Abstract:
Provided is an LED retrofit lamp interfacing with a high intensity discharge (HID) ballast that includes a lighting source having a plurality of light emitting diodes (LEDs), one or more heat sink components dissipating heat generated by the LEDs, and an LED driver configured to operate the LEDs. The LED retrofit lamp is disposed within an HID housing and the HID ballast is electrically connected with the LED driver, and supplies power to the LED driver for operating the LEDs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a non-provisional application claiming priority to Provisional Application Ser. No. 62/031,366 filed Jul. 31, 2014, the contents of which are incorporated herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to light emitting diode (LED) lamps. In particular, the present invention relates a LED retrofit lamp for a high intensity discharge (HID) ballast. 
       BACKGROUND 
       [0003]    A HID lamp is an arc-type lamp which produce light by forming an electric arc between electrodes housed in a fused alumina arc tube or transparent fused quartz filled with gas and metal salts. Once the arc is started using the gas, the metal salts are evaporated to form a plasma. The HID lamp converts input electrical energy into light energy by using input electrical energy to increase the energy in the plasma, producing light based on the collision of electrons and ions with neutral metal atoms. 
         [0004]      FIG. 1  illustrates an example of a conventional HID lamp  10  having an outer ellipsoidal-shaped bulb  12  including an internal phosphor coating  14 . The HID lamp  10  further includes an arc tube  16  connected to a support structure  18 . A starting resistor  20  is connected with a starting electrode  22  for initiating the arc. A lower end of the bulb  12  is seated within a cap  24  for connecting to a power source. A ballast is used to operate the HID lamp  10 . 
         [0005]    In LED applications, light is generated more efficiently than in the HID applications. Light is generated when a conduction band electron re-combines with a hole in a valance band of the semiconductor. The semiconductor is created by doping a dielectic therein with donor (n-type) or acceptor (p-type) atoms. The LED is created by a sandwich of the n-type and p-type materials, such that the energy drop from conduction to valance band is equal to the energy of the light emitted (i.e., desired frequency or wavelength). 
         [0006]    The LED is a structure that includes free electrons and holes such that when an electric field is applied across it, energy is transferred to the electrons and the holes more directly by increasing the drift velocity. Thus, more electrons can make the transition from the valence band to the conduction band, creating holes, and the electrons therefore recombine with holes generating a desired radiation. 
       SUMMARY OF THE EMBODIMENTS  
       [0007]    Embodiments of the present invention provide a LED retrofit lamp for an HID ballast and a method for replacing an existing HID lamp with the LED retrofit lamp and interfacing an LED driver with the existing HID ballast. 
         [0008]    In one exemplary embodiment, an LED retrofit lamp interfacing with a HID ballast is provided. LED retrofit lamp includes a lighting source comprising a plurality of LEDs, one or more heat sink components dissipating heat generated by the LEDs, and an LED driver configured to operate the LEDs. The LED retrofit lamp is disposed within an HID housing and the HID ballast is electrically connected with the LED driver, and supplies power to the LED driver for operating the LEDs. 
         [0009]    According to yet another exemplary embodiment, a method is provided. The method includes disposing a LED retrofit lamp into an existing HID lamp housing, electrically connecting an LED driver of the LED retrofit lamp with the existing HID ballast, supplying output voltage from the HID ballast to the LED driver, and regulating the output voltage and operating LEDs of the LED retrofit lamp using the regulated DC output voltage 
         [0010]    The foregoing has broadly outlined some of the aspects and features of various embodiments, which should be construed to be merely illustrative of various potential applications of the disclosure. Other beneficial results can be obtained by applying the disclosed information in a different manner or by combining various aspects of the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings, in addition to the scope defined by the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic illustrating an example of a HID lamp. 
           [0012]      FIGS. 2A and 2B  are schematics each illustrating an LED retrofit lamp that can be implemented within one or more embodiments of the present invention. 
           [0013]      FIG. 3  is an exploded view of the LED retrofit lamp shown in  FIG. 2B . 
           [0014]      FIG. 4  is a schematic illustrating the LED retrofit lamp disposed within an existing HID lamp housing that can be implemented within one or more embodiments of the present invention. 
           [0015]      FIG. 5  is a circuit schematic illustrating the electrical connection between a HID ballast and a LED driver in accordance with one or more embodiments of the present invention. 
