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.
Background of the Invention:
A two-wheeler vehicle such as bike, motorbike, scooter and the like comprises a 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), and a tail stop light associated with brakes.
In the prior art, said lights incorporates incandescent bulbs. The automobile industry is evolving and moving towards replacing incandescent bulbs with the light emitting diode (LED) for the fact that LED has an extremely long lifespan and are energy efficient as compared to any other lighting technology. As LED is a constant current device, replacement of incandescent bulbs with LED necessitates use of some additional components such as buck/boost converter, current driver, power controller and the like.
By way of example, E.P. Patent no. 2538753 discloses a driver device for light-emitting diodes, comprising: - a controllable first power source configured to produce a first voltage at its output and a buck converter having an input coupled to the output of said first power source, and an output for coupling light-emitting diodes thereto. Further, the E.P. Patent discloses that same principle can be applied in cases where there are multiple buck converters that all receive their input voltages from a common controllable first power source. In such a case it may happen that different numbers of serially coupled LEDs are driven by different ones of the buck converters.
By way of example, Non- Patent Literature "LED Controllers and Switches Improve Matrix Lighting" as may be downloaded from https://www.planetanalog.com/author.asp7section id=3406&doc id=565004 discloses a led driving circuit with multiple buck converters. It has been felt that the use of multiple buck converters will increase the cost.
By way of example, U.S. Patent No. 20040155844 discloses a driver circuit for energizing a plurality of LEDs, said driver circuit comprising: a constant current source responsive to a first input to produce a current and connectable to an emitter comprising a plurality of LEDs, said constant current source configured to monitor an electrical current through the plurality

of LEDs and limit said current to said current; a controller programmed to; monitor the state of a synchronization input to the controller; provide said first input to said constant current source in a predetermined pattern, initiation of said pattern alternatively controlled by the controller or by a change of state of said synchronization input; and produce a synchronization output indicating initiation of said pattern by said controller; and a synchronization circuit electrically connected to a synchronization line, said synchronization circuit responsive to a change in the electrical potential present on the synchronization line from a first electrical potential to a second electrical potential to provide said synchronization input to the controller and responsive to said synchronization output from the controller to apply said second electrical potential to said synchronization line, wherein initiation of said pattern is triggered by the change of electrical potential on the synchronization line if said synchronization input is present before the controller produces said synchronization output and initiation of said pattern by said controller is triggered by the controller if said synchronization input is not present before the controller produces said synchronization output.
Thus, it has been felt that the existing LED-based illumination systems suffer from several disadvantages including high cost, large size, increased complexity, high heat dissipation etc. Therefore, a simpler and cost-efficient LED-based illumination 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.
Accordingly, the present invention provides a LED-based illumination device (206) for vehicular application, said LED-based illumination system (206) being connected between a
power supply device (202) and a plurality of LED-based devices (204i n), the LED-based
illumination system (206) being configured to receive the input voltage from the power supply device (202) and provide preconfigured constant driving currents for driving each of
the plurality of the LED-based devices (2041 n). In an embodiment of the invention the
LED-based illumination system (206) comprises a buck converter (208) configured to receive the input voltage and generate a preconfigured driving voltage. In an embodiment of the invention, the LED-based illumination system (206) further comprises a plurality of driver

circuits (210i n) adapted to receive the preconfigured driving voltage as produced by the
buck converter (208) and generate preconfigured constant driving currents along a plurality
of current flow paths (212i n) that are parallel to each other for supply to the LED-based
device (204i n) connected thereto. In a further embodiment of the invention, the LED-
based illumination system (206) comprises a control unit (214) adapted to set an impairment
flag if the output voltage (VOUTi n) in any of the plurality of current flow paths (212i n) is
greater than a threshold value (Ui n) corresponding thereto.
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 LED-based devices incorporated in a two-wheeled vehicle in accordance with the teachings of
Applicant's co-pending patent application NO. ;
Figure 2 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) in accordance with the teachings of the present application;
Figure 3 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) having therein over-voltage signal generation devices (216i....n) in accordance with the teachings of the present application;
Figure 4 demonstrates a circuit (200) for providing a constant current to four LED-based devices, the circuit incorporating the LED based illumination device (206) having four over-voltage signal generation devices specifically adopted for providing supply to the four LED based devices;

