SYSTEMS AND METHODS FOR INTEGRITY CHECKS FOR SAFETY FEATURES IN A POWER DISTRIBUTION NETWORK

Safety power disconnection integrity check for power distribution over power conductors to radio communications circuits monitors the integrity of circuit breakers may be used in an operating protection circuit as well as the integrity of current sensors in the operating protection circuit. Such monitoring includes testing the ability of individual switches to disconnect, testing the correctness of a leakage current sensor reading, and testing a correctness of an over current sensor reading. To perform these tests, the individual element is isolated and provided a test current. Any alarms generated by the element under test are diverted so that operation continues normally. Testing the safety power elements ensures that faults in the systems are detected and corrected so as to improve overall safety. Further, manual testing, which may interrupt service, is avoided.

BACKGROUND

The disclosure relates generally to a power distribution network having safety features and, more particularly, to checking the integrity of such safety features. While a variety of environments are amenable to this integrity check, the power distribution network may be positioned in a distributed radio communication system (DCS) such as a distributed antenna systems (DAS) or a small cell radio access network for example.

The seemingly ubiquitous nature of power outlets leads many individuals to take the availability of electrical power for granted. Homes and offices routinely have an outlet on multiple, if not all, walls. Likewise, overhead lighting is readily powered such that a simple flick of a switch turns on such overhead lighting. However, as anyone who has wired a building for power will tell you, there are many factors which must be considered when routing electrical conductors to carry power to outlets and overhead lighting.

While conventional power outlets are seemingly ubiquitous, there are many situations where it is inconvenient or inappropriate to use such power outlets to provide power to some device. As noted above, lighting may have power supplied directly thereto without having to use an intermediate outlet. Similarly, high-power devices may be hard wired to have power supplied directly. Distributed communication systems are one such situation and may require a power distribution network or power distribution network that has a centralized power source and one or more subunits that receive power from the centralized power source. The problems of distributing power to radio communication circuits are not limited to communication systems. Lighting systems, smart homes with powered elements, Ethernet switches, water heating systems, server farms, call centers, or the like may all have distributed power systems.

Some regulations, such as International Electric Code (IEC) 60950-21, may limit the amount of direct current (DC) that is remotely delivered by the power source to the remote subunits to less than the amount needed to power the subunits during peak power consumption periods for safety reasons, such as in the event a human contacts the wire. One solution to remote power distribution limitations is to employ multiple conductors and split current from the power source over the multiple conductors, such that the current on any one electrical conductor is below the regulated limit. Another solution includes delivering remote power at a higher voltage so that a lower current can be distributed at the same power level. For example, assume that 300 Watts (W) of power is to be supplied to a subunit by the power source. If the voltage of the power source is 60 Volts (V), the current will be 5 Amperes (A) (i.e., 300 W/60 V). However, if a 400 V power source is used, then the current flowing through the wires will be 0.75 A. Delivering high voltage through electrical conductors may be further regulated to prevent an undesired current from flowing through a human in the event that a human contacts the electrical conductor. Likewise, there may be a need to prevent the line current from exceeding maximum allowed current values. Such regulations necessitate a variety of safety features and protection circuits. Once installed, the safety measures and protection circuits may fail and detection of such may be helpful.

No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinence of any cited documents.

SUMMARY

Exemplary aspects of systems and methods for integrity checks for safety features in a power distribution network are disclosed. In particular, the integrity of circuit breakers used in an operating protection system as well as the integrity of current sensors may be checked. In a specific exemplary aspect, such a check may include testing the ability of individual switches to disconnect, testing the correctness of a leakage current sensor reading, and testing the correctness of an over current sensor reading. To perform these tests, an individual element is isolated and provided a test current. Any alarms generated by the element under test are diverted or suppressed so that operation (i.e., power distribution) continues normally. The safety features remain intact during testing by virtue of the redundant circuits not being tested simultaneously. Testing the safety power elements ensures that faults in the systems are detected and corrected so as to improve overall safety. Furthermore, manual testing, which may interrupt power delivery, is avoided.

In this regard, in one exemplary aspect, a method of testing integrity for safety elements in a power distribution network configured to deliver power to remote elements is disclosed. The method comprises, during interrupt windows where a remote element decouples from a power conductor, testing an over current circuit in a power distribution circuit for integrity. The method also comprises testing a leakage current circuit in the power distribution circuit for integrity. The method also comprises testing a switch that decouples a power source from the power conductor in the power distribution circuit for integrity.

In another exemplary aspect, a method for testing integrity for an over current circuit in a power distribution network configured to deliver power to remote elements is disclosed. The method comprises, during interrupt windows where a remote element decouples from a power conductor, receiving a first voltage at an amplifier. The method also comprises receiving a second voltage at the amplifier. The method also comprises comparing an output of the amplifier to a reference value with a comparator. The method also comprises, when the output of the amplifier exceeds the reference value, providing an output to a latch circuit. The method also comprises detecting an output of the latch circuit with a management circuit.

In another exemplary aspect, a method for testing integrity for a leakage current circuit in a power distribution network configured to deliver power to remote elements is disclosed. The method comprises, during interrupt windows where a remote element decouples from a power conductor, receiving a first voltage at an amplifier. The method also comprises receiving a second voltage at the amplifier. The method also comprises comparing an output of the amplifier to a reference value with a comparator. The method also comprises, when the output of the amplifier exceeds the reference value, providing an output to a latch circuit. The method also comprises detecting an output of the latch circuit with a management circuit.

In another exemplary aspect, a method for testing integrity for a switch in a power distribution network configured to deliver power to remote elements is disclosed. The method comprises, during interrupt windows where a remote element decouples from a power conductor, injecting a test current. The method also comprises opening the switch. The method also comprises receiving a first voltage at an amplifier. The method also comprises receiving a second voltage at the amplifier. The method also comprises comparing an output of the amplifier to a reference value with a comparator. The method also comprises, when the output of the amplifier exceeds the reference value, providing an output to a latch circuit. The method also comprises, when the output of the amplifier does not exceed the reference value, providing no output to the latch circuit. The method also comprises detecting an absence of an output of the latch circuit with a management circuit.

In another exemplary aspect, a power distribution network with an integrity self test feature is disclosed. The power distribution network comprises a management circuit. The power distribution network also comprises an over current test circuit under control of the management circuit. The power distribution network also comprises a leakage current test circuit under control of the management circuit. The management circuit is configured to, during interrupt windows where a remote communication element decouples from a power conductor, test an over current circuit in a power distribution circuit for integrity. The management circuit is also configured to test a leakage current circuit in the power distribution circuit for integrity. The management circuit is also configured to test a switch that decouples a power source from the power conductor in the power distribution circuit for integrity.

In another exemplary aspect, a power distribution network with an over current self test circuit is disclosed. The power distribution network comprises an over current amplifier configured to receive a first voltage and a second voltage. The power distribution network also comprises an over current comparator coupled to an output of the over current amplifier and configured to compare a signal from the over current amplifier to a reference value. The power distribution network also comprises a latch circuit coupled to the over current comparator and configured to receive an output from the over current comparator when the signal from the over current amplifier exceeds the reference value. The power distribution network also comprises a management circuit coupled to an output of the latch circuit.

