Abstract:
An active arc suppression circuit and systems and methods of use to suppress arcing in an electro-mechanical apparatus. The preferred circuit includes an electro-mechanical switch and a solid state shunt switch for temporarily shunting current around the electro-mechanical switch for a predetermined period of time. The preferred circuit also includes an electro-mechanical switch controller for delaying the activation of the electro-mechanical switch until after the predetermined period of time for shunting current through the solid state shunt switch has commenced. The preferred circuit may be used with power control equipment and systems, including in remotely controllable systems for telecommunications, computing, and other networks. In a particularly preferred embodiment, multiple such circuits may be disposed in a power controller housing to provide independent active arc suppression control of multiple power outputs also disposed in the power controller housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation-in-part of, and hereby incorporates by reference, the applicant&#39;s U.S. patent application Ser. No. 09/689,157, filed Oct. 12, 2000, now U.S. Pat. No. 6,741,435 entitled POWER CONTROLLER WITH DC-SUPPRESSION RELAYS, which claims priority through the applicant&#39;s Provisional U.S. Patent Application Ser. No. 60/224,387, filed Aug. 9, 2000, with the same title. 

   FIELD OF THE INVENTION 
   The present invention relates to an active arc-suppression relay. More particularly, the present inventions relates to an active arc-suppression relay having a active power shunt circuit to shunt current around another power relay, most preferably in response to a control command received over a network. 
   BACKGROUND 
   There is a growing need for competitive local exchange carriers to manage remote power control functions of internetworking devices at telephone company (telco) central offices. Competitive local exchange carriers (CLECs), incumbent local exchange carriers (ILECs), independent telephone companies, and other next generation service providers are now all offering a digital subscriber line (DSL) service that promises high-speed Internet access for both homes and businesses. DSL is expected to replace integrated services digital network (ISDN) equipment and lines, and DSL competes very well with the T 1  line that has historically been provided by ILECs. A DSL drop costs about $40-60 per month, and is expected to quickly become the dominant subscriber-line technology. 
   The DSL service is provided by a switch that is co-located in a telco central office, that is, a digital subscriber line access multiplexer (DSLAM). Many new competitive local exchange carriers are now deploying DSL service in several states. They are installing digital subscriber line access multiplexers in many locations. Such digital subscriber line access multiplexers are now available from a number of different manufacturers, for example, Paradyne, Copper Mountain, Ascend, etc. 
   Nearly all such digital subscriber line access multiplexers are powered by 48-VDC battery power and all have operator console ports. And for emergencies, these DSLAMs usually have two independent 48-VDC battery power supplies, for example, an A-channel and a B-channel. Most commercial DSLAMs are also controlled by large operating systems that host various application software. Unfortunately, this means most DSLAMs have the potential to fail or lock-up, for example, due to some software bug. 
   When a digital subscriber line access multiplexer does lock-up, the time-honored method of recovering is to cycle the power, that is, reboot. But when a digital subscriber line access multiplexer is located at a telco central office, such location practically prevents it being easy to reboot manually. 
   There are many large router and ATM switch farms around the country that are equipped by the leading vendors, for example, Cisco, Bay Networks/Nortel, Ascend, Lucent, Fore, etc. So each of these too has the potential to lock-up and need rebooting, and each of these is very inconvenient to staff or visit for a manual reboot when needed. 
   Server Technology, Inc., of Reno, Nev., markets a 48-VDC remote power manager and intelligent power distribution unit that provides for remote rebooting of remote digital subscriber line access multiplexers and other network equipment in telco central offices and router farms. The SENTRY 48-VDC is a network management center that eliminates the dispatching of field service technicians to cycle power and rectify locked-up digital subscriber line access multiplexers. 
   Statistics show that seventy percent or more of all network equipment lock-ups can be overcome by rebooting, for example, cycling power off and on. A remote power controller, like the SENTRY, can reduce network outages from hours to minutes. 
   In a typical installation, the telco central office provides the competitive local exchange carriers with bare rack space and a 48-VDC power feed cable that can supply 60-100 amps. The single power input is conventionally distributed through a fuse panel to several digital subscriber line access multiplexers in a RETMA-type equipment rack. Individual fuses in such fuse panel are used to protect each DSLAM from power faults. 
   But such fuses frequently weld themselves to their sockets in the fuse panel due to loose contacts and high amperage currents. It is ironic therefore that many digital subscriber line access multiplexers do not have power on/off switches. Thus the fuse often must be pried out and put back in or replaced so the DSLAM can be powered-off for rebooting. But when the fuse is welded, removing the fuse without damaging the fuse panel can be nearly impossible. 
