FIELD OF THE INVENTION

The present invention relates to an electronic device, and more particularly to a light-emitting unit and a light-emitting method thereof.

BACKGROUND OF THE INVENTION

Nowadays, halogen lamps are widely applied in daily life, such as light-emitting units serving as motor vehicle lighting, searchlights and emergency lamps. In general, a light-emitting unit for use of motor vehicle illumination and the like includes two light-emitting electrodes. When driving at night, the driver of a motor vehicle can choose one of the light-emitting electrodes to work according to needs, so that he can use high beam lighting and low beam lighting in an alternate way, thereby obtaining a clear watch of roads and guaranteeing a safe drive.

Fig. 1 is a schematic view of a conventional light-emitting unit. As shown in Fig.l, the light-emitting unit includes a horn optical reflector 100, a first light-emitting electrode 200 and a second light-emitting electrode 300. The first light-emitting electrode 200 is disposed in the optical reflector 100, near to the small dimension end of the optical reflector 100. The second light-emitting electrode 300 is disposed in the optical reflector 100, further away from the small dimension end of the optical reflector 100 than the light-emitting electrode 200. The first light-emitting electrode 200 and the second light-emitting electrode 300 are connected with a power supply and a light-emitting electrode selecting device (not shown), respectively.

Figs. 2 and 3 are schematic views of a beam emitted from a light-emitting unit as shown in Fig. 1 when the light-emitting electrode 200 and the light-emitting electrode 300 are selected to work, respectively. In Fig. 2, after a light from the light-emitting electrode 200 is reflected by the inner wall of the optical reflector 100, the outer ray of the light beam forms an angle α with the vertical axis of the optical reflector 100. In Fig. 3, after a light from the light-emitting electrode 300 is reflected by the inner wall of the

optical reflector 100, the outer ray of the light beam forms an angle β with the vertical axis of the optical reflector 100. Since the light-emitting electrode 200 is much closer to the small dimension end of the optical reflector 100 as compared with the light-emitting electrode 300, α is smaller than β.

With the light-emitting electrode selecting device of the light-emitting unit, the driver can choose to turn on one of the light-emitting electrodes to emit light and keep the other from working according to needs. In such a case, the light-emitting unit only emits two kinds of light beams each having a fixed opening angle, namely the first kind of light beams (having an opening angle of 2α) when the first light-emitting electrode 200 is working, and the second kind of light beams (having an opening angle of 2β) when the second light-emitting electrode 300 is working. Except the above two kinds of light beams, the light-emitting unit cannot provide other opening-angle light beams, and consequently, it cannot meet the needs of other opening-angle light beams.

Therefore, there is a need to provide a light-emitting unit capable of providing beams with various opening angles, but not limited to fixed opening angles, so as to satisfy the needs of light beams with various opening angles.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light-emitting unit and a light emitting method so as to overcome the above-mentioned defects in the prior art, which light-emitting unit provides light beams with different opening results according to needs.

According to an embodiment of the present invention, there is provided a light-emitting unit comprising: at least two light-emitting means for emitting light alternately; reflecting means for reflecting at least part of said light to form a light beam and emit it; and controlling means for controlling the time when said two light-emitting means work alternately, so that said light beam can achieve an expected opening result.

According to another aspect of the present invention, the controlling means turns on the at least two light-emitting means periodically.

According to a further aspect of the present invention, a frequency that the controlling means alternately turns on said at least light-emitting means is relatively high, e.g. higher than 100 Hz.

According to an even further aspect of the present invention, there is provided a light emitting method including the steps of: emitting light alternately using at least two light sources; forming and emitting a light beam by reflecting at least part of light from said light sources; and controlling the time when said at least two light sources emit light alternately so that said light beam achieves an expected opening result.

Since the controlling means is capable of alternately turning on the at least two light-emitting means according to needs and controlling, periodically and in a relatively high frequency, the at least two light-emitting means to be turned on alternately, the opening angle of a light beam from the light-emitting unit varies between a maximum value and a minimum value continuously, rather than being set on some value or values.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of a conventional light-emitting unit;

Fig. 2 is a schematic view of a light beam from a light-emitting unit shown in Fig. 1 when a first light-emitting electrode is turned on;

Fig. 3 is a schematic view of a beam from a light-emitting unit shown in Fig. 1 when a second light-emitting electrode is turned on;

Fig. 4 is a schematic view of circuit connection of a light-emitting unit according to an embodiment of the present invention;

