Power supply device, power converter, electric axle drive, motor vehicle and method for operating a power supply device

Abstract

The approach presented here provides a power supply device (120) for an inverter (108) for a motor vehicle (100), wherein the power supply device (120) comprises a flyback converter unit (200) with a transformer core (210), a plurality of primary windings (220, 225, 230) coupled to the transformer core (210) and each supplied by a power supply connection (255), and at least one secondary winding coupled to the transformer core (210), wherein the flyback converter unit (200) is configured to transfer electrical energy from at least one of the primary windings (220, 225, 230) to the at least one secondary winding (240, 245, 250).Furthermore, the power supply device (120) comprises a converter control unit (270) configured to apply a voltage and / or current to the primary windings (220, 225, 230) at different times, wherein the converter control unit (270) is further configured to apply a voltage and / or current to one of the primary windings (220, 225, 230) at one time and to disconnect other primary windings (220, 225, 230) from their respective associated power supply connections (255).

Description

[0001] The present invention relates to a power supply device, a power converter, an electric axle drive, a motor vehicle and a method for operating a power supply device according to the dependent claims.

[0002] Flyback converters, which can be powered from different sources, can be used to supply energy to electrical components. However, to avoid short circuits or circuit problems, solutions are usually employed that only use the source with the highest voltage for power supply, meaning that other power sources are generally not used to power such a flyback converter. This leads to such an approach sometimes being unreliable and not always robust, especially if the power source supplying the highest voltage fails or becomes unstable.

[0003] Against this background, the present invention provides an improved power supply device for an inverter for a motor vehicle, an improved power converter, an improved electric axle drive, an improved motor vehicle, and an improved method for operating a power supply device according to the main claims. Advantageous embodiments are described in the dependent claims and the following description.

[0004] The present approach creates a power supply device for an inverter for a motor vehicle, wherein the power supply device has the following features: - a flyback converter unit comprising a transformer core, a plurality of primary windings coupled to the transformer core and each of which can be supplied to a power supply terminal, and at least one secondary winding coupled to the transformer core, wherein the flyback converter unit is configured to transfer electrical energy from at least one of the primary windings to the at least one secondary winding; and - a converter control unit configured to apply a voltage and / or current to the primary windings at different times, wherein the converter control unit is further configured to apply a voltage and / or current to one of the primary windings at one time and to disconnect other primary windings from their respective associated power supply connections.

[0005] The approach presented here is based on the understanding that using a flyback converter or flyback converter unit with multiple primary windings, which are used in a timed sequence to transfer energy from one of these primary windings via the transformer core to the secondary winding, significantly improves the robustness and stability of the power supply. This allows several different energy sources, connected, for example, to the respective power supply terminal of one of the primary windings, to supply energy that is transferred to the secondary winding. At the same time, this decoupling of the component connected to the secondary winding from the components connected to the individual primary windings can be achieved.This allows for an integrated power supply solution from multiple, for example unregulated, sources, enabling the generation of regulated output voltages for load circuits. Simultaneously, the power can be distributed between the corresponding inputs or primary windings independently of their voltage values. Therefore, changes in the power supply from individual energy sources connected to the respective primary windings do not necessarily lead to voltage drops at the components connected to at least one secondary winding, even when an energy source is added or removed from one of the primary windings. This also eliminates the need for separate voltage regulation for one, several, or each unregulated input via a separate primary winding.

[0006] A particularly advantageous embodiment of the approach proposed here is one in which the individual primary windings of the flyback converter unit are configured to be supplied by different voltage values ​​and / or different current values ​​and / or power values, and / or in which the primary windings are electrically isolated from one another. Such an embodiment offers the advantage that, by enabling the use of differently configured energy sources at the respective primary windings, a reliable, continuous, and, as far as possible, uninterrupted energy supply via the transformer core to the at least one secondary winding can be ensured.

[0007] Another conceivable embodiment of the approach proposed here involves the converter control unit being designed to cyclically apply a voltage and / or current to each of the primary windings. By cyclically repeating the application of a voltage and / or current to each of the individual primary windings, a continuous and as uniform as possible transfer of electrical energy from multiple inputs or primary windings via the transformer core to the secondary winding can be achieved.

