Abstract:
A circuit arrangement for selective powering of distributed loads (D 1 -D 7, 220 - 226, 213   a - 213   e ) is provided, comprising a plurality of load segments ( 10, 20, 30, 40, 50, 60, 70 ), each being electrically connected to at least one supply terminal al for receiving a variable voltage, wherein each load segment ( 10, 20, 30, 40, 50, 60, 70 ) comprises at least a load unit (D 1 -D 7, 220 - 226, 213   a - 213   e ) and a proximity sensor unit ( 11 ), coupled with said load unit and comprising at least a reactive device (L 1 -L 7 , L 1   a -L 7   a , C 1 -C 7 , C 1   a -C 7   a,    214   a - 214   e,    215   d ) having a reactance, said reactance depending on the proximity of a detection object ( 100, 102 ). In order to provide a simple and accurate way for user interactive powering of loads (D 1 -D 7, 220 - 226, 213   a - 213   e ), during operation an operating voltage is provided to at least one load unit (D 1 -D 7, 220 - 226, 213   a - 213   e ), depending on the reactance of at least one reactive device (L 1 -L 7 , L 1   a -L 7   a , C 1 -C 7 , C 1   a -C 7   a,    214   a - 214   e,    215   d ) of said load segments ( 10, 20, 30, 40, 50, 60, 70 ), so that said operating voltage depends on the proximity of said detection object ( 100, 102 ).

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is the U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/IB2012/056972, filed on Dec. 5, 2012, which claims the benefit of 61/569417, filed on Dec. 12, 2011. These applications are hereby incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The invention relates to a circuit arrangement for selective powering of distributed loads, an LED lamp and a method of selective powering of distributed loads. 
     BACKGROUND ART 
     With the increasing importance of LED-based lighting, LEDs already have a significant role in the area of decorative lighting. The low power consumption and long lifetime of LEDs make them a highly favorable choice for various applications. Moreover, LEDs having various colors are known in the art. It is also known, for instance, to combine red, green and blue LEDs to create the impression of a virtually unlimited variety of colors. 
     Especially when controlling numerous LEDs to create certain distributed effects, like LEDs on a string of lights or on a lighting surface, the cost of control electronics has to be taken into account. While relatively cheap LEDs are available today, a need exists to control the LED arrangement by means of simple and cheap control elements. 
     For decorative and/or user interactive LEDs and other kinds of loads, it is often desirable to detect the place where a certain effect is desired. For instance, in a string of 
     LEDs, one can think of a user indicating one or several LEDs to be activated, which indication is detected by some kind of sensor. After said detection, a driver or the like has to deliver the energy to this specific location. For many applications, resolution and accuracy requirements put on the detection are quite high, in order to avoid a mismatch between desired and realized effect. 
     For optical effects like the ones created with LEDs, the control may be based on cameras and a dedicated picture processing algorithm. In this case, good alignment can be expected. For other, non-optical effects, the determination of the actual effect position is quite complicated, so that there is hardly any possibility of applying a feedback signal to the controller. In addition to these control problems, the driver has to offer a high resolution in order to reproduce most of the desired effects at the specific location. 
     However, the detection and control devices known in the art are quite complicated, especially when a large area and/or many devices have to be controlled. This in turn leads to relatively high costs. 
     It is therefore an object of the present invention to provide cost-efficient and accurate means for user interactive powering of loads. 
     DISCLOSURE OF INVENTION 
     The problem is solved by a circuit arrangement according to claim  1 , an LED lamp according to claim  14  and a method according to claim  15 . 
     The basic idea of the invention is to provide operating power to multiple loads in a distributed arrangement in dependence on the physical proximity of a detection object to a proximity sensor unit comprising a variable reactance. When said detection object is present, a change in said reactance occurs, causing a change in an operating voltage for the load. This operating voltage may be decreased or, preferably, increased as a result of the presence of said detection object, thus providing power to the load. 
     The invention accordingly provides a circuit arrangement for selective powering of distributed loads. In this context, “distributed” means that the loads are positioned in different locations. They may be next to each other or spaced apart. They may in particular be arranged in a one-dimensional way, like on a string, or in a two-dimensional way. “Load” here and in the following refers to any device that consumes power when a voltage is applied to it. The power may be transformed into light, mechanical energy, heat etc. Preferably, the load unit is non-linear, i.e. the power consumption of the load exhibits a non-linear relationship with the applied operating voltage. 
