Converter, motor vehicle and method for controlling a half-bridge circuit

Abstract

This invention relates to a converter with a half-bridge circuit, the half-bridge circuit having at least one active half-bridge branch (3), the phase terminals (4) of which are respectively connected to corresponding reference potentials (7, 8) via corresponding switching devices (5, 6), wherein the control device (9) of the converter is configured to alternately switch the corresponding switching devices (5, 6) to be on and off, wherein the first and second switching devices (5, 6) respectively include a parallel circuit of at least one first type transistor (10) and at least one second type transistor (11), wherein the control device (9) is configured to, on the one hand, satisfy the first selection When condition (23) is met, in order to switch the corresponding switching device (3) to conduct, only the first type transistor (10) is switched to conduct, and / or - on the other hand, when the second selection condition (24) is met, in order to switch the corresponding switching device (5, 6) to conduct, the first type transistor (10) (which is a metal-oxide-semiconductor field-effect transistor and / or uses silicon carbide as the semiconductor material) is not switched to conduct, or the first type transistor (10) is switched to conduct only in the sub-time period of the corresponding time period in which the second type transistor (11) of the same switching device (5, 6) is switched to conduct.

Description

Technical Field

[0001] This invention relates to a converter with a half-bridge circuit, the half-bridge circuit having at least one active half-bridge branch, the phase terminals of which are respectively connected to corresponding reference potentials via corresponding switching devices. The converter's control device is configured to alternately switch the corresponding switching devices to be on and off, wherein the first and second switching devices each comprise a parallel circuit of at least one transistor of a first type and at least one transistor of a second type. Furthermore, this invention relates to a motor vehicle and a method for controlling a half-bridge circuit. Background Technology

[0002] To power the drive motor from the DC on-board electrical grid, electric vehicles use converters, or inverters. These converters can be manufactured as modules, for example, by providing active half-bridge branches on three substrates, whereby the substrates are mounted in a housing, which additionally includes, for example, intermediate circuit capacitors and control devices. The half-bridge branches typically use silicon-insulated-gate bipolar transistors (SiGBTs) as semiconductor switches. However, such converters exhibit higher losses during partial load operation because a significant voltage drop occurs across the SiGBTs when switching them on, even with a small current being introduced.

[0003] To avoid this situation, alternative transistor technologies can be used instead of silicon-insulated-gate bipolar transistors (SiGBTs). For example, using silicon carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) as semiconductor switches can reduce losses during partial load operation. However, a disadvantage here is that higher losses occur in this transistor at high currents, and thus when driving the motor at full load or acceleration.

[0004] One possible solution to optimize the efficiency of motor vehicles is to provide separate drive units for the front and rear axles, and to use independent inverters with different half-bridge technologies for the drive units. However, implementing two independent inverter modules in a motor vehicle increases technical complexity, cost, and structural space requirements, and is therefore particularly disadvantageous for economy vehicles or small vehicles with low drive power.

[0005] A converter combining different transistor types is known from patent document DE 10 2018 110 808 A1. Here, transistors with different band gap sizes are used in order to connect the corresponding phase terminals to two reference potentials.

[0006] Patent document CN 110034686 A uses a half-bridge in a DC-DC voltage converter, which employs a parallel circuit of a silicon carbide metal-oxide-semiconductor field-effect transistor (MOSFET) and a silicon insulated-gate bipolar transistor (SIB). Here, the MOSFET is switched on before the SIB and switched off after the SIB, thus performing the SIB switching process essentially without a voltage drop across the SIB. By appropriately designing the transistor dimensions, low switching losses can be achieved within a certain load range. Summary of the Invention

[0007] The object of the present invention is to further reduce losses in converters, especially in converters for drive motors of motor vehicles, wherein efficiency improvement should be achieved, particularly under both low and high loads.

