Patent Publication Number: US-11394294-B2

Title: Systems and methods for alternating current (AC) input selection for power transformer

Description:
PRIORITY APPLICATION 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/939,936, filed Nov. 25, 2019, and entitled “SYSTEMS AND METHODS FOR ALTERNATING CURRENT (AC) INPUT SELECTION FOR POWER TRANSFORMER,” the contents of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The disclosure relates generally to distribution of power to one or more power consuming devices over power wiring and, more particularly, to power conversions that may occur from an external power source for use by remote units of a distributed system, and more particularly to a connector used to provide a voltage level selection to a power converter. 
     Electrical power consumption is prevalent throughout modern society. Provision of electrical power requires power generation and power delivery through a power grid to a destination, where the power must be conditioned to an appropriate level for use at the destination. In some instances, the destination is merely an intermediate destination, with further downstream destinations. In such a case, power may be passed on through a sub-network or sub-grid to such further downstream destinations. 
     In most power grid systems, the electrical power is sent at relatively high voltages and low currents in an alternating current (AC) format so that power losses on transmission lines are kept comparatively low pursuant to Ohm&#39;s Law relating to power dissipation (e.g., for a simple model, power dissipated equals the square of current multiplied by resistance (i.e., I 2 R)). This high voltage signal is then converted to a lower voltage level suitable for use at the destination. When there are further downstream destinations, additional power loss may occur at voltage level conversion. 
     A few exemplary destinations that have further downstream destinations include remote lighting systems, data centers, and distributed communication systems. In most cases, the power arrives from the power grid at a relatively high AC voltage and is converted to direct current (DC) with an adjusted voltage level. The circuitry to perform such conversions induces power loss in the form of heat because of low efficiencies. Further, such circuitry is typically expensive because it operates in relatively high frequencies to conserve space and may be temperature limited. For example, many commercial products for such circuitry begin to become increasingly less efficient at temperatures above fifty degrees centigrade (50° C.) and even more steeply less efficient at temperatures above seventy-five degrees centigrade (75° C.). Some implementations have implemented air conditioning or heat exchangers to help ameliorate these heat limitations, but both solutions impose penalties in terms of cost, size, and/or providing additional potential points of failure. 
     The inventors of the present disclosure have previously proposed an improved power conversion system for use with a reduced cost of installation (capital expense) as well as a reduced operating expense profile. While the previous disclosure does meet those needs, the previous disclosure has room for improvement at the input point where an external power line couples to the power conversion system. 
     No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents. 
     SUMMARY 
     Embodiments of the disclosure relate to systems and methods for an alternating current (AC) input selection for a power transformer. In particular, a connector is provided that is pre-wired to utilize internal wiring in the power transformer to provide a desired connection. A first option allows two transformers&#39; input winding to be in series while a second option allows the two transformers&#39; input winding to be in parallel. By moving the wiring into the connector, installation is simplified as the wiring has already been done. The installer need only attach the correct plug based on the desired voltage and couple the plug to the transformer. Further, the manipulation of thick wires is also avoided by the installer, further simplifying the installation process. 
     One embodiment of the disclosure relates to a power distribution system comprising a power management circuit (PMC). The PMC comprises a power source input port configured to receive an AC power signal from an external power grid. The PMC also comprises a transformer for providing isolation between the external power grid and a power distribution line. The transformer comprises a transformer input port coupled to the power source input port. The transformer input port comprises a connector having a first half and a second half. The first half is selectively removable from the second half. The first half contains a jumper. The transformer also comprises two input coils coupled to the second half of the connector of the transformer input port, at least one output coil coupled to the two input coils, and a transformer output port coupled to the at least one output coil. The PMC also comprises a rectifier coupled to the transformer output port and a power factor correction (PFC) converter coupled to the rectifier. The PFC converter is configured to be coupled to a power load. 
     An additional aspect of the disclosure relates to a method for conditioning power for provision to a distributed power network. The method comprises receiving an AC power signal from a power grid at a transformer input port comprising a connector. The method also comprises passing current through a jumper in a first half of the connector to a second half of the connector. The method also comprises passing the current to two input coils in a transformer from the second half of the connector. The method also comprises isolating a PMC from the power grid with the transformer. The method also comprises rectifying an output of the transformer to provide a rectified signal. The method also comprises performing a PFC conversion on the rectified signal. The method also comprises providing power. 
     An additional aspect of the disclosure relates to a distributed communication system (DCS). The DCS comprises a central unit. The central unit is configured to distribute one or more downlink communication signals over one or more downlink communication links to a plurality of remote units. The central unit is also configured to distribute received one or more uplink communication signals from the plurality of remote units from one or more uplink communication links to one or more source communication outputs. The DCS also comprises the plurality of remote units. Each remote unit among the plurality of remote units is configured to distribute at least one received downlink communication signal among the one or more downlink communication signals from the one or more downlink communication links to one or more client devices. Each remote unit among the plurality of remote units is also configured to distribute the one or more uplink communication signals from the one or more client devices to the one or more uplink communication links. The DCS also comprises a power distribution circuit. The power distribution circuit comprises a power source input port configured to receive an AC power signal from an external power grid. The power distribution circuit also comprises a transformer for providing isolation between the external power grid and a power distribution line. The transformer comprises a transformer input port coupled to the power source input port. The transformer input port comprises a connector having a first half and a second half. The first half is selectively removable from the second half. The first half contains a jumper. The transformer also comprises two input coils coupled to the second half of the connector of the transformer input port, at least one output coil coupled to the two input coils, and a transformer output port coupled to the at least one output coil. The power distribution circuit also comprises a rectifier coupled to the transformer output port and a PFC converter coupled to the rectifier. The PFC converter is configured to be coupled to a power load. 