     The circuit arrangement according to the invention comprises a plurality of load segments. Each load segment is electrically connected to at least one supply terminal for receiving a variable voltage, i.e., the supply terminal has to be suited for providing such a voltage. For example, the supply terminal may be permanently connected (e.g. by soldering) to a voltage supply or it may form a part of a plug-and-socket system, where the variable voltage is provided externally. A variable voltage in this case refers to an alternating voltage in the broadest sense, i.e. any voltage that changes over time, like sine wave, square wave, triangular wave, pulsed etc. Preferably, the variable voltage is a pulsed voltage, as will be discussed in the following. 
     Each load segment comprises at least a load unit and a proximity sensor unit. 
     In this context, a load unit can be any kind of device or part of a device that is a load in the abovementioned sense. It is conceivable that the circuit arrangement comprises loads that are not associated with a proximity sensor unit; these, however, are not regarded as a part of a load segment in the abovementioned sense. 
     The proximity sensor unit is coupled with said load unit at least during operation and comprises at least a reactive device. The reactive device has a reactance, which depends on the proximity of a detection object. The reactance of any—capacitive or inductive—device coincides with an electric or magnetic field that is generated by the device. This field may be modified by an object entering the field. For instance, a ferromagnetic object entering the magnetic field of an inductor will change said field, thereby changing the inductance of the inductor and thus changing its reactance. A similar effect occurs when a dielectric object enters the field of a capacitor. According to the invention, this effect is used to detect whether an object is in the vicinity of the reactive device or not. Within the scope of the invention, the reactance may be due to capacitance and/or inductance, e.g. the reactive device may comprise at least one capacitor and/or inductor having a variable reactance. 
     As will be explained below, it is preferred that the proximity sensor unit and the load unit to which it is coupled are disposed relatively close to each other. In this case, each load segment forms a “segment” in a spatial sense. However, it is also conceivable that there is no strict spatial relationship between the sensor unit and the load unit of one load segment. 
     It should be noted that it is within the scope of the invention that at least one load segment may comprise more than one load unit and/or more than one sensor unit. Also, a proximity sensor unit may comprise more than one reactive device. It is also within the scope of the invention that at least some reactive devices or different load segments are not separate components, but form a single entity. 
     During operation of the inventive circuit arrangement, an operating voltage is provided to at least one load unit, depending on the reactance of at least one reactive device of one of the load segments, so that said operating voltage depends on the proximity of said detection object. This means that the circuit arrangement is disposed such that the reactance of at least one reactive device affects the operating voltage supplied to at least one load unit. Preferably, the operating voltage is changed even if the voltage applied at the supply terminal is not changed. Since the above-mentioned voltages may be time-dependent, the change may refer to the time development, e.g. to the frequency, pulse width, pulse delay etc. 
     The operating voltage thus is controlled by the reactive device, so that advantageously no further driver electronics are necessary e.g. for processing a detection signal and controlling the operating voltage. Said control is provided by the load segments themselves by means of simple and cheap components, as will be explained below. The cost of an inventive circuit arrangement accordingly is proportional to the number of load segments. However, irrespective of whether only a few or hundreds of load elements are comprised, said control is always provided without the need for additional systems. Thus, the inventive circuit arrangement provides a very simple and cost-effective way of controlling loads. In one embodiment, the reactive device of a load segment controls the amount of power provided to the load unit in this segment. In another embodiment, the reactive device of a load segment influences a voltage signal, so that the power delivered to the load unit in a different segment is changed. 
     In operation, a suitable object may be placed near a reactive device, for instance a ferromagnetic object may be placed near an inductor. The magnetic field will be altered by the object, i.e. the inductance of the inductor and therefore its reactance will increase. As will be explained further with respect to preferred embodiments, the circuit arrangement is designed so that this change of reactance will lead to a change of the operating voltage applied to at least one load unit. In particular, the voltage change may be an increase which leads to an activation of the load unit. 
     Within the scope of the invention, the voltage applied to one load unit may depend on the reactance of several reactive devices. On the other hand, the reactance of one reactive device may influence the voltage applied to several load units. 
