This application is based on and claims the benefit of Taiwan Application No. 100116845 filed May 13, 2011 the entire disclosure of which is incorporated by reference herein.
1. Technical Field
The present disclosure relates to a lighting device, a lamp and a lighting method.
2. Description of Related Art
Light emitting diode (LED) is a solid state device generally made of compound semiconductor material for converting electrical energy to light. LEDs have the advantages of long lifetime, high stability and low power consumption. LEDs are initially employed in indication, traffic sign and sign board applications, and then gradually applied to general lighting applications as white LEDs are successfully developed.
A white LED known to the inventor(s) is made by coating yellow Yttrium aluminum garnet (YAG) phosphor over a blue LED chip. A part of light emitted from the blue LED chip is absorbed by the YAG phosphor, and then the YAG phosphor responsively generates wavelength-converted light. The wavelength-converted light, which is yellow light, is mixed with the non-converted light of the blue LED chip to generate white light.
The white LED manufactured by above-mentioned approach has a relatively high color temperature (cold white light) because non-converted light of the blue LED chip occupies a dominant part in the spectrum of the white LED.
To reduce the color temperature, red phosphor is added in the yellow YAG phosphor of the above-mentioned white LED. The red phosphor absorbs blue light and emits red light. The red light is mixed with the original white light with a relatively high color temperature to generate white light with a lower color temperature (warm white light).
The inventor(s) had several observations as follows. The yellow phosphor might have difficulty to mix uniformly with red phosphor which might result in the above-mentioned red-phosphor-added white LED providing non-uniform illumination. The white LED has lower lighting efficiency because the blue light is additionally absorbed by the red phosphor, besides the yellow phosphor. Moreover, the conversion efficiencies of the yellow phosphor and the red phosphor tend to decay with the usage of the white LED. The white LED tends to exhibit a color temperature shift after a period of operation time.
Accordingly, the lighting device according to one aspect of the present invention comprises a lighting engine and at least one wavelength-converting element. The lighting engine comprises a circuit board, a blue light emitting diode (LED) and a red LED. The blue LED and the red LED are arranged on the circuit board. The wavelength-converting element covers at least the blue LED. A partial light emitted from the lighting engine is converted by the wavelength-converting element to generate a wavelength-converted light. The wavelength-converted light is mixed with a non-converted light of the lighting engine to generate a white light having a color temperature between 2580K and 3220K located on the black-body radiation of CIE-1931 chromaticity diagram.
Accordingly, the lighting method according to another aspect of the present invention comprises: turning on a lighting engine to emit a light with chromaticity within a region defined by color points (0.5745, 0.3370), (0.3420, 0.1796), (0.3075, 0.0839), and (0.6581, 0.2518) in CIE-1931 chromaticity diagram; and exciting a phosphor to emit a wavelength-converted light and mixing the wavelength-converted light with a non-converted light of the lighting engine to form a white light, wherein the white light has a color temperature within 2580K to 3220K located on the black-body radiation of CIE-1931 chromaticity diagram.
Accordingly, the lamp according to still another aspect of the present invention comprises a lighting engine, a wavelength-converting element, a shell and a heat sink module. The lighting engine comprises a circuit board, a first lighting element and a second lighting element, where the first lighting element and the second lighting element are arranged on the circuit board. The wavelength-converting element covers at least partial portion of the lighting engine. The shell is made of transparent material. The heat sink module is assembled with the shell such that the lighting engine and the wavelength-converting element are arranged between the shell and the heat sink module. The lamp emits a white light with a color temperature within 2580K to 3220K located on the black-body radiation of CIE-1931 chromaticity diagram.
In one or more embodiments, each of the first light emitting elements 114 has a blue LED chip with a junction for emitting blue light, and the driving voltage range of each first light emitting element 114 is from 2.4 to 4 V. Each of the second light emitting elements 116 has a red LED chip with a junction for emitting red light, and the driving voltage range of each second light emitting element 116 is from 1.8 to 3.0 V. The first light emitting elements 114 and the second light emitting elements 116 are first connected in serial connection into one or more strings of mixed blue and red LED chips and then the strings are connected in parallel connection as shown in
In one or more embodiments, each of the first light emitting elements 114 has a blue LED chip with multiple junctions each for emitting blue light, wherein the multiple junctions have one or more serial interconnections and/or parallel interconnections, e.g., by semiconductor process. Each of the second light emitting elements 116 has a red LED chip with multiple junctions each for emitting red light, wherein the multiple junctions have one or more serial interconnections and/or parallel interconnections, e.g., by semiconductor process. As shown in
In one or more embodiments, each first light emitting element 114 has multiple blue LED chips, and each second light emitting element 116 has multiple red LED chips. The blue LED chips and the red LED chips are connected in serial and/or parallel connection, e.g., by packaging process, into a single package as shown in
With reference again to
A part of light emitted from the lighting engine 110 is wavelength-converted in the wavelength-converting element 120 to generate wavelength-converted light. Another part of light emitted from the lighting engine 110 passes through the transparent shell without exciting the wavelength conversion material and is not wavelength-converted (non-converted). The wavelength-converted light is mixed with the non-converted light of the lighting engine 110 to form warm white light. As shown in
With reference again to
With reference again to
The conductive connector 150 is arranged on the second side 136 of the heat sink module 130 and is adapted to be screwed into the socket of a lamp. The conductive connector 150 can be electrically connected to an AC power source, and can be an E26 or E27 connector.
The driving circuit 160 is arranged within the heat sink module 130 and electrically connected to the lighting engine 110 and the conductive connector 150. With reference also to
Moreover, the lighting device 10 further comprises a dimming controller 170 electrically connected to the driving circuit 160 and adapted to control the on/off operation and the brightness of the first light emitting elements 114 and/or the second light emitting elements 116.
