Method and apparatus for providing welding power

Abstract

Methods and apparatus are disclosed for providing welding power. An example welding-type power supply includes a transformer having a first secondary winding and a second secondary winding, a switching element configured to control current flow from the first secondary winding and the second secondary winding to an output, and a control circuit configured to control the switching element to selectively output a positive output voltage and a negative output voltage without a separate rectifier stage by selecting a first subset of the switching elements to perform rectification based on an output voltage polarity.

Description

[0001] This application is a divisional application of the invention patent application filed on July 3, 2018, with international application number PCT / US2018 / 040735, national application number 201880048713.1, and entitled "Method and apparatus for providing welding electricity".

[0002] Related applications

[0003] This international application claims priority to U.S. Patent Application No. 15 / 663,251, filed July 28, 2017, entitled “Methods and Apparatus to Provide Welding Power”. The entire contents of U.S. Patent Application No. 15 / 663,251 are incorporated herein by reference. Background Technology

[0004] This disclosure generally relates to welding systems, and more specifically, to methods and apparatus for providing welding power.

[0005] In recent years, welding equipment has incorporated switch-mode power supplies for converting and / or regulating input power into welding power. Switch-mode power supplies, or inverter-based power supplies, use semiconductor devices instead of bulkier magnetic components, which significantly reduces the weight and size of welding power supplies that incorporate inverter-based power supplies. Summary of the Invention

[0006] Methods and apparatus for providing welding electricity are disclosed, substantially as illustrated in at least one of the accompanying drawings and described in conjunction with at least one of the accompanying drawings, and are set forth more fully in the claims. Attached Figure Description

[0007] Figure 1 This is a circuit diagram of a standard full-bridge soldering output circuit.

[0008] Figure 2 It is a diagram. Figure 1 A graph showing the welding current output of a conventional full-bridge welding output circuit under different commutation schemes.

[0009] Figure 3 This is a circuit diagram of a conventional half-bridge soldering output circuit.

[0010] Figure 4 This is a circuit diagram of an output circuit soldered according to an example of an aspect of this disclosure.

[0011] Figure 5 Illustration Figure 4The example is the operation of a welding output circuit, where the output has an electrode with negative polarity and a positive input polarity.

[0012] Figure 6 Illustration Figure 4 The example is the operation of a welding output circuit, where the output has a positive electrode polarity and a positive input polarity.

[0013] Figure 7 Illustration Figure 4 The example is the operation of a welding output circuit, where the output has positive electrode polarity and negative input polarity.

[0014] Figure 8 Illustration Figure 4 The example demonstrates the operation of the output circuit during the freewheeling phase when there is no input power supplied by the primary-side inverter.

[0015] Figure 9 yes Figure 4 A graph showing the voltage and current in the welding output circuit.

[0016] Figure 10 Illustration Figure 4 The example demonstrates the operation of the output circuit during the reverse power transfer from the output stage to the input stage.

[0017] Figure 11 Is it like this? Figure 10 During the reverse power transmission illustrated Figure 4 A graph showing the voltage and current in the welding output circuit.

[0018] Figure 12 yes Figure 4 The welding output circuit is in Figure 10 The diagram illustrates the current output during reverse power transmission.

[0019] Figure 13 yes Figure 4 A circuit diagram of an example welding output circuit, wherein the example welding output circuit includes an example heat sink assembly configuration for dissipating heat from the switching elements.

[0020] Figure 14 This is a circuit diagram of an example welding output circuit according to aspects of this disclosure, wherein the example welding output circuit uses a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0021] Figure 15 This is a circuit diagram of an example soldered output circuit according to an aspect of this disclosure, wherein the example soldered output circuit uses multiple transformers.

[0022] Figure 16 This is a block diagram of an example implementation of a control circuit, wherein the control circuit is configured to output a PWM signal to control... Figure 4 and / or Figure 14 Switching elements.

[0023] The accompanying drawings are not necessarily drawn to scale. Where appropriate, similar or identical reference numerals are used to denote similar or identical parts. Detailed Implementation

[0024] The disclosed example provides alternating current (AC) output from a welding power supply based on a switch-mode power supply (SMPS). Compared to conventional full-bridge and half-bridge power supply circuits, the disclosed example power supply uses semiconductor devices on the SMPS secondary circuit side of the isolation barrier circuit to combine the rectifier stage with the commutation stage.

[0025] The disclosed example methods and apparatus can be used to return nonfunctional quantities stored in an induction welding circuit on the secondary side (e.g., the output side) of an isolation barrier circuit to the primary side (e.g., the input circuit) of the isolation barrier circuit by operating in a reverse manner.

[0026] As used herein, the term "welding power" refers to power suitable for welding, plasma cutting, induction heating, CAC-A and / or hot wire welding / preheating (including laser welding and laser cladding). As used herein, the term "welding power supply" refers to any device capable of supplying power for welding, plasma cutting, induction heating, CAC-A and / or hot wire welding / preheating (including laser welding and laser cladding) when power is applied thereto, including (but not limited to) inverters, converters, resonant power supplies, quasi-resonant power supplies, and the control circuitry and other auxiliary circuitry associated therewith.

[0027] As used herein, the term “welding voltage” refers to the voltage applicable to welding, plasma cutting, induction heating, CAC-A and / or hot wire welding / preheating (including laser welding and laser cladding).