[0008] According to the present invention, this objective is achieved by a converter of the type described at the beginning, wherein the control device is configured to,

[0009] -On the one hand, when the first selection condition is met, in order to switch the corresponding switching device to conduct, only the transistor of the first type is switched to conduct, and / or

[0010] - On the other hand, when the second selection condition is met, the first type of transistor is not switched on, or the first type of transistor is switched on only during a sub-time period of a corresponding time period in which the second type of transistor of the same switching device is switched on in order to switch the corresponding switching device on, the first type of transistor being a metal-oxide-semiconductor field-effect transistor and / or using silicon carbide as the semiconductor material.

[0011] Converters used in motors, especially drive motors in motor vehicles, must provide significantly different current intensities at different times. This arises partly from the phase power supply to the motor, which is at least approximately sinusoidal, and partly from the supply of alternating currents with significantly different amplitudes to the motor according to the required power or torque. It is known within the scope of this invention that losses in the converter or in the corresponding half-bridge branches can be reduced by switching the corresponding switching devices on in different ways in different operating states.

[0012] As will be explained more precisely later, in particular, the first selection condition is met for low loads or the current supplied, and the second selection condition is met for high loads or the current supplied. For example, if a silicon carbide metal-oxide-semiconductor field-effect transistor (SiMOT) is combined with a silicon-insulated-gate bipolar transistor (SiGBT) to form a switching device, it can be advantageous to switch only the SiMOT to conduct in order to provide low phase current, and only the SiGBT to conduct in order to provide high phase current, or alternatively, to switch the SiGBT to conduct before the SiMOT and after the SiMOT.

[0013] A partial time period does not include the entire time period, and in particular, it is time-separated not only from the beginning of the time period but also from its end. In other words, switching only the first type of transistor to conduct within a partial time period means switching the first type of transistor to conduct after the second type of transistor and switching the first type of transistor to deactivate before the second type of transistor.

[0014] Switching a transistor to be on or off can be understood as corresponding switching states, i.e., when the transistor is operating as a semiconductor switch, the switching state corresponds to the closing or opening of the switch. Here, although, for example, for a metal-oxide-semiconductor field-effect transistor (MOSFET), conductivity exists in the off state due to the inherent diode, the MOSFET disrupts the potential balance between the phase output and the corresponding reference potential as long as the potential at the phase output is between the phase output and the reference potential. Therefore, it is typically only important during no-load conditions or during commutation.

[0015] Alternating current is typically provided at the phase output. The operation of the active half-bridge branch is well known and will not be explained in detail here. To provide a sinusoidal voltage profile, especially by switching the same switching device to conduction and de-conduction in a relatively rapid sequence within the corresponding half-wave, the pulse width for switching to conduction can be varied. Each time the corresponding switching device is switched to conduction, the type of transistor to be controlled or the order in which the transistor types are controlled can be selected in the described manner, especially by providing different selection conditions even at different times within the corresponding half-wave, particularly because different current intensities are provided.

[0016] The first type of transistor can be a metal-oxide-semiconductor field-effect transistor (MOSFET) and / or use silicon carbide as the semiconductor material, and / or the second type of transistor can be an insulated-gate bipolar transistor (IGBT) and / or use silicon as the semiconductor material. The name MOSFET stands for metal-oxide-semiconductor field-effect transistor. Preferably, silicon carbide metal-oxide-semiconductor field-effect transistors are used as the first type.

[0017] The name IGBT stands for Insulated Gate Bipolar Transistor. In particular, silicon-insulated gate bipolar transistors are used as a second type of transistor.

[0018] The satisfaction of the first and / or second selection conditions can be related to the current intensity determined, predetermined, or predicted through the phase connectors. In the simplest case, the phase current can be measured, which can be done within the converter itself, with respect to the load, or on the connecting wires. However, it is also feasible to manipulate the converter to provide a specific current intensity, thereby directly pre-setting the current intensity. In particular, the current intensity can be predicted when information about the load, such as the motor model, or at least information about the inductance of the coil here is known. Corresponding schemes for obtaining the current intensity through the phase connectors are known and therefore will not be explained in detail. As mentioned at the beginning, it is known that different manipulation schemes are suitable for different transistor types when the current intensity through the phase connectors varies in order to achieve optimal converter efficiency.

