DE102021005981A1 - Transformer head for contactless absorption of energy, system for contactless transmission of energy and operating method - Google Patents

Abstract

The invention relates to a pick-up (50) for receiving energy without contact, comprising at least one secondary winding (L2), at least one secondary capacitor (C2) which can be connected in series with the secondary winding (L2), and a rectifier circuit (60) which on the input side can be connected in series with the secondary capacitor (C2) and with the secondary winding (L2), a switching device (70) being connected in parallel with the secondary capacitor (C2), by means of which the secondary capacitor (C2) can be short-circuited, and the rectifier circuit (60) has a first switching unit (V1), a second switching unit (V2), a third switching unit (V3) and a fourth switching unit (V4), wherein the switching units (V1, V2, V3, V4) each have a parallel circuit consisting of a controllable switch (S1 , S2, S3, S4) and a diode (D1, D2, D3, D4). The invention also relates to a system for contactless transmission of energy, comprising at least one pick-up (50) according to the invention and an energy source (40), which has a current source (42) and a primary conductor (L1), the at least one secondary winding (L2) and the primary conductor (L1) are inductively coupled. The invention also relates to a method for operating a system according to the invention.

Description

The invention relates to a pick-up for the contactless acquisition of energy, which comprises at least one secondary winding, at least one secondary capacitor which can be connected in series with the secondary winding, and a rectifier circuit which can be connected in series with the secondary capacitor and with the secondary winding on the input side. The invention also relates to a system for contactless transmission of energy, which comprises at least one pick-up according to the invention, and a method for operating a system according to the invention.

Inductive charging systems are known for supplying mobile consumers with electrical energy. Inductive charging systems allow contactless energy transfer to mobile consumers. The mobile consumers are, in particular, autonomously driving vehicles that have a chargeable battery for storing electrical energy.

From the DE 10 2004 055 154 B4 a system for contactless energy transfer is known. The system includes a power source connected to an elongate primary conductor. A mobile consumer, which can be moved along the primary conductor, has a pick-up. The pick-up has a winding which is inductively coupled to the primary conductor. This inductive coupling means that energy can be transmitted from the primary conductor to the consumer's pick-up.

the DE 10 2010 050 935 B4 discloses a device for contactless energy transfer to a vehicle. In this case, energy is transmitted inductively from a stationary coil arrangement with a coil winding to a secondary winding provided in the vehicle.

From the EP 2 223 408 B1 a system for contactless energy transmission and an associated operating method are known. The system has a plurality of secondary windings and a plurality of secondary capacitors which are connected in series to form a series resonant circuit. The secondary windings are inductively coupled to a stationary primary conductor. The system also has a rectifier circuit which is connected to the series resonant circuit on the input side.

From the DE 10 2015 210 825 A1 a transformer arrangement is known which has a primary circuit, a secondary circuit and a rectifier. An impedance of the rectifier can be set using a control device.

From the JP 2012-19603 A a non-contact transmitter is known which has a coil with a core and a rectifier circuit.

From the DE 10 2010 022 143 A1 an arrangement for inductive energy transmission to an electrical load is known. The arrangement includes a primary conductor, a secondary winding and several capacitances.

The invention is based on the object of further developing a pick-up for the contactless absorption of energy, a system for the contactless transmission of energy and an associated operating method.

The object is achieved according to the invention by a pick-up for contactless absorption of energy with the features specified in claim 1. Advantageous refinements and developments are the subject of the dependent claims. The object is also achieved by a system for contactless transmission of energy with the features specified in claim 6. Advantageous refinements and developments are the subject of the dependent claims. The object is also achieved by a method for operating a system according to the invention with the features specified in claim 7 . Advantageous refinements and developments are the subject of the dependent claims.

A pick-up according to the invention for contactless absorption of energy comprises at least one secondary winding, at least one secondary capacitor which can be connected in series with the secondary winding, and a rectifier circuit which can be connected in series with the secondary capacitor and with the secondary winding on the input side. In this case, a switching device is connected in parallel to the secondary capacitor, by means of which the secondary capacitor can be short-circuited. The rectifier circuit has a first switching unit, a second switching unit, a third switching unit and a fourth switching unit, the switching units each comprising a parallel circuit made up of a controllable switch and a diode.