In another exemplary aspect, a power distribution network with a leakage self test circuit is disclosed. The power distribution network comprises a leakage amplifier configured to receive a first voltage and a second voltage. The power distribution network also comprises a leakage comparator coupled to an output of the leakage amplifier and configured to compare a signal from the leakage amplifier to a reference value. The power distribution network also comprises a latch circuit coupled to the leakage comparator and configured to receive an output from the leakage comparator when the signal from the leakage amplifier exceeds the reference value. The power distribution network also comprises a management circuit coupled to an output of the latch circuit.

In another exemplary aspect, a distributed communication system (DCS) is disclosed. The DCS comprises a central unit. The central unit is configured to distribute received one or more downlink communications signals over one or more downlink communications links to one or more remote subunits. The central unit is also configured to distribute received one or more uplink communications signals from the one or more remote subunits from one or more uplink communications links to one or more source communications outputs. The DCS also comprises a plurality of remote subunits. Each remote subunit comprises a power input port configured to be coupled to a power conductor and receive a power signal from a power source therefrom. Each remote subunit also comprises a switch coupled to the power input port. Each remote subunit also comprises a first power output port configured to be coupled to a second power conductor to provide power from the remote subunit to a second remote subunit. Each remote subunit also comprises a controller circuit. The controller circuit is configured to, during an interrupt window, open the switch to decouple the power conductor from the power source. The remote subunit is configured to distribute the received one or more downlink communications signals received from the one or more downlink communications links to one or more client devices. The remote subunit is also configured to distribute the received one or more uplink communications signals from the one or more client devices to the one or more uplink communications links. The DCS also comprises a power distribution network. The power distribution network comprises a management circuit. The power distribution network also comprises an over current test circuit under control of the management circuit. The power distribution network also comprises a leakage current test circuit under control of the management circuit. The management circuit is configured to, during interrupt windows where a remote communication element decouples from the power conductor, test an over current circuit in a power distribution circuit for integrity. The management circuit is also configured to test a leakage current circuit in the power distribution circuit for integrity. The management circuit is also configured to test a switch that decouples the power source from the power conductor in the power distribution circuit for integrity.

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.

DETAILED DESCRIPTION

Exemplary aspects of systems and methods for integrity checks for safety features in a power distribution network are disclosed. In particular, the integrity of circuit breakers used in an operating protection system as well as the integrity of current sensors may be checked. In a specific exemplary aspect, such a check may include testing the ability of individual switches to disconnect, testing the correctness of a leakage current sensor reading, and testing the correctness of an over current sensor reading. To perform these tests, an individual element is isolated and provided a test current. Any alarms generated by the element under test are diverted or suppressed so that operation (i.e., power distribution) continues normally. The safety features remain intact during testing by virtue of the redundant circuits not being tested simultaneously. Testing the safety power elements ensures that faults in the systems are detected and corrected so as to improve overall safety. Furthermore, manual testing, which may interrupt power delivery, is avoided.

In effect, by providing a built in test (BIT) apparatus and procedure, a self-test feature allows the integrity of the overall system to be monitored in essentially real time through frequent monitoring. The ability to test while the system is in operation eliminates the need to stop operation of the communication system for testing of the integrity of the protection circuits. Further, fault recognition is performed in a small time period. As noted, manual testing may be avoided thereby reducing maintenance costs while improving the overall reliability of the safety system at minimal additional cost.

A power distribution network rarely exists in isolation. Rather, a power distribution network provides infrastructure to some other system, a few of which are briefly discussed with reference toFIGS. 1-3. A more detailed discussion of a power distribution network with safety features is provided with reference toFIG. 4andFIG. 5. A discussion of exemplary aspects of the integrity checks begins below atFIG. 6.

In this regard,FIG. 1illustrates a block diagram of a distributed communication system (DCS)100. The DCS100may include a head end unit (HEU)102that communicates through a communication medium104with a remote antenna unit (RAU)106. The communication medium104may be a wire-based or optical fiber medium. The RAU106includes a transceiver and an antenna (not illustrated) that communicate wirelessly with mobile terminals and other user equipment (also not illustrated). Because the RAU106sends and receives wireless signals and may potentially perform other functions, the RAU106consumes power. That power may, in some instances, be provided locally. More commonly, the RAU106receives power from a power source108that transmits power to the RAU106over power lines110formed from a positive power line110+ and a negative power line110−. The power lines110may 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 lines110may couple to multiple RAUs106(even though only one is illustrated inFIG. 1). The power source108may be coupled to an external power grid112.

Similarly,FIG. 2illustrates a data center system200having a power source108coupled to remote data servers202through power lines204. The power source108is coupled to the external power grid112. As with the RAU106, the data servers202may consume power supplied through the power lines204.

Similarly,FIG. 3illustrates a lighting system300having a power source108coupled to remote lighting units302through power lines304. The power source108is coupled to the external power grid112. As with the RAU106, the remote lighting units302may consume power supplied through power lines304.

It should be appreciated that there may be other contexts that may use a power distribution network and the examples provided inFIGS. 1-3are not intended to be limiting. As a note of nomenclature, the RAU106, the remote data servers202, and the lighting units302are sometimes referred as remote units, remote elements, or even remote subunits in that they are subunits of the entirety of the power distribution network.

The present disclosure provides a way for safety elements within a power distribution network to be tested while the power distribution network is actively delivering power to remote subunits. Before addressing exemplary aspects of the safety feature integrity checks of the present disclosure, a more detailed discussion of a power distribution network that is designed to provide power to a load in a remote subunit while having appropriate power safety elements is provided. Thus, depending on the nature of the associated system, the loads may be macrocells, remote units, RAUs, RANs, shared spectrum cells that use licensed or unlicensed bandwidth, small cell radio nodes, head end units, remote radio units, remote radio heads, cameras, lighting elements, servers, or other electrical power consuming devices.

In this regard,FIG. 4provides a block diagram of a power distribution network400capable of effectuating communication between a power source402and a remote subunit404. The power source402is coupled to the remote subunit404through power conductors406. The power conductors406may include a positive power conductor406P and a negative power conductor406N. The power source402may include a controller circuit408with optional sub circuits410(1)-410(4) configured to control switches412(1)-412(4) that connect power supplies414P and414N to the power conductors406P and406N, respectively. Current sensors416(1)-416(4) may be provided in the power source402. The current sensors416(1)-416(4) may be used to detect unsafe operating conditions. It is these switches412(1)-412(4) and current sensors416(1)-416(4) that are tested to verify that they are operating correctly.

With continued reference toFIG. 4, the remote subunit404may include a control circuit418that controls a switch420. The switch420may decouple a load422from the power conductors406. A voltage sensor424may be provided that monitors the voltage levels on the power conductors406and reports the same to the control circuit418.

In operation, the remote subunit404opens and closes the switch420to decouple the load422periodically, thereby interrupting current supplied to the load422while leaving the voltage on the power conductors406high. A timing diagram500is provided inFIG. 5that illustrates operating of the switch420and the corresponding changes in current measured on the power conductors406. Opening and closing of the switch420creates power transfer windows502(sometimes referred to as a power transfer period) and power interrupt windows504(sometimes referred to as a power interrupt period). Collectively a single power transfer window502and an adjacent power interrupt window504have a period that is termed herein a “pulse repetition interval” or “PRI.” The power source402may monitor current on the power conductors406with the current sensors416(1)-416(4) to make sure that the power interrupt windows504occur. If current is detected during a power interrupt window504(e.g., at506inFIG. 5), the controller circuit408may infer that an external load such as a human is touching the power conductor(s)406creating an unsafe situation. Accordingly, the controller circuit408may open one or more of the switches412(1)-412(4) to disconnect the power conductors406from the power source402as shown at508inFIG. 5.