[0019] The first selection condition is satisfied when or only when the current intensity is less than a predetermined first limit. As explained at the beginning, it may be particularly suitable to switch the silicon carbide metal-oxide-semiconductor field-effect transistor to conduct only when the required current is low. Alternatively or supplementarily, the second selection condition is satisfied when or only when the current intensity reaches or exceeds the first limit or a predetermined second limit. As already described above, the control strategy explained for the second selection condition is particularly suitable for high current intensities.

[0020] In the simplest case, a first limit is used for the two selection conditions, thus ensuring that either the first or second selection condition is always met, depending on the current intensity. The corresponding control can be implemented with low technical complexity and good efficiency has been achieved. In particular, in this case, when the second selection condition is met, only the second type of transistor is switched on to turn on the corresponding switching device. However, as explained below, it can be advantageous to select another control strategy between the first and second limits, i.e., for medium to high output currents, to further improve efficiency.

[0021] The control device can be configured to, when a third selection condition is met (the third selection condition is met when or only when the current intensity value reaches or exceeds the first limit and is less than the second limit), switch the second type of transistor to conduct only during a sub-time period in which the first type of transistor of the same switching device is switched on. This sub-time period is shorter than the time period and, in particular, is spaced apart from the start and end times of the time period.

[0022] The use of the third selection condition can be particularly combined with a design in which, when the second selection condition is met, the first type of transistor is switched on only during a sub-period of the corresponding time period in which the same switching device's second type of transistor is switched on. Ultimately, this means that, not only when the second selection condition is met but also when the third selection condition is met, and thus especially at medium and high currents, both transistor types are switched on to switch the switching device on, wherein different switching sequences are used during the time period in which the switching device is switched on.

[0023] The phase connector can only be connected to the corresponding reference potential via transistors of the first and second types. In particular, no separate unloaded diode is connected between the phase connector and the corresponding reference potential. Unloaded or current-driven switching during the commutation phase can be achieved or performed via the inherent diode of the first transistor type, such as a silicon carbide metal-oxide-semiconductor field-effect transistor. This further reduces the technical complexity of implementing the converter according to the invention.

[0024] For at least one of the switching devices, at least one corresponding transistor of both the first and second types, especially a plurality of corresponding parallel transistors, can be arranged on a common substrate. Alternatively or supplementarily, all transistors of a half-bridge branch, or at least one half-bridge branch, can be arranged on a common substrate. In particular, the same number of transistors of the first and second types are used. Using a common substrate further reduces the technical complexity of the converter and thus further reduces its manufacturing complexity. For example, the three-phase converter is then constructed on a common carrier or housing by fixing three substrates, each carrying transistors of a half-bridge branch.

[0025] For at least one of the switching devices, at least one corresponding transistor of not only the first type but also the second type, especially multiple transistors connected in parallel, can be contacted via a common conductive contact surface. Heat dissipation can be improved by using a common contact surface, particularly a large area. For example, in copper-clad ceramic substrate interconnect technology, the described contact is achieved by using a common large-area copper electrode.

[0026] The converter according to the invention is particularly a three-phase converter, which includes three half-bridge branches connected between reference potentials.

[0027] In addition to the converter according to the invention, the invention also relates to a motor vehicle having an electric motor, particularly a drive motor, wherein the motor vehicle includes a converter according to the invention for supplying power to the electric motor. As already explained, especially for supplying power to the drive motor in the motor vehicle, different phase currents are required at different times, and thus, the design of the converter according to the invention can achieve particularly high efficiency improvements.

[0028] Furthermore, the present invention relates to a method for controlling a half-bridge circuit, the half-bridge circuit having at least one active half-bridge branch, the phase terminals of the half-bridge branch being respectively connected to a corresponding reference potential via corresponding switching devices, wherein the switching devices are alternately switched to be on and off, wherein the first and second switching devices respectively comprise a parallel circuit of at least one transistor of a first type and at least one transistor of a second type, wherein...

