The present invention relates to a Light Emitting Diode (LED) based illumination system for
vehicular applications such as two-wheeler, bike, motorbike, scooter and the like. In
particular, the invention relates to controlling illumination of light-emitting diodes of a
vehicular lamp.
Background of the Invention:
The vehicle includes a multitude of lights such as position indicating light, left & right
winkers at the front, left & right winkers at the rear, a license plate illuminating light (located
near a rear license plate), headlight and a tail stop light associated with brakes.
Out of these lights, two lights namely Tail-Stop Light and Headlight are adapted to output
two levels of illumination. For example, the headlight is configured to output a first level of
illumination when it is operated in a low beam state and output a second level of illumination
(which is higher than the first level of illumination) when it is operated in high beam state or
pass beam state. Likewise, the Tail-Stop Light is configured to output a first level of
illumination when it is operated in tail light state (when the ignition switch is switched ON)
and is configured to output a second level of illumination (which is higher than the first level
of illumination) when it is operated in stoplight state (i.e. when the brake is pressed).
Therefore, a first prior art practice is to provide two sets of LEDs in the LED-based Headlight
and in the LED-based Tail-Stop Light. When the LED-based Headlight and LED-based TailStop Light is required to output the first level of illumination, one of the two sets of LEDs is
operated using a first current driver. In particular, a control unit provides an enable signal to
the first current driver thereby bringing the first current driver to ON state. On the other hand,
when the LED-based Headlight and Tail-Stop Light is required to output the second level of
illumination, both sets of LEDs are operated using the first current driver and a second
current driver. In particular, the control unit provides a first enable signal to the first current
driver and a second enable signal to the second current driver thereby bringing the first
current driver and the second current driver to ON state. The aforesaid arrangement is widely
followed for the reason that it is simple. However, this arrangement is not cost-effective and
necessitates the use of a higher number of current drivers (which provide a constant current to
the LEDs).
3
A second prior art practice that is followed is to configure a single current driver to produce a
constant current which corresponds to the second level of illumination and then digitally
modulates the constant current using pulse width modulation signal. In this approach, the
control unit provides an enable signal to the current driver thereby bringing the current driver
to ON state and a pulse width modulator selectively supplies pulse width modulation signal to
the current driver. While in the approach, the number of current drivers is less, the circuit,
however, becomes complicated on account of the use of a pulse width modulator, which
supplies the pulse width modulation signal to the current driver.
Thus, it has been felt that the existing LED-based illumination systems and more particularly,
LED-based Tail-Stop Light illuminating system and LED-based Headlight illuminating
system suffers from several disadvantages including high cost, large size, increased
complexity, high heat dissipation etc. Therefore, a simpler and cost-efficient LED-based TailStop Light illuminating system or LED-based Headlight illuminating system is required.
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.
The present invention relates to a device (100) for controlling illumination of light-emitting
diodes (LEDs) of a vehicular lamp (102) in accordance with an embodiment of the invention.
The device (100) comprises a constant current driver (104) driving the light-emitting diodes
(LEDs) of the vehicular lamp (102). The device further comprises a first current setting unit
(106) connected to the constant current driver (104) and a second current setting unit (108)
connected to the constant current driver (104) via the first current setting unit (106).
Furthermore, the device (100) comprises a control unit (110) adapted to provide an OFF
signal to the first current setting unit (106) and an ON signal to the second current setting unit
(108), thereby setting a current output by the constant current driver (104) at a first constant
value. The control unit (110) is further adapted to provide an ON signal to the first current
setting unit (106) and an OFF signal to the second current setting unit (108), thereby setting a
current output by the constant current driver (104) at a second constant value, the second
constant value being greater than the first constant value.
4
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 illustrates a device for controlling illumination of light-emitting diodes (LEDs) of a
vehicular lamp in accordance with an embodiment of the invention;
Figure 2 illustrates a current setting device for controlling illumination of light-emitting
diodes (LEDs) of a vehicular lamp in accordance with an embodiment of the invention;
Figure 3 illustrates a non-limiting example of the current setting device for controlling
illumination of light-emitting diodes (LEDs) of a vehicular lamp in accordance with an
embodiment of the invention;
Figure 4 illustrates the circuit for controlling illumination of LED-based Tail-Stop Light in
accordance with an embodiment of the invention; and
Figure 5 illustrates the circuit for controlling illumination of LED-based Headlight in
accordance with an embodiment of the 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 THE INVENTION
5
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.
