Abstract:
Disclosed is an LED bulb having many advantages over previous bulbs. The bulb is designed with ease of fabrication and low cost in mind. A main support is made of chromed copper, used for both its reflectivity, its readily availability, and its relative low cost. A collection of bright LEDs are electrically coupled to a driving circuit formed on a board that is housed within the main support. The LEDs are mounted on a circuit board flexible enough to form into a desired shape while rigid enough to withstand normal movements. The LED circuit board includes multiple polished or shiny areas, also called lands or panels made to reflect light away from the bulb. The panels are electrically insulated from the operating circuit and prevent injury should the bulb be broken and the components be touched, even while operating.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This disclosure claims benefit of U.S. provisional application 61/601,941, filed Feb. 22, 2012, entitled METHOD OF PRODUCING LED LIGHTING APPARATUS AND APPARATUS PRODUCED THEREBY, and claims benefit of U.S. provisional application 61/614,298, filed Mar. 22, 2012 entitled DRIVING CIRCUIT FOR LIGHT EMITTING DIODE APPARATUS AND METHOD OF OPERATION, the contents of both of which are incorporated by reference herein. Additionally this disclosure is related to US non-provisional patent application entitled DRIVING CIRCUIT FOR LIGHT EMITTING DIODE APPARATUS AND METHOD OF OPERATION, filed on even date herewith Ser. No. 13/774,915, which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This disclosure is directed to lighting, and, more particularly, to a new Light Emitting Diode (LED) lighting apparatus and a method to make such an apparatus. 
     BACKGROUND 
     Light Emitting Diodes (LEDs) are specialized diodes made from semiconductor material or materials. LEDs differ from standard diodes in that, when LEDs are energized by small amounts of electric current, they emit light that is visible to humans. Early generation LEDs generated primarily red, yellow, or green colored lights, but relatively recent advances in LED technology provide blue and white LED lights as well. White LEDs may be particularly bright, and, because they are made of a stable, solid state material, have a very long working lifetime. Additionally, LEDs operate at relatively low voltage, and their electrical current requirements are decreasing as LED technology matures. 
     LEDs have found their way into a variety of lights previously served by incandescent, florescent, or other lighting technology. For instance, LEDs may be found in taillights of many vehicles, such as automobiles and trucks. They also have found niche use in flashlights as well. LEDs have not been as successful making inroads into home or industrial lighting; however, primarily due to their relative high cost compared to the very mature standard incandescent bulb, which has been available for at least 50 years, and is very cost-efficiently made. Even the latest florescent bulbs, known as Compact Florescent Lights (CFL), have been available in the United States for approximately 15 years, and are thus a mature technology when compared to LED lighting. Maturity brings with it lower fabrication cost and increased consumer awareness, both of which combine to create a product having large consumer following and sales. Present LED light bulbs are currently too expensive to fabricate and operate to favorably compete in the residential and industrial lighting market. 
     Embodiments of the invention address this and other limitations of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an LED bulb according to embodiments of the invention. 
         FIG. 2A  is a side view of a support tube housing a circuit board for a driving circuit of the LED bulb of  FIG. 1  according to embodiments. 
         FIG. 2B  is a top view of an LED configuration according to embodiments of the invention. 
         FIG. 3  is a diagram illustrating a series of panels of a printed circuit board used for constructing the LED bulb of  FIG. 1 , according to embodiments of the invention. 
         FIGS. 4A and 4B  are block diagrams illustrating steps of fabrication and partial shaping for an LED printed circuit board according to embodiments of the invention. 
         FIG. 5  is a flow diagram of an example method used to create the LED bulb of  FIG. 1  according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side view of an LED bulb  10  according to embodiments of the invention. In general, the LED bulb  10  has a bulb shape, with the larger end containing a number of LED devices, and the smaller end used for inserting the bulb  10  into a standard electrical socket to provide power for the bulb. 
     A base  12 , such as a standard Edison screw  12 , includes threads to mate with a standard 120-volt lamp socket (not shown), although other sockets or voltages may be used as well, depending on local standards. As illustrated in  FIGS. 1 and 2A . A support body  16  within the bulb  10 , which may be tubular shaped, has a multitude of uses. In some embodiments, the support  16  may be made of metal, which may be used to conduct electricity from the base  12  to a driving circuit, described below. The metal for the support body  16  may be, for instance, chromed copper with a diameter of ¾ inch. Not only is copper an excellent conductor of heat, which is useful for carrying heat away from the LED devices, but also chroming the surface of the support  16  has the added benefit of reflecting light from the LED devices, increasing the overall efficiency of the LED bulb. The support  16  may be shaped to interface with the base  12 , such as by forming or turning a number of threaded ridges into the support. Before turning, an additional layer may be added to the support. For instance, a thicker piece of copper  13  may be attached on the outside of the support  16  at the base end of the support, and the turnings made in this thicker piece of copper. Other ways of creating a threaded portion for the support  16  may be used as well. The support  16  may also function as a shield for ElectroMagnetic Interference (EMI) that may be generated by the driving circuit for the LED bulb  10 . 
