Abstract:
A system and method for controlling a light output from a LED-based lighting solution is provided that may receive phase-cut AC signals and/or external digital control signals. The invention is capable of receiving both a phase-cut AC signal and an external digital control signal simultaneously and providing a desired light output from a LED-based lighting solution. The system generally includes a power source electronically connected to one or more dimmers and an AC power output of the dimmer connected to a solid state lighting device such as an LED. The system is capable of receiving signals from a wired and/or wireless external digital control device to additionally control the desired light output from a LED-based lighting solution.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/275,542, filed Jan. 6, 2016, the contents of which are incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention is in the field of Solid State Lighting (SSL), and more particularly to circuits and techniques for digital dimming of SSLs in the presence of analog phase-cut dimming. 
       BACKGROUND 
       [0003]    Providing dimming capabilities to lighting applications saves energy and enhances ambiance. Thus, a substantial portion of the lighting infrastructure for both residential and commercial applications includes some form of dimming such as a phase-cut dimmer. Phase-cut dimmers function by isolating the light fixture from the AC mains during part of the AC cycle. If the AC main cycles at 60 Hz, the phase-cut dimmer would thus isolate the light fixture at a 120 Hz rate. The phase cutting is defined with regard to the zero crossing of the AC mains. If the phase cutting begins at the zero crossing, the resulting phase-cut dimmer is denoted as a leading-edge dimmer. If the phase cutting ends at the zero crossing, the resulting phase-cut dimmer is denoted as a trailing-edge dimmer. 
         [0004]    An incandescent or fluorescent bulb may be directly powered by a phase-cut dimmer without any modification. But incandescent and fluorescent bulbs are being rapidly replaced by light emitting diode (LED)-based lighting solutions due to the improved efficiency, longer usable lifespan, and lack of toxic materials in LEDs. However, the replacement of incandescent (or fluorescent) bulbs by LEDs leads to some integration issues with regard to being powered through a phase-cut dimmer. Regardless of whether the phase-cut dimmer is a leading-edge or a trailing-edge dimmer, a conventional LED cannot typically be powered through a phase-cut dimmer without some adaptations. For example, an incandescent bulb filament cools relatively slowly and thus continues to output light during the periods in which the phase-cut dimmer isolates the incandescent bulb from the AC mains. In contrast, an LED fixture reacts very rapidly to the current isolation through the phase-cut dimmer. A conventional LED will thus be prone to flicker and other disconcerting issues if powered through a phase-cut dimmer without further adaptations. In addition, LED fixtures typically require a bleeder circuit to provide a sufficient latching current for a phase-cut dimmer such as a triac device. 
         [0005]    As compared to the analog dimming applied through a phase-cut dimmer, LED fixtures are more readily dimmed through digital approaches in which the power-switch controller for the switching power converter for the LED applies the dimming. For example, the Zigbee alliance has promulgated a standard denoted as the Zigbee Light Link for wirelessly controlling the digital dimming of LED fixtures. But these digital approaches function as an alternative to phase-cut dimmers. The combination of conventional digital control of LED dimming and phase-cut dimming results in flicker, multi-firing, phase angle distortion, and other undesirable effects. 
         [0006]    Accordingly, there is a need in the art for improved digital LED dimming techniques and systems that are compatible with the presence of a phase-cut dimmer. 
       SUMMARY 
       [0007]    A controller for controlling the cycling of a power switch in a switching power converter is configured to respond to both analog and digital dimming commands. In particular, the controller includes a phase-angle sensor for determining the amount of phase-cut angle from a phase-cut dimmer. Based upon the analog dimming application in a preceding cycle of a rectified input voltage during the preceding cycle, the controller determines a number of constant current pulses that will be driven through the power switch in a current cycle of the rectified input voltage. The controller is further configured to adjust the number of constant current pulses responsive to a digital dimming command. In this fashion, digital and analog dimming techniques are combined without the conventional risk of flicker, multi-firing, phase angle distortion and other undesirable effects. 
         [0008]    These advantageous features may be better appreciated through a consideration of the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  an example Solid State Lighting (SSL) system including a controller configured to respond to both analog and digital dimming commands. 
           [0010]      FIG. 2  shows operational waveforms of the SSL shown in  FIG. 1  during a period of no digital or analog (phase-cut) dimming. 
