[0001] The present disclosure described herein relates to a power supply
5 system of an electric vehicle and a method of operating such a power supply
system that enables efficient or better utilization of its components along with
their reduced size.
BACKGROUND
[0002] In the present state-of-the-art, an on-board charger circuit of a power
10 supply system of an electric vehicle like battery electric vehicle (BEV), plug-in
hybrid electric vehicle (PHEV), etc. is only used in AC charging mode of the
electric vehicle for energy conversion from grid alternating current (AC) to direct
current (DC) for charging of a traction battery pack of the power supply system.
However, a separate standalone direct current-direct current (DC-DC) converter is
15 employed in all modes of the electric vehicle be it driving mode, AC Charging
mode and DC charging mode wherein the DC-DC converter derives power from
the traction battery pack and supplies a low DC voltage power for operating
auxiliary loads as well as charging up an auxiliary battery through a bus. The onboard charger circuit despite generally being rated for higher power compared to
20 the standalone DC-DC converter is left out of the power supply system entirely
during the driving mode and the DC charging mode of the electric vehicle. This
results in the non-utilization of the on-board charger circuit of the power supply
system during a good part of the electric vehicle’s operational cycle.
[0003] In view of the above, there is a need to increase the utilization of the
25 on-board charger circuit. It is a further need to downsize the components of the
power supply system particularly the stand-alone DC-DC converter so that
3
packaging requirements, cooling requirements, as well as cost and power losses,
may be reduced.
OBJECTS OF THE DISCLOSURE
[0004] Some of the objects of the present disclosure, which at least one
5 embodiment herein satisfy, are listed herein below.
[0005] It is a general or primary object of the present disclosure to provide a
power supply system of an electric vehicle and a method of operating such a
power supply system that results in efficient or better utilization of the
components of the power supply system.
10 [0006] It is another object of the present disclosure to provide a power supply
system of an electric vehicle and a method of operating such a power supply
system that results in the downsized or reduced size of the components of the
power supply system that further reduces packaging requirements, cooling
requirements as well as cost and power losses.
15 [0007] These and other objects and advantages will become more apparent
when reference is made to the following description and accompanying drawings.
SUMMARY
[0008] This summary is provided to introduce concepts related to a power
supply system of an electric vehicle and a method of operating such a power
20 supply system. 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.
[0009] The subject matter disclosed herein relates to a power supply system of
25 an electric vehicle. The power supply system comprises a higher-level vehicle
controller to receive and detect signals regarding a mode of operation of the
4
electric vehicle, the mode of operation being an alternating current, AC, charging
mode, a direct current, DC, charging mode, or a driving mode, an on-board
charger circuit, battery circuit and a standalone DC-DC converter circuit having
an on-board charger controller, battery circuit controller, and a standalone DC-DC
5 converter controller, respectively that are controlled by the higher-level vehicle
controller based on the signals received and detected by the higher-level vehicle
controller. As per the present disclosure the on-board charger circuit comprising a
power factor corrector (PFC) and a direct current-direct current (DC-DC)
converter operates in the DC charging mode and the drive mode as well in
10 addition to the AC charging mode, wherein during the AC charging mode, a pair
of relays S1 and S2 connected with a PFC output bus and a DC-DC converter
output bus, respectively are actuated by receiving signals from the higher-level
vehicle controller via the on-board charger controller such that a DC voltage from
the on-board charger circuit or the DC-DC converter is supplied to a traction
15 battery pack via the DC-DC converter output bus and during the DC charging
mode or the drive mode, a relay S3 connected with the PFC output bus and the
DC-DC converter output bus or the rectifier output bus and a relay switch S4
connected with a low DC voltage bus that is in turn connected with the DC-DC
converter output bus or the rectifier output bus are actuated by receiving signals
20 from the higher-level vehicle controller via the on-board charger controller such
that the DC voltage from the traction battery pack is passed through the DC-DC
converter and converted to a low DC voltage which is available at the low DC
voltage bus to be supplied to auxiliary loads and auxiliary battery of the electric
vehicle.
25 [0010] In an aspect, during the DC charging mode and the drive mode of the
electric vehicle the relays S1 and S2 are kept unactuated.
[0011] In an aspect, the standalone DC-DC converter circuit comprises a
standalone DC-DC converter that has a power rating less than the power rating of
the DC-DC converter of the on-board charger circuit and that operates mainly
5
during the AC charging mode to supply low DC voltage to the auxiliary loads and
the auxiliary battery of the electric vehicle.
[0012] In an aspect, the power supply system comprises a set of master relays
that are connected with the auxiliary loads and controlled by the higher-level
5 vehicle controller by receiving signals via a bus such that during the AC charging
mode, the standalone DC-DC converter supplies DC voltage to a set of auxiliary
loads identified by the higher-level vehicle controller as “essential during AC
charging” and the higher-level vehicle controller by sending a signal disconnects
those master relays that are connected with a set of auxiliary loads identified as
10 “non-essential during AC charging”.
[0013] In an aspect, the master relays are kept unactuated by the higher-level
vehicle controller during the DC charging mode and the drive mode of the electric
vehicle.
[0014] In an aspect, before the commencement of any mode of operation of
15 the electric vehicle, if the voltage of the auxiliary battery is less than a threshold
voltage limit, the higher-level vehicle controller sends a signal to the on-board
charger controller and the standalone DC-DC converter controller such that the
DC-DC converter supplies low DC voltage to the auxiliary battery along with the
standalone DC-DC converter till the threshold power limit of the auxiliary battery
20 is attained and only then the mode of operation is allowed to commence, by the
higher-level controller.
[0015] The subject matter disclosed herein also relates to a method of
operating a power supply system of an electric vehicle. The method comprises
receiving and detecting by a higher-level vehicle controller of the power supply
25 system, signals regarding a mode of operation of the electric vehicle, the mode of
operation being an alternating current, AC, charging mode, a direct current, DC,
charging mode, or a driving mode, and controlling by the higher-level vehicle
controller an on-board charger controller, battery circuit controller and standalone
6
DC-DC converter controller of an on-board charger circuit, battery circuit and
standalone DC-DC converter circuit, respectively based on the signals received
and detected by the higher-level vehicle controller. As per the present disclosure
the on-board charger circuit comprising a power factor corrector (PFC) and a
5 direct current-direct current (DC-DC) converter, operates in the DC charging
mode and the drive mode as well in addition to the AC charging mode, wherein
during the AC charging mode, a pair of relays S1 and S2 connected with a PFC
output bus and a DC-DC converter output bus, respectively are actuated by
receiving signals from the higher-level vehicle controller via the on-board charger
10 controller such that a DC voltage from the onboard charger circuit or the DC-DC
converter is supplied to a traction battery pack via the DC-DC converter output
bus, and during the DC charging mode or the drive mode, a relay S3 connected
with the PFC output bus and the DC-DC converter output bus or the rectifier
output bus and a relay switch S4 connected with a low DC voltage bus that is in
15 turn connected with the DC-DC converter output bus or the rectifier output bus
are actuated by receiving signals from the higher-level vehicle controller via the
onboard charger controller such that the DC voltage from the traction battery pack
is passed through the DC-DC converter and converted to a low DC voltage which
is available at the low DC voltage bus to be supplied to auxiliary loads and the
20 auxiliary battery of the electric vehicle.