     In one embodiment of the invention, an operating voltage is provided during operation to the load unit of one of said load segments, depending on the reactance of the reactive device of said load segment. In this case, control is localised within each load segment, i.e. the proximity of said detection object to said one load segment causes a decrease or, preferably increase of an operating voltage that is provided at least to the load unit of the same load segment. Hence, each load segment may have its own, local control system, which can be very simple and which eliminates the need for complicated elements like processors or the like. However it is conceivable that here the operating voltage depends to some extent on the reactance of other reactive devices. 
     It is preferred that the sensor unit and the load unit of one load segment are located close or adjacent to each other. In this case, the effect (for instance, the activation) may occur next to the cause, i.e. where the object is placed. In other words, the “addressing” of a particular load is realized by interaction with an object in proximity to the circuit arrangement. 
     The inventive circuit arrangement is particularly useful if at least one of said load units is a solid state light generation unit and most preferably an LED unit. The LED unit may comprise one or more light emitting devices, which may be e.g. an inorganic LED, organic LED (OLED), a solid state laser or the like. However, additionally, each load element may comprise a loudspeaker, a vibration device (motor), a heating element, an energy transfer coil etc. It is also conceivable within the scope of the invention to combine different load units, for instance by using LEDs for some load units and vibration devices for others. Further, a load unit may be an LED unit and comprise e.g. a combination of an LED and a vibration device. If several devices are combined in one load unit, these may be connected in series and/or in parallel. Further elements may be present, e.g. elements to provide voltage or current to one of the load units in a load segment, based on the current consumption of another segment. This enables certain characteristics, e.g. nonlinearity of one load segment, to be “copied” to other load segments or the nonlinearity of one load to be copied to another load within the same load segment. A corresponding embodiment, which may include a current mirror device, will be explained in greater detail hereinbelow. 
     Furthermore, the load units do not necessarily form separate parts. In one preferred embodiment of the invention, at least some LED units form an integral part of one OLED. OLEDs having an extended planar structure can be produced. In this case, certain areas of the light-emitting plane may be selectively activated by locally applying a voltage. One or several of these OLEDs may be used and the reactive devices may form a grid or the like below or above the light-emitting plane. 
     In a preferred embodiment, the plurality of load segments are arranged in a spatial relation with each other adjacent to a detection area. In this detection area, a detection object can cause a change in the reactance of a reactive device. In this embodiment, the load segments may be spaced apart, or adjacent to each other or they may even form a single component. The latter may in particular apply to the load units of the load segments. The detection area may have different shapes. It may be planar, convex or concave. If the load segments are essentially aligned in a one-dimensional manner, the detection area can be narrow and elongate or even tubular, thus surrounding the load segments. 
     In particular, the sensor units of the load segments may be arranged adjacent the detection area. The detection area preferably corresponds to a surface of a device into which the circuit arrangement is integrated. In this case, the distance of an object from the surface corresponds to the distance from the respective load segment (or, in particular, the sensor unit). The load segments may also be arranged in a one-dimensional way along a detection axis, which may be straight or curved. In a two-dimensional arrangement, the sensor units and/or the load units may be arranged in parallel to a detection plane, for example along a first and a second perpendicular axis, i.e., the respective units may form a two-dimensional, “Cartesian” grid. 
     In a preferred embodiment of the circuit arrangement, a plurality of load segments comprise at least a first and a second segment input terminal and a first and a second segment output terminal, wherein the input terminals of a first load segment are connected to the at least one supply terminal. Further load segments are arranged so that their segment input terminals are connected to segment output terminals of a neighbouring load segment, i.e. the load segments are connected in series. Thus, a first propagation path for the variable voltage is formed by said first segment input and output terminals of said plurality of load segments. A second propagation path for said variable voltage is formed by the second input and output terminals of said plurality of load segments. Thus, the first segment input/output terminals and the second input/output terminals are the connection points of two linear or two-dimensional structures, and the variable voltage applied to the supply terminal may propagate from one segment to the next. Certainly, the first segment input/output terminals should be electrically connected with each other either directly or indirectly, i.e. using intermediate components. The same applies to the connection of said second segment input/output terminals. The propagation speed of the variable voltage signal—and its shape—can be modified, depending on the reactance of each load segment. This will be explained further below. 
