Patent Publication Number: US-2013229120-A1

Title: Solid State Lighting System, Apparatus and Method with Flicker Removal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is continuation-in-part of and claims priority to U.S. patent application Ser. No. 13/664,068, filed Oct. 30, 2012, inventors Vladimir Korobov et al., entitled “Dimmable Solid State Lighting System, Apparatus and Method, with Distributed Control and Intelligent Remote Control”, which is a conversion of and claims priority to U.S. Provisional Patent Application Ser. No. 61/606,837, filed Mar. 5, 2012, inventors Vladimir Korobov et al., entitled “A Power Control Unit for Power Supply to Driverless LED Lighting Apparatuses”, which are commonly assigned herewith, the entire contents of which are incorporated herein by reference with the same full force and effect as if set forth in their entireties herein, and with priority claimed for all commonly disclosed subject matter. 
    
    
     FIELD OF THE INVENTION 
     The present invention in general is related to power conversion, and more specifically, to a system, apparatus and method for eliminating or diminishing perceived visual flicker from solid state lighting devices powered by an AC source, such as bulbs and luminaries having light emitting diodes (“LEDs”) powered by an AC line or other AC power sources. 
     BACKGROUND OF THE INVENTION 
     Electrical lighting devices of many kinds, shapes and operational principles and capabilities, have gone through various generations of development since Edison&#39;s first incandescent electric light bulb. Today it is commonplace to find incandescent, Halogen and compact fluorescent light (“CFL”) bulbs of all forms and shapes, as well as the beginning of a more modern kind of an electric lighting device that is based on light emitting diodes (LEDs). Such modern electric lighting devices can be found, for example, in the form of LED bulbs, LED luminaries, and the like. While the initial cost of such LED electric lighting devices may be higher than some of the other existing lighting solution, these costs may be offset due to the much longer lifetime of LED electric lighting devices and their significantly lower energy consumption costs. In addition, LED-based lighting generally provides better color rendering than CFL bulbs, i.e., a better quality of light, and are more environmentally friendly, both having many recyclable components and lacking the hazardous disposal issues of CFL bulbs. 
     Prior art LED bulbs and systems, however, tend to be overly complicated and typically incompatible with existing dimmer switches. Some require control methods that are complex, some are difficult to design and implement, and others require many electronic components. A large number of components results in an increased cost and reduced reliability. Many LED drivers utilize a current mode regulator with a ramp compensation in a pulse width modulation (“PWM”) circuit. Other attempts provide solutions outside the original power converter stages, adding additional feedback and other circuits, rendering the LED driver even larger and more complicated. 
     For example, each individual, typical prior art LED bulb includes, in addition to the LEDs themselves, co-located LED driver circuitry comprising an AC/DC rectifier, a DC/DC converter, a current source, complicated circuitry for analog and PWM dimming, an additional dummy load for compatibility with existing triac-type dimmer switches, and additional feedback circuitry. A typical dummy load and special circuitry is required to support stable operation of a dimmer switch by providing a load to the dimmer during turn on, typically at a frequency of 60 Hz or 120 Hz, and reduces energy conversion efficiency. The significant gap between the high voltages of an input AC voltage and the lower DC voltages required for LEDs needs complex power conversion circuitry which may have as many as forty to seventy components, for example, with additional 10%-15% power losses from the conversion. Also for example, a dimmable LED driver may easily have 30% more circuitry than a nondimmable LED driver, and requires considerably more engineering resources to develop. In addition, a typical triac dimmer presents a comparatively poor interface to an AC line for solid state lighting, corrupting the power factor, introducing additional, nonfundamental harmonics, creating electromagnetic interference (“EMI”) and audio noise problems, and increasing the input RMS current, further requiring corresponding increases in the value of service circuit breakers. 
     Incandescent lamps typically have thermal time constants of tens of milliseconds. During zero-crossings of the AC voltage, they remain at approximately a constant temperature, and thus continue emitting light. More efficient light sources such as LEDs, however, typically have much shorter illumination time-constants. For example, an LED can be turned off in less than a single microsecond. These types of light sources will then turn off during zero-crossings of the AC voltage. More specifically, typical LEDs will turn off whenever the AC voltage is less than a threshold level, which may depend on the configuration of the LEDs, such as whether there are multiple LEDs in a series connection, for example. For ease of reference and discussion, when the AC voltage is less than such a threshold level, it may be referred to as a zero crossing, it being understood that the voltage may be greater than zero and, for a rectified AC voltage, will never actual cross a zero value. Using AC power provided by a utility having a frequency of 50 Hz in Europe or 60 Hz in the United States, a full wave rectified voltage provided to the LEDs will be below the threshold voltage (i.e., have a zero crossing) at a frequency of 100 Hz or 120 Hz. As a result, the LEDs will turn off at these regular intervals, and the emitted light generally will be perceived by humans to flicker and may have other undesirable effects. 
     To prevent these undesirable effects, the prior art has traditionally included circuitry to prevent turn-off of the light source during AC zero crossings, typically using energy storage devices such as one or more capacitors, so that while the AC line voltage is low, energy to run the light source is available from the energy storage device. Typically, such a capacitor is charged during the time when the AC line voltage is high, and discharged during the time when the AC line voltage is low or otherwise below a threshold level. 
     Use of such a storage capacitor in providing power to solid state lighting, such as LED bulbs and system, has several significant drawbacks. For example, while the power factor should be comparatively high for the more energy efficient light sources, if the capacitor is connected to the output of the input rectifier bridge, the power factor becomes comparatively poor. If the capacitor is connected elsewhere in the circuit, it requires additional circuitry to operate, typically increasing costs. In addition, the capacitance value or rating of the capacitor must be comparatively large, and typically to accommodate the high voltage and large capacitance, the capacitor should be an electrolytic type. These electrolytic capacitors cost a significant amount of money as a proportion of the total cost of the LED lighting system or bulb, and further, do not have significant longevity, thereby seriously reducing the expected life of the LED lighting system or bulb. 
     As a consequence, a need remains for a comparatively lower cost and higher longevity solution to provide LED-based lighting, using an apparatus, method and system which avoids these problems, substantially eliminating perceived flicker while simultaneously using power circuitry that does not require any significant storage capacitance. Such an apparatus, method and system also may be suitable for replacing the problematic triac dimmer switches and other legacy wall-mounted switches, while simultaneously allowing the use of LED bulbs and luminaries which either utilize new interface standards or are compatible with existing or legacy interface standards, such as typical Edison-based sockets and interfaces, e.g., E12, E14, E26, E27, or GU-10 lighting standards. Such an apparatus, method and system should provide the capability for dimmable LED-based lighting, including remotely controlled dimming and color control, using LED bulbs and luminaries having comparatively few components, allowing lower cost manufacturing and corresponding savings to the consumer. Lastly, such an apparatus, method and system should provide comparative ease of use for a consumer, both for installation and bulb replacement. 
     SUMMARY OF THE INVENTION 
     The exemplary embodiments of the present invention provide numerous advantages. Exemplary embodiments provide a comparatively lower cost solution to provide LED-based lighting. Various exemplary or representative apparatuses, methods and systems are disclosed which are suitable for replacing the problematic triac dimmer switches and other legacy wall-mounted switches. Various exemplary or representative apparatuses, methods and systems are disclosed which further provide for the use of LED bulbs and luminaries which either utilize new interface standards or are compatible with existing or legacy interface standards, such as typical Edison-based sockets and other standard interfaces mentioned above and below. Various exemplary embodiments provide the capability for dimmable LED-based lighting, including remotely controlled dimming and color control, using LED bulbs and luminaries having comparatively few components, allowing lower cost manufacturing and corresponding savings to the consumer. In addition, various exemplary or representative apparatuses, methods and systems are disclosed which provide comparative ease of use for a consumer, both for installation and bulb replacement. 
     An exemplary or representative distributed solid-state lighting system is disclosed, which comprises a central power source coupleable to an AC input power source, and one or more terminal lighting apparatuses coupled to and spaced apart from the central power source. 
     An exemplary or representative central power source comprises: an AC/DC rectifier coupled to a DC/DC converter to convert the AC input power to a first DC voltage level; a central user interface to receive user input for a selected brightness level; and a central controller coupled to the DC/DC converter, the central controller to provide a first control signal to the DC/DC converter in response to the user input to provide a second DC voltage level corresponding to the selected brightness level. 
     In an exemplary or representative embodiment, each terminal lighting apparatus may comprise: a plurality of light emitting diodes; a current source or regulator coupled to the plurality of light emitting diodes; and a terminal controller coupled to the current source or regulator and, in response to the second DC voltage level, to provide a second control signal to the current source or regulator to provide a selected current level of the plurality of light emitting diodes corresponding to the selected brightness level. 
     Another exemplary or representative distributed solid-state lighting system is disclosed, comprising: a central power source coupleable to an AC input power source, the central power source to provide a selected DC output voltage level corresponding to a user selected brightness level; and one or more terminal lighting apparatuses coupled to and spaced apart from the central power source, each terminal lighting apparatus comprising: a plurality of light emitting diodes; and a current source or regulator coupled to the plurality of light emitting diodes. 
     Yet another exemplary or representative distributed solid-state lighting system is disclosed, comprising: one or more terminal lighting apparatuses, each terminal lighting apparatus comprising a plurality of light emitting diodes coupled to a current source or regulator; and a central power source coupleable to an AC input power source and coupled to and spaced apart from the one or more terminal lighting apparatuses, the central power source to provide a selected DC output voltage level to the one or more terminal lighting apparatuses. In various exemplary or representative embodiments, the selected DC output voltage level corresponds to a user selected brightness level. 
     In various exemplary or representative embodiments, for example, the central controller is to determine the second DC voltage level Vout as: 
         V out= pΔV outmax+ V outmin 
     in which “ρ” is a user selectable brightness level and corresponds to 
     
       
         
           
             
               ρ 
               = 
               
                 
                   I 
                   out 
                 
                 
                   I 
                   outn 
                 
               
             
             , 
           
         
       
     
     ΔVoutmax=Voutmax−Voutmin, Iout is the selected current level of the plurality of light emitting diodes for one or more terminal lighting apparatuses, Ioutn is the nominal current level of the plurality of light emitting diodes for one or more terminal lighting apparatuses, Voutmax=Vinmax in which Vinmax is the maximum input voltage to the one or more terminal lighting apparatuses, and Voutmin=Vinmin in which Vinmin is the minimum input voltage to the one or more terminal lighting apparatuses. 
     Also in various exemplary or representative embodiments, for example, the terminal controller is to determine the LED current Iout as proportional to the input voltage Vin, in which Iout is the selected current level of the plurality of light emitting diodes for the terminal lighting apparatus having the terminal controller, and Vin the sensed input voltage of the terminal lighting apparatus. Such proportionality may be linear or nonlinear, as described in greater detail below. 
     In various exemplary or representative embodiments, the terminal controller is to determine the LED current Iout as linearly proportional to the input voltage Vin, namely, Iout=μVin, in which μ is a linear transfer function, Iout is the selected current level of the plurality of light emitting diodes for the terminal lighting apparatus having the terminal controller, and Vin the sensed input voltage of the terminal lighting apparatus. 
     In another exemplary or representative embodiment, also for example, the terminal controller is to determine the LED current Iout as linearly proportional to the input voltage Vin, namely, Iout=μVin, where μ is a linear transfer function, 
     
       
         
           
             
               μ 
               = 
               
                 
                   
                     ( 
                     
                       
                         V 
                         in 
                       
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                         V 
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                     ) 
                   
                    
                   
                     I 
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                   Δ 
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                     V 
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             , 
           
         
       
     
     in which ΔVinmax=Vinmax−Vinmin, Iout is the selected current level of the plurality of light emitting diodes for one or more terminal lighting apparatuses, Ioutn is the nominal current level of the plurality of light emitting diodes for one or more terminal lighting apparatuses, Vinmax is the maximum input voltage to the one or more terminal lighting apparatuses, Vinmin is the minimum input voltage to the one or more terminal lighting apparatuses, and Vin the sensed input voltage of the terminal lighting apparatus. 
     In a selected exemplary or representative embodiment, the central user interface further comprises a scanner to scan a plurality of machine-readable encoded fields. Also for example, the plurality of machine-readable encoded fields may comprise data encoding a plurality of operational parameters for a given terminal lighting apparatus, such as any of the various Vinmax, Vinmin, and ΔVinmax parameters mentioned above. In various exemplary or representative embodiments, the central controller further is to utilize the plurality of operational parameters to determine the second DC voltage level provided to the one or more terminal lighting apparatuses. 
     In various exemplary or representative embodiments, the plurality of operational parameters comprise at least two operational parameters selected from the group consisting of: a maximum input voltage, a minimum input voltage, a maximum input current, a minimum input current, a nominal power level, a voltage level at a nominal current level, a minimum dimming level, an adjustable color temperature range, a unique identifier, and combinations thereof. 
     In an exemplary or representative embodiment, a current source or regulator comprises: a fuse; and a thermal current regulator. 
     In another exemplary or representative embodiment, a current source or regulator comprises a converter selected from the group consisting of: a buck converter; a boost converter; a buck-boost converter; a flyback converter; a sepic converter; and combinations thereof. 
     In yet another exemplary or representative embodiment, a current source or regulator comprises: a fuse; a current source; and a voltage divider to provide an operating voltage to the current source. 
     In an exemplary or representative embodiment, a terminal lighting apparatus may further comprise: a terminal controller coupled to the current source or regulator and, in response to the second DC voltage level, provides a second control signal to the current source or regulator to provide a selected current level of the plurality of light emitting diodes corresponding to the selected brightness level. 
     In another exemplary or representative embodiment, the plurality of light emitting diodes further comprise a plurality of series-connected light emitting diodes forming a plurality of channels of light emitting diodes, each channel corresponding to a different emission color of light emitting diodes, and wherein each terminal lighting apparatus further comprises: a remote user interface to receive user input for a selected emission color or color temperature of a plurality of emission colors and color temperatures. 
     In yet another exemplary or representative embodiment, a system may further comprise: an inverter to convert the second DC voltage level to an AC voltage level having a frequency in the range of about 500 Hz to 90 kHz. For such an exemplary or representative embodiment, a current source or regulator may comprise: a transformer; and a rectifier. 
     As another exemplary or representative embodiment, the plurality of light emitting diodes may be coupled in series to form a series-connected current path and the current source or regulator may comprise: a transformer; a rectifier; and a plurality of switches coupled to the plurality of light emitting diodes to switch a selected light emitting diode in or out of the series-connected current path. 
     Exemplary or representative methods of providing power to a spatially-distributed plurality of terminal lighting apparatuses, each comprising a plurality of light emitting diodes, are also disclosed. An exemplary or representative method comprises: receiving a selected brightness level through a user interface; using a central controller, determining a dimming level “ρ”; using a central controller, determining an output voltage or output current level; rectifying an input AC voltage (current) and providing corresponding DC output voltage and current levels; and monitoring output voltage or output current levels and providing a first feedback signal to maintain the output voltage or output current level at the determined level. 
     In an exemplary or representative method embodiment, the output voltage is calculated as Vout=ρΔVoutmax+Voutmin, in which “ρ” is a user selectable brightness level and corresponds to 
     