[0016] In an aspect, the method comprises detecting by the higher-level
vehicle controller, before the commencement of any mode of operation of the
electric vehicle, whether the voltage of the auxiliary battery is less than a
threshold voltage limit, and sending a signal by the higher-level vehicle controller
25 to the on-board charger controller and the standalone DC-DC converter controller
such that the DC-DC converter and the standalone DC-DC converter supplies low
DC voltage to the auxiliary battery till the threshold power limit of the auxiliary
battery is attained and only then allowing the mode of operation to commence, by
the higher-level controller.
7
[0017] In an aspect, the method comprises identifying by the higher-level
vehicle controller a set of auxiliary loads as “essential during charging” and “nonessential during charging” and by sending signals via a bus actuating only those
master relays that are connected with the set of auxiliary loads identified as
5 ‘essential during charging’ and disconnecting those master relays that are
connected with the set of auxiliary loads identified as “non-essential during
charging” such that DC voltage is supplied by the DC-DC converter and the
standalone DC-DC converter to only the set of auxiliary loads identified as
‘essential during charging’.
10 [0018] In an aspect, the method comprises detecting by the higher-level
vehicle controller, during the DC charging mode or the drive mode of the electric
vehicle, a drop in voltage of the low DC voltage bus or rise in the temperature of
the DC-DC converter and enabling operation of the standalone DC-DC converter
along with the DC-DC converter.
15 [0019] The solution proposed by the present disclosure as mentioned above
resolves an unbalance by repurposing the larger circuit i.e. the DC-DC converter
present as a part of the on-board charger circuit and further downsizing the
smaller component i.e. the standalone DC-DC converter so that these may be
operated more efficiently and excessive stress on one circuit or component is
20 reduced. At the vehicle level, such a solution implies cost and power loss
reduction. Also, coolant requirements may be reduced, resulting in the usage of
air cooling over liquid cooling for the downsized circuit. Further, system power
security is increased by the redundancy of power converters and the option to use
both converters in parallel enables faster auxiliary battery charging and the option
25 for user/ customer to derive larger power from in-vehicle low voltage socket(s) to
charge multiple gadgets/ hand-held devices.
[0020] To further understand the characteristics and technical contents of the
present subject matter, a description relating thereto will be made with reference
8
to the accompanying drawings. However, the drawings are illustrative only but
not used to limit the scope of the present subject matter.
[0021] Various objects, features, aspects, and advantages of the inventive
subject matter will become more apparent from the following detailed description
5 of preferred embodiments, along with the accompanying drawing figures in which
like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] It is to be noted, however, that the appended drawings illustrate only
typical embodiments of the present subject matter and are therefore not to be
10 considered for limiting of its scope, for the invention may admit to other equally
effective embodiments. The detailed description is described with reference to the
accompanying figures. The illustrated embodiments of the subject matter will be
best understood by reference to the drawings, wherein like parts are designated by
like numerals throughout. The following description is intended only by way of
15 example, and simply illustrates certain selected embodiments of devices, systems,
and methods that are consistent with the subject matter as claimed herein,
wherein:
[0023] FIG. 1 illustrates a block diagram of an existing power supply system
of an electric vehicle;
20 [0024] FIG. 2 illustrates a block diagram of the structure of a DC-DC
converter of an on-board charger circuit of an existing power supply system;
[0025] FIG. 3 illustrates a block diagram of the structure of a modified DCDC converter of an on-board charger circuit of a power supply system in
accordance with the present disclosure;
25 [0026] FIG. 4 illustrates a block diagram of a power supply system of an
electric vehicle in accordance with the present disclosure; and
9
[0027] FIGS. 5A and 5B illustrate a method of operating a power supply
system of an electric vehicle in accordance with the present disclosure.
[0028] The figures depict embodiments of the present subject matter for the
purposes of illustration only. A person skilled in the art will easily recognize from
5 the following description that alternative embodiments of the structures and
methods illustrated herein may be employed without departing from the principles
of the disclosure described herein.
DETAILED DESCRIPTION
[0029] The detailed description of various exemplary embodiments of the
10 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
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
15 within the spirit and scope of the present disclosure as defined by the appended
claims.
[0030] 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,
20 and embodiments of the present disclosure, as well as specific examples, are
intended to encompass equivalents thereof.
[0031] The terminology used herein is to describe 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
25 well, unless the context 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,
10
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.
[0032] It should also be noted that in some alternative implementations, the
5 functions/acts noted may occur out of the order noted in the figures. For example,
two figures shown in succession may be executed concurrently or may sometimes
be executed in the reverse order, depending upon the functionality/acts involved.
[0033] Unless otherwise defined, all terms (including technical and scientific
terms) used herein have the same meaning as commonly understood by one of
10 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.
15 [0034] In the following detailed description of the embodiments of the
disclosure, reference is made to the accompanying drawings that form a part
hereof, and in which are shown by way of illustration specific embodiments in
which the disclosure may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art to practice the disclosure, and it
20 is to be understood that other embodiments may be utilized and that changes may
be made without departing from the scope of the present disclosure. The
following description is, therefore, not to be taken in a limiting sense.
[0035] Hereinafter, a description of an embodiment with several components
in communication with each other does not imply that all such components are
25 required. On the contrary, a variety of optional components are described to
illustrate the wide variety of possible embodiments of the present disclosure.
11
[0036] Reference is made to FIG. 1 that shows a block diagram of an existing
power supply system (PSS) 100 of an electric vehicle. The PSS 100 comprises a
separate higher-level vehicle controller 10, an on-board charger circuit 20, battery
circuit 30, an inverter and motor circuit 40, and a standalone DC-DC converter
5 circuit 50 communicatively or electrically coupled with each other.