As different remote subunits404may have minor differences in the rate with which the switch420is activated by the control circuit418, the power source402may initially synchronize to the timing generated by the remote subunit404. A synchronization process may run in the background and may halt only during data transfers. In essence, the synchronization process allows the power source402to learn the switching rate of the remote subunit404and “know” when to expect a power interrupt window504by the remote subunit404.

As will be explained in greater detail beginning with reference toFIG. 6, exemplary aspects of the present disclosure test the switches412(1)-412(4) and the current sensors416(1)-416(4) that are used to provide the safety features described inFIG. 4.

In this regard,FIG. 6shows a simplified version of a power distribution network600. The power distribution network600has a transmitter602that may be in the power source402ofFIG. 4and a receiver604corresponding to the remote subunit404. The transmitter602receives a first signal V_IN_P from a positive power source606(also referred to as Vp inFIG. 6) and a second signal V_IN_N from a negative power source608(also referred to as Vn inFIG. 6). A positive conductor610P and a negative conductor610N couple the transmitter602to the receiver604. A timing control circuit612in the receiver604opens and closes a receiver switch614(analogous to the switch420) periodically or according to other commands. When the receiver switch614is open, a load616(also referred to as Rload inFIG. 6) is disconnected or decoupled from the transmitter602. The transmitter602further has a positive over current (OC) and leakage protection circuit618P and a negative OC and leakage protection circuit618N. The transmitter602outputs signals V_OUT_P onto the positive conductor610P and V_OUT_N onto the negative conductor610N (shown inFIG. 7).

Progressively more detail of the transmitter602is provided inFIG. 7, where a management circuit700(also referred to as a control circuit and/or a microcontroller (μC)) provides control signals to control the positive OC and leakage protection circuit618P and the negative OC and leakage protection circuit618N. To reduce the impact of a safety feature failure, exemplary aspects of the present disclosure provide for redundancy in the positive OC and leakage protection circuit618P and the negative OC and leakage protection circuit618N. Specifically, the positive OC and leakage protection circuit618P includes a first switch702P and a second switch704P (analogous to the switches412(1)-412(2) ofFIG. 4) while the negative OC and leakage protection circuit618N includes a first switch702N and a second switch704N (analogous to the switches412(3)-412(4) ofFIG. 4). Likewise, the positive OC and leakage protection circuit618P includes a first OC and leakage sensor706P and a second OC and leakage sensor708P, while the negative OC and leakage protection circuit618N includes a first OC and leakage sensor706N and a second OC and leakage sensor708N. Additionally, ammeters (A) formed by shunt resistors710P,712P are provided for the positive OC and leakage protection circuit618P while ammeters (A) formed by shunt resistors710N,712N are provided for the negative OC and leakage protection circuit618N.

An overview of the method for checking integrity of safety elements is provided inFIG. 8which illustrates, through a flowchart, process800, which begins when the remote subunit404,604disconnects (block802) by opening its switch420or614. The controller circuit408(or other control circuit) tests switches412(1)-412(4),702,704with a test current (block804). The controller circuit408(or other control circuit) tests leakage current sensors416(1)-416(4),706,708within the current measurement circuit with a test current (block806). The controller circuit408(or other control circuit) tests over current sensors416(1)-416(4),706,708within the current measurement circuit with a test current (block808). The controller circuit408determines if there was a fault (block810) in any of the blocks804,806, or808. If the answer is no, then the remote subunit404,604reconnects (block812) and the system continues to operate in normal mode. If there was a fault at block810, then the controller circuit408may open the switches412(1)-412(4),702,704and generate an alarm (block814). Note that because the remote subunit404,604operates independently from the controller circuit408, the remote subunit404,604may reconnect to the power conductors (not shown in the process800) even though there is no power being provided thereover once the switches412(1)-412(4),702,704are opened. Note that the order of the testing may be varied without departing from the scope of the present disclosure. Likewise, the frequency of the testing may be varied. In an exemplary aspect, the testing is done once a second. In another exemplary aspect, at least a portion of testing is done during every window in which the remote subunit404,604is decoupled from the power conductors406,610. Other testing frequencies may be employed without departing from the present disclosure.

To assist in fault detection, each of the elements (primary and redundant or back-up) of the positive OC and leakage protection circuit618P and the negative OC and leakage protection circuit618N must be tested. The primary way to test each element is through the use of a test current. However, just sending a test current through the elements may result in false alarms as current may be detected by protection elements at times when there should be no current flow (e.g., because the receiver604is disconnected).FIGS. 9A and 9Bprovide a still more detailed view of the transmitter602and particularly of the negative OC and leakage protection circuit618N with the understanding that the positive OC and leakage protection circuit618P is substantially similar.FIG. 9Bis an enlarged version of the right half ofFIG. 9Ato assist in viewing the elements that are otherwise rather small inFIG. 9A.

With reference toFIGS. 9A and 9B, the negative OC and leakage protection circuit618N includes the first switch702N and the second switch704N in the form of transistors as well as the first OC and leakage sensor706N and the second OC and leakage sensor708N. Further, shunt resistors710N,712N are provided (also labeled Rs_nA and Rs_nB). While the shunt resistors710N,712N are placed at specific points inFIG. 7, it should be appreciated that an ammeter (shunt resistor) can be placed in any place along the P/N branches. Within the first OC and leakage sensor706N are a first over current circuit900A and a first leakage current circuit902A. Within the second OC and leakage sensor708N are a second over current circuit900B and a second leakage current circuit902B. A test current is provided by a voltage source904, which in an exemplary aspect provides five volts (5 V) to produce the test current. A ground (GND) is provided proximate the voltage source904.

Beginning with the first over current circuit900A, exemplary aspects of the present disclosure use an over current test circuit to test the shunt resistors710N,712N, an amplifier906A, a comparator908A, and a one-shot latch910A, also referred to as a latch circuit or one-shot latch circuit. In particular, the management circuit700connects the voltage source904using a variety of switches as explained further below. In an exemplary aspect, the voltage source904is an existing voltage source, but could be dedicated for the transmitter602. The management circuit700also closes a switch912A within the first over current circuit900A using a signal914A (also referred to as an overcurrent injection enable (OC_INJECTION_EN) signal). Closing the switch912A connects the voltage source904to the amplifier906A and thus injects a test voltage (which is designed to be equivalent to the voltage generated by the load current (the current when a normal load616is connected to the transmitter602) on the shunt resistor712N) into the input of the amplifier906A. It should be appreciated that the amplifier906A receives voltages from both the upward or upstream side915A and the downward or downstream side915B of the shunt resistor712N. Note that when the second over current circuit900B is tested, the upward side915C of the shunt resistor710N and the downward side915D of the shunt resistor710N are used to feed values to the amplifier906B. Returning to the first over current circuit900A, the differential signal formed at the two inputs of the amplifier906A is then amplified by the amplifier906A. Assuming that there is no current across the shunt resistor712N, the only signal that is amplified is the injected test signal. The amplified signal916A is provided to the comparator908A, which compares the amplified signal916A to an over current reference value provided by circuit918A. The current present at the upward side915A should be zero to avoid inaccuracy (assuming no external load). However, because the test signal is present, and because the test signal should be higher than the threshold, the comparator908A will output a signal to the one-shot latch910A. The one-shot latch910A outputs a signal920A that is provided to the management circuit700and to an AND gate922A, which in turn provides an output to a NOR gate924A. The NOR gate924A is coupled to an AND gate926A, which in turn provides an on/off signal to a driver928A for the second switch704N.

