Abstract:
Circuits to provide phase-cut analog dimming of solid state light sources are presented. Each circuit comprises an anchoring circuit to communicate with a dimming controller circuit, the anchoring circuit having a proportional direct current (DC) voltage input, a biasing voltage input, a connection to a ground reference, and an output in communication with a dimming controller circuit. The anchoring circuit provides a reference voltage to permit phase cut dimming to be operable at a plurality of line voltages.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/979,251, entitled “CIRCUIT FOR PHASE-CUT ANALOG DIMMING OF SOLID STATE LIGHT SOURCES”, filed on Apr. 14, 2014, and U.S. Provisional Application No. 62/078,184, entitled “PEAK DETECTOR TO ENABLE UNIVERSAL VOLTAGE PHASE CUT DIMMING”, filed on Nov. 11, 2014, the entire contents of both of which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to lighting, and more specifically, to electronic drivers that power one or more solid state light sources. 
       BACKGROUND 
       [0003]    Conventional wall dimmers work quite smoothly with traditional (e.g., incandescent) lamp technology, and results in light that looks very appealing. It is aesthetically pleasing and economical in its implementation. To be fully embraced by end users, this is the benchmark dimming of solid state light sources needs to hit and then surpass. Unfortunately, dimmed solid state light sources often do not fare so well. Substantial power savings alone do not overcome the desire of the end user who is looking to re-create the effect and response of their existing lighting infrastructure. 
         [0004]    The two major types of phase-cut dimmers used today (so-called because they remove, or cut, selected portions from each AC half-cycle wave) are leading-edge dimmers (LEDIM) and trailing-edge dimmers (TEDIM). 
         [0005]    Consider an environment such as restaurants. Restaurants are quintessential environments for dimmer use, with the business norm being that lighting is in some dimmed mode, usually within the bottom 20% of the full-light level, to create a traditional intimate dining experience. By varying dimming, restaurants create areas of high luminance contrast ratios by having a low level background light between tables with often a highlight lamp or central candle placed on the table to create pools of lighting. After closing, and during the day, the restaurant may also require 100% lighting levels for cleaning, next day preparations, and so on. Movie theaters are another example of an environment where lighting is required in both dimmed mode (during the showing of a movie) and high luminance (non-dimmed) mode (before and after the movie is shown). 
       SUMMARY 
       [0006]    Conventional techniques for dimming solid state light sources usually involve complicated circuitry to work with a traditional phase-cut dimmer or simply bypass or require the removal of a traditional phase-cut dimmer. Thus, there is currently no solution in particular for phase-cut dimming at 277 VAC applied to an analog primary-side regulated fly-back topology. Some analog solid state light source power supplies having universal input voltage capability (120 VAC and 277 VAC) may need phase-cut dimming (PCD) at 277 VAC, especially in retrofit applications. A primary-side regulated analog fly-back converter, in which the multiplier pin of the controller has to be conditioned to make the converter respond properly to either 120V or 277V, can operate with universal input voltage, but PCD is only suitable at 120V. Embodiments described herein solve the above mentioned problem, by introducing a circuit that enables the analog converter to be properly dimmed at 277V as well as 120V. 
         [0007]    In an embodiment, there is provided a circuit. The circuit includes an anchoring circuit in communication with a dimming controller circuit, the anchoring circuit including a proportional direct current (DC) voltage input, a biasing voltage input, a connection to a ground reference, and an output in communication with the dimming controller circuit; wherein the anchoring circuit provides a reference voltage to permit phase cut dimming to be operable at a plurality of line voltages. 
