Patent Publication Number: US-7911151-B2

Title: Single driver for multiple light emitting diodes

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of provisional application Ser. No. 60/468,538, file May 7, 2003, which the subject matter is incorporated herein by reference. 
     The present invention generally relates to light emitting diodes (“LEDs”). The present invention specifically relates to a family of driver circuit arrangements for operating multiple LEDs in generating various colors of light including white light. 
     As is well known in the art, red LEDs, green LEDs, blue LEDs, and amber LEDs are utilized to generate various colors of light, including white light, in various applications (e.g., liquid crystal display backlighting and white light illumination). To generate a desired color of light, each colored LED is independently controlled to provide a proper ratio of red, green, blue and amber lights for generating the desired color of light (e.g., 50% red, 20% blue, 20% green and 10% amber). To this end, each colored LED has historically been operated by its own driver circuit. For example, U.S. Pat. No. 6,507,159 discloses three LED drivers to control red LEDs, green LEDs, and blue LEDs, respectively. 
     The present invention provides a single driver circuit having an independent light control capacity for multiple LEDs. 
     One form of the present invention is a LED driver circuit comprising a power source and a switching LED cell, which employs one or more LEDs for radiating a light of any color. In operation, the power source provides power at a power conversion frequency, and the switching LED cell switches between a radiating mode and a disabled mode at a LED driving frequency. During the radiating mode, a LED current flows from the power source through the LED(s) whereby the LED(s) radiate the light. During the disabled mode, the flow of the current from the power source through the LED(s) is impeded to prevent a radiation of the light from the LED(s). 
     A second form of the present invention is a switching LED cell comprising an input terminal, an output terminal, and one or more LEDs for radiating a light of any color. The switching LED cell switches between a radiating mode and a disabled mode at a LED driving frequency. During the radiating mode, a LED current flows from a power source applied between the input and output terminals through the LED(s) whereby the LED(s) radiate the light. During the disabled mode, the flow of the current from the power source through the LED(s) is impeded to prevent a radiation of the light from the LED(s). 
    
    
     
       The foregoing forms as well as other forms, features and advantages of the present invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof. 
         FIGS. 1 and 2  illustrate a schematic diagram of a first baseline embodiment in accordance with the present invention of a current-source driven switching LED cell; 
         FIGS. 3 and 4  illustrate a schematic diagram of a second baseline embodiment in accordance with the present invention of a current-source driven switching LED cell; 
         FIGS. 5 and 6  illustrate a schematic diagram of a third baseline embodiment in accordance with the present invention of a current-source driven switching LED cell; 
         FIG. 7  illustrates a schematic diagram of a first embodiment in accordance with the present invention of a current source LED driver circuit employing a single current-driven switching LED cell; 
         FIG. 8  illustrates a schematic diagram of a second embodiment in accordance with the present invention of a current source LED driver circuit employing a single current-driven switching LED cell; 
         FIG. 9  illustrates a schematic diagram of a third embodiment in accordance with the present invention of a current source LED driver circuit employing a single current-driven switching LED cell; 
         FIG. 10  illustrates a schematic diagram of a fourth embodiment in accordance with the present invention of a current source LED driver circuit employing a single current-driven switching LED cell; 
         FIG. 11  illustrates a schematic diagram of a fifth embodiment in accordance with the present invention of a current source LED driver circuit employing a single current-driven switching LED cell; 
         FIGS. 12 and 13  illustrate a schematic diagram of a first baseline embodiment in accordance with the present invention of a voltage-source driven switching LED cell; 
         FIGS. 14 and 15  illustrate a schematic diagram of a second baseline embodiment in accordance with the present invention of a voltage-source driven switching LED cell; 
         FIGS. 16 and 17  illustrate a schematic diagram of a third baseline embodiment in accordance with the present invention of a voltage-source driven switching LED cell; 
         FIG. 18  illustrates a schematic diagram of a first embodiment in accordance with the present invention of a voltage source LED driver circuit employing a single voltage-driven switching LED cell; 
         FIG. 19  illustrates a schematic diagram of a second embodiment in accordance with the present invention of a voltage source LED driver circuit employing a single voltage-driven switching LED cell; 
         FIG. 20  illustrates a schematic diagram of a first baseline embodiment in accordance with the present invention of a current source LED driver circuit employing multiple current-driven switching LED cells; 