Fig. 5a is a schematic view of a light-emitting unit according to an embodiment of the present invention, when the turn-on time ratio of a first light-emitting electrode to a second light-emitting electrode is 0.5 : 0.5;

Fig. 5b is a light beam from a light-emitting unit in a case shown in Fig. 5a;

Fig. 6a is a schematic view of a light-emitting unit according to an embodiment of the present invention, when the turn-on time ratio of a first light-emitting electrode to a second light-emitting electrode is 0.25 : 0.75;

Fig. 6b is a light beam from a light-emitting unit in a case shown in Fig. 6a;

Fig. 7a is a schematic view of a light-emitting unit according to an embodiment of the present invention, when the turn-on time ratio of a first light-emitting electrode to a second light-emitting electrode is 0.75 : 0.25;

Fig. 7b is a light beam from a light-emitting unit in a case shown in Fig. 7a; and

Fig. 8 is a flow chart illustrating a light emitting method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the drawings. In all the accompanying drawings used for describing the following embodiments, portions having the same function will be marked as the same numeral, and description thereof will be omitted.

Fig.4 is a schematic view of circuit connection of a light-emitting unit 400 according to an embodiment of the present invention. An optical reflector is not shown in Fig. 4. As shown in Fig. 4, the light-emitting unit 400 comprises a first light-emitting electrode 200 and a second light-emitting electrode 300. The first light-emitting electrode 200 is connected in series with a first switch Sl to form a first branch, and the second light-emitting electrode 300 forms a second branch with a second switch S2. The first branch and the second branch are connected in parallel and connected with an AC power supply via a power-supply circuit 500.

The light-emitting unit 400 further comprises controlling means 600 for controlling on and off of the first switch Sl and the second switch S2. In the present embodiment, the controlling means 600 is a duty cycle controller. After circuit of the light-emitting unit 400 is switched on, the controlling means 600 can control switches Sl

and S2 to be turned on alternately in a switch on-off period so that the light-emitting electrodes 200 and 300 work alternately. For instance, the light-emitting electrode 200 works for 30% time of the period, while the light-emitting electrode 300 works for the remainder 70% time of the period.

Connected with the light-emitting unit 400 is the power-supply circuit 500. The circuit 500 comprises an AC/DC converter 510 and a half-bridge converter 520. The converter 510 may comprise a rectifier, e.g. a bridge type rectifier, and the Half-bridge converter 520 is formed by IC-driven half-bridge circuits or self-oscillation type half-bridge circuits.

An AC voltage of the AC power supply is converted into a DC voltage by the AC/DC converter 510 and then applied to the first branch and the second branch by the half-bridge converter 520 as supply voltage of the first light-emitting electrode 200 and the second light-emitting electrode 300. An output voltage of the half-bridge converter 520 is a high-frequency voltage.

The controlling means 600 is used for controlling the on/off lasting time of the first switch Sl and the second switch S2. Under the control of the controlling means 600, the second switch S2 is off when the first switch Sl is on, and is on when the first switch

51 is off.

According to the embodiment of the present invention, the controlling means 600 controls on and off of the first switch Sl and the second switch S2 in a duty cycle. A switching frequency of the duty cycle may be adjusted according to needs. Preferably, the frequency is a frequency range unperceivable to eyes, e.g. over 100 Hz, so that people cannot perceive illuminating/blanking of the first light-emitting electrode 200 and the second light-emitting electrode 300.

In addition, the controlling means 600 controls the on time ratio of the first switch Sl to the second switch S2 within a cycle.

Assuming that the ratio of the turn-on time of the first switch Sl in a cycle to the lasting time T of this cycle is Rl and the ratio of the turn-on time of the second switch

52 to the lasting time T of this cycle is R2, (Rl + R2) / T = 1.

Under the control of the controlling means 600, the angle γ between the outer ray of a light beam from the light-emitting unit and the vertical axis of the optical reflector 100 has such a relation with the coefficient Rl, the coefficient R2, the angle α and the angle β as follows: γ = α * Rl + β * R2

It can be seen that, a variation range of the angle γ is α < γ < β. By adjusting the coefficients Rl and R2 or the angle α or β, the angle γ can be adjusted easily. The coefficient Rl and the coefficient R2 can be adjusted by adjusting the turn-on time of the first switch Sl and the second switch S2 in a cycle, while the angle α or β can be achieved by adjusting the opening angle of the optical reflector 100 and/or the position of the first light-emitting electrode 200 and/or the second light-emitting electrode 300.

