DC voltage converter for bidirectional electric power transfer from the primary side to the secondary side of the DC voltage converter or vice versa

Abstract

A DC voltage converter (10) for transmitting electric power from the secondary side to the primary side of the DC voltage converter (10), wherein the DC voltage converter has an active clamped flyback converter circuit on the primary side, the active clamped flyback converter circuit having a controlled first switch (1) and a controlled second switch (2), and the primary side is inductively coupled to the secondary side, wherein the current of the secondary coil (6) on the secondary side is connected by a single controlled secondary side third switch (3) for inductive coupling with the primary side, and the DC voltage converter has a regulating device (12), which connects the third switch (3) together with the first switch (1) to be conductive in multiple parts of a regulating cycle.

Description

Technical Field

[0001] The invention relates to a DC voltage converter with an asymmetrical topology for bidirectional electrical power transmission from the primary side to the secondary side or vice versa, which connects the current of the secondary coil on the secondary side by means of a single controlled switch. Background Art

[0002] So-called DC / DC converters or DC voltage converters are used to transfer electrical power between two DC voltage levels. There are a large number of possible topologies for such converters. One of these is the so-called active-clamped flyback topology, which is also referred to as an active-clamped flyback converter and is characterized by a small number of electronic components. In this case, the rectifier on the secondary side is implemented as a controlled switch.

[0003] DE 195 07 084 A1 proposes a flyback converter constructed as a switching regulator, whose rectifier can be bridged in the output circuit by an electronic switch. The electronic switch is controlled to be synchronously turned on with the coupling regulator adjustment mechanism (Schaltregler-Stellglied). The coupling regulator of the present invention has good efficiency and good synchronization characteristics. The electronic switch is connected in parallel to the rectifier on the secondary side. According to the present invention, its control is carried out synchronously and in an opposite rhythm with the control of the coupling regulator adjustment mechanism, that is, when the coupling regulator adjustment mechanism is blocked via the pulse width modulator PBM, the field effect transistor is controlled to be turned on and thus bridges the rectifier with low resistance.

[0004] With this circuit topology and the corresponding known modulation method, ie the actuation pattern or also the voltage-time curve of the power states of the three controlled switching transistors, the electrical power flows from the primary side to the secondary side of the circuit.

[0005] For bidirectional operation, the active clamped flyback converter topology is symmetrically expanded in the prior art. (Gang Chen, Yim-Shu Lee, SYR Hui, Dehong Xu and Yousheng Wang, "Active Clamped Bidirectional Flyback Converter", IEEE Transactions on Industrial Electronics, Vol. 47, No. 4, pp. 770-779, August 2000) Therefore, in addition, operation from the secondary side to the primary side is also possible only for symmetry reasons.

[0006] Such DC voltage converters are used, for example, as onboard power converters for electric vehicles, wherein, in general, electrical power is conducted from a significantly higher voltage on the primary side to the secondary side, thus, for example, from 400 V to 12 V. This results in scenarios in which a reversed power flow must be provided with as little circuit complexity as possible. Summary of the invention

[0007] The object of the present invention is to provide a DC voltage converter having a circuit topology corresponding to a controlled rectifier and an actively clamped flyback converter in the secondary circuit, which allows a primary-side to primary-side electrical power transmission.

[0008] According to the invention, a DC voltage converter according to the invention, a method for transmitting electrical power, a computer program product, a computer-readable storage medium and a drive system are provided, which at least partially have the mentioned effects. Advantageous embodiments are the subject of the following description.