       
         
           
             
               ρ 
               = 
               
                 
                   I 
                   out 
                 
                 
                   I 
                   outn 
                 
               
             
             , 
           
         
       
     
     ΔVoutmax=Voutmax−Voutmin, Iout is the selected current level of the plurality of light emitting diodes for one or more terminal lighting apparatuses, Ioutn is the nominal current level of the plurality of light emitting diodes for one or more terminal lighting apparatuses, Voutmax=Vinmax in which Vinmax is the maximum input voltage to the one or more terminal lighting apparatuses, and Voutmin=Vinmin in which Vinmin is the minimum input voltage to the one or more terminal lighting apparatuses. 
     An exemplary or representative method may further comprise: using an input scanner, receiving a plurality of operational parameters corresponding to a selected terminal LED lighting apparatus. For example, the plurality of operational parameters may be encoded in a UPC-barcode or QR code format. 
     An exemplary or representative method may further comprise: receiving an input voltage; using a terminal controller and using the received input voltage level, calculating or determining an LED current level Iout for the plurality of light emitting diodes of a selected terminal lighting apparatus of the plurality of terminal lighting apparatuses; setting the LED current level to the value of Iout; and monitoring the LED current level and providing a second feedback signal to maintain the LED current level at the determined level lout. 
     In another exemplary or representative embodiment, a method is disclosed for dimming a brightness level of a terminal lighting apparatus, comprising a plurality of light emitting diodes, with the exemplary or representative method comprising: receiving an input voltage at the terminal lighting apparatus; using a terminal controller and using the received input voltage level, calculating or determining an LED current level Iout; setting the LED current level to the value of Iout; and monitoring the LED current level and providing a feedback signal to maintain the LED current level at the determined level Iout. 
     For example, the LED current level Iout may be calculated as Iout=μVin, where μ is a selected transfer function, Iout is the selected current level of the plurality of light emitting diodes, and Vin the sensed input voltage of the selected terminal lighting apparatus, as mentioned above. Also for example, μ may be a linear transfer function, such as 
     
       
         
           
             
               μ 
               = 
               
                 
                   
                     ( 
                     
                       
                         V 
                         in 
                       
                       - 
                       
                         V 
                         inmin 
                       
                     
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                    
                   
                     I 
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     or μ may be a nonlinear transfer function, as mentioned above and as further described below. 
     In another exemplary or representative embodiment, the LED current level Iout is determined using the sensed value of Vin as an index into a look up table stored in memory. 
     An exemplary or representative kit for a distributed solid-state lighting system is also disclosed. For example, such a kit may comprise: a central power source and one or more terminal lighting apparatuses. Such a central power source may comprise: an AC/DC rectifier coupled to a DC/DC converter to convert an AC input power to a first DC voltage level; a central user interface to receive user input for a selected brightness level; and a central controller coupled to the DC/DC converter, the central controller to provide a first control signal to the DC/DC converter in response to the user input to provide a second DC voltage level corresponding to the selected brightness level. Each terminal lighting apparatus may comprise: a plurality of light emitting diodes; a current source or regulator coupled to the plurality of light emitting diodes; and a terminal controller coupled to the current source or regulator and, in response to the second DC voltage level, to provide a second control signal to the current source or regulator to provide a selected current level of the plurality of light emitting diodes corresponding to the selected brightness level. 
     In an exemplary or representative kit, for example, each terminal lighting apparatus is embodied as an LED bulb or luminary having an interface compatible with an interface standard selected from a group consisting of: an E12 lighting standard, an E14 lighting standard, an E26 lighting standard, an E27 lighting standard, a GU-10 lighting standard, and combinations thereof. 
     In another exemplary or representative embodiment, a solid-state lighting apparatus is provided which is coupleable to an AC input power source having an AC line frequency, with the apparatus comprising: an AC rectifier to convert an AC voltage level to a rectified voltage level; a plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes; a plurality of first switches correspondingly coupled to the plurality of segments of light emitting diodes to switch a selected segment of light emitting diodes into or out of a series light emitting diode current path; a first terminal controller coupled to the plurality of first switches to control switching of a corresponding segment of light emitting diodes into the series light emitting diode current path; a second switch coupled in series with each segment of light emitting diodes of the plurality of segments of light emitting diodes to control current through the series light emitting diode current path; and a second terminal controller coupled to the second switch, the second terminal controller to turn the second switch on and off at a switching frequency at least about four to about one thousand times greater than the AC line frequency and thereby correspondingly turn on and off the plurality of light emitting diodes at the switching frequency. In an exemplary or representative embodiment, the apparatus may further comprise: a first capacitor coupled to the AC rectifier; and a third switch coupled to the first capacitor and to the second terminal controller; wherein the second terminal controller further is to turn the third switch on and off to control charging of the first capacitor. In an exemplary or representative embodiment, the apparatus also may further comprise: one or more light emitting diodes coupled to the first capacitor; and/or a second, filter capacitor. 
     In an exemplary or representative embodiment, the second terminal controller further is to turn the second switch on and off in response to a plurality of voltage threshold levels. In an exemplary or representative embodiment, the second terminal controller may comprise: a plurality of comparators, each comparator to compare a rectified AC voltage level to a corresponding predetermined voltage threshold level; and may further comprise: a rectified AC voltage level peak detector. 
     In various exemplary or representative embodiments, the second terminal controller further is to turn the second switch on and off in response to a random or pseudo-random signal; the second terminal controller further is to turn the second switch on and off at a frequency which is not a harmonic of the AC line frequency; and/or the second terminal controller further is to turn the second switch on and off in response to a dimming level signal provided by a central controller to control a level of light emission from the plurality of light emitting diodes. 
     In another exemplary or representative embodiment, a method of providing power to a plurality of light emitting diodes couplable to receive a rectified AC voltage is disclosed, with the plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes each comprising at least one light emitting diode, the plurality of segments of light emitting diodes coupled to a plurality of first switches, a second switch coupled in series with each segment of light emitting diodes of the plurality of segments of light emitting diodes, and with the method comprising: using a first terminal controller coupled to the plurality of first switches, switching a selected segment of light emitting diodes into or out of a series light emitting diode current path; and using a second terminal controller coupled to the second switch, turning the second switch on and off at a switching frequency at least about four to about one thousand times greater than the AC line frequency and thereby correspondingly turning on and off the plurality of light emitting diodes at the switching frequency. 
     In an exemplary or representative embodiment, the method may further comprise: using the second terminal controller, turning a third switch on and off to control charging of a capacitor. In another exemplary or representative embodiment, the step of turning the second switch on and off further comprises turning the second switch on and off in response to a plurality of voltage threshold levels. 
     In an exemplary or representative embodiment, the method may further comprise: using the second terminal controller, comparing a rectified AC voltage level to a plurality of corresponding predetermined voltage threshold levels, and also may further comprise: using the second terminal controller, detecting a peak of a rectified AC voltage level. 
     In another exemplary or representative embodiment, the step of turning the second switch on and off further comprises turning the second switch on and off in response to a random or pseudo-random signal. In another exemplary or representative embodiment, the step of turning the second switch on and off further comprises turning the second switch on and off at a frequency which is not a harmonic of the AC line frequency. In yet another exemplary or representative embodiment, the step of turning the second switch on and off further comprises turning the second switch on and off in response to a dimming level signal provided by a central controller to control a level of light emission from the plurality of light emitting diodes. 
     In another exemplary or representative embodiment, a solid-state lighting apparatus is disclosed which is coupleable to an AC input power source having an AC line frequency, with the apparatus comprising: an AC rectifier to convert an AC voltage level to a rectified voltage level; a plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes; a plurality of first switches correspondingly coupled to the plurality of segments of light emitting diodes to switch a selected segment of light emitting diodes into or out of a series light emitting diode current path; a first terminal controller coupled to the plurality of first switches to control switching of a corresponding segment of light emitting diodes into the series light emitting diode current path; a second switch coupled in series with each segment of light emitting diodes of the plurality of segments of light emitting diodes to control current through the series light emitting diode current path; and a second terminal controller coupled to the second switch, the second terminal controller to turn the second switch on and off in response to a plurality of voltage threshold levels and at a switching frequency at least about four to about one thousand times greater than the AC line frequency and thereby correspondingly turn on and off the plurality of light emitting diodes at the switching frequency. 
     In another exemplary or representative embodiment, a solid-state lighting apparatus is disclosed which is coupleable to an AC input power source having an AC line frequency, with the apparatus comprising: an AC rectifier to convert an AC voltage level to a rectified voltage level; a plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes; a plurality of first switches correspondingly coupled to the plurality of segments of light emitting diodes to switch a selected segment of light emitting diodes into or out of a series light emitting diode current path; a first terminal controller coupled to the plurality of first switches to control switching of a corresponding segment of light emitting diodes into the series light emitting diode current path; a second switch coupled in series with each segment of light emitting diodes of the plurality of segments of light emitting diodes to control current through the series light emitting diode current path; and a second terminal controller coupled to the second switch, the second terminal controller to turn the second switch on and off in response to a random or pseudo-random signal and thereby correspondingly turn on and off the plurality of light emitting diodes at a random or pseudo-random switching frequency, which may be at least about four to about one thousand times greater than the AC line frequency. 
     In an exemplary or representative embodiment, the second terminal controller further is to turn the second switch on and off in response to a dimming level signal provided by a central controller to control a level of light emission from the plurality of light emitting diodes. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the present invention will be more readily appreciated upon reference to the following disclosure when considered in conjunction with the accompanying drawings, wherein like reference numerals are used to identify identical components in the various views, and wherein reference numerals with alphabetic characters are utilized to identify additional types, instantiations or variations of a selected component embodiment in the various views, in which: 
         FIG. 1  is a block diagram illustrating an exemplary or representative lighting system, an exemplary or representative central (host) power source, and a first exemplary or representative terminal LED lighting apparatus. 
         FIG. 2  is a flow diagram illustrating an exemplary or representative preoperational method for set up and exchange modes of an exemplary or representative lighting system and an exemplary or representative central (host) power source. 
         FIG. 3 , divided into  FIGS. 3A and 3B , is a flow diagram illustrating an exemplary or representative method of operating an exemplary or representative lighting system, an exemplary or representative central (host) power source, and an exemplary or representative terminal LED lighting apparatus. 
         FIG. 4  is a graph illustrating exemplary or representative voltage and current waveforms for intelligent dimming using an exemplary or representative lighting system, an exemplary or representative central (host) power source, and an exemplary or representative terminal LED lighting apparatus. 
         FIG. 5  is a block and circuit diagram illustrating a second exemplary or representative terminal LED lighting apparatus for use in a comparatively low voltage DC system. 
         FIG. 6  is a block and circuit diagram illustrating a third exemplary or representative terminal LED lighting apparatus for use in a comparatively high voltage DC system. 
         FIG. 7  is a block diagram illustrating a second exemplary or representative system having both comparatively high and low DC levels. 
         FIG. 8  is a block and circuit diagram illustrating a fourth exemplary or representative terminal LED lighting apparatus for use in a comparatively high frequency system. 
         FIG. 9  is a block and circuit diagram illustrating a fifth exemplary or representative terminal LED lighting apparatus for use in a comparatively high frequency system. 
         FIG. 10  is a block and circuit diagram illustrating a sixth exemplary or representative terminal LED lighting apparatus for use in a comparatively high frequency system. 
         FIG. 11  is a block and circuit diagram illustrating a seventh exemplary or representative terminal LED lighting apparatus for a comparatively low voltage DC system. 
         FIG. 12  is a block and circuit diagram illustrating an eighth exemplary or representative terminal LED lighting apparatus for a comparatively low voltage DC system. 
         FIG. 13  is a block and circuit diagram illustrating a ninth exemplary or representative terminal LED lighting apparatus for a comparatively low voltage DC system. 
         FIG. 14  is a block and circuit diagram illustrating a tenth exemplary or representative terminal LED lighting apparatus for a comparatively low voltage DC system. 
         FIG. 15  is a diagram illustrating exemplary or representative machine-readable encoded fields, such as barcode fields or QR code fields, for use with an exemplary or representative apparatus, method and system. 
         FIG. 16  is a graphical diagram illustrating an exemplary or representative full wave rectified voltage, zero crossing intervals, operating regions and non-operating regions of various exemplary embodiments. 
         FIG. 17  is a block and circuit diagram illustrating an eleventh exemplary or representative terminal LED lighting apparatus for use in a system having a typical 50 Hz or 60 Hz AC line voltage or in a comparatively higher frequency system. 
         FIG. 18  is a block and circuit diagram illustrating control circuitry which may be utilized in a second terminal (or remote) controller. 
         FIG. 19  is a block and circuit diagram illustrating additional control circuitry which may be utilized in a second terminal (or remote) controller. 
         FIG. 20  is a graphical diagram illustrating an exemplary or representative full wave rectified voltage, zero crossing intervals, and on and off intervals of various exemplary embodiments, when the on and off times are modulated by a random or pseudo-random signal. 
     