Figure 5 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) having
therein output voltage sensors (220i n) in accordance with the teachings of the present
application;
Figure 6 demonstrates a circuit (200) for providing a constant current to four LED-based devices, the circuit incorporating the LED based illumination device (206) having four output voltage sensors specifically adopted for providing supply to the four LED based devices; Figure 7 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) having input voltage sensor (224) in accordance with the teachings of the present application; Figure 8 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) having
driver circuit control switch (226i n) dedicated for each driver circuit (210i n) in
accordance with the teachings of the present invention;
Figure 9 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) having a
single driver circuit control switch (226i n) for all driver circuits (210i n) in accordance
with the teachings of the present invention; and
Figure 10 demonstrates a circuit (200) for providing a constant current to a plurality of LED-based devices the circuit incorporating the LED based illumination device (206) comprising various other features in accordance with the teachings 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.
Referring to Figure 1, a two-wheeled vehicle may be provided with a circuit (100) that
comprises a power supply device (102) and a plurality of LED-based devices (104i n). The
circuit (100) is disclosed in Applicant's co-pending patent application No. ,
complete contents of which are incorporated herein. The circuit (100) may comprise a power
controller (106) connected between the power supply device (102) and the plurality of LED-
based devices (104i n). The power controller (106) is configured to receive input voltage
from the power supply device (102) and provide constant driving currents to each of the
plurality of the LED-based devices (104i n). The power controller (106) comprises a buck
converter (108) configured to receive the input voltage and generate the preconfigured driving voltage. The power controller (106) further comprises a plurality of driver circuits
(110i n) connected to the buck converter (108). The plurality of driver circuits (110i n)
being connected so as to be parallel to each other. Each of the plurality of driver circuits
(110i n) receives the preconfigured driving voltage as produced by the buck converter
(108) and generates preconfigured constant driving current for supply to LED-based device
(104i n) connected thereto. The power controller (106) may additionally comprise a
capacitor (112) to act as a backup in an event of non-availability of input voltage from the power supply device (102). A reverse protection device (114) is provided in the path between the power supply device (102) and the capacitor (112).
The power controller (106) further comprises a plurality of diodes (116i...n) connected after a junction terminal (JT), wherein the junction terminal being located between the buck
converter (108) and the plurality of current drivers (110i n)- The plurality of diodes
(116i...n) provide safeguard against "wire harness output short to power supply device condition".
However, in the circuit (100) it is not possible to detect the wire harness output short to power supply device condition as the junction terminal is prohibited from reaching a voltage which is substantially equal to the input voltage as being supplied by the power supply device. Thus, providing an error signal for example, on an instrument cluster (or a dashboard), which is generally beneficial for the end user, is not possible with the circuit (100). Also, by providing the plurality of diodes (116i...n), the minimum voltage required for the circuit to function increases. Since, the LED-based devices are incorporated in a two-

wheeled vehicle having limited voltage, an increase in the minimum voltage required for the circuit to function is a substantial drawback. Accordingly, there exists a need to address the aforesaid disadvantages.
Referring to Figure 2, there is illustrated a circuit (200) for providing a constant current to a plurality of LED-based devices incorporated in a two-wheeled vehicle in accordance with an embodiment of the invention. The circuit (200) comprises a LED-based illumination device (206) connected between a power supply device (202) and a plurality of LED-based devices
(204i J. In an embodiment, the power supply device (202) may include a battery or a
combination of ACG and regulator/rectifier. The LED-based illumination device (206) is
configured to receive the input voltage from the power supply device (202) and provide
constant driving currents to each of the plurality of the LED-based devices (204i n).
In an embodiment of the invention, the LED-based illumination device (206) comprises a buck converter (208) configured to receive the input voltage and generate a preconfigured
driving voltage, and a plurality of driver circuits (210i n) connected in parallel to each
other and to an output of the buck converter (208). Each of the plurality of driver circuits
(210i n) is configured to receive the preconfigured driving voltage as produced by the buck
converter (208) and generate the preconfigured constant driving currents along a plurality of
current flow paths (212i n) that are parallel to each other for providing to the plurality of
LED-based devices (204i n) connected thereto. The LED-based illumination device (206)
further comprises a control unit (214) adapted to set an impairment flag if the output voltage
in any of the plurality of current flow paths (212i n) is greater than a threshold value
corresponding thereto. It may be noted that setting of the impairment flag, is indicative of "wire harness output short to power supply device condition", as only during "wire harness output short to power supply device condition" the voltage in any of the plurality of current flow paths can exceed the threshold value corresponding thereto.
Now comparing the LED-based illumination device (206) with the power controller (106), it can be observed that the LED-based illumination device (206) is provided with a control unit (214) adapted to set an impairment flag, while no such control unit is made available in the power controller (106). As each current flow path in the power controller (106) comprises a diode (116i...n), during "wire harness output short to power supply device condition" no current flows through any of the plurality of current flow paths and hence, no voltage is available for detection. Thus, even if the power controller (106) is provided with a control