     In the embodiment described above, the load unit is preferably connected between said first and said second propagation path. Preferably, the load unit can be connected between the first segment input terminal and the second input terminal of a given load segment or between the first segment output terminal and the second segment output terminal, i.e, between corresponding points of the two propagation paths. However, it may also be connected between the first segment input terminal and the second segment output terminal or even between terminals belonging to different load segments. 
     In one embodiment of the invention, the reactive device comprises at least a first reactive element. This reactive element may be an inductor or a capacitor. Herein, the first reactive element is arranged so that propagation of the variable voltage from one load segment to a neighbouring load segment is delayed, wherein the delay depends on the reactance of the first reactive element. In this embodiment, the speed of the variable voltage along one propagation path may be delayed depending on the reactance of the reactive element. It is particularly advantageous if the reactive device comprises an inductor and a capacitor. 
     In one embodiment, the reactive device further comprises a second reactive element, wherein the first and the second reactive element are disposed so that the proximity of the detection object has a greater influence on the reactance of the first reactive element than on the reactance of the second reactive element. Preferably, the first reactive element and the second reactive element are arranged so that the distance between the first reactive element and the detection area is less than the distance between the second reactive element and said detection area. Thus, an object placed in or near the detection area will usually have a greater influence on the reactance of the first reactive element. In particular, the influence on the second reactive element may be negligible. Therefore, if the two reactive elements correspond to different propagation paths, the delay in one propagation path will be more affected by the proximity of a detection object than the delay in the other propagation path. Hence, if the applied voltage is chosen properly, voltage differences between given points of the two paths will depend on the proximity of a detection object. 
     In a particularly preferred embodiment, the first reactive element is a first inductor that is arranged between the first segment input terminal and the first segment output terminal. Thus, the first inductor is connected “in series” with respect to the first propagation path. In this embodiment, the reactance of the first inductor depends on the proximity of a detection object. If the load unit is connected between the first and the second input (output) terminal and a voltage difference occurs between these terminals, this difference is applied to the load unit. The existence and strength of this voltage difference will depend on the propagation speed of the voltage signals in the respective propagation paths. This speed, in turn, depends on the delay caused by the reactance of the first inductor. 
     Alternatively or additionally, the first reactive element may be a first capacitor that is connected between said first propagation path and a reference terminal for a reference potential. Thus, the first capacitor is connected “in parallel” with respect to the first propagation path. In an operational state, the reference terminal is connected to this reference potential, which is preferably ground potential. The first capacitor can be connected between the first segment input terminal or the first segment output terminal and the reference terminal. Anyway, in this embodiment, the reactance of the first capacitor depends on the proximity of a detection object. 
     Preferably, the circuit arrangement further comprises a second inductor that is arranged between the second segment input terminal and the second segment output terminal. 
     Alternatively or additionally, the circuit arrangement may comprise a second capacitor that is connected between the second propagation path and a reference terminal for a reference potential. This reference terminal may be identical or different from the abovementioned reference terminal. Usually, both terminals will be identical and connected to ground potential. 
     According to one embodiment, the type and/or arrangement of the second inductor is identical to that of the first inductor or the type and/or arrangement of the second capacitor is identical to that of the first capacitor, respectively. More generally, the first and the second inductor (or capacitor, respectively) may be disposed so that they have the same effect on the propagation of the variable voltage signal. Thus, the two propagation paths may have identical conductive properties, as long as no detection object is present. 
     Operation of the circuit arrangement typically requires some kind of voltage supply. Preferably, the circuit arrangement comprises a driver unit, which is connected with the at least one supply terminal for providing at least one pulsed voltage signal to the load segments. The shape of the pulses may be e.g. rectangular, triangle-shaped, half-wave-shaped, Gaussian or other convenient shapes. The (temporal and spatial) distance of the pulses may advantageously be chosen such that if reflections occur in the circuit arrangement, no significant interaction between consecutive pulses is possible. It is within the scope of the invention that different pulsed signals are applied if several input terminals are present. 
     In particular, it is conceivable that two voltage signals are applied from opposite sides of the propagation paths, i.e. one signal may start in the first propagation path at the first load segment and a second signal may start in the second propagation path at the “last” load segment. This principle is described e.g. in WO 2010/064184. Superposition of the pulses may occur at a certain load segment and cause the activation of the load unit. If the speed of one signal is altered by the proximity of a detection object, the position of the “constructive” superposition will shift to a different load segment. 
