LED LUMINOUS SOURCE SIMULATING A FLAME LIGHT

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This invention concerns a LED luminous source simulating the light of a flame. There are LED luminous sources substituting flame lighting sources and in particular candles. Besides being a substitute for a candle, some of these luminous sources are also trying to simulate its presence, but the simulation of the flame so far has been approximate.

One of these imitations, described for instance in the document US2003035291 , provides for a body of a translucid material with a transparency resembling that of paraffin and a cavity holding a LED. The intensity of the light emitted by the LED is varying according to a pseudo-casual variability criterion, for the purpose of simulating the glow of a flame. However, an observer cannot be deceived by such a simulation, owing to both the excessively abrupt changes of the emitted light and the static orientation of the same.

Other imitations provide for the presence of several LEDs supplied according to a pseudo-casual rule. Even in this case, however, the imitation of the flame turns out to be approximate, because of both the un- natural and exceedingly abrupt variations of the emitted light and the directional changes of the false flame, as well as because the power supplies to the individual LEDS are not correlated with each other.

The present invention aims at overcoming the limitations and imperfections of the known art, by realizing a LED luminous source capa- ble of reproducing a flame-like luminous source more faithfully, so as to be confused with the same.

For this purpose, the luminous source according to the invention is characterized by the fact that:

- on two coplanar axes essentially perpendicular to each other, there are at least two LEDs for each axis, in a position opposite the crossing point of the two axes;

- the total LED piloting current l _τ is equally shared between the two axes, and on each axis, the total LED piloting current of one half axis is shared, with respect to the total LED piloting current of the other half axis, according to a sharing percentage variable in a pseudo-casual manner, where such variability is characterized by variation steps of a value not exceeding 1/10 of said total LED piloting current I ₁ -.

The characteristics of the invention will be better evident from the description to follow, which refers to examples of embodiments of a non-iimiting character, made with reference to the attached drawings, wherein the various figures schematically show:

Figures 1A and 1 B: a partial top view and, respectively, a side view of an embodiment of a LED luminous source according to the invention in its simplest version with 4 LEDS, with an image of the flame as it appears when the LED piloting current is distributed among the LEDs at an equal percentage;

Figures 2A and 2B: the same views of Fig. 1A and 1 B, with a different conformation of the flame, due to a different distribution of the LED piloting current;

Figures 3A, 3B, 4A and 4B: variants of the previous figures, concerning the addition of a central LED;

Figure 5: a block diagram of an electrical supply circuit of the LEDs of the previous figures; Figures 6A-6D, 7A-7D, 8A-8C: partial top views of other possible variants of previous embodiment examples. The Figures 1A and 1 B represent a partial top view and a side view, respectively, of an embodiment example of a LED luminous source according to the invention, in its simplest version with 4 LEDs.

As can be seen, the luminous source provides for the presence of four LEDs that can be considered positioned on two coplanar axes essentially perpendicular to each other (east-west axis and north- south axes of Fig. 1A), with two LEDs for each axis set up in an opposite

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position with respect to the intersection of the two axes.

The total LED piloting current l _τ is equally shared among the two axes, and on each axis the LED piloting current of one side of the axis is shared, with respect to the LED piloting current of the other side, ac- cording to a sharing percentage that is variable in time in a pseudo-casual manner, with variation steps not exceeding 1/10 of said total current l _τ , so as to prevent the discontinuity of the tip shifts of the flame (in its various positions) from becoming evident to the observer. In fact this LED piloting criterion simulates a casual and continuous shifting of the tip of the flame, which resembles the tip shifts of a real flame. According to a preferred solution, the value of said variation steps is chosen at a value not exceeding 1/300 of the total current I ₁ ,

In the figures the various parts represent: 1. a LED of a preferably amber color (emission at ab. 590 nm). 5. a typical opalescent cylindrical diffuser for an electrical candle,

6. a cylindrical LED support, simulating the image of a candle;

7. an image of the false flame;

8. the tip of the flame.

In particular, Figure 1B represents the case of a pilot current distributed among the LEDs at an equal percentage (the LED piloting current of the LEDs of the same axis being shared between the two LEDs by 50%). In this case the image of the flame turns out to be essentially symmetrical with respect to the continuous vertical line passing through the crossing point of the two axes, the tip "8" of the flame being set up on said vertical line.