[0037] The higher-level vehicle controller 10 assesses the electric vehicle’s
‘wakeup or initiate’ mode based on inputs received via a communication bus 10a
that carries information regarding the driver’s action indicating key insertion or
start switch press to wake up the electric vehicle in ‘drive’ mode or via a
10 communication bus 10b that carries information regarding the driver’s action
indicating alternating current (AC) charging plug connection to wake up the
electric vehicle in ‘AC charging’ mode or via a communication bus 10c that
carries information regarding the driver’s action indicating direct current (DC)
charging plug connection to wake up the electric vehicle in ‘DC charging’ mode.
15 The information over communication bus 10a, 10b, and 10c may be different
based on vehicle architecture and choice of charging protocol. In an aspect, when
a protocol like CCS2.0 is used, an AC charging socket 61 and a DC charging
socket 63 may be housed together and accordingly, the communication bus 10b
and 10c can be the same. However, in another aspect, a protocol such as
20 CHAdeMO is used in the existing PSS 100 that require two different sockets 61
and 63. Likewise, the communication bus 10b and 10c are also separate.
[0038] The on-board charger circuit 20 derives power for charging from the
AC charging socket 61 via an AC input bus 61a. The on-board charger circuit 20
comprises a power factor corrector (PFC) 21, a direct current-direct current (DC25 DC) converter 22, and an on-board charger controller 23 as part of its power
circuit. The battery circuit 30 comprises a battery circuit controller 31, a traction
battery pack 32, vehicle main relays 33, and DC fast charging relays 34 as shown
in FIG. 1. The DC-DC converter 22 is connected with the traction battery pack 32
via a DC-DC converter output bus 22a that is connected with the vehicle main
12
relays 33. During AC charging mode, the PFC 21 is commanded by the on-board
charger controller 23 via a bus 23a such that the PFC 21 maintains a power factor
of the on-board charger circuit 20 close to unity. The PFC 21 receives AC voltage
input via the AC input bus 61a and converts the AC input voltage to DC voltage
5 available at a PFC output bus 21a. Since the PFC’s 21 primary function is power
factor control, thus this DC voltage obtained at the PFC output bus 21a may not
be suitable for directly supplying to the traction battery pack 32. The traction
battery pack 32 requires to be charged at different voltages at different states of
charge, temperatures, and states of power usage by other loads such as the air
10 conditioning system, the heater, etc. A charge power limit is a function of these
parameters and is calculated/ estimated by the battery circuit controller 31 and
communicated to the higher-level vehicle controller 10 via a bus 31a. The higherlevel vehicle controller 10 further estimates/ calculates a correct value of charging
current set-point or the charging voltage set-point based on information received
15 from the battery circuit controller 31 as well as the mode of vehicle operation (AC
Charging or DC Charging) and power limits of the PSS’s components and
harness. In case of AC charging mode, the higher-level vehicle controller 10
calculates a suitable current set-point for AC charging taking into account, the
traction battery pack 32 charging power limit, communicated by the battery circuit
20 controller 31 as well as states of operation of other in-vehicle loads including
loads such as air conditioning and auxiliary components, the power output limits
of an AC mains supply and the on-board charger circuit 20. The higher-level
vehicle controller 10, in turn, communicates with the on-board charger controller
23 via a bus 10d and sets a suitable charging current/ charging voltage set-point
25 which would, in turn, enable the on-board charger controller 23 to operate the
DC-DC converter 22 via a bus 23b, in such a way that the desired charging DC
voltage is available at the DC-DC converter output bus 22a. The DC voltage
available at the DC-DC converter output bus 22a is fed to the traction battery
pack’s 32 input terminals when the vehicle main relays 33 are closed by the
30 higher-level vehicle controller 10 via an actuation signal carried in a bus 10e.
13
Alternatively, the battery circuit controller 31 may accomplish this. The battery
circuit controller 31 receives sensor signals from the traction battery pack 32 via
bus 32a and assesses the safe state of the traction battery pack 32. It
communicates the same along with other data via the bus 31a.
5 [0039] When the higher-level vehicle controller 10 is woken up in the ‘DC
charging’ mode, in coordination with the battery circuit controller 31, it
communicates with the DC charging socket 63 via the communication bus 10c
and consequently actuates the DC fast charging relays 34 via an actuation signal
carried in a bus 34a to make the DC voltage directly available to the traction
10 battery pack 32 via a bus 63a. The on-board charger circuit 20 is not used in this
mode.
[0040] When the higher-level vehicle controller 10 is woken up in the ‘drive’
mode via key insertion or pressing of start switch by the driver as indicated by
communication bus 10a, the higher-level vehicle controller 10, in coordination
15 with the battery circuit controller 31 actuates the vehicle main relays 33 and wake
up an inverter 41 of the inverter and motor circuit 40 via a communication bus
10f. The inverter 41 powers a motor 42 by drawing power or DC voltage from the
traction battery pack 32 via DC input bus 41a and supplies multiphase AC voltage
via a bus 41b and a receives sensor signals from the motor 42 via a bus 41c. In
20 this mode also, the on-board charger circuit 20 remains idle.
[0041] The standalone DC-DC converter circuit 50 comprises a standalone
DC-DC converter 51 and a standalone DC-DC converter controller 52. The
standalone DC-DC converter circuit 50 works in every operational mode and is
concerned with supplying DC voltage to a low voltage bus 51a from the
25 standalone DC-DC converter 51 to supply power to the auxiliary loads 65 via a
bus 65a as well as an auxiliary battery 67 via a bus 67a. The standalone DC-DC
converter 51 powers its own controller 52 via a bus 52a, the inverter’s controller
(present inside the inverter 41) via a bus 41d, the battery circuit controller 31 via a
14
bus 31b, the on-board charger controller 23 via a bus 23c, the higher-level vehicle
controller 10 via a bus 10g and the auxiliary battery 67 via a bus 67a. All the
controllers and components such as audio system, infotainment system, lighting
system, blower, controllers such as anti-lock braking system (ABS), power
5 windows, wiper systems, power steering system, power supply to sensors such as
accelerator pedal and brake pedal sensors, automated seat adjustment system, seat
warmers/ coolers, a heater of the heating, ventilating and air conditioning
(HVAC) system and the like that requires low voltage may be thought of
constituting the auxiliary loads 65.