[0029] -On the one hand, when the first selection condition is met, in order to switch the corresponding switching device to conduct, only the transistor of the first type is switched to conduct, and / or

[0030] - On the other hand, when the second selection condition is met, the first type of transistor (which is a metal-oxide-semiconductor field-effect transistor and / or uses silicon carbide as the semiconductor material) is not switched on, or the first type of transistor is switched on only during a sub-time period in which the second type of transistor of the same switching device is switched on in order to switch the corresponding switching device on.

[0031] The advantages of this control method have been explained with reference to the converter according to the invention. This method is particularly applicable to controlling half-bridge circuits in converters according to the invention. In relatedly, features relating to the control of half-bridge circuits, already explained with respect to the converter according to the invention, can be transferred to the method according to the invention in a manner that possesses the advantages described herein, and features explained with respect to the method according to the invention can be transferred to the converter according to the invention. In particular, in the method according to the invention, the satisfaction of the first and / or second selection conditions can also be related to current intensities determined, predetermined, or predicted by the phase connector, especially as explained with respect to the converter according to the invention, and / or the third selection condition explained with respect to the converter according to the invention can be used. Attached Figure Description

[0032] Other advantages and details of the invention will become apparent from the embodiments described below and the dependent drawings. Wherein, schematically:

[0033] Figure 1 An embodiment of a motor vehicle according to the present invention is shown, the motor vehicle including an embodiment of a converter according to the present invention, the half-bridge circuit of the converter being controlled according to an embodiment of the method according to the present invention.

[0034] Figure 2 and Figure 3 Examples of manipulation strategies for different transistor types are shown, and

[0035] Figure 4 A half-bridge module according to an embodiment of a converter based on the present invention is shown, which implements a half-bridge branch. Detailed Implementation

[0036] Figure 1 A motor vehicle 1 is shown, whose motor 13 or its coil 14 is powered by a converter 2. For example, the converter is powered by direct current from the vehicle's onboard electrical grid via a battery 15, and the converter provides three-phase alternating current for operating the motor 13.

[0037] To provide three-phase alternating current, three half-bridges 3 are used, with corresponding phase terminals 4 of each half-bridge (providing alternating current to the corresponding phase at the phase terminal) connected to reference potentials 7 and 8 via corresponding switching devices 5 and 6. The control device 9, which controls the operation of the switching devices 5 and 6 to provide the alternating current, is also powered by battery 15 in this example. In a practical technical solution, it is particularly advantageous to supply power to the control device 9 via the low-voltage vehicle power grid and to supply power to the converter 2 via the reference potentials 7 and 8 from the high-voltage power supply of the vehicle 1.

[0038] As is known from the prior art, the switching devices 5 and 6 are intermittently operated by the control device 9 to provide sinusoidal voltage or current curves at the corresponding phase terminals 4, wherein an approximately 90° phase shift is obtained between the current and voltage due to the almost purely inductive load of the motor 13. The voltage at the phase terminals 4 can be adapted to the reference potential 7 by intermittently switching the switching device 5 to conduction, and conversely, to the reference potential 8 by intermittently switching the switching device 6 to conduction. Here, in order to achieve an approximately sinusoidal voltage curve, the time for switching the corresponding switching devices 5 and 6 to conduction is adjusted according to the current phase of the alternating current. Furthermore, the amplitude of the voltage curve and the resulting current curve is adjusted by extending or shortening the time for switching the corresponding switching devices 5 and 6 to conduction. This process of supplying power to the motor via a converter is known, wherein silicon-insulated gate bipolar transistors are typically used as the switching devices 5 and 6.

[0039] Alternatively, switching devices 5 and 6 in the converter 2 are formed by parallel circuits of at least one first-type transistor 10, such as a silicon carbide metal-oxide-semiconductor field-effect transistor, and at least one second-type transistor 11, such as a silicon-insulated-gate bipolar transistor. For clarity, in Figure 1 The corresponding switching devices 5 and 6 are shown only one of transistors 10 and 11 respectively. Typically, multiple identical transistors 10 and 11 are connected in parallel to provide higher power.

