Patent Grant
10036516
The present invention relates to a lamp, and more particularly to a light emitting diode (LED) lamp.
An existing LED lamp typically includes a heatsink, a reflector, a diffuser plate, and a substrate having LED chips disposed thereon. Light of different colors emitted by the LED chips is synthesized into white light. Currently, it has been one of the main technical hotspots in the field of LED lighting to realize a color temperature adjustable lamp with a high color rendering index, and a method of mixing light of LEDs of different color temperatures or wavelengths is usually employed. However, it is not easy to achieve a high color rendering index, especially a high special color rendering index R9, which is required in many applications (for example, commodity exhibition). Therefore, attempts have been made to utilize a combination of phosphors or LEDs of different wavelengths. For example, in a patent application entitled “Method for Obtaining Color Temperature Adjustable White Light with High Color Rendering Index by Using Combination of White, Red and Blue LEDs” and published on Aug. 18, 2010 with a publication number CN101808451A, a blue LED chip is used to excite mixed yellow and green phosphors to produce warm white light, and then, the warm white light is mixed with a red LED light source and a blue LED light source of another wavelength to produce color temperature adjustable white light with a high color rendering index.
The above solution has several deficiencies below. 1. The coated phosphor is a mixture of a yellow phosphor and a green phosphor, a mixing ratio is not easy to control, and chrominance parameters of the finally synthesized white light are affected by an undesirable mixing ratio. Moreover, green fluorescent light is partially absorbed by the yellow phosphor, so that the excitation efficiency is reduced, the difficulty of setting the mixing ratio is further increased, and the design cost of the lamp is high. 2. Although the mixed white light is adjustable within the range of 2700K-6500K, the special color rendering index R9 is greater than 90 only, and the chromaticity difference ΔC is less than or equal to 0.01, so that the performance parameters cannot satisfy applications with high requirements. Moreover, the special color rendering index R9 is greater than 90 only within the range of 2700K-5000K, and R9 greater than 90 cannot be achieved within the entire adjustable color temperature range. 3. The two set blue LED chips have unequal peak wavelengths, increasing material selection and manufacturing costs.
The technical problem to be solved by the present invention is: in order to overcome the above deficiencies of the prior art, an LED lamp is provided, in which a color temperature is adjustable within the range of 2700K-6500K, a general color rendering index Ra is more than 90, a special color rendering index R9 is more than 95, a chromaticity difference ΔC is less than 0.0054, and meanwhile the design and manufacturing costs of the lamp are low.
The technical problem of the present invention is solved through the following technical solution.
An LED lamp includes a heatsink, a reflector, a diffuser plate, and a substrate having an LED light source module disposed thereon, in which the LED light source module includes at least one group of LED light source components, and the LED lamp further includes three drive circuits and a control circuit; the LED light source components include a first LED light source providing blue-green light, a second LED light source providing yellow light, and a third LED light source providing red light; the first light source includes a first blue LED chip having a peak wavelength of 445-455 nm, a green phosphor having a peak wavelength of 500-520 nm is coated on the first blue LED chip, and blue light accounts for a luminous power proportion of 0.43-0.57 in the provided blue-green light; the second light source includes a second blue LED chip having a peak wavelength of 445-455 nm, a yellow phosphor having a peak wavelength of 557-570 nm is coated on the second blue LED chip, and blue light accounts for a luminous power proportion of 0-0.08 in the provided yellow light; the third light source includes a third red LED chip having a peak wavelength of 624-630 nm; the control circuit stores a correspondence table of a luminous flux ratio of each light source and chrominance parameters of a mixed light source; at the luminous flux ratio of each light source, the chrominance parameters satisfy the following conditions: a color temperature is adjustable within a range of 2700K-6500K, and at each color temperature, a general color rendering index Ra of the light source is greater than or equal to 90, a special color rendering index R9 is greater than or equal to 95, and a chromaticity difference ΔC is less than 0.0054; the control circuit selects, according to a mixed color temperature required by a user, a corresponding luminous flux ratio of each light source, determines a drive current of each light source according to the luminous flux ratio of each light source, and separately outputs the calculated drive current to a corresponding drive circuit; and the three drive circuits output the received drive currents to corresponding LED light sources and drive the corresponding LED light sources to emit light.
Compared with the prior art, the present invention has the following beneficial effects.
