Abstract:
A system for dimming one or more light sources includes a first light source that emits a light of a first brightness according to an operating condition of the first light source, a second light source that emits a light of a second brightness according to an operating current of the second light source, wherein the light of the first brightness is different than that of the light of the second brightness, and one or more components that references the operating condition of the first light source, wherein, in response to the referenced operating condition of the first light source, the one or more components modifies the operating current of the second light source to substantially match the light of the second brightness to the light of the first brightness. A method for dimming one or more light sources is also disclosed.

Description:
The invention relates in general to a system and method for dimming one or more light sources. 
   Light emitting diodes (LEDs) have a longer life, preferable efficiency (emitted light/emitted heat), and preferable efficacy (lumens/watt) when compared to other readily available light sources, such as, for example, incandescent light sources. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The disclosure will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1A  illustrates a topographical view of a circuit diagram for dimming light emitted by one or more LEDs in accordance with an exemplary embodiment of the invention; 
       FIG. 1B  illustrates a topographical view of a component-level circuit diagram according to the circuit of  FIG. 1A ; 
       FIG. 2A  illustrates a topographical view of a circuit diagram for dimming light emitted by one or more LEDs in accordance with an exemplary embodiment of the invention; 
       FIG. 2B  illustrates a topographical view of a component-level circuit diagram according to the circuit of  FIG. 2A ; 
       FIG. 3A  illustrates a topographical view of a circuit diagram for dimming light emitted by one or more LEDs in accordance with an exemplary embodiment of the invention; 
       FIG. 3B  illustrates a topographical view of a component-level circuit diagram according to the circuit of  FIG. 3A ; 
       FIG. 4A  illustrates a topographical view of a circuit diagram for dimming light emitted by one or more LEDs in accordance with an exemplary embodiment of the invention; 
       FIG. 4B  illustrates a topographical view of a component-level circuit diagram according to the circuit of  FIG. 4A ; 
       FIG. 5  is an example of a pulse-width modulation (PWM) signal of a power supply defined by a duty cycle; 
       FIG. 6  is an example of a PWM signal for dimming an incandescent light source and an LED in accordance with an exemplary embodiment of the invention; 
       FIG. 7  is a dimming curve of an incandescent light source and LED that is referenced from a PWM duty cycle vs. time chart; 
       FIG. 8  is a flow chart illustrating a method for dimming one or more light sources in accordance with an exemplary embodiment of the invention; and 
       FIG. 9  illustrates a topographical view of a circuit diagram for diming light emitted by one or more LEDs in accordance with an exemplary embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   The Figures illustrate an exemplary embodiment of a system and method for dimming one or more light sources in accordance with an embodiment of the invention. It is to be generally understood that the nomenclature used herein is simply for convenience and the terms used to describe the invention should be given the broadest meaning by one of ordinary skill in the art. 
   I. Dimming with Filter 
   Referring initially to  FIG. 1A , a circuit for dimming (i.e., reducing the brightness of) light emitted by one or more incandescent light sources  12  and one or more light emitting diodes (LEDs)  14  is shown generally at  10  according to an embodiment. Light that is emitted from the incandescent light source  12  is shown generally at L 1 , and light that is emitted from the LED  14  is shown generally at L 2 . 
   The circuit  10  also includes a power supply that is shown generally at  16 . Also, the circuit  10  includes logic/driver circuitry that is shown generally at  18 . The implementation of the logic/driver circuitry  18  may improve the dimming of the light, L 1 , L 2 , provided, respectively, by the one or more incandescent light sources  12  and one or more LEDs  14 . Nodes are shown generally at  20 - 30  that connect the above-described components  12 - 18  to define the circuit  10 . 
   According to an embodiment, the circuit  10  may incorporate a system dimming operation when it is desired to dim the light, L 1 , L 2 , from the incandescent light source  12  and LED  14 . According to an embodiment, the system dimming operation is conducted such that the incandescent light source  12  and LED  14  are dimmed in concert (i.e., the perceivable emitted brightness and subsequent extinguishing of the light, L 1 , L 2 , occurs simultaneously and is substantially the same). In general, the system dimming operation is initiated by influencing the power supply  16  with a pulse width modulation (PWM) control signal  50 . 
   Referring to  FIG. 5 , a PWM control signal  50  is shown according to an embodiment. In general, a PWM control signal  50  is defined by a period of time, T, including a non-zero (on signal) duration over a sampling of time, τ, and a zero (off signal) duration over a sampling of time, T−τ. The non-zero duration, τ, divided by the period, T, is the duty cycle, D, of the PWM control signal  50 . The duty cycle, D, is expressed below in equation 1) as follows: 
   