           [0016]      FIG. 6  is a circuit schematic illustrating a HID voltage control circuit that can be implemented within one or more embodiments of the present invention. 
           [0017]      FIGS. 7A and 7B  are schematics illustrating LED retrofit lamps according to one or more alternative embodiments of the present invention. 
           [0018]      FIG. 8  is a graph illustrating the optical distribution of the LED retrofit lamp according to one or more embodiments of the present invention. 
           [0019]      FIG. 9  is a flow diagram for a method replacing an existing HID lamp with the LED retrofit lamp and interfacing an LED driver with the existing HID ballast that can be implemented within one or more embodiments of the present invention. 
       
    
    
       [0020]    The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the disclosure. Given the following enabling description of the drawings, the novel aspects of the present disclosure should become evident to a person of ordinary skill in the art. This detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of embodiments of the invention. 
       DETAILED DESCRIPTION 
       [0021]    As required, detailed embodiments are disclosed herein. It must be understood that the disclosed embodiments are merely exemplary of various and alternative forms. As used herein, the word “exemplary” is used expansively to refer to embodiments that serve as illustrations, specimens, models, or patterns. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. In other instances, well-known components, systems, materials, or methods that are known to those having ordinary skill in the art have not been described in detail in order to avoid obscuring the present disclosure. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art. 
         [0022]    Embodiments of the present invention provide an LED retrofit lamp for HID lamps and a method for interfacing an LED driver with an existing HID ballast. Details regarding the LED retrofit lamp are described below with reference to  FIGS. 2A ,  2 B and  3 . 
         [0023]      FIGS. 2A and 2B  are schematics each illustrating an LED retrofit lamp  100 ,  200  that can be implemented within one or more embodiments of the present invention. As shown in  FIG. 2A , the LED retrofit lamp  100  includes a base  102 , a cap portion  104 , a printed circuit board (PCB)  106  including openings  107  therein. LEDs  108  are mounted to and thermally connected with the PCB  106 , to allow more efficient transfer of heat from the LEDs  108  to the ambient air. 
         [0024]    The LED&#39;s  108  can be mounted in a linear pattern on the PCB  106 , as shown in  FIGS. 2A and 2B . This linear pattern extends along a same length as that of an arc-length of a standard HID lamp, and thereby more closely mimic the optical distribution of the HID lamp, as shown in  FIG. 8 . 
         [0025]    Referring to  FIG. 8 , as shown in the graph  800 , when LEDs  108  are not formed on top of the LED retrofit lamp  100  (see arrow  802 ), the LEDs  108  produce light at a smaller distance compared to when the LEDs  108  are formed on top of the LED retrofit lamp  100  (see arrow  804 ) 
         [0026]    The openings  107  are formed between the LEDs  108  and allow air flow between the LED  108  s, for enhanced cooling. As shown in  FIG. 2B , the LED retrofit lamp  200  includes all the elements of LED retrofit lamp  100  including a base  202 , a cap portion  204 , a PCB  206  including openings  207  and LEDs  208  mounted on the PCB  206 . The LED retrofit lamp  200  further includes a heat sink  212  having a plurality of heat sink components (e.g., fins)  214 , for better thermal management. 
         [0027]    The heat sink fins  214  are formed in a “tulip” shape, however the present invention is not limited hereto and may vary accordingly. The heat sink fins  214  enhance the radiative and convective heat dissipation. The heat sink fins  214  may be formed of a composite structure out of a plurality of predominantly parallel, axially oriented carbon fibers that have been laminated to an underlying material such as a thermo-formable plastic. 
         [0028]    A thermal conduction path would be formed from a rear side of the PCB  206  and would be axially along the carbon fibers which are oriented perpendicular to the optical axis of the lamp. The heat is transmitted along the carbon fibers allowing for convective heat transfer to the environment. The heat sink fins  214  may be formed comparable to that disclosed in the Application entitled Crystalline-Graphic-Carbon-Based Hybrid Thermal Optical Element for Lighting Apparatus by Gary Allen et al., the contents of which are incorporated herein by reference. 
         [0029]    The LED retrofit lamps  100 ,  200  are supplied power by an LED driver (as depicted in  FIG. 3 ).  FIG. 3  is an exploded view of the LED retrofit lamp  200  shown in  FIG. 2B . The LED driver  220  is housed within a hollow region  215  of the heat sink  212 . LEDs  208  are disposed in the top surface and side surfaces of the LED retrofit lamp  200  to further enhance the illumination and light distribution of the lamp  200 . The LED driver  220  includes various electrical components for driving the LEDs  208 . Details regarding the LED driver  220  will be discussed below with reference to  FIG. 5 . 