In the LED lamp of the present invention, the LED light source components are a first blue LED chip, a second blue LED chip, and a third red LED chip that are specially disposed so as to produce mixed light of a specific spectral power distribution. Meanwhile, the control circuit pre-stores a correspondence table of a luminous flux ratio of each light source satisfying conditions and chrominance parameters, selects a luminous flux ratio of each light source according to a required color temperature, and accordingly determines a drive current, outputs the drive current to each light source and drive the light source to emit light, so that the required color temperature is obtained, and meanwhile, a general color rendering index Ra of the light source is greater than or equal to 90, a special color rendering index R9 is greater than or equal to 95, and a chromaticity difference ΔC is less than 0.0054. In the LED lamp of the present invention, on the premise that the color temperature is adjustable within the range of 2700K-6500K, the general color rendering index Ra is greater than or equal to 90, the special color rendering index R9 is greater than or equal to 95, and the chromaticity difference ΔC is less than 0.0054, so that the chrominance parameters are desirable and can satisfy applications with high requirements. Meanwhile, the problem of a mixing ratio of different types of phosphors is not involved in the LED light source components, and the two blue LED chips have the same peak wavelength, so that both the design cost and the manufacturing cost of the lamp are low.
The present invention is described in further detail below through specific embodiments with reference to accompanying drawings.
The present invention uses a combination of a single type of blue LED having a peak wavelength of 445-455 nm, which is used to separately excite a green phosphor (having a peak wavelength of 500-520 nm) and a yellow phosphor (having a peak wavelength of 557-570 nm) to produce blue-green light and yellow light, and a red LED having a peak wavelength of 624-630 nm to achieve LED white light in which a color temperature is adjustable within the range of 2700K-6500K, a general color rendering index Ra is greater than or equal to 90, a special color rendering index R9 is greater than or equal to 95, and a chromaticity difference ΔC is less than 0.0054.
The LED light source components include a first LED light source 401 providing blue-green light, a second LED light source 402 providing yellow light, and a third LED light source 403 providing red light.
The first light source 401 includes a first blue LED chip having a peak wavelength of 445-455 nm, and a green phosphor having a peak wavelength of 500-520 nm is coated on the first blue LED chip, so that the first blue LED chip excites the green phosphor to produce blue-green light. By adjusting the adhesive powder proportion and coating amount of the green phosphor, blue light accounts for a luminous power proportion of 0.43-0.57 in the produced blue-green light (in the blue-green light, luminous power proportions of the blue light and green light add up to 1, that is, the green light also accounts for a luminous power proportion of 0.43-0.57). In this specific embodiment, a blue LED chip having a peak wavelength of 446 nm is used to excite a 507 nm green phosphor, and blue light accounts for a luminous power proportion of 0.44 in the blue-green light.
The second light source 402 includes a second blue LED chip having a peak wavelength of 445-455 nm, a yellow phosphor having a peak wavelength of 557-570 nm is coated on the second blue LED chip, so that the second blue LED chip excites the green phosphor to produce yellow light. By adjusting the adhesive powder proportion and coating amount of the yellow phosphor, blue light (transmitted through the blue LED chip) accounts for a luminous power proportion of 0-0.08 in the produced yellow light (that is, the yellow light accounts for a luminous power proportion of 0.92-1). In this specific embodiment, a blue LED chip having a peak wavelength of 446 nm is used to excite a 558 nm yellow phosphor, and blue light accounts for a luminous power proportion of 0.07 in yellow light.
The third light source includes a third red LED chip having a peak wavelength of 624-630 nm and provides red light. In this specific embodiment, a red LED having a peak wavelength of 627 nm is used.
It should be noted that when a combination of other values within the ranges is selected, peaks of the waveforms in
During operation of circuit components in the LED lamp, the control circuit 6 stores a correspondence table of a luminous flux ratio of each light source and chrominance parameters of a mixed light source; at the luminous flux ratio of each light source, the chrominance parameters satisfy the following conditions: a color temperature is adjustable within the range of 2700K-6500K, and at each color temperature, a general color rendering index Ra of the light source is greater than or equal to 90, a special color rendering index R9 is greater than or equal to 95, and a chromaticity difference ΔC is less than 0.0054; the control circuit selects, according to a mixed color temperature required by a user, a corresponding luminous flux ratio of each light source, determines a drive current of each light source according to the luminous flux ratio of each light source, and outputs the calculated drive currents to corresponding drive circuits 701, 702, and 703 respectively.
The three drive circuits 701, 702, and 703 output the received drive currents to corresponding LED light sources 401, 402, and 403 and drive the corresponding LED light sources to emit light. The three drive circuits 701, 702, and 703 drive the three LED light sources by means of pulse width modulation (PWM). The PWM mode is used to adjust and control the pulse width of an input current of each LED light source so that the LED light source always operates at a full-amplitude current and zero, thereby reducing the color spectrum offset. PWM signals may be generated by using a single-chip microcomputer with a 16-bit timer, and divided into 65536 gray levels. In this way, the control precision can be improved and the light can be changed gently.