In normal operation (i.e., not during a test), the arrival of the signal920A from the one-shot latch910A at the driver928A is indicative of an over current situation. To prevent the signal920A from being passed to the NOR gate924A, the management circuit700may send a signal930A (also labeled OC_TEST_EN) to the AND gate922A. The signal930A effectively turns off the AND gate922A, which blocks delivery of the signal920A to the NOR gate924A. Since the management circuit700knows that it should expect the signal920A as a result of the injected voltage during the interrupt window from the one-shot latch910A, the management circuit700can treat the test as a success and ignore the alarm that is implicit in the arrival of the signal920A. Finally, a signal932A is sent from the management circuit700to clear the one-shot latch910A and the signal930A is deasserted. If no signal920A is received at the management circuit700, then the management circuit700may determine that the over current circuit900A has a failure and generate an appropriate alarm and/or indicate a service call is appropriate. While the first over current circuit900A is being tested, the second over current circuit900B remains active and able to test for a normal over current condition.

The second OC and leakage sensor708N (only illustrated inFIG. 9A) is substantially similar to the first OC and leakage sensor706N with corresponding elements differentiated by a “B” label (e.g., the amplifier906B, comparator908B, etc.). It should further be appreciated that the first and second OC and leakage sensors706P and708P are likewise substantially similar allowing for the differences between positive conductor lines and negative conductor lines as is well understood.

An overview of the current levels and signals of the over current circuit900A is provided in timing diagram1000ofFIG. 10AwhileFIG. 10Bshows a flowchart illustrating a process1020associated with testing the over current circuit900A. In particular, the activity of the receiver switch614ofFIG. 6is provided on the first row1002. When the receiver switch614is “on,” current flows across the power conductors406P,406N,610P,610N and power is supplied to the receiver404,604. As noted, the receiver604periodically opens the receiver switch614(i.e., turns it “off”) as indicated at1002A,1002B, etc. The times1002A,1002B, etc. when the receiver switch614is off are referred to as the interrupt windows or interrupt periods. In an exemplary aspect, the interrupt window is 0.5 ms and the connection window is 3.5 ms. The signal930A is illustrated in the second row1004, where the over current test is enabled across multiple interrupt periods and the AND gate922A is turned off. Normal leakage testing continues to occur as evidenced by third row1006where no leakage pulses1006A,1006B, etc. are reported by a signal948A of a timed latch938A, also referred to as a latch circuit or timed latch circuit. However, when the test voltage is injected, and the switch912A is enabled as illustrated by the signal914A in the fourth row1008at times1008A,1008B, etc., the one-shot latch910A generates signal920A, shown in the fifth row1010. An alarm would normally activate at time1010A and is cleared by signal932A (not shown inFIG. 10A). An additional alarm may be generated at time1010B (and again be cleared by signal932A, still not shown inFIG. 10A). However, because signal930A is active, no alarm is generated and nothing turns off the switches702N,704N, and the management circuit700concludes that the over current circuit900A is operational.

Turning toFIG. 10B, the process1020associated with testing the over current circuit900A begins with an interrupt window (block1022) (e.g.,1002A). The amplifier906A is a difference amplifier and receives a first voltage (block1024) such as the voltage at the upstream side915A of the shunt resistor712N. The amplifier906A receives a second voltage (block1026) such as the voltage at the downstream side915B of the shunt resistor710N. The amplifier906A amplifies the differential signal and provides an output to the comparator908A. The comparator908A compares the output of the amplifier906A to a reference value (block1028) from circuit918A. When the output of the amplifier906A exceeds the reference value from the circuit918A (block1030), the comparator908A provides an output to the one-shot latch910A (block1032). The management circuit700detects the output signal920A of the one-shot latch910A (block1034). The process1020continues by testing a second over current circuit (block1036). Note that the process1020may be spread out over a series of interrupt windows. Thus, block1036may take place at a subsequent interrupt window than the original interrupt window of block1022. Note that if the output of the amplifier906A does not exceed the reference value at block1030, then the management circuit700may determine if there is still an interrupt window (block1038). If the answer is no, then the management circuit700may end the test and indicate a failure (block1040) since there was no indication that the test voltage was detected.

In contrast to the over current circuit900A which tests whether the elements that detect an over current situation which would potentially damage the power source, a leakage current test circuit tests the first leakage current circuit902A to determine whether there is any leakage current in the power distribution network600that would be indicative of an external load. Again, it should be appreciated that only one side is tested at a time so that the other side can detect a real leakage current situation. The first leakage current circuit902A includes the shunt resistors710N,712N, an amplifier934A, a comparator936A, and the timed latch938A (which in this case is 4 ms corresponding to an exemplary PRI). In particular, the leakage current test is based on an injection of a test current by passing a current through a resistor940and a closed switch942. The switch942is closed by a leakage injection enable signal944A from the management circuit700. Because the leakage current will go to both leakage current circuits902A,902B when the switch942is closed, to avoid a false alarm, the threshold of the side not under test is increased by using a leakage reference circuit945A,945B in conjunction with the opposite comparator936A,936B (i.e., the leakage reference circuit945B is coupled to the comparator936A and the leakage reference circuit945A is coupled to the comparator936B). While not shown inFIG. 9A or 9B, it should be appreciated that the management circuit700may send a signal (also not shown) to the respective leakage reference circuit depending on which side is being tested. For the side that is not under test, the appropriate leakage reference circuit945A,945B provides a value equal to the sum of the original threshold value and the value created by the voltage source904and the resistor940. For the side under test, the injected test current will emulate the leakage and be detected by the amplifier934A. In particular, the amplifier934A (which is also a difference amplifier) receives a signal from the upward side915A of the shunt resistor712N and a signal from the downward side915D of the shunt resistor710N. The difference between these signals is amplified by the amplifier934A. Similarly, the amplifier934B receives the same two signals. The amplified signal from the amplifier934A is compared to the threshold value by the comparator936A. Because this side is under test, the leakage reference circuit945B is not active. The comparator936A will output a signal946A to the timed latch938A. The timed latch938A, having received a pulse during the interrupt window, will output a signal948A, which is passed to the management circuit700and to an input of an AND gate950A. The AND gate950A is coupled to the NOR gate924A. The AND gate950A also receives a signal952A from the management circuit700. The AND gate950A is the alarm generator circuit. However, the signal952A from the management circuit700prevents the AND gate950A from generating an alarm during the testing phase. However, as the leakage current circuit902B is not under test, its corresponding AND gate950B may still generate an alarm if a leakage current in excess of the elevated threshold (the injected test current plus the original leakage current signal) is detected. If the timed latch938A does not trip, then there is a fault in the leakage current circuit902A and an alarm may be generated. If, however, the timed latch938A did trip, then the test was satisfied, the switch942is opened while the timed latch938A is cleared, the reference circuit945A (i.e., the circuit for the side not under test) is set by the management circuit700to its default value, and normal operation resumes.

