A fail-safe power supply system for auxiliary devices in electric vehicles and method therefor

Abstract

The present disclosure provides a fail-safe power delivery system (202) and a corresponding method for safely supplying power to auxiliary devices in electric vehicles. In particular, the disclosed fail-safe power delivery system (202) starts a DC-DC converter (110, 214, 322) via a charging start by at least one supercapacitor (330). Furthermore, the proposed fail-safe power delivery system (202) connects the load (i.e., the auxiliary device) to the DC-DC converter (110, 214, 322) as soon as the DC-DC converter (110, 214, 322) is ready to supply power to the load, thereby ensuring voltage regulation of the DC-DC converter (110, 214, 322) under all load conditions.

Description

The present invention relates generally to supplying power to auxiliary devices in an electric vehicle, and more particularly, the present invention relates to implementing charge start techniques that ensure voltage regulation during power supply to auxiliary devices via a DC-DC converter.The following description includes information that may be helpful in understanding the present invention. This does not represent an admission that the information provided herein belongs to the prior art or is relevant to the invention claimed herein, or that an explicit or implicit publication belongs to the prior art.In vans and cars that have a device for establishing a vehicle body builder's energy interface, such as a 400V or 12V supply, to power auxiliary devices such as cooling systems or electrical equipment or additional HVAC systems, the power launch mechanism is traditionally designed to draw power directly from the transmission via a dynamo system. However, with the progress in automobile technology, such small-sized transporters and cars are increasingly electrically operated, and therefore, the charge start mechanism has also switched from mechanical to electrical by the use of a low-voltage battery (LV battery) and a DC-DC converter that can supply the auxiliary devices with the required voltage.However, the low voltage battery to be installed in the electric vehicles is heavy, causes high packaging costs, and requires periodic maintenance, and for this reason, the power supply of auxiliary devices through the low voltage battery and the DC / DC converter is not advisable.Further, the traditionally employed charge start mechanism for the DC-DC converter has various disadvantages. For example, DC-DC converters typically have an LLC (Inductor-Inductor-Capacitor) configuration for voltage-less switching (ZVS), and such an LLC configuration provides inefficient voltage regulation, particularly in open-circuit states, because in LLC-type circuits, a certain amount of power (corresponding to the low-voltage battery voltage) is always required to charge the inductors and the capacitor, and therefore the DC-DC converter switches to burst mode, i.e., the circuit is temporarily disabled, particularly in open-circuit states or in low-load states.There are certain solutions in the prior art that aim to start the DC-DC converter circuit. One of these solutions is described in CN112542944A (hereinafter referred to as '944 publication).The '944 publication discloses a method and apparatus for starting a DC-DC circuit with the aim of overcoming the disadvantages that arise in overcoming the over-current problem in the DC-DC circuit by using additional charging devices. In particular, the '944 publication discloses a DC-DC circuit that includes a boost module. The boost module includes a first backup capacitor (C 1) and a second backup capacitor (C 2), and is electrically connected to a storage battery pack via a contactor (K). The starting method of the DC-DC circuit includes the steps of: in response to the voltage value of the second back-up capacitor (C 2) being less than a second preset voltage value, closing the contactor (K) to cause the battery pack to charge the second back-up capacitor (C 2); in response to the voltage value of the second back-up capacitor (C 2) being greater than or equal to the second preset voltage value and the voltage value of the first back-up capacitor (C 1) being less than a first preset voltage value, starting a step-down mode of the boost module to allow the battery pack to charge the first back-up capacitor (C 1) by the second back-up capacitor (C 2). In response to the voltage value of the first back-up capacitor (C 1) being equal to or higher than the first preset voltage value, the contactor (K) is opened and an open start is performed.However, the '944 publication also uses additional storage battery packs to implement the switching between the boost mode and the buck mode of the DC-DC circuit.Therefore, there is a need for a system that overcomes the above-mentioned limitations and provides an efficient