LED lamp assembly

An exemplary LED lamp includes a housing having an opening, a printed circuit board, at least one LED, a light reflective element, at least one light-shielding sheet and a lamp cover. The printed circuit board is positioned on a bottom of the housing. The LED is electrically connected with the printed circuit board. The light reflective element defines at least one through hole, the LED passing through the corresponding through hole. The at least one light-shielding sheet corresponds to the at least one LED respectively. Each light-shielding sheet comprises a bottom reflective plate and a pair of opposite sidewalls extending from two opposite ends of the bottom reflective plate. A plurality of light holes is defined at ends of the bottom reflective plate adjacent to the two opposite sidewalls. The lamp cover is fixed on the opening of the housing. The LED lamp assembly has a uniform luminance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to two copending U.S. patent applications, application Ser. No. 11/766,106 filed on Jun. 21, 2007, entitled “LED LAMP ASSEMBLY”, application Ser. No. 11/773,979, filed on Jul. 6, 2007, entitled “LED LAMP ASSEMBLY”. In the copending applications, the inventor is Shao-Han Chang. All of the copending applications have the same assignee as the present application. The disclosures of the above identified application are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lamp assembly, and particularly to a light emitting diode lamp assembly employed in a direct type backlight module of a liquid crystal display.

2. Discussion of the Related Art

Typically, light emitting diodes (LEDs) are preferred over other types of light sources because LEDs exhibits low energy consumption, long service life, and other advantages. Therefore, LEDs are widely used as light sources.

FIG. 1illustrates a typical LED lamp assembly10using LEDs as a light source. The LED lamp assembly10includes a housing11, a printed circuit board12, a plurality of side-lighting type LEDs13, a light reflective module14, a plurality of circular reflective layers15and a lamp cover16. The housing11is an elongated, hollow structure having an opening112. The LEDs13are arranged apart and electrically connected to the printed circuit board12. The printed circuit board12with the LEDs13is disposed on a bottom surface of the housing11. The light reflective module14includes a rectangular bottom reflective plate144and four connecting sidewalls142extending from a periphery of the bottom reflective plate144. The bottom reflective plate144defines a plurality of through holes146, configured for allowing the light-emitting portions of the LEDs13to pass through. The light reflective module14can be correspondingly mounted into the housing11via the opening112. The circular reflective layers15are positioned at the tops of the LEDs13respectively. The lamp cover16is fixed on the opening112of the housing11. Light from the light-emitted portions of the LEDs13is substantially reflected at the sidewalls142and the bottom reflective plate144, finally outputted from the lamp cover16. With the help of the light reflective module14, an efficiency of utilization of light energy of the LED lamp assembly10is increased.

Nevertheless, the brightness above the LEDs13of the LED lamp assembly10is decreased due to the light reflection off the circular reflective layers15, and a plurality of dark areas between the two adjacent LEDs13still occur. Accordingly a uniform brightness of the LED lamp assembly10is low.

What is needed, therefore, is an LED lamp assembly that overcomes the above mentioned disadvantages.

SUMMARY

An LED lamp assembly according to a preferred embodiment includes a housing having an opening, a printed circuit board, at least one LED, a light reflective element, at least one light-shielding sheet and a lamp cover. The printed circuit board is positioned on a bottom of the housing. The LED is electrically connected with the printed circuit board. The light reflective element defines at least one through hole, the LED passing through the corresponding through hole. The at least one light-shielding sheet corresponds to the at least one LED respectively. Each light-shielding sheet comprises a bottom reflective plate and a pair of opposite sidewalls extending from two opposite ends of the bottom reflective plate. A plurality of light holes is defined at ends of the bottom reflective plate adjacent to the two opposite sidewalls. The lamp cover is fixed on the opening of the housing. In addition, the light reflective element in the LED lamp assembly can be replaced by a high reflective layer formed on a top surface of the printed circuit board or a high reflective plate positioned on a top surface of the printed circuit board.