     A circuit board  14 , hereinafter called the main board  14 , may be conveniently partially or fully contained within the support  16 . The main board  14  supports circuitry  40  used to convert the energy supplied from the socket (not shown) into which the bulb  10  is inserted, as described below. 
     Partially surrounding the support body  16  is a portion of body plastic  18 , which is preferably clear so that light reflected from the chromed metal support body  16  may be reflected away from the LED bulb  10 , increasing the efficiency of the bulb. As described below, the overall shape of the body plastic  18  allows some of a series of LEDs mounted over the body plastic to shine downward, toward the base  12  of the bulb  10 . Differently than other LED bulbs, heat fins are not required on LED bulbs as illustrated in  FIG. 1 . The absence of heat fins allows much more light to reflect from body of the bulb, because no fins are present to block or diffuse the light. 
     The body plastic  18  includes a recess  50  structured to receive an edge or lip of a bulb cover  20 . The bulb cover  20  is preferably glass, although other materials such as plastic may also be used. The recess structure  50  of the body plastic  18  may use friction or a mechanical lip to hold the cover  20  in place, or other methods may be used, such as glue. In other embodiments the bulb cover  20  threads into the recess structure  50 . 
     As illustrated in  FIGS. 1 and 2B , the bulb cover  20  covers a circuit board  22  used for supporting a number of individual LED devices  30  in the bulb  10 . The LED devices  30  are the light-generating portion of the LED bulb  10 . In one embodiment, the LED devices are approximately 0.2 inches square, and manufactured by Nichia of Japan. 
     As illustrated in outline in  FIG. 3 , the circuit board  22  on which the LED devices  30  are placed is referred to herein as the LED board. In the embodiment illustrated, the LED board  22  includes twelve individual panels or panels  26  on which one of the individual LED devices  30  is placed. Circuit areas  25  are located within the panels  26  and provide electrical connection (not shown) between the individual LED devices  30  and the driving circuit  40 , described above. Of course, more or fewer than twelve panels  26  may be used on other embodiments. 
     As illustrated, there are six panels  26  having a generally rectangular shape and six panels having a generally trapezoidal shape. Each individual panel  26  is separated by a fold zone  31 , the function of which is described below. A separate panel  28  may be differently shaped from the others. As illustrated in  FIGS. 1 and 2B , the panel  28  may be secured to the top of the circuit board  22  after it has been formed into a dome shape during production of the bulb  10 . The panel  28  may be made from the same blank as the circuit board  22 , or may be fabricated separately. In other embodiments, each individual panel  26  may be individually made, although there are benefits to having them made together, as described below. 
     As illustrated in  FIGS. 4A and 4B , the circuit board  22  is first produced in a planar shape. Later, after the LED devices  30  have been installed on the circuit board  22 , the circuit board is treated so that it may be shaped into its final form for installation in the bulb  10 . In other embodiments the circuit board  22  may be shaped before the LED devices  30  are secured thereon. 
     In  FIGS. 4A and 4B  the circuit board  22  is a two-layer printed circuit board with electrical traces on the top and bottom of the board  22 . In other embodiments boards having more or fewer layers could be used. 
     In detail,  FIG. 4A  illustrates a first state of the circuit board  22 . The circuit board  22  has an upper layer of conductive material, which may be tin-covered copper, illustrated as surfaces  24 . The function of surface  24  is at least two-fold. First, the surface  24 , because it is a shiny metal, tends to reflect light from the LED devices  30  placed on it. Secondly, because metal has a high rate of thermal conductivity (heat transfer), surface  24  is used as a heat sink, structured to carry heat away from the LED devices  30 . As described below, the metal surface  24  is not necessarily connected to any electrical portion of the bulb  10 . Instead, the surface  24  may be insulated from the driving circuitry. One benefit of such a configuration is that this prevents any potential for electrical shock should the bulb cover  20  ever break and the components covered by the bulb cover  20  become exposed. 
     A bottom layer  27  of the LED board  22  includes traces, such as copper traces used to deliver the signal generated by the main board  14  to the LED devices  30  themselves. An example of the bottom layer  27  of an example LED board  22  is illustrated in  FIG. 3A . Generally, the bottom layer  27  is also made of copper, or tin plated copper. The copper layer  27  is thick enough so that it may be bent without breaking, as described below. The bottom layer  27  provides an electrical path for the main board  14  to power all of the LED devices  30 , as described below. 
     Referring back to  FIG. 4A , in production, the LED devices  30  may be placed on the circuit board  22  or into through-holes in the LED board  22  (not shown) by manual or mechanical means. Presently, cost-effective high-volume production is typically performed by a pick and place machine, and this design supports such production. 
     In one embodiment, after the LED devices  30  are placed on the LED board  22 , they are connected by through-hole plating to the bottom layer  27 , thereby allowing them to be in electrical contact with the driving circuitry  40  on the main board  14 . Next, a groove  23  is formed in the LED board  22  along the fold zones  31  ( FIG. 3 ), weakening the board in the grooved areas. Generally, the groove is formed between the panels  26 . The groove  23  may be formed in a number of ways. For instance, the groove may be plunge routed, or formed with a milling machine that can perform X,Y,Z routing. 