     
       
         
           
             
               
                 D 
                 = 
                 
                   τ 
                   T 
                 
               
             
             
               
                 1 
                 ) 
               
             
           
         
       
     
   
   In general, when the power supply  16  is influenced by the PWM control signal  50  (i.e., when the duty cycle, D, is less than 100%), a very fast on/off application of voltage is provided to the incandescent light source  12  and the LED  14 , which may be defined by, for example, a frequency of the power supply (e.g., approximately 128 Hz). Thus, as the duty cycle, D, is reduced, the duration of voltage on time (i.e., time that current that is passing through the incandescent light source  12  and the LED  14 ) is reduced. Accordingly, when the on-time voltage is reduced, the time average intensity of emitted light, L 1 , L 2 , is reduced. Thus, because of the rapid voltage on/off time, the human eye, E ( FIG. 1A ), can not resolve the on/off fluctuations of the respectively-emitted light, L 1 , L 2 , by the incandescent light source  12  and the LED  14  so as to give the appearance that the light, L 1 , L 2 , provided by the incandescent light source  12  and LED  14  is dimming. 
   Referring to  FIGS. 6 and 7 , the relationship between the PWM control signal  50  and a system dimming curve  75  is shown according to an embodiment. In general, the dimming curve  75  is defined by the perceivable emission of light, L 1 , L 2 , of both incandescent light source  12  and LED  14  where, at 100% of the duty cycle, D, the incandescent light source  12  and LED  14  provide a maximum brightness level of the emitted light, L 1 , L 2 , which is shown generally at  75   a  ( FIG. 7 ), and, shortly after the duty cycle, D, is reduced to 0%, no light, L 1 , L 2 , is emitted by the incandescent light source  12  and LED  14 , which is shown generally at  75   b  ( FIG. 7 ). 
   According to an embodiment, the system dimming curve  75  is generally modeled by the PWM control signal  50  that is utilized for controlling the illumination/dimming of an incandescent light source. The filament, F ( FIG. 1A ), of an incandescent light source retains heat and provides light shortly after voltage is removed from the incandescent light source (i.e., the filament of the incandescent light source may include ‘a thermal inertia’ or ‘a volumetric heat capacity’). Thus, at a time  50   X1  ( FIG. 7 ), the dimming curve  75  generally indicates that the incandescent light source  12  (and LED  14 ) may provide an emission of light even though no current is passing through the incandescent light source  12  according to the duty cycle, D, of the PWM control signal  50  being approximately equal to 0%. Thus, in the absence of the logic/driver circuitry  18 , the light, L 2 , emitted by the LED  14  would otherwise prematurely extinguish before the light, L 1 , of the incandescent light source  12 . 
   In addition to the difference in dimming of the light, L 1 , L 2 , at time  50   X1 , an irregularity in the conventional dimming of an LED  14  may also be perceivable to the human eye, E, at times, which are designated generally at  50   X2  in the absence of the logic/driver circuitry  18 . Unlike incandescent light sources  12 , LEDs  14  are solid state devices that are activated and emit light, L 2 , only when provided with a positive electric polarity (i.e., LEDs  14  will ‘turn on’/emit light, L 2 , when provided with a positive/non-zero signal, and will ‘turn off’/emit no light, L 2 , when provided with a zero/negative signal). Incandescent light sources  12 , conversely, are activated and emit light, L 1 , regardless of a positive or negative electrical polarity. As such, the LEDs  14  turn on and off at a very fast rate according to the characteristics of the power supply, whereas, incandescent light sources  12  may not appear to turn off (i.e., emit no light, L 1 ) in view of the characteristic of the power supply. 
   Accordingly, when, for example, the duty cycle, D, is modulated at time a  50   X2  (see, e.g.,  FIG. 6 ) the light, L 2 , emitted by the LED  14  would otherwise appear to dim with an apparent irregularity in the absence of the logic/driver circuitry  18  at the times  50   X2 . Thus, as illustrated in  FIG. 7 , when the duty cycle, D, is modulated, noticeable flicker of the LED  14  would otherwise then be perceivable by the human eye, E, at times  50   X2 , whereas the incandescent light source  12  may appear to dim without flickering/an irregularity. 
   Referring to  FIG. 1B , a component-level diagram of the circuit  10  of  FIG. 1A  is shown according to an embodiment. According to an embodiment, the logic/driver circuitry  18  provides a system dimming curve  75  that removes the dimming irregularities of the LED  14  at the times  50   X1 ,  50   X2  as described above. 
   According to an embodiment, the logic/driver circuitry  18  may be defined to include a low pass filter. The low pass filter may be defined to include, for example, a resistor  18   a , a capacitor  18   b , and an inductor  18   c . In operation, the components defining the filter  18   a - 18   c  remove any abrupt current transitions that are introduced by the PWM control signal  50  in order to introduce a current that drives the LED  14  in a manner to provide a brightness/dimming of light, L 2 , that is matched to the brightness/dimming of light, L 1 , of the incandescent light source  12 . 
