Abstract:
LED light bulbs capable of providing even luminous intensity distribution are disclosed. An illustrative LED light bulb includes a base, a light transmissive cover and upstanding light bars. The base is capable of being in electrical communication with a power source and has a screw axis and a periphery. The light transmissive cover is substantially mounted on the periphery. The upstanding light bars are mounted radically around the screw axis and located between the screw axis and the periphery. The upstanding light bars are arranged to substantially shine inward to the screw axis.

Description:
BACKGROUND 
       [0001]    The present disclosure relates generally to LED light bulbs, and more specifically to LED light bulbs capable of replacing conventional light bulbs. 
         [0002]    As well known in the art, there are different kinds of lighting fixtures developed in addition to the familiar incandescent light bulb, such as halogen lights, florescent lights and LED (light emitting diode) lights. LED light bulbs have several advantages. 
         [0003]    For example, LEDs have been developed to have lifespan up to 50,000 hours, about 50 times long as a 60-watt incandescent bulb. This long lifespan makes LED light bulbs suitable in places where changing bulbs is difficult or expensive (e.g., inaccessible places like the exterior of buildings). Furthermore, an LED requires minute amount of electricity to reach a luminous efficacy about 10 times higher than an incandescent bulb and 2 times higher than a florescent light. As power consumption and conversion efficiency are big concerns in the art, LED light bulbs are expected to replace several kinds of lighting fixtures in the long run. 
         [0004]    Unlike incandescent light bulbs and florescent lights whose lights are omnidirectional, an LED transmits a focused beam of light. Defined by ENERGY STAR, a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy, any lighting fixture proclaiming to replace an existing standard omnidirectional lamp or bulb is required to meet specific luminous intensity distribution.  FIG. 1  demonstrates a lighting fixture intended to replace omnidirectional lamps or bulbs. There are some requirements for lighting fixtures intended to replace omnidirectional lamps or bulbs. As shown in  FIG. 1 , the distribution of luminous intensity shall be even within zone Z front  the 0° to 135° zone, (vertically axially symmetrical) and the luminous intensity at any angle within zone Z front  shall not differ from the mean luminous intensity for the entire zone Z front  by more than 20%. Furthermore, at least 5% of total flux must be emitted in zone Z rear , the 135° to 180° zone, in the proximity of the base contact. Light reflectors, diffusers, and lens have been employed in LED light bulbs, to spread out the focused light beam of an LED. Nevertheless, it is still a challenge for an LED light bulb to meet the intensity distribution requirements of ENERGY STAR. 
       SUMMARY 
       [0005]    Embodiments of the present application disclose an LED light bulb including abase, a light transmissive cover and upstanding light bars. The base is capable of being in electrical communication with a power source and has a screw axis and a periphery. The light transmissive cover is substantially mounted on the periphery. The upstanding light bars are mounted radically around the screw axis and located between the screw axis and the periphery. The upstanding light bars are arranged to substantially shine inward to the screw axis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The present application can be more fully understood by the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0007]      FIG. 1  demonstrates a lighting fixture intended to replace omnidirectional lamps or bulbs; 
           [0008]      FIG. 2A  shows a LED light bulb according to an embodiment of the present application; 
           [0009]      FIGS. 2B and 2C  illustrate the cross section and top view of the LED light bulb in  FIG. 2A , respectively; 
           [0010]      FIG. 3  demonstrates a reflector as a reflective cone with a tilted sidewall while light bars are on the sidewall of the reflector; 
           [0011]      FIGS. 4A and 4B  demonstrate a reflector including both a reflective flat portion and a square pyramid; 
           [0012]      FIG. 5  shows a top view of an LED light bulb, in which each light bar  14  is positioned to substantially face a joining edge of a square pyramid; 
           [0013]      FIG. 6A  demonstrates a reflector with a hollow hexagonal prism; 
           [0014]      FIG. 6B  demonstrates a reflector with a solid hexagonal prism; 
           [0015]      FIGS. 7A ,  7 B,  7 C and  7 D demonstrate four reflectors; each having a protruding portion with a multi-layer structure; 
           [0016]      FIGS. 8A and 8B  show perspective and top views of a reflector, and  FIGS. 9A and 9B  show those of another reflector, according to embodiments of the present application 
           [0017]      FIGS. 10A and 10B  show perspective and top view of a reflector according to an embodiment of the application, and FIG. 
