Patent Application
20120081033
1. Field of the Invention
The present invention relates to a white light emitting diode, and more particularly to a white light emitting diode which can be controlled to adjust lights for generating different color temperature.
2. Description of Prior Art
A light emitting diode (LED) is a kind of semiconductor device, which exploits the property of direct-bandgap semiconductor material to convert electric energy into light energy efficiently and has the advantages of long lifetime, high stability and low power consumption. The LED is primarily used for the applications of indication lamp, traffic sign and sign broad; however, the white LED extends to lighting field when white light LED is successfully developed.
The traditional method of manufacturing a white light emitting diode, is to coat a blue light emitting diode chip with yellow phosphor layer comprising Yttrium Aluminum Garnet fluorescent material. The yellow phosphor is excited by the blue light of the blue light emitting diode chip and emits yellow light, the emitted yellow light is mixed with the blue light to generate white light. However, the blue light occupies major portion of the white light spectrum, thus the white light emitting diode having the problems of high color temperature and the non-uniformity in the mixed light.
Moreover, an improved lighting module is proposed to mix the light of white light emitting diodes mentioned above and the light of red light emitting diodes (or green light emitting diodes) to solve the problem of high color temperature. However, the light emitting diodes of different colors are made of different material, thus the circuit design for the white light emitting diode becoming difficult. The chromatic characteristic and the lifetime of each lighting module are different because each light emitting diode also has different temperature characteristic and lifetime. This causes inconvenience for user.
In order to solve the above-mentioned problems of traditional white light emitting diode, such as high color temperature, non-uniform mixed light and inconvenience in use, the object of the present invention is to provide a white light emitting diode to generate white lights with different color temperatures, and mix the white lights with different color temperatures to adjust the resulting color temperature of the white light emitting diode.
Therefore, the present invention provides a white light emitting diode. The white light emitting diode comprises a light emitting diode chip, a first wavelength conversion layer and a second wavelength conversion layer.
The light emitting diode chip which emitting blue light comprises a first lighting area and a second lighting area. The first lighting area and the second lighting area are conducted with at least two currents, respectively.
The first wavelength conversion layer is coated on the first lighting area and generates a first conversion light upon excitation by the blue light which emits from the light emitting diode chip. A warm white light is generated by mixing the blue light and the first conversion light.
The second wavelength conversion layer is coated on the second lighting area and generates a second conversion light upon excitation by the blue light which emits from the light emitting diode chip. A cold white light is generated by mixing the blue light and the second conversion light. The amount of the current can be controlled to modify the luminescence intensity of each light area to adjust the color temperature of the white LED.
The white light emitting diode divides the light emitting diode chip into at least two lighting areas and covers different wavelength conversion layers on each lighting area, thus mixing the white lights with different color temperatures to modify the resulting color temperature of the white LED. The white light emitting diode according to the present invention has simple manufacture process and effectively solves the problem of unequal lifetime of different LEDs and the problem of difficult circuit design due to different driving voltages for different LEDs.
The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which:
Referring to
The blue light emitting diode chip 10 emits blue light and comprises a first lighting area 12 and a second lighting area 14. The first lighting area 12 conducts a first current, and the second lighting area 14 conducts a second current. In this embodiment, the blue light emitting diode chip comprises sixteen lighting units 100, which are arranged in accordance with a matrix pattern. The first lighting area 12 and the second lighting area 14 comprise eight lighting units 100 electrically connected in series, respectively. However, in the practical application of the present invention is not limited by the above example.
Referring to
Referring to
The second wavelength conversion layer 30 is coated on the second lighting area 14. The second wavelength conversion layer 30 comprises yellow photoluminescence phosphor. The second wavelength conversion layer 30 generates a second conversion light L2 upon excitation by the blue light when conducted the second current I2 to the second area 14. A cold white light Lc is generated by mixing the blue light which emits from the light emitting diode chip and the second conversion light L2. In more particularly, the color temperature of the cold white light is in the range between 5000K and 10000K.
When the first lighting area 12 and the second lighting area 14 conduct the first current I1 and the second current I2, respectively, a middle area between the first lighting area 12 and the second lighting area 14 emits a light mixture of the warm white light Lw and the cold white light Lc to generated a neutral white light. In more particularly, the color temperature of the neutral white light is in the range from 3800K to 5000K.
Moreover, the luminous flux of the lighting areas 12, 14 is directly proportional to the current flow through the lighting area 12, 14, thus the color temperature of the white light emitting diode 1 can be adjusted by controlling the current flow of the first current I1 and the second current I2 when the number of the lighting units 100 of the first lighting area 12 and the second lighting area 14 are the same. A neutral white light is generated by mixing the warm white light Lw and the cold white light Lc while the first current I1 is equal to the second current I2. The luminous flux of the warm white light Lw is also the same as the luminous flux of the cold white light Lc. A warmer neutral white light is generated by mixing the warm white light Lw and the cold white light Lc while the first current I1 is larger than the second current I2. The luminous flux of the warm white light Lw is also larger than the luminous flux of the cold white light Lc. Thus, a warm white light is generated by the white light emitting diode 1 while the second current I2 is equal to zero. A colder neutral white light is generated by mixing the warm white light Lw and the cold white light Lc while the first current I1 less than the second current I2. The luminous flux of the warm white light Lw is also less than the luminous flux of the cold white light Lc. Thus, a cold white light is generated by the white light emitting diode 1 while the first current I1 is equal to zero.
Referring to the
Referring to
The table below shows test data of the white light emitting diode according to the present invention. The white light emitting diode under a test comprises six lighting units arranged in accordance with a matrix pattern. The first lighting area and the second lighting area comprise three lighting units electrically connected in series, respectively. The first light units and the second lighting units are conducted with the first current and the second current, respectively. The first current is equal to the second current. The CIE coordinates in rows with number 1 to 3 are (0.3263, 0.3397), (0.3266, 0.3394), and (0.3263, 0.3398), which are corresponding to color temperatures of 3012K, 2990K, 2982K, respectively, where those color temperatures indicate cold white light. The CIE coordinates in rows with number 4 to 6 are (0.4404, 0.4160), (0.4410, 0.4150), and (0.4422, 0.4162), which are corresponding to color temperatures of 3012K, 2990K, 2982K, respectively, where those color temperatures indicate warm white light. The row with number 7 in the table is a white light emitting diode consisted of the six light units mentioned above. The white light emitting diode has CIE coordinate (0.3752, 0.3733), which is corresponding to color temperature of 4108K for emitting neutral white light.
To sum up, the white light emitting diode according to the present invention divides the blue light emitting diode into at least two lighting areas and covers different wavelength conversion layers on each of the lighting areas. At least two currents are conducted to any lighting area which needs to be conducted and the amount of the current is controlled to generate white light with different color temperature at the same time. Moreover, color temperature can be further fine-tuned by mixing the white lights with different color temperatures. The white light emitting diode according to the present invention has simple manufacture process and effectively solves the problem of unequal lifetime of different LEDs and the problem of difficult circuit design due to different driving voltages for different LEDs.
Although the present invention has been described with reference to the foregoing preferred embodiments, it will be understood that the invention is not limited to the detail thereof. Various equivalent variations and modifications can still occur to those skilled in this art in view of the teachings of the present inventions. Thus, all such variations and equivalent modifications are also embraced within the scope of the invention as define in the appended claims.