           [0011]      FIG. 3  illustrates the SSL system of  FIG. 1  including a phase-cut dimmer. 
           [0012]      FIG. 4A  illustrates the input voltage waveform from the rectification of an AC mains voltage for the SSL system of  FIG. 1  in the presence of a leading-edge phase-cut dimmer application. 
           [0013]      FIG. 4B  illustrates the constant-peak-current pulses of the power switch in the SSL system of  FIG. 1  in the presence of the leading-edge phase-cut dimmer application of  FIG. 4A  and as further adjusted by a digital dimming command. 
           [0014]      FIG. 4C  illustrates the bleeder circuit operation for the SSL system of  FIG. 1  in the presence of the leading-edge phase-cut dimmer application of  FIG. 4A  and as further adjusted by a digital dimming command. 
           [0015]      FIG. 5A  illustrates the division of an input voltage waveform from the rectification of an AC mains voltage into a no-dimming range, a hybrid dimming range, and a constant-peak-current dimming range. 
           [0016]      FIG. 5B  illustrates the current pulses through the power switch for the hybrid dimming range of  FIG. 5A . 
           [0017]      FIG. 6  is a more detailed block diagram for the primary controller in the SSL system of  FIG. 1 . 
           [0018]      FIG. 7A  illustrates the input voltage waveform from the rectification of an AC mains voltage for the SSL system of  FIG. 1  in the presence of a trailing-edge phase-cut dimmer application. 
           [0019]      FIG. 7B  illustrates the constant-peak-current pulses of the power switch in the SSL system of  FIG. 1  in the presence of the trailing-edge phase-cut dimmer application of  FIG. 7A  and as further adjusted by a digital dimming command. 
           [0020]      FIG. 7C  illustrates the bleeder circuit operation for the SSL system of  FIG. 1  in the presence of the trailing-edge phase-cut dimmer application of  FIG. 7A  and as further adjusted by a digital dimming command. 
           [0021]      FIG. 7D  illustrates the repositioning of the constant-peak-current pulses of  FIG. 7B  so as to be located in the maximum-voltage range for the input voltage waveform of  FIG. 7A . 
           [0022]      FIG. 8  illustrates the SSL system of  FIG. 1  integrated with a wireless receiver configured to receive the digital dimming command. 
           [0023]      FIG. 9  illustrates the current waveforms for with and without digital dimming in the absence of a phase-cut dimmer, with and without digital dimming with a leading-edge phase-cut dimmer, and with and without digital dimming with a trailing-edge phase-cut dimmer. 
       
    
    
       [0024]    Embodiments of the present disclosure and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. 
       DETAILED DESCRIPTION 
       [0025]    The following discussion will be directed to a non-isolated buck-boost power converter having a controller configured for digital dimming in the presence of a phase-cut dimmer. But it will be appreciated that the resulting digital control techniques may be widely applied to other types of switching power converters such as flyback converters that must power an LED fixture through a phase-cut dimmer. Turning now to the drawings,  FIG. 1  shows an LED fixture  100  that includes a buck-boost power converter. A diode bridge DB 1  and a bulk capacitor C 1  provide an unregulated DC voltage from the phase-cut AC mains voltage (the phase-cut dimmer is not shown for illustration clarity). An inductor L 1 , a power switch transistor S 1 , and a controller U 1  comprise the power stage. An output stage is comprised of a rectifier diode D 1  and an output capacitor C 2 . An output voltage across output capacitor C 2  powers an LED (LED 1 ). Controller U 1  regulates the output voltage (or output current) by controlling the on and off cycles of power switch transistor S 1 . A bleeder circuit  105  includes a resistor R 1  in series with a bleeder switch transistor S 2 . In alternative embodiments, bleeder circuit  105  instead is implemented through a time-division multiplexing of the power switch transistor S 1 . In such embodiment, however, bleeder switch transistor S 2  would instead be coupled in parallel with the sense resistor so that the sense resistor can be bypassed when the power switch S 1  is used to conduct bleeder current. Controller U 1  thus implements the cycling of power switch transistor S 1  as well as a cycling of bleeder switch transistor S 2  within bleeder circuit  105  regardless of the bleeder circuit embodiment. It will be appreciated that separate integrated circuits may be used to perform these functions as explained further herein. 