[0040] In contrast, the use of semiconductor switches in conventional switching devices 5 and 6 would require additional unloaded diodes, which are unnecessary here because the silicon carbide metal-oxide-semiconductor field-effect transistor already has an inherent diode 12. Thus, despite the need for parallel circuits of different types of transistors 10 and 11, the technical complexity for implementing the circuit shown remains relatively low.

[0041] Control device 9 operates different types of transistors 10 and 11 separately, thereby enabling, for example, control techniques to switch only transistor 11 to conduct, only transistor 10 to conduct, or both transistors to conduct, to switch switching devices 5 and 6 to conduct as a whole. It is known that losses in converter 2 can be reduced when at least one parameter of converter 2 is evaluated and, based on that parameter, different control models are used to switch corresponding switching devices 5 and 6 to conduct for transistors 10 and 11. Here, the following examples discuss the correlation between switching characteristics and the current supplied at phase connector 4. Alternatively or additionally, the temperature of converter 2, or the temperature of individual components of converter 2, may also be considered, for example.

[0042] exist Figure 2 The first possible operating strategy of inverter 2 is schematically illustrated. Here, the x-axis 16 shows the time curve, and the y-axis 17 shows the current intensity 21 at the phase junction 4 of the corresponding half-bridge branch 3. As explained above, the time curve of current intensity 21 is at least approximately sinusoidal.

[0043] Such operation should switch the corresponding switching devices 5 and 6 to be conductive, such that when the first selection condition 23 is met, only the first type of transistor 10 is switched on to switch the corresponding switching devices 5 and 6 to conduct. When the second selection condition 24 is met, instead of switching the corresponding switching devices 5 and 6 to conduct, only the second type of transistor 11 is switched on. Here, the first selection condition is met when the value of the current intensity 21 is less than the predetermined limit 18. Conversely, if the value of the current intensity 21 is greater than the limit 18, the second selection condition 24 is met instead.

[0044] This leads to, Figure 2 In the shaded area 19, that is, at low current intensities, only transistor 10, i.e., the silicon carbide metal-oxide-semiconductor field-effect transistor in this example, is switched. This is advantageous because the silicon carbide metal-oxide-semiconductor field-effect transistor exhibits smaller losses at low currents compared to using a silicon-insulated-gate bipolar transistor. However, at higher currents, smaller losses can be achieved by using a silicon-insulated-gate bipolar transistor to switch switching devices 5 and 6 to conduct compared to using a silicon carbide metal-oxide-semiconductor field-effect transistor. Figure 2 In the non-shaded region 20 where a high current intensity 21 occurs, only the second type transistor 11 is switched on in order to switch the corresponding switching devices 5 and 6 on.

[0045] The described operating strategy can be implemented relatively simply technically, as such limit comparisons can be performed directly, for example, by a comparator. For instance, the current intensity 21 can be obtained via current sensor 22. Alternatively, it is also feasible to obtain the current intensity indirectly from the control information for converter 2, for example by means of known parameters of motor 13, and especially by means of the inductance of coil 14 to predict the current intensity.

[0046] Since the satisfaction of selection conditions 23 and 24 is related to the current intensity 21, such as reducing the amplitude 30 of the alternating current supplied to coil 14, the first selection condition 21 is satisfied for a longer time and the selection condition 24 is satisfied for a shorter time, because the current amplitude 21 remains below the limit 18 for most of the running time.

[0047] exist Figure 3 The text shows the relationship with... Figure 2 The curves showing the same current intensity 21 are shown in the figure, where, Figure 3 In this case, a different operating strategy is used for converter 2, which, although more technically complex to implement, achieves further efficiency improvements.

