111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US007053560Bl
`
`c12) United States Patent
`Ng
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,053,560 Bl
`May 30,2006
`
`(54) BI-DIRECTIONAL LED-BASED LIGHT
`
`Inventor: James K. Ng, Seattle, WA (US)
`(75)
`(73) Assignee: Dr. LED (Holdings), Inc., Tortola (VG)
`( *) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 210 days.
`(21) Appl. No.: 10/714,761
`
`5/1998 Britten ....................... 362/231
`5/2000 Rossner .................. 315/185 R
`2/2001 Patel et al .................. 315/307
`9/2001 Chang eta!. ........... 315/185 R
`6/2002 Nerone ....................... 315/291
`
`5,749,646 A *
`6,069,452 A *
`6,191,541 B1 *
`6,288,497 B1 *
`6,411,045 B1 *
`* cited by examiner
`Primary Examiner-Wilson Lee
`(74) Attorney, Agent, or Firm-Jeffrey Pearce
`
`(22) Filed:
`
`Nov. 17, 2003
`
`(57)
`
`ABSTRACT
`
`(51)
`
`Int. Cl.
`HOSB 41100
`(2006.01)
`(52) U.S. Cl. .............................. 315/185 R; 315/185 S;
`362/800
`(58) Field of Classification Search ... ... ... ... 315/185 R,
`315/185 S, 200 A, 200 R, 291, 316, 312,
`315/324, 224, 307, 247; 362/800, 231, 296
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,939,426 A * 7/1990 Menard et al.
`
`At least one pair of LEDs, preferably of the super-lumines(cid:173)
`cent type, are connected in parallel but with reverse polarity
`in series with at least one resistor and driven by a voltage
`source, which may deliver unrectified alternating current. An
`array of m series-connected LED pairs may be included in
`n parallel paths. The printed circuit board in which the LED
`pair(s) is mounted is adapted to fit into after-market fittings
`originally intended to receive incandescent light bulbs. In
`some embodiments, contacts are formed in the edges of
`lateral protrusions in the PCB.
`
`315/185 R
`
`18 Claims, 4 Drawing Sheets
`
`200
`~
`
`~ ~
`o:;1
`
`~ ~
`o;1
`
`~
`D~.
`IJ
`
`~ ~
`o:;n
`
`~ ~
`
`02n
`
`k2
`
`IPR PAGE 1
`
`Acuity v. Lynk
`Acuity Ex.
`
`1002
`
`

`
`U.S. Patent
`
`May 30,2006
`
`Sheet 1 of 4
`
`US 7,053,560 Bl
`
`FIG.1
`
`k2
`
`FIG. 2
`
`200
`~
`
`k2
`
`IPR PAGE 2
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`

`
`U.S. Patent
`
`May 30,2006
`
`Sheet 2 of 4
`
`US 7,053,560 Bl
`
`FIG. 3
`
`100
`
`300
`
`330
`
`FIG. 4
`
`FIG. 5
`
`410
`412
`414
`
`411
`
`410
`412
`414
`
`430
`
`430
`
`IPR PAGE 3
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`

`
`U.S. Patent
`
`May 30,2006
`
`Sheet 3 of 4
`
`US 7,053,560 Bl
`
`FIG. 6
`
`FIG. 7
`
`FIG. 8
`
`300
`
`411
`413
`415
`
`410
`412
`414
`
`430
`
`701 702
`
`412
`
`600
`
`~
`
`p
`-t-
`
`~---
`
`--
`' ' ' ' l
`632 i
`i+-wi --+i
`
`FIG. 9
`
`FIG.10
`
`300
`
`T1
`
`901
`
`902
`
`IPR PAGE 4
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`

`
`U.S. Patent
`
`May 30,2006
`
`Sheet 4 of 4
`
`US 7,053,560 Bl
`
`FIG. 11
`
`FIG. 12
`
`~~~
`
`1100
`
`FIG.13
`
`FIG.14
`
`FIG.15
`
`1300
`
`1302
`
`1302
`
`1320
`
`1322
`
`IPR PAGE 5
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`

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`US 7,053,560 Bl
`
`1
`BI-DIRECTIONAL LED-BASED LIGHT
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to lights that use multiple light(cid:173)
`emitting diodes, as well as to fixtures for mounting such
`lights.