and safe charge start mechanism for the DC-DC converter.The present disclosure overcomes one or more shortcomings of the prior art and provides additional advantages. Embodiments and aspects of the disclosure described in detail herein are considered part of the claimed disclosure.In a non-limiting embodiment of the present disclosure, a fail-safe power supply system for auxiliary devices in electric vehicles is disclosed. The system includes a primary power network including at least one ignition switch. The system further includes a secondary power network including a DC-DC converter connected to at least one auxiliary device via a second relay. The system further includes a fail-safe unit including at least one supercapacitor connected to the primary power network via a first relay and to the secondary power network via a disconnect unit, and a control unit operatively coupled to the fail-safe unit, the primary power network, and the secondary power network. In an embodiment, the control unit is configured to receive a signal for supplying power to the at least one auxiliary device. The controller is further configured to charge the at least one supercapacitor to a predefined level. The controller is further configured to discharge the at least one supercapacitor and simultaneously charge an output capacitor associated with the DC-DC converter using the discharge current from the at least one supercapacitor to enable the DC-DC converter to transition to the buck mode. Moreover, the control unit is configured to allow the DC-DC converter to securely supply power to the at least one auxiliary device once the DC-DC converter has entered the buck mode.In a further non-limiting embodiment of the present disclosure, the isolation unit connecting the fail-safe unit to the secondary power network includes at least: a fuse connected to an output end of the fail-safe unit, and a diode pair connected to an output end of the fuse. In one aspect, the fuse and diode pair are configured to prevent current flow from the secondary power grid to the primary power grid while supplying power to the at least one auxiliary device.In a further non-limiting embodiment of the present disclosure, the controller is further configured to close the first relay to charge the at least one supercapacitor using the primary power grid, and simultaneously open the second relay to disconnect the at least one auxiliary device from the at least one supercapacitor while charging the at least one supercapacitor.In a still further non-limiting embodiment of the present disclosure, the controller is further configured to open the first relay while the second relay is maintained in the open state during charging of the output capacitor to disconnect the primary power network from the secondary power network.In a still further non-limiting embodiment of the present disclosure, the controller is further configured to close the second relay while maintaining the first relay in the open state to allow the DC-DC converter to supply power to the at least one auxiliary device once the DC-DC converter has entered the buck mode.In a yet further non-limiting embodiment of the present disclosure, a method for securely supplying power to auxiliary devices in electric vehicles is disclosed. The method includes receiving a signal to supply power to the at least one auxiliary device. The method further comprises charging at least one supercapacitor of a fail-safe unit to a predefined level. Further, the method includes discharging the at least one supercapacitor and simultaneously charging an output capacitor associated with a DC-DC converter using the discharge current from the at least one supercapacitor to enable the DC-DC converter to transition to the buck mode. The method further includes allowing the DC-DC converter to safely supply power to the at least one auxiliary device once the DC-DC converter has entered the buck mode.In a yet further non-limiting embodiment of the present disclosure, the method further comprises closing a first relay to charge the at least one supercapacitor using the primary power grid, and simultaneously opening a second relay to disconnect the at least one auxiliary device from the at least one supercapacitor while charging the at least one supercapacitor.In a still further non-limiting embodiment of the present disclosure, the method further comprises opening the first relay while maintaining the second relay in the open state during charging of the output capacitor to disconnect the primary power network from a secondary power network.In a still further non-limiting embodiment of the present disclosure, the method further comprises closing the second relay while maintaining the first relay in the open state to allow the DC-DC converter to supply power to the at least one auxiliary device once the DC-DC converter has entered