     It is preferred that the driver is configured to provide pulsed voltage signals with a given time relationship to the first and second input terminals of said first load segment. The time evolution of the voltage at either input terminal may be the same, but the starting point of the time evolution may be different, i.e., the driver may apply some “offset” delay to one of the voltage signals. If there is no such delay and the signals are applied simultaneously, the initial conditions for each of the voltage signals are identical. Hence, if the following load segments are symmetric regarding the elements between the first segment input and output terminal on the one hand and the elements between the second input and output terminal on the other hand, the signals will propagate with equal speed and shape. Only if the reactance of a reactive device is changed, a delay and/or distortion of one signal may occur. However, it may be necessary to apply some offset delay at the first or second input terminal in order to compensate for some kind of unwanted delay effects occurring within the circuit arrangement. 
     In this case, it is possible to use pulsed voltage signals with an amplitude that is at least equal to a threshold voltage of the load element. The threshold voltage is a voltage which is critical for the activation of the load unit. Below the threshold voltage, there is no perceptible activation of the load. Therefore, in the abovementioned case, no voltage is applied to the load element if the pulses along the two propagation paths overlap completely, but a voltage above the threshold voltage may be applied if there is some delay in one of the pulses. 
     However, numerous other embodiments are conceivable. For instance, positive pulses in the first propagation path may be combined with negative pulses in the second propagation path. If these are applied with an “offset” delay, normally no overlap occurs. If the pulses overlap due to a delay by a detection object, the difference between the positive and negative pulses leads to effective adding of voltages which may activate the load element. 
     In another embodiment of the invention, the reactive device comprises at least a capacitor, which is arranged in series with the load unit. The capacitor will block any direct current, while its reactance will allow some frequency-dependent current flow if an alternating voltage is applied. Since the load unit is connected in series, the current flowing through it will be the same as that through the capacitor. Depending on the voltage applied, it is possible to choose the characteristics of the capacitor such that no perceptible activation of the load unit occurs without any object in the proximity. If a detection object enters the electric field generated by the capacitor, said field will be affected, leading to a change of the reactance of the capacitor. This, in turn, may lead to an increased current through the load unit, resulting in activation, e.g. lighting up of an LED. Usually, the detection object will increase the capacitance of the capacitor; therefore its reactance will be reduced when a detection object is in the proximity e.g. in a detection area. In this context, the detection object may be the hand or foot of a user, since the human body has a considerable relative permittivity, which will affect the reactance of the capacitor when placed in the field generated by said capacitor. 
     Preferably, the capacitor is configured so that the voltage applied to the load unit is below a threshold voltage if no detection object is in proximity to said load segment and said voltage is at least temporarily above said threshold voltage if said detection object is in proximity to said load segment in said detection plane. Thus, the load unit remains inactive if no object is in proximity to the load segment and will become active when an object comes near. If the load unit is an LED, the threshold voltage is the forward voltage. 
     There are several conceivable embodiments of a capacitor. In a preferred embodiment, the capacitor comprises first and second electrodes, which are disposed in the proximity of the detection area. More preferably, the first and second electrodes are planar-shaped and disposed in parallel to a two-dimensional detection area. In particular, the detection area itself may be planar. It is conceivable that the capacitors of several load segments have individual first (second) electrodes, while they share a common second (first) electrode. 
     As mentioned above, the invention is particularly useful for operation of LEDs. Therefore, the present invention also provides an LED lamp which comprises a circuit arrangement as depicted above. The surface of the lamp may correspond to a detection plane, on which an object —including the hand of a user—is placed to change the voltage applied to the individual LEDs, OLEDs or parts of an OLED. 