   In addition, the logic/driver circuitry  18  may be defined to include a transistor  18   d , such as, for example, a field effect transistor (FET). Also, the logic/driver circuitry may be defined to include a current limiting resistor  18   e  that dictates the current through the LED  14 . 
   According to an embodiment, it will be appreciated that the circuit  10  is not limited to one incandescent light source  12  and one LED  14 . For example, according to an embodiment, the component-level circuit diagram of  FIG. 1B  may include an array of LEDs  14 . 
   According to an embodiment, the one or more LEDs  14  may have any desirable substrate that provides any desirable color of light, L 2 . As such, the one or more LEDs  14  may include, but is not limited to, any well known LED substrate that includes, for example, aluminum gallium arsenide (AlGaAs) that emits light, L 2 , of a red or infrared color, gallium phosphide (GaP) that emits light, L 2 , of a red, yellow, or green color, silicon carbide (SiC) that emits light, L 2 , of a blue color, or the like. Also, the one or more incandescent light sources  12  may be any desirable incandescent light source that is produced for a wide range of voltages ranging from, for example, a few volts to several hundred volts with corresponding brightness levels. 
   In addition, the power supply  16  is not limited to provide a particular type of signal. For example, the power supply  16  may be defined by and generate any desirable signal, such as, for example, a direct current (DC) low voltage battery signal, a half-wave rectified DC signal, a full-wave rectified DC signal, an alternating current (AC) signal, a PWM signal, or the like. 
   II. Dimming with Microprocessor 
   Referring to  FIG. 2A , a circuit for dimming light emitted by one or more incandescent light sources  102  and one or more LEDs  104  is shown generally at  100  according to an embodiment. Light that is emitted from the incandescent light source  102  is shown generally at L 1 , and light that is emitted from the LED  104  is shown generally at L 2 . 
   The circuit  100  also includes a power supply that is shown generally at  106 . Also, the circuit  100  includes logic/driver circuitry that is shown generally at  108 , and a voltage/current sense resistor that is shown generally at  110 . The implementation of the logic/driver circuitry  108  may improve the dimming of the light, L 1 , L 2 , provided, respectively, by the one or more incandescent light sources  102  and one or more LEDs  104 . Nodes are shown generally at  112 - 128  that connect the above-described components  102 - 110  to define the circuit  100 . 
   According to an embodiment, the circuit  100  may incorporate a system dimming operation function when it is desired to dim the light, L 1 , L 2 , from the incandescent light source  102  and LED  104 . According to an embodiment, the system dimming operation is conducted such that the incandescent light source  102  and LED  104  are dimmed in concert (i.e., the perceivable emitted brightness and subsequent extinguishing of the light, L 1 , L 2 , occurs simultaneously and is substantially the same). In general, the system dimming operation is initiated by modulating the PWM control signal  50 , the operation of which is similarly described above in  FIGS. 5-6 . In addition, as similarly described above, a system dimming curve  75  is shown generally in  FIG. 7 . 
   Referring to  FIG. 2B , a component-level diagram of the circuit  100  of  FIG. 2A  is shown according to an embodiment. According to an embodiment, the logic/driver circuitry  108  provides a system dimming curve  75  that removes dimming irregularities of the LED  104  at times  50   X1 ,  50   X2  as described above. 
   The logic/driver circuitry  108  may be defined to include a microprocessor  108   a , or, alternatively, an application specific integrated circuit (ASIC). In operation, according to an embodiment, the PWM control signal  50  may influence the current through, and, correspondingly, the dimming of the incandescent light source  102 . The voltage/current sense resistor  110 , which may be defined by, for example, a 0.1Ω, resistance, may sense the current through the incandescent light source  102  and provide the value of the sensed current through the incandescent light source  102  to the microprocessor  108   a  or ASIC driver. 
   Upon learning the value of the sensed current through the incandescent light source  102 , the microprocessor  108   a  may refer to a pre-programmed look-up table, which is shown below at Table 1. According to an embodiment, the value of the sensed current through the incandescent light source  102  may be equated or otherwise referenced to a duty cycle, D, of the PWM control signal  50 , which is shown in the left column of Table 1. When the duty cycle, D, of the PWM control signal  50  is determined, an output effective current of the LED  104  is located in the look-up table, and, the maximum current, A, of the power supply  106  is limited according to a corresponding value located value in the look-up table. 
   