         [0030]    In accordance with the embodiments, the LED retrofit lamp  100  or  200  is fitted within an existing HID lamp housing  300  (e.g., the HID outer bulb) as shown in  FIG. 4 . For the purposes of illustration only, the LED retrofit lamp  200  is shown fitting within the HID lamp housing  300 . As shown the LED retrofit lamp  200  interfaces seamlessly with the existing HID lamp housing  300 . The LED driver  220  shown in  FIG. 3  interfaces with the HID ballast associated with the existing HID lamp housing  300 . 
         [0031]    Details regarding the electrical connection between the LED driver  220  and the HID ballast will now be discussed with reference to  FIG. 5 . 
         [0032]      FIG. 5  is a schematic illustration of the electrical connection between a HID ballast  320  and a LED driver  400  in accordance with one or more embodiments of the present invention. As shown in  FIG. 5 , the HID ballast  320  is a choke ballast however the present invention is not limited hereto and may be applied to all types of HID ballasts. The HID ballast  320  includes an AC input  310  for receiving AC power from an AC power supply, and outputs  330  and  332  of the HID ballast  320  are connected with the LED driver  400 . 
         [0033]    Output  330  is connected to a bridge rectifier  402  of the LED driver  400  via a fuse  334 . The output  332  is connected directly to the bridge rectifier  402 , via fuse  334 . The bridge rectifier  402  includes a plurality of diodes for delivering a rectified voltage (e.g., DC voltage) to the LED driver  400 . The bridge rectifier  402  is connected with a buck circuit  404  for lowering the DC output of the bridge rectifier  402  to a desired DC output for LEDs  408 . 
         [0034]    The LEDs  408  are representative of the LEDs  108  and  208  of the LED retrofit lamps  100 ,  200  shown in  FIGS. 2A and 2B . The buck circuit  404  includes a capacitor  409  and a voltage divider  410 . The rectified voltage is filtered by the capacitor  409 , and applied across the voltage divider  410 . 
         [0035]    The buck circuit  404  further includes a switch controller  420  which is an integrated circuit (IC) that receives a plurality of electrical signals at a plurality of input pins thereof. The switch controller  420  also provides a switch signal to the converting switch  430 . The input pins include, for example, a DRIVE pin  1 , CS pin  2 , BOS pin  3 , Ground (GND) pin  4 , DIM pin  5 , NC pin  6 , VCC pin  7  and TEST pin  8 . The switch controller  420  is not limited to a particular type of switch controller and therefore include any switch controller suitable for the purpose set forth herein. 
         [0036]    The controller supply voltage, Vcc, is applied to the switch controller  420  at the Vcc pin  7  and is used to power the switch controller  420 . The converting switch  430  is coupled with the DRIVE pin  1  such that a gate of the converting switch  430  is controlled by the DRIVE pin  1  of the switch controller  420 . The converting switch  430  is coupled with an inductor  440  and when the converting switch  430  is closed, the inductor is connected to ground via resistor  442 , forming a controlled power switch path for charging and discharging the inductor  440 . The buck circuit  404  further includes a diode  444  and two output capacitors  450  and  452 . 
         [0037]    When the converting switch  430  is switched ON, it is supplying the LED load (i.e., LEDs  408 ) with current. Initially current flow to the LED load (LEDs  408 ) is restricted as energy is also being stored in the inductor  440 , therefore the current in the LED load and the charge on the output capacitors  450 , 452  builds up gradually during the ‘ON’ period. Throughout the ON period, there will be a large positive voltage on the cathode of the diode  444 , therefore the diode  444  will be reverse biased and therefore play no part in the action. When the converting switch  430  switches off, the energy stored in the magnetic field around the inductor  440  is released back into the circuit. The voltage across the inductor  440  is then in reverse polarity to the voltage across the inductor  440  during the ‘ON’ period, and sufficient stored energy is available in the collapsing magnetic field to keep current flowing for at least part of the time the converting switch  430  is open. The inductor  440  now causes current to flow around the circuit via the LED load and the diode  444 , which is now forward biased. Once the inductor  440  has returned a large part of its stored energy to the circuit and the load voltage begins to fall, the charge stored in the output capacitors  450 ,  452  becomes the main source of current, keeping current flowing through the LED load until the next ‘ON’ period begins. 
