This relates generally to systems for controlling light emitting diode (LED) lighting fixtures using a warm dimming process to regulate the illumination provided by strings of LEDs.
LED lighting fixtures are increasingly popular alternatives to traditional incandescent and compact florescent lighting. This is likely because of the increased efficiency and much longer life afforded by LEDs when compared to incandescent and even compact florescent alternatives.
However, despite the benefits of LED-based lighting, LED's are more difficult to dim than traditional incandescent lighting. In particular, LED fixtures (which, as used herein, could also refer to LED bulbs for insertion into lamps or lighting devices), generally constructed of a plurality of individual LEDs, are subject to flicker, pixilation (the effect of individual LEDs being visible to an observer of the fixture), and the lack of changes in the color or warmth of the light provided by the fixture as the light output of the LEDs is reduced. Exemplary known systems employ pulse width modulation (PWM) techniques to regulate LEDs strings to produce a dimming effect. However, dimming produced using PWM regulation circuitry is subject to lighting abnormalities and issues with the quality of light produced by the LED. What is needed is a system and method for controlling the output of LED lighting fixtures that applies a warm dimming technique to improve the lighting characteristics as the fixture is dimmed while retaining the efficiency inherent in LED lighting.
Embodiments of the invention comprise current regulation circuitry that is configured to selectively dim portions of a string of LEDs used in a light fixture. These portions may be comprised of groups of LEDs that exhibit a particular color temperature and are regulated such that the light output and the color temperature of the fixture may be selectively and independently adjusted. In an exemplary embodiment, a string comprising a plurality of LEDs is provided with a voltage source and a constant current source. The exemplary embodiment also comprises at least one differential current regulation circuit connected in parallel with at least a portion of the string of LEDs such that the differential current regulating circuit can increase or decrease the light output of the portion with which the differential current regulating circuit is in parallel.
In an exemplary embodiment, a warm dim circuit comprises at least first and second pluralities of LEDs electrically connected in series between a voltage source and a current source. The exemplary embodiment also comprises a dimmable LED segment controller configured to illuminate and independently dim at least one of the pluralities of LEDs, a lighting control unit that is in communication with the dimmable LED segment controller. The dimmable LED segment controller comprises a differential current regulation circuit that dims the plurality of LEDs.
In another exemplary embodiment, warm dimming of a string of LEDs is accomplished by arranging a string of LEDs comprising a plurality of segments formed from LEDs with a similar color temperature. A voltage source is provided to the string and an adjustable constant current source is connected in series with the string. A differential current regulation circuit is connected in parallel with at least one of the plurality of segments and controlled by a control signal such that the current through the segment is regulated to adjust the brightness of the segment. In such an embodiment, the constant current source is controlled by a current source control signal which adjusts the current through the string of LEDs to further control the brightness of the LEDs which are comprised be the string.
In still another embodiment of the invention, a warm dim circuit comprises at least first, a second, and a third plurality of LEDs electrically connected in series with a voltage source and a current source. The color temperature of the first plurality of LEDs is cooler than that of the second plurality and the color temperature of the second plurality is cooler than that of the third plurality. The exemplary embodiment also comprises a first dimmable LED segment controller configured to illuminate and independently dim the first plurality of LEDs and a second dimmable LED segment controller configured to illuminate and independently dim the second plurality of LEDs. The exemplary embodiment comprises a control unit that is in communication with the dimmable LED segment controller where the control unit comprises an algorithm that dims the first plurality of LEDs, then the second plurality of LEDs and then causes the current source to reduce the current through the third plurality of LEDs in order to simulate a warm dimming effect.
The above and other aspects and advantages of the general inventive concepts will become more readily apparent from the following description and figures, illustrating by way of example the principles of the general inventive concepts.
These and other features of the general inventive concept will become better understood with regard to the following description and accompanying drawings in which:
This Detailed Description merely describes exemplary embodiments of the invention and is not intended to limit the scope of the claims in any way. Indeed, the invention as claimed is broader than and unlimited by the preferred embodiments, and the terms used in the claims have their full ordinary meaning.