An overview of the current levels and signals of the leakage current circuit902A is provided in timing diagram1100ofFIG. 11A. In particular, the activity of the receiver switch614ofFIG. 6is provided on the first row1002. When the receiver switch614is “on,” current flows across the power conductors610N,610P and power is supplied to the receiver604. As noted, the receiver604periodically opens the receiver switch614(i.e., turns it “off”) as indicated at1002A,1002B, etc. The second row1102shows the adjustment of the threshold values. Normally, the leakage threshold is some small value Vt as shown by the second row1102. That is, if current is detected above Vt, it is generally assumed that there is an improper short on the conductors. While Vt could be zero, there may be noise on the conductors, which makes a higher value more appropriate. However, the nature of the leakage test is to send a known current through the leakage sensors and generate an alarm if the leakage sensors do not detect the expected current induced by the injected known current. To avoid a false positive, the side not under test must have its detection threshold adjusted. Thus, during a test, as indicated by the assertion1104A of the leakage injection enable signal944A (turning on switch942) in row1104, the threshold of the side not under test (e.g., circuit902B) is elevated to1102B corresponding to Vt plus some known test value Tv. Meanwhile, the threshold1102A for the side under test (e.g., circuit902A) remains at Vt (i.e., the original threshold value). The leakage injection enable signal944A may be asserted only after the threshold is elevated to1102B and may be deasserted before the threshold is lowered back to1102A to avoid a false positive. In this fashion, the side not under test (e.g.,902B) will generate the expected no leakage pulses1106A,1106B,1106C.

Row1108illustrates signal952A from the management circuit700to the AND gate950A. Since the AND gate950A is the alarm generator circuit, use of the signal952A from the management circuit700prevents the AND gate950A from generating an alarm during the testing phase. Row1110represents the no leakage pulse signal from the circuit902A (i.e., the device under test), and is, as illustrated, asserted1110A in the first interrupt window1002A (i.e., before the test starts), but not present in subsequent interrupt windows1002B, etc. (i.e., while the test is occurring). Row1112illustrates the signal of leakage detection. Specifically, this signal is detected by the management circuit700and shows that the leakage detection circuit detected the test leakage current. If no leakage signal was detected during the test, the management circuit700concludes that the leakage detection circuit is damaged and will disconnect the power conductor406and the remote subunit404from the power source414by opening switches412(1)-412(4).

The process1150for testing the leakage current circuit902A is provided as a flowchart inFIG. 11B. In this regard, the process1150begins with an interrupt window (block1152) (e.g.,1002A). The amplifier934A receives a first voltage (block1154) such as at the upstream side915A of the shunt resistor712N. The amplifier934A receives a second voltage (block1156) such as at the downstream side915D of the shunt resistor710N. The amplifier934A amplifies the differential signal and provides an output to the comparator936A. The comparator936A compares the output of the amplifier934A to a reference value (block1158) from circuit944B. When the output of the amplifier934A exceeds the reference value from the circuit944B (block1160), the comparator936A provides an output to the timed latch938A (block1162). The management circuit700detects the signal948A of the timed latch938A (block1164) and the latch938A is cleared (block1165). The process1150continues by testing a second leakage current circuit (block1166). Note that the process1150may be spread out over a series of interrupt windows. Thus, block1166may take place at a subsequent interrupt window than the original interrupt window of block1152. Note that if the output of the amplifier934A does not exceed the reference value at block1160, then the management circuit700may determine if there is still an interrupt window (block1168). If the answer is no, then the management circuit700may end the test by indicating a fail (block1170) and generating an alarm.

The circuitry to perform the test of the switches702N and704N is also shown inFIGS. 9A and 9B. In particular, the test current is supplied by the voltage source904during an interrupt period. The switch702N or704N under test will be opened so as to create a “no leakage pulse” at the appropriate leakage current circuit902A,902B. If the associated leakage current circuit902A,902B does not detect a no leakage condition, then the switch702N,704N is not able to open and an alarm is generated. To do this, the switch942is closed, the voltage source904is connected, and the test current is activated. The reference level in the leakage reference circuit945A is increased to avoid a false alarm in the untested circuit. As with the leakage current test, the increment in value should be proportional to the injected current. The leakage enable signal952A is generated by the management circuit700to prevent a false activation of the switches702N,704N. A signal954A is generated by the management circuit700, which allows a switching signal from an AND gate956A. Alternatively, the signal954A may be generated by the management circuit700synchronously to the power interrupt window. The signal948A from the timed latch938A is also sampled by the management circuit700. A decision is made by the management circuit700whether the switch being tested is operational and whether future system operation is safe. The leakage current injection is then turned off by the management circuit700(i.e., by disconnecting the voltage source904or opening switch942). The leakage current threshold value of the untested circuit is set back to its default value and the timed latch938A is cleared by signal960A.

An overview of the current levels and signals of the switch testing is provided in timing diagram1200ofFIG. 12A. In particular, the activity of the receiver switch614ofFIG. 6is provided on the first row1002. As inFIG. 10A, when the receiver switch614is “on,” current flows across the power conductors610P,610N and power is supplied to the receiver604. As noted, the receiver604periodically opens the receiver switch614(i.e., turns it “off”) as indicated at1002A,1002B, etc. As described in reference toFIG. 11A, row1102shows the leakage thresholds for the device under test (threshold1102A, Vt) and the device not under test (threshold1102B, Vt+Tv).

As further explained in reference toFIG. 11A, row1104represents the leakage injection enable signal944A and its assertion and use. Assuming no actual leakage, the side not under test (e.g.,902B) generates the expected no leakage pulses1106A,1106B,1106C as shown by the third row1106. The signal of row1202corresponds to the signal MOSFET_ON_OFF from management circuit700inFIGS. 9A, 9Band turns the switch704N off at times1202A and1202B. The switch702N is thus open when a no leakage pulses1204A and1204B for the side under test are generated as shown in line1204. Because the switch702N is open when the pulses1204A and1204B are generated, no leakage alarm is generated at times1206A or1206B in line1206.

A process1250is provided inFIG. 12Bas a flowchart for the testing of the switches702N,704N. The process1250begins with an interrupt window (block1252) (e.g.,1002A). The management circuit700opens a switch702N (block1254). The amplifier934A receives a first voltage (block1256) such as at the upstream side915A of the shunt resistor712N. The amplifier934A receives a second voltage (block1258) such as at the downstream side915D of the shunt resistor710N. The amplifier934A amplifies the differential signal and provides an output to the comparator936A. The comparator936A compares the output of the amplifier934A to a reference value (block1260) from circuit944B. When the output of the amplifier934A exceeds the reference value from the circuit944B (block1262), the comparator936A provides an output to the timed latch938A (block1264). The management circuit700detects the signal948A of the timed latch938A (block1266). The process1250continues by testing a second switch704N (block1268). Note that the process1250may be spread out over a series of interrupt windows. Thus, block1268may take place at a subsequent interrupt window than the original interrupt window of block1252. Note that if the output of the amplifier934A does not exceed the reference value at block1262, then the management circuit700may determine if there is still an interrupt window (block1270). If the answer is no, then the management circuit700may end the test and indicate a failure (block1272).