`2. Description of the Related Art
`Incandescent light bulbs are commonly used for indicator
`lamps, task lamps, general lighting, decorative lamps, warn(cid:173)
`ing lamps, traffic lamps and the like. However, incandescent
`bulbs, and to a lesser extent even plasma-based fluorescent
`and halogen lights, are generally inefficient in terms of
`energy use and are subject to frequent replacement due to 15
`their limited lifetime. Significant savings can be made by the
`use light bulbs where the source of light is light-emitting
`diodes (LED).
`LEDs are much more efficient (in terms of lumens per
`watt) than incandescent and fluorescent lights; moreover, 20
`LEDs generally last much longer. This is particularly true of
`the class of LEDs known as "super-luminescent" or "super(cid:173)
`bright," which have already found uses in such applications
`as automobile tail lights and traffic signal lights.
`Being diodes, one problem with LEDs is that they are 25
`direct-current (DC) devices that are easily damaged by too
`high reverse voltage, whereas the power supplies for many
`devices that would benefit from the advantages of LEDs
`deliver alternating current (AC). Even low-voltage light
`fixtures typically use a 12V AC power source, which is 30
`transformed from, for example, 120V AC at 60 Hz.
`One common way to provide direct current to LEDs from
`an AC source is to include in the power-supply circuit a
`full-wave rectifier and a current-limiting device such as a
`power resistor. One drawback of this approach is that four 35
`rectifYing diodes are typically needed and each of these
`rectifYing diodes must carry half the full current load of all
`the LEDs.
`Another known way to provide DC current to LEDs is to
`include in the power-supply circuit a half-wave rectifier and,
`again, a current-limiting device such as a power resistor.
`This is a much simpler circuit than is needed for full-wave
`rectification, but even it has at least three major drawbacks:
`First, the light emitted from the LEDs will flicker, for
`example, at 120Hz in case the AC power source frequency
`is 60 Hz. Second, when the supplied voltage is negative, this
`circuit assumes that the LEDs will evenly divide the reverse
`voltage among themselves. Failure to do so can lead to a
`cascade failure of the LEDs; this failure is most prominent
`in transient conditions. Third, the rectifYing diode must
`carry the full current load of the LEDs.
`Even assuming that the power supply problems of the
`LEDs are overcome, there must still be some convenient
`way to mount and install the lights themselves. There are of
`course many different types of light fixtures for the many
`different common types of incandescent light bulbs. These
`fixtures feature an array of different types of physical
`connections with wedge, screw-in, bayonet, flange, bi-pin
`and other bases. This means that any after-market LED(cid:173)
`based light bulb replacement must be able to correctly
`connect to the different types of existing sockets of the bulbs
`it is intended to replace. It would be possible to mount LED
`units within the casings-usually bulbs--of the original
`lights, but this complicates the manufacture of such LED
`replacements.
`Yet another concern is that incandescent elements can
`typically be mounted without regard to polarity, whereas
`
`2
`existing LED arrangements cannot. When installing an LED
`replacement in a DC system such as an automobile taillight,
`there is therefore a risk of incorrect installation because even
`with a given fitting, the polarity of the wiring is not always
`the same from one car manufacturer to another.
`What is needed is an LED lighting arrangement that
`eliminates or at least reduces the problems mentioned above.
`Furthermore, some fitting is needed to enable easy after(cid:173)
`market LED replacement. This invention provides such an
`10 arrangement and fitting.