         FIG. 21  illustrates a schematic diagram of a first baseline embodiment in accordance with the present invention of a voltage source LED driver circuit employing multiple voltage-driven switching LED cells; 
         FIG. 22  illustrates a schematic diagram of a first embodiment in accordance with the present invention of the current source LED driver illustrated in  FIG. 20 ; 
         FIG. 23  illustrates a schematic diagram of a second embodiment in accordance with the present invention of the current source LED driver illustrated in  FIG. 20 ; 
         FIG. 24  illustrates a schematic diagram of a third embodiment in accordance with the present invention of the current source LED driver illustrated in  FIG. 20 ; 
         FIG. 25  illustrates a schematic diagram of a fourth embodiment in accordance with the present invention of the current source LED driver illustrated in  FIG. 20 ; 
         FIG. 26  illustrates a schematic diagram of a first embodiment in accordance with the present invention of the voltage source LED driver illustrated in  FIG. 21 ; 
         FIG. 27  illustrates a schematic diagram of a second embodiment in accordance with the present invention of the voltage source LED driver illustrated in  FIG. 21 ; 
         FIG. 28  illustrates a schematic diagram of a third embodiment in accordance with the present invention of the voltage source LED driver illustrated in  FIG. 21 ; 
         FIG. 29  illustrates a schematic diagram of a fourth embodiment in accordance with the present invention of the voltage source LED driver illustrated in  FIG. 21 ; 
         FIG. 30  illustrates a block diagram of an embodiment in accordance with the present invention of an LED driver circuit employing at least one switching LED cell. 
     
    
    
       FIGS. 1-6  and  12 - 17  illustrate a baseline LED matrix L 11 -LXY for designing a current-source driven switching LED cell ( FIGS. 1-6 ) or a voltage-source driven switching LED cell ( FIGS. 12-17 ) of the present invention. A LED design of either switching LED cell involves (1) a selection of one or more LEDs within LED matrix L 11 -LXY, where X≦1 and Y≧1, (2) a selection of a color for each LED selected from LED matrix L 11 -LXY, and (3) for multiple LED embodiments, a selection of one or more series connections and/or parallel connections of the multiple LEDs selected from LED matrix L 11 -LXY. For embodiments of either switching LED cell employing multiple LEDs, the LEDs having similar operating current specifications are preferably connected in series, and the LEDs having similar operating voltage specifications are preferably connected in parallel. Those having ordinary skill in the art will appreciate that a LED design of a switching LED cell of the present invention is without limit. 
       FIGS. 1 and 2  illustrate a baseline current-source driven switching LED cell  30  further employing a switch SW 1  (e.g., a semiconductor switch) connected in series to LED matrix L 11 -LXY, and a switch SW 2  (e.g., a semiconductor switch) connected in parallel to the series connection of switch SW 1  and LED matrix L 11 -LXY. To facilitate an understanding of cell  30 , the following description of the operation modes of cell  30  is based on an inclusion of each LED within LED matrix L 11 -LXY. However, in practice, a cell design of a current-source driven switching LED cell based on cell  30  can include any number and any arrangement of LEDs from LED matrix L 11 -LXY as would be appreciated by those having ordinary skill in the art. 
     In a radiating mode of cell  30  as illustrated in  FIG. 1 , switch SW 1  is closed and switch SW 2  is opened whereby a current i PM1  can sequentially flow through an input terminal IN 1 , switch SW 1 , LED matrix L 11 -LXY, and an output terminal OUT 1  to thereby radiate a color of light in dependence upon the selected color(s) of the LEDs. In a disabled mode of cell  30  as illustrated in  FIG. 2 , switch SW 1  is opened and switch SW 2  is closed to thereby impede a flow of current i PM1  through LED matrix L 11 -LXY whereby the LEDs do not radiate the color of light. Current i PM1  constitutes a pulse modulated current due to a complementary opening and closing of switches SW 1  and SW 2  at a LED driving frequency (e.g., 200 Hz), which can be accomplished by conventional techniques as would occur to those having ordinary skill in the art. 
     Multiple LED embodiments of switching LED cell  30  can further include one or more additional switches (e.g., semiconductor switches) distributed throughout the LEDs of LED matrix L 11 -LXY whereby a color level and/or a color intensity of the light radiated by the LEDs can be varied in dependence on an opening and a closing of the additional switches relative to the opening and closing of switches SW 1  and SW 2  as illustrated in  FIGS. 1 and 2 . Such multiple LED embodiments may operate switches SW 1  and SW 2  as well as the additional switches at the same or different LED driving frequencies. Current i PM1  may consist of multiple pulse modulated currents at various LED driving frequencies in embodiments where the additional switches are individually operated at different LED driving frequencies or are operated in multiple groups at different LED driving frequencies. 
