FIELD OF INVENTION
[001] The present invention in general relates to a system for heat management of Light Emitting Diode (LED) devices. The present invention in particular relates to a system for heat management of LED lighting devices through combination of conduction and convection of heat emitted by LED lighting devices. BACKGROUND OF THE INVENTION
[002] LEDs are basically specialised type of diode as they have very similar electrical characteristics to a PN junction diode. LED allows passing of current in its forward direction but block the flow of current in the reverse direction. Light emitting diodes (LED) are made from a very thin layer of fairly heavily doped semiconductor material and depending on the semiconductor material used and the amount of doping, when forward biased an LED will emit a coloured light at a particular spectral wavelength. When the diode is forward biased, electrons from the semiconductors conduction band recombine with holes from the valence band and releases sufficient energy to produce photons which emit monochromatic (single colour) of light.
[003] The Light Emitting Diode (LED) devices are typically made of a diode mounted onto a die or chip, where the diode is surrounded by an encapsulant. The die is connected to a power source, which, in turn, transmits power to the diode. In most cases, the LED device is supported in a reflector cup that is attached to an electrode (the cathode), while the top face of the chip is connected with a bonding wire to a second electrode (the anode).
[004] The LED lighting devices converts electrical energy into light and heat energy when electrical energy is supplied to LED device through point of source or Chip on Board (COB). The Chip on Board (COB) LEDs are basically multiple LED chips (typically nine or more) bonded directly to a substrate by the manufacturer to form a single module. Since the individual LEDs used in a COB are chips and not traditionally packaged, the chips can be mounted such that they take up less space and the highest potential of the LED chips can be obtained. As per the principle of

LED point source, only 40% of electrical energy is converted into light energy whereas almost 60% of electrical energy is converted into heat energy which results in increasing the temperature of the point of source or COB source. If the heat that is being generated by LED is not effectively removed from the system, the LEDs will run at high temperatures, thereby lowering the efficiency and reducing the reliability of the LED lighting system. The higher temperature at junction for longer period leads to short life of lighting device and also deteriorates the colour stability and lumen output of the LED.
[005] In order to remove excessive heat generated at junction, a heat management system is required to remove excess heat from the junction at the earliest and providing thermal stability to the LED device. As per the theory of thermal management system, heat transfer takes place by three modes- conduction, convection and radiation. A heat management system extracts the heat energy from the heat source through conduction mode and thereafter, heat is further dissipated to the ambient environment by convection mode. Radiation plays negligible role in earthly environment compared to heat dissipation needs in space applications and dynamic systems.
[006] Heat dissipation of LED lighting device is essential for controlling the temperature of the device. The life of the device depends upon the junction temperature of LEDs. Higher the temperature at the junction, lower is the useful life of LEDs. Also, the stability of colour of light and lumen output stability depends upon the stability of the junction temperature and time, after the operation of device. [007] The present invention pertains to a heat management system for LED lighting device that facilitates lowering of junction temperature and acquiring stability of the device at a comparatively reduced time frame. [008] US patent: US20110267821 Al discloses a lighting device that comprises one or more solid state light emitters (e.g., one or more light emitting diodes) and two or more heat dissipation elements. It describes plurality of heat dissipation elements where the majority of the heat transferred from the light source is transferred by conduction and combination of conduction and convection. It also discloses that the component or components of the thermal management system of

the lighting device is/are selected so as to extract heat from the light source(s) and dissipate the extracted heat to a surrounding environment at such a rate that a temperature is maintained at or below a particular temperature (e.g., to maintain a junction temperature of a solid state light emitter at or below a 25,000 hour rated lifetime junction temperature for the solid state light source in a 25°C. surrounding environment. The focus of the cited prior art is to design a right reflector that is to be placed in the path of emitted light and do not take into account of stabilization of junction temperatures of LEDs linked with colour stability and lumen stability of emitted light. Also the applicability of the prior art is limited depending upon the reflector requirement for both high power and low power LED lighting devices. [009] US Patent: US20110215697A1 discloses a LED lamp with active cooling element and where the heat dissipation form the phosphor carrier is achieved through a combination of convection thermal dissipation and conduction through the heat sink structure. Solid state lamp or bulb structures are disclosed that can provide an essentially omnidirectional emission pattern from directional emitting light sources, such as forward emitting light sources. The present invention is also directed to lamp structures using active elements to assist in thermal management of the lamp structures and in some embodiments to reduce the convective thermal resistance around certain of the lamp elements to increase the natural heat convection away from the lamp. Some embodiments include integral fans or other active elements that move air over the surfaces of a heat sink, while other embodiments comprise internal fans or other active elements that can draw air internal to the lamp. The fan's movement of the air over these surfaces can agitate otherwise stagnant air to decrease the convective thermal resistance and increasing the ability of the lamp to dissipate heat generated during operation. The cited prior art is based on forced convection method of heat management system. The working of the cited prior art is more cumbersome due to involvement of electronics components and also extra energy is spent in controlling the fan movement. The present is simple and robust with no electronic components attached. [0010] US Patent: US20150252997A1 describes a micro-channel heat sink for LED headlamp. It discloses various embodiments of a heat sink for semiconductor

