Circuit arrangement for providing a DC voltage in a vehicle and method of operating a circuit arrangement

Abstract

A circuit arrangement for providing a DC voltage in a vehicle and a method for operating the circuit arrangement. The circuit arrangement includes at least one secondary-sided inductance of a vehicle-sided pick-up portion for receiving a magnetic field and for producing an electric output voltage, at least one rectifier for rectifying the output voltage of the at least one inductance, and at least one source element or drain element. The rectifier and the source element are connected such that an output voltage of the circuit arrangement is a sum of an output voltage of the rectifier and an output voltage of the source element or the rectifier and the drain element are connected such that an output voltage of the circuit arrangement is a difference between an output voltage of the rectifier and an input voltage of the drain element.

Claims

1. A circuit arrangement for providing a DC voltage in a vehicle, wherein the circuit arrangement comprises at least one secondary-sided inductance of a vehicle-sided pick-up portion for receiving a magnetic field and for producing an electric output voltage, at least one rectifier for rectifying the output voltage of the at least one inductance, and at least one source element or drain element, wherein the rectifier and the source element are connected such that an output voltage of the circuit arrangement is a sum of an output voltage of the rectifier and an output voltage of the source element or the rectifier and the drain element are connected such that an output voltage of the circuit arrangement is a difference between an output voltage of the rectifier and an input voltage of the drain element, wherein the source element or the drain element are provided by a voltage converter, wherein the voltage converter transforms a direct current input voltage with a given level to a direct current output voltage with a desired level, wherein an output voltage of the circuit arrangement is equal to an input voltage of the source element or an output voltage of the drain element.

2. The arrangement of claim 1, wherein the output voltage of the rectifier is equal to an input voltage of the source element or an output voltage of the drain element.

3. The arrangement of claim 1, wherein an output of the rectifier is connected in series to an output of the source element or an input of the drain element.

4. The arrangement of claim 1, wherein a configuration of the voltage converter is chosen depending on a ratio of a desired output voltage of the circuit arrangement and the output voltage of the rectifier.

5. The arrangement of claim 1, wherein the voltage converter is designed as a bidirectional converter which is being operable as a buck-boost-converter.

6. The arrangement of claim 1, wherein the arrangement further comprises a traction battery, wherein the traction battery is connected to a voltage output of the circuit arrangement.

7. A vehicle comprising the circuit arrangement according to claim 1, wherein electric voltage produced by magnetic induction can be transformed by the circuit arrangement such that a desired DC voltage is provided.

8. A method of operating an electric circuit arrangement, wherein: at least one secondary-sided inductance of a pick-up portion receives a magnetic field and produces an output voltage, at least one rectifier rectifies the output voltage of the at least one secondary-sided inductance, wherein at least one source element is operated such that a sum of an output voltage of the rectifier and an output voltage of the source element is regulated according to desired parameters or at least one drain element is operated such that a difference between an output voltage of the rectifier and an input voltage of the drain element is regulated according to desired parameters, wherein the source element or the drain element are provided by a voltage converter, wherein the voltage converter transforms a direct current input voltage with a given level to a direct current output voltage with a desired level, wherein an output voltage of the circuit arrangement is equal to an input voltage of the source element or an output voltage of the drain element.

9. The method of claim 8, wherein: at least one voltage converter converts an input voltage of the voltage converter, and the voltage converter is operated such that a sum of an output voltage of the rectifier and an output voltage of the voltage converter is regulated according to desired parameters or the voltage converter is operated such that a difference between an output voltage of the rectifier and an input voltage of the voltage converter is regulated according to desired parameters.

10. The method of claim 8, wherein the source element or the drain element are operated such that the output voltage of the circuit arrangement is regulated to a desired voltage level.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Examples of the invention will be described with references to the attached figures. The figures show:

(2) FIG. 1 a schematic block diagram of a circuit arrangement for charging a traction battery according to the state of the art,

(3) FIG. 2a a schematic block diagram of a first circuit arrangement according to the invention,

(4) FIG. 2b a schematic block diagram of another circuit arrangement according to the invention,

(5) FIG. 3 a schematic block diagram of a resonant converter,

(6) FIG. 4 a schematic block diagram of a circuit arrangement using a step-down converter,

(7) FIG. 5a a schematic operational diagram of the circuit arrangement shown in FIG. 2a with the voltage converter being operated in a source mode,

