WELDING EQUIPMENT AND METHOD FOR OPERATING A WELDING EQUIPMENT

Description

[0001] The present invention relates to a method for operating a welding machine, wherein a DC voltage converter of the welding machine converts an input DC voltage applied to an input terminal into an output DC voltage applied to an output terminal, wherein at least one switching element of the DC voltage converter is switched at a switching frequency, wherein a welding phase is provided for the welding machine, during which the switching frequency corresponds to a normal switching frequency and during which an arc burns, which is ignited at the beginning of the welding phase.Furthermore, the present invention relates to a welding machine with a DC-DC converter and a welding power section, wherein the DC-DC converter is configured to convert an input DC voltage applied to an input terminal into an output DC voltage applied to an output terminal, which is present at the power section input of the welding power section of the welding machine, wherein the DC-DC converter comprises at least one switching element in a branch and a control unit, wherein the control unit is configured to switch the switching element at a switching frequency corresponding to a normal switching frequency during a welding phase of the welding machine, during which an arc is burning, which is ignited at the beginning of the welding phase, and wherein the welding power section is configured to regulate the output DC voltage applied to the power section input to a welding voltage applied to a power section output during the welding phase.

[0002] DC-DC converters transform an input DC voltage into an output DC voltage. In a boost converter, also called a step-up converter, the output DC voltage is higher than the input DC voltage, whereas in a buck converter, also called a step-down converter, the output DC voltage is lower than the input DC voltage. Boost converters are particularly common in welding technology.

[0003] In a welding machine, for example, a boost converter is used as a DC-DC converter, which converts an input DC voltage at one end into a higher output DC voltage at the other. During the welding process, energy is transferred from the input to the output during each welding phase, with each welding phase beginning with the ignition of an electric arc. The output of the DC-DC converter can be equipped with a parallel intermediate circuit capacitor, so that the output DC voltage is present across the intermediate circuit capacitor. To provide sufficient welding voltage during the welding process, a welding power stage is connected downstream of the output of the DC-DC converter, i.e., the intermediate circuit capacitor.The welding power unit regulates the output DC voltage to a suitable, preferably galvanically isolated, welding voltage and / or welding current, whereby the welding voltage / current can be output in pulses and / or continuously, depending on the desired welding process. Such a welding device is disclosed, for example, in EP 2850725 B1.

[0004] When a welding machine is in operation, the welding phases are interrupted by idle phases during which no welding takes place. During these idle phases, the DC-DC converter continues to transfer a small amount of energy to the welding power unit connected to the output, for example, to operate control electronics, regulation units, displays, etc., within the welding machine. Since no arc is burning during the idle phase, the amount of energy is lower. However, the DC-DC converter is active during both the welding and idle phases of the welding machine, and significant energy losses naturally occur within the DC-DC converter even during the idle phases.

[0005] It is therefore an object of the present invention to provide a DC voltage converter for a welding machine which enables a clean and controlled start of the welding phase.

[0006] This problem is solved according to the invention by a method according to claim 1. Furthermore, the problem is solved by a welding machine according to claim 7. During the welding phase, energy is transferred from the input of the DC-DC converter to the output of the DC-DC converter. The regulation to the welding voltage is, of course, only an example; naturally, the output DC voltage can be regulated such that a welding current is established, or that both a welding voltage and a welding current are established. In this context, this is referred to as constant voltage / constant current regulation.

[0007] Since the switching element of the DC-DC converter is not deactivated during the welding machine's idle phase, but merely its switching frequency is reduced to the idle switching frequency, the desired DC output voltage for the welding phase is maintained at the output terminal during this time. This DC output voltage is sufficient for operating the welding machine during the idle phase (for example, powering control electronics units, regulators, displays, etc.). In contrast to continuous operation of the switching element at the normal switching frequency (even during the idle phase), using the idle switching frequency significantly reduces energy losses during the idle phase.

[0008] Furthermore, the output DC voltage, which is present at the output terminal even during the idle phase, ensures that a controlled and clean start to the welding process is guaranteed right from the start of the welding phase.