unit, the power controller (106) would not be in a position to set the impairment flag. Also, as the LED-based illumination device (206) does not contain the diodes (116i...n) in each of the
current flow paths (212i n), the minimum voltage required for the circuit to function is not
increased.
As shown in Figure 3, in an embodiment of the invention, each of the plurality of current
flow paths (212i n) is provided with an over-voltage signal generation device (216i n)-
Each of the over-voltage signal generation device (216i n) is adapted to generate over-
voltage signal if the output voltage (VOUTi n) in the current flow path (212i n) to which
the over-voltage signal generation device is connected becomes greater than the threshold value corresponding thereto. The control unit (214) is operably coupled to the over-voltage
signal generation devices (216i n) and is adapted to set the impairment flag in response to
receiving the over-voltage signal from any of the over-voltage signal generation devices
(216i n)- In an embodiment of the invention, the over-voltage signal generation device
(216i n) comprises a comparator (218i n) adapted to generate the over-voltage signal if
the output voltage (VOUTi n) in the current flow path (212i n) to which it is connected
becomes greater than the threshold value (Ui n) corresponding thereto.
Figure 4, is a block diagram of a possible embodiment of the circuit (200) comprising 4 LED-based devices (204i, 2042, 2043, and 2044). The LED-based illumination device (206) defines four different electrical paths (212i, 2122, 2123, and 2124), each of which is parallel to one another. In each electrical path (212i, 2122, 2123, and 2124), one driver circuit (210i, 2IO2, 2103, and 2IO4) is provided. Furthermore, to each electrical path (212i, 2122, 2123, and 2124), one LED-based device (204i, 2042, 2043, and 204^ is connected. The LED-based illumination device (206) comprises four over-voltage signal generation devices (2161, 2I62, 2I63, and 2I64) connected to each of the four electrical paths (212i, 2122, 2123, and 2124). The over-voltage signal generation devices (2161, 2I62, 2I63, and 2I64) are connected downstream of the driver circuit (210i, 2IO2, 2103, and 2IO4). Each of the over-voltage signal generation device (2161, 2I62, 2I63, and 2I64) is adapted to generate over-voltage signals (Si, S2, S3 and S4) if the output voltage (VOUTi, VOUT2, VOUT3, and VOUT4) in the current flow path (212i, 2122, 2123, and 2124) downstream of the driver circuits (210i, 2IO2, 2IO3, and 2IO4) becomes greater than a threshold value corresponding thereto (Ui, U2, U3 and U4). Thus, by way of example, the first over-voltage signal generation device (2161) will generate a first over voltage signal (Si) in case the output voltage VOUTi in the first current flow path