     The present invention further provides a method of selective powering of distributed loads with a circuit arrangement comprising a plurality of load segments, each being electrically connected to at least one supply terminal for receiving a variable voltage, wherein each load segment comprises at least a load unit and a proximity sensor unit, coupled with said load unit and comprising at least a reactive device having a reactance, said reactance depending on the proximity of a detection object. According to the inventive method, an operating voltage is provided to at least one load unit depending on the reactance of at least one reactive device so that said operating voltage depends on the proximity of said detection object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects, features and advantages of the present invention will be apparent from and elucidated with reference to the description of preferred embodiments in conjunction with the enclosed figures, in which: 
         FIG. 1  shows a first embodiment of a circuit arrangement according to the present invention; 
         FIG. 2  illustrates the propagation of pulsed voltage signals in the circuit arrangement of  fig.1  with no detection object present; 
         FIG. 3  illustrates the propagation of pulsed voltage signals in the circuit arrangement of  FIG. 1  in the presence of a detection object; 
         FIG. 4  shows a detail of a variant of the circuit arrangement shown in  FIGS. 1-3 ; 
         FIG. 5  schematically shows a perspective view of another embodiment of a circuit arrangement according to the present invention; and 
         FIG. 6  shows several different LED arrangements for the circuit arrangement in  FIG. 5 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a circuit arrangement  1  according to the present invention. The circuit arrangement  1  comprises seven load segments  10 ,  20 ,  30 ,  40 ,  50 ,  60 ,  70 , which are identical in setup. Therefore, only the setup of the first load segment  10  will be described in detail hereinafter. The first load segment  10  comprises a first segment input terminal  12 , a first segment output terminal  13 , a second segment input terminal  14  and a second segment output terminal  15 . In this case, the output terminals  13 ,  15  are identical to the input terminals  22 ,  24  of a second load segment  20 . 
     As can be seen from  FIG. 1 , the layout of the circuit arrangement  1  as well as that of the first load segment  10  are largely symmetric. A first inductor L 1  is connected between the first segment input terminal  12  and the first segment output terminal  13 , while an e.g. identical second inductor L 1   a  is connected between the second input terminal  14  and the second output terminal  15 . Further, a first capacitor C 1  is connected between the first segment output terminal  13  and a reference terminal  91 . Accordingly, a second capacitor C 1   a  is connected between the second segment output terminal  15  and the reference terminal  91 . At least in an operational state, the reference terminal  91  is connected to ground. The abovementioned inductors L 1 , L 1   a  and capacitors C 1 , C 1   a  constitute a proximity sensor unit  11 . The circuit arrangement  1  is disposed so that the first inductor L 1  is closer to a detection area than the second inductor L 1   a . The same applies to the respective inductors L 2  to L 7  and L 2   a  to L 7   a  in the remaining load segments  20 - 70 . If the circuit arrangement  1  is built into a device with a surface, the detection area may be located adjacently above the surface. 
     Along the first segment input and output terminals of the consecutive load segments  10 - 70 , a first propagation path for a variable voltage signal is formed, while a second propagation path for a variable voltage signal is formed along the second input and output terminals of the load segments  10 - 70 . In the embodiment shown, the first and second propagation paths are supplemented by two inductors L 8 , L 8   a , which are disposed opposite the first load segment  10 . 
     Referring to the first load segment  10  again, a LED D 1  is connected between the first segment output terminal  13  and the second segment output terminal  15 . The voltage applied to the LED D 1  is therefore identical to the difference between the voltages applied to the first and the second segment output terminal  13 ,  15 , or, more generally speaking, a voltage difference between the first and second propagation path. 
     The first and second input terminals  12 ,  14  are connected to a supply terminal  90 . In an operational state, the supply terminal  90  is connected to a driver unit (not shown), which is configured to apply a variable voltage signal being, according to the present example, a pulsed voltage signal. 
       FIG. 2  shows the propagation of said pulsed voltage signal through the first and second propagation paths if no detection object is present. In this case, the driver unit applies a negative rectangle pulse  300  to the supply terminal  90 . Accordingly, this pulse  300  is applied to the first and second segment input terminals  12 ,  14 . Due to the symmetrical layout of the two propagation paths, the propagation of the voltage signals will be identical. 
     In the upper part of  FIG. 2 , above the circuit arrangement, the time development of the voltage pulses  301  to  307  at the respective first segment output terminals is shown for certain time periods around the points in time t 1 , t 2 , t 3  etc., in which the voltage pulse passes the respective first segment output terminals. Accordingly, below the circuit arrangement  1 ,  FIG. 2  shows the time development of the voltage pulses  301   a  to  307   a  at the respective second segment output terminals for these time periods. Since, for instance, the LED D 1  of the first load segment  10  is connected between the first segment output terminal  13  and the second segment output terminal  15 , the difference of the voltage pulses  301 ,  301   a  occurring at these terminals  13 ,  15  is applied to the LED D 1 . However, since the reactance of the corresponding inductors L 1 , L 1   a  and that of the corresponding capacitors C 1 , C 1   a  is identical, the delay of the voltage signal by the first inductor L 1  and the first capacitor C 1  on the one hand and the second inductor L 1   a  and the second capacitor C 1   a  on the other hand is the same. Therefore, the difference between these voltages, which is applied to the LED D 1 , is zero. The same applies to the voltage difference in the other load segments  20  to  70 . This voltage difference is shown in the lowest part of  FIG. 2 . 
