Current regulator arrangement for a lamp arrangement, and method for operating a lamp arrangement

Abstract

A current regulator arrangement (10, 10a) for a lamp arrangement (12, 14, 16), in particular a laser diode arrangement, having a DC voltage source (20) which provides an upper and a lower voltage level (22, 24) different than ground, is characterised by at least one current regulator (26, 28, 30, 26a) which is connected to the DC voltage source (20) and has at least one transformer (40, 42, 44, 40a, 40b) which is connected at the upper and lower voltage level (22, 24), wherein a current measuring device (52, 54, 56, 52a, 52b) that senses the output current of the current regulator (26, 28, 30, 26a) is provided and is connected to a control device (58) which generates an actuation signal (60) for the transformer (40, 42, 44, 40a, 40b).

Description

[0001] Current controller arrangement for a lighting arrangement and method for operating a lighting arrangement

[0002] The invention relates to a current controller arrangement for a lighting arrangement, in particular a laser diode arrangement, comprising a DC voltage source that provides an upper and a lower voltage level different from ground. Furthermore, the invention relates to a method for operating a lighting arrangement, in particular a laser diode arrangement.

[0003] EP 2 667 687 A1 discloses an operation control device for operating a lighting arrangement, which in particular has a series connection of light-emitting diodes. The operation control device has a converter that is controlled by a switching signal from a control device and provides an output current at its output. Both a lighting arrangement and an output capacitor are connected to this output. A control switch is controlled by the control device via a pulse-width-modulated control signal and is connected in series with the lighting arrangement. Before the control switch is closed, the output capacitor is charged during a charging period, and the output current is increased. As a result, the current rise phase is already carried out before the control switch is closed, so that flickering effects of the lighting arrangement are avoided even with small pulse widths of the control signal.

[0004] If laser diodes are to be controlled as light sources, it is necessary that this is done with high dynamics and high efficiency.

[0005] The object of the present invention is therefore to provide a control concept for a lighting arrangement, in particular a laser diode arrangement.

[0006] This object is achieved according to the invention by a current controller arrangement for a lighting device arrangement, in particular a laser diode arrangement, with a DC voltage source which provides an upper and a lower voltage level different from ground, with at least one current controller connected to the DC voltage source, which current controller has at least one converter which is connected to the upper and lower voltage levels, wherein a current measuring device which detects the output current of the current converter is provided, which current measuring device is connected to a control device which generates a control signal for the converter.

[0007] Because two voltage levels are provided, the current controller does not have to cover the entire voltage range between 0 volts and the upper voltage level. Because a lower voltage level is provided, a smaller voltage range needs to be covered, which increases efficiency. This results in fewer switching losses in the converter, so that it can be operated at a higher frequency and can be designed dynamically, while at the same time achieving higher efficiency for the overall arrangement. The arrangement according to the invention achieves the dynamics of analog drivers, so that these can be omitted. The current controller arrangement according to the invention also has a good efficiency, in particular when the lighting arrangement is operated at a lower power, for example only 50% of the maximum power.

[0008] The DC voltage source is preferably configured to generate the two voltage levels from a mains voltage. This can be achieved, for example, using a flyback converter or a resonant converter in combination with a rectifier.

[0009] According to the invention, it is particularly provided that the current of the lighting arrangement is adjusted exclusively via the current controller. In particular, no voltage measurement is necessary. Furthermore, no switch for turning the lighting arrangement on and off is provided or required.

[0010] The converter can have at least one switching element controlled by the control device. According to the invention, a clocked current controller concept with high dynamics and high efficiency is provided. By appropriately controlling the switching element as a function of the measured current, a current for the lighting arrangement can be generated particularly reliably and dynamically. The current controller arrangement according to the invention operates without measuring a voltage. In particular, no voltage is set, but only the current that supplies the lighting arrangement.

[0011] The lower voltage level can be at least 65%, preferably at least 70%, of the upper voltage level. This allows a narrow voltage range to be set that must be covered by the converter. The lower voltage level can be set, in particular, depending on the lamp arrangement to be operated. The lower voltage level is preferably slightly lower than the threshold voltage required to turn on a laser diode.

[0012] Particular advantages arise when the current controller is arranged in a floating configuration. The current controller is thus not connected to ground. This measure allows for improved EMC performance and prevents interference with controller operation due to an unwanted ground fault. A ground fault can be detected, for example, via an additional voltage measurement and communicated to the user.