Color temperature when used with regard to lighting refers to the appearance of the light produced. Generally, these color temperatures are referred to in units of degrees kelvin (K). Color temperatures with higher numbers (i.e., 5000K) are more blue-white and are referred to as “cooler” colors. Color temperatures with lower numbers (i.e., 2700K) are more yellow or reddish-white and are known as “warmer” colors. Depending upon the application, a lighting fixture can be configured to produce a color between the cooler and warmer colors. As used herein, the term “warm dimming” refers to a shift from cooler colors to warmer colors as a lighting fixture is caused to dim in brightness. Incandescent lamps generally exhibit warm dimming as a natural result of the filament cooling as the lamp output is reduced. Because of familiarity with the characteristics of incandescent lighting, and warm dimming simulates the twilight dimming of an actual sunset, this characteristic is a desirable lighting attribute in many contexts.
LED fixtures generally do not naturally exhibit a warm dimming characteristic due to the relatively fixed color output produced by LEDs. In order to simulate this characteristic, LEDs having varied color outputs are combined in various intensity ratios.
Exemplary embodiments of the invention disclosed herein utilize a novel method of producing a warm dimming effect in LED fixtures. Such embodiments achieve this effect using a combination of LED segments of various color temperatures. As used herein, an LED “segment” is a subset of an LED string. These segments are regulated by a novel differential current circuit, which will now be described in detail.
An exemplary embodiment is shown in
Ics=Ie1+Ie2
Because the current provided by the current source 110 is a constant, the above equation can be rewritten as:
Constant Current=Ie1+Ie2
Or
Ie2=Constant Current−Ie1
Thus, any change in Q1104 current is reflected in Q2112 current. Thus, it can be concluded that in a design such as illustrated in
This effect can be applied to control the output of an LED string by affecting the current flow thru the string. As is illustrated in
Ics=Ie1+Id1
The current that flows through the current source 110 is essentially constant provided the current source is operated within its linear range. Therefore, the current in D1302 representing the LED can be defined by:
const−Ie1=Id1
As noted above, the light output of D1302 is a function of the current through D1. It can be concluded from the above equation that the current through D1302 can be controlled by affecting the value of Ie1. Because the value of Ie1 is varied by changing the input value to Q1104 at IN1102, it can be inferred that the input value to Q1 controls the current through D1 and thus its light output.
The current source 110 and R1304 can be selected to enable a desired light output range. The current source 110 current value Ics is selected by turning Q1104 off (removing the current supplied at IN1102) and adjusting Ics for peek light output at D1302. R1304 is then selected such that when the voltage applied to the base of Q1 (Vin1) is at its maximum value, the current thru R1304 is equal to Ics, thereby depriving Rd1206 of any current (or any desired operating point between full illumination and off).
In an exemplary embodiment, warm dimming is achieved by combining a plurality of separate warm white LED segments, each with a warmer color temperature than the previous segment, into a string. The combined color temperature and light output of the segments results in the desired light output and color temperature when the string is fully illuminated. In order to warm dim such a configuration, the coolest color temperature LED segment is dimmed followed by the next coolest color temperature LED segment and so-on until it all LEDs in the string are dimmed to the desired light output level. In an exemplary embodiment with three segments of LEDs, the final segment is comprised of 2200K LEDs that dim from approximately 15% maximum light output down to shut-off.
In exemplary embodiments, the LED segments of different colors are physically arranged on a circuit board or other carrier in concentric “rings” or loci of LEDs, e.g., two, three, or four concentric “rings” or loci of LEDs. In some exemplary systems, three concentric rings or loci of LEDs are used: four inner LEDs, nine middle LEDs, and seven outer LEDs. In some exemplary embodiments, the outer (e.g., 7) LEDs are 4000K, the middle (e.g., 9) LEDs are 2700K, and the center (e.g., 4) LEDs are 2200K. In exemplary embodiments, the outer (e.g., 7) LEDs are just inside a circle that is about 1⅛″, e.g., 1.14″ in diameter, the middle (e.g., 9) LEDs are just inside a circle that is about three quarters of an inch, e.g., 0.83″ in diameter, and the center (e.g., 4) LEDs are just inside a circle that is about a half inch, e.g., 0.51″ in diameter. Thus, each locus of LEDs forms an n-sided polygon (“n-gon”) that fits just inside a correspondingly sized circle. In exemplary dimming embodiments simulating an incandescent light bulb being dimmed, one starts by dimming the coolest correlated color temperature (CCT) LEDs (e.g., 4000K) until they are off, then dimming the next coolest CCT LEDs (e.g., 2700K) until they are off, then dimming the inner (e.g., 4) 2200K LEDs from approximately 15% down to shut-off.