[0009] Preferably, during the welding phase, the output DC voltage is regulated to a welding voltage by a welding power unit, whereby a load is supplied with the welding voltage.

[0010] Preferably, the branch comprises an inductor and a freewheeling diode, wherein a first coil terminal of the inductor is connected to the input terminal and a second coil terminal of the inductor is connected to a first switch terminal of the switching element and an anode of the freewheeling diode, wherein a second switch terminal of the switching element is connected to ground and a cathode of the freewheeling diode is connected to the output terminal.

[0011] This arrangement describes a boost converter, and the invention can also be applied to other embodiments of boost converters. It is also conceivable that the method according to the invention could be applied to another type of DC-DC converter (step-down converter, buck-boost, etc.).

[0012] Preferably, at least one further switching element of at least one further branch of the DC-DC converter is switched at at least one further switching frequency, wherein in the welding phase the at least one further switching frequency corresponds to another normal switching frequency. The method according to the invention can therefore also be applied to DC-DC converters with multiple switching elements.

[0013] The DC-DC converter can comprise at least one further branch with at least one further switching element, at least one further inductor, and at least one further freewheeling diode, wherein in the at least one further branch, a first coil terminal of the at least one further inductor is connected to the input voltage, and a second coil terminal of the at least one further inductor is connected to a first switch terminal of the at least one further switching element and to an anode of the at least one further freewheeling diode, wherein a second switch terminal of the at least one further switching element is connected to ground, and a cathode of the at least one freewheeling diode is connected to the output terminal, wherein the control unit is configuredduring the welding phase of the welding machine, at least one further switching element with at least one further switching frequency corresponding to another normal switching frequency is to be switched.

[0014] This describes a multi-branch boost converter, although of course other multi-branch boost converters, buck converters or generally DC voltage converters comprising a control unit according to the invention are also conceivable.

[0015] One additional normal switching frequency can correspond to the normal switching frequency. This allows for particularly simple control of the switching elements by the control unit during the welding phase. It is especially advantageous if the switching elements of the branches are switched with a phase shift. Thus, in a converter with n branches, the i-th branch (with 1 ≤ i ≤ n) is switched on with a time shift of (T * (i-1)) / n periods relative to the first branch, where T corresponds to the period. This method is known as "interleaved operating mode".

[0016] Preferably, during the idle phase, at least one further switching frequency is switched with a further idle switching frequency lower than the further normal switching frequency.

[0017] Accordingly, the control unit can be designed to switch at least one further switching element with a further idle switching frequency lower than the further normal switching frequency during the idle phase.

[0018] If the DC-DC converter has at least one additional switching element, a number of these switching elements, preferably all switching elements, can each be switched with an no-load switching frequency lower than the other normal switching frequency in order to further reduce the no-load power loss.

[0019] It can correspond to at least one further idle switching frequency of the idle switching frequency, which makes it possible to control the switching elements by the control unit particularly easily during the idle phase.

[0020] Preferably, at least one additional switching element is deactivated during the idle phase. Accordingly, the control unit can be designed to deactivate at least one additional switching element during the idle phase.

[0021] Thus, if multiple switching elements are present, several switching elements, preferably all but one, can be deactivated to achieve a maximum reduction in no-load power loss during the idle phase. At least one switching element is operated at the no-load switching frequency during this time to prevent a drop in the output DC voltage during the idle phase and to enable a rapid start to the welding process right from the beginning of the welding phase. Reductions in no-load power loss from 43 W to 2 W were measured when the DC-DC converter has three branches, each with one switching element, wherein, during the no-load phase of the welding machine, a first switching element of the first branch is operated at an no-load switching frequency of 2 kHz, and the remaining switching elements of the second and third branches are deactivated. According to the invention, a switching element, preferably via an interface, e.g.,A control signal transmitted via an RS-485 bus switches the DC-DC converter from the welding phase to the idle phase and / or from the idle phase to the welding phase. The control signal can be triggered by actuating a switch / button, for example, located on the welding torch, to initiate or end the welding process, but this is not part of the protection request. The control signal can also be triggered in other ways to indicate the start or stop of the welding phase.