The AC power supplied by the conductive connector 150 is converted into stable DC power by the driving circuit 160, and the lighting engine 110 is driven by the DC power. A part of the light of the lighting engine 110 is wavelength-converted by the wavelength-converting element 120 to form wavelength-converted light. White light having a color temperature from 2580K to 3220K on the black-body radiation of the CIE-1931 chromaticity diagram is generated by mixing the wavelength-converted light and non-converted light emitted by the lighting engine 110.
With reference again to
A part of light emitted from the first light emitting elements 214 of the lighting engine 210 is wavelength-converted in the corresponding wavelength-converting elements 220 to generate wavelength-converted light. Another part of light emitted from the first light emitting elements 214 passes through the transparent shell without exciting the wavelength conversion material and is not wavelength-converted. The part of light emitted from the first light emitting elements 214 that is not wavelength-converted and the light emitted from the second light emitting elements 216 together define non-converted light. The wavelength-converted light is mixed with the non-converted light of the lighting engine 210 to form warm white light. The thus-formed warm white light has a color temperature within 2580K to 3220K on the black-body radiation of the CIE-1931 chromaticity diagram
To realize a lighting device 20 with warm white light having a color temperature between 2580K and 3220K, a part of light emitted from the first light emitting elements 214 is converted by the corresponding wavelength-converting elements 220, and mixed light formed by mixing the wavelength-converted light and the non-converted light of the first light emitting elements 214 and the second light emitting elements 216 corresponds to the region defined by the 4 color points Q1 (0.3162, 0.5367), Q2(0.2620, 0.3878), Q3(0.3822, 0.3827), and Q4 (0.4308, 0.4639) in the CIE-1931 chromaticity diagram, as shown in
With reference again to
The heat sink module 230 is assembled with the cover 240 such that the lighting engine 210 and the wavelength-converting element 220 are arranged between the cover 240 and the heat sink module 230.
The conductive connector 250 is assembled to one side of the heat sink module 230, which is opposite to the cover 240. The conductive connector 250 is adapted to be screwed into the socket of a lamp. The conductive connector 250 can be electrically connected to an AC power source, and can be an E26 or E27 connector.
The driving circuit 260 is arranged within the heat sink module 230 and electrically connected to the lighting engine 210 and the conductive connector 250. The driving circuit 260 is functioned to convert AC power input from the conductive connector 250 into DC power to drive the lighting engine 210 for illumination.
The circuit of the lighting device of the second embodiment is similar to that of the first embodiment, and the detailed description thereof is omitted here for brevity.
First, a lighting engine 30 is turned on. The lighting engine 30 comprises at least a blue LED 32 and at least a red LED 34. The blue LED emits blue light Lb with a wavelength between 445 to 465 nm, and the red LED emits red light Lr with a wavelength between 600 to 640 nm. The lighting engine 30 emits light Lt when it is turned on, where the light Lt is the mixture of the blue light Lb and the red light Lr. The chromaticity of the light Lt corresponds to the region defined by the 4 color points P1 (0.5745, 0.3370), P2 (0.3420, 0.1796), P3 (0.3075, 0.0839), and P4 (0.6581, 0.2518) in the CIE-1931 chromaticity diagram.
Afterward, the emitted light of the lighting engine 30 excites a wavelength conversion material, e.g., a phosphor 36, where the phosphor 36 can be YAG phosphor, silicate phosphor, Terbium aluminum garnet (TAG) phosphor, oxide phosphor, nitride phosphor, or aluminum oxide phosphor.
In the lighting engine 30, the blue LED 32 emits first blue light Lb1, which excites the phosphor 36 to generate wavelength-converted light Ly from the phosphor 36. Mixed light generated by mixing the wavelength-converted light Ly and second blue light (non-converted light) Lb2 has chromaticity corresponding to the region defined by the 4 color points Q1 (0.3162, 0.5367), Q2(0.2620, 0.3878), Q3(0.3822, 0.3827), and Q4 (0.4308, 0.4639) in the CIE-1931 chromaticity diagram. The blue light Lb includes the two portions, namely, the first blue light Lb1 and the second blue light Lb2.
The wavelength-converted light Ly is mixed with the non-converted light of the lighting engine 30 (including the second blue light Lb2 and the red light Lr) to form white light having a color temperature within 2580K to 3220K on the black-body radiation of the CIE-1931 chromaticity diagram.
To sum up, in some embodiments of the present invention, at least one red LED is employed to provide a red color portion in the warm white light generated by the lighting device. In comparison with known white light sources using red phosphor excited by a blue LED as a red light source, the lighting device in accordance with some embodiments has a higher efficiency, a lower likelihood of color temperature shift, and better color rendering property.
The first and/or second light emitting elements are not necessarily LEDs. For example, in one or more embodiments, first and/or second light emitting elements include one or more laser diodes, organic light-emitting diodes (OLED) or other light emitting devices.
The first and/or second light emitting elements do not necessarily emit blue and/or red light, and may be configured to emit light of other colors. In one or more embodiments, the first light emitting element is configured to emit light of a wavelength different from that of the second light emitting element. The wavelength-converting element is configured to be excited by the light emitted by at least one of the first or second light emitting elements to generate wavelength-converted light which is mixed with the non-converted light to provide light in a predetermined color temperature range.
Although several embodiments of the present invention have been described in detail, it will be understood that the disclosure is not limited to such details. Various substitutions and modifications will occur to those of ordinary skill in the art in light of the foregoing description. Therefore, all such substitutions and modifications are intended to be embraced within the scope of this disclosure.
Number | Date | Country | Kind |
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100116845 | May 2011 | TW | national |