Patent Document

CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 60,809,487, filed on May 31, 2006, which is hereby incorporated by reference. 
     
     BACKGROUND 
       [0002]    The invention relates generally to welding systems, and more particularly to an electronic polarity reversing switch for a multi-process welding power source. 
         [0003]    Welding systems generally support different types of processes, including MIG welding (metal inert gas welding), TIG welding (tungsten inert gas welding), stick welding and the like. Generally, a welding system includes a single output connection and, thus, the welding system only supports a single process at a time. Welding systems typically include a single power source configured to output power capable of independently supporting each of these specific welding processes. Unlike a welding system that connects to only a single process at a time, multi-process welding systems may be configured to connect to multiple processes at the same time. Thus, a multi-process welding system may include a power source configured to output power based on the welding process being performed at that time. 
         [0004]    Certain welding processes supported by a multi-process welding power sources require reversal of output polarity between DCEP (Direct Current Electrode Positive) and DCEN (Direct Current Electrode Negative). Accordingly, a power source may need to switch outputs between the two polarities. Switching between DCEP and DCEN generally includes a manual process to reverse the output polarity of a multi-process welding power source. Switches generally include a rotary type switch mounted proximate to the power source or separate process selector switches located remotely. Therefore, the user must not only understand which output polarity is appropriate for a given welding process, but the user must also physically reverse the switch. A switch proximate to the power source may require the user to return to the power source from the work to change the polarity. The distance between the workpiece and the power source can be significant and require an increased amount of time and effort to make the change. A separate process selector switch may allow for switching from a remote location, however, this method requires an additional apparatus and complicates connection of the weld output control cables. 
       BRIEF DESCRIPTION 
       [0005]    In certain embodiments, a multi-process power supply includes outputs configured to provide power at multiple polarities. For example, in one embodiment, a system includes a multi-process power supply, including a control circuit configured to enable output of power at a first polarity, a second polarity opposite from the first polarity or a combination thereof, based on a desired process selected from a plurality of different processes. 
         [0006]    In accordance with another embodiment, a system includes, a power circuit comprising switches configured to route an input power, a first output configured to provide an output power comprising a first polarity, a second output configured to provide an output power comprising a second polarity. The system also includes a control circuit coupled to the power circuit and configured to provide a switch control signal to a switch such that power is output on the first or second output with a polarity controlled automatically in response to an input control signal representative of a welding process, a cutting process, or a combination thereof. 
         [0007]    In accordance with yet another embodiment, a method for providing power includes receiving a power, receiving a signal indicative of a welding process, or a cutting process, determining an output polarity based on the signal, transmitting a control signal to switches based on the output polarity and routing the power to an output configured to output the power with the output polarity. 
     
     
       DRAWINGS 
         [0008]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0009]      FIG. 1  is a diagram of an exemplary system having a multi-source power supply in accordance with certain embodiments of the present technique; 
           [0010]      FIG. 2  is a diagram of an exemplary shared power source of  FIG. 1  in accordance with certain embodiments of the present technique; 
           [0011]      FIG. 3  is a flowchart illustrating an exemplary method of providing an output from the shared power source of  FIG. 2  in accordance with embodiments of the present technique; and 
           [0012]      FIGS. 4-10  are schematic diagrams of alternate embodiments of the shared power source of  FIG. 2  in accordance with embodiments of the present technique. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As discussed in greater detail below, various welding systems are integrated together in a single multi-process power supply. For example, welding torches, cutting torches or other welding devices may all be coupled to a multi-process power supply, wherein each welding device can receive an output polarity (e.g., DCEP or DCEN) used by each of the processes performed by the respective devices. The multi-process power supply may include a shared power source that is configured to output multiple forms of power used by each of the welding systems. As discussed below, some embodiments of the shared power source include power circuitry comprising switches and rectifiers configured to receive and route the power to the appropriate outputs of the shared power source. In some embodiment, the power source includes a control circuit to automatically control switches to configure the output polarity of the power circuitry based on the process and/or device being used. In some embodiments, the control circuit may automatically remove power from the unused electrical connections (e.g., the output studs) of the power source. Further, embodiments may comprise multiple forms of transformers (e.g., center-tapped transformers and single secondary winding transformers) operating in reverse or forward biased modes. 