         [0026]    During periods of no dimming (neither digital nor analog), controller U 1  may operate using conventional peak-current control. In that regard, controller U 1  senses the peak current through inductor L 1  during each on cycle of power switch transistor S 1  through an input signal I_SENSE that may be obtained from, for example, a sense resistor (not illustrated). The input current from the AC mains without any phase-cut dimming is sinusoidal as shown in  FIG. 2 . To provide a suitably high power factor, controller U 1  controls the peak current for each cycle of the power switch transistor S 1  to mimic this sinusoidal profile as also shown in  FIG. 2 . Raising or lowering the I_Peak threshold envelope achieves output regulation. This control scheme is commonly referred to as current shaping. The output regulation from controller U 1  maintains a constant light output regardless of the AC mains input voltage. But controller U 1  departs from this peak current control methodology in the presence of digital dimming and/or phase-cut dimming as explained further herein. 
         [0027]    The integration of LED fixture  100  with a phase-cut dimmer  300  is shown in  FIG. 3 . In this embodiment, phase-cut dimmer  300  comprises a triac device that performs a leading-edge phase-cut of the AC input current from the AC mains. When the triac device is conducting electricity, a minimum holding current is required to maintain the triac in the conducting state. Because incandescent lighting solutions typically present a linear resistive load and are relatively inefficient, maintaining the minimum holding current and keeping a triac device in the conducting state is usually not a problem for an incandescent application. However, in the case of LED-based lighting solutions, which typically present substantially non-linear resistive loads and are much more efficient, maintaining a minimum load while the triac is in the conducting/on state is more complicated. The increased efficiency of the LED fixture may cause the triac to misfire (conduct insufficient holding current) over the whole conduction angle. Moreover, different triac devices often have different minimum holding currents that further complicate the design of LED-based lighting solutions for use with dimmer switches. If the minimum holding current is not met, the triac device resets thereby pre-maturely switching to the off state. This can cause light flicker, color shifting, and/or complete failure of the LED-based lighting solution. 
         [0028]    To insure the triac device remains in the on state as defined by the dimming setting, it is conventional for LED-based lighting solutions to include a bleeder circuit such as bleeder circuit  105  shown in  FIG. 1 . A bleeder circuit adds to the over-all load that the SSL draws from the AC power circuit. One use of a bleeder circuit is to provide the necessary current to keep the triac device in the on state at the desired periods. Another use of a bleeder circuit is to aid LED-based lighting solutions in detecting the phase angle of the AC input voltage. After detecting the phase angle of the AC input voltage after the triac of the dimmer switch starts to conduct, and once the desired amount of energy is delivered to the load, the LED-based lighting solution initiates on and off cycles of energy to maintain proper output regulation. Once the proper output regulation is reached, the LED-based lighting solution may suspend its on and off cycles. During this time, a bleeder circuit is used to maintain a load on the triac device. 
         [0029]    The intelligent control as disclosed herein can reduce power dissipation of the bleeder circuit, while maintaining proper operation of a phase-cut dimmer switch and accurate detection of phase angle to maintain the correct light output related to dimming settings. A phase-angle sensor (discussed further below) in controller U 1  detects when the AC input voltage crosses a preset value, such as when the voltage crosses, or is near, the zero line, 0V. When the AC input voltage is at or near the zero crossing, controller U 1  may enable bleeder circuit  105 . Bleeder circuit  105  is disabled while the switching cycles of the power switch transistor S 1  have been enabled. In some embodiments, controller U 1  may dissipate multiple levels of energy as desired. For example, during periods where the switching cycles are enabled, the input current to the SSL may still be below the holding current of the dimmer switch. In this case, a small amount of additional energy may be expended by bleeder circuit  105  to insure the triac remains in the on state while the power converter switching cycles are enabled. Once the switching cycles have been terminated, based on maintaining the desired output regulation, bleeder circuit  105  control operates as described herein. Another advantage of using the disclosed intelligent control is to avoid enabling bleeder circuit  105  when the amount of energy stored in the bulk capacitor is at the maximum for each AC half cycle. This increases the overall system efficiency while insuring the proper operation of the phase-cut dimmer. 