   The Server Technology SENTRY 48-VDC accepts from the telco or other site host an A-power feed cable and B-power feed cable. Internally, DC-power is distributed to a set of “A” and “B” rear apron output terminal blocks that are protected by push-to-reset circuit breakers. The fuse panel is no longer required. The A-feed and B-feed are then matched to the newer digital subscriber line access multiplexers that also require A-power supply and B-power supply inputs. 
   Sometimes digital signaling lines can lose the carrier. In such cases, the respective DSLAM must be rebooted to restore the DS3 line. A technician is conventionally required to visit the DSLAM, and use a console port to monitor how the software reboots, and if communications are correctly restored to the DS3. 
   A SENTRY 48-VDC can be used to remotely power-off the digital subscriber line access multiplexer in the event the carrier is lost. A companion asynchronous communications switch can be used to establish a connection to the DSLAM&#39;s console port. Power can be cycled to the DSLAM, and the asynchronous communications switch used to monitor the reboot operation to make certain that the carrier to the DS3 line is restored. The asynchronous communications switch is a low-cost alternative to the expensive terminal server typically used for console port access. The reboot process and the console port monitoring process can both be managed from an operations center, without the need to dispatch technical personnel to the remote location. 
   The floor space that a competitive local exchange carrier&#39;s equipment rack sits upon is very expensive, so the equipment placed in the vertical space in a rack (“U-space”) must be as compact as possible. A typical rack may house several digital subscriber line access multiplexers, a terminal server, a fuse panel, and 48-VDC modems. A SENTRY 48-VDC uses “2 U or 3 U” (3.5 or 5.25 inches) of vertical RETMA-rack space, and combines the functions of a fuse panel, a terminal server, and a modem. As many as sixteen 10-amp devices, eight 20 amp devices, or four 35-amp devices can be supported. 
   Power controllers, like the Server Technology SENTRY, have long used electro-mechanical relays to open and close the 48-volt supply lines to the network equipment. Unfortunately, the same physical phenomena that welds the fuses in their holders can also weld or destroy the contacts of these relays. 
   Most electric welders generate the high heats necessary to fuse metal together by arcing a direct current (DC) low voltage (under 50-volts) and high current (over 50-amps) across an electrode gap. Such conditions occur in a power controller&#39;s relay, especially when the relay contacts are opening. The mass inertia of the contact mechanism has to be overcome before the contacts can open. The contacts accelerate apart, but are moving only very slowly at the start. Electric arcs, once generated, will continue even though the electrode separation distance is increased. This is the so-called Jacob&#39;s Ladder effect. The ionized air and the heated contacts increase the distance an arc can bridge. The arcing stops only after the contacts are very wide apart. 
   In contrast, a pair of open relay contacts will not arc until the contacts get very close to one another. By this time, the contact closure is moving at its near maximum velocity. So the remaining gap that needs to be closed up when the arc commences will vanish quickly. 
   One prominent prior art arc suppression circuit consists of a capacitor in series with a resistor and a diode in parallel interconnecting the input and the output of the electro-mechanical relay. This type of conventional circuit shunts some electricity around the electro-mechanical relay when it is activated, reducing the extent of arcing that might otherwise take place. This conventional circuit is, however, relatively slow acting circuit (in passive response to the activation of the electro-mechanical relay to open or stop the flow of current from, for example, the input to the output) and does not completely eliminate all arcing between separating contacts in an electro-mechanical relay. Over an extended period of activation of this type of electro-mechanical relay circuit with passive arc suppression, electro-mechanical relay contacts often burn up and fail. 
   BRIEF SUMMARY OF THE PRESENT INVENTION 
   The present invention provides one or more active arc-suppression circuits and systems and methods of use such circuits. In the preferred embodiment, at least one of the active arc-suppression circuits includes an active shunt switch in conjunction with an electro-mechanical power relay. Most preferably, the active arc-suppression circuit is included in a direct current power controller system in network communication with a separate power manager system to control direct current power to computing systems, communications equipment, or other electrical equipment. 
