Abstract:
A dimmer system for a luminaire is provided. The dimmer system has a dimmer that receives a first current and supplies a reduced-magnitude current. The dimmer system also has a boosting system that receives the reduced-magnitude current and supplies a boosted current to a light source or lamp if the reduced-magnitude current is being received in conjunction with the initial turn-on of the dimmer. The boosted current can be provided for a predetermined period of time. The boosted current can also be provided as pulses of boosted current interspersed with pulses of the reduced-magnitude current. The boosted current can have the magnitude of the first current or range from 70% to 100% of the first current.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates generally to apparatus and methods for providing dimming functionality for luminaires. More specifically, the disclosure relates to methods and apparatus for providing dimming functionality for light sources without an undesirable delay between activation of the dimmer and illumination of the light source. 
       BACKGROUND 
       [0002]    Dimmers for incandescent light bulbs are in wide use in the lighting industry, and are installed in millions of buildings worldwide. Dimmers are used to cause bulbs to provide less light than they would if provided with the full power from the main circuit. In most electrical systems, main power is provided with alternating current (AC). Dimmers operate by “chopping up” the AC signal—specifically, for a given cycle of the AC wave, preventing some proportion of the wave from being transmitted to the luminaire. As more dimming is desired, a larger proportion of the wave is blocked. By blocking a portion of the wave, the total root-mean-square (“RMS”) voltage provided to the light source falls. 
         [0003]    This system of dimming is very effective for incandescent bulbs, for which the total illumination has a direct relationship with the RMS voltage provided to the bulb. This dimming technology does not work as well, however, for some other types of light sources, including, but not limited to, luminaires with light emitting diode (“LED”) light sources, organic light emitting diode (“OLED”) light sources, or compact fluorescent bulbs. This is because OLED light sources, LED light sources, and compact fluorescent bulbs have an electronic ballast (for compact fluorescent bulbs) or driver (for OLED and LED light sources) that converts the main current into current that is appropriate for the given light source. The ballast/driver requires electrical power to perform its conversion. When the power provided to the ballast/driver is reduced by the dimmer, the ballast/driver may not function properly. This may manifest itself in several ways. For example, the light source may fail to illuminate entirely, or there may be a noticeable delay before the light source illuminates. In lighting applications, neither result is desirable. 
       SUMMARY 
       [0004]    The present invention provides a dimmer system for a luminaire. The dimmer system includes a dimmer that receives a first current and provides a reduced-magnitude current. The dimmer system also includes a boosting system that receives the reduced-magnitude current. If the boosting system determines that the reduced-magnitude current is being received as part of the initial turn-on of the dimmer, the boosting system provides a boosted current to a light source. The light source can be a light emitting diode. 
         [0005]    The magnitude of the boosted current can be the magnitude of the first current, or some proportion thereof, such as 70-100%. The boosting system provides the boosted current for a predetermined period of time, which can be about 0.5 seconds. The boosted current can also be pulsed, wherein pulses of boosted current are interspersed with pulses of the reduced-magnitude current. 
         [0006]    The present invention also provides a method for dimming a light source. A first current is received from a power source. The magnitude of the first current is reduced. It is then determined whether the reduced-magnitude current is being received as part of a turn-on of a dimmer. If the reduced-magnitude current is being received as part of a turn-on of a dimmer, a boosted current is provided to a light source. The light source can be a light emitting diode. 
         [0007]    The boosted current can be provided for a predetermined period, such as 0.5 seconds. The boosted current can be pulsed such that pulses of the boosted current are interspersed with pulses of the reduced-magnitude current. 
         [0008]    The present invention also provides a method for providing light. A first current is received from a power source. The magnitude of the first current is reduced based on the dimmer setting and the reduced-magnitude current is provided to a boosting system. If it is determined that the reduced-magnitude current is being received in connection with the turn-on of the dimmer, a boosted current is provided to a light source that is sufficient to illuminate the light source. 
