an auxiliary
battery (105), the VCU (200) comprising:

one or more processors (202) coupled to a memory (206), and an efficiency controller (208), the efficiency controller (208) is to:
calculate an efficiency (T|T) of the low voltage system (107);
increase output current (lout) by a predefined unit of the DC-DC converter (104);
calculate an efficiency (T|T+I) of the low voltage system (107) at increased output current (lout);
compare the calculated efficiency (T|T+I) of the low voltage system (107) at increased output current (lout) with the efficiency (T|T); and
increase the output current (lout) by a predefined unit of the DC-DC converter (104) when the calculated efficiency (T|T+I) of the low voltage system (107) at increased output current (lout) is more than the efficiency (T|T).
9. The vehicle controller unit (VCU) (200) as claimed in claim 8, wherein the VCU (200) turns ON the DC-DC converter (104) when required current load (Iioad) is more than a predefined current threshold (Ith) and state of charge (SOC) of the auxiliary battery (105) is less than predefined threshold SOC value (SOCth).
10. The VCU (200) as claimed in claim 8, wherein the efficiency controller (208) decrease output current by a predefined unit of the DC-DC converter (104) when the calculated efficiency (r|) of the low voltage system (107) is more than predefined threshold efficiency (r|Th).
11. The VCU (200) as claimed in claim 10, wherein the efficiency controller (208):
compares the calculated efficiency (T|T+I) at decreased current with the calculated efficiency (T|T) of the low voltage system (107); and
decreases output current (lout) by a predefined unit of the DC-DC converter (104) when the calculated efficiency (T|T+I) is more than calculated efficiency (T|T) of the low voltage system (107).

12. The VCU (200) as claimed in claim 8, wherein the efficiency controller (208) calculates losses of the low voltage system (107) by combining losses of the DC-DC converter (104) and losses of the auxiliary battery (105).
13. The VCU (200) as claimed in claim 8, wherein the VCU (208) is to:
charge the auxiliary battery (105) when state of charge (SOC) of the auxiliary battery (105) is less than threshold value of the state of charge (SOCth).
14. The VCU (200) as claimed in claim 8, wherein the efficiency controller
(208) is to:
calculate efficiency (T|T) of the low voltage system (107) when the auxiliary battery (105) is in charging mode and receiving power from the DC-DC converter (104).