[0048] Here, if the value of current intensity 21 is lower than the limit 18 and thus the first selection condition 23 is met, the control transistors 10, 11 (and in accordance with) Figure 2 (The same situation in the operating strategy). Therefore, in order to switch the corresponding switching devices 5 and 6 to conduct, in the smaller shaded area 27 (as in the case of...). Figure 2 (The situation is the same in the shaded area 19), except that the first type of transistor 10 is switched on.

[0049] However, when the current intensity 21 exceeds the limit 18, in principle, both types of transistors 10 and 11 will be switched on when the corresponding switching devices 5 and 6 are switched on. However, different timing sequences are used here.

[0050] exist Figure 3 Under the operating strategy shown, the second selection condition 24 is satisfied only when the value of current intensity 21 exceeds the second limit 26, as shown in the large shaded area 29. During operation in area 29, in order to switch the corresponding switching devices 5 and 6 to conduct, the second type transistor 11, i.e., a silicon-insulated gate bipolar transistor, is always switched to conduct, and transistor 10 is switched to conduct only after a short delay of, for example, a few nanoseconds. Switching to the off state is performed in the reverse order, that is, the first type transistor 10 is switched to off first, and then, immediately after a short delay, the second type transistor 11 is switched to off. It is known that this switching characteristic for providing large currents is advantageous, especially under high loads at converter 2.

[0051] exist Figure 3 In the unshaded region 28, the current intensity 21 is between limits 18 and 26, thus satisfying the third selection condition 25. In this region 28, when switching the corresponding switching devices 5 and 6 to conduct, the first type transistor 10 is switched to conduct first, followed by the second type transistor 11 after a short delay. Disconnection is performed in the reverse order, so the second type transistor 11 is switched to disconnect first, followed immediately by the first type transistor 10. This switching characteristic results in the second type transistor 11, i.e., the silicon-insulated gate bipolar transistor, having almost no voltage during its switching process. This reduces switching losses that dominate power loss at medium current intensities, thus optimizing the switching characteristic at medium current intensities.

[0052] Figure 4 The structure of half-bridge branch 3 as a semiconductor module is schematically shown. Three of these semiconductor modules can be mounted, for example, onto a common bracket or a common housing to provide a converter module.

[0053] The common substrate 38 carries all transistors 10 and 11 of the half-bridge branch 3 and thus carries transistors 10 and 11 of different types. The transistors 10 and 11 of the switching device 5 are contacted through a common conductive contact surface 31, which is at a reference potential 7 when the converter 2 is operating. The corresponding transistors of the switching device 6 are also arranged on a common conductive contact surface 32, which is at the potential of the phase junction 4 when the converter 2 is operating.

[0054] exist Figure 4 In the example shown, not only in the first but also in the second switching devices 5 and 6, two transistors 10 of the first type and two transistors 11 of the second type are connected in parallel. To change the power of the half-bridge branch 3, more or fewer transistors 10 and 11 of the same type may also be connected in parallel.

[0055] By using large-area common contact surfaces 31 and 32 for the transistors 10 and 11 of the corresponding switching devices 5 and 6, these contact surfaces 31 and 32 can also be well used for heat conduction. In particular, the contact surfaces 31 and 32 can be copper surfaces, and a "copper-clad ceramic substrate" structure can be realized.

[0056] In addition, the substrate 38 carries another conductive contact surface 33 for providing a reference potential 8 and contact surfaces 34 to 37 for providing gate voltages to the corresponding gate terminals 39 of transistors 10 and 11, wherein, in order to enable independent control of each type, separate contact surfaces 34-37 are provided for different types of transistors 10 and 11.