     As illustrated in  FIGS. 3 and 4A , the LED board  22  begins as a flat, semi-circular piece of circuit board. A milling machine may cut the individual panels  26  in the LED board  22  by cutting the outer shape of the LED board. This step may take place near the time when grooves  23  between the individual faces are routed, as described with reference to  FIG. 2B . Alternatively, the grooves may be made later. The difference is that, to cut out the outline shape for the LED board  22 , the cutting head cuts all the way through the circuit board material, while the cutting head cutting the groove  23  only cuts partially through the circuit board material. In one embodiment, the cutting head cuts out the general shape of the LED board  22 , then cuts grooves  23  between the individual panels  26 . 
     After the LED board  22  is cut to shape and grooves  23  are formed, the LED board  22  may be shaped for placement into the bulb  10 . First, the panel  28  that will be the top of the bulb  10  is bent to align the top portion of the LED board  22  with a hole  32  in the body plastic  18  ( FIG. 1 ). Then, each of the individual panels  26  of the LED board  22  in the same horizontal row are bent 60 degrees from one another, to form a generally “bullet” or dome shaped LED board, as illustrated in  FIG. 1 . The bending of the LED board  22  may be guided by mating or receiving surfaces on the body plastic  18 , generally forming an elongated six-sided shape, with twelve panels  26  each including a respective LED device  30 . In embodiments having different number of panels  26  for the LEDs  30 , the number of receiving surfaces on the body plastic  18  would also be different so as to receive the panels  26 . 
     The LED bulb  10  may be assembled in a straightforward manner, which keeps production costs low. Many of these steps and ones in the previous section are illustrated in  FIG. 5 . 
     According to some methods of assembly, first, the metal support body  16  is inserted into the body plastic  18 , which is shaped to receive it. The main board  14 , which has the driving circuitry  40  formed thereon, is inserted into the metal support body  16 . The main board  14  includes a tab  46  ( FIG. 1 ), which is used to provide a mechanical and electrical connection to the LED board  22 . The circuit board  14  is aligned to its position, and a securing means, such as a screw  45 , is used to attach the circuit board to the body plastic  18 . 
     Next, and after the LED board  22  has had its LED devices  30  installed thereon and the grooves  23  are formed, the main board  14  is electrically connected to the LED board. In one embodiment the driving circuit  40  includes two terminations, which are electrically coupled, for example by wire, to two terminations in the LED board  22 , respectively. The terminations may be labeled for clarity. 
     Next, the LED board  22 , now shaped, is set on the mating portions of the body plastic  18 , and aligned with the tab  46 , as shown in  FIG. 2B . A temporary screw may hold the LED board  22  in place while solder pads on the tab  46  of the main board  14  are soldered to receiving areas of the LED board  22 , thereby establishing an electrical connection between the driving circuitry  40  on the main board  14  and the LED devices  30  of the LED board  22 . 
     In other embodiments, this top board that includes panel  28  includes a hole to receive the screw  33 , which is tightened to hold the top board against the LED board  22 . The LED board  22 , in turn, is held fast to the body plastic  18  by the force of the screw. In most embodiments the third board has no electrical connections but may be covered with a reflective surface, such as tin. 
     Next the base Edison socket  12  is attached to the metal support body  16 , such as by screwing the socket onto the ridges of the metal support body. Then the Edison socket  12  is soldered to a wire connecting the socket to the driving circuit  40  on the main board  14 . Excess solder may be removed by trimming or sanding, for instance. Finally, the cover  20 , which may be made of glass or clear plastic is inserted into the recess  50  of the body plastic. The cover  20  may be secured by gluing, for instance, then trimmed as a finishing step. 
     One of the features of the LED bulb  10  according to embodiments of the invention is its ability to prevent electrical shocks. First, when the LED bulb  10  is fully assembled, i.e., the bulb cover  20  is attached to the body plastic  18 , then none of the electrical components within the LED bulb are capable of being touched because they are covered with either a plastic or glass insulator. However, even when the bulb cover  20  is not present, for instance if the bulb cover is made of glass and the glass breaks, no electrical components are exposed. More particularly, the LED devices  30  on the LED board  22  are all coupled using through-holes to the underside of the LED board. Since the LED devices  30  cover the through holes in the LED board  22 , there is no possibility of touching the electrical circuit that drives the LED devices. The circuit made by the bottom layer  27  of the LED board  22  ( FIGS. 4A and 4B ) is physically covered by the LED board  22  itself. The bottom layer  27  is also effectively insulated by being placed against the previously shaped body plastic  18 . Even further, the driving circuitry  40  on the main board  14  is fully surrounded by the support  16 , which is yet further surrounded by the body plastic  18 . This further prevents the driving circuitry from being touched even if the bulb cover  20  is not present on the LED bulb  10 .