LED-based electric lamp

Disclosed is an LED-based bulb-type lamp, including a cooling structure and a plurality of LEDs thermally connected to the cooling structure. The lamp includes at least three separate LED arrays oriented substantially parallel to its central longitudinal axis, such that the LEDs are interspersed among a plurality of light-transmission sub-areas of the LED-based lamp. One or more portions of the cooling structure of the lamp extend to its outer surface, as assembled, such that light-transmissive and heat-dissipating areas are spread over the outer surface, for example, in an alternating manner.

TECHNICAL FIELD

The present invention is directed generally to an electric lamp. More particularly, various inventive methods and apparatus disclosed herein relate to a bulb type LED-based electric lamp.

BACKGROUND

Illumination devices based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust lighting units that enable general illumination, as well as a variety of lighting effects in many applications. Some of these lighting units employ two or more groups or “channels” of LEDs which produce light of different colors, each controllably supplied with the predetermined current to enable generation and mixing of light to produce general illumination with desired attributes or a desired lighting effect.

Some of the known LED-based approaches for replacing incandescent light bulbs have a number of shortcomings. For example, one such lamp, shown inFIG. 1A, has a bulb mounted on a socket. A light source, comprising a plurality of LEDs mounted on a PCB, is arranged inside the bulb. The PCB is provided with venting holes that function as cooling means (not shown). A part of the PCB is formed as a base plate on which the bulb, embodied as a protective dome, is mounted, said dome surrounding the light source and parts of the PCB and the cooling means. The dome has a translucent outer surface for transmitting light originating from the light source during operation of the lamp. A lamp axis extends through a central end of the socket and a central extremity of the bulb. The desired omnidirectional light distribution of this lamp is impeded by the base plate on which the dome is mounted. Furthermore, disposing the protective dome over the PCBs and LEDs compromises heat dissipation.

Referring toFIG. 1B, another known LED-based alternative to incandescent light bulbs, particularly A55 and A60 types, is a MASTER LEDbulb available from Koninklijke Philips Electronics N.V., featuring a plurality of LED light sources disposed over a heat sink and emitting dimmable light towards a diffusing dome cover.

Recently, legislation has been enacted to spur development of ultra-efficient solid-state lighting products to replace the common light bulb. The legislation challenges industry to develop viable replacement technologies for two of today's most widely used and inefficient technologies −60 W incandescent lamps and PAR 38 halogen lamps.

Accordingly, it would be desirable to provide an improved lighting device employing LED light sources, optionally addressing one or more of the drawbacks of conventional technologies, while providing quality illumination with high color rendering. It is also desirable for this lighting device to optionally substantially retain commonly encountered form factors, so that existing hardware, sockets, and power connections could be employed, thereby further reducing costs and reducing waste associated with retooling, and facilitating adoption of this improved LED-based electric lamp.

SUMMARY

The present disclosure is related to inventive methods and apparatus for energy-efficient LED-based lamps. For example, LED-based lamps disclosed herein may have standard form factors, so that they may be used with existing lighting hardware. More particularly, various embodiments of the present disclosure are directed to high-output LED-based lamps suitable for replacement of conventional sources, in terms of size, shape, operating environment, and/or light quantity, distribution, and/or quality.

Generally, in one aspect, an LED-based lamp includes a socket surrounding a longitudinal lamp axis. The lamp also includes cooling structure having a plurality of substantially planar surfaces radially arranged about the lamp axis and a plurality of protruding portions. Each of the protruding portions is positioned between two of the surfaces and extends outward and away from the lamp axis and each of the surfaces. Each of the surfaces is substantially parallel to the lamp axis. The lamp also includes a plurality of LED PCBs, driving electronics, and a plurality of light transmittable caps. Each of the LED PCBs is coupled to a single of the surfaces. The driving electronics are substantially enclosed within the cooling structure and are electrically coupled to each of the LED PCBs and to the socket. The light transmittable caps are each positioned over a single of the LED PCBs and each extends between two adjacent of the protruding portions.

In some embodiments, the lamp further includes a plurality of thermal pads each interposed between a single of the LED PCBs and a single of the surfaces. The lamp may further include a plurality of reflectors each placed over a single of the LED PCBs and containing at least one LED opening therein. In some version of those embodiments each of the reflectors includes a pair of side extensions each covering at least some of a single of the protruding portions.

In some embodiments, the protruding portions include a longitudinally extending cooling channel therein. In some versions of those embodiments, the cooling channel extends below the light transmittable caps in a direction toward the socket. The periphery of the protruding portions may optionally generally conform to the periphery of the light transmittable caps.