the buck mode.The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, other aspects, embodiments and features will become apparent by reference to the drawings and the following detailed description.The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below, taken in conjunction with the drawings, in which like reference numerals identify corresponding ones throughout. Some embodiments of the system and / or the methods according to embodiments of the present subject matter will now be described, by way of example only, and with reference to the accompanying figures, in which: FIG. 1 illustrates, by way of a block diagram, an example environment 100 for securely supplying power to auxiliary devices in an electric vehicle, in accordance with an embodiment of the present disclosure, FIG. 2 illustrates a block diagram 200 of a fail-safe power supply system for supplying power to auxiliary devices in an electric vehicle according to an embodiment of the present disclosure, FIG. 3 illustrates, by way of a circuit diagram 300, the arrangement of various components for securely supplying power to auxiliary devices in an electric vehicle according to an embodiment of the present disclosure; and FIG. 4 illustrates, via a flow chart, an example method 400 for securely supplying power to auxiliary devices in an electric vehicle, in accordance with an embodiment of the present disclosure.It should be appreciated by those skilled in the art that all block diagrams included herein represent conceptual views of exemplary systems embodying the principles of the present subject matter. It will also be understood that all flowcharts, flowcharts, state transition diagrams, pseudo code, and the like represent various processes that may be substantially embodied on a computer readable medium and executed by a computer or processor, whether or not that computer or processor is explicitly shown.In the foregoing, the features and technical advantages of the present disclosure have been generally outlined in order to better understand the following detailed description of the disclosure. It will be understood by those skilled in the art that the disclosed concept and specific embodiment may be readily utilized as a basis for modifying or designing other structures to achieve the same purposes of the present disclosure.The novel features believed characteristic of the disclosure, both as to organization and function, and other objects and advantages will be better understood from the following description when taken in conjunction with the accompanying drawings. It is expressly understood, however, that the individual figures are for purposes of illustration and description only and are not intended to define the limits of the present disclosure.With advances in automobile technology, vans and cars that are increasingly electrically operated via a device for establishing a power interface of the body builder, such as a 400 V or 12 V supply, for supplying power to auxiliary devices such as cooling systems, the power to such auxiliary devices is generally provided by a low voltage battery (LV battery) and a DC / DC converter. However, the low voltage battery to be installed in electric vehicles is heavy, causes high packaging cost, and requires periodic maintenance, and thus the power supply to auxiliary devices through the low voltage battery and the DC / DC converter is not advisable. Further, the traditionally employed charge start mechanism for the DC-DC converter suffers from poor voltage regulation, particularly during open-circuit conditions, i.e. when no auxiliary device is connected to the DC-DC converter.To overcome the above-mentioned challenges, the present disclosure provides a fail-safe power supply system and method for securely supplying power to auxiliary devices in electric vehicles. In particular, the disclosed fail-safe power supply system starts the DC-DC converter via a charge start by at least one supercapacitor. Further, the proposed fail-safe power supply system connects the load (i.e., the auxiliary device) to the DC-DC converter when the DC-DC converter is ready to supply power to the loads, and thus ensures the voltage regulation of the DC-DC converter under all load conditions. A detailed description of the proposed solution is provided in the following paragraphs.FIG. 1 is a block diagram of an example environment 100 for securely supplying power to auxiliary devices in an electric vehicle according to an embodiment of the present disclosure. Those skilled in the art will appreciate that the terms "load" and "auxiliary device(s)" are used interchangeably in the specification. The example environment 100 shows a primary power network 102 connected to a fail-safe unit 104 via a first relay 114. The fail-safe unit 104 is connected to a secondary power network 108 via a disconnect unit 108. The secondary