         [0038]    By way of example, the HID ballast  320  may be an electromagnetic ballast or an electronic ballast. When the HID ballast  320  is an electromagnetic ballast, it may include ignitor. If the HID ballast  320  includes an ignitor, HID voltage control circuit  600  shown in  FIG. 6  is implemented to clamp a pulse of the ignitor to a predetermined acceptable level, prior to transmitting the voltage to the LED driver  400 . 
         [0039]    The circuit  600  includes a plurality of resistors R 1 , R 2 , R 3  and R 4  and a bi-directional transient voltage suppressor (TVS) diode bridge  610  to eliminate transient voltages (i.e., unwanted spikes or surges) from the HID ballast  320  from being transmitted to the LED driver  400 . 
         [0040]    The present invention provides several ways to enhance thermal management of the LED retrofit lamps  100 ,  200  shown in  FIGS. 2A and 2B . These additional aspects will now be described below with references to  FIGS. 2A ,  2 B,  7  and  8 . 
         [0041]    Referring back to  FIGS. 2A and 2B , as previously mentioned, the PCBs  106  and  206  may include openings  107 ,  207  for further enhancing heat dissipation of the LEDs  108  and  208 . Further, as shown in  FIG. 2B , the heat sink  212  enables the dissipation of additional heat from the LEDs  108  and  208  through the PCBs  106  and  206 . The heat sink fins  214  of the heat sink  212  may be formed of one or more material layers including a thermally conductive material and a high reflective material. 
         [0042]    As shown in  FIG. 7A , the openings  207  may be larger than that shown in  FIG. 2B , for better air flow to thereby further enhance heat dissipation the LEDs  108 . Further, the heat sink fins  214  may be coated with a protective coating layer (e.g., a first protective layer  700 ) including, for example, a conformal coating or gels, or a matte finish coating, a white reflective coating or clear coating to provide a hard scratch abrasion type surface and electrical insulation. The conformal coating or gels cure in place, to form a resilient protective layer on the heat sink surface. This layer can also provide electrical isolation. 
         [0043]    As depicted in  FIG. 7B , the heat sink fins  214  may be coated with the first protective coating layer  700  and the LEDs  208  may be coated with a second protective coating layer  702 . The second protective coating layer  702  may be formed of the same material as that of the first protective coating layer  700  or of a different material. For example, the second protective coating layer  702  may be an organic polysilazane coating to enable to LEDs  208  exposed without need for any additional protective coating. Another form of this protective layer can be a transparent hard plastic material such as polymethyl methacrylate (PMMA) or polycarbonate shield. In other embodiments, the LED retrofit lamps  100  and  200  may further include a fan to drive more heat transfer from the LEDs  108  and  208  to the ambient air. 
         [0044]      FIG. 9  is a flow diagram illustrating an exemplary method of replacing an existing HID lamp with the LED retrofit lamp and interfacing an LED driver with the existing HID ballast that can be implemented within one or more embodiments of the present invention. As shown in  FIG. 9  with reference made to  FIGS. 4 and 5 , the method  900  begins at operation  910  where an LED retrofit lamp  200  is disposed within a HID lamp housing  300 . 
         [0045]    From operation  910 , the process continues to operation  920  where the existing HID ballast  320  is electrically connected with the LED driver  400 . During operation, at operation  930 , input voltage received at the HID ballast  320  is transmitted to the LED driver  400 . At operation  940 , a bridge rectifier  402  of the LED driver  400  rectifies the voltage received and transmits the voltage to a buck circuit  404  connected thereto. At operation  950 , the buck circuit  404  lowers the voltage to a predetermined acceptable level for operating the LEDs  208  of the LED retrofit lamp. 
         [0046]    As noted above, if the HID ballast  320  includes an ignitor, the ignitor pulse is controlled via a HID voltage control circuit  600  between the HID ballast  320  and the input to the LED driver  400 , to protect the LED driver  400  from any undesired voltage (e.g., voltage surges or spikes). 
         [0047]    Embodiments of the present invention provide the advantages of utilizing an existing HID envelope and ballast and adding the light generation method of an LED retrofit lamp disposed within the existing HID envelope using the LED driver in electrical communication with the HID ballast. 
         [0048]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.