devices and methods for using and constructing the same. In the cited prior art, a heat sink for cooling a semiconductor device is disclosed that includes a base plate including a first side and a second side; a leg extending from the second side of the base plate, the leg including a distal end opposite the base plate and opposing walls extending between the base plate and distal end. The cited prior art discloses about liquid coolant that is forced using external pump through headers ending in microchannels for extracting and dissipating heat from the system. The working of the prior art is energy intensive process.
[0011] US Patent: US9565733B2 describes a variable lumen output and color spectrum for LED lighting. The cited prior art refers about a thermal monitoring module and/or an adaptive heat sink that may be used to accommodate changes in lumen output during peak usage times of the day. It further discloses a temperature module to determine a temperature associated with the LED lighting system and compare it with the maximum value and a manual, user selectable turbo boost mode to set a current flow to the LED lighting system at a second, higher unsustainable value for the given environment and a threshold module to automatically decrease the current flow to the LED lighting system based on the determined temperature being within a predetermined range of the maximum value, such that the LED lighting system is automatically transitioned out of the manually selected turbo boost mode. The cited prior art provides for flexibility of varying color temperature and lumen output. It does not provide for quick stabilization of system parameters. Also the applicability of the cited prior art is limited to indoor/decorative lighting where different color light chromaticity is required.
[0012] The cited prior art discloses different method and system for thermal management of heat generated by LED devices. The present invention proposes a simple and efficient system for heat management of LED devices. OBJECTIVE
[0013] It is therefore the object of the present subject matter to overcome the aforementioned and other drawbacks in prior method/product/apparatus.

[0014] The principal objective of the present invention is to provide a heat
management system for LED lighting device.
[0015] Yet another objective of the present invention is to provide a heat
management system for LED lighting devices that is light in weight.
[0016] Still another objective of the present invention is to provide a heat
management system for LED lighting devices that extracts heat from LED lighting
device by combination of conduction and convection mode of heat transfer.
[0017] Still another objective of the present invention is to provide a light weight
and non-expensive heat management system for LED lighting devices.
[0018] Yet another objective of the present invention is to provide for a heat
management for LED lighting device that stores excess heat generated by LED
lighting device.
[0019] Yet another objective of the present invention is to provide a heat
management system that facilitates LED device to gain stability at a reduced time
frame.
[0020] These and other objects and advantages of the present subject matter will be
apparent to a person skilled in the art after consideration of the following detailed
description taken into consideration with accompanying drawings in which
preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION:
[0021] Solution to one or more drawbacks of existing heat management system of the LED devices is disclosed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.
[0022] According to the present invention, a heat management system for LED device is proposed. The heat management system comprises of a LED device that is connected to a Printed Circuit Board (PCB). The PCB mechanically supports and electrically connects electronic or electrical components of LED device