         [0030]    Operation of this intelligent control will first be explained in the presence of analog dimming (phase-cut dimming) but with no digital dimming being applied by the user. This intelligent control is fundamentally the same regardless of whether phase-cut dimmer  300  is a leading-edge dimmer or a trailing-edge dimmer. The resulting current waveforms for a leading-edge dimmer application are shown in  FIG. 4A  and  FIG. 4B . In particular,  FIG. 4A  shows a cycle of the rectified input voltage after application of a leading-edge dimming by leading-edge dimmer  300 . The leading edge of the input voltage cycle starting from the zero crossing for the AC mains voltage is blocked by the triac while the triac is in the non-conducting state. After sensing the phase angle for the amount of leading-edge dimming applied through the triac in a previous cycle of the AC input voltage, controller U 1  determines a number N of constant peak current pulses each having a peak current value of I_PEAK that is sufficient to maintain the input current to the LED fixture above the triac holding current. The intelligent control disclosed herein maintains the peak current I_PEAK at a constant value with each switching cycle, beginning at leading edge of the phase-cut input current as shown in  FIG. 4B . For each switching cycle, U 1  places the power switch transistor S 1  in the off state when it reaches the constant I_Peak threshold. The I_Peak threshold is established to insure sufficient triac holding current. Dimming control is thus established through the number N of such constant peak current pulses. Adjusting the point at which the switching cycles are terminated within each AC half cycle, which is illustrated by a regulation threshold, provides output regulation. The I_Peak threshold may also be raised or lowered to provide a further means of output regulation. 
         [0031]    Should a user adjust the dimming, the amount of leading edge cutting is adjusted accordingly through the dimmer setting ( FIG. 3 ). To increase light output, the dimmer switch would be adjusted, effectively increasing the phase angle (decreasing the phase-cut). As the dimming is eliminated, the controller U 1  may transition from the control scheme shown in  FIG. 4B  to the scheme discussed with regard to  FIG. 2 . This creates two problems, first, at the boundary between the two switching control schemes, there may be a noticeable light flicker. More problematic, if the dimmer switch setting caused a phase angle near the threshold where these control schemes are transitioned, there may be a constant back and forth transition between the control modes, causing light flicker even when the dimmer switch is in the steady state. Bleeder circuit  105  is maintained off during the switching cycles of  FIG. 4B  but may otherwise maintained be maintained on as shown in  FIG. 4C . 
         [0032]    To ease the transition from the constant peak current pulses of  FIG. 4B  to the current shaping control discussed with regard to  FIG. 2 , a hybrid control scheme may be implemented by controller U 1  that combines current shaping and switching cycle modulation to ensure sufficient holding current to maintain proper operation of the dimmer switch, improve total harmonic distortion (THD) performance and thus increases power factor correction (PFC) even when connected via a phase-cut dimmer switch, provide a smooth control transition from the various control schemes, prevent any light flicker, and insure consistent performance across multiple types of dimmer switches (e.g. leading, trailing, leading/trailing). 
         [0033]    One example hybrid control scheme includes the following control modes: 
         [0034]    1) Control mode A describes AC current shaping when connected directly to the AC mains (no phase-cut dimming being applied by the user) as discussed with regard to  FIG. 2   
         [0035]    2) Control mode B corresponds to the fixed peak current pulses of  FIG. 4B , and 
         [0036]    3) Control mode C corresponds to a hybrid control mode, which includes partial I_Peak current shaping, improving THD characteristics while also insuring sufficient load current. This allows for improved THD characteristics and for smooth transitioning between control modes A and B. 
         [0037]      FIG. 5A  shows an example mode assignment for a half wave of the AC input voltage. Between the zero crossing and a relatively minor percentage for the trailing edge dimming, control mode A is applied. From the relatively minor percentage to a greater percentage application of the leading-edge dimming, control mode C is applied by controller U 1 . Finally, from edge of the control mode C to a 100% dimming application, controller U 1  applies control mode B. The regime for control mode B may also be denoted as “dual loop I_PEAK” regime since it involves the application of both current shaping and also maintaining a certain minimum value for each current pulse to assure that a sufficient triac holding current is conducted. 
