The present invention relates to a Light Emitting Diodes (LEDs) based illumination system
for vehicular application such as two-wheeler, bike, motorbike, scooter and the like. In
particular the invention relates to a control device (206) for providing pre-configured constant
driving currents to a plurality of LED-based vehicular lights (2041...n).
Background of the Invention:
The two-wheeler vehicle such as bike, motorbike, scooter and the like comprises a head light
(which in turn comprises a low beam head light and a high beam head light), a position light,
left & right winkers at the front, left & right winkers at the rear, an illumination light located
near the rear license plate and a tail stop light associated with brakes.
In the prior art, the said lights incorporate incandescent bulbs. But the automobile industry is
evolving and moving towards replacing incandescent bulbs with the light emitting diodes
(LED) based vehicular lamps. The replacement of incandescent bulbs with LED based
vehicular lamps necessitates some additional components such as buck/boost converter,
current driver, power controller and the like.
A conventional circuit (100) for illuminating the LED based vehicular lamps is illustrated in
Figure 1. The circuit (100) comprises a power source (102), which may be for example, a
battery or a combination of Alternating Current Generator and Regulator/Rectifier (ACG-RR)
as carried by the vehicle. The circuit (100) further comprises plurality of LED based
vehicular lamps (1041....N). For the purposes of simplicity, only two LED based vehicular
lamps (1041 and 1042) are illustrated in Figure 1. The LED based vehicular lamps (1041 and
1042) are connected to the power source (102) via a power control device (106) which is
configured to receive the input voltage from the power supply (102) and provide constant
driving currents for illuminating each of the plurality of the LED-basedvehicular light
(1041and 1042). The circuit furthermore comprises switches (1081 and 1082) for controlling
the operation of the LED based vehicular lights. The power source (102) and the plurality of
LED-basedvehicular lamps (1041 and 1042) are connected to vehicle’s ground (110).
The power control device (106) provides constant currents to the LED-basedvehicular light
(1041 and 1042) connected thereto. In one option, the power control device (106) may
comprise a buck converter (114) configured to receive the input voltage and generate a
preconfigured driving voltage; and a plurality of linear driver elements (1121........n) connected
in parallel to each other and to an output of the buck converter (114). Since, in Figure 1, only
two LED based vehicular lamps (1041 and 1042) are illustrated, only two linear driver
elements (1121 and 1122) are shown.
The power control device (106) comprises a controller (124) that is connected to the switches
(1081 and 1082) for sensing their operation and based on their operation, control operation of
the linear driver elements (1121 and 1122). To enable the controller (124) to sense operation
of the switches (1081 and 1082), each switch is connected to the controller (124) via a switch
sensing resistance (1161, 1162) and a voltage divider element (1181, 1182).
The power control device (106) may additionally comprise a capacitor (120) that acts as a
short-time alternative power source (102). The power control device (106) may additionally
comprise a diode (122) which may be connected at the input of the capacitor (120).
The components of the power control device (106) are connected to a power control device
ground terminal (126). In particular, the buck converter (114), the linear driver elements
(1121, and 1122), the controller (124), and the switch sensing resistances (1161, 1162), the
capacitor (120), and the voltage divider elements (1181, 1182) are connected to the power
control device ground terminal (126). The power control device ground terminal (126) is then
connected to the vehicle’s ground (110) via a power control device ground wire (128).
It has been observed that as long as the power control device ground terminal (126) is
connected to vehicle’s ground (110), the power control device (106) performs as per the
requirement. On the other hand, if due to any reason, the electrical path between the power
control device ground terminal (126) and the vehicle’s ground (110) is interrupted, as shown
by arrow (130) in Figure 2, problems are faced.
Without wanting to be limited to specific instances, one instance when the electrical path
between the power control device ground terminal (126) and the vehicle’s ground (110) is
interrupted includes the power control device ground wire (128) getting disconnected from
the power control device ground terminal (126). Another instance when the electrical path
between the power control device ground terminal (126) and the vehicle’s ground (110) is
interrupted includes the power control device ground wire (128) getting disconnected from
vehicle ground (110). There may be other ways by which the electrical path between the
power control device ground terminal (126) and the vehicle’s ground (110) may get
interrupted.