[0009] A DC voltage converter for transmitting electric power from the secondary side to the primary side of a DC voltage converter is provided. The DC voltage converter includes a transformer separated in current, which has a primary side primary coil and a secondary side secondary coil. The primary coil is connected to a first primary voltage interface on the one hand and is connected to a second primary voltage interface in series with a first switch on the other hand. A capacitor is connected in series with a second switch in parallel with the primary coil. The secondary coil is connected to the first secondary voltage interface on the one hand and is connected to the second secondary voltage interface in series with a third switch on the other hand. In addition, the DC voltage converter includes a regulating device, which is configured to repeatedly open and close the first switch, the second switch and the third switch, especially according to a control mode, or to disconnect and connect accordingly. Here, when the second switch is connected, the first switch is disconnected, and vice versa, to generate an alternating voltage in the primary coil. The third switch is disconnected and connected according to the switching state of the first switch. The regulating device is provided to set the time for switching on the third switch to a time before the first switch is switched off and the second switch is switched on, in order to enable a power flow from the secondary side to the primary side.

[0010] The opening of the first switch and the closing of the second switch and their reversal are always carried out with a dead time, thereby ensuring that the first switch and the second switch are never switched on at the same time. The opening of the third switch is advantageously carried out shortly before the current through the switch passes through zero. Depending on the operating point, different time intervals are thus obtained between the opening of the second switch and the opening of the third switch.

[0011] The second switch and the third switch are disconnected at the same time. The second switch and the third switch are connected at slightly different time points. Therefore, the second switch and the third switch are connected and disconnected at almost the same time. The third switch is connected for a longer duration than the second switch, in particular 1-20% of the duration of the second switch being connected. In this way, the third switch can be disconnected when its current passes through zero as described. Minimum conduction losses and connection losses for the switch are thereby achieved. The longer the third switch is connected compared to the second switch, the more power is transferred from the secondary side to the primary side.

[0012] Advantageously, a circuit topology is provided which has a control device which enables a transfer of electrical power from the secondary side to the primary side of the DC voltage converter.

[0013] In another embodiment of the present invention, the regulating device is configured to set the time for switching on the third switch to a time after the first switch is switched off and the second switch is switched on, so as to enable a power flow from the primary side to the secondary side.

[0014] The second switch and the third switch are disconnected, in particular, at the same time. The second switch and the third switch are connected at slightly different time points. Therefore, the second switch and the third switch are connected and disconnected at almost the same time. The third switch is connected for a shorter duration than the second switch, in particular 1-20% of the duration of the second switch being connected. The shorter the time the third switch is connected compared to the second switch, the more power is transferred from the primary side to the secondary side.

[0015] Advantageously, a circuit topology is provided which has a control device which also enables a transfer of electrical power from the primary side to the secondary side of the DC voltage converter.

[0016] In another design scheme of the present invention, the regulating device is configured to set the time point for turning on the third switch to a time point before or after turning off the first switch and turning on the second switch according to a preset power transfer direction, so as to adjust the power flow corresponding to the preset power transfer direction.

[0017] A DC voltage converter is provided, which adapts the power transmission direction through the DC voltage converter according to a preset, in that the switching-on time point of the third switch is set to a time point that is set before or after the switching state of the first switch according to the switching state of the first switch. A DC voltage converter is advantageously provided, whose power transmission direction is presettable.

[0018] In another embodiment of the present invention, the regulating device is configured to adjust the interval of the time point of turning on the third switch before or after the time point of turning on the first switch according to a predeterminable power, wherein the interval is increased when the power to be transmitted is large and is reduced when the power is small.

[0019] A DC voltage converter is provided which adapts the power via the DC voltage converter according to a presetting by changing the ratio of the switch-on time of the third switch to the switch-on time of the second switch. A DC voltage converter is advantageously provided whose power is presetting.

[0020] In other words, a circuit is provided for a DC voltage converter, in particular with an actively clamped flyback converter topology, having a regulating device which performs a modulation method for switch control, which modulation method enables an electrical power flow from the secondary side to the primary side, in particular without generating any additional expenditure on further electronic components in the circuit.

[0021] The DC voltage converter according to the invention for transmitting electric power from the secondary side to the primary side of the DC voltage converter has, in particular, an active clamped flyback converter circuit on the primary side. The circuit couples the current in the primary loop using a controlled first switch. The circuit can be implemented using different but functionally equivalent topologies.