Claims

1. A converter having a half-bridge circuit, the half-bridge circuit having at least one live half-bridge branch (3), the phase connections (4) of the half-bridge branch being connected to a respective reference potential (7, 8) via a respective switching device (5, 6), wherein, The control device (9) of the converter is set up to switch the respective switching device (5, 6) alternately into conduction and into disconnection, wherein the first and second switching device (5, 6) each comprises a parallel circuit of at least one transistor (10) of a first type and at least one transistor (11) of a second type, characterized in that a first selection condition (23) is fulfilled when or only when the value of the current intensity (21) is less than a preset first limit value (18); a second selection condition (24) is fulfilled when or only when the value of the current intensity (21) reaches or exceeds a preset second limit value (26); a third selection condition is fulfilled when or only when the value of the current intensity (21) reaches or exceeds the first limit value (18) and is less than the second limit value (26), wherein the fulfillment of the first and / or second selection condition (23, 24) is related to the current intensity (21) obtained or preset or predicted through the phase connection (4), wherein the control device (9) is set up to - switch only the transistor (10) of the first type into conduction in order to switch the respective switching device (3) into conduction when the first selection condition (23) is fulfilled, - switch neither the transistor (10) of the first type into conduction nor always the transistor (11) of the second type into conduction in order to switch the respective switching device (5, 6) into conduction when the second selection condition (24) is fulfilled and only after a delay time the transistor (10) of the first type of the same switching device (5, 6) is switched into conduction; and - switch the transistor (10) of the first type into conduction and only after a further delay time the transistor (11) of the second type of the same switching device (5, 6) is switched into conduction when the third selection condition (25) is fulfilled.

2. The current transformer of claim 1, wherein, The transistor (10) of the first type is a MOSFET and / or uses silicon carbide as semiconductor material and / or the transistor (11) of the second type is an IGBT and / or uses silicon as semiconductor material.

3. A current transformer according to claim 1 or 2, characterised in that The phase connection (4) is connected to the respective reference potential (7, 8) only through the transistor (10, 11) of the first and second type.

4. A current transformer according to claim 1 or 2, characterised in that For at least one of the switching devices (5, 6) at least one respective transistor (10, 11) of the first and second type is arranged on a common substrate (38) and / or all transistors (10, 11) of the half-bridge branch (3) or at least one of the half-bridge branches (3) is arranged on a common substrate (38).

5. The current transformer of claim 1 or 2, wherein For at least one of the switching devices (5, 6) at least one respective transistor (10, 11) of the first and second type is contacted through a common conductive contact surface (31, 32).

6. The current transformer of claim 5, wherein, The at least one respective transistor (10, 11) comprises a plurality of transistors (10, 22) in parallel.

7. A motor vehicle having an electric machine, characterized in that The motor vehicle comprises a converter according to any one of claims 1 to 6 for energizing an electric machine.

8. Motor vehicle according to claim 7, characterized in that The electric machine is a drive machine.

9. A method for controlling a half-bridge circuit, the half-bridge circuit having at least one live half-bridge branch (3), the phase connections (4) of the half-bridge branch being connected to a respective reference potential (7, 8) by means of a respective switching device (5, 6), wherein, alternately switching the switching devices (5, 6) into conduction and into disconnection, respectively, wherein the first and second switching devices (5, 6) each comprise a parallel circuit of at least one transistor (10) of a first type and at least one transistor (11) of a second type, characterized in that the first selection condition (23) is fulfilled when or only when the value of the current intensity (21) is less than a first limit value (18) which is preset, the second selection condition (24) is fulfilled when or only when the value of the current intensity (21) reaches or exceeds a second limit value (26) which is preset, and the third selection condition is fulfilled when or only when the value of the current intensity (21) reaches or exceeds the first limit value (18) and is less than the second limit value (26), wherein the fulfillment of the first and / or second selection condition (23, 24) is related to the current intensity (21) which is obtained through the phase connection (4) or which is preset or predicted, - when the first selection condition is fulfilled, for switching the respective switching device (5, 6) into conduction, only the transistor (10) of the first type is switched into conduction, - when the second selection condition is fulfilled, for switching the respective switching device (5, 6) into conduction, the transistor (10) of the first type is not switched into conduction or the transistor (11) of the second type is always switched into conduction and the transistor (10) of the first type of the same switching device (5, 6) is only switched into conduction after a delay time, and - when the third selection condition (25) is fulfilled, the transistor (10) of the first type is switched into conduction and the transistor (11) of the second type of the same switching device (5, 6) is only switched into conduction after a further delay time.

Images