10 [0042] Before the activation of the standalone DC-DC converter controller 52
by the higher-level vehicle controller 10 via a bus 10h, which might be a
hardwired signal path, the auxiliary battery 67 temporary powers all connected
low voltage loads via the bus 67a. Once the standalone DC-DC converter
controller 52 is commanded to start operation by the higher-level vehicle
15 controller 10, a set voltage level may be commanded by the higher-level vehicle
controller 10 via the bus 10h, such that the auxiliary battery 67 may recover its
drained energy while the standalone DC-DC converter 51 takes over as the main
supplier of low DC voltage in the electric vehicle. The starting of the standalone
DC-DC converter 51 requires that the traction battery pack 32 be connected to the
20 vehicle power circuit via the vehicle main relays 33. Once the vehicle main relays
33 are closed by the higher-level vehicle controller 10 in co-ordination with the
battery circuit controller 31, the standalone DC-DC converter 51 is commanded to
output a low DC voltage by the higher-level vehicle controller 10. The standalone
DC-DC converter controller 52 commands the standalone DC-DC converter 51
25 via a bus 52b in such a way that the DC voltage available at a DC-DC converter
input bus 51b can be converted to the low voltage DC as per requirement at the
low voltage bus 51a.
[0043] Both the standalone DC-DC Converter 51 and the DC-DC converter
22 are identical in the structure, being unidirectional and isolated DC-DC
15
converters working at different voltages or power levels. The DC-DC converter
22 generally has a higher power rating compared to the standalone DC-DC
converter 51. The DC voltage at the DC-DC converter output bus 22a is the same
as that in the DC-DC converter input bus 51b. In an aspect, the buses used for
5 communication or signal transmission are any standard communication bus
including controller area network (CAN) bus.
[0044] FIG. 2 shows a block diagram of a structure of a commonly used
unidirectional DC-DC converter that can be used to represent both DC-DC
converters 22 and 51 in general. However, for the explanation, reference is made
10 to the internal DC-DC converter 22 of the on-board charger circuit 20. The DCDC converter 22 comprises an inverter 202 which can be a half-bridge or a fullbridge inverter with an insulating gate bipolar transistor (IGBT) or metal-oxidesemiconductor field-effect transistor (MOSFET) switches that are operated by the
on-board charger controller 23 by a feedback signal 204 carried in the bus 23b.
15 The inverter 202 to which the PFC 21 is coupled via the PFC output bus 21a
converts the DC voltage available at the PFC output bus 21a into a high-frequency
AC voltage available at an inverter’s output bus 202a. An isolation transformer
206 to which the inverter 202 is coupled via the inverter’s output bus 202a serves
to galvanically isolate the source (AC grid voltage) from the rest of the vehicle
20 power circuit. The isolated AC voltage available at isolation transformer’s output
bus 206a is applied to a rectifier 208. The rectifier 208 may consist of a full bridge
rectifier to convert the isolated AC voltage available at the isolation transformer’s
output bus 206a into DC voltage available at the rectifier’s output bus 208a. A DC
link capacitor can be used as a part of the rectifier 208 to smoothen and filter the
25 DC output voltage. Current and/or voltage feedback obtained at the rectifier 208
can be transmitted back to the on-board charger controller 23 via a feedback
signal 210 for closed-loop control of charging current/ voltage as desired by the
higher-level vehicle controller 10.
16
[0045] The existing PSS 100 thus uses the DC-DC converter 22 of the onboard charger circuit 20 only during one of the three modes i.e. during AC
charging while the standalone DC-DC converter 51 is used in all three modes (AC
charging, DC charging and drive mode).
5 [0046] The standalone DC-DC converter 51 provides low DC voltage to the
auxiliary loads 67. In a small passenger vehicle, such standalone DC-DC
converter 51 may be rated at 1.5 kW. The standalone DC-DC converter 51 is also
expected to meet this load demand as well as charge up the auxiliary battery 67 at
all times, i.e. during all modes of operation of the electric vehicle. The DC-DC
10 converter 22 requires to be rated similar to the on-board charger circuit’s net
output power capacity and may be between 3.5 kW to 11 kW for a small
passenger vehicle. Thus the larger power rated DC-DC converter 22 is left
unutilized during the other operating modes i.e. the DC charging and the drive
mode which put together account for the greater part of the operational time of the
15 electric vehicle. Also, during the AC charging mode, where the electric vehicle is
configured to draw very low current from the grid to minimize the on-board
charger circuit’s 20 sizes as well as to operate cost-effectively using low power
residential supply, charging rates are generally slow and a small passenger car
might take upwards of 8 hours to charge up to 80 % from a low state of charge of
20 the traction battery pack 32.
[0047] Such large charging runs are generally expected to be carried out by a
user/ driver/ customer at their convenience during night time, or the office parking
spaces during workdays. Public charging stations that are tuned for fast charging
generally would prefer using DC fast charging such that wait times and queues
25 can be minimized. Taking this into consideration, it is very unlikely that the
driver/ user/ customer may be physically present inside the vehicle during AC
Charging. This implies that the usage of in-vehicle auxiliary loads 65 such as
lighting, audio system, wipers and power windows, blower, etc. will be close to
none during AC charging mode. Also, if a public charger is being used for AC
17
charging, it would only be worthwhile and economical for a user to not stress the
electrical system by consuming extra power through the low voltage bus 51a by
operating auxiliary loads 65 that are not necessary during charging as this may
prolong the charging time and result in longer charging time and higher bills. This
5 implies that an auxiliary DC power consumption during AC charging mode of
operation may be very low and most of the capacity of the standalone DC-DC
converter 51 is left unutilized during this mode. As mentioned previously, during
the drive mode and DC charging modes, the on-board charger circuit 20 stays idle
which includes the DC-DC converter 22, thereby placing additional stress on the
10 standalone DC-DC converter 51, since the user/ driver/ customer is free to switch
on all loads on the DC low voltage bus and is more likely to do so. Thus there is a
utilization unbalance wherein a larger circuit (the DC-DC converter 22) is utilized
during a minority of the time (only during the AC charging mode) whereas a
smaller circuit (the standalone DC-DC converter 51) is used in all modes of
15 operation.
[0048] The present disclosure aims to resolve this unbalance by repurposing
the larger circuit and further-downsizing the smaller circuit so that these may be
operated more efficiently and excessive stress on one circuit may be reduced. At
the vehicle level, such a solution would imply cost reduction. Also, coolant
20 requirements may be reduced, resulting in the usage of air cooling as opposed to
liquid cooling for the down-sized circuit.