(212i) downstream of the driver circuit (210i) exceeds the first threshold value Ui. Likewise, the second over-voltage signal generation device (2162) will generate a second over voltage signal (S2) in case the output voltage VOUT2 in the second flow path (2122) downstream of the driver circuits (2IO2) exceeds the second threshold value U2; the third over-voltage signal generation device (2163) will generate a third over voltage signal (S3) in case the output voltage VOUT3 in the third current flow path (2123) downstream of the driver circuit (2IO3) exceeds the third threshold value U3; and the fourth over-voltage signal generation device (2164) will generate a fourth over voltage signal (S4) in case the output voltage VOUT4 in the fourth current flow path (2124) downstream of the driver circuit (2IO4) exceeds the fourth threshold value U4.
It may be noted that the threshold values (Ui, U2, U3 and U4) corresponding to each of four current flow paths (212i, 2122, 2123, and 2124) may be same or different and can be set by the user.
In an embodiment of the invention, the threshold values (Ui, U2, U3 and U4) corresponding to each of four current flow paths (212i, 2122, 2123, and 2124) may be set on the basis of voltage requirement of each of the four LED-based devices (204i, 2042, 2043, and 2044). By way of example, if the first LED-based device (204i) connected to the first current flow path (212{) has a first voltage requirement of VRi, the first threshold value Ui may be set on the basis of the first voltage requirement of VRi. Likewise, if the second LED-based device (2042) connected to the second current flow path (2122) has a second voltage requirement of VR2, the second threshold value U2 may be set on the basis of the second voltage requirement of VR2; if the third LED-based device (204s) connected to the third current flow path (2123) has a third voltage requirement of VR3, the third threshold value U3 may be set on the basis of the third voltage requirement of VR3; and if the fourth LED-based device (2044) connected to the fourth current flow path (2124) has a fourth voltage requirement of VR4, the fourth threshold value U4 may be set on the basis of the fourth voltage requirement of VR4.
In accordance an alternative embodiment of the invention, the threshold values (Ui, U2, U3, and U4) corresponding to the four current flow paths (212i, 2122, 2123, and 2124) is set as a constant value. By way of example, the constant value thus set may be determined based on the LED device having the maximum voltage requirement. Let's consider a scenario wherein the 4 LED devices four LED-based devices (204i, 2042, 2043, and 2044) have 7.5V, 6.8V, 6.1V, and 5.4V as their voltage requirement, the threshold value corresponding to all the

current flow paths can be set to a constant value, which depends upon 7.5V (the maximum voltage requirement among all the connected LED devices).
In an embodiment of the invention, each of the over-voltage signal generation devices (216i, 2I62, 2I63, and 2I64) comprises a comparator (218i, 2I82, 2I83, and 2I84). For example, the first over-voltage signal generation device (2161) comprises a first comparator (2181), the second over-voltage signal generation device (2162) comprises a second comparator (2182), the third over-voltage signal generation device (2163) comprises a third comparator (2183), and fourth over-voltage signal generation device (2164) comprises a fourth comparator (2184). In relation to the comparators (2181, 2182, 2183, and 2184), the threshold values (Ui, U2, U3 and U4) may be set by controlling Vcc (i.e. Comparator reference voltage) of each of the comparators. Thus, by way of example, in relation to the first comparator, the first threshold value Ui may be set by controlling Vcci. Likewise, in relation to the second comparator, the second threshold value U2 may be set by controlling VCC2; in relation to the third comparator, the third threshold value U3 may be set by controlling VCC3; and in relation to the fourth comparator, the fourth threshold value U4 may be set by controlling VCC4.
The control unit (214) is operably coupled to the over-voltage signal generation devices (216i, 2I62, 2I63, and 2I64) and is adapted to set the impairment flag in response to receiving the over-voltage signal from any of the four over-voltage signal generation devices (2161, 2162, 2163, and 2164). Thus, the control unit (214) may set the impairment flag in response to receiving any of Si, S2, S3 or S4.
Referring to Figure 5, in an embodiment of the invention, each of the plurality of current
flow path (212i n) is provided with an output voltage sensor (220i n) for sensing the
voltage (VOUTi n) after output terminal of each of the plurality of driver circuits
(210i n). In this embodiment, the current flow paths (212i n) are not provided with over-
voltage signal generation device (2161 n)- In accordance with this embodiment of the
invention, the control unit (214) is configured to receive output voltages (VOUTi n) as
sensed by each of the output voltage sensors (220i n), compare each of the received output
voltage (VOUTi n) with a threshold value corresponding thereto (Ui n), and set the
impairment flag if any of the received output voltage (VOUTi n) is greater than the
threshold value (Ui n) corresponding thereto. It may be noted that the control unit (214) is
operably coupled to a memory unit (222) and is configured to extract there-from the threshold
value (Ui n) corresponding to each of the output voltage sensors (220i n).