In particular, when the electrical path between the power control device ground terminal
(126) and the vehicle’s ground (110) is interrupted, the linear driver element to which an
LED-based vehicular light (1042) having the minimum voltage drop is connected generates
excess heat and over a period of time, may get damaged.
In Figure 2, it can be seen that the LED-based vehicular light (1041) is shown to comprise of
three LED connected in series while the LED-based vehicular light (1042) is shown to
comprise of two LED connected in series. If all the LEDs are taken to be of equal rating in
terms of voltage drop, then the LED-based vehicular light (1042) will have the minimum
voltage drop. Thus, the linear driver element (1162) is said to be connected to LED-based
vehicular lamp having the minimum voltage drop. Thus, when the electrical path between the
power control device ground terminal (126) and the vehicle’s ground (110) is interrupted,
linear driver element (1162) generates excess heat and over a period of time, may get
damaged.
Thus, there exists a need to provide a solution to address the aforesaid problem facedwhen
the electrical path between the power control device ground terminal (126) and the vehicle’s
ground is interrupted.
Summary of the Invention:
This summary is provided to introduce a selection of concepts in a simplified format that is
further described in the detailed description of the invention. This summary is neither
intended to identify key or essential inventive concepts of the invention and nor is it intended
for determining the scope of the invention.
Accordingly the present invention provides a control device (206) for providing
preconfigured constant driving currents to a plurality of LED based vehicular lights (2041
.....n). The control device (206) comprises a buck converter (214) configured to receive input
voltage and generate a preconfigured driving voltage. The control device (206) further
comprises a plurality of liner driver elements (2121...n) connected in parallel to each other and
to an output of the buck converter, each of the plurality of linear driver elements being
configured to receive the preconfigured driving voltage as produced by the buck converter
(214) and generate a preconfigured constant current for driving a LED-based vehicular light
(2041 and 2042) connected thereto. The control device (206) further comprises a governing
unit (230) adapted to keep the buck converter (214) in a non-operating state, if the voltage at
an input of the buck converter (214) is outside a predetermined range.
In an embodiment of the invention, the control device (206) comprises a control device
ground terminal (226) connectable to vehicles ground terminal (210).
In another embodiment of the invention,the control device (206) and the plurality of LED
based vehicular lights (2041...n) from part of a circuit (200), the circuit (200) further
comprising a power source (202) and plurality of switches (2081...n) for controlling operation
of a respective LED-based vehicular light (2041 and 2042).
In yet another embodiment of the invention, the control device (206) comprises a controller
(224) connected to the switches (2081...n) for sensing their operation and based on their
operation, control operation of the corresponding linear driver element(s).
In still another embodiment of the invention, the controller (224) is connected to the switches
(2081...n), via a corresponding switch sensing resistance (2161, 2162) and voltage divider
element (2181, 2182).
In a further embodiment of the invention, the governing unit (230) exercises direct control
over the buck converter (214) by providing an enable signal to the buck converter (214).
In a furthermore embodiment of the invention, the governing unit (230) comprises a voltage
divider element (234, 236) configured to receive the input voltage and generate a
corresponding voltage signal, and an analog to digital converter (238) connected to the output
of the voltage divider (234, 236) and being adapted to generate the enable signal, the analog
to digital converter (238) being connected to an enable pin of the buck converter (214) for
providing the enable signal to the buck converter (214).
In another embodiment of the invention, the governing unit (230) is coupled to the controller
(224) and exercises indirect control over the buck converter (214).
In an embodiment of the invention, the controller (224) is adapted to provide an enable signal
to the buck converter (214) in response to receiving a control signal from the governing unit
(230).
In another embodiment of the invention, the governing unit (230) comprises a voltage divider
element (234, 236) configured to receive the input voltage and generate a corresponding
voltage signal, and an analog to digital converter (238) connected to the output of the voltage
divider (234, 236) and being adapted to generate a control signal, the analog to digital
converter (238) is connected to the controller (224) for providing the control signal to the
controller (224), and the controller (224) is adapted to provide an enable signal to the buck
converter (214) in response to receiving a control signal from the analog to digital converter
(238).
