# Patent

## Title
Power converter system

## Abstract

A system and method for integrating communications equipment. The system includes a power supply in which the power supply provides power to telephone equipment located in a centralized unit and at least one power converter for receiving the power from the power supply and having a chassis for supporting at least one power converter module. The power converter converts the power from the power supply into at least one output voltage for powering a second set of communications equipment, and the second set of communications equipment is located in the centralized unit. In one arrangement, the second set of communications equipment can include cable television equipment.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not Applicable)
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to electrical equipment and more particularly, to power converters.
2. Description of Related Art
In today's telecommunications industry, consolidation has become prevalent, and as a result, several companies have began to offer telephone and cable television service. Generally, telephone utilities use a negative (−)48 volts DC (VDC) to power telephone equipment located at a central operations facility. For example, many telephone service providers employ −48VDC power from one or more battery primary power source buses to power such equipment. Multiple buses may be used to ensure operation in the event of a bus power failure.
In contrast, cable television companies typically rely on standard 110 Volt AC (VAC) primary source power to operate the equipment necessary to provide cable television services. In many cases, this primary source power is converted to 24 VDC to operate the cable television headend equipment. Moreover, the 110 VAC power supply is typically backed up with a generator or a stand alone 110 VAC backup system, each of which can supply the required voltage to operate the headend equipment in the event of a power failure. As a result, should a single communications entity desire to supply telephone and cable television services to the consuming public, such an endeavor creates a need for numerous power supplies, including associated backup sources, and for large amounts of space to accommodate the necessary equipment, particularly if the operation is to be centered at a sole location. Thus, what is needed in the art is a system for integrating the equipment to provide these services that does not require large amounts of room in which to operate.
SUMMARY OF THE INVENTION
The present invention concerns a system for integrating communications equipment. The system includes a power supply in which the power supply provides power to telephone equipment located in a centralized unit and at least one power converter for receiving power from the power supply and having a chassis for supporting at least one power converter module. The power converter converts the power from the power supply into at least one output voltage for powering a second set of communications equipment, and the second set of communications equipment is located in said centralized unit. In one arrangement, the second set of communications equipment can be cable television equipment, and the chassis can have at least one connector on a backplane circuit board and at least one channel.
In addition, the connector can detachably receive the power converter module, and the at least one channel can guide the power converter module to and from the connector. As such, the power converter module can be replaceable with a second power converter module as the power converter receives the power from the power supply. In another arrangement, the power supply can be an approximate negative 48 volts DC power supply, and the output voltage can be a voltage selected from at least an approximate positive 24 volts DC and an approximate positive 28 volts DC.
In one aspect of the invention, the power converter module can include selection structure to permit selection between a plurality of the output voltages. Specifically, the power converter module can include a voltage divider network having a plurality of resistors and a plurality of outputs in which at least a portion of the outputs can be coupled to the resistors. The selection structure can include a jumper wire for selectively coupling at least one of the outputs to a ground potential. Alternatively, the selection structure can include a switch for selectively coupling at least one of the outputs to a ground potential.
In yet another aspect of the invention, each power converter module can be an independent power converter module, and the power supply can be a single power source bus. In an alternative arrangement, the power converter modules can be grouped in redundant pairs such that each redundant pair can include at least one active power converter module and at least one standby power converter module. Moreover, the power supply can include at least two power source buses such that each power source bus can supply power to a redundant pair such that the power source buses are substantially equally loaded. The power source buses can be redundant power source buses such that each redundant pair will continue to operate if one of said redundant power source buses fails.
The present invention also concerns a method for integrating communications equipment. The method includes the steps of receiving power from a power supply used to power telephone equipment in a centralized unit, converting the power from the power supply into at least one output voltage with a power converter having a chassis for supporting at least one power converter module, and powering a second set of communications equipment with the at least one output voltage. The second set of communications equipment is located in the centralized unit. In one arrangement of the method, the second set of communications equipment can be cable television equipment.
In another arrangement, the chassis can have at least one connector on a backplane circuit board and at least one channel in which the connector can detachably receive the power converter module and the at least one channel can guide the power converter module to and from the connector. The method can also include the steps of removing the power converter module when the power converter module fails and replacing the failed power converter module with a second power converter module such that the removing and replacing steps can be performed as the power converter receives the power from the power supply.