         [0009]    Providing sufficient boosted current can involve providing the boosted current for a predetermined period of time, such as 0.5 seconds. Providing sufficient boosted current can also involve monitoring the current drawn by a light source, and determining whether the current exhibits a signature that indicates that the light sources being illuminated. The light source can be a light emitting diode, and can include a driver. 
         [0010]    These and other aspects, features, and embodiments of the invention will become apparent to a person of ordinary skill in the art upon consideration of the following detailed description of exemplary embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the exemplary embodiments of the present invention and the advantages thereof, reference is now made to the following description in conjunction with the accompanying drawings in which: 
           [0012]      FIG. 1  is a block diagram illustrating an exemplary system for dimming a light source according to one exemplary embodiment; 
           [0013]      FIG. 2  is a flow chart describing an exemplary method for dimming a light source according to one exemplary embodiment; and 
           [0014]      FIG. 3  is a flow chart describing an exemplary method for boosting current magnitude according to one exemplary embodiment. 
       
    
    
       [0015]    The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments. As one of skill in the art would understand, the electrical characteristics and response of certain components can often be replicated by the use of other components and/or combinations of components. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements. 
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0016]    The present invention is directed to electrical lighting devices. In particular, certain exemplary embodiments of this invention are directed to providing a dimmer that illuminates a light source, such as a compact fluorescent bulb, LED, or OLED. The present invention illuminates the light source without an undesirable delay between activation of the dimmer and illumination of the light source. 
         [0017]    The invention may be better understood by reading the following description of non-limiting, exemplary embodiments with reference to the attached drawings, wherein like or corresponding, but not necessarily identical, parts of each of the figures are identified by the same reference characters, and which are briefly described as follows.  FIG. 1  is a block diagram describing an exemplary system  100  for dimming a light source  125 . The system  100  includes a power source  105  that is electrically coupled to a dimmer  110 . The power source  105  delivers power to the system  100 . In one exemplary embodiment, the power source  105  is an alternating current mains power source operating at, for example, 120/240 volts at 60 Hz in the United States, 230 volts at 50 Hz in the United Kingdom, or another combination of magnitude and frequency. Generally, the magnitude and frequency of the mains power depends on the standard adopted by the region in which the system  100  is installed. 
         [0018]    The dimmer  110  is electrically coupled to the power source  105  and a booster system  115 . In one exemplary embodiment, current from the power source  105  is electrically delivered to the dimmer  110 . In certain exemplary embodiments, the dimmer  110  is a dimmer switch. The exemplary dimmer switch  110  is capable of being configured in many different forms including, but not limited to, a rotary dimmer, a slide dimmer, a touch-pad dimmer, and the like. The exemplary dimmer  110  reduces the magnitude of the current received from the power source  105 . Specifically, the dimmer  110  outputs a reduced-magnitude current as compared to the current received from the power source  105  depending on the setting of the dimmer  110 . In one exemplary embodiment, the dimmer  110  outputs a reduced-magnitude current by reducing the RMS voltage of the current received from the power source  105 , which occurs by cutting off a portion of the input current waveform. The cut-off portion of the input current waveform grows or shrinks in proportion to the dimmer  110  setting. In this embodiment, the dimmer  110  employs a microcontroller, ASIC, or other component that is configured to cut off a portion of the input waveform. In an alternative embodiment, the dimmer  110  uses discrete components, such as a triac to cut off a portion of the input waveform. As one of ordinary skill in the art would understand, however, the invention is not limited to these methods of reducing the magnitude of the input current, as there are several well known methods of reducing the magnitude of a current. Further, as one of ordinary skill in the art would understand, in certain cases, the dimmer  110  setting would be such that the magnitude of the input current would not be reduced, such as when the dimmer  110  is set to deliver full power to the light source  125 . 
         [0019]    The boosting system  115  is electrically coupled to the dimmer  110  and a driver  120 . In the exemplary embodiment, the reduced-magnitude current is electrically transmitted from the dimmer  110  to the boosting system  115 . The exemplary boosting system  115  electrically supplies either a boosted current or the reduced-magnitude current to the driver  120 , as described below. The driver  120  then electrically supplies a current to the light source  125 . 