     Additional features and advantages will be set forth in the detailed description which follows and, in part, will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understand the nature and character of the claims. 
     The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and operation of the various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram of an exemplary distributed communication system (DCS) in the form of a distributed antenna system (DAS) illustrating a remote power source delivering power to a remote antenna unit (RAU); 
         FIG. 1B  is a schematic diagram of an exemplary data center illustrating a remote power source delivering power to a data server; 
         FIG. 1C  is a schematic diagram of an exemplary distributed lighting system illustrating a remote power source delivering power to a remote lightning element; 
         FIG. 2  is a schematic diagram of a conventional power conversion element at a remote power source with an inefficient transfer mechanism; 
         FIG. 3  is an exemplary schematic diagram of an efficient power conversion element according to an exemplary aspect of the present disclosure; 
         FIG. 4A  is a simplified illustration of a parallel input transformer for use in the power conversion element of  FIG. 3 ; 
         FIG. 4B  is a simplified illustration of a series input transformer for use in the power conversion element of  FIG. 3 ; 
         FIG. 4C  is an exemplary wiring diagram for a first connector to achieve a 110 Volt (V) connection with the windings in series; 
         FIG. 4D  is an exemplary wiring diagram for a second connector to achieve a 220 V connection with the windings in parallel; 
         FIG. 4E  illustrates perspective views of an exemplary connector that may house the wiring arrangements of  FIGS. 4A-4D ; 
         FIGS. 5A-5C  are various views of an exemplary power conversion element installed in an outdoor environment; 
         FIG. 6  is a flowchart illustrating an exemplary process of the power conversion element of  FIG. 3  converting power to a desired level for use by a distributed power system; 
         FIG. 7  is a schematic diagram of an exemplary optical-fiber based DCS in the form of a DAS that includes a power conversion element according to the present disclosure; 
         FIG. 8  is a schematic diagram of an exemplary building infrastructure with a deployed DCS and a power conversion element such as that proposed in  FIG. 3 ; 
         FIG. 9  is a schematic diagram of a power distribution system in a DCS according to an exemplary aspect of the present disclosure; and 
         FIG. 10  is a schematic diagram of a generalized representation of an exemplary computer system that can be included in any component in a power distribution system, wherein an exemplary computer system is adapted to execute instructions from an exemplary computer-readable link. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the disclosure relate to systems and methods for an alternating current (AC) input selection for a power transformer. In particular, a connector is provided that is pre-wired to utilize internal wiring in the power transformer to provide a desired connection. A first option allows two transformers&#39; input winding to be in series while a second option allows the two transformers&#39; input winding to be in parallel. By moving the wiring into the connector, installation is simplified as the wiring has already been done. The installer need only attach the correct plug based on the desired voltage and couple the plug to the transformer. Further, the manipulation of thick wires is also avoided by the installer, further simplifying the installation process. 
     Before addressing particulars of the present disclosure, a brief discussion of power distribution systems that may benefit from the present disclosure is provided with reference to  FIGS. 1A-1C . To further assist in understanding the advantages and differences of the present disclosure, a conventional power management circuit (PMC) is described with reference to  FIG. 2 . A discussion of the PMC that may use the present disclosure that is used in the systems of  FIGS. 1A-1C  begins below with reference to  FIG. 3 . Exemplary connectors according to the present disclosure are discussed beginning below with reference to  FIG. 4C . 
     In this regard,  FIG. 1A  illustrates a simplified block diagram of a distributed communication system (DCS)  100 . The DCS  100  may include a head end unit (HEU)  102  that communicates through a communication medium  104  with a remote antenna unit (RAU)  106 . The communication medium  104  may be a wire-based or optical fiber medium. The RAU  106  includes a transceiver and an antenna (not illustrated) that communicate wirelessly with mobile terminals and other user equipment (also not illustrated). Because the RAU  106  sends and receives wireless signals and may potentially perform other functions, the RAU  106  consumes power. That power may, in some instances, be provided locally. More commonly, the RAU  106  receives power from a power source  108  that transmits power to the RAU  106  over power lines  110  formed from a positive power line  110 + and a negative power line  110 −. The power lines  110  may be many meters long, for example, extending through an office building, across multiple floors of a multi-story building, or the like. Further, the power lines  110  may couple to multiple RAUs  106  (even though only one is illustrated in  FIG. 1 ). The power source  108  may be coupled to an external power grid  112 . The external power grid  112  may be operated by a power company and may carry a high voltage (e.g., 35,000 volts (V)), low frequency (e.g., 50 hertz (Hz) or 60 Hz (or in some rare instances 400 Hz)) alternating current (AC) power signal on high power lines, although the voltage level is typically stepped down to 100 V AC or 240 V AC. In contrast, the RAU  106  may use a 110 V or 220 V DC power signal. The power source  108  includes a PMC therein that changes the AC power signal of the external power grid  112  to a voltage level suitable for use by the RAU  106 . 
     Similarly,  FIG. 1B  illustrates a data center system  120  having a power source  108  coupled to remote data servers  122  through power lines  124 . The power source  108  is coupled to the external power grid  112  and includes a PMC (not illustrated) according to the present disclosure. As with the RAU  106 , the data servers  122  may need a different voltage signal than that provided by the external power grid  112 . 
     Similarly,  FIG. 1C  illustrates a lighting system  130  having a power source  108  coupled to remote lighting units  132  through power lines  134 . The power source  108  is coupled to the external power grid  112  and includes a PMC (not illustrated) according to the present disclosure. As with the RAU  106 , the remote lighting units  132  may need a different voltage signal than that provided by the external power grid  112 . 