[0028] The disclosed example welded power supply includes: a transformer having a primary winding and a secondary winding; switching elements for controlling the current flow from the primary winding and the secondary winding to the output; and a control circuit configured to select a first subset of the switching elements to perform rectification based on the commanded output voltage polarity, thereby controlling the switching elements to selectively output positive and negative output voltages without requiring a separate rectifier stage.

[0029] In some instances, the control circuit selects a second subset of switching elements based on the commanded output voltage polarity and controls this second subset to couple to the primary and secondary windings. In some such instances, the second subset differs from the first subset. In some instances, the control circuit selects both a first subset and a second subset of switching elements based on both the input voltage polarity and the commanded output voltage polarity. In some instances, the control circuit reselects the second subset of switching elements when the commanded output voltage polarity changes.

[0030] Some examples of welded power supplies also include: a primary converter circuit for converting input power into intermediate power with an intermediate frequency, wherein a transformer receives the intermediate power at the primary winding of the transformer. In some such examples, control circuitry controls switching elements to supply energy to the primary converter circuit via a first and a second primary winding. Some examples also include: a first heat sink for dissipating heat from at least two switching elements of a first group sharing a first electrical node; and a second heat sink for dissipating heat from at least two switching elements of a second group sharing a second electrical node.

[0031] In some instances, the transformer includes a primary winding, and control circuitry controls the conduction of current through all switching elements when no voltage is substantially applied to the primary winding. In some instances, each of the switching elements comprises an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET) with a freewheeling diode.

[0032] The disclosed welding power supply includes: a transformer having a primary winding and a secondary winding; a first switching element; a second switching element; a third switching element; a fourth switching element; and a control circuit. The first switching element is coupled between the primary winding and a first output terminal of the welding power supply; the second switching element is coupled between the secondary winding and the first output terminal of the welding power supply; the third switching element is coupled between the primary winding and the second output terminal of the welding power supply; and the fourth switching element is coupled between the secondary winding and the second output terminal of the welding power supply. The control circuit controls the switching elements to output a welding voltage of a first polarity by controlling the first and second switching elements as a center tap operation between the primary and secondary windings, while simultaneously operating the third and fourth switching elements as rectifiers. The control circuit further controls the switching elements to output a welding voltage of a second polarity by controlling the third and fourth switching elements as a center tap operation between the primary and secondary windings, while simultaneously operating the first and second switching elements as rectifiers.

[0033] In some instances, the first, second, third, and fourth switching elements comprise at least one of an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET) with a freewheeling diode. In some instances, the control circuit controls the first of the third or fourth switching elements to conduct and controls the other of the third or fourth switching elements to turn off based on the polarity of the primary winding voltage of the transformer. In some instances, the control circuit controls the first of the first or second switching elements to conduct and controls the other of the first or second switching elements to turn off based on the polarity of the primary winding voltage of the transformer.

[0034] Some examples of welded power supplies also include a primary converter circuit for converting input power into intermediate power with an intermediate frequency, wherein a transformer receives the intermediate power at the primary winding of the transformer. In some such examples, a control circuit controls first, second, third, and fourth switching elements to supply energy to the primary converter circuit via the primary and secondary windings.

[0035] In some instances, when no voltage is substantially applied to the primary winding of the transformer, the control circuit controls the first, second, third, and fourth switching elements to conduct current. In some instances, the first, second, and third switching elements are connected in series between the first and second output terminals, and the second, second, and fourth switching elements are also connected in series between the first and second output terminals.

[0036] In some instances, each of the first, second, third, and fourth switching devices conducts an average of half of the output current at the first and second output terminals. Some instances also include: a first heat sink for dissipating heat from the first and second switching elements; and a second heat sink configured to dissipate heat from the third and fourth switching elements.

[0037] Figure 1 This is a circuit diagram of a conventional full-bridge soldering output circuit 100. The conventional full-bridge soldering output circuit 100 includes a primary (input) side switch-mode power supply 102, which generates a high-frequency (e.g., 18 to 100 kHz) signal to the primary winding 104 of a transformer 106. The transformer 106 provides isolation between the primary side of the transformer (e.g., the primary power supply 102) and the secondary side 108 of the transformer 106.

[0038] Secondary side 108 generates output voltage and current, for example, for welding applications. Secondary side 108 includes a rectifier stage 110, a commutation stage 112, and auxiliary circuitry 114. Rectifier stage 110 converts high-frequency signals into DC current. Commutation stage 112 includes four transistors 116a to 116d, which are arranged in a bridge to convert the DC current from rectifier stage 110 into a lower-frequency (e.g., 20 to 400 Hz) AC current (e.g., current suitable for welding). Auxiliary circuitry 114 disposes of the reactive power present during commutation by clamping the output voltage and returning excess energy to the output.

[0039] The secondary side 108 generates an output voltage between the welding electrode 118 (e.g., via a welding torch) and the workpiece 120. The welding cable and / or the secondary side 108 may have an output inductance represented by inductor 122 and / or a physical inductor. Other inductive sources (e.g., coupling coil 124 for high-frequency arc initiation) may also provide a reactive component.

