(19)United States
`<12)Patent Application
`Mazzochette
`
`Publication
`
`(miPub.No.:US 2008/0165535A1
`(43)Pub. Date:
`Jul. 10, 2008
`
`US 20080l65535Al
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`(54) THERMALLY-MANAGED LED-BASED
`Rl<.(4li.§5l<.DDOWN L[(|ll
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`ABSTRACT
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`362/294
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`Correspondence Address:
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`Patent Application Publication
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`Jul. 10, 2008 Sheet 1 of 5
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`Patent Application Publication
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`Jul. 10, 2008 Sheet 2 of 5
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`Patent Application Publication
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`Jul. 10, 2008 Sheet 3 0f5
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`Patent Application Publication
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`Jul. 10, 2008 Sheet 5 of 5
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`US 2008/0165535 Al
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`I
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`END /l
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`FIG. 5
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`

`

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`US 2008/0 I65535 Al
`
`Jul. 10, 2008
`
`THER\1ALLY-\1Al\'AGE]') LEI)-BASED
`RECESSED DOVVNLIGHTS
`
`FIELD OF TIIE INVENTION
`
`[0001] The present invention relates generally to recessed
`lighting, and more particularly to an apparatus for retrofitting
`I.ED-based recessed lamps into incandescent or fluorescent
`recessed lighting fixtures.
`
`BACKGROUND OF TIIE INVENTION
`
`[0002] There are many types of lighting fixtures for the
`home or olfice which are known in the art. These include
`Edison based fixtures, surface mounted fixtures, track-light­
`ing fixtures, and recessed fixtures. These fixtures have tradi­
`tionally come in three types: incandescent, fluorescent, and
`high intensity discharge (HID) lights. All three suffer from
`inelliciency, relatively short life, a11dhigh heat dissipation.
`For example, incandescent lamps produce in the area of 14 to
`l7 lumens per watt. In addition, incandescent light sources
`use a thin filament which glows when heated by electrical
`power and tends to burn out easily. Typical, incandescent
`lamps have to be replaced every 2000 hours. Fluorescent
`lamps are a11improvement over incandescent lamps, produc­
`ing 50to 120 lumens perwatt, and lasting about 15,000hours.
`HID lamps last about 20,000 hours.
`[0003] To overcome inefficiency and to extend lifetime,
`LED-based lighting fixtures have been introduced. A white
`light ca11be produced by combining a blue led With a phos­
`phor, or by combining red, green, and blue LEDs. These
`combination LEDs can be formed into incandescent-like
`bulbs and reces sed cylindrical or rectangular fixtures. In order
`to avoid replacing the large base of existing incandescent­
`based recessed lights, LED light fixtures can be designed to
`be retrofitted into existing fluorescent rectangular or cylindri­
`cal “can” incandescent or fluorescent fixtures. The LED
`recessed lamps in the prior art, however, operate generally at
`low wattages, typically about three watts. If the wattage is
`raised to increase brightness, say to about 5-50 watts, the
`increased heat dissipation causes the LEDs to drift out of
`current-voltage specification, thereby introducing unwanted
`color variations and even failure. 111some circumstances.
`depending on the thermal environment of an LED recessed
`lamp, ventilation may be needed for poWerdissipation as low
`as 2 watts (or a light output of about 100 lumens or more).
`[0004] As such, there is a need in the art for an improved
`retrofittable LED-based recessed light that can operate at
`relatively high Wattageswithout incmring color variations or
`risking failure at high output power.
`
`SUMMARY OE THE INVENTION
`
`[0005] The above-described problems are addressed and a
`technical solution is achieved in the an by an LED down light
`replacement apparatus for insertion into a recessed-light
`housing can, Whichincludes an LED light source, a means for
`mounting the LED light source within the housing ca11,an
`LED driver circuit elecLrically connected to the LED light
`source, and means for removing heat generated by the LED
`light source. 111some embodiments. the recessed-light hous­
`ing can is part of the apparatus; in other embodiments, the
`apparatus is inserted into an existing housing can after remov­
`ing a11existing incandescent or fluorescent light assembly.
