Abstract:
A light emitting diode (LED) bulb has a shell. An LED is within the shell. The LED is electrically connected to a driver circuit, which is electrically connected to a base of the LED bulb. The LED bulb also has a heatsink between the shell and base. A thermal break partitions the heatsink into an upper partition adjacent the shell and a lower partition adjacent the base.

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates generally to a heatsink for a light emitting diode (LED) bulb, and more specifically to a partitioned heatsink for improved cooling of different components of a LED bulb. 
     2. Description of Related Art 
     Traditionally, lighting has been generated using fluorescent and incandescent light bulbs. While both types of light bulbs have been reliably used, each suffers from certain drawbacks. For instance, incandescent bulbs tend to be inefficient, using only 2-3% of their power to produce light, while the remaining 97-98% of their power is lost as heat. Fluorescent bulbs, while more efficient than incandescent bulbs, do not produce the same warm light as that generated by incandescent bulbs. Additionally, there are health and environmental concerns regarding the mercury contained in fluorescent bulbs. 
     Thus, an alternative light source is desired. One such alternative is a bulb utilizing an LED. An LED comprises a semiconductor junction that emits light due to an electrical current flowing through the junction. Compared to a traditional incandescent bulb, an LED bulb is capable of producing more light using the same amount of power. Additionally, the operational life of an LED bulb is orders of magnitude longer than that of an incandescent bulb, for example, 10,000-100,000 hours as opposed to 1,000-2,000 hours. 
     The lifetime and performance of an LED bulb depends, in part, on its operating temperature. The lifetime of the LED bulb driver circuit may limit the overall lifetime of the LED bulb if the driver circuit operates at high temperature for long periods of time. Similarly, the lifetime of the LEDs that produce the light may be reduced by excessive heat. Additionally, high operating temperatures can reduce the light output of the LEDs. 
     While both the driver circuit and LEDs are sensitive to high operating temperatures, these components are also responsible for generating heat. LEDs are about 80% efficient, meaning that 20% of power supplied to LEDs is lost as heat. Similarly, the driver circuit that supplies current to the LED is about 90% efficient, meaning that 10% of the power supplied to it is lost as heat. 
     The operating temperature of a LED bulb depends on many factors. For example, each individual LED produces heat. Therefore, the number and type of LEDs present in the bulb may affect the amount of heat the LED bulb produces. Additionally, driver circuitry may also produce significant amounts of heat. 
     Other factors may determine the rate at which generated heat is dissipated. For example, the nature of the enclosure into which the LED bulb is installed may dictate the orientation of the LED bulb, the insulating properties surrounding the LED bulb, and the direction of the convective air stream flowing over the LED bulb. Each of these factors may have a dramatic effect on the build up of heat in and around the LED bulb. 
     Accordingly, LED bulbs may require cooling systems that account for the different sources of heat, the ability of components to withstand elevated temperatures, and the variables associated with the dissipation of heat. 
     BRIEF SUMMARY 
     One embodiment of a light emitting diode (LED) bulb has a shell. An LED is within the shell. The LED is electrically connected to a driver circuit, which is electrically connected to a base of the LED bulb. The LED bulb also has a heatsink between the shell and base. A thermal break partitions the heatsink into an upper partition adjacent the shell and a lower partition adjacent the base. 
    
    
     