In another aspect of the invention, the method can also include the steps of providing the power converter module with selection structure to permit selection between a plurality of the output voltages and selecting at least one of the output voltages to power the cable television equipment. Additionally, the method can include the step of grouping the power converter modules into redundant pairs such that each of the redundant pairs can include at least one active power converter module and at least one standby power converter module and the power supply can have at least two power source buses such that each power source bus supplies power to a redundant pair and the step of substantially equally loading the power source buses with the redundant pairs.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a perspective view of a system for converting power in accordance with the inventive arrangements.
FIG. 2 illustrates a perspective view of the system of FIG. 1 with a portion of the system removed in accordance with the inventive arrangements.
FIG. 3 illustrates a rear perspective view of the system of FIG. 1 in accordance with the inventive arrangements.
FIG. 4 illustrates a block diagram of the system shown in FIG. 1 in accordance with the inventive arrangements.
FIG. 5 illustrates an alternative block diagram of the system shown in FIG. 1 in accordance with the inventive arrangements.
FIG. 6 illustrates an example of a power converter module in accordance with the inventive arrangements.
FIG. 7 illustrates an example of a switch that can be used in the power converter module shown in FIG. 6 in accordance with the inventive arrangements.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a perspective view of a power converter 100 is shown. The power converter 100 can include a chassis 110 and one or more power converter modules 112 in which the chassis supports the power converter modules 112. Although FIG. 1 illustrates the power converter 100 as having four power converter modules 112, it is understood that the invention is not so limited, as the power converter 100 can include any suitable number of power converter modules 112. The power converter 100 can receive power from a power supply (not shown) and can convert this power into one or more output voltages. As will be described below, this power conversion can be used to integrate communications equipment.
In one arrangement, the chassis 110 can include one or more slots 114 for receiving any suitable type of fastener (not shown) that can enable the chassis 110 of the power converter 100 to be coupled to an equipment rack (not shown). In addition, the power converter 100 can have dimensions that enable the power converter 100 to be placed in an equipment rack that is typically used to house electronic equipment. More specifically, the power converter 100 can be mounted in a volumetric configuration commonly referred to in the industry as a rack unit (RU).
As an example, the power converter 100 can include a face plate 115 having a length of approximately nineteen inches and a height of roughly one and three-quarters inches. As such, the power converter 100 requires very little storage space, and numerous power converters 100 can be fitted in a specific location. Of course, those of ordinary skill in the art will appreciate that the invention is not limited in this regard, as the power converter 100 can be built to fit within any other suitable rack space. In fact, the power converter 100 is not even limited to being stored on an equipment rack, as the power converter 100 can be stored or mounted in any other suitable fashion.
Referring to FIG. 2, a perspective view of the power converter 100 of FIG. 1 is shown with a portion of the power converter 100 cut away to illustrate several internal components. For purposes of clarity, one of the power converter modules 112 has been removed from the power converter 100 (this removability feature will be described below). As shown, the power converter 100 can include a backplane circuit board 116, at least one connector 118 coupled to the backplane circuit board 116 and at least one channel 120. The power converter module 112 can include a circuit board 122 having one or more electrical connections 124 disposed on one end of the circuit board 122. For simplicity, the components on the circuit board 122 are not shown; however, these components will be described in relation to a later drawing.
Referring to FIG. 3, a rear perspective view of the power converter 100 is shown. The power converter 100 can include one or more sets of contacts 125. The sets of contacts 125 can be input contacts for receiving input signals such as an input signal from a power supply, output contacts for outputting output voltages produced by the power converter 100 and alarm contacts for outputting alarm signals. Each of these sets of contacts 125 can be electrically coupled to the backplane circuit board 116 (see FIG. 2).