     
       
             
             
             
           
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               PWM 
               Output Effective Current 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               100 
               1.00 A 
             
             
                 
               90 
               0.98 A 
             
             
                 
               80 
               0.87 A 
             
             
                 
               70 
               0.76 A 
             
             
                 
               60 
               0.65 A 
             
             
                 
               50 
               0.55 A 
             
             
                 
               40 
               0.45 A 
             
             
                 
               30 
               0.35 A 
             
             
                 
               20 
               0.25 A 
             
             
                 
               10 
               0.15 A 
             
             
                 
               0 
               0.05 A 
             
             
                 
                 
             
           
        
       
     
   
   According to an embodiment as shown above in Table 1, the output effective current values may be provided in a linear relationship. However, it will be appreciated that the output effective current values may not necessarily include a linear relationship and may be defined by, for example, an exponential relationship, a logarithmic relationship, or the like. 
   In addition, the logic/driver circuitry  108  may be defined to include a transistor  108   b , such as, for example, a field effect transistor (FET). In operation, the transistor  108   b  operates as a switch. Also, the logic/driver circuitry  108  may be defined to include a current limiting resistor  108   c  that dictates the current through the LED  104 . 
   According to an embodiment, it will be appreciated that the circuit  100  is not limited to one incandescent light source  102  and one LED  104 . For example, according to an embodiment, the component-level circuit diagram of  FIG. 2B  may include an array of LEDs  104 . As similarly described above, the one or more LEDs  104  may have any desirable substrate that provides any desirable color of light, L 2 . Also, the one or more incandescent light sources  102  may be defined by any desirable incandescent light source that is produced for a wide range of voltages ranging from, for example, a few volts to several hundred volts with corresponding brightness levels. 
   In addition, the power supply  106  is not limited to provide a particular type of signal. For example, the power supply  106  may be defined by and generate any desirable signal, such as, for example, a direct current (DC) low voltage battery signal, a half-wave rectified DC signal, a full-wave rectified DC signal, an alternating current (AC) signal, a PWM signal, or the like. 
   III. Dimming with Optical Current Regulation 
   Referring to  FIG. 3A , a circuit for dimming light emitted by one or more incandescent light sources  202  and one or more LEDs  204  is shown generally at  200  according to an embodiment. Light that is emitted from the incandescent light source  202  is shown generally at L 1 , and light that is emitted from the LED  204  is shown generally at L 2 . 
   The circuit  200  also includes a power supply that is shown generally at  206 . Also, the circuit  200  includes logic/driver circuitry that is shown generally at  208 , and an optical sensor is shown generally at  210 . The implementation of the logic/driver circuitry  208  and the optical sensor  210  may improve the dimming of the light, L 1 , L 2 , provided, respectively, by the one or more incandescent light sources  202  and one or more LEDs  204 . Nodes are shown generally at  212 - 228  that connect the above-described components  202 - 210  to define the circuit  200 . 