Exemplary circuits that embody the differential current circuit described herein are shown in
“Logic,” synonymous with “circuit” as used herein includes, but is not limited to, analog hardware, digital hardware, firmware, software and/or combinations of each to perform one or more functions or actions. For example, based on a desired application or needs, logic may include a software controlled processor, discrete logic such as an application specific integrated circuit (ASIC), programmed logic device, or other processor.
“Computer” or “processor” as used herein includes, but is not limited to, any programmed or programmable electronic device or coordinated devices that can store, retrieve, and process data and may be a processing unit or a distributed processing configuration. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), floating point units (FPUs), reduced instruction set computing (RISC) processors, digital signal processors (DSPs), field programmable gate arrays (FPGAs), etc. Computer devices herein can have any of various configurations, such as handheld computers (e.g., so-called smart phones), pad computers, tablet laptop computers, desktop computers, and other configurations, and including other form factors. Logic may also be fully embodied as software.
“Software,” as used herein, includes but is not limited to one or more computer readable and/or executable instructions that cause a processor or other electronic device to perform functions, actions, processes, and/or behave in a desired manner. The instructions may be embodied in various forms such as routines, algorithms, modules or programs including separate applications or code from dynamically linked libraries (DLLs). Software may also be implemented in various forms such as a stand-alone program, a web-based program, a function call, a subroutine, a servlet, an application, an app, an applet (e.g., a Java applet), a plug-in, instructions stored in a memory, part of an operating system, or other type of executable instructions or interpreted instructions from which executable instructions are created. It will be appreciated by one of ordinary skill in the art that the form of software is dependent on, for example, requirements of a desired application, the environment it runs on, and/or the desires of a designer/programmer or the like.
“Data storage device,” as used herein, means a device for non-transitory storage of code or data, e.g., a device with a non-transitory computer readable medium.
“Non-transitory computer readable medium,” as used herein, means any suitable non-transitory computer readable medium for storing code or data, such as a magnetic medium, e.g., fixed disks in external hard drives, fixed disks in internal hard drives, and flexible disks; an optical medium, e.g., CD disk, DVD disk, and other media, e.g., ROM, PROM, EPROM, EEPROM, flash PROM, external flash memory drives, etc.
An exemplary constant current regulator is the Shenzhen Sunmoon Micro SM2082D, however, similar controllable constant current regulators can be used in other exemplary embodiments. The current source control signal 502 is applied in conjunction with the first control signal 412 such that the second segment of LEDs 404 is caused to dim concurrently with (or independently of) the first segment 402.
The LED string in this embodiment has three subsets 812, 814, 816, where each subset of an LED string having one or more LEDs connected electrically in series may be referred to individually as “segments” of the complete LED string 802. As illustrated, the two differential circuits 808 and 810 are place in parallel with two independent LED string segments 812, 814, respectively, with different forward voltages. It should be noted that the differential current circuits 808 and 810 can be placed at any locations along the LED string 802 in order to achieve a desired lighting effect. Additional differential circuits like circuit 808 and 810 can be added if more control over the LEDs 802 is desired. In the illustrated embodiment, the forward voltage of a segment of the LED string 802 is defined by the transistor and series resistor of the differential current circuit 808.
