Abstract:
An LED power supply device may include a power supply to control an LED component, a control unit to control the power supply, the control unit having a control interface for applying external control signals to the power supply, and a voltage supply unit connected to a connection of the power supply, wherein the control unit receives operating voltage from the voltage supply unit for continuous operation in an activated and non-activated control state of the LED component, wherein the voltage supply unit comprises a capacitor coupled to an output side of the power supply, the capacitor configured to supply a capacitor voltage as operating voltage to the LED power supply device, and wherein the control unit is configured to charge the capacitor using pulse-like control of the power supply such that, in the non-activated control state, a maximum charging voltage lies below the LED threshold voltage.

Description:
BACKGROUND 
       [0001]    The present invention relates to an LED power supply device. An exemplary power supply device is described in EP 1 374 366 B1 which is used to minimize the standby power requirements in a digital addressable lighting interface (DALI). DALI refers to an industrial standard used for implementing flexibility in the control of luminaries. In particular, the DALI standard specifies how to control and monitor the status of individual and group addressable lighting equipment such as electronic ballasts and illumination sensors. 
         [0002]    An arrangement of an LED power supply device is shown in  FIG. 4  according to the prior art. The arrangement includes a two-stage power supply device consisting of a primary stage  10 , which is regulated and provided with a power factor correction and a secondary stage  14  which is coupled to the primary stage  10  via a transformer unit  12 . The secondary stage  14  is connected at the output side via an output  16  to a power consumer (not shown) that receives power from the power supply device, such as an LED. An output-side smoothing capacitor  18  is provided to ensure that a direct signal that is output from secondary stage  14  is stripped of high-frequency components. 
         [0003]    The primary stage  10  of the power supply arrangement of  FIG. 4  is controlled by a control unit  20 , which is in turn coupled via an interface module  24  to a DALI input connection (DALI line)  22 . In addition, a voltage supply module  26  is coupled to the control unit  20 , and receives supply voltage from the power supply input connection (Mains)  28 . The voltage supply module  26  is connected in such a manner that the control unit  20  can be kept in continuous operation. This arrangement makes it possible to respond at any time to control request or status commands received via the DALI interface  24 , particularly during periods when the power supply components  10 ,  12 ,  14  and the power consumer coupled to the output  16  are deactivated. 
         [0004]    In a prior art power supply device of the type shown in  FIG. 4 , which embodies the basic principle set forth in EP 1 374 366 B1, a microcontroller is typically used to form the control unit  20  or DALI interface unit  24 . Notably, to achieve continuous operation, the voltage supply unit  26  draws electrical power from the power supply input  28 . This arrangement is disadvantageous in at least two respects. On the one hand, additional design or circuit outlay is used to support the continuous supply of voltage to the control unit  20 . Additionally, the energy balance of a control device constructed in this manner may degrade due to the continuous electrical power consumption, particularly during off, idling or standby operating states of a power consumer connected at the output side  16 . This is critical particularly for those arrangements in which the idling, standby or off phases are relatively long in comparison to activation phases, which may lead to the mean power drawn from the mains exceeding predetermined limits. 
       SUMMARY 
       [0005]    It is therefore the object of the present invention to simplify design of an LED power supply device and ensure a permanent operational readiness of the control unit assigned to a power supply, and in particular to make the LED power supply device DALI compatible. As a result, a mean power consumption may be lowered, particularly for devices having alternating activation and deactivation (standby) periods. 
         [0006]    These objects are achieved by means of an LED power supply device whose features are set forth below and recited in the present claims. Advantageous embodiments are described in the dependent claims. 
         [0007]    In contrast to the prior art, in the present embodiments, the operating voltage of the control unit is advantageously drawn from the output of a power supply rather than from the input. More specifically, the operating voltage of the control unit is drawn from a capacitor voltage of a smoothing-and-buffer capacitor that is located at the power supply output connection to a load, such as an LED means (also referred to herein as an “LED component”). 