Referring back to FIG. 2, the connector 18 can include one or more terminals 126 for electrically receiving one or more of the connections 124 of the circuit board 122 of the power converter module 112. As a result, the power converter module 112 can be in electrical contact with one or more of the sets of contacts 125 (see FIG. 3). This receipt of the connections 124 by the terminals 126 of the connector 118 can be detachable such that the power converter module 112 can selectively engage the connector 118. In addition, the channels 120 can guide the edges of the circuit board 122 of the power converter module 112 to and from the connector 118. In one arrangement, the chassis 110 and the power converter module 112 can include one or more apertures 128 for receiving one or more fasteners 130. These fasteners 130 can be used to secure the power converter module 112 to the chassis 110. Also, the power converter module 112 can have a handle 132 for facilitating the removal of the power converter module 112 from the chassis 110. These features of the power converter 100 allow the power converter modules 112 to be easily replaced with other power converter modules 112 or removed for effecting changes in the output voltages generated by the power converter 100.
In view of the power converter module 112 being detachably engageable with the connector 118, the power converter modules 112 can be replaced or temporarily removed without shutting down the power supply providing power to the power converter 100. This feature, commonly referred to in the art as “hot swappability” or “hot swappable,” is desirable primarily because of two reasons: (1) as it is unnecessary to shut down the power supply, no other power converter modules 112 or other equipment receiving power from the power supply are affected when a power converter module 112 is removed; and (2) operator and system safety and efficiency are increased.
Referring to FIG. 4, a block diagram of the power converter 100 is shown. In this particular arrangement, the power converter 100 is receiving power from at least one power supply 134, and each of the power converter modules 112 is actively generating an output voltage. Thus, each of the power converter modules 112 can be referred to as independent power converter modules 112. This arrangement may be particularly useful if a large number of power converters 100 must be positioned in a relatively small area. Referring to FIG. 5, an alternative to the above block diagram is illustrated. Here, the power converter 100 is receiving power from at least one power supply 134; however, the power converter modules 112 can be grouped in redundant pairs 135 (see dashed outline) such that each of the redundant pairs 135 includes at least one active power converter module 112A and at least one standby power converter module 112B. For purposes of the invention, an active power converter module is a power converter module actively supplying an output voltage, while a standby power converter module is a power converter module that may supply an output voltage if an active power converter module fails or is removed from the power converter 100.
Referring to both FIGS. 4 and 5, in either arrangement, the power supply 134 providing power to the power converter 100 can be a power source used to supply power to telephone equipment 136. Further, the output voltages that the power converter 100 generates from this power supply 134 can be used to power a second set of communications equipment 138, such as cable television equipment.
The telephone equipment 136 and the second set of communications equipment 138 can be located in a centralized unit 140, represented by the dashed outline. As an example, the centralized unit 140 can be a central communications office that houses telephone equipment for routing telephone calls and cable television headend equipment for delivering cable television service to cable television subscribers. It must be noted, however, that the invention is not limited to these examples, as the power supply 134 can be used to supply power to any other suitable equipment and the output voltages produced by the power converter 100 can be used to power components other than cable television equipment. Moreover, the equipment that is powered by the power supply 134 and the equipment receiving the output voltages generated by the power converter 100 are not restricted to being located in a centralized unit, as such equipment can be positioned at other suitable locations.
If the power supply 134 is supplying power to the telephone equipment 136 and the power converter 100 is providing output voltages for cable television equipment, the power supply 134 can be an approximate −48VDC power supply, and the output voltages can be either approximately +24VDC or approximately +28VDC. These values are based on industry standards, as −48VDC is typically used to power centrally located telephone equipment and +24VDC or +28VDC is generally used to power cable television headend components. Nevertheless, the invention is in no way limited to these particular values. In fact, the power converter 100 can also receive and modify AC or time-varying signals.
Moving back to FIG. 4, in one arrangement, the power supply 134 can be a single power bus source supplying power to each of the power converter modules 112. A diode 142 can be placed on the ground side of the power supply 134 to ensure that current does not flow in a reverse direction. Each of the power converter modules 112 can output at least one output voltage, and a diode 144 can also be placed on each output voltage connection 145 to prevent current flow in a reverse direction. Additionally, a relay 146 can be positioned on these connections 145 in which the relay 146 can provide normally open or normally closed status monitoring signals to a number of alarm contacts 148. The diodes 142, 144 and the relays 146 can be placed on the backplane circuit board 116 (see FIG. 2), and the alarm contacts 148 and the output voltage connections 145 can be part of the sets of contacts 125 described in relation to FIG. 3. It is important to note that more than one power supply 134 may be utilized with this embodiment.