[0022] The controlled second switch in the primary circuit, in particular together with the capacitor, causes active clamping and limits the voltage on the primary side, in order in particular to reduce the load on the first switch. The primary side of the DC voltage converter is inductively coupled to the secondary side. This allows an electrically inductive and galvanically separated power transfer between the primary side and the secondary side in both directions.

[0023] The secondary side is inductively coupled to the primary side via a secondary coil. The current passing through the secondary coil is coupled by means of a third secondary switch, in particular a single controlled switch. In this case, the DC voltage converter has a regulating device, in particular a regulating circuit. In the case of inductive coupling, the coupling can be implemented so that the voltage on the coupled primary side primary coil is opposite to the voltage of the other coupled secondary coil. For this purpose, the coil windings forming the inductance can have different winding directions.

[0024] The primary side is defined as the side of the DC voltage converter having a controlled half-bridge with a first switch and a second switch, wherein the two controlled switches can be activated alternately in particular such that they are never connected conductively at the same time during operation.

[0025] With such a DC voltage converter, a power flow from the secondary side to the primary side can be carried out, in particular without additional electronic components.

[0026] Compared to an actively clamped flyback converter that controls the power flow from the primary side to the secondary side, when the controlled third switch on the secondary side is connected to be conductive, i.e., turned on, the first switch on the primary side is connected to be non-conductive for the reverse power flow, thereby achieving electrical power flow from the secondary side to the primary side.

[0027] As a result, electrical power is inductively transferred from the secondary side to the primary side. Before the energy is given to the primary-side load, it is stored in the capacitor and then in the primary-side primary coil.

[0028] With the modulation method presented here, i.e. the sequence of the control signals of the regulating device for the third switch, the first switch and the second switch are operated in so-called “zero voltage switching” (ZVS), i.e. they are only actively connected to be non-conductive but not actively connected to be conductive.

[0029] The disconnection process of the third switch, that is, the connection to non-conductivity, is carried out by means of a blocking time delay of the reverse-conducting diode of the third switch or by means of "reverse recovery". This operating mode is also called "zero current switching" (ZCS). The third switch is also turned on by means of ZCS.

[0030] This topology reduces the load on the first switch in the non-conductive state since the current of the primary coil is commutated to the circuit part having the second switch and the limiting capacitor.

[0031] The primary side of the DC voltage converter can have a pair of connections which are connected to the flyback converter circuit, so that during operation of the DC voltage converter, electrical power can be provided at these connections with a power flow from the secondary side to the primary side.

[0032] The secondary side of the DC voltage converter can have a pair of secondary voltage interfaces, which are connected to the secondary coil and the third switch, so that during operation of the DC voltage converter, electrical power can be received at these secondary voltage interfaces using a power flow from the secondary side to the primary side.

[0033] For this purpose, the pair of secondary-side connections can be electrically connected to a third series circuit formed by a third switch and a secondary coil.

[0034] According to one embodiment of the invention, the first series circuit is connected in parallel with the first intermediate circuit capacitor. This results in a constant voltage at the primary-side connection of the DC voltage converter. Alternatively, the first intermediate circuit capacitor can also be a component of another circuit, to which the DC voltage converter according to the invention is electrically connected and is therefore not a component of the DC voltage converter.

[0035] According to one design of the present invention, the third series circuit is connected in parallel with the second intermediate circuit capacitor, thereby smoothing the voltage on the secondary side interface of the DC voltage converter. Alternatively, the second intermediate circuit capacitor can also be a component of another circuit, and the DC voltage converter according to the present invention is electrically connected to the other circuit.