     Historically, the PMC would operate at a high frequency so that internal components such as a transformer could be relatively small. Thus, as illustrated in  FIG. 2 , a PMC  200  may include a power source input  202  configured to be coupled to the external power grid  112 . An AC power input signal  204  is passed from the power source input  202  to a rectifier  206  containing a diode  206 A. The AC power input signal  204  may be, for example, 220 V AC, having already been stepped down from the high voltage of the external power grid  112 . The rectifier  206  converts the AC power input signal  204  into a DC power signal  208 . The DC power signal  208  is provided to a first non-isolated DC-to-DC converter  210  that acts as a power factor converter to assure that the phase between the voltage and current is fixed at a desired level. The first non-isolated DC-to-DC converter  210  may also step up the voltage in an intermediate DC power signal  212  to 400 V (or step down the voltage depending on the input voltage). The intermediate DC power signal  212  is provided to a second isolated DC-to-DC converter  214 , which includes a transformer  216 . The transformer  216  may be a relatively high frequency device and accordingly, may be relatively small, but may not have a high efficiency. In fact, the overall efficiency of the PMC  200  may be between 85-95%, largely due to the transformer  216  within the second isolated DC-to-DC converter  214 . The second isolated DC-to-DC converter  214  may further step down the voltage to a desired voltage level such as, for example, 380 V (or as low as 48 V or 57 V), in an output signal  218 . The output signal  218  may be output onto a power distribution line  220  for distribution to one or more distributed elements  222 . The distributed elements  222  may be RAUs, lighting elements, or data servers. 
     While the PMC  200  may be relatively small, it may suffer from low efficiency as explained above. This inefficient behavior results in power loss in the form of heat. Unfortunately, such heat degrades performance of the PMC  200  such that less power is output. Most commercially available PMCs begin to lose power output at 50 degrees centigrade (° C.). Given that current requirements mandate operation at temperatures at or above 60° C. for applications that are outdoors such as solar fields or other outdoor systems as well as some indoor installations such as above the ceilings where there is limited airflow or other heavy industrial/manufacturing environments, such commercially available PMCs are inadequate. One way this inadequacy is addressed is through the use of an air conditioning unit. Such an air conditioning unit imposes an additional power requirement on the power distribution system and imposes a size penalty on the cabinet in which the PMC may be located. An alternate technique is through the use of a heat exchanger. However, such a heat exchanger imposes a substantial size penalty on the cabinet. 
     Deficiencies of the PMC  200  are corrected by an improved design which inverts the position of the transformer and allows the transformer to operate at low frequencies, which improves the overall efficiency of the PMC, reduces heat losses, and improves performance without imposing an undue size penalty on the PMC. Accordingly, the improved PMC described below with reference to  FIG. 3  is readily deployed in outdoor environments without the need for an air conditioning apparatus or heat exchangers. 
     In this regard,  FIG. 3  illustrates a PMC  300  according to an exemplary aspect of the present disclosure. The PMC  300  may include a power source input port  302  configured to be coupled to the external power grid  112 . A power input signal  304  is passed from the power source input port  302  to a transformer  306  and, particularly, to a transformer input port  308 . In an exemplary aspect, the transformer  306  is housed in a separate casing from other portions of the PMC  300 . As the power input signal  304  is typically a low frequency AC signal, such as 60 Hz in the United States or 50 Hz in Europe, the transformer  306  may be a relatively high efficiency transformer (e.g., in excess of 99% efficient). This low frequency operation may result in a larger transformer compared to the transformer  216  of  FIG. 2 , but compared to the heat exchanger and air conditioning equipment required for the high frequency transformer  216 , the net result is still a smaller overall device. The transformer  306  includes at least one input coil  310  and at least one output coil  312 , although as explained below with reference to  FIGS. 4A and 4B , there may be more than one input coil and more than one output coil. Further, if there is a three-phase AC input, there may be three different transformers, each connected to a different AC input phase. The rest of the discussion of  FIG. 3  will focus on a single phase input. As is understood, the input coil  310  couples magnetically to the output coil  312  and creates an AC power signal  314  at a transformer output port  316 . The transformer  306  helps isolate the external power grid  112  from the remainder of the PMC  300  as well as any downstream elements within a power distribution network associated with the PMC  300 . 
     With continued reference to  FIG. 3 , the transformer  306  outputs the AC power signal  314 , which may still be at a line voltage level such as 220 V. The AC power signal  314  or a signal from an optional battery  318  is provided to an AC input port  320  of a rectifier  322 . The rectifier  322  changes the AC power signal  314  into a first DC power signal  324  available at a rectifier output port  326 . The rectifier  322  may include a diode  322 A. The first DC power signal  324  is provided to a converter input port  327  on a power factor correction (PFC) converter  328 . In an exemplary aspect, the PFC converter  328  may be a DC-to-DC converter. The PFC converter  328  acts as a power factor correction converter to assure that the phase between the voltage and current consumption is fixed at a desired level and may also step up the voltage to a higher voltage (e.g., 380 V) (or step down to a lower voltage) in a second DC power signal  330  provided at a converter output port  332 . The PFC converter  328  also makes sure the second DC power signal  330  may be output onto a power distribution line  334  for distribution to one or more distributed elements  336 . Alternatively, the converter output port  332  may be coupled to a local load (not shown) and power provided thereto. The distributed elements  336  may be RAUs, lighting elements, or data servers. It should be noted that the optional battery  318  may be advantageously positioned to the secondary side of the transformer  306  as illustrated so that the battery  318  may be optimized (i.e., have a narrower input voltage range closely correlated to the operating voltage) regardless of the AC voltage from the grid. Further note that the battery  318  may more properly be any form of uninterruptable power supply (UPS) or an AC battery. 