`
`SUMMARY OF THE INVENTION
`
`A lighting arrangement comprises a source of electrical
`power and at least one pair of light-emitting diodes (LEDs)
`driven by the power source. The power source may have
`different characteristics. Advantageously, the power source
`supplies unrectified alternating current to each LED pair,
`although various embodiments of the invention provide
`advantages even in applications whose power source sup(cid:173)
`plies direct current.
`The LEDs are connected in parallel such that an anode of
`a first one of the LEDs in the pair is electrically connected
`to the cathode of the other, second LED in the pair, and the
`anode of the second LED is electrically connected to the
`cathode of the first LED in the pair. One of each pair of
`LEDs is thus forward biased to produce light regardless of
`the instantaneous polarity of electrical current supplied to
`the LED pair by the power source.
`A current-limiting device such as a resistor may be
`connected in series between the power source and each LED
`pair.
`Any number of LED pairs may be included in the arrange(cid:173)
`ment. For example, m LED pairs may be connected in series
`in each of n parallel paths.
`In one embodiment of the invention, a printed circuit
`board (PCB) base that has front and rear surfaces is manu(cid:173)
`factured with laterally extending side-edge protrusions.
`Contact surfaces are then provided on edge surfaces of the
`40 protrusions, for example, by deposition. The PCB base may
`then be used to form a mounting substrate for the LED pairs.
`One way to create the protrusions along the periphery of
`the base is to bore or route through-holes in the PCB with a
`pitch or indexing corresponding to at least one internal
`45 mating surface of a light fixture. By positioning the protru(cid:173)
`sions so that they mate with at least one internal contact
`surface of a light fixture, this embodiment of the invention
`may be used as an after-market replacement for existing
`light bulbs designed for screw-in, bayonet, flanged, etc.,
`50 fittings. One alternative embodiment of the invention pro(cid:173)
`vides a base suitable for installation in a wedge-based fitting.
`For fittings such as screw-in and bayonet fittings, etc., the
`base may also be provided with an arrangement for biasing
`the contact surfaces of the protrusions into electrical contact
`55 with the internal contact surfaces of the fittings. One way to
`do this is to provide in the PCB base at least one slot so as
`to form a region of lateral compression. In these cases, the
`PCB base should have a width equal to or slightly greater
`than an internal dimension of the light fixture. Upon instal-
`60 lation of the PCB base in the fixture, compression of the
`PCB base will then create a lateral biasing force.
`In yet another embodiment of the invention, a separate
`pair of parallel-connected LEDs are mounted on the front
`and back surfaces of the PCB base, with one LED in each
`65 pair being forward biased at the same time as a correspond(cid:173)
`ing LED in the other pair. Front-and-back illumination is
`then provided by the LED pairs on the single PCB substrate.
`
`IPR PAGE 6
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`

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`US 7,053,560 Bl
`
`3
`In still another embodiment of the invention, a plurality of
`LED pairs are mounted on a single printed circuit board
`(PCB) base, including at least three pairs producing light of
`each of three colors, such as red, green and blue such that
`objects illuminated by the arrangement will appear to a 5
`viewer to be illuminated by white light.
`In most implementations of the invention, the LEDs in
`each pair will be normal single-die LEDs. Another aspect of
`the invention provides, however, for a multi-die LED such
`that the LED pair comprises two LED dies mounted with 10
`reverse polarity within a single LED casing.
`When the LEDs are driven from an AC power source,
`each LED element in a coupled pair will have a duty cycle
`of 50%. This arrangement allows for substantial thermal
`advantages. In applications of the invention in which a 15
`plurality-in some cases even dozens-of LED pairs are
`mounted on a single printed circuit board (PCB) base, they
`may be densely mounted, separated by no more than 1 mm.
`
`4
`contacts k1, k2 by a power (or, equivalently, voltage or
`current) source S that delivers either alternating or direct
`current.