When the switching device is open, the secondary capacitor and the secondary winding form an oscillating circuit. Depending on the activation of the switching device and the switch, a pick-up according to the invention can be operated in several operating states to supply a downstream load. At the Ver need it is, for example, a resistive load, a drive converter or a rechargeable battery. An output current supplied by the rectifier circuit on the output side can be predetermined by selecting a suitable operating state.

The rectifier circuit can be operated passively. In passive operation of the rectifier circuit, the controllable switches are open and the rectifier circuit acts like a B4 bridge rectifier. Positive half cycles of the secondary current flow through the first diode and the fourth diode. Negative half waves of the secondary current flow through the second diode and the third diode. The rectifier circuit can also be operated synchronously. In synchronous operation of the rectifier circuit, the first switch and the fourth switch are closed for positive half-waves of the secondary current, and the second switch and the third switch are opened. In the case of negative half-cycles of the secondary current, the second switch and the third switch are closed, and the first switch and the fourth switch are opened. Positive half cycles of the secondary current flow through the first switch and the fourth switch. Negative half cycles of the secondary current flow through the second switch and the third switch.

According to a preferred embodiment of the invention, when the switching device is open, the secondary winding, the secondary capacitor and the rectifier circuit form a series circuit. When the switching device is closed, the secondary winding and the rectifier circuit form a series circuit. The secondary capacitor is short-circuited when the switching device is closed.

According to an advantageous embodiment of the invention, the switching device has a first switching transistor and a second switching transistor, each of which includes a parallel connection of a controllable switching path and an inverse diode. In this case, the first switching transistor and the second switching transistor are connected in such a way that the first inverse diode and the second inverse diode are connected back-to-back in series. The switching device can be switched relatively quickly and with low losses by the switching transistors.

According to a preferred embodiment of the invention, the switching units are each in the form of MOSFETs, ie metal oxide semiconductor field effect transistors, each of said diodes representing a body diode of the respective switching unit. According to a preferred embodiment of the invention, the switching transistors are each designed as MOSFETs, with each of said inverse diodes representing a body diode of the respective switching unit. Metal oxide semiconductor field effect transistors can be switched relatively quickly and with low losses, while being inexpensive and reliable.

According to an advantageous development of the invention, the rectifier circuit is connected to a smoothing capacitor on the output side. As a result, an output current supplied by the rectifier circuit on the output side is smoothed and residual ripples are reduced.

A system according to the invention for the contactless transmission of energy comprises at least one pick-up according to the invention and an energy source, which has a current source and a primary conductor. The at least one secondary winding of the pick-up and the primary conductor of the energy source are inductively coupled. The secondary winding and the primary conductor form a transformer.

A system according to the invention can advantageously be used to supply electrical energy to a load connected downstream of the pick-up. The consumer is, for example, a resistive load, a drive converter or a chargeable battery. In this case, energy can be transmitted inductively from the energy source to the pick-up. The pick-up can be operated in a number of operating states, and an output current supplied on the output side can be predetermined by selecting a suitable operating state.

In a method according to the invention for operating a system according to the invention for contactless transmission of energy, the primary conductor is traversed by a primary current supplied by the power source and having a fundamental frequency and a fundamental period; a secondary current is thereby induced in the secondary winding. An output voltage drops on the output side of the rectifier circuit, and an output current is supplied by the rectifier circuit on the output side, in particular for supplying a consumer connected downstream of the pick-up.

The fundamental period is the reciprocal of the fundamental frequency. In this case, energy is transmitted inductively from the energy source to the pick-up, and a load connected downstream of the pick-up is supplied with electrical energy. The consumer is, for example, a resistive load, a drive converter or a chargeable battery.

According to an advantageous development of the invention, the system is operated in a first operating state. Here is the switching device closed. The rectifier circuit is operated passively or synchronously.

In the first operating state, a non-resonant operation of the system according to the invention takes place. The secondary capacitor is short-circuited. If an ohmic load with a constant resistance is connected as a consumer, the output voltage is constant. With variable resistance, the output voltage falls as the resistance decreases. The output voltage is maximum when idling. In the event of a short circuit, the current is limited by a leakage inductance of the transformer.

According to an advantageous development of the invention, the system is operated in a second operating state. In this case, the switching device is closed. In a first period of time, which is greater than or equal to the basic period, the second switch and the fourth switch are closed, and the first switch and the third switch are open. In a second time period, which is at least half the size of the basic period, the rectifier circuit is operated passively or synchronously.

The first time period is preferably equal to the basic period or equal to an integer multiple of the basic period. The second period of time is preferably equal to half the basic period or equal to an integral multiple of half the basic period.