       FIGS. 3 and 4  illustrate a baseline current-source driven switching LED cell  31  employing a circuit arrangement of switches SW 11 -SW 1 Y (e.g., semiconductor switches) connected to LED matrix L 11 -LXY. Cell  31  further employs a switch SW 3  (e.g., a semiconductor switch) connected in parallel to the circuit arrangement of switches SW 1 -SW 1 Y and LED matrix L 11 -LYX. To facilitate an understanding of cell  31 , the following description of the operation modes of cell  31  is based on an inclusion of each switch SW 1 -SW 1 Y and each LED within LED matrix L 11 -LXY. However, in practice, a cell design of a current-source driven switching LED cell based on cell  31  can include any number and any arrangement of switches SW 11 -SW 1 Y and LEDs of LED matrix L 11 -LXY as would be appreciated by those having ordinary skill in the art. 
     In a radiating mode of cell  31  as illustrated in  FIG. 3 , switch SW 3  is opened and switches SW 11 -SW 1 Y are closed whereby current i PM1  can sequentially flow through an input terminal IN 2 , switches SW 11 -SW 1 Y, LED matrix L 11 -LXY and an output terminal OUT 2  to thereby radiate a color of light in dependence upon the selected color(s) of the LEDs. In a disabled mode of cell  31  as illustrated in  FIG. 4 , switch SW 3  is closed and switches SW 11 -SW 1 Y are opened to thereby impede a flow of current i PM1  through LED matrix L 11 -LXY whereby the LEDs do not radiate the color of light. Again, current i PM1  constitutes a pulse modulated current due to the complementary opening and closing of switch SW 3  and switches SW 11 -SW 1 Y at a LED driving frequency (e.g., 200 Hz), which can be accomplished by conventional techniques as would occur to those skilled in the art. In alternative operating embodiments of cell  31 , switches SW 11 -SW 1 Y can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM1  may consist of multiple pulse-modulated currents at varying LED driving frequencies. 
     Embodiments of switching LED cell  31  can further include one or more additional switches (e.g., semiconductor switches) distributed throughout the LED matrix L 11 -LXY whereby a color level and/or a color intensity can be varied in dependence on an opening and a closing of the additional switches relative to the opening and closing of switch SW 3  and switches SW 11 -SW 1 Y as illustrated in  FIGS. 3 and 4 . Such multiple LED embodiments may operate switch SW 3  and switches SW 11 -SW 1 Y as well as the additional switches at the same or different LED driving frequencies. Current i PM1  may consist of multiple pulse modulated currents at various LED driving frequencies in embodiments where the additional switches are individually operated at different LED driving frequencies or are operated in multiple groups at different LED driving frequencies. 
       FIGS. 5 and 6  illustrate a baseline current-source driven switching LED cell  32  employing a circuit arrangement of switches SW 11 -SWX 1  (e.g., semiconductor switches) connected to the LED matrix L 11 -LXY. To facilitate an understanding of cell  32 , the following description of the operation modes of cell  32  is based on an inclusion of each switch SW 1 -SWX 1  and each LED within LED matrix L 11 -LXY. However, in practice, a cell design of a current-source driven switching LED cell based on cell  32  can include any number and any arrangement of switches SW 11 -SWX 1  and LEDs of LED matrix L 11 -LXY as would be appreciated by those having ordinary skill in the art. 
     In a radiating mode of cell  32  as illustrated in  FIG. 5 , switches SW 11 -SWX 1  are opened whereby current i PM1  can sequentially flow through an input terminal IN 3 , LED matrix L 11 -LXY and an output terminal OUT 3  to thereby radiate a color of light in dependence upon the selected color(s) of the LEDs. In a disabled mode as illustrated in  FIG. 6 , selected switches SW 11 -SWX 1  are closed to thereby impede a flow of current i PM1  through LED matrix L 11 -LXY whereby the LEDs do not radiate the color of light. Again, current i PM1  constitutes a pulse modulated current due to the complementary opening and closing of switches SW 11 -SWX 1  at a LED driving frequency (e.g., 200 Hz), which can be accomplished by conventional techniques as would occur to those skilled in the art. In alternative operating embodiments of cell  32 , switches SW 11 -SWX 1  can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM1  may consist of multiple pulse modulated currents at various LED driving frequencies. 