         [0008]    In accordance with the present embodiments, this arrangement enables the power supply output voltage to be used as a “voltage supply unit,” so that no separate current supply unit is necessary. Rather, the function of the current supply unit is accomplished by providing suitable functionality of the power supply itself. In this arrangement, the property of the LED component located at the output to act as a load may be exploited. In particular, at voltage levels below the LED threshold voltage, the lighting means are deactivated, i.e., no lighting operation takes place. At the same time, by providing suitable pulse-like control of the control unit, an output voltage signal of the power supply may be used to load the output-side smoothing-and-buffer capacitor. The output-side smoothing-and-buffer capacitor is loaded in such a manner that its capacitor voltage is sufficient to maintain the desired continuous operation of the control unit even though the capacitor voltage remains below the LED threshold voltage. 
         [0009]    Therefore, the present embodiments advantageously exploit the ability of a smoothing capacitor (which is typically already present in LED power supply devices and has a large capacitance) to act as a voltage supply of the control unit. In particular, in preferred embodiments, the output-side capacitor is provided with charge pulses that serve two purposes. Firstly, in order to maintain an OFF or standby state, the charge pulses are provided in a manner that prevents the capacitor voltage from reaching the LED means threshold voltage. At the same time, the charge pulses are provided in a manner that maintains the capacitor voltage at or above the minimum operating voltage necessary for continuous operation of the control unit. 
         [0010]    According to preferred embodiments, regular periodic charge pulses are used to charge the output-side capacitor. In various embodiments, the ratio of pulse duration (that is, the ON portion of a pulse period) of charge pulses of this type to a total pulse period length is typically below 10%, further preferably below 5% and even further preferably below 2%. 
         [0011]    In preferred embodiments, the arrangement of  FIG. 1  is used in conjunction with (LED) switching power supplies, which are constructed as single phase at the primary stage and preferably employ a power factor correction (PFC). A secondary stage is coupled to such a primary stage through a transformer unit, and typically includes rectifier means. An output-side capacitor that functions as a smoothing-and-buffer capacitor is connected downstream of the secondary stage. For power supplies having a single phase primary stage, the present embodiments are particularly advantageous, since component and control outlay is considerably reduced compared to conventional designs. Thus, noticeable savings result for power supply costs. 
         [0012]    Another advantage provided by the present embodiments is that voltage is supplied to the control unit via an output side voltage supply. Therefore, when the control unit accesses the primary stage of the power supply, it is galvanically isolated from the primary stage along a suitable control line. In some embodiments, this may be accomplished using optocouplers or other devices. For an output that is galvanically isolated from the mains, it is possible to arrange a set of series-connected LEDs so that the total voltage does not exceed the level of 60V. This keeps the total voltage in conformance with the safety extra low voltage (SELV) standard, which enables simpler and less costly mounting of the LED lighting on a heat sink. 
         [0013]    In preferred embodiments, a DALI interface is coupled to the control unit. In this respect, EP 1 374 366 B1 and corresponding U.S. Pat. No. 6,762,570 provide an exemplary DALI specification and are incorporated by reference herein in their entirety. In other embodiments, the LED power supply device may employ other control and/or interface configurations. Moreover, the present embodiments also cover other power supply consumers that behave in the manner of an LED, such that operation does not take place below a threshold voltage, but which nonetheless enable continuous operation of a control unit that is buffered by an output capacitance. 
         [0014]    Whilst in some embodiments an LED means (component) may be provided in the form of an individual (performance) LED, preferably an LED component contains a group of LED semiconductors (or “LEDs”) that are arranged in a series circuit for providing a load. An overall threshold voltage for the LED component thereby results from the sum of the individual threshold voltages of the group of LED semiconductors. In these embodiments, LED series circuits of between 3 and 20 individual LEDs, preferably between 4 and 12 individual LEDs, have proven particularly beneficial. 
         [0015]    Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments, as well as on the basis of the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows a block diagram of an LED power supply device according to a first preferred embodiment; 
           [0017]      FIG. 2  shows an exemplary flow chart depicting a charging operation mode of the output-side capacitor for supplying voltage to the control unit during a deactivated operating state (standby) of the attached LED load; 
           [0018]      FIG. 3  shows an exemplary signal diagram for showing a curve of the capacitor voltage (upper part of  FIG. 3 ) in the standby state relatively to charge pulses connected through the control unit (lower part of  FIG. 3 ); 
           [0019]      FIG. 4  shows a block diagram analogous to  FIG. 1  for illustrating an LED power supply device of a conventional type. 
       
    
    
       [0020]    For the further description, the reference numbers used in connection with   FIG. 4  apply analogously for corresponding components or functional groups. 