power network 108 comprises at least one DC-DC converter 110 connected to an auxiliary device 112 via a second relay 116.In an exemplary embodiment, the primary power network 102 may include at least one ignition switch, a plurality of sensors, and a plurality of electronic control units (ECUs) configured to control operation of the electric vehicle. For example, the primary power network 102 may include an Advanced Driver Assistance (ADA) system, an internal HVAC system, etc. Further, in an exemplary embodiment, the fail-safe unit 104 may include at least one supercapacitor. However, those skilled in the art will appreciate that fail-safe unit 104 may include additional components such as a booster module (not shown). Further, the isolation unit 106 connecting the fail-safe unit 104 to the secondary power network 108 may include at least one fuse and a diode pair to provide additional safety by preventing transient currents from flowing from the secondary power network 108 to the primary power network 102. A detailed explanation of the operation of the individual components mentioned above will be discussed in the following sections in connection with FIGS. 2 and 3.FIG. 2 shows a block diagram 200 of a fail-safe power supply system for supplying power to auxiliary devices in an electric vehicle according to an embodiment of the present disclosure. A fail-safe power supply system 202, as shown in FIG. 2, includes a plurality of components 204 operatively coupled to a controller 218. The plurality of components 204 includes a primary power network 206 connected to a fail-safe unit 208 via a first relay 220. The fail-safe unit 208 is connected to a secondary power network 212 via a disconnect 210. The secondary power network 212 comprises at least one DC-DC converter 214 connected to an auxiliary device 216 via a second relay 222. Further, the isolation unit 210 connecting the fail-safe unit 208 to the secondary power network 212 may include at least one fuse and a diode pair to provide additional safety.In one embodiment, the controller 218 may further include at least one processor (not shown) implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitry, and / or any devices that manipulate signals based on operating instructions. Additionally, those skilled in the art will appreciate that the primary power network 206, the fail-safe unit 208, the isolation unit 210, the secondary power network 212, the DC-DC converter 214, the auxiliary device 216, the first relay 220, and the second relay 222 illustrated in FIG. 2 may be analogous to the primary power network 102, the fail-safe unit 104, the one or more components 106, the secondary power network 108, the DC-DC converter 110, the auxiliary device 112, the first relay 114, and the second relay 114, as illustrated in FIG. 1, respectively. The operation of the fail-safe power supply system 202 will be explained in the following paragraphs in conjunction with FIG. 3.In an example embodiment, the controller 218 may receive a signal to provide power to at least one auxiliary device 216 in the electric vehicle. In an exemplary aspect, the at least one auxiliary device 216 may be, but is not limited to, a cooling system, electrical equipment, or a high voltage air conditioning (HVAC) system. Upon receiving this signal, the controller 218 may close a first relay 306 shown in FIG. 3 and adjust a delay of a predefined time depending on the capacitance of the at least one supercapacitor 330 to charge at least one supercapacitor 330 of a fail-safe unit 308 to a predefined level. In an example embodiment, the at least one supercapacitor 330 may be charged using power from the primary power grid 206 through an ignition switch 304. Further, the controller 218 may simultaneously open a second relay 336 to disconnect the at least one auxiliary device 216 from at least one supercapacitor 330 while charging the at least one supercapacitor 330. In particular, by opening the second relay 336, the controller 218 may ensure that the at least one auxiliary device 320 is in an open state while the at least one supercapacitor 330 is being charged. In an example embodiment, power is not to flow from the at least one supercapacitor 330 to the secondary power network 212 until the at least one supercapacitor 330 is charged to the predefined level, thereby ensuring isolation between the primary power network 206 and the secondary power network 212. Further, in an exemplary aspect, the secondary power network 212 of FIG. 2 of FIG. 3 may include a battery 326 and the at least one auxiliary device 320 connected to the input and output ends of a DC-DC converter 322, respectively, which further includes an output capacitor 324. Further, those skilled in the art may also appreciate that the predefined level to which the at least one supercapacitor 330 may be charged may correspond to either a