While the above discussion contemplates a single management circuit700operating all the testing of the safety elements, it should be appreciated that each safety element may be tested through its own management circuit (not shown). The separate management circuit version may be easier to implement, but may add complexity for software updates (as multiple instances of the software will require updates). However, evaluating such tradeoffs is a well understood part of the normal design process.

A simplified flowchart of a process1400including all three tests is set forth inFIG. 14. The process1400includes, during interrupt windows where a remote communication element decouples from a power conductor, testing an over current circuit in a power distribution circuit for integrity (block1402); testing a leakage current circuit in the power distribution circuit for integrity (block1404); and testing a switch that decouples a power source from the power conductor in the power distribution circuit for integrity (block1406).

Note that the present disclosure may be used in a cascaded power distribution network.FIG. 13is a schematic diagram illustrating the power distribution network400ofFIG. 4in the exemplary form of a DCS (or other communications system) with the power source402positioned in a power head unit1300, which is configured to distribute power to a plurality of remote subunits404(1)-404(X), where at least one remote subunit404(E) is cascaded relative to another. Each remote subunit404(1)-404(X) includes a remote power input1302(1)-1302(X) coupled to the power conductors406(1)-406(X), respectively, which are configured to be coupled to the power source402as previously described inFIG. 4. The power source402includes a plurality of power outputs1304(1)-1304(X) each configured to be coupled to a power conductor406. The remote subunits404(1)-404(X) may also have remote power outputs1306(1)-1306(X) that are configured to carry power from the respective power conductors406(1)-406(X) received on the remote power inputs1302(1)-1302(X) to an extended remote subunit, such as extended remote subunit404(E). Also, as shown inFIG. 13, the extended remote subunit404(E) may be coupled to the remote subunit404(1) and also configured to receive power from the power source402via the remote subunit404(1).

Note that any of the referenced inputs herein can be provided as input ports or circuits, and any of the referenced outputs herein can be provided as output ports or circuits.

In the interests of completeness, one exemplary DCS having a power distribution network is explored below with reference toFIGS. 15-19and an exemplary computer that may be used at various locations within a power distribution network is illustrated inFIG. 20. It should be appreciated that the precise context for the power distribution network is not central to the present disclosure.

In this regard,FIG. 15illustrates a wireless distributed communication system (WDCS)1500that is configured to distribute communications services to remote coverage areas1502(1)-1502(N), where ‘N’ is the number of remote coverage areas. The WDCS1500inFIG. 15is provided in the form of a distributed antenna system (DAS)1504. The DAS1504can be configured to support a variety of communications services that can include cellular communications services, wireless communications services, such as RF identification (RFID) tracking, Wireless Fidelity (Wi-Fi), local area network (LAN), and wireless LAN (WLAN), wireless solutions (Bluetooth, Wi-Fi Global Positioning System (GPS) signal-based, and others) for location-based services, and combinations thereof, as examples. The remote coverage areas1502(1)-1502(N) are created by and centered on remote units1506(1)-1506(N) connected to a central unit1508(e.g., a head-end controller, a central unit, or a head-end unit). The central unit1508may be communicatively coupled to a source transceiver1510, such as for example, a base transceiver station (BTS) or a baseband unit (BBU). In this regard, the central unit1508receives downlink communications signals1512D from the source transceiver1510to be distributed to the remote units1506(1)-1506(N). The downlink communications signals1512D can include data communications signals and/or communication signaling signals, as examples. The central unit1508is configured with filtering circuits and/or other signal processing circuits that are configured to support a specific number of communications services in a particular frequency bandwidth (i.e., frequency communications bands). The downlink communications signals1512D are communicated by the central unit1508over a communications link1514over their frequency to the remote units1506(1)-1506(N).

With continuing reference toFIG. 15, the remote units1506(1)-1506(N) are configured to receive the downlink communications signals1512D from the central unit1508over the communications link1514. The downlink communications signals1512D are configured to be distributed to the respective remote coverage areas1502(1)-1502(N) of the remote units1506(1)-1506(N). The remote units1506(1)-1506(N) are also configured with filters and other signal processing circuits that are configured to support all or a subset of the specific communications services (i.e., frequency communications bands) supported by the central unit1508. In a non-limiting example, the communications link1514may be a wired communications link, a wireless communications link, or an optical fiber-based communications link. Each of the remote units1506(1)-1506(N) may include an RF transmitter/receiver1516(1)-1516(N) and a respective antenna1518(1)-1518(N) operably connected to the RF transmitter/receiver1516(1)-1516(N) to wirelessly distribute the communications services to user equipment (UE)1520within the respective remote coverage areas1502(1)-1502(N). The remote units1506(1)-1506(N) are also configured to receive uplink communications signals1512U from the UE1520in the respective remote coverage areas1502(1)-1502(N) to be distributed to the source transceiver1510.

Because the remote units1506(1)-1506(N) include components that require power to operate, such as the RF transmitter/receivers1516(1)-1516(N) for example, it is necessary to provide power to the remote units1506(1)-1506(N). In one example, each remote unit1506(1)-1506(N) may receive power from a local power source. In another example, the remote units1506(1)-1506(N) may be powered remotely from a remote power source(s). For example, the central unit1508may include a power source1522that is configured to remotely supply power over the communications links1514to the remote units1506(1)-1506(N). For example, the communications links1514may be cables that include electrical conductors for carrying current (e.g., direct current (DC)) to the remote units1506(1)-1506(N). If the WDCS1500is an optical fiber-based WDCS in which the communications links1514include optical fibers, the communications links1514may be a “hybrid” cable that includes optical fibers for carrying the downlink and uplink communications signals1512D,1512U and separate electrical conductors for carrying current to the remote units1506(1)-1506(N).

The DAS1504and its power distribution network400can be provided in an indoor environment as illustrated inFIG. 16.FIG. 16is a partially schematic cut-away diagram of a building infrastructure1600employing the power distribution network400. The building infrastructure1600in this embodiment includes a first (ground) floor1602(1), a second floor1602(2), and an Fth floor1602(F), where ‘F’ can represent any number of floors. The floors1602(1)-1602(F) are serviced by the central unit1508to provide antenna coverage areas1604in the building infrastructure1600. The central unit1508is communicatively coupled to a signal source1606, such as a BTS or BBU, to receive the downlink electrical communications signals. The central unit1508is communicatively coupled to the remote subunits to receive uplink optical communications signals from the remote subunits. The downlink and uplink optical communications signals are distributed between the central unit1508and the remote subunits over a riser cable1608in this example. The riser cable1608may be routed through interconnect units (ICUs)1610(1)-1610(F) dedicated to each floor1602(1)-1602(F) for routing the downlink and uplink optical communications signals to the remote subunits. The ICUs1610(1)-1610(F) may also include respective power distribution circuits that include power sources as part of the power distribution network400, wherein the power distribution circuits are configured to distribute power remotely to the remote subunits to provide power for operating the power-consuming components in the remote subunits. For example, array cables1612(1)-1612(2F) may be provided and coupled between the ICUs1610(1)-1610(F) that contain both optical fibers to provide the respective downlink and uplink optical fiber communications media and power conductors (e.g., electrical wire) to carry current from the respective power distribution circuits to the remote subunits.