         [0008]    In a related embodiment, the anchoring circuit may include a first resistor including a first lead coupled to a positive proportional DC voltage and including a second lead; a second resistor including a first lead coupled to a biasing voltage and including a second lead; a third resistor including a first lead coupled to the biasing voltage and including a second lead; a fourth resistor including a first lead coupled to the second lead of the second resistor and including a second lead; a fifth resistor including a first lead coupled to a second lead of the third resistor and including a second lead; a first transistor including a first lead coupled to the second lead of the second resistor, a second lead coupled to the second lead of the first resistor, and a third lead coupled to the ground reference; a second transistor including a first lead coupled to the second lead of the fourth resistor, a second lead coupled to the second lead of the third resistor, and a third lead coupled to the ground reference; and a third transistor including a first lead coupled to the second lead of the fifth resistor, a second lead including an output of the anchoring circuit, and a third lead coupled to the ground reference. 
         [0009]    In a further related embodiment, the first transistor may include a silicon controlled rectifier (SCR) and the first lead of the SCR may include an anode, the second lead may include a gate, and the third lead may include a cathode. In another further related embodiment, the second transistor may include an NPN transistor and the first lead of the NPN transistor may include a base of the NPN transistor, the second lead may include an emitter of the NPN transistor, and the third lead may include a collector of the NPN transistor. In still another further related embodiment, the third transistor may include a MOSFET and the first lead of the MOSFET may include a gate of the MOSFET, the second lead may include a drain of the MOSFET, and the third lead may include a source of the MOSFET. 
         [0010]    In yet another further related embodiment, for a first input voltage the third transistor may be open, the second transistor may be closed, and the first transistor may be open. In still yet another further related embodiment, for a second input voltage the third transistor may be closed, the second transistor may be open, and the first transistor may be closed. 
         [0011]    In another related embodiment, the anchoring circuit may include: a first resistor comprising a first lead coupled to a line voltage and comprising a second lead; a second resistor comprising a first lead coupled to a second lead of the first resistor and comprising a second lead coupled to the ground reference; a diode comprising a first lead comprising an anode coupled to the second lead of the first resistor and comprising a second lead comprising a cathode; a third resistor comprising a first lead coupled to the second lead of the diode and comprising a second lead; a fourth resistor comprising a first lead coupled to the second lead of the third resistor and comprising a second lead coupled to the ground reference; a first capacitor comprising a first lead coupled to the second lead of the diode, and comprising a second lead coupled to the ground reference; a first transistor comprising a first lead coupled to the second lead of the fourth resistor, a second lead comprising an output of the anchoring circuit, and a third lead coupled to the ground reference; and a second capacitor comprising a first lead coupled to the second lead of the first transistor, and comprising a second lead capable of being coupled to the dimming controller circuit. 
         [0012]    In a further related embodiment, the first transistor may include a MOSFET and wherein the first lead of the MOSFET may include a gate of the MOSFET, the second lead may include a drain of the MOSFET, and the third lead may include a source of the MOSFET. 
         [0013]    In another embodiment, there is provided a phase cut dimming circuit. The phase cut dimming circuit includes: a dimming controller circuit, the dimming controller circuit comprising an input receiving a line voltage, a connection to a ground, and an output; an anchoring circuit in communication with the dimming controller circuit, the anchoring circuit comprising an input, a connection to a ground, and an output in communication with the dimming controller circuit; wherein the anchoring circuit provides a reference voltage to permit phase cut dimming to be operable at a plurality of line voltages. 
         [0014]    In a related embodiment, the dimming controller circuit may include a controller comprising an input coupled to a center point of a voltage divider circuit, the controller providing an output to couple to a primary side regulated analog flyback converter; and a voltage divider circuit coupled between the line voltage and the ground, wherein the voltage divider circuit may include: a first resistor comprising a first lead coupled to the input of the controller and a second lead coupled to the ground; a second resistor comprising a first lead coupled to the input of the controller and a second lead coupled to the line voltage, and wherein the first lead of the second resistor and the first lead of the first resistor comprise the center point of the voltage divider circuit; and a third resistor comprising a first lead coupled to the center point of the voltage divider circuit and a second lead to couple to an input of the anchoring circuit. 