value equal to the full charge capacitance of the at least one supercapacitor 330 or a value less than the full charge capacitance of the at least one supercapacitor 330.Once the at least one supercapacitor 330 is charged to the predefined level, the controller 218 may open the first relay 306 while maintaining the second relay 336 in the open state, and then discharge the at least one supercapacitor 330 to charge the output capacitor 324, which is connected to the output end of the DC-DC converter 322, to allow the DC-DC converter 322 to transition to the buck mode. By allowing the output capacitor 324 to be charged via the at least one supercapacitor 330, the fail-safe power supply system 202 obviates the use of an additional low voltage battery traditionally used to charge such output capacitor and ultimately start the DC-DC converter. By maintaining the second relay 336 in an open state in an exemplary embodiment, the controller 218 may further ensure that the at least one auxiliary device 320 is not connected to the DC-DC converter 322 before entering the buck mode, thereby ensuring efficient voltage regulation. Further, by opening the first relay 306, the controller 218 may ensure that the primary power network 202 is completely disconnected from the secondary power network 212 while the at least one supercapacitor 330 is being discharged.To provide additional security to the primary power network 202, the fail-safe power supply system 202 further includes the isolation unit 210. Isolation unit 210 may include a fuse 312 connected to the output end of fail-safe unit 308 as shown in FIG. 3, and a diode pair 334 connected in series to the output of fuse 312. In an exemplary embodiment, the controller 218 may actuate the fuse 312 and the diode pair 334 to ensure that no return current flows from the secondary power grid 212 to the primary power grid 202.Once the DC-DC converter 322 has entered the buck mode, the controller 218 may close the second relay 336 to connect the at least one auxiliary device 320 to the DC-DC converter 322 such that the DC-DC converter 322 may supply power to the at least one auxiliary device 320. Further, at this time, the controller 218 may also maintain the primary relay 306 in the open state to maintain isolation between the primary power network 206 and the secondary power network 212.In further aspects of the invention, upon receiving a signal to stop power supply to the at least one auxiliary device 320, the controller 218 may shut down the at least one auxiliary device 320 by ensuring that a current flowing from the DC-DC converter 322 to the at least one auxiliary device 320 is less than a predefined value. Once the current is less than the predefined value, the controller 218 may open the second relay 336 to disconnect the at least one auxiliary device 320 from the DC-DC converter 322 and thus shut down the at least one auxiliary device 320.In this way, the fail-safe power delivery system 202 ensures that power is delivered to the at least one auxiliary device 320 in a safe manner while ensuring full galvanic isolation between the primary power grid 206 and the secondary power grid 212 as well as efficient voltage regulation by the DC-DC converter 322.FIG. 4 illustrates a flowchart of an example method 400 for securely supplying power to auxiliary devices in an electric vehicle, according to an embodiment of the present disclosure. The method 400 may also be described in the general context of computer-executable instructions. In general, computer-executable instructions may include routines, programs, objects, components, data structures, procedures, modules, and functions that perform particular functions or implement particular abstract data types.The order in which method 400 is described is not to be interpreted as limiting, and any number of the described method blocks may be combined in any order to implement the method. In addition, individual blocks may be removed from the methods without departing from the scope and spirit of the described subject matter.In step 402, the method 400 may include receiving a signal for supplying power to at least one auxiliary device 112, 216, 320. In one embodiment, the controller 218 may be used to receive the signal.In step 404, method 400 may include charging at least one supercapacitor 330 of a fail-safe unit 104, 208, 308 to a predefined level. In an exemplary embodiment, the controller 218 for charging the at least one supercapacitor 330 may close a first relay 306 shown in FIG. 3 and adjust a delay of a predefined time depending on the performance of the at least one supercapacitor 330. Further, the controller 218 may simultaneously open a second relay 336 to disconnect the at least one auxiliary device 112, 216, 320 from the at least one supercapacitor 330 while charging the at least one supercapacitor 330.In step 406, the