     Embodiments of switching LED cell  32  can further include one or more additional switches (e.g., semiconductor switches) distributed throughout the selected LEDs whereby a color level and/or a color intensity can be varied in dependence on an opening and a closing of the additional switches relative to the opening and closing of switches SW 11 -SWX 1  as illustrated in  FIGS. 5 and 6 . Such multiple LED embodiments may operate switches SW 11 -SWX 1  as well as the additional switches at the same or different LED driving frequencies. Current i PM1  may consist of multiple pulse modulated currents at various LED driving frequencies in embodiments where the additional switches are individually operated at different LED driving frequencies or are operated in multiple groups at different LED driving frequencies. 
     Referring to  FIGS. 1-6 , the number and arrangements of a current source LED driver of the present invention employing a current source and one of the current source driven switching LED cells  30 - 32  are without limit.  FIGS. 7-11  illustrate several exemplary embodiments of current source LED drivers of the present invention. 
       FIG. 7  illustrates a current source LED driver  40  employing a current source CS 1  in the form of a Buck converter having a known arrangement of a battery B 1 , a semiconductor switch Q 1 , a diode D 1  and an inductor L 1 . Current source CS 1  is conventionally operated by an application of a gate signal to a gate of semiconductor switch Q 1  at a power conversion frequency (e.g., 100 KHz) as would occur to those having ordinary skill in the art. 
       FIG. 8  illustrates a current source LED driver  41  employing a current source CS 2  in the form of a Cuk converter having a known arrangement of a battery B 2 , an inductor L 2 , a semiconductor switch Q 2 , a capacitor C 1 , a diode D 2  and an inductor L 3 . Current source CS 2  is conventionally operated by an application of a gate signal to a gate of semiconductor switch Q 2  at a power conversion frequency (e.g.,  100  KHz) as would occur to those having ordinary skill in the art. 
       FIG. 9  illustrates a current source LED driver  42  employing a current source CS 3  in the form of a Zeta converter having a known arrangement of a battery B 3 , a semiconductor switch Q 3 , an inductor L 4 , a capacitor C 2 , a diode D 3  and an inductor L 5 . Current source CS 3  is conventionally operated by an application of a gate signal to a gate of semiconductor switch Q 3  at a power conversion frequency (e.g., 100 KHz) as would occur to those having ordinary skill in the art. 
       FIG. 10  illustrates a current source LED driver  43  employing a current source CS 4  in the form of a Forward converter having a known arrangement of a battery B 4 , a transformer T 1 , a semiconductor switch Q 4 , a diode D 4 , a diode D 5  and an inductor L 6 . Driver  43  further employs version  32   a  of cell  32  ( FIGS. 5 and 6 ). Current source CS 4  is conventionally operated by an application of a gate signal to a gate of semiconductor switch Q 4  at a power conversion frequency (e.g., 100 KHz) as would occur to those having ordinary skill in the art. 
     Referring to  FIGS. 7-10 , drivers  40 - 43  further employ a version  32   a  of cell  32  ( FIGS. 3 and 4 ) having an illustrated circuit arrangement of switches SW 11 -SW 41  and LEDs L 11 -L 41 . LED L 11 , LED L 21 , LED L 31  and/or LED L 41  can be implemented as a plurality of LEDs in any desired circuit arrangement that may include additional switches. In one embodiment, LED L 11  consists of one or more red LEDs, LED L 21  consists of green LEDs, LED L 31  consists of blue LEDs, and LED L 41  consists of one or more amber LEDs. 
     Cell  32   a  has fifteen (15) radiating modes with each radiating mode of cell  32   a  involving a selective opening of one or more of the switches SW 11 -SW 41  whereby current i PM1  flows through one or more of the LEDs L 11 -L 41  to thereby radiate a color of light in dependence upon which LEDs L 11 -L 41  are radiating light. In a disabled mode of cell  32   a , switches SW 11 -SW 41  are closed to thereby impede a flow of current i PM1  through the LEDs L 11 -L 41  whereby LEDs L 11 -L 41  do not radiate the color of light. Cell  32   a  switches between one of the radiating modes and the disabled mode at a LED driving frequency (e.g., 200 Hz) in dependence upon conventional control signals selectively applied to switches SW 11 -SW 41 . In alternative operating embodiments of cell  32   a , switches SW 11 -SW 41  can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM1  may consist of multiple pulse modulated currents at various LED driving frequencies. 