         [0014]      FIG. 1  is a diagram of an exemplary system  10  having a multi-process power supply  12  in accordance with certain embodiments of the present technique. As illustrated, the welding power supply  12  includes a shared power source  14 , which is configured to supply power to a plurality of different welding devices connected to the power supply  12  and/or the shared power source  14  simultaneously. 
         [0015]    Generally, the welding power supply  12  may receive an input power from an alternating current power source  16 , such as an AC power grid, and provide the input power to the shared power source  14 . The shared power source  14  may condition the input power and provide an output power in accordance with the demands of the system  10 . As depicted, in  FIG. 2 , the shared power source  14  includes a transformer  18 , power circuitry  20  and a control circuit  22 . The power from the power source  16  is input to the shared power source  14  via the transformer  18 . The transformer  18  may receive the input power via a primary winding and condition the power via a secondary winding that is coupled to the power circuitry  20 . In some embodiments, the transformer  18  may include a plurality of elements and configurations. For example, as will be discussed in greater detail below with regard to  FIGS. 4-8 , the transformer  18  may comprise a center-tapped transformer  16  having two secondary windings configured to operate as forward-biased or reverse-biased. Further, in other embodiments that are discussed in greater detail below with regard to  FIGS. 9 and 10 , the transformer  18  may comprise a single secondary winding that is configured to operate as forward-biased or reverse-biased. In addition, as depicted in  FIGS. 4-10 , the shared power source  14  may include an additional secondary winding coupled to a boost output control circuit  23  coupled to the power circuitry  20 . The boost output control circuit  23  may provide additional power to the power circuit  20  if demanded by the connected devices and the respective processes. 
         [0016]    The output of the transformer  18  may be routed via the power circuitry  20  to outputs of the shared power source  14 . In some embodiments, the power circuitry  20  may include a variety of devices and configurations to route the power to outputs of the shared power source  14  and the welding power supply  12 . For example, as is discussed in greater detail below with regard to  FIGS. 4-10 , the power circuitry  20  includes rectifiers and switches configured to route the power from the transformer  18  to a DCEP output or a DCEN output of the shared power source  14 . In some embodiments, the control circuit  22  may open or close the switches to route power based on a process being performed. 
         [0017]    The power output from the power circuitry  20  of the shared power source  14  may be provided to devices coupled to the welding power supply  12 . For example, as illustrated in  FIG. 1 , a TIG welding torch  28  and supply cable  30  are coupled to a connector  32  on the face of the welding power supply  12 . The connector  32  may include an electrical connection configured to electrically couple an output of the shared power source  14  (e.g., an output stud) to an electrical conductor within the supply cable  30 . The electrical conductor within the supply cable  30  may provide an electrically conductive path to route power from the connector to an electrode  34  disposed within the TIG welding torch  28 . To initiate a weld, a user may position the electrode  34  proximate to a workpiece  36  and provide a signal (e.g., a trigger signal) to the welding power supply  12  and/or the shared power source  14  to provide a current output. A current loop may be formed via the connector  32 , the supply cable  30 , the electrode  34 , the workpiece  36 , a work clamp  38  and a cable  40  that is electrically coupled to a connector  42  on the face of the welding power supply  12 . The connector  42  includes an electrical connection configured to electrically couple the cable  40  to an output of the shared power source  14  (e.g., a work output stud) to complete the current path. As will be appreciated, the current flow creates an electric arc between the electrode  34  and the workpiece  36 . The electric arc generates heat that melts the workpiece  36  to create a weld. 