In the second operating state, non-resonant operation of the system according to the invention takes place. The secondary capacitor is short-circuited. In the first time period, when the second switch and the fourth switch are closed, the rectifier circuit is short-circuited on the input side. In the second period, the leakage inductance of the transformer frees itself against the smoothing capacitor. If an ohmic load with a constant resistance is connected as a consumer, then the output voltage depends on the ratio of the second time period to the sum of the first time period and the second time period. The greater this ratio, the greater the output voltage. The output voltage is less than or equal to the output voltage in the first operating state. If the second period of time is infinitely long, the rectifier circuit is continuously operated passively or synchronously, as in the first operating state.

According to an advantageous development of the invention, the system is operated in a third operating state. In this case, the rectifier circuit is operated passively or synchronously. The switching device is closed in a first time period, which is greater than or equal to the basic period. In a second time period, which is at least half as long as the basic period, the switching device is open.

The first time period is preferably equal to the basic period or equal to an integer multiple of the basic period. The second period of time is preferably equal to half the basic period or equal to an integral multiple of half the basic period.

In the third operating state, the system according to the invention is operated in sections with resonant operation. If an ohmic load with a constant resistance is connected as a consumer, then the output voltage depends on the ratio of the second time period to the first time period. The greater this ratio, the greater the output voltage. The output voltage is greater than or equal to the output voltage in the first operating state. If the first period of time is infinitely long, the switching device is permanently closed, as in the first operating state.

According to an advantageous development of the invention, the system is operated in a fourth operating state. In this case, the switching device is open. The rectifier circuit is operated passively or synchronously.

In the fourth operating state, the system according to the invention is operated in full resonant mode. The output voltage is at least approximately constant and at least approximately independent of the resistance of an ohmic load that is connected as a consumer. The output voltage is greater than the output voltage in the first operating state.

The fourth operating state corresponds to the third operating state when the second period of time is infinite.

According to an advantageous development of the invention, the system is operated in a fifth operating state. In this case, the switching device is open. In a first period of time, which is greater than or equal to the basic period, the second switch and the fourth switch are closed, and the first switch and the third switch are open. In a second time period, which is at least half the size of the basic period, the rectifier circuit is operated passively or synchronously.

The first time period is preferably equal to the basic period or equal to an integer multiple of the basic period. The second period is preferably equal to half the basic period or equal to an integer multiple of half the basic period.

In the fifth operating state, there is fully resonant operation of the system according to the invention with amplification. The output voltage depends on the ratio of the sum of the first time period and the second time period to the second time period. In the first period, when the second switch and the fourth switch are closed, the rectifier circuit is short-circuited on the input side and the secondary winding and the secondary capacitor form a parallel resonant circuit with no load. The parallel resonant circuit oscillates, generating a high secondary current. In the second period, the energy contained in the parallel resonant circuit is largely discharged via the rectifier circuit into the smoothing capacitor and the connected load.

Regardless of the current operating state of the system, the switching device is preferably switched on at a point in time when a voltage present at the secondary capacitor has a zero crossing.

The invention is not limited to the combination of features of the claims. For the person skilled in the art, there are further meaningful combinations of claims and/or individual claim features and/or features of the description and/or the figures, in particular from the task and/or the task arising from comparison with the prior art.

• 1: eine schematische Darstellung eines Systems zur berührungslosen Energieübertragung.

The invention will now be explained in more detail with reference to figures. The invention is not limited to the exemplary embodiments shown in the figures. The figures represent the subject matter of the invention only schematically. It shows:

• 1 : a schematic representation of a system for contactless energy transmission.

1 shows a schematic representation of a system for contactless transmission of energy. The system comprises an energy source 40 and a pick-up 50. Within the system, energy can be transmitted from the energy source 40 to the pick-up 50 without contact. The pick-up 50 is connected to a consumer 80 by means of electrical lines and transmits electrical energy to the consumer 80 via said electrical lines.

The pick-up 50 is part of a mobile device. In the present case, the mobile device is an autonomously driving vehicle. The pick-up 50 is used for the contactless absorption of energy for the mobile device, in particular for the consumer 80. The consumer 80 is, for example, a resistive load, in particular a driver circuit for controlling a drive motor of the mobile device or a light source. In this case, the electrical energy transmitted by the pick-up 50 is consumed directly by the consumer 80 . For example, the load 80 is a chargeable battery. In this case, the electrical energy transmitted by the pick-up 50 is stored in the consumer 80 and later consumed by other components of the mobile device.