FIG. 17is a schematic diagram of an exemplary optical fiber-based DAS1700in which a power distribution network can be provided. In this example, the power distribution network400is provided in a DCS which is the DAS1700in this example. Note that the power distribution network400is not limited to being provided in a DCS. A DAS is a system that is configured to distribute communications signals, including wireless communications signals, from a central unit to a plurality of remote subunits over physical communications media, to then be distributed from the remote subunits wirelessly to client devices in wireless communication range of a remote subunit. The DAS1700in 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)1704(1)-1704(T) are provided in a central unit1706to receive and process downlink electrical communications signals1708D(1)-1708D(S) prior to optical conversion into downlink optical communications signals. The downlink electrical communications signals1708D(1)-1708D(S) may be received from a base transceiver station (BTS) or baseband unit (BBU) as examples. The downlink electrical communications signals1708D(1)-1708D(S) may be analog signals or digital signals that can be sampled and processed as digital information. The RIMs1704(1)-1704(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 toFIG. 17, the central unit1706is configured to accept the plurality of RIMs1704(1)-1704(T) as modular components that can easily be installed and removed or replaced in a chassis. In one embodiment, the central unit1706is configured to support up to twelve (12) RIMs1704(1)-1704(12). Each RIM1704(1)-1704(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 unit1706and the DAS1700to support the desired radio sources. For example, one RIM1704(1)-1704(T) may be configured to support the Personal Communication Services (PCS) radio band. Another RIM1704(1)-1704(T) may be configured to support the 700 MHz radio band. In this example, by inclusion of these RIMs1704(1)-1704(T), the central unit1706could be configured to support and distribute communications signals, including those for the communications services and communications bands described above as examples.

The RIMs1704(1)-1704(T) may be provided in the central unit1706that 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 & TTE frequencies (880-915 MHz on uplink and 925-960 MHz on downlink), EU R & TTE frequencies (1710-1785 MHz on uplink and 1805-1880 MHz on downlink), EU R & 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).

With continuing reference toFIG. 17, the received downlink electrical communications signals1708D(1)-1708D(S) are provided to a plurality of optical interfaces provided in the form of optical interface modules (OIMs)1710(1)-1710(W) in this embodiment to convert the downlink electrical communications signals1708D(1)-1708D(S) into downlink optical communications signals1712D(1)-1712D(S). The notation “1-W” indicates that any number of the referenced component 1-W may be provided. The OIMs1710(1)-1710(W) may include one or more optical interface components (OICs) that contain electrical-to-optical (E-O) converters1716(1)-1716(W) to convert the received downlink electrical communications signals1708D(1)-1708D(S) into the downlink optical communications signals1712D(1)-1712D(S). The OIMs1710(1)-1710(W) support the radio bands that can be provided by the RIMs1704(1)-1704(T), including the examples previously described above. The downlink optical communications signals1712D(1)-1712D(S) are communicated over a downlink optical fiber communications link1714D to a plurality of remote subunits (e.g., remote subunits404) provided in the form of remote subunits 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 communications signals1712D(1)-1712D(S) can be distributed to each remote subunit. Thus, the distribution of the downlink optical communications signals1712D(1)-1712D(S) from the central unit1706to the remote subunits is in a point-to-multipoint configuration in this example.

With continuing reference toFIG. 17, the remote subunits include optical-to-electrical (O-E) converters1720(1)-1720(X) configured to convert the one or more received downlink optical communications signals1712D(1)-1712D(S) back into the downlink electrical communications signals1708D(1)-1708D(S) to be wirelessly radiated through antennas1722(1)-1722(X) in the remote subunits to user equipment (not shown) in the reception range of the antennas1722(1)-1722(X). The OIMs1710(1)-1710(W) may also include O-E converters1724(1)-1724(W) to convert received uplink optical communications signals1712U(1)-1712U(X) from the remote subunits into uplink electrical communications signals1726U(1)-1726U(X) as will be described in more detail below.

With continuing reference toFIG. 17, the remote subunits are also configured to receive uplink electrical communications signals1728U(1)-1728U(X) received by the respective antennas1722(1)-1722(X) from client devices in wireless communication range of the remote subunits. The uplink electrical communications signals1728U(1)-1728U(X) may be analog signals or digital signals that can be sampled and processed as digital information. The remote subunits include E-O converters1729(1)-1729(X) to convert the received uplink electrical communications signals1728U(1)-1728U(X) into uplink optical communications signals1712U(1)-1712U(X). The remote subunits distribute the uplink optical communications signals1712U(1)-1712U(X) over an uplink optical fiber communications link1714U to the OIMs1710(1)-1710(W) in the central unit1706. The O-E converters1724(1)-1724(W) convert the received uplink optical communications signals1712U(1)-1712U(X) into uplink electrical communications signals1730U(1)-1730U(X), which are processed by the RIMs1704(1)-1704(T) and provided as the uplink electrical communications signals1730U(1)-1730U(X) to a source transceiver such as a BTS or BBU.

Note that the downlink optical fiber communications link1714D and the uplink optical fiber communications link1714U coupled between the central unit1706and the remote subunits may be a common optical fiber communications link, wherein for example, wave division multiplexing (WDM) may be employed to carry the downlink optical communications signals1712D(1)-1712D(S) and the uplink optical communications signals1712U(1)-1712U(X) on the same optical fiber communications link. Alternatively, the downlink optical fiber communications link1714D and the uplink optical fiber communications link1714U coupled between the central unit1706and the remote subunits may be single, separate optical fiber communications links, wherein for example, wave division multiplexing (WDM) may be employed to carry the downlink optical communications signals1712D(1)-1712D(S) on one common downlink optical fiber and the uplink optical communications signals1712U(1)-1712U(X) on a separate, only uplink optical fiber. Alternatively, the downlink optical fiber communications link1714D and the uplink optical fiber communications link1714U coupled between the central unit1706and the remote subunits may be separate optical fibers dedicated to and providing a separate communications link between the central unit1706and each remote subunit.

FIG. 18is a schematic diagram of an exemplary mobile telecommunications environment1800that includes an exemplary radio access network (RAN) that includes a mobile network operator (MNO) macrocell employing a radio node, a shared spectrum cell employing a radio node, an exemplary small cell RAN employing a multi-operator radio node located within an enterprise environment as DCSs, and that can include one or more power distribution networks, including the power distribution network400. The environment1800includes exemplary macrocell RANs1802(1)-1802(M) (“macrocells1802(1)-1802(M)”) and an exemplary small cell RAN1804located within an enterprise environment1806and configured to service mobile communications between a user mobile communications device1808(1)-1808(N) to an MNO1810. A serving RAN for a user mobile communications device1808(1)-1808(N) is a RAN or cell in the RAN in which the user mobile communications devices1808(1)-1808(N) have an established communications session with the exchange of mobile communications signals for mobile communications. Thus, a serving RAN may also be referred to herein as a serving cell. For example, the user mobile communications devices1808(3)-1808(N) inFIG. 18are being serviced by the small cell RAN1804, whereas user mobile communications devices1808(1) and1808(2) are being serviced by the macrocell1802. The macrocell1802is an MNO macrocell in this example. However, a shared spectrum RAN1803(also referred to as “shared spectrum cell1803”) includes a macrocell in this example and supports communications on frequencies that are not solely licensed to a particular MNO and thus may service user mobile communications devices1808(1)-1808(N) independent of a particular MNO. For example, the shared spectrum cell1803may be operated by a third party that is not an MNO and wherein the shared spectrum cell1803supports Citizen Broadband Radio Service (CBRS). Also, as shown inFIG. 18, the MNO macrocell1802, the shared spectrum cell1803, and/or the small cell RAN1804can interface with a shared spectrum DCS1801supporting coordination of distribution of shared spectrum from multiple service providers to remote subunits to be distributed to subscriber devices. The MNO macrocell1802, the shared spectrum cell1803, and the small cell RAN1804may be neighboring radio access systems to each other, meaning that some or all can be in proximity to each other such that a user mobile communications device1808(1)-1808(N) may be able to be in communications range of two or more of the MNO macrocell1802, the shared spectrum cell1803, and the small cell RAN1804depending on the location of user mobile communications devices1808(1)-1808(N).