    
    
     DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS 
     While the present invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described herein in detail specific exemplary embodiments thereof, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. In this respect, before explaining at least one embodiment consistent with the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of components set forth above and below, illustrated in the drawings, or as described in the examples. Methods and apparatuses consistent with the present invention are capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purposes of description and should not be regarded as limiting. 
     As mentioned above, an exemplary or representative distributed solid-state lighting system comprises a central power source coupleable to an AC input power source, and one or more terminal lighting apparatuses coupled to and spaced apart from the central power source.  FIG. 1  is a block diagram illustrating an exemplary or representative lighting system  100 , an exemplary or representative central (host) power source  125 , and a first exemplary or representative terminal LED lighting apparatus  150 . Referring to  FIG. 1 , a lighting system  100  comprises a central (host) power source  125  and one or more terminal LED lighting apparatuses  150 . The one or more terminal LED lighting apparatuses  150  are coupled, in parallel, to a power transmission line  195  coupled to the central (host) power source  125 . Any number of terminal LED lighting apparatuses  150  may be utilized, up to the driving capacity of the central (host) power source  125 . The power transmission line  195  may be any type of power distribution line, currently known or developed in the future, with any corresponding power rating, such as a typical 2, 3, or 4 or more wire system found in a typical home, office, factory, etc., rated for 15-30 A, for example and without limitation. 
     For example and without limitation, in an exemplary or representative embodiment, a central (host) power source  125  may be embodied to have a legacy-compatible form factor and installed in a standard junction box to replace an existing or legacy light switch, such as a triac-based dimmer switch. Similarly, in a first alternative, terminal LED lighting apparatuses  150  may be embodied as LED bulbs and/or luminaries compatible with existing or legacy form factor and interface standards, such as typical Edison-based sockets and interfaces, e.g., E12, E14, E26, E27, or GU-10 lighting standards, and following the input of operational parameters into the central (host) power source  125  as discussed below, may be inserted into existing lighting sockets to replace legacy incandescent or CFL bulbs, also for example and without limitation. A central (host) power source  125  and a terminal LED lighting apparatuses  150 , of course, are not required to be compatible with existing or legacy systems, and in other embodiments, may have any selected or desired form factor and electrical interface. Accordingly, in a second alternative, terminal LED lighting apparatuses  150  may be embodied as LED bulbs and/or luminaries which have a new and different form factor and/or interface (e.g., so that they are not inserted by mistake into a legacy socket which is not coupled to a central (host) power source  125 ), and following the input of operational parameters into the central (host) power source  125  as discussed below, may be inserted into corresponding lighting sockets configured to the new and different interface standard, also for example and without limitation. 
     The system  100 , therefore, is not required to and generally does not utilize LED driver circuitry which is co-located with the LEDs, such as an AC/DC rectifier or a DC/DC converter. Rather, a distributed system  100  is implemented, with centrally located drive and control circuitry, along with some or no distributed control and regulation circuitry which may be co-located with the LEDs, depending upon the desired sophistication of the selected terminal LED lighting apparatus  150 . 
     An exemplary or representative central (host) power source  125  typically comprises an AC/DC rectifier  105 , a DC/DC converter  110 , a central (host) controller  120 , and a user interface  135 . The AC/DC rectifier  105  is coupled to an alternating current (“AC”) line  130 , also referred to herein equivalently as an AC power line or an AC power source, such as a household AC line or other AC mains power source provided by an electrical utility, and converts the input AC voltage and current to DC. The AC/DC rectifier  105  may be any type of rectifier, currently known or developed in the future, such as a full-wave rectifier, a full-wave bridge, a half-wave rectifier, an electromechanical rectifier, or another type of rectifier, for example and without limitation. The direct current (“DC”) voltage/current from the AC/DC rectifier  105  is then up converted to a higher DC voltage/current level or down converted to a lower DC voltage/current level using DC/DC converter  110 , which may be any type of DC/DC converter having any configuration, currently known or developed in the future, such as a buck converter, a boost converter, a buck-boost converter, a flyback converter, etc., and may be operated in any number of modes (discontinuous current mode, continuous current mode, and critical conduction mode), any and all of which are considered equivalent and within the scope of the present invention, for example and without limitation. 
     The DC/DC converter  110  is controlled by the central (host) controller  120 , which receives one or more feedback signals from the DC/DC converter  110  and which provides one or more current and/or voltage set or other control signals to the DC/DC converter  110 , based upon user input, such as a selected dimming level or color temperature, and based upon the input of various operational parameters for the system  100 . Based upon such user preferences and input operational parameters, as discussed in greater detail below, the central (host) controller  120  calculates or otherwise determines the voltage and/or current settings for one or more control signals provided to the DC/DC converter  110 , to control the output DC voltage, current and/or power levels provided as input voltage, current and/or power levels to the terminal LED lighting apparatuses  150 . For example, the DC/DC converter  110  typically includes a MOSFET (not separately illustrated) operable in a linear mode (and also typically in a saturation mode) and under the control of one or more control signals provided by the central (host) controller  120 , to raise or lower the output DC voltage, current and/or power levels. The various operational parameters for the system  100 , such as maximum and minimum voltage, current and/or power levels, discussed in greater detail below, are provided to the central (host) controller  120  via the user interface  135 , and may be stored in a memory (typically non-volatile) that may be provided within the central (host) controller  120  or stored within an optional memory  115 . Also as described in greater detail below, these various operational parameters may be varied throughout the use and lifetime of the system  100  such as, for example, when any of the one or more terminal LED lighting apparatuses  150  are removed or replaced. The central (host) controller  120  (and any optional memory  115 ) may be implemented as currently known or developed in the future, as described in greater detail below, such as using a processor, a controller, a state machine, combinational logic, etc., for example and without limitation. 
     Also illustrated in  FIG. 1  are various optional input and output (“I/O”) devices and articles of manufacture which may be utilized with or incorporated within a user interface  135  and/or  165  for system display and input of user preferences and operational parameters for the system  100 , illustrated as wireless remote control  175 , machine-readable encoded fields  170  (e.g., a non-transitory, scannable (or otherwise tangible and machine-readable) encoded article of manufacture such as a UPC-type barcode or a QR (“Quick Response”) code), a display  190  (such as a touch screen display, an LED display, an LCD display, etc.), a switch control  185  (such as an on/off switch, a dimming input (e.g., dimming knob, slideable dimming control, or control button(s)), and/or a keypad  180 , any of which may be implemented as currently known or developed in the future. While the user interfaces  135 ,  165  are illustrated as having wireless communication capability (e.g., Bluetooth, IR, IEEE 802.11, etc.), in various exemplary embodiments, any of the various controllers  120 ,  160  instead may be implemented to have such wireless capability for user communication. 
     An exemplary or representative terminal LED lighting apparatus  150  comprises one or more light emitting diodes (“LEDs”)  140 , and optionally and in any of various combinations, may further comprise a current source (or regulator)  145 , a terminal (or remote) controller  160 , one or more sensors  155 , a user interface  165 , and potentially an optional memory circuit (not separately illustrated, and which also may be included within a terminal (or remote) controller  160 ). One or more exemplary or representative terminal LED lighting apparatuses  150  are typically distributed in different locations within one or more rooms of an office, house, etc., and are coupled in parallel to power transmission line  195 , each via a corresponding current source (or regulator)  145 , to receive power from the DC/DC converter  110  of the central (host) power source  125 . Those having skill in the electronic arts will recognize that instead of utilizing a current source (or regulator)  145 , a power regulator (not separately illustrated) may be utilized equivalently, controlling the power (both current and voltage) provided to the LEDs  140 . Accordingly, use of such a power regulator is considered equivalent and within the scope of the disclosure. 
     The current source (or regulator)  145  may be implemented to be quite simple or complex, as currently known or developed in the future, with many exemplary or representative embodiments illustrated in greater detail below, and provides power (voltage and current) to the LEDs  140 , which may be any type or kind of LEDs, currently known or developed in the future, with any corresponding lumen output, color temperature, power, current and voltage ratings, and which may have any of various configurations, such as parallel, serial, and/or combinations of both. In other exemplary embodiments, the current source (or regulator)  145  may be optional and omitted, or otherwise may have so few components that regulation is minimal, such as merely providing current and temperature overload protection. The terminal (or remote) controller  160  also may include internal memory capabilities and may be implemented as currently known or developed in the future, as described in greater detail below, such as using a processor, a controller, a state machine, combinational logic, etc., also for example and without limitation. Optional sensors  155  and user interface  165  may be implemented to be simple or complex, as currently known or developed in the future, with many exemplary or representative embodiments illustrated in greater detail below. For example and without limitation, a sensor  155  may be implemented as a current sense resistor or a voltage divider. Also for example, a user interface  165  may be implemented simply to receive wireless signals (e.g., for dimming or color temperature control over the individual terminal LED lighting apparatuses  150 ) from a wireless remote control  175 . 
     As illustrated in  FIG. 1 , the terminal LED lighting apparatus  150  is particularly suitable for dimming applications. Other embodiments of terminal LED lighting apparatuses  150  are also illustrated with fewer components (e.g., only current and temperature overload protection) and, of course, allows less control over output brightness levels. Referring to  FIG. 1 , the exemplary or representative terminal LED lighting apparatus  150  utilizes the terminal (or remote) controller  160  to receive feedback signals from one or more sensors  155  (such as any of LED current levels, output power, LED DC voltage levels, etc.), receive user input via remote user interface  165 , and provide control signals (such as LED set current levels for a desired dimming level) to the current source (or regulator)  145 . As mentioned above, the terminal LED lighting apparatus  150  may be operated in any of various modes, such as continuous current mode, discontinuous current mode, or other modes, any and all of which are within the scope of the disclosure. 
     The central (host) controller  120  (and, therefore, also the central (host) power source  125  and system  100 ) has three operational modes: a set (or set up) operational mode, an automatic operational mode, and an exchange operational mode). As discussed in greater detail below with reference to  FIG. 15 , in exemplary embodiments, the terminal LED lighting apparatus  150  housing and/or its labeling or packaging includes an article of manufacture comprising one or more machine-readable encoded fields  170 , such as a scannable (or otherwise machine-readable) barcode or QR code, which includes a plurality of data fields encoding operational parameter information, such as minimum and maximum voltage and current levels for the selected type of terminal LED lighting apparatus  150  (or, as another option, for its incorporated string of LEDs  140 ). Other optional parameters may also be included within the machine-readable encoded fields  170 , such as maximum or minimum power levels, maximum operating temperature, etc. During set up (or set) or exchange operational modes, such machine-readable encoded fields  170  are scanned or otherwise read through the user interface  135 , a display  190 , or wireless remote control  175 , or another device which may function as such a remote control  175 , such as a smartphone with a corresponding scanning application, as known or developed in the future. In addition to UPC barcodes and QR encoding, any other type of machine-readable data encoding (and corresponding reading and uploading method) is considered equivalent and within the scope of the disclosure, including those that merely provide an index, link, number or identification into a look up table stored in a memory and having the corresponding operational parameters. The operational parameters for each terminal LED lighting apparatus  150  are thereby uploaded into the user interface  135  and stored in a memory  115  or internal memory of a central (host) controller  120 , and the corresponding terminal LED lighting apparatus  150  may then be installed (e.g., inserted into a socket) of the system  100 . Similarly, during an exchange mode, operational parameters may be deleted from memory for a terminal LED lighting apparatus  150  that is being removed from the system  100 , also by scanning of its machine-readable encoded fields  170 , and the operational parameters of the replacement terminal LED lighting apparatus  150  are then scanned and thereby uploaded into the central (host) power source  125 . This creates significant flexibility for the system  100  over its lifetime, which is not constrained by static operational parameters that are fixed by a manufacturer during device assembly, and instead may be modified and adjusted for user preferences and use of different types of terminal LED lighting apparatuses  150 , including those from different manufacturers. 
     It should also be understood, however, that in the event machine-readable encoded fields  170  are not available for any reason, the corresponding data may be entered (and deleted) manually, such as through other devices, such as display  190  (e.g., a touchscreen) or keypad  180 . 
     In addition, while system  100  is illustrated with the central (host) power source  125  functioning as a 2-way switch, those of skill in the art will recognize that the central (host) power source  125  may be easily extended to 3-way embodiments, 4-way embodiments, etc. 
       FIG. 2  is a flow diagram illustrating an exemplary or representative preoperational method for set up and exchange modes of an exemplary or representative lighting system  100  and an exemplary or representative central (host) power source  125 . Beginning with start step  200 , via user interface  135  or remote control  175 , a user may have the central (host) power source  125  enter the exchange mode, step  205 , such as to remove a failed LED bulb and replace it with a new one. The user may remove a terminal LED lighting apparatus  150 , such as a failed LED bulb, from its current location, step  210 , and delete the corresponding operational parameters from memory, such as by scanning the machine-readable encoded fields  170 , step  215 . When an additional terminal LED lighting apparatus  150  is to be removed, step  220 , the method returns to steps  210  and  215 . When all terminal LED lighting apparatuses  150  have been removed, step  220 , or when the user has the central (host) power source  125  enter the set up mode in step  225 , new operational parameters of a new or replacement terminal LED lighting apparatus  150  are input via user interface  135  or remote control  175  and stored in memory, such as optional memory  115  or a memory within central (host) controller  120 , step  230 . The user then installs a new or replacement terminal LED lighting apparatus  150 , such as by screwing it into a standard socket, step  235 . When an additional terminal LED lighting apparatus  150  is to be added, step  240 , the method returns to step  230 . When all terminal LED lighting apparatuses  150  have been added, step  240 , the central (host) controller  120  may then calculate or otherwise determine the nominal output voltage, current and/or power levels to be provided by the DC/DC converter  110  and other parameters, step  245 , as discussed in greater detail below, and the method may end, return step  250 . 
     Typically, a dimming level is set by user interface  135  (manually) or by a remote control  175 . In set mode, the central (host) controller  120  gets information from the machine-readable encoded fields  170  via the user interface  135  to set the maximum (and/or minimum) operational parameters of the central (host) power source  125  and saves this in the memory as a network configuration, including the number of terminal LED lighting apparatus  150   es  and their operational parameters, such as maximum voltages, current, power, etc. In exchange mode, the central (host) controller  120  gets the corresponding information on the failed terminal LED lighting apparatus  150  and the new, replacement terminal LED lighting apparatus  150 , and recalculates or reconfigures the system  100  (or network) settings. Depending upon the degree of sophistication of the system  100 , the information input during set and exchange modes may also include the (network) location of the particular terminal LED lighting apparatus  150  within the system  100 . In automatic mode, the central (host) controller  120  performs various calculations, discussed below, provides corresponding control signals to the DC/DC converter  110 , and sets the dimming level for the terminal LED lighting apparatuses  150  based on the signals from the remote control  175  or user interface  135  (e.g., which may be manually input via display  190 , switch control  185 , or keypad  180 ). 
     In an exemplary embodiment, the central (host) controller  120  calculates or otherwise determines the dimming level “ρ” for the plurality of terminal LED lighting apparatuses  150 , in which (Equation 1): 
     