[0036] According to one measure to improve the invention, it is proposed that at least one of the three switches of the DC voltage converter is produced based on silicon technology, silicon carbide technology or gallium nitride technology. Compared to MOSFETs based on silicon technology as electronic switches, for example, a higher efficiency of the DC voltage converter can be achieved by using components based on another production technology, because lower losses occur.

[0037] According to one measure improving the invention, it is proposed that one or all three switches of the DC voltage converter are designed as high electron mobility transistors HEMTs (German: Transistor mit hoher Elektronenbeweglichkeit), junction field effect transistors jFETs (English: junction-fet, or non-insulated-gate-fet, non-insulated gate field effect transistors NIGFET) (German: Sperrschicht-Feldeffekttransistor), power MOSFETs, insulated gate bipolar transistors IGBTs (English: insulated-gate bipolar transistor) (German: Bipolar transistor mit isolierterGate-Elektrode) or thyristors. In addition, cascodes, i.e. series circuits of normally open components and low-voltage semiconductors, or also high electron mobility transistors (HEMTs) can be used for controlling the current flow.

[0038] Furthermore, further unipolar components can be used for controlling the current flow. The advantage of a lower forward voltage, as in the case of MOSFET transistors, is achieved with unipolar components.

[0039] Furthermore, the invention relates to a method for controlling a DC voltage converter for transferring electrical power from the secondary side of the DC voltage converter to the primary side. In this case, the DC voltage converter comprises a transformer having a primary coil on the primary side and a secondary coil on the secondary side. The primary coil is connected to a first primary voltage interface on the one hand and to a second primary voltage interface in series with a first switch on the other hand. A capacitor is connected or coupled in series with the second switch in parallel with the primary coil. The secondary coil is connected to the first secondary voltage interface on the one hand and to the second secondary voltage interface in series with a third switch on the other hand. The DC voltage converter further comprises a regulating device for controlling or executing the following steps:

[0040] The first switch, the second switch and the third switch are repeatedly opened and closed, wherein when the second switch is closed, the first switch is continuously opened, and vice versa, to generate an alternating current in the primary coil. The third switch is opened and closed according to the switching state of the first switch. The regulating device also controls other steps: the time point of closing the third switch is preset to a time point before the first switch is opened and the second switch is closed, so as to enable power flow from the secondary side to the primary side.

[0041] Advantageously, a method for controlling a DC voltage converter is provided, which method enables a transmission of electrical power from a secondary side to a primary side of the DC voltage converter.

[0042] In another embodiment of the present invention, the regulating device also controls other steps:

[0043] The time point at which the third switch is turned on is preset as a time point after the first switch is turned off and the second switch is turned on, so as to enable power flow from the primary side to the secondary side.

[0044] Advantageously, a method for controlling a DC voltage converter is provided, which method also enables a transmission of electrical power from the primary side to the secondary side of the DC voltage converter.

[0045] In another embodiment of the present invention, the regulating device also controls other steps:

[0046] Determine the power transfer direction that can be preset;

[0047] According to the determined power transfer direction, the time point for turning on the third switch is preset to a time point before or after turning off the first switch and turning on the second switch.

[0048] A method for controlling a DC voltage converter is provided, wherein the method adapts the power transmission direction by the DC voltage converter according to a presetting, in that the time point of switching on the third switch is set to a time point according to the switching state of the first switch, which time point is set before or after the time point of switching off the first switch. A method for controlling a DC voltage converter is advantageously provided, wherein the power transmission direction to be adjusted can be presetting by the DC voltage converter.

[0049] In other words, a method for controlling a DC voltage converter is provided to transfer electrical power from the secondary side of the DC voltage converter to the primary side. The DC voltage converter has an active clamped flyback converter circuit, in particular on the primary side, which has a controlled first switch and a controlled second switch. Here, the primary side of the DC voltage converter is inductively coupled to the secondary side by means of a primary side primary coil and a secondary side secondary coil. The current passing through the secondary coil is connected in the DC voltage converter by a third switch, in particular a single switch. In particular, the first switch and the second switch are alternately connected to conduction, corresponding to connection, in particular with a dead time offset for power transmission. In accordance with the method, in particular, the third switch and the second switch are synchronously connected to non-conduction, corresponding to disconnection, in particular with a dead time offset.