     This changes, however, if an object  100  with magnetic layer  101  enters the detection area, as shown in  FIG. 3 . In this case, the object  100  in the detection area is adjacent to the fourth to seventh load segments  40 ,  50 ,  60 ,  70 . Therefore, the inductance of the first inductors L 4 , L 5 , L 6 , L 7  of these load segments will be increased, which corresponds to an increase of the reactance. Since the second inductors L 4   a , L 5   a , L 6   a , L 7   a  of these load segments are disposed at a greater distance from the detection area, they are virtually unaffected by the presence of the detection object  100 . Therefore, the time evolution of the voltage pulses  304   a ,  305   a ,  306   a ,  307   a  at the respective second segment output terminals is unchanged in relation to  FIG. 2 . However, the voltage pulses  304 ,  305 ,  306 ,  307  at the respective first segment output terminals exhibit an increasing delay. Therefore, the difference between the voltages at the first and second segment output terminals, which is again shown in the lowest part of  FIG. 3 , is zero for the first three load segments  10 ,  20 ,  30 , but, for the fourth to seventh load segment  40 ,  50 ,  60 ,  70 , it exhibits negative pulses  304   b ,  305   b ,  306   b ,  307   b , which are followed by positive pulses  304   c ,  305   c ,  306   c ,  307   c . Since the amplitude of the pulse  300  is chosen to be above the forward voltage of the LEDs, the corresponding LEDs D 4 , D 5 , D 6 , D 7 —or at least some of them—will temporarily light up. The voltage applied to the load has both polarities. With the single LEDs D 1  to D 7  used here, only one polarity of the pulse will be used to generate light, while the LEDs D 1  to D 7  may have to be protected from the reverse bias voltage. As will be explained later in combination with a capacitive embodiment, both polarities of a load voltage may be used to power the LED by using extra components or multiple LED junctions. These methods can be applied here, too. 
     If the LED of each load segment is disposed near the respective proximity sensor unit, the light effect will appear at or near the location where the object  100  is placed. Therefore, “addressing” of the LED is achieved by very simple and cheap components. It is understood that although the above described embodiment comprises seven load segments, it is possible to include several tens or even hundreds of load segments. 
     It should be noted that the voltage pulses shown in the lowest part of  FIG. 3  do not take into account the power consumption of the LEDs when they light up. For ease of illustration, this influence has been neglected. 
     Now, referring to  fig.4 , there is shown a detail of an alternative embodiment of the circuit arrangement shown in  FIGS. 1-3 . In this embodiment the nonlinearity of the LED D 1  (a first load) of one load segment is “copied” to a second load R 1  in the same load segment. For the sake of clarity, only the part from the first and the second inductor L 1 , L 1   a  of the first load segment  10  to the first and second inductor L 2 , L 2   a  of the second load segment  20  is shown. The following load segments may be designed similarly. 
       FIG. 4  illustrates a unipolar embodiment, which employs a current mirror device formed by two transistors Q 1 , Q 2 . As shown in  FIG. 4 , the current into the LED D 1  flows through one leg (collector) of a first transistor Q 1  of the current mirror device Q 1 , Q 2 . The second load R 1  (schematically shown as a resistor), which does not show a nonlinear behaviour, is connected to the second leg (collector) of a second transistor Q 2  of the current mirror device. As long as there is no current through the LED D 1 , there will also be no current in the second load R 1 , regardless of the characteristic of the second load R 1 . As soon as there is a current flow in the LED D 1 , there may also be a current in the second load R 1 . Accordingly, the nonlinear behaviour of the LED D 1  is “copied” to second load R 1 . 
     The maximum current in the second load R 1  will be the minimum of a) the original load current of the second load R 1  at the current voltage in the second load segment  10  and b) the current in the LED D 1  multiplied by the current transfer ratio of the current mirror Q 1 , Q 2 . 
