ENERGY SUPPLY CIRCUIT FOR A LIGHTING MODULE

Abstract

The invention relates to an energy supply circuit (5) for a lighting module (4) for a motor-vehicle headlamp, wherein the lighting module (4) comprises a shunt resistor (R.sub.sext) and at least one light source (D1, D2, Dn) that can be electrically supplied at least partially via the shunt resistor (R.sub.sext), wherein the lighting module (4) also has at least three electrical connections (A1, A2, A3), wherein a first connection (A1) and a second connection (A2) are provided for electrically contacting the shunt resistor (R.sub.sext) and a third connection (A3) is provided for electrically contacting the at least one light source (D1, D2, Dn) connected downstream, wherein the electrical connections (A1, A2, A3) are designed as externally contactable connections, wherein the energy supply circuit (5) has a control unit (3) for outputting a supply current (Iv) controlled so as to be constant to the at least one light source (D1, D2, Dn) of the lighting module (4), wherein the control unit (3) has an auxiliary resistor (Rs), which is connected in parallel with the shunt resistor (R.sub.sext).

Claims

1. An energy supply circuit (5) for a lighting module (4) for a motor vehicle headlight, wherein the lighting module (4) includes a shunt resistor (Rs.sub.ext) and at least one light source (D1, D2, Dn) that can be electrically supplied, at least partially, via the shunt resistor (Rs.sub.ext), wherein the lighting module (4) also has at least three electrical connections (A1, A2, A3), wherein a first connection (A1) and a second connection (A2) are provided for electrically contacting the shunt resistor (Rs.sub.ext), and a third connection (A3) is provided for electrically contacting the at least one light source (D1, D2, Dn) connected downstream, wherein the electrical connections (A1, A2, A3) are designed as externally contactable connections, the energy supply circuit (5) comprising: a control unit (3) for outputting a supply current (Iv), controlled to a constant value, to the at least one light source (D1, D2, Dn) of the lighting module (4), wherein the control unit (3) has at least three electrical connections (A1, A2, A3) for connection to the electrical connections (A1, A2, A3) of the lighting module (4), wherein the control unit (3) is configured for conducting at least a portion of the supply current (Iv) via the shunt resistor (Rs.sub.ext) toward the at least one light source (D1, D2, Dn) and measuring the voltage difference (U.sub.Rsext) present at the shunt resistor (Rs.sub.ext), wherein for controlling the current (Iv), the voltage difference (U.sub.Rsext) at the shunt resistor (Rs.sub.ext) is controlled to a constant value, wherein the control unit (3) has an auxiliary resistor (Rs) that is connected in parallel to the shunt resistor (Rs.sub.ext).

2. The energy supply circuit (5) of claim 1, wherein the auxiliary resistor (Rs) is topologically accommodated within the control unit (3).

3. The energy supply circuit (5) of claim 1, wherein the auxiliary resistor (Rs) has a value between 0.1 and 2.

4. The energy supply circuit (5) of claim 1, wherein the control unit (3) for controlling a supply current (Iv) that is output at the lighting module (4) has a transistor switch (T) connected in series with the lighting module (4), and a capacitor (C) connected in parallel.

5. A circuit arrangement comprising: the energy supply circuit (5) of claim 1; and a lighting module (4) for a motor vehicle headlight, wherein the lighting module has a shunt resistor (Rs.sub.ext) and at least one light source (D1, D2, Dn) that can be electrically supplied, at least partially, via the shunt resistor (Rs.sub.ext), wherein the lighting module (4) also has at least three electrical connections (A1, A2, A3), wherein a first connection (A1) and a second connection (A2) are provided for electrically contacting the shunt resistor (Rs.sub.ext), and a third connection (A3) is provided for electrically contacting the at least one light source (D1, D2, Dn) connected downstream, wherein the electrical connections (A1, A2, A3) are designed as externally contactable connections.

6. The circuit arrangement of claim 5, wherein the lighting module (4) has at least two, three, or more than three light sources.

7. The circuit arrangement of claim 5, wherein the at least one light source (D1, D2, Dn) is an LED, an OLED, or a laser diode.

8. The circuit arrangement of claim 5, wherein the shunt resistor (Rs.sub.ext) has a value between 0.2 and 2.

9. The circuit arrangement of claim 5, wherein the shunt resistor (Rs.sub.ext), the at least one light source (D1, D2, Dn), and the at least three connections (A1, A2, A3) are situated on a shared circuit carrier.

10. A motor vehicle headlight, comprising at least one energy supply circuit (5) of claim 1.

11. A motor vehicle having at least one, preferably two, motor vehicle headlights according to claim 10.

12. The energy supply circuit (5) of claim 3, wherein the auxiliary resistor (Rs) has a value between 0.15 and 1.

13. The energy supply circuit (5) of claim 3, wherein the auxiliary resistor (Rs) has a value between 0.2 and 0.75.

14. The circuit arrangement of claim 8, wherein the shunt resistor (Rs.sub.ext) has a value between 0.3 and 1.50.

15. The circuit arrangement of claim 8, wherein the shunt resistor (Rs.sub.ext) has a value between 0.5 and 1.

16. The circuit arrangement of claim 9, wherein the shared circuit carrier comprises a printed circuit board.

17. A motor vehicle headlight comprising at least one circuit arrangement of claim 5.

18. A motor vehicle having at least one, preferably two, motor vehicle headlights according to claim 17.

Description

[0019] The invention is described in greater detail below with reference to one non-limiting exemplary embodiment that is illustrated in the figures, which show the following:

[0020] FIG. 1 shows a schematic illustration of a circuit arrangement according to the prior art, and

[0021] FIG. 2 shows a schematic illustration of a circuit arrangement according to the invention.