         [0018]    Similarly, power may be supplied to another welding device coupled to the welding power supply  12 . For example, as illustrated in  FIG. 1 , a MIG welding gun  44  and supply cable  46  are coupled to a connector  48  on the face of the welding power supply  12 . The connector  48  includes an electrical connection configured to electrically couple an output of the shared power source  14  (e.g., an output stud) to an electrical conductor within the supply cable  46 . The electrical conductor within the supply cable  46  provides an electrically conductive path to route power from the shared power source  14  to a consumable electrode  50  disposed within the MIG welding gun  44 . To initiate a weld, a user may position the consumable electrode  50  proximate to the workpiece  36  and provide a signal (e.g., a trigger signal) to the welding power supply  12  and/or the shared power source  14  to provide a current output. A current loop may be formed via the connector  48 , the supply cable  46 , the consumable electrode  50 , the workpiece  36 , the work clamp  38  and the cable  40  that is electrically coupled to the connector  42  on the face of the welding power supply  12 . As will be appreciated, the current flow creates an electric arc between the consumable electrode  50  and the workpiece  36 . The electric arc generates heat that melts the workpiece  36  and the consumable electrode  50  to create a weld. 
         [0019]    The welding power supply  12  may be configured to provide power to any number of welding devices (such as a TIG torch  28 , MIG gun  44  and the like), cutting devices (e.g., plasma cutting torch), and so forth. For example, as described in further detail below, the power circuit  20  of the shared power source  14  may include circuitry configured to output current to multiple DCEP output studs and/or multiple DCEN output studs. In such a configuration, each of the output studs may be electrically coupled to a connection on the face of the power supply  12  in a similar configuration to the output connectors  32  and  48  depicted in  FIG. 1 . Accordingly, multiple devices may be connected to the power supply  12  at the multiple connectors. For example, if there are three DCEP connections and three DCEN connections, a TIG torch may be connected to each of the three DCEN connections, two MIG guns may be connected to two of the DCEP connections and a stick welding gun (stinger) may be coupled to the third DCEP connection. Any compatible welding, cutting or other device may be coupled to the connectors in any combination. For example, a plasma cutter may be attached to one of the connectors, and another connector may not even have a device connected to it. 
         [0020]    As depicted, the welding power supply  12  includes connector  42  configured to couple to the cable  40  electrically coupled to the workpieces  36  via the workclamp  38 . Therefore, a user may switch between using the TIG torch  28  to weld the workpiece  36  and, alternatively, welding with the MIG gun  44 . 
         [0021]    The welding system  10  may include a variety of other components used for welding operations. For example, as depicted in  FIG. 1 , the welding system  10  includes a shielding gas source  60  configured to provide a shielding gas to the welding devices (such as the TIG torch  28  and the MIG gun  44 ). As depicted the shielding gas is provided to the welding power supply  12  via a gas conduit  62  and routed via the welding power supply  12  to the supply cables  30  and  46  and the TIG torch  28  and MIG gun  44 , respectively. Further, as depicted, the welding power supply  12  may include a wire feeder  64  configured to provide a welding wire  66  to the MIG gun  44  via the supply cable  46 . The welding system  10  may include any variety of devices used by the processes supported by the welding power supply  12 . 
         [0022]    The remainder of this discussion focuses on embodiments of the shared power source  14 . More specifically, the following embodiments consider systems and methods implemented with the shared power supply  14  to provide the required/requested power to outputs of the shared power source  14 . These outputs are configured to supply power to the power supply  12  and/or connected welding devices. 
         [0023]    Turning now to  FIG. 3 , depicted is a flowchart illustrating a method for outputting power from the shared power source  14  in accordance with the requirements of the system  10 , and more specifically in accordance with the requirements of the devices connected to power supply  12 . As discussed above, the shared power source  14  may be contained within the power supply  12  and configured to output power with a given polarity based on a particular process being performed. For example, when performing MIG welding, the MIG gun  44  may be operated in a DCEP mode to increase the heat generated at the electrode  50  and/or to reduce burn through at the workpiece  36 . However, when performing welding with another connected device, such as TIG welding, the TIG torch  28  may be operated in a DCEN mode to reduce the heat concentration at the electrode  34  and to increase the heat within the workpiece  36 . Accordingly, a first step may include selecting a welding process, as depicted by block  68 . In an embodiment, selecting the welding process may include providing an input signal indicative of the process and/or the desired output polarity to an input of the control circuit  22 . For example, the control circuit  22  may include an input configured to receive a signal indicative of the output needed to perform the current process. An embodiment may include a switch on the welding device (such as the TIG torch  28  and the MIG gun  44 ) that transmits a signal to the control circuit  22  in response to its activation by an operator. In another embodiment, the user may simply pull a trigger on the given device (e.g., the TIG torch  28  or MIG gun  44 ) to initiate a weld and the control circuit  22  may recognize the demand as a request to select a process. 
