WO2020092717A1

WO2020092717A1 - Light guide panel with onboard driver

Info

Publication number: WO2020092717A1
Application number: PCT/US2019/059081
Authority: WO
Inventors: Christopher LE BLANC; Andrew MCALEAVEY
Original assignee: Elemental LED, Inc.
Priority date: 2018-10-31
Filing date: 2019-10-31
Publication date: 2020-05-07

Abstract

LED-based light guide panels (LGPs) with an onboard driver are disclosed. The driver accepts power in a first form and convert it to a second form suitable for driving LED light engines. The driver may be a switched-mode power supply or a simpler driver architecture that is particularly adapted for LGP applications. In some embodiments, the driver may comprise a DC/DC converter. The driver may be placed in the frame of the LGP, or in a driver layer that lies beneath the light guide. In some embodiments, control elements may also be embedded within the frame. For example, the LGP may include a motion or occupancy sensor that changes the state of the LGP or turns it off when the area around the LGP is unoccupied. The LGP may also include an internal network interface that allows it to be controlled by an external system.

Description

LIGHT GUIDE PANEL WITH ONBOARD DRIVER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/753,322, filed October 31, 2018, and to U.S. Patent Application No. 16/356,493, filed March 18, 2019. The contents of those applications are incorporated by reference herein in their entireties.

TECHNICAL FIELD

[0002] The invention relates to light guide panels, and in particular, to light guide panels with onboard drivers.

BACKGRONUD

[0003] Light guide panels (LGPs) are flat-panel luminaires that are used to deliver well-diffused light over an area. They are typically used either to provide primary illumination for a room or area, or to backlight signs and displays.

[0004] LGPs are a type of light guide, a cousin of fiber optics - in an LGP, light is emitted into the edge of a panel. The panel is usually made of a transparent plastic like polymethyl methacrylate (PMMA) or polycarbonate that has a higher refractive index than air. By total internal reflection, the LGP contains much of the light, directs it, and diffuses it. In most modem LGPs, small surface defects are introduced into one surface of the LGP in order to reduce total internal reflection and release well-diffused light over the entire visible surface of the LGP.

[0005] Basic light guide technology has been available for many decades. For example, U.S. Patent 2,443,561, issued in the late l940s, describes a crib light that uses a light guide panel - in this case, an incandescent lamp emits light into the edge of a plastic panel which is bent in a U-shape and hung over the sidewall of a crib such that the occupant of the crib is protected from the electrical elements and lamp. While innovative, products like this relied on bulky, hot incandescent lamps as light sources.

[0006] In recent decades, lighting based on light emitting diodes (LEDs) has become dominant in both residential and commercial settings. The rise of LED lighting has brought with it a resurgence in light guide technology and a number of sophisticated, LED- based LGPs. In contrast to its incandescent and fluorescent forebears, LED lighting is smaller, lighter, and generates less heat - particularly suitable for LGP applications, in which the objective is to emit light directly into the thin edge of a plastic or glass panel.

[0007] While LEDs may be well suited for LGP applications, LED-based LGPs are not without their issues. One issue is voltage. Most LEDs operate at low voltage using direct current (DC) power. Most household and commercial power is high voltage alternating current (AC) power. (Although the definitions of low and high voltage vary according to the authority one consults, for purposes of this description, a voltage under about 50V may be considered to be low voltage.) In order to convert from high-voltage AC to low-voltage DC, a driver is used. “Driver” is the general term for a device capable of meeting the power needs of an LED luminaire. In most LED applications, the driver is a switched-mode power supply. Physically, the driver is usually a“brick” - a rectilinear enclosure that varies in size and weight depending, in part, on the amount of power it is designed to supply. Drivers may be either attached to an LGP (e.g., along the rear face of the panel) or placed elsewhere with a low-voltage lead wire that connects electrically to the LGP. Regardless of whether they are physically attached to the LGP or installed separately, drivers can be a burden.

SUMMARY OF THE INVENTION

[0008] One aspect of the invention relates to LED-based light guide panels with onboard drivers. The drivers may be disposed in the frame of the LGP or in a layer under the light guide itself. If the driver is disposed in the frame, it may extend along one side of the frame, two sides of the frame, or all sides of the frame, depending on the number of components and the space provided. Other techniques, like the use of double-sided PCBs, may be used to fit driver components into the frame. If the driver is disposed in a driver layer under the light guide itself, the PCB carrying the driver components may be encapsulated in order to provide a flat, generally even surface behind the light guide. The encapsulant may be reflective (e.g., infused or mixed with white pigment) so that the encapsulant can also serve as a reflective backing to redirect light that escapes the light guide back into the light guide. If an encapsulant is not used, stand-offs may be used to maintain the spacing between the PCB on which driver components are mounted and a separate reflective layer that backs the light guide. The drivers themselves may be full switched-mode power supplies of typical architecture, or they may have any number of alternative constructions that are specialized for the purpose of driving LED light engines, preferably with minimal visible flicker.

[0009] Another aspect of the invention relates to LGPs that have both driver and control circuits disposed within their frames. As one example, an LGP may have an occupancy or motion sensor embedded in the frame. The occupancy or motion sensor would be connected to the driver circuits to cause the LGP to dim or to turn off when the surrounding area is unoccupied. In some embodiments, the onboard circuits may include a network interface, so that the state of the LGP and its light output may be monitored and controlled remotely.

