背景技术：
[0003]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.
[0004]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.
[0005]Embodiments of the invention address this and other limitations of the prior art.
具体实施方式：
[0012]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.
[0013]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.
[0014]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.
[0015]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.
[0016]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.
[0017]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.
[0018]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.
[0019]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.
[0020]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.
[0021]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.
[0022]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.
[0023]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.
[0024]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.
[0025]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.
[0026]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.
[0027]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.
[0028]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.
[0029]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.
[0030]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.
[0031]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.
[0032]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.
[0033]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.
[0034]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.