The energy source 40 includes a current source 42 and a primary conductor L1. The primary conductor L1 is in the form of a conductor loop and has a first inductance. The primary conductor L1 is laid, for example, in a floor on which the mobile device is moving. For example, the primary conductor L1 is also laid in a rail on which the mobile device moves. The mobile device moves on the floor, for example in a technical facility such as a production plant. The primary conductor L1 is laid close to the surface of the floor. The pick-up 50 of the mobile device is located in the immediate vicinity of the ground above the primary conductor L1 and can be moved in particular along the primary conductor L1.

The primary conductor L1 is electrically connected to the power source 42 and has a primary current I1 flowing through it, which the power source 42 supplies. The primary current 11 is a medium-frequency alternating current and in the present case has a fundamental frequency F0 of 50 kHz. A current intensity of the primary current 11 is presently 60 A. Other fundamental frequencies, for example from 25 kHz to 100 kHz, and other current intensities, for example from 30 A to 90 A, are also conceivable.

The mobile device pick-up 50 includes a secondary winding L2 and a secondary capacitor C2. The secondary winding L2 has a second inductance. The secondary capacitor C2 can be connected in series with the secondary winding L2. In this case, the secondary capacitor C2 and the secondary winding L2 form a series resonant circuit. The resonant frequency of this series resonant circuit corresponds to the fundamental frequency F0 of the primary current 11.

The pick-up 50 is arranged in such a way that the secondary winding L2 and the primary conductor L1 are inductively coupled via a magnetic coupling M. The secondary winding L2 and the In this case, the primary conductor L1 forms a transformer. Energy can thus be transmitted from the energy source 40 to the secondary winding L2 of the pick-up 50 and thus to the mobile device, in particular while the mobile device is traveling along the primary conductor L1. The magnetic coupling M of an open transformer is relatively weak due to the distance and geometry and typically has a coupling factor K of about 0.5 to 0.9.

The mobile device pick-up 50 includes a rectifier circuit 60. The rectifier circuit 60 has a first input 61 connected to the secondary capacitor C2 and a second input 62 connected to the secondary winding L2. In the illustration shown here, the rectifier circuit 60 is therefore connected in series on the input side with the secondary capacitor C2 and with the secondary winding L2, that is to say with the series resonant circuit.

The rectifier circuit 60 has a positive output 63 and a negative output 64 . An output voltage UA drops between the positive output 63 and the negative output 64 . The pick-up 50 has a smoothing capacitor CA connected between the positive 63 and negative 64 outputs.

The rectifier circuit 60 is thus connected on the output side to the smoothing capacitor CA, at which the output voltage UA is present.

The consumer 80 is also connected between the positive output 63 and the negative output 64 . The rectifier circuit 60 is thus connected on the output side to the consumer 80, to which the output voltage UA is also present. The rectifier circuit 60 supplies an output current IA on the output side. The output current IA is largely a direct current. The output current IA therefore flows almost exclusively through the consumer 80.

The rectifier circuit 60 has a first switching unit V1, a second switching unit V2, a third switching unit V3 and a fourth switching unit V4. The first switching unit V1 includes a parallel circuit made up of a controllable first switch S1 and a first diode D1. The second switching unit V2 includes a parallel circuit made up of a controllable second switch S2 and a second diode D2. The third switching unit V3 includes a parallel circuit made up of a controllable third switch S3 and a third diode D3. The fourth switching unit V4 includes a parallel circuit made up of a controllable fourth switch S4 and a fourth diode D4.

The first switching unit V1 is connected between the first input 61 and the positive output 63 . The second switching unit V2 is connected between the first input 61 and the negative output 64 . The third switching unit V3 is connected between the second input 62 and the positive output 63 . The fourth switching unit V4 is connected between the second input 62 and the negative output 64 . Said switching units V1, V2, V3, V4 are oriented in such a way that the associated diodes D1, D2, D3, D4 form a bridge rectifier between the inputs 61, 62 and the outputs 63, 64.

Said switching units V1, V2, V3, V4 are each designed as a metal oxide semiconductor field effect transistor, for example as a normally blocking n-channel MOSFET. Each of the said diodes D1, D2, D3, D4 represents a body diode of the respective switching unit V1, V2, V3, V4. However, it is also conceivable that the diodes D1, D2, D3, D4 than from the switches S1 , S2, S3, S4 separate switching elements are formed.