       FIG. 11  illustrates a current source LED driver  44  employing current source CS 1  ( FIG. 7 ) and a version  31   a  of cell  31  ( FIGS. 3 and 4 ) having an illustrated circuit arrangement of switch SW 3 , switches SW 11 -SW 14  and LEDs L 11 -L 14 . LED L 11 , LED L 12 , LED L 13  and/or LED L 14  can be implemented as a plurality of LEDs in any desired circuit arrangement that may include additional switches. In one embodiment, LED L 11  consists of one or more red LEDs, LED L 12  consists of green LEDs, LED L 13  consists of blue LEDs, and LED L 14  consists of one or more amber LEDs. 
     Cell  31   a  has fifteen (15) radiating modes with each radiating mode of cell  31   a  involving an opening of switch SW 3  and a selective closing of one or more of the switches SW 11 -SW 14  whereby current i PM1  flows through one or more of the LEDs L 11 -L 14  to thereby radiate a color of light in dependence upon which LEDs L 11 -L 14  are radiating light. In a disabled mode of cell  31   a , switch SW 3  and switches SW 11 -SW 14  are closed to thereby impede a flow of current i PM1  through the LEDs L 11 -L 14  whereby LEDs L 11 -L 14  do not radiate the color of light. Cell  31   a  switches between one of the radiating modes and the disabled mode at a LED driving frequency (e.g., 200 Hz) in dependence upon conventional control signals selectively applied to switches SW 11 -SW 14 . In alternative operating embodiments of cell  31   a , switches SW 11 -SW 14  can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM1  may consist of multiple pulse modulated currents at various LED driving frequencies. 
       FIGS. 12 and 13  illustrate a baseline voltage-source driven switching LED cell  50  further employing a switch SW 5  (e.g., a semiconductor switch) connected in parallel to LED matrix L 11 -LXY, and a switch SW 4  (e.g., a semiconductor switch) connected in series to the parallel connection of switch SW 5  and LED matrix L 11 -LXY. To facilitate an understanding of cell  50 , the following description of the operation modes of cell  50  is based on an inclusion of each LED within LED matrix L 11 -LXY. However, in practice, a cell design of a voltage-source driven switching LED cell based on cell  50  can include any number and any arrangement of LEDs from LED matrix L 11 -LXY as would be appreciated by those having ordinary skill in the art. 
     In a radiating mode of cell  50  as illustrated in  FIG. 12 , switch SW 4  is closed and switch SW 5  is opened whereby a current i PM1  can sequentially flow through an input terminal IN 4 , switch SW 4 , LED matrix L 11 -LXY, and an output terminal OUT 4  to thereby radiate a color of light in dependence upon the selected color(s) of the LEDs. In a disabled mode of cell  50  as illustrated in  FIG. 13 , switch SW 4  is opened and switch SW 5  is closed to thereby impede a flow of current i PM1  through LED matrix L 11 -LXY whereby the LEDs do not radiate the color of light. Current i PM1  constitutes a pulse modulated current due to the complementary opening and closing of switches SW 4  and SW 5  at a LED driving frequency (e.g., 200 Hz), which can be accomplished by conventional techniques as would occur to those having ordinary skill in the art. 
     Multiple LED embodiments of switching LED cell  50  can further include one or more additional switches (e.g., semiconductor switches) distributed throughout the LEDs of LED matrix L 11 -LXY whereby a color level and/or a color intensity of the light radiated by the LEDs can be varied in dependence on an opening and a closing of the additional switches relative to the opening and closing of switches SW 4  and SW 5  as illustrated in  FIGS. 12 and 13 . Such multiple LED embodiments may operate switches SW 4  and SW 5  as well as the additional switches at the same or different LED driving frequencies. Current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies in embodiments where the additional switches are individually operated at different LED driving frequencies or are operated in multiple groups at different LED driving frequencies. 
       FIGS. 14 and 15  illustrate a baseline voltage-source driven switching LED cell  51  employing a circuit arrangement of switches SW 11 -SW 1 Y (e.g., semiconductor switches) connected to LED matrix L 11 -LXY. To facilitate an understanding of cell  51 , the following description of the operation modes of cell  51  is based on an inclusion of each switch SW 1 -SW 1 Y and each LED within LED matrix L 11 -LXY. However, in practice, a cell design of a voltage-source driven switching LED cell based on cell  51  can include any number and any arrangement of switches SW 11 -SW 1 Y and LEDs of LED matrix L 11 -LXY as would be appreciated by those having ordinary skill in the art. 
