Abstract:
Disclosed herein is a lighting apparatus using white-light Light-Emitting Diodes (LEDs). The lighting apparatus includes white-light LEDs, first LEDs, second LEDs, a substrate, a driving unit, and wires. The white-light LEDs emit light having a first peak value in a wavelength range of about 440 to 460 nm and a second peak value in a wavelength range of about 520 to 600 nm as a main light source. The first LEDs emit light having a third peak value in a wavelength range of about 610 to 625 nm as an auxiliary light source. The second LEDs emit light having a fourth peak value in a wavelength range of about 492 to 500 nm as an auxiliary light source. The substrate allows the LEDs to be disposed thereon. The driving unit drives the LEDs. The wires connect the substrate to the driving unit.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a lighting apparatus using white-light Light-Emitting Diodes (LEDs), and, more particularly, to a lighting apparatus that is capable of additionally outputting light of wavelengths which is not output by a lighting apparatus using white-light LEDs and which is used to enable the human optic nerves to perform their optic functionality under natural light conditions, thereby improving both color rendering and sharpness. 
         [0003]    2. Description of the Related Art 
         [0004]    Fluorescent lamp lighting apparatuses are being widely used as the main lighting apparatuses of public facilities or homes. Recently, various types of lighting apparatuses using LEDs, which have half the power consumption of the fluorescent lamp lighting apparatuses, have been developed and widely used. 
         [0005]    Meanwhile, since natural light (solar light) has a wide wavelength distribution of 380 to 780 nm and human eyesight is adapted to natural light, humans feel comfortable and, also, human eyesight can be protected when humans view objects that are illuminated with natural light. 
         [0006]    Furthermore, it is important to make the color of the light of a lighting apparatus approximate the light color under natural light conditions by improving color rendering representative of the extent of approximating color under natural light conditions. 
         [0007]    Therefore, conventional lighting apparatuses using LEDs have attempted to improve color rendering by combining other LEDs having various wavelengths so that the light emitted by the total LEDs can approximate natural light. However, since it is difficult to manufacture LEDs having various wavelengths due to their cost and the yields of manufacturing processes, it is common to construct lighting apparatuses using a plurality of white-light LEDs which are advantageous in terms of both manufacturing cost and yield. Such white-light LEDs are manufactured chiefly by combining blue LEDs with yellow phosphor. 
         [0008]    Here, the white-light LEDs have a spectral distribution such as that shown in  FIG. 1 , and generally emit light having a first peak value in a wavelength range of about 440 to 460 nm and a second peak value in a wavelength range of about 520 to 600 nm. 
         [0009]    However, such white-light LEDs have poor color rendering (at a level at which the Color Rendering Index (CRI) thereof is 65-75) and low sharpness because there are many wavelengths which exist in natural light but are not emitted by the white-light LEDs. 
       SUMMARY OF THE INVENTION  
       [0010]    Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a lighting apparatus which is capable of improving both color rendering and sharpness while utilizing inexpensive white-light LEDs as a main light source. 
         [0011]    In order to accomplish the above object, one aspect of the present invention provides a lighting apparatus using white-light LEDs, including white-light LEDs for emitting light having a first peak value in a wavelength range of about 440 to 460 nm and a second peak value in a wavelength range of about 520 to 600 nm as a main light source; first LEDs for emitting light having a third peak value in a wavelength range of about 610 to 625 nm as an auxiliary light source in order to improve color rendering; second LEDs for emitting light having a fourth peak value in a wavelength range of about 492 to 500 nm as an auxiliary light source in order to improve sharpness; a substrate for allowing the white-light LEDs, the first LEDs, and the second LEDs to be disposed thereon; a driving unit for driving the white-light LEDs, the first LEDs, and the second LEDs; and wires for connecting the substrate to the driving unit. 