Other advantages and novel features will become more apparent from the following detailed description of various embodiments, when taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

References will now be made to the drawings to describe preferred embodiments of the present LED lamp assembly, in detail.

Referring toFIGS. 2 through 5, an LED lamp assembly20in accordance with a first preferred embodiment of the present invention is shown. The LED assembly20includes a housing21, a printed circuit board22, a plurality of side-emitting type LEDs23, a light reflective element24, a plurality of light-shielding sheets25, and a lamp cover26. The housing21is an elongated, hollow structure including four sidewalls214. The sidewalls214cooperatively defines a receiving opening212. The LEDs23are separately arranged and electrically connected to the printed circuit board22. The printed circuit board22including the LEDs23is disposed in the receiving opening212on a bottom surface of the housing21.

Referring toFIG. 5, each LED23includes a base portion231, a semiconductor chip233fixed on the base portion231, and an optical lens235. The optical lens235is bonded or snap-fitted onto the base portion231sealing the semiconductor chip233within. A width of the base portion231is larger than that of the optical lens235.

Also referring toFIGS. 2 through 4, the light reflective element24includes a base241and four sidewalls242extending from a periphery of the base241. The base241and the sidewalls242cooperatively define a cavity243. The base241defines a plurality of through holes244for allowing the optical lenses235of the LEDs23to pass through the corresponding through holes244. The base portions231of the LEDs23support the light reflective element24.

Each light-shielding sheet25includes a bottom reflective plate251and a pair of opposite sidewalls252extending from two opposite ends of the bottom reflective plate251. A plurality of light holes257are defined at ends of the bottom reflective plate251adjacent to the two opposite sidewalls252. In this embodiment, the light holes257are of the same shapes and sizes, and are formed in a matrix manner at the ends of the light-shielding sheet25. Each light-shielding sheet25is disposed in the cavity243of the light reflective element24and the two opposite sidewalls252of each light-shielding sheet25are connected to the sidewalls242of the light reflective element24respectively. Each LED23is covered by the corresponding light-shielding sheet25. Generally, the light-shielding sheet25is integrally manufactured by stamping a raw metal sheet. Surfaces of the bottom reflective plate251and the sidewalls252are high reflective surfaces; the bottom reflective plate251and the sidewalls252are made of a combination of metal materials and/or plastic materials.

The lamp cover26is fixed on the opening212of the housing21. The lamp cover26can be either a transparent plate or a light diffusion plate. The sidewalls242of the light reflective element24and the sidewalls214of the housing21may, correspondingly, further define a plurality of latching elements (not shown), thus the light reflective element24and the housing21can be assembled together securely.

Also referring toFIG. 5, in assembled, the light-shielding sheets25, and the light reflective element24cooperatively define a light-mixing space28. Light from the optical lens235of the LEDs23is reflected many times between the bottom reflective plate251of the light-shielding sheets25and the base241of the light reflective element24before substantially exiting at an area between the two adjacent light-shielding sheets25. As a result, a light brightness above the gaps of the LED lamp assembly20is increased. In addition, a light brightness above the LEDs23of the LED lamp assembly20is decreased due to the light reflection of the light-shielding sheets25. Furthermore, some of the light projects to the lamp cover26via the light holes257of the light-shielding sheets25. Since the light holes257are formed on the two sides of each of the light-shielding sheets25adjacent to the sidewalls214of the housing21, a light brightness of the two side portions of the LED lamp assembly20is increased. Thus, a uniformity of light output from the LED lamp assembly20is increased.

Referring toFIG. 6, an LED lamp assembly30in accordance with a second preferred embodiment of the present invention is shown. The LED assembly30includes a housing31, a printed circuit board32, a plurality of side-emitting type LEDs33, a light reflective element34, a plurality of light-shielding sheets35, and a lamp cover36. The LED lamp assembly30is similar in principle to the LED lamp assembly20of the first preferred embodiment except that the light reflective element34is different from the light reflective element24. The light reflective element34includes a base341and a plurality of sidewalls342separate from the base341. The base341defines a plurality of through holes (not labeled) for allowing the base portion331of the LEDs33to pass through the corresponding through holes. The base341is in contact with the printed circuit board32. The plurality of sidewalls343is fixed to corresponding sidewalls (not labeled) of the housing31. The light-shielding sheets35, and the light reflective element34cooperatively define a light-mixing space38.