Referring once again to FIG. 5, the power supply 134 can include two power source buses. In this example, each power supply 134 can provide power to two separate power converter modules 112, each of which make up part of a redundant pair 135. Protection diodes 150 can be placed on the ground side of the power supplies 134. In each redundant pair 135, the active power converter module 112A can generate the output voltages. Should an active power converter module 112A in a particular redundant pair 135 fail or otherwise be removed, the standby power converter module 112B in that redundant pair will provide the output voltage.
To designate a power converter module 112 in a redundant pair 135 as a standby power converter module 112B, one or more resistors 153 may be placed on the output of a power converter module 112. Such a process can lower the output voltage such that the relevant diode 152 will remain off. Those of ordinary skill in the art will appreciate that the standby power converter module 112B may remain energized. It is understood that either of the power converter modules 112 in a redundant pair may serve as a standby power converter module 112B. Additionally, those of ordinary skill in the art will appreciate that other suitable techniques for converting a power converter module 112 into a standby power converter module 112B may be employed.
Each voltage output connection can include a diode 152, which can prevent current from flowing into a standby power converter module 112B, a failed or removed power converter module 112 or the backplane circuit 116 (see FIG. 2). Similar to the embodiment illustrated in FIG. 4, a relay 146 can be coupled to the output connection 151 for purposes of supplying signals to the alarm contacts 148. Also, the diodes 150, 152 and the relays 146 can be part of the backplane circuit board 116 of FIG. 2, and the alarm contacts 148 and the output connections 151 can be part of the sets of contacts 125 shown in FIG. 3.
In addition to power converter module 112 redundancy, the arrangement illustrated in FIG. 5 provides a reliable power source in that the power converter 100 may continue to operate if one of the power supplies 134 fails. Specifically, each power supply 134 can provide power to a power converter module 112 in each redundant pair 135. Thus, if a power supply 134 goes down, at least one of the power converter modules 112 in each redundant pair 135 will continue to output the required voltage.
Although FIG. 5 illustrates each power supply 134 as supplying power to an active power converter module 112A in one redundant pair 135 and a standby power converter module 112B in the other redundant pair 135, the invention is not limited in this regard. For example, a power supply 134 can provide power to the active power converter modules 112A in both redundant pairs 135. The other power supply 134 can be coupled to the standby power converter modules 112B, which can provide power to the standby power converter modules 112B if the power supply 134 coupled to the active power converter modules 112A fails.
Nonetheless, the arrangement illustrated in FIG. 5 can ensure substantially equal loading of the power supplies 134. That is, during normal operation, both power supplies 134 can supply power to an equal number of active power converter modules 112A, which can increase the life of the components that make up each power supply 134. Of course, it is understood that the invention is not limited to either of the embodiments discussed in relation to FIGS. 4 and 5, as other suitable configurations of the power converter modules 112 can be used with the invention.
Referring to FIG. 6, a schematic of one example of a power converter module 112 in accordance with the inventive arrangements is shown. The input voltage signal can be received from the power supply 134 at a node 154 and can pass through a fuse F1. As noted earlier, the input voltage signal can be an approximate −48VDC signal with the node 154 having a voltage of approximately 0 volts and the input ground VinGND having a voltage of approximately −48VDC; of course, the input voltage signal can have any other suitable magnitude or polarity. A protection diode D1 can protect the power converter module 112 by clamping the input voltage signal. The input voltage signal can then pass though a filter circuit 156, which can filter out noise in the input voltage signal. As shown, the filter circuit 156 can include capacitors C1, C2 and an inductor L1. The power converter module 112 can also include energy storage capacitors C3, C4 and C5 and a bleeder resistor R1, and a diode D2 can be coupled to VinGND and the primary windings of a transformer T1.
A transistor Q1, resistors R2 and R3, diodes D3, D4 and a capacitor C6 can form a voltage regulator 158, which can provide starting power to an integrated circuit (IC) 160. In one arrangement, the IC 160 can be a current mode PWM controller. As an example, the IC 160 can be series model UC2845N manufactured by STMicroelectronics of Geneva, Switzerland. Those of ordinary skill, however, will appreciate that other ICs may be used with the invention. In another arrangement, pin 6 of the IC 160 can be coupled to the gate of the transistor Q5 through a resistor R4, and the drain of the transistor Q5 can be coupled to the primary windings of the transformer T1. Resistors R4 and R18 can set the voltage at the gate of the transistor Q5, and a protection diode D8 can be coupled to the gate. Pin 3 of the IC 160 can be a current sensor coupled to the source of the transistor Q5 through a resistor R19, and a filtering capacitor C20 can also be coupled to pin 3. In addition, resistors R20 and R21 can be current sensors and can provide to pin 3 voltage that is proportional to the source current of the transistor Q5.