[0040] Figure 1 The conventional full-bridge topology has drawbacks, including excessive losses due to the continuous current flowing through three of the semiconductor devices on the secondary side 108 (e.g., a diode in the rectifier stage 110 and two transistors 116a to 116d in the commutation stage 112). Another disadvantage of the full-bridge topology is that only two of the four transistors 116a to 116d are used at any given time, while the other two transistors 116a to 116d (and their associated current paths) remain idle. Furthermore, the full-bridge topology requires auxiliary circuitry 114 to handle (e.g., clamp) the unused energy stored in the output inductor.

[0041] Figure 2 It is a diagram. Figure 1 The diagram illustrates examples of welding current outputs 202 and 204 of a conventional full-bridge welding output circuit 100 under different commutation schemes. One advantage of the full-bridge over other conventional topologies (e.g., half-bridge topologies) is that the full-bridge welding output circuit 100 can hard-commutate the current or switch the current from one group of transistors 116a to 116d to another group of transistors 116a to 116d, and thus change the direction of the current through the use of clamping. Output current 202 illustrates the output using the hard-commutation scheme, and output current 204 illustrates the soft-commutation scheme using auxiliary circuit 114. The use of output inductor 122 arranged in the DC branch achieves a more square-shaped output current as shown in hard-commutated output current 202. However, hard-commutated output current 202 results in a significant change in current (e.g., dI / dt in the output inductor).

[0042] Figure 3 This is the circuit diagram for a standard half-bridge soldering output circuit 300. (Similar to...) Figure 1 The full-bridge circuit 100 and the half-bridge solder output circuit 300 include a primary (input) side switch-mode power supply 302, which generates a high-frequency (e.g., 18 to 100 kHz) signal to the primary winding 304 of the transformer 306. In the half-bridge solder output circuit 300, the windings of the transformer 306 must be configured to operate in both the first and third quadrants. The transformer 306 provides isolation between the primary side of the transformer (e.g., the primary power supply 302) and the secondary side 308 of the transformer 306.

[0043] The half-bridge welding output circuit 300 includes two independent rectifier stages 310 and 312 for converting a high-frequency signal from transformer 306 into DC current. Rectifier stage 310 performs rectification of the EN polarity, and rectifier stage 312 performs rectification of the EP polarity. The half-bridge welding output circuit 300 includes a commutation stage 314, which includes two transistors 316a and 316b to select between the two rectifier stages 310 and 312. By alternately changing the selection between rectifier stages 310 and 312, the output current between the welding electrode 318 and the workpiece 320 is a lower frequency AC current (e.g., 20 to 400 Hz) suitable for welding.

[0044] The half-bridge welding output circuit 300 includes auxiliary circuitry 322 for clamping the voltage and returning any nonfunctional quantities present during commutation to the output.

[0045] The advantages of the half-bridge soldering output circuit 300 over the full-bridge soldering output circuit 100 include the removal of a semiconductor device in the conduction path, which reduces heat loss. The half-bridge soldering output circuit 300 also reduces component costs by replacing transistors with cheaper diodes.

[0046] Figure 4 This is a circuit diagram of the example soldering output circuit 400. The example soldering output circuit 400 is an improvement over the full-bridge and half-bridge circuits described above. In the half-bridge circuit 300, there are two sets of rectifiers (e.g., one set for EP current flow and another for EN current flow). Transistors are then arranged to select between the two sets of rectifiers based on the desired output polarity. In contrast, in the example soldering output circuit 400, the same semiconductor devices selectively perform rectification and commutation.

[0047] As explained in more detail below, the welding output circuit 400 includes a transformer 402, which has a primary winding 404, a first-stage winding 406, and a second-stage winding 408. The welding output circuit 400 includes a set of switching elements 410a to 410d and a control circuit 412 for controlling the switching elements. The welding output circuit 400 outputs AC and / or DC welding-type power via output terminals 414 and 416. In the illustrated example, the first output terminal 414 is coupled to a workpiece 418 (e.g., via a work cable), and the second output terminal 416 is coupled to a welding electrode 420 (e.g., via a welding torch and welding cable).

[0048] Example switching elements 410a to 410d are insulated-gate bipolar transistors (IGBTs) with a freewheeling diode packaged within them. However, in other examples, other types of switching elements may be used. The following discussion... Figure 14 The illustration shows an example of using a metal-oxide-semiconductor field-effect transistor (MOSFET) as a switching element. Switching element 410a is coupled between the secondary winding 406 and the output terminal 414 of the solder output circuit 400. Switching element 410c is coupled between the secondary winding 408 and the output terminal 414. Switching element 410b is coupled between the secondary winding 406 and the output terminal 416. Switching element 410a, secondary winding 406, and switching element 410b are connected in series between the output terminals 414 and 416, and switching elements 410c, secondary winding 408, and switching element 410d are connected in series between the output terminals 414 and 416.