         [0020]    In one exemplary embodiment, the boosting system  115  modifies the magnitude of the reduced-magnitude current and outputs a boosted current that is appropriate to cause a given light source  125  to illuminate without an undesirable delay after activation of the dimmer  110 . In one exemplary embodiment, the boosting system  115  senses that the dimmer  110  has been activated and outputs the boosted current, which in one exemplary embodiment, is a proportion of the current received from the power source  105 . By way of example, the boosting system  115  can output a boosted current that is 100% of the full current, or some smaller proportion thereof, such as 90%, 80%, or 70%. The precise proportion of the current from the power source  105  that the boosting system  115  outputs can vary based on specific details associated with the system, such as the type of light source  125  and driver  120  used, and the magnitude and frequency of the current received from the power source  105 . A person of ordinary skill in the art, upon reading this disclosure, would be capable of selecting an appropriate boosted current. 
         [0021]    In one exemplary embodiment, the boosting system  115  electrically supplies to the driver  120  the boosted current for a predetermined period of time that is sufficient to cause the driver  120  to quickly move to an operational state, thereby illuminating the light source  125 . After the predetermined period expires, the boosting system  115  electrically supplies to the driver  120  the reduced-magnitude current. By way of example only, the predetermined period of time is approximately one half of one second. As one of skill in the art would understand, however, the duration of the output of the boosted current can be modified to suit the precise configuration of the driver  120  and light source  125  used in the system, as well as the desired light output. As one of skill in the art would further understand—assuming by way of example that that the boosted current is greater in magnitude than the reduced-magnitude current—the application of the boosted current may result in a brief “flash,” or period of time in which the light source  125  receives more current than would normally be delivered by the dimmer  110  at that setting, which therefore illuminates the light source at a brighter level until the end of the predetermined period. Accordingly, as one of skill in the art would understand, in this embodiment, one consideration in selecting the predetermined period of time is a balance between providing sufficient power to cause the driver  120  to become operational while also minimizing the duration of any momentary flash that may occur. 
         [0022]    In an alternative exemplary embodiment, the boosting system  115  senses both the activation of the dimmer  110  and the level at which the dimmer  110  is set. By way of example, there are dimmer  110  levels at which the reduced-magnitude current is sufficiently high to cause the light source  125  to illuminate immediately. This exemplary boosting system  115  determines the minimum dimmer setting required for immediate illumination. By way of example, the boosting system  115  is programmed with a minimum dimmer  100  setting. When the dimmer  110  is activated, the dimmer setting is compared to the minimum dimmer  100  setting, and if the result of the comparison is that the dimmer  110  is set at or above that minimum level, the boosting system  115  electrically supplies the reduced-magnitude current, rather than the boosted current, to the driver  120 . 
         [0023]    In another alternative exemplary embodiment, the boosting system  115  provides a pulsed boosted current, wherein the boosting systems  115  electrically supplies bursts of the boosted current interspersed with bursts of the reduced-magnitude current to the driver  120 . By way of example only, the bursts of boosted current are sufficiently brief such that any flash caused by a burst is too brief for the human eye to detect it. 
         [0024]    In one exemplary embodiment, the boosting system  115  has a microprocessor, microcontroller, or other similar control system that provides the boosting current and reduced-magnitude current to the driver  120  as set forth in the above-described exemplary embodiments of the present invention. The microprocessor, microcontroller, or other similar control system also senses when the dimmer has been initially turned on and the length of time over which the boosting system  115  has provided the boosting current. The microprocessor, microcontroller, or other similar control system is optionally electrically coupled to the dimmer  110  and receives a signal from the dimmer indicative of the dimmer setting. Alternatively, the boosting system  115  includes discrete circuit components that provide the same functionality. 