[0013] A particularly simple converter design is achieved by utilizing it as a buck converter. Alternatively, it would be conceivable to design the converter as a boost converter or flyback converter.

[0014] To provide a suitable, low-ripple current, it is advantageous for the current controller to have an inductance. The inductance is preferably part of a low-pass filter. According to the invention, a low-pass filter or EMC filter can therefore be connected downstream of the converter. According to one embodiment of the invention, the current controller can have several converters connected in parallel, which are controlled with a clock stagger. This measure can further increase the dynamic range and reduce ripple.

[0015] Furthermore, it is conceivable for the current controller arrangement to comprise several current controllers connected in parallel, which are controlled with a clock stagger. The current controller arrangements can control different lighting arrangements, in particular strings of laser diodes. This measure can also reduce the ripple of a laser arrangement comprising several such strings of laser diodes.

[0016] The scope of the invention also includes a method for operating a lighting arrangement, in particular a laser diode arrangement, comprising the method steps:

[0017] - Providing a first and a second DC voltage level;

[0018] - Detecting the current at the output of a current controller,

[0019] - Generating a control signal for controlling a converter of the current controller connected to the first and second voltage levels as a function of the measured current to generate a predetermined current through the current controller.

[0020] The current for the lighting arrangement is thus adjusted by current modulation. The current is generated exclusively by a current controller, without the need for voltage measurement. Because two DC voltage levels are used, to which the converter is connected, only small voltage differences need to be overcome. Switching losses that can occur with a switching element in the converter can thus be reduced. Furthermore, high dynamic range is possible.

[0021] In particular, the duty cycle of the control signal can be adjusted depending on the measured current. This measure allows the current intensity of the current controller's output current to be adjusted.

[0022] In particular, this measure eliminates the need to provide a switch in series with the lighting arrangement to turn it on and off. This significantly reduces the control and circuitry effort compared to the state of the art.

[0023] The control signal can preferably be generated at a frequency in the range of 500 kHz to 2 MHz, in particular 1 MHz. Thus, the method can be implemented at a very high clock frequency, in particular a significantly higher clock frequency than in the prior art.

[0024] To reduce ripple, multiple converters can be controlled with clock-shifted control signals. All converters can be controlled with signals of the same frequency.

[0025] Further features and advantages of the invention will become apparent from the following detailed description of exemplary embodiments of the invention with reference to the figures of the drawing, which illustrate details essential to the invention, as well as from the claims. The features shown therein are not necessarily to scale and are presented in such a way that the special features of the invention can be clearly seen. The various features can be implemented individually or in combinations in variants of the invention.

[0026] The schematic drawing shows embodiments of the invention and explains them in more detail in the following description.

[0027] They show:

[0028] Fig. 1 shows a first embodiment of a current controller arrangement; and

[0029] Fig. 2 shows a second embodiment of a current controller assembly. Figure 1 shows a current controller assembly 10 for a lighting device assembly 12, wherein, in the illustrated embodiment, additional lighting device assemblies 14, 16 are also shown. In the illustrated embodiment, the lighting device assemblies 12, 14, 16 comprise series circuits of laser diodes 18. Other circuit configurations of the laser diodes 18 are also conceivable.

[0030] A DC voltage source 20 provides an upper voltage level 22 and a lower voltage level 24. The lower voltage level 24 is different from ground. In the embodiment shown in Figure 1, several current controllers 26, 28, 30 are provided, which are connected in parallel to the upper and lower voltage levels 22, 24. One of the lighting arrangements 12, 14, 16 is connected to the output of each of the current controllers 26, 28, 30.

[0031] Each current controller 26, 28, 30 has a converter 40, 42, 44, which in the exemplary embodiment are designed as buck converters. Each converter 40, 42, 44 has two switching elements S1, S2. An inductor 46, 48, 50 is connected between each of the switching elements S1, S2. The inductors 46, 48, 50 can be part of a low-pass filter. A current measuring device 52, 54, 56 is arranged at the output of the inductors and thus at the output of the current controllers 26, 28, 30. The current supplied by the current controllers 26, 28, 30 is measured by these current measuring devices 52, 54, 56 and fed to a control device 58. The control device 58 generates a control signal 60 of a predetermined frequency for the converters 40, 42, 44, taking into account the measured current. The switching elements S1, S2 of the different converters 40, 42, 44 can be controlled with a clock offset.