Generally, in another aspect, an LED-based lamp includes a socket surrounding a longitudinal lamp axis and a cooling structure having a plurality of protruding portions and a plurality of light-transmission sub-areas. The light-transmission sub-areas are each generally defined between a pair of the protruding portions. The protruding portions and the light-transmission sub-areas are arranged about the lamp axis in an alternating configuration. The lamp also includes a plurality of LED arrays, driving electronics, and a plurality of light transmittable caps. Each of the LED arrays is retained within a single of the light-transmission sub-areas. The driving electronics are substantially enclosed within the cooling structure and are electrically coupled to each of the LED arrays and to the socket. Each of the caps covers a single of the light transmission sub-areas. The periphery of the light transmittable caps may optionally substantially conform to the periphery of the protruding portions.

In some embodiments the LED arrays each include a flexible electrical connection member electrically coupled thereto and electrically coupled to the driving electronics. In some version of those embodiments an interconnection PCB is electrically interposed between the flexible electrical connection member and the driving electronics. The interconnection PCB may optionally be accessible via at least one electrical connection opening through the cooling structure that is near an end of the LED-based lamp distal the socket.

In some embodiments, the light transmission sub-areas are all substantially the same size. In some versions of those embodiments, the number of the light transmission sub-areas is from two to four.

In some embodiments, the lamp further includes a plurality of reflectors each placeable over a single of the LED arrays and containing at least one LED opening therein. In some versions of those embodiments each of the LED arrays includes a LED PCB compressed between a single of the reflectors and the cooling structure.

Generally, in another aspect, an LED-based lamp includes a socket surrounding a lamp axis, driving electronics electrically coupled to the socket, and at least three interconnection connection members each electrically coupled to the driving electronics. A cooling structure is also provided and surrounds the interconnection connection members and at least partially surrounds the driving electronics. The cooling structure has a plurality of interspersed light-transmission sub-areas arranged about the lamp axis. A plurality of LED arrays are each retained within a single of the light-transmission sub-areas. A plurality of flexible electrical connection members are each electrically and physically coupled to a single of the LED arrays and electrically and physically coupled to a single of the interconnection connection members. The flexible electrical connection members each extend through a single of a plurality of pathways through the cooling structure.

In some embodiments, each of the pathways is a recess atop the cooling structure enclosed with a top cover installed thereover.

In some embodiments, the interconnection connection members are all coupled to an interconnection PCB. Also, each recess may retain an extension extending from a light-transmissive cap provided across a single of the light-transmission sub-areas.

Generally, in another aspect, an LED-based lamp includes a socket surrounding a lamp axis, driving electronics electrically coupled to the socket, and at least three interconnection connection members electrically coupled to the driving electronics and positioned more distal the socket than a majority of the driving electronics are to the socket. A cooling structure is also provided that surrounds the interconnection connection members and at least partially surrounding the driving electronics. The cooling structure has a plurality of interspersed light-transmission sub-areas arranged about the lamp axis. The lamp also includes a plurality of LED arrays each retained within a single of the light-transmission sub-areas and a plurality of flexible electrical connection members each electrically and physically coupled to a single of the LED arrays and electrically and physically coupled to a single of the interconnection connection members. The flexible electrical connection members each extend through a single of a plurality of recesses atop the cooling structure. The recesses are enclosed by a top cover installed thereover and coupled to the cooling structure.

In some embodiments, the interconnection connection members are all coupled to an interconnection PCB.

In some embodiments, the lamp further includes a plurality of light-transmissive caps each provided across a single of the light-transmission sub-areas.

In some embodiments, the light-transmissive caps each include an extension extending through a single of the recesses.

In some embodiments, the lamp further includes a plurality of reflectors each placeable over a single of the LED arrays and containing at least one LED opening therein. In some versions of those embodiments the reflectors each include an extension extending through a single of the recesses. In some versions of those embodiments each of the LED arrays includes a LED PCB compressed between a single of the reflectors and the cooling structure. The lamp may further include a plurality of thermal interface pads each interposed between a single LED PCB and the cooling structure.

Implementing various inventive concepts disclosed herein, these LED-based lamps efficiently integrate compact power supply and control components for driving high-intensity LEDs together with thermal management and optical systems, providing for a form and function fit equivalent to common general-purpose incandescent light bulbs, for example, an A19 bulb in accordance with ANSI C78.20-2003, with a single contact medium screw base E26/24. Furthermore, LED-based lamps according to various embodiments disclosed herein contemplate producing a substantially omnidirectional pattern of light distribution with dimming ability.

