Converter Circuit

Abstract

The disclosure relates to a power component for providing an electric current, having plates aligned parallel to one another which are connected to the current inputs and the current outputs of power semiconductors embedded in a component carrier. High currents, for example for resistance welding, can thereby be controlled without excessive heat losses resulting in an increase in temperature of the entire arrangement and thereby in a reduction of the service life.

Claims

1. A converter circuit arrangement for electric current for resistance welding, the converter circuit arrangement comprising: a component carrier, the component carrier being arranged between an electrically conductive first current conducting plate and an electrically conductive second current conducting plate, the component carrier being substantially parallel to both the first current conducting plate and the second current conducting plate; and a converter circuit having a first controllable switching device and a second controllable switching device interconnected with one another, the first controllable switching device and the second controllable switching device each having a separate control connection and each being at least partially embedded in the component carrier, the first controllable switching device and the second controllable switching device being connected to the first current conducting plate and the second current conducting plate such that that an output of the converter circuit is realized by one of the first current conducting plate and the second current conducting plate and an input of the converter circuit is realized by the other of the first current conducting plate and the second current conducting plate.

2. The converter circuit arrangement according to claim 1, the component carrier comprising: a plurality of conducting planes, the input of the converter circuit being connected to a first conducting plane of the plurality of conducting planes and the output of the converter circuit being connected to a second conducting plane of the plurality of conducting planes, the second conducting plane being separate from the first conducting plane, wherein the control connections of the first controllable switching device and the second controllable switching device are connected to at least one third conducting plane of the plurality of conducting planes that is arranged between the first conducting plane and the second conducting plane such that the control connections of the first controllable switching device and the second controllable switching device are separately actuable via the at least one third conducting plane.

3. The converter circuit arrangement according to claim 1, further comprising: control lines arranged substantially similarly to one another and configured to actuate the control connections of the first controllable switching device and the second controllable switching device on the component carrier.

4. The converter circuit arrangement according to claim 1, further comprising: mechanical contacts configured to serve as an input-side connection to a transformer winding and as an output-side connection to a load.

5. The converter circuit arrangement according to claim 4, wherein the converter circuit is realized as a center point circuit, the converter circuit arrangement further comprising: additional mechanical contacts configured to connect an output side of the load to a center tap of the transformer winding.

6. The converter circuit arrangement according to claim 3, further comprising: an actuating device configured to actuate the control connections of the first controllable switching device and the second controllable switching device, the actuating device being at least partially embedded in the component carrier, the actuating device being connected to the control lines via conductor paths.

7. The converter circuit arrangement according to claim 1, further comprising: load current measuring circuits configured to measure current of each of the first controllable switching device and the second controllable switching device, the load current measuring circuits being at least partially embedded in the component carrier.

8. The converter circuit arrangement according to claim 7, wherein: at least one of the first current conducting and the second current conducting plate is constructed in a plurality of parts; the first controllable switching device is electrically mounted on a first part of the plurality of parts of the at least one of the first current conducting and the second current conducting plate; and the second controllable switching device is electrically mounted on a second part of the plurality of parts of the at least one of the first current conducting and the second current conducting plate.

9. A transformer for resistance welding comprising: a converter circuit arrangement having (i) a component carrier, the component carrier being arranged between an electrically conductive first current conducting plate and an electrically conductive second current conducting plate, the component carrier being substantially parallel to both the first current conducting plate and the second current conducting plate, and (ii) a converter circuit having a first controllable switching device and a second controllable switching device interconnected with one another, the first controllable switching device and the second controllable switching device each having a separate control connection and each being at least partially embedded in the component carrier, the first controllable switching device and the second controllable switching device being connected to the first current conducting plate and the second current conducting plate such that that an output of the converter circuit is realized by one of the first current conducting plate and the second current conducting plate and an input of the converter circuit is realized by the other of the first current conducting plate and the second current conducting plate; and a transformer having a primary winding and a secondary winding, the secondary winding being connected to the input of the converter circuit of the converter circuit arrangement, wherein the converter circuit is arranged on the transformer.

10. A resistance welding device having: a full bridge circuit attached to a DC link direct voltage; a converter circuit arrangement having (i) a component carrier, the component carrier being arranged between an electrically conductive first current conducting plate and an electrically conductive second current conducting plate, the component carrier being substantially parallel to both the first current conducting plate and the second current conducting plate, and (ii) a converter circuit having a first controllable switching device and a second controllable switching device interconnected with one another, the first controllable switching device and the second controllable switching device each having a separate control connection and each being at least partially embedded in the component carrier, the first controllable switching device and the second controllable switching device being connected to the first current conducting plate and the second current conducting plate such that that an output of the converter circuit is realized by one of the first current conducting plate and the second current conducting plate and an input of the converter circuit is realized by the other of the first current conducting plate and the second current conducting plate; and a transformer having a primary winding connected an output of the full bridge and a secondary winding connected to the input of the converter circuit of the converter circuit arrangement, wherein the converter circuit is arranged on the transformer and the output of the converter circuit is attached to welding electrodes which are held by a pair of welding tongs.