The mobile device transmitter head 50 includes a switching device 70. The switching device 70 is connected in parallel with the secondary capacitor C2. When the switching device 70 is opened, the secondary capacitor C2 and the secondary winding L2 form an oscillating circuit. When switching device 70 is closed, secondary capacitor C2 is shorted. The secondary capacitor C2 can thus be short-circuited by means of the switching device 70.

The switching device 70 has a first switching transistor V5 and a second switching transistor V6. The first switching transistor V5 includes a parallel circuit made up of a controllable first switching path S5 and a first inverse diode D5. The second switching transistor V6 includes a parallel circuit made up of a controllable second switching path S6 and a second inverse diode D6.

The first switching transistor V5 and the second switching transistor V6 are connected in such a way that the fifth inverse diode D5 and the sixth inverse diode D6 are connected back-to-back in series. This means that one of said inverse diodes D5, D6 is always switched in the reverse direction. When the first switching path S5 and the second switching path S6 are open, the switching device 70 is open. When the first switching path S5 and the second switching path S6 are closed, the switching device 70 is closed.

Said switching transistors V5, V6 of the switching device 70 are each formed as a metal oxide semiconductor field effect transistor, for example as a normally blocking n-channel MOSFET. Each of said inverse diodes D5, D6 represents a body diode of the respective switching transistor V5, V6.

The pick-up 50 has a control unit, not shown here, for driving the switches S1, S2, S3, S4 and the switching paths S5, S6. The control unit is designed, for example, in the form of a microcontroller.

As already mentioned, the primary current I1, which the current source 42 supplies, flows through the primary conductor L1. The magnetic coupling M thereby induces a secondary current 12 in the secondary winding L2. The secondary current 12 has the same fundamental frequency F0 as the primary current 11. The secondary current 12 flows through the inputs 61, 62 into the rectifier circuit 60.

When the switching device 70 is open, the secondary current I2 flows through the oscillating circuit formed by the secondary capacitor C2 and the secondary winding L2. When switching device 70 is closed, secondary current I2 flows through secondary winding L2 and through switching device 70, but not appreciably through secondary capacitor C2.

The rectifier circuit 60 can be operated passively. In this case, the controllable switches S1, S2, S3, S4 are open, and the rectifier circuit 60 acts like a B4 bridge rectifier. Positive half cycles of the secondary current 12 flow through the first diode D1, the fourth diode D4 and the outputs 63, 64. Negative half cycles of the secondary current 12 flow through the second diode D2, the third diode D3 and the outputs 63, 64. The output voltage UA between the positive output 63 and the negative output 64 is thus always positive.

The rectifier circuit 60 can also be operated synchronously. In the case of positive half-waves of the secondary current I2, the first switch S1 and the fourth switch S4 are closed, and the second switch S2 and the third switch S3 are opened. In the case of negative half-waves of the secondary current I2, the second switch S2 and the third switch S3 are closed, and the first switch S1 and the fourth switch S4 are opened. Positive half cycles of the secondary current 12 flow through the first switch S1, the fourth switch S4 and the outputs 63, 64. Negative half cycles of the secondary current 12 flow through the second switch D2, the third switch D3 and the outputs 63, 64. The output voltage UA between the positive output 63 and the negative output 64 is thus always positive.

During passive operation of the rectifier circuit 60, a forward voltage drops across the diodes D1, D2, D3, D4. During synchronous operation of the rectifier circuit 60, a forward voltage drops across the switches S1, S2, S3, S4, which is lower than the forward voltage of the diodes D1, D2, D3, D4. The output voltage UA is therefore higher in synchronous operation than in passive operation.