         [0025]    In yet another alternative exemplary embodiment, the boosting system  115  monitors conditions in the system to determine when the boosted current (or the pulsed boosted current) has been provided to the driver  120  for a sufficient period of time, such that it becomes appropriate to provide the reduced-magnitude current to the driver  120 . By way of example, when the driver  120  is in a state wherein it is charging to come up to operational status, but has not yet begun to power the light source  125 , the current draw by the driver  120  will exhibit a detectable signature that differs from the signature exhibited by the driver  120  when it has reached a steady state and the light source  125  turns on. In one exemplary embodiment, the boosting system  115  monitors the current entering the driver  120 , and when the boosting system  115  detects the change in signature, the boosting system  115  switches from supplying the boosted current (or pulsed boosted current) to supplying the reduced-magnitude current to the driver  120 . 
         [0026]    As described above, the system  100  also includes a driver  120  electrically coupled to the boosting system  115  and the light source  125 . The exemplary driver  120  converts the current received from the boosting system  115  into a signal that is appropriate for the type of light source  125  that is connected to the system  100 . By way of example, drivers  120  for LED or OLED light sources  125  convert either the boosted current or the reduced-magnitude current into direct current of the proper magnitude for the LEDs or OLEDs. Drivers  120  electrically connected to compact fluorescent light sources (which, in that case, are referred to as ballasts) convert either the boosted current or the reduced-magnitude current into high frequency alternating current that is appropriate for fluorescent operation. In either case, the drivers  120  themselves require energy to perform their assigned function. 
         [0027]      FIG. 2  is a flow chart describing an exemplary method  200  for dimming according to an exemplary embodiment.  FIG. 2  will be discussed with reference to  FIG. 1 . In step  205 , the dimmer  110  receives current from the power source  105 . In step  210 , the magnitude of the power is reduced using the dimmer  110 . In step  215 , the boosting system  115  performs an inquiry to determine if it is receiving power for the first time after being turned off. In one exemplary embodiment, this determination is made by a controller in the boosting system  115 . If the answer to the inquiry in step  215  is affirmative, the “Yes” branch is followed to step  220 , wherein the boosting system  115  boosts the current as described above. The method  220  will be discussed in greater detail with respect to  FIG. 3 . Once the current has been boosted by the boosting system  115 , the process proceeds to step  225 , wherein the output of the boosting system  115  is electrically supplied to the driver  120 , which then illuminates the light source  125 . The method  200  concludes at the END step. Returning to the inquiry in step  215 , if it is determined that the system has not just been turned on, then the “No” branch is followed to step  225 , wherein the reduced-magnitude current received by the boost system  115  in step  210  is electrically supplied to the driver  120 . 
         [0028]      FIG. 3  is a flow chart diagram describing an exemplary method  220  for boosting current magnitude. Referring now to  FIGS. 1-3 , the boosting system  115  provides current with an increased magnitude to the driver  120  in step  305 . As discussed above, in one exemplary embodiment, the boosting system  115  electrically supplies the driver  120  with the current received from the power source  105 , or some proportion thereof Alternatively, the boosting system  115  electrically supplies the driver  120  a pulsed current that alternates between the reduced-magnitude current and the full current. 
         [0029]    In step  310 , an inquiry is conducted to determine if sufficient boosting has been provided by the boosting system  115 . In one exemplary embodiment, the determination is made once the boosting system  115  has provided the boosted current for a predetermined period of time. Alternatively, the boosting system  115  makes the determination based on whether the signature of the driver&#39;s  120  current draw indicates that the driver  120  has finished powering up and is illuminating the light source  125 . If the answer to the inquiry is affirmative, the method follows the “Yes” branch and proceeds to step  315 , wherein the output of the dimmer  110  is electrically supplied to the driver  120 . The method then returns to step  225  of  FIG. 2 . Turning again to step  310 , if it is determined that sufficient boosting has not been provided by the boosting system  115 , the “No” branch is followed back to step  305  and the boosting system  115  continues to electrically supply boosted current to the driver  120 . 
         [0030]    Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons of ordinary skill in the art upon reference to the description of the invention. It should be appreciated by those of ordinary skill in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or methods for carrying out the same purposes of the invention. It should also be realized by those of ordinary skill in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the scope of the invention.