As used herein for purposes of the present disclosure, the term “LED” should be understood to include any electroluminescent diode or other type of carrier injection/junction-based system that is capable of generating radiation in response to an electric signal. Thus, the term LED includes, but is not limited to, various semiconductor-based structures that emit light in response to current, light emitting polymers, organic light emitting diodes (OLEDs), electroluminescent strips, and the like. In particular, the term LED refers to light emitting diodes of all types that may be configured to generate radiation in one or more of the infrared spectrum, ultraviolet spectrum, and various portions of the visible spectrum (generally including radiation wavelengths from approximately 400 nanometers to approximately 700 nanometers). It also should be appreciated that LEDs may be configured and/or controlled to generate radiation having various bandwidths (e.g., full widths at half maximum, or FWHM) for a given spectrum (e.g., narrow bandwidth, broad bandwidth), and a variety of dominant wavelengths within a given general color categorization.

For example, one implementation of an LED configured to generate essentially white light (e.g., a white LED) may include a number of dies which respectively emit different spectra of electroluminescence that, in combination, mix to form essentially white light. In another implementation, a white light LED may be associated with a phosphor material that converts electroluminescence having a first spectrum to a different second spectrum. In one example of this implementation, electroluminescence having a relatively short wavelength and narrow bandwidth spectrum “pumps” the phosphor material, which in turn radiates longer wavelength radiation having a somewhat broader spectrum.

It should also be understood that the term LED does not limit the physical and/or electrical package type of an LED. For example, as discussed above, an LED may refer to a single light emitting device having multiple dies that are configured to respectively emit different spectra of radiation (e.g., that may or may not be individually controllable). Also, an LED may be associated with a phosphor that is considered as an integral part of the LED (e.g., some types of white LEDs). In general, the term LED may refer to packaged LEDs, non-packaged LEDs, surface mount LEDs, chip-on-board LEDs, T-package mount LEDs, radial package LEDs, power package LEDs, LEDs including some type of encasement and/or optical element (e.g., a diffusing lens), etc.

The term “light source” should be understood to refer to any one or more of a variety of radiation sources, including, but not limited to, LED-based sources (including one or more LEDs as defined above).

The term “color temperature” generally is used herein in connection with white light, although this usage is not intended to limit the scope of this term. Color temperature essentially refers to a particular color content or shade (e.g., reddish, bluish) of white light. The color temperature of a given radiation sample conventionally is characterized according to the temperature in degrees Kelvin (K) of a black body radiator that radiates essentially the same spectrum as the radiation sample in question. Black body radiator color temperatures generally fall within a range of from approximately 700 degrees K (typically considered the first visible to the human eye) to over 10,000 degrees K; white light generally is perceived at color temperatures above 1500-2000 degrees K. Lower color temperatures generally indicate white light having a more significant red component or a “warmer feel,” while higher color temperatures generally indicate white light having a more significant blue component or a “cooler feel.”

The terms “lighting unit” or “lighting device” is used herein to refer to an apparatus including one or more light sources of same or different types. A given lighting unit may have any one of a variety of mounting arrangements for the light source(s), enclosure/housing arrangements and shapes, and/or electrical and mechanical connection configurations. Additionally, a given lighting unit optionally may be associated with (e.g., include, be coupled to and/or packaged together with) various other components (e.g., control circuitry) relating to the operation of the light source(s). The term “LED-based lighting device” refers to a lighting unit that includes one or more LED-based light sources as discussed above, alone or in combination with other non LED-based light sources. A “multi-channel” lighting unit refers to an LED-based or non LED-based lighting unit that includes at least two light sources configured to respectively generate different spectrums of radiation, wherein each different source spectrum may be referred to as a “channel” of the multi-channel lighting unit.

According to certain embodiments, the first channel includes a first plurality of white LEDs in series with each other, and the second channel includes a second plurality of red LEDs (e.g., two LEDs) in series with each other. A desired color temperature of the light may be controlled by adjusting the current through the two channels. For example, in many embodiments, the currents through the channels are controlled such that the essentially white light generated by the lamp has a correlated color temperature in the range from approximately 2700K to 3000K with a Color Rendering Index (CRI) exceeding 90.