`[0006] The means for removing heat generated by the LED
`light source can include a heat sink in thennal contact with the
`
`LED light source, and a fan and/or ventilation holes in the top
`of the housing can. When the apparatus includes a fan, the fan
`can be motuited on the heat sink or on a top surface of the
`housing ca11.The apparatus ca11include a trim and a ventila­
`tion cone with a conical llange protruding therefrom. Air is
`drawn in through the heat sink by the fan and directed
`between the fan and the housing can out through a space
`between the trim or housing can and the truncated conical
`flange of the ventilation cone.
`[0007] The LED driver circuit converts AC current to con­
`stant DC current for driving the I.ED light source. The LED
`light source can include a plurality of blue LEDs coated with
`a phosphor, or a combination of red, green, and blue LED
`arrays.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0008] The present invention Will be more readily under­
`stood from the detailed description of exemplary embodi­
`ments presented below considered in conjtuiction with the
`attached drawings. of Which:
`[0009] FIG. 1 is a schematic diagram of the structure of a
`retrofittable recessed “can”-type LED down light fixture,
`according to an embodiment of the present invention;
`[0010] FIG. 2 is an electrical schematic diagram ofa con­
`stant current source driver circuit for operating the LEDs
`contained in the LED light fixture of FIG. 1;
`[0011] FIG. 3 is a schematic diagram showing how air is
`circulated to remove heat from the LED light fixture of FIG.
`1;
`l-‘IG.4 is a schematic diagram showing how heat is
`[0012]
`ventilated in closed spaces according to a second embodi­
`ment of the present invention; and
`[0013] FIG. Sis a flow chart illustrating the steps for retro­
`fitting the LED light of FIG. 1 into existing incandescent or
`fluorescent fixtures.
`[0014]
`It is to be understood that the attached drawings are
`for purposes of illustrating the concepts of the invention a11d
`may not be to scale.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`[0015] FIG. l is a schematic diagram of the structure ofa
`retrofittable recessed LED down light fixture, according to an
`embodiment of the present invention, generally indicated at
`l0. The recessed lighting fixture l0 includes a housing can I2,
`base 14, generally annular trim 16, and mounting brackets 18,
`20 interconnected as shown and defining an interior portion
`22 of the lighting fixture 10. The housing ca1112 includes a
`generally cylindrical wall portion 24 and circular top portion
`26 having an upper sLu'face28 and a lower surface 30, con­
`nected by a11angled truncated conical side portion 32. The
`mounting brackets 18, 20 are mounted between adjacent lloor
`joists (not shown) with the base 14 resting on an upper surface
`34 of a ceiling 36. The trim 16 extends from the ca1112 and lies
`flush with a lower surface 38 of the ceiling 36. A pair of
`can-to-base attachment screws 40, 42 secure the base 14to the
`mounting brackets 18. 20. Ajunction box 44 is mounted 011
`the base l4 adjacent the can 12. A BX-type electrical conduit
`and cable 46 extends from the junction box 44 to the Wall
`portion 24 of the can 12 for providing AC power to the
`lighting fixture 10.