For the LED segment controller topology shown in
Conventional LED dimming can be achieved using the LED dimming configuration shown in
However, if the total current through the system is linearly decreased by adjusting the current through the voltage controlled constant current source 1002 while keeping the control voltage 1014 of the second differential current control circuit 1010 at zero, and, at the similar linear rate as the voltage controlled constant current source 1002, apply a first control voltage 1012 to the first differential current control circuit 1008, the output of the LED string 1006 would decrease and color temperature would begin to change due to the current through the first LED segment 1016 (3000K) being decreased. As the control voltage 1012 of the first differential current control circuit 1008 approaches its maximum value (defined by differential current circuit component selection), the current through the first LED segment 1016 (3000K) will approach zero, resulting in only the second LED segment 1018 (2700K) and the third LED segment 1020 (2200K) LEDs being illuminated. While maintaining the first control voltage 1012 at its maximum value, a second control voltage 1014 is applied to the second differential current control circuit 1010. As this second control voltage 1014 reaches its maximum, the LED fixture's brightness will be decreased while the color temperature would begin to be warmer as the result of the second LED segment 1018 decreasing in brightness, leaving the third LED segment 1020 illuminated. As the second control voltage 1014 approaches it maximum value (defined by differential current circuit component selection), the current through the second LED segment 1018 (2700K) will approach zero, resulting in only the third LED segment 1020 (2200K) remaining fully illuminated. Continued dimming may be achieved by reducing the control voltage 1022 to the voltage controlled constant current source 1002 with the result being that the third LED segment 1020 continues to dim until the LED fixture has reached its maximum level of dimming.
In some exemplary embodiments, warm dimming is achieved by combining three separate warm white LED segments as illustrated in the exemplary embodiment of
While the present invention and associated inventive concepts have been illustrated by the description of various embodiments thereof, and while these embodiments have been described in considerable detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, although the exemplary embodiments pertain to warm dimming, the differential current circuits can be used for other dimming of LEDs, such as constant color dimming or even cool dimming. As another example, dimming can be done in response to any of a number of different inputs, e.g., user input via a user interface (with associated user interface circuitry in the circuit and associated code in the control unit), user input via a communications link, such as BLE (with associated user communications circuitry in the circuit and associated code in the control unit), or other inputs, such as light sensors to dim as ambient light gets dimmer (with associated light intensity sensor circuitry in the circuit and associated code in the control unit). Moreover, in some instances, elements described with one embodiment may be readily adapted for use with other embodiments. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the general inventive concepts.
The present application is being filed as a non-provisional patent application claiming priority/benefit under 35 U.S.C. § 119(e) from U.S. Provisional Patent Application No. 62/420,198 filed on Nov. 10, 2016, the entire disclosure of which is incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
6340868 | Lys et al. | Jan 2002 | B1 |
6577080 | Lys et al. | Jun 2003 | B2 |
6897624 | Lys et al. | May 2005 | B2 |