         [0012]    In order to accomplish the above object, another aspect of the present invention provides an LED lamp using white-light LEDs, including a base configured to receive Alternating Current (AC) power; white-light LEDs disposed on a lower surface of the LED lamp, and configured to emit light having a first peak value in a wavelength range of about 440 to 460 nm and a second peak value in a wavelength range of about 520 to 600 nm as a main light source; first LEDs disposed on the lower surface of the LED lamp, and configured to emit light having a third peak value in a wavelength range of about 610 to 625 nm as an auxiliary light source in order to improve color rendering; second LEDs disposed on the lower surface of the LED lamp, and configured to emit light having a fourth peak value in a wavelength range of about 492 to 500 nm as an auxiliary light source in order to improve sharpness; a driving unit configured to drive the white-light LEDs, the first LEDs, and the second LEDs; and a substrate configured such that terminals of the white-light LEDs, the first LEDs and the second LEDs and the driving unit are disposed thereon and AC power is supplied by the base thereto. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the office upon request and payment of the necessary fee. 
           [0014]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0015]      FIG. 1  is a diagram showing an embodiment of the distribution of wavelengths of white-light LEDs; 
           [0016]      FIG. 2  shows screen captures showing the color rendering simulation results of the distribution of wavelengths of white-light LEDs; 
           [0017]      FIGS. 3 and 4  are graphs showing the distributions of wavelengths that were obtained by a color rendering simulator when LEDs with wavelengths in a range of about 492 to 500 nm and LEDs with wavelengths in a range of about 610 to 625 nm were added to white-light LEDs, in the present invention; 
           [0018]      FIG. 5  is a perspective view showing a desk lamp to which the present invention has been applied; 
           [0019]      FIG. 6  is a diagram showing the structure of a substrate that is used to apply the present invention to a desk lamp; 
           [0020]      FIG. 7  is a diagram showing a structure in which the substrate of  FIG. 6  is fastened to a lampshade; 
           [0021]      FIG. 8  is a diagram showing the distribution of wavelengths that is obtained when the present invention is applied; 
           [0022]      FIG. 9  is a perspective view of an incandescent lamp-type LED lighting apparatus to which the present invention has been applied; and 
           [0023]      FIG. 10  is a side view of the incandescent lamp-type LED lighting apparatus to which the present invention has been applied. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. 
         [0025]    Since using LEDs with various wavelengths in order to improve the color rendering of white-light LEDs having a spectral distribution as shown in  FIG. 1  is disadvantageous in that it is difficult to manufacture LEDs with various wavelengths and the manufacturing cost and yield thereof are undesirable as described above, it is preferable to use LEDs having only special wavelengths, which considerably affect color rendering, as an auxiliary light source while using white-light LEDs, which are excellent in yield and unit cost because they are inexpensive and the manufacturing process thereof is simple, as a main light source, thereby improving color rendering as a whole. 
         [0026]    Furthermore, in the field of lighting apparatuses, sharpness as well as color rendering is important. To be a desirable lighting apparatus, the sharpness of the lighting apparatus as well as the color rendering thereof should be improved. 
         [0027]    Meanwhile, according to the investigation of the inventor of the present invention, the result that the CRI was considerably improved by adding auxiliary light source LEDs having a peak value in a wavelength range of about 610 to 625 nm to main light source white-light LEDs was obtained by CRI simulation. 
         [0028]    In particular, CRI simulation showed that adding a combination of auxiliary light source LEDs having a peak value in a wavelength range of about 610 to 625 nm and auxiliary light source LEDs having a peak value in a wavelength range of about 492 to 500 nm to white-light LEDs resulted in improving the CRI slightly further up to about 92 or higher (in  FIGS. 3 and 4 , CRI simulation values are illustrated as being 94.96 and 96.57, respectively), and the sharpness as observed by the naked eye was considerably improved. As a result, the inventor come to the conclusion that such a combination of white-light LEDs and such types of auxiliary light source LEDs is the optimum combination that is capable of improving both color rendering and sharpness. 
         [0029]    Referring to  FIG. 2  in detail, the graphs are screen captures which are obtained using a CRI simulator. In the upper graph of this drawing, the distribution of the wavelengths of white-light LEDs is represented by using colors for the respective wavelengths. In the lower graph thereof, the distribution of wavelengths is represented using a red line. From the lower graph, it can be seen that this distribution of wavelengths is similar to the distribution of wavelengths shown in the graph of  FIG. 1 . 
         [0030]      FIG. 3  shows a simulation result in which when the distribution of wavelengths of LEDs (red line) having a peak value in a wavelength range of about 492 to 500 nm and the distribution of wavelengths of LEDs (green line) having a peak value in a wavelength range of about 610 to 625 nm were added to the distribution of wavelengths of white-light LEDs (blue line), a CRI (Ra) of 94.96 was obtained, as shown in the lower graph. 