   According to an embodiment, the circuit  200  may incorporate a system dimming operation function when it is desired to dim the light, L 1 , L 2 , from the incandescent light source  202  and LED  204 . According to an embodiment, the system dimming operation is conducted such that the incandescent light source  202  and LED  204  are dimmed in concert (i.e., the perceivable emitted brightness and subsequent extinguishing of the light, L 1 , L 2 , occurs simultaneously and is substantially the same). In general, the system dimming operation is initiated by influencing the power supply  206  with a PWM control signal  50 , which is similarly described above in  FIGS. 5 and 6 . In addition, as similarly described above, a system dimming curve  75  is shown generally in  FIG. 7 . 
   Referring to  FIG. 3B , a component-level diagram of the circuit  200  of  FIG. 3A  is shown according to an embodiment. According to an embodiment, the logic/driver circuitry  208  and optical sensor  210  provide a system dimming curve  75  that removes dimming irregularities of the LED  204  at the times  50   X1 ,  50   X2  as described above. 
   The logic/driver circuitry  208  may be defined to include a low pass filter. The low pass filter may be defined to include, for example, an inductor  208   a  and a capacitor  208   b . In addition, the logic/driver circuitry  208  may also include a current limiting resistor  208   c . In operation, the components defining the filter  208   a ,  208   b  remove any abrupt current transitions that are introduced by the PWM control signal  50  in order to introduce a current that drives the LED  204  in a manner to provide a brightness/dimming of light, L 2 , that is matched to the light, L 1 , of the incandescent light source  202 . 
   In addition, the optical sensor  210  may also assist in the matching of the emitted light, L 1 , of the LED  204  with the light, L 1 , emitted by the incandescent light source  202 . According to an embodiment, the optical sensor  210  includes a transistor  210   a  and is optically connected with (i.e., electrically de-coupled from) the incandescent light source  202 . Operationally, the optical sensor senses the luminance/brightness of the light, L 1 , from the incandescent light source  202  to control the output of the transistor  210   a  to thereby allow more or less current to the LED  204  for increasing or decreasing the brightness of the light, L 2 , from the LED  204 . 
   According to an embodiment, it will be appreciated that the circuit  200  is not limited to one incandescent light source  202  and one LED  204 . For example, according to an embodiment, the component-level circuit diagram of  FIG. 3B  may include an array of LEDs  204 . 
   According to an embodiment, the one or more LEDs  204  may have any desirable substrate that provides any desirable color of light, L 2 . As such, the one or more LEDs  204  may include, but is not limited to, any well known LED substrate that includes, for example, aluminum gallium arsenide (AlGaAs) that emits light, L 2 , of a red or infrared color, gallium phosphide (GaP) that emits light, L 2 , of a red, yellow, or green color, silicon carbide (SiC) that emits light, L 2 , of a blue color, or the like. Also, the one or more incandescent light sources  202  may be any desirable incandescent light source that is produced for a wide range of voltages ranging from, for example, a few volts to several hundred volts with corresponding brightness levels. 
   In addition, the power supply  206  is not limited to provide a particular type of signal. For example, the power supply  206  may be defined by and generate any desirable signal, such as, for example, a direct current (DC) low voltage battery signal, a half-wave rectified DC signal, a full-wave rectified DC signal, an alternating current (AC) signal, a PWM signal, or the like. 