In yet embodiment of the invention, the governing unit (230) exercises direct control over the
buck converter (214) by interrupting supply of the input voltage to the buck converter.
In still another embodiment of the invention, the governing unit (230) comprises a voltage
divider element (234, 236) configured to receive the input voltage and generate a
corresponding voltage signal; and a transistor-based switch (232) connected between the
input line and the buck converter, the transistor-based switch (232) adapted to interrupt
supply of the input voltage to the buck converter (214) based on the voltage signal received
from the voltage divider element (234, 236).
To further clarify the advantages and features of the present invention, a more particular
description of the invention will be rendered by reference to specific embodiments thereof,
which is illustrated in the appended drawings. It is appreciated that these drawings depict
only typical embodiments of the invention and are therefore not to be considered limiting of
its scope. The invention will be described and explained with additional specificity and detail
with the accompanying drawings.
Brief Description of the drawings:
These and other features, aspects, and advantages of the present invention will become better
understood when the following detailed description is read with reference to the
accompanying drawings in which like characters represent like parts throughout the
drawings, wherein:
Figure 1 demonstrates a circuit (100) for providing a constant current to a plurality of LEDbased devices incorporated in a two-wheeled vehiclein accordance with the teachings of prior
art;
Figure 2 demonstrates the circuit (100) of the prior art with the electrical path between the
power control device ground terminal (126) and the vehicle’s ground (110) being interrupted;
Figure 3 demonstrates a circuit (200) for providing supply to plurality of LED based
vehicular lights (2041 and 2042), wherein the circuit (200) comprises a control device (206)
constructed in accordance with one embodiment of the present invention;
Figure 4 demonstrates a circuit (200) for providing supply to plurality of LED based
vehicular lights (2041 and 2042), wherein the circuit (200) comprises a control device (206)
constructed in accordance with another embodiment of the present invention;
Figure 5 demonstrates the circuit (200) for providing supply to plurality of LED based
vehicular lights (2041 and 2042), wherein the circuit (200) comprises a control device (206)
constructed in accordance with yet another embodiment of the present invention;
Figure 6 demonstrates an elaborate view of the governing unit as shown in figure 3 in
accordance with an embodiment of the present invention;
Figure 7 demonstrates an elaborate view of the governing unit as shown in figure 4, in
accordance with an embodiment of the present invention; and
Figure 8 demonstrates an elaborate view of the governing unit as shown in figure 5, in
accordance with an embodiment of the present invention.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for
simplicity and may not have been necessarily been drawn to scale. For example, the flow
charts illustrate the method in terms of the most prominent steps involved to help to improve
understanding of aspects of the present invention. Furthermore, in terms of the construction
of the device, one or more components of the device may have been represented in the
drawings by conventional symbols, and the drawings may show only those specific details
that are pertinent to understanding the embodiments of the present invention so as not to
obscure the drawings with details that will be readily apparent to those of ordinary skill in the
art having benefit of the description herein.
DETAILED DESCRIPTION OF FIGURES
For the purpose of promoting an understanding of the principles of the invention, reference
will now be made to the embodiment illustrated in the drawings and specific language will be
used to describe the same. It will nevertheless be understood that no limitation of the scope of
the invention is thereby intended, such alterations and further modifications in the illustrated
system, and such further applications of the principles of the invention as illustrated therein
being contemplated as would normally occur to one skilled in the art to which the invention
relates.
It will be understood by those skilled in the art that the foregoing general description and the
following detailed description are explanatory of the invention and are not intended to be
restrictive thereof.
Reference throughout this specification to “an aspect”, “another aspect” or similar language
means that a particular feature, structure, or characteristic described in connection with the
embodiment is included in at least one embodiment of the present invention. Thus,
appearances of the phrase “in an embodiment”, “in another embodiment” and similar
language throughout this specification may, but do not necessarily, all refer to the same
embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a
non-exclusive inclusion, such that a process or method that comprises a list of steps does not
include only those steps but may include other steps not expressly listed or inherent to such
process or method. Similarly, one or more devices or sub-systems or elements or structures or
components proceeded by "comprises... a" does not, without more constraints, preclude the
existence of other devices or other sub-systems or other elements or other structures or other
components or additional devices or additional sub-systems or additional elements or
additional structures or additional components.