       
         
           
             
               ρ 
               = 
               
                 
                   I 
                   out 
                 
                 
                   I 
                   outn 
                 
               
             
             , 
           
         
       
     
     where Iout is the LED  140  current in a terminal LED lighting apparatus  150  for a user determined or selected dimming level and Ioutn is the nominal LED  140  current in a terminal LED lighting apparatus  150  with no dimming (e.g., full brightness). In turn, Iout and Ioutn are related as follows (Equation 2): 
     
       
         
           
             
               
                 I 
                 out 
               
               = 
               
                 
                   I 
                   outn 
                 
                  
                 
                   ( 
                   
                     1 
                     - 
                     
                       
                         
                           V 
                           inmax 
                         
                         - 
                         
                           V 
                           in 
                         
                       
                       
                         
                           V 
                           inmax 
                         
                         - 
                         
                           V 
                           inmin 
                         
                       
                     
                   
                   ) 
                 
               
             
             , 
           
         
       
     
     where Vin is the input voltage to the terminal LED lighting apparatus  150 , Vinmax is the maximum input voltage to the terminal LED lighting apparatus  150 , Vinmin is the minimum input voltage to the terminal LED lighting apparatus  150 , resulting in the dimming level “ρ” (Equation 3): 
     
       
         
           
             ρ 
             = 
             
               
                 ( 
                 
                   1 
                   - 
                   
                     
                       
                         V 
                         inmax 
                       
                       - 
                       
                         V 
                         in 
                       
                     
                     
                       
                         V 
                         inmax 
                       
                       - 
                       
                         V 
                         inmin 
                       
                     
                   
                 
                 ) 
               
               . 
             
           
         
       
     
     In turn, the relationship between the input voltage to the terminal LED lighting apparatus  150  and the selected dimming level is (Equation 4): 
         V in=ρ( V   inmax   −V   inmin )+ V   inmin ,
 
       or Equation 5: 
         V in=ρΔ V inmax+ V inmin
 
     where (Equation 6): ΔVinmax=Vinmax−Vinmin 
     A dimming transfer function “μL” may then be calculated or otherwise determined as (Equation 7): 
     
       
         
           
             
               μ 
               = 
               
                 
                   
                     I 
                     out 
                   
                   
                     I 
                     in 
                   
                 
                 = 
                 
                   
                     Δ 
                      
                     
                         
                     
                      
                     
                       V 
                       in 
                     
                      
                     
                       I 
                       outn 
                     
                   
                   
                     Δ 
                      
                     
                         
                     
                      
                     
                       V 
                       inmax 
                     
                      
                     
                       V 
                       in 
                     
                   
                 
               
             
             , 
           
         
       
     
     where ΔVin=Vin−Vinmin, namely, the change in input voltage provided to the terminal LED lighting apparatus  150  from the minimum voltage input to the terminal LED lighting apparatus  150 , where Vin the sensed input voltage of the terminal LED lighting apparatus  150 . (Equivalently, ΔVin could be defined as a change from the maximum input voltage, where ΔVin=Vinmax−Vin, namely, the change in input voltage provided to the terminal LED lighting apparatus  150  from the nominal or maximum voltage input to the terminal LED lighting apparatus  150  without dimming, also where Vin the sensed input voltage of the terminal LED lighting apparatus  150 .) For example, using the calculated transfer function μ, each terminal (or remote) controller  160  may calculate or otherwise determine the current to be provided to LEDs  140  as (Equation 8): 
         I out=μ V in.
 
     As discussed in greater detail below, this relationship between input voltage and current to be provided to the LEDs  140  is quite powerful and highly novel, as dimming control can be provided to each terminal LED lighting apparatus  150  by a change in the output voltage provided by the central (host) power source  125 . Sensing the input voltage Vin, the terminal (or remote) controller  160  then determines the appropriate, corresponding current level Iout to be provided to the LEDs  140 , thereby raising or lowering (dimming) the output brightness level accordingly. This is very different than prior art dimming through a triac-based device, which provides dimming by clipping or eliminating a portion of the AC voltage/current provided to the lamp. 
     It should also be noted that while the various exemplary equations and transfer function illustrate a linear relationship between the input voltage Vin and the current level Iout to be provided to the LEDs  140 , nonlinear relationships are also within the scope of the disclosure and considered equivalent (and are illustrated and discussed with reference to  FIG. 4 ). 
     Assuming that voltage drop in the transmission power line  195  is negligible, the output voltage of the central (host) power source  125  can be considered to be effectively equal to the input voltage to the terminal LED lighting apparatuses  150 , such that (Equations 8, 9, 10 and 11): 
         V out= V in; 
         V outmin= V inmin; 
         V outmax= V inmax; and 
       Δ V outmax=Δ V inmax.
 
     It should be noted, for each of these parameters, when a DC voltage and current are not being utilized, such as in the high frequency system discussed below, the voltage and current amplitudes may be utilized equivalently for these calculations. As a result, the central controller  120  may determine the second DC voltage level Vout as (Equation 12): Vout=ρΔVoutmax+Voutmin, in which “ρ” is a user selectable brightness level and corresponds to 
     
       
         
           
             
               ρ 
               = 
               
                 
                   I 
                   out 
                 
                 
                   I 
                   outn 
                 
               
             
             , 
           
         
       
     
     ΔVoutmax=Voutmax−Voutmin, Iout is the selected current level of the plurality of light emitting diodes  140  for one or more terminal lighting apparatuses  150 , Ioutn is the nominal current level of the plurality of light emitting diodes  140  for one or more terminal lighting apparatuses  150 , Voutmax=Vinmax in which Vinmax is the maximum input voltage to the one or more terminal lighting apparatuses  150 , and Voutmin=Vinmin in which Vinmin is the minimum input voltage to the one or more terminal lighting apparatuses  150 . Similarly, the terminal controller  160  may determine the LED current Iout as linearly proportional to the input voltage Vin (Equation 13): Iout=μVin, where μ is a linear transfer function, 
     
       
         
           
             
               μ 
               = 
               
                 
                   
                     ( 
                     
                       
                         V 
                         in 
                       
                       - 
                       
                         V 
                         inmin 
                       
                     
                     ) 
                   
                    
                   
                     I 
                     outn 
                   
                 
                 
                   Δ 
                    
                   
                       
                   
                    
                   
                     V 
                     inmax 
                   
                    
                   
                     V 
                     in 
                   
                 
               
             
             , 
           
         
       
     
     in which ΔVinmax=Vinmax−Vinmin, Iout is the selected current level of the plurality of light emitting diodes  140  for one or more terminal lighting apparatuses  150 , Ioutn is the nominal current level of the plurality of light emitting diodes  140  for one or more terminal lighting apparatuses  150 , Vinmax is the maximum input voltage to the one or more terminal lighting apparatuses  150 , Vinmin is the minimum input voltage to the one or more terminal lighting apparatuses  150 , and Vin the sensed input voltage of the one or more terminal lighting apparatuses  150 . 
     As part of the set up or exchange process (step  245 ), or upon powering on (powering up) of the system  100 , the parameters Vout, Voutmin, Voutmax, and ΔVoutmax may be calculated by the central (host) controller  120  using the various input operational parameters and the number of terminal LED lighting apparatuses  150  in the system  100 , or may be input via user interface  135  or remote control  175 . Similarly, the parameters Ioutn, Vinmin, Vinmax and ΔVinmax (and other parameters) for one or more terminal LED lighting apparatuses  150  may be provided directly to the terminal LED lighting apparatus(es)  150  by the manufacturer as part of or otherwise during device manufacture (e.g., input and stored in a terminal (or remote) controller  160  and its associated memory (not separately illustrated)), or may be calculated by the terminal (or remote) controller  160  using its input operational parameters, or may be input via remote user interface  155  or remote control  175 . As yet another alternative, during either set up (or exchange mode) or powering on, the central (host) power source  125  may transmit these values to the terminal LED lighting apparatuses  150 , such as through various handshaking mechanisms and/or power line signaling. 
       FIG. 3  is a flow diagram illustrating an exemplary or representative method of operating an exemplary or representative lighting system  100 , an exemplary or representative central (host) power source  125 , and an exemplary or representative terminal LED lighting apparatus  150 . The automatic mode method begins, start step  300 , when the system  100  is powered on by the user, and the user selects a brightness level, such as by pressing a button, flipping a switch, or moving a slideable indicator, for example and without limitation. (As part of step  300 , if not performed as step  245  mentioned above, the various operational parameters mentioned above may be determined and stored in the memories of the central (host) power source  125  and the terminal LED lighting apparatus  150 .) The central (host) controller  120  determines what brightness level has been selected, step  305 , and calculates or determines a dimming level p, step  310 , that corresponds to the selected brightness level. Based on the dimming level p, in step  315 , the central (host) controller  120  determines the output voltage and/or current levels, with Vout=ρΔVoutmax+Voutmin, and provides corresponding control signals, to the DC/DC converter  110 . For example, the calculated value of Vout may be provided as a reference voltage level in a feedback loop within the central (host) controller  120  or the DC/DC converter  110 . The AC/DC rectifier  105  rectifies the input AC voltage and the DC/DC converter  110 , using the control signals from the central (host) controller  120 , provides power, as the corresponding DC output voltage and current levels, to the terminal LED lighting apparatuses  150  over power transmission line(s)  195 , step  320 . The central (host) controller  120  monitors the DC output voltage and current levels, and provides any feedback signals to the DC/DC converter  110  to maintain the desired DC output voltage and current levels, step  325 . When the system  100  has not been powered off, step  330 , the method continues, and determines whether there has been any change in the selected dimming level, step  335 . When there is a change to the selected dimming level, step  335 , the method iterates, returning to step  305  and repeating steps  305 - 330 , and continues to provide the selected DC output voltage and current levels at the new dimming level. When the system  100  has been powered off, step  330 , the method may end, return step  370 . 
     As long as the system  100  has not been powered off, the method continues and the terminal LED lighting apparatuses  150  continue to receive input power from the DC/DC converter  110  at the selected DC output voltage and current levels. Continuing to refer to  FIG. 3 , a terminal (or remote) controller  160  monitors (senses and/or measures) the input voltage level (and/or current level) to the terminal LED lighting apparatus  150 , such as through a voltage sensor, step  340 , and calculates or otherwise determines the dimming transfer function μ and calculates of otherwise determines lout, step  345 . For example, the transfer function may be calculated as 
     
       
         
           
             
               μ 
               = 
               
                 
                   
                     ( 
                     
                       
                         V 
                         in 
                       
                       - 
                       
                         V 
                         inmin 
                       
                     
                     ) 
                   
                    
                   
                     I 
                     outn 
                   
                 
                 
                   Δ 
                    
                   
                       
                   
                    
                   
                     V 
                     inmax 
                   
                    
                   
                     V 
                     in 
                   
                 
               
             
             , 
           
         
       
