Patent Publication Number: US-8994296-B1

Title: External control module for an LED driver

Description:
RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/528,802, filed Aug. 30, 2011, and titled “External Control Module For An LED Driver,” the entire contents of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to light fixtures, and more particularly to systems, methods, and apparatuses for driving current for LED light fixtures. 
     BACKGROUND 
     For many years, fluorescent light fixtures have dominated markets for lighting applications. Recently, advances in light emitting diode (“LED”) technology have allowed LED light fixtures to compete with linear fluorescent products on light output, uniformity, and efficacy. As a wide variety of LED light fixtures have become available, different LED drivers are needed to provide a constant current output to the different LED light fixtures. 
     Typically, different LED fixtures require different lumen levels. Different lumen levels are achieved by applying different drive current output levels. Presently, LED drivers produce constant current outputs. LED drivers do not have the capability to adjust or change the current level of the constant current output above a particular current limit. One reason for this is that safety regulations require that LED drivers have no capacity or capability for an end user to adjust current levels beyond certain limits. If the current output of an LED driver could be increased by an end user without a set limit, the LED driver could overheat an LED light fixture, which, for example, could cause fire. Thus, the LED driver must be configured to have at least either a constant current output or a limit to the maximum current output of the LED driver (e.g., for LED drivers with dimming capability) when it leaves the custody of the manufacturer. To this end, LED light fixture manufacturers typically inventory or stock a broad spectrum of constant current output LED drivers. When LED light fixtures are manufactured, LED drivers are matched with LED light fixtures according to the proper constant current output requirements for the LED light fixtures. No matter what the constant current output requirements may be for LED light fixtures, the manufacturers have at least one LED driver that provides the constant current output required. This approach may require manufacturers to inventory or stock many different LED drivers. 
     Currently, direct current settable/configurable electronic drivers for power LED and LED modules are known, which have multi-voltage and multi-current functionality. The multi-power driver is supplied with a dip-switch for selection of the current output. The dip-switch is incorporated into the LED driver so that anyone may adjust the current output, including the end user. For example, TCI Professional Light Applications markets a MAXI JOLLY driver. Such multi-voltage and multi-current LED drivers do not qualify for UL certification in the United States because end users could unwittingly increase the current output to such a level that the LED driver could over heat a LED light fixtures, which could cause fire. 
     Further, in the context of fluorescent light fixtures, U.S. Pat. No. 7,880,405 discloses an electronic ballast that is operable to receive a ballast factor setting that enables the ballast to provide a desired ballast factor when the ballast drives a fluorescent lamp. The method comprises the steps of: (1) receiving a request for the ballast adaptable to be configured with the desired ballast factor; (2) providing the ballast; and (3) configuring the ballast to have the desired ballast factor. The desired ballast factor is substantially prevented from subsequently being adjusted. 
     What is needed is a current output programmable LED driver, such that once a current output is set by a manufacturer, the current output cannot further be adjusted by an end user. 
     SUMMARY 
     In general, the disclosure relates to setting current output of an LED driver. In an exemplary embodiment, an external control module for setting a current output of an LED driver includes a plurality of voltage referenced elements. The external module also includes a plurality of switches. Each switch of the plurality of switches is coupled to a corresponding voltage referenced element of the plurality of voltage referenced elements. The external control module further includes an enclosure covering the plurality of switches, wherein the enclosure substantially prevents adjustment of switch positions of the plurality of switches. 
     In another exemplary embodiment, a process for manufacturing LED light fixtures includes identifying a current requirement of an LED light fixture. The process includes identifying an LED driver and connecting an external control module to the identified LED driver. The process also includes using the external control module to set the current output of the LED driver to substantially match the current requirement of the LED light fixture. The process further includes assembling the LED driver with the LED light fixture. 
     In yet another exemplary embodiment, a process for manufacturing an external control module for setting a current output of a light emitting diode (LED) driver includes identifying a current requirement of a light fixture. The process also includes identifying an LED driver and connecting an external control module to the identified LED driver. The process further includes adjusting a setting of the external control module to correspond to the current output of the LED driver that substantially matches the current requirement of the LED light fixture. The process also includes enclosing the external control module to substantially limit adjustment of the setting of the external control module. 