         [0031]      FIG. 4  shows a simulation result in which when more LEDs (green) having a peak value in a wavelength range of about 610 to 625 nm were used, unlike in  FIG. 3 , a CRI (Ra) of 96.57 was obtained. 
         [0032]    Here, in order to improve the sharpness of a lighting apparatus which emits small quantities of wavelengths in a wavelength range of about 492 to 500 nm, it is necessary to increase illuminance to bring about higher brightness, which requires higher power consumption. Since a lighting apparatus which emits an appropriate amount of light of wavelengths in a range of about 492 to 500 nm can achieve a sharpness identical to that at higher illuminance at higher power consumption, these wavelengths are the core wavelengths in the present invention. 
         [0033]    Accordingly, in order to improve both color rendering and sharpness, the lighting apparatus according to the present invention uses white-light LEDs as a main light source and additionally uses LEDs having a peak value in a wavelength range of about 492 to 500 nm and LEDs having a peak value in a wavelength range of about 610 to 625 nm as an auxiliary light source. 
         [0034]    Here, the LED lighting apparatus according to the present invention may be applied not only to movable lighting apparatuses (for example, fluorescent lamp-type desk lamps widely used in study rooms, and incandescent lamp-type floor lamps widely used in western countries) but also to stationary lighting apparatuses (for example, fluorescent lamp-type square and circular lamps widely used as bedroom lamps and/or living room lamps). 
         [0035]    Now, the case where the present invention has been applied to a fluorescent lamp-type desk lamp will be described with reference to  FIGS. 5 to 7 . 
         [0036]      FIG. 5  illustrates the fluorescent lamp-type desk lamp according to the present invention. A substrate  4 , such as that shown in  FIG. 6 , is disposed inside a lampshade  8 , and white-light LEDs  1 , LEDs  2  having a peak value in a wavelength range of about 492 to 500 nm, and LEDs  3  having a peak value in a wavelength range of about 610 to 625 nm are appropriately arranged on the substrate  4 . Here, the LEDs  1 ,  2  and  3  are disposed in various arrangements, such as in an alternate arrangement or in an arrangement in which the same type of LEDs are arranged in the same row (for example, in  FIG. 6 , the white-light LEDs  1  are arranged in the center portions, and the LEDs  2  having a peak value in a wavelength range of about 492 to 500 nm and the LEDs  3  having a peak value in a wavelength range of about 610 to 625 nm are arranged in a row above the center portion and a row below the center portion). An appropriate number of LEDs  2  and  3  are used depending on the intensity of the light of all the white-light LEDs  1  and the intensity of the light of each LED  2  or  3 . 
         [0037]    Furthermore, substrate wiring (not shown) for supplying power for driving the LEDs  1 ,  2  and  3  is disposed on the back of the substrate  4 , and the substrate wiring is connected to wires  6  and  7  on a substrate wiring connection part  5 . 
         [0038]    Thereafter, the lampshade  8  according to the present invention is formed by fastening the substrate  4  to the lampshade  8  using one or more screws or by fastening the substrate  4  by inserting it into an elastic locking structure  9  disposed on the lampshade  8 , as shown in  FIG. 7 . The desk lamp according to the present invention is formed by combining the lampshade  8  with an extendable member  10  (through which the wires  6  and  7  pass through) and the base  11 , as shown in  FIG. 5 . 
         [0039]    Here, a driving unit  12  for LEDs  1 ,  2  and  3  is mounted in the base  11 , and the output of the driving unit  12  is connected to the wires  6  and  7 . 
         [0040]    Now, when a user applies domestic AC power to the driving unit  12  in the base  11  by turning on a switch  13 , the output of the driving unit  12  is supplied to the LEDs  1 ,  2  and  3  through the wirings  6  and  7 . 
         [0041]    That is, when a user turns on the switch  13 , the LEDs  1 ,  2  and  3  are all turned on. The white-light LEDs  1  emit light having a wavelength distribution such as that shown in  FIG. 1 , the LEDs  2  emit light having a peak value in a range of about 492 to 500 nm, and LEDs  3  emit light having a peak value in a range of about 610 to 625 nm. As a whole, a lighting apparatus using white-light LEDs having a wavelength distribution, such as that shown in  FIG. 8 , is formed. 