[0049] Typically, control circuit 412 controls the output voltage, output current, and / or output frequency via welding output circuit 400. Therefore, control circuit 412 controls rectification and commutation functions via switching elements 410a to 410d to ensure that welding output circuit 400 outputs a welding voltage with the desired polarity (e.g., EP or EN). Control circuit 412 selects and controls a first subset of switching elements 410a to 410d based on the output polarity (e.g., EN or EP) to act as the center tap between secondary windings 406, 408. Control circuit 412 selects and controls a second subset of switching elements 410a to 410d based on the input polarity at primary winding 404 to perform rectification by conducting and / or blocking current. When the output polarity changes (e.g., from EN to EP or from EP to EN), control circuit reselects the first and second subsets of switching elements 410a to 410d. Therefore, compared to conventional output topologies, the control circuit 412, transformer 402, and switching elements 410a to 410d allow for both positive and negative output voltages and currents without requiring a separate rectifier stage.

[0050] like Figure 5 As illustrated, control circuit 412 outputs a welding voltage with EN polarity by controlling switching elements 410b and 410d to be constantly switched on (e.g., conducted) as a center tap operation between secondary windings 406 and 408. Control circuit 412 controls switching elements 410a and 410c to operate as rectifiers that selectively conduct current based on the voltage across secondary windings 406 and 408.

[0051] like Figure 6 and Figure 7 As illustrated, control circuit 412 outputs a welding voltage with EP polarity by controlling switching elements 410a and 410c to be constantly switched on (e.g., conducted) as a center tap operation between secondary windings 406 and 408. Control circuit 412 controls switching elements 410b and 410d to operate as rectifiers that selectively conduct current based on the voltage across secondary windings 406 and 408.

[0052] When one polarity is selected and the primary winding 404 is supplied with an input voltage, two of the switching elements 410a to 410d are controlled to conduct, which configures the transformer 402 as a secondary section with a center tap and two output rectifiers. However, the orientation of the secondary windings 406, 408 can be configured based on which two of the switching elements 410a to 410d are used to implement the center tap between the secondary windings 406, 408.

[0053] Because each of the example switching elements 410a to 410d has a diode component that can conduct current during rectification, the IGBT components of the switching elements 410a to 410d do not necessarily need to be controlled to conduct current when the switching elements 410a to 410d would allow current to flow during rectification. However, when the switching elements 410a to 410d are not conducting current, the control circuit 412 controls the IGBT components of the switching elements 410a to 410d to block current during rectification. For example, in Figure 5 In the illustrated EN output polarity and input polarity, the control circuit 412 may or may not control the IGBT conduction current of the switching element 410c (e.g., "on"), but instead controls the blocking current of the switching element 410a (e.g., "off").

[0054] In the welding output circuit 400, switching elements 410a to 410d implement two sets of rectifiers, and control circuit 412 selects the set of rectifiers that will provide the output current. Each of the switching elements 410a to 410d conducts half the average of the output current.

[0055] The welding output circuit 400 receives AC power at an intermediate frequency from the primary-side inverter 422. The primary-side inverter 422 can generate the intermediate frequency from a primary power source (e.g., mains power and / or an engine-driven generator). Although transformer 402 is shown as a single transformer, the welding output circuit 400 may include multiple transformers arranged in parallel or series. See below for further details. Figure 15 This describes an example using multiple transformers. The primary-side inverter 422 and the welded output circuit 400 are capable of operating in any of the four quadrants of the V / A diagram (e.g., the power supply and power consumption quadrants).

[0056] The welding output circuit 400 is illustrated as having an output inductor 424 and a coupling coil 426. The output inductor 424 and the coupling coil 426 may be similar to or identical to... Figure 1 The inductor 122 and the coupling coil 124.

[0057] Example welding output circuit provides similar Figure 3 The conventional half-bridge topology offers advantages in terms of thermal dissipation (compared to full-bridge and / or other topologies), where the output current flows through only two of the semiconductor devices. However, compared to a conventional half-bridge topology with two separate sets of rectifiers, and only one set conducting at a given time, the example soldered output circuit 400 has higher utilization of all switching elements 410a to 410d.

[0058] By incorporating rectifier and current steering functions within the same semiconductor device, the example soldering output circuit 400 simplifies the routing of high-current paths and / or improves thermal management by grouping the semiconductor device to as few as two circuit locations from which heat is generated. For example, heat sinks can be used more efficiently (e.g., the duty cycle of the heat sink can be increased (e.g., up to 100%)). In some such examples, the heat sink can be configured such that its area always dissipates power, resulting in more efficient use of its footprint, which enables a more compact soldering power supply design.

[0059] Figure 8 Illustration Figure 4 The example welding output circuit 400 operates during a freewheeling phase when there is no power supplied by the primary-side inverter 422. The freewheeling phase can occur between positive and negative voltage cycles on the primary section 404 of the transformer supplied by the primary-side inverter 422. During the freewheeling phase, the energy stored in the secondary windings 406, 408 and / or the output inductor 424 is discharged to the welding output (e.g., discharged to an arc). The current Io is shunt between the two secondary windings 406, 408 such that each of the secondary windings conducts Io / 2. Figure 8 In the illustrated EP output polarity, control circuit 412 controls the conduction of switching elements 410a and 410c. Control circuit 412 may also control the conduction of switching elements 410b and 410d via transistors (e.g., synchronous rectification), and / or allow the associated diode conduction current of switching elements 410b and 410.