[0010] Yet another aspect of the invention relates to snap-frame LGPs that have a driver disposed within their frames. In snap-frame LGPs according to embodiments of the invention, the frame comprises a base and a cover that is hingedly mounted on the base for movement between open and closed positions. The driver is arranged such that when the cover is in the open position, the driver is not exposed, and remains isolated in a compartment within the frame.

[0011] In a further aspect of the invention, an LGP has an onboard driver that takes power in a first form and outputs power in a second form suitable for driving LED light engines. In some embodiments of the invention, the first form may be direct current (DC) power and the second form may also be DC power. In those embodiments, the LGP may be powered over data lines.

[0012] Other aspects, features, and advantages of the invention will be set forth in the description that follows.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0013] The invention will be described with respect to the following drawing figures, in which like numerals represent like features throughout the invention, and in which:

[0014] FIG. 1 is a front elevational view of a light guide panel (LGP) according to one embodiment of the invention;

[0015] FIG. 2 is a cross-sectional view of the LGP taken through Line 2-2 of FIG. i ; [0016] FIG. 3 is a cross-sectional view of a light guide panel (LGP) according to another embodiment of the invention;

[0017] FIG. 4 is a cross-sectional view of a light guide panel (LGP) according to yet another embodiment of the invention;

[0018] FIG. 5 is a partial cross-sectional view of a snap-frame light guide panel (LGP) according to a further embodiment of the invention;

[0019] FIG. 6 is a front elevational view of an LGP according to another embodiment of the invention;

[0020] FIG. 7 is a schematic diagram of control components in the LGP of FIG.

6;

[0021] FIG. 8 is a schematic diagram of control components for an LGP according to a further embodiment of the invention;

[0022] FIG. 9 is a rear elevational view of an LGP powered over data lines according to yet another embodiment of the invention; and

[0023] FIG. 10 is a schematic illustration of the power conversion, control, and interface components of the LGP of FIG. 9.

DETAILED DESCRIPTION

[0024] FIG. 1 is a front elevational view of a light guide panel (LGP), generally indicated at 10, according to an embodiment of the present invention. The LGP 10 of the illustrated embodiment is square, although it may be rectangular or essentially any other shape. Specifically, the sides of LGP 10 may be either rectilinear or curved.

[0025] The LGP 10 has a frame 12, which is comprised of miter-cut segments of extruded metal or plastic in the illustrated embodiment. For example, the frame 12 may be made of extruded aluminum, which may be anodized, powder coated, painted, or surface- treated in any known way. The frame 12 may be either a fixed frame or a so-called snap frame, although for ease of explanation, the remainder of this description assumes that the frame 12 is a fixed frame. In a snap frame, the front segments of the frame are pivotably attached to the sides of the frame 12, typically spring-biased to move or“snap” between open and closed positions. Snap frames provide easy access to the components inside the frame 12, and are often used when an LGP is used to backlight a photograph, advertisement, or some other kind of applique, in which case the snap frame provides access to install and replace the applique.

[0026] The LGP 10 also has a relatively large light-emitting area 14, the details of which will be explained below. In order to draw power from a standard wall receptacle, the LGP 10 has a power cord 16 that emerges from the frame 12. The power cord 16 would typically be a high-voltage alternating current (AC) plug. However, in some embodiments, the LGP 10 may be hard-wired to an electrical power source. In that case, the power cord 16 may be, e.g., a plenum-rated cable. Alternatively, instead of a power cord 16, the LGP 10 may include lead wires intended to be connected to power within a junction box.

[0027] FIG. 2 is a cross-sectional view of the LGP 10, taken through Line 2-2 of FIG. 1. As shown, the frame 12 has substantial interior space, with each piece of the frame being D-shaped, U-shaped, or some other appropriate shape that allows the frame 12 to wrap around both sides of the LGP 10. The light-emitting area 14 has several distinct layers with edges that rest in the frame 12, such that the frame 12 supports the LGP 10. The frame 12 also acts to prevent light leaks; thus, the connection between the frame 12 and the light- emitting area 14 is usually at least substantially light-tight. While not shown in FIG. 2, light blocking tape may be applied to the interface between the frame 12 and the light-emitting area 14 if necessary, especially on the rear side. The light-blocking tape may be, e.g., metalized or black.

[0028] Within the light-emitting area 14, the light guide 18 itself is the primary layer. The light guide 18 is comprised of a material that is at least translucent and that has a higher refractive index than that of air. Typically, the light guide 18 would be made of a transparent material, like glass, poly(methyl methacrylate) (PMMA), or polycarbonate, although other materials are possible. Plastics are often preferred over glass because of the susceptibility of glass to breakage, but in embodiments that require long endurance and resistance to extreme environments, glass may be a suitable choice. In many embodiments, the upper surface of the central portion of the light guide 18 will be patterned with microdots, abrasions, or other features that act to reduce total internal reflection and release the trapped light rays as desired. These types of light-releasing features are usually applied uniformly over the central portion of the upper surface, so that the LGP 10 provides a well-diffused, even light output over the entire light guide 18. For example, microdots may be laser-etched into the material of the light guide 18. While a uniform distribution of such features is the norm for most general applications, microdots, abrasions, and other light-releasing features may be applied to the upper surface of the light guide 18 in particular patterns or shapes if the objective is to create a specific type of light output pattern or to create selective bright spots over the area of the light guide 18. This could be done for decorative or functional effect.