     These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  shows exemplary system including an external control module connected to an LED driver included in an LED light fixture; 
         FIG. 2  illustrates an exemplary top view pinout of an LED driver; 
         FIG. 3  shows an exemplary circuit diagram of an external control module; 
         FIG. 4A  is a top view of an exemplary printed circuit board of an external control module prior to being populated with components; 
         FIG. 4B  illustrates a top view of the exemplary printed circuit board of  FIG. 4A  after being populated with components; 
         FIG. 5  illustrates an exemplary graph of a base 10 logarithm [log] of an equivalent resistance (Rset) of one of more resistors in an external control module plotted against current output (in amperes) of an LED driver; 
         FIG. 6A  is an exemplary schematic diagram of an LED light fixture having ten LEDs that are driven by an LED driver; 
         FIG. 6B  is an exemplary schematic diagram of an LED light fixture having twelve LEDs that are driven by an LED driver; and 
         FIG. 7  is a flow chart of a process for manufacturing LED light fixtures. 
     
    
    
     The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as there may be other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the exemplary embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements. 
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Embodiments of the disclosure are directed to systems, methods, and apparatuses for controlling current outputs of LED drivers. Embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     In an exemplary embodiment, an external control module may be connected to an LED driver, while an LED light fixture is being assembled at a manufacturing facility. At least one dip switch of the external control module may be used to select individual resistors, which in turn control the current output of the LED driver. In the place of the dip switch, any switch or switches, such as a rotary switch or a potentiometer may be used as known to persons of skill in the art. Once the current output of the LED driver has been set by the external control module, the external control module may remain connected to the driver. The LED driver, with the current output set, and the external control module may be installed while manufacturing the LED light fixture. 
     Because LED drivers may be configured or set to produce a variety of current outputs, fewer LED drivers may need to be maintained in inventory. Through the use of an external control module, the output current may be adjusted down to any desired level between 0% and 100% of the maximum output current. In some embodiments, the output current may be adjusted down to about 50% of the maximum output current of an LED driver depending on Power Factor or total harmonic distortion (THD) requirements. For example, an LED driver that produces a maximum current output of 2100 milliamperes (mAmps) may be configured or set to produce a current output between 1365 mAmps and 2100 mAmps. As another example, an LED driver that produces a maximum current output of 1400 mAmps may be configured or set to produce a current output between 910 mAmps and 1400 mAmps. As still a further example, an LED driver that produces a maximum current output of 1000 mAmps may be configured or set to produce a current output between 650 mAmps and 1000 mAmps. By way of these exemplary LED drivers, a manufacturer could use only three LED drivers to provide any current outputs within the range of 650 mAmps to 2100 mAmps. 
     According to alternative embodiments, an external control module may be used to monitor the current and communicate to the driver for end of life situations. Other controls may be incorporated into this device such as day light harvesting, wireless dimming, emergency lighting, etc. 
     Referring to  FIG. 1 , an LED driver  6  and an external control module  10  are shown connected to an LED light fixture  8 . At a manufacturing facility, before the light fixture goes to customers, the external control module  10  may be connected to the LED driver  6  to set a current output for the LED driver  6 , depending on the current requirement of the LED light fixture  8 . 
     The external control module  10  includes a circuit board  12 , a plurality of switches  16  (shown in  FIG. 1  as a DIP switch), a plurality of resistors  14 , and a connector  18 . The external control module  10  may also include an enclosure  20 . The enclosure  20  is detached from the rest of the external control module  10  in  FIG. 1 . When the enclosure  20  is placed over the circuit board  12  covering the plurality of switches  16 , the enclosure  20  substantially prevents adjustment of the switch positions of the plurality of switches  16 . Wires  22  are attached to the connector  18  and provide a connection between the external control module  10  and the LED driver  6 . 
     Referring to  FIG. 2 , an exemplary pinout of the LED driver  6  is illustrated. The LED driver  6  may have the following pins: SET +, SET −, V in+ , V in− , LED +, and LED −. A power supply (a wall outlet) may be connected to the V in+  and V in−  pins. The external control module  10 , shown in  FIG. 1 , may be connected to the SET + and SET − pins to set a current output on the LED + and LED − pins of the LED driver  6 . For example, one of the wires  22  shown in  FIG. 1  may be connected to the SET + pin and the other one of the wires  22  may be connected to the SET − pin of the LED driver  6 . The LED driver  6  may provide a current output to a light fixture, such as the LED light fixture  8  of  FIG. 1 , via the LED + and LED − pins. 