   In a particularly preferred embodiment, an active direct current arc-suppressor circuit for network appliance power managers comprises an active solid state power shunt relay in conjunction with an electro-mechanical relay to control the flow of battery current to a network appliance by remote control. The preferred electro-mechanical relay includes electrical contacts that open to interrupt the flow of current in response to an off-command signal. The preferred active solid state power shunt relay is connected in shunt across the relay contacts to temporarily divert such flow of current from the electro-mechanical relay. A timing circuit preferably is connected to respond to an off-command signal by first turning on the shunt solid state switch, then opening the relay contacts, and then turning off the shunt solid state switch. The shunt solid state switch is sized to carry the full rated peak current of the relay contacts, but preferably only for the few milliseconds that are needed to allow the relay contacts to fully separate. 
   The present invention can preferably provide an electro-mechanical power controller or switch with more reliable relay operation. Most preferably, the electro-mechanical power controller or switch also is relatively economical and longer lasting than conventional electro-mechanical power controllers or switches. 
   The present active arc suppression invention may be used in other environments as well, in order to suppress arcing across electro-mechanical components in circuitry. 
   These features and many other objects and advantages of the present invention will become apparent to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures. It is to be understood, however, that the scope of the present invention is to be determined not by whether a given embodiment meets all objects or advantages set forth herein but rather by the scope of the claims as issued. 

   
     DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments are shown in the accompanying drawings wherein: 
       FIG. 1  is schematic circuit diagram of one power controller embodiment of the present invention that includes a conventional DC arc-suppression circuit along with an active solid state shunting switch and circuit; 
       FIG. 2  is a timing diagram showing various signal points within the preferred embodiment of  FIG. 1 ; 
       FIG. 3  is a functional block diagram showing a preferred dual-source battery power manager wired to power-cycle DSLAM, routers, and other network devices; and 
       FIG. 4  is a schematic circuit diagram of a second preferred power controller embodiment of the present invention, utilizing a microprocessor to control timing of activation of solid state switches (transistors) including an active solid state shunting switch and circuit. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a power controller embodiment of the present invention, referred to herein by the general reference numeral  100 , including both conventional passive  101  and active  103  arc suppression circuitry. The power controller  100  connects to a computer data network  102 , for example, the Internet, and can send status and receive commands with a network client  104 . A power-OFF command raises a signal line  105  and triggers a mono-stable multivibrator  106 . A twenty millisecond long pulse is fed to an opto-isolated solid state switch or photo relay  108  through a dropping resistor  110 . This turns-on a power metal-oxide-semiconductor field-effect transistor (MOSFET)  111  for the period of the twenty millisecond long pulse from the mono-stable multivibrator  106 . 
   The raising of signal line  105  by the power-OFF command also is fed through a two-millisecond capacitor-drain delay circuit  112  and is forwarded to another opto-isolated solid state switch  114  through a dropping resistor  116 . This turns on a MOSFET transistor  115 , which in turn energizes an inductive armature  118  in an electro-mechanical relay  119 . 
   A set of station batteries  120 , for example, a 48-volt bank at a Telco Central Office, are connected through a master switch  122  and a pair of normally closed relay contacts  124  to a load  126 . Network routers, bridges, and other computer network equipment are examples of what is represented by load  126 . A suppression diode  128  helps control transients that occur across the load during the operation of the relay contacts  124 . A sense resistor  130  is useful for the monitoring of load currents with a voltmeter or oscilloscope (not shown). 
   The conventional arc-suppression circuit  101  is somewhat redundant and comprises a capacitor  132  in series with a parallel resistor  134  and diode  136 , which collectively are connected across the relay contacts  124  to provide additional reduction of arcing and contact  124  burning, particularly in the case of any failure of the active arc suppression circuit  103 . Alternatively, the conventional arc suppression circuit  101  may be omitted, which reduces cost and bulk of the arc suppression circuitry overall. 
     FIG. 2  schematically illustrates some of the signal timing that occurs in the power controller  100  of  FIG. 1  during operation. In this context, signal-A  202  corresponds to the output of the network client  104 , for example, signal line  105 . Signal-B  204  corresponds to the load current, as seen as a voltage across sense resistor  130 . Signal-C  206  corresponds to the output of the mono-stable multivibrator  106 . Signal-D  208  corresponds to the output of the delay circuit  112  as seen by the dropping resistor  116 . Signal-E  209  corresponds to the output of the station batteries through the master switch  122 . (See also  FIG. 4  and associated text infra.) 