       DETAILED DESCRIPTION 
       [0021]      FIG. 1  shows an LED power supply device (also referred to herein as “power supply apparatus”) as an exemplary embodiment. The terms “power supply device” and “power supply apparatus,” as used herein, generally refer to equipment that includes a power supply as well as additional components such as a controller, as detailed further below. The term “power supply,” on the other hand, as used herein may refer specifically to components such as a primary stage, secondary stage and transformer, without necessarily including controller and other components. As seen in  FIG. 1 , the LED power supply device includes a primary stage  10  and a secondary stage  14  of a power supply. The secondary stage  14  is connected downstream to the primary stage  10 , via a transformer unit  12 .  FIG. 1  further illustrates an output-side smoothing-and-buffer capacitor (CBULK)  18 , which is arranged electrically parallel to a pair of output connections  16 . 
         [0022]    In various embodiments, at the output connections  16  an LED component (not shown) is provided. In one example, an LED component may include a series connection of six performance LEDs, which enable a luminous power of approximately 60 watts. The cumulative threshold voltage of this series arrangement lies in the range of approximately 17 to 18 volts. 
         [0023]    As shown in the exemplary embodiment of  FIG. 1 , the primary stage  10  of the power supply comprises a single-phase switching power supply having power factor correction (PFC), which may occur in response to a current-setting signal sent via a control line pair  30 . As illustrated, the current-setting signal is sent via an optocoupler unit  32  from a control unit  20 . Upstream of the control unit  20  is a DALI interface that includes an interface module  24  and an interface-compliant two-wire connection  22  connected in the previously described manner. In addition, the control unit  20  is coupled via a standby control line  34  and optocoupler  36  to the primary stage  10 . Using control line  34 , the power supply can be placed into a deactivation state. In particular, the optocoupler  36  may digitally decouple the control unit  20  from the primary stage  10  using an ON/OFF signal. For example, when the optocoupler  36  is actively controlled the power supply is placed in an “OFF” state. 
         [0024]    In different embodiments, the power supply components  10 ,  12 ,  14  may be arranged differently. In one example, the capacitor  18  has a typical capacitance of 18,000 μF. An exemplary implementation of the power supply components  10 ,  12 ,  14  is disclosed in EP 2 259 415 A2 and corresponding U.S. Pat. No. 8,098,506, and in particular,  FIG. 1  therein. In particular, the unit  116  of  FIG. 1  of EP 2 259 415 A2 may be implemented in the manner disclosed in  FIG. 1  of EP 2 270 965 and corresponding U.S. Pat. No. 7,110,270, which together with U.S. Pat. No. 8,098,506, are incorporated by reference herein in their entirety. Advantageously, the primary power stage enables a single phase design with a PFC function, without incurring a significant current inrush, since no energy storage occurs on the primary side. Thus, advantageously, a beneficial load factor can be achieved, in addition to reduced loading of the current supply of the control unit  20 , as explained below. Moreover, this facilitates the delivery of a maximum permissible harmonic portion of the current drawn from the mains (standard EN61000-3-2 class C for lighting devices). 
         [0025]    The control unit, which in the present embodiments is provided on the secondary side, is coupled to the capacitor voltage of the output side smoothing-and-buffer capacitor  18 . As  FIG. 3  details, the capacitor voltage is always held above an operating voltage minimum (dashed line  40 ) and also kept below the (cumulative) LED threshold voltage  42  during the deactivated lighting state of the LED component. 
         [0026]    In one exemplary implementation, charging of the capacitor unit  18  occurs as follows: during the standby operation of the capacitor  18  shown in  FIG. 3 , charging is carried out using pulses of the power supply arrangement  10 ,  12 ,  14 .  FIG. 3  depicts a set of regular pulses  44 , which result in a steep ramp increase (for example, approximately 2 to 3 msec in duration)  46  to an upper ramp voltage (shown as “upper limit” in  FIG. 3 ). This upper ramp voltage may have a value of approximately 15 volts, which lies below the threshold voltage  42 , which may be approximately 17 to 18 volts. At the end of the ON portion of a pulse  44 , the capacitor voltage falls during the duration of the OFF portion along a relatively long ramp  47  (for example, approximately 3 to 5 sec), until a subsequent pulse  44  raises the capacitor voltage again. As illustrated, each subsequent pulse  44  is generated before the capacitor voltage reaches the lower operating threshold  40 . In various embodiments, a duty cycle for the ON portions of  FIG. 3  is approximately 5%, preferably less than 2%, further preferably below 1%. 