The control circuit 6 adjusts the drive currents through the drive circuits, so as to control the luminous flux output of each light source, so that the LED lamp outputs mixed white light obtained after mixing at corresponding luminous flux ratios, so that mixed white light at a desired color temperature is output, and at the color temperature, a general color rendering index Ra is more than 90 and a special color rendering index R9 is more than 95.
How to obtain the correspondence table of luminous flux ratios and chrominance parameters of the mixed light source is described in detail below.
First, chrominance parameters such as a color temperature, a color rendering index, and a chromaticity difference of a light source are determined by a relative spectral power distribution of light obtained after mixing three colors. The relative spectral power distribution S(λ) of the mixed light is calculated as shown in equation (1):
S(λ)=K1*SB_G(λ)+K2*SB_Y(λ)+K3*SR(λ) (1)
where SB_G(λ), SB_Y(λ), and SR(λ) are respectively relative spectral power distributions of blue-green light, yellow light, and red light participating in light mixing, and K1, K2, and K3 are luminous power ratios corresponding to the blue-green, yellow, and red LEDs participating in light mixing. Therefore, relative spectral power distributions of LEDs participating in light mixing and luminous power ratios among them must be known in order to determine a color temperature and a color rendering index of mixed light. As described earlier, when the peak wavelengths of the used LED chips and phosphors and the amounts of the phosphors are determined, the power distribution of the mixed light is determined (as shown in
After the luminous power ratios K1, K2, and K3 satisfying conditions are obtained, because of the correspondence between luminous power ratios and luminous flux ratios, luminous flux ratios can be calculated according to the luminous power ratios. The calculation equations are:
In the equations, ηn, Kn, and LERn respectively correspond to a luminous flux ratio, a luminous power ratio, and an efficacy of radiation of each light source (corresponding to the blue-green light when n=1, corresponding to the yellow light when n=2, and corresponding to the red light when n=3), the value of αmis 6831 m/W, V(λ) is a luminosity function, and S(λ) is relative spectral power distribution data of the corresponding light source.
The correspondence between the luminous flux ratio of each light source and the color temperature, the general color rendering index Ra, the special color rendering index R9, and the chromaticity difference ΔC of the mixed light source can be obtained according to the above calculation method, and the color temperature is adjustable within the range of 2700K-6500K, and at each color temperature, the general color rendering index Ra of the mixed light source is greater than or equal to 90, the special color rendering index R9 is greater than or equal to 95, and the chromaticity difference ΔC is less than 0.0054.
Still using the situation in which the blue LED chip having a peak wavelength of 446 nm, the red LED chip having a peak wavelength of 627 nm, the green phosphor having a peak wavelength of 507 nm, and the yellow phosphor having a peak wavelength of 558 nm are combined, and blue light accounts for a luminous power proportion of 0.44 and a luminous power proportion of 0.07 in blue-green light and yellow light respectively as an example for description, the obtained correspondence table of the luminous flux ratio of the mixed white light and various chrominance parameters is shown in the following table, and the obtained relative spectral power distribution of the mixed white light is shown in
As can be known from the above table, by controlling luminous flux ratios of three LEDs, namely, the blue-green, yellow, and red LEDs, mixed light with a corresponding color temperature at the ratios can be obtained, the color temperature is adjustable within the range of 2700K-6500K, and meanwhile, the general color rendering index Ra is more than 90, the special color rendering index R9 is more than 95 with a maximum of 98, the chromaticity difference ΔC is less than 0.0054, and the luminous efficacy of radiation (LER) is more than 314 lm/W with a maximum luminous efficacy of radiation (LER) of 348 lm/W.
As can be known from the relative spectral power distribution diagram of the mixed white light in
In the LED lamp according to this specific embodiment, three LED light sources are used, that is, a blue LED chip is used to excite a green phosphor to produce blue-green light, a blue LED chip is used to excite a yellow phosphor to produce yellow light, and a red LED chip is used to produce red light. Mixed light of a specific spectral power distribution is produced through a combination of peak wavelengths within certain ranges together with proportions of blue light in the blue-green light and the yellow light. During operation, a control circuit and drive circuits are used to adjust currents of different LED light sources, so as to adjust luminous flux outputs of different LED light sources and adjust luminous flux ratios among them, so that mixed white light at the corresponding color temperature at each luminous flux ratio is obtained, and the white light has desirable chrominance parameters, that is, the color temperature is adjustable while ensuring a high color rendering index and a desirable chromaticity difference and efficacy of radiation, thereby satisfying applications with high requirements. Meanwhile, the problem of a mixing ratio of the phosphors is not involved in the light source components of the LED lamp, and the two blue LED chips have the same peak wavelength, so that both the design cost and the manufacturing cost of the lamp are low. Second specific embodiment
This specific embodiment is different from the first specific embodiment in that: based on the first specific embodiment, this specific embodiment further defines that multiple LED light sources are arranged in a circular array, and defines the setting of a radius r of the circle, preferable configuration of the reflector, the substrate, and the diffuser plate, and so on.