Since the base341is disposed on the printed circuit board32, the light-mixing space38is larger than the light-mixing space28of the first preferred embodiment. Light from the LEDs33can mix more fully in the light-mixing space38when compared with the light-mixing space28. Therefore, the uniformity of light output from the LED lamp assembly30is better than the uniformity of light output from the LED lamp assembly20.

Referring toFIGS. 7 and 8, an LED lamp assembly40in accordance with a third preferred embodiment of the present invention is shown. The LED assembly40is similar in principle to the LED assembly20of the first preferred embodiment, however a high reflective layer421is formed on a top surface of the printed circuit board42instead of the light reflective element24of the LED assembly20.

The light-shielding sheets45, the housing41, and the high reflective layer421formed on the top surface of the printed circuit board42cooperatively define a light-mixing space48. Light from LEDs43is reflected many times between the high reflective layer421and the bottom reflective plate451of the light-shielding sheet45before substantially exiting at an area between the two adjacent light-shielding sheets45. As a result, a light brightness above the gaps of the LED lamp assembly40is increased. In addition, a light brightness above the LEDs43of the LED lamp assembly40is decreased due to the light reflection of the light-shielding sheets45. Furthermore, some of the light projects to the lamp cover46via the light holes457of the light-shielding sheets45. Since the light holes457are formed on each of the light-shielding sheets45adjacent to the sidewalls414of the housing41, a light brightness of the two side portions of the LED lamp assembly40is increased. Thus, a uniformity of light output from the LED lamp assembly40is increased.

It should be noted that, the high reflective layer421formed on the top surface of the printed circuit board42can be replaced by a high reflective plate, in order to form a light-mixing space between the high reflective plate and the bottom reflective plate451of the light-shielding sheet45.

It is to be understood that, by selecting the size and shape of the light holes257, or distribution of the light holes257, a uniformity of the light brightness above the light-shielding sheets25of the LED lamp assembly20is adjustable. In an alternative embodiment, in order to obtain a good optical performance such as uniformity of light output from the LED lamps assembly20,30,40, each light-shielding sheet25,35,45, of the LED lamps assembly20,30,40, may have the same distributions as shown inFIGS. 9 through 13.

Referring toFIG. 9, a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is circular. The shape and the area of each of the light holes are the same. A mid-point is defined in the light-shielding sheet. The light holes are arranged apart along a plurality of imaginary circles and the center of a row of light holes intersects with the perimeter of an imaginary circle. The imaginary circles have a same center collinear with the mid-point of the light-shielding sheet.

Referring toFIG. 10, a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is circular, but have a different radius. A mid-point is defined in the light-shielding sheet. The light holes are arranged apart along a plurality of imaginary circles and the center of a row of light holes intersects with the perimeter of an imaginary circle. The imaginary circles have a same center collinear with the mid-point of the light-shielding sheet. The radius of the light holes increase along a direction away from the center of the imaginary circles.

Referring toFIG. 11, a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an elongated opening parallel to the sidewalls of the housing of the LED lamp assembly. At each end of the light-shielding sheet, the three light holes are separated to each other uniformly. Length of the three light holes is the same.

Referring toFIG. 12, a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an elongated opening parallel to the sidewalls of the housing of the LED lamp assembly. At each end of the light-shielding sheet, the three light holes are separated to each other uniformly. Lengths of the three light holes progressively increase along a direction away from a middle portion of the light-shielding sheet.

Referring toFIG. 13, a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an annular opening. At each end of the light-shielding sheet, the three light holes are separated to each other uniformly. The annular light holes have a same center that is a mid point of the light-shielding sheet.