[0008] According to a further embodiment, the converter control unit can be configured to activate the individual primary windings in essentially equal intervals, with the intervals assigned to the individual primary windings not overlapping in time. Activation here can be understood as releasing a current flow or applying a voltage to the respective primary winding within an interval. At the same time, however, this activation can also include blocking the current flow to the respective primary winding within this interval, thus ensuring that only one of the primary windings is supplied with a current and / or voltage during the respective interval.Such an embodiment offers the advantage that by choosing to activate the respective primary windings in essentially equal interval sections (which may differ, for example, only by ten percent in their duration), a continuous and as uniform as possible supply of energy from different sources to the individual primary windings can be achieved.

[0009] Energy extraction from individual sources can be very flexibly implemented in one of the primary windings. The converter control unit is designed to control an active time period in each interval segment, during which the respective primary winding is supplied with voltage and / or current, and an inactive time period, during which the respective primary winding is not supplied with voltage and / or current. This makes it possible to flexibly define time periods within the individual interval segments assigned to the primary windings, during which the primary winding is actively energized (active time period) and not energized (inactive time period).This allows, on the one hand, flexible extraction of electrical energy from the respective source connected to the primary winding, and at the same time ensures that energy is reliably transferred to the secondary winding via only one of the primary windings.

[0010] According to a further embodiment of the approach proposed here, the converter control unit can be configured to vary the lengths of the active time periods of interval sections assigned to different primary windings and / or to vary the lengths of the inactive time periods of interval sections assigned to different primary windings. Such an embodiment makes it possible to respond to the different energy supply capacities of the respective energy sources connected to the primary windings. At the same time, it can also accommodate, for example, the adjustment of different input voltages applied to the different primary windings, thus contributing to a continuous, uniform, and, as far as possible, fail-safe transfer of electrical energy to the secondary winding.

[0011] A particularly advantageous embodiment of the approach proposed here comprises at least one additional secondary winding coupled to the transformer core. This allows for the control of at least one further component on the secondary side, independent of operation or power supply by the (first) secondary winding.

[0012] According to one embodiment, highly efficient energy transfer can be achieved if the converter control unit is configured to operate the flyback converter unit in DCM mode and / or in gap mode, particularly if the converter control unit is configured to operate the flyback converter unit in DCM mode and / or in gap mode during each interval segment. Operation in DCM mode thus enables the deepest possible discharge of a storage inductor (or a corresponding storage capacitor), thereby reducing the switching frequencies required to charge this storage element.

[0013] A particularly advantageous embodiment of the approach proposed here is that of a power converter, especially an inverter, with a power supply device according to a variant presented herein. The advantages presented here can also be implemented quickly and efficiently with such an embodiment.

[0014] The advantages described here can also be realized in an embodiment of the proposed approach as an electric axle drive for a motor vehicle, comprising at least one electric machine, a transmission unit, and a power converter according to a variant presented here. The transmission unit can include a gearbox for reducing the speed of the electric machine and / or a differential.

[0015] Also presented is a motor vehicle comprising an electric axle drive according to a variant presented here and / or a power converter according to a variant presented here and / or a power supply device according to a variant presented here.

[0016] Furthermore, an embodiment of the approach proposed here is advantageous which is designed as a method for operating a power supply device according to a variant presented here for a power converter for a motor vehicle, wherein the method comprises the following steps: - Applying a voltage and / or current to a first of the primary windings at a first time; and - Outputting a voltage and / or current to a second of the primary windings at a second time point different from the first, whereby no voltage and / or current is applied to the first primary winding at the second time point.

[0017] The approach presented here further creates a control unit designed to execute, control, and implement the steps of a variant of the method presented here in corresponding units. This embodiment of the invention, in the form of a control unit, also allows the underlying problem to be solved quickly and efficiently.

[0018] A control unit can be an electrical device that processes electrical signals, such as sensor signals, and outputs control signals accordingly. The control unit can have one or more suitable interfaces, which can be implemented in hardware and / or software. In hardware implementations, the interfaces can, for example, be part of an integrated circuit in which the device's functions are implemented. The interfaces can also be separate integrated circuits or consist at least partially of discrete components. In software implementations, the interfaces can be software modules, such as those found on a microcontroller alongside other software modules.

[0019] A computer program product with program code that can be stored on a machine-readable medium such as semiconductor memory, hard disk memory or optical memory and is used to carry out the method according to one of the embodiments described above is also advantageous when the program is executed on a computer or control unit.