[0029] The light guide 18 is backed by a reflective layer 20, which may, for example, be a coated white sheet of paper, a plastic sheet, a metallized sheet of paper or plastic, a metal sheet or foil, or another type of light-reflective coating. The reflective layer 20 reflects any light that might escape from the rear of the light guide 18 back into the light guide 18. A backing layer 22, typically sheet metal or plastic, provides additional support for the light-emitting area 14.

[0030] One or more strips of LED linear lighting 23 are mounted within the frame 12 to emit light into the side edges of the light guide 18. As the term is used here,“LED linear lighting” refers to a class of LED lighting in which a number of LED light engines 26 are mounted on a long, thin printed circuit board (PCB) 24, usually at a regular pitch or spacing from one another. The PCB 24 may be flexible, semi-rigid, or rigid. Rigid PCB 24 is used in many rectilinear LGP applications, although flexible PCB 24 may be useful if the LGP 10 is curved. While LED linear lighting for general applications is made in a variety of sizes, and PCBs may range, e.g., from 5-l4mm wide, LGP applications typically use the narrowest PCB possible, typically on the order of 5-8mm. In addition to the LED light engines 26, the PCB 24 may include other circuit components, although LED light engines used in LGP applications are often driven in a constant current mode that does not require many or any additional components on the PCB. If the LED light engines 26 are driven in a constant voltage mode, the PCB may include resistors, current controllers, or other such components.

[0031] As used here, the term“LED light engine” refers to a single LED or multiple LEDs that are packaged in a single package for mounting on a printed circuit board, usually by surface mounting. Most packages have standardized shapes and sizes and a standard set of solder pads for surface mounting. In LGP applications, the smallest possible packages are usually used, and the LED light engines 26 are usually spaced at a very tight pitch, so as to produce as continuous a strip of light as possible. However, the nature of the package of the LED light engine and the spacing of the LED light engines 26 along the PCB 24 may vary. [0032] Within the LED light engine, the LED or LEDs themselves may be of several different types and configurations. For example, many commercial LEDs actually emit blue light. However, for most applications, white light is much more desirable than blue light. Thus, the LED light engine 26 might contain one or more blue LEDs packaged with a phosphor that absorbs the emitted blue light and emits light of a broader spectrum, usually white light of some type. Such LED light engines are often referred to as“blue pump” light engines. The LED light engines 26 may also be RGB light engines; that is, they may include red, green, and blue LEDs that can be activated in various combinations to produce various colors. RGB LED light engines do not typically require a phosphor.

[0033] In the illustrated embodiment, the LED light engines 26 emit light into the light guide 18 along two edges. However, depending on the size of the LGP 10 and a number of other factors, LED light engines 26 may emit light into one edge of the light guide 18, two edges of the light guide 18, or even all edges of the light guide 18.

[0034] The PCBs 24 of the illustrated embodiment are mounted on divider panels 28 that are positioned such that the LED light engines 26 are as close to the edges of the light guide 18 as possible. The divider panels 28 themselves are mounted to the interior surfaces of the frame 12, e.g., in channels provided for that purpose. If mounted in channels, the divider panels 28 may be removable. Alternatively, the divider panels 28 may be soldered, spot welded, or adhered in place, if desired. Aside from positioning the LED light engines 26, the divider panels 28 act as heat sinks to draw away the heat generated by the LED light engines 26, and also serve the purpose of dividing the frame 12 into separate compartments. In some cases, the compartment that houses the LED linear lighting 25 may be low voltage, and the other compartment may be high voltage, since such divisions are often required by electrical safety regulations. Of course, other arrangements for placing LED light engines 26 close to the edges of a light guide may be used.

[0035] LGPs according to embodiments of the invention carry internal driver components. In the LGP 10 of FIGS. 1 and 2, the driver, generally indicated at 30, is placed within the frame 12. As can be seen in FIG. 2, the driver 30 extends along one side of the frame 12. Depending on the features of the driver 30 and the amount of space that is necessary, the driver 30 may use all available space in all sides of the frame. As the term is used here,“driver” refers to any components needed to convert high-voltage AC power to low-voltage DC power and to drive the LED linear lighting 25, thus, the terms“driver” and “driver components” will be used interchangeably in this description. The driver components 30 may simply be mounted on a printed circuit board that is adhered to the interior of the frame 12 and connected where necessary to the LED linear lighting 25 on the other side of the dividing panel 28. In other words, the internal arrangement of the LGP 10, with divider panels 28 creating separate compartments, may make it unnecessary for the driver 30 or driver components 30 to be separately encased or enclosed. However, in some cases, despite the internal arrangement of the frame 12, safety regulations may require the driver 30 or driver components 30 to be encased in some sort of enclosure. If so, the enclosure may be metal, plastic, or even a flame-treated cardboard, to name but a few options.

[0036] The driver 30 may have any components or architecture necessary to convert power from high-voltage AC to low-voltage DC. In some cases, the driver 30 may have all of the components of a traditional switched-mode power supply or, in some cases, a linear power supply. For example, U.S. Patent No. 10,028,340, the contents of which are incorporated by reference in their entirety, discloses a small AC-to-DC converter intended for use with LED light engines, and the driver 30 may have at least some of these components. The driver of this patent includes its own dimming control, although LGPs according to embodiments of the invention may or may not include their own onboard controls, as will be described in more detail below. As was noted briefly above, the driver 30 may be a constant current driver or a constant voltage driver, although constant current drivers are more typical in LGP applications.