         [0015]    In another related embodiment, the anchoring circuit may include: a first resistor comprising a first lead coupled to a positive proportional DC voltage and comprising a second lead; a second resistor comprising a first lead coupled to a biasing voltage and comprising a second lead; a third resistor comprising a first lead coupled to the biasing voltage and comprising a second lead; a fourth resistor comprising a first lead coupled to the second lead of the second resistor and comprising a second lead; a fifth resistor comprising a first lead coupled to a second lead of the third resistor and comprising a second lead; a first transistor comprising a first lead coupled to the second lead of the second resistor, a second lead coupled to the second lead of the first resistor, and a third lead coupled to the ground reference; a second transistor comprising a first lead coupled to the second lead of the fourth resistor, a second lead coupled to the second lead of the third resistor, and a third lead coupled to the ground reference; and a third transistor comprising a first lead coupled to the second lead of the fifth resistor, a second lead comprising an output of the anchoring circuit, and a third lead coupled to the ground reference. In a further related embodiment, the first transistor may include a silicon controlled rectifier (SCR) and the first lead of the SCR may include an anode, the second lead may include a gate, and the third lead may include a cathode. 
         [0016]    In another further related embodiment, the second transistor may include an NPN transistor and the first lead of the NPN transistor may include a base of the NPN transistor, the second lead may include an emitter of the NPN transistor, and the third lead may include a collector of the NPN transistor. In yet another further related embodiment, the third transistor may include a MOSFET and wherein the first lead of the MOSFET may include a gate of the MOSFET, the second lead may include a drain of the MOSFET, and the third lead may include a source of the MOSFET. 
         [0017]    In still another further related embodiment, for a first input voltage, the third transistor may be open, the second transistor may be closed, and the first transistor may be open. In yet still another further related embodiment, for a second input voltage, the third transistor may be closed, the second transistor may be open, and the first transistor may be closed. 
         [0018]    In still yet another further related embodiment, the anchoring circuit may include: a first resistor comprising a first lead coupled to a line voltage and comprising a second lead; a second resistor comprising a first lead coupled to a second lead of the first resistor and comprising a second lead coupled to the ground reference; a diode comprising a first lead comprising an anode coupled to the second lead of the first resistor and comprising a second lead comprising a cathode; a third resistor comprising a first lead coupled to the second lead of the diode and comprising a second lead; a fourth resistor comprising a first lead coupled to the second lead of the third resistor and comprising a second lead coupled to the ground reference; a first capacitor comprising a first lead coupled to the second lead of the diode, and comprising a second lead coupled to the ground reference; a first transistor comprising a first lead coupled to the second lead of the fourth resistor, a second lead comprising an output of the anchoring circuit, and a third lead coupled to the ground reference; and a second capacitor comprising a first lead coupled to the second lead of the first transistor, and comprising a second lead capable of being coupled to the dimming controller circuit. 
         [0019]    In a further related embodiment, the first transistor may include a MOSFET and wherein the first lead of the MOSFET may include a gate of the MOSFET, the second lead may include a drain of the MOSFET, and the third lead may include a source of the MOSFET. 
         [0020]    Note that each of the different features, techniques, configurations, etc. discussed herein can be executed independently or in combination. Accordingly, the present invention can be embodied and viewed in many different ways. Also, note that this summary section herein does not specify every embodiment and/or incrementally novel aspect of the present disclosure or claimed invention. Instead, this summary only provides a preliminary discussion of different embodiments and corresponding points of novelty over conventional techniques. For additional details, elements, and/or possible perspectives (permutations) of the invention, the reader is directed to the Detailed Description section and the corresponding figures as further discussed below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The foregoing and other objects, features and advantages disclosed herein will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles disclosed herein. 
           [0022]      FIG. 1  depicts a schematic of a conventional controller and support circuitry for handling a single line voltage. 
           [0023]      FIG. 2  depicts a schematic of a conventional controller and support circuitry for handling multiple line voltages. 