[0022] According to the invention, a parameter defined in the welding machine causes a switch from the welding phase to the idle phase and / or from the idle phase to the welding phase. The control signal is triggered by this parameter.

[0023] The parameters used are a reduced or increased welding voltage and a specific current flow on the output side, e.g., a reduced or increased current. This allows the need to switch to or from the idle phase to be detected. Event-driven switching to or from the idle phase is also possible, where an event could be, for example, a short circuit during the welding process.

[0024] The parameter can, for example, be detected and / or processed by a controller or control system of the welding machine.

[0025] The present invention is described below with reference to the Figuren 1 bis 7 In more detail, the invention is explained, and exemplary, schematic, and non-restrictive embodiments are shown. This includes showing Fig.1 a DC / DC converter, Fig.2 a welding machine with a DC / DC converter and a welding power unit, Fig.3 a single-branch boost converter as a DC voltage converter, Fig.4 a multi-branch boost converter as a DC voltage converter, Fig.5 a welding machine with a rectifier, a multi-phase boost converter and a welding power section, Fig.6 a progression of the switching states of the switching elements, Fig.7 a curve of the output DC voltage.

[0026] Fig. 1 Figure 2 represents a schematic DC-DC converter. A DC-DC converter converts an input DC voltage Ue into an output DC voltage Ua, where the input DC voltage Ue is applied to an input terminal Ue+ and the output DC voltage Ua is applied to an output terminal Ua+. More precisely, the input DC voltage Ue is connected between the input terminal Ue+ and a ground U-, and the output DC voltage Ue is connected between the output terminal Ue- and a ground U-an. Typically, a common ground U- is used in the DC-DC converter 2; however, it is also possible, for example, by using a suitable circuit topology for the input and output sides, to use different grounds U-, which can be achieved through galvanic isolation, for example, via a transformer.

[0027] A DC / DC converter 2 can be used in a welding machine 1, as described in Fig. 2 The diagram is schematically illustrated. A DC output voltage Ua is generated by the DC-DC converter 2 at the output terminal Ua+. The welding machine 1 also includes a welding power unit 5 with a power input and a power output. During a welding phase X, the welding power unit regulates the DC output voltage Ua applied to the power input to a welding voltage Ua' applied to the power output. The welding voltage Ua' can be continuous or pulsed. During the idle phase L, the DC output voltage Ua is applied to the power input of the welding power unit 5. Regulation to the welding voltage Ua' is shown here only as an example. Regulation can also be applied to a welding current or alternately to a welding current and the welding voltage. The regulation is accordingly adapted to the welding process.

[0028] During the welding phase X, the DC-DC converter 2 is operated by a control unit 3, which can be analog or digital, at a switching frequency f1 corresponding to a normal switching frequency f1x. This means that a switching element S1 of the DC-DC converter 2 is switched at a switching frequency f1. According to the invention, the switching frequency f1 is divided into a normal switching frequency f1x – which corresponds to the switching frequency f1 – and an idle switching frequency f1L, depending on the phase, and switched accordingly.

[0029] After welding phase X, the welding machine 1 is switched to an idle phase L. According to the prior art, the DC-DC converter 2 continues to operate at its normal switching frequency f1x during this idle phase L, with corresponding losses. In contrast, according to the invention, the DC-DC converter 2 operates at an idle switching frequency f1L lower than the normal switching frequency f1x during the idle phase L of the welding machine 1. This minimizes losses and prevents the output DC voltage Ua from dropping during the idle phase L. Consequently, the welding process can begin immediately after the end of the idle phase L and the start of welding phase X.

[0030] During welding phase X, a load Z (in Fig. 2 (shown with a dashed line) - during a welding process, an electric arc is connected to the output terminal Ua+ or to the power output of the welding power unit 5, thus transferring energy from the input side to the output side. During welding phase X, an electric arc burns, which is ignited at least at the beginning of welding phase X. In the idle phase L, the load is not connected to the output terminal Ua+ or to the welding power unit 5, so no energy is delivered on the output side and no arc burns.