     In a radiating mode of cell  51  as illustrated in  FIG. 14 , switches SW 11 -SW 1 Y are closed whereby current i PM1  can sequentially flow through an input terminal IN 5 , switches SW 11 -SW 1 Y, LED matrix L 11 -LXY and an output terminal OUT 5  to thereby radiate a color of light in dependence upon the selected color(s) of the LEDs. In a disabled mode of cell  51  as illustrated in  FIG. 15 , switches SW 11 -SW 1 Y are opened to thereby impede a flow of current i PM1  through LED matrix L 11 -LXY whereby the LEDs do not radiate the color of light. Again, current i PM1  constitutes a pulse modulated current due to the opening and closing of switches SW 11 -SW 1 Y at a LED driving frequency (e.g., 200 Hz), which can be accomplished by conventional techniques as would occur to those skilled in the art. In alternative operating embodiments of cell  51 , switches SW 11 -SW 1 Y can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies. 
     Embodiments of switching LED cell  51  can further include one or more additional switches (e.g., semiconductor switches) distributed throughout the LED matrix L 11 -LXY whereby a color level and/or a color intensity can be varied in dependence on an opening and a closing of the additional switches relative to the opening and closing of switches SW 11 -SW 1 Y as illustrated in  FIGS. 14 and 15 . Such multiple LED embodiments may operate switches SW 11 -SW 1 Y as well as the additional switches at the same or different LED driving frequencies. Current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies in embodiments where the additional switches are individually operated at different LED driving frequencies or are operated in multiple groups at different LED driving frequencies. 
       FIGS. 16 and 17  illustrate a baseline voltage-source driven switching LED cell  52  employing a circuit arrangement of switches SW 11 -SWX 1  (e.g., semiconductor switches) connected to the LED matrix L 11 -LXY. Cell  52  further employs a switch SW 6  (e.g., a semiconductor switch) connected in series to the circuit arrangement of switches SW 11 -SWX 1  and LED matrix L 11 -LXY. To facilitate an understanding of cell  52 , the following description of the operation modes of cell  52  is based on an inclusion of each switch SW 1 -SWX 1  and each LED within LED matrix L 11 -LXY. However, in practice, a cell design of a voltage-source driven switching LED cell based on cell  52  can include any number and any arrangement of switches SW 11 -SWX 1  and LEDs of LED matrix L 11 -LXY as would be appreciated by those having ordinary skill in the art. 
     In a radiating mode of cell  52  as illustrated in  FIG. 16 , switch SW 6  is closed and switches SW 11 -SWX 1  are opened whereby current i PM1  can sequentially flow through an input terminal IN 6 , LED matrix L 11 -LXY and an output terminal OUT 6  to thereby radiate a color of light in dependence upon the selected color(s) of the LEDs. In a disabled mode as illustrated in  FIG. 17 , selected switches SW 11 -SWX 1  are closed to thereby impede a flow of current i PM1  through LED matrix L 11 -LXY whereby the LEDs do not radiate the color of light. Again, current i PM1  constitutes a pulse modulated current due to the complementary opening and closing of switch SW 6  and switches SW 11 -SWX 1  at a LED driving frequency (e.g., 200 Hz), which can be accomplished by conventional techniques as would occur to those skilled in the art. In alternative operating embodiments of cell  52 , switches SW 11 -SW 1 Y can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies. 
     Embodiments of switching LED cell  52  can further include one or more additional switches (e.g., semiconductor switches) distributed throughout the selected LEDs whereby a color level and/or a color intensity can be varied in dependence on an opening and a closing of the additional switches relative to the opening and closing of switch SW 6  and switches SW 11 -SWX 1  as illustrated in  FIGS. 16 and 17 . Such multiple LED embodiments may operate switch SW 6  and switches SW 11 -SWX 1  as well as the additional switches at the same or different LED driving frequencies. Current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies in embodiments where the additional switches are individually operated at different LED driving frequencies or are operated in multiple groups at different LED driving frequencies. 
     Referring to  FIGS. 12-17 , the number and arrangements of a voltage source LED driver of the present invention employing a voltage source and one of the voltage source driven switching LED cells  50 - 52  are without limit.  FIGS. 18 and 19  illustrate several exemplary embodiments of voltage source LED drivers of the present invention. 
       FIG. 18  illustrates a voltage source LED driver  60  employing a voltage source VS 1  in the form of a Boost converter having a known arrangement of a battery B 5 , an inductor L 7 , a semiconductor switch Q 5 , a diode D 6  and a capacitor C 2 . Voltage source VS 1  is conventionally operated by an application of a gate signal to a gate of switch Q 5  at a power conversion frequency (e.g., 100 KHz) as would occur to those having ordinary skill in the art. 