`[0016] An LED array assembly 47 is affixed orretrofitted to
`the interior 22 of the lighting fixture 10. The LED array
`assembly 47 includes an LED array 48 comprising parallel
`
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`US 2008/0 I65535 Al
`
`Jul. 10, 2008
`
`banks (not shown) of LEDs (not shown). A sealed reflector
`cone 50 focuses and directs light from the LED array 48 out
`of the light fixture 10. A heat sink 52 is mounted Withinthe
`housing car1 12. Tl1e heat sink 52 may be perforated with a
`plurality of vent holes 54. Mounting brackets 56, 58 mount
`the LED array assembly 47 to the can 12 and tl1eheal sink 52
`to the sealed reflector cone S0, respectively. The heat sink is
`also removably attached to ar1outer thermal ventilation cone
`60. One or more trim retention springs 62 tensively cormects
`a truncated conical flange 64 of the ventilation cone 60 to the
`wall portion 24 of tl1eca1112, while the LED array adjustment
`bracket 66 extends from the heat sink 52 and mounts the I .ED
`array assembly 47 to another side of the wall portion 24 of the
`can 12 via an LED array position adjustment screw 68. The
`adjustment screw 68 and the bracket 66 allow for flne tuning
`of placement of the LED array assembly 47 within the interior
`22 of the light fixture 10. Means for mounting the LED array
`assembly 47 within the housing can I2 can include other
`structures known in tl1e art, including but not
`limited to
`screws, rivets, clamps, straps, weld, crirnped metal, etc. The
`position of the mounting bracket 66 i11relation to the venti­
`lation cone 60 is such that openings 70 for escaping hot air
`exist between the flange 64 and the trim 16 or the can 12.
`Aspects of ventilation of air to carry away heat from the
`fixture 10 will be discussed below ir1connection with FIGS. 3
`and 4.
`[0017] An LED driver circuit 72 is electrically connected to
`the LED array 48 for providing constant DC current to each of
`the banks ofI.EDs. In the present embodiment, the heat sink
`52 is mounted in thermal contact with the LED driver circuit
`72 and the LED array assembly 47 and intemally with respect
`to the can 12. In other embodiments. the LED driver circuit 72
`can be mounted externally on the base 14 outside of the can
`12, including on or in the electricaljunction box 44.AC power
`leads 74 extend from the BX-type electrical conduit and cable
`46 into the interior 22 of the lighting fixture 10 and are
`electrically comiected to power leads 76 of the LED driver
`circuit 72 via wire wrap screws 78. Electrical cormections
`(not shown) between the LED array 48 and the LED driver
`circuit 72 can be made through or around the heat sink 52. In
`the present embodiment, a fan 80, preferably a low noise fan,
`is mounted above LED driver circuit 72. The fan 80 is located
`within the interior 22 of the lighting fixture 10 below or in
`contact with the lower surface 30 of tl1ecircular top portion 26
`of the can 12. In other embodiments,
`the fan 80 can be
`mounted exterior to the light fixture 10 above the upper sur­
`face 28 of the circular top portion 26 of the can 12. Certain
`parts common to most or all recessed lights have been omitted
`from FIG. 1 for simplicity of the drawings but are neverthe­
`less present in the present embodiment. These include various
`scrmvs, a lens inserted within the trim 16, and an optional
`secondary optic.
`[0018] FIG. 2 is an electrical schematic diagram ofa con­
`stant current source driver circuit 72 for operating the LED
`array 48 in the LED light fixture 10 ofEIG. l. The LED array
`48 includes series/parallel connections ofa bank 82 of LEDs
`88a-8812,a bank 84 ofLEDs 90a-9011,and a bank 86 ofLEDs
`92a-9212.ln a preferred embodiment, each of the banks of
`LEDs 82, 84, 86 include blt|eLEDs coated witha phosphor to
`produce white light. Altematively, each of the banks 82, 84,
`86 can be composed of series/parallel cormections of any
`combination and number of red, greer1,and blue LEDs. The
`banks of LEDs 82, 84, 86 can be protected from an overvolt­
`age by means of a varistor 94. In a preferred embodiment, the
`
`banks ofLEDs 82, 84. 86 and the varistor 94 are included in
`a single integrated package, such as the NT-52Dl-0430,