[0020] The invention is explained in more detail by way of example with reference to the accompanying drawings. These show: Fig. 1 a schematic representation of an exemplary embodiment of a motor vehicle; Fig. 2 a schematic simplified representation of an embodiment of a power supply device, such as that which can be used in the approach presented here; Fig. 3 a more detailed description of an exemplary embodiment of a power supply device; Fig. 4 a diagram of an exemplary switching cycle for controlling the switches to apply a voltage or current to the primary windings; Fig. 5 a diagram with a more detailed representation of switching states, current flow and voltage at the respective primary windings over time; Fig. 6 a flowchart of an embodiment of a method for operating a variant of a power supply device for an inverter for a vehicle presented here; and Fig. 7 a block diagram of an embodiment of a control unit for carrying out a method for operating a variant of a power supply device for an inverter for a vehicle presented here.

[0021] In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, without repeating these elements.

[0022] Fig. Figure 1 shows a schematic representation of an embodiment of a motor vehicle 100, for example, a passenger car or a truck. The vehicle 100 has an electric axle drive 102 for driving the wheels of the vehicle 100. The electric axle drive 102 comprises an electric machine 104, optionally a transmission unit 106, and an inverter 108, which can also be referred to as a power converter. The vehicle 100 further comprises a power source 110, for example, a battery. According to this embodiment, the inverter 108 is connected between the power source 110 and the electric machine 104 and is configured to convert a direct current voltage supplied by the power supply unit 110 into an alternating current voltage, for example, a three-phase alternating current voltage, and to supply it to the electric machine 104.The electric machine 104 is designed to provide, when driven by alternating voltage, a torque to drive at least one wheel of the vehicle 100. For this purpose, the electric machine 104 is connected either via the transmission device 106 or directly to an axle or at least one wheel of the vehicle 100.

[0023] The inverter 108 includes a power supply device 120 according to a variant presented here, which is described in more detail below.

[0024] Fig. Figure 2 shows a schematic simplified representation of an embodiment of a power supply device 120, such as can be used in the approach presented here. The power supply device 120 comprises a flyback converter unit 200, which has a transformer core 210. On a primary side 215 of the flyback converter unit 200, several primary windings, specifically a first primary winding 220, a second primary winding 225 up to an nth primary winding 230, are arranged and coupled to the transformer core 210 (for example, inductively). On a secondary side 235 of the flyback converter unit 200, several secondary windings, specifically a first secondary winding 240, a second secondary winding 245 up to an mth secondary winding 250, are also arranged and coupled to the transformer core 210 (for example, inductively).To transfer electrical energy from the primary side 215 to the secondary side 235, a power source 260 is connected to each of the power supply terminals 255 of the primary windings 220, 225, and 240. The output of energy from the respective power source 260 to the primary windings 220, 225, and 230 is controlled by corresponding switches 265, which are controlled by a converter control unit 270. A highly advantageous timing switching pattern is used, which will be described in more detail below.

[0025] A current flowing through one or more of the primary windings 220, 225 and / or 230 then causes the formation of a magnetic field, which couples via the transformer core 210 to the secondary winding(s) 240, 245 and 250 respectively. This then provides a reliable power supply for the loads 275 connected to the secondary windings 240, 245 and 250 respectively.

[0026] Fig. Figure 3 shows a more detailed representation of an exemplary embodiment of a power supply device 120, in which the components important for the approach presented here are shown in more detail. However, the specific circuit implementation of the individual modules of the power supply device 120 as a triple-input / quadruple-output power supply device 120 is not necessarily complete, but is only schematically indicated for the sake of clarity.

[0027] In order to achieve the particularly efficient and robust energy transmission through the approach presented here, a particularly favorable switching cycle for opening and closing the switches 265 is provided, as described above.