6
Referring to Figure 1, there is illustrated a device (100) for controlling illumination of lightemitting diodes (LEDs) of a vehicular lamp (102) in accordance with an embodiment of the
invention. The device (100) comprises a constant current driver (104) driving the lightemitting diodes (LEDs) of the vehicular lamp (102). The device further comprises a first
current setting unit (106) connected to the constant current driver (104) and a second current
setting unit (108) connected to the constant current driver (104) via the first current setting
unit (106).
Furthermore, the device (100) comprises a control unit (110) adapted to provide an OFF
signal to the first current setting unit (106) and an ON signal to the second current setting unit
(108), thereby setting a current output by the constant current driver (104) at a first constant
value. The control unit (110) is further adapted to provide an ON signal to the first current
setting unit (106) and an OFF signal to the second current setting unit (108), thereby setting a
current output by the constant current driver (104) at a second constant value, the second
constant value being greater than the first constant value.
In particular, the device (100) is adapted to control illumination of LED-based Headlight
(102) and comprises a control unit (110) adapted to provide an OFF signal to the first current
setting unit (106) and an ON signal to the second current setting unit (108), thereby setting a
current output by the constant current driver (104) at a first constant value for low headlight
operation. The control unit (110) is further adapted to provide an ON signal to the first
current setting unit (106) and an OFF signal to the second current setting unit (108), thereby
setting a current output by the constant current driver (104) at a second constant value for
high beam/pass beam, the second constant value being greater than the first constant value.
Similarly, the device (100) may be adapted to control illumination of LED-based Tail-Stop
Light (102) and comprises a control unit (110) adapted to provide an OFF signal to the first
current setting unit (106) and an ON signal to the second current setting unit (108), thereby
setting a current output by the constant current driver (104) at a first constant value for tail
light operation. The control unit (110) is further adapted to provide an ON signal to the first
current setting unit (106) and an OFF signal to the second current setting unit (108), thereby
setting a current output by the constant current driver (104) at a second constant value for
stop light operation, the second constant value being greater than the first constant value.
7
Now referring to Figure 2, each current setting unit (106,108) includes an element imparting
resistance (112, 114) and an associated switching unit (116, 118) and the control unit (110) is
coupled to the switching units (116 and 118) forming part of the first and the second current
setting units (106, 108).
By way of a non-limiting example, as illustrated in Figure 3, the first current setting unit
(106) connected to the constant current driver (104) and the second current setting unit (108)
connected to the constant current driver (104) via the first current setting unit (106) comprise:
a first element imparting resistance (112) connected to the constant current driver (104), a
second element imparting resistance (114) and a first switching unit (116) connected in
parallel with each other and to the first element imparting resistance (112); and a second
switching unit (118) connected in series with the second element imparting resistance (114).
The first switching unit (116) and the second switching unit (118) are connected to the
ground.
When the first current setting unit (106) and the second current setting unit (108) are having
the aforesaid construction, by providing an OFF signal to the first switching unit (116) and an
ON signal to the second switching unit (118), both the first element imparting resistance
(112) and the second element imparting resistance (114) gets connected to the constant
current driver (104). Thus, the current output by the constant current driver (104) gets set at a
first constant value. On the other hand, by providing an ON signal to the first switching unit
(116) and an OFF signal to the second switching unit (118), only the first element imparting
resistance (112) gets connected to the constant current driver (104). Thus, the current output
by the constant current driver (104) gets set at a second constant value, which is greater than
the first constant value.
In an embodiment of the invention, the first element imparting resistance and the second
element imparting resistance (112, 114) may both be resistors. In an alternative embodiment
of the invention, the first element imparting resistance and the second element imparting
resistance (112, 114) may both be inductors. In another alternative embodiment of the
invention, the first element imparting resistance and the second element imparting resistance
(112, 114) may both be diodes. In another alternative embodiment of the invention, the first
element imparting resistance and the second element imparting resistance (112, 114) may
both be transistors. In yet another alternative embodiment of the invention, one of the first
elements imparting resistance or the second element imparting resistance (112 or 114) may
8
be a resistor while the other may be an inductor or a diode or a transistor. In a further
alternative embodiment of the invention, one of the first element imparting resistance or the
second element imparting resistance (112 or 114) may be an inductor while the other may be
a resistor or a diode or a transistor or Field Effect Transistor (FET) (including MOSFET).