       DESCRIPTION OF THE FIGURES 
         FIG. 1  depicts an exemplary embodiment of an LED light bulb with a partitioned heatsink. 
         FIG. 2  depicts an exploded view of the exemplary embodiment. 
         FIG. 3  depicts another exemplary embodiment of an LED light bulb with a partitioned heatsink. 
         FIG. 4  depicts an exploded view of exemplary embodiment of  FIG. 3 . 
         FIG. 5  depicts an exploded view of yet another exemplary embodiment. 
         FIG. 6  depicts a cross-section view of the exemplary embodiment of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the various embodiments. Thus, the various embodiments are not intended to be limited to the examples described herein and shown, but are to be accorded the scope consistent with the claims. 
       FIG. 1  depicts an exemplary embodiment of LED bulb  100  using partitioned heatsink  102  for improved cooling. Thermal break  104  partitions heatsink  102  into upper heatsink partition  106  and lower heatsink partition  108 . The amount of heat that may be dissipated by each partition depends, in part, on the amount of surface area that is exposed away from the bulb. The more surface area exposed to the environment outside of the LED bulb, the more heat that may be dissipated. 
     Heatsink  102  may be made of any materials that exhibit suitable thermal conductivity. For example, metals such as aluminum or copper are often used for heatsink applications. In this exemplary embodiment, a plurality of fins  120  increases the surface area of the heatsink and helps dissipate heat generated by LED bulb  100  into the surrounding environment. Heatsink  102  may be shaped to make LED bulb  100  resemble a common A19 bulb form factor. 
     Thermal break  104  may be made by cutting or otherwise removing a portion of heatsink  104  to create a void. Alternatively, heatsink  102  may be fabricated, using metal casting or other suitable manufacturing processes, with thermal break  104  in place. 
     Thermal break  104  may be maintained with a thermally insulting material that completely or partially fills thermal break  104 . For example, as depicted in  FIG. 1 , thermal break  104  may be maintained by connector piece  124  between upper partition  106  and lower partition  108 . Connector piece  124  holds upper partition  106  in proper alignment with lower partition  108  while maintaining thermal break  104  as a void. Depending on how connector piece  124  is shaped connector piece  124  may form part or all of thermal break  124 . Suitable materials for connector piece  124  include glass-filled nylon, ceramics, ceramic derivatives, and materials with low thermal conductivity. As an alternative to thermal break  104  being a void, a thermally insulting material may maintain thermal break  104  by partially or completely fill thermal break  104  using injection molding or other suitable manufacturing processes. 
       FIG. 2  depicts an exploded view of LED bulb  100 . Connector piece  124  forms the thermal break between upper partition  106  and lower partition  108 . 
     Referring back to  FIG. 1 , the location of thermal break  104  may be selected to allocate portions of heatsink  102  between driver circuit  110  and LEDs  114 . The size of the portions allocated to driver circuit  110  and LEDs  114  affects the ability of heatsink  102  to cool those components. Factors that may be considered in allocating the portions heatsink  102  between driver circuit  110  and LEDs  114  include the amount of heat generated by each component, the sensitivity of each component to elevated temperatures, and other paths that each component may have for dissipating heat. 
     Driver circuit  110 , which is located substantially within bulb base  112 , controls the drive current delivered to LEDs  114  that are mounted on LED mounts  116 , which are disposed within bulb  116 . LED mounts  114  may help transfer heat from LEDs  114  to heatsink  102 . LED mounts  116  may be formed as part of the heatsink. Alternatively, LED mounts  116  may be formed separate from the heatsink, but are still thermally coupled to the heatsink. As another alternative, LED mounts  116  may be omitted, and the LEDs  114  may be mounted in a manner to thermally couple LEDs  114  to upper partition  106 . 
     Thermal vias or a metal core printed circuit board (PCB) may facilitate heat transfer from drive circuit  110  to heatsink  102  at position  122 . For example, in this exemplary embodiment, driver circuit  110  may produce less heat than LEDs  114 , but driver circuit  110  may also be more sensitive to high temperatures. Specifically, driver circuit  110  may be able to operating in temperatures up to 90° C. without damage, but LEDs  114  may be able to operate in temperatures up to 120° C. without damage. Additionally, LEDs  114  may be able to dissipate some heat out of shell  118 , especially if shell  118  is filled with a thermally conductive liquid. Therefore, in this exemplary embodiment, thermal break  104  is placed to allocate the majority of heatsink  102  in the form of lower heatsink partition  108  to cooling driver circuit  110 . The rest of heatsink  104  is allocated to cooling LEDs  114  in the form of upper heatsink partition  106 . 
     In addition to allocating partitions of heatsink  102  to driver circuit  110  and LEDs  114 , thermal break  104  may also prevent heat from LEDs  114  from affecting driver circuit  110 . Without thermal break  104  heat from LEDs  114  may degrade or damage driver circuit  110  because LEDs  114  produce more heat than driver circuit  110  and driver circuit  110  is more sensitive to heat than LEDs  114 . 
       FIG. 3  depicts another exemplary embodiment of LED bulb  300  using partitioned heatsink  302  for optimal cooling. Thermal break  304  partitions heatsink  302  into upper partition  306  and lower partition  308 . 
       FIG. 4  depicts an exploded view of LED bulb  300 . In this exemplary embodiment, connector piece  400  implements thermal break  304 . 
     As compared to heatsink  102  of LED bulb  100  ( FIG. 1 ), heatsink  302  of LED  300  is partitioned so that upper partition  306  is a greater proportion of heatsink  302  as compared to the proportion that upper partition  106  uses of heatsink  102  ( FIG. 1 ). By dedicating more of heatsink  302  to upper partition  306 , heatsink  302  may be able to dissipate more heat generated by LEDs of LED bulb  300  as compared to the ability of heatsink  102  to dissipate heat generated by LEDs  114  ( FIG. 1 ). 
       FIG. 5  depicts yet another exemplary embodiment of LED bulb  500  using partitioned heatsink  502  for improved cooling. Thermal break  504  partitions heatsink  502  into upper partition  506  and lower partition  508 . The amount of heat that may be dissipated by each partition depends, in part, on the amount of exposed surface area. The more surface area exposed to the environment outside of the LED bulb, the more heat that may be dissipated. Connector piece  510  implements thermal break  504 . LED bulb  500  includes driver circuit  512  within lower partition  508  and base  514 . 
       FIG. 6  depicts a cross-section of LED bulb  500 . As shown in  FIG. 6 , lower partition  508  substantially surrounds driver circuit  512 . This may allow for better heat transfer from driver circuit  512  to lower partition  508 , which may allow driver circuit  512  to operate at a cooler temperature. 
     Although a feature may appear to be described in connection with a particular embodiment, one skilled in the art would recognize that various features of the described embodiments may be combined. Moreover, aspects described in connection with an embodiment may stand alone.