Reference List

40

energy source

42

power source

50

pick-up

60

rectifier circuit

61

first entrance

62

second entrance

63

positive outcome

64

negative output

70

switching device

80

consumer

V1...V4

first ... fourth switching unit

D1...D4

first ... fourth diode

S1...S4

first... fourth switch

V5...V6

first ... second switching transistor

D5...D6

first ... second inverse diode

S5...S6

first ... second contact gap

APPROX

smoothing capacitor

C2

secondary capacitor

L1

primary conductor

L2

secondary winding

M

magnetic coupling

11

primary current

12

secondary current

i.a

output current

u.a

output voltage

F0

fundamental frequency

T0

basic period

K

coupling factor

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102004055154 B4 [0003]
• DE 102010050935 B4 [0004]
• EP 2223408 B1 [0005]
• DE 102015210825 A1 [0006]
• JP 2012019603 A [0007]
• DE 102010022143 A1 [0008]

Claims (12)

Transformer head (50) for receiving energy without contact, comprising at least one secondary winding (L2), at least one secondary capacitor (C2) which can be connected in series with the secondary winding (L2), and a rectifier circuit (60) which is connected to the secondary capacitor ( C2) and can be connected in series with the secondary winding (L2), characterized in that a switching device (70) is connected in parallel to the secondary capacitor (C2), by means of which the secondary capacitor (C2) can be short-circuited, and in that the rectifier circuit (60) has a first switching unit (V1), a second switching unit (V2), a third switching unit (V3) and a fourth switching unit (V4), wherein the switching units (V1, V2, V3, V4) each have a parallel circuit consisting of a controllable switch (S1 , S2, S3, S4) and a diode (D1, D2, D3, D4). pick-up (50) according to claim 1 , characterized in that when the switching device (70) is open, the secondary winding (L2), the secondary capacitor (C2) and the rectifier circuit (60) form a series circuit, and that when the switching device (70) is closed, the secondary winding (L2) and the rectifier circuit (60 ) form a series connection. Pickup head (50) according to one of the preceding claims, characterized in that the switching device (70) has a first switching transistor (V5) and a second switching transistor (V6), each of which is a parallel circuit comprising a controllable switching path (S5, S6) and an inverse diode (D5, D6), wherein the first switching transistor (V5) and the second switching transistor (V6) are connected in such a way that the first inverse diode (D5) and the second inverse diode (D6) are connected back-to-back in series. Transmitter head (50) according to one of the preceding claims, characterized in that the switching units (V1, V2, V3, V4) are each designed as MOSFETs, each of said diodes (D1, D2, D3, D4) being a body diode of the respective switching unit (V1, V2, V3, V4) and/or that the switching transistors (V5, V6) are each designed as MOSFETs, each of said inverse diodes (D5, D6) being a body diode of the respective switching unit (V5, V6) represents. Transmitter head (50) according to one of the preceding claims, characterized in that the rectifier circuit (60) is connected to a smoothing capacitor (CA) on the output side. System for contactless transmission of energy, comprising at least one pick-up (50) according to one of the preceding claims and a power source (40) having a current source (42) and a primary conductor (L1), wherein the at least one secondary winding (L2) and the primary conductor (L1) are inductively coupled. Procedures for operating a system claim 6 , characterized in that the primary conductor (L1) is traversed by a primary current (11) supplied by the current source (42) and having a fundamental frequency (F0) and a fundamental period (T0); a secondary current (12) is induced in the secondary winding (L2); an output voltage (UA) drops on the output side of the rectifier circuit (60), and an output current (IA) is supplied by the rectifier circuit (60) on the output side. procedure after claim 7 , characterized in that the system is operated in a first operating state, wherein the switching device (70) is closed, and wherein the rectifier circuit (60) is operated passively or synchronously. procedure after claim 7 , characterized in that the system is operated in a second operating state, wherein the switching device (70) is closed, and wherein in a first time period, which is greater than or equal to the basic period (T0), the second switch (S2) and the fourth Switch (S4) are closed, and the first switch (S1) and the third switch (S3) are open, and wherein the rectifier circuit (60) is passive in a second time period which is at least half as long as the basic period (T0). or operated synchronously. procedure after claim 7 , characterized in that the system is operated in a third operating state, with the rectifier circuit (60) being operated passively or synchronously, and with the switching device (70) being closed for a first time period which is greater than or equal to the basic period (T0), and with in a second period of time which is at least half as large as the basic period (T0), the switching device (70) is open. procedure after claim 7 , characterized in that the system is operated in a fourth operating state, wherein the switching device (70) is open, and wherein the rectifier circuit (60) is operated passively or synchronously. procedure after claim 7 , characterized in that the system is operated in a fifth operating state, wherein the switching device (70) is open, and wherein in a first time period, which is greater than or equal to the basic period (T0), the second switch (S2) and the fourth Switch (S4) are closed, and the first switch (S1) and the third switch (S3) are open, and wherein the rectifier circuit (60) is passive in a second time period which is at least half as long as the basic period (T0). or operated synchronously.

Images