For example, when Rl = R2 =0.5, α = 10°, and β = 50°, γ = 10 ^o x0.5 + 50° x0.5 = 30°

In other words, where α = 10° and β = 50°, if the controlling means 600 controls the turn-on time of the fist switch Sl to be equal to that of the second switch S2, the angle of a light beam from the light-emitting unit is 30°.

Fig. 5a is a schematic view of a light-emitting unit according to an embodiment of the present invention, when the turn-on time ratio of a first light-emitting electrode to a second light-emitting electrode is 0.5 : 0.5 and Fig. 5b is a light beam from a light-emitting unit in a case shown in Fig. 5a.

In Fig. 5a, the hatched portion above the upper axis means that the first light-emitting electrode 200 emits light, and the non-hatched portion means that the first light-emitting electrode 200 does not emit light. The hatched portion above the lower axis means that the second light-emitting electrode 300 emits light, and the non-hatched portion means that the second light-emitting electrode 300 does not emit light. It can be seen that, the first light-emitting electrode 200 emits light in a time period between tl to t2, while the second light-emitting electrode 300 emits light in a time period between t2 to t3, .... Thus, the first light-emitting electrode 200 and the second light-emitting electrode 300 emit light alternately, and they emit light for the same time in a cycle.

In Fig. 5b, light beams represented by numerals 1 and 1 ' are formed by the first light-emitting electrode 200, light beams represented by numerals 2 and 2' are formed by the second light-emitting electrode 300, and light beams represented by numerals 3 and 3' are perceivable to people and emitted from the light-emitting unit.

Since the duty cycle can be set shorter, although the first light-emitting electrode 200 and the second light-emitting electrode 300 do not emit light synchronously, light beams perceivable to people from the light-emitting unit can be as shown by numerals 3 and 3' in Fig. 5b.

Fig. 6a is a schematic view of a light-emitting unit according to an embodiment of the present invention, when the turn-on time ratio of a first light-emitting electrode to a second light-emitting electrode is 0.25 : 0.75; and Fig. 6b is a light beam from a light-emitting unit in a case shown in Fig. 6a. Fig. 7a is a schematic view of a light-emitting unit according to an embodiment of the present invention, when the turn-on time ratio of a first light-emitting electrode to a second light-emitting electrode is 0.75 : 0.25; and Fig. 7b is a light beam from a light-emitting unit in a case shown in Fig. 7a.

The cases shown in Figs. 6a, 6b and Figs. 7a, 7b are similar to those shown in Figs. 5a, 5b. What is different is that, since the turn-on time ratio of the first light-emitting electrode 200 to the second light-emitting electrode 300 is different, the opening angle of a light beam perceivable to people from the light-emitting unit is different.

The object of the present invention may be achieved by reflection controlling means. The reflection controlling means can control an opening angle of an optical reflector so as to adjust an angle between the outer ray of an emitted light beam and the vertical axis of said light beam.

The object of the present invention may further be achieved by another kind of controlling means. The another kind of controlling means can control the position of a light-emitting electrode with respect to an optical reflector so as to adjust an angle between the outer ray of a light beam emitted from a light-emitting unit and the vertical axis of said light beam.

Fig. 8 is a flow chart illustrating a light emitting method according to an

embodiment of the present invention. First, light is emitted alternately using at least two light sources (step S810); then, a light beam is formed and emitted by reflecting at least part of light from said light sources (step S820); and lastly, the time when said at least two light sources emit light alternately is controlled so that said light beam achieves an expected opening result (step S830). The switching frequency of said at least two light sources is greater than a switching frequency visually perceivable. And said expected opening result is an angle between the outer ray of said light beam and the axis of said light beam.

A light-emitting electrode according to the present invention may be a halogen lamp or other light-emitting electrode capable of emitting light in a high frequency.

Light-emitting electrodes included in a light-emitting unit according to the present invention are not limited to two. Where three electrodes or more are included, identical or better results can be produced provided that controlling means alternately turns on each of the light-emitting electrodes in a certain duty cycle.

Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that the present invention is not limited to the disclosed embodiments. On the contrary, it is intended that the present invention covers various alternations and equivalent arrangements as falling within the spirit and scope of the appended claims. The scope of the amended claims conforms to a widest interpretation so as to include all the alternations and the equivalent structures and functions.