     Referring to  FIG. 3 , a circuit diagram  30  of an external control module  10  is illustrated. In an exemplary embodiment, the external control module  10  is electrically coupled to an LED driver (not shown), such as the LED driver  6  of  FIG. 2 , via circuit leads  1  and  2  and via the connector  18 . The circuit leads  1  and  2  of the external control module  10  are electrically coupled to the SET + and SET − pins of the LED driver  6 , respectively. For example, the circuit leads  1  and  2  of the external control module  10  may be electrically coupled to the SET + and SET − pins of the LED driver  6  via the connector  18 . The external control module  10  includes the plurality of resistors  14  and the plurality of switches  16 . The plurality of resistors  14  includes five resistors R 1  through R 5 . In an exemplary embodiment, the two or more of the five resistors R 1  through R 5  may be connected in parallel. 
     The plurality of switches  16  includes five switches SW 1  through SW 5 . Each of the five switches SW 1  through SW 5  may be independently set to a closed switch position (i.e., closed) or to an open switch position (i.e., open). Each of the five switches SW 1  through SW 5  is coupled to a corresponding resistor of the five resistors R 1  through R 5 . Switch SW 1  is coupled to resistor R 1 , switch SW 2  is coupled to resistor R 2 , switch SW 3  is coupled to resistor R 3 , switch SW 4  is coupled to resistor R 4 , and switch SW 5  is coupled to resistor R 5 . 
     In an exemplary embodiment, one or more of the switches SW 1  through SW 5  may be in a closed switch position (i.e., closed). By closing a particular switch of the five switches SW 1  through SW 5 , a corresponding resistor of the five resistors R 1  through R 5  that is coupled in series with the closed switch becomes electrically coupled to the circuit leads  1  and  2 . Accordingly, current may flow between the circuit leads  1  and  2  through a closed switch (e.g., SW 1  set to have a closed switch position) and a resistor (e.g., R 1 ) that is coupled in series with the particular closed switch. Two or more of the five resistors R 1  through R 5  become connected in a parallel configuration when corresponding two or more of the five switches SW 1  through SW 5  are in a closed switch position. A parallel configuration of two or more of the five resistors R 1  through R 5  results in a total (equivalent) resistance between the circuit leads  1  and  2  that is based on the parallel configuration of the two or more resistors. 
     In an exemplary embodiment, resistor R 1  is a 0 ohm resistor, resistor R 2  is a 133 ohm resistor, resistor R 3  is a 340 ohm resistor, resistor R 4  is a 510 ohm resistor, and resistor R 5  is an 1150 ohm resistor. In this exemplary embodiment, when switch SW 1  is closed (i.e., in a closed switch position) and all other switches are open (i.e., in open switch positions), only resistor R 1  out of the five resistors R 1  through R 5  is electrically coupled between the circuit leads  1  and  2 . When only resistor R 1  of the five resistors R 1  through R 5  is coupled between the circuit leads  1  and  2 , the external control module produces a current output of approximately 1.00 Amp that may be provided to a light fixture. When switch SW 2  is closed and all other switches are open, only resistor R 2  out of the five switches R 1  through R 5  is electrically coupled between the circuit leads  1  and  2 . When only resistor R 2  out of the five resistors R 1  through R 5  is coupled between the circuit leads  1  and  2 , the external control module  10  produces a current output of approximately 1.20 Amp that may be provided to the light fixture. When switch SW 3  is closed and all other switches are open, only resistor R 3  out of the five switches R 1  through R 5  is electrically coupled between the circuit leads  1  and  2 . When only resistor R 3  out of the five resistors R 1  through R 5  is coupled between the circuit leads  1  and  2 , the external control module  10  produces a current output of approximately 1.40 Amp that may be provided to the light fixture. When switch SW 4  is closed and all other switches are open, only resistor R 4  out of the five switches R 1  through R 5  is electrically coupled between the circuit leads  1  and  2 . When only resistor R 4  out of the five resistors R 1  through R 5  is coupled between the circuit leads  1  and  2 , the external control module  10  produces a current output of approximately 1.50 Amp that may be provided to the light fixture. When switch SW 5  is closed and all other switches are open, only resistor R 5  out of the five switches R 1  through R 5  is electrically coupled between the circuit leads  1  and  2 . When only resistor R 5  out of the five resistors R 1  through R 5  is coupled between the circuit leads  1  and  2 , the external control module  10  produces a current output of approximately 1.70 Amp that may be provided to the light fixture. 