           [0018]      10 C shows an LED light bulb with the reflector; 
           [0019]      FIG. 11A  shows another reflector according to an embodiment of the application, and  FIG. 11B  shows a perspective view of an LED light bulb with the reflector in  FIG. 11A ; 
           [0020]      FIGS. 12A and 12B  show that light bars are bent inward and outward, respectively; 
           [0021]      FIG. 13A  shows a light bar with a heat sink; 
           [0022]      FIG. 13B  shows a top view of a LED bulb with the light bar of  FIG. 13A ; 
           [0023]      FIGS. 14A and 14B  show a light bar, whose heat sink extends to join a bulb; 
           [0024]      FIG. 14C  shows that an exterior of a LED light bulb is formed by a bulb and heat sinks; 
           [0025]      FIG. 15A  shows an AC-powered LED according to an embodiment of the application; and 
           [0026]      FIG. 15B  lists the configurations of four exemplified LEDs. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following embodiments are described in sufficient detail to enable those skilled in the art to make and use the present application. It is to be understood that other embodiments would be evident based on the present disclosure, and that improves or mechanical changes may be made without departing from the scope of the present application. 
         [0028]    In the following description, numerous specific details are given to provide a thorough understanding of the application. However, it will be apparent that the application may be practiced without these specific details. In order to avoid obscuring the present application, some well-known configurations and process steps are not disclosed in detail. 
         [0029]    LED light bulb  10  according to an embodiment of the present application is shown in  FIG. 2A . The cross section and top view of the LED light bulb  10  are shown in  FIGS. 2B and 2C , respectively. LED light bulb  10  includes a bulb  12 , light bars  14 , a reflector  16 , and a base  18 . The LED light bulb  10  may be DC powered (e.g., from a battery, 6-12V) or AC powered (e.g., 110-120 or 220-240 VAC) or solar powered (e.g., connected to a solar cell). 
         [0030]    In the non-limiting embodiment of  FIGS. 2A ,  2 B, and  2 C, the base  18  has an Edison male screw base contact  19  that screws into a matching socket to electrically communicate with an electric power source (such as a branch circuit not shown). However, the application is not limited to this type of contact, and the LED light bulb  10  may have any other suitable contact, such as but not limited to, a single pin bayonet base, a double pin bayonet base (with one negative and one positive terminal in the base to match two contact points in a corresponding socket), a flange base, an MR16 socket base, or a wired connection. Positioned between the base contact  19  and the reflector  16  is a heat sink  17  with fins  15  to dissipate to the air the heat generated by light bars  14 , which is electrically driven by an LED driving circuitry  20  encapsulated inside the base  18 . The bulb  12  and the base  18  substantially define an internal space to seal the light bars  14  and the reflector  16 . The place where the bulb  12  joins base  18  defines the periphery  11 . In some embodiments, the bulb  12  is transparent or translucent glass. The bulb  12  is made by a polymer, such as polyurethane (PU), polycarbonate (PC), polymethylmethacrylate (PMMA), or polyethylene (PE), or a thermally conductive material, such as ZnO. The reflector  16  on the base  18  has a protruding portion  22  with an apex  23  substantially aligned to screw axis  24  of the LED light bulb  10 . The curved surface of the reflector  16  reflects incoming light beams. The reflector  16  comprises Al, Ag or white paint, e.g., a TiO 2 /resin mixture. The light bars  14 , up standing inside bulb  12 , are positioned on the reflector  16  that each having LEDs  30  longitudinally arranged or mounted thereon (e.g., in a pattern roughly in parallel with the length of the light bar  14 ). In another option, the positioning of the light bars  14  on the reflector  16  includes sticking. Accordingly, in a light bar  14 , some LEDs  30  are close to the base  18 , and some are upheld about in the middle of the internal space. The light bars  14  are also mounted radically around the protruding portion  22  in a circular pattern somewhere between the screw axis  24  and the periphery  11 . Each light bar  14  has an emanating side arranged to basically face the screw axis  24  and shine inward to the screw axis  24  and the protruding portion  22 . The emanating side has LEDs  30  mounted thereon. Shown in  FIGS. 2A and 2B , each light bar  14  is a stick in shape with an upper portion of which has LEDs shining inside the internal space, and a lower portion of which is buried under the reflector  16  and mounted to the LED driving circuitry  20 . In some embodiments, each light bar  14  has a back side (opposite the emanating side) with a reflective surface. 
         [0031]    It is also obvious that some light beams from LEDs  30  can reach the direction opposite the base  18 , that is, some light beams shine upward. Nevertheless, some light beams of the LED light bulb  10  can follow an angle nearby the base  18 , that is, some light beams seemly shine downward. In  FIG. 2B , there are several dash-lines with arrows to refer light beams from an LED  30   a.  The LED  30   a,  being on the far end of light bar  14 , is in a top part of the LED light bulb  10 , such that the light beams exemplified in  FIG. 2B  can reach, directly or reflectively, a surrounding area in proximity of the base  18 . Accordingly, the LED  30   a  is capable of making the LED light bulb  10  shine downward to an area adjacent to the base  18 . Because the LED  30   a  is held up inside the LED light bulb  10  and shines inward, it is much easier for the LED light bulb  10  to emit some light in the 135° to 180° zone of  FIG. 1 . The light bars  14 , the LEDs  30 , and the reflector  16  could be well designed or arranged to make the LED light bulb  10  a replacement of a standard omnidirectional light bulb having a luminous intensity distribution meeting the requirements of ENERGY STAR. 