           [0024]      FIG. 3  depicts a graph of the voltage and power provided by the circuit of  FIG. 2 . 
           [0025]      FIG. 4  depicts a graph showing a dimming range for a first line voltage. 
           [0026]      FIG. 5  depicts a graph showing a dimming range for a second line voltage. 
           [0027]      FIG. 6  depicts a schematic of another conventional controller and support circuitry for handling multiple line voltages. 
           [0028]      FIG. 7  depicts a graph of the voltage and current provided by the circuit of  FIG. 6 . 
           [0029]      FIG. 8  depicts a graph showing a dimming range for a first line voltage for the circuit of  FIG. 6 . 
           [0030]      FIG. 9  depicts a graph showing a dimming range for a second line voltage for the circuit of  FIG. 6 . 
           [0031]      FIG. 10  depicts a schematic of a first circuit to provide phase-cut analog dimming of solid state light sources according to embodiments disclosed herein. 
           [0032]      FIG. 11  depicts a graph showing a dimming range for multiple line voltages for the circuit of  FIG. 10 , according to embodiments disclosed herein. 
           [0033]      FIG. 12  depicts a schematic of the first circuit to provide phase-cut analog dimming of solid state light sources including an anchoring circuit according to embodiments disclosed herein. 
           [0034]      FIG. 13  depicts a schematic of a second circuit to provide phase-cut analog dimming of solid state light sources according to embodiments disclosed herein. 
           [0035]      FIG. 14  depicts a graph showing a dimmer at minimum light in a trailing edge mode according to embodiments disclosed herein. 
           [0036]      FIG. 15  depicts a graph showing a dimmer at minimum light in a leading edge mode according to embodiments disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing embodiments of the invention. Upon reading the following description in light of the accompanying figures, those skilled in the art will understand the concepts of the invention and recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
         [0038]    Embodiments shown and described throughout allow analog primary-side regulated fly-back converters to be upgraded to enable phase cut dimming at, for example, 277 VAC, by using a low cost analog anchoring circuit. The circuit enables a linear range of clean dimming for solid state light sources. Referring to  FIG. 1 , a dedicated voltage (either 120 or 277 Volts Alternating Current (VAC)) configuration  10  is shown in which a voltage V 1  at a multiplier pin MULT of a controller U 1  is simply taken from a voltage-divider of a line voltage V line , given by V 1 =V line R 1 /(R 1 +R 2 ). Using this configuration, phase-cut dimming is possible, but not for universal voltage operation. That is, a change in the line voltage V line  results in corresponding changes required in the first resistor R 1 , which has a first lead and a second lead, and the second resistor R 2 , which also has a first lead and a second lead. The first lead of the second resistor R 2  is connected to the line voltage V line , and the second lead of the second resistor R 2  is connected to the first lead of the first resistor R 1 . The second lead of the first resistor R 1  is connected to ground. 
         [0039]    When universal input voltage operation is needed, a modified circuit  20  including extra circuitry than shown in  FIG. 1  is required around the multiplier pin MULT of the controller U 1 , like the one shown in  FIG. 2 , in order to make the circuit  20  deliver the same level of power at both 120 VAC and 277 VAC. Here, the line voltage V line  appears in the form of a proportional direct current (DC) voltage  174  at an input of a voltage-to-current device, which is actually an NPN transistor, with an input current i 3  being a collector current. The collector of the NPN transistor (i.e., the voltage-to-current device) is connected to a third resistor R 3 , which is connected to the voltage divider formed by the first resistor R 1  and the second resistor R 2 . More specifically, the third resistor R 3  has a first lead, connected to the collector of the NPN transistor, and a second lead, connected to the voltage divider (i.e., to the second lead of the second resistor R 2  and the first lead of the first resistor R 1 ). A capacitor C 1 , having a first lead and a second lead, is in parallel across the first resistor R 1 , such that the first lead of the capacitor C 1  is connected to the first lead of the first resistor R 1 , and the second lead of the capacitor C 1  is connected to the second lead of the first resistor R 1 . At 120 VAC, with no dimming, the proportional DC voltage V 4  is relatively low and drives the NPN transistor into cut-off, so the voltage V 1  at the multiplier pin MULT follows the voltage-divider effect given by the selected first resistor R 1  and the second resistor R 2 . At 277 VAC, with no dimming, the proportional DC voltage V 4  goes high, the NPN transistor enters its active region, and the collector current i 3  increases, pulling the voltage V 1  down in such a way that output power remains the same as at 120 VAC. This is illustrated in a graph  30  shown in  FIG. 3 . All component values are tuned to give the same output power during no-dimming operation at both points A and B in the graph  30 . 