`In applications that require illumination (such as reading
`lights) as opposed to simple indication (such as on/off), the
`LEDs D+ and D- are preferably of the super-luminescent
`type, for obvious reasons. Even a minimally skillful elec(cid:173)
`trical engineer will be able to choose the actual type ofLEDs
`used, as well as the type and value of the resistor R, to fit the
`needs of a given application given the specifications of the
`power source S, in particular, its peak delivered voltage.
`Assume for the sake of illustration that when the source
`S supplies positive voltage, current is flowing in the clock(cid:173)
`wise direction (viewed as in FIG. 1); negative output voltage
`therefore gives a counter-clockwise current flow. The opera(cid:173)
`tion of the LED pair D+ and D- then follows from the known
`properties of diodes: When the source S is producing posi(cid:173)
`tive voltage, LED D+ will be forward biased and will light
`up, whereas LED D- will be reverse biased at the forward
`20 bias voltage of D+ and will not give off light. The reverse
`voltage over D- will be kept within safe limits (typically less
`than 4.0V for a white color LED and less than 2.0V for a red
`LED), at the forward bias voltage of D+, as D+ will be
`conductive. Current through D+ will be limited by the
`25 resistor R. When the source voltage polarity switches, so too
`does the conductive LED in the pair: D- will become
`conductive and D+ will be reverse biased at the forward bias
`voltage of D-. The two paired LEDs D+ and D- thus operate
`as a single "AC LED" in that, as long as the supply voltage
`30 is above the minimum forward turn-on voltage, one LED of
`the pair will always be producing light.
`Some of the advantages even of the basic embodiment of
`the invention shown in FIG. 1 are:
`The only diodes required are those that actually produce
`35 light-no rectifying elements are needed at all.
`The invention will work whether the voltage source S
`delivers alternating or direct current. When operating with a
`DC voltage source, only one of the LEDs will be active, but
`on the other hand, the assembly of only three components R,
`40 D+ and D- will work equally well regardless of the polarity
`of the voltage source S.
`Each LED D+ and D- is protected from reverse voltage
`breakdown by the other LED in the pair.
`When operating with an AC voltage source, flicker is
`greatly reduced. In fact, at typical supply frequencies, for
`example, 60Hz, D+ and D- will both appear as 120Hz but
`totally out of phase with each other; therefore, little flicker
`will be apparent to a viewer at all.
`When powered from an AC source, the peak current of
`50 each LED may reach a value higher than the allowed
`continuous DC current. In such case, the LEDs will emit a
`higher peak brightness intensity while maintaining lower
`temperature than when driven at the maximum allowable
`DC current, which reduces the risk of damage and premature
`55 failure.
`FIG. 2 illustrates a generalized embodiment of the inven(cid:173)
`tion: Rather than a single LED pair D+ and D- being
`connected in parallel with reverse polarity, an m-by-n array
`200 of such LED pairs Dif +and Dif- is provided (i=1, ... ,
`60 m;j=1, ... , n), withmLED pairs connected in series in each
`of n parallel paths.
`A separate current-limiting device, R1, again, usually a
`resistor, is preferably included in each parallel path in series
`with the LED pairs. Although not strictly necessary to the
`65 invention (a single current-limiting device could be used as
`shown in FIG. 1), this reduces the load through any given
`resistor (for example) and allows for variation in the number
`
`45
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a circuit drawing of the simplest embodiment of
`an "AC LED" according to the invention.
`FIG. 2 is a circuit drawing of a generalized embodiment
`of the invention, including an LED array.
`FIG. 3 is a plan view of a printed circuit board (PCB) from
`which several PCB bases are manufactured for an embodi(cid:173)
`ment of the invention suitable for use as an after-market
`replacement for light with a typical screw-in fitting.
`FIG. 4 is plan view of a single PCB base separated from
`the PCB shown in FIG. 3.
`FIG. 5 illustrates an example of a trace pattern used in the
`embodiment of the invention that provides an AC LED for
`screw-in fittings.