   IV. Dimming with a Microprocessor and Optical Sensing 
   Referring to  FIG. 4A , a circuit for dimming light emitted by one or more incandescent light sources  302  and one or more LEDs  304  is shown generally at  300  according to an embodiment. Light that is emitted from the incandescent light source  302  is shown generally at L 1 , and light that is emitted from the LED  304  is shown generally at L 2 . 
   The circuit  300  also includes a power supply that is shown generally at  306 . Also, the circuit includes an optical sensor  308 , logic/driver circuitry that is shown generally at  310 , and a voltage/current sense resistor that is shown generally at  312 . The implementation of the optical sensor  308 , the logic/driver circuitry  310 , and the voltage/current sense resistor  312  may improve the dimming of the light, L 1 , L 2 , provided, respectively, by the one or more incandescent light sources  302  and one or more LEDs  304 . Nodes are shown generally at  314 - 340  that connect the above-described components  302 - 312  to define the circuit  300 . 
   According to an embodiment, the circuit  300  may incorporate a system dimming operation function when it is desired to dim the light, L 1 , L 2 , from the incandescent light source  302  and LED  304 . According to an embodiment, the system dimming operation is conducted such that the incandescent light source  302  and LED  304  are dimmed in concert (i.e., the perceivable emitted brightness and subsequent extinguishing of the light, L 1 , L 2 , occurs simultaneously and is substantially the same). In general, the system dimming operation is initiated by modulating the PWM control signal  50 , which is similarly described above in  FIGS. 5 and 6 . In addition, as similarly described above, a system dimming curve  75  is shown generally in  FIG. 7 . 
   Referring to  FIG. 4B , a component-level diagram of the circuit  300  of  FIG. 4A  is shown according to an embodiment. According to an embodiment, the optical sensor  308 , logic/driver circuitry  310 , and voltage/current sense resistor  312  provide a system dimming curve  75  that removes dimming irregularities of the LED  304  at the times  50   X1 ,  50   X2 . 
   In general, the circuit  300  includes a combination of similar operational features shown and described above in  FIGS. 2B and 3B . The optical sensor  308  includes a transistor  308   a  and is optically connected with (i.e., electrically de-coupled from) the incandescent light source  302 . Operationally, the optical sensor  308  is a passive element that senses the luminance/brightness of the light, L 1 , from the incandescent light source  302  to control the output of the transistor  308   a.    
   The output of the output of the optical sensor&#39;s transistor  308   a  may be, for example, a luminance value ranging between 0%-100%. The luminance value is then provided as an input to the microprocessor  310   a . Output of the microprocessor  310   a  is provided to a transistor  310   b  and then to a current limiting resistor  310   c.    
   Upon learning the luminance value from the optical sensor&#39;s transistor  308   a , the microprocessor  310   a  may refer to a pre-programmed look-up table, which is shown below at Table 2. According to an embodiment, the luminance value (see, e.g., the left column in the look-up table in Table 2) may be equated or otherwise referenced to an output effective current for driving the logic/controller transistor  310   b  (see, e.g., the right column in the look-up table in Table 2). As a result, the output effective current for driving the transistor  310   b  regulates a current from the power supply  306  that is provided to increase or decrease the brightness of the LED  304  according to the brightness/luminance of the incandescent light source  302 . 
   