     When two or more resistors of the five resistors R 1  through R 5  are coupled in parallel between the circuit leads  1  and  2  by closing two or more of the five switches SW 1  through SW 5 , the external control module may produce other current output amounts corresponding to the equivalent resistance of the two or more resistors that are coupled in parallel between the circuit leads  1  and  2 . For example, resistors R 2  and R 3  may be connected in parallel between the circuit leads  1  and  2  by closing switches SW 2  and SW 3 . As another example, resistors R 2  and R 4  may be connected in parallel between the circuit leads  1  and  2  by closing switches SW 2  and SW 4 . In yet another example, resistors R 2 , R 3 , and R 5  may be connected in parallel between the circuit leads  1  and  2  by closing switches SW 2 , SW 3 , and SW 5 . The current output produced by the external control module  10  corresponds to the equivalent resistance of the two or more resistors that are electrically coupled between the circuit leads  1  and  2 . Using different combinations of closed and open switches, various permutations of parallel configurations of the plurality of resistors  14  may be achieved to expand flexibility of the external control module  10  to produce a desired current output. 
     Although  FIG. 3  shows five resistors R 2  through R 5 , in alternative embodiments, the plurality of resistors  14  may include more than five resistors or fewer than five resistors. Additionally, the resistance values and current output values described with respect to  FIG. 3  are exemplary, and, in other embodiments, the resistance values may correspond to different current outputs of an LED driver. Further, although  FIG. 3  shows that the external control module  10  includes the plurality of resistors  14 , in alternative embodiments, the external control module  10  may include other resistive elements instead of resistors. In addition, each resistor R 1  through R 5 , although shown as a single resistor, may include more than one resistor. Further, other voltage referenced elements (e.g., Zener diodes) may be used instead of the plurality of resistors  14 . For example, Zener diodes may be coupled between the circuit leads  1  and  2  in a substantially similar configuration as the plurality of resistors  14 . 
     Referring to  FIG. 4A , a top view of a printed circuit board  12  of the external control module  10  is shown. In  FIG. 4A , the printed circuit board  12  is shown prior to populating the printed circuit board  12  with components, such as resistors and switches. The printed circuit board  12  includes traces  42  electrically coupling the five resistors R 1  through R 5 , the five switches SW 1  through SW 5 , and the connector  18  as described with respect to  FIG. 3 . 
       FIG. 4B  illustrates a top view of the printed circuit board  12  of  FIG. 4A  after the printed circuit board  12  is populated with components. The plurality of switches  16  (e.g., a DIP switch) including the five switches SW 1  through SW 5  is attached to the printed circuit board. The plurality of resistors  14  including the five resistors R 1  through R 5  is also attached to the printed circuit board  12 . Further, the connector  18  is attached as shown. 
       FIG. 5  illustrates an exemplary graph  50  of a current output (in amperes) and base 10 logarithm, [log], of an equivalent resistance (Rset). The curve  52  is an exemplary illustration of the relationship between the base 10 logarithm, [log], of the equivalent resistance (Rset) of one or more resistors of the plurality of resistors  14  of  FIGS. 1 ,  3 , and  4 B and the current output of the LED driver  6 . The x-axis is the base 10 logarithm [log] of the equivalent resistance (Rset) of one or more resistors that are coupled to a corresponding closed switch of the plurality of switches  16 . For example, Rset may correspond to an equivalent resistance of one or more of the five resistors R 1  through R 5  of  FIG. 3  that are coupled to a corresponding switch SW 1  through SW 5  that is in a closed switch position. To illustrate, if switches SW 2  and SW 3  of  FIG. 3  are closed, the equivalent resistance Rset is determined based on resistances of resistors R 2  and R 3  that are in a parallel configuration. 
     The y-axis represents a current output (in amperes) of the LED driver  6  of  FIGS. 1 and 2 . For example, if the LED driver  6  has a maximum current output of 2 Amps, one or more resistors of the plurality of resistors  14  may be configured to set the output current of the LED driver  6  within the range of 1.2 Amps through 2.0 Amps. 
     Typical LED drivers experience a total harmonic distortion (THD) as high as 20% when the output current is set at 65% or lower of the maximum output current. For most LED drivers, it is possible to control the current output between 65% through 100% of the maximum current output of the LED driver without the THD falling outside an acceptable range. Some LED drivers may also operate within acceptable TDH range even when the current output of the LED drivers is outside of the 65% to 100% of the maximum output current. For example, in an exemplary embodiment, the LED driver  6  may operate within acceptable TDH range when generating current output that is approximately 50% to 100% of the maximum output current of the LED driver  6 . 