[0037] However, the driver 30 of the LGP 10 need not include all of the components of a switched-mode power supply or a linear power supply. For example, U.S. Patent No. 10,028,345, the contents of which are hereby incorporated by reference in their entirety, discloses linear lighting with on-board driver circuits. In the embodiments disclosed in that patent, a rectifier rectifies incoming, high-voltage power, and the rectified high- voltage power is fed directly to LEDs. The LEDs either have sufficiently high forward voltages or are sufficient in number to accept the rectified, high-voltage power. Some embodiments described in that patent also filter the incoming power to reduce flicker in the LED light engines 26. In effect, U.S. Patent No. 10,028,345 discloses a simplified driver that produces a power signal that has significant ripple or noise but is still appropriate for powering LEDs, rather than converting AC power into“perfect” DC power with no ripple or noise. Such simplified driver circuits may be used for the driver 30 in embodiments of the present invention, especially if the LED light engines 26 have high forward voltages or are provided in sufficient number within the circuit. U.S. Patent 9,491,821, the contents of which are incorporated by reference in their entirety, discloses another type of simplified driver and LED circuit that takes AC power as input and may be suitable for use in some embodiments of the invention.

[0038] In some cases, the LED light engines 26 may all be connected in series with the driver 30. In other cases, as disclosed in U.S. Patent No. 10,028,345, the PCB 24 may be divided physically and electrically into repeating blocks, with each repeating block having several LED light engines 26. Each of the repeating blocks is typically electrically in parallel with power and ground, such that the failure of any one repeating block will not cause the entire strip of LED linear lighting 25 to go dark.

[0039] In FIG. 2, a set of wires 29 penetrate the divider panel 28 on one side and are connected to the PCB 24 to power the linear lighting 25. Linear lighting 25 on opposite sides of the LGP 10 would typically be connected by wires run along the frame 12. The method of connecting the linear lighting 25 and the driver 30 is not critical, so long as it complies with any applicable safety regulations.

[0040] While the driver 30 and the LED linear lighting 25 are shown as being separate components of the LGP 10 in the embodiment of FIGS. 1 and 2, they may be integrated or cooperate to a greater degree in some cases. For example, since LEDs are diodes, they can be connected together in a full-bridge rectifier configuration to rectify their own AC power, rather than requiring an additional rectifier as part of the driver 30.

[0041] Although some aspects of this description focus on low-voltage DC LED light engines 26, high-voltage AC LED light engines may also be used. High-voltage LED light engines are LED light engines that are packaged or otherwise integrated with drive circuits that can take high-voltage AC power as input and produce a power signal appropriate for their LEDs. These sorts of LED light engines can typically be installed as-is, and may not require the separate compartments and internal frame dividers described here. Unless this description makes an explicit distinction between high-voltage LED light engines and low- voltage LED light engines, references to one should be construed to cover the other as well.

[0042] As was noted briefly above, the spatial arrangement within the frame 12 may vary from embodiment to embodiment, and various techniques may be used to reduce the amount of space that components require in order to make those components fit within as small a footprint as possible. For example, U.S. Application No. 16/130,094, filed September 13, 2018 and incorporated by reference herein in its entirety, discloses a PCB for linear LED lighting that is double-sided. Such an arrangement may provide either more space for housing driver components 30, or may help those components fit in a smaller footprint.

[0043] The location of the driver 30 and the form factor of the LGP 10 may also vary from embodiment to embodiment. FIG. 3 is a cross-sectional view of another embodiment of an LGP, generally indicated at 100, according to another embodiment of the invention.

[0044] Like the LGP 10 described above, the LGP 100 of FIG. 3 has a large light- emitting area 102 and a frame 104. The frame 104 differs from the frame 12 of the LGP 10 described above - specifically, the frame 104 does not house a driver 30. As shown, the frame 104 is generally C-shaped and wraps around the LGP 100 with a much smaller width than the frame 30 of the previous embodiment. While the frame 104 may be a metal extrusion, e.g., an aluminum extrusion, in some cases, the frame 104 may be little more than a light-tight metallic foil with adhesive that wraps around the LGP 100.

[0045] As shown in FIG. 3, LED light engines 106 mounted on appropriate PCBs 108 are placed at respective edges of a light guide 110. The PCBs 108 would typically be linear, and could be either rigid or flexible. A rigid PCB 108 may be used with LGPs 100 that have rectilinear shapes and sides; a flexible PCB 108 may be useful if the LGP 100 has curved sides.

[0046] The light guide 110, as with the previous embodiment, is typically a sheet of glass, PMMA, polycarbonate, or some other material that is at least translucent and has a refractive index higher than that of air. The central portion of the light guide 110 may be provided with light-releasing features, like microdots or abrasions, as was described above.

[0047] In the LGP 10 of FIG. 2, the light guide 18 is backed by a reflective sheet 20 that reflects any rearward-escaping light back up toward the emitting upper surface of the light guide 18. The arrangement of the LGP 100 of FIG. 3 is different. In LGP 100 of FIG. 3, the light guide 110 is backed by a driver layer 112. The driver layer 112 comprises a PCB 114 on which driver components 116, 118, 120, 122, 124 are mounted. As shown, low- voltage output wires 128 exit the driver layer 112, connecting with each of the PCBs 128 to provide DC power for the LED light engines 106. [0048] The PCB 114 may be either metallic (e.g., aluminum or copper) or plastic/ceramic (e.g., FR4, Mylar, polyimide), but is metallic in the embodiment of FIG. 3. As is known in the art, a metallic PCB may act as a heat sink and help to dissipate heat generated by driver components 116, 118, 120, 122, 124 and LED light engines 106. In the illustrated embodiment, the PCB 114 and driver components 116, 118, 120, 122, 124 are encapsulated at least on their front side by a plastic resin 126. The resin 126 provides a generally flat, even upper surface that matches the generally flat lower surface of the light guide 110 that rests atop it, and typically includes white colorant or other additives that allow the resin 126 to perform the function of a reflective layer.