A given light source may be configured to generate electromagnetic radiation within the visible spectrum, outside the visible spectrum, or a combination of both. Hence, the terms “light” and “radiation” are used interchangeably herein. Additionally, a light source may include as an integral component one or more filters (e.g., color filters), lenses, or other optical components. Also, it should be understood that light sources may be configured for a variety of applications, including, but not limited to, indication, display, and/or illumination. An “illumination source” is a light source that is particularly configured to generate radiation having a sufficient intensity to effectively illuminate an interior or exterior space. In this context, “sufficient intensity” refers to sufficient radiant power in the visible spectrum generated in the space or environment (the unit “lumens” often is employed to represent the total light output from a light source in all directions, in terms of radiant power or “luminous flux”) to provide ambient illumination (i.e., light that may be perceived indirectly and that may be, for example, reflected off of one or more of a variety of intervening surfaces before being perceived in whole or in part).

The term “spectrum” should be understood to refer to any one or more frequencies (or wavelengths) of radiation produced by one or more light sources. Accordingly, the term “spectrum” refers to frequencies (or wavelengths) not only in the visible range, but also frequencies (or wavelengths) in the infrared, ultraviolet, and other areas of the overall electromagnetic spectrum. Also, a given spectrum may have a relatively narrow bandwidth (e.g., a FWHM having essentially few frequency or wavelength components) or a relatively wide bandwidth (several frequency or wavelength components having various relative strengths). It should also be appreciated that a given spectrum may be the result of a mixing of two or more other spectra (e.g., mixing radiation respectively emitted from multiple light sources).

For purposes of this disclosure, the term “color” is used interchangeably with the term “spectrum.” However, the term “color” generally is used to refer primarily to a property of radiation that is perceivable by an observer (although this usage is not intended to limit the scope of this term). Accordingly, the terms “different colors” implicitly refer to multiple spectra having different wavelength components and/or bandwidths. It also should be appreciated that the term “color” may be used in connection with both white and non-white light.

DETAILED DESCRIPTION

Known LED-based approaches for replacing incandescent light bulbs have a number of shortcomings. For example, in one approach desired omnidirectional light distribution is impeded by a horizontal base plate upon which the LEDs are mounted. Moreover, in such an approach a protective dome that surrounds the LEDs compromises heat dissipation. Recent legislation has challenged industry to develop improved LED-based approaches for replacing incandescent bulbs.

Accordingly, it would be desirable to provide an improved lighting device employing LED light sources, optionally addressing one or more of the drawbacks of conventional technologies, while providing quality illumination with high color rendering. More generally, Applicants have recognized and appreciated that it would be beneficial to provide an LED-based lamp that may optionally retain commonly encountered form factors.

In view of the foregoing, various embodiments and implementations of the present invention are directed to an LED-based electric lamp.

In some embodiments, the LED-based lamps contemplated herein deliver a total luminous flux greater than 600 lumens, and, in some specific embodiments, greater than 900 lumens, while consuming 10 Watts of electric energy or less. As discussed in more detail below, the lamps may have an even distribution of luminous intensity within the 0° to 150° axially symmetrical area. Preferably, luminous intensity at any angle within this zone shall not differ from the mean luminous intensity for the entire 0° to 150° zone by more than 10%.

One aspect of the present disclosure generally relates to orienting at least three separate LED arrays substantially parallel to a central longitudinal axis of the device by, for example, disposing them on PCBs attached to surfaces of a heat sink. Another aspect focuses on extending one or more portions of the heat sink to the outer surface of the device, as assembled, such that its light-transmissive and heat-dissipating areas are spread over the outer surface, for example, in an alternating manner. Such configuration of the heat sink increases the surface area exposed to the ambient atmosphere, and hence increases and improves the heat dissipating capacity of the device, with little or no increase in the size or weight of the device. Thus, in some embodiments, the light-transmitting surface of the device is divided into sub-areas by the extended portions of the heat sink. As a result, the light distribution may be tuned, for example, via setting the orientation and configuration of sub-areas of the light-transmitting surface and associated arrays of LEDs. In other embodiments, the light distribution may be controlled via control of the intensity of the arrays of LEDs, and/or possibly even within arrays the intensity of individual LEDs may be controlled. By setting the orientation and/or intensity of the illumination from individual sub-areas, the lamp may achieve an equal luminous intensity, as perceived by an observer, within a space angle of 300° (i.e. the equal luminous intensity is observed from all directions except from directions within a cone around the socket and having its apex inside the bulb on the axis, with the cone having an apex angle of) 60°. Equal luminous intensity in this respect means an average light intensity with a variation in light intensity of plus or minus 10-15%.