(8) FIG. 5b a schematic operational diagram of the circuit arrangement shown in FIG. 2a with the voltage converter being operated in a drain mode,

(9) FIG. 6a a schematic operational diagram of the circuit arrangement shown in FIG. 2b with the voltage converter being operated in a source mode,

(10) FIG. 6b a schematic operational diagram of the circuit arrangement shown in FIG. 2b with the voltage converter being operated in a drain mode,

(11) FIG. 7 a schematic block diagram of a charging circuit arrangement,

(12) FIG. 8 a schematic block diagram of a first step-down converter with galvanic separation,

(13) FIG. 9 a schematic block diagram of a second step-down converter with galvanic separation,

(14) FIG. 10 a schematic block diagram of a third step-down converter with galvanic separation,

(15) FIG. 11 a schematic block diagram of a fourth step-down converter with galvanic separation, and

(16) FIG. 12 a schematic block diagram of a universal converter with galvanic separation.

DETAILED DESCRIPTION OF THE INVENTION

(17) FIG. 1 shows a schematic block diagram of a circuit arrangement for charging a traction battery 1 of an electric vehicle. The circuit arrangement comprises a secondary-sided inductance 2 of a pick-up portion (not shown). The secondary-sided inductance 2 receives a magnetic field and produces an electric output voltage which is an alternating voltage. Furthermore, the circuit arrangement comprises a rectifier 3 for rectifying the output voltage of the inductance 2. Also, the circuit arrangement comprises a voltage converter 4 which transforms the direct or constant output voltage of the rectifier 3 at a given voltage level to a direct or constant voltage with a desired level which is consequently used to charge the battery 1. Therefore, a battery voltage U.sub.bat is equal to an output voltage of the voltage converter 4.

(18) FIG. 2a shows a schematic block diagram of a first circuit arrangement according to the invention. The circuit arrangement comprises a traction battery 1, a secondary-sided inductance 2 which can e.g. be provided by a winding structure, a rectifier 3, and voltage converter 4. An output voltage of the rectifier 3 is denoted by U.sub.1 and falls across a first output terminal 3a and a second output terminal 3b of the rectifier 3. The output voltage U.sub.1 of the rectifier 3 is a voltage generated by the rectifier by rectifying an alternating input voltage provided by the inductance 2 during inductive power transfer.

(19) If the converter 4 is operated in source mode, e.g. provides a source element, an output voltage of the converter 4 is denoted by U.sub.out and falls across a first terminal 4a and a second terminal 4b of the converter 4. The output voltage U.sub.out is directed from the first terminal 4a to the second terminal 4b. In this case, the first terminal 4a and the second terminal are output terminals of the converter 4. If the converter 4 is operated in drain mode, e.g. provides a drain element, an input voltage of the converter 4 is denoted by U.sub.in and falls across the first terminal 4a and the second terminal 4b of the converter 4. The input voltage U.sub.out is directed from the second terminal 4b to the first terminal 4a. In this case, the first terminal 4a and the second terminal are input terminals of the converter 4.

(20) A battery voltage U.sub.bat which serves for charging the battery 1 is equal to the sum of the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.out of the converter 4 if the converter 4 is operated in the source mode. Alternatively, the battery voltage U.sub.bat is equal to the difference between the output voltage U.sub.1 of the rectifier 3 and the input voltage U.sub.in of the converter 4 if the converter 4 is operated in the drain mode. It is shown that the first output terminal 3a of the rectifier 3 is connected to a third terminal 4c of the converter 4. Also, the second output terminal 3b of the rectifier 3 is connected to a fourth terminal 4d of the converter 4. If the converter 4 is operated in a source mode, the terminals 4c, 4d are input terminals of the converter 4. In this case, the output voltage U.sub.1 of the rectifier 3 is an input voltage of the converter 4. If the converter 4 is operated in a drain mode, the terminals 4c, 4d are output terminals of the converter 4. In this case, the output voltage U.sub.1 of the rectifier 3 is equal to an output voltage of the converter 4. The first output terminal 3a of the rectifier 3 is also connected to a positive input terminal 1a of the traction battery 1. A negative input terminal 1b of the traction battery 1 is connected to the second terminal 4b of the converter 4. The battery voltage U.sub.bat falls across the terminals 1a, 1b of the traction battery 1 and is directed from the positive input terminal 1a to the negative input terminal 1b of the traction battery 1.