[0049] As per the solution of the present disclosure, the DC-DC converter 22
is repurposed or configured to act as a primary DC-DC converter of the electric
vehicle for feeding the low voltage bus 51a during the DC charging mode and
25 drive mode. The standalone DC-DC Converter 51 is used as a primary DC-DC
converter of the electric vehicle during the AC charging mode only. Further, the
DC-DC converter 51 is significantly downsized (up to 75 %) due to the prospect
of low load power demand during the AC charging mode of operation. In an
example, a 1.5 kW rated DC-DC converter 51 for a small passenger vehicle can
18
be downsized to 375W. Using a set of switches and some additional harnessing,
the DC-DC converter 22 may be converted into a converter that outputs DC
voltage for charging the traction battery pack 32 during AC charging mode, while
it uses the same DC voltage from the traction battery pack 32 as input and outputs
5 low DC voltage to the low voltage bus 51a to power the auxiliary loads 65 and
auxiliary battery 67 during the drive mode and DC charging mode. During these
modes of operation, the standalone DC-DC converter 51 may be switched off/ not
used at all or even it may be used in parallel with the larger DC-DC converter 22
to supply exceptionally large DC loads if any. To limit the DC loads during AC
10 charging mode, to prevent overloading of the downsized standalone DC-DC
converter 51, segregation of loads into “Essential during AC charging” and “Nonessential during AC charging” is performed via a set of master relays. In an
aspect, the power supply system comprises a set of master relays that are
connected with auxiliary loads 65 and controlled by the higher-level vehicle
15 controller 10 by receiving signals via a bus such that during the AC charging
mode, the standalone DC-DC converter 51 is able to supply power or low DC
voltage to only those auxiliary loads identified by the higher-level vehicle
controller 10 as “essential during AC charging” and the higher-level vehicle
controller 10 by sending a signal to the master relays disconnects only those loads
20 that are deemed “non-essential during AC charging”.
[0050] FIG. 3 shows a block diagram of a structure of a modified DC-DC
converter 22' of the on-board charger circuit 20. A set of relays or switches S1,
S2, S3, & S4 are used in two different combinations to ‘re-wire’ the DC-DC
converter 22' to output two different voltages from two different sources.
25 [0051] When the electric vehicle is woken up in the AC charging mode by
connecting an AC plug to the grid, the higher-level vehicle controller 10 activates
the on-board charger circuit 20 by sending control signals or communication
signals to the on-board charger controller 23 via the bus 10d. The on-board
charger controller 23 interprets the mode of wakeup from the information
19
received from the higher-level vehicle controller 10 and configures the DC-DC
converter 22' such that it is ready to output DC voltage to charge the traction
battery pack 23 via the DC-DC converter output bus 22a. The on-board charger
controller 23 sends signal 302 for relay switch S1 and signal 304 for relay switch
5 S2 to establish a direct path for DC-DC power conversion from the PFC output
bus 21a to the DC-DC converter output bus 22a which carries power at the
appropriate voltage/ current level as commanded by the higher-level vehicle
controller 10 into the traction battery pack 32. During this time the standalone
DC-DC converter 51 is operated as the primary DC-DC converter for the electric
10 vehicle to supply low DC voltage or power to the auxiliary loads 65 via low
voltage bus 51a. When the higher-level controller 10 detects the driver’s intention
to start the vehicle in AC charging mode, it commands the DC-DC converter’s
controller 52 by sending control signals via the bus 10h such that it wakes up and
starts DC-DC conversion by deriving DC voltage from the traction battery pack
15 32 via the DC-DC converter input bus 51b.
[0052] When the vehicle is woken up in a DC charging or drive mode, the
higher-level vehicle controller 10 activates the on-board charger circuit 20 by
sending control or feedback signals to the on-board charger controller 23 via the
bus 10d. The on-board charger controller 23 interprets the received signals and
20 proceeds to re-configure the DC-DC converter 22' such that it starts operating as
the primary DC-DC converter in the electric vehicle. To achieve this, the relay
switch S3 connected with the PFC output bus 21a and the DC-DC converter
output bus 22a via a bus 22b and a relay switch S4 connected with a low voltage
bus 22c that is connected with the DC-DC converter output bus 22a are actuated
25 by receiving signals 306 and 308, respectively sent by the on-board charger
controller 23 while the relays S1 and S2 remain unactuated. This re-configures the
DC-DC converter 22' such that DC voltage or power available from the traction
battery pack 32 is fed to the inverter 202 by the bus 22b such that low DC voltage
output is available at the low voltage bus 22c through the isolation transformer
30 206 and the rectifier 208 to be supplied to the auxiliary loads 65 and auxiliary
20
battery 67. The standalone DC-DC converter 51 'remains un-operational during
DC charging mode and drive mode.
[0053] FIG. 4 shows a block diagram of a power supply system (PSS) 100' of
an electric vehicle as per the present disclosure. The PSS 100' is different from
5 PSS 100 in that the low voltage bus 22c is connected to the low voltage bus 51a
such that the DC-DC converter 22' of the on-board charger circuit 23 is connected
to the auxiliary loads 65 and the auxiliary battery 67 as the primary DC-DC
converter during DC charging or drive modes. The downsized and standalone DCDC converter 51' is kept un-operational by the higher-level vehicle controller 10
10 since the DC-DC converter 22' is rated higher in capacity and is capable to be
used in a standalone fashion for supplying power to all the auxiliary loads 65.
comprises a set of master relays 69 that is connected with the auxiliary loads 65
and controlled by the higher-level vehicle controller 10 by receiving signals via a
bus 69a such that during the AC charging mode, the standalone DC-DC converter
15 51' supplies DC voltage to a set of auxiliary loads 65 identified by the higher-level
vehicle controller 10 as “essential during AC charging” and the higher-level
vehicle controller 10 by sending a signal disconnects the master relays 69 that is
connected with a set of auxiliary loads 65 identified as “non-essential during AC
charging”. The master relays 69 are operated or controlled by the higher-level
20 vehicle controller 10 by receiving signals via the bus 69a and can be of normally
open (NO) or normally closed (NC) type relays. Disconnection of some loads
deemed ‘non-essential during AC charging’ out of auxiliary loads 65 ensures that
these loads cannot be switched on as long as the vehicle is in the AC charging
mode such that the smaller/ downsized standalone DC-DC Converter 51' is never
25 overloaded. Auxiliary loads 65 that may be deemed “non-essential during AC
charging” may include the audio system, infotainment system, lighting system,
blower, controllers such as ABS and ESP, power windows, wiper systems, power
steering system, power supply to sensors such as accelerator pedal and brake
pedal sensors, automated seat adjustment system, seat warmers/ coolers, the
30 heater of the HVAC system and the like. This minimizes the chances of
21
accidentally overloading the downsized standalone DC-DC converter 51'. After
completion of AC charging, the charging plug may be disconnected and the
vehicle may be brought into the drive mode or the DC charging mode by insertion
of key/ pressing the start switch or by insertion of the DC charging plug
5 respectively. When the mode of wakeup is DC charging or drive mode, the
higher-level vehicle controller 10 doesn’t actuate the master relays 69.