Referring toFIG. 2Aa side view of a first embodiment of a LED-based lamp1is shown. The lamp1has a socket5, an E27 Edison fitting, in which the bulb3comprising cooling means21is mounted. The outer surface15of bulb3is formed both by light transmittable surface sub-areas23, four arches25(of which only two are shown) and an adjoining top27of the cooling means, which feature is more clearly visible in the top view shown inFIG. 2Balong axis11. The cooling means21extend from inside the bulb into the outer surface of the bulb and are formed as solid arches. In the embodiment ofFIG. 2A, surfaces are mutually flush at locations at the outer surface of the bulb where said surfaces of both the cooling means and the light transmittable sub-areas border each other. The cooling means hamper only to a small extent the distribution of light as emitted by the light source (not shown) through the light transmittable surface15, and to a significantly lesser degree than the prior art lamp as shown inFIG. 1B. The spatial light intensity distribution of the lamp ofFIG. 2Aas a function of the angle β is shown inFIG. 2C. In the plot shown inFIG. 2C, the angle B=0° refers to the light intensity as measured along the axis11in the direction from socket5towards bulb3.

InFIG. 2Da perspective view, partly broken away, of a second embodiment of the lamp1is shown, i.e. the light transmittable sub-areas are formed by releasably fixed light transmittable parts, of which two are left out, which light transmittable parts are provided with click/snap elements enabling easy assembly onto the lamp by interconnecting with clicking elements32provided on the cooling means21. Some of the components inside the bulb3are visible, including the light source7which is made up of a plurality of LEDs7a,7bmounted on a PCB9, and cooling means21which extend from the PCBs inside the bulb into the outer surface15of the bulb. The PCBs9are arranged around axis11. The cooling means are shaped as recesses extending from the bulb outer surface towards the axis and are coated on a side29facing the LEDs with a reflective coating31to counteract light losses due to absorption of light by the cooling means and thus to increase the efficiency of the lamp. Each PCB and subgroups of LEDs is proximate to its respective cooling means, and as a result a relatively very efficient cooling is obtained. The LEDs can comprise: —a combination of Red, Green, Blue, White (RGBW) LEDs, —RGBW—Amber LEDs, —LEDs of different color temperature, —LEDs which are all of the same color, or Blue/UV-LEDs in combination with a remote phosphor provided on or in the light transmittable parts. In the lamp ofFIG. 2Dthe LEDs are of different color temperature, i.e. 2500K and 7000K, of which the emission intensity can be controlled independently to adjust the emitted color temperature of the lamp.

FIG. 3Ashows a side view of a third embodiment of a lamp1. The lamp1has a socket5, an E27 Edison fitting, in which the bulb3comprising cooling means21is mounted. The outer surface15of the bulb is formed both by six light transmittable surface sub-areas23of the same shape, six corrugated arches25(of which only four are shown) and an adjoining top27of the cooling means. In the lamp ofFIG. 3Athe light transmittable sub-areas each are surrounded by respective cooling means. The cooling means are not flush with the light transmittable surface but are partly laid over said surface, such that the cooling means together with the light transmittable surface form an undulated bulb outer surface. The cooling means in this lamp do not extend from inside the bulb into and beyond the outer surface15of the bulb, but only form part of the bulb outer surface.FIG. 3Bshows a vertical cross-section of the lamp1ofFIG. 3A. As the lamp is a DC lamp, an electronic driver circuit33is provided inside a cavity35in the bulb3which converts the alternating mains voltage into an appropriate DC voltage. The cavity35has an annular outer wall formed by the PCBs9of heat conducting material around the axis11, and thus acts as a cooling means, on which PCBs the LEDs (not shown) are (to be) mounted, the six arches being thermally connected to said wall at the bulb outer surface, and an electrically insulating wall36shielding the driver from the PCBs. Thus, efficient cooling of both the LEDs and the driver circuit is obtained. The lamp ofFIG. 3Bcomprises Blue-LEDs whose radiation is converted into visible light by a remote phosphor YAG-Ce coating37which is provided on an inner surface24of the light transmittable sub-areas23.