         [0038]      FIG. 5B  illustrates the current pulses for an example of the control mode C corresponding to the leading-edge dimming application shown in  FIG. 5A . The peak current of each pulse is above a minimum value (I_Peak minimum) that guarantees that the triac holding current is maintained. Given this minimum, the peak current is then shaped according to the input current cycle. Adjusting the I_Peak threshold and/or the number N of current pulses in mode C provides output regulation. Use of control mode C can provide improved total harmonic distortion (THD) performance when a phase-cut dimmer switch is used because it may allow for a smoother transition from modes A and B during events when the dimmer switch setting is adjusted. For example, going from a large phase-cut (low light output) to a small, or no phase-cut (maximum light output) would correspond to a transition from mode B to mode C and then from mode C to mode A. Conversely, a transition from no dimming to a sufficiently large amount of dimming would correspond to a transition from mode A to mode C and from mode C to mode B. 
         [0039]    Controller U 1  is shown in more detail in  FIG. 6 . A phase angle sensor  605  receives the rectified input voltage (or a divided version or this voltage) to calculate the amount of phase cut dimming with regard to the zero crossing of the AC mains input voltage. A peak current (Vpeak) control module  600  controls the on and off cycling of power switch transistor S 1  responsive to the Isense input. In control mode B (in the presence of a significant amount of trailing edge dimming for example) peak current control module  600  thus responds to the amount of leading-edge dimming detected by phase angle sensor  605  in one cycle of the rectified input voltage to calculate the number N of constant peak current pulses that will be applied in the subsequent cycle of the rectified input voltage. Advantageously, peak current control module  600  is further configured to reduce this number N in the presence of a digital dimming command such as received over an I2C bus at a receiver  610 . Referring again to  FIG. 4B , peak current control module  600  would implement a number N of constant peak current pulses in the absence of any digital dimming. But peak current control module  600  would then reduce this number N of constant peak current pulses responsive to the application of a digital dimming command. For example, should the digital dimming command call for a dimming of 50%, peak current control module  600  may reduce by 50% the number N of constant current pulses that follow the leading edge of the analog dimming as set by the triac. Peak current control module  600  also controls the on and off state of bleeder switch transistor S 2  such that this transistor is off during the constant peak current pulses but is otherwise turned on in the remainder of the rectified input voltage cycle as shown in  FIG. 4C . In this fashion, analog and digital dimming is combined without the conventional problems of flicker and resetting of the triac. 
         [0040]    The combination of digital dimming with a trailing-edge analog dimmer will now be discussed.  FIG. 7A  illustrates a cycle for the rectified input voltage in the presence of a trailing-edge dimmer application. Peak current control module  600  operates analogously as discussed with regard to leading-edge dimming in that it would calculate a number N of constant current pulses to be applied in the current cycle for the rectified input voltage based upon the detected phase angle. Advantageously, this number N may then be adjusted based upon the application of a digital dimming command (if present). 
         [0041]    As shown in  FIG. 7B , the constant current pulses may start from the zero crossing of the AC mains input voltage. Controller U 1  maintains bleeder circuit  105  off while the constant current pulses are active but otherwise maintains bleeder circuit  105  on as shown in  FIG. 7C . Note, however, that bleeder circuit operation then occurs while there is a maximum amount of energy stored in the output capacitor C 2  ( FIG. 1 ) as highlighted in  FIG. 7A . To prevent this energy dissipation, controller U 1  may be configured to move the constant current pulses such that they end near the trailing edge of the rectified input voltage as determined by the amount of trailing-edge dimming as shown in  FIG. 7D . In this fashion, bleeder circuit  105  will not be cycled on during the most dissipative portion of the rectified input voltage cycle, which advantageously reduces power consumption. 
         [0042]    To receive a wireless digital dimming command, a switching power converter LED driver  800  such as the buck-boost converter discussed with regard to  FIG. 1  is associated with an RF receiver such as an RF-MCU module  820  as shown in  FIG. 8 . A wireless device  805  (i.e. a smart phone, tablet, digital controller, or another digital equivalent input source) provides a digital dimming command to RF-MCU module  820  using a suitable wireless protocol such as ZigBee, Bluetooth, or WiFi. A triac dimmer  810  coupled to an AC mains  815  may be a leading-edge, trailing-edge, leading-trailing, and/or another phase-cut dimmer. A diode bridge  825  rectifies the resulting phase-cut input voltage and current from triac dimmer  810  regardless of the phase of the applied dimming (i.e. full phase, partial phase, or minimum phase). Should the user apply no digital dimming, LED driver  800  operates as discussed previously. RF-MCU  820  module communicates with LED driver  800  over a suitable interface such as an I2C bus. An auxiliary power supply  830  provides a power supply voltage to the LED driver  800  and RF-MCU module  820  by regulating from the rectified input voltage. 