`FIG. 6 shows an example of component layout on the
`PCB base illustrated in FIGS. 4 and 5, as well as how this
`PCB base can be screwed into a typical socket.
`FIG. 7 is a side view of the arrangement shown in FIG. 6.
`FIG. 8 illustrates a preferred way to spring-bias the PCB
`base of FIGS. 4-7 so as to improve electrical contact
`between the base and the screw-in socket.
`FIG. 9 illustrates an embodiment of the invention suitable
`for after-market installation in a wedge-type fitting.
`FIG. 10 illustrates an embodiment of the invention in
`which two AC LEDs according to the invention are provided
`on a single PCB substrate.
`FIG. 11 illustrates one example of how several LEDs of
`different colors may be mounted on a PCB base and elec(cid:173)
`trically connected as in FIG. 2 so as to approximate a
`full-spectrum light source.
`FIG. 12 is a side view of the arrangement shown in FIG.
`11.
`FIGS. 13 and 14 are side and top views, respectively, of
`a dual-element AC LED according to the invention in a
`single capsule.
`FIG. 15 illustrates an alternative layout of connectors and
`LED elements for the dual-element AC LED.
`
`DETAILED DESCRIPTION
`
`FIG. 1 is a circuit diagram that illustrates the fundamental
`embodiment of the invention: A pair of LEDs D+ and D- are
`connected in parallel, with reverse polarity (with the anode
`of D+ connected to the cathode D- and the anode of D(cid:173)
`connected to the cathode of D+), in series with a current(cid:173)
`limiting device, R, typically a resistor, and driven via
`
`IPR PAGE 7
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`

`
`US 7,053,560 Bl
`
`5
`or characteristics of the diodes in each parallel path. The
`value( s) of R1 may be chosen using normal design methods,
`taking into account the number and characteristics of the
`LEDs and the properties of the voltage source S.
`Each LED pair in the array may use the same diode type 5
`(and/or color) and be arranged the same as all other pairs,
`although this is not strictly necessary as long as standard
`measures (such as adjusting the appropriate resistor values)
`are taken to ensure proper voltage and current supply to the
`LEDs. In FIG. 2, the same number (m) of LED pairs is 10
`shown in each of the n parallel LED paths. This is not
`necessary to the invention; rather, unequal numbers of LED
`pairs may be included in different paths-again, using
`separate resistors R1 in each path facilitates this option.
`The operation of each pair ofLEDs in the array will be the 15
`same as described above for the single pair D+ and D- shown
`in FIG. 1: At any given time, at most one LED in each pair
`will be forward biased and therefore giving off light, the
`other being reverse biased and therefore turned off.
`FIG. 3 illustrates a standard printed circuit board (PCB) 20
`100, from which a plurality of bases are to be manufactured.
`For the sake of simplicity, only a single base 300 is described
`in detail. Any number (including a single one) of identical
`bases may be made from the PCB 100.
`As FIG. 3 shows, a plurality of through-holes or routes 25
`(illustrated using a heavier lines) are cut or bored through the
`PCB, preferably by conventional 1 mm routing, so as to
`form a plurality of laterally extending protrusions 410-415,
`and preferably a bottom protrusion 430, which extends out
`from the outer edge of the base 300. In the preferred 30
`embodiment of the invention, the routes are curved, at least
`substantially semi-circular, although this is not essential and
`will depend on the cross-sectional geometry of the threaded
`or slotted contact surface of the fitting the base 300 is to be
`installed in (see below); thus, the protrusions could be 35
`right-angled or other have some other shape.
`After routing, the routes 410-415, 430 are treated, pref(cid:173)
`erably using a standard PCB plating process, to deposit an
`electrically conductive material such as copper on the inside,
`upper, and lower surfaces of the routes. The PCB base 300 40
`is then either punched out of the larger PCB 100 by using a
`pre-designed punch-and-die set or scored and broken along
`the lines defining the rest (other than the protrusions) of the
`periphery of the base 300. FIG. 4 illustrates the base 300
`after separation from the PCB 100. In the figures, six 45
`side-edge protrusions 410-415 are shown merely by way of
`example; the actual number used may vary and in any given
`implementation of the invention will depend on the needs of
`that implementation.