         [0040]    When phase-cut dimming is performed at 120 VAC, the proportional DC voltage  174  decreases when the dimmer is slid down. This does not affect the situation with the voltage  171 , as the NPN transistor remains in cut-off, so the third resistor R 3  between the voltage divider and the NPN transistor (shown in  FIG. 2 ) is not in the circuit. The output power goes with the dimmer action, from 0V to point A, and the voltage V 1  remains at the same level in at point A as shown in a graph  40  of  FIG. 4 . However, if the same circuit is used for phase-cut dimming at 277 VAC, no linearity shows up between the output light and the dimmer position, from 0V to point B, as illustrated in a graph  50  of  FIG. 5 . Therefore, the circuit of  FIG. 2  is not recommended for 277 VAC phase-cut dimming purposes, as it produces non-linear results. 
         [0041]    Referring now to  FIG. 6 , a circuit  60  is shown that allows a proper response of the converter for universal input voltage. When operating at a first voltage, for example 120 VAC, a switch Q 1  (which in some embodiments is a MOSFET) is maintained open, in which case the voltage V 1  at the multiplier pin MULT of the controller U 1  is taken from a straightforward voltage divider of the rectified line voltage V line , given by V 1 =V line *R 1 /(R 1 +R 2 ). A capacitor C 1  is present to reduce noise at the multiplier pin MULT. When operating at a second voltage, for example 277 VAC, the switch Q 1  should be maintained closed. This places the first resistor R 1  in parallel with the third resistor R 3 , which furnishes a lower voltage V 1 , making the circuit deliver just about the same output current as at the first voltage (e.g., 120 VAC), as shown in  FIG. 7 , which is a graph  70  of the voltage V 1  at the multiplier pin MULT and an output current I out  at 120 VAC and 277 VAC operation. A second capacitor C 2 , in parallel with the capacitor C 1 , reinforces the bypass action at the multiplier pin MULT. 
         [0042]    Looking again at the graph  70  of  FIG. 7  when dimming is applied, the behavior of the output current I out  versus the dimmer position is not the same for dimming at the first voltage (i.e., 120 VAC) as for dimming at the second voltage (i.e., 277 VAC). When a dimmer is connected at the first voltage (i.e., 120 VAC), the output current I out  will substantially follow the position of the dimmer. But when dimming occurs at the second voltage (i.e., 277 VAC), there is a challenge of the output current I out  going high, which occurs somewhere in between 120 VAC and 277 VAC, possibly around the midway point, resulting in an “overlight” situation. Graphs  80  and  90  of  FIGS. 8 and 9 , respectively, illustrate the situation comparing the output current lout for 120 VAC dimming ( FIG. 8 ) with 277 VAC dimming ( FIG. 9 ).  FIG. 9  also shows what the desired behavior of the output current I out  at 277 VAC dimming should be. Embodiments make the desired behavior happen when phase-cut dimming occurs at the second voltage (e.g., 277 VAC), without going into the unwanted “overlight” situation. 
