GB2460302A

GB2460302A - Light emitting diode light source with globular envelope

Info

Publication number: GB2460302A
Application number: GB0809885A
Authority: GB
Inventors: William Frank Stevens
Original assignee: BRIGHTERLIGHT LED Ltd
Current assignee: BRIGHTERLIGHT LED Ltd
Priority date: 2008-05-30
Filing date: 2008-05-30
Publication date: 2009-12-02
Also published as: GB0809885D0

Abstract

A light source has a generally globular envelope with part spherical end portion 17, a cylindrical central portion 13, and mount portion 14 supported on a cap for releasable attachment to a lamp-holder. The end portion 17 can be formed separately from the central and mount portions 13 and 14 and snap fitted thereto. The envelope has a plurality of apertures and a like plurality of individual light emitting diodes (LEDs) 18 are mounted one in each aperture, to direct light out of the envelope. A pair of interconnected control circuit boards 24, 25 is arranged within the envelope and electrically connected to the contacts 28 of the cap as well as to the LEDs 18 such that all the LEDs will be illuminated when current is supplied to a lamp-holder carrying the light source.

Description

LED LIGHT SOURCE

This invention relates to a light source having a plurality of light emitting diodes. For convenience, a light emitting diode is hereinafter referred to as a "LED".

For a number of reasons, not the least of which is the relative inefficiency of an incandescent lamp, there has been a tendency to replace conventional incandescent lighting by a'ternative forms of lighting, induding both gas discharge tubes and LEDs which are more energy efficient. A problem associated with LEDs is that the light emitted by a single LED is a relatively narrow beam and thus the light from an LED does not spread out within a space in the same way as does the light from either an incandescent lamp or a gas discharge tube. Though this problem can be al'eviated to some extent by careful design of the body supporting the diode itself, this has the effect of lowering the intensity of the light from the LED, as the light intensity of a LED is in general much less than that which can be obtained from an incandescent lamp. As such, LED light sources have not been widely used to provide the same kind of broad background lighting as can be obtained from an incandescent lamp or gas discharge tube.

More recently, ight bulbs incorporating a plurality of LEDs have been used to rep'ace halogen spot lights such as those known as GU1O lamps. Using high intensity LEDs and providing an array of those LEDs within an envelope the same shape and size as that of a conventional GUi 0 lamp provides a beam similar to that of a GU1O spotlight but of a lower intensity. The light from such a replacement LED source is not generalised to provide space lighting; it still is very much a spothght beam, but the Ufe and reUabity of a LED-based source is much greater than that of a halogen bulb.

There is a demand for more economic light sources than incandescent lamps, and an LED light source able to give generalised lighting may well be capable of fufiUing that demand. With that in mind, this invention provides a light source comprising a generally globular envelope supported on a cap adapted for releasable attachment to a lamp-holder so as to be supported thereby and to make electrical connections to conductors associated with the lamp-holder, the envelope having a plurality of apertures therethrough and there being a like plurality of individual LEDs mounted one in each aperture, the light source further comprising a control circuit arranged within the envelope and e'ectrically connected to the cap, the LEDs being electrica'ly connected to the control circuit such that the LEDs will be illuminated when current is supplied to a lamp-holder supporting the light source.

It will be appreciated that the light source of this invention has a globular envelope which supports the plurality of individual LED sources distributed around the envelope with an internal arrangement adapted to power all of the LEDs when the light source is mounted in a lamp holder and electrical power is supplied thereto. Even though the enve'ope has a plurality of individual light sources, when viewed from a distance the light source will appear to be somewhat similar to an incandescent lamp, in that light is distributed generally all around the light source rather than in the form of a spotUght beam such as is achieved with GUi 0 replacement LED lamps.

For convenience in manufacture, it is preferred for the envelope to have a substantially cylindrica' portion, a part spherical end portion closing one end of the central portion and a mount portion extending from the other end of the central portion, the cap being connected to the mount portion. Preferably, each of said portions supports a multiplicity of LEDs arranged therearound, to direct light away from the associated portion.

Conveniently, the central and mount portions are formed integraUy and the end portion is formed separately but is snap-fitted to the end of the central portion remote from the mount portion in order to complete the globular envelope. By having the end portion formed separate'y but fitted to the central portion during manufacture, access to the interior of the globular envelope can be had in order to al'ow fitting of the control circuit within the envelope and the inter-connection of the plurality of LEDs to that control circuit.