11. The converter circuit arrangement according to claim 1, wherein the first controllable switching device and the second controllable switching device are each completely embedded in the component carrier.

12. The converter circuit arrangement according to claim 3, wherein the control lines are arranged symmetrically to one another.

13. The converter circuit arrangement according to claim 6, wherein the actuating device is completely embedded in the component carrier.

14. The converter circuit arrangement according to claim 7, wherein the load current measuring circuits are completely embedded in the component carrier.

15. The converter circuit arrangement according to claim 8, wherein the at least one of the first current conducting and the second current conducting plate that is constructed in the plurality of parts an input-side current conducting plate.

16. The converter circuit arrangement according to claim 8, wherein the at least one of the first current conducting and the second current conducting plate is constructed in two parts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Exemplary embodiments of the disclosure are presented in the drawings an are explained in more detail in the description below.

[0030] In the drawings:

[0031] FIG. 1 shows, in broadly schematic form, a center point circuit as a preferred embodiment;

[0032] FIG. 2 shows, in broadly schematic form, a first preferred construction;

[0033] FIG. 3 shows, in broadly schematic form, a half bridge as a preferred circuit.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a center point circuit. A full bridge is illustrated on the left in the drawing. This comprises a first and a second bridge arm. A DC (link) voltage L(+) and L() is applied in parallel to both bridge arms. Each of the bridge arms comprises two switches QA, QB and QC, QD, for example in the form of IGBTs. The switch pair QA, QB is associated with the first bridge arm and the switch pair QC, QD is associated with the second bridge arm. The primary winding 18a of a welding transformer 18 is arranged in the bridge branch.

[0035] The converter according to the disclosure is shown on the right in the drawing. This converter is arranged on two secondary windings 18b of the welding transformer 18. Both secondary windings 18b are connected in series and form a center tap 17 at the contact point of the series connection. A first secondary branch and a second secondary branch are thereby produced. A first welding electrode 13 of a pair of electrical resistance welding tongs is connected to the center tap 17, which resistance welding tongs can have both a positive and a negative potential during the welding procedure. A second welding electrode 13 is connected to the power semiconductors 11 (Q1) and 12 (Q2). The first power semiconductor 11 is arranged in the first secondary branch and the second power semiconductor 12 is arranged in the second secondary branch. A current measuring device 14, 15 for the branch currents IQ1, IQ2 is provided in each of the branches. The components of the circuit arrangement shown in FIG. 1, in particular Q1 and Q2 and preferably also the current measuring devices 14, 15, and the connecting lines between the components are at least partially, and preferably completely, embedded in a component carrier (not shown, see FIG. 2, reference sign 21).

[0036] The secondary-side power semiconductors 11, 12 serve to apply a welding current to a workpiece by means of the welding electrodes 13. The power semiconductors 11, 12 are preferably equipped with freewheeling diodes as overvoltage protection (not shown). The freewheeling diodes can also be integrated in the power semiconductors 11, 12.

[0037] A magnetic field sensor (not shown) is preferably arranged on the welding transformer 18. The signals of the magnetic field sensor are preferably evaluated by the actuating device (not shown, see FIG. 2, reference sign 26), so that the power semiconductors 11, 12 can also be switched using the evaluation result of the sensor signal. The system performance can be influenced by the magnetic field sensor.

[0038] The power semiconductors 11, 12 are preferably arranged symmetrically on the component carrier. This symmetrical design enables a uniform current distribution, which has an advantageous effect on the system performance.

[0039] FIG. 2 shows a first preferred embodiment for the structural implementation of the converter in a sandwich construction. A plurality of power semiconductors 25 are shown, which are embedded in a printed circuit board 21 and which, as shown in FIG. 1 (see reference signs 11 and 12), are interconnected with one another. The power semiconductors 11 and 12 shown in FIG. 1 are realized in the example here by two power semiconductor groups 11 and 12 in each case, with each power semiconductor group 11, 12 comprising a plurality of individual power semiconductors which are operated in parallel with one another and of which there can theoretically be any number, which depends on the current to be provided. The number of power semiconductors 25 used which is illustrated here in the drawing should therefore only be regarded as an example. Each power semiconductor group 11 and 12 preferably comprises n power semiconductors, where n can be a positive whole number excluding zero.

[0040] Two copper plates 23a, 23b are provided as electrically conductive current input plates 23a, 23b, and a copper plate 22 is likewise provided as electrically conductive current outlet plate 22, preferably with integrated cooling measures 24, 27 such as, for example, a cooling channel through which a coolant, such as water, can be supplied and discharged during operation. Molybdenum could alternatively also be used as a material for the plates 22, 23a, 23b.