         [0032]    In  FIGS. 2A ,  2 B and  2 C, the reflector  16  with the protruding portion  22  has a profile like a horn with a curved sidewall, and the light bars  14  are positioned on the curved sidewall. In another option, the positioning of the light bars  14  on the reflector  16  includes sticking. However the application is not limited to this type of profile, and the reflector  16  may have any other suitable profile, such as but not limited to, a cone, a pyramid, a cylinder, a uniform prism, or any polyhedron. A different profile of a reflector could yield a different luminous intensity distribution.  FIG. 3  demonstrates the reflector  36  as a reflective cone with a tilted sidewall while the light bars  14  are positioned on the sidewall of the reflector  36 .  FIGS. 4A and 4B  demonstrate the reflector  46  including both a reflective flat portion  44  facing upward opposite to a base and a square pyramid  42  as a protruding portion, while the light bars  14  up stand on the flat portion  44 . Shown in  FIGS. 4A and 4B , each light bar  14  is positioned to substantially face a joining triangle face of the square pyramid  42 . Accordingly to another embodiment of the application,  FIG. 5  shows a top view of a LED light bulb, in which the reflector  56  also has the square pyramid  52  as a protruding portion but each light bar  14  is positioned to substantially face a joining edge of the square pyramid  52 .  FIG. 6A  demonstrates the reflector  66  with a hexagonal prism  62  as a protruding portion and the light bars  14  facing sidewalls of the hexagonal prism  62 . Unlike the hexagonal prism  62  of  FIG. 6A  which has a hollow body, the hexagonal prism  64  on the reflector  68  of  FIG. 6B  has s solid body. 
         [0033]      FIGS. 7A ,  7 B,  7 C and  7 D demonstrate four reflectors  72 ,  74 ,  76 , and  78 , each having a protruding portion with a multi-layer structure. In  FIG. 7A , each layer in protruding portion  73  is a cuboid, and the upper layer the smaller bottom face. In  FIG. 7B , each layer of the protruding portion  75  is a cylinder. Each cuboid of the protruding portion  77  in  FIG. 7C  has curved sidewalls. So does each cylinder of the protruding portion  79  in  FIG. 7D . 
         [0034]    In some embodiments, the sidewalls of a protruding portion might be concave.  FIGS. 8A and 8B  show perspective and top views of the reflector  90 , and  FIGS. 9A and 9B  show those of another reflector  96 , according to embodiments of the application. As demonstrated in  FIGS. 8A ,  8 B,  9 A, and  9 B, each of the protruding portions  92  and  94  has curved sidewalls where the light bars  14  face. The bottom of the protruding portion  94  touches the boundary circle where the reflector  96  conjoins a bulb, but the bottom of the protruding portion  92  does not. 
         [0035]      FIGS. 10A and 10B  show perspective and top views of a reflector  102  according to an embodiment of the application, and  FIG. 10C  shows the LED light bulb  100  with the reflector  102 . The reflector  102  basically has a flat portion  104 , a square pyramid  106  as a protruding portion, and four fins  108 , all functioning to reflect light beams. Each fin  108  is connected to a joining edge of the square pyramid  106  and may extend outward to join the bulb  110 . As shown in  FIG. 10C , the reflective fins  108  and the bulb  110  form an exterior of the LED light bulb  100 . Shown in  FIG. 11A  is another reflector  112  according to an embodiment of the application.  FIG. 11B  shows a perspective view of the LED light bulb  120  with the reflector  112  in  FIG. 11A . Unlike the reflector  102  of  FIG. 10A  whose reflective fins  108  have top edges at a distance away from the bulb  110 , the reflective fins  114  of the reflector  112  divide the internal space of the bulb  116  into several isolated spaces. In another embodiment, the reflective fins  114  may track the envelope of the bulb  120  to the top and the apex of the protruding portion of the reflector  112  may also extend to the top of the bulb  120 . The face of the reflector  112  between the reflective fins  114  may vary in shape, for example, a flat, curved, or angled side face.  FIG. 11B  also demonstrates the fins  114  and the bulb  116  form an exterior of the LED light bulb  120 . 