Pin 8 of the IC 160 can be coupled to VinGND through the resistor R22 and a capacitor C21, and a filtering capacitor C22 can also be coupled to pin 8. For purposes of providing feedback, a feature that will be described below, pin 1 of the IC 160 can be coupled to pin 8 of an IC 162 (pin 1 can also be coupled to VinGND through a capacitor C23). Finally, pins 2 and 5 of the IC 160 can be coupled to VinGND, while pin 4 can be coupled to VinGND through the capacitor C21.
From the filter circuit 156, the input voltage signal is fed to the primary windings of the transformer T1, where the input voltage signal can be converted to the desired output voltage. The conversion can be controlled through the operation of the transistor Q5. In particular, as those of ordinary skill in the art will appreciate, the frequency or the duty cycle of the gate drive input signal to the transistor Q5 can control the value of the voltage on the secondary windings of the transformer T1. This conversion can be a change in the magnitude of the voltage input signal. Additionally, different types of transformers can be used to change the polarity of the input voltage signal.
The power converter module 112 can also include an IC 164, which can be a voltage regulator for supplying power to the IC 160 once the circuit is stabilized. For example, the input voltage signal can be supplied to pin 3 of the IC 164 through a diode D5. The IC 164, through pin 1, can provide voltage to pin 7 of the IC 160. The voltage from pin 1 of the IC 164 can cause the voltage regulator 158 to shut down. Filtering capacitors C7, C8 and C9 can also be inserted in this section of the power converter module 112.
Referring back to transformer T1, the converted signal, which will now be referred to as a voltage output signal, can be filtered by capacitor C10. In addition, a resistor R5 can be used to limit the amount of current through the capacitor C10, and the output voltage signal can pass through rectifier 166. Once rectified, the output voltage signal can pass through jumper J1, and a filter circuit 168 can filter the signal; filter circuit 168 can comprise capacitors C11, C12, C13, C14 and C15 and inductors L2 and L3. The output voltage signal can be received at a node 170, and protection diode D6 can clamp the output voltage.
In one arrangement, the IC 162 can be a dual channel optocoupler IC. As an example, the IC 162 can be series model PS2501-2 manufactured by NEC of Tokyo, Japan. Of course, the invention is not limited to this particular model, as other suitable ICs can be used with the invention. Pin 1 of the IC 162 can be coupled to the output side of the power converter module 112 at a node 172 through a resistor R6 and a filtering capacitor C16. A voltage divider network 174 can be also coupled to the output side of the power converter module 112 at the node 172. The voltage divider network 174 can include resistors R7, R8, R9, R10 and R11, a capacitor C17 and a diode D7 and can provide the IC 162 with a reference voltage, the use of which will be explained below. A coupling capacitor C18 can be used to couple pin 4 and pin 5 of the IC 162 to limit oscillations in the power converter module 112. In addition, pin 3 of the IC 162 can be coupled to the output side of the power converter module 112 at a node 176 through a resistor R12, and pin 4 can be coupled to output ground, or VoutGND, for purposes of indicating that the power converter module 112 is operational.
For example, when the power converter module 112 is operational such that an output voltage signal is being generated, the voltage on pin 6 of the IC 162 will be low, which will cause a transistor Q4 to turn on and a transistor Q3 to turn off. As a result, the voltage on the collector of the transistor Q3 will be high (from pin 1 of the IC 164), and current will flow through a green LED 178. The green LED 178 can be part of a dual colored LED 182 coupled between the transistor Q3 and the transistor Q4. Conversely, if the power converter module 112 is not operational, the voltage from the IC 164 across resistor R18 will cause the transistor Q4 to turn off and the transistor Q3 to turn on. Thus, the voltage at a node 184 will be high, and the voltage at the collector of the transistor Q3 will be low, which causes the red LED 180 to illuminate. Referring to FIGS. 1 and 2, the dual colored LED 182 can be positioned on the front of the power converter module 112 to indicate that the power converter module 112 is operational or that a failure has occurred.
