Lighting equipment

Abstract

Lighting device for a motor vehicle, wherein the lighting device comprises at least one semiconductor light source arrangement (4) and means for regulating or controlling the supply current for the at least one semiconductor light source arrangement (4), wherein the means comprise at least one resistive element (3) with a temperature-dependent resistance value, wherein at least one suppressor diode (8) is provided which is connected in a parallel branch to the at least one semiconductor light source arrangement (4), and wherein at least one capacitor (9) is connected in parallel to the at least one suppressor diode (8).

Description

Technical field

[0001] The invention relates to a lighting device according to claim 1.

[0002] Publication US 2013 / 0127353 A1 discloses a driver circuit for solid-state light sources that includes a dimming function and color control.

[0003] Furthermore, circuit arrangements for the operation of light-emitting diodes are known from the publications US 2011 / 0273102 A1 and US 2008 / 0224636 A1. Description of the invention

[0004] The object of the present invention is to provide an improved lighting device that can be operated on the vehicle electrical system voltage of a motor vehicle.

[0005] This problem is solved by a lighting device having the features of claim 1. Particularly advantageous embodiments are found in the dependent claims.

[0006] The invention relates in particular to a lighting device operable on the vehicle electrical system voltage of a motor vehicle with a circuit for protecting current-operated semiconductor light sources for signaling and lighting purposes.

[0007] The lighting device according to the invention is preferably used in automotive engineering in the front and rear lights. The semiconductor light sources of the lighting device according to the invention must be protected against positive and negative voltage spikes. Such voltage spikes can occur during load changes, battery disconnection, and jump-starting from another vehicle. For protection against voltage spikes, preferably at least one suppressor diode is provided. Current regulation is preferably achieved via at least one resistor element with a temperature-dependent resistance value. Brief description of the drawings

[0008] The invention will now be explained in more detail using exemplary embodiments. The figures show: Fig. 1 a circuit diagram of a lighting device according to the first embodiment of the invention Fig. 2 a circuit diagram of a lighting device according to the second embodiment of the invention Fig. 3 a circuit diagram of a lighting device according to the third embodiment of the invention Fig. 4 a circuit diagram of a lighting device according to the fourth embodiment of the invention Fig. 5 a circuit diagram of a lighting device according to the fifth embodiment of the invention Fig. 6 a circuit diagram of a lighting device according to the sixth embodiment of the invention Fig. 7 a circuit diagram of a lighting device according to the seventh embodiment of the invention Fig. 8 a circuit diagram of a lighting device according to the eighth embodiment of the invention Fig. 9 a circuit diagram of a lighting device according to the ninth embodiment of the invention Fig. 10 a circuit diagram of a lighting device according to the tenth embodiment of the invention Preferred embodiment of the invention

[0009] For the sake of simplicity, identical or similar features are also referred to by the same reference symbols in the following text.

[0010] The lighting device according to the first embodiment of the invention comprises a semiconductor light source arrangement consisting of four light-emitting diodes 4 connected in series. A circuit diagram of the lighting device of the first embodiment is shown in Fig. Figure 1 shows the lighting device. It is operated using the vehicle's electrical system voltage and is designed for supply voltages in the range of 6 V to 16 V DC. In the figures, reference numeral 1 denotes the positive terminal of the vehicle's electrical system voltage source. The negative terminal, or the one connected to ground potential, of the vehicle's electrical system voltage source is not marked with a reference numeral in the figures.

[0011] To protect the LEDs of the semiconductor light source arrangement 4 against positive overvoltage and high temperature, a resistor element 3 with a temperature-dependent resistance value is connected upstream of the semiconductor light source arrangement 4, which limits the current through the LEDs. The resistor element 3 is designed as a PTC thermistor.

[0012] Additionally, the lighting device includes a parallel circuit of two resistors 5, 6, which are connected in series to the series circuit of semiconductor light source arrangement 4 and PTC resistor 3.

[0013] By appropriately dimensioning the resistance values ​​of resistors 5, 6 and the PTC thermistor 3, a desired nominal current for the semiconductor light source arrangement of the lighting device is defined. In the case of increased operating temperature, the resistance value of the PTC thermistor 3 increases, thereby limiting the current through the PTC thermistor 3 and thus also through the LEDs of the semiconductor light source arrangement connected in series with it.

[0014] A diode 2 at the voltage input 1 of the lighting device protects the circuit and the lighting device from major damage in case of reverse polarity, i.e., if the lighting device is installed with reversed electrical connections. The diode 2 protects the LEDs of the semiconductor light source arrangement 4 from negative voltages up to approximately 600 V. A capacitor 9, in conjunction with a suppressor diode 8 (also known as a transzorb diode), dampens any voltage spikes and limits them to a fixed value.

[0015] The suppressor diode 8 is connected in parallel to the series circuit consisting of PTC thermistor 3, semiconductor light source arrangement 4 and parallel connection of resistors 5, 6.