[0041] The material thickness of the plates 23a/b, 22 can be, for example, in the millimeter range (e.g. 2 mm). A current connection (e.g. source or drain) of those power semiconductors 25 which represent Q1 of FIG. 1 (e.g. MOSFET) is preferably connected to the current input plate 23a, and a current connection (e.g. drain or source) of those semiconductors 25 which represent Q2 of FIG. 1 is preferably connected to the current input plate 23b. Both copper plates 23a, 23b are preferably aligned in an electrically insulated manner next to one another and parallel to the opposite current output plate 22. Further current connections (e.g. drain or source) of those power semiconductors 25 which represent Q1 and Q2 are preferably connected to one another by means of the single-piece current outlet plate 24. The current input plate 23a and the current input plate 23b are preferably designed to connect the rectifier according to the disclosure to the secondary winding 18b (FIG. 1).

[0042] Depending on the desired application, alternative circuit arrangements to this are also conceivable (not shown). Alternatively, the current connection (e.g. drain or source) of those semiconductors 25 which represent Q1 of FIG. 1 (e.g. MOSFET) is connected to a first current output plate (not shown), and the current connection (e.g. drain or source) of those semiconductors 25 which represent Q2 of FIG. 1 is connected to a second current output plate (not shown). Both current output plates (not shown) are then aligned in an insulated manner next to one another and parallel to a single opposite current input plate (not shown). The current connections (e.g. source or drain) of those power semiconductors 25 which represent Q1 and Q2 are connected to one another by means of the single-part current input plate in this alternative solution.

[0043] In a further preferred embodiment, both the current input plate and the current output plate are constructed in a plurality of parts and arranged parallel to and opposite one another in order to surround power semiconductors whereof the inputs and/or outputs are not connected to one another circuit-wise and are actuable by means of freely accessible control connections between both plates.

[0044] The copper plates 23a,b and 22, which are arranged parallel to and flush with one another in their edge region, are connected to one another at least in their edge region by means of an electrically non-conductive connecting means (not shown), so that the copper plates 23a,b and 22 form a housing together with the connecting means. The connecting means can be a casting compound; however it can alternatively also be realized by a plastics material such as a hard plastics material or a soft plastics material. The connecting means enables the realization of a housing, which also meets an IP rating, depending on the application.

[0045] Positively engaging contact means can be provided at the edge of both copper plates 23a,b and 22 for attaching the connecting means, which contact means ensure a firm contact between connecting means and copper plates 23a,b and 22.

[0046] The thickness of the printed circuit board 21 can be in the micrometer range, for example 100 micrometers. The control connections of the power semiconductors 25 are likewise comprised by the printed circuit board 21 and can be connected by means of an actuating device 26 for the power semiconductors 11, 12, which actuating device is likewise comprised by the printed circuit board 21 or integrated in the printed circuit board.

[0047] As shown in the drawing, the applied current (I, direction of the arrow is relevant) can be controlled by means of the control connections and take a specifiable direction from the current input plates 23a, 23b to the current output plate 22. The waste heat (heat losses) occurring during operation of the arrangement can, at the same time, be dissipated, in particular accelerated, in both directions by means of the current input plates 23a, 23b and the current outlet plate 22 if cooling channels 23, 27 are provided in all plates 22, 23a, 23b or a cooling channel 23, 27 is provided in at least one of the plates 22, 23a, 23b.

[0048] FIG. 3 shows an embedded half bridge circuit in schematic form. The bridge is between a first 31 and a second 36 potential and is realized by means of two MOSFET switches 32, 35 whereof the control connections (shown open) are actuable by the actuating device 26 (see FIG. 2). A first electrode of a pair of welding tongs 34 is electrically connected between both MOSFET switches 32, 35. A second electrode of the welding tongs is connected in this example to the potential 36. Both potentials 31, 36 are preferably provided by the secondary windings shown in FIG. 1.

LIST OF REFERENCE SIGNS

[0049] 11,12 Power switches, MOSFETs output-side [0050] 13 Load, welding tongs [0051] 14, 15 Current measuring circuit [0052] 16 Primary-side transformer link [0053] 17 Center tap, transformer [0054] 18 Transformer [0055] 18a Primary winding, transformer [0056] 18b Secondary winding, transformer [0057] QA, QB, QC, QD Power switches, MOSFETS input-side [0058] IQ1, IQ2 Welding current [0059] L(+), L() DC link direct voltage of the welding inverter [0060] 21 Printed circuit board [0061] 22 Current input plate, copper plate [0062] 23a, 23b Current output plate(s), copper plate(s) [0063] 24 Integrated water cooling [0064] 25 Embedded semiconductors in the printed circuit board, converter circuit [0065] 26 Actuating means for control connections of the power switches [0066] 27 Integrated water cooling [0067] I Welding current [0068] 31, 36 Voltage supply [0069] 32, 35 Control means [0070] 33 Measuring means for current [0071] 34 Welding tongs