[0031] During the idle phase L according to the invention, switching losses are lower than during the welding phase X, since the switching element S1 switches less frequently due to the lower idle switching frequency f1L. The DC-DC converter 2 continues to provide the welding machine 1 with a sufficiently high output DC voltage Ua to power the control electronics units, control units, displays, etc., located in the welding machine 1.

[0032] In Fig. 3 Figure 2 shows a simple single-branch boost converter, also known as DC-DC converter 2. The boost converter comprises a single branch A with an inductor L1, a freewheeling diode D1, and a switching element S1. The inductor L1 and the freewheeling diode D1 are connected in series. One coil terminal of the inductor L1 is connected to the input terminal Ue+, and a second coil terminal of the inductor L1 is connected in series with an anode of the freewheeling diode D1. A cathode of the freewheeling diode D1 is connected to the output terminal Ua+. The DC-DC converter 2 is further connected at its output terminal Ua+ to the first capacitor terminal of an intermediate circuit capacitor Ca, and the second capacitor terminal of the intermediate circuit capacitor Ca is connected to ground U-. The output DC voltage Ua is thus applied across the intermediate circuit capacitor Ca.

[0033] The second coil terminal of inductor L1 (and thus also the anode of freewheeling diode D1) is connected to ground U- via the switching element S1 (e.g., a MOSFET, GTO thyristor, bipolar transistor, etc.). The switching element S1 is opened and closed at a switching frequency f1, for which a control unit 3 is provided. Typical switching frequencies f1 are 20 kHz to 150 kHz, although higher switching frequencies f1 are conceivable, particularly with the use of advanced semiconductor technologies. The duty cycle of the switching element S1 is, for example, 0 to 95%.

[0034] With the switching element S1 closed, the anode of the freewheeling diode D1 is connected to ground U- and with the switching element S1 open, it is separated from ground U-.

[0035] When the switching element S1 is closed (conducting phase), the second coil terminal of inductor L1 is connected to ground U-, thus applying the input voltage Ue to inductor L1. This causes a coil current iL to flow through inductor L, which increases from the moment switching element S1 closes. Energy is (temporarily) stored in inductor L by this coil current iL. Since the anode of the freewheeling diode D1 is also connected to ground U- by the closed switching element S1, the freewheeling diode D1 is reverse-biased.

[0036] When the switching element S1 is opened (blocking phase), the coil current iL is maintained by the inductor L1. This increases the potential at the second terminal of the inductor L1 and consequently also at the anode of the freewheeling diode D1. As soon as the potential at the anode of the freewheeling diode D1 exceeds the voltage at the cathode of the freewheeling diode D1 by more than the threshold voltage of the freewheeling diode D1, the freewheeling diode D1 switches on. The coil current iL flows through the freewheeling diode D1 and the DC link capacitor Ca to ground U-, thus charging the DC link capacitor Ca. Meanwhile, at least some of the energy stored in the magnetic field of the inductor L1 and the energy supplied via the input DC voltage Ue are transferred to the DC link capacitor Ca. The DC link capacitor Ca is therefore charged while the current in the inductor L1 decreases, with the output DC voltage Ua being present across the DC link capacitor Ca.

[0037] If the switching element S1 is closed again after a blocking phase (conducting phase), the output DC voltage Ua applied to the intermediate circuit capacitor Ca is initially held at its value by the intermediate circuit capacitor Ca. During the conducting phase, there is no direct energy flow from the input side to the output side; however, the inductor L is recharged.

[0038] During the welding phase X, the switching element S1 is switched by a control unit 3 with a switching frequency f1 corresponding to a normal switching frequency f1x. This normal switching frequency f1x and the associated duty cycle are to be designed in such a way as to prevent a drop in the output DC voltage Ua during the conduction phases of the switching element S1.

[0039] According to the invention, during the idle phase L, the switching element is switched at a switching frequency f1 corresponding to an idle switching frequency f1L, which is lower than the normal switching frequency f1x. Preferably, the control unit 3 performs this switching. This significantly reduces losses and prevents the output DC voltage Ua from dropping to a lower value during the idle phase L, ensuring that the welding process can begin immediately after the end of the idle phase L and the start of the welding phase X. Naturally, the idle switching frequency f1L and the associated duty cycle must also be designed accordingly to prevent a drop in the output DC voltage Ua during the conduction phases of the switching element S1, even during the idle phase L.