The Figures 2A and 2B are again relating to the LED candle shown in the previous figures, and differ from the latter by a different conformation of the flame due to a different distribution of the LED piloting current. In particular, they refer to a case wherein the LED piloting current of a same axis is absent on one LED, but is 100% present on the other LED. In this case the image 7 of the flame appears inclined, with the tip of

the flame essentially at the same distance from the vertical planes passing through the two axes.

According to another preferred solution, even the total LED piloting current l _τ is made variable in a pseudo-casual manner for the pur- pose of simulating casual variations of the flame luminosity, for instance due to some combustion irregularities of the candle.

According to a further preferred solutions, even the frequency value at which said variation steps of the LED piloting current are following each other is made vary in a pseudo-casual manner, so as to simulate shifting speeds of the flame tip that are variable in a casual manner, such as those due to the action of air currents on the candle.

The Figures 3A, 3B, 4A and 4B represent a variant of the previous figures, concerning the addition of a central LED 9, preferably of a reddish orange/red color (emission at about 615 nm), allocated on the confluence of the two axes, for the purpose of simulating the presence of a luminous lower core 10 inside the flame, such as that present in true candle flames next to the wick.

According to a preferred solution, said central LED is piloted by a current fit to produce a lighting emission lower than the 20% of the over- all lighting emission of the lateral LEDS and variable in a pseudo-casual manner.

Figure 5 represents a block diagram of an electrical supply circuit of the LEDs shown in the previous figures (the blocks drawn in dotted lines concern the example of the Figures 3A and 3B, 4A and 4B). The meaning of the various blocks is as follows: 11 : a battery 12: a DC/DC converter

13: a micro-controller with a supporting circuitry and firmware implementing the laws of a pseudo-casual variability of the LED piloting current; 14: regulating stages of the LED piloting current;

15: one (or more) LEDs of the eastern side of the horizontal axis;

16: one (or more) LEDs of the western side of the horizontal axis; 17: one (or more) LEDs of the northern side of the vertical axis; 18: one (or more) LEDs of the southern side of the vertical axis; 19: a central LED as shown in the Figures 3A and 3B, 4A and 4B. The blocks 20 and 21 refer to two preferred solutions for regulating and piloting the LED supply circuit.

The block 20 is in fact representing one or more keys capable of setting up the controlling algorithm for the pseudo-casual supply of the LEDs, and in particular for the value of the resulting lighting intensity. The block 21 represents on the contrary a sensor of the environmental luminosity that regulates the value of the lighting intensity resulting, in relation to the value of the environmental luminosity.

It is evident that the examples of embodiment formerly described may undergo numerous modifications, adaptations, variants and substitutions of elements with others of a functionally equivalent type, without thereby abandoning the core of the invention and the range of protection of the claims to follow.

In this regard, it should be noted that a variant may regard the shape and coloring of the LEDs. Whilst the Figure 6A in fact repeats the LED conformations of the Figures 3A and 3B (four lateral LEDs of an elliptical cross-section and a central LED of a circular cross-section), the Figure 6B shows 5 LEDs of a circular cross-section, and the Figure 6C shows 5 LEDs, one central with a circular cross-section and four lateral two- colored LEDs "2" with an amber or reddish-orange/red emission. Another variant may regard the number of LEDs present on each side of the two axes, number not necessarily limited to one single LED per side. The Figures 7A, 7B, 7C and 7D in fact show possible arrangements with one central LED and 8 lateral LEDs, 4 for each axis. In particular, the lateral LEDs of Figure 7B may be two-colored, of an amber or reddish-orange/red color, while the LEDs "3" in Figure 7C may be of an amber color, and the LEDs "4" may be of a reddish-orange/red color.

A further variant may concern the number of axes, as more than one pair of orthogonal axes may be present. The Figures 8A, 8B and 8C in fact illustrate examples of arrangements with two pairs of orthogonal axes at a 45° distance from each other.

Another variant could concern the arrangement of the LEDs with an elliptical cross-section, which may, as shown in the examples of the Figures 8C ₁ 6D, 7C ₁ 7D, 8A, 8B and 8C ₁ have their major axes converging toward each other.