     
     and the current Iout may be calculated as Iout=μVin, by digital or analog devices, as mentioned above. The terminal (or remote) controller  160  sets the LED  140  current level to the calculated value of Iout, such as by providing control signals to the current source (or regulator)  145 , step  350 , and the current source (or regulator)  145  provides power to the LEDs  140  at this set current level Iout, step  355 . Using sensor(s)  155 , the terminal (or remote) controller  160  monitors the LED  140  current (and/or voltage) levels, provides feedback signals to the current source (or regulator)  145  to adjust or maintain the LED  140  current (and/or voltage) levels at the selected Iout level (or a lower level, if needed, based on input parameters, such as maximum current levels, for example), step  360 . When there has been no change in the input voltage level (and/or current level) to the terminal LED lighting apparatus  150 , step  365 , the method continues, returning to step  355  to continue providing power to the LEDs  140 . When there is a change in the input voltage level (and/or current level) to the terminal LED lighting apparatus  150 , step  365 , the method returns to step  345  and iterates. 
     It should also be noted that instead of calculating a transfer function in step  345 , a terminal (or remote) controller  160  may also be configured to utilize the sensed input voltage Vin (or corresponding current level) as an index into a look up table, stored in memory, which then provides a corresponding level of Iout which may be utilized to set the LED  140  current level. In addition, as illustrated in  FIG. 4 , various nonlinear transfer functions may also be utilized. 
     It should be noted and those having skill in the art will recognize that the steps illustrated in  FIG. 3  may occur in a wide variety of orders, and may operate as simultaneous, iterative loops until the system  100  is powered off, a first loop occurring at the central (host) power source  125 , and a second loop occurring at each of the terminal LED lighting apparatus  150 . In addition, various steps are continuous, such as monitoring step  340 , which operates as long as the system  100  is powered on. For a first loop occurring at the central (host) power source  125 , for example, unless the system  100  is powered off, and unless there is a change in the dimming level, step  320  continues, in which the AC/DC rectifier  105  rectifies the input AC voltage and the DC/DC converter  110 , using the control signals from the central (host) controller  120 , continues to provide the same level of DC output voltage and current levels to the terminal LED lighting apparatuses  150  over power transmission line(s)  195 . Also unless powered off, when there is a change in the dimming level, the method will iterate to generate new DC output voltage and current levels to the terminal LED lighting apparatuses  150 , and will continue to provide this new level until the dimming level changes again or the system is powered down. Similarly, for a second loop occurring at the terminal LED lighting apparatuses  150  (generally simultaneously with the first loop once in steady state), unless there is a change in the input voltage level (and/or current level), current (and/or voltage) will continue to be provided to the LEDs  140  at the set level of Iout, with corresponding feedback control (steps  355  and  360 ). When there is a change in the input voltage (and/or current) level, the method will also iterate to generate a new current level Iout and provide power to the LEDs  140  at this new current level. 
       FIG. 4  is a graph illustrating exemplary or representative voltage and current waveforms for intelligent dimming using an exemplary or representative lighting system  100 , an exemplary or representative central (host) power source  125 , and an exemplary or representative terminal LED lighting apparatus  150 , and provides a useful summary of the dimming methodology described above. As discussed above, when powered on, the central (host) power source  125  will provide an output voltage corresponding to a desired dimming level, which is the input voltage Vin to the terminal LED lighting apparatus  150 , and which varies between a minimum input voltage Vinmin and a maximum input voltage Vinmax, illustrated as line  251 . Based upon the input voltage Vin, the terminal (or remote) controller  160  determines the level of LED  140  current Iout that provides the selected dimming level, which may be a linear relationship between Vin and Iout illustrated as line  252 , or any of various nonlinear relationships, illustrated as lines  253  and  254  for example. For example, an input voltage Vin sensed at level “A”, would map through the corresponding transfer function to an LED  140  current Iout having a level “B” for the linear transfer function illustrated as line  252  and also for the nonlinear (sigmoidal) transfer function illustrated as line  254 , but would map through the corresponding transfer function to an LED  140  current Iout having a level “C” for the nonlinear transfer function illustrated as line  253 . Those having skill in the art will recognize that there are advantages to each of these transfer functions, such as the degree of lighting control which may be provided to the user in different regions of dimming, e.g., finer control in certain percentage intervals or equal control throughout the entire 0% to 100% dimming. Using the variation in input voltage Vin, the terminal (or remote) controller  160  is able to correspondingly adjust the LED  140  current level from no (0%) dimming to 100% dimming (when the voltage level is insufficient to turn on the LEDs  140  and no current flows through the LEDs  140 ). In addition, such dimming of the LEDs  140  is provided without any issues of stability, flicker, or the other problems associated with prior art triac-based dimming. 
     Referring again to  FIG. 3 , those having skill in the art will also recognize that many of the illustrated steps may be omitted or varies, and will depend in large part upon the type of terminal LED lighting apparatus  150  utilized within the system  100 . A wide variety of exemplary or representative types of terminal LED lighting apparatuses  150  are illustrated and discussed below with reference to  FIGS. 5-14 . For example, several illustrated examples of terminal LED lighting apparatuses  150  do not include any terminal (or remote) controller  160 , any sensors  155 , or any remote user interface  165 , and for those embodiments, only steps  300 ,  315 ,  320 ,  325 ,  330  and  370  may be executed, with all other steps omitted. For these implementations, most of the lighting control is performed by the central (host) power source  125 , with limited control by the terminal LED lighting apparatus  150  (e.g., current and/or temperature overload control, passive current control, etc.). For some of these embodiments, dimming may occur by varying the output voltage Vout of the central (host) power source  125 , thereby increasing or decreasing LED  140  current passively within the terminal LED lighting apparatus  150 . 
     It should also be noted that depending upon the type of terminal LED lighting apparatus  150  utilized in the system  100 , different operational parameters may be utilized to determine the output voltage Vout of the central (host) power source  125 , such as the minimum or the maximum current ratings of the selected terminal LED lighting apparatus  150 . In addition, those having skill in the art will also recognize that while several different types of terminal LED lighting apparatuses  150  may be utilized concurrently within the system  100 , in other circumstances, only one type of terminal LED lighting apparatus  150  should be selected for implementation of a selected system  100 . 
     It should also be noted that depending upon the implementation of a system  100 , different types of wiring may be utilized, in addition to power transmission lines  195 , such as communication wiring, which may allow for additional data communication between and among the central (host) power source  125  and the terminal LED lighting apparatuses  150 . In addition, additional control and data transmission may be provided using various power line signaling methods known or developed in the future. Also, depending upon the implementation, wireless communication may also occur between and among the central (host) power source  125  and the terminal LED lighting apparatuses  150  using the wireless capabilities which may be implemented in the user interfaces  135 ,  165 . This additional potential for control may be utilized, for example and without limitation, for color mixing and temperature control (e.g.,  FIG. 14 ) and for differential dimming among the terminal LED lighting apparatuses  150 . For example, such differential dimming may be performed using network addresses for the terminal LED lighting apparatuses  150  within the system  100  and power line signal or wireless communication. 
       FIG. 5  is a block and circuit diagram illustrating a second exemplary or representative terminal LED lighting apparatus  150 A for use in a comparatively low voltage DC system  100 A, in which the output voltage Vout of the central (host) power source  125  is a comparatively lower DC voltage, typically less than about 60V DC (to provide self-voltage capability), indicated by designating the power transmission line as low voltage DC lines  195 A. In addition to terminal LED lighting apparatuses  150 A being able to be used in such a system  100 A, other types of terminal LED lighting apparatuses  150  ( 150 F,  150 G,  150 H, and  150 J illustrated in  FIGS. 11-14 ) may also be utilized in a comparatively low DC voltage system  100 A. As illustrated in  FIG. 5 , central (host) power source  125  is coupled to an AC input  130 , and a plurality of terminal LED lighting apparatuses  150 A are connected in parallel to the transmission lines  195 A. The selection of self-powering voltage allows the terminal LED lighting apparatus  150 A to employ a low voltage topology. As illustrated, the current source (or regulator)  145 A utilizes a buck topology comprised of inductor  408 , diode  406 , and MOSFET  404 , using a current sense resistor  402  as a sensor  155 A, and using a terminal (or remote) controller  160 . The series connected string of LEDs  140  is driven by a current regulated source, and the LEDs  140  do not require binning during manufacturing. While a buck converter is illustrated, any other type of converter may be utilized equivalently, including buck-boost, sepic, flyback, and many others currently known or developed in the future. 
       FIG. 6  is a block and circuit diagram illustrating a third exemplary or representative terminal LED lighting apparatus for use in a comparatively high voltage DC system  100 B, in which the output voltage Vout of the central (host) power source  125  is a comparatively higher DC voltage, in the range of about 300V, for example and without limitation, indicated by designating the power transmission lines as low voltage DC lines  195 B. As illustrated in  FIG. 6 , central (host) power source  125  is coupled to an AC input  130 , and a plurality of terminal LED lighting apparatuses  150 B are connected in parallel to the transmission lines  195 B. As illustrated, the current source (or regulator)  145 B utilizes a high voltage flyback topology comprising transformer  410 , snubber circuit  412 , rectifier (diode)  414 , filter capacitor  416 , and MOSFET  418 , using a current sense resistor  402  as a sensor  155 A, and using a terminal (or remote) controller  160 . 
       FIG. 7  is a block diagram illustrating an exemplary or representative system  100 C having both comparatively high and low DC levels, respectively illustrated using transmission lines  195 B and  195 A, and with an additional DC/DC converter  110 A to convert the higher voltage on lines  195 B to a lower DC voltage on lines  195 A. 
       FIG. 8  is a block and circuit diagram illustrating a fourth exemplary or representative terminal LED lighting apparatus  150 C for use in a comparatively high frequency system  100 D, which can be either a comparatively high or low voltage AC, and may have a wide range of suitable frequencies (e.g., about 500 Hz to 90 kHz), such as 60 kHz, for example and without limitation, indicated by designating the power transmission lines as high frequency lines  195 C. As illustrated in  FIG. 8 , central (host) power source  125 A is coupled to an AC input  130 , and a plurality of terminal LED lighting apparatuses  150 C are connected in parallel to the transmission lines  195 C. Not separately illustrated, the central (host) power source  125 A for this embodiment will generally also comprise a high frequency inverter to create the high frequency AC voltage on lines  195 C. As illustrated, the current source (or regulator)  145 C comprises a high frequency transformer  420 , a rectifier  422  (e.g., a bridge rectifier), an optional filter capacitor  424 , and may also include an additional current regulator (not separately illustrated) connected between the rectifier  422  and the capacitor  424 . The optional filter capacitor  424  may be utilized to effectively remove any appreciable voltage ripple and provide flicker-free drive of the LEDs  140 . An advantage of this topology is the comparatively small size of the current source (or regulator)  145 C due to the small size of the high frequency transformer  420 . Such a high frequency current source (or regulator)  145 C may be implemented using a wide variety of topologies, currently known or developed in the future, such as those illustrated in  FIGS. 9 and 10  discussed below. 
       FIG. 9  is a block and circuit diagram illustrating a fifth exemplary or representative terminal LED lighting apparatus  150 D for use in a comparatively high frequency system  100 E, which also can be either a comparatively high or low voltage AC, and may have a wide range of suitable frequencies (e.g., about 500 Hz to 90 kHz), such as 60 kHz, for example and without limitation, as discussed above. As illustrated in  FIG. 9 , central (host) power source  125 A is coupled to an AC input  130 , and a plurality of terminal LED lighting apparatuses  150 D are connected in parallel to the transmission lines  195 C. Also not separately illustrated, the central (host) power source  125 A for this embodiment will generally also comprise a high frequency inverter to create the high frequency AC voltage on lines  195 C. As illustrated, the current source (or regulator)  145 C is also utilized, as discussed above. In this embodiment, which may be very effective at high frequency, a plurality of switches  426  are utilized to selectively bypass selected LEDs  140  of the illustrated plurality of series-connected LEDs  140 . Initially, when the AC voltage is low (e.g., near a zero crossing), all of the switches are on and only a few or minimal number of LEDs  140  are connected in series to receive power (via rectifier  422  and transformer  420 ). As the instantaneous AC voltage increases, more LEDs  140  are switched into the series-connected path of LEDs  140 , such as by sequentially turning off switches  426 , and as the instantaneous AC voltage decreases, more LEDs  140  are switched out of the series-connected path of LEDs  140 , such as by sequentially turning on switches  426 . The optional filter capacitor  424  also may be utilized to effectively remove any appreciable voltage ripple and provide flicker-free drive of the LEDs  140 . 
       FIG. 10  is a block and circuit diagram illustrating a sixth exemplary or representative terminal LED lighting apparatus  150 E for use in a comparatively high frequency system  100 F, which also can be either a comparatively high or low voltage AC, and may have a wide range of suitable frequencies (e.g., about 500 Hz to 90 kHz), such as 60 kHz, for example and without limitation, as discussed above. As illustrated in  FIG. 10 , central (host) power source  125 A is coupled to an AC input  130 , and a plurality of terminal LED lighting apparatuses  150 E are connected in parallel to the transmission lines  195 C. Not separately illustrated, the central (host) power source  125 A for this embodiment also will generally also comprise a high frequency inverter to create the high frequency AC voltage on lines  195 C. As illustrated, the current source (or regulator)  145 D comprises a high frequency transformer  420 , a rectifier  422  (e.g., a bridge rectifier), and a capacitor  428 , which may be coupled on either the primary or the secondary side of the transformer  420 . The capacitor  428  adds and additional impedance in series with the LEDs  140  and may be utilized to effectively improve their VA (Volt and Ampere) characteristics, providing a more stable current with voltage variation. The total impedance will be (Equation 12): 
     
       
         
           
             
               Z 
               = 
               
                 
                   
                     
                       X 
                       c 
                       2 
                     
                     + 
                     
                       1 
                       
                         K 
                         t 
                         4 
                       
                     
                   
                 
                  
                 
                   R 
                   LED 
                   2 
                 
               
             
             , 
           
         
       