     
       
             
             
             
           
             
             
             
           
         
             
                 
               TABLE 2 
             
             
                 
                 
             
             
                 
                 
               Output Effective Current 
             
             
                 
               Illuminance (%) 
               (PWM to Transistor) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               100 
               1.00 A 
             
             
                 
               90 
               0.98 A 
             
             
                 
               80 
               0.87 A 
             
             
                 
               70 
               0.76 A 
             
             
                 
               60 
               0.65 A 
             
             
                 
               50 
               0.55 A 
             
             
                 
               40 
               0.45 A 
             
             
                 
               30 
               0.35 A 
             
             
                 
               20 
               0.25 A 
             
             
                 
               10 
               0.15 A 
             
             
                 
               0 
               0.05 A 
             
             
                 
                 
             
           
        
       
     
   
   According to an embodiment as shown above in Table 2, the output effective current valves may be provided in a linear relationship. However, it will be appreciated that the output effective current values may not necessarily include a linear relationship and may be defined by, for example, an exponential relationship, a logarithmic relationship, or the like. 
   According to an embodiment, it will be appreciated that the circuit  300  is not limited to one incandescent light source  302  and one LED  304 . For example, according to an embodiment, the component-level circuit diagram of  FIG. 4B  may include an array of LEDs  304 . 
   According to an embodiment, the one or more LEDs  304  may have any desirable substrate that provides any desirable color of light, L 2 . As such, the one or more LEDs  304  may include, but is not limited to, any well known LED substrate that includes, for example, aluminum gallium arsenide (AlGaAs) that emits light, L 2 , of a red or infrared color, gallium phosphide (GaP) that emits light, L 2 , of a red, yellow, or green color, silicon carbide (SiC) that emits light, L 2 , of a blue color, or the like. Also, the one or more incandescent light sources  302  may be any desirable incandescent light source that is produced for a wide range of voltages ranging from, for example, a few volts to several hundred volts with corresponding brightness levels. 
   In addition, the power supply  306  is not limited to provide a particular type of signal. For example, the power supply  306  may be defined by and generate any desirable signal, such as, for example, a direct current (DC) low voltage battery signal, a half-wave rectified DC signal, a full-wave rectified DC signal, an alternating current (AC) signal, a PWM signal, or the like. 
   Referring to  FIG. 8 , a method for operating the circuits  10 ,  100 ,  200 ,  300  is shown generally at  800  according to an embodiment. At step, S. 801 , prior to a system dimming operation at step S. 803 , the incandescent light source  12 ,  102 ,  202 ,  302  and the LED  14 ,  104 ,  204 ,  304  may be enabled to emit light, L 1 , L 2 , respectively, at step, S. 802 . Then, at step, S. 803 , the duty cycle, D, of a PWM control signal  50  is modulated to initiate a system dimming operation. During the system dimming operation, as explained above, the human eye, E, perceives a reduced brightness of the light, L 1 , L 2  emitted by the light sources  12 ,  14  as defined by the PWM control signal  50 . 
   At step, S. 804 , the logic/driver  18 ,  108 ,  208 ,  310  references an operating condition of the incandescent light source  12 ,  102 ,  202 ,  302 . According to an embodiment, step, S. 804 , may include: a direct referencing of the operating current of the incandescent light source  12 ,  102 ,  202 ,  302  ( FIGS. 1B and 2B ), a direct sensing of the luminescent output of the incandescent light source  12 ,  102 ,  202 ,  302  ( FIG. 3B ), or a direct sensing of the operating current and/or luminescent output of the incandescent light source  12 ,  102 ,  202 ,  302  ( FIG. 4B ). 