         [0027]    The operation depicted in  FIG. 3  indicates that although the primary stage  10  is activated briefly during the ON periods, during the longer OFF state of the LED at the output  16 , the power supply arrangement  10 ,  12 ,  14  is deactivated. In the typical case where the ON:OFF ratio is less than 5%, and in the optimum case less than 1%, the average current uptake of the control unit is substantially lower than the nominal load current for controlling the LED load. The averaged energy consumption of the voltage supply operation shown in  FIG. 3  thus results in a very low mean power draw from the mains. In particular the mean power draw from the mains may lie below the idling power consumption required by relevant guidelines. 
         [0028]    In this manner, since the power supply components themselves perform the role of voltage supply unit in connection with the capacitor  18 , additional circuit outlay for a voltage supply unit for the control unit  20  is dispensed with. Moreover, the commonly used capacitor  18 , which typically has a large capacitance, is synergistically employed to enable the supply of voltage to the control unit  20  as described above. 
         [0029]      FIG. 2  illustrates an exemplary method which may be implemented by means of a software routine. In one example, the software routine is executed by control unit  20  that is embodied as a microcontroller. Referring also to  FIGS. 1 and 3  by way of example, a standby state (corresponding to a predetermined signal level) is entered at block  50 . In one implementation, a standby command is sent via the DALI interface  22 ,  24  to a control unit, such as control unit  20 . Subsequently, a check is carried out within a first decision loop  52  as to whether the capacitor voltage (U-Bulk) at the output capacitor (see capacitor  18 ) lies below the operating voltage limit  40  for a voltage supply, such as the voltage supply of the control unit  20 . Thereupon, if the operating voltage is below the operating voltage limit, the primary stage, such as primary stage  10 , is activated using a control unit, such as control unit  20 . In this manner, as illustrated by the increasing signal  46  in  FIG. 3 , the capacitor voltage increases and may continue to do so until an upper threshold is reached. 
         [0030]    At decision step  54  a determination is made as to whether the capacitor voltage has reached or exceeded the upper threshold (see threshold  42  of  FIG. 3 ). If, at decision step  54 , the capacitor voltage is reached or exceeded, the method proceeds to step  56 , where the charging process is ended (power OFF). The method then proceeds to decision loop  58 . In accordance with decision loop  58 , as long as the power supply device remains in standby operation and is not switched on again, the method branches back to decision step  52 . If an ON command is received, the method proceeds to exit the standby mode. 
         [0031]    In the manner disclosed hereinabove, by use of a two stage power supply arrangement, and without any additional power supply unit, a control unit of a power supply apparatus is maintained in continuous operation at an operating voltage below a lighting and response threshold voltage for the lighting means load. Because of the very short switch-on times for the minimum voltage required to maintain the capacitor charging or control unit operating voltage, the effective power consumption due to this additional operating mode remains negligible. 
         [0032]    In addition, as illustrated in  FIG. 1 , because of the galvanic isolation of the controller from the network, in some embodiments, an additional input connection  70  may be provided for the control unit. As depicted in  FIG. 1 , the input connection  70  can be supplied with a voltage, PWM signal or resistance wiring. This may be useful, for example, for enabling a dimming operation of the power supply, in the event that no DALI (or other) interface to control the lighting means is connected to the power supply device. 
         [0033]    Notably, the present invention is not limited to the exemplary embodiments shown. Although the present invention is in particular beneficial for use together with a DALI interface, as described hereinabove, any desired additional configurations of the control unit  20  can be provided to enable a permanent (continuous) operating voltage supply (and therefore reaction readiness) of a power supply during standby operation of an appended load. 
         [0034]    The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. In particular, embodiments in which various configurations of extraction electrodes and plasma chamber in order to provide a desired ion beam for implantation into a substrate are possible. Moreover, an embodiment in which the plasma potential is modulated at various power levels and frequencies is also possible. In addition, embodiments are contemplated in which substrate movements can be either continuous for blanket implants or stepwise for selective emitter implantation. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Thus, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.