method 400 may include discharging the at least one supercapacitor 330 and simultaneously charging an output capacitor 324 connected to the DC-DC converter 322 using the discharge current from the at least one supercapacitor 330 to enable the DC-DC converter 322 to transition to the buck mode. In an exemplary embodiment, to charge the output capacitor 324, the controller 218 may open the first relay 306 such that the primary power network 202 is fully isolated from the secondary power network 212 while the at least one supercapacitor is being discharged. The controller 218 may further maintain the second relay 336 in the open state to ensure that the at least one auxiliary device 320 is not connected to the DC-DC converter 322 before entering the buck mode.In step 408, the method 400 may include allowing the DC-DC converter 322 to safely supply power to the at least one auxiliary device 112, 216, 320 once the DC-DC converter 322 has entered the buck mode. In an exemplary embodiment, to supply power to the at least one auxiliary device 112, 216, 320, the controller 218 may close the second relay 336 to connect the at least one auxiliary device 320 to the DC-DC converter 322.The steps illustrated serve to explain the exemplary embodiments shown. It is to be understood that as technology advances, the manner in which certain functions are performed will change. These examples are provided herein by way of illustration and not limitation. Moreover, the boundaries of the functional building blocks have been arbitrarily defined herein for ease of description. Alternative boundaries may be defined as long as the specified functions and relationships thereof are appropriately performed.Moreover, one or more computer readable storage media may be used in implementing embodiments consistent with the present disclosure. A computer readable storage medium is understood to mean any type of physical memory on which information or data readable by a processor can be stored. Thus, a computer readable storage medium may store instructions for execution by one or more processors, including instructions that cause the processor or processors to perform steps or steps consistent with the embodiments described herein. The term "computer readable medium" is understood to include tangible elements and to exclude carrier waves and transitory signals, i.e., is non-transitory. Examples thereof include random access memory (RAM), read only memory (ROM), volatile memory, non-volatile memory, hard disks, CD-ROMs, DVDs, flash drives, floppy disks, and any other known physical storage media.Suitable processors include, for example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a graphics processing unit (GPU), multiple microprocessors, one or more microprocessors in conjunction with a DSP core, a controller, a microcontroller, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), any other type of integrated circuit (IC), and / or a state machine.In one embodiment, the present disclosure provides for ASIL (Automotive Safety Integrity Level) safety of the primary power grid by establishing a full galvanic isolation between the primary and secondary power grids.In one embodiment, the present disclosure ensures the ASIL safety of the primary power grid by implementing back voltage protection through a dual diode configuration.In one embodiment, the present disclosure ensures the ASIL safety of the primary power grid by implementing a fail-safe fuse in the fail-safe power supply system.In one embodiment, the present disclosure provides an effective methodology that ensures that the charging start of the output capacitor of the DC-DC converter is always successfully performed, thereby ensuring successful start of the DC-DC converter in the buck mode.In one embodiment, the present disclosure ensures proper voltage regulation during operation of the DC-DC converter.List of reference numbers:102, 206 Primary power network 108, 212 Secondary power network 104, 208, 308 Fail-safe unit 106, 210 Isolation unit 110, 214, 322 DC-DC converters 114, 220, 306 First relay 116, 222, 336 Second relay 112, 216, 320 At least one auxiliary device 218 Control unit 304 Ignition switch 330 At least one supercapacitor 332 Fuse 334 Diode pair 324 Output capacitorReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedCN 112542944A

[0006]

Claims