In the LED lamp according to this specific embodiment, the components, the connection between the components, and the operation process of the components are all the same as those in the first embodiment, and will not be repeated herein. Only the further defined contents are described in detail below.
In this specific embodiment, light spots of blue-green light, yellow light, and red light projected on a target diffuser panel are equal in size and uniform in illuminance by reasonably arranging the LED light source array; a frosted reflector is used to compress the light spots; a diffuser plate made from a PC or PMMA material or frosted glass is used to perform secondary light and color uniformization; and a substrate plated with a reflective film is used to collect rays reflected by the reflector and the diffuser plate to the bottom, thereby improving the light utilization rate of the system.
All the LED light sources are arranged in a circular array, and the blue-green, yellow, and red LED light sources have the same light distribution curve and are all in the same circular array; then light spots of blue-green, yellow, and red LEDs projected on a target diffuser plate are equal in size and uniform in illuminance, so that white light synthesized on the surface of the diffuser plate also has a uniform color temperature distribution.
Preferably, the blue-green, yellow, and red LED light sources all have a Lambertian light distribution curve, and have a same half-intensity angle; then a radius of the circular array is
where m is a coefficient related to the half-intensity angle of the LED light sources,
θ is the half-intensity angle, and z is a distance between the LED light sources and the diffuser plate. Because the blue-green, yellow, and red LED light sources are all located on the same plane, i.e., the substrate, the LED light source is one of the blue-green, yellow, and red LED light sources. The most uniform illuminance of the light spot output by the LED lamp can be achieved by setting the radius of the circle according to the above method. Illustration is made by using the design of a down lamp having an output light spot of 8 inches (203 mm) as an example; then, LED light sources are arranged in a circular array, the numbers of blue-green, yellow, and red LEDs are separately 6, LEDs of different colors are arranged alternately, z is set to 80 mm, and when the half-intensity angle θ is 60°, the radius value r of the circular array through which the most uniform illuminance is achieved is calculated to be 65 mm At this time, when the blue-green light, yellow light, and red light are disposed in a circular array having a radius of 65 mm to form the LED lamp, obtained diagrams illustrating light spots in an illuminance simulation design of the array of the blue-green, yellow, and red LED light sources on the surface of the diffuser plate are shown in
Further preferably, the reflector in the LED lamp is a frosted reflector. The frosted reflector mainly can collect edge rays and compress the light spots of the LED light source array output to the reflector to make the light spots have the same size as the light spots on the diffuser plate.
Still further preferably, the substrate in the LED lamp is plated with a reflective film. The substrate plated with the reflective film can collect rays reflected by the reflector and the diffuser plate to the bottom, thereby improving the light utilization rate of the system.
Still further preferably, the diffuser plate in the LED lamp is a PC diffuser plate (polycarbonate, PC for short in English), a PMMA diffuser plate (polymethylmethacrylate, PMMA for short in English) or frosted glass, so that the diffuser plate can perform secondary light and color uniformization so as to improve the uniformity of emergent light.
The above contents are further detailed descriptions of the present invention made through specific preferred embodiments, and it cannot be considered that specific implementations of the present invention are limited to the descriptions. Persons of ordinary skill in the art can make several replacements or obvious variations having the same performance or usage without departing from the idea of the present invention, and the replacements or variations should all be considered as falling within the protection scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013 1 0377015 | Aug 2013 | CN | national |
This present application is a Continuation Application of PCT application No. PCT/CN2014/083406 filed on Jul. 31, 2014, which claims the benefit of Chinese Patent Application No. 201310377015.5 filed on Aug. 26, 2013, the contents of which are hereby incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20110279015 | Negley | Nov 2011 | A1 |
| 20120056216 | Mitsuishi | Mar 2012 | A1 |
| 20140246990 | Kim | Sep 2014 | A1 |
| Number | Date | Country |
|---|---|---|
| 101808451 | Aug 2010 | CN |
| Number | Date | Country | |
|---|---|---|---|
| 20160153622 A1 | Jun 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2014/083406 | Jul 2014 | US |
| Child | 15014043 | US |