   With reference back to  FIGS. 1 and 2 , during operation, at a time t0 the power controller  100  is energized and master switch  122  is closed to provide power from the station batteries  120  to the electro-mechanical relay  119  and the passive  101  and active  103  arc suppression circuits. At a time t 1 , the network client  104  receives a power-OFF command, and signal-A  202  is raised on signal line  105 . This triggers the mono-stable multivibrator  106  and causes a twenty millisecond pulse output to appear as signal-C  206 . This turns-on the MOSFET  111  for the twenty millisecond period of the pulse output at signal-C  206 . The signal-A  202  being raised also causes signal-D  208  to be asserted, but with a two millisecond delay brought about by the capacitor-based delay circuit  112 . This energizes electro-mechanical relay  118  and pulls open contacts  124  within the electro-mechanical relay  118 . The delay of two-milliseconds is represented by the slope of signal-D between times t 1  and t 2 . The solid state shunt switch (MOSFET)  111  turns off at time t 3 , having done its job of shunting the load current while the relay contacts were breaking or opening. Signal-B  204  therefore automatically falls back to zero at time t 3 , at which time output current is off. 
   At time t 4 , the network client  104  receives a power-ON command, and signal-A  202  is lowered. This causes signal-D  208  to drop and the relay contacts  124  close at time t 4 . The mono-stable multivibrator  106  is unaffected because it is positive-edge triggered only. At time t 5 , the master switch  122  is opened, which causes signal-E and signal-B (output) to drop to zero. 
   The mono-stable multivibrator  106  can be implemented with a National Semiconductor NE555. The opto-isolated solid state switches  108 ,  144  can be implemented with an MSD-W6225DDX, by MagnaCraft, Inc. 
     FIG. 3  represents a system  300  that includes a dual 100-amp battery source power manager  302  wired to power-cycle two DSLAMs  304 ,  305  four routers  306 ,  307 ,  308 ,  309  and two generic network devices  310 ,  311 . 
   The chassis are all mounted in a single RETMA-rack or housing  312 . An A-channel power connector  314  and a B-channel power connector  316  on the power manager  302  receive two circuits of 48-volt DC battery power from a telco site. A pair of batteries  318  and  320  represents these sources. A plurality of power control modules  322 - 329  internal to the power manager  302  are independently controlled from a network connection  330  and can individually control A-channel and B-channel DC-power supplied to each DSLAM  304 ,  305 , routers  306 ,  307 ,  308 ,  309 , and generic network devices  310 ,  311 . The power control modules  322 - 329  include the DC arc-suppression circuitry of  FIG. 1  or alternatively of  FIG. 4 . 
   When any of the DSLAMs  304 ,  305 , routers  306 ,  307 ,  308 ,  309 , and generic network devices  310 ,  311  need to be remotely rebooted, an appropriate network data is sent to the responsible power control modules  322 - 329  to cause both A-channel and B-channel DC power to cycle off and on. 
   With reference now to  FIG. 4 , an alternative DC-arc suppression circuit, generally  400 , receives IPM input  402  from an intelligent power module (not shown), which includes the network client  104  of  FIG. 1 . The IPM input  402  is received by a microcontroller  404  loaded with microcode to provide the timing functionality of the mono-stable multivibrator  106  and the capacitor-based delay circuit  112  of  FIG. 1 . A shunt signal output  408  from microcontroller  404  is connected through shunt signal line  406  to a first current limiting resistor  410  and then to a solid state shunt signal switch  412 . In turn, solid state shunt signal switch  412  is connected by shunt power switch line  414  to a solid state shunt power switch  416 . 
   A −48 volt power source  460  is connected through relay current input line  418  and is connected to the current input contact  420  in an electro-mechanical relay, generally  422 . The electro-mechanical relay  422  includes an inductive armature (not shown), which is connected to controllably activate contact arm  424  to move contact arm from a closed position in contact with the current input contact  420  to an open position distal from the current input contact  420 . Contact arm  424  is connected to a −48 volt relay current output line  426 . 
   The solid state shunt signal switch  412  has a shunt switch power input  428  connected to the −48 volt relay current input line  418  and a shunt switch power output  430  connected to the −48 volt relay current output line  426 . When turned on by solid state shunt signal switch  412 , the solid state shunt power switch  416  shunts available current from the −48 volt relay input line  418  to the −48 volt relay current output line  426 . 
   The −48 volt relay current output line  426  is connected to a load output connector  432 , which in turn is connected to a load  444 . A positive return connector  434  also is connected to the load  444  and to the positive return line  436  in the DC-arc suppression circuit  400 . 
   An electro-mechanical relay signal output  448  from microcontroller  404  is connected through relay signal line  450  through a second current limiting resistor  452  to a relay control solid state switch  454 . In turn, the relay control output line  456  of the relay control solid state switch  454  is connected to the electro-mechanical relay  422 . When relay control solid state switch  454  is turned on by electro-mechanical relay signal output  448 , the electro-mechanical relay  422  is activated to move contact arm  424  distal from current input contact  420 . 