In an embodiment of the invention, the first switching unit (116) and the second switching
unit (118) may both be semiconductor-based switches. For example, the semiconductor-based
switches may be transistors or Field Effect Transistor (FET) (including MOSFET).
Referring to Figure 4, there is illustrated a circuit (200) for controlling illumination of LEDbased Tail-Stop Light (102) in accordance with a preferred embodiment of the invention. The
circuit (200) comprises a power source (120), 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 an LED-based Tail-Stop Light (102). The
circuit furthermore comprises switches (1221, 1222) for controlling the operation of the LEDbased Tail-Stop Light (102).
The LED-based Tail-Stop Light (102) is connected to the power source (120) via a device
(100) which is configured to receive the input voltage from the power source (120) and
provide a first constant driving current or a second constant driving current to LED-based
Tail-Stop Light (102).
In an embodiment of the invention, the circuit may comprise two switches (1221 and 1222)
for tail light operation and stop light operation. When a first switch (1221) corresponding to
the ignition switch alone is switched ON by the user, the control unit (110) is adapted to
provide an OFF signal to the first current setting unit (106) and an ON signal to the second
current setting unit (108), thereby setting a current output by the constant current driver (104)
at a first constant value for tail light operation. When the second switch (1222) corresponding
to brake is actuated by the user (and irrespective of the actuation state of the first switch
(1221)), the control unit (110) is adapted to provide an ON signal to the first current setting
unit (106) and an OFF signal to the second current setting unit (108), thereby setting a current
output by the constant current driver (104) at a second constant value for stop light operation.
In an embodiment of the invention, the device (100) further comprises a buck converter (124)
is connected between a power source (120) and the constant current driver (104). The buck
9
converter is adapted to receive an input voltage from the power source (120) and generate a
preconfigured driving voltage to be supplied to the constant current driver (104).
In an embodiment of the invention, a capacitor (126) is provided to act as a backup in an
event of non-availability of input voltage from the power source (120). In an embodiment of
the invention, a reverse protection device (128) is provided in the path between the power
source (120) and the capacitor (126).
Now referring to Figure 5, there is illustrated a circuit (200) for controlling illumination of
LED-based Headlight (102). The circuit (200) comprises a power source (120), 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
an LED-based headlight (102). The circuit furthermore comprises switches (1221, 1222, and
1223) for controlling the operation of the LED-based headlight (102).
The LED-based headlight (102) is connected to the power source (120) via a device (100)
which is configured to receive the input voltage from the power source (120) and provide a
first constant driving current or a second constant driving current to LED-based headlight
(102).
In an embodiment of the invention, the circuit may comprise three switches (1221, 1222, and
1223) for low beam operation, high beam operation, and pass beam operation. When a first
switch (1221) corresponding to low beam is actuated by the user, the control unit (110) is
adapted to provide an OFF signal to the first current setting unit (106) and an ON signal to
the second current setting unit (108), thereby setting a current output by the constant current
driver (104) at a first constant value for low beam operation. When the second switch (1222)
corresponding to high beam is actuated by the user, the control unit (110) is adapted to
provide an ON signal to the first current setting unit (106) and an OFF signal to the second
current setting unit (108), thereby setting a current output by the constant current driver (104)
at a second constant value for high beam operation. When the third switch (1223)
corresponding to pass beam is actuated by the user, the control unit (110) is adapted to
provide an ON signal to the first current setting unit (106) and an OFF signal to the second
current setting unit (108), thereby setting a current output by the constant current driver (104)
at a second constant value for pass beam operation.
10
In an embodiment of the invention, the device (100) further comprises a buck converter (124)
is connected between a power source (120) and the constant current driver (104). The buck
converter is adapted to receive an input voltage from the power source (120) and generate a
preconfigured driving voltage to be supplied to the constant current driver (104).
In an embodiment of the invention, a capacitor (126) is provided to act as a backup in an
event of non-availability of input voltage from the power source (120). In an embodiment of
the invention, a reverse protection device (128) is provided in the path between the power
source (120) and the capacitor (126).
Comparing the solution as proposed by the invention with the first prior art practice, it can be
observed that the present invention does not necessitate the use of two sets of current drivers.
Comparing the solution as proposed by the invention with the second prior art practice, it can
be observed that the present invention merely uses two elements imparting resistance (112,
114) and two switching units (116, 118) to obtain the necessary functionality. Thus, the
complexity of the device and the cost of the device is substantially reduced.