         [0043]    The presently disclosed circuits for phase-cut analog dimming of solid state light sources allow the primary-side regulated power supply to be compatible with leading edge and trailing edge dimmers for both 120 VAC and 277 VAC.  FIG. 10  shows a circuit  100 , which is substantially similar to the circuit  20  of  FIG. 2 , except that the NPN transistor is replaced with an anchoring circuit  110 , such that the first lead of the third resistor R 3  is connected to the anchoring circuit  110 . At 120 VAC, the anchoring circuit  110  makes the third resistor R 3  to be out of the circuit (such that the current i 3 =0, or a voltage between the anchoring circuit  110  and the third resistor R 3  V 3 =the voltage V 1 , which is at a high level), and stays like that during the whole sliding range of the phase-cut dimmer. At 277 VAC, the anchoring circuit makes the third resistor R 3  to be in the circuit (that is, the voltage V 3 ≈0), so the voltage V 1  is at a low level, and stays like that for the whole sliding range of the 277V dimmer. This allows the phase cut dimming at 277 VAC to be done in such a way that the output current, and thus the light output by the solid state light source(s) driven by that output current, goes with the dimmer action, as illustrated in a graph  111  shown in  FIG. 11 . 
         [0044]    A schematic of a circuit  120  including the anchoring circuit  110  in detail and the rest of the circuit  100  of  FIG. 10  is shown in  FIG. 12 . A MOSFET Q 3  having three leads, that is, a gate, a source, and a drain, is connected between the third resistor R 3  and ground. More specifically, the source is connected to the first lead of the third resistor R 3 , the drain is connected to ground, and the gate is connected to a fourth resistor R 4 . The fourth resistor R 4  has a first lead, which is connected to a fifth resistor R 5 , and a second lead, which is connected to the gate of the MOSFET Q 3 . The fifth resistor R 5  has a first lead and a second lead, where the second lead is connected to the first lead of the fourth resistor R 4  and to an NPN transistor Q 2  having three leads, that is, a base, a collector, and an emitter. More specifically, the second lead of the fifth resistor R 5  and the first lead of the fourth resistor R 4  are connected to the collector of the NPN transistor Q 2 . The emitter of the NPN transistor Q 2  is connected to ground. The base of the NPN transistor Q 2  is connected to a sixth resistor R 6 , which has a first lead and a second lead. The second lead of the sixth resistor R 6  is connected to the base of the NPN transistor Q 2 , while the first lead of the sixth resistor R 6  is connected to a seventh resistor R 7 . The seventh resistor R 7  has a first lead, which is connected to the first lead of the sixth resistor R 6 , and a second lead, which is connected to the first lead of the fifth resistor R 5 . The sixth resistor R 6  and the seventh resistor R 7  are each connected to a silicon controller rectifier Q 1 , which has three leads, that is, an anode, a gate, and a cathode. Thus, the first lead of the sixth resistor R 6  and the first lead of the seventh resistor R 7  are both connected to the anode of the silicon controller rectifier Q 1 . The cathode of the silicon controller rectifier Q 1  is connected to ground, and the gate of the silicon controller rectifier Q 1  is connected to an eighth resistor R 8 . The eighth resistor R 8  has a first lead, connected to the proportional DC voltage V 4 , and a second lead, connected to the gate of the silicon controller rectifier Q 1 . 
         [0045]    In order to differentiate between operating and dimming at 120 VAC in comparison with operating and dimming at 277 VAC, the following happens. The MOSFET Q 3  is open when the circuit  120  normally operates at 120 VAC, and along the whole sliding range of the phase-cut dimmer at 120 VAC. During all these events, the NPN transistor Q 2  remains closed, and the silicon controller rectifier Q 1  remains open. The MOSFET Q 3  is closed when the circuit  120  is powered with 277 VAC, and along the whole sliding range of the phase-cut dimmer at 277 VAC. During all these events, the NPN transistor Q 2  remains open, and the silicon controller rectifier Q 1  remains closed. 