     Referring to  FIG. 6A , an exemplary system  60  including an LED driver  6  and an LED light fixture  64  including ten LEDs is illustrated. The LED light fixture  64  including the ten LEDs is driven by an LED driver  6 . For example, the LED light fixture  64  may be a high powered LED light fixture. The LED driver  6  is coupled to a power supply via the Vin pins.  FIG. 6B  illustrates an exemplary system  66  including an LED driver  6  and an LED light fixture  68  having twelve LEDs. For example, the LED light fixture  68  may be a high powered LED light fixture. The LED light fixture  68  including the twelve LEDs is driven by an LED driver  6 . As an example, the LED light fixture  64  of  FIG. 6A  could have a power requirement of 1600 mAmp while the LED light fixture  68  of  FIG. 6B  could have a power requirement of 2000 mAmp. When these LED light fixtures  64 ,  68  of  FIGS. 6A and 6B  are manufactured, identical LED drivers, each having a maximum current output of 2100 mAmp, may be set for each light fixture  64 ,  68 . For example, the LED driver  6  may have a maximum current output of 2100 mAmp and may be set to 1600 mAmp for the LED light fixture  64  of  FIG. 6A  and may be set to 2000 mAmp for the LED light fixture  68  of  FIG. 6B . Accordingly, a manufacture may stock or inventory a single type of 2100 mAmp LED drivers for use with both LED light fixture  64  and  68  of  FIGS. 6A and 6B , respectively. 
       FIG. 7  is a flow chart of a process  70  for manufacturing LED light fixtures. Following a start of the process at  72 , the process  70  includes identifying a current requirement of a light fixture, at  74 . For example, a current requirement of an LED light fixture, such as the LED light fixture  8  of  FIG. 1 , the LED light fixture  64  of  FIG. 6A  and the LED light fixture  68  of  FIG. 6B  may be identified. The process  70  further includes identifying an LED driver, at  76 . The current requirement of the LED light fixture may be between approximately 50% and approximately 100% of the current rating (i.e., the maximum current output) of the LED driver. For example, if the current requirement of the light fixture is 1800 mAmp, an LED driver that has a current rating of 2100 mAmp may be identifier. 
     An external control module is connected to the identified LED driver, at  78 . For example, the external control module  10  of  FIG. 1  may be connected to the LED driver  6  of  FIGS. 1 and 2 . The external control module is used to set the current output of the LED driver to substantially match the current requirement of the LED light fixture, at  80 . A setting of the external control module may be adjusted to correspond to a current output of the LED driver that substantially matches the current requirement of the LED light fixture. For example, by setting the switch position of each switch of the plurality of switches  16  of  FIGS. 1 , and  3  to an open or closed switch position, the current output of the LED driver  6  of  FIGS. 1 and 2  may be set to substantially match the current requirement of an LED light fixture. As described with respect to  FIG. 3 , the current output of the LED driver  6  of  FIGS. 1 and 2  may correspond to the equivalent resistance of one or more resistors of the plurality of resistors  14  that have a corresponding switch in a closed switch position. The LED driver is assembled with the LED light fixture, at  82 . The LED light fixture is then ready for distribution to end users. The process  70  ends at  84 . 
     In an exemplary embodiment, the process  70  may also include enclosing (not shown) the external control module to substantially limit adjustment of the setting of the external control module. For example, the external control module  10  may include an enclosure, such as the enclosure  20  of  FIG. 1 , to substantially cover the plurality of switches  16  (e.g., a DIP switch in  FIG. 1 ) once switch positions of the plurality of switches is set. Enclosing the external control module  10  may limit subsequent adjustability of the switch positions of the plurality of switches  16 , for example, by consumers. 
     The invention may be applied to any LED driver for any light fixture application, including indoor and outdoor LED light fixtures. The LED drivers may also have any maximum output current ratings. 
     Another aspect of the invention is to include control features. One example of a control feature is adjustment over time of the current output of an LED driver by an external control module. For example, an LED driver having a maximum current output of 2 Amps may be initially set to generate 1.7 Amps. Over time, the external control module may adjust the LED driver to generate current output that is higher or lower than the 1.7 Amps. For example, the current output of the LED driver may be set to increase over time. In an exemplary embodiment, a microcontroller may be included in the external control module to provide control functionality. Alternatively, the external control module may have a microcontroller interface to allow adjustment of control settings to increase or decrease the current output of the LED driver without exceeding the maximum current output of the LED driver. In general, control functionality may be implemented using a microcontroller or a resistor set. Further, light or current sensors or time monitoring features may also be added. Thus, if the current requirements of the LED light fixtures change over time, the microcontroller of the external control module may adjust the current output in response to the changed current requirements. 
     Although the inventions are described with reference to preferred embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. From the foregoing, it will be appreciated that an embodiment of the present invention overcomes the limitations of the prior art. Those skilled in the art will appreciate that the present invention is not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the exemplary embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments of the present invention will suggest themselves to practitioners of the art. Therefore, the scope of the present invention is not limited herein.