[0040] Fig. 4 Figure 2 shows a multi-branch boost converter as a DC-DC converter. The design is identical to the one in Figure 2. Fig.3 The DC-DC converter 2 shown is identical, except that it has not just one branch A, but at least one additional branch B, C. Thus, a total of multiple parallel branches A, B, C are provided; in this case, three branches A, B, C – meaning two additional branches B, C. Each branch A, B, C comprises an inductor L1, L2, L3, a switching element S1, S2, S3, and a freewheeling diode D1, D2, D3, which are connected in the respective branch A, B, C analogously to the single-branch DC-DC converter 2 described above. The first coil terminals of the inductors L1, L2, L3 are connected to the input terminal Ue, and the cathodes of the freewheeling diodes D1 are connected to the first capacitor terminal of the intermediate circuit capacitor Ca and thus to the output terminal Ua. It is also possible to provide a separate intermediate circuit capacitor Ca for each branch A, B, C (not shown), with these intermediate circuit capacitors Ca being connected in parallel to each other.

[0041] The second terminals of the switching elements S1, S2, S3 are each connected to ground U- and are controlled by the control unit 3 with a switching frequency f1, f2, f3, i.e. closed and opened.

[0042] A control unit 3 is provided for controlling the switching frequencies f1, f2, f3. By implementing the unit in multiple branches A, B, C, a higher output power can be generated than if a single branch A, B, C (with the same dimensions) were active. However, a higher no-load power loss also occurs during the idle phase L due to the switching losses of the higher number of switching elements S1, S2, S3 and inductors L1, L2, L3.

[0043] In the welding phase X, the further switching elements S2, S3 are each switched with a further switching frequency f2, f3 corresponding to a normal switching frequency f2x, f3x, whereby the normal switching frequencies f2x, f3x can correspond to the normal switching frequency f1x.

[0044] According to the invention, during the idle phase L, the further switching elements S2, S3 are each switched at a further switching frequency f2, f3 corresponding to a further idle switching frequency f2L, f3L, which is lower than the further normal switching frequency f2x, f3x. The further idle switching frequencies f2L, f3L can correspond to the idle switching frequency f1L. During the idle phase L, one or more of the further switching elements S2, S3 can also be deactivated. However, at least one switching element S1 switches at the idle switching frequency f1L during this time.

[0045] The additional switching elements S2, S3 can also be switched with a further idle switching frequency f2L, f3L as a further switching frequency f2, f3, whereby the further idle switching frequencies f2L, f3L are each smaller than the normal switching frequency f2x, f3x, which also results in lower switching losses for the additional switching elements S2, S3, since they switch less frequently than during the welding phase X.

[0046] Preferably, during the idle phase L, all switching elements S1, S2, S3 are switched with idle switching frequencies f1L, f2L, f3L smaller than the respective normal switching frequency f1x, f2x, f3x, wherein the idle switching frequencies f1L, f2L, f3L are preferably identical.

[0047] However, it is particularly advantageous if a switching element S1 of branch A is switched during the idle phase L at the idle switching frequency f1L, which is lower than the normal switching frequency f1x, and the other switching elements S2, S3 of the other branches B, C are deactivated (lock-out phase), which means that the other switching elements S2, S3 are permanently open. This allows for a particularly low idle power loss.

[0048] Fig. 5 Figure 1 schematically represents a welding machine 1, which, as an example, includes a multi-branch boost converter as a DC-DC converter 2. Of course, welding machines 1 with single-branch boost converters, single-branch buck converters, or multi-branch buck converters are also conceivable. The number of branches A, B, C is only three as an example; any number of branches A, B, C is possible. In principle, other topologies can also be used for the DC-DC converter 2.