     Driver  60  further employs a version  51   a  of cell  51  ( FIGS. 13 and 14 ) having an illustrated circuit arrangement of switches SW 11 -SW 14  and LEDs L 11 -L 14 . LED L 11 , LED L 12 , LED L 13  and/or LED L 14  can be implemented as a plurality of LEDs in any desired circuit arrangement that may include additional switches. In one embodiment, LED L 11  consists of one or more red LEDs, LED L 12  consists of green LEDs, LED L 13  consists of blue LEDs, and LED L 14  consists of one or more amber LEDs. 
     Cell  51   a  has fifteen (15) radiating modes with each radiating mode of cell  51   a  involving a selective opening of one or more of the switches SW 11 -SW 14  whereby current i PM1  flows through one or more of the LEDs L 11 -L 14  to thereby radiate a color of light in dependence upon which LEDs L 11 -L 14  are radiating light. In a disabled mode of cell  51   a , switches SW 11 -SW 14  are closed to thereby impede a flow of current i PM1  through the LEDs L 11 -L 14  whereby LEDs L 11 -L 14  do not radiate the color of light. Cell  51   a  switches between one of the radiating modes and the disabled mode at a LED driving frequency (e.g., 200 Hz) in dependence upon conventional control signals selectively applied to switches SW 11 -SW 14 . In alternative operating embodiments of cell  51   a , switches SW 11 -SW 14  can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies. 
       FIG. 19  illustrates a voltage source LED driver  61  employing a voltage source VS 2  in the form of a Flyback converter having a known arrangement of a battery B 6 , a semiconductor switch Q 6 , a transformer T 2 , and a diode D 7 . Voltage source VS 2  is conventionally operated by an application of a gate signal to a gate of switch Q 6  at a power conversion frequency (e.g., 100 KHz) as would occur to those having ordinary skill in the art. 
     Driver  61  further employs a version  52   a  of cell  52  ( FIGS. 16 and 17 ) having an illustrated circuit arrangement of switch SW 6 , switches SW 11 -SW 41  and LEDs L 11 -L 41 . LED L 11 , LED L 21 , LED L 31  and/or LED L 41  can be implemented as a plurality of LEDs in any desired circuit arrangement that may include additional switches. In one embodiment, LED L 11  consists of one or more red LEDs, LED L 21  consists of green LEDs, LED L 31  consists of blue LEDs, and LED L 41  consists of one or more amber LEDs. 
     Cell  52   a  has fifteen (15) radiating modes with each radiating mode of cell  52   a  involving a closing of switch SW 6  and a selective opening of one or more of the switches SW 11 -SW 41  whereby current i PM2  flows through one or more of the LEDs L 11 -L 41  to thereby radiate a color of light in dependence upon which LEDs L 11 -L 41  are radiating light. In a disabled mode of cell  52   a , switch SW 6  is opened and switches SW 11 -SW 41  are closed to thereby impede a flow of current i PM2  through the LEDs L 11 -L 41  whereby LEDs L 11 -L 41  do not radiate the color of light. Cell  52   a  switches between one of the radiating modes and the disabled mode at a LED driving frequency (e.g., 200 Hz) in dependence upon conventional control signals selectively applied to switches SW 11 -SW 41 . In alternative operating embodiments of cell  52   a , switches SW 11 -SW 41  can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. In such a case, current i PM2  may consist of multiple pulse modulated currents at various LED driving frequencies. 
       FIG. 20  illustrates a baseline current source LED driver  70  employing a current source Is and a cell matrix  30 ( 11 )- 30 (XY) for designing one of numerous embodiments of a current source LED driver of the present invention. A driver design of a current source LED driver of the present invention involves (1) a selection of one or more current-source driven switching LED cells  30  within cell matrix  30 ( 11 )- 30 (XY), where X≧1 and Y≧1, (2) a LED design of each cell  30  selected from cell matrix  30 ( 11 )- 30 (XY), and (3) for multiple cell embodiments, a selection of one or more series connections and/or parallel connections of the multiple cells  30  selected from cell matrix  30 ( 11 )- 30 (XY). For driver embodiments employing multiple cells  30 , the cells  30  having similar operating current specifications are preferably connected in series, and the cells  30  having similar operating voltage specifications are preferably connected in parallel. Those having ordinary skill in the art will appreciate that a driver design of a current source LED driver based on driver  70  of is without limit.  FIGS. 22-25  illustrate several exemplary embodiment of current source LED drivers based on driver  70 . 