     
     where Xc is the impedance of the capacitor  428 , Kt is the transformer ratio, and R LED  is the equivalent LED  140  impedance. 
       FIG. 11  is a block and circuit diagram illustrating a seventh exemplary or representative terminal LED lighting apparatus  150 F for a comparatively low voltage DC system  100 A, such as illustrated in  FIG. 5  and discussed above for other terminal LED lighting apparatuses  150 A. An exemplary or representative terminal LED lighting apparatus  150 F is coupleable to transmission power lines  195 A, and comprises a plurality of LEDs  140  coupled in series to a current source (or regulator)  145 E comprising very few components, namely, a fuse  432  and a thermal current regulator  434 . For this comparatively simple terminal LED lighting apparatus  150 F embodiment, the fuse  432  operates as known in the art to open circuit at or above a predetermined LED  140  current, while the thermal current regulator  434  will reduce the LED  140  current if the temperature of the terminal LED lighting apparatus  150 F exceeds a predetermined threshold and thereby keep the LED  140  current within predetermined limits, and allowing use of the terminal LED lighting apparatus  150 F with a central (host) power source  125  with an output voltage rout which may produce a wide range of LED  140  currents. As discussed above, as an option, such an embodiment may also include in its housing, labeling and/or packaging, machine-readable encoded fields  170  which may be scanned into the central (host) power source  125  during set up or during exchange modes, which will typically include encoded information for minimum and maximum voltage and minimum and maximum current for the terminal LED lighting apparatuses  150 F, and possibly a network address for the apparatus  150 F. As mentioned above, these maximum and minimum voltage and current parameters may also be provided on the basis of minimum and maximum LED  140  voltage levels, minimum and maximum LED  140  current, for the incorporated string of LEDs  140 . These operational parameters may also be manually entered, as discussed above. For example, for this embodiment, minimum input voltage and minimum input current levels for the terminal LED lighting apparatus  150 F are typically entered and stored in the central (host) power source  125 . 
     A plurality of terminal LED lighting apparatuses  150 F may be utilized in a system  100 A up to the power capacity of the central (host) power source  125 , with operational parameters input into the system  100 A during set up and/or exchange modes as previously discussed. During operation (automatic mode), the central (host) power source  125  is turned on and provides a minimum output voltage Vout, and then typically progressively ramps up the output voltage Vout, typically below or up to a maximum Vout that is based on the minimum and maximum voltage and current parameters for the plurality of terminal LED lighting apparatuses  150 F, so that at least minimum voltage and current are provided to the terminal LED lighting apparatuses  150 F and the maximum voltage and current of the terminal LED lighting apparatuses  150 F generally are not exceeded, as discussed above. For example, in an exemplary embodiment, during operation (automatic mode), Vout=Vinmin for the terminal LED lighting apparatuses  150 F. Also or example, a Vout may be determined by the central (host) controller  120  to be based upon an output voltage that would be required to provide an output current which is greater than, by a selected percentage, the sum of the minimum LED  140  currents for all of the terminal LED lighting apparatus  150 F included within the system  100 A, such as Vout=τ1.1Σminimum I LED  (where τ is a transfer function or other conversion factor), or setting Voutmax=the minimum V LED , or setting the output current of the central (host) power source  125 =1.1Σminimum I LED , or based upon a range in between minimum and maximum voltage and current levels of the terminal LED lighting apparatuses  150 F, such as maximum V LED ≧Vout≧minimum V LED , or 1.1Σ minimum I LED ≦output current of the central (host) power source  125 ≦0.8 Σ maximum I LED , etc., for example and without limitation. For this embodiment, the output current and voltage of the central (host) power source  125  also is typically monitored, with feedback provided as discussed above, so that these current and voltage levels are within an acceptable margin and do not exceed the current and voltage limits discussed above for the plurality of terminal LED lighting apparatuses  150 F. 
       FIG. 12  is a block and circuit diagram illustrating an eighth exemplary or representative terminal LED lighting apparatus  150 G for a comparatively low voltage DC system  100 A, such as illustrated in  FIG. 5  and discussed above for other terminal LED lighting apparatuses  150 A and  150 F. An exemplary or representative terminal LED lighting apparatus  150 G is coupleable to transmission power lines  195 A, and comprises a plurality of LEDs  140  coupled to a current source (or regulator)  145 F. For this representative embodiment, the current source (or regulator)  145 F comprises a fuse  432 , a current source  436  which is controlled by a voltage provided by a voltage divider comprising a plurality of resistors  433 ,  438 , and  435 , and zener diode  437 . For this moderately complicated terminal LED lighting apparatus  150 G embodiment, the fuse  432  also operates as known in the art to open circuit at or above a predetermined LED  140  current, while the control voltage provided to the current source  436  by the voltage divider components is typically stably fixed by the resistors  435 ,  438  and zener diode  437 , with the current source  436  providing a comparatively constant LED  140  current limit. Also as discussed above, as an option, such an embodiment may also include in its housing, labeling and/or packaging, machine-readable encoded fields  170  which may be scanned into the central (host) power source  125  during set up or during exchange modes, which will typically include encoded information for minimum and maximum voltage and minimum and maximum current for the terminal LED lighting apparatuses  150 G, and possibly a network address for the apparatus  150 G. As mentioned above, these maximum and minimum voltage and current parameters may also be provided on the basis of minimum and maximum LED  140  voltage levels, and minimum and maximum LED  140  current levels, for the incorporated string of LEDs  140 . These operational parameters may also be manually entered, as discussed above. For example, for this embodiment, minimum input voltage and minimum input current levels for the terminal LED lighting apparatus  150 G are typically entered and stored in the central (host) power source  125 . 
     A plurality of terminal LED lighting apparatuses  150 G may be utilized in a system  100 A up to the power capacity of the central (host) power source  125 , with operational parameters input into the system  100 A during set up and/or exchange modes as previously discussed. During operation (automatic mode), the central (host) power source  125  is turned on and provides the selected output voltage Vout, typically at (or below) a maximum Vout that is based on the minimum and maximum voltage and current parameters of the terminal LED lighting apparatuses  150 G, so that at least minimum voltage and current is provided to the terminal LED lighting apparatuses  150 G and the maximum voltage and current of the terminal LED lighting apparatuses  150 G generally is not exceeded, also as discussed above. For example, in an exemplary embodiment, during operation (automatic mode), Voutmax=Vinmin for the terminal LED lighting apparatuses  150 G. Also for example, a Vout may be determined by the central (host) controller  120  to be based upon a selected percentage above the sum of the minimum LED  140  currents for all of the terminal LED lighting apparatus  150 G included within the system  100 A, such as Vout ∝1.1Σ minimum I LED , or setting Voutmax=the minimum V LED , or setting the output current of the central (host) power source  125 =1.1Σ minimum I LED , or based upon a range in between minimum and maximum voltage and current levels of the terminal LED lighting apparatuses  150 G, such as maximum V LED ≧Vout≧minimum V LED , or 1.1Σ minimum I LED ≦output current of the central (host) power source  125 ≦0.8Σ maximum I LED , etc., for example and without limitation. For this embodiment, the output current and voltage of the central (host) power source  125  also is typically monitored, with feedback provided as discussed above, so that these current and voltage levels are within an acceptable margin and do not exceed the current and voltage limits discussed above for the plurality of terminal LED lighting apparatuses  150 G. 
     For example, in an exemplary embodiment, during operation (automatic mode), Voutmax=Vinmin for the terminal LED lighting apparatuses  150 G, and the output current of the central (host) power source  125  is monitored such that the output current≦1.1Σ minimum I LED . 
       FIG. 13  is a block and circuit diagram illustrating a ninth exemplary or representative terminal LED lighting apparatus  150 H for a comparatively low voltage DC system  100 A, such as illustrated in  FIG. 5  and discussed above for other terminal LED lighting apparatuses  150 A,  150 F, and  150 G. An exemplary or representative terminal LED lighting apparatus  150 H is coupleable to transmission power lines  195 A, and comprises a terminal (or remote) controller  160 , and a plurality of LEDs  140  coupled to a current source (or regulator)  145 G. For this representative embodiment, the current source (or regulator)  145 G comprises a fuse  432 , a current regulator  440 , and a voltage divider comprising a plurality of resistors  433 ,  438 , and  435 , and zener diode  437 , which is utilized to provide operating voltages for the terminal (or remote) controller  160  and the current regulator  440 . The current regulator  440 , for example, may be implemented as a buck converter or a flyback converter, or any other converter or current regulator topology, and may typically comprise an inductor, a MOSFET, a sense resistor, and a diode (as previously illustrated and previously discussed with reference to  FIG. 5 ), for example and without limitation. For this terminal LED lighting apparatus  150 H embodiment, the fuse  432  also operates as known in the art to open circuit at or above a predetermined LED  140  current, while the operational voltage provided to the current source  436  by the voltage divider components is typically stably fixed by the resistors  435 ,  438  and zener diode  437 . The LED  140  current, however, is typically determined by control signals provided to the current regulator  440  by the terminal (or remote) controller  160 , based upon a sensed or measured value of Vin, as discussed above, such as with reference to  FIG. 3 , based upon the value of Vout provided by the central (host) power source  125  for a selected dimming level “ρ”. Also as discussed above, as an option, such an embodiment may also include in its housing, labeling and/or packaging, machine-readable encoded fields  170  which may be scanned into the central (host) power source  125  during set up or during exchange modes, which will typically include encoded information for minimum and maximum voltage and minimum and maximum current for the terminal LED lighting apparatuses  150 H, and possibly a network address for the apparatus  150 H. As mentioned above, these maximum and minimum voltage and current parameters may also be provided on the basis of minimum and maximum LED  140  voltage levels, and minimum and maximum LED  140  current levels, for the incorporated string of LEDs  140 . These operational parameters may also be manually entered, as discussed above. 
     A plurality of terminal LED lighting apparatuses  150 H may be utilized in a system  100 A up to the power capacity of the central (host) power source  125 , with operational parameters input into the system  100 A during set up and/or exchange modes as previously discussed. For example, during set up or exchange modes for a first embodiment, minimum and maximum input voltage and minimum and maximum input current levels for the terminal LED lighting apparatus  150 H are typically entered and stored in the central (host) power source  125 . For example, during set up or exchange modes for a second embodiment, maximum input voltage and minimum (and optionally) maximum input current levels for the terminal LED lighting apparatus  150 H are typically entered and stored in the central (host) power source  125 . For either or both embodiments, the central (host) controller  120  then sets Voutmax=Vinmax for the terminal LED lighting apparatuses  150 H, without manual override, and sets a limit for output current from the central (host) power source  125  equal to 1.1Σ minimum I LED  for the terminal LED lighting apparatuses  150 H. 
     During operation (automatic mode), the central (host) power source  125  is turned on and provides the selected output voltage Vout, typically at (or below) the maximum Voutmax that is based on the maximum voltage parameter of the terminal LED lighting apparatuses  150 H. For example, when turned on, the central (host) power source  125  may automatically provide Voutmax, for maximum brightness, or may provide a lower Vout corresponding to its last dimming setting by the user. Concurrently, the central (host) controller  120  monitors output current from the central (host) power source  125  and provides corresponding feedback signals to maintain output current≦1.1Σ minimum I LED , for example, so that the output current levels are within an acceptable margin and do not exceed the current limits discussed above for the plurality of terminal LED lighting apparatuses  150 H. Similarly for this embodiment, in addition to monitoring output current, the output voltage Vout of the central (host) power source  125  also is typically monitored, with feedback provided as discussed above, so that the selected dimming level is provided and further, that the output voltage levels are within an acceptable margin and do not exceed the voltage limits discussed above for the plurality of terminal LED lighting apparatuses  150 H. 
       FIG. 14  is a block and circuit diagram illustrating a tenth exemplary or representative terminal LED lighting apparatus  150 J for a comparatively low voltage DC system  100 A, such as illustrated in  FIG. 5  and discussed above for other terminal LED lighting apparatuses  150 A,  150 F,  150 G, and  150 H. In this exemplary embodiment, the terminal LED lighting apparatus  150 J functions similarly to terminal LED lighting apparatus  150 H, but now includes multiple series-connected (strings) or channels of LEDs  140 , illustrated as channel one LEDs  140   1 , channel two LEDs  140   2 , through channel “N” LEDs  140   N , each of which is controlled by a corresponding current regulator  440 , illustrated respectively as current regulator  440   1 , current regulator  440   2 , through current regulator  440   N . Each of the LED  140  channels may provide a different color, color temperature, or other lighting effect, for example and without limitation, such as channel one comprising red LEDs  140   1 , channel two comprising green LEDs  140   2 , through channel “N” comprising blue LEDs  140   N , etc. There may be any number of LED  140  channels. In turn, each of the various current regulators  440  are separately (and/or independently) controlled by a terminal (or remote) controller  160 A, which has expanded capability to independently control each channel, rather than controlling the current through a single string of LEDs through a single current regulator  440 . In addition, the terminal LED lighting apparatus  150 J optionally includes a remote user interface  165  and one or more sensors  155  (which, for example, may be implemented as current sense resistors (e.g.,  402 ) within each current regulator  440 , or which may provide additional sensing capabilities). 
     An exemplary or representative terminal LED lighting apparatus  150 J also is coupleable to transmission power lines  195 A, and comprises a terminal (or remote) controller  160 A, and a plurality of strings of LEDs  140  which are coupled to a current source (or regulator)  145 H. For this representative embodiment, the current source (or regulator)  145 H comprises a fuse  432 , a plurality of current regulators  440 , and a voltage divider comprising a plurality of resistors  433 ,  438 , and  435 , and zener diode  437 , which is utilized to provide operating voltages for the terminal (or remote) controller  160 A, the current regulators  440 , the optional remote user interface  165 , and the sensor(s)  155  (depending upon the type of sensor(s)  155  utilized). The current regulators  440 , for example, may be implemented as a buck converter or a flyback converter, or any other converter or current regulator topology, and may typically comprise an inductor, a MOSFET, a sense resistor, and a diode (as previously illustrated and previously discussed with reference to  FIG. 5 ), for example and without limitation. For this terminal LED lighting apparatus  150 J embodiment, the fuse  432  also operates as known in the art to open circuit at or above a predetermined LED  140  current, while the operational voltage provided to the current source  436  by the voltage divider components is typically stably fixed by the resistors  435 ,  438  and zener diode  437 . 
     The currents of the various LED  140  channels, however, are separately (and/or independently) determined by control signals provided to the respective current regulators  440  by the terminal (or remote) controller  160 . In one exemplary embodiment, the terminal (or remote) controller  160 A may determine each such LED  140  current based upon a sensed or measured value of Vin, as discussed above, such as with reference to  FIG. 3 , based upon the value of Vout provided by the central (host) power source  125  for a selected dimming level “ρ”. In another exemplary embodiment, the terminal (or remote) controller  160 A may determine each such LED  140  current separately (and/or independently), not only based upon a sensed or measured value of Vin, but also based upon color mixing and color temperature control, for any selected lighting effect, and separate dimming for each LED  140  channel, such as provided through the remote user interface  165  for user control, or through sensor(s)  155  (which may override or supplement the remote control by the user), or as potentially communicated by the central (host) controller  120 , also separately (and/or independently) for each LED  140  channel, such as through additional wiring, wireless communication, or power line signaling as mentioned above. 