[0028] Fig. Figure 4 shows a diagram of an exemplary switching cycle for controlling switches 265 to apply a voltage or current to the primary windings. The diagram is from Fig. Figure 4 shows a time course on the abscissa and the activation state of the respective primary winding for current supply in different interval sections 400 on the ordinate. For example, the top row shows the activation state of the first primary winding 220, labeled SEC-1, while the second row shows the activation state of the second primary winding 225, labeled SEC-2, and the bottom row shows the activation state of the third primary winding 230, labeled SEC-3. The diagram shows that Fig. 4. Furthermore, the activation states of the respective primary windings 220, 225, and 235 are repeated cyclically, whereby at any given time only one of the primary windings is open in an activation state, and the other two are not in that activation state. This results in current flowing through only one of the primary windings at any given time, so that the magnetic fields at the transformer core are generated only by current flowing through one of the primary windings 220, 225, or 230. In this context, an activation state can be understood as a state in which only one of the primary windings 220, 225, or 230 may be / is being energized.It is not necessarily the case that the switch 265 of the respective primary winding needs to be permanently closed during the activation state; the activation state only permits the control of one switch 265 of one of the primary windings. Thus, in each of the individual interval sections 400, only one of the switches 265 is closed, and all other switches 265 are open. At the same time, the diagram shows... Fig. 4. It can be seen that in this embodiment, the interval sections 400 are of equal length for all primary windings 220, 225, and 230 of the switches 265, so that the energy source 260 can supply a current flow through each primary winding for the same duration. In this case, such a duration Tsec of an interval section 400 is one-third of a total cycle time Tsw, after which the switching pattern of the switches 265 is repeated.

[0029] Fig. Figure 5 shows a diagram with a more detailed representation of switching states (PWM_1, PWM_2, PWM_3), current flow (Ipri_1, Ipri_2, Ipri_3), and voltage (Vds_1, Vds_2, Vds_3) at the respective primary windings 220, 225, 230 over the time plotted on the abscissa. This includes exemplary primary-side operating waveforms for an interleaved flyback power supply with three inputs or primary windings in the Fig. 5 shown. From the representation of the Fig. Figure 5 further shows that within the interval sections 400, active time sections 500 can be provided or controlled by the converter control unit, during which the relevant primary winding can be supplied with a current or voltage. Conversely, inactive time sections 510 can also be provided or controlled by the converter control unit within the interval sections 400, during which the relevant primary windings are not supplied with a current or voltage. The active and inactive time sections can be designed with different lengths for the different primary windings. By selecting the active and inactive time sections, a very flexible supply of electrical energy to the primary windings can be enabled, thus creating a very robust and reliable power supply device. From the representation of the Fig. 5. It is further evident that the voltages on all primary windings have a very similar time course, which is due to the coupling of all primary windings with the transformer core, so that a voltage is induced even in inactive primary windings. Furthermore, in the Fig. 5. The current flow in the coils of the secondary side is shown in the bottom line.

[0030] The approach presented here can therefore be used to propose a design for a reliable power supply that a. works in environments where the availability of all power sources is not guaranteed. b. allows a current to be dynamically distributed among the available power sources, regardless of their voltage. c. enables galvanic isolation between the available power sources to ensure their compatibility. d. does not need to interrupt the power supply to the load when the sources are available.

[0031] The concept proposed here is exemplified in the Fig. 2 is described as a block diagram with n inputs and m outputs. In this description, a symmetrical nested flyback converter is proposed, in which the different power conversion sections are switched at the same frequency but in different phases. The controlled switching sections in the case described here are flyback primary windings (as voltage sources). The angle (θsec) or the time interval (tsec) for each switching section is θsec = 2π / n rad for converters with n inputs tsec= Tsw / n for converters with n inputs and Tsw the switching time of the section.

[0032] For a case of n = 3 inputs, the respective interval sections or operating zones in a switching cycle are defined for each switching section in the Fig. 4 shown.

[0033] Within the Tsec time, the corresponding switching section or interval section 400 is operated only in DCM mode. Operating the individual sections in DCM mode is particularly advantageous for the concept's functionality. Here, the switching condition "DCM mode for a section 400" in the current control means that the following two events should be completed within the Tsec time. a. The primary side of interval section 400 should imprint the current flow to the controller value "comp" in the time Tonsec1 b. and the secondary windings discharge the current flow in Tdissec1 completely (to zero) into the load c. One condition for the DCM mode for an interval section of 400 is that Tonsec1 + Tdissec1 < Tsec

[0034] In a source converter with n inputs, there are "n" Tsec sections, each of which, for example, performs a charge and a complete discharge in their phased Tsec durations.

[0035] The design of the DCM mode with the circuit parameters (Lp, Rsns, snubber, etc.) for each primary side can be done under the assumption that Tsec is the cycle period (not Tsw), for power Psec = P total / n

[0036] The design of the DCM mode (Cout values) for all secondary windings can be carried out assuming Tsec as the time span.

[0037] Although each primary part operates at a frequency of 1 / Tsw, the secondary windings on the secondary side operate at a frequency of 1 / Tsec = n / Tsw.