[0016] Capacitor 9 is connected in parallel to the series circuit consisting of PTC thermistor 3, semiconductor light source assembly 4, and the parallel connection of resistors 5 and 6. Capacitor 8 is also connected in parallel to suppressor diode 8.

[0017] The light-emitting diodes of the semiconductor light source arrangement 4 are thus protected against excessive voltage and current as well as against high temperature.

[0018] The current flowing through resistor 7 signals to a control unit (not shown) the presence of the lighting device and the defect of one or more LEDs in the semiconductor light source assembly. Resistor 7 is connected in parallel to the series circuit consisting of PTC thermistor 3, semiconductor light source assembly 4, and the parallel connection of resistors 5 and 6. Fig. 2

[0019] The circuit in Fig. 2 according to the lighting device according to the second embodiment of the invention has the same function as the one in Fig. 1. Additionally, a MOSFET 11 is provided which bypasses resistors 5 and 6 depending on the voltage drop across the Zener diode 10. In the case of an input voltage or supply voltage below the forward voltage of the LEDs 4, resistors 5 and 6 are bypassed by means of the MOSFET 11 and the Zener diode 10. This allows the LEDs 4 to be operated even with a significantly reduced input voltage. This function is required for the so-called start-stop function in automotive engineering, in which the vehicle's engine is switched off when stopped at a red light. The start-stop function allows the input voltage to drop as low as 6V. Fig. 3

[0020] The circuit in Fig. 3 according to the lighting device according to the third embodiment of the invention has the same function as the one in Fig. 1 and Fig. 2. In the circuit according to Fig. 3. If the input voltage is too low, one of the LEDs of the semiconductor light source arrangement 4 and the resistors 5, 6 are bridged to increase the current for the remaining LEDs of the semiconductor light source arrangement 4 and thereby achieve a greater luminosity (lumens). Fig. 4

[0021] The circuit according to Fig. 4 according to the lighting device according to the fourth embodiment of the invention has the same function as the one according to Fig. 1, however, the semiconductor light source arrangement of the lighting device has five instead of four LEDs connected in series. Fig. 5

[0022] The in Fig. The fifth embodiment of the lighting device according to the invention, as illustrated in Figure 5, has a semiconductor light source arrangement with five LEDs connected in series and corresponds in function to the circuit according to Figure 5. Fig. 2. Fig. 6

[0023] The in Fig. Figure 6 shows the sixth embodiment of the lighting device according to the invention, which has a semiconductor light source arrangement with five LEDs connected in series and corresponds in function to the circuit according to Figure 6. Fig. 3. Fig. 7

[0024] At the in Fig. In the circuit shown in Figure 7, according to the seventh embodiment of the lighting device according to the invention, the semiconductor light source arrangement 4 has three LEDs connected in series. Its basic function corresponds to the circuit shown in Figure 7. Fig. 1, but differs by a resistor 14, which is connected in parallel to the PTC thermistor 3. The rated current is set using resistor 14 for the LEDs of the semiconductor light source arrangement with higher forward voltage. Fig. 8

[0025] The circuit in Fig. According to the eighth embodiment of the lighting device according to the invention, the device has a semiconductor light source arrangement 4 with three light-emitting diodes connected in series. Its function corresponds to the circuit according to Fig. 1, but differs by a PTC thermistor 13, which is connected in parallel to the PTC thermistor 3. The PTC thermistor 13 is used to adjust the rated current in LEDs with higher forward voltage and temperature. Fig. 9

[0026] The circuit according to Fig. 9, according to the ninth embodiment of the lighting device according to the invention, has a semiconductor light source arrangement 4 with three LEDs connected in series. It has the same function as the one described in Fig. 5 Circuit arrangement shown according to the fifth embodiment of the lighting device according to the invention. Fig. 10

[0027] The circuit in Fig. 10 according to the tenth embodiment of the lighting device according to the invention has a semiconductor light source arrangement 4 with three light-emitting diodes connected in series. It has the same function as the one in Fig. 6 Circuit arrangement shown according to the sixth embodiment of the lighting device according to the invention.

Claims

[1] Lighting device for a motor vehicle, wherein the lighting device comprises at least one semiconductor light source arrangement (4) and means for regulating or controlling the supply current for the at least one semiconductor light source arrangement (4), wherein the means comprise at least one resistive element (3) with a temperature-dependent resistance value, wherein at least one suppressor diode (8) is provided which is connected in a parallel branch to the at least one semiconductor light source arrangement (4), and wherein at least one capacitor (9) is connected in parallel to the at least one suppressor diode (8). [2] Lighting device according to claim 1, wherein the means comprise at least one further resistance element (5, 6). [3] Lighting device according to one of claims 1 to 2, wherein the means comprise at least one transistor (11). [4] Lighting device according to one of claims 1 to 3, wherein the means comprise at least one Zener diode (10).

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