6936978 | Morgan et al. | Aug 2005 | B2 |
6967448 | Morgan et al. | Nov 2005 | B2 |
7031920 | Dowling et al. | Apr 2006 | B2 |
7132785 | Ducharme | Nov 2006 | B2 |
7186003 | Dowling et al. | Mar 2007 | B2 |
7221104 | Lys et al. | May 2007 | B2 |
7248239 | Dowling et al. | Jul 2007 | B2 |
7253566 | Lys et al. | Aug 2007 | B2 |
7352138 | Lys et al. | Apr 2008 | B2 |
7427840 | Morgan et al. | Sep 2008 | B2 |
7453217 | Lys et al. | Nov 2008 | B2 |
7525254 | Lys et al. | Apr 2009 | B2 |
7550931 | Lys et al. | Jun 2009 | B2 |
7703943 | Li et al. | Apr 2010 | B2 |
7845823 | Muellet et al. | Dec 2010 | B2 |
7883226 | Li | Feb 2011 | B2 |
7915627 | Li | Mar 2011 | B2 |
8142051 | Ducharme | Mar 2012 | B2 |
8147081 | Mrakovich et al. | Apr 2012 | B2 |
8188502 | Li | May 2012 | B2 |
8203260 | Li et al. | Jun 2012 | B2 |
8212469 | Rains, Jr. et al. | Jul 2012 | B2 |
8322896 | Falicoff et al. | Dec 2012 | B2 |
8338849 | Tischler et al. | Dec 2012 | B2 |
8384114 | Tischler et al. | Feb 2013 | B2 |
8414151 | Allen et al. | Apr 2013 | B2 |
8450759 | Cheng | May 2013 | B2 |
8456109 | Wray | Jun 2013 | B1 |
8466611 | Negley et al. | Jun 2013 | B2 |
8545033 | Gielen et al. | Oct 2013 | B2 |
8562161 | Tong et al. | Oct 2013 | B2 |
8581520 | Wray | Nov 2013 | B1 |
8598809 | Negley et al. | Dec 2013 | B2 |
8604678 | Dai et al. | Dec 2013 | B2 |
8604684 | Pickard | Dec 2013 | B2 |
8610341 | Dai et al. | Dec 2013 | B2 |
8614539 | Dai et al. | Dec 2013 | B2 |
8632196 | Tong et al. | Jan 2014 | B2 |
8680544 | Wang | Mar 2014 | B2 |
8686449 | Li | Apr 2014 | B2 |
8729589 | Hussell et al. | May 2014 | B2 |
9198242 | Chu | Nov 2015 | B2 |
9241384 | van de Ven et al. | Jan 2016 | B2 |
9380671 | Janos et al. | Jun 2016 | B1 |
9482397 | Grajcar | Nov 2016 | B2 |
9807835 | Janos et al. | Oct 2017 | B1 |
20060050509 | Dowling et al. | Mar 2006 | A9 |
20070228931 | Kim et al. | Oct 2007 | A1 |
20100052560 | Li et al. | Mar 2010 | A1 |
20110128718 | Ramer et al. | Jun 2011 | A1 |
20110204805 | Li et al. | Aug 2011 | A1 |
20110215701 | Tong et al. | Sep 2011 | A1 |
20110227102 | Hussell et al. | Sep 2011 | A1 |
20120056543 | Yang | Mar 2012 | A1 |
20120140435 | Li et al. | Jun 2012 | A1 |
20120155076 | Li et al. | Jun 2012 | A1 |
20120223632 | Hussell et al. | Sep 2012 | A1 |
20120223657 | Van de Ven | Sep 2012 | A1 |
20120224363 | Van De Ven | Sep 2012 | A1 |
20120229032 | Van De Ven et al. | Sep 2012 | A1 |
20120262902 | Pickard et al. | Oct 2012 | A1 |
20120281387 | Tung et al. | Nov 2012 | A1 |
20120286646 | Sakuta et al. | Nov 2012 | A1 |
20120287601 | Pickard et al. | Nov 2012 | A1 |
20120306370 | Van De Ven et al. | Dec 2012 | A1 |
20120306375 | Van De Ven | Dec 2012 | A1 |
20130003346 | Letoquin et al. | Jan 2013 | A1 |
20130009179 | Bhat et al. | Jan 2013 | A1 |
20130027904 | Fan | Jan 2013 | A1 |
20130050979 | Van De Ven et al. | Feb 2013 | A1 |
20130051002 | Draper et al. | Feb 2013 | A1 |
20130051003 | Fan | Feb 2013 | A1 |
20130093362 | Edwards | Apr 2013 | A1 |
20130094176 | Deeman et al. | Apr 2013 | A1 |
20130094177 | Edwards | Apr 2013 | A1 |
20130094178 | Huang et al. | Apr 2013 | A1 |
20130170175 | Negley et al. | Jul 2013 | A1 |
20130181619 | Tischler et al. | Jul 2013 | A1 |
20130208457 | Durkee et al. | Aug 2013 | A1 |
20130229104 | Green et al. | Sep 2013 | A1 |
20130235557 | Hadrath et al. | Sep 2013 | A1 |
20130279151 | Ouderkirk et al. | Oct 2013 | A1 |
20130306998 | Ulasyuk | Nov 2013 | A1 |
20130320834 | Ulasyuk | Dec 2013 | A1 |
20130334956 | Bretschneider | Dec 2013 | A1 |
20140003048 | Tong et al. | Jan 2014 | A1 |
20140021493 | Andrews et al. | Jan 2014 | A1 |
20140049172 | Bakk | Feb 2014 | A1 |
20140361696 | Siessegger | Dec 2014 | A1 |
20160212811 | Cheng | Jul 2016 | A1 |
Number | Date | Country |
---|---|---|
2015183810 | Dec 2015 | WO |
Number | Date | Country | |
---|---|---|---|
62420198 | Nov 2016 | US |