     To provide a balanced output power signal  330 , resistors  338 A and  338 B may be connected to the converter output port  332  or the power distribution line  334 . The resistors  338 A and  338 B may be identical, and may for example, be five kiloohms (5 kΩ). Note that there may be instances where a balanced output power signal is not needed. For example, if a coax cable is used to provide power, one of the conductors is always grounded (i.e., the shield). 
     By moving the transformer in front of the rectifier and using a low frequency AC transformer, the overall efficiency of the PMC  300  may be in excess of 98%. This provides a substantial power savings and appurtenant reduction in waste heat. The reduction in waste heat allows the elimination of air conditioning equipment and/or a heat exchange structure. 
     As a note of nomenclature, PMC  300  refers to the circuitry between and including the power source input port  302  and the converter output port  332 . It should be appreciated, that the transformer  306  (and the battery  318 ) may be distinct from the rectifier  322  and PFC converter  328 . For ease of distinguishing these, the combination of the rectifier  322  and the PFC converter  328  is referred to herein as a power conditioning element  340 . 
     While the discussion above relating to  FIG. 3  provides a single output, it should be appreciated that there may be plural outputs and plural coils in the transformer  306 . The PMC  300  may be readily modified to accommodate such plural outputs. The transformer  306  provides plural outputs to multiple rectifier/PFC converter pairs. It may be appropriate to provide multiple outputs when different power factors are desired. Likewise, the coils of the transformer  306  may be arranged in serial or parallel fashion to provide different power levels. However, it may be challenging to wire the coils of the transformer  306  into serial or parallel fashion in the field as such wiring may entail manipulation of thick electrical conductors and may be subject to human error if the wiring is done improperly. 
     To achieve such plural outputs from the transformer  306 , a modification to the transformer input port  308  may be made as illustrated in  FIGS. 4A and 4B . In particular, in  FIG. 4A , the transformer input port  308  of the transformer  306 A may be modified to have a parallel input port  308 A. Jumpers  400  and  402  are used between electrical nodes  1 - 3  and  2 - 4  to provide input coils  404  and  406  between electrical nodes  1 - 2  and  3 - 4  on the output side of connection node  408 . The jumper  400  between nodes  1 - 3  means that the input voltage appears on both input coils  404  and  406  at the same time (since both are attached to the input line), and goes out at node  4  at the same time since the bottom of coil  404  is coupled to the bottom of coil  406  by the jumper  402  between nodes  2 - 4 . Output coils  410  and  412  couple to respective transformer output ports (not shown). Note that there is no requirement for multiple output coils, even if there are multiple input coils. 
     Similarly, in  FIG. 4B , the transformer input port  308  of the transformer  306 B may be modified to a series input port  308 B. Jumper  420  is used between electrical nodes  2 - 3  to provide input coils  422  and  424  between electrical nodes  1 - 2  and  3 - 4  on the output side of connection node  426 . Current flows in at node  1 , through the first input coil  422 , then from node  2  to node  3  through the jumper  420 , then through the second input coil  424  and out through the node  4 . Output coils  428  and  430  couple to respective transformer output ports (not shown). Again, note that there is no requirement for multiple output coils, even if there are multiple input coils. 
     It should be appreciated that wiring the input wires to the nodes  1  and  4  in either input port  308 A or input port  308 B as well as wiring in the jumpers  400  and  402  or jumper  420  may involve manipulating heavy wire (e.g., 1 AWG (American wire gauge)). Manipulation of such heavy wire can be challenging for an installation technician. Likewise, it is possible that human error may introduce error in placement of the jumpers or the like. 
     Exemplary aspects of the present disclosure provide a connector that pre-wires the jumpers to minimize the amount of wiring that the installation technician must perform and reduce the likelihood of human error. 
     In this regard,  FIG. 4C  shows a connector  440  for use with the transformer  306 A that includes the input port  308 A and particularly includes the pre-wired jumpers  400  and  402 . In an exemplary aspect the connector  440  has a structure similar to a SO-HMK-004-FC heavy duty connector sold by Zhejiang SMICO Electric Power Equipment Co. Ltd. of NO 374-376 Kaichuang Road, Baitawang Industrial Zone, Beibaixiang, Wenzhou, Zhejiang, 325603 China. The jumpers  400 ,  402  are placed in a first half  440 A of the connector  440 , which plugs into a second half  440 B of the connector  440 . The first half  440 A has four electrical contacts corresponding to nodes  1 - 4  and the second half  440 B has a complementary second set of four electrical contacts configured to mate to the first set of four electrical contacts. Power conductors  452 +,  452 − are connected to positive and negative terminals  454 +,  454 −, respectively. This connection is made by the installation technician. In contrast, the second half  440 B is pre-wired to the terminals  454 +,  454 − and the input coils  404 ,  406  at the time of manufacture of the transformer  306 A. The installation technician then merely puts the appropriate first half  440 A of the connector  440  (as opposed to the first half  460 A described below with reference to  FIG. 4D ) to make the desired jumper connections. In this fashion, the installation technician does not have to wire the jumpers. 