Figure 6, is a block diagram of a possible embodiment of the circuit (200) comprising 4 LED-based devices (2041, 2042, 2043, and 2044) and wherein the LED-based illumination device (206) includes four output voltage sensors (220i, 2202, 2203, and 22O4). The LED-based illumination device (206) of Figure 6 also defines four different electrical paths (212i, 2122, 2123, and 2124), each of which is parallel to one another. To each electrical path (212i, 2122, 2123, and 2124), one LED-based device (204i, 2042, 2043, and 2044) is connected. In each electrical path (212i, 2122, 2123, and 2124), one driver circuit (210i, 2IO2, 2103, and 2IO4) is provided. In each of the four electrical paths (2121, 2122, 2123, and 2124), an output voltage sensor (220i, 2202, 2203, and 22O4) is connected. In particular, the output voltage sensors (220i, 2202, 2203, and 22O4) are connected downstream of the driver circuit (210i, 2IO2, 2IO3, and 2IO4). Each of the output voltage sensors (220i, 2202, 22O3, and 22O4) is adapted to sense voltage signals (VOUTi, VOUT2, VOUT3, and VOUT4) after output terminal of each of the driver circuits (210i, 2IO2, 2IO3, and 2IO4).
Thus, by way of example, the first output voltage sensor (220i) is connected to the first current flow path (212i) downstream of the first driver circuit (210i) and is adapted to sense the output voltage VOUTi. Likewise, the second output voltage sensor (22O2) is connected to the second current flow path (2122) downstream of the second driver circuit (2IO2) and is adapted to sense the output voltage VOUT2; the third output voltage sensor (22O3) is connected to the third current flow path (212s) downstream of the third driver circuit (2IO3) and is adapted to sense the output voltage VOUT3; and the fourth output voltage sensor (22O4) is connected to the fourth current flow path (2124) downstream of fourth second driver circuit (2IO4) and is adapted to sense the output voltage VOUT4.
Each of the output voltage sensors (220i, 2202, 22O3, and 22O4) is connected to the control unit (214) and provide to the control unit (214) an indication as to output voltage as sensed (VOUTi, VOUT2, VOUT3, and VOUT4).
The control unit (214) is adapted to set the impairment flag if the output voltage (VOUTi, VOUT2, VOUT3, and VOUT4) in the current flow path (212L 2122, 2123, and 2124) downstream of the driver circuits driver circuit (210i, 2IO2, 2IO3, and 2IO4) becomes greater than a threshold value corresponding thereto (Ui, U2, U3 and U4). Thus, by way of example, the control unit (214) will set the impairment flag if the output voltage VOUTi in the first current flow path (212i) exceeds the first threshold value Ui. Likewise, the control unit (214)

will set the impairment flag if the output voltage VOUT2 in the second flow path (2122) exceeds the second threshold value U2; the control unit (214) will set the impairment flag if the output voltage VOUT3 in the third current flow path (212s) exceeds the third threshold value U3; and the control unit (214) will set the impairment flag if the output voltage VOUT4 in the fourth current flow path (2124) exceeds the fourth threshold value U4.
It may be noted that the threshold values (Ui, U2, U3 and U4) corresponding to each of four current flow paths (212i, 2122, 2123, and 2124) are stored in a memory (222). The control unit will fetch the threshold values (Ui, U2, U3 and U4) from the memory (222) and do the comparison as mentioned in the above paragraph.
It may be noted that the threshold values (Ui, U2, U3 and U4) corresponding to each of four current flow paths (212i, 2122, 2123, and 2124) may be same or different and can be set by the user. As mentioned above in relation to Figure 4, in an embodiment of the invention, the threshold values (Ui, U2, U3 and U4) corresponding to each of four current flow paths (212i, 2122, 2123, and 2124) may be set on the basis of voltage requirement of each of the four LED-based devices (204i, 2042, 2043, and 2044). As mentioned above in relation to Figure 4, in an alternative embodiment, the threshold values (Ui, U2, U3, and U4) corresponding to the four current flow paths (212i, 2122, 2123, and 2124) may be set as a constant value.
As an example, let's consider a scenario wherein the LED-based illumination device (206) receives an input voltage of the order of 12V from a battery and 4 LED-based devices (204i, 2042, 2043, and 2044) each having a voltage requirement of about 7.5V is connected to the output of the LED-based illumination device (206). In this scenario, the buck converter (208) may be configured to produce a preconfigured driving voltage of about 9V. Thus, in one embodiment of the invention, the threshold values (Ui, U2, U3, and U4) corresponding to the four current flow paths (212i, 2122, 2123, and 2124) may be set as a constant value which may be about 9V. Thus, if the output voltage in a particular current flow path increases beyond 9V (i.e. VOUTI > 9V or VOUT2 > 9V or VOUT3 > 9V or VOUT4 > 9V), an impairment flag may be set.
One scenario which is commonly faced in a vehicle includes change in the input voltage over time. If the input voltage being supplied changes over time, and in particular, if the input voltage being supplied reduces over time, it may be advantageous to consider additional factors for setting the impairment flag.