InFIG. 18, the mobile telecommunications environment1800in this example is arranged as an LTE (Long Term Evolution) system as described by the Third Generation Partnership Project (3GPP) as an evolution of the GSM/UMTS standards (Global System for Mobile communication/Universal Mobile Telecommunications System). It is emphasized, however, that the aspects described herein may also be applicable to other network types and protocols. The mobile telecommunications environment1800includes the enterprise environment1806in which the small cell RAN1804is implemented. The small cell RAN1804includes a plurality of small cell radio nodes1812(1)-1812(C). Each small cell radio node1812(1)-1812(C) has a radio coverage area (graphically depicted in the drawings as a hexagonal shape) that is commonly termed a “small cell.” A small cell may also be referred to as a femtocell or, using terminology defined by 3GPP, as a Home Evolved Node B (HeNB). In the description that follows, the term “cell” typically means the combination of a radio node and its radio coverage area unless otherwise indicated.

InFIG. 18, the small cell RAN1804includes one or more services nodes (represented as a single services node1814) that manage and control the small cell radio nodes1812(1)-1812(C). In alternative implementations, the management and control functionality may be incorporated into a radio node, distributed among nodes, or implemented remotely (i.e., using infrastructure external to the small cell RAN1804). The small cell radio nodes1812(1)-1812(C) are coupled to the services node1814over a direct or local area network (LAN) connection1816as an example, typically using secure IPsec tunnels. The small cell radio nodes1812(1)-1812(C) can include multi-operator radio nodes. The services node1814aggregates voice and data traffic from the small cell radio nodes1812(1)-1812(C) and provides connectivity over an IPsec tunnel to a security gateway (SeGW)1818in a network1820(e.g., evolved packet core (EPC) network in a 4G network, or 5G Core in a 5G network) of the MNO1810. The network1820is typically configured to communicate with a public switched telephone network (PSTN)1822to carry circuit-switched traffic, as well as for communicating with an external packet-switched network such as the Internet1824.

The environment1800also generally includes a node (e.g., eNodeB or gNodeB) base station, or “macrocell”1802. The radio coverage area of the macrocell1802is typically much larger than that of a small cell where the extent of coverage often depends on the base station configuration and surrounding geography. Thus, a given user mobile communications device1808(1)-1808(N) may achieve connectivity to the network1820(e.g., EPC network in a 4G network, or 5G Core in a 5G network) through either a macrocell1802or small cell radio node1812(1)-1812(C) in the small cell RAN1804in the environment1800.

FIG. 19is a schematic diagram illustrating exemplary DCSs1900that support 4G and 5G communications services. The DCSs1900inFIG. 19can include one or more power distribution networks, including the power distribution network400inFIG. 4, configured to perform a line capacitance discharge of power conductors between a power source and a remote unit(s) when a safety disconnect of the power source is performed in response to a measured current from the connected power source when the remote unit is decoupled from the power source. The DCSs1900support both legacy 4G LTE, 4G/5G non-standalone (NSA), and 5G communications systems. As shown inFIG. 19, a centralized services node1902is provided that is configured to interface with a core network to exchange communications data and distribute the communications data as radio signals to remote subunits. In this example, the centralized services node1902is configured to support distributed communications services to a millimeter wave (mmW) radio node1904. The functions of the centralized services node1902can be virtualized through an x2 interface1906to another services node1908. The centralized services node1902can also include one or more internal radio nodes that are configured to be interfaced with a distribution node1910to distribute communications signals for the radio nodes to an open RAN (O-RAN) remote unit1912that is configured to be communicatively coupled through an O-RAN interface1914.

The centralized services node1902can also be interfaced through an x2 interface1916to a BBU1918that can provide a digital signal source to the centralized services node1902. The BBU1918is configured to provide a signal source to the centralized services node1902to provide radio source signals1920to the O-RAN remote unit1912as well as to a distributed router unit (DRU)1922as part of a digital DAS. The DRU1922is configured to split and distribute the radio source signals1920to different types of remote subunits, including a lower-power remote unit (LPR)1924, a radio antenna unit (dRAU)1926, a mid-power remote unit (dMRU)1928, and a high-power remote unit (dHRU)1930. The BBU1918is also configured to interface with a third party central unit1932and/or an analog source1934through an radio frequency (RF)/digital converter1936.

FIG. 20is a schematic diagram representation of additional detail illustrating a computer system2000that could be employed in any component or circuit in a power distribution network, including the power distribution network400inFIG. 4, configured to perform a line capacitance discharge of power conductors between a power source and a remote unit(s) when a safety disconnect of the power source is performed in response to a measured current from the connected power source when the remote unit is decoupled from the power source. In this regard, the computer system2000is 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 system2000inFIG. 20may 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 communications services. The computer system2000may be connected (e.g., networked) to other machines in a 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 system2000may 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's computer.

The exemplary computer system2000in this embodiment includes a processing device or processor2002, a main memory2004(e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM), such as synchronous DRAM (SDRAM), etc.), and a static memory2006(e.g., flash memory, static random access memory (SRAM), etc.), which may communicate with each other via a data bus2008. Alternatively, the processor2002may be connected to the main memory2004and/or static memory2006directly or via some other connectivity means. The processor2002may be a controller, and the main memory2004or static memory2006may be any type of memory.

The processor2002represents one or more general-purpose processing devices, such as a microprocessor, central processing unit, or the like. More particularly, the processor2002may 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 processor2002is configured to execute processing logic in instructions for performing the operations and steps discussed herein.

The computer system2000may further include a network interface device2010. The computer system2000also may or may not include an input2012, configured to receive input and selections to be communicated to the computer system2000when executing instructions. The computer system2000also may or may not include an output2014, 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 system2000may or may not include a data storage device that includes instructions2016stored in a computer-readable medium2018. The instructions2016may also reside, completely or at least partially, within the main memory2004and/or within the processor2002during execution thereof by the computer system2000, the main memory2004and the processor2002also constituting computer-readable medium. The instructions2016may further be transmitted or received over a network2020via the network interface device2010.

While exemplary aspects of the present disclosure have been discussed in the context of the remote subunit404disconnecting from the power source402, the present disclosure is not so limited. In particular, the present disclosure may be used with systems that disconnect from the power source with appropriate changes to the data modulation. That is, data is transferred from the power source to the remote subunits by changing the PRI and data from the remote subunit to the power source is modulated by extending an interrupt time period (i.e., a switch at the remote subunit will keep the circuit open for longer). Data received at the power source will be detected by measuring the time extension of the default interrupt time period and data received at the remote subunit will be detected by measuring the time interval between PM rising edges using current measurements.

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'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.

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.