[0049] Welding machine 1 further includes a rectifier stage 4 on the input side. Rectifier stage 4 is connected to the three mains phases P1, P2, P3 of an AC mains supply and comprises one lower rectifier diode Du1, Du2, Du3 and one upper rectifier diode Do1, Do2, Do3 for each mains phase P1, P2, P3. Of course, the rectifier diodes Du1, Du2, Du3, Do1, Do2, Do3 can also be formed by switching elements. The anodes of the lower rectifier diodes Du1, Du2, Du3 are each connected to ground U-, and the cathodes of the lower rectifier diodes Do1, Do2, Do3 are connected to the respective mains phases P1, P2, P3. The anodes of the upper rectifier diodes Do1, Do2, Do3 are also connected to the respective mains phase P1, P2, P3, the cathodes of the upper rectifier diodes Do1, Do2, Do3 are connected to the input terminal Ue+ of the DC voltage converter 2.Furthermore, rectifier stage 4 includes a smoothing capacitor Ce, which connects the cathodes of the upper rectifier diodes Do1, Do2, Do3 to the anodes of the lower rectifier diodes Du1, Du2, Du3. The basic operating principle of rectifier stage 4 is well understood, so it will not be discussed in detail here.

[0050] Rectifier stage 4 is considered optional. A welding machine 1 can also be used which does not include rectifier stage 4 and is operated, for example, in interleaved mode.

[0051] The DC-DC converter 2 of the welding machine 1 is, as can be seen from the Fig. 3 und 4 As described, it is operated. A control unit 3 is provided for controlling the switching frequencies f1, f2, f3. In the welding phase X, the switching frequencies f1, f2, f3 correspond to the normal switching frequency f1x, f2x, f3x, for example 35 kHz. In the welding phase X of the welding machine 1, a load Z (in Fig. 5 (shown with dashed lines) is connected to the output side of the DC-DC converter 2 via the welding power section 5. During the no-load phase L, no energy is supplied to the load Z on the output side.

[0052] During the no-load phase L of welding machine 1, at least one switching element S1 is switched with an no-load switching frequency f1L as the switching frequency f1, where the no-load switching frequency f1L is lower than the normal switching frequency f1x. The output DC voltage Ua across the intermediate circuit capacitor Ca is thus maintained during the no-load phase L.

[0053] According to the invention, a control signal S, preferably transmitted via an interface and triggered by a parameter P defined in the welding machine 1, causes the DC-DC converter 2 to switch from the welding phase X to the open-circuit phase L and / or from the open-circuit phase L to the welding phase X. This can be achieved by supplying the control unit 3 with the control signal S and / or the parameter P, as shown in Fig. 5 hinted at.

[0054] Fig. 6 Figure 1 illustrates the switching patterns of the switching elements S1, S2, and S3 of a three-branch DC-DC converter 2. The switching elements S1, S2, and S3 are controlled with a phase shift during the welding phase X. As can be seen, during the no-load phase L, switching element S1 is switched with an no-load switching frequency f1L that is lower than the normal switching frequency f1x. Advantageously, the other switching elements S2 and S3 are deactivated during the no-load phase L (as shown).

[0055] According to the state of the art, during the idle phase L all switching elements S1, S2, S3 would continue to be operated at their respective normal switching frequencies f1x, f2x, f3x, resulting in energy losses.

[0056] To prevent energy losses during the no-load phase L, the DC-DC converter 2 can also be deactivated, i.e., switched off, during the welding machine's no-load phase. This is achieved by no longer energizing the switching elements S1, S2, and S3, leaving them open. However, this causes the output DC voltage Ua to drop because the intermediate circuit capacitor Ca on the output side discharges during the no-load phase L and is no longer supplied with energy from the input side. Consequently, it is possible that the welding machine 1 will not receive enough voltage to operate the control electronics units, regulation units, displays, etc., which then need to be powered by an alternative source.

[0057] Furthermore, if DC-DC converter 2 is deactivated during the idle phase L of welding machine 1, the problem can arise that for a subsequent welding phase of the welding machine, DC-DC converter 2 must first return to a suitable operating state in order to provide the required energy or output DC voltage Ua on the output side. It can take some time until this suitable operating state is reached, resulting in a delay tv of, for example, 50 ms, before welding machine 1 is ready for another welding operation. Therefore, if switching elements S1, S2, S3, and thus DC-DC converter 2, are deactivated during the idle phase L of welding machine 1, a new, immediate start of the actual welding process, i.e., ignition of the arc, cannot be controlled or prevented.does not occur at the intended time, so that the stable welding phase begins late or the arc does not ignite or ignites with difficulty.