[0032] By adjusting the duty cycle of the control signal 60, which can have a frequency of 1 MHz, the current generated by the respective current controller 26, 28, 30 can be adjusted. It is therefore not necessary to provide an additional switch in series with the lighting arrangements 12, 14, 16. Furthermore, it is not necessary to measure a voltage and take it into account when generating the control signal. It can also be seen that the current controllers 26, 28, 30 are arranged in a floating manner. The converters 40, 42, 44 only need to switch the voltage difference between the upper voltage level 22 and the lower voltage level 24, corresponding to the voltage U2. As a result, the inventive concept has a high dynamic response and a high degree of efficiency.

[0033] In the embodiment of a current controller arrangement 10a according to Figure 2, a DC voltage source 20 is also provided, which provides an upper and lower voltage level 22, 24. In this embodiment, the current controller 26a assigned to the lighting device arrangement 12 has several converters 40, 40a, 40b connected in parallel to the upper and lower voltage levels 22, 24. Accordingly, inductors 46, 46a, 46b are connected downstream of the converters 40, 40a, 40b. Current devices 52, 52a, 52b are provided at the output of the inductors 46, 46a, 46b, respectively. The current measuring devices 52, 52a, 52b detect the output current at the respective inductors 46, 46a, 46b. In particular, the current measuring devices 52, 52a, 52b, as well as the current measuring devices 52, 54, 56 described in Figure 1, are arranged between the inductors 46, 48, 50, 46, 46a, 46b and the lighting arrangements 12, 14, 16.The detected current is taken into account by a control device 58 to generate a control signal 60 for the converters 40, 40a, 40b. The switching elements S1, S2 of the respective converters 40, 40a, 40b are controlled with a clock offset to reduce ripple.

Claims

Patent claims 1. Current controller arrangement (10, 10a) for a lighting device arrangement (12, 14, 16), in particular a laser diode arrangement, with a DC voltage source (20) which provides an upper and a lower voltage level (22, 24) different from ground, characterized by at least one current controller (26, 28, 30, 26a) connected to the DC voltage source (20) and having at least one converter (40, 42, 44, 40a, 40b) connected to the upper and lower voltage levels (22, 24), wherein a current measuring device (52, 54, 56, 52a, 52b) is provided which detects the output current of the current controller (26, 28, 30, 26a) and is connected to a control device (58) which generates a control signal (60) for the converter (40, 42, 44, 40a, 40b) are generated.

2. Current controller arrangement according to claim 1, characterized in that the converter (40, 42, 44, 40a, 40b) has at least one switching element (S1, S2) which is controlled by the control device (58).

3. Current controller arrangement according to one of the preceding claims, characterized in that the lower voltage level (24) is at least 65%, preferably at least 70% of the upper voltage level (22).

4. Current controller arrangement according to one of the preceding claims, characterized in that the current controller (26, 28, 30, 26a) is arranged floating.

5. Current controller arrangement according to one of the preceding claims, characterized in that the converter (40, 42, 44, 40a, 40b) is designed as a step-down converter.

6. Current controller arrangement according to one of the preceding claims, characterized in that the current controller (26, 28, 30, 26a) has an inductance (46, 48, 50, 46a, 46b), which is preferably a component of a low-pass filter.

7. Current controller arrangement according to one of the preceding claims, characterized in that the current controller (26a) has a plurality of converters (40, 40a, 40b) connected in parallel, which are controlled in a clock-shifted manner.

8. Current controller arrangement according to one of the preceding claims, characterized in that the current controller arrangement (10) has a plurality of current controllers (26, 28, 30) connected in parallel, which are controlled in a clock-shifted manner.

9. Method for operating a lighting arrangement (12, 14, 16), in particular a laser diode arrangement, comprising the following method steps: - providing a first and a second DC voltage level (22,24), - detecting the current at the output of a current controller (26, 28, 30, 26a), - generating a control signal (60) for controlling a converter (40, 42, 44, 40a, 40b) of the current controller (26, 28, 30, 26a) connected to the first and second voltage levels (22, 24) as a function of the measured current to generate a predetermined current through the current controller (26, 28, 30, 26a).

10. Method according to claim 9, characterized in that the duty cycle of the control signal (60) is adjusted as a function of the measured current.

11. Method according to claim 9 or 10, characterized in that the control signal (60) is generated with a frequency in the range 500kHz-2MHz, preferably 1MHz.

12. Method according to one of the preceding claims, characterized in that several converters (40, 42, 44, 40a, 40b) are controlled with clock-offset control signals (60).

Images