[0054] In an aspect, during the AC charging mode, the auxiliary battery 67
may have a lower state of charge and is below a threshold voltage limit and thus
may need to be charged for some time to ensure safe continuity of operations. In
10 the existing PSS 100, this is carried out by the standalone DC-DC converter 51
after the traction battery pack 32 is connected to the rest of the power circuit. The
standalone DC-DC converter 51, however, is expected to supply power in parallel
to other auxiliary loads 65. This might result in slower charging of the auxiliary
battery 67 and consequent drain out resulting in a reduction of power security in
15 the vehicle. However, in the PSS 100', after the vehicle is woken up in AC
charging mode, once a detection is made by the higher-level vehicle controller 10,
that the state of charge of the auxiliary battery 67 is lower than a certain threshold,
it would suspend the AC charging start-up procedure and use the internal DC-DC
converter 22' in parallel with the standalone DC-DC converter 51' to quickly
20 charge up the auxiliary battery 67. Once the auxiliary battery 67 is charged up
above a certain threshold state of charge, the DC-DC converter 22' is reconfigured by the higher-level vehicle controller 10 such that the DC-DC
converter 22' supplies power to the traction battery pack 32 only and then the
power supply to the auxiliary battery 67 and the auxiliary loads 65 is then taken
25 care of solely by the standalone DC-DC converter 51'.
[0055] In an aspect, during the drive mode or DC charging mode of wakeup,
the auxiliary battery 67 may have a lower state of charge and may be below a
threshold voltage limit and need to be charged up quickly, same as above. In this
case, also, both the converters 22' and 51' can be simultaneously activated by the
22
higher-level vehicle controller 10 to quickly charge up the auxiliary battery 67.
Once the auxiliary battery 67 is sufficiently charged, the downsized standalone
DC-DC converter 51' can be disconnected by command or signal from the higherlevel vehicle controller 10 such that the DC-DC converter 22' of the is the sole
5 supplier of the power to the auxiliary battery 67 and the auxiliary loads 65.
[0056] Further, in an aspect, during incidences of unusually high power
consumption by the auxiliary loads 65 during the drive mode or DC charging
mode, while the DC-DC converter 22' is the sole DC-DC converter active, the
standalone DC-DC converter 51' may be activated by a command from the higher10 level vehicle controller 10 to aid the DC-DC converter 22' in supplying the
excessive load such that over-heating of the DC-DC converter 22' may be
avoided. Information about overheating of the DC-DC converter 22' may be
obtained via signals 204 and 210 by the on-board charger controller 23 via the bus
23b and then sent to the higher-level vehicle controller 10 via the bus 10d. This
15 might increase system safety and prolong component life.
[0057] During incidences of unusually high 12 V loads during the driving or
DC charging modes of operation, while the DC-DC Converter 22’ is the sole DCDC converter active, high load current draw may result in a voltage drop at the
low voltage DC bus 65a. When such a voltage drop is detected, the DC-DC
20 converter 51' may be activated by a command from the higher-level vehicle
controller 10 to aid the DC-DC converter 22’ in supplying the excessive load such
that over-heating of the DC-DC converter 22’ may be avoided. Information about
overheating of the DC-DC converter 22’ may be obtained via temperature
feedback signals by the on-board charger’s controller 23 via the bus 23b and then
25 relayed to the higher-level vehicle controller 10 via 10d. This might increase
system safety and prolong component life.
[0058] Also, the customer/ user/ driver is provided with a choice to use/
charge more devices from in-vehicle sockets which may be used for charging
23
multiple handheld devices, etc. Such power may be drawn from in-vehicle low
voltage sockets/ USB ports commonly available below the Instrument panel/
dashboard or near seats inside a vehicle. These additional external loads may be
considered part of the low voltage auxiliary loads 65 of the vehicle. In the best5 case scenario with the DC-DC converter 51' and the DC-DC converter stage 22’
supplying power to the low voltage DC bus 65a together (in parallel) during the
drive mode or the DC charging mode, a provision for drawing up to 3.8 kW of
power for the auxiliaries can be made if the vehicle employs an on-board charger
circuit 20 of 3.5 kW rating and a DC-DC converter 51' which has been downsized
10 (employing the proposed architecture) to about 375 W. If it is assumed that the
vehicle is a small passenger car, with the in-vehicle loads drawing a maximum of
1.5 kW in total, this architecture, therefore, may be used to supply an additional
2.3 kW for external loads through a plurality of in-vehicle low voltage sockets for
the users’ convenience during the drive and DC charging modes of operation.
15 [0059] Therefore, the PSS 100' results in an efficient or better utilization of
the system components inside the electric vehicle and enable further downsizing
of one component such that cost and coolant requirements are reduced and
packaging efficiency increases. System power security is increased by the
redundancy of power converters and the option to use both converters in parallel
20 may enable faster auxiliary battery charging and the option for user/ customer to
derive larger power from in-vehicle low voltage socket to charge multiple
gadgets/ handheld devices.
[0060] FIG. 5 illustrates a method 500 of operating a power supply system
100' of an electric vehicle in accordance with the present disclosure.
25 [0061] The method 500 comprises receiving and detecting by the higher-level
vehicle controller 10 of the power supply system, ‘wakeup’ signals regarding a
mode of operation of the electric vehicle, the mode of operation being an
alternating current, AC, charging mode, a direct current, DC, charging mode, or a
24
driving mode represented at block 502 and 504 respectively. The higher-level
vehicle controller 10 further sends a signal to the on-board charger controller 23,
battery circuit controller 31 and standalone DC-DC converter controller 52 of the
on-board charger circuit 20, battery circuit 30, and standalone DC-DC converter
5 circuit 50, respectively to ensure safety check represented by block 504.
[0062] At step 506, the higher-level vehicle controller 10 checks or
determines whether all safety checks are passed. If the safety checks are not
passed an error is indicated and the operation is stopped as represented at block
508. If the safety checks are passed, then traction battery pack 32 of the battery
10 circuit 30 is connected by closing vehicle main relays 33 by the higher-level
vehicle controller 10 through the bus 10e, represented by block 510.