         [0043]    LED driver  800  includes the controller U 1  discussed previously. Based upon the digital dimming command from RF-MCU module  820 , controller U 1  adjusts the number of current pulses from whatever value the phase cut angle provides. In other words, a given phase cut maps into a given number of constant peak current pulses (which may be current shaped in mode C for a suitable range of phase angle as discussed above). This number of pulses is further adjusted based upon the digital dimming command. 
         [0044]    The resulting advantageous combination of phase cut dimming and digital dimming may be summarized with regard to  FIG. 9 , which is organized into two columns. The left-most column corresponds to no digital dimming whereas the right-most column corresponds to the application of some degree of digital dimming (e.g., 1 to 99% of the maximum available power).  FIG. 9  is also organized into three rows. An upper-most row corresponds to no phase-cut dimming A middle row corresponds to the application of a leading edge phase-cut dimmer whereas the bottom row corresponds to the application of a trailing-edge phase-cut dimmer. The upper row thus corresponds to the current shaping control discussed with regard to  FIG. 2 . The application of leading-edge or trailing edge dimming without any digital dimming thus corresponds to  FIGS. 4B and 7D , respectively. The application of leading-edge or trailing edge dimming in the presence of digital dimming similarly corresponds to  FIGS. 4B and 7D , respectively. As shown in  FIG. 9 , the addition of digital dimming reduces the number of constant peak current pulses in both the leading-edge and trailing-edge dimming applications. 
         [0045]    In one embodiment, external digital control is set as a high priority but uses the phase-cut dimmer angle as the upper limit on light output. In this control scheme, external digital control cannot go above the dimmer phase determined limit; however, external digital control can adjust the output downward by adjusting the regulation threshold, thereby adjusting the number of PMW pulses. External digital control can work at any phase angle of the phase-cut dimmer to regulate LED output (i.e. operational state, brightness/current, and/or color/temperature). 
         [0046]    In another embodiment of, phase-cut dimmer angle is set as a high priority, but external digital control is set as the upper limit. Phase-cut dimmer is limited by the external digital control determined upper limit; however, phase-cut dimming can adjust the output downward by adjusting the phase-cut dimmer angle. External digital control can work at any phase angle of the phase-cut dimmer to regulate LED output (i.e. operational state, brightness/current, and/or color/temperature). 
         [0047]    In yet another embodiment, the regulation threshold/dimming ratio is the product of the external digital control ratio and phase-cut dimming ratio. External digital control can work at any phase angle of the phase-cut dimmer to regulate LED output (i.e. operational state, brightness/current, and/or color/temperature). 
         [0048]    In another embodiment, the phase-cut dimmer angle can be used to adjust warm or cool LED color temperature (i.e. lower dimmer phase to achieve warmer light color). The warmer versus cooler light control could also be reversed where the low dimming phase is cooler, and this control method would still fall under the spirit and intent of this invention. 
         [0049]    In another embodiment, more than one phase-cut dimmer is connected to the LED-based lighting solution. In another embodiment, more than one external digital control is connected to the LED-based lighting solution. In yet another embodiment, a combination of one or more phase-cut dimmers and one or more digital dimmer control interfaces are connected to the LED-based lighting solution. In yet another embodiment, an external digital control can be replaced by an analog dimming signal. In yet another embodiment, the external digital control interface can be replaced by a variable voltage (i.e. 0-10 v) dimmer signal. In yet another embodiment, the last adjustment dimmer source, whether it is phase-cut dimmer or external digital control, determines the final regulated LED current. 
         [0050]    As those of some skill in this art will by now appreciate and depending on the particular application at hand, many modifications, substitutions and variations can be made in and to the materials, apparatus, configurations and methods of use of the devices of the present disclosure without departing from the scope thereof. In light of this, the scope of the present disclosure should not be limited to that of the particular embodiments illustrated and described herein, as they are merely by way of some examples thereof, but rather, should be fully commensurate with that of the claims appended hereafter and their functional equivalents.