`manufactured by Lamina Ceramics, Inc. In other embodi­
`ments, each of the LEDs can be discrete, or come in multi­
`color die packages. The banks 82, 84, 86 of LEDs are driven
`by one or more LED driver circuits 96a-96n cormected in
`parallel and protected from reverse currents by diodes 98a­
`9811. The number of LED driver circuits 9611-9614needed
`depends upon the current drive requirements of the banks of
`LEDs 82, 84, 86. ln a preferred embodiment, approximately
`1400 mA is needed to optimally drive the NT-52Dl-0430
`LED array device. This is accomplished by cormecting a pair
`of LED drivers in parallel, each of which can driveup to about
`700 mA, such as a pair ofI.ED l20AO7OOC24EXitanium
`LED drivers from Advance, Inc. The LED driver circuits
`96a-9611have inputs 100a-10011for providing l20VAC main
`voltage to the LED driver circuits 96a-96n and a pair of DC
`outputs 10211-10211for providing DC current to the banks of
`LEDs 82, 84, 86. The LED driver circuits 96a-9612can option­
`ally be provided with a pair of inputs 104a-104/2to provide
`dimmer control of the banks ofLEDs 82, 84, 86 by means of
`pulse width modulation teclmiques, as is known in the art. For
`example,
`the LED driver
`circuits
`96a-96n
`car1 be
`LEDO024VlOB Xitanium LED drivers from Advance, Inc.,
`which have a pair of light dimming inputs 104a-104n. The
`predetermined DC output current is converted to an AC out­
`put signal having a rectangular shape with a duty cycle which
`varies between 0% and l00% when a DC voltage is varied
`between 0 V to 10 V at inputs 104a-10412. The DC inputs
`104a-104:2can be driven directly from a DC source, or can be
`derived from l20V AC main power via a light dimming
`circuit 106. The light dimming circuit 106 can be driven at
`inputs I08 by a traditional thyristor based AC light dimmer,
`whose output signal is converted to a proportional DC voltage
`in the range of OV-10 V. Those skilled in the art would know
`how to convert an AC voltage with a variable duty cycle to a
`proportional DC voltage.
`[0019] FIG. 3 is a schematic diagam showing how air is
`circulated to remove heat from the LED light fixture of FIG.
`1. Air is drawn ir1tothe ca1112 of the light fixture 10 through
`the ventilation cone 60 by the fan 80 through the vent holes 54
`in the heat sink S2 (arrows A). The now hot air is drawn
`through fins in the heat sink 52, through the far180 and is then
`forced down into the interior 22 of the lighting fixture 10
`between the can 12 and the ventilation cone 60 (arrows B).
`Cooler air is exhausted through the openings 70 between the
`flange 64 and the trim 16 (arrows C) or can I2.
`[0020]
`In an alternative embodiment, the heat sink 52 has
`no vent holes. An LED array assembly 47 includes a fan
`which is motuited above a heat sink, and the heat sink is
`mounted above an LED array 48. The LED array assembly is
`suspended within an open ventilation cone. Air is drawn into
`the can 12 of the light fixture 10 through the open ventilation
`cone by the fan 80 through fins in the heat sink 52, thence
`through the fan 80. The air is then forced down into the
`interior 22 of the lighting fixture 10 between the can 12 and
`the open ventilation cone. Cooler air is exhausted through the
`openings 70 between the flange 64 and the trim 16 or the can
`12.
`[0021] FIG. 4 depicts another alternate embodiment of the
`ligl1ti11gfixture shown in FIGS. 1-3. Elements illustrated i11
`FIG. 4 which correspond to the elements described above in
`connection with the embodiment of FIGS. 1-3 have been
`identified by corresponding reference numbers increased by
`
`

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`US 2008/0 I65535 Al
`
`Jul. 10, 2008
`
`one hundred. Unless otherwise indicated. both embodiments
`have the same construction and operation.
`[U022] HG. 4 shows how heat is ventilated in closed spaces
`according to a second embodiment of tl1eprese11tinvention.A
`lighting fixture 110 is inserted into a closed-space ceiling
`structure 226. The ligl1ting fixture 110 includes a can 112,
`which has a circular top portion I 26 having an upper surface
`128 which can be perforated by a plurality of vent holes 228.
