Patent Application
20050242360
1. Field of the Invention
The preferred embodiment of the present invention relates to a white light apparatus with adjustable color temperature and method of producing white light thereof, and particularly to a method of utilizing one luminescent component which is controlled by varying driving current for decreasing or increasing color temperature value of the white light from the white light apparatus.
2. Description of Prior Art
A white light source is generally provided via mixing light source of different wavelength, and white light sensed by human vision is generally composed of light of at least two colors. For instance, a conventional white light source can be realized by mixing red light, green light and blue light with suitable intensity ratio. Alternatively, the white light source can be realized by mixing yellow light and blue light with suitable intensity ratio. Nowadays, most white light apparatus include fluorescent lamps, incandescent lamps, and white light-emitting diodes (white LED) that are currently under development. The color temperature of white light provided by a fluorescent lamp is about 7500 K, and the color temperature of white light provided by an incandescent lamp is about 3000 K.
Conventionally, there are many methods of obtaining a white light apparatus. The first conventional method is to use three light-emitting diodes (LEDs) to provide red, green and blue light by controlling a corresponding driving current respective to each LED. One of the three LEDs is made of InGaAlP, and the other two are made of GaN. The red, green and blue light emitted from the three LEDs are mixed together, thereby to produce white light.
The second conventional method is similar to the first conventional methods; the difference therebetween is that the second methods uses only two LEDs made of GaN and InGaAlP to provide blue light and yellow-green light or green light and red light for producing white light.
The third conventional method was developed by Japan Nichia Chemical Industries, Ltd., in 1996 and provides a white light apparatus using a blue light-emitting diode of an InGaN semiconductor combined with a yttrium aluminum garnet (“YAG:Ce”) phosphor material, which emits yellow light. The mixture of these blue and yellow emitted lights can also be perceived as white light by an observer.
The fourth conventional method was developed by Sumitomo Electric in 1999, and provides a white LED made of a ZnSe material. This method firstly forms a CdZnSe film on a ZnSe single crystal base. The CdZnSe film emits a blue light with a driving current, and the base is excited by a part of the blue light and then emits a yellow light. The blue light and the yellow light are mixed together for producing white light.
The fifth method uses an ultraviolet LED to excite much phosphor powder to emit lights with multiple colors, and mixture of these multiple colors of emitted light are perceived as white light by an observer.
However, the conventional methods as described above suffer from the following disadvantages. Except the first and second conventional methods, the other conventional methods can only provide a white light with a single constant color temperature; i.e., the color temperature thereof cannot be adjusted. On the other hand, although the first conventional method can generate the white light of different color temperature by modulating the corresponding driving current respective to each LED, it is expensive and complicated since each LED needs an independent controlling circuit. Similar to the first conventional method, the second conventional method can also generate the white light in different color temperature values by modulating the corresponding driving current respective to each LED. However, only two kinds of lights are available for producing white light in this method, so that color temperature of the white light is adjustable in a limited range, and is unable to attain color temperatures of some common light sources, such as 7500 K of a fluorescent lamp or 3000 K of an incandescent lamp.
Therefore, the preferred embodiment of the present invention provides an improved white light luminescence method and a luminescent device for the same that can overcome or at least reduce the disadvantages set forth above.
In accordance with one aspect of the present invention, a method of producing a white light with adjustable color temperature includes: providing a blue light-emitting diode emitting a blue light which has a wavelength in a range from 400 nm to 500 nm; preparing a phosphor powder emitting a phosphor light which has a wavelength in a range from 540 nm to 700 nm, wherein the phosphor light is mixed with the blue light of the blue light-emitting diode to produce a white light with a color temperature value above 6500 K; and adding an orange light-emitting diode emitting a light which has a wavelength in a range from 540 nm to 600 nm, wherein the orange light-emitting diode can be controlled by a driving current for adjusting the color temperature of the white light.
In accordance with another aspect of the present invention, a white light apparatus with adjustable color temperature includes: a blue light-emitting diode emitting a blue light; a phosphor powder emitting a phosphor light, wherein the phosphor light is mixed with the blue light of the blue light-emitting diode to produce a white light with a high or a low color temperature value; and a luminescent component emitting a light which has a wavelength in a range from 480 nm to 600 nm, wherein the luminescent component can be controlled by a driving current for adjusting the color temperature of the white light.
Other objectives, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:
The preferred embodiment of the present invention is intended to a white light apparatus with adjustable color temperature and a method of producing a white light thereof.
The second luminescent component 14 is a phosphor powder, preferable to a phosphor powder emitting a yellow light. The phosphor powder can emit a phosphor light 24 (shown in
The third luminescent component 16 is an orange light-emitting diode having a luminescent layer that is made of a nitride semiconductor or a phosphide semiconductor. The orange light-emitting diode is controlled due to an adjustable driving current, to emit an orange light 26 with reference to 592 nm (shown in
Next, the white light apparatus 10 is provided for producing the white light with adjustable color temperature, as following steps. Firstly, the blue light-emitting diode is provided for emitting the blue light. Secondly, the phosphor powder is prepared for emitting a phosphor light mixed with the blue light of the blue of light-emitting diode to produce the white light with a high or a low color temperature value (i.e. above or below 6500 K). Sequentially, the orange light-emitting diode or blue-green light-emitting diode of the third luminescent component 16 can be adjusted by varying the driving current inputted into the third luminescent component 16, thereby to decrease or increase the color temperature value of the white light of the white light apparatus 10.
Preferably, the phosphor powder is selected from a group consisting of Y3Al5O12:Ce, Gd, CaS:Eu and SrGa2S4:Eu. The phosphor powder is prepared by one of a solid reaction method and a chemical synthesizing method. The chemical synthesizing method is a citrate gel method or a co-precipitation method.
To sum up, the white light apparatus provided by the preferred embodiment of the present invention has peculiar advantages over prior art white light apparatus in following aspects:
1. In the preferred embodiment of the present invention, the color temperature value of the white light emitted from the white light apparatus can be adjusted by varying a driving current value of applying to the third luminescent component 16.
For example, the color temperature value of the white light of the white light apparatus can be adjusted in either 7500 K of the phosphor lamp or 3000 K of the incandescent lamp.
2. In the preferred embodiment of the present invention, only one chip is required for controlling the driving current to the third luminescent component 16, so that driving circuit of the preferred embodiment of the present invention can be simple and cheaper.
3. In the preferred embodiment of the present invention, the phosphor powder is of crystal structure, thereby to improve uniformity of the white light of the white light apparatus.
There has thus been described a new, novel and heretofore unobvious white light apparatus with adjustable color temperature which eliminates the aforesaid problem in the prior art. Furthermore, those skilled in the art will readily appreciate that the above description is only illustrative of specific embodiments and examples of the invention. The invention should therefore cover various modifications and variations made to the herein-described structure and operations of the invention, provided they fall within the scope of the invention as defined in the following appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 93111938 | Apr 2004 | TW | national |