A fail-safe power supply system (202) for auxiliary devices in electric vehicles, the system comprising: a primary power network (102, 206) comprising at least one ignition switch (304); a secondary power network (108, 212) comprising a DC-DC converter (110, 214, 322) connected to at least one auxiliary device (112, 216, 320) via a second relay (116, 222, 336); a fail-safe unit (104, 208, 308) comprising at least one supercapacitor (330) connected to the primary power network (102, 206) via a first relay (114, 220, 306) and to the secondary power network (108, 212) via a disconnect unit (106, 210); a controller (218) operatively coupled to the fail-safe unit (104, 208, 308), the primary power network (102, 206), and the secondary power network (108, 212), the controller (218) configured to: receive a signal for supplying power to the at least one auxiliary device (112, 216, 320); charge the at least one supercapacitor (330) to a predefined level; discharge the at least one supercapacitor (330), and simultaneously charge an output capacitor (324) associated with the DC-DC converter (110, 214, 322) using the discharge current from the at least one supercapacitor (330) to enable the DC-DC converter (110, 214, 322) to transition to the buck mode; and enable the DC-DC converter (110, 214, 322) to safely supply power to the at least one auxiliary device (112, 216, 320) once the DC-DC converter (110, 214, 322) has entered the buck mode.The system of claim 1, wherein the isolation unit (106, 210) connecting the fail-safe unit (104, 208, 308) to the secondary power network (108, 212) comprises at least: a fuse (332) connected to an output end of the fail-safe unit (104, 208, 308); and a diode pair (334) connected to an output end of the fuse (332), wherein the fuse (332) and the diode pair (334) are configured to prevent current flow from the secondary power network (108, 212) to the primary power network (102, 206) while supplying power to the at least one auxiliary device (112, 216, 320).The system of claim 1, wherein the controller (218) is further configured to: close the first relay (114, 220, 306) to charge the at least one supercapacitor (330) using the primary power network (102, 206); and simultaneously open the second relay (116, 222, 336) to disconnect the at least one auxiliary device (112, 216, 320) from the at least one supercapacitor (330) while the at least one supercapacitor (330) is being charged.The system of claim 1, wherein the controller (218) is further configured to: open the first relay (114, 220, 306) while the second relay (116, 222, 336) is maintained in the open state during charging of the output capacitor (324) to disconnect the primary power network (102, 206) from the secondary power network (108, 212).The system of claim 1, wherein the controller (218) is further configured to: close the second relay (116, 222, 336) while maintaining the first relay (114, 220, 306) in the open state to enable the DC-DC converter (110, 214, 322) to supply power to the at least one auxiliary device (112, 216, 320) once the DC-DC converter (110, 214, 322) has entered the buck mode.A method for securely supplying power to auxiliary devices in electric vehicles, comprising: receiving a signal for supplying power to at least one auxiliary device (112, 216, 320); charging at least one supercapacitor (330) of a fail-safe unit (104, 208, 308) to a predefined level; discharging the at least one supercapacitor (330) and simultaneously charging an output capacitor (324) associated with a DC-DC converter (110, 214, 322) using discharge current from the at least one supercapacitor (330) to enable the DC-DC converter (110, 214, 322) to transition to the buck mode; and enable the DC-DC converter (110, 214, 322) to securely supply power to the at least one auxiliary device (112, 216, 320) once the DC-DC converter (110, 214, 322) has entered the buck mode.The method of claim 6, further comprising: closing a first relay (114, 220, 306) to charge the at least one supercapacitor (330) using a primary power grid (102, 206); and simultaneously opening a second relay (116, 222, 336) to disconnect the at least one auxiliary device (112, 216, 320) from the at least one supercapacitor (330) while the at least one supercapacitor (330) is being charged.The method of claim 6, further comprising: opening the first relay (114, 220, 306) while the second relay (116, 222, 336) is maintained in the open state during charging of the output capacitor (324) to disconnect the primary power network (102, 206) from a secondary power network (108, 212).The method of claim 6, further comprising: closing the second relay (116, 222, 336) while maintaining the first relay (114, 220, 306) in the open state to allow the DC-DC converter (110, 214, 322) to supply power to the at least one auxiliary device (112, 216, 320) once the DC-DC converter (110, 214, 322) has entered the buck mode.The method of claim 6, wherein the isolation unit (106, 210) connecting the fail-safe unit (104, 208, 308) to the secondary power network (108, 212) comprises at least: a fuse (332) connected to an output end of the fail-safe unit (104, 208, 308); and a diode pair (334) connected to an output end of the fuse (332) to prevent current flow from the secondary power network (108, 212) to the primary power network (102, 206).

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