[0038] A central compensation circuit for current control can be designed so that the single control voltage “COMP” is generated for all (interval) sections, allowing the appropriate converter control unit to be designed and used jointly by all controllers to generate PWM.

[0039] The concept can also be extended to non-isolated buck-boost versions.

[0040] This reveals an approach where, for example, n phase clock generator ICs with outputs connected to “digital isolators” (if isolation between inputs is required) can be used, and n “PWM controllers” can control the power supply device. Each primary page is designed to operate in DCM mode. The total power of the load can be dynamically distributed evenly across the connected inputs (the design of the DCM mode should meet this requirement).

[0041] A common "master" control voltage (COMP) is supplied by the feedback AUX winding, as found, for example, in the lower part of the Fig. 3 is reproduced, generated and divided by all slave input sections using galvanic isolators (capacitive, inductive or optical isolators for isolated inputs (otherwise a direct connection for non-isolated inputs would have to be provided for such circuits)

[0042] Significant advantages over prior art solutions include the absence of any time-dependent switching between "dual input mode" and "single input mode," as well as any drop in output voltages. For example, the load percentage at source 1 (150V in) changes from 50% to 100% and back to 50% as soon as source 2 becomes available. This change in load percentage is reflected in the change in the primary current of source 2. A rectified peak load current and a corresponding switching frequency can be stabilized much more effectively. The concept presented here can be similarly extended to multiple sources.

[0043] Essentially, several problems can be solved with the approach presented here: 1. An integrated solution can be implemented: a. Multiple unregulated sources can generate regulated output voltages for load circuits. b. Power sharing between the inputs can be performed independently of their voltage values. 2. There is no change or drop in the output voltage over time when adding or removing a source. 3. Separate voltage regulators for each unregulated input can be avoided.

[0044] The approach presented here enables the realization of novel features and advantages for an energy supply device: 1. Nested flyback primary windings are now feasible, wound on a single transformer core. 2. Operation of each primary-controlled switching section in DCM mode can be achieved with an isolated phase-shifted clock for isolated inputs. 4. Lower overall system costs and less space is required on the circuit board. 5. Reliability and flexibility can be improved.

[0045] A DCM flyback converter circuit with multiple inputs and a corresponding operating procedure are presented.

[0046] The approach presented here can therefore be used to implement a switching power supply with multiple inputs, which 1. Can draw power from all or several available power sources simultaneously, regardless of their voltage level. 2. Allows the addition or removal of one or more power sources without affecting the power supply to the load circuits. 3. ensures galvanic isolation between all connections (input and output).

[0047] It is now also possible to implement a switching power supply or a power converter with multiple inputs, which 1. Can draw power from all or several available power or energy sources simultaneously, regardless of their voltage level. 2. Allows the addition or removal of one or more power sources without affecting the power supply to the load circuits. 3. ensures galvanic isolation between all connections (input and output).

[0048] Fig. Figure 6 shows a flowchart of an embodiment of a method 600 for operating a variant of a power supply device for an inverter for a vehicle presented here, wherein the method 600 has a step 610 of applying a voltage and / or a current to a first of the primary windings at a first time and a step 620 of outputting a voltage and / or a current to a second of the primary windings at a second time different from the first, wherein at the second time no voltage and / or current is applied to the first primary winding.

[0049] Fig.Figure 7 shows a block diagram of an embodiment of a control unit 700 for carrying out a method 600 for operating a variant of a power supply device for an inverter for a vehicle presented herein. The control unit 700 comprises a unit 710 for applying a voltage and / or current to a first primary winding at a first time point and a unit 720 for outputting a voltage and / or current to a second primary winding at a second time point different from the first, wherein no voltage and / or current is applied to the first primary winding at the second time point. The control unit 700 can, for example, be part of the converter control unit 270 in order to energize or de-energize the corresponding primary windings in an advantageous switching cycle.

[0050] The embodiments described and shown in the figures are only examples. Different embodiments can be combined completely or with respect to individual features. An embodiment can also be supplemented by features from another embodiment.

[0051] Furthermore, the process steps according to the invention can be repeated and carried out in a different order than described.