[0060] Figure 9 yes Figure 4 A graph illustrating the voltages and currents in the welding output circuit 400. This graph shows the primary winding voltage 902 and primary winding current 904 at the primary winding 404. The graph further illustrates a primary current 906 (e.g., flowing through the secondary winding 406 and switching elements 410a, 410b) and a secondary current 908 (e.g., flowing through the secondary winding 408 and switching elements 410c, 410d). The example primary winding voltages 902 and currents 904, 906, 908 are illustrated for EP polarity operation of the example welding output circuit 400. Figure 8 The continuous flow phase illustrated occurs during instance time periods 910 and 912.

[0061] Figure 10 Illustration Figure 4 The example welding output topology operates during reverse power transfer from the welding output circuit 400 to the primary inverter 422. During reverse power transfer mode, the welding output circuit supplies power to the primary inverter 422 via transformer 402.

[0062] In the conventional half-bridge topology discussed above, the current must reach zero before its polarity can be reversed during commutation. Reducing the current to zero is done via additional circuitry (e.g., clamping or other "auxiliary" converter circuitry) or by allowing the current to freewheel in the power supply and decay naturally in the soldering circuitry. In contrast, the example soldering output circuitry can reverse the power flow to return the unused energy to the primary inverter 422. Using the power reversal mode, the example control circuitry 412 can more efficiently manage the reduction of current before polarity reversal.

[0063] When current flows with polarity EP, control circuit 412 switches the output polarity selection to EN and controls switching elements 410a to 410d to return power to the primary inverter 422 during the EP current polarity period, according to the EN output polarity. Control circuit 412 controls switching elements 410b and 410d to be on (e.g., conducting), and control elements 410a and 410c act as rectifiers. Control circuit 412 controls the transistors of switching elements 410a and 410c to synchronize with the primary inverter 422. Without synchronization control, the soldering output circuit 400 will not have a valid path for current in the soldering output circuit 400. When the voltage on the primary inverter 422 is positive, control circuit 412 controls switching element 410c to be on, and controls switching element 410a to be on when the voltage on the primary inverter 422 is negative.

[0064] exist Figure 10 In the illustrated operation, control circuitry 412 configures the secondary windings 406, 408 of transformer 402 as a current-feed push-pull converter. Switching elements 410a, 410c act as source transistors feeding the push-pull converter. Primary inverter 422 includes switching devices that act as rectifiers for the push-pull converter to return energy to, for example, a DC bus and / or an energy storage device, which supplies power to primary inverter 422 during normal operation (e.g., to provide power to the welding output).

[0065] In a similar manner, when current flows with the EN polarity, the example control circuit 412 can control the switching elements 410a to 410d to return power according to the EP output polarity.

[0066] During reverse power transfer operation, energy is transferred from the output circuit at the secondary side of transformer 402, and the output current decreases. The voltage applied across the output inductor 424 and coupling coil 426 to the output circuit inductor (e.g., from output terminal 416 to electrode 420) is V. arc+V (e.g., inverter voltage), where Varc is the arc voltage between electrode 420 and workpiece 418, and V is the voltage across the primary winding 404 of transformer 402. Secondary windings 406 and 408 also have... Figure 10 The voltage V shown in the diagram. In the absence of reverse power transfer operation mode, the voltage applied to the output circuit inductor is V. arc The control circuit 412 can control the rate of current reduction by modulating the pulse width of the primary inverter 422, thereby obtaining the average voltage V across the output inductor 424 and the coupling coil 426. arc +αV, where α is the duty cycle. A wider pulse (e.g., a higher α) results in a larger reverse voltage, which removes more energy from the secondary circuitry and reduces the output current more quickly.

[0067] Figure 11 Is it like this? Figure 10 During the reverse power transmission operation illustrated Figure 4 The voltage and current curves in the welding output topology. Figure 11 Chart illustrations Figure 10 The primary winding voltage 1102 and primary winding current 1104 of the primary winding 404 are shown in the figure. The figure also illustrates the primary winding current 1106 flowing through the secondary winding 408 and the secondary winding current 1108 flowing through the secondary winding 406.

[0068] Figure 12 yes Figure 4 The welding output circuit 400 is in Figure 10 The diagram illustrates the current output 1202 during reverse power transmission operation. Figure 12 The diagram also illustrates a current output 1204 using natural current decay, where reverse power transfer is not used, and as in a conventional half-bridge topology, allows the welding output current to decay before commutation. Compared to a current output 1204 using natural decay, the use of reverse power transfer allows for a more rapid current reduction and thus achieves additional heat input by providing a higher current output before commutation.

[0069] The use of the reverse power delivery mode offers significant advantages, including handling reactive power present in the welding output circuit 400, which must be removed from the welding output circuit 400 for commutation (e.g., reducing the current to 0A before increasing it in the opposite polarity). Energy is stored in the internal output inductor 424, the parasitic inductance of the welding cable, and / or other inductive elements. In conventional topologies, current reduction is typically performed by a clamping capacitor connected to the welding circuit. The energy received at the clamping capacitor is then handled by a separate circuit that returns the reactive power to the inverter input, dissipates the energy through a high-power resistor, and / or recycles the energy back to the welding circuit. In contrast, the disclosed example directs the reactive power toward a source of input power (e.g., the primary side of transformer 402, primary inverter 422, and / or other connected circuitry) for handling by the main welding power supply without requiring any additional circuitry.