The number of LEDs supported by the globular envelope may depend upon the intended light intensity to be obtained from the light source and is limited merely by the physical parameters of both the envelope and each LED. A typical arrangement may have as many as 25 LEDs though good results can be obtained from lesser numbers and perhaps from 14 to 18 LEDs.

The control circuit is preferably formed on a printed circuit board which is fitted within the envelope and includes terminations for the LEDs. In order to facilitate manufacture and the soldering of the LEDs it is advantageous to provide two separate but electrically interconnected circuit boards mounted parallel to one another within the envelope, with terminations for some of the LEDs on one board and terminations for the remainder of the LEDs on the other board. For example, where each LED has a pair of wires ("tails') for the supply of current to the LED, it is convenient for each of those wires to be directly soldered to terminations provided on the printed circuit boards.

Depending upon the number of LEDs employed in the light source of this invention and also on the intended voRage of the electricity supply to the lamp-holder, all of the LEDs mounted within the envelope are connected in series and the control circuit includes a current-Umiting resistor in series with the LEDs. f relatively large numbers of LEDs are provided, it would be possible to arrange those LEDs in two or more groups with the LEDs of each group being arranged electrically in series but with the groups in parallel. In either case, for a light source intended to be powered from an AC mains supply, the control circuit may include a rectifying circuit in order to supply DC to the LEDs and further may io include a voltage-reducing network.

Depending upon the intended use, all of the LEDs may be of the same colour and typicaUy may emit white light. In the alternative, LEDs which emit coloured light may be employed and for novelty applications LEDs of different colours may be used. Further, the g'obular envelope may be clear so as better to emulate a conventional incandescent lamp, or the envelope may be opaque.

In the alternative, the envelope may be translucent and coloured, in order to give an aesthetically pleasing effect for certain applications.

The cap conveniently is configured to suit a conventional lamp ho'der.

Thus, the cap may be a standard bayonet (BC or B22) cap or a smal' bayonet (SBC or B15) cap or may be a conventiona' Edison screwed cap, of standard (E27), small (E14) or miniature (ElO) size.

By way of example only, one specific embodiment of light source of this invention will now be described in detai', reference being made to the accompanying drawings in which:-Figure 1 is a side view of the light source having a plurality of LEDs; Figure 2 s as cross-section through the light source showing the internal configuration thereof; Figures 3 and 4 are cross-sections through the light source taken along the lines 3-3 and 4-4 marked on Figure 2; and Figure 5 is a schematic circuit diagram of the control circuit within the light source of Figures 1 to 4.

Referring initially to Figures 1 and 2, there is shown an embodiment of mu'ti-LED light source of this invention, comprising a generally globular envelope supporting an E14 (SES) cap 11 for screwing into an E14 lamp holder of a conventional design. The envelope 10 has a first part 12 including a generally cylindrical portion 13 and a generally conical mount portion 14 having a boss 15 at its end remote from the central portion and by means of which the cap 11 is cemented to the first part 12. The open-end of the central portion 13 is closed by a second part 16 in the form of an end portion 17 of generally part spherical shape and which is snap-fitted to the first part by inter-engaging lips as shown in Figure 2.

Each of the envelope portions 13, 14 and 17 supports a plurality of individual LED5 18 spaced around the periphery of the enve'ope. Each LED has a cylindrical body 20 with a part-spherical end face 21, the opposed end of the cylindrical body being planar and including a mounting flange 22. The flange of each LED is received in a corresponding recess pre-formed in the enve'ope 10 with a pair of holes extending through the envelope at each recess so that the connecting tails 23 of each LED may pass into the interior of the envelope 10.

Though not shown in the drawings, the edge of the mounting flange 22 of each LED has a flat formed thereon adjacent the positive tail of the LED; each recess has a corresponding flat in order that when an LED s fitted into that recess, the LED has a known orientaUon with respect to the envelope so that the positive ta of the LED enters the envelope through a predefined hole.

Mounted at the lower end of the central portion 1 3 is a lower circular printed circuit board 24 (Figure 4) and mounted in the open-end of the end portion 17 of the envelope is an upper circular printed circuit board 25 (Figure 3), the two boards being electricay connected together by plug-in links 26. The lower circuit board 24 has a first connection to the screw-thread of the E14 cap 11 by wire 27 and a second connection to the central conductor 28 of the El 4 io cap through a resistor 29 and a parael-connected capacitor (not shown). The resistor and capacitor are located within a chamber 30 formed within the E14 cap and held in place by the cement 31 bonding the cap to boss 15 of the mount portion 14.