         [0024]    In response to the signal received, the control circuit  20  may select an output configuration, as depicted at block  70 . For example, in a configuration where the shared power source  14  includes a single DCEP output and a single DCEN output, the control circuit  20  may interpret the control signal and determine if the shared power source  14  should provide power on the DCEP output or the DCEN output. Accordingly, the control circuit  20  may switch between DCEP and DCEN outputs based on interpretations of the control signal. In an embodiment where the shared power source  14  includes multiple DCEP outputs and multiple DCEN outputs, the control circuit  20  may also process the control signal to identify which specific output requires DCEP or DCEN power. For example, in a shared power source  14  that includes multiple DCEP and DCEN outputs (as discussed in further detail with regard to  FIGS. 5 and 6 ), the control circuit may activate or deactivate additional switches within the power circuitry  20  to enable output on one of the output studs while disabling output on other output studs. Thus, after identifying the power output required/requested by the signal, the control circuit  22  may operate the switches to configure the output power, as depicted by block  72 . With the power circuit  20  configured, the shared power source  14  may output power, as depicted by block  74 . For example, the shared power source  14  may output power to an output stud that is electrically coupled to a connector  32  and  48  on the power supply  12 . Therefore a device coupled to the connector  32  and  48  may be powered accordingly. 
         [0025]    Turning now to  FIG. 4 , depicted is an embodiment of the shared power source  14  comprising an output configured to provide electronic polarity reversal. The shared power source  14  includes power circuitry  20  and a control circuit  22  configured to route power from the transformer  18  in accordance with a selected welding process. In one embodiment, the shared welding power source  14  may be configured to operate in a DCEP mode. For example, a high-frequency current is delivered to the torch  28  and  44  and the workpiece  36  and returned to the power source  14  based on the configuration of the transformer  18 . In an embodiment that includes a center tapped transformer  18 , the transformer  18  may include a first secondary winding  78  and a second secondary winding  80  configured to receive power from a primary winding electrically coupled to the external power source  16 . In an embodiment in which the transformer  18  is configured to operate in a forward-biased mode, the control circuit  22  may enable a first switch  82  to enable current to flow across the first switch  82 . Accordingly, a positive weld current flows from a first terminal  84  through a first rectifier  86 , the first switch  82  and the first DCEP output stud  88 . As discussed previously, the first DCEP output stud  88  may be electrically coupled to a welding device, such as a MIG gun  44 , configured to operate in DCEP mode. Welding current is returned to the power source  14  via the work output stud  90 . As discussed previously, the work output stud  90  may be electrically coupled to a workpiece  36  via a connector  42  and  58 , cable  40  and  56  and work clamp  38  and  54 . Accordingly, returning welding current flows through the work output stud  90 , the output inductor  92  and the center-tap connection  94  of the transformer  18 . 
         [0026]    In an embodiment configured to output power to device connected to a DCEP output and including the transformer  18  configured to operate in a reverse-biased mode, current may flow in an alternate path. For example, similar to the forward-biased DCEP mode, the controller circuit  22  may enable a first switch  82  to allow current to flow across the first switch  82 . Accordingly, a positive weld current may flow from a second terminal  96  through a second rectifier  98 , the first switch  82  and a first DCEP output stud  88 . Welding current is returned to the power source  14  via the work output stud  90 . Accordingly, welding current flows through the work output stud  90 , the output inductor  92  and the center-tap connection  94  of the transformer  18 . 