[0070] Another advantage of the reverse power transfer function is the increase in the voltage applied to the output circuit inductor (e.g., V). arc +αV). The increased voltage causes the current ratio to only V. arc The rate of natural decay of the driving force decreases more rapidly. Increased voltage is particularly advantageous when operating circuits with high inductance. Furthermore, control circuitry 412 can control the rate of current decay by modulating the duty cycle α. Conventionally, current decay is either rapid (i.e., hard commutation by dumping energy into a high-voltage clamping circuit) or slow, natural decay. Waiting for the current to decay naturally reduces the available heat input to the welding output because more time is spent at a lower current than desired. By controlling the current slope, control circuitry 412 can improve arc stability and / or reduce noise while maintaining heat input.

[0071] Using the disclosed example circuit in reverse power delivery mode will achieve an output current that is closer to a square wave (e.g., more similar to...). Figure 2 The hard-commutated output current 202 is used to control and limit dI / dt.

[0072] Figure 13 yes Figure 4The circuit diagram of an example soldering output circuit 400 is provided, wherein the example soldering output circuit 400 includes example heat sink assemblies 1302 and 1304 for dissipating heat from switching elements 410a to 410d. Example switching elements 410a to 410d may be discrete semiconductor devices (e.g., TO-247 packages, TO-220 packages, etc.) and / or semiconductor devices with packages having non-isolated base plates. In these examples, the heat sink fins of switching elements 410a to 410d are connected to one of only two nodes. Therefore, example heat sink assemblies 1302 and 1304 can provide heat dissipation and cooling for the entire soldering output circuit 400 through only two independent non-isolated heat sinks.

[0073] Conventional topologies require at least three heatsink assemblies. In contrast, the example solder output circuit 400 does not isolate heatsink assemblies 1302, 1304 from switching elements 410a to 410d, thus reducing the number of heatsinks. This reduction in heatsinks reduces cost and / or improves the thermal performance of the solder output circuit 400 by removing at least one thermal resistance (relative to conventional topologies) from the switching elements 410a to 410d and removing at least one component that might fail under thermomechanical stress cycling. Furthermore, heatsink assemblies 1302, 1304 can serve as part of the current conduction path, thus simplifying the electrical routing of the circuit and / or board.

[0074] Compared to conventional topologies where current is concentrated through specific switching devices while other devices remain relatively idle, the disclosed example welded output circuit balances the current flowing through the path because the switching elements 410a to 410d either function as rectifiers or switches at any given time, and thus balance the heat dissipation between the switching elements 410a to 410d. Therefore, the heat dissipation by the heat sink assemblies 1302, 1304 is more uniformly distributed compared to conventional topologies, where some devices remain idle and corresponding areas of the heat sink are cold, while other devices and heat sink areas are hotter. Because heat sink assemblies 1302 and 1304 dissipate approximately the same amount of heat regardless of the output polarity, the two heat sink assemblies 1302, 1304 can be designed to be similar or identical.

[0075] Figure 14 This is a circuit diagram of an example soldering output circuit 1400, which uses a metal-oxide-semiconductor field-effect transistor (MOSFET). The example soldering output circuit 1400 is similar to... Figure 4The welding output circuit 400 includes a transformer 402 (e.g., primary winding 404 and secondary windings 406, 408), control circuitry 412, terminals 414, 416, a primary inverter 422, an output inductor 424, and a coupling coil 426. An example welding output circuit 1400 includes switching elements 1402a to 1402d (e.g., corresponding to switching elements 410a to 410d). Each of the example switching elements 1402a to 1402d includes a MOSFET transistor. Because the MOSFET transistor has an intrinsic diode connected in parallel with the transistor, the use of switching elements 1402a to 1402d containing the MOSFET transistor allows the intrinsic diode to be used for rectification (e.g., as a rectifier diode).

[0076] When the MOSFET channel is turned on, the MOSFET conducts current in either direction. Due to the low-voltage components, the channel resistance during conduction can be significantly lower than the voltage drop across the PN junction of a conventional fast diode rectifier. Example control circuit 412 can control the switching elements 1402a to 1402d selected for rectification using synchronous rectification to reduce power consumption in the switching elements 1402a to 1402d performing rectification. For example, for... Figure 6 and Figure 7 The illustrated EP output polarity, although the MOSFETs of switching elements 1402b and 1402d can be controlled to be off (e.g., blocked or not conducted) to allow the associated intrinsic diode to conduct, the control circuit 412 can synchronously turn on the MOSFETs of switching elements 1402b and 1402d (e.g., conduct) with the polarity of the voltage on the primary winding 404. When the voltage applied to the primary winding 404 is positive (e.g., ...), Figure 6 When the voltage applied to the primary winding 404 is negative (e.g., ...), the control circuit 412 can synchronously turn on the IGBT of the switching element 1402b and turn off the IGBT of the switching element 1402d. In contrast, when the voltage applied to the primary winding 404 is negative (e.g., ...), Figure 7 When switching element 1402d is turned on, control circuit 412 can synchronously turn off the IGBT of switching element 1402b. Therefore, using synchronous rectification with MOSFETs coupled to low-voltage MOSFETs further reduces power losses in the rectifier function. By using MOSFET transistors, the number of nodes, current paths, and / or high-current interconnects in the solder output circuit 1400 is reduced (relative to...). Figure 4 The soldering output circuit 400 simplifies component layout and / or reduces costs.