[0049] Any kind of encapsulant may be used as the resin 126, provided that the encapsulant is rated for the heat and other environmental conditions of use and will not cause electrical shorts in the circuits of the PCB 114. In some cases, the resin 126 may be required to carry a particular flame rating. The resin 126 may be applied by resin casting over the populated PCB 114 or by low- or high-pressure injection molding to overmold the PCB 114. Examples of suitable resins 126 may include SEPLIR 126 FR-CG (S.E. Speciale Engines srl, Torino, Italy) a white, two-part polyurethane thermoset resin with added ceramic components, and the TECHNOMELT^® series of polyamide thermoplastic resins (Henkel AG, Diisseldorf, Germany). As is known in the art, thermoplastic and thermoset resins are processed and applied differently.

[0050] The overall thickness of the driver layer 112 may be any thickness necessary, and would typically be determined, at least in part, by the maximum height of the driver components 116, 118, 120, 122, 124 on the PCB 114. The resin 126 that encapsulates the PCB 114 need not be particularly thick - in some embodiments, thicknesses of 1 mm or less may be used. However, the completed driver layer 112 will most advantageously be of a uniform thickness with a generally flat upper surface. While the lower surface of the driver layer 112 is less critical because it does not act as an optical reflector or perform another such secondary function, for convenience, it will typically also be generally flat. Although FIG. 3 shows the PCB 114 itself as the rearmost layer of the LGP 100, additional backing layers may be used. As with the previous embodiment described above, light-blocking or metalized tape may be used at the interface of frame 104 and light guide 102 in order to create a light tight connection. [0051] In some embodiments, the light guide 110 and the driver layer 112 may be made integrally. For example, after the resin 126 is added to the driver layer 112, the light guide 110 could be injection molded, cast, or otherwise formed directly on top of the driver layer 112. Alternatively, the light guide 110 could be formed separately and attached to the driver layer 112 by any number of optical adhesives. In most embodiments, though, the two layers 110, 112 may be entirely separate and bound only at the edges by the frame 104. While the two layers 110, 112 are shown as directly in contact, in some cases, a small air gap may be created in order to assist with total internal reflection in the light guide 110.

[0052] As can be appreciated from FIG. 3, the arrangement of the light guide 110 and the driver layer 112 provides for much more area in which to place driver components 116, 118, 120, 122, 124, because the driver layer 112 would typically have the same dimensions as the light guide 110 itself. This may be particularly suitable for embodiments in which it is desirable for the driver to be a full switched-mode power supply. It may also be helpful for embodiments in which controls are to be integrated into the LGP 100 as well as driver components 116, 118, 120, 122, 124. As described here, the term“controls” refers to any components that can be used to change the nature of the light output of the LGP 100, or that interface with other systems that can be used to change the nature of the light output of the LGP 100. These may include dimmers, color controllers, wired (e.g., Ethernet) or wireless network interfaces (e.g. WiFi, Bluetooth, near-field communication, etc.), motion and occupancy sensors, and other such components. Beyond those advantages, the encapsulated driver layer 112 may be useful in situations in which the LGP 100 is expected to be placed in wet locations or exposed to other kinds of harsh environments.

[0053] While the resin 126 may seal the PCB 114 and may conveniently also serve as a reflector for the light guide 110, its presence does add weight to the LGP 100 and may make it more time-consuming to manufacture. In some embodiments, those are relevant considerations.

[0054] FIG. 4 is a cross-sectional view of an LGP, generally indicated at 200, according to another embodiment of the invention. LGP 200 has a light guide 202, a frame 204, and LED light engines 206 arranged on linear PCBs 208 to emit light into the light guide 202. As with the PCB 108 of LGP 100, the PCB 208 may be either rigid or flexible, depending primarily on the shapes of the sides of the LGP 200. The arrangement of the light guide 202 is thus largely unchanged relative to that of the LGP 100 described above. [0055] A reflective backing layer 210 backs the light guide 202, and as with similar structures described above, may be either a metallized paper or plastic, a white sheet, or anything else that can reflect escaping light back into the light guide 202. LGP 200 also has a driver layer 212 beneath the reflective backing layer 210, but the configuration of the driver layer 212 differs substantially from that of the embodiments described above.

[0056] The driver layer 212 does include a PCB 214 on which a number of driver components 216, 218, 220, 222, 224 are mounted. However, driver layer 212 is not encapsulated. Instead, spacing is maintained by a series of stand-offs 226, 228, 230 mounted to and between the PCB 214 and the reflective backing layer 210. The number and size of stand-offs 226, 228, 230 may vary from embodiment to embodiment, but a sufficient number is provided to support the light guide 202 and its reflective backing layer 210 evenly across the whole of the LGP 200. In some cases, the thickness of the driver layer 212 may be reduced somewhat as compared with the driver layer 112 described above. As with LGP 100, wires 232 exit the driver layer 212 to supply DC power to the PCBs 208 for the light engines 206.

