Abstract:
A light emitting diode (LED) tube is disclosed. The LED tube comprises a print circuit board comprising a plurality of LEDs arranged on one side; a housing adapted to receive the print circuit board, the housing comprises a first phosphor layer and a second phosphor layer coated on an outer surface of the housing, the housing is rotatable around the print circuit board; and a connector attached to one end of the housing, the connector is adapted to provide electrical power to the plurality of LEDs.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure generally relates to a light emitting diode tube. 
       DESCRIPTION OF RELATED ART 
       [0002]    In recent years, due to excellent light quality and high luminous efficiency, light emitting diodes (LEDs) have increasingly been used to substitute for incandescent bulbs, compact fluorescent lamps, or fluorescent tubes as light sources of illumination devices. 
         [0003]    One characteristic of color is the color temperature, which is the temperature at which an ideal black-body radiator radiates light of comparable hue to that of the light source. Users may like to have light with different color temperatures depending on different ambiances. For example, users may like to have white light with a bit of yellow at one time, but may like to have white light with a bit of blue at another time. However, the color temperature of a lamp may be a fixed character of the light source at the time of manufacturing and may not be adjusted by the users. 
         [0004]    Therefore, an LED tube is desired to overcome the above described shortcomings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0006]      FIG. 1  is an isometric, assembled view of an LED tube in accordance with one embodiment of the present disclosure. 
           [0007]      FIG. 2  is an exploded view of the LED tube in  FIG. 1 . 
           [0008]      FIG. 3  is a cross-sectional view of the LED tube in  FIG. 1 . 
           [0009]      FIG. 4  is a cross sectional view of the LED tube in  FIG. 1 , wherein a housing of the LED tube is rotated to a first position. 
           [0010]      FIG. 5  is a cross-sectional view of the LED tube in  FIG. 1 , wherein the housing of the LED tube is rotated to a second position. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of an LED tube will now be described in detail below and with reference to the drawings. 
         [0012]    Referring to  FIGS. 1-2 , an LED tube  100  in accordance with an embodiment includes a print circuit board  110 , a housing  120  for receiving the print circuit board  110  and a connector  130  connected to each end of the housing  120 . 
         [0013]    The print circuit board  110  may be elongated and rectangular. Preferably, the print circuit board  110  is Al-based print circuit board with good heat dissipation. A length of the print circuit board  110  may be substantially the same as that of the housing  120 , while a width of the print circuit board  110  may be slightly less than that of the housing  120 . A plurality of LEDs  111  may be arranged on the print circuit board  110 . In one embodiment, the plurality of LEDs  111  is arranged on one side of the print circuit board  110  in a direction of the length of the printed circuit board  110 . 
         [0014]    The housing  120  may be tubular and made of transparent or semi-transparent materials such as polycarbonate (PC) and polymethyl methacrylate (PMMA). A first phosphor layer  121  and a second phosphor layer  122  are arranged on different portions of an outer surface of the housing  120 . The first phosphor layer  121  and a second phosphor layer  122  are semi-circle cylinder shaped and made of different materials, thereby different colors of light may be generated when the light from the plurality of LEDs  111  passes through the first phosphors layer  121 , and/or second phosphor layers  122 . In one embodiment, each of the phosphor layer  121  and the second phosphor layer  122  covers substantially one half of the outer surface of the housing  120 , so that the combination of the first and second phosphor layers  121  and  122  covers the entire outer surface of the housing  120 . Referring also to  FIG. 3 , the first phosphor layer  121  and the second phosphor layer  122  are symmetric to a plane on which a longitudinal central axis of the housing  120  is located. A protrusion  123  may be formed at an inner wall of the housing  120  to limit a rotating angle of the housing  120  relative to the plurality of LEDs  111 . In one embodiment, the protrusion  123  is aligned with a joint of the first phosphor layer  121  and the second phosphor layer  122 . 