         [0027]    The welding circuit depicted in  FIG. 4  may also include a configuration to operate in a DCEN mode. In an embodiment configured to output power to a DCEN output and where the transformer  18  is configured to operate in a forward-biased mode, the controller circuit  22  may enable a second switch  100  to allow current to flow across the second switch  100 . Accordingly, positive weld current flows from the center-tap connection  94  of the transformer  18 , through the output inductor  92 , and the work output stud  90 . As discussed previously, the weld output stud  90  may be electrically coupled to a workpiece  36  via a connector  42 , cable  40  and work clamp  38 . Welding current is returned to the power source  14  via the DCEN output stud  102 . As discussed previously, the second weld output stud  102  may be electrically coupled to a welding device, such as a TIG torch  28 , configured to operate in DCEN mode. Accordingly, welding current flows through the first DCEN output stud  102 , the second switch  100 , a third rectifier  104  and second terminal  96  of the transformer  18 . 
         [0028]    In an embodiment, configured to output power to a DCEN output and where the transformer  18  is configured to operate in a reverse-biased mode, current may flow in an alternate path. For example, similar to the forward-bias DCEN mode, the controller circuit  22  may enable the second switch  100  to enable current to flow across the second switch  100 . Accordingly, a positive weld current may flow from the center-tap  94 , through the output inductor  92 , and the work output stud  90 . Welding current is returned to the power source  14  via the first DCEN output stud  102 , the second switch  100 , a fourth rectifier  106  and the first terminal  84  of the transformer  18 . 
         [0029]    The topology depicted in  FIG. 4  provides a DCEP and DCEN output on two separate outputs (DCEP output stud  88  and DCEN output stud  102 ). Thus, the shared power source  14  may support a DCEP device and a DCEN device simultaneously and may switch the output between the two devices without requiring a user to reconnect the devices and/or manually switch a control. As discussed below, the topology of the shared welding power source  14  depicted in  FIG. 4  may be modified to support an infinite number of DCEP and DCEN devices. 
         [0030]    Turning now to  FIG. 5 , depicted is a shared welding power source  14  including an electronic polarity reversal power output that comprises three DCEP output studs  88 ,  108  and  110  and three DCEN output studs  102 ,  112  and  114 . An embodiment includes a second DCEP output stud  108  and a third DCEP output stud  110  in parallel with the first DCEP output stud  88 . In this configuration, multiple welding devices may be connected to DCEP outputs  88 ,  108  and  110  simultaneously. For example, current may be provided to three separate MIG guns  44  electrically coupled to the DCEP output studs  88 ,  108  and  110  and returned to the shared power source  14  via the workpiece  36  electrically coupled to the work output stud  90 . Similarly, multiple devices may be coupled to the DCEN output studs  102 ,  112  and  114  simultaneously. For example, current may be supplied to the workpiece  36  electrically coupled to the work output stud  90  and returned to the shared power source  14  via one of three separate TIG torches  28  electrically coupled to the DCEN output studs  102 ,  112  and  114 . 
         [0031]    The topology depicted in  FIG. 5  may be advantageous because an infinite number of DCEP output studs  88 ,  108  and  110  and DCEN output studs  102 ,  112  and  114  may be provided from the shared power source  14  that comprises two switches  82  and  100 . Thus, the cost and complexity of the system may be minimized. However, in such a system, when one of the output studs  88 ,  102 ,  108 ,  110 ,  112  and  114  is “live” (i.e., has voltage potential), the other output studs may also remain “live.” For example, if the first switch  82  is enabled, and current is provided to the DCEP output studs  88 ,  108  and  110 , current may flow to a MIG gun  44  connected to one of the first DCEP output studs  88  and current potential may be provided at the second and third DCEP output studs  108  and  110  and/or any devices connected to them. Similarly, if the second switch  100  is closed, all of the DCEN output studs  102 ,  112  and  114  may be live at the same time. 