For example, under a scenario wherein: (a) the LED-based illumination device (206) has 4 LED-based devices (204i, 2042, 2043, and 2044) each having a voltage requirement of about 7.5V connected thereto; (b) the threshold values (Ui, U2, U3, and U4) corresponding to the four current flow paths (212i, 2122, 2123, and 2124) has been set as a constant value of about 9V; and (c) the LED-based illumination device (206) receives an input voltage of the order of about 9.0 to about 9.7V from the battery (instead of 12V); the output voltage in the four current flow paths (212i, 2122, 2123, and 2124) will not exceed 9V even under "wire harness output short to power supply device condition" and hence, it may be advantageous to consider additional factors for setting the impairment flag.
In this regard, attention is drawn to Figure 7, wherein the LED-based illumination device (206) is additionally provided with an input voltage sensor (224). The input voltage sensor (224) is connected before the buck converter (208) and hence, senses the voltage as being supplied by the power source (202) (i.e. VIN). In this embodiment, the current flow paths
(212i n) are not provided with over-voltage signal generation device (2161 n), instead,
each of the plurality of current flow path (212i n) is provided with an output voltage sensor
(220i n) for sensing the voltage (VOUTi n) after output terminal of each of the plurality
of driver circuits (210i n). In accordance with this embodiment of the invention, the control
unit (214) is configured to receive output voltages (VOUTi n) as sensed by each of the
output voltage sensors (220i n) and the input voltage (VIN) as sensed by the input voltage
sensor (224). The control unit (214) is further configured to compare each of the received
output voltage (VOUTi n) with the received input voltage (VIN) and to determine
differences therebetween (VDIFFi n). The control unit (214) is further configured to set the
impairment flag if any of the differences (VDIFFi n) is less than a threshold value (X). It
may be noted that the control unit (214) is operably coupled to the memory unit (222) and is configured to extract there-from the threshold value (X).
The control unit (214) may be configured such that it first determines as to whether any of the output voltages is greater than the corresponding threshold value i.e. is VOUTi > Uj (wherein "i" is an integer having a value greater than 0 and equal to or less than n). In case the output voltage in any of the current flow path VOUTi is greater than the corresponding threshold value Ui, the control unit is configured to set the impairment flag. If however VOUTi < Ui,
the control unit may determine (VDIFFi n) and in case any one of VDIFFi is less than the
threshold value X, set the impairment flag.

It may be noted that the LED-based illumination devices of the present invention are not only capable of detecting "wire harness output short to power supply device condition", but are also capable of localizing as to which wire harness has been shorted to power supply device. For instance, if we take into consideration the LED-based illumination device shown in Figure 4, if the first over-voltage signal generation device (2161) generates the first over voltage signal (Si), it can be said that the first current flow path (212i) has been shorted to power supply device. Likewise, if we take into consideration the LED-based illumination device shown in Figure 6, if the control unit (214) determines that output voltage VOUT2 in the second flow path (2122) exceeds the second threshold value U2, it can be said that the second current flow path (2122) has been shorted to power supply device. Similarly, if we take into consideration the LED-based illumination device shown in Figure 7, if the control unit (214) determines that output voltage VOUT3 in the third flow path (2123) does not exceed the third threshold value U3, but that the voltage difference (VDIFF3) between the output voltage in the third flow path (VOUT3) and the input voltage (VIN) is less than the threshold value (X), it can be said that the third current flow path (2123) has been shorted to power supply device.
In addition to setting the impairment flag (or in other words, detecting the wire harness output short to power supply device condition), in an embodiment of the invention, the control unit
(214) may be further configured to control the ON/OFF state of the driver circuits (210i „)•
In an embodiment of the invention, to enable the control unit (214) control the ON/OFF state
of the driver circuits (210i n), the LED-based illumination device (206) further comprises
at least one driver circuit control switch (226i n). In an embodiment of the invention, the
control unit (214) may generate at least one control signal (CSi n) and provide the at least
one control signal (CSl....n) to the at least one driver circuit control switch (226i n) thereby
control the ON/OFF state of the driver circuits (210i n).
In an embodiment of the invention, the control unit (214) may selectively control the
ON/OFF state of the driver circuits (210i n) i.e. the control unit (214) may keep one or
more of the driver circuits in ON state while may keep the remaining of the driver circuits in OFF state. In a non-limiting example of the invention, the control unit (214) may selectively
control the ON/OFF state of the driver circuits (210i n) based on the localizing as to which
wire harness has been shorted to power supply device. In another non-limiting example of the invention the control unit (214) may selectively control the ON/OFF state of the driver