[0077] In some instances, the solder output circuit may include a combination of MOSFETs and IGBTs to implement switching elements.

[0078] Figure 15This is a circuit diagram of an example soldering output circuit 1500, which uses multiple transformers. When using discrete devices, it is advantageous to use two or more transformers 1502, 1504. Transformer 1502 has a primary winding 1506 and secondary windings 1508, 1510. Transformer 1504 has a primary winding 1512 and secondary windings 1514, 1516. The primary windings 1506 and 1512 are arranged in series, and the secondary windings 1508, 1510, 1514, and 1516 are connected in parallel.

[0079] The welding output circuit 1500 includes switching elements 1518a to 1518h for coupling secondary windings 1508, 1510, 1514, and 1516 to output terminals 1520 and 1522. Example switching elements 1518a to 1518h are implemented using MOSFETs. Control circuitry 1524 controls the switching elements 1518a to 1518h to conduct and / or block current. However, the PN junction in each of the switching elements 1518a to 1518h can conduct current when the switching element is controlled to be off or non-conducting. Example welding output circuit 1500 includes an output inductor 1526 and a coupling coil 1528.

[0080] Connecting the primary windings 1506 and 1512 of transformers 1502 and 1504 in series causes transformers 1502 and 1504 to each conduct substantially the same amount of current and / or dissipate substantially the same thermal load, thus improving reliability. Forced current sharing also results in the current flowing through the secondary-side commutator and rectifier switching elements 1518a to 1518h being shunt substantially equally. When the solder output circuit 1500 is constructed using discrete devices (e.g., TO-220 packages, TO-247 packages, etc.), the switching elements can share the load current equally across the resistance (e.g., due to parameter variations, unequal cooling, etc.).

[0081] In some instances, the turns ratio of transformers 1502 and 1504 may be lower than the turns ratio when using a single transformer (e.g., as in...). Figure 4 (In the middle) This is because the voltage has been divided between the primary windings 1506 and 1512. For example, instead of a 4:1 turns ratio for a single transformer, two transformers configured in series can use a 2:1 turns ratio. A lower turns ratio simplifies transformer design and / or improves parameters such as leakage inductance.

[0082] Although Figure 15 The illustration shows two transformers, 1502 and 1504, connected in series, but other examples may include multiple transformers to share current across more paths.

[0083] Figure 16This is a block diagram of an example implementation of control circuit 412, wherein control circuit 412 is configured to output a PWM signal to control Figure 4 and / or Figure 14 The switching elements 410a to 410d and / or 1402a to 1402d.

[0084] Figure 16 Example controller 412 can be used to control AC and DC welding outputs, for example, pulsed DC applications (EN and / or EP polarities). It rapidly reduces the current in the welding circuit (as described above). Figure 13 The ability to control the slope of the current (as discussed above) provides benefits even when DC welding and the polarity of the current does not need to be reversed. For example, example control circuit 412 can improve pulsed DC applications (EN or EP) by controlling the output current to more closely match an ideal square pulse train (e.g., a pulse train with zero current rise time and / or zero current fall time). As an additional or alternative, in GMAW, after the short-circuit condition has been cleared and the output current is high, control circuit 412 can then more quickly return to the lower current level required by the arc. In a conventional DC topology, the only driver for reducing current is the resistive losses in the welding power supply, welding circuit, and arc. As explained above, control circuit 412 can control switching elements 410a to 410d and / or 1402a to 1402d in the reverse mode described above to add an additional modulated voltage, thereby reducing the output current more quickly.

[0085] By selecting appropriate switching elements 410a to 410d and / or 1402a to 1402d, the control circuit 412 can operate in direct power mode or reverse power mode and effectively apply a positive or negative voltage source to the output. Conventional soldering processes regulate the output current to the desired commanded current. For example... Figure 16 As shown, the control circuit 412 receives a desired current command 1602 and a current feedback signal 1604. The control circuit 412 compares the current command 1602 with the current feedback signal 1604 to generate an error signal 1606. The current command 1602 and the current feedback signal 1604 contain corresponding signal polarities, and the error signal 1606 also contains polarity information.

[0086] Control circuit 412 includes a dynamic controller 1608 for determining, based on error signal 1606, both the amplitude 1610 and polarity 1612 of the voltage source to be applied to the welding output to obtain the commanded current. Example control circuit 412 may be implemented by an analog proportional-integral-derivative (PID) controller, but other analog and / or digital control schemes may also be used. The amplitude 1610 and polarity 1612 signals are then provided to pulse width modulator (PWM) circuit 1614 to generate gate selection commands 1616a to 1616d with appropriate pulse widths to control switching elements 410a to 410d and / or 1402a to 1402d. PWM circuit 1614 may further generate PWM signals 1616e, 1616f to control one or more switching elements of primary inverter 422. PWM circuit 1614 may be of voltage-mode control type or current-mode control type. Using a PWM signal allows the control circuit 418 to perform fully dynamic control over the sources applied to the output (e.g., amplitude and polarity), and thus produces improved instantaneous results.