         [0036]    Previous embodiments demonstrate light bars each standing as a straight line, but the application is not limited to.  FIG. 12A  shows that the light bars  82  are all bent inward to the protruding portion  81 , forming a shape like a flower bud.  FIG. 12B  shows, nevertheless, that light bars  84  are all bent outward (convex from the perspective on the protruding portion  81 ), forming a shape like a blossom. 
         [0037]    For high power LEDs, a light bar might be equipped with a heat sink of its own.  FIG. 13A  shows a light bar  130 , including LEDs  136  mounted on its emanating side  132  and a heat sink  138  on its back side  134 .  FIG. 13B  is the same with the top view of  FIG. 2C , but the light bars therein are replaced by light bar  130  of  FIG. 13A . Similarly,  FIGS. 14A and 14B  show a light bar  140 , whose heat sink  142  extends to join bulb  12 .  FIG. 14C  shows the bulb  12  and the heat sink  142  form an exterior of the LED light bulb  148 . As the heat sink  142  is exposed, a very short thermal dissipation path is formed for effective heat dissipation from the LEDs, to the heat sink  142 , and to the air. 
         [0038]    In a non-limiting embodiment, a light bar includes ZnO, Al or a thermally conductive printed circuit board to conduct the heat generated from the LEDs thereon to a heat sink. In one embodiment, the light bar includes ZnO nanowire formed thereon for improving heat radiation. The light bar has a thermal conductivity of 10-16 W/m·K. In another embodiment, a light bar has a transparent or translucent printed circuit board allowing certain percent of light to pass through. As shown in the drawings of  FIGS. 4A ,  4 B,  6 A and  6 B, the light bars  14  are mounted on a reflector in a circular pattern. The four light bars  14  in  FIG. 4A  or  4 B form seemly a square, and the six light bars  14  in  FIG. 6A  or  6 B form a hexagon. In other words, light bars in an embodiment of the application can be arranged in a polygon pattern surrounding a screw axis. 
         [0039]    In one non-limiting embodiment, the LEDs in a LED light bulb all are of the same color. In another embodiment, the LEDs have different colors, which for example are green, red, blue, and white. For example, the LEDs on a light bar according to an embodiment of the application are white and red LEDs sequentially and alternatively arranged in a predetermined line pattern, and the ratio of the number of the white LEDs to the red ones is about  3  to create a warm white LED light bulb.  FIG. 15A  shows an AC-powered LED  150 , which, for example, can be any one of the LEDs mounted on a light bar of an LED light bulb according to an embodiment of the application. The LED  150  has several LED chips  154  arranged in a 2×2 array and a rectifier  152 . Each LED chip  154  has micro LEDs  156  connected in series, and all LED chips  154  are coupled to have all micro LEDs  156  connected in series. The rectifier  152  are coupled to a branch circuit, which is alternative-current 110V or 220V for example, and provides a rectified direction-current voltage source to drive micro LEDs  156 . The LED chips  154  may be the same or different from each other. For example, one of LED chips  154  might be a blue LED chip, in which each blue micro LED thereof has a light-emitting layer made of indium gallium nitride (InGaN) to emit blue light with a peak wavelength between 440 to 480 nanometers. A white LED chip could be generated by coating a blue LED chip with a fluorescent material that converts some of the blue light into yellow light with a peak wavelength between 579 to 595 nanometers, and the micro LEDs in the white LED chip are referred to as white micro LEDs. The fluorescent material could be YAG or TAG as known in the art. One of LED chips  154  might be a red LED chip, in which each red micro LED thereof has a light-emitting layer made of aluminum gallium indium phosphide (AlGaInP) to emit a light with a peak wavelength between 600 to 650 nanometers. 
         [0040]    Optimizing the numbers of white, blue, and red LED chips or the numbers of white, blue, and red micro LEDs in the LED  150  can render it having not only a desired color temperature but also the capability of operating in a specific-voltage branch circuit. The table in  FIG. 15B  shows the chip numbers and the micro LED numbers in four exemplified LEDs for different branch circuits. Taking LED1 in the second row as an example, the LED1 is suitable to operate with a branch voltage of 110 ACV, and has 2 white LED chips and 2 red LED chips, each white LED chip having 12 white micro LEDs and each red LED chip having 6 red micro LEDs. LED2 to LED4 are not detailed because they are self-explanatory in view of the explanation of LED1. In one embodiment, the power ratio from that total consumed by all white micro LEDs to that total consumed by all red micro LEDs in a LED when driven is between 2 to 4, or about 3. The color temperature of an LED in an embodiment is between 2000K to 5000K, or preferably between 2000K to 3500K. 
         [0041]    While the application has been described by way of example and in terms of preferred embodiment, it is to be understood that the application is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.