         [0042]    Furthermore, when an anti-glare filter is additionally attached to the lampshade  8  of  FIG. 5 , glaring can be prevented. 
         [0043]    Furthermore, although the desk lamp has been described as an example of the movable lighting apparatus, the present invention may be applied to the case where such a substrate is mounted in a built-in square or circular lamp installed in a living room or a bedroom or a streetlamp or security lamp installed on an outdoor street, which is a stationary lighting apparatus. 
         [0044]    Thereafter, an incandescent lamp-type LED lighting apparatus formed by applying the principle of the present invention to an LED lamp having an incandescent lamp-type socket will be described with reference to  FIGS. 9 and 10 . 
         [0045]    Since the incandescent lamp-type LED lighting apparatus of the present invention is formed by screwing the LED lamp (which is usually covered with a transparent or translucent protective cover), such as that shown in  FIGS. 9 and 10 , into an existing incandescent lamp-type lighting apparatus, only the LED lamp unique to the present invention will be described in detail below. 
         [0046]    The LED lamp  20  is screwed into the incandescent lamp socket (fastening structure) of the incandescent lamp-type lighting apparatus by means of a metallic base  21 , and is connected to an AC power source. 
         [0047]    Furthermore, a plurality of LEDs  23 ,  24  and  25  is arranged at the lower end of the LED lamp  20 . 
         [0048]    Although in  FIG. 9 , the white-light LEDs  23  are illustrated as being arranged on the center portion and the LEDs  24  having a peak value in a wavelength range of about 492 to 500 nm and the LEDs  25  having a peak value in a wavelength range of about 610 to 625 nm are illustrated as being arranged in the outer portion, they may be disposed in various arrangements as needed. 
         [0049]    Furthermore, as shown in  FIG. 10 , a driving unit  27  for driving LEDs  23 ,  24  and  25  is disposed on a substrate  26  inside the LED lamp  20 , and AC power is supplied to the driving unit  27  via the base  21 , and the terminals of the LEDs  1 ,  2  and  3  are connected to the substrate  26 . 
         [0050]    Here, the number and the intensity of the light of the LEDs  23 ,  24  and  25  are appropriately determined depending on the number of watts of the LED lamps  20  used and the desired color rendering and sharpness. 
         [0051]    Now, when the LED lamp  20  as shown in  FIGS. 9 and 10  is screwed into the socket of the incandescent lamp-type lighting apparatus (not shown), by means of the base  21  of the LED lamp  20  and then a user turns on the power, AC power is supplied to the driving unit  27  and the LEDs  23 ,  24  and  25  are all lighted up. The white-light LEDs  23  emits light having a wavelength distribution, such as that shown in  FIG. 1 , the LEDs  24  emits light having a peak value in a wavelength range of about 492 to 500 nm, and the LEDs  25  emit light having a peak value in a wavelength range of about 610 to 625 nm. As a whole, the LED lamp for the lighting apparatus using white-light LEDs, having a wavelength distribution, such as that shown in  FIG. 8 , is formed. 
         [0052]    Furthermore, although in  FIGS. 9 and 10 , the LEDs  23 ,  24  and  25  have been illustrated as being mounted on the lower surface of the LED lamp  20  according to the present embodiment, at least some of the LEDs  23 ,  24  and  25  may be mounted on respective ends or circumferential surfaces of columns protruding from the lower surface, or may be mounted on the side circumferential surface of the LED lamp  20 . 
         [0053]    Meanwhile, although the incandescent lamp-type LED lamp has been described as an example of the LED lamp, it is possible to apply the substrate of the LED combination according to the present invention to a fluorescent lamp-type LED lamp, a substitute LED lamp for halogen lamp, and a substitute LED lamp for a Parabolic Aluminized Reflector (PAR) lamp. 
         [0054]    In accordance with the above-described present invention, there can be provided a lighting apparatus that is capable of additionally outputting light of wavelengths which is not output by a lighting apparatus using white-light LEDs and which is used to enable the human optic nerves to perform their optic functionality under natural light conditions, thereby improving both color rendering and sharpness. 
         [0055]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.