         [0032]    A topology of the shared power source  14  may include various other components (such as additional switches) to more efficiently route the power and limit the number of live output studs. Turning now to  FIG. 6 , depicted is a modified topology including additional switches to limit the number of live weld output studs. In an embodiment, the shared power circuit  14  may include power circuitry  20  that includes additional switches  116 ,  118 ,  120  and  122  configured to provide an open or closed circuit to the each of individual output studs. In an embodiment, the control circuit  22  may open or close the switches  82 ,  100 ,  116 ,  118 ,  120  and  122  to coordinate the power output to each respective output stud. For example, as depicted in  FIG. 6 , the first DCEP switch  82 , the second DCEP switch  116  and the third DCEP switch  118  may be configured such that closing or opening the switches  100 ,  116  and  118  may complete or disconnect the current path to the first DCEP output stud  88 , the second DCEP output stud  108  and the third DCEP output stud  110 , respectively. Similarly, the first DCEN switch  100 , the second DCEN switch  120  and the third DCEN switch  122  may be configured such that closing or opening the switches  100 ,  120  and  122  may complete or disconnect the current path to the first DCEN output stud  102 , the second DCEN output stud  112  and the third DCEN output stud  114 , respectively. Thus, the shared power source  14  may output a current via a single output stud  102 ,  112  and  114  without producing a current potential on any of the other output studs. For example, if the shared power source  14  operates in DCEP mode, the control circuit  22  may enable the first DCEP switch  82  to provide current to the first DCEP output stud  88  and disable the other switches  100 ,  116 ,  118 ,  120  and  122  to ensure the other output studs  102 ,  108 ,  110 ,  112  and  114  are not live. In other words, the control circuit  22  may only close the switches  82 ,  100 ,  116 ,  118 ,  120  and  122  that correspond to output studs configured to be live. Further, an embodiment may include any number of switches and output studs to enable connection to any number of welding devices (such as TIG torches  28  and MIG guns  44 ), cutting devices, and so forth. For example, the power circuitry  20  may include any number of output studs and a corresponding number of switches. 
         [0033]    The control circuitry  20  depicted in  FIG. 6  offers flexibility by allowing a user and/or the control circuit  22  to specify which output stud receives power. In an embodiment, the control circuit  20  may detect that a device is not connected to an output stud  88 ,  102 ,  108 ,  110 ,  112  and  114  and open a respective switch  82 ,  100 ,  116 ,  118 ,  120  and  122  to prevent a potential at the studs  88 ,  102 ,  108 ,  110 ,  112  and  114 . For example, the system  10  may provide an electrical signal on an input of the control circuit  20  when a device is connected and the control circuit  22  may “unlock” the switch and enable the control circuit  20  to close the switch. Similarly, a signal may be input to the control circuit  20  to alert the control circuit  20  that an output stud does not have a device connected and, thus, the control circuit  22  may “lock” the respective switch open to prevent power from being delivered to the specific output stud. 
         [0034]    An alternative embodiment of the shared power source  14  may include a configuration of two output rectifiers and four switches, as compared to the four rectifiers included in the embodiments of  FIG. 4-6 . Turning now to  FIG. 7 , the shared power source  14  includes power circuitry  20  comprising two output rectifiers and four switches, as depicted. In an embodiment, the control circuit  22  is configured to control the states of the four switches  124 ,  126 ,  128  and  130  in a manner similar to those described with reference to  FIGS. 4-6 . For example, the control circuit  22  may receive a control signal indicative of which output stud requires power and the control circuit  22  may open or close the switches  124 ,  126 ,  128  and  130 , accordingly. In an embodiment, where the shared power source  14  is configured to provide power to a device connected to the DCEP output stud and includes a center-tapped transformer  18  configured to operate in a forward-biased mode, the control circuit  22  may enable the first switch  124  and the fourth switch  130 . Accordingly, a positive weld current flows from the first terminal  84  through a first rectifier  132 , the first switch  124  and the DCEP output stud  88 . Welding current is returned to the power source  14  via the work output stud  90 . Accordingly, welding current flows through the fourth switch  130 , the output inductor  92  and the center-tap connection  94 . 