[0022] Unless stated otherwise, identical reference numerals denote the same features in the figures described below.

[0023] FIG. 1 shows a schematic illustration of a circuit arrangement according to the prior art. The circuit arrangement includes a lighting module 4 and an energy supply circuit 5 that supplies power to the lighting module 4. As described in the introduction, the lighting module 4 has multiple light sources D1, D2, through Dn, which may be supplied with power by connections A1 and A2 of the energy supply device 5 via the corresponding connections A1 and A2. The lighting module has a coding resistor Rc, which via specially designed connections A3 and A4 contacts an evaluation unit 2 situated at the energy supply device 5, and may be evaluated. A coding resistor is associated with each brightness class, so that, via the evaluation of the resistance value, conclusions may be drawn concerning the brightness class of the lighting module 4, and a suitable supply current may be set. For this purpose, the evaluation unit 2 is connected to the control unit 3. A power supply unit 1, for example a voltage source, is provided for feeding the energy supply device 5.

[0024] FIG. 2 shows a schematic illustration of a circuit arrangement according to the invention, comprising a lighting module 4 according to the invention, and an energy supply circuit 5 according to the invention for supplying power to the lighting module 4. The lighting module 4, in contrast to the prior art, has a shunt resistor Rs.sub.ext and at least one light source that is electrically supplied, at least partially, via the shunt resistor Rs.sub.ext; three light sources D1, D2, through Dn are illustrated in the present example. As indicated by the dashed line, the number of light sources may also differ from the number shown. In this exemplary embodiment, light-emitting diodes have been used as light sources. The lighting module 4 has three electrical connections A1, A2, and A3, wherein the connections A1 (first connection) and A2 (second connection) are provided for electrically contacting the shunt resistor Rs.sub.ext. The third connection A3 is provided for electrically contacting the light sources D1 through Dn, the connections A1 through A3 being designed as externally contactable connections in order to be contacted by the energy supply device 5. The power supply unit 1 may be a voltage source, for example, in which the current Iv may be provided by appropriately controlling the transistor T. Any given types of energy sources may generally be used as the power supply unit 1. For example, clocked as well as linear power sources may be used, wherein power supply units that are integrated into the energy supply device 5 or also discretely designed power supply units may be used.

[0025] The energy supply device 5 is configured for delivering a constant supply current to the light sources D1 through Dn. For this purpose, the energy supply device has a control unit 3 for outputting a supply current Iv, controlled to a constant value, to the light sources D1 through Dn of the lighting module 4.

[0026] In the exemplary embodiment shown, the supply current Iv is made up of two components, namely, a component that flows across the shunt resistor Rs.sub.ext (I.sub.Rse), and a component that flows across an auxiliary resistor Rs (I.sub.Rs). The energy supply unit 5 has at least three electrical connections A1, A2, and A3 which correspond to the electrical connections of the lighting module 4. The control unit 3 is configured for measuring the voltage difference U.sub.Rsext present at the shunt resistor Rs.sub.ext (i.e., the electrical potential difference between the connections A1 and A2 and A1 and A2) and using them as a control variable. For example, a transistor switch T may be controlled via a PWM signal, so that it may be ensured that an output voltage Ua is present between the connections A1 and A3, resulting in a desired voltage value (0.1 V or 0.2 V, for example) and thus a desired current at the resistor Rs.sub.ext. The output voltage Ua may be assisted by a capacitor C.

[0027] The auxiliary resistor Rs is typically an integral part of the energy supply circuit 5 and is connected in parallel to the shunt resistor Rs.sub.ext, thus relieving the shunt resistor Rs.sub.ext. Providing the auxiliary resistor Rs, which is connected in parallel to the shunt resistor Rs.sub.ext, allows a minimum current IRs to be applied to the light sources D1 through Dn. In addition, such an arrangement ensures that an increased power output to the light sources D1 through Dn may be achieved by reducing the shunt resistance Rs.sub.ext, as the result of which the power loss realized at the shunt resistor Rs.sub.ext is reduced, and the efficiency of the energy supply circuit 5 may be increased. It is important in the invention that the shunt resistor Rs.sub.ext influences the overall resistance, and thus influences the value of the current applied to the light sources D1 through Dn.

[0028] The energy supply device 5 must therefore be connected to the lighting module 4 in order to ensure that at least a portion of the total supply current Iv flows across the shunt resistor Rs.sub.ext. The shunt resistor Rs.sub.ext is adapted to the brightness of the particular light sources D1 through Dn, and ensures that lighting modules 4 of different brightness classes are operated at different current levels, so that differences in brightness between the lighting modules 4 may be compensated for. It is thus possible to operate lighting modules 4 of different brightness classes at the same brightness, using identical supply devices 5, and at the same time to dispense with providing a coding resistor Rc that is to be externally contacted, and an associated evaluation unit 2. In addition, lighting modules 4 of different brightness classes may thus be used for a vehicle headlight, for example.

[0029] In view of this teaching, those skilled in the art are able to arrive at other embodiments of the invention (not shown) without inventive activity. The invention is therefore not limited to the embodiment shown. In addition, individual aspects of the invention or of the embodiment may be taken and combined with one another. The lighting module 4 and the energy supply circuit 5 involve a joint inventive concept. The concepts underlying the invention, which may be carried out in a variety of ways by those skilled in the art with an awareness of this description, and which are still maintained as such, are essential.