FIG. 4toFIG. 8, respectively, show a fourth, a fifth, a sixth, a seventh and an eighth embodiment of a lamp1in which on the outer surface15of the bulb3alternative arrangements of cooling means21and light transmittable sub-areas23are shown. The lamp inFIG. 4has parallel annular rings of cooling means; the lamp inFIG. 5has an interdigitated (finger-like or comb-like mean) cooling mean21with the light transmittable sub-areas23. Three finger-like cooling areas form an interdigitated mean with three sub-areas of the light transmittable surface. The lamp1inFIG. 6shows an embodiment in which the cooling means21are arranged adjacent the socket5and at the top27of the lamp comprising one integral light transmittable surface22, i.e. without intermediate sub-areas.FIGS. 7 and 8show alternative embodiments of the shape of the bulb, i.e. inFIG. 7the bulb is tube-shaped and inFIG. 8the bulb is a six-sided polygon (hexagon) with a patched mean formed by the cooling means and the sub-areas23of the light transmittable surface22. Furthermore, in each of saidFIGS. 4 to 8, a plane P1parallel to an axis11is shown as well as a plane P2perpendicular to said axis. The axis11extends through an end17of a socket5and an extremity19of bulb3. In all the embodiments shown inFIGS. 4 to 8at least one plane, either plane P1or plane P2or both plane P1and plane P2, crosses two or more times a boundary10between the cooling means21and the light transmittable surface22or sub-areas23thereof. InFIG. 4plane P1crosses said boundary three times, and plane P2crosses no boundary10. InFIG. 5plane P1crosses no boundary while plane P2crosses said boundary10six times. InFIG. 6Plane P1crosses said boundary two times, and Plane P2crosses no boundary10. InFIG. 7Plane P1crosses said boundary10one time, and Plane P2crosses said boundary six times. InFIG. 8both Plane P1and Plane P2cross said boundary10eight times. In the lamp ofFIG. 7the bulb outer surface15has an interdigitated mean of the cooling means21and the sub-areas23of the light transmittable surface22. The interdigitated mean extends in axial direction over a length L over the bulb outer surface15. Preferably the length L should be at least ¼ of an axial height H of the bulb3.

FIG. 9shows a vertical cross-section of a ninth embodiment of the lamp1. The lamp is both an actively cooled and passively cooled lamp. Active cooling means41, in the Figure a double fan working in two, transverse directions, is provided inside a cavity35in the bulb3which enhances the cooling capacity of and control of the cooling of the lamp. Grates43are provided to enable forced flow of air, indicated by arrows45, through the cavity. The cavity35has an outer wall formed by the PCBs9of heat conducting material, which thus acts as a passive cooling means, on which the LEDs7a,7b,7care mounted. Thus, efficient cooling of the lamp is obtained.

Referring toFIGS. 10-17, various aspects of a tenth embodiment of a LED-based lamp101is illustrated. The LED-based lamp101includes three separate LED PCBs109, each containing red and blue LEDs107. One or more thermal sensors may optionally be mounted on each LED PCB109and utilized to maintain a desired balance between the amounts of red and blue light. In some embodiments each PCB109contains 2-4 red LEDs and 2-4 blue LEDs. For example, in one embodiment each PCB109contains 3 red Phoenix LEDs available from Epistar (emitting at approximately 614 nm) and 3 blue Rebel LEDs available from Philips Lumileds (emitting at approximately 452-480 nm). In some embodiments, the PCBs109may be formed from a ceramic material selected to have its thermal expansion coefficient substantially matching that of the LEDs107to improve reliability of the solder joint between the LEDs107and the underlying LED PCBs109.

A separate driver PCB151contains a driver circuit133and is electrically coupled to an interconnection PCB154for connecting the LED PCBs109to the driver circuit133. In some embodiments, the driver circuit133is a dimming dual channel driver having an isolated first stage integrated circuit and a second stage Buck-Boost converter. For example, some suitable embodiments of the driver circuit133are disclosed in a co-pending International Application Serial No. PCT/IB2010/053734, filed on Aug. 18, 2010, incorporated herein by reference. Other driver circuitry may alternatively be utilized. For example, in some embodiments a single channel driver having an isolated first stage integrated circuit may be utilized.

The interconnection PCB154is provided near the top of the lamp101when assembled and includes four separate male connections152for interfacing with corresponding female connections1091of the LED PCBs109. The interconnection PCB154is accessible via recesses102aatop planar surfaces102and is also accessible through a large opening atop cooling structure121when top cover138is removed. As illustrated inFIGS. 10,15, and16, the interconnection PCB151may optionally rest atop a driver insulator156that at least partially surrounds the driver circuit133. As illustrated in various Figures (e.g.,FIGS. 11,14,15, and17), recesses102amay enable a flexible printed circuit connection1092(a flexible electrical connection member) to extend between and electrically connect each LED PCB109to the interconnection PCB154. As described in detail herein, the flexible printed circuit connection1092extends between and electrically connects the female connections1091to the LED PCB109. In alternative embodiments other connections may be utilized including, for example, male connections on the flexible printed circuit connection1092, female connections on the interconnection PCB154, and/or non-flexible connections.