[0087] The methods and systems of the present invention can be implemented in hardware, software, and / or a combination of hardware and software. The methods and / or systems of the present invention can be implemented in a centralized manner in at least one computing system, or in a distributed manner, wherein different elements are distributed across several interconnected computing systems. Any kind of computing system or other device suitable for performing the methods described herein is appropriate. A typical combination of hardware and software may comprise a general-purpose computing system having a program or other code that, when loaded and executed, controls the computing system to cause the computing system to perform the methods described herein. Another typical embodiment may comprise an application-specific integrated circuit or chip. Some embodiments may comprise a non-transitory machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, etc.) on which one or more lines of code are stored, said code being executable by a machine to cause the machine to perform the processes as described herein. As used herein, the term "non-transitory machine-readable medium" is defined to include all types of machine-readable storage media and does not contain propagating signals.

[0088] As used herein, the terms “circuit” and “circuit system” mean: physical electronic components, any analog and / or digital components, electrical components and / or control components, such as microprocessors or digital signal processors (DSPs), including discrete and / or integrated components or portions and / or combinations thereof (i.e., hardware); and configurable hardware, any software and / or firmware (“code”) executed by the hardware and / or otherwise associated with the hardware. As used herein, for example, a particular processor and memory may constitute a first “circuit” when executing a first line or more of code, and may constitute a second “circuit” when executing a second line or more of code. As used herein, “and / or” means any one or more items in a list joined by “and / or”. As an example, “x and / or y” means any element in the set of three elements {(x),(y),(x,y)}. In other words, “x and / or y” means “one or both of x and y”. As another example, “x, y, and / or z” means any element in the seven-element set {(x),(y),(z),(x,y),(x,z),(y,z),(x,y,z)}. In other words, “x, y, and / or z” means “one or more of x, y, and z”. As used herein, the term “exemplary” means serving as a non-limiting example, illustration, or description. As used herein, the term “for example” refers to a list of one or more non-limiting examples, illustrations, or descriptions. As used herein, a circuit is “operable” to perform a function as long as it includes the hardware and code necessary (if needed) to perform that function, regardless of whether the execution of the function is disabled or inactive (e.g., by user-configurable settings, factory tuning, etc.).

[0089] While the methods and / or systems of the present invention have been described with reference to certain embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted without departing from the scope of the methods and / or systems of the present invention. For example, the blocks and / or components of the disclosed examples can be combined, divided, rearranged, and / or otherwise modified. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this disclosure without departing from its scope. Therefore, the methods and / or systems of the present invention are not limited to the specific embodiments disclosed. In fact, the methods and / or systems of the present invention will encompass all embodiments falling within the scope of the appended claims, both literally and according to the principle of equivalents.

Claims

1. A welding-type power supply, comprising: A transformer having a primary winding, a first-stage winding, and a second-stage winding; An input circuit configured to provide an input voltage to the primary winding of the transformer; A first switching element is coupled between the primary winding and the first output terminal of the welded power supply. A second switching element is coupled between the second stage winding and the first output terminal of the welded power supply; A third switching element is coupled between the primary winding and the second output terminal of the welded power supply. A fourth switching element is coupled between the secondary winding and the second output terminal of the welded power supply. as well as Control circuit, the control circuit being configured to: By selectively controlling one of the first, second, third, and fourth switching elements based on the command output voltage polarity and the input voltage polarity to the transformer, the first, second, third, and fourth switching elements can be controlled to selectively output a positive or negative output voltage without requiring a separate rectifier stage. as well as Before changing from the first output voltage polarity to the second output voltage polarity, the first, second, third, and fourth switching elements are controlled to reverse the power flow so that the reactive power is returned to the input circuit via the transformer.

2. The welding-type power supply according to claim 1, wherein the control circuit is configured to control the first switching element, the second switching element, the third switching element, and the fourth switching element to configure the primary winding and the secondary winding of the transformer as a current-feeding push-pull converter.

3. The welding power supply according to claim 1, wherein the control circuit is configured to change the polarity of the command output voltage to a second polarity when the welding power supply outputs a first output voltage polarity, and to control the first switching element, the second switching element, the third switching element, and the fourth switching element based on the command output voltage polarity.

4. The welding-type power supply according to claim 1, wherein the control circuit is configured to reverse the power flow to return reactive power to the input circuit by means of the following steps when the welding-type power supply outputs a first output voltage polarity: Control the third and fourth switching elements to turn on; The first and second switching elements are controlled as rectifiers, synchronized with the polarity of the input voltage to the transformer.

5. The welding-type power supply according to claim 4, wherein the control circuit is configured to reverse the power flow to return reactive power to the input circuit by means of the following steps when the welding-type power supply outputs a second output voltage polarity: Control the first and second switching elements to turn on; The third and fourth switching elements are controlled as rectifiers, synchronized with the polarity of the input voltage to the transformer.

6. The welding-type power supply according to claim 1, further comprising controlling the rate of current reduction during reverse power flow by controlling a pulse width modulation signal used to control the input circuit.

7. The welding-type power supply according to claim 6, wherein the control circuit includes a switch-mode power supply.

8. The welding-type power supply according to claim 1, wherein the reactive power is transmitted from the output inductor to the input circuit.

9. The welding-type power supply according to claim 1, wherein the reverse power flow causes a current drop that is faster than the decay of the natural current.

10. The welding-type power supply according to claim 9, wherein the current drop is further driven by the arc voltage.

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