(21) FIG. 2b shows a schematic block diagram of another circuit arrangement according to the invention. In contrast to the circuit arrangement shown in FIG. 2a, the second output terminal 3b of the rectifier 3 is connected to the first terminal 4a of the converter 4. The second terminal 4b of the converter 4, the fourth terminal 4d of the converter 4 and the negative input terminal 1b of the battery 1 are connected to a common potential, e.g. a ground level. If the converter 4 is operated in a source mode, the terminals 4c, 4d are input terminals of the converter 4. In this case, the output voltage of the circuit arrangement, e.g. the battery voltage U.sub.bat, is an input voltage of the converter 4. If the converter 4 is operated in a drain mode, the terminals 4c, 4d are output terminals of the converter 4. In this case, the output voltage of the circuit arrangement, e.g. the battery voltage U.sub.bat, is equal to an output voltage of the converter 4.

(22) The rectifier 3 can be an arbitrary rectifier known from the state of the art, e.g. a diode rectifier, a two-phase bridge rectifier or another rectifier.

(23) In FIG. 2a and in FIG. 2b, a two-phase connection between the inductance 2 and the rectifier 3 is shown. It is to be understood that this does not constrain the scope of the invention. The inductance 2 and the rectifier 3 can also be connected by a three-phase connection e.g. if the inductance 2 generates a three-phase output voltage.

(24) FIG. 3 shows a schematic block diagram of a resonance converter 5 which can be used as the converter 4 shown in FIGS. 2a, 2b. The resonant converter 5 comprises an inverter 6 for producing an intermediate alternating voltage from a constant input voltage which falls across a first input terminal 5c and a second input terminal 5d of the resonant converter 5. Furthermore, the resonant converter 5 comprises a transformer 7 which transforms the intermediate voltage at a given voltage level or at a given voltage amplitude to a transformed intermediate voltage with a desired voltage level or desired voltage amplitude. Furthermore, the resonant converter 5 comprises a rectifier 8 to rectify the transformed intermediate alternating voltage and to provide a constant output voltage which falls across a first output voltage terminal 5a of the resonant converter 5 and a second output terminal 5b of the resonant converter 5.

(25) In FIG. 4 a schematic block diagram of a circuit arrangement using a step-down converter 9 is shown. It is shown that the step-down converter 9 comprises a switch 10, a diode 11, an inductance 12 and a capacitance 13, which are connected in a known manner. A third terminal 9c of the step-down converter 9 is connected to a first output terminal 3a of the rectifier 3. A first terminal 9a of the step-down converter 9 is connected to a second output terminal 3b of the rectifier 3. A positive input terminal 1a of the traction battery 1 is connected to the first output terminal 3a of the rectifier 3. A fourth terminal 9d of the step-down converter 9 is connected to ground. A second terminal 9b of the step-down converter 9 is connected to a negative input terminal 1b of the traction battery 1. A battery voltage U.sub.bat in this case is equal to a sum of the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.out of the step-down converter 9 if the step-down converter 9 is operated in a source mode.

(26) In FIG. 5a, a schematic operational diagram of the circuit arrangement shown in FIG. 2a with the voltage converter 4 being operated in a source mode is shown. It is shown that the first output terminal 3a of the rectifier 3 provides a higher potential than the second output terminal 3b of the rectifier 3. Therefore, the output voltage U.sub.1 of the rectifier 3 is directed from the first output terminal 3a to the second output terminal 3b. In the source mode, a potential of the first terminal 4a is higher than a potential of the second terminal 4b. Therefore, the output voltage U.sub.out of the converter 4 is directed from the first terminal 4a to the second terminal 4b. An energy flow E is symbolized by an arrow 62. It is directed from an input side of the converter 4 to an output side of the converter 4. The input side is provided by the third and fourth terminal 4c, 4d of the converter 4 which are, in the source mode, input terminals. The output side is provided by the first and second terminal 4a, 4b of the converter 4 which are, in the source mode, output terminals. In FIG. 5a, the battery voltage U.sub.bat is equal to the sum of the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.out of the converter 4.