         [0035]    In an embodiment where the shared power source  14  is configured to output power to the DCEP output stud  88  and the center-tapped transformer  18  is configured to operate in a reverse-biased mode, current may flow in an alternate path. For example, similar to the forward-biased DCEP mode, the controller circuit  22  may enable the first switch  124  and the forth switch  130  to enable current flow across the first switch  124  and the forth switch  130 . Accordingly, a positive weld current may flow from the second terminal  96  through a second rectifier  134 , the first switch  124  and the DCEP output stud  88 . Welding current is returned to the shared power source  14  via the work output stud  90  and flows through the fourth switch  130 , the output inductor  92  and the center-tap connection  94 . 
         [0036]    The shared power source  14  depicted in  FIG. 7  may also be configured to provide power to the DCEN output  102 . In an embodiment where the transformer  18  is configured to operate in a forward-biased mode, the controller circuit  22  may enable the second switch  126  and the third switch  128  to enable current flow across the second switch  126  and the third switch  128 . Accordingly, a positive weld current may flow from the first terminal  84  of the transformer  18 , through the third switch  128 , and the work output stud  90 . Welding current is returned to the power source  14  via the DCEN output stud  102  and flows through the second switch  126 , output inductor  92  and the center-tap connection  94 . 
         [0037]    In an embodiment where the shared power source  14  is configured to provide power to the DCEN output  102  and where the center-tapped transformer  18  is configured to operate in a reverse-biased mode, current may flow in an alternate path. For example, similar to the forward-biased DCEN mode, the controller circuit  22  may enable the second switch  126  and the third switch  128  to enable current flow across the second switch  126  and the third switch  128 . Accordingly, a positive weld current may flow from the second terminal  96 , through the second rectifier  134 , the third switch  128  and the work output stud  90 . Welding current is returned to the shared power source  14  via the DCEN weld output stud  102  and flows through the second switch  126 , the output inductor  92  and the center-tap connection  94  of the transformer  18 . 
         [0038]    Although the embodiment depicted in  FIG. 7  delivers power to the DCEP output stud  88  and the DCEN output stud  102  as demanded, such a configuration also makes both output studs  88  and  102  live at the same time. To resolve the issue, an embodiment may be configured to limit outputs to live output studs and non-live output studs. Turning now to  FIG. 8 , an embodiment is depicted that limits outputs on the DCEP output stud  88  and the DCEN output stud  102 . For example, in an embodiment wherein the system is configured to output power to a DCEP output stud and where the transformer  18  is configured to operate in forward bias, the control circuit may enable the fifth switch  136  and the fourth switch  130 . Accordingly, a positive weld current flows from the first terminal  84  through the first rectifier  132 , the fifth switch  136  and the DCEP output stud  88 . Welding current is returned to the power source  14  via the work output stud  90  and the welding current flows through the fourth switch  130 , the output inductor  92  and the center-tap connection  94 . 
         [0039]    In an embodiment where the shared power source  14  is configured to provide power to the DCEP output stud  88  and the transformer  18  is configured to operate in a reverse-biased mode, current may flow in an alternate path. For example, similar to the forward-biased DCEP mode, the controller circuit  22  may enable the fifth switch  136  and the fourth switch  130  to enable current flow across the fifth switch  136  and the fourth switch  130 . Accordingly, a positive weld current may flow from the second terminal  96  through the second rectifier  134 , the fifth switch  136  and the DCEP output stud  88 . Welding current is returned to the power source  14  via the work output stud  90  and flows through the fourth switch  130 , the output inductor  92  and the center-tap connection  94 . 
         [0040]    In an embodiment where the shared power source  14  is configured to output power to the DCEN output stud  102 , the control circuit  22  may enable and disable switches similar to the embodiment discussed with reference to  FIG. 7 . 