     Alternative embodiments may include a current measuring resistor in series with the LED D 1 , and a controlled current or voltage source for setting the current in the second load. 
     Besides the current ratio, also additional offsets may be introduced, e.g. by having diodes in series with the second load R 1 . 
     Referring to  FIG. 5 , there is shown a different embodiment of a circuit arrangement  201  according the present invention, which is shown in a perspective view. Herein, the reactive elements are constituted by a plurality of capacitors. These capacitors are constituted by a series of primary electrodes  230  to  236  which are disposed in parallel to a two-dimensional detection area. Next to these primary electrodes, a secondary electrode  237  is also disposed in parallel to the detection area. This means that the capacitors have one common secondary electrode  237 . Alternatively, individual secondary electrodes might be used. The secondary electrode  237  is connected to a first terminal  281  of a driver unit  280 . Each of the primary electrodes  230  to  236  is connected in series with a load unit  220  to  226 , which is in turn connected to a second terminal  282  of the driver unit  280 . For instance, the first primary electrode  230  is connected in series with a first load unit  220 . Herein, the load units  220  to  226 , which are only schematically shown, can be e.g. LED units. 
     In an operational state, the driver unit  280  applies an alternating voltage to its terminals  281 ,  282 , which may be sine-shaped. The size and arrangement of the primary and secondary electrodes are chosen so that the capacitance of the capacitors is rather low. Therefore, the reactance of the capacitor is rather high, which results in a rather low voltage applied to the load unit. If the load units  220  to  226  are LED units, an off state of the LED can be assured by using additional load elements, such as resistors, to bypass small signals. If, however, a dielectric object, like a hand  102  of a user, is in proximity to the primary and secondary electrodes, the capacitance is increased and the reactance is decreased. Hence, the voltage applied to the load unit becomes higher which may lead to its activation.  FIG. 5  shows a hand  102  of a user placed over several primary electrodes  230 ,  231 ,  232 ,  233 , which leads to the activation of the corresponding load units  220 ,  221 ,  222 ,  223 . For instance, LEDs comprised in the load units may light up where the hand  102  of the user is close to the surface in which the circuit arrangement  201  is embedded. 
       FIG. 6  shows different diode arrangements that may be used as load units  220  to  226 , e.g. in the circuit arrangement in  FIG. 5 . For ease of illustration, the different load segments  213   a  to  213   e  are shown as parts of one circuit. However, in a circuit arrangement as shown in  FIG. 5 , usually only one type of load segment is used. 
     A first load unit  213   a  comprises two anti-parallel LEDs. This is the simplest design that allows lighting of one LED irrespective of the voltage polarity. The primary and secondary electrodes and the detection object (hand of a user) are schematically represented by an adjustable capacitor  214   a . Here, a resistor my be placed in parallel with the two LEDs to ensure off state or a dim light level when no object is in the detection area. 
     In a second load unit  213   b , the two anti-parallel LEDs are connected in series with a resistor R, which may serve to limit the current through the LEDs. In a third load unit  213   c , each of the anti-parallel LEDs is replaced by two LEDs connected in series. The third load unit  213   c  is connected in series with an adjustable capacitor  214   c  and a non-adjustable capacitor  215   c . However, a non-adjustable capacitor may also be employed in connection with the other load units shown. In a fourth load unit  213   d , an LED is integrated into a bridge rectifier. Here, both terminals of the rectifier are connected to adjustable capacitors  214   d ,  215   d . Again, two adjustable capacitors may also be used in connection with the other load units shown. In a fifth load unit  213   e , four LEDs serve as diodes for a bridge rectifier. 
     It should be noted that the load units  213   a  to  213   e  shown in  FIG. 6  could also be used in the circuit arrangement of  fig.1  instead of the single LEDs. 
     Other variations to the disclosed embodiments can be understood and effected by those skilled in the art of practicing the claimed invention from the drawings, the disclosure and the appended claims. 
     In the foregoing description and in the appended claims, a reference to the singular is also intended to encompass the plural and vice versa and reference to a specific number of features or devices is not to be construed as limiting the invention to the specific numbers of features or devices. Moreover, expressions such as “include” or “comprise” do not exclude other elements and the indefinite article “a” or “an” does not exclude a plurality. 
     The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.