         [0046]    This is summarized in Table 1. To make these conditions happen, the action of the silicon controller rectifier (SCR) Q 1  has to be set by choosing the values of the seventh resistor R 7  and the eighth resistor R 8  in such a way that the silicon controller rectifier Q 1  triggers at 277 VAC, but not at 120 VAC. In addition, a biasing voltage V′ cc , applied to the first lead of the fifth resistor R 5  and the second lead of the seventh resistor R 7 , is incorporated to maintain the status of the silicon controller rectifier Q 1 , the NPN transistor Q 2 , and the MOSFET Q 3 , as required. To avoid loading problems at turn-on, the biasing voltage V′ cc  is separated from a regular voltage V cc  assigned to a microcontroller U 1 , being both originated from the same auxiliary winding in a transformer (not shown). 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 State of switches during full range of dimming 
               
             
          
           
               
                 V line   
                 Q 1   
                 Q 2   
                 Q 3   
                 PCD 
               
               
                   
               
               
                 120 VAC 
                 open 
                 close 
                 open 
                 Whole range 
               
               
                 277 VAC 
                 close 
                 open 
                 close 
                 Whole range 
               
               
                   
               
             
          
         
       
     
         [0047]      FIG. 13  shows a circuit  130  to allow a proper response to phase-cut dimming for universal input voltage. The circuit  130  includes the controller U 1 , with the multiplier pin MULT, connected to a voltage divider formed by the first resistor R 1  and the second resistor R 2 , with the voltage V 1  and the line voltage V line , and the third resistor R 3  and the capacitor C 1  all connected as described above. The circuit  130  also includes a second capacitor C 2  having a first lead and a second lead, with the first lead connected to the first lead of the third resistor R 3  and the second lead connected to the second lead of the third resistor R 3 , such that the second capacitor C 2  is in parallel with the third resistor R 3 . The circuit  130  also includes a MOSFET Q 4 , having three leads, that is, a gate, a source, and a drain. The source is connected to the first lead of the third resistor R 3  and the first lead of the second capacitor C 2 . The drain is connected to ground, and the gate is connected to the fourth resistor R 4  and the fifth resistor R 5 . The fourth resistor R 4  and the fifth resistor R 5  each have a first lead and a second lead, where the second lead of the fourth resistor R 4  is connected to the first lead of the fifth resistor R 5 , and both are connected to the gate of the MOSFET Q 4 . The second lead of the fifth resistor R 5  is connected to ground. The first lead of the fourth resistor R 4  is connected to a first lead of a third capacitor C 3 , which also has a second lead connected to ground. Thus, the third capacitor C 3  is in parallel with the series connection of the fourth resistor R 4  and the fifth resistor R 5 . The first lead of the fourth resistor R 4  is also connected to a diode D 1 , which has two leads, that is, an anode and a cathode. The cathode of the diode D 1  is connected to the first lead of the fourth resistor R 4  and the first lead of the third capacitor C 3 . The anode of the diode D 1  is connected to the sixth resistor R 6 , which has a first lead and a second lead, and to the seventh resistor R 7 , which has a first lead and a second lead. The first lead of the seventh resistor R 7  is connected to the anode of the diode D 1 , and the second lead of the seventh resistor R 7  is connected to ground. The first lead of the sixth resistor R 6  is connected to the anode of the diode D 1  and the second lead of the sixth resistor R 6  is connected to the line voltage V line . 