Unless otherwise defined, all technical and scientific terms used herein have the same
meaning as commonly understood by one of ordinary skilled in the art to which this invention
belongs. The system, methods, and examples provided herein are illustrative only and not
intended to be limiting.
Embodiments of the present invention will be described below in detail with reference to the
accompanying drawings.
Now referring to Figure 3, there is illustrated a circuit (200) for illuminating the LED based
vehicular lights. The circuit (200) comprises a power source (202), which may be for
example, a battery or a combination of Alternating Current Generator and Regulator/Rectifier
(ACG-RR) as carried by the vehicle. The circuit (200) further comprises plurality of LED
based vehicular lights (2041 and 2042), only two of them are illustrated in Figure 3 for the
purposes of ease. The circuit (200) furthermore comprises switches (2081 and 2082) for
controlling the operation of the LED based vehicular lights (2041 and 2042). The power
source (202) and the plurality of LED-basedvehicular lights (2041 and 2042) are connected to
vehicle’s ground via vehicle ground wire (210).
The LED based vehicular lights (2041 and 2042) are connected to the power source (202) via
a power control device (206)which is configured to receive the input voltage from the power
source (202) and provide constant driving currents for illuminating each of the plurality of the
LED-basedvehicular lights (2041 and 2042).
The control device (206) comprises a buck converter (214) which is configured to receive
input voltage and generate a preconfigured driving voltage. The control device (206)
furthermore comprises plurality of liner driver elements (2121...n) which are connected in
parallel to each other and to an output of the buck converter (214). Each of the plurality of
linear driver elements (2121...n) is configured to receive the preconfigured driving voltage as
produced by the buck converter (214) and generate a preconfigured constant current for
driving a LED-based vehicular light (2041...n). The control device (206) further comprises a
governing unit (230) which is adapted to keep the buck converter (214) in a non-operating
stateif the voltage at an input of the buck converter (214) is outside a predetermined range.
In one option, the control device (206) comprises a controller (224) that is connected to the
switches (2081...n) for sensing their operation and based on their operation, control the
operation of the corresponding linear driver element(s). To enable the controller (224) sense
operation of the switches (2081...n), each switch is connected to the controller (224) via a
switch sensing resistance (2161, 2162) and a voltage divider element (2181, 2182).
The components of the control device (206) are connected to a power control device ground
terminal (226). In particular, the buck converter (214), the plurality of linear driver element
(2121...n), the controller (224), the switch sensing resistances (2161, 2162), the voltage divider
elements (2181, 2182) and the governing unit (230) are connected to the power control device
ground terminal (226). The power control device ground terminal (226) is then connected to
the vehicle’s ground (210) via a ground wire (228).
In the circuit (200) as shown in Figure 3, as long as the power control device ground terminal
(226) is connected to vehicle’s ground (210) the voltage at an input of the buck converter
(214) is within a predetermined range. On the other hand, if the electrical path between the
control device ground terminal (226) and the vehicle’s ground (210) is interrupted, the
voltage at the input of the buck converter (214) falls outside the predetermined range.
By way of a non-limiting example, the predetermined range may be governed by the voltage
being supplied by the power source (202) (which may not be constant, for battery). By way of
another non-limiting example, the predetermined range may be governed by the minimum
voltage at which the control device (206) has to come to operating state. By way of another
non-limiting example, the predetermined range may be governed by a voltage drop across a
LED based vehicular light (2041...n) that is connected to the linear drive elements (2121...n). By
way of a non-limiting example, the predetermined range may be governed by the voltage
being supplied by the power source (202) and a voltage drop across an LED based vehicular
light (2041...n) which is having the minimum voltage requirement. By way of a non-limiting
example, the predetermined range may be governed by the voltage being supplied by the
power source (202); a voltage drop across an LED based vehicular light (2041...n) which is
having the minimum voltage requirement and a minimum voltage at which the power control
device (206) has to come to operating state. Thus, based on one or more these factors, the
predetermined range may be set.