circuits (210i n) based on the nature of the load thus connected. For instance, a driver
circuit driving a predetermined type of LED-based device may be kept in ON state despite detection of the wire harness short to power supply device condition while the remaining driver circuits (i.e. the driver circuits that are NOT driving the predetermined type of LED-based device) may be kept in OFF state.
In an embodiment of the invention as illustrated in Figure 8, each driver circuit (210i n)
forming part of the LED-based illumination device (206) is provided with a dedicated driver
circuit control switch (226i n) and each of the driver circuit control switch (226i n) is
connected to the control unit (214). Also, the control unit (214) is adapted to generate and
provide dedicated control signal to the driver circuit control switch (226i n) to selectively
control the ON/OFF state of the driver circuits (210i n).
In an alternative embodiment of the invention, the control unit (214) may uniformly control
the ON/OFF state of the driver circuits (210i n) i.e. the control unit (214) may keep all of
the driver circuits (210i n) in ON state or keep all of the driver circuits (210i n) in OFF
state.
It may be noted that the control unit (214) may keep all of the driver circuits (210i n) in
ON state or keep all of the driver circuits (210i n) in OFF state even in the LED-based
illumination device (206) as shown in Figure 8. For this purpose, the control unit (214) is
merely required to generate a single control signal and provide the single control signal to all
of the dedicated driver circuit control switch (226i n).
It may be noted that in an alternative embodiment as shown in Figure 9, a single driver
circuit control switch (226) is shared by of all the driver circuits (210i n). The single driver
circuit control switch (226) is connected to the control unit (214). The control unit generates
and provides a single control signal to the single driver circuit control switch (226) and thus
controls the ON/OFF state of all driver circuits (210i n).
In an embodiment of the invention, once the control unit (214) detects the wire harness output short to battery condition, the control unit (214) may be further configured to generate error signal. In an embodiment of the invention as shown in Figure 10, the LED based illumination device (206) may further comprise an error signal output device (228) and the control unit (214) may be further adapted to provide the error signal to the error signal output