         [0048]    When operating at a first voltage, for example 120 VAC, the MOSFET Q 4  is maintained open, in which case the voltage V 1  at the multiplier pin MULT of the controller U 1  is taken from a straightforward voltage divider of the rectified line voltage, given by V 1 =V line *R 1 /(R 1 +R 2 ). The capacitor C 1  is present to reduce noise at the multiplier pin MULT. When operating at a second voltage, for example 277 VAC, the MOSFET Q 4  is maintained closed, placing the first resistor R 1  in parallel with the third resistor R 3 , which results in a lower voltage V 1 , making the circuit  130  deliver just about the same output current as when operating at the first voltage (e.g., 120 VAC). The second capacitor C 2  is also now in parallel with the capacitor C 1 , which reinforces the bypass action at the multiplier pin MULT. The third capacitor C 3  is of a value (for example, ˜1 μF) in order to be always charged in one direction through the diode D 1  up to a voltage V p , which is proportional to the peak voltage detected from the rectified line voltage V line . The MOSFET Q 4  turns on or off, according to the value of the voltage V p . When operating with no dimmer at a first voltage (e.g., 120V), the voltage V p  will be proportional to a first peak value (e.g., 170V). When operating with no dimmer at a second voltage (e.g., 277V), the voltage V p  will be proportional to a second peak value (e.g., 392V). In consequence, resistance ratios R 7 /(R 6 +R 7 ) and R 5 /(R 4 +R 5 ) are selected in such a way that at the first voltage (e.g., 120V), the MOSFET Q 4  is continuously open, and at the second voltage (e.v., 277V), the MOSFET Q 4  is continuously closed. 
         [0049]    In addition, the resistance ratios R 7 /(R 6 +R 7 ) and R 5 /(R 4 +R 5 ) have to meet another important condition. When a phase-cut dimmer/phase cut dimming circuitry is connected to the circuit  130 , for any possible input voltage, along any position of the dimmer, and using either trailing-edge or leading-edge mechanism, the gate voltage at the MOSFET Q 4  should be in such a way that the MOSFET Q 4  will unambiguously either continuously open during dimming at the first voltage or continuously close during dimming at the second voltage. This unambiguousness of the voltage V p  should occur even at the minimum position of the dimmer, which usually is not less than 30° in commercially available cut-phase dimmers. 
         [0050]      FIGS. 14 and 15  show graphs  140 ,  150  of the state of switches over the range of dimming. The graphs  140 ,  150  show that, for both leading-edge (the graph  140 ) and trailing-edge (the graph  150 ) operation, the detectable peak value for the first voltage (e.g., 120V) goes from a first value (e.g., 85V) up to a second value (e.g., 170V), and for the second voltage (e.g., 277V), the detectable peak goes from a third value (e.g., 196V) up to a fourth value (e.g., 392V). This means that the lowest detectable peak at dimming at the second voltage will always be higher than the second value. Therefore, selecting the resistance ratios as, for example, R 7 /(R 6 +R 7 )=0.03 and R˜(R 4 +R 5 )=0.96, assures an unmistaken operation during any phase cut dimming. Thus, embodiments such as shown in  FIG. 13  provide a simple, low-cost configuration to enable the driver to perform reliable operation during dimming at multiple input voltages, such as but not limited to both 120V and 277V. 
         [0051]    Unless otherwise stated, use of the word “substantially” may be construed to include a precise relationship, condition, arrangement, orientation, and/or other characteristic, and deviations thereof as understood by one of ordinary skill in the art, to the extent that such deviations do not materially affect the disclosed methods and systems. 
         [0052]    Throughout the entirety of the present disclosure, use of the articles “a” and/or “an” and/or “the” to modify a noun may be understood to be used for convenience and to include one, or more than one, of the modified noun, unless otherwise specifically stated. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
         [0053]    Elements, components, modules, and/or parts thereof that are described and/or otherwise portrayed through the figures to communicate with, be associated with, and/or be based on, something else, may be understood to so communicate, be associated with, and or be based on in a direct and/or indirect manner, unless otherwise stipulated herein. 
         [0054]    Although the methods and systems have been described relative to a specific embodiment thereof, they are not so limited. Obviously many modifications and variations may become apparent in light of the above teachings. Many additional changes in the details, materials, and arrangement of parts, herein described and illustrated, may be made by those skilled in the art.