Thus, by detecting the input of the buck converter (214) as being outside the predetermined
range, an interruption between the electrical path between the power control device (206)
ground terminal (226) and the vehicle’s ground (210) can be detected. If in response to such
detection, the buck converter (214) is maintained in non-operating state, none of the linear
driver elements (2121...n) generate excess heat and or gets damaged. Thus, the problem faced
in the problem is fully and satisfactorily solved.
The governing unit (230) as proposed by the present invention detects the input of the buck
converter (214) and detects whether the input of the buck converter (214) is outside the
predetermined range. In case the input of the buck converter (214) is outside the
predetermined range, the governing unit (230) keeps the buck converter (214) in nonoperating state.
In an embodiment of the invention, the governing unit (230) may exercises direct control
over the buck converter (214) by providing an enable/disable signal to the buck converter
(214) and keeps the buck converter (214) in operating state or in non-operating state. This
aspect is demonstrated in Figure 3 which is characterized by a direct connection between the
governing unit (230) and the buck converter (214).
In an alternative embodiment of the invention, the governing unit(230) exercisesindirect
control over the buck converter (214) and keeps the buck converter (214) in operating state or
in non-operating state. As indicated above, the control device (206) comprises a controller
(224) that controls the operation of the buck converter (214). Thus, by way of a non-limiting
example, the governing unit (230) may exercise control over the buck converter (214) via the
controller (224) and keeps the buck converter (214) in operating state or in non-operating
state. This aspect is demonstrated in Figure 4, wherein the governing unit (230) can be seen
to be coupled to the controller (224) and the controller (224) is coupled to the buck converter
(214). As there is no other difference between the circuit (200) or the control device (206)
shown in Figure 3 and the circuit (200) or the control device (206) shown in Figure 4, the
remaining part is not being described.
In an alternative embodiment of the invention the governing unit (230) may be adapted to
exercise control over the buck converter (214) by interrupting supply of the input/output
voltage to the buck converter. This aspect is demonstrated in Figure 5, wherein the governing
unit (230) is shown to additionally comprise a switch (232) connected in series and to the
input/output line which supplies voltage to the buck converter (214). By controlling the state
of the switch (232), the buck converter (214) may be kept in any one of operating/nonoperating state.
Now referring to Figure 6, construction of the governing unit (230) in the circuit (200) of
Figure 3 is elaborately illustrated and the remaining aspects have been not shown. It can be
seen that the governing unit (230) in one embodiment comprises a voltage divider (234, 236)
comprising a first resistor (234) and a second resistor (236) which are connected in series and
to the input line which supplies voltage to the buck converter (214). The voltage divider
element (234, 236) configured to receive the input voltage and generate a corresponding
voltage signal. The governing unit (230) further comprises an analog to digital converter
(238) connected to the output of the voltage divider (234, 236) and it is adapted to generate a
control signal. The analog to digital converter (238) is connected to the buck converter (214)
and is adapted to provide the control signal to the buck converter.
Now referring to Figure 7, construction of the governing unit (230) in the circuit (200) of
Figure 4 is elaborately illustrated and the remaining aspects have been not shown. It can be
seen that the governing unit (230) in one embodiment comprises a voltage divider (234, 236)
comprising a first resistor (234) and a second resistor (236) which are connected in series and
to the input line which supplies voltage to the buck converter (214). The governing unit (230)
further comprises an analog to digital converter (238) which receives an output from the
voltage divider. The analog to digital converter (238) converts the output as received from the
voltage divider (234, 236) into digital signal and then feeds the same to the controller (224).
The controller (224) based on the digital signal received from the analog to digital converter
(238) keeps the buck converter (214) in operating state or in non-operating state.
Now referring to Figure 8, construction of the governing unit (230) in the circuit (200) of
Figure 5 is illustrated. It can be seen that the governing unit (230) inthis embodiment
comprises a voltage divider element (234, 236) comprising a first resistor (234) and a second
resistor (236) which are connected in series and to the input/output line which supplies
voltage to the buck converter (214). The voltage divider element (234, 236) is configured to
generate a corresponding voltage signal. The voltage signal thus generated is provided to a
base terminal of a transistor based switch (232), which is connected between the input/output
line & the buck converter. If the voltage signal provided to the base terminal of the transistor
based switch (232) is within the predetermined range, the transistor based switch (232) is
within the predetermined range, the transistor based switch comes to ON state and supplies
the input/output voltage to the buck converter. On the other hand, when the voltage signal is
outside the predetermined range, the transistor based switch (232) is in an off state &
therefore, interrupts supply of input/output voltage to the buck converter.