`FIG. 5 illustrates one example of a pattern of traces T1, 50
`T2, T3 used to create the electrical connections symbolized
`in FIG. 1, with the traces corresponding to the similarly
`numbered leads in FIG. 1. The dark dots represent solder
`pads used to electrically connect component leads to the
`traces. As part of plating the protrusions 410-415 some of 55
`the conductive plating material will be deposited on the
`inside, upper and lower surfaces of the base 300 as well so
`as to join with adjacent portions of the trace T3. The trace
`T3 will therefore be in electrical contact with the inner
`surfaces of the protrusions. Similarly, the conductive mate(cid:173)
`rial deposited on the bottom edge protrusion 430 will be
`electrically connected to the trace Tl.
`FIGS. 6 and 7 illustrate one example of how the LEDs D+,
`D- and the current-limiting element (here, resistor) R can be
`mounted on the base 300. In FIG. 6, the distance between the
`centers of the LEDs is indicated as d. This distanced should
`be kept as small as possible so as to reduce any parallactic
`
`6
`optical effects when the user views the light and thus to
`increase the impression that the LED pair is a single AC
`LED. For example, when using standard 5 mm LEDs, which
`have a diameter of approximately 5 mm, d should be from
`five to eight millimeters, and preferably from five to six
`millimeters; in other words, the LEDs should either just
`touch, or be no more than 3 mm apart, and preferably no
`more than 1 mm. FIG. 7 is a side view of the PCB 300 with
`the components D+, D- and R mounted.
`Even though LEDs will typically generate less than 0.1 W
`of power each, applications such as those that have limited
`space but require high light intensity also require very close
`packing of multiple LEDs. In existing arrangements, this
`leads to severe problems of heat dissipation. One advantage
`of connecting the LEDs in pairs (especially in the multi(cid:173)
`LED embodiments of the invention shown below) to form
`an "AC LED" is that each LED is only "on" about half the
`time; this reduces generated heat and gives better opportu(cid:173)
`nity for effective heat dissipation. Even disregarding the
`thermal advantages of the LEDs' 50% duty cycles, the
`invention still will operate much cooler than a typically
`halogen bulb, whose operating temperature is as high and
`potentially dangerous as 200° C.
`FIG. 6 also illustrates a screw-in fitting 600 typically used
`to receive incandescent bulbs. Inner and outer dimensions
`(usually, diameters) of the fitting 600 are shown as wi and
`wo, respectively. The vertical separation (viewed as in FIGS.
`4-6), that is, the pitch p, of the protrusions 410-415 is then
`chosen to match the pitch p of the internal contact threading
`610 of the screw-in fitting 600 the light is to be installed in.
`The width w of the main portion (without the protrusions
`410-415) of the base 300 is preferably chosen to be the same
`or slightly less than the inner diameter of the screw-in fitting
`600. When the base 300 is screwed into the fitting 600, the
`helical inner contact surface 610 of the fitting will electri(cid:173)
`cally contact at least one (and usually all) of the plated
`protrusions 410-413; the trace T1 will be electrically con(cid:173)
`nected with the other contact 632 of the fitting via the
`protrusion contact 430. In a different but preferred embodi(cid:173)
`ment of the base 300, the width w is preferably slightly
`greater than wi; this is described below in conjunction with
`FIG. 8.
`FIG. 8 shows the preferred method according to the
`invention for providing a lateral biasing force to increase the
`contact between the plated protrusions 410-413 and the
`inner contact surface(s) 610 of a fitting: Using conventional
`techniques, slots 701, 702 are cut or punched into the base
`300 so as to preferably extend in the direction in which the
`base is installed in the fitting. In the illustrated example, the
`slots are therefore vertical. The illustrated slots are straight,
`but this is not required by the invention and will in many
`cases depend on the layout of traces. Curved slots are also
`possible, or slots with a more complicated geometry.