device (228). The error signal output device (228) may be a visual output providing device that may be disposed on the instrument cluster of the vehicle. Alternatively, the error signal output device (228) may be an audio output providing device that may be disposed at a suitable location on the vehicle.
The LED based illumination device (206) may further comprise an error signal storing unit (230) and the control unit (214) may be further adapted to provide the error signal to the error signal storing unit (230). The error signal thus stored on the error signal storing unit (230) may be used for diagnostic purposes.
In an embodiment of the invention, the LED-based illumination device (206) may comprise a capacitor (232) to act as a backup in an event of non-availability of input voltage from the power supply device (202).
In an embodiment of the invention, the LED-based illumination device (206) may further comprise a reverse protection device (234) provided in a path between the power supply device (202) and the capacitor (232).
In an embodiment of the invention, the output voltage sensors may be resistor connected in shunt with the current flow paths. In an embodiment of the invention, the input voltage sensor may be a resistor connected in shunt with buck converter.
In an embodiment of the invention, each of the driver circuit control switch (226i....n) is a transistor. It may be noted that as operation of the driver circuit control switches (218i....n) that
are placed in conjunction with the driver circuits (210i n) come into picture only under
wire harness output short to battery condition, despite placing the driver circuit control
switches (218i....n) in conjunction with the driver circuits (210i n), the minimum voltage
required for the circuit to function does not increase. Thus, the circuit (200) does not need an increased minimum voltage for its proper functioning.
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 LED-based illumination device (206) for vehicular application, said LED-based
illumination system (206) being connected between a power supply device (202) and
a plurality of LED-based devices (204i n), the LED-based illumination system
(206) being configured to receive the input voltage from the power supply device (202) and provide preconfigured constant driving currents for driving each of the
plurality of the LED-based devices (2041 n), the LED-based illumination system
(206) comprising:
a buck converter (208) configured to receive the input voltage and generate a preconfigured driving voltage;
a plurality of driver circuits (210i n) adapted to receive the preconfigured
driving voltage as produced by the buck converter (208) and generate preconfigured
constant driving currents along a plurality of current flow paths (212i n) that are
parallel to each other for supply to the LED-based device (2041 n) connected
thereto;
a control unit (214) adapted to set an impairment flag if the output voltage
(VOUTi n) in any of the plurality of current flow paths (212i n) is greater than a
threshold value (Ui n) corresponding thereto.
2. The LED-based illumination device for vehicular application as claimed in claim 1,
wherein each of the plurality of current flow path is provided with an over-voltage
signal generation device (216i n), the over-voltage signal generation device
(216i n) being adapted to generate an over-voltage signal (Si n) if the output
voltage (VOUTi n) in the current flow path (212i n) is greater than the threshold
value (Ui n) corresponding thereto.
3. The LED-based illumination device for vehicular application as claimed in claim 3,
wherein the over-voltage signal generation device (216i n) comprises a comparator
(218i....n) adapted to generate the over-voltage signal (Si n) if the output voltage
(VOUTi n) in the current flow path (212i n) is greater than the threshold value
(Ui n) corresponding thereto.
4. The LED-based illumination device for vehicular application as claimed in claim 3,
wherein the control unit (214) is operably coupled to the over-voltage signal

generation devices (2161 n) and is adapted to set the impairment flag in response to
receiving the over-voltage signal (Si n) from any of the over-voltage signal
generation devices (2161 n)-
5. The LED-based illumination device for vehicular application as claimed in claim 1,
wherein each of the plurality of current flow paths (212i n) is provided with an
output voltage sensor (220i n) for sensing the output voltage (VOUTi n) after
output terminal of each of the plurality of driver circuits (210i n).
6. The LED-based illumination device for vehicular application as claimed in claim 5,
wherein control unit (214) is configured to receive output voltages (VOUTi n) as
sensed by each of the output voltage sensors (220i n), compare each of the received
output voltage with a threshold value (Ui n) corresponding thereto, and set the
impairment flag if any of the received output voltage (VOUTi n) is greater than the
threshold value corresponding thereto (Ui n).
7. The LED-based illumination device for vehicular application as claimed in claim 6,
wherein control unit (214) is operably coupled to a memory unit (222) and is
configured to extract there-from the threshold value (Ui n) corresponding to each of
the output voltage sensors (220i n)-
8. The LED-based illumination device for vehicular application as claimed in claim 1,
wherein the control unit (214) is configured to receive input voltage (VIN) as sensed
by an input voltage sensor (224), receive output voltages (VOUTi n) as sensed by
each of the output voltage sensors (220i n), compare each of the received output
voltage (VOUTi n) with the received input voltage (VIN) to determine differences
therebetween (VDIFFi n), and set the impairment flag if any of the differences
(VDIFFi n) is less than a threshold value (X).
9. The LED-based illumination device for vehicular application as claimed in claim 1,
wherein each of the driver circuits (210i n) has a dedicated driver circuit control
switch (226i n) for controlling an ON/OFF state of the driver circuit (210i n).
10. The LED-based illumination device for vehicular application as claimed in claim 9,
wherein the control unit (214) is adapted to provide control signals (CSi....n) to each of
the driver circuit control switches (226i n), each of the control signals (CSi....n)

being same or different, thereby controlling the ON/OFF state of the driver circuit
(210! n).
11. The LED-based illumination device for vehicular application as claimed in claim 1, wherein the control unit (214) is further adapted to generate an error signal (ES) in response to setting the impairment flag and provide the error signal (ES) to an error signal output device (228) or error signal storing unit (230).
12. The LED-based illumination device for vehicular application as claimed in claim 1 comprises: a capacitor (232) to act as a backup in an event of non-availability of input voltage from the power supply device (202).
13. The LED-based illumination device for vehicular application as claimed in claim 12 comprises: a reverse protection device (234) is provided in the path between the power supply device (202) and the capacitor (232).