[0063] At block 512, the battery circuit controller 31 with the help of a
voltage sensor measures the voltage of the auxiliary battery 67a and relays the
measured voltage to the higher-level vehicle controller 10 through the bus 31a.
15 The higher-level vehicle controller 10, at block 514, determines whether the
voltage of the auxiliary battery 67 is critically low or below the threshold voltage
limit.
[0064] If the voltage of the auxiliary battery 67 is critically low or below the
threshold voltage limit, the higher-level vehicle controller 10 identifies a set of
20 auxiliary loads 65 as “essential during charging” and “non-essential during
charging” and by sending signals via a bus 69a actuates only those master relays
69 that are connected with the set of auxiliary loads 65 identified as ‘essential
during charging’ and disconnecting those master relays 69 that are connected with
the set of auxiliary loads 65 identified as “non-essential during charging” such
25 that DC voltage is supplied by the DC-DC converter 22' and the standalone DCDC converter 51' to only those set of auxiliary loads 65 identified as ‘essential
during charging’, represented by blocks 516 and 518, respectively. Further, the
power or DC voltage is supplied to the auxiliary battery 67 also. At step 519a,
25
method 500 comprises measuring the voltage of the auxiliary battery 67 by a
voltage sensor. If the voltage of the auxiliary battery 67 is above the threshold
voltage limit the flow of the method 500 is directed to step 512 as represented at
step 519b otherwise the voltage sensor keeps measuring the voltage of the
5 auxiliary battery 67 till the voltage is above the threshold voltage limit.
[0065] If the voltage of the auxiliary battery 67 is not critically low or below
the threshold voltage limit, the higher-level vehicle controller 10 detects the type
of mode of operation of the electric vehicle represented by block 520. If the
detected mode of operation is the AC charging mode at block 521, the pair of
10 relays S1 and S2 connected with the PFC output bus 21a and the DC-DC
converter output bus 22a, respectively are actuated by receiving signals from the
higher-level vehicle controller 10 via the on-board charger controller 23 such that
a DC voltage from the on-board charger circuit 20 or the DC-DC converter 22' is
supplied to the traction battery pack 32 via the DC-DC converter output bus 22a,
15 represented by block 524.
[0066] In an aspect, if found necessary, the higher-level vehicle controller 10
identifies a set of auxiliary loads 65 as “essential during AC charging” and “nonessential during AC charging” and enables DC voltage from the standalone DCDC converter 51' to be supplied to the set of auxiliary loads 65 identified as
20 “essential during AC charging” by actuating only those master relays 69
connected with the set of auxiliary loads 65 identified as “essential during AC
charging” and disconnects the master relays 69 that is connected with a set of
auxiliary loads 65 identified as “non-essential during AC charging”, represented
by block 522.
25 [0067] If the detected mode of operation is not AC charging mode and is
rather DC charging mode or drive mode, the higher-level vehicle controller 10
enables DC voltage supply to all the auxiliary loads 65 and auxiliary batter 67 as
represented by block 526. During the DC charging mode or the drive mode, the
26
relay S3 connected with the PFC output bus 21a and the DC-DC converter output
bus 22a or the rectifier output bus 208a and a relay switch S4 connected with a
low DC voltage bus 22c that is in turn connected with the DC-DC converter
output bus 22a or the rectifier output bus 208a are actuated by receiving signals
5 from the higher-level vehicle controller 10 via the onboard charger controller 23
such that the DC voltage from the traction battery pack 32 is passed through the
DC-DC converter 22' and converted to a low DC voltage which is available at the
low DC voltage bus 22c to be supplied to auxiliary loads 65 and auxiliary battery
67 of the electric vehicle. The standalone DC-DC converter 51' does not supply
10 power to the auxiliary loads 65 and auxiliary battery 67 in DC charging mode and
drive mode represented by block 528.
[0068] At block 530 and 532, the method 500 comprises measuring and
detecting by the higher-level vehicle controller 10, during the DC charging mode
or the drive mode of the electric vehicle, a drop in voltage of a low DC voltage
15 bus 65a or rise in temperature of the DC-DC converter 22' and if the measured
voltage or the temperature is low or high respectively, enabling power supply
from the standalone DC-DC converter 51' as well along with the DC-DC
converter 22' that helps in load sharing thereby maintaining voltage and
temperature, represented by block 534 i.e. power or DC voltage supply to the
20 auxiliary loads 65 and auxiliary loads 67 takes place both with the standalone DCDC converter 51' as along with the DC-DC converter 22'. If there is no low
voltage or temperature rise then load sharing by the standalone DC-DC converter
51' along with the DC-DC converter 22' is not performed.
TECHNICAL ADVANTAGES
25 [0069] The present disclosure provides a power supply system of the electric
vehicle and the method of operating such a power supply system that results in
efficient or better utilization of the components of the power supply system.
27
[0070] The present disclosure provides a power supply system of the electric
vehicle and the method of operating such a power supply system that results in the
downsized or reduced size of the components of the power supply system that
further reduces packaging requirements, cooling requirements as well as cost, and
5 power losses.
[0071] While the foregoing describes various embodiments of the present
disclosure, other and further embodiments of the present disclosure may be
devised without departing from the basic scope thereof. The scope of the
invention is determined by the claims that follow. The present disclosure is not
10 limited to the described embodiments, versions or examples, which are included
to enable a person having ordinary skill in the art to make and use the present
disclosure when combined with information and knowledge available to the
person having ordinary skill in the art.

We claim:

1. A power supply system (100') of an electric vehicle, the power supply
system (100') comprising:
a higher-level vehicle controller (10) to receive and detect signals regarding
5 a mode of operation of the electric vehicle, the mode of operation being an
alternating current, AC, charging mode, a direct current, DC, charging mode, or a
driving mode;
an on-board charger circuit (20), battery circuit (30) and a standalone
DC-DC converter circuit (50) having an on-board charger controller (23), battery
10 circuit controller (31), and a standalone DC-DC converter controller (52),
respectively that are controlled by the higher-level vehicle controller (10) based
on the signals received and detected by the higher-level vehicle controller (10),
characterized in that
the on-board charger circuit (20) comprising a power factor corrector, PFC,
15 (21) and a direct current-direct current, DC-DC, converter (22'), operates in the
DC charging mode and the drive mode as well in addition to the AC charging
mode, wherein
during the AC charging mode, a pair of relays S1 and S2 connected with a
PFC output bus (21a) and a DC-DC converter output bus (22a), respectively are
20 actuated by receiving signals from the higher-level vehicle controller (10) via the
onboard charger controller (23) such that a DC voltage from the onboard charger
circuit (20) or the DC-DC converter (22') is supplied to a traction battery pack
(32) via the DC-DC converter output bus (22a), and
during the DC charging mode or the drive mode, a relay S3 connected with
25 the PFC output bus (21a) and the DC-DC converter output bus (22a) or the
rectifier output bus (208a) and a relay switch S4 connected with a low DC voltage
bus (22c) that is in turn connected with the DC-DC converter output bus (22a) or
the rectifier output bus (208a) are actuated by receiving signals from the higherlevel vehicle controller (10) via the onboard charger controller (23) such that the
30 DC voltage from the traction battery pack (32) is passed through the DC-DC
29
converter (22') and converted to a low DC voltage which is available at the low
DC voltage bus (22c) to be supplied to auxiliary loads (65) and auxiliary battery
(67) of the electric vehicle.