         [0041]    The configuration depicted in  FIG. 8  can be modified to include any number of output studs. For example, an additional set of switches may be provided similar to fifth switch  136  and sixth switch  138  illustrated in  FIG. 8 . Other embodiments may include the addition of output studs in parallel with the DCEP output stud  108  and/or the DCEN output studs  102 . For example, the shared power source  14  may include additional DCEP output studs and DCEN output studs coupled in parallel to the DCEP output stud  108  and the DCEN output stud  102 , respectively, in a manner similar to the configuration illustrated in  FIGS. 5 and 6 . An embodiment may include additional switches to limit outputs between the additional output studs. For example, additional switches can be added before each output stud, similar to switches  116 ,  118 ,  120  and  122  illustrated in  FIG. 6 , to further control the output current and limit the outputs on the live and non-live output studs. 
         [0042]    The shared power source  14  may include a transformer  18  with a single secondary winding. For example, as depicted in  FIG. 9 , the transformer  18  includes a single secondary winding  140  comprising a first terminal  142  and a second terminal  144 . In an embodiment where the transformer  18  is configured to operate in a forward-biased mode, a positive weld current may flow from the first terminal  142  and through the first rectifier  132 , and, then, may be routed via the switches  136  and  128  to the DCEP output stud  88  or the work output stud  90 , based on the control circuit  22  setting for DCEP or DCEN output. Power may be returned from the work output stud  90  or the DCEN output stud  102  via the switches  130  and  126 , and flow through the inductor  92 , the fourth rectifier  148  and the second terminal  144 . 
         [0043]    In an embodiment where the transformer  18  is configured to operate in a reverse-biased mode, a weld current may flow from the second terminal  144 , through the third rectifier  134  and routed via the switches  136  and  128  to the DCEP output stud  88  or the work output stud  90 , based on the control circuit  22  setting for DCEP or DCEN output. Power may be returned from the work output stud  90  or the DCEN output stud  102  via the switches  130  and  126 , and flow through the inductor  92 , the second rectifier  146  and the first terminal  142 . Accordingly, other embodiments may be configured to include a single secondary coil transformer  18 . For example, the shared power source  14  depicted in  FIG. 7  may be modified to include a single secondary coil transformer  18  and four rectifiers to route the output of the transformer  18  via the switch and the output studs  88 ,  90  and  102 . 
         [0044]    The flexibility of the shared power source  14  may be increased by dividing the shared power source  14  into a power source circuit and a remote polarity reversing circuit. For example, the shared power source  14  depicted in  FIG. 10  includes a power source circuit  150  and a polarity reversing circuit  152  configured to operate remotely. In such a configuration, the shared power source  14  and/or the power supply  12  may include the power source circuit  150  and the polarity reversing circuit  152  as separate units. Thus, multiple configurations of the polarity reversing circuit  152  may be exchanged with the power source circuit  150 . For example, the circuits depicted in  FIGS. 7 and 8  may be divided in a similar manner to provide a remote polarity reversing circuit  152  coupled to a power source circuit  150  including a center-tapped transformer  18 . In another embodiment, a power source circuit  150  including a transformer  18  comprising a single secondary winding  140  may be coupled to a polarity reversing circuit  152  that including four switches  124 ,  126 ,  128  and  130  coupled to the control circuit  22 . Other embodiment may include separating portions of the circuits depicted in  FIG. 4-6  in a similar manner to comprise a remote polarity reversing circuit  142 . 
         [0045]    Previous discussions have referred to switches  82 ,  100 ,  116 ,  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  136  and  138  that are provided to route power within the shared power source  14  and the respective power circuitry  20 . The switches  82 ,  100 ,  116 ,  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  136  and  138  are controllable via signal from a control circuit  22  based on a signal received and/or a mode established by the control circuit  22 . The switches  82 ,  100 ,  116 ,  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  136  and  138  may include devices such as a thyristor configured to conduct or not conduct current based on a signal (such as a signal from the control circuit  22 ) received at their gate. Embodiments may include other similar switching devices. For example, the switches  82 ,  100 ,  116 ,  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  136  and  138  may include insulated gate bipolar transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs) and/or electromechanical contactors. 
         [0046]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Technology Category: 7