Abstract:
A light emitting diode device includes a light emitting diode illumination element, a solar cell unit generating power for the illumination element and a rechargeable cell unit storing the power.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The disclosure relates to a light emitting diode (LED) device, and particularly to a light emitting diode device providing its own power for illumination. 
         [0003]    2. Description of Related Art 
         [0004]    Nowadays, with the earth resources being depleted day by day, the cost of investment for energy increases significantly. For the sake of saving energy of the world and earth protection, energy efficiency is more and more emphasized, and has found widespread applications in a variety of fields. With an optical spectrum providing a chromatic diagram approaching natural sunlight, and high illumination efficiency, LEDs are gaining popularity in lighting devices such as streetlamps, standing lamps, industrial lighting, and many other applications. A scientific literature can be referred for related researches: “Solid State Lighting: Toward Superior Illumination”, published on No. 10, Vol. 93, Proceeding of the IEEE, October of 2005. However, light emitting diode devices normally require power supply from an external source. 
       SUMMARY 
       [0005]    Therefore, a light emitting diode device supplying its own power is required. 
         [0006]    The disclosure provides a light emitting, including an illumination element comprising a plurality of light emitting diodes (LED), a solar cell unit generating electrical power, a rechargeable cell unit storing power that the solar cell unit generates, which is then provided to the illumination element. The light emitting diode device further comprises a recharging and discharging controller, which, in a charging mode manages charging of the rechargeable cell unit, and in a discharging mode controls the brightness of the illumination element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an illustration diagram showing a LED source device according to an embodiment of this disclosure. 
           [0008]      FIG. 2  is a cross sectional view showing a solar cell unit of a LED source device according to an embodiment of this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    A detailed description of the disclosure follows with reference to the accompanying drawings. 
         [0010]      FIG. 1  and  FIG. 2  illustrate an exemplary LED light device  10  according to the disclosure, which comprises a solar cell unit  100 , a rechargeable cell unit  110 , and an LED illumination element  120 . 
         [0011]    The solar cell unit  100  comprises a substrate  17  having a loading surface  172 . A rear metal layer  16 , a P-type semiconductor layer  15 , a P-N junction layer  14 , an N-type semiconductor layer  13 , a transparent conductive oxide layer  12 , and a front metal layer  11  are sequentially formed on the loading surface  172 . 
         [0012]    The substrate  17  is flexible material, about 10 μm to 100 μm thick, such as aluminum magnesium alloy foil, aluminum stainless steel sheet, polymer sheet, single silicon, polysilicon or glass material, or others, with materials disclosed here only for illustration and not limitation. 
         [0013]    The rear metal layer  16  can be silver, copper, molybdenum, aluminum, copper and aluminum alloy, silver and copper alloy, copper and molybdenum alloy or other. An electrical connect end  161  is provided on one side of the rear metal layer  16 . 
         [0014]    The P-type semiconductor layer  15  may be any amorphous silicon (P-a-Si) material, and particularly can be hydrogenous P-type amorphous silicon (P-a-Si:H). The P-type semiconductor layer may be III-V compound, particularly aluminum, gallium or doped semiconductor material, such as AlGaN or AlGaAs. 
         [0015]    An exemplary material of the P-type semiconductor  15  is P-type amorphous silicon. Because the light absorbency of amorphous silicon is about 500 times that of crystal silicon, an amorphous silicon P-type semiconductor layer can be much thinner than a crystal silicon P-type semiconductor layer with the same requirement of light absorbency. Therefore, amorphous silicon material is more suitable for use in solar cells than crystal silicon. 
         [0016]    The P-N junction layer  14  may be III-V compound or I-III-VI compound, such as cadium telluride (CdTe), or copper indium selenide (CuInSe2) for better connection. The P-N junction layer may also be copper indium gallium selenide (CuIn1-XgaSe2, CIGS). The P-N junction layer  14  transforms photons to electron-hole pairs and forms barrier potential. 
         [0017]    The N-type semiconductor layer  13  may be N-type amorphous silicon (N-a-Si), particularly hydrogenous N-type amorphous silicon (N-a-Si:H). The N-type semiconductor layer  13  may also be made of III-V compound or II-VI compound, particularly N, P or doped semiconductor, such as GaN or InGaP. 
         [0018]    The transparent conductive layer  12  may be made of, for example, Indium Tin Oxide (ITO), ZnO, or other. 
         [0019]    The front metal layer  11  may be silver, copper, molybdenum, aluminum, copper aluminum alloy, silver copper alloy, or copper molybdenum alloy. The front metal layer  11  and the rear metal layer  16  of the solar cell unit  100  can be connected to the anode and cathode of the rechargeable battery  110  through an electrical connecting end  161  for charging. 
         [0020]    The rechargeable battery  110  may be lithium ion/lithium polymer cells, providing power to LED illumination element  120  with a compact profile. 
         [0021]    In this embodiment, the LED illumination element  120  includes a plurality of LED arrays, with the area of the solar cell unit  100  determined by the required photoelectrical transformation efficiency and power that the solar cell unit needs. 
         [0022]    The LED light device  10  further comprises a module chip acting as a recharge/discharge controller  130 , which comprises a first DC/DC converter  132 , a second DC/DC converter  134 , and a PWM (pulse width modulation) controller  136 . 
         [0023]    The solar cell unit  100  is electrically connected to a rechargeable cell unit  110  through the first DC/DC converter  132 , and the rechargeable cell unit  110  is electrically connected to the LED illumination element  120  through the second DC/DC converter  134 . 
         [0024]    The PWM controller  136  is electrically connected to the rechargeable cell unit  110 , the first DC/DC converter  132 , the LED illumination element  120 , and the second DC/DC converter  134 . 
         [0025]    In a charging mode, the PWM controller  136  receives a voltage feedback signal VF and a current feedback signal IF from the rechargeable battery unit  110 , and provides a first PWM output signal (shown as “I” in  FIG. 2 ) to the first DC/DC converter  132 , precisely controlling the rechargeable battery unit  110 . 
         [0026]    In a discharging mode, the PWM controller  136  receives an illumination feedback signal LF, and provides a second PWM output signal (shown as “II” in  FIG. 2 ) to the second DC/DC converter  134 , precisely controlling the brightness of the LED illumination element  120 . A duty cycle is predetermined by the second PWM output signal, which controls the ratio of a turn-on time and a turn-off time of the LED illumination element  120 , thereby controlling the brightness thereof. 
         [0027]    The LED light source further comprises a solar cell unit and a rechargeable cell unit providing power to the solar cell unit. The LED illumination element is thus powered by the rechargeable battery unit, with no requirement for an external power supply. 
         [0028]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.