       FIG. 22  illustrates a red cell  30 R, a green cell  30 G, and a blue cell  30 B connected in parallel to current source I S .  FIG. 23  illustrates red cell  30 R, green cell  30 G, and blue cell  30 B connected in series to current source I S .  FIG. 24  illustrates red cell  30 R connected in series current source I S  and a parallel connection of green cell  30 G and blue cell  30 B.  FIG. 25  illustrates red cell  30 R and a series connection of green cell  30 G and blue cell  30 G connected in parallel to current source I S . Referring to  FIGS. 22-25 , current source (e.g., CS 1 -CS 4  illustrated in  FIGS. 7-10 ) provides pulse modulate current I PM1  to cells  30 R,  30 G and  30 B in dependence upon the switching of each cell  30 R,  30 G and  30 B between their respective radiating and disabled modes at the same LED driving frequency or at various LED driving frequencies where current I PM1  may consist of multiple pulse modulated currents at various LED driving frequencies. 
       FIG. 21  illustrates a baseline voltage source LED driver  80  employing a voltage source V S  and a cell matrix  50 ( 11 )- 50 (XY) for designing one of numerous embodiments of a voltage source LED driver of the present invention. A driver design of a voltage source LED driver of the present invention involves (1) a selection of one or more voltage-source driven switching LED cells  50  within cell matrix  50 ( 11 )- 50 (XY), where X≧1 and Y≧1, (2) a LED design of each cell  50  selected from cell matrix  50 ( 11 )- 50 (XY), and (3) for multiple cell embodiments, a selection of one or more series connections and/or parallel connections of the multiple cells  50  selected from cell matrix  50 ( 11 )- 50 (XY). For driver embodiments employing multiple cells  50 , the cells  50  having similar operating current specifications are preferably connected in series, and the cells  50  having similar operating voltage specifications are preferably connected in parallel. Those having ordinary skill in the art will appreciate that a driver design of a voltage source LED driver based on driver  80  of is without limit.  FIGS. 26-29  illustrate several exemplary embodiment of voltage source LED drivers based on driver  80 . 
       FIG. 26  illustrates a red cell  50 R, a green cell  50 G, and a blue cell  50 B connected in parallel to voltage source V S .  FIG. 27  illustrates red cell  50 R, green cell  50 G, and blue cell  50 B connected in series to voltage source Vs.  FIG. 28  illustrates red cell  50 R connected in series voltage source V S  and a parallel connection of green cell  50 G and blue cell  50 B.  FIG. 29  illustrates red cell  50 R and a series connection of green cell  50 G and blue cell  50 G connected in parallel to voltage source V S . Referring to  FIGS. 26-29 , voltage source (e.g., V S1  and V S2  illustrated in  FIGS. 18 and 19 ) provides pulse modulate current I PM1  to cells  50 R,  50 G and  50 B in dependence upon the switching of each cell  50 R,  50 G and  50 B between their respective radiating and disabled modes at the same LED driving frequency or at various LED driving frequencies where current I PM2  may consist of multiple pulse modulated currents at various LED driving frequencies. 
       FIG. 30  illustrates a block diagram of an embodiment in accordance with the present invention of an LED driver circuit employing at least one switching LED cell. The LED driver circuit  100  includes a power supply  110  providing power  120  to a cell matrix  130  including at least one switching LED cell  132 . 
     The power supply  110 , such as a current source or a voltage source, includes a semiconductor switch  112  which receives a gate signal  114  at a gate of the semiconductor switch  112  at a power conversion frequency (e.g., 100 KHz). Exemplary power supplies are illustrated in  FIGS. 7-11  and  FIGS. 18-19 . 
     Referring to  FIG. 30 , the cell matrix  130  includes at least one switching LED cell  132  which includes at least one switch  134 . The switch  134  receives a control signal  136  which operates the switch  134  to switch the switching LED cell  132  between the radiating mode and the disabled mode at a LED driving frequency (e.g., 200 Hz). When the switching LED cell  132  includes a number of switches, the switches can be individually operated at different LED driving frequencies or operated in groups at different LED driving frequencies. Exemplary cell matrices are illustrated in  FIGS. 20-29  and exemplary switching LED cells with switches are illustrated in  FIGS. 1-19 . 
     While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.