Light emitting device

A light emitting device includes a light-emitting diode (LED) light source module, a heat-dissipating unit and a phosphor-converted cover. The heat-dissipating unit is disposed below the LED light source module. The phosphor-converted cover covers the LED light source module. The phosphor-converted cover has an accommodating space, at least one air channel and a first air hole. The LED light source module is located in the accommodating space, and the first air hole is located above the LED light source module and connected to the air channel. An outside fluid passes through the accommodating space via the air channel to discharge heat generated by the LED light source module to outside via the first air hole. An aperture of the first air hole is between 0.01 millimeters and 1 millimeter.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 101224088, filed on Dec. 12, 2012. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a light emitting device, more particularly, to a light emitting device utilizing a light-emitting diode as a light source.

2. Description of Related Art

With development of optoelectronic techniques, light emitting mechanism of light emitting devices has evolved from thermoluminescence into electroluminescence (EL). Light emitting devices with electroluminescence mechanism usually emit light in different colors by using a phosphor, which is a common method used for converting a wavelength of the light emitted by the light emitting device.

In regard to an LED illuminating device, a phosphor-converted cover is usually disposed above an LED light source module so as to emit light in different colors. A white-light conversion may then begin once the light emitted from the LED light source module is emitted to the phosphor-converted cover. However, heat generated by the LED light source module and heat generated during the white-light conversion may both be accumulated on the phosphor-converted cover, causing temperature of the phosphor-converted cover to rise. Since the phosphor-converted cover is composed by a phosphor and a high-molecular material or a glass, an effect of thermal quenching of luminescence may occur when the temperature of the phosphor-converted cover rises. As a result, efficiency of a phosphor-conversion may be reduced thereby generating a color washout phenomenon.

SUMMARY OF THE INVENTION

The invention is directed to a light emitting device having favorable efficiency in heat dissipation and capable of reducing color washout phenomenon.

The invention provides a light emitting device including a light-emitting diode (LED) light source module, a heat-dissipating unit and a phosphor-converted cover. The heat-dissipating unit is disposed below the LED light source module. The phosphor-converted cover covers the LED light source module. The phosphor-converted cover has an accommodating space, at least one air channel and a first air hole. The LED light source module is located in the accommodating space, and the first air hole is located above the LED light source module and connected to the air channel. An aperture of the first air hole is between 0.01 millimeters and 1 millimeter.

According to an embodiment of the invention, the phosphor-converted cover is fixed on the heat-dissipating unit, and the air channel is defined between the phosphor-converted cover and the heat-dissipating unit.

According to an embodiment of the invention, the phosphor-converted cover is fixed on the LED light source module, and the air channel is defined between the phosphor-converted cover and the LED light source module.

According to an embodiment of the invention, the at least one air channel includes a plurality of air channels, the phosphor-converted cover has a plurality of second air holes connected to each other, and the plurality of second air holes are located at a bottom edge of the phosphor-converted cover, and the plurality of air channels are defined by the plurality of second air holes and the LED light source module, and the bottom edge is directly contacted with the LED light source module.

According to an embodiment of the invention, a number of the second air holes is at least two.

According to an embodiment of the invention, the second air holes are arranged at equidistant intervals.

According to an embodiment of the invention, an aperture of each of the second air holes is between 0.01 millimeters and 1 millimeter.

According to an embodiment of the invention, the heat-dissipating unit has an upper surface, and the LED light source module is disposed on the upper surface. An area confined by the bottom edge of the phosphor-converted cover is 0.5 times to 0.9 times a surface area of the upper surface of the heat-dissipating unit.

According to an embodiment of the invention, a shape of the phosphor-converted cover is a hemisphere.

According to an embodiment of the invention, the LED light source module includes a substrate and at least one light-emitting diode (LED) chip. The LED chip is disposed on the substrate and electrically connected to the substrate.

According to an embodiment of the invention, the substrate includes an aluminum substrate, a copper substrate, a ceramic substrate, a glass fiber substrate or a printed circuit board.

According to an embodiment of the invention, the heat-dissipating unit includes a heat-dissipating block, a heat-dissipating sink, a heat-dissipating plate body or a heat pipe.

Based on above, since the phosphor-converted cover has the air channel and the air hole connected to each other, heat generated by the LED light source module may be transferred to outside through the heat-dissipating unit, an outside fluid may also pass through the accommodating space via the air channel, so as to discharge heat generated by the LED light source module to outside via the air hole by convection effect which reduces the temperature in the accommodating space. Accordingly, the light emitting device of the invention may have improved heat-dissipating efficiency and efficiency of a phosphor-conversion of the phosphor-converted cover may also be improved to reduce color washout phenomenon.

Several exemplary embodiments accompanied with figures are described in detail below to further describe the invention in details.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1Ais a schematic cross-sectional view illustrating a light emitting device according to an embodiment of the invention.FIG. 1Bis a top view illustrating a phosphor-converted cover of the light emitting device depicted inFIG. 1A. Referring toFIG. 1AandFIG. 1Btogether, a light emitting device100aincludes a light-emitting diode (LED) light source module110, a heat-dissipating unit120and a phosphor-converted cover130a. The heat-dissipating unit120is disposed below the LED light source module110. The phosphor-converted cover130acovers the LED light source module110. The phosphor-converted cover130ahas an accommodating space132, at least one air channel134aand a first air hole136. The LED light source module110is located in the accommodating space132, and the first air hole136is located above the LED light source module110and connected to the air channel134a. An outside fluid F is suitable to pass through the accommodating space132via the air channel134ato discharge heat generated by the LED light source module110to outside via the first air hole136. More preferably, an aperture D of the first air hole136is between 0.01 millimeters and 1 millimeter.