using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. The LED device is mounted with a LED driver that delivers power to the LED device in a regulated manner. The heat management system further comprises of a plate fastened to the PCB that extracts and stores heat generated by LED device at PCB and a heat dissipation structure. The plate and the heat dissipation structure are monolithically joined together. The plate extracts heat from LED device in conduction mode and slowly and gradually transfers the heat to heat dissipation structure which in turn gradually dissipates the heat stored in the plate to atmosphere in convection mode.
[0023] In an aspect of the present invention, the heat dissipation structure is an open celled structure.
[0024] In an aspect of the present invention, the plate is fastened at the base of Printed Circuit Board (PCB) of LED device by means of screws and kept in direct contact with PCB.
[0025] In an aspect of the present invention, the heat dissipation structure is a three dimensional polygon shaped structure.
[0026] In an aspect of the present invention, the plate is a solid plate and made from conducting materials.
[0027] In an aspect of the present invention, the area of heat dissipation structure is greater than the area of the solid plate.
[0028] In an aspect of the present invention, the plate and heat dissipation structure are of same shape.
[0029] In an aspect, the plate and the heat dissipation structure are made of conducting materials.
[0030] In an aspect, the plate stores the extracted heat that is then dissipated to the heat dissipation structure for further dissipation by convection mode. [0031] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0032] It is to be noted, however, that the appended drawings illustrate only typical
embodiments of the present subject matter and are therefore not to be considered
for limiting of its scope, for the invention may admit to other equally effective
embodiments. The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number
identifies the figure in which the reference number first appears. The same numbers
are used throughout the figures to reference like features and components. Some
embodiments of system or methods in accordance with embodiments of the present
subject matter are now described, by way of example, and with reference to the
accompanying figures, in which:
[0033] Fig. la schematically illustrates the heat management system employed
over the LED device according to the present invention;
[0034] Fig. lb schematically illustrates angular view of LED lighting device and
heat management system employed over the LED device;
[0035] Fig. 2 is a schematic illustration of a heat management system for LED
device;
[0036] Fig. 3 is a front view of a heat management system for LED device;
[0037] Fig. 4a is a back view of a heat management system for LED device; and
[0038] Fig. 4b illustrates heat transfer regions of the heat management system.
DETAILED DESCRIPTION OF THE CURRENT INVESTIGATION
[0039] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments

herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
[0040] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and detailed in the following description. Descriptions of well-known components and processing techniques are omitted to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0041] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0042] These and other advantages of the present subj ect matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various

arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope. [0043] The performance of LED lighting devices depends upon several factors, such as lumen output, colour stability, and life of the device. The performance driven factors can be directly linked with the efficiency of heat management system of the lighting device. Electrical energy supplied to LED device through point source or chip on Board (COB) is converted into light and heat energy. The Chip on Board (COB) LEDs are basically multiple LED chips (typically nine or more) bonded directly to a substrate by the manufacturer to form a single module. Since the individual LEDs used in a COB are chips and not traditionally packaged, the chips can be mounted such that they take up less space and the highest potential of the LED chips can be obtained. Approximately, 40% of electrical energy is converted into light whereas around 60% of electrical energy is converted into heat. The heat generated results in raising the temperature of LED device that effects efficiency and performance of the device. Higher temperature of LED device leads to shortening life of LED device and deteriorates its colour stability and lumen output. Therefore, it is essential to effectively and quickly remove heat generated in the LED device.
[0044] The present invention proposes a heat management system 100 for removal of heat from LED device. In reference to Fig. la and lb, a LED device 101 comprises of Printed Circuit Board (PCB) 102 that mechanically supports the LED device 101 and electrically connects the electronic or electrical components of LED device 101 using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. The LED device 101 is also mounted with an LED driver 103 that delivers power to the LED device 101 in a regulated manner. The LED driver 103 prevents the LED device 101 from having a premature failure by controlling thermal runaway, which is a phenomenon wherein with an increase in the temperature of an operating LED, the forward voltage (i.e. the voltage the LED requires to conduct electricity and light up) decreases thereby increasing the current. A heat management system 100 is also provided to the LED device 101 at

PCB 102. The heat management system 100 comprises of two components: a plate 104 and a heat dissipation structure 105. In the preferred embodiment, the heat dissipation structure (105) is an open celled structure.
[0045] In reference to Fig. 2, the plate 104 is a solid plate and is made of any conducting materials. As an exemplary model, the plate 104 and heat dissipation structure 105 is made of aluminium due to reason that it is light weight and inexpensive and is a good conducting material. The plate 104 is fastened to the PCB 102 of the LED device 101 by any fastening means. As an exemplary model, the plate 104 is fastened to the PCB 102 by means of plurality of screws 106. The other fastening means could be nut-bolt, rivets, washers or inserts. [0046] The plate 104 is directly in face to face contact with the PCB 102. The plate 104 and the heat dissipation structure 105 are monolithically joined together to form the system 100. The heat dissipation structure 105 is constructed in a three-dimensional hollow polygon structure.
[0047] In the proposed invention, an optimal balance is created between conduction and convection modes of heat transfer by effectively sizing the plate 104 and heat dissipation structure 105 to gain desirable benefits. The plate 104 plays dual role in the system 100, firstly, it extracts heat immediately from the PCB 102 and secondly, it holds the heat like a small reservoir temporarily till the convection of heat starts at the heat dissipation structure 105.
[0048] The stored heat at the plate 104 is dissipated gradually in the ambient atmosphere by convection through heat dissipation structure 105. Convection depends upon the ambient air temperature and surface area of solid in vicinity with air. As air is bad conductor of heat, some time is spent in forming the temperature gradient and forming the air plume through heat dissipation structure 105 by buoyancy effect.
[0049] In reference to Fig.3, a top view of the heat management system 100 is illustrated. The area of heat dissipation structure 105 is kept greater than the area of the plate. The ratio of face of heat dissipation structure 105 to area of plate 104 is to be kept greater than 1 but not more than 3 times. The greater area of the heat dissipation structure 105 enables faster heat dissipation. If areas of plate 104 and