(27) FIG. 5b shows a schematic operational diagram of the circuit arrangement shown in FIG. 2a with the voltage converter 4 being operated in a drain mode. In the drain mode, a potential of the second terminal 4b is higher than a potential of the first terminal 4a. Therefore, the input voltage U.sub.in of the converter 4 is directed from the second terminal 4b to the first terminal 4a. An energy flow E is symbolized by an arrow 62. It is directed from an input side of the converter 4 to an output side of the converter 4. The input side is now provided by the first and second terminal 4a, 4b of the converter 4 which are, in the drain mode, input terminals. The output side is provided by the third and fourth terminal 4c, 4d of the converter 4 which are, in the drain mode, output terminals. In FIG. 5b, the battery voltage U.sub.bat is equal to the difference between the output voltage U.sub.1 of the rectifier 3 and the input voltage U.sub.in of the converter 4.

(28) For the circuit arrangement shown in FIG. 5a and FIG. 5b, a configuration of the converter 4 can be chosen depending on a ratio of a desired output voltage of the circuit arrangement, e.g. the battery voltage U.sub.bat, and the output voltage U.sub.1 of the rectifier 3.

(29) If, with reference to FIG. 5a, for all operational states of the circuit arrangement, e.g. for all possible output voltages U.sub.1 of the rectifier 3, the desired output voltage of the circuit arrangement is higher than the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.1 of the rectifier 3 is higher than or equal to a half of the desired output voltage of the circuit arrangement, the converter configuration has to be chosen such that the converter 4 is operable as a step-down converter. If, for all operational states of the circuit arrangement, the desired output voltage of the circuit arrangement is higher than the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.1 of the rectifier 3 is lower than a half of the desired output voltage of the circuit arrangement, the converter configuration has to be chosen such that the converter 4 is operable as a step-up converter. If, for all operational states of the circuit arrangement, the desired output voltage of the circuit arrangement is higher than the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.1 of the rectifier 3 fluctuates between values being higher than a half of the desired output voltage of the circuit arrangement and values being lower than a half of the desired output voltage of the circuit arrangement, the converter configuration has to be chosen such that the converter 4 is operable as both, a step-down converter or a step-up converter.

(30) If, with reference to FIG. 5b, for all operational states of the circuit arrangement, the desired output voltage of the circuit arrangement is lower than the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.1 of the rectifier 3 is lower than two times the desired output voltage of the circuit arrangement, the converter configuration has to be chosen such that the converter 4 is operable as a step-down converter.

(31) If, for all operational states of the circuit arrangement, the desired output voltage of the circuit arrangement is lower than the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.1 of the rectifier is equal to or higher than two times the desired output voltage of the circuit arrangement, the converter configuration has to be chosen such that the converter 4 is operable as a step-up converter.

(32) If, for all operational states of the circuit arrangement, the desired output voltage of the circuit arrangement is lower than the output voltage U.sub.1 of the rectifier 3 and the desired output voltage of the circuit arrangement fluctuates between values being higher than two times the desired output voltage of the circuit arrangement and values being lower than a two times the desired output voltage of the circuit arrangement, the converter configuration has to be chosen such that the converter 4 is operable as both, a step-down converter or a step-up converter.

(33) It is to be denoted that the resonant converter 5 shown in FIG. 3 can be operated as a step-down or step-up converter. Preferably, the converter 4 is designed as a bidirectional buck-boost converter 4 which can be used in all of the previously described scenarios as well as in scenarios wherein the output voltage U.sub.1 of the rectifier 3 fluctuates between values being higher than the desired output values of the circuit arrangement and values being lower than the desired output values of the circuit arrangement. The bidirectional converter 4 allows an energy E flowing in the directions shown in FIG. 5a and FIG. 5b (see arrows 62).

(34) FIG. 6a shows a schematic operational diagram of the circuit arrangement shown in FIG. 2b with the voltage converter 4 being operated in a source mode. It is shown that the first output terminal 3a of the rectifier 3 provides a higher potential than the second output terminal 3b of the rectifier 3. Therefore, the output voltage U.sub.1 of the rectifier 3 is directed from the first output terminal 3a to the second output terminal 3b. In the source mode, a potential of the first terminal 4a is higher than a potential of the second terminal 4b. Therefore, the output voltage U.sub.out of the converter 4 is directed from the first terminal 4a to the second terminal 4b. An energy flow E is symbolized by an arrow 62. It is directed from an input side of the converter 4 to an output side of the converter 4. The input side is provided by the third and fourth terminal 4c, 4d of the converter 4 which are, in the source mode, input terminals. The output side is provided by the first and second terminal 4a, 4b of the converter 4 which are, in the source mode, output terminals.