More specifically, the LED light source module110of the present embodiment includes a substrate112and at least one light-emitting diode (LED) chip114, in which the LED chip114is disposed on the substrate112and electrically connected to the substrate112. Herein, the substrate112is, for example, an aluminum substrate, a copper substrate, a ceramic substrate, a glass fiber substrate or a printed circuit board. The heat-dissipating unit120is disposed below the LED light source module110, in which heat generated by the LED chip114may be transferred to outside through the heat-dissipating unit120in form of thermal conduction. Herein, the heat-dissipating unit120is, for example, a heat-dissipating block, a heat-dissipating sink, a heat-dissipating plate body or a heat pipe. More specifically, according to the present embodiment, the phosphor-converted cover130ais fixed on the heat-dissipating unit120, and the air channel134ais defined by the phosphor-converted cover130aand the heat-dissipating unit120. Herein, a shape of the phosphor-converted cover130ais, for example, a hemisphere; and a method used to fix the phosphor-converted cover130aon the heat-dissipating unit120may be, for example, latching, locking or adhering, the invention is not limited thereto.

Since the phosphor-converted cover130ahas the air channel134aand the first air hole136connected to each other, heat generated by the LED light source module110may be transferred to outside through the heat-dissipating unit120, and the outside fluid F may also pass through the accommodating space132via the air channel134a, so as to discharge heat generated by the LED light source module110to outside via the first air hole136by stack effect which increases convection to reduce temperature in the accommodating space132. Accordingly, the light emitting device100aof the present embodiment may have improved heat dissipation efficiency and efficiency of a phosphor-conversion of the phosphor-converted cover130amay also be improved to reduce color washout phenomenon. In addition, the aperture D of the first air hole136is between 0.01 millimeters and 1 millimeter, and a location of the air channel134ais substantially lower than a location of the LED light source module110, as shown inFIG. 1A. Therefore, this design of the air channel134aand the first air hole136will not cause the light emitting device100ato generate a light-leaking phenomenon.

It should be noted that, structures and positions of the phosphor-converted cover130aare not particularly limited in the invention, even though the air channel134aof the phosphor-converted cover130aas embodied above is defined as an interval between the phosphor-converted cover130aand the heat-dissipating unit120while having the phosphor-converted cover130afixed on the heat-dissipating unit120. However, in other embodiments not shown, the phosphor-converted cover may also be fixed on the LED light source module, and the air channel of the phosphor-converted cover may also be defined as an interval between the phosphor-converted cover and the LED light source module. Said embodiment still belongs to a technical means adoptable in the present invention and falls within the protection scope of the present invention.

Moreover, it should be noted that, a profile of the first air hole136of the present embodiment is a circle as shown inFIG. 1Bwhen viewing from atop, thus the aperture D of the first air hole136is substantially a diameter of the first air hole136. However, in other embodiments, the profile of the first air hole136may also be other shapes when viewing from atop. In that case, the aperture D of the first air hole136is substantially a maximal length of the first air hole136. Moreover, in other applications, the light emitting device100aof the present embodiment may also be suspended on the ceiling or the wall for lighting. In this case, the outside fluid F is suitable to pass through the accommodating space132via the first air hole136to discharge heat generated by the LED light source module110to outside via the air channel134a. Said embodiment still belongs to a technical means adoptable in the present invention and falls within the protection scope of the present invention.

Referring toFIG. 2AandFIG. 2Btogether, as another embodiment of the invention, a phosphor-converted cover130bof a light emitting device100bis fixed on the LED light source module110, the phosphor-converted cover130bhas a plurality of second air holes135connected to each other, and a plurality of air channels134bare defined by the plurality of second air holes135and the LED light source module110. More specifically, the second air holes135are located at a bottom edge131of the phosphor-converted cover130b, and the bottom edge131is directly contacted with the LED light source module110. Herein, a number of the second air holes135is at least two, for example, four; and the second air holes135are arranged at equidistant intervals. As a result, airflow may be evenly distributed so as to improve dissipation efficiency. Herein, an aperture d of each of the second air holes135is between 0.01 millimeters and 1 millimeter.

It should be noted that, relation between an area confined by the bottom edge131of the phosphor-converted cover130band a surface area of a surface contacted with the heat-dissipating unit120is not particularly limited in the invention. Although, the area confined by the bottom edge131of the phosphor-converted cover130bas embodied above is substantially equal to or slightly less than the surface area of the surface contacted with the heat-dissipating unit120. However, in other embodiments, referring toFIG. 3, the LED light source module110of a light emitting device100cis disposed on a upper surface122of a heat-dissipating unit120c, and an area confined by the bottom edge131of the phosphor-converted cover130bis 0.5 times to 0.9 times the surface area of the upper surface122of the heat-dissipating unit120c. In other words, the surface area of the upper surface122of the heat-dissipating unit120cis substantially greater than the area confined by the bottom edge131of the phosphor-converted cover130b. Said embodiment still belongs to a technical means adoptable in the present invention and falls within the protection scope of the present invention.

In view of above, since the phosphor-converted cover has the air channel and the air hole connected to each other, heat generated by the LED light source module may be transferred to outside through the heat-dissipating unit, the outside fluid may also pass through the accommodating space via the air channel, so as to discharge heat generated by the LED light source module to outside via the air hole by convection effect which reduces the temperature in the accommodating space. Alternatively, the outside fluid may pass through the accommodating space via the air hole to discharge heat generated by the LED light source module to outside via the air channel. Accordingly, the light emitting device of the invention may have improved dissipation efficiency and efficiency of a phosphor-conversion of the phosphor-converted cover may also be improved to reduce color washout phenomenon.