Referring back to FIG. 6, resistors R13, R14 and R15 can set the voltage at which the transistors Q4 and Q3 turn on and current limiting resistors R16 and R17 can protect the transistors Q3 and Q4. Finally, the base of the transistor Q3 can be coupled to VoutGND through a capacitor C19.
As noted earlier, pin 8 of the IC 162 can be coupled to pin 1 of the IC 160, a configuration that can provide IC 160 with feedback from the output side of the power converter module 112. This feedback feature can permit the output voltage to be adjusted. To effect such a change, the reference voltage of the voltage divider network 174 can be varied. In particular, the voltage divider network 174 can be coupled to any number of outputs 186. Based on which output 186 is grounded, the reference voltage produced by the voltage divider network 174 can be adjusted.
As an example, an output 186 can be coupled to the resistor R8 and another output 186 can be coupled to the resistor R9, both of which are part of the voltage divider network 174. In one arrangement, a jumper wire J2 can be coupled to one of these outputs 186, for example, the output 186 coupled to the resistor R8, which can cause that output 186 to be grounded to VoutGND. The remaining output 186, coupled to resistor R9 will remain open. Thus, the differences in the resistances between the resistors R8 and R9 can produce different reference voltages in the voltage divider network 174.
Referring to FIG. 7, in another arrangement, a switch 188 can be used to select between the outputs 186 for purposes of generating various reference voltages to be supplied to the IC 162 (only a portion of the power converter module 112 is illustrated here). It is understood, however, that the invention is not limited to either of these examples, as any other suitable mechanism for producing different reference voltages can be used with the invention. In addition, the power converter module 112 is not limited to merely two outputs 186, as the power converter module 112 can include any suitable number of outputs 186 coupled to any suitable number of resistors in the voltage divider network 174 to generate any suitable number of reference voltages. As shown in FIGS. 6 and 7, one or more resistors 153 can be placed on one or more of the outputs 186 for converting the power converter modules 112 to a standby power converter module (see discussion relating to FIG. 5 also).
Referring to both FIGS. 6 and 7 and as apparent to one of ordinary skill in the art, if the reference voltage produced by the voltage divider network 174 is modified by the grounding of a different output, the voltage on pin 8 of IC 162 can change, which can lead to a voltage change on pin 1 of the IC 160. This change in voltage on pin 1 of the IC 160 can cause the IC 160 to correspondingly alter the frequency or the duty cycle of the gate drive input signal to the transistor Q5, which can cause the magnitude of the voltage of the output voltage signal to change.
Although the present invention has been described in conjunction with the embodiments disclosed herein, it should be understood that the foregoing description is intended to illustrate and not limit the scope of the invention as defined by the claims.

## Claims

1. A system for integrating communications equipment, comprising:
a power supply, wherein said power supply provides power to telephone equipment located in a central office of a telephony network for providing telephone service to a plurality of telephony network subscribers; and
at least one power converter for receiving power from said power supply, said at least one power converter having:
an active power converter module configured to receive power from said power supply and having a first output voltage connection that connects to a second set of communications equipment, the active power convener module operating to convert the power from the power supply into at least one output voltage to power said second set of communications equipment,
a standby power converter module configured to receive power from the power supply and having a second output voltage connection that connects to said second set of communications equipment, the standby power converter module operating to convert the power into at least one output voltage to power said second set of communications equipment when the active power converter fails,
a chassis having first and second backplane circuit board connectors and first and second channels aligned respectively with the first and second backplane circuit board connectors such that the first and second electrical connectors detachably connect to the active and standby power convener modules respectively, the first and second channels guiding the active and standby power converter modules to and from the first and second connectors respectively,
a first relay connected to the first output voltage connection for providing a first monitoring signal that indicates whether the active power convener module is operable,
a second relay connected to the second output voltage connection for providing a second monitoring signal that indicates whether the standby power converter module is operable regardless of whether the standby power converter is operating to convert power into the at least one output voltage.

2. The system according to claim 1, wherein said second set of communications equipment comprises cable television equipment.