Lighting equipment

Abstract

A lighting device (101) for a motor vehicle comprising: a control unit (107) to which a light module (106) is connected; a series connection of bridgeable semiconductor light sources (44-48), wherein the lighting device (101) has a headlight housing (102) in which two light modules (105, 106) are arranged and supplied with electrical energy by the control unit (107) which is remotely connected via connecting lines (110); wherein the control unit (107) is arranged on the outside of the headlight housing (102) in a control unit housing (108); characterized in that the protection circuit (2) is designed to protect the series connection of the bridgeable semiconductor light sources (44-48); that the protection circuit (2) comprises a series connection of a current measuring element (8) and an actuator (10); and that a Zener diode (18) is connected between an actuator terminal (22) of the actuator (10) and an input. (9) of the actuator (10) is arranged,that the control unit (107):- has an input with two input terminals (26, 28) which can be connected to the vehicle's electrical system via a plug / socket element (109),- includes a buck converter comprising a switch (34), a diode (36) and a coil (38), and- has an output capacitor (40) and an input capacitor (42).

Description

The invention relates to a lighting device according to the preamble of claim 1. A lighting device according to the preamble of claim 1 is already known from DE 10 2009 060 791 A1. This lighting device comprises a light module comprising several semiconductor light sources connected in series. A circuit arrangement associated with at least one of the semiconductor light sources is connected in parallel. In the event of a detected fault in one of the semiconductor light sources, the defective semiconductor light source is bypassed by means of a bypass. From DE 10 2008 021 534 A1, a lighting device is known in which individual light-emitting diodes or individual series circuits of light-emitting diodes of at least one light-emitting diode arrangement can be switched on and off separately. A control arrangement is provided for regulating an operating voltage depending on a voltage applied to a current source. From DE 10 2011 005 582 A1, a lighting device is known in which a series circuit of light sources is supplied with power via a DC / DC switching regulator. The respective light sources are switched on and off individually by means of switching elements connected in parallel to each light source. The switching elements are controlled by a microcontroller. The light sources can be dimmed by pulse-width modulation of the control signal. DE 10 2013 221 715 A1 discloses an LED circuit arrangement and a method for operating an LED circuit arrangement. DE 197 34 750 A1 discloses a rear light for motor vehicles. The subsequently published German patent DE 10 2015 208 995 A1 discloses a protection circuit. It is known that control units for controlling semiconductor light sources have an output capacitance. Furthermore, it is known that lighting systems for motor vehicles feature series circuits of semiconductor light sources, which can be bridged individually or across multiple semiconductor light sources to generate animations, dimming, or lighting effects such as a sweeping turn signal. This bridging is accomplished by means of electronic switches, for example, transistors. Switching individual semiconductor light sources on and off thus represents a highly transient process. The object of the invention is therefore to improve the operation of series-connected, bridgeable semiconductor light sources. The problem underlying the invention is solved by a lighting device according to claim 1, wherein the lighting device includes a protective circuit. Advantageous embodiments are specified in the dependent claims. Further features important to the invention are found in the following description and in the drawings, whereby the features can be important to the invention both individually and in various combinations, without this being explicitly stated again. The protection circuit for a series connection of bridgeable semiconductor light sources in a motor vehicle's lighting system comprises a series connection of a current measuring element and an actuator. A Zener diode is arranged between an actuator terminal and an input of the actuator. This limits the output current towards the semiconductor light sources. Advantageously, this protects the semiconductor light sources from overcurrent and thus from damage. Particularly when a first group of semiconductor light sources is bridged, a second group can be protected from overcurrent by limiting the output current of the protection circuit. Simultaneously, current ripples occurring at the input of the protection circuit can be filtered out by the actuator, thereby improving electromagnetic compatibility. In an advantageous further development, the Zener diode, the actuator and the resistor limit the output current to a maximum value. In an advantageous further development, another resistor is arranged in the reverse direction of the Zener diode, which is connected in series with the Zener diode to an input of the protection circuit. In a further advantageous embodiment, the actuator is a pnp bipolar transistor. The use of a pnp bipolar transistor allows for a simpler design of the protection circuit. Furthermore, a bipolar transistor has the advantage over a field-effect transistor that, due to lower component tolerances, it enables more stable operation under given operating conditions. In an advantageous embodiment, the current measuring element is a resistor. The protection circuit is part of a lighting module for a vehicle lighting system. This makes it possible to use control units with output capacitance to operate a series circuit of individually bridgeable semiconductor light sources. The protection circuit is part of a control unit for a lighting module in a motor vehicle's lighting system. This allows the lighting module to be connected directly to the control unit without the risk of damage or destruction to the individually or multiple bridgeable semiconductor light sources. Further features, applications, and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, which are illustrated in the figures of the drawings. All described and illustrated features, individually or in any combination, constitute the subject matter of the invention, irrespective of the claims or their cross-references, and irrespective of their formulation or representation in the description or in the drawings. The same reference numerals are used for functionally equivalent quantities and features in the figures, even in different embodiments. In the drawings: Fig. 1 shows a lighting device for motor vehicles; Fig. 2 shows a protective circuit; and Figs. 3 and 4 each show a schematic view of a control unit and a light module, respectively. Figure 1 shows a lighting device for motor vehicles in its entirety designated by reference numeral 101. In the illustrated embodiment, the lighting device 101 is designed as a motor vehicle headlight. Of course, the lighting device 101 can also be designed as a light or similar device arranged at the rear or side of the motor vehicle. In particular, the lighting device 101 is a turn signal for the motor vehicle. The headlight 101 comprises a housing 102, which is preferably made of plastic. In a light emission direction 103, the headlight housing 102 has a light emission opening, which is closed by a transparent cover 104. The cover 104 is made of colorless plastic or glass. The cover 104 can be designed as a so-called clear lens without optically effective profiles (for example, prisms).Alternatively, the disc 104 can be provided, at least in some areas, with optically effective profiles that in particular cause a scattering of the passing light in a horizontal direction. Inside the headlight housing 102, two light modules 105 and 106 are arranged in the illustrated embodiment. The light modules 105 and 106 are arranged either fixedly or movable relative to the housing 