(35) FIG. 6b shows a schematic operational diagram of the circuit arrangement shown in FIG. 2b with the voltage converter 4 being operated in a drain mode. In the drain mode, a potential of the second terminal 4b is higher than a potential of the first terminal 4a. Therefore, the input voltage U.sub.in of the converter 4 is directed from the second terminal 4b to the first terminal 4a. An energy flow E is symbolized by an arrow 62. It is directed from an input side of the converter 4 to an output side of the converter 4. The input side is now provided by the first and second terminal 4a, 4b of the converter 4 which are, in the drain mode, input terminals. The output side is provided by the third and fourth terminal 4c, 4d of the converter 4 which are, in the drain mode, output terminals.

(36) According to the statements concerning FIG. 5a and FIG. 5b, a configuration of the converter 4 in the circuit arrangement shown in FIGS. 6a, 6b can be chosen depending on a ratio of a desired output voltage of the circuit arrangement, e.g. the battery voltage U.sub.bat, and the output voltage U.sub.1 of the rectifier 3. The input voltage of the converter 4 in the source mode is, in contrast to FIG. 5a, equal to the desired output voltage of the circuit arrangement, e.g. the battery voltage U.sub.bat. The output voltage of the converter 4 in the drain mode is, in contrast to FIG. 5b, equal to the desired output voltage of the circuit arrangement, e.g. the battery voltage U.sub.bat. This has to be considered when choosing the configuration of the converter 4.

(37) FIG. 7 shows a schematic block diagram of a charging circuit arrangement for a battery 20. The charging circuit arrangement comprises input terminals 21 for receiving an alternating input voltage. Furthermore, the charging circuit arrangement comprises a rectifier 3 and a voltage converter 4. The voltage converter 4 and the rectifier 3 are connected such that a battery voltage U.sub.bat is equal to a sum of the output voltage U.sub.1 of the rectifier 3 and the output voltage U.sub.out of the voltage converter 4 if the converter 4 is operated in a source mode. If the voltage converter 4 is operated in a drain mode, the battery voltage U.sub.bat is equal to a difference between the output voltage U.sub.1 of the rectifier 3 and the input voltage U.sub.in of the voltage converter 4. The rectifier 3 and the voltage converter 4 can be designed as disclosed with reference to FIG. 2a to FIG. 6b.

(38) FIG. 8 shows a schematic block diagram of a first step-down converter 22 with galvanic separation which can be used instead of the step-down converter 9 shown in FIG. 4. The step-down converter 22 is also known as forward converter. On the primary side, the step-down converter 22 comprises an input capacitance 23, a primary winding 24, and a switching element 25, wherein a series connection of the primary winding 24 and the switching element 25 is connected in parallel to the input capacitance 23. The switching element 25 can be a transistor. Additionally, the primary side comprises a demagnetization winding 26 and a diode 27, wherein a series connection of the demagnetization winding 26 and the diode 27 is connected in parallel to the input capacitance 23. The secondary side comprises a secondary winding 28 and a secondary rectifier comprising diodes 29, 30. Furthermore, the secondary side comprises an inductance 31 and an output capacitance 32.

(39) FIG. 9 shows a schematic block diagram of a second step-down converter 33 with galvanic separation which can be used instead of the step-down converter 9 shown in FIG. 4. The step-down converter 33 is also known as push-pull converter with a parallel power supply. On the primary side, the step-down converter 33 comprises an input capacitance 23, a primary winding, and switching elements 34, 35, wherein a circuit branch comprising the primary winding and the switching elements 34, 35 is connected in parallel to the input capacitance 23. The primary winding comprises a first winding element 36 and a second winding element 37 wherein a connection point of the winding elements 36, 37 is connected to the input capacitance 23 and the remaining terminals of the winding elements 36, 37 are connected to the switching elements 34, 35 respectively. The secondary side comprises a secondary winding 38 and a secondary rectifier comprising diodes 39, 40, 41, 42. Furthermore, the secondary side comprises an inductance 31 and an output capacitance 32.