     Similarly,  FIG. 4D  shows a connector  460  for use with the transformer  306 B that includes the input port  308 B and particularly includes the pre-wired jumper  420 . As mentioned above, in an exemplary aspect, the connector  460  has a structure similar to a SO-HMK-004-FC heavy duty connector sold by Zhejiang SMICO Electric Power Equipment Co. Ltd. of NO 374-376 Kaichuang Road, Baitawang Industrial Zone, Beibaixiang, Wenzhou, Zhejiang, 325603 China. The jumper  420  is placed in a first half  460 A of the connector  460 , which plugs into a second half  460 B of the connector  460 . The first half  460 A has four electrical contacts corresponding to nodes  1 - 4  and the second half  460 B has a complementary second set of four electrical contacts configured to mate to the first set of four electrical contacts. Power conductors  452 +,  452 − are connected to positive and negative terminals  454 +,  454 −, respectively. This connection is made by the installation technician. In contrast, the second half  460 B is pre-wired to the terminals  454 +,  454 − and the input coils  422 ,  424  at the time of manufacture of the transformer  306 B. The installation technician then merely puts the appropriate first half  460 A of the connector  460  (as opposed to the first half  440 A described above with reference to  FIG. 4C ) to make the desired jumper connections. In this fashion, the installation technician does not have to wire the jumpers. 
     It should be appreciated that the first halves  440 A,  460 A may have appropriate indicia printed thereon to facilitate selection and use of the desired connection. 
       FIG. 4E  illustrates perspective views of the connector  440 , which from an external perspective may look identical to the connector  460 . The difference being in the placement of the internal jumpers  400 ,  402  or  420  (not shown in  FIG. 4E ). 
     While the PMC  300  may be housed in a variety of structures, one such exemplary structure suitable for outside deployment is illustrated in  FIGS. 5A-5C . In particular, a power conversion element  500  includes a transformer housing  502  and a power conditioning element housing  504 . The transformer housing  502  may be affixed to a pole by U-shaped threaded members  506  or the like. The transformer housing  502  may contain the transformer  306  ( FIG. 3 ) therein. Similarly, the power conditioning element housing  504  may contain the power conditioning element  340  therein. The transformer housing  502  may include a grounding screw element  508  secured on an external surface  510 . In an exemplary aspect, the grounding screw element  508  may include two dual grounding contacts, one of which may be coupled to a grounding element  512  secured to an external surface  514  of the power conditioning element housing  504 . The transformer housing  502  may be closed with an epoxy resin to render the housing waterproof as well as provide heat dissipation. The transformer housing  502  further may have a power input aperture  516  that receives a power cable  518  from the power grid  112 . Likewise, the power conditioning element housing  504  may have power output apertures  520  that have power distribution cables  522  extending therefrom. Fins  524  may be integrally formed with the power conditioning element housing  504  to assist in heat dissipation. The power conditioning element housing  504  may contain other electronics or circuits to achieve functionality unrelated (or at best tangentially related) to the present disclosure. 
     Before providing a more detailed discussion of an exemplary distributed system in which the PMC  300  may be used,  FIG. 6  provides a flowchart outlining a process  600  of using the PMC  300 . In this regard, the process  600  begins when the PMC  300  receives an AC power signal from a power grid such as the external power grid  112  (block  602 ). The PMC  300  is isolated from the power grid with the transformer  306  (block  604 ). The output of the transformer  306  is rectified into a rectified DC signal (block  606 ) by the rectifier  322 . The PFC converter  328  takes the rectified DC signal and performs a PFC conversion on the rectified signal (block  608 ), and power is provided to the distributed power network (block  610 ). 
     While the PMC  300  is well suited for use in a variety of distributed systems such as a distributed data center or a distributed lighting system, one such distributed system is explored with reference to  FIGS. 7-9  for better understanding of such an exemplary environment. In particular,  FIGS. 7-9  illustrate a distributed communication system with a distributed power management system that includes the PMC  300 . 
     In this regard,  FIG. 7  is a schematic diagram of such an exemplary distributed communication system (DCS)  700  having a power distribution system therein. The DCS  700  is a distributed antenna system (DAS)  702  in this example. A DAS is a system that is configured to distribute communication signals, including wireless communication signals, from a central unit to a plurality of remote units over physical communication media, to then be distributed from the remote units wirelessly to client devices in wireless communication range of a remote unit. The DAS  702  in this example is an optical fiber-based DAS that is comprised of three (3) main components. One or more radio interface circuits provided in the form of radio interface modules (RIMs)  704 ( 1 )- 704 (T) (generically a RIM  704 ) are provided in a central unit  706  to receive and process downlink electrical communication signals  708 D( 1 )- 708 D(S) prior to optical conversion into downlink optical communication signals. The downlink electrical communication signals  708 D( 1 )- 708 D(S) may be received from a base transceiver station (BTS) or baseband unit (BBU) as examples. The downlink electrical communication signals  708 D( 1 )- 708 D(S) may be analog signals or digital signals that can be sampled and processed as digital information. The RIMs  704 ( 1 )- 704 (T) provide both downlink and uplink interfaces for signal processing. The notations “1-S” and “1-T” indicate that any number of the referenced component, 1-S and 1-T, respectively, may be provided. 
     With continuing reference to  FIG. 7 , the central unit  706  is configured to accept the plurality of RIMs  704 ( 1 )- 704 (T) as modular components that can easily be installed and removed or replaced in a chassis. In one embodiment, the central unit  706  is configured to support up to twelve (12) RIMs  704 ( 1 )- 704 ( 12 ). Each RIM  704 ( 1 )- 704 (T) can be designed to support a particular type of radio source or range of radio sources (i.e., frequencies) to provide flexibility in configuring the central unit  706  and the DAS  702  to support the desired radio sources. For example, one RIM  704  may be configured to support the Personal Communication Services (PCS) radio band. Another RIM  704  may be configured to support the 700 MHz radio band. In this example, by inclusion of these RIMs  704 , the central unit  706  could be configured to support and distribute communication signals, including those for the communication services and communication bands described above as examples. 