heat dissipation structure 105 are kept same, there will be a very little dissipation of heat from the heat dissipation structure 105 as the heat will be entrapped between the plate 104 and the heat dissipation structure 105, same phenomena will occur if the area of heat dissipation structure 105 is kept less than area of the plate 104. [0050] The plate 104 extracts and stores heat from the PCB 102 in conduction mode as it is directly in contact with the PCB 102. The temperature at the LED junction is also affected by the parameters of the plate 104 such as its thickness and material properties such as thermal conductivity.
[0051] In reference to Fig.4, a back view of heat management system 100 is illustrated. As per the figure, the shape of outer circumference of plate 104 and heat dissipation structure 105 are to be kept same, for e.g., circular shape for both, the plate 104 and the heat dissipation structure 105.
[0052] In reference to Fig. 4b, the region covered by the plate 104 is conductive region and the region covered by the heat dissipation structure 105 is convective region. Conductive region is immediately behind the PCB 102. In this region heat is not dissipated immediately due to limited air flow and gets stored temporarily in the plate 104. In the convective region, i.e. in the region of heat dissipation structure 105, the heat transfer is maximum due to air flow.
[0053] The proposed invention facilitates controlling of junction temperature with the help of disclosed embodiments by means of combination of conduction and convection. The plate 104 facilitates dissipation of heat through conduction and the heat dissipation structure 105 dissipates heat in convection mode. The junction temperature can be easily controlled and customized by appropriate selection of plate 104 material where efficiency is correlated with dimensions. Also, the colour stability and lumen stability is linked with thermal stability that is ensured by the present invention. The thermal analysis of the proposed invention is given below:

Graph 1

5

Graph 2

13

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60- SO KB
Time, :a-- rr:wbl 0p#r» C4IL-frd sruito^s * f*j ^Qii3 5MT-=

Graph 3
[0054] The above graph of thermal analysis shows that the junction temperature of LED devices 101 can be easily controlled by varying the parameters of plate 104 i.e thermal conductivity by using different conducting materials to manufacture the plate 104 and dimensions of the plate 104. The graph depicts that the proposed invention improves thermal performance of LED device 101. The LED device 101 quickly stabilizes to a desired temperature limit. Also the overall effect/result on temperature rise across LED device 101 is like that of critically damped system [0055] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

Reference numerals:
100- Heat management system for LED device
101- LED device
102- Printed Circuit Board
103- LED driver
104- Plate
105- Heat dissipation structure
106- Screws

We claim:
1.A heat management system (100) for LED devices, the system (100)
comprises:
a LED device (1) connected to a Printed Circuit Board (PCB) (102) that mechanically supports and electrically connects electronic or electrical components of LED device (101) together with the PCB (102) mounted with an LED driver (103) that delivers power to the LED device (101) in a regulated manner;
a plate (104) fastened to the PCB (102), using fastening means
(106), to extract and temporarily storing the heat generated by
LED device (101) at PCB (102); and
a heat dissipation structure (105) monolithically joined to the
plate (104); wherein the plate (104) extracts heat from PCB (102) in conduction mode and the heat dissipation structure (105) dissipates the stored heat to atmosphere in convection mode.
2. The system as claimed in claim 1, wherein the heat dissipation structure (105) is an open celled structure.
3. The system (100) as claimed in claim 1, wherein the plate is fastened at the base of Printed Circuit Board (PCB) of LED device by means of screws and kept in direct contact with PCB.
4. The system (100) as claimed in claim 2, wherein the open celled structure (105) is a three dimensional polygon shaped structure.
5. The system (100) as claimed in claim 1, wherein the of plate (104) and open celled structure (105) are of same shape.
6. The system (100) as claimed in claim 2, wherein the area of open celled structure (105) is greater than the area of the plate (104).
7. The system (100) as claimed in claim 1, wherein the plate (104) is a solid plate manufactured of conducting material.

8. The system (100) as claimed in claim 2, wherein the open celled structure (105) is made of conducting materials.
9. The system (100) as claimed in claim 2, wherein the plate (104) stores the extracted heat that is then dissipated to the open celled structure (105) for further dissipation by convection mode.