`The width w of the main portion of the base 300 (not
`including the protrusions) may then be slightly greater than
`the inner diameter wi of the fitting 600. When the base 300
`is installed, for example, screwed in, it will therefore com(cid:173)
`press laterally, squeezing together the slots 701, 702. The
`flexibility of the PCB material itself will bias the protrusions
`60 410-415 outward against the inner contact surfaces 610 of
`the fitting 600.
`Another way to bias the base against the inner contact
`surface(s) 610 of the fitting 600 would be to mount an
`electrically conductive compression spring (not shown) on
`65 the bottom protrusion 430 and to connect this spring to the
`trace Tl. The biasing force would then be vertical, which
`would tend to force the upper plated edges of the edges of
`
`IPR PAGE 8
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`

`
`US 7,053,560 Bl
`
`7
`the protrusions 410-415 into physical and thus electrical
`contact with the inner contact surface (s) 610 of the fitting
`600.
`The invention is easily adapted for use in other types of
`fittings besides the screw-in fitting shown in FIG. 6. For
`example, using only two plated protrusions, one on either
`side, the base 300 could be used to fit into a standard bayonet
`fitting. By adjusting the vertical separation (from zero
`upward) of the protrusions, and the base width, most stan(cid:173)
`dard bayonet fittings could be accommodated, regardless of
`their degree of indexing. A flanged base can also be created
`using a similar technique.
`The "AC LED" according to the invention may of course
`also be used in fittings that do not require screwing in or
`rotation at all. FIG. 9 illustrates, for example, how the base
`300 may be formed so as to fit into a standard wedge-type
`fitting. In this case, no special protrusions are required at all.
`Rather, standard contacts 901, 902 are bonded onto the PCB
`so as to contact the traces leading current from the two
`different poles of the voltage source. The lateral separation
`of the contacts 901, 902 will of course be chosen to match
`the positions of the female contacts (usually, spring-biased
`contacts in slots) into which the base 300 is to be fitted. Note
`that this embodiment of the base 300 may be made excep(cid:173)
`tionally compact, in most cases little larger (and possibly
`even smaller) than the incandescent bulb it replaces.
`FIG. 10 illustrates just one of many different ways in
`which more than one LED pair, in this case D 11 +, D 11 -, and
`D21 +, D21 - may be mounted on a single base 300. Depend(cid:173)
`ing on the needs of the particular implementation, the two 30
`pairs may be connected either in series (comparing with
`FIG. 2, m=2 and n=1) or in parallel (m=1 and n=2). If the
`LED pairs are connected in parallel, then separate resistors
`R 1 and R2 are preferably included, one in each path. Traces
`to supply current to the LEDs may then be routed in any
`known manner, also depending on the type of fitting the light
`is to be used in.
`The usefulness of the configuration shown in FIG. 9 is
`more than simply the doubling the number of LEDs active
`at any one time. One additional advantage is that it allows
`for front-and-back illumination coverage. Most common
`LEDs have up to approximately 50-degree illumination
`coverage; front-and-back mounting would therefore provide
`roughly 1 00-degree coverage. The degree of coverage in any
`given implementation of the illustrated embodiment of the
`invention will of course depend on the degree of coverage of
`the chosen LEDs.
`It would also be possible to bend the leads of the LEDs,
`or to mount them differently, so that they extend laterally out
`from the base 300 rather than perpendicularly away from its
`surface.
`Still another advantage arises in industries such as the
`automotive industry. Taillights in a car are DC devices, but
`the fittings are usually polarized nonetheless, such that the
`invention, in particular, the base 300, would be able to fit in
`the fitting in only one orientation. Because the invention
`provides an "AC LED," polarity will not make any differ(cid:173)
`ence. On the other hand, the "correct" orientation of the
`invention for a given car model, or in a given fitting (left as
`opposed to right, for example) might be such that a single 60
`LED pair, as shown in FIGS. 6 and 7, would be facing
`backwards. The twin-pair LED arrangement of FIG. 10
`would eliminate this concern.