(40) FIG. 10 shows a schematic block diagram of a third step-down converter 43 with galvanic separation which can be used instead of the step-down converter 9 shown in FIG. 4. The step-down converter 43 is also known as push-pull converter with a half-bridge control. On the primary side, the step-down converter 43 comprises input capacitances 23, input resistances 44, a primary winding 45, and switching elements 46, 47. A series connection of the input resistances 44 is connected in parallel to a series connection of the input capacitances 23 and a series connection of the switching elements 46, 47. One terminal of the primary winding 45 is connected to a connection point of the switching elements 46, 47, wherein another terminal of the primary winding 45 is connected to a connection point of the input capacitances 23 and a connection point of the input resistances 44. The secondary side of the step-down converter 43 equals the secondary side of the step-down converter 33 shown in FIG. 9.

(41) FIG. 11 shows a schematic block diagram of a fourth step-down converter 48 with galvanic separation which can be used instead of the step-down converter 9 shown in FIG. 4. The step-down converter 48 is also known as push-pull converter with a full-bridge control. On the primary side, the step-down converter 48 comprises an input capacitance 23, a primary winding 49, and switching elements 50, 51, 52, 53. A series connection of two switching elements 50, 51 is connected in parallel to a series connection of the other two switching elements 52, 53 and to the input capacitance 23. One terminal of the primary winding 49 is connected to a connection point of the switching elements 50, 51, wherein another terminal of the primary winding 49 is connected to a connection point of the other switching elements 52, 53. The secondary side of the step-down converter 43 equals the secondary side of the step-down converter 33 shown in FIG. 9.

(42) FIG. 12 shows a schematic block diagram of a universal converter 54 with galvanic separation. On a primary side, the universal converter 54 a first leg 55 which comprises a first switching element T11 and a second switching element T12, which are connected in series. Diodes D11, D12 are connected antiparallel to each switching element T11, T12. Correspondingly, the universal converter 54 comprises a second leg 56 which comprises a first switching element T13 and a second switching element T14, which are connected in series. Diodes D13, D14 are connected antiparallel to each switching element T13, T14. Correspondingly, the universal converter 54 comprises a third leg 57 which comprises a first switching element T15 and a second switching element T16, which are connected in series. Diodes D15, D16 are connected antiparallel to each switching element T15, T16. All legs 55, 56, 57 of the primary side are connected in parallel. Also, all legs 55, 56, 57 of the primary side are connected in parallel to connecting terminals 58c, 58d of the primary side of the universal converter 54.

(43) On a secondary side, the universal converter 54 comprises a first leg 59 which comprises a first switching element T21 and a second switching element T22, which are connected in series. Diodes D21, D22 are connected antiparallel to each switching element T21, T22. Correspondingly, the universal converter 54 comprises a second leg 60 on the secondary side which comprises a first switching element T23 and a second switching element T24, which are connected in series. Diodes D23, D24 are connected antiparallel to each switching element T23, T24. Correspondingly, the universal converter 54 comprises a third leg 61 on the secondary side which comprises a first switching element T25 and a second switching element T26, which are connected in series. Diodes D25, D26 are connected antiparallel to each switching element T25, T26. All legs 59, 60, 61 of the secondary side are connected in parallel. Also, all legs 59, 60, 61 of the secondary side are connected in parallel to connecting terminals 58a, 58b of the secondary side of the universal converter 54.

(44) The switching elements T11, . . . , T26 are designed as switching elements T11, . . . , T26 with a predetermined conducting direction. Antiparallel in this context means that the conduction direction of the diodes D11, . . . , D26 is oriented antiparallel to the conducting direction of the switching elements T11, . . . , T26.

(45) Furthermore, the universal converter 54 comprises a first winding structure N11 and a second winding structure N12 on the primary side. The first winding structure N11 is electrically arranged between a connecting point of the first switching element T11 and the second switching element T12 of the first leg 55 of the primary side and a connecting point of the first switching element T13 and the second switching element T14 of the second leg 56 of the primary side. Correspondingly, the second winding structure N12 is electrically arranged between a connecting point of the second switching element T13 and the second switching element T14 of the second leg 56 of the primary side and a connecting point of the first switching element T15 and the second switching element T16 of the third leg 57 of the primary side.

(46) Furthermore, the universal converter comprises a first winding structure N21 and a second winding structure N22 on the secondary side. The first winding structure N21 is electrically arranged between a connecting point of the first switching element T21 and the second switching element T22 of the first leg 59 of the secondary side and a connecting point of the first switching element T23 and the second switching element T24 of the second leg 60 of the secondary side. Correspondingly, the second winding structure N22 is electrically arranged between a connecting point of the second switching element T23 and the second switching element T24 of the second leg 60 of the secondary side and a connecting point of the first switching element T25 and the second switching element T26 of the third leg 61 of the secondary side.