[0052] If an embodiment includes an “and / or” connection between a first feature and a second feature, this can be interpreted as meaning that the embodiment according to one embodiment has both the first feature and the second feature, and according to another embodiment either only the first feature or only the second feature. Reference sign 100 motor vehicles 102 electric axle drive 104 electric machine 106 Gearbox unit 108 inverters 110 Energy source 120 energy supply units 200 flyback converter unit 210 transformer core 215 Primary page 220 first primary winding 225 second primary winding 230 nth primary winding 235 Secondary page 240 first secondary winding 245 second secondary winding 250 m secondary winding 255 power supply connections 260 Energy source 265 switches 270 Converter control unit 275 Last 400 interval section 500 Active time period 510 Inactivity period 600 methods for operating a variant of an energy supply device presented here 610 steps of applying pressure 620th step of spending 700 control unit 710 units for application 720 units to spend

Claims

[1] Power supply device (120) for an inverter (108) for a motor vehicle (100), wherein the power supply device (120) has the following features: - a flyback converter unit (200) comprising a transformer core (210), a plurality of primary windings (220, 225, 230) coupled to the transformer core (210) and each supplied by a power supply terminal (255), and at least one secondary winding coupled to the transformer core (210), wherein the flyback converter unit (200) is configured to transfer electrical energy from at least one of the primary windings (220, 225, 230) to the at least one secondary winding (240, 245, 250); and - a converter control unit (270) configured to apply a voltage and / or a current to the primary windings (220, 225, 230) at different times, wherein the converter control unit (270) is further configured to apply a voltage and / or a current to one of the primary windings (220, 225, 230) at one time and to disconnect other primary windings (220, 225, 230) from the respective associated power supply connection (255). [2] Energy supply device (120) according to claim 1, characterized by , that the individual primary windings (220, 225, 230) of the flyback converter unit (200) are designed to be supplied by different voltage values ​​and / or different current values ​​and / or power values ​​and / or wherein the primary windings (220, 225, 230) are electrically insulated from each other. [3] Energy supply device (120) according to any one of the preceding claims, characterized by, that the converter control unit (270) is designed to cyclically apply a voltage and / or a current to the primary windings (220, 225, 230). [4] Energy supply device (120) according to any one of the preceding claims, characterized by , that the converter control unit (270) is designed to activate the individual primary windings (220, 225, 230) in interval sections (400) of substantially equal length, wherein the interval sections (400) assigned to the individual primary windings (220, 225, 230) do not overlap in time. [5] Energy supply device (120) according to claim 4, characterized by, that the converter control unit (270) is configured to control an active time period (500) in each of the interval sections (400) in which the relevant primary winding (220, 225, 230) is supplied with a voltage and / or a current and to control an inactive time period (510) in which the relevant primary winding (220, 225, 230) is not supplied with a voltage and / or a current. [6] Energy supply device (120) according to claim 5, characterized by , that the converter control unit (270) is designed to make the active time periods (500) of interval periods (400) assigned to different primary windings (220, 225, 230) of different lengths and / or to make the inactive time periods (510) of interval periods (400) assigned to different primary windings (220, 225, 230) of different lengths. [7] Energy supply device (120) according to one of the preceding claims, characterized by at least one further secondary winding (245, 250) coupled to the transformer core (210). [8] Energy supply device (120) according to any one of the preceding claims, characterized by , that the converter control unit (270) is configured to operate the flyback converter unit (200) in a DCM mode and / or in a gap operation, in particular wherein the converter control unit (270) is configured to operate the flyback converter unit (200) in each of the interval sections (400) in the DCM mode and / or in a gap operation. [9] Power converter (108), in particular inverter, with a power supply device (120) according to one of the preceding claims. [10] Electric axle drive (102) for a motor vehicle (100) comprising at least one electric machine, a transmission device and a power converter, characterized bythat the power converter is designed according to claim 10. [11] Motor vehicle (100) comprising an electric axle drive (102) according to claim 10 and / or a power converter according to claim 9 and / or a power supply device (120) according to any one of claims 1 to 8. [12] Method (600) for operating a power supply device (120) according to any one of claims 1 to 8 for an inverter (108) for a motor vehicle (100), wherein the method (600) comprises the following steps: - Applying (610) a voltage and / or current to a first of the primary windings (220) at a first time; and - Outputting (620) a voltage and / or current to a second of the primary windings (225, 230) at a second time different from the first, wherein at the second time no voltage and / or current is applied to the first primary winding (220). [13] Control unit (270, 700) configured to perform and / or control the steps (610, 620) of the method (600) according to claim 12 in corresponding units (710, 720). [14] Computer program configured to execute and / or control the steps (610, 620) of the method (600) according to claim 12. [15] Machine-readable storage medium on which the computer program according to claim 14 is stored.

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