     The RIMs  704 ( 1 )- 704 (T) may be provided in the central unit  706  that support any frequencies desired, including, but not limited to, licensed US FCC and Industry Canada frequencies (824-849 MHz on uplink and 869-894 MHz on downlink), US FCC and Industry Canada frequencies (1850-1915 MHz on uplink and 1930-1995 MHz on downlink), US FCC and Industry Canada frequencies (1710-1755 MHz on uplink and 2110-2155 MHz on downlink), US FCC frequencies (698-716 MHz and 776-787 MHz on uplink and 728-746 MHz on downlink), EU R &amp; TTE frequencies (880-915 MHz on uplink and 925-960 MHz on downlink), EU R &amp; TTE frequencies (1710-1785 MHz on uplink and 1805-1880 MHz on downlink), EU R &amp; TTE frequencies (1920-1980 MHz on uplink and 2110-2170 MHz on downlink), US FCC frequencies (806-824 MHz on uplink and 851-869 MHz on downlink), US FCC frequencies (896-901 MHz on uplink and 929-941 MHz on downlink), US FCC frequencies (793-805 MHz on uplink and 763-775 MHz on downlink), and US FCC frequencies (2495-2690 MHz on uplink and downlink). 
     To the extent it is used herein, radio frequency signals may include analog or digital signals and may include representations of the data in the signals and specifically includes signals such as those used in ORAN and CPRI systems. 
     With continuing reference to  FIG. 7 , the received downlink electrical communication signals  708 D( 1 )- 708 D(S) are provided to a plurality of optical interfaces provided in the form of optical interface modules (OIMs)  710 ( 1 )- 710 (W) in this embodiment to convert the downlink electrical communication signals  708 D( 1 )- 708 D(S) into downlink optical communication signals  712 D( 1 )- 712 D(S). The notation “1-W” indicates that any number of the referenced component 1-W may be provided. The OIMs  710  may include one or more optical interface components (OICs) that contain electrical-to-optical (E-O) converters  716 ( 1 )- 716 (W) to convert the received downlink electrical communication signals  708 D( 1 )- 708 D(S) into the downlink optical communication signals  712 D( 1 )- 712 D(S). The OIMs  710  support the radio bands that can be provided by the RIMs  704 , including the examples previously described above. The downlink optical communication signals  712 D( 1 )- 712 D(S) are communicated over a downlink optical fiber communication link  714 D to a plurality of remote units  718 ( 1 )- 718 (X) provided in the form of remote antenna units in this example. The notation “1-X” indicates that any number of the referenced component 1-X may be provided. One or more of the downlink optical communication signals  712 D( 1 )- 712 D(S) can be distributed to each remote unit  718 ( 1 )- 718 (X). Thus, the distribution of the downlink optical communication signals  712 D( 1 )- 712 D(S) from the central unit  706  to the remote units  718 ( 1 )- 718 (X) is in a point-to-multipoint configuration in this example. 
     With continuing reference to  FIG. 7 , the remote units  718 ( 1 )- 718 (X) include optical-to-electrical (O-E) converters  720 ( 1 )- 720 (X) configured to convert the one or more received downlink optical communication signals  712 D( 1 )- 712 D(S) back into the downlink electrical communication signals  708 D( 1 )- 708 D(S) to be wirelessly radiated through antennas  722 ( 1 )- 722 (X) in the remote units  718 ( 1 )- 718 (X) to user equipment (not shown) in the reception range of the antennas  722 ( 1 )- 722 (X). The OIMs  710  may also include O-E converters  724 ( 1 )- 724 (W) to convert received uplink optical communication signals  712 U( 1 )- 712 U(X) from the remote units  718 ( 1 )- 718 (X) into uplink electrical communication signals  726 U( 1 )- 726 U(X) as will be described in more detail below. 
     With continuing reference to  FIG. 7 , the remote units  718 ( 1 )- 718 (X) are also configured to receive uplink electrical communication signals  728 U( 1 )- 728 U(X) received by the respective antennas  722 ( 1 )- 722 (X) from client devices in wireless communication range of the remote units  718 ( 1 )- 718 (X). The uplink electrical communication signals  728 U( 1 )- 728 U(X) may be analog signals or digital signals that can be sampled and processed as digital information. The remote units  718 ( 1 )- 718 (X) include E-O converters  730 ( 1 )- 730 (X) to convert the received uplink electrical communication signals  728 U( 1 )- 728 U(X) into uplink optical communication signals  712 U( 1 )- 712 U(X). The remote units  718 ( 1 )- 718 (X) distribute the uplink optical communication signals  712 U( 1 )- 712 U(X) over an uplink optical fiber communication link  714 U to the OIMs  710 ( 1 )- 710 (W) in the central unit  706 . The O-E converters  724 ( 1 )- 724 (W) convert the received uplink optical communication signals  712 U( 1 )- 712 U(X) into uplink electrical communication signals  732 U( 1 )- 732 U(X), which are processed by the RIMS  704 ( 1 )- 704 (T) and provided as the uplink electrical communication signals  726 U( 1 )- 726 U(X) to a source transceiver such as a base transceiver station (BTS) or baseband unit (BBU). 