[0057] As was described above, the frame of the LGP may be either fixed or a snap frame. FIG. 5 is a partial cross-sectional view of a snap-frame LGP, generally indicated at 240, according to another embodiment of the invention. More specifically, FIG. 5 illustrates one side of the snap-frame LGP 240. The snap-frame LGP 240 has a frame 242 that is divided into two parts: a base 244 and a cover 246. The light guide 248, backed by a reflective backing layer 250, is secured in the base 244 of the frame 242.

[0058] The base 244 and cover 246 of the frame 242 are typically extrusions, although they may be machined or molded in some cases. The bottom 252 of the base 244 extends somewhat below the reflective backing layer 250. Close to its edge, the bottom 252 of the base 244 forms a small channel 254. One or more fasteners 256, which may be bolts, screws, or rivets, extend through the channel 254 into the reflective backing layer 250 and the light guide 248, fixedly securing the light guide 248 and its backing layer 250 to the base 244. In other embodiments, adhesive or other means of fastening may be used.

[0059] The upper portion of the base 244 forms a first hinge portion 258. A complementary second hinge portion 260 on the cover 246 fits over the first hinge portion 258 and allows the cover 246 to rotate between open and closed positions. In the illustrated embodiment, the first hinge portion 258 is male and the second hinge portion 260 is female, but that need not be the case in all embodiments. Opposite the first hinge portion 258, the base 244 defines a groove 262. A resilient member 264, such a leaf spring, has a first end resting in the groove 262 and extends across the width of the cover 246 with a second end resting in a groove 266 defined in the cover 246. Positioned in this way, the resilient member 264 causes the cover 246 to“snap” between open and closed positions on the base.

[0060] The snap-frame LGP 240 has linear lighting 268 mounted on the inner sidewall of the base 244, positioned to emit light into the edge of the light guide 248. However, in comparison standard snap-frames, the base 244 of the frame 242 includes additional dividers that divide the base 244 into compartments. Specifically, a first dividing wall 270 extends downwardly from the upper portion of the base 244, terminating at the surface of the light guide 248. A second vertical dividing wall 272 arises from the bottom 252 of the base 244 and extends upwardly, terminating at the underside of the backing layer 250. The two walls 270, 272 may be vertically aligned with one another or the walls 270, 272 may be placed at slightly different locations.

[0061] The arrangement of the walls 270, 272 creates two compartments within the frame 242. The first compartment 274 houses the linear lighting 268. In some embodiments, the wall surfaces of the first compartment 274 may be polished so as to reflect more light into the light guide 248.

[0062] The second compartment 276 in the illustrated embodiment lies between the bottom 252 of the base 244 and the backing layer 250 of the light guide 248. As shown, driver components 278, 280, 282 are disposed on a PCB 284 that is secured to the inner surface of the bottom 252. The driver components 278, 280, 282 receive their input power through an external connection (not shown in FIG. 5). Low-voltage DC output wires 286 extend through the second dividing wall 272 to provide power for the linear lighting 268.

[0063] Compared with the LGPs 10, 100, 200 described above, FIG. 5 illustrates that the interior arrangement of an LGP frame 12, 104, 204, 242 may differ considerably from embodiment to embodiment. The LGP 242 of FIG. 5 may use any of the types of drivers described above, ranging from a full switched-mode power supply to a simpler rectifier arrangement. In some cases, the amount of space available within the LGP frame 242 may dictate the nature of the driver or driver components 278, 280, 282, with smaller frames having simpler, less space-consuming driver components 278, 280, 282. As can also be seen from FIG. 5, while the connection between the cover 246 and the base 244 may be fairly typical for a snap-frame LGP, the additional walls 270, 272 within the base 244 are not. The walls 270, 272 serve the additional purpose of isolating the linear lighting 268 and the driver components 278, 280, 282, so that when the cover 246 is opened, those elements are not exposed. This may make a snap frame LGP 240 that includes an onboard driver safer to use.

[0064] As was described above, LGPs according to embodiments of the invention may include controls onboard as well as driver components. FIG. 6 is a front elevational view of an LGP, generally indicated at 300, according to another embodiment of the invention. Like the other embodiments, LGP 300 has a frame 302, a light-emitting area 304, and a power cord or connection 306 that protrudes from the frame 302.

[0065] LGP 300 has driver and control components embedded within the frame 302. Those components may be arranged essentially as shown in FIG. 2 with respect to LGP 10, or they may be arranged differently. Externally, one difference between LGP 300 and LGP 10 is that LGP 300 includes a sensor window 308 in a portion of the frame. In the embodiment of FIG. 6, the sensor window 308 is positioned along the front of one of the members, but in other embodiments, the sensor window 308 may be on the side of the frame, less visible from the front. As will be described below in more detail, the sensor window 308 allows a motion sensor, occupancy sensor, or other such element to observe the area around the LGP 300 to determine when that area is unoccupied. Thus, the sensor window 308 is preferably transparent to whatever type of radiation is used by the underlying sensor.

