Light fixture with at least one LED

Abstract

A light fixture having at least one LED and at least one filament, wherein the at least one filament is connected in series to the at least one LED. A current supplied to the at least one LED in the light fixture is regulated by the electrical properties of the at least one filament. Thus the at least one LED in the light fixture can be run without an electrical driver.

Claims

1. A light fixture comprising: at east one LED; and at least one filament wherein the at least one filament is connected in series to the at least one LED.

2. The light fixture of claim 1, wherein the light fixture comprises a glass bulb and the at least one filament is arranged within the glass bulb, wherein the glass bulb is filled with a protective.

3. The light fixture of claim 1, wherein the light fixture comprises a glass bulb and the at least one filament is arranged within the glass bulb, wherein the glass bulb is filled with a gas comprising at least one halogen.

4. The light fixture of claim 1, wherein the light fixture has a first connector and a second connector for coupling to a supply voltage.

5. The light fixture of claim 4, wherein the light fixture comprises at least one first LED and a second LED which are connected to one another in an antiparallel arrangement.

6. The light fixture of claim 4, wherein the light fixture comprises a rectifier which is coupled to the first connector and the second connector.

7. The light fixture of claim 1, wherein the light fixture comprises at least one first LED and one second LED which are connected to one another in parallel.

8. The light fixture of claim 1, wherein the light fixture comprises at least one first LED and one second LED which are connected to one another in series.

9. The light fixture of claim 7, wherein the at least one first LED and the one second LED have a different forward voltage.

10. The light fixture of claim 1, wherein between 15% and 30% of a voltage drop across the at least one LED and the at least one filament occurs on the at least one LED.

11. The light fixture of claim 1, wherein between 20% and 25% of a voltage drop across the at least one LED and the at least on filament occurs on the at least one LED.

12. The light fixture of claim 1, wherein the light fixture comprises a glass bulb, and a thermal shield, wherein the at least one LED and the at least one filament are arranged in the glass bulb, wherein the thermal shield is arranged between the at least one LED and the at least one filament.

13. The light fixture of claim 1, wherein the at least one LED and the at least one filament generate an optical performance, wherein between 70% and 90% of the optical performance is generated by the at least one LED.

14. The light fixture of claim 1, wherein the at least one LED and the at least one filament generate an optical performance, wherein between 75% and 85% of the optical performance is generated by the at least one LED.

15. The light fixture of claim 1, wherein the at least one LED and the at least one filament generate an optical performance, wherein 80% of the optical performance is generated by the at least one LED.

16. The light fixture of claim 3, wherein the gas is comprised of bromine.

17. The light fixture of claim 4, wherein the supply voltage has an alternating current.

18. The light fixture of claim 1, wherein the light fixture comprises a glass bulb and the at least one filament is arranged within the glass bulb, wherein the glass bulb is filled with a protective gas which comprises a mixture of 93% argon and 7% nitrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Exemplary embodiments of the present invention are described in greater detail below with reference to the appended drawings. In the drawings:

[0023] FIG. 1 shows a schematic representation of a wiring diagram for a first exemplary embodiment of a light fixture according to the invention;

[0024] FIG. 2 shows a schematic representation of a wiring diagram for a second exemplary embodiment of a light fixture according to the invention;

[0025] FIG. 3 shows a schematic representation of an exemplary embodiment of a light fixture according to the invention;

[0026] FIG. 4 shows a schematic representation of a further exemplary embodiment of a light fixture according to the invention; and

[0027] FIG. 5 shows the optical performance P.sub.opt as a function of the voltage U.sub.LED occurring across the LEDs at a supply voltage of U.sub.V=220 V.

DETAILED DESCRIPTION

[0028] The same references are used below for elements which are the same and equivalent.

[0029] FIG. 1 shows a schematic representation of a wiring diagram for a first exemplary embodiment of a light fixture according to the invention. An alternating current voltage source U.sub.V, which can for example provide an alternating current voltage with an amplitude of 220 V, serves as voltage supply. The series connection of a filament GF and two LEDs (LED1, LED2) are connected in an antiparallel arrangement and are coupled between connectors of the alternating current voltage source U.sub.V. The region 10 shown by a broken line indicates which components can preferably be arranged on a printed circuit board.

[0030] As can be seen, the filament GF is not arranged on the printed circuit board 10. The outline 12 shown by a broken line should indicate that the filament GF can be operated in the same atmosphere as the LEDs, for example in a protective gas known from conventional incandescent lamps, which preferably comprises a mixture of 93% argon and 7% nitrogen, but no halogen. Alternatively, the filament GF can be operated in a different atmosphere as the LEDs (LED1, LED2) in order to produce a halogen bulb by means of the filament GF. In this case the filament GF is operated in a separate glass bulb which is filled with a gas which comprises at least one halogen, in particular bromine.

[0031] The exemplary embodiment illustrated in FIG. 1 has the advantage that through the illustrated antiparallel connection of the two LEDs (LED1, LED2), both partial waves of the alternating current supply voltage U.sub.V can be used for generating LED light. As is obvious for a person skilled in the art, further LEDs could be connected in parallel to the two LEDs (LED1, LED2) preferably in two antiparallel packages, in order to minimize fluctuations in brightness. Furthermore, one or more LEDs can be connected in series to each LED (LED1, LED2), in each case also in two antiparallel packages in order to prevent fluctuations in brightness. One LED (LED1 or LED2) can consist, for example, of several semiconductor chips, for example 3 V (InGaN), and several high voltage chips, for example 48 V, which are connected in series or in parallel. Thus, the operation of the LEDs can be adapted in a suitable manner to the alternating current supply voltage U.sub.V.