(47) It is important that the number of turns of all winding structures N11, N12, N21, N22 is equal.

(48) The shown universal converter 54 is capable of transferring energy from the primary side to the secondary side and vice versa. An energy flow E (see arrow 62) can therefore be directed in both directions. Also or simultaneously, the universal converter can be operated as a step-down converter or step-up converter. This means that a voltage U.sub.fs which falls across the terminals 58c, 58d of the universal converter 54 can be converted to a higher or lower voltage U.sub.ss which falls across the terminals 58a, 58b of the universal converter 54. Also, a voltage U.sub.ss which falls across the terminals 58a, 58b of the universal converter 54 can be converted to a higher or lower voltage U.sub.fs which falls across the terminals 58c, 58d of the universal converter 54.

(49) If the universal converter 54 is operated as a step-up converter which converts the voltage U.sub.fs falling across the terminals 58c, 58d of the primary side to a higher voltage U.sub.ss falling across the terminals 58a, 58b of the secondary side and an energy flow E is directed from the primary side to the secondary side, the switching elements T11, T12, T13, T14 of the first and second leg 55, 56 of the primary side are operated whereas the switching elements T15, T16 of the third leg 57 of the primary side are inactive. In this case, the switching elements T11, T12, T13, T14 of the first and second leg 55, 56 of the primary side are operated as a full-bridge inverter. In this case, a voltage ratio of U.sub.fs/U.sub.ss=1:2 can be achieved.

(50) If the universal converter 54 is operated as a step-up converter which converts the voltage U.sub.ss falling across the terminals 58a, 58b of the secondary side to a higher voltage U.sub.fs falling across the terminals 58c, 58d of the primary side and an energy flow E is directed from the secondary side to the primary side, the switching elements T21, T22, T23, T24 of the first and second leg 59, 60 of the secondary side are operated whereas the switching elements T25, T26 of the third leg 61 of the secondary side are inactive. In this case, the switching elements T21, T22, T23, T24 of the first and second leg 59, 60 of the secondary side are operated as a full-bridge inverter. In this case, a voltage ratio of U.sub.fs/U.sub.ss=2:1 can be achieved.

(51) If the universal converter 54 is operated as a step-down converter which converts the voltage U.sub.fs falling across the terminals 58c, 58d of the primary side to a lower voltage U.sub.ss falling across the terminals 58a, 58b of the secondary side and an energy flow E is directed from the primary side to the secondary side, the switching elements T11, T12, T15, T16 of the first and third leg 55, 57 of the primary side are operated whereas the switching elements T13, T14 of the second leg 56 of the primary side are inactive. In this case, the switching elements T11, T12, T15, T16 of the first and third leg 55, 57 of the primary side are operated as a full-bridge inverter. In this case, a voltage ratio of U.sub.fs/U.sub.ss=2:1 can be achieved.

(52) If the universal converter 54 is operated as a step-down converter which converts the voltage U.sub.ss falling across the terminals 58a, 58b of the secondary side to a lower voltage U.sub.fs falling across the terminals 58c, 58d of the primary side and an energy flow E is directed from the secondary side to the primary side, the switching elements T21, T22, T25, T26 of the first and third leg 59, 61 of the secondary side are operated whereas the switching elements T23, T24 of the second leg 60 of the secondary side are inactive. In this case, the switching elements T21, T22, T25, T26 of the first and third leg 59, 61 of the secondary side are operated as a full-bridge inverter. In this case, a voltage ratio of U.sub.fs/U.sub.ss=1:2 can be achieved.

(53) According to a desired operating mode, different switching elements T11, . . . T16, T21, . . . , T26 of the universal converter 54 are operated, e.g. clocked. The shown universal converter 54 can be used as the voltage converter 4 shown in FIG. 2a or FIG. 2b. In this case, the terminals 58c, 58d of the universal converter 54 correspond to terminals 4c, 4d of the voltage converter 4 and the terminals 58a, 58b of the universal converter 54 correspond to terminals 4a, 4b of the voltage converter 4 shown in FIG. 2a or FIG. 2b.

(54) It is to be noted that the shown universal converter 54 and the previously described methods of operating the universal converter 54 can be subject of an independent invention.