[0066] FIG. 7 is a schematic diagram of a circuit that uses a motion or occupancy sensor to control LGP 300. A set of high-voltage inputs 310 enter the frame 302 and are connected to a set of driver components 312 concealed within the frame 302. The driver components 312 may be arranged as shown in FIG. 2, or they may have any other workable arrangement. A sensor 314 is electrically connected between the low-voltage output of the driver components 312 and the linear LED lighting 316 that emits into the light guide of LGP 300. The sensor 314 physically lies beneath the sensor window 308 in the frame 302, and acts as a switch, powered by the driver components 312 and turning the linear LED lighting 316 on when it is activated. The sensor 314 may be, e.g., a photodiode sensitive to infrared light with appropriate onboard electronics. In some cases, the onboard electronics may, e.g., switch the LGP 300 off after the area has been unoccupied for some span of minutes or hours. [0067] FIG. 8 is a schematic diagram of a circuit that is a variation of the circuit shown in FIG. 7. In the circuit of FIG. 7, the controls are limited to turning the LGP 300 on or off. The circuit of FIG. 8 uses driver components 402, linear LED lighting 316, and a sensor 404 that lies beneath the sensor window 308 of the frame 302. However, instead of the sensor 404 directly acting as a switch, the sensor 404 and driver components 402 are connected to and controlled by a controller 406. The controller 406 takes the output signal from the sensor 404 and controls the driver components 402 to supply power to the linear LED lighting 316. This arrangement is much more flexible in its applications. For example, in response to signals from the sensor 404 that the area around the LGP has been unoccupied for some period of time, the controller 406 could lower the voltage output to the LGP, thereby dimming it to some preselected level, e.g., 75%, 50%, 25% etc. The controller 406 could also elect to turn the LGP off entirely. While this could be done by directing the driver components 402 to zero the voltage output to the linear LED lighting 316, in some cases, a switch may be installed between the driver components 402 and the linear LED lighting 316. That switch would be controlled by the controller 406.

[0068] The controller 406 could also be a programmable color controller that changes the color of light emitted by RGB light engines, either in response to output from the sensor 404 or according to a program. For example, the controller 406 could use the DMX512 protocol for controlling lighting.

[0069] The controller 406 may be a microprocessor, an application-specific integrated circuit, a field-programmable gate array (FPGA), or any other suitable type of device. The controller 406 may also be an embedded system that includes a variety of integrated components. For example, in the illustration of FIG. 8, the controller 406 includes a network interface 408 that allows the controller 406 to be connected wirelessly to an external system for programming and control purposes. The network interface 408 may be, e.g., a WiFi interface, a Bluetooth interface, or a near-field communication (NFC) interface. The network interface 408 may be used to set parameters for the LGP, e.g., the amount of time before the controller 406 takes action to change the light output of the LGP after receiving a signal from the sensor 404 indicating that the area around the LGP is unoccupied, whether the controller 406 changes the light output of the LGP or turns it off when the sensor 404 indicates that the area around the LGP is unoccupied, and if the LGP is to be dimmed, the pre-set dimming levels. The external system that interfaces with the controller 406 may coordinate the operation of a number of LGPs throughout a building.

[0070] As those of skill in the art will appreciate, embodiments of the invention allow the placement of drivers, controls, and other elements within an LGP. One advantage is that these types of components can be included in an LGP without changing the fundamental form factor of the LGP. Distributing components along the frame, beneath the light guide, or in other locations eliminates the need for an external driver or controller, or for a driver or controller that is fixed to the rear of the LGP. This may result in an LGP with a more uniform profile that is more convenient to install and use.

[0071] Although the description above focuses on high-voltage AC to low-voltage DC power conversion, there are situations in which DC/DC conversion could be used, and LGPs according to embodiments of the invention may include DC/DC conversion components. Thus, some portions of this description may refer generally to a driver that accepts power in a first form and converts or outputs the power in a second form that is suitable to power the LGP. The second form may differ from the first form in power type (AC or DC), voltage, frequency, phase, or any other characteristic. For example, the first form may be high-voltage AC and the second form may be low-voltage DC, or both the first and second forms may be DC, but the second form may have a different voltage than the first form.

[0072] As one example, DC/DC conversion could be useful when using Power over Ethernet (PoE), or other methods for transmitting power over data lines. PoE refers to a collection of standards for providing DC power over twisted-pair Ethernet cabling.

[0073] FIG. 9 is a rear elevational view of a light guide panel, generally indicated at 500, according to another embodiment of the invention. LGP 500 is network-connected and uses PoE. More specifically, LGP 500 has a frame 502 and a light-emitting area 504, the backing layer 506 of which is visible in the view of FIG. 9. As compared with LGP 10 of FIG. 1, LGP 500 has no power cord 16; instead, an RJ-45 Ethernet jack 508 is provided in an upper corner of the frame 502. The Ethernet jack 508 supplies both power and, if needed, data.

[0074] LGP 500 may have essentially the same form and features of the embodiments described above. For example, the frame 502 may be either fixed or a snap frame, and may include onboard controllers, sensors, and other such components. As with other embodiments, the LGP 500 may have any shape, although the LGP 500 of FIG. 9 is rectangular.

[0075] FIG. 10 is a schematic diagram of the circuitry within LGP 500. From the RJ-45 connector 508, a set of DC power lines 510 connects to a DC/DC converter 512. As those of skill in the art will understand, there may be additional Ethernet interface hardware between the connector 508 and the other components, but this is omitted from the view of FIG. 10 for the sake of simplicity.

[0076] The DC/DC converter 512 may be of any type that can make the necessary power conversion. In the more recent PoE standards, the DC power may be at a voltage of, e.g., 41-57V, with a current of up to 960 mA. By contrast, the linear lighting 514 that provides light for LGP 500 may be configured to operate, e.g., at 12V or 24V. The circuit components of the DC/DC converter 512 would be distributed within the frame 502 of LGP 500, as shown and described above with respect to AC/DC conversion.