[0032] In the exemplary embodiment of a light fixture according to the invention which is illustrated in FIG. 2, a bridge rectifier 14 is connected between the two connectors of the alternating current supply voltage U.sub.V, which comprises four diodes, D1, D2, D3, D4, in a known manner. The series connection of a filament GF and two LEDs (LED1, LED2) is connected between the outputs of the bridge rectifier 14. Two LEDs (LED1, LED2) as well as the bridge rectifier 14 are arranged on a circuit board 10. Instead of the series connection of the two LEDs (LED1, LED2) illustrated in FIG. 2, several LEDs can also be connected in parallel, wherein in turn each LED connected in parallel can be replaced by a series connection of several LEDs. In this waythis also applies for FIG. 1an optimal co-ordination between the alternating current supply voltage U.sub.V, the filament GF, and the LEDs can be achieved in order to set a brightness of the light emitted by a light fixture according to the invention or the color point as required. Thus, furthermore, an optimal distribution of the alternating current supply voltage U.sub.V between the LEDs and the filament GF can be set.

[0033] The resistance of the filament GF defines the current also flowing through the at least one LED. The ratio of the light from the at least one LED and from the filament GF can be set, as mentioned, by means of a suitable choice of the resistance of the filament GF. The light of the two light sources is mixed, so that an efficient and, at the same time, largely flicker-free light is generated.

[0034] FIG. 3 shows an exemplary embodiment of a light fixture 16 according to the invention using the example of an A-lamp with a base 18 of the E27 type. This has a glass bulb 20, filled with a protective gas atmosphere, conventional for incandescent lamps, which can, for example, comprise 93% argon and 7% nitrogen, but no halogen. A filament GF and a plurality of LEDs, of which a LED (LED1) is illustrated to exemplify at least one LED, are arranged inside the glass bulb 20. In order to thermally decouple the LED (LED1) and the filament GF, the LED (LED1) is arranged close to the base 18, and the filament GF thereof is spatially separated therefrom as far as possible. Due to this spatial separation the service life of the LED (LED1) is not negatively influenced by the thermal radiation emitted by the filament GF. For further thermal decoupling, or alternatively, a thermal shield could be arranged between the LED (LED1) and the filament GF. This may for example be a metallic reflector.

[0035] In the exemplary embodiment illustrated in FIG. 4 of a light fixture 16 according to the invention, a further glass bulb 22 in which the filament GF is arranged is arranged inside the glass bulb 20. The atmosphere inside the glass bulb 22 contains at least one halogen, in particular bromine. In this case a halogen bulb 24 is produced by the filament GF and the glass bulb 22 together with the filling. The protective gas atmosphere already known from the exemplary embodiment illustrated in FIG. 3 can be provided inside the glass bulb 20. In this case two LEDs (LED1, LED2) are arranged inside the glass bulb 20, but outside the glass bulb 22. Of course, there can be one or more of LEDs, for example one, two, three, four etc.

[0036] FIG. 5 shows the characteristic of the optical output P.sub.opt (a.u.=arbitrary units) as a function of the voltage U.sub.LED occurring across the at least one LED at a supply voltage of U.sub.V=220 V. The difference between the alternating current supply voltage U.sub.V and the voltage occurring across the at least one LED therefore corresponds to the voltage occurring across the filament GF.

[0037] Accordingly, the working point is fixed by means of the number of LEDs connected in series, i.e. in particular the forward voltages thereof, as well as the resistance of the filament GF. As can be seen, the optical performance P.sub.opt emitted by the filament GF is greater the lower the voltage U.sub.LED is across the at least one LED. In the case of the proportion of the optical performance P.sub.opt supplied by the at least one LED, a maximum is obtained at a voltage of U.sub.LED=80 V. For the sum of the two optical partial powers, i.e. the power of the filament GF as well as the power of the at least one LED, a maximum is obtained at a voltage of U.sub.LED=54 V. At this working point the entire system would achieve an efficiency greater than 20%. If it is assumed that an incandescent lamp usually has an efficiency between 2% and 5% this results in a significant increase in the efficiency relative to an incandescent lamp alone. If LEDs are operated alone, an efficiency between 25% and 30% could be achieved, but at the expense of a costly electronic driver. This electronic driver can be omitted in a light fixture according to the invention. In this respect it should be noted that a maximum degree of efficiency can be achieved if the at least one LED and the at least one filament are designed in such a way that between 20% and 25% of the voltage drop occurs on the at least one LED. Conversely, from the representation of FIG. 5 it may be concluded that an optimal degree of efficiency is produced when the at least one LED and the at least one filament GF are designed in such a way that between 75% and 85%, in particular 80%, of the optical performance P.sub.opt is generated by the at least one LED.

LIST OF REFERENCES

[0038] 10 printed circuit board [0039] 12 outline [0040] 14 bridge rectifier [0041] 16 light fixture [0042] 18 base [0043] 20 glass bulb [0044] 22 glass bulb [0045] 24 halogen bulb [0046] D1, D2, D3, D4 diodes [0047] GF filament [0048] LED1, LED2 LEDs [0049] P.sub.opt optical performance [0050] U.sub.LED voltage [0051] U.sub.V supply voltage