         [0015]    One connector  130  may be attached to each end of the housing  120 . Each connector  130  may include a base  131  and two electrode pins  132  extending through the base  131  for electrically connecting the plurality of LEDs  111  to an external power source. Referring also to  FIG. 3 , two securing sections  133  may be formed on an inner sidewall of the base  131  to secure the print circuit board  110  to the base  131 . The base  131  may has an inner diameter substantially the same as an outer diameter of the housing  120  and the multiple layers of difference phosphors deposited on the outer surface of the housing  120 . The securing section  133  may be located on an imaginary circle having a diameter substantially the same as an inner diameter of the housing  120  and is homocentric as the base  131 . A gap is defined between an outer edge of the base  131  and the securing section  133  for receiving the housing  120 . 
         [0016]    To assemble the LED tube  100 , the printed circuit board  110  with the plurality of LEDs  111  arranged thereon may be inserted into the housing  120 , one connector  130  may be attached to each end of the housing  120  with the securing sections  133  aligned with edges of the printed circuit board  120 , and each end of the print circuit board  110  may be securely attached to one connector  130  by the securing sections  133 . In one embodiment, each end of the housing  120  may be received in the gap between the base  131  and the securing section  133  such that the housing  120  may be rotated freely around the connector  130  and the print circuit board  110 . 
         [0017]    Referring to  FIG. 3 , the housing  120  may be rotated so that the plurality of LEDs face the first phosphor layer  121  and the second phosphor layer  122  synchronously, i.e., both the first phosphor layer  121  and the second phosphor layer  122  are in an illuminating area of the plurality of LEDs  111 .  FIG. 3  shows an embodiment wherein a surface area of the first phosphor layer  121  facing the plurality of LEDs  111  is same as that of the second phosphor layer  122 . In other embodiments, the housing  120  may be rotated to achieve different ratios of coverage areas between the first phosphor layer  121  and the second phosphor layer  122  in the illuminating area of the plurality of LEDs  111 . 
         [0018]    When a voltage is applied to the plurality of LEDs  111 , the plurality of LEDs  111  emit light with a first wavelength. The first phosphor layer  121  absorbs part of the light with the first wavelength and emits light with a second wavelength different from the first wavelength. The second phosphor layer  122  absorbs part of the light with the first wavelength and emits light with a third wavelength different from either of the first wavelength and second wavelength. Light with the first wavelength from the LEDs  111 , light with the second wavelength from the first phosphor layer  121 , and light with the third wavelength from the second phosphor  122  are mixed together to form mixed light with a first color temperature different from that of the light directly from the plurality of LEDs  111 . 
         [0019]    Referring to  FIG. 4 , to adjust the color temperature of the LED tube  100 , the housing  120  may be rotated to a position where plurality of the LEDs  111  only face the first phosphor layer  121 , i.e., only the first phosphor layer  121  is in the illuminating area of the plurality of LEDs  111 . The first phosphor layer  121  absorbs part of light with the first wavelength and emits light with a second wavelength. Light with the first wavelength and light with the second wavelength are mixed together to form mixed light with a second color temperature. 
         [0020]    Referring to  FIG. 5 , to further adjust the color temperature of the LED tube  100 , the housing  120  may be rotated to a second position where the plurality of LEDs  111  only faces the second phosphor layer  122 , i.e., only the second phosphor layer  122  is in the illuminating area of the plurality of LEDs  111 . The second phosphor layer  122  absorbs part of light with the first wavelength and emits light with a third wavelength. Light with the first wavelength and light with the third wavelength are mixed together to form mixed light with a third color temperature. 
         [0021]    In the present disclosure, the housing  120  with the first and the second phosphor layers  121  and  122  deposited on the outer surface of the housing  120  may be rotated around the print circuit board  110  to obtain light with different color temperatures. To adjust the color temperature of the LED tube  100 , the user only needs to rotate the housing  120  to a position corresponding to the color temperature, without replacing the whole LED tube  100 . As a result, cost may be reduced. 
         [0022]    The housing  120  may be rotated to other positions than the first position and the second position. When the illuminating area of the plurality of LEDs  111  are blocked by both the first phosphor layer  121  and the second phosphor layer  122 , the color temperature of the LED tube  100  will change according to the ratio of coverage areas between the first phosphor layer  121  and the second phosphor layer  122 . In other embodiments, three or more different phosphor layers may be arranged along a direction encircling the longitudinal central axis of the housing  120 . 
         [0023]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.