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 device (100) for controlling illumination of light-emitting diodes (LEDs) of a
vehicular lamp, comprising:
a constant current driver (104) driving the light-emitting diodes (LEDs) (102)
of the vehicular lamp;
a first current setting unit (106) connected to the constant current driver (104);
a second current setting unit (108) connected to the constant current driver
(104) via the first current setting unit (106); and
a control unit (110) adapted to provide:
an OFF signal to the first current setting unit (106) and an ON signal to the
second current setting unit (108), thereby setting a current output by the constant
current driver (104) at a first constant value; and
an ON signal to the first current setting unit (106) and an OFF signal to the
second current setting unit (108), thereby setting a current output by the constant
current driver (104) at a second constant value, the second constant value being
greater than the first constant value.
2. The device as claimed in claim 1, wherein each current setting unit (106, 108) include
an element imparting resistance (112, 114) and an associated switching unit (116,
118).
3. The device as claimed in claim 1, wherein the first current setting unit (106)
connected to the constant current driver (104) and the second current setting unit
(108) connected to the constant current driver (104) via the first current setting unit
(106) comprise:
a first element imparting resistance (112) connected to the constant current
driver (104);
a second element imparting resistance (114) and a first switching unit (116)
connected in parallel with each other and to the first element imparting resistance
(112); and
a second switching unit (118) connected in series with the second element
imparting resistance (114), the first switching unit (116) and the second switching unit
(118) being connected to ground.
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4. The device as claimed in claim 2, wherein the elements imparting resistance
(112,114) are selected from a group of resistance, inductor, diode, transistor, and
Field Effect Transistor (FET).
5. The device as claimed in claim 2, wherein the switching unit (116, 118) is a
semiconductor-based switching unit selected from a group consisting of a transistor, a
Field Effect Transistor (FET).
6. The device as claimed in claim 1, comprising a buck converter (124) connected
between a power source (120) and the constant current driver (104); the buck
converter (124) being adapted to receive input voltage from the power source (120)
and generate a preconfigured driving voltage to be supplied to the constant current
driver (104); a capacitor (126) provided to act as a backup in an event of nonavailability of input voltage from the power source (120); and a reverse protection
device (128) is provided in the path between the power source (120) and the capacitor
(126).
7. A circuit for controlling illumination of light-emitting diodes (LEDs) of a vehicular
lamp, comprising:
a power source (120);
a LED-based vehicular lamp (102);
a plurality of switches (1221, ....n) for controlling the operation of the LEDbased vehicular lamps (102); and
a device (100) as claimed in claim 1 configured to receive the input voltage
from a power source (120) and control signals from the switches (122), the device
(100) being further configured to provide a first constant driving current or a second
constant driving current to the LED-based vehicular lamp (102).
8. The circuit as claimed in claim 7, wherein the LED-based vehicular lamp (102) is a
LED-based headlight (102), the circuit comprises:
a first switch (1221) corresponding to low beam state of the headlight, a second switch
(1222) corresponding to high beam state of the headlight, and a third switch (1223)
corresponding to pass beam state of the headlight,
the control unit (110), in response to actuation of the first switch (1221), is adapted to
provide an OFF signal to the first current setting unit (106) and an ON signal to the
13
second current setting unit (108), thereby setting a current output by the constant
current driver (104) at a first constant value for low beam operation;
the control unit (110), in response to actuation of the second switch (1222) is adapted
to provide an ON signal to the first current setting unit (106) and an OFF signal to the
second current setting unit (108), thereby setting a current output by the constant
current driver (104) at a second constant value for high beam operation; and
the control unit (110), in response to actuation of the third switch (1223) is adapted to
provide an ON signal to the first current setting unit (106) and an OFF signal to the
second current setting unit (108), thereby setting a current output by the constant
current driver (104) at a second constant value for pass beam operation
9. The circuit as claimed in claim 7, wherein the LED-based vehicular lamp (102) is a
Tail-Stop Light (102), the circuit comprises:
a first switch (1221) corresponding to tail light;
a second switch (1222) corresponding to brake light;
the control unit (110), in response to actuation of the first switch (1221), being
adapted to provide an OFF signal to the first current setting unit (106) and an ON
signal to the second current setting unit (108), thereby setting a current output by the
constant current driver (104) at a first constant value for tail light operation; and
the control unit (110), in response to actuation of the second switch (1222),
being adapted to provide an ON signal to the first current setting unit (106) and an
OFF signal to the second current setting unit (108), thereby setting a current output by
the constant current driver (104) at a second constant value for stop light operation.