102. For example, a dynamic cornering light function can be implemented by moving the light modules 105 and 106 relative to the housing 102 in a horizontal direction. Moving the light modules 105 and 106 about a horizontal axis, i.e., in a vertical direction, allows for headlight range control. The light modules 105 and 106 are designed to generate a desired light distribution, such as low beam, high beam, city light, country road light, motorway light, fog light, static or dynamic cornering light, or any other static or adaptive light distribution.The light modules 105 and 106 generate the desired lighting function either individually or in combination by superimposing the partial light distributions supplied by each individual light module 105 and 107 to achieve the desired overall light distribution. The light modules 105 and 106 can be configured as reflection modules and / or projection modules. Of course, the headlight housing 102 can also contain more or fewer than the two light modules 105, 106 shown. A control unit 107 is arranged in a control unit housing 108 on the outside of the headlight housing 102. Of course, the control unit 107 can also be arranged at any other location on the headlight 101. In particular, a separate control unit can be provided for each of the light modules 105, 106, with the control units being an integral part of the light modules 105, 106. Naturally, the control unit 107 can also be arranged remotely from the headlight 101. The control unit 107 serves to control and / or regulate the light modules 105, 106 or subcomponents of the light modules 105, 106, such as light sources of the light modules 105, 106. The control of the light modules 105, 106 or the subcomponents by the control unit 107 is effected via connecting lines 110, which are only symbolically represented in Fig. 1 by a dashed line.The light modules 105 and 106 are supplied with electrical energy via lines 110. Lines 110 are routed through an opening in the headlight housing 102 into the control unit housing 108 and connected there to the circuitry of the control unit 107. If several control units are integrated into the light modules 105 and 106, lines 110 and the opening in the headlight housing 102 can be omitted. For improved EMC shielding, the control unit housing 108 is made of an electrically conductive material, in particular metal, preferably die-cast aluminum. The cables 110 are also shielded for improved EMC shielding, in particular by means of a metal braid surrounding the cables 110 or a metal-plastic braid. Furthermore, an opening is provided in the control unit housing 108 in which a plug / socket element 109 is arranged. The control unit 107 can be connected to a higher-level control unit (for example, a so-called body controller) and / or to a vehicle power supply (for example, a vehicle battery) via the plug / socket element 109. The light modules 105 and 106 of the lighting device 101 use one or more semiconductor light sources, in particular light-emitting diodes (LEDs), as light sources. LED spotlights 101, which have a large number of LEDs, are increasingly being used. Variable light distributions can be achieved by switching individual LEDs or groups of LEDs on and off. Typically, several LEDs are connected in a series circuit (also called a branch or chain). Naturally, the multiple LEDs in the series circuit can be bridged not only individually but also in multiples. Fig. 2 shows a protection circuit 2 in which a current sensor 8, also referred to as the first resistor, and an actuator 10 in the form of a PNP bipolar transistor are connected in series between an input 4 and an output 6. The actuator has an input 9, an output 11, and an actuator terminal 22. The input 9 can also be referred to as the emitter. The output 11 can also be referred to as the collector. The actuator terminal 22 can also be referred to as the base. The series connection of the current sensor 8 and the actuator 10 is arranged between a first input terminal 12 and a first output terminal 14. Of course, a protection circuit 2 can also be built using an npn bipolar transistor as an actuator 10 to improve the operation of the series connection of bridgeable semiconductor light sources. A Zener diode 18 and a second resistor 20 are connected in series between the first input terminal 12 and a second input terminal 16. The Zener diode 18 is connected to the current measuring element 8 on the side of the current measuring element 8 facing away from the actuator 10. A center tap between the Zener diode 18 and the second resistor 20 is connected to the control terminal 22 of the actuator 10. The output 6 is formed by the first output terminal 14 and a second output terminal 24. Thus, the Zener diode 18 is arranged between the control terminal 22 of the actuator 10 and the input 9 of the actuator 10. The Zener diode 18 is reverse-biased from the input 9 of the actuator 10 to the control terminal 22 of the actuator 10. In the reverse bias of Zener diode 18, a breakdown voltage U18 is shown, above which the Zener diode 18 conducts in reverse bias. A voltage U8 drops across the current measuring element 8. The actuator 10, in the form of a PNP bipolar transistor, has a base-emitter voltage UBE. The Zener diode 18, connected between the input 4 of the protection circuit 2 and the correspondingly operated control terminal 22 of the actuator 10, limits the output current IA of the protection circuit 2 to a maximum value Imax. The maximum value Imax is determined according to the following equation 1. The current measuring element 8 has a resistance value R8. Fig. 3 shows a schematic view of the control unit 107, which is connected to the light module 106 via the connecting lines 110. An input of the control unit 107 and its input terminals 26 and 28 are connected to the vehicle's electrical system (not shown). The output terminals 30 and 32 of the control unit 107 are connected to the connecting lines 110. The control unit 107 includes a buck converter comprising a switch 34, a diode 36, and an inductor 38. Furthermore, the control unit 107 includes an output capacitor 40 and an input capacitor 42. The light module 106 includes the protection circuit 2, with input terminals 12 and 16 coinciding with the input of the light module 106. Semiconductor light sources 44-48 are arranged in series at the output of the protection circuit 2. The semiconductor light sources 44-48 can be individually bypassed by means of associated switches 54-58. Of course, several semiconductor light sources 44-48 can also be bypassed together by means of a common switch (not shown). By limiting the output current IA of the protection circuit 2, any switching states of the switches 54-58 can now be implemented. This advantageously decouples the control of the switches 54-58 from the behavior of the control unit 107. In particular, discharging the output capacitor 40 does not lead to an increased current through the unbridged semiconductor light sources 44-48 after some of the semiconductor light sources 44-48 have been bridged. Rather, the protection circuit 2 limits the current emanating from the control unit 107. Furthermore, current ripples generated by the buck converter can be smoothed out by the protection circuit 2. Fig. 4 shows a schematic view of the control unit 107, which includes the protection circuit 2. The light module 106 is simplified as a result and thus comprises the series connection of semiconductor light sources 44-48 and the associated switches 54-58. The control unit 107 and the light module 106 are connected by the connecting lines 110, with input terminals 70 and 72 of the light module 106 being connected via the connecting lines 110 to the output terminals 14 and 24 of the control unit 107. The output terminals 14 and 24 of the protection circuit 2 coincide with the output terminals of the control unit 107. The protection circuit 2 provides short-circuit protection between the output terminals 14 and 24. In Fig. 4, the control unit 107 has the output capacitor 40, which can have a lower capacitance due to the inclusion of the protection circuit 2.