The cooling structure121has a central axially extending opening therein for receiving the driver circuit133and at least partially enclosing it. As a result, the driver circuit133can be disposed at least partially inside the cooling structure121and proximate to the LEDs107. Optionally, when the lamp101is assembled, the driver circuit133may be sealed from the three separate optical chambers of the lamp101that each houses one of the LED PCBs109. The driver circuit133is illustrated as being received wholly within driver insulator156. The driver insulator156insulates the driver electronics, both thermally and electrically from the cooling structure121when disposed in the central opening thereof. In alternative embodiments driver circuit133may extend beyond driver insulator156or driver insulator156may be omitted. For example, in some embodiments the driver PCB151may extend beyond driver insulator156and be in contact with plastic shell157. The driver insulator156may be retained within the central opening of the cooling structure121utilizing, for example, snap/click or other interfacing structure of the driver insulator156and the cooling structure121and/or adhesive.

The cooling structure121further has three planar surfaces102for receiving the LED PCBs109. Three protruding portions125of the cooling structure121extend to the outer surface of the lamp101when assembled. Each of the protruding portions125includes a first arch125A and a second arch125B defining a channel therebetween. The depicted arches125A,125B are substantially parallel with one another and the peripheral edges thereof are spaced approximately thirty degrees apart relative to the central longitudinal axis of the lamp101. The peripheral edges of adjacent arches125A,125B of adjacent protruding portions125are spaced approximately ninety degrees apart relative to the central longitudinal axis of the lamp101. In alternative embodiments more arches may be provided with one or more of the protruding portions125. For example, in some embodiments an additional vertically extending arch may be provided interposed between the first arch125A and the second arch125B. Also, in alternative embodiments the protruding portions125may only include a single arch or may include structure interconnecting the arches125A.

In various embodiments (including the depicted embodiment ofFIGS. 10-17), the arches125A,125B of each protruding portion125form a longitudinal channel or a slit therebetween to further improve heat dissipation efficiency due to the thermal chimney effect. The longitudinal channel may optionally extend below (in a direction toward screw cap158) the light-transmissive caps141as illustrated, for example, inFIG. 10. Although depicted as an open channel along the entire length thereof, in alternative embodiments the channel may optionally be completely surrounded by protruding portion125along portions of the length thereof. In some embodiments the outer edges of the protruding portions125are curved to generally match the profile of the light-transmissive caps141that are discussed below. Collectively, the protruding portions125and light-transmissive caps141may generally define a bulb103. The areas between adjacent protruding portions125may generally define light transmission sub-areas. In alternative embodiment the light-transmissive caps141may optionally extend over top of all or portions of the protruding portions125.

To facilitate efficient heat dissipation, the material of the cooling structure121may be selected to have a coefficient of thermal conductivity of at least 1 W/mK, more preferably 10 W/mK or more even more preferably 20 W/mK or more and up to 101 or 500 W/mK. Suitable materials for the cooling means are metals such as aluminum, copper, alloys thereof, or thermally conductive plastics, for example as available via Coolpoly®, for example white/black Coolpoly® D3606 having a thermal conductivity of 1.5 W/mK, or white Coolpoly® D1202 having a thermal conductivity of 5 W/mK. In one particular embodiment, the heatsink is made of thixomolded Mg-based alloy (such as AZ91D).

The injection-molded light-transmissive plastic caps141may optionally be provided with phosphor conversion material coated thereon. In some embodiments the phosphor conversion material may include a LuAG/YAG phosphor mixture. The caps141also optionally diffuse the light output from the LEDs107. Embodiments of lamp101produce white light by combining light generated directly by blue and red of LEDs107and indirectly by phosphor-conversion of some of the blue light. This approach may be advantageous for its efficiency of generating white light at CRI>90. Heat generation in phosphor is taken away from the blue LED package, while red LEDs have sharper spectral distribution than red phosphor would have. Optically, the shape of the caps141may be optimized for omnidirectional uniformity of the radiation distribution taking into account positioning of the LEDs107relative to the longitudinal axis of the device. In some embodiments, each light-transmissive cap141can be releasably fixed onto the heat sink, for example, via a click/snap connection which enables ready exchange of these parts. The replace-ability feature renders the device to have the advantage that properties of light-transmissive caps141may be chosen as desired and the beam properties may be easily adjustable. The light-transmissive caps141may be provided, for example, with diffusely transparent or translucent characteristics, optionally with a reflective pattern, or, for example with a transparent characteristic provided with a chosen blend of remote phosphor material to set the color or color temperature of the lamp. In the case where the light-transmissive caps141are optical elements via which the direction of the light rays emitted by LEDs107are controlled, the beam characteristics or the light distribution is relatively easily adjustable via selection of optical characteristics thereof.