[0058] (The welding phase begins with the ignition of the arc). It is in Fig. 7 The output DC voltage Ua is shown as a dashed line in the case of deactivation of all branches during the no-load phase L. As can be seen, the output DC voltage Ua drops to the input DC voltage Ue during the no-load phase L of a boost converter. After switching back to the welding phase X, there is a certain delay time tv, here 50 ms, until the output DC voltage Ua reaches its full value again, meaning that the welding process can only start with a time delay.

[0059] In contrast, in Fig. 7The output DC voltage Ua for switching one or more switching elements S1, S2, S3 according to the invention during the no-load phase L is shown as a solid line. Since at least one switching element S1, S2, S3 continues to switch with an no-load switching frequency f1L, f2L, f3L, the output DC voltage Ua remains constant even during the no-load phase L. Therefore, after the end of the no-load phase L and the beginning of the welding phase X, the welding process can begin immediately, as the DC-DC converter 2 continuously supplies the required output DC voltage Ua. The DC-DC converter 2 thus provides the welding power unit 5 with the output DC voltage Ua required for an optimal start to the welding phase X.Delays between the planned start of the welding process and the actual switching of the DC-DC converter 2 to welding phase X are prevented by the already sufficiently high output DC voltage Ua at the DC voltage output Ua+. The welding process therefore starts immediately after the idle phase L at the beginning of welding phase X. The losses of the DC-DC converter 2 are minimal.

Claims

1. Method for operating a welding device (1), wherein a DC-to-DC converter (2) of the welding device (1) converts an input DC voltage (Ue) present at an input connection (Ue+) into an output DC voltage (Ua) present at an output connection (Ua+), which output DC voltage (Ua) is present at a power unit input of a welding power unit (5) of the welding device (1), wherein at least one switch element (S1) of a branch (A) of the DC-to-DC converter (2) is switched with a switching frequency (f1), wherein a welding phase (X) is provided for the welding device (1), during which the switching frequency (f1) corresponds to a normal switching frequency (f1x) and during which an arc burns, which is ignited at the beginning of the welding phase (X), and wherein the welding power unit (5) controls the output DC voltage (Ua) present at the power unit input to a welding voltage (Ua') present at a power unit output in the welding phase (X), characterized in that a stand-by phase (L), in which no arc burns and no welding is carried out, is provided for the welding device (1), during which the at least one switch element (S1) is switched with a switching frequency (f1) corresponding to a stand-by switching frequency (f1L) lower than the normal switching frequency (f1x), wherein a transmitted control signal (S), which is preferably transmitted via an interface, and which is triggered by a parameter (P) determined in the welding device (1), wherein a reduced or increased welding voltage and a reduced / increased current flow on the output side can be used as the parameter (P), effects a switchover from the welding phase (X) into the stand-by phase (L) and / or from the stand-by phase (L) into the welding phase (X), and in that the output DC voltage (Ua) is maintained during the stand-by phase (L) in order to provide the welding power unit (5) with the output DC voltage (Ua) required for an optimal start of the welding phase (X).

2. Method according to claim 1, characterized in that at least one further switch element (S2, S3) of at least one further branch (B, C) of the DC-to-DC converter is switched with at least one further switching frequency (f2, f3), wherein in the welding phase (X) the at least one further switching frequency (f2, f3) corresponds to a further normal switching frequency (f2x, f3x), in order to transmit energy from the input connection (Ue+) to the output connection (Ua+).

3. Method according to claim 2, characterized in that the at least one further normal switching frequency (f2x, f3x) corresponds to the normal switching frequency (f1x).

4. Method according to any one of claims 1 to 3, characterized in that, in the stand-by phase (L), the at least one further switching frequency (f2, f3) is switched with a further stand-by switching frequency (f2L, f3L) lower than the further normal switching frequency (f2x, f3x).