Claims

A lighting device (101) for a motor vehicle comprising: a control unit (107) to which a light module (106) is connected; a series connection of bridgeable semiconductor light sources (44-48), wherein the lighting device (101) has a headlight housing (102) in which two light modules (105, 106) are arranged and supplied with electrical energy by the control unit (107) which is remotely connected via connecting lines (110); wherein the control unit (107) is arranged on the outside of the headlight housing (102) in a control unit housing (108); characterized in that the protection circuit (2) is designed to protect the series connection of the bridgeable semiconductor light sources (44-48); that the protection circuit (2) comprises a series connection of a current measuring element (8) and an actuator (10); and that a Zener diode (18) is connected between an actuator terminal (22) of the actuator (10) and an input. (9) of the actuator (10) is arranged,that the control unit (107):- has an input with two input terminals (26, 28) which can be connected to the vehicle's electrical system via a plug / socket element (109),- includes a buck converter comprising a switch (34), a diode (36) and a coil (38), and- has an output capacitor (40) and an input capacitor (42). The lighting device according to claim 1, wherein the Zener diode (18), the actuator (10) and the current measuring element (8) limit an output current (IA) to a maximum value (Imax). The lighting device according to claim 1 or 2, wherein a resistor (20) is arranged in the reverse direction of the Zener diode (18), which is connected in series with the Zener diode (18) to an input (4) of the protection circuit (2). The lighting device according to one of the preceding claims, wherein the actuator (10) is a pnp bipolar transistor. The lighting device according to one of the preceding claims, wherein the current measuring element (8) is a resistor. The lighting device according to one of the preceding claims, wherein the series connection of the current measuring element (8) and the actuating element (10) is arranged between a third input terminal (12) and a first output terminal (14), wherein a first side of the switch (34) is connected to the first input terminal (26) of the two input terminals (26, 28) and a first side of the input capacitor (42), wherein a second side of the switch (34) is connected to a cathode of the diode (36) and a first side of the coil (38), wherein a second side of the coil (38) is connected to a first side of the output capacitor (40) and the third input terminal (12), wherein a second input terminal (28) of the two input terminals (26, 28) of the input is connected to the second side of the input capacitor (42), the second side of the output capacitor (40), and an anode of the diode (36) is connected.

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