   At step, S. 805 , in response to the referencing of the operating condition of the incandescent light source  12 ,  102 ,  202 ,  302 , the logic/driver circuitry  18 ,  108 ,  208 ,  310  and/or optical sensor  210 ,  308  adjusts the operating current of the LED  14 ,  104 ,  204 ,  304 . According to an embodiment, step, S. 805 , may include: a filtering of the operating current of the incandescent light source  12 ,  102 ,  202 ,  302  ( FIG. 1B ). According to an embodiment, step, S. 805 , may include associating the operating current of the incandescent light source  12 ,  102 ,  202 ,  302  with an operating current value of the LED  14 ,  104 ,  204 ,  304  in a look-up table and selecting an operating current of the LED  14 ,  104 ,  204 ,  304  from the look-up table in view of the operating current of the incandescent light source  12 ,  102 ,  202 ,  302  ( FIG. 2B ). According to an embodiment, step, S. 805  may include regulating an operating current of the LED  14 ,  104 ,  204 ,  304  through a transistor  210   a  of an optical sensor ( FIG. 3B ). According to an embodiment, step, S. 805  may include associating the luminescent output of the incandescent light source  12 ,  102 ,  202 ,  302  with an operating current value of the LED  14 ,  104 ,  204 ,  304  in a look-up table and selecting an operating current of the LED  14 ,  104 ,  204 ,  304  from the look-up table in view of the luminescent output of the incandescent light source  12 ,  102 ,  202 ,  302  ( FIG. 4B ). 
   Once the operating current of the LED  14 ,  104 ,  204 ,  304  is adjusted at step, S. 805 , the LED  14 ,  104 ,  204 ,  304  will emit light, L 2 , that is dimmed and extinguishes in concert at similar rate as that of the light, L 1 , emitted by the incandescent light source  12 ,  102 ,  202 ,  302  so that the light, L 2 , does not flicker or prematurely extinguish in comparison to the dimming and extinguishing of the light, L 1 , provided by the incandescent light source  12 ,  102 ,  202 ,  302 . 
   Although incandescent light sources  12 ,  102 ,  202 ,  302  have a relatively poor life, efficiency, and efficacy, incandescent light sources  12 ,  102 ,  202 ,  302  are gradually being replaced with or supplemented by LEDs  14 ,  104 ,  204 ,  304  in a circuit due to the fact that LEDs are becoming more affordable. Thus, the inventive circuits  10 ,  100 ,  200 ,  300  provide a solution to the differences and drawbacks associated with the dimming behavior/simultaneous extinguishing of the emitted light, L 1 , L 2  of incandescent light sources and LEDs in a same circuit. 
   Accordingly, the circuit  10 ,  100 ,  200 ,  300  may often be implemented in a variety of home, outdoor, automotive, aircraft, aerospace, and military applications. According to an embodiment, in an automotive application, the incandescent light source  12 ,  102 ,  202 ,  302  may be utilized to emit light, L 1 , from a headliner or overhead storage bin (not shown), and the LEDs  14 ,  104 ,  204 ,  304  may be utilized to emit light, L 2 , from an instrument panel/radio display, headlight/headlamp, beverage holder, interior trim panel (not shown), or the like. 
   In an alternative embodiment, as seen in  FIG. 9 , it will be appreciated that the incandescent light source  12 ,  102 ,  202 ,  302  may be utilized as a reference component (and not as a viewable illumination component) that regulates the behavior of the LEDs  14 ,  104 ,  204 ,  304  as described above. As shown in  FIG. 9 , light, L 1 , from the incandescent light source  12 ,  102 ,  202 ,  302  may not necessarily be viewable by an occupant, and, as such, no comparison of the emitted L 1 , L 2  is permitted to be seen by the human eye, E. In this embodiment, for example, the incandescent light source  12 ,  102 ,  202 ,  302  may be positioned on or proximate a circuit board, B, carrying components of the circuit  10 ,  100 ,  200 ,  300 . Accordingly, for example, the circuit board, B, may be positioned behind, for example, vehicle structure, such as, for example, an instrument panel, P, that prevents the occupant to view the light, L 1 , whereas the light, L 2 , from the LED  14 ,  104 ,  204 ,  304  is provided proximate or within the passenger compartment area to permit the occupant to view the light, L 2 , from the LED  14 ,  104 ,  204 ,  304 . Alternatively, the incandescent light source  12 ,  102 ,  202 ,  302  may be located within the passenger compartment area, but, may include, for example, an opaque surface that blocks emission of the light, L 1 . Thus, the LEDs  14 ,  104 ,  204 ,  304  may be dimmed and behave similarly to that of an incandescent light source  12 ,  102 ,  202 ,  302  such that the viewer/occupant does not, or, is restricted from/unable to see the emitted light, L 1 , from the incandescent light source  12 ,  102 ,  202 ,  302 . 
   The present invention has been described with reference to certain exemplary embodiments thereof. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the exemplary embodiments described above. This may be done without departing from the spirit of the invention. The exemplary embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is defined by the appended claims and their equivalents, rather than by the preceding description.