5. Method according to claim 4, characterized in that the at least one further stand-by switching frequency (f2L, f3L) corresponds to the stand-by switching frequency (f1L).

6. Method according to any of claims 1 to 3, characterized in that, in the stand-by phase (L), the at least one switch element (S1) and / or at least one of the further switch elements (S2, S3) is deactivated.

7. Welding device (1) comprising a DC-to-DC converter (2) and a welding power unit (5), wherein the DC-to-DC converter (2) is designed to convert an input DC voltage (Ue) present at an input connection (Ue) into an output DC voltage (Ua) present at an output connection (Ua), which output DC voltage is applied to a power unit input of the welding power unit (5) of the welding device (1), wherein the DC-to-DC converter (2) comprises at least one switch element (S1) in a branch (A) and a control unit (3), the control unit (3) being designed to switch the switch element (S1) in a welding phase (X) of the welding device (1), during which an arc burns, which is ignited at the beginning of the welding phase (X), with a switching frequency (f1) corresponding to a normal switching frequency (f1x), and wherein the welding power unit (5) is designed to control the output DC voltage (Ua) present at the power unit input to a welding voltage (Ua') present at a power unit output in the welding phase (X), characterized in that the control unit (3) is designed, in a stand-by phase (L) of the welding device (1) in which phase no arc burns and no welding is carried out, to switch the at least one switch element (S1) with a switching frequency (f1) corresponding to a stand-by switching frequency (f1L) lower than the normal switching frequency (f1x), wherein a transmitted control signal (S), which is preferably transmitted via an interface, and which is triggered by a parameter (P) determined in the welding device (1), wherein a reduced or increased welding voltage and a reduced / increased current flow on the output side can be used as the parameter (P), is provided to effect a switchover from the welding phase (X) into the stand-by phase (L) and / or from the stand-by phase (L) into the welding phase (X), and in that the control unit (3) is designed to maintain the output DC voltage (Ua) during the stand-by phase (L) in order to provide the welding power unit (5) with the output DC voltage (Ua) required for an optimal start of the welding phase (X).

8. DC-to-DC converter (1) according to claim 7, characterized in that the branch (A) comprises an inductor (L1) and a freewheeling diode (D1), wherein a first coil terminal of the inductor (L1) is connected to the input connection (Ue+) and a second coil terminal of the inductor (L) is connected to a first switch terminal of the switch element (S1) and to an anode of the freewheeling diode (D1), wherein a second switch terminal of the switch element (S1) is connected to ground (U-) and a cathode of the freewheeling diode (D1) is connected to the output connection (Ua+).

9. Welding device (1) according to claim 8, characterized in that the DC-to-DC converter (2) comprises at least one further branch (B, C) having at least one further switch element (S2, S3), at least one further inductor (L) and at least one further freewheeling diode (D), wherein, in the at least one further branch (B, C), a first coil terminal of the at least one further inductor (L) is in each case connected to the input voltage (Ue), and a second coil terminal of the at least one further inductor (L) is in each case connected to a first switch terminal of the at least one further switch element (S2, S3) and in each case to an anode of the at least one further freewheeling diode (D2), wherein a second switch terminal of the at least one further switch element (S2, S3) is in each case connected to ground (U-), and a cathode of the at least one freewheeling diode (D) is in each case connected to the output connection (Ua+), and in that the control unit (3) is designed to switch the at least one further switch element (S2, S3) with at least one further switching frequency (f2, f3) corresponding to a further normal switching frequency (f2x, f3x) during the welding phase (X) of the welding device (1).

10. Welding device (1) according to claim 9, characterized in that the control unit (3) is designed to switch the at least one further switch element (S2, S3) with a further stand-by switching frequency (f2L, f3L) lower than the further normal switching frequency (f2x, f3x), preferably corresponding to the stand-by switching frequency (f1L), in the stand-by phase (L) of the welding device (1).

11. Welding device (1) according to any of claims 7 to 10, characterized in that the control unit (3) is designed to deactivate the at least one switching element (S1) and / or at least one of the further switching elements (S2, S3) in the stand-by phase (L) of the welding device (1).