The lower circuit board 24 also supports a bridge rectifier 32 and has a plurality of terminations 33 for the LED5 mounted in the central portion 13 and mount portion 14 of the envelope 10. The upper circuit board 25 carries a resistor 34 and also has a plurality of terminations 35 for the LED5 mounted in the end portion 17 of the envelope. When fully assembled as shown in Figure 2, all of the LEDs are connected in series and also in series with resistor 34, across the output of the bridge rectifier 32. The rectifier 32 is supplied with AC current from the cap 11 but through the resistor 29 and capacitor in parallel. A schematic circuit diagram is shown in Figure 5.

In use, the cap 11 is threaded into a conventional E14 lamp holder and when AC current of a suitable voltage is supplied to that holder, all of the LEDs will simultaneously be illuminated such that the light source radiates light generaUy around the source. f aU of the LEDs are of the same colour, and preferab'y white, the ght source wifi emu'ate an incandescent tamp but the indMdual LEDs cou'd be of different colours in order to provide an aesthetically appealing light source.

The envelope 10 could be opaque or could be translucent; in the latter case, it could be clear or coloured if an interesting and attractive appearance is required, since some of the light from the LEDs will radiate out of the envelope so making the whole of the envelope appear to glow.

Claims

CLAIMS1. A ght source comprising a generay globular envelope supported on a cap adapted for releasable attachment to a lamp-holder so as to be supported thereby and to make electrical connections to conductors associated with the lamp-holder, the envelope having a plurality of apertures therethrough and there being a like plurality of individual LEDs mounted one in each aperture, the light source further comprising a control circuit arranged within the env&ope and electrically connected to the cap, the LEDs being electrically connected to the control circuit such that the LEDs will be illuminated when current is supplied to a lamp-holder supporting the light source.
2. A light source as claimed in any of the preceding daims, wherein the LEDs are distributed around the surface of the envelope thereby to direct light generally away from that envelope.
3. A ight source as claimed in claim 2, wherein the envelope has a substantially cylindrica' central portion, a part-spherical end portion closing one end of the central portion and a mount portion extending from the other end of the central portion to the cap, each said portion supporting a multiplicity of LEDs to direct light away therefrom.5. A ight source as claimed in 3, wherein the end portion is formed separately from the central and mount portions and is snap-fitted thereto during manufacture of the ight source.6. A light source as claimed in any of the preceding calms, wherein the envelope supports from 8 to 25 LEDs and preferably from 14 to 18 LEDs.7. A light source as claimed in any of the preceding cairns, wherein the control circuit is provided on a printed circuit board which includes terminations for the LEDs, whereby current is supped to the indkiidual LEDS from the cap when connected to an energised lap-holder.8. A ght source as claimed in claim 7, wherein the printed circuit board is mounted within the envelope and each LED has a pair of lead wires which are directly soldered to the terminations of the printed circuit board.9. A light source as claimed in any of claims 1 to 6, wherein the control circuit is provided on a pair of interconnected printed circuit boards mounted in a substantially parallel disposition within the envelope and having terminations for the LEDs, whereby current is supplied from the cap to the individual LEDS when the light source is carried by an energised lap-holder.10. A light source as claimed in any of the preceding claims, wherein the LEDs are connected in series and the control circuit includes a current limiting resistor in series with the LEDs.11. A light source as claimed in claim 1 0, wherein the control circuit includes a rectifier for supplying direct current to the LEDs from an alternating current supply fed to a lamp-holder supporting the light source.12. A light source as claimed in claim 11, wherein the rectifier comprises a full-wave bridge rectifier.13. A light source as claimed in claim 11 or claim 12, wherein the rectifier is supplied with alternating current through a voltage limiting network.14. A light source as claimed in claim 13, wherein said network comprises a parallel-connected capacitor and resistor.15. A light source as claimed in any of the preceding claims, wherein the cap is complementarily-formed to a conventional Edison-screwed or bayonet lamp-holder for supporting thereby and electrically connecting thereto.16. A light source as claimed in claim 1 and substantially as hereinbefore described with reference to and as Illustrated In the accompanying drawings.