     Note that the downlink optical fiber communication link  714 D and the uplink optical fiber communication link  714 U coupled between the central unit  706  and the remote units  718 ( 1 )- 718 (X) may be a common optical fiber communication link, wherein for example, wave division multiplexing (WDM) may be employed to carry the downlink optical communication signals  712 D( 1 )- 712 D(S) and the uplink optical communication signals  712 U( 1 )- 712 U(X) on the same optical fiber communication link. Alternatively, the downlink optical fiber communication link  714 D and the uplink optical fiber communication link  714 U coupled between the central unit  706  and the remote units  718 ( 1 )- 718 (X) may be single, separate optical fiber communication links, wherein for example, wave division multiplexing (WDM) may be employed to carry the downlink optical communication signals  712 D( 1 )- 712 D(S) on one common downlink optical fiber and the uplink optical communication signals  712 U( 1 )- 712 U(X) carried on a separate, only uplink optical fiber. Alternatively, the downlink optical fiber communication link  714 D and the uplink optical fiber communication link  714 U coupled between the central unit  706  and the remote units  718 ( 1 )- 718 (X) may be separate optical fibers dedicated to and providing a separate communication link between the central unit  706  and each remote unit  718 ( 1 )- 718 (X). 
     Relevant to the current discussion, a power source such as the external power grid  112  may provide power to the remote units  718 ( 1 )- 718 (X) through a power distribution system  734 . The power distribution system  734  includes the PMC  300 . A power signal  736  may be provided to the remote units  718 ( 1 )- 718 (X) through the power distribution line  334 , which may be a unitary serial line for the remote units  718 ( 1 )- 718 (X) or parallel lines (not shown) that connect directly to each of the remote units  718 ( 1 )- 718 (X) or some combination of serial and parallel lines. 
     The DCS  700  in  FIG. 7  can be provided in an indoor environment as illustrated in  FIG. 8 .  FIG. 8  is a partially schematic cut-away diagram of a building infrastructure  800  employing the DCS  700 . With reference to  FIG. 8 , the building infrastructure  800  in this embodiment includes a first (ground) floor  802 ( 1 ), a second floor  802 ( 2 ), and an Fth floor  802 (F), where ‘F’ can represent any number of floors. The floors  802 ( 1 )- 802 (F) are serviced by the central unit  706  to provide antenna coverage areas  804  in the building infrastructure  800 . The central unit  706  is communicatively coupled to a signal source  806 , such as a BTS or BBU, to receive the downlink electrical communication signals  708 D( 1 )- 708 D(S). The central unit  706  is also coupled to a power source such as external power grid  112 . The central unit  706  is communicatively coupled to the remote units  718 ( 1 )- 718 (X) to receive the uplink optical communication signals  712 U( 1 )- 712 U(X) from the remote units  718 ( 1 )- 718 (X) as previously described in  FIG. 7 . The downlink and uplink optical communication signals  712 D( 1 )- 712 D(S),  712 U( 1 )- 712 U(X) are distributed between the central unit  706  and the remote units  718 ( 1 )- 718 (X) over a riser cable  808  in this example. The riser cable  808  may be routed through interconnect units (ICUs)  810 ( 1 )- 810 (F) dedicated to each floor  802 ( 1 )- 802 (F) for routing the downlink and uplink optical communication signals  712 D( 1 )- 712 D(S),  712 U( 1 )- 712 U(X) and power signals  736 ( 1 )- 736 (X) to the remote units  718 ( 1 )- 718 (X). The ICUs  810 ( 1 )- 810 (F) may alternatively include power distribution circuits  812 ( 1 )- 812 (F) like the power distribution system  734  in  FIG. 7  that include power sources and are configured to distribute power remotely to their respective remote units  718 ( 1 )- 718 (X) to provide power for operations. For example, array cables  814 ( 1 )- 814 ( 2 F) may be provided and coupled between the ICUs  810 ( 1 )- 810 (F) that contain both optical fibers to provide respective downlink and uplink optical fiber communication links  714 D( 1 )- 714 D( 2 F),  714 U( 1 )- 714 U( 2 F) and power conductors  816 ( 1 )- 816 ( 2 F) (e.g., electrical wire) to carry current from the respective power distribution circuits  812 ( 1 )- 812 (F) to the remote units  718 ( 1 )- 718 (X). 
       FIG. 9  is a schematic diagram illustrating the power distribution system  734  in the exemplary form of the DCS  700  with the PMC  300  configured to distribute power to a plurality of remote units  718 ( 1 )- 718 (X). Common components between the DCS  700  and the power distribution system  734  in  FIG. 7  are shown with common element numbers and will not be re-described. As shown in  FIG. 9 , a plurality of remote units  718 ( 1 )- 718 (X) are provided. Each remote unit  718 ( 1 )- 718 (X) includes a remote power input  909 ( 1 )- 909 (X) coupled to the power distribution lines  334 +( 1 ),  334 −( 1 )- 334 +(X),  334 −(X), respectively, which are configured to be coupled to the PMC  300 . The PMC  300  includes a plurality of distribution power outputs  903 ( 1 )- 903 (X) coupled to respective power distribution lines  334 +( 1 ),  334 −( 1 )- 334 +(X),  334 −(X). The power distribution lines  334 +( 1 ),  334 −( 1 )- 334 +(X),  334 −(X) are also coupled to the remote power inputs  909 ( 1 )- 909 (X). The remote units  718 ( 1 )- 718 (X) may also have remote power outputs  902 ( 1 )- 902 (X) that are configured to carry power from the respective power distribution lines  334 +( 1 ),  334 −( 1 )- 334 +(X),  334 −(X) received on the remote power inputs  909 ( 1 )- 909 (X) to an extended remote unit, such as extended remote unit  718 (E). 