`Note that LEDs are typically so cheap that it would in
`most cases be better simply to have "idle" LEDs rather than 65
`having separate "left-handed" or "right-handed" bases.
`Rather than allow an LED pair to illuminate to no purpose
`
`8
`(for example, the pair facing away from any potential
`viewers), it would also be possible to route current to the two
`LED pairs through a switch (double-pole double-throw) so
`that only one pair is activated at any time; if the PCB is
`mounted "backwards" then the user can flip the switch and
`activate the other LED pair.
`FIGS. 11 and 12 illustrate, respectively, top and side
`views of an embodiment of a multi-element, multi-path AC
`LED configuration that provides substantially full-spectrum
`10 light, at least at distances from the light assembly that users
`will normally be located for reading, working, etc. In this
`embodiment, several LEDs are mounted in any known
`manner so as to extend at least substantially perpendicular
`from a PCB base 1100. Again, the LEDs are preferably
`15 mounted close together; as before, the LEDs should either
`just touch, or be no more than 3 mm apart, and preferably no
`more than 1 mm apart. LEDs are included that emit three
`different wavelengths, that is, colors, preferably red, blue
`and green, (or any other combination of colors) which, when
`20 mixed, are perceived by a viewer as being full spectrum
`white. The LEDs are preferably distributed so that no color
`clearly predominates in any particular region of the layout.
`In this multi-color embodiment of the invention, the
`LEDs are preferably connected as reversed-polarity pairs as
`25 shown in FIG. 2, with a resistive element (labeled "R") for
`each electrically parallel branch. Thus, the LEDs will be of
`six "types" D+" D-" D+ g' D-g' D+ 6 , and D-6 , that is,
`permutations of color (indicated by subscripts r, g, and b for
`red, blue and green) and polarity.
`All LED pairs emitting the same color may comprise one
`parallel branch of the configuration shown in FIG. 2, but this
`is not necessary. Rather, LED pairs of different colors may
`instead be connected in the same parallel path; this would
`enable the full-spectrum light effect even in the very unlikely
`35 event that one or more parallel paths were to fail. It would
`also be possible to include different numbers of LED pairs
`for different colors so as to properly balance the luminance
`for each color to create the most white effect; in this case, it
`is advantageous to series-connect the LEDs of each color so
`40 that proper resistance values can be chosen in each parallel
`path.
`At a typical user's normal reading or working distance
`from the assembly, the light from the LEDs will be so
`"mixed" that the user will not be able to distinguish any red,
`45 green, or blue hues unless he is looking directly at the
`assembly. When looking at an illuminated object located at
`distances beyond about 20 em from the assembly, and
`possibly even closer, the user will perceive the mixture of
`red, green, and blue as pure white, or, rather, full-spectrum
`50 light illuminating the object. Contrast this with a conven(cid:173)
`tional "white" LED, which is simply a blue-light LED
`coated with phosphorous so as to introduce a yellow com(cid:173)
`ponent to the spectrum and produce a "pseudo-white" color.
`In one prototype of the multi-element embodiment of the
`55 invention illustrated in FIGS. 11 and 12, the base 1100 was
`substantially round, with a diameter chosen so the base
`would fit and could be used as an aftermarket insert into
`common halogen fixtures. The illustrated embodiment is
`particularly advantageous for mounting within existing
`MRll or MR16 fixtures with a bi-pin base and mirror
`reflector (hence the "MR"), or the smaller G4 fixture. The
`structures used to connect the LEDs electrically to the power
`supply will be chosen depending on which type of conven(cid:173)
`tional lighting assembly is to be replaced.
`It is of course not necessary for the LEDs in the