[0077] As shown in FIG. 10, in cases where the LGP 500 includes sensors and control components, signal lines 516 run from the connector 508 or Ethernet interface to an onboard controller or other onboard electronics. In LGP 500, an onboard controller 518 receives the control signals from the signal lines 516 and controls the DC/DC converter 512 and linear lighting 514 accordingly. If a photosensor 520 is installed, the controller 518 may take input from the sensor 520 as well. While the primary network interface of LGP 500 may be the Ethernet interface, the controller 518 also has a wireless network interface 522 that may connect via Bluetooth, WiFi, or other protocols.

[0078] Thus, LGP 500 is powered through an Ethernet cable and may also accept data signals over that same interface in order to control it in coordination with other lighting within a building or area. A secondary wireless interface 522 may allow localized inspection or control of the state of LGP 500. The controller 518 may be programmed with an order of precedence in order to resolve any conflicts between control signals that arrive via the Ethernet interface and control signals that arrive via the wireless interface 522.

[0079] While the invention has been described with respect to certain embodiments, the description is intended to be exemplary, rather than limiting. Modifications and changes may be made within the scope of the invention, which is defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A light guide panel, comprising:

a light guide having a refractive index higher than that of air;

a reflective backing layer attached to a reverse side of light guide;

LED light engines positioned along at least one edge of the light guide, the LED light engines being arranged to emit light into the at least one edge of the light guide;

a frame surrounding at least edges of the light guide, the reflective backing layer, and the LED light engines, the frame having disposed in it a driver, the driver being adapted to accept power in a first form and to provide power in a second form suitable for driving the LED light engines, the first form different than the second form;

wherein the LED light engines are electrically connected to the power output of the driver.

2. The light guide panel of claim 1, wherein the first form comprises alternating current (AC) power and the second form comprises direct current (DC) power.

3. The light guide panel of claim 2, wherein the driver comprises a switched-mode power supply.

4. The light guide panel of claim 2, wherein the driver comprises a rectifier.

5. The light guide panel of claim 1, wherein the first form comprises direct current (DC) power at a first voltage and the second form comprises DC power at a second voltage different from the first voltage.

6. The light guide panel of claim 5, wherein the DC power at the first voltage is supplied over data lines.

7. The light guide panel of claim 1, wherein the frame comprises:

an internal divider dividing an interior of the frame into first and second compartments, the first compartment being open to the at least one edge of the light guide, the LED light engines provided in the first compartment and the driver provided in the second compartment.

8. The light guide panel of claim 7, wherein the LED light engines comprise LED linear lighting.

9. The light guide panel of claim 7, wherein the divider faces the at least one edge of the light guide and a printed circuit board (PCB) of the LED linear lighting is disposed on the LED linear lighting.

10. The light guide panel of claim 1, wherein the frame comprises:

a base having a first groove;

a cover hingedly connected to the base for movement between open and closed positions, the cover having a second groove; and

a resilient member having a first end disposed in the first groove and a second end disposed in the second groove.

11. The light guide panel of claim 10, wherein the base is attached to the light guide.

12. The light guide panel of claim 11, wherein:

the base includes one or more walls, the one or more walls isolating the driver components and the LED light engines such that the driver and the LED light engines are not exposed when the cover is in the open position.

13. The light guide panel of claim 10, wherein:

the base includes one or more walls defining first and second compartments within the base, the first compartment open to the at least one edge of the light guide and having the LED light engines disposed therein, and the second compartment having the driver disposed therein.

14. A light guide panel, comprising:

a light guide having a refractive index higher than that of air; LED light engines positioned along at least one edge of the light guide, the LED light engines being arranged to emit light into the at least one edge of the light guide;

a driver layer disposed beneath the light guide, the driver layer including

a printed circuit board (PCB), and

driver components disposed on and electrically connected to the PCB that are adapted to accept power in a first form and to provide power in a second form suitable for driving the LED light engines, the first form different than the second form; and a frame surrounding at least edges of the light guide, the LED light engines, and the driver layer.

15. The light guide panel of claim 14, wherein the first form comprises alternating current (AC) power and the second form comprises direct current (DC) power.

16. The light guide panel of claim 15, wherein the driver components comprise a switched-mode power supply.

17. The light guide panel of claim 15, wherein the driver components comprise a rectifier.

18. The light guide panel of claim 14, wherein the first form comprises direct current (DC) power at a first voltage and the second form comprises DC power at a second voltage different from the first voltage.

19. The light guide panel of claim 18, wherein the DC power at the first voltage is supplied over data lines.

20. The light guide panel of claim 14, wherein the PCB and driver components are encapsulated with a resin such that the driver layer has an even, generally flat upper surface that abuts a lower surface of the light guide.

21. The light guide panel of claim 20, wherein the resin has reflective properties and serves as a reflective layer.

22. A light guide panel, comprising:

a light guide having a refractive index higher than that of air;

a reflective backing layer attached to a reverse side of light guide;

a frame surrounding at least edges of the light guide, the reflective backing layer, and the LED light engines, the frame including a driver and a sensor, the driver supplying power to the LED light engines, and the sensor operationally coupled to the LED light engines.

23. The light guide panel of claim 22, wherein the sensor is a motion sensor or an occupancy sensor.

24. The light guide panel of claim 22, further comprising a controller within the frame, the controller being coupled to the driver components and to the motion sensor or the occupancy sensor to control the LED light engines.

25. The light guide panel of claim 24, wherein the LED light engines are RGB LED light engines and the controller is a color controller.

26. The light guide panel of claim 22, further comprising a network interface within the frame.