5 2. The system (100') as claimed in claim 1, wherein during the DC charging
mode and the drive mode of the electric vehicle the relays S1 and S2 are kept
unactuated.
3. The system (100') as claimed in claim 1, wherein the standalone DC-DC
10 converter circuit (50) comprises a standalone DC-DC converter (51') that has a
power rating less than the power rating of the DC-DC converter (22') of the onboard charger circuit (20) and that operates mainly during the AC charging mode
to supply low DC voltage to the auxiliary loads (65) and the auxiliary battery (67)
of the electric vehicle.
15
4. The system (100') as claimed in claim 1, comprises a set of master relays
(69) that are connected with the auxiliary loads (65) and controlled by the higherlevel vehicle controller (10) by receiving signals via a bus (69a) such that during
the AC charging mode, the standalone DC-DC converter (51') supplies DC
20 voltage to a set of auxiliary loads (65) identified by the higher-level vehicle
controller (10) as “essential during AC charging” and the higher-level vehicle
controller (10) by sending a signal disconnects those master relays (69) that are
connected with a set of auxiliary loads (65) identified as “non-essential during AC
charging”.
25
5. The system (100') as claimed in claim 4, wherein the master relays (69)
are kept unactuated by the higher-level vehicle controller (10) during the DC
charging mode and the drive mode of the electric vehicle.
30
6. The system (100') as claimed in claim 1, wherein before the
commencement of any mode of operation of the electric vehicle, if the voltage of
the auxiliary battery (67) is less than a threshold voltage limit, the higher-level
vehicle controller (10) sends a signal to the on-board charger controller (23) and
5 the standalone DC-DC converter controller (51') such that the DC-DC converter
(22') supplies low DC voltage to the auxiliary battery (67) along with the
standalone DC-DC converter (51') till the threshold power limit of the auxiliary
battery (67) is attained and only then the mode of operation is allowed to
commence, by the higher-level controller (10).
10
7. A method of operating a power supply system (100') of an electric
vehicle, the method comprising:
receiving (502) and detecting (504) by a higher-level vehicle controller (10)
of the power supply system, signals regarding a mode of operation of the electric
15 vehicle, the mode of operation being an alternating current, AC, charging mode, a
direct current, DC, charging mode, or a driving mode;
controlling (506) by the higher-level vehicle controller (10) an on-board
charger controller (23), battery circuit controller (31) and standalone DC-DC
converter controller (52) of an on-board charger circuit (20), battery circuit (30)
20 and standalone DC-DC converter circuit (50), respectively based on the signals
received and detected by the higher-level vehicle controller (10), characterized
in that
the on-board charger circuit (20) comprising a power factor corrector, PFC,
(21) and a direct current-direct current, DC-DC, converter (22'), operates in the
25 DC charging mode and the drive mode as well in addition to the AC charging
mode, wherein
during the AC charging mode, a pair of relays S1 and S2 connected with a
PFC output bus (21a) and a DC-DC converter output bus (22a), respectively are
actuated by receiving signals from the higher-level vehicle controller (10) via the
30 onboard charger controller (23) such that a DC voltage from the onboard charger
31
circuit (20) or the DC-DC converter (22') is supplied to a traction battery pack
(32) via the DC-DC converter output bus (22a), and
during the DC charging mode or the drive mode, a relay S3 connected with
the PFC output bus (21a) and the DC-DC converter output bus (22a) or the
5 rectifier output bus (208a) and a relay switch S4 connected with a low voltage bus
(22c) that is in turn connected with the DC-DC converter output bus (22a) or the
rectifier output bus (208a) are actuated by receiving signals from the higher-level
vehicle controller (10) via the onboard charger controller (23) such that the DC
voltage from the traction battery pack (32) is passed through the DC-DC converter
10 (22') and converted to a low DC voltage which is available at the low DC voltage
bus (22c) to be supplied to auxiliary (65) and the auxiliary battery (67) of the
electric vehicle.
8. The method as claimed in claim 7, comprises detecting (514) by the
15 higher-level vehicle controller (10), before the commencement of any mode of
operation of the electric vehicle, whether the voltage of the auxiliary battery (67)
is less than a threshold voltage limit, and sending a signal by the higher-level
vehicle controller (10) to the on-board charger controller (23) and the standalone
DC-DC converter controller (52) such that the DC-DC converter (22') and the
20 standalone DC-DC converter (51') supplies low DC voltage to the auxiliary
battery (67) till the threshold power limit of the auxiliary battery (67) is attained
and only then allowing the mode of operation to commence, by the higher-level
controller (10).
25 9. The method as claimed in claim 8, comprises identifying (522) by the
higher-level vehicle controller (10) a set of auxiliary loads (65) as “essential
during charging” and “non-essential during charging” and by sending signals via a
bus (69a) actuating only those master relays (69) that are connected with the set of
auxiliary loads (65) identified as ‘essential during charging’ and disconnecting
30 those master relays (69) that are connected with the set of auxiliary loads (65)
32
identified as “non-essential during charging” such that DC voltage is supplied by
the DC-DC converter (22') and the standalone DC-DC converter (51') to only the
set of auxiliary loads (65) identified as ‘essential during charging’.
5 10. The method as claimed in claim 1, comprises detecting (532) by the
higher-level vehicle controller (10), during the DC charging mode or the drive
mode of the electric vehicle, a drop in voltage of a low DC voltage bus (65a) or
rise in temperature of the DC-DC converter (22') and enabling (534) power supply
from the standalone DC-DC converter (51') as well along with the DC-DC
10 converter (22').