`Openings are not provided between the flange 164 and the
`trim 116. A fan 180, preferably a low noise fan, may or may
`not be provided. The ceiling structure 226 includes a ceiling
`230 and a floor 232 above the ceiling 230 separated by a
`plurality offioorjoists 234. A ceiling vent 236 is provided in
`the ceiling 230, while an optional exterior vent 238 111aybe
`provided in the floor joists 234. Optional insulation 240 can
`cover a lowerportion242 of the ceiling structure 226 between
`the plurality of [loorjoists 234, the ceiling vent 236, and the
`lighting fixture 110, thereby defining an interior space 244
`between the insulation 240 and the floor 232.
`[0023]
`In operation, air is drawn through the ventilation
`cone 160 by the optional fan 180 or by natural convection
`(arrows D). The now hot air rises or is drawn in through the
`vent holes 154 in the heat sink 152. The air is drawn through
`fins in the heat sink 152, through the fan 18!), and exits
`through the vent holes 184 in the circular top portion 126 of
`the can 1 12. The wann air (arrows E) is cooled in the interior
`space 244, becoming heavier. The cooler air exits though the
`ceiling vent 236 and the optional exterior vent 238 (arrows F).
`[0024] FIG. S is a flow chart showing the steps for retrofit­
`ting the LED light of FIG. 1 into existing incandescent or
`fluorescent fixtures. For illustrative purposes, it is assumed
`that a traditional incandescent or fluorescent recessed lighting
`fixture shares the same mechanical parts as the embodiments
`ofthe present invention except forthose parts associated with
`the LED array assembly 47, unless otherwise noted. At step
`25!), an incandescent or fluorescent bulb is removed. At step
`252, the trim 16 is removed by disconnecting the trim reten­
`tion spring(s) 62. At step 254, the can-to-base attachment
`screws 40, 42 are removed. At step 256, an adjustable bulb
`mounting base screw associated with a bulb base is removed.
`At step 258, the bulb base is removed by cutting wires near the
`bulb base.At step 260, the incandescent/fluorescent can is slid
`out of the opening of the base 14. At step 262, the armored
`(BX) cable 46 is removed from the incandescent /fluorescent
`can. At step 264, the BX cable 46 is attached to the can 12. At
`step 266, the LED ca1112 is inserted i11tothe opening of the
`base 14.At step 268, the base 12 is attached to the can-to-base
`attachment screws 40, 42. At step 270, the AC power leads 74
`extending from the BX-type electrical conduit a11dcable 46
`are electrically connected to power leads 76 ofthe I FD driver
`circuit 72 via wire wrap screws 78. At step 272, the LED array
`adjustment bracket 66 is attached to the can 12 using the LED
`array position adjustment scrmv 68. At step 274, the lens is
`replaced with one appropriate for LEDs. At step 276, an
`optional secondary optic is inserted.
`[D025] The present
`invention l1as been described in the
`context of “can insert”-type LED down light fixtures 1|), 110.
`ln a can-insert type LED dow11light fixture, the can does not
`need to be replaced. A separate housing insert is mounted
`inside the existing luminaire housing. The new separate hous­
`ing contains the LED array, heat sink, a11doptional driver,
`optic, and fan. The present invention is also applicable to
`other LED recessed down light fixture types known in the art,
`such as can-replacement-type and LED module insert type
`
`down light fixtures. ln a can-replacement-type fixture, the
`entire housing ca11is removed a11dreplaced with a housing
`containing the LEDs, heat sink, and optional driver, optic, and
`fa11.1n the LED module insert type fixture, a separate LED
`array assembly is mounted inside the existing housing can
`The LED array assembly includes a heat sink, and optional
`driver, optic, a11dfa11.The advantage of this approach is that
`the installer is 11otrequired to perform any complicated or
`potentially performance degrading assembly of the LED, heat
`sink, fa11,etc.; i.e., it does 11otrequire that the housing be
`replaced. For a can-replacement-type fixture, the LED array
`assembly 47 can be equipped with a fan 80 mounted above a
`heat sink S2 located within the interior 22 of a lighting fixture
`10, or the fan 80 can he mounted exterior to the light fixture I 0
`abovethe upper surface 28 of the circula