     Also as discussed above, as an option, such an embodiment may also include in its housing, labeling and/or packaging, machine-readable encoded fields  170  which may be scanned into the central (host) power source  125  during set up or during exchange modes, which will typically include, for each LED  140  channel of each terminal LED lighting apparatus  150 J, encoded information for minimum and maximum voltage and minimum and maximum current, and possibly a network address for the apparatus  150 J. As mentioned above, these maximum and minimum voltage and current parameters may also be provided on the basis of minimum and maximum LED  140  voltage levels, and minimum and maximum LED  140  current levels, for each of the incorporated channels of LEDs  140 . These operational parameters may also be manually entered, as discussed above. 
     A plurality of terminal LED lighting apparatuses  150 J may be utilized in a system  100 A up to the power capacity of the central (host) power source  125 , with operational parameters input into the system  100 A during set up and/or exchange modes as previously discussed. For example, during set up or exchange modes for a first embodiment, minimum and maximum input voltage and minimum and maximum input current levels for the terminal LED lighting apparatus  150 J are typically entered and stored in the central (host) power source  125 . For example, during set up or exchange modes for a second embodiment, maximum input voltage and minimum (and optionally) maximum input current levels for the terminal LED lighting apparatus  150 J are typically entered and stored in the central (host) power source  125 . For either or both embodiments, the central (host) controller  120  then sets Voutmax=Vinmax for the terminal LED lighting apparatuses  150 H, without manual override, and sets a limit for output current from the central (host) power source  125  equal to 1.1Σ minimum I LED  for the terminal LED lighting apparatuses  150 J. 
     During operation (automatic mode), the central (host) power source  125  is turned on and provides the selected output voltage Vout, typically at (or below) the maximum Voutmax that is based on the maximum voltage parameter of the terminal LED lighting apparatuses  150 J. For example, when turned on, the central (host) power source  125  may automatically provide Voutmax, for maximum brightness, or may provide a lower Vout corresponding to its last dimming setting by the user. Concurrently, the central (host) controller  120  monitors output current from the central (host) power source  125  and provides corresponding feedback signals to maintain output current≦1.1Σ minimum I LED , for example, so that the output current levels are within an acceptable margin and do not exceed the current limits discussed above for the plurality of terminal LED lighting apparatuses  150 J. Similarly for this embodiment, in addition to monitoring output current, the output voltage Vout of the central (host) power source  125  also is typically monitored, with feedback provided as discussed above, so that the selected dimming level is provided and further, that the output voltage levels are within an acceptable margin and do not exceed the voltage limits discussed above for the plurality of terminal LED lighting apparatuses  150 J. 
     In addition, using one or more terminal LED lighting apparatuses  150 J, via central or remote user interfaces  135 ,  165 , a user may select any of a wide range of lighting effects and a wide variety of brightness levels, such as color mixing, color temperature, and various architectural lighting effects, any and all of which may also include different levels of dimming. 
       FIG. 15  is a diagram illustrating exemplary or representative machine-readable encoded fields  170 , such as barcode fields or QR code fields, for use with an exemplary or representative apparatus, method and system. The machine-readable encoded fields  170  may have any selected, suitable or appropriate format, known or developed in the future, such as the vertical lines, bars and spaces of a linear or matrix UPC barcode, or the various QR encoded fields. As illustrated in  FIG. 15 , exemplary machine-readable encoded fields  170  comprises a plurality of fields  501 - 510 , not all of which are required to be used, and many of which may be optional, including one or more power fields, such as maximum or nominal power rating field  501 ; one or more voltage fields, such as maximum voltage field  502  and minimum voltage field  503 ; one or more current fields, such as maximum current field  504  and minimum current field  505 ; a nominal voltage/current field  506 , specifying the LED  140  voltage at nominal current; a minimum dimming level (voltage or current) field  507 ; an adjustable color temperature range field  508 ; a unique number or identification (I.D.) field  509  for the particular terminal LED lighting apparatus  150 ; and a field  510  for any other drive or network parameters. Not separately illustrated in  FIG. 15  may be fields for format information, error correction, manufacturer, model number, etc. 
     As mentioned above, this data input (e.g., scanned) from machine-readable encoded fields  170  will be stored in the controller  120  memory and used for technical purposes to program the central (host) controller  120  as described above. Another application of this information is suggested and may be used for generating lighting reports for the user, with performance metrics over time, and as an example and without limitation, may include any of the various following information, such as: number of terminal LED lighting apparatuses  150  installed and dates of installation; number of terminal LED lighting apparatuses  150  which failed; a listing of failed terminal LED lighting apparatuses  150  with total hours of performance; average annual or daily consumed power, annual, daily, etc.; average daily on time; and average daily dimming level. 
     In one exemplary or representative embodiment, a user is provided with a retrofitting kit, as mentioned above. Such a retrofitting kit may include a central (host) power source  125 , with or without a dimmer function, having a form factor suitable for replacing a standard lighting or dimmer switch as described above, and one or more terminal LED lighting apparatuses  150  (as LED bulbs) designed to operate in conjunction with the central (host) power source  125 . A user wishing to retrofit a lighting system would be able to easily replace a legacy wall switch with the central (host) power source  125  having a legacy-compatible form factor provided in the retrofitting kit, connecting it properly to the electrical supply line and to the feed lines to the lighting load(s). The terminal LED lighting apparatuses  150  (as LED bulbs) can then be installed in place of the original incandescent of CFL bulbs used as terminators on the feed lines connected to the retrofitted central (host) power source  125 . 
     In another exemplary embodiment, the retrofitting kit may also include one or more lighting sockets (not separately illustrated) which each have a mating form factor or interface, designed or adapted to fit the form factor or interface of the one or more terminal LED lighting apparatuses  150 . A user wishing to retrofit a lighting system would be able to easily replace existing, legacy lighting sockets with the new sockets having the new mating or otherwise compatible form factor provided in the retrofitting kit, connecting it properly to the feed lines from the central (host) power source  125  (and to any existing ground or neutral). 
       FIG. 16  is a graphical diagram illustrating an exemplary or representative full wave rectified voltage, zero crossing intervals, and on and off intervals of various exemplary embodiments, such as the embodiment illustrated and discussed below with reference to  FIG. 17 .  FIG. 17  is a block and circuit diagram illustrating an eleventh exemplary or representative terminal LED lighting apparatus  150 K for use in a system  100 G having a typical 50 Hz or 60 Hz AC line voltage or in a comparatively higher frequency system. 
     Referring to  FIG. 16 , the voltage level illustrated by line  512  is a typical representation of a full wave rectified AC voltage. Those having skill in the electronic arts will recognize, however, that actual voltages in any system will depart from and may vary significantly from this stylized representation. As illustrated, below a first threshold (voltage level  514 ), there is a zero crossing interval  522 , as mentioned above. For various prior art devices such as a switched mode power supply (“SMPS”), when such a rectified line voltage is below the first threshold, the SMPS is off as there is insufficient voltage to operate the SMPS circuitry, or to operate the light source properly. Above the first threshold value (voltage level  514 ), the SMPS  20  is on and any connected LEDs are emitting light. As the rectified line voltage ( 512 ) is below the threshold value (voltage level  514 ) twice during each line cycle, the off-frequency for such a device is twice that of the line frequency. 
       FIG. 17  is a block and circuit diagram illustrating an eleventh exemplary or representative terminal LED lighting apparatus  150 K for use in a system  100 G having a typical 50 Hz or 60 Hz AC line voltage or in a comparatively higher frequency system, which also can be either a comparatively high or low voltage AC, and may have a wide range of suitable frequencies (e.g., about 50 Hz to 90 kHz), for example and without limitation, as discussed above. As illustrated in  FIG. 17 , central (host) power source  125 A is coupled to an AC input  130 , and a plurality of terminal LED lighting apparatuses  150 K are connected in parallel to the transmission lines  195 D. Also not separately illustrated, the central (host) power source  125 A for this embodiment will generally also comprise an inverter to create the AC voltage on lines  195 D, at any selected frequency (e.g., about 50 Hz to 90 kHz). Alternatively, lines  195 D may be coupled directly to an AC power source, such as the illustrated AC input  130 , e.g., provided by an electrical utility. When LEDs  140 ,  140 A are not included, the circuitry of the terminal LED lighting apparatus  150 K may be considered to be a switched mode power supply (SMPS), also within the scope of this disclosure. 
     As illustrated, a current source (or regulator)  145 K is also utilized, and as discussed above, generally includes a rectifier  422  (which may be full wave or half wave) and may also include (as an option) transformer  420 . In this embodiment of current source (or regulator)  145 K, which may be very effective at a wide range of frequencies, a plurality of switches, embodied using transistors  540  (illustrated as transistors  540 A and  540 B) are utilized to selectively bypass selected LEDs  140  of the illustrated plurality of series-connected LEDs  140 . Initially, when the AC voltage is low, all of the switches  540  (and switch Q 1  (transistor  538 ) are on and only a few or minimal number of LEDs  140  are connected in series to receive power (via rectifier  422  and optional transformer  420  (used at high frequencies)). As the instantaneous AC voltage increases, more LEDs  140  are switched into the series-connected path of LEDs  140 , such as by sequentially turning off transistors  540  (while leaving switch Q 1  (transistor  538 ) on), and as the instantaneous AC voltage decreases, more LEDs  140  are switched out of the series-connected path of LEDs  140 , such as by sequentially turning on transistors  540  (also while leaving switch Q 1  (transistor  538 ) on). Also when switch Q 2  (transistor  534 ) is on, capacitor  530  is charged, and is utilized to effectively remove or diminish any AC line harmonics. An optional filter capacitor  424  also may be utilized, e.g., also to effectively remove or diminish any AC line harmonics, and is typically implemented with a comparatively small capacitance value to avoid adversely affecting the power factor. Also as illustrated, one or more resistors  542  may also be utilized in series with the series-connected LEDs  140 . 
     In this representative embodiment, current source (or regulator)  145 K, in addition to a first terminal (or remote) controller  160 , further comprises a second terminal (or remote) controller  550 , switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ) (also embodied or implemented using transistors such as the illustrated FETs, and which also may be implemented to be complementary), capacitor  530 , one or more additional LEDs  140 A (designated as  140  to distinguish it or them from the series-connected LEDs  140 ), and typically also a resistor  536 , which may operate as a sense (or sensing) resistor. The second terminal (or remote) controller  550  senses the rectified AC voltage at node  31 , and turns the switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ) on (conducting) or off (non-conducting). As discussed in greater detail below, and under the control of the second terminal (or remote) controller  550 , depending upon the sensed AC voltage level (node  31 ): (1) switch Q 2  (transistor  534 ) is on and switch Q 1  (transistor  538 ) is off; or (2) switch Q 2  (transistor  534 ) is off and switch Q 1  (transistor  538 ) is on; or (3) both switch Q 2  (transistor  534 ) and switch Q 1  (transistor  538 ) are on; or (4) both switch Q 2  (transistor  534 ) and switch Q 1  (transistor  538 ) are off. In a representative embodiment, switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ) may be implemented to be complementary, such that when switch Q 2  (transistor  534 ) is on then switch Q 1  (transistor  538 ) is off, and vice-versa (cases (1) and (2) above). By using various comparators, for example, various thresholds may be set in the second terminal (or remote) controller  550  and/or first terminal (or remote) controller  160  and utilized to control the switching of the various switches switch Q 1  (transistor  538 ), switch Q 2  (transistor  534 ), and switches  540  (e.g., transistors  540 A and  540 B). 
     As a result, the current through the various LEDs  140  and/or  140 A and corresponding light emission may be controlled, turned off and on, at any of various threshold levels, and thereby at any selected frequency, separate from and largely independent from the AC line frequency. For example, while five on ( 520 ) and six off ( 521 ) intervals are illustrated in  FIG. 16  during each one-half period of the line voltage (and occurring at corresponding voltage threshold levels  514 ,  515 ,  516 ,  517 , and  518 ), those having skill in the electronic arts will recognize that tens or hundreds or thousands of intervals may be utilized, e.g., to have a resulting on/off frequency from 50 Hz to 50 kHz, for example and without limitation. In addition, as illustrated and discussed below with reference to  FIG. 20 , such on/off intervals may also be implemented to be effectively random or pseudo-random. 
     Referring again to  FIG. 17 , while the rectified line voltage  512  is below a first threshold  514 , the LEDs  140  are turned off by switch Q 1  (transistor  538 ) as there is insufficient operational voltage for the LEDs  140  (and potentially insufficient voltage for the other circuitry). Above the first threshold  514 , the LEDs  140  are turned on by switch Q 1  (transistor  538 ). When the rectified line voltage (on line  512 ) is above a second, higher threshold  515 , the LEDs  140  may again be turned off, also using switch Q 1  (transistor  538 ). Above the third threshold  516 , the LEDs  140  are turned on by switch Q 1  (transistor  538 ). When the rectified line voltage (on line  512 ) is above a fourth, higher threshold  517 , the LEDs  140  may again be turned off, also using switch Q 1  (transistor  538 ). When the rectified line voltage (one line  512 ) is above a fifth, yet higher threshold  518 , the LEDs  140  are again turned on, also via switch Q 1  (transistor  538 ). The LEDs  140  may thus be turned on and off many times during each rectified half cycle, such as the illustrated five times for example and without limitation, resulting in an on and off frequency several (e.g., ten) times that of the line frequency, also for example and without limitation. In exemplary embodiments, on and off frequencies on the order of comparatively low (e.g., four to six times the AC line frequency or comparatively high (e.g., over 30 kHz) are implemented, as more mid-range frequencies may be problematic for pets. 
     In a representative embodiment, the switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ) are implemented to be complementary, so that when switch Q 1  (transistor  538 ) is on, switch Q 2  (transistor  534 ) is off, and vice-versa. As a result, the capacitor  530  is charged during intervals ( 521 ), when the LEDs  140  are off. In addition, depending upon the AC voltage level (node  31 ), during these intervals ( 521 ) when switch Q 2  (transistor  534 ) is on, and whenever capacitor  530  is discharging, light is emitted from LED  140 A. Based upon the AC voltage level (node  31 ) and/or the sensed voltage level from resistor  536  (node  32 ), the second terminal (or remote) controller  550  sets the charging current for the capacitor  530 . In an exemplary embodiment, the charging current is set to be about or approximately the same as the current the LEDs  140  would draw when switch Q 1  (transistor  538 ) is on, thereby tending to eliminate or reduce high frequency harmonics in the AC line current. For reducing power losses, the energy stored in capacitor  530  is discharged through one or more LEDs  140 A and further providing light output. In representative embodiments, the one or more LEDs  140 A may have the same or different color (spectrum) emission compared to the LEDs  140 , providing for further regulation of the characteristics of the light output. 