       FIG. 10  is a schematic diagram representation of additional detail illustrating a computer system  1000  that could be employed in any component of a power distribution system configured to receive power from a power source and distribute the received power to one or more remote units for powering their operations. The power distribution system may be, without limitation, the power distribution system  734  in  FIG. 7 . In this regard, the computer system  1000  is adapted to execute instructions from an exemplary computer-readable medium to perform these and/or any of the functions or processing described herein. 
     The computer system  1000  in  FIG. 10  may include a set of instructions that may be executed to program and configure programmable digital signal processing circuits in a DCS for supporting scaling of supported communication services. The computer system  1000  may be connected (e.g., networked) to other machines in a local area network (LAN), an intranet, an extranet, or the Internet. While only a single device is illustrated, the term “device” shall also be taken to include any collection of devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. The computer system  1000  may be a circuit or circuits included in an electronic board card, such as a printed circuit board (PCB), a server, a personal computer, a desktop computer, a laptop computer, a personal digital assistant (PDA), a computing pad, a mobile device, or any other device, and may represent, for example, a server or a user&#39;s computer. 
     The exemplary computer system  1000  in this embodiment includes a processing device or processor  1002 , a main memory  1004  (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM), such as synchronous DRAM (SDRAM), etc.), and a static memory  1006  (e.g., flash memory, static random access memory (SRAM), etc.), which may communicate with each other via a data bus  1008 . Alternatively, the processor  1002  may be connected to the main memory  1004  and/or static memory  1006  directly or via some other connectivity means. The processor  1002  may be a controller, and the main memory  1004  or static memory  1006  may be any type of memory. 
     The processor  1002  represents one or more general-purpose processing devices, such as a microprocessor, central processing unit, or the like. More particularly, the processor  1002  may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or other processors implementing a combination of instruction sets. The processor  1002  is configured to execute processing logic in instructions for performing the operations and steps discussed herein. 
     The computer system  1000  may further include a network interface device  1010 . The computer system  1000  also may or may not include an input  1012 , configured to receive input and selections to be communicated to the computer system  1000  when executing instructions. The computer system  1000  also may or may not include an output  1014 , including, but not limited to, a display, a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device (e.g., a keyboard), and/or a cursor control device (e.g., a mouse). 
     The computer system  1000  may or may not include a data storage device that includes instructions  1016  stored in a computer-readable medium  1018 . The instructions  1016  may also reside, completely or at least partially, within the main memory  1004  and/or within the processor  1002  during execution thereof by the computer system  1000 , the main memory  1004  and the processor  1002  also constituting computer-readable medium. The instructions  1016  may further be transmitted or received over a network  1020  via the network interface device  1010 . 
     While the computer-readable medium  1018  is shown in an exemplary embodiment to be a single medium, the term “computer-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “computer-readable medium” shall also be taken to include any medium that is capable of storing, encoding, or carrying a set of instructions for execution by the processing device and that cause the processing device to perform any one or more of the methodologies of the embodiments disclosed herein. The term “computer-readable medium” shall accordingly be taken to include, but not be limited to, solid-state memories, optical medium, and magnetic medium. 
     The embodiments disclosed herein include various steps. The steps of the embodiments disclosed herein may be formed by hardware components or may be embodied in machine-executable instructions, which may be used to cause a general-purpose or special-purpose processor programmed with the instructions to perform the steps. Alternatively, the steps may be performed by a combination of hardware and software. 
     The embodiments disclosed herein may be provided as a computer program product, or software, that may include a machine-readable medium (or computer-readable medium) having stored thereon instructions, which may be used to program a computer system (or other electronic devices) to perform a process according to the embodiments disclosed herein. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes: a machine-readable storage medium (e.g., ROM, random access memory (“RAM”), a magnetic disk storage medium, an optical storage medium, flash memory devices, etc.); and the like. 
     Unless specifically stated otherwise and as apparent from the previous discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing,” “computing,” “determining,” “displaying,” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data and memories represented as physical (electronic) quantities within the computer system&#39;s registers into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices. 
     The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatuses to perform the required method steps. The required structure for a variety of these systems will appear from the description above. In addition, the embodiments described herein are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the embodiments as described herein. 
     Those of skill in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithms described in connection with the embodiments disclosed herein may be implemented as electronic hardware, instructions stored in memory or in another computer-readable medium and executed by a processor or other processing device, or combinations of both. The components of the distributed antenna systems described herein may be employed in any circuit, hardware component, integrated circuit (IC), or IC chip, as examples. Memory disclosed herein may be any type and size of memory and may be configured to store any type of information desired. To clearly illustrate this interchangeability, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. How such functionality is implemented depends on the particular application, design choices, and/or design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present embodiments. 
     The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Furthermore, a controller may be a processor. A processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The embodiments disclosed herein may be embodied in hardware and in instructions that are stored in hardware, and may reside, for example, in RAM, flash memory, ROM, Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a remote station. In the alternative, the processor and the storage medium may reside as discrete components in a remote station, base station, or server. 
     It is also noted that the operational steps described in any of the exemplary embodiments herein are described to provide examples and discussion. The operations described may be performed in numerous different sequences other than the illustrated sequences. Furthermore, operations described in a single operational step may actually be performed in a number of different steps. Additionally, one or more operational steps discussed in the exemplary embodiments may be combined. Those of skill in the art will also understand that information and signals may be represented using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips, that may be references throughout the above description, may be represented by voltages, currents, electromagnetic waves, magnetic fields, or particles, optical fields or particles, or any combination thereof. 
     Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.