   With reference now to  FIGS. 2 and 4 , the timing of the microcontroller-based power controller of  FIG. 4  commences with power controller energized to provide current to load  444 . At this time t 0 : (i) the station batteries or other −48 volt power supply (not shown in  FIG. 4 ) are switched “on” to supply power, signal-E, through the −48 volt connector  460  and its mating + return connector  436 ; and (ii) the microcontroller  404  has already signaled relay control solid state switch  454  through relay signal line  450  to turn “on,” so that the contact arm  424  is in contact with current input contact  420 . This causes load output current signal-B to flow, also reflected as voltage across sense resistor  130 . 
   At time t 1 , the IPM (not shown) issues a power-OFF command by raising signal-A on the IPM input  402  to the microcontroller  404 . In turn, the microcontroller raises signal-C on shunt signal line  406 , causing the solid state shunt signal switch  412  to turn on the solid state power shunt switch  416 . The solid state power shunt switch  412  thus provides a current shunt from the −48 volt relay current input line  418  to the −48 volt relay current output line  426 . 
   At time t 2 (two milliseconds after time t 1 ), the microcontroller  404  raises signal-D on the relay signal line  450 , which causes relay control solid state switch  454  to turn on and in turn activate an inductive armature (not shown in  FIG. 4 ) in the electro-mechanical relay  422  to move the contact arm  424  to an open position distal from the current input contact  420  so that current cannot jump (arc across) the gap between the contact arm  424  and the current input contact  420 . 
   At time t 3 (twenty milliseconds after time t 1 ), the microcontroller lowers signal-C, causing the solid state power shunt relay  416  to turn off and terminate the flow of current from the shunt switch power input  428  to the shunt switch power output  430 . Since there then remains no path for current flow from the −48 volt relay input line  418  to the −48 volt relay current output line  426 , output current signal-B drops to zero (turns off). 
   At time t 4 , the IPM (not shown) issues a power-ON command by lowering signal-A on the IMP input  402  to the microcontroller. In turn, the microcontroller  404  lowers signal-D, causing the electro-mechanical relay  422  to move the contact arm  424  into contact with the current input contact  420 . Since there is now a path for current flow from the −48 volt relay input line  418  to the −48 volt relay current output line  426 , output current signal-B raises (turns on). 
   At time t 5 , the station batteries or other −48 volt power supply (not shown in  FIG. 4 ) stops supplying power, signal-E, through the −48 volt connector  460  and it&#39;s mating + return connector  436 . As a result, signal-B, current through load  444  and voltage as measured at sense resistor  130  also drop to zero. 
   In the preferred embodiment of  FIG. 4 , the microcontroller  404  is a model PIC16F84 manufactured by MicroChip. The solid state shunt signal switch  412  is a model TLP595G manufactured by Toshiba. The solid state shunt power switch  416  is a model IRFUO24N manufactured by International Rectifier. The solid state relay control switch  454  is a model TLP595G manufactured by Toshiba. The electro-mechanical relay  422  is an MSD 976XAXH-24D manufactured by MagnaCraft, Inc. 
   It can thus be seen that the applicant has invented an active arc suppression circuit for suppressing arcs across electro-mechanical elements within circuitry. The active arc suppression circuit preferably utilizes one or more solid state switches to temporarily shunt power around the electro-mechanical elements, and in this matter, the active arc suppression circuit can provide relatively economical, reliable, and long lasting electro-mechanical circuitry such as electro-mechanical power relay circuits for example. The active arc suppression circuit can also provide reliable power control for electrical components and equipment, including telecommunications, computing, and related equipment. In addition, the power control may be accomplished remotely and yet reliably through network communication with a power controller including one or more active arc suppression circuits. Multiple active arc suppression circuits and associated power relay circuits may be disposed in one or more housings and, for example, used to remotely and independently control power to multiple electrical components. 
   The present active arc suppression apparatus, system, and method of use may be used in other environments that include other electro-mechanical components, such as electro-mechanical fuses or fuse switches, that may be subject to arcing. The present arc suppression technique may also be utilized in any environment in which arcing is a problem in closing or powering-on electrical equipment. 
   It is therefore to be understood that the preceding is a detailed description of preferred embodiments, not all embodiments, of the present invention. The scope of the invention therefore is to be determined by the following claims.