       FIG. 18  is a block and circuit diagram illustrating some control circuitry which may be utilized in a second terminal (or remote) controller  550 , including a first comparator  560 , a second comparator  565  through an Nth comparator  570 . As illustrated, the rectified AC line voltage (from node  31 ) is input into each of the first comparator  560 , the second comparator  565  and through the Nth comparator  570 . The second inputs into each of the first comparator  560 , second comparator  565  through Nth comparator  570  are corresponding threshold voltage settings, V SET1 , V SET2  through V SETN , which may be provided as known in the electronic arts and corresponding circuitry is not separately illustrated. The first comparator  560  implements an under-voltage lock out, e.g., during a zero crossing interval, keeping switch Q 1  (transistor  538 ) off until the rectified line voltage (at node  31 ) meets a first threshold level (e.g.,  514 ), such that the voltage level is high enough for proper operation. Each additional comparator second comparator  565  through Nth comparator  570  senses additional, corresponding voltage thresholds, to turn switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ) on or off as previously discussed. Additional circuitry such as diodes  561 ,  562  and  563  (and/or logic and other circuitry, not separately illustrated), may be provided to avoid conflict, such that only one of the outputs from the plurality of comparators is utilized to determine the on and off states of the switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ), e.g., the output signal from the second comparator  565  to turn on the switch Q 1  (transistor  538 ) will override the output signal from the first comparator  560  to turn off the switch Q 1  (transistor  538 ). 
     Hysteresis may also be implemented in any of the plurality of comparators  560 ,  565  through  570 . For example, the Nth comparator  570  may be utilized to turn on switch Q 1  (transistor  538 ) at voltage level  518  and keep switch Q 1  (transistor  538 ) on (providing current through LEDs  140 ) through the peak AC voltage and until the AC voltage level declines back to voltage level  518  (as illustrated in  FIG. 16 ). 
       FIG. 19  is a block and circuit diagram illustrating additional control circuitry which may be utilized in a second terminal (or remote) controller  550 , including a peak AC line voltage detector  585  (implemented using a capacitor  575  and a resistor  580 , coupled to an additional, second rectifier  590 , which also may be a full or half wave rectifier, e.g., a diode bridge). The peak AC line voltage detector  585  is also utilized within the second terminal (or remote) controller  550 , as mentioned above for the Nth comparator  570 , for switching switches Q 1  (transistor  538 ) and Q 2  (transistor  534 ) on and off. The capacitor  575  is charged through the second rectifier  590  to a level below the peak AC line voltage, such as to a voltage level lower than the peak AC line voltage by two diode voltage level drops (when the second rectifier  590  is implemented as a diode bridge, for example). The capacitor  575  remains at this voltage level for several AC line cycles and gradually discharges through resistor  580 , reaching a steady-state over several line cycles. When the AC line voltage increases, the voltage on the capacitor  575  also increases, and can be utilized to detect the peak voltage. Similar circuitry may also be utilized to provide the various threshold voltage levels (V SET1 , V SET2  through V SETN ) to the corresponding second inputs of the first comparator  560 , second comparator  565  through Nth comparator  570 . 
       FIG. 20  is a graphical diagram illustrating an exemplary or representative full wave rectified voltage, zero crossing intervals, and on and off intervals of various exemplary embodiments, when the on and off times of the switch Q 1  (transistor  538 ) and switch Q 2  (transistor  534 ) are modulated by a random or pseudo-random signal (illustrated on line  60 ) rather than voltage thresholds. As illustrated, when the signal  60  is high, the switch Q 1  (transistor  538 ) is off and there is no current through and no light emission from LEDs  140 . When the signal  60  is low, except for zero crossing intervals  522 , the switch Q 1  (transistor  538 ) is on and there is current through and light emission from LEDs  140 . The resulting on and off pattern of light emission eliminates or diminishes not only perceived visual flicker, but also any stroboscopic effects with harmonics of the AC line voltage. The signal  60  may be generated as a frequency which is not a harmonic of the AC line voltage, or preferably as a frequency that is not any low-order fractional harmonic of the AC line voltage. 
     The present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. In this respect, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of components set forth above and below, illustrated in the drawings, or as described in the examples. Systems, methods and apparatuses consistent with the present invention are capable of other embodiments and of being practiced and carried out in various ways. 
     Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative and not restrictive of the invention. In the description herein, numerous specific details are provided, such as examples of electronic components, electronic and structural connections, materials, and structural variations, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, components, materials, parts, etc. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention. In addition, the various Figures are not drawn to scale and should not be regarded as limiting. 
     Those having skill in the electronic arts will recognize that the various single-stage or two-stage converters may be implemented in a wide variety of ways, in addition to those illustrated, such as flyback, buck, boost, and buck-boost, for example and without limitation, and may be operated in any number of modes (discontinuous current mode, continuous current mode, and critical conduction mode), any and all of which are considered equivalent and within the scope of the present invention. 
     Reference throughout this specification to “one embodiment”, “an embodiment”, or a specific “embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention and not necessarily in all embodiments, and further, are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner and in any suitable combination with one or more other embodiments, including the use of selected features without corresponding use of other features. In addition, many modifications may be made to adapt a particular application, situation or material to the essential scope and spirit of the present invention. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered part of the spirit and scope of the present invention. 
     It will also be appreciated that one or more of the elements depicted in the Figures can also be implemented in a more separate or integrated manner, or even removed or rendered inoperable in certain cases, as may be useful in accordance with a particular application. Integrally formed combinations of components are also within the scope of the invention, particularly for embodiments in which a separation or combination of discrete components is unclear or indiscernible. In addition, use of the term “coupled” herein, including in its various forms such as “coupling” or “couplable”, means and includes any direct or indirect electrical, structural or magnetic coupling, connection or attachment, or adaptation or capability for such a direct or indirect electrical, structural or magnetic coupling, connection or attachment, including integrally formed components and components which are coupled via or through another component. 
     As used herein for purposes of the present invention, the term “LED” and its plural form “LEDs” should be understood to include any electroluminescent diode or other type of carrier injection- or junction-based system which is capable of generating radiation in response to an electrical signal, including without limitation, various semiconductor- or carbon-based structures which emit light in response to a current or voltage, light emitting polymers, organic LEDs, and so on, including within the visible spectrum, or other spectra such as ultraviolet or infrared, of any bandwidth, or of any color or color temperature. 
     A “controller” or “processor”  120 ,  160  may be any type of controller or processor, and may be embodied as one or more controllers  120 ,  160 , configured, designed, programmed or otherwise adapted to perform the functionality discussed herein. As the term controller or processor is used herein, a controller  120 ,  160  may include use of a single integrated circuit (“IC”), or may include use of a plurality of integrated circuits or other components connected, arranged or grouped together, such as controllers, microprocessors, digital signal processors (“DSPs”), parallel processors, multiple core processors, custom ICs, application specific integrated circuits (“ASICs”), field programmable gate arrays (“FPGAs”), adaptive computing ICs, associated memory (such as RAM, DRAM and ROM), and other ICs and components, whether analog or digital. As a consequence, as used herein, the term controller (or processor) should be understood to equivalently mean and include a single IC, or arrangement of custom ICs, ASICs, processors, microprocessors, controllers, FPGAs, adaptive computing ICs, or some other grouping of integrated circuits which perform the functions discussed below, with associated memory, such as microprocessor memory or additional RAM, DRAM, SDRAM, SRAM, MRAM, ROM, FLASH, EPROM or EPROM. A controller (or processor) (such as controller  120 ,  160 ), with its associated memory, may be adapted or configured (via programming, FPGA interconnection, or hard-wiring) to perform the methodology of the invention, as discussed below. For example, the methodology may be programmed and stored, in a controller  120 ,  160  with its associated memory (and/or memory  115 ) and other equivalent components, as a set of program instructions or other code (or equivalent configuration or other program) for subsequent execution when the processor is operative (i.e., powered on and functioning). Equivalently, when the controller  120 ,  160  may implemented in whole or part as FPGAs, custom ICs and/or ASICs, the FPGAs, custom ICs or ASICs also may be designed, configured and/or hard-wired to implement the methodology of the invention. For example, the controller  120 ,  160  may be implemented as an arrangement of analog and/or digital circuits, controllers, microprocessors, DSPs and/or ASICs, collectively referred to as a “controller”, which are respectively hard-wired, programmed, designed, adapted or configured to implement the methodology of the invention, including possibly in conjunction with a memory  115 . 
     The optional memory  115 , which may include a data repository (or database), may be embodied in any number of forms, including within any computer or other machine-readable data storage medium, memory device or other storage or communication device for storage or communication of information, currently known or which becomes available in the future, including, but not limited to, a memory integrated circuit (“IC”), or memory portion of an integrated circuit (such as the resident memory within a controller  120 ,  160  or processor IC), whether volatile or non-volatile, whether removable or non-removable, including without limitation RAM, FLASH, DRAM, SDRAM, SRAM, MRAM, FeRAM, ROM, EPROM or EPROM, or any other form of memory device, such as a magnetic hard drive, an optical drive, a magnetic disk or tape drive, a hard disk drive, other machine-readable storage or memory media such as a floppy disk, a CDROM, a CD-RW, digital versatile disk (DVD) or other optical memory, or any other type of memory, storage medium, or data storage apparatus or circuit, which is known or which becomes known, depending upon the selected embodiment. The memory  115  may be adapted to store various look up tables, parameters, coefficients, other information and data, programs or instructions (of the software of the present invention), and other types of tables such as database tables. 
     As indicated above, the controller  120 ,  160  is hard-wired or programmed, using software and data structures of the invention, for example, to perform the methodology of the present invention. As a consequence, the system and method of the present invention may be embodied as software which provides such programming or other instructions, such as a set of instructions and/or metadata embodied within a non-transitory computer readable medium, discussed above. In addition, metadata may also be utilized to define the various data structures of a look up table or a database. Such software may be in the form of source or object code, by way of example and without limitation. Source code further may be compiled into some form of instructions or object code (including assembly language instructions or configuration information). The software, source code or metadata of the present invention may be embodied as any type of code, such as C, C++, SystemC, LISA, XML, Java, Brew, SQL and its variations (e.g., SQL 99 or proprietary versions of SQL), DB2, Oracle, or any other type of programming language which performs the functionality discussed herein, including various hardware definition or hardware modeling languages (e.g., Verilog, VHDL, RTL) and resulting database files (e.g., GDSII). As a consequence, a “construct”, “program construct”, “software construct” or “software”, as used equivalently herein, means and refers to any programming language, of any kind, with any syntax or signatures, which provides or can be interpreted to provide the associated functionality or methodology specified (when instantiated or loaded into a processor or computer and executed, including the controller  160 ,  260 , for example). 
     The software, metadata, or other source code of the present invention and any resulting bit file (object code, database, or look up table) may be embodied within any tangible, non-transitory storage medium, such as any of the computer or other machine-readable data storage media, as computer-readable instructions, data structures, program modules or other data, such as discussed above with respect to the memory  160 , e.g., a floppy disk, a CDROM, a CD-RW, a DVD, a magnetic hard drive, an optical drive, or any other type of data storage apparatus or medium, as mentioned above. 
     In the foregoing description and in the Figures, sense resistors are shown in exemplary configurations and locations; however, those skilled in the art will recognize that other types and configurations of sensors may also be used and that sensors may be placed in other locations. Alternate sensor configurations and placements are within the scope of the present invention. 
     As used herein, the term “DC” denotes both fluctuating DC (such as is obtained from rectified AC) and constant voltage DC (such as is obtained from a battery, voltage regulator, or power filtered with a capacitor). As used herein, the term “AC”denotes any form of alternating current with any waveform (sinusoidal, sine squared, rectified sinusoidal, square, rectangular, triangular, sawtooth, irregular, etc.) and with any DC offset and may include any variation such as chopped or forward- or reverse-phase modulated alternating current, such as from a dimmer switch. 
     With respect to sensors, we refer herein to parameters that “represent” a given metric or are “representative” of a given metric, where a metric is a measure of a state of at least part of the regulator or its inputs or outputs. A parameter is considered to represent a metric if it is related to the metric directly enough that regulating the parameter will satisfactorily regulate the metric. For example, the metric of LED current may be represented by an inductor current because they are similar and because regulating an inductor current satisfactorily regulates LED current. A parameter may be considered to be an acceptable representation of a metric if it represents a multiple or fraction of the metric. It is to be noted that a parameter may physically be a voltage and yet still represents a current value. For example, the voltage across a sense resistor “represents” current through the resistor. 
     In the foregoing description of illustrative embodiments and in attached figures where diodes are shown, it is to be understood that synchronous diodes or synchronous rectifiers (for example relays or MOSFETs or other transistors switched off and on by a control signal) or other types of diodes may be used in place of standard diodes within the scope of the present invention. Exemplary embodiments presented here generally generate a positive output voltage with respect to ground; however, the teachings of the present invention apply also to power converters that generate a negative output voltage, where complementary topologies may be constructed by reversing the polarity of semiconductors and other polarized components. 
     For convenience in notation and description, a transformers may be referred to as a “transformer,” although in illustrative embodiments, it may behave in many respects also as an inductor. Similarly, inductors, using methods known in the art, can, under proper conditions, be replaced by transformers. We refer to transformers and inductors as “inductive” or “magnetic” elements, with the understanding that they perform similar functions and may be interchanged within the scope of the present invention. 
     Furthermore, any signal arrows in the drawings/Figures should be considered only exemplary, and not limiting, unless otherwise specifically noted. Combinations of components of steps will also be considered within the scope of the present invention, particularly where the ability to separate or combine is unclear or foreseeable. The disjunctive term “or”, as used herein and throughout the claims that follow, is generally intended to mean “and/or”, having both conjunctive and disjunctive meanings (and is not confined to an “exclusive or” meaning), unless otherwise indicated. As used in the description herein and throughout the claims that follow, “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Also as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     The foregoing description of illustrated embodiments of the present invention, including what is described in the summary or in the abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. From the foregoing, it will be observed that numerous variations, modifications and substitutions are intended and may be effected without departing from the spirit and scope of the novel concept of the invention. It is to be understood that no limitation with respect to the specific methods and apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.