While certain present preferred embodiments of the invention have been illustrated and
described herein, it is to be understood that the invention is not limited thereto. Clearly, the
invention may be otherwise variously embodied, and practiced within the scope of the
following claims.

WE CLAIM:

1. A control device (206) for providing pre-configured constant driving currents to a
plurality of LED-based vehicular lights, (2041...n) said control device (206)
comprising:
a buck converter (214) configured to receive input voltage and generate a
preconfigured driving voltage;
a plurality of liner driver elements (2121...n) connected in parallel to each other and to
an output of the buck converter, each of the plurality of linear driver elements being
configured to receive the preconfigured driving voltage as produced by the buck
converter (214) and generate a preconfigured constant current for driving a LEDbased vehicular light (2041...n) connected thereto;
a governing unit (230) adapted to keep the buck converter (214) in a non-operating
state, if the voltage at an input of the buck converter (214) is outside a predetermined
range.
2. The control device as claimed in claim 1, wherein the control device (206) comprises
a control device ground terminal (226) connectable to vehicles ground terminal (210).
3. The control device as claimed in claim 1, wherein the control device (206) and the
plurality of LED based vehicular lights (2041...n) from part of a circuit (200), the
circuit (200) further comprising a power source (202) and plurality of switches
(2081...n) for controlling operation of a respective LED-based vehicular light (2041...n).
4. The control device as claimed in claim 1, wherein the control device (206) comprises
a controller (224) connected to the switches (2081...n) for sensing their operation and
based on their operation, control operation of the corresponding linear driver
element(s).
5. The control device as claimed in claim 1, wherein the controller (224) is connected to
the switches (2081...n), via a corresponding switch sensing resistance (2161, 2162) and
voltage divider element (2181, 2182).
6. The control device as claimed in claim 1, wherein the governing unit (230) exercises
direct control over the buck converter (214) by providing an enable signal to the buck
converter.
7. The control device as claimed in claim 6, wherein the governing unit (230) comprises
a voltage divider element (234, 236) configured to receive the input voltage and
generate a corresponding voltage signal, and an analog to digital converter (238)
connected to the output of the voltage divider and being adapted to generate the
enable signal, the analog to digital converter (238) being connected to an enable pin
of the buck converter (214) for providing the enable signal to the buck converter
(214).
8. The control device as claimed in claim 1, wherein the governing unit (230) is coupled
to the controller (224) and exercises indirect control over the buck converter (214).
9. The control device as claimed in claim 8, wherein the controller (224) is adapted to
provide an enable signal to the buck converter (214) in response to receiving a control
signal from the governing unit (230).
10. The control device as claimed in claim 8, wherein the governing unit (230) comprises
a voltage divider element (234, 236) configured to receive the input voltage and
generate a corresponding voltage signal, and an analog to digital converter (238)
connected to the output of the voltage divider (234, 236) and being adapted to
generate a control signal, the analog to digital converter (238) being connected to the
controller (224) for providing the control signal to the controller (224), and the
controller (224) is adapted to provide an enable signal to the buck converter (214) in
response to receiving a control signal from the analog to digital converter (238).
11. The control device as claimed in claim 1, wherein the governing unit (230) exercises
direct control over the buck converter (214) by interrupting supply of the input
voltage to the buck converter (214).
12. The control device as claimed in claim 11, wherein the governing unit (230)
comprises:
a voltage divider element (234, 236) configured to receive the input voltage and
generate a corresponding voltage signal; and
a transistor-based switch (232) connected between the input line and the buck
converter (214) , the transistor-based switch (232) adapted to interrupt supply of the
input voltage to the buck converter (214) based on the voltage signal received from
the voltage divider element (234, 236).