In the depicted embodiment the light-transmissive caps141may be removably attached to the cooling structure121. Each of the light-transmissive caps141includes a lower protrusion141B (See e.g.,FIGS. 10 and 15) that may be received in a corresponding receptacle102B (See e.g.,FIGS. 11 and 15) below each planar surface102. Each light-transmissive cap141also includes an upper extension141A (See e.g.,FIGS. 10,14, and15) that may be placed through a corresponding recess102A (See e.g.,FIGS. 11,14, and15) above each planar surface102when the top cover138is un-attached. Each of the upper extensions141A includes a pair of opposed side protrusions that prevent the upper extension141A from being removed from a recess102A when the top cover138is attached (See e.g.,FIG. 14).

Three reflectors143(corresponding to the number of LED PCBs109) are illustrated inFIGS. 10,12,15, and17. The reflectors143may collect light that might otherwise be absorbed by the cooling structure121and direct the light toward light-transmissive caps141. In some embodiments the reflectors143may be made of microcellular PET GB material. In other embodiments the reflectors143may be made of polycarbonate material. The reflectors143include openings144that each surround an individual of the LEDs107. In other embodiments the opening(s)144may be sized to surround multiple LEDs107. The reflectors143generally conform to the shape of a single of the segments of the cooling structure121. The reflectors143each include side extensions143A,143B that contact and/or are immediately adjacent faces of protruding portions125of the cooling structure121. Also, the reflectors143each include top and bottom extensions143C,143D that may contact and/or be immediately adjacent other portions of the cooling structure121. The reflectors143also include an extension extending rearward from the top extension143C that may be received in recess102A to help retain reflector143in position in a similar manner as described with respect to upper extension141A of light-transmissive caps141. Such extension may also optionally contain structure that interfaces with corresponding structure on light-transmissive caps141to help retain light-transmissive caps141in position.

Thermal interface pads145are interposed between the LED PCBs109and the cooling structure121. The thermal interface pads145assist in connecting the LED PCBs109thermally to the cooling structure121. The illustrated thermal interface pads145only physically contact the planar surfaces102but in alternative embodiments may optionally include extensions that physically contact the protruding portions125of the cooling structure121. Ceramic screws are also included and each extends through openings of a single of reflectors143, LED PCBs109, and thermal interface pads145and is received in a receptacle in one of planar surfaces102to thereby secure the thermal pads145, LED PCBs109, and reflectors143to the cooling structure121.

The lamp101also includes a base which, in the depicted embodiment, includes an Edison screw cap158and a plastic shell157to electrically isolate the Edison screw cap158from the cooling structure121. The plastic shell157also includes prongs for snap connection to the cooling structure121as illustrated inFIG. 15. In some embodiments the plastic shell157may support the driver PCB151and/or driver insulating shell156.

In some embodiments the major steps for assembling the lamp101may include the following, presented in a functional, but not particular, order. Sub-assembly and testing of the LED PCBs109. Fastening each set of the reflectors143, LED PCBs109, and thermal interface pads145to a designated surface on the cooling structure121with one screw (repeat three times). Slide the driver circuit153into the insulating shell156. Connect driver circuit153to the interconnection PCB154. Insert the insulating shell156into the cavity of the cooling structure121. Connect the three LED PCBs109to the interconnection PCB154. Snap-connect the Edison shell157to the cooling structure121. Crimp, and solder two wires from the driver electronics PCB151to the Edison screw cap158and screw on the Edison screw cap158. Snap-connect the light-transmissive caps141to the cooling structure121. Snap connect the top cover138to the cooling structure121.

Referring now toFIG. 18, an exploded view of an eleventh embodiment of a LED-based lamp201is illustrated. The eleventh embodiment201contains some similarities with the tenth embodiment and like numbering between the two generally refers to like parts. Four LED PCBs209are provided on four opposed planar surfaces202of the cooling structure221. The LED PCBs209include rigid connections2092formed therewith that connect to corresponding connection members on interconnection PCB254provided near the bottom of the lamp close to the Edison shell257. The interconnection PCB254is electrically connected to driving circuit233which, in turn, is electrically connected to the Edison screw cap258. An insulator256is provided that is slidably placeable over driving circuit233. Four separate protruding portions225are also provided and do not extend below the four separate light-transmissive caps241when the lamp200is assembled. Four separate thermal pads245and reflectors243are also provided. The thermal pads245include extensions that are adjacent an optionally contact walls of the protruding portions225.