[0050] With this method, the DC voltage converter described can convey electrical power from its secondary side to its primary side. To this end, when the controlled third switch on the secondary side is switched on, the first switch on the primary side is then switched off, thereby obtaining an electrical power flow from the secondary side to the primary side.

[0051] The method can also be carried out with all other above-described embodiments of the DC converter.

[0052] Furthermore, the present invention relates to a computer program product, wherein the computer program product comprises instructions which, when the program is executed by a computer, cause the computer to carry out the above-described method.

[0053] Furthermore, the present invention relates to a computer-readable storage medium, which includes the following instructions, which, when executed by a computer, cause the computer to implement the above-mentioned method.

[0054] The invention further relates to a system having a first DC power supply and a second DC power supply, the first DC power supply having a first voltage and the second DC power supply having a second voltage. The first voltage is higher than the second voltage. The system further comprises a DC voltage converter as described above. The first DC power supply of the first voltage is electrically connected to the primary side of the DC voltage converter and the second DC power supply of the second voltage is connected to the secondary side of the DC voltage converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The embodiments of the present invention are Figure 1 and 2 , and is explained in detail later.

[0056] Figure 1 : Topologies of DC voltage converters;

[0057] Figure 2 a: a control signal of the third switch; and

[0058] Figure 2 b: Current flow on the primary and secondary sides. DETAILED DESCRIPTION

[0059] Figure 1 The topology of a DC voltage converter 10 is shown, in which a first switch 1 is electrically connected to a primary coil 5 on the primary side of the DC voltage converter 10 in a first series circuit. A second switch 2 is arranged on the primary side and electrically connected to a capacitor 4 in a second series circuit, wherein the second series circuit is connected in parallel to the primary coil 5 on the primary side. The first contact of the first series circuit on the primary coil 5 side is connected to a first primary voltage interface 11a on the primary side of the DC voltage converter 10 and the second contact of the first series circuit on the first switch 1 side is connected to a second primary voltage interface 11b on the primary side of the DC voltage converter 10. A voltage U1 is applied between these interfaces 11a and 11b on the primary side. This topology of the primary side of the DC voltage converter shows an example for an active clamped flyback converter circuit. The first intermediate circuit capacitor 7 can be electrically connected to the first and second primary voltage interfaces 11a, 11b on the primary side as described above.

[0060] The secondary side of the DC voltage converter 10 has a controlled third switch 3, which forms a third electrical series circuit with the secondary coil 6 of the secondary side. The first contact of the third series circuit on the side of the secondary coil 6 forms a first secondary voltage interface 9a on the secondary side of the DC voltage converter 10, and the second contact of the third series circuit on the side of the third switch 3 forms a second secondary voltage interface 9b on the secondary side of the DC voltage converter 10. A voltage U2 is applied between these interfaces 9a and 9b on the secondary side. The second intermediate circuit capacitor 8 can be electrically connected to the first and second secondary voltage interfaces 9a, 9b on the secondary side as described above.

[0061] The primary coil 5 on the primary side and the secondary coil 6 on the secondary side are inductively coupled to one another. In particular, the inductor is designed as windings of a transformer that are galvanically separated from one another.

[0062] Figure 1In the embodiment of the invention, the controlled switches 1, 2, 3 are implemented as n-channel MOSFET transistors, but other unipolar components can also be used to control the current flow. The advantage of a lower forward voltage (Durchlassspannung) as in MOSFET transistors is achieved by using unipolar components. Examples of this have already been mentioned in the description.

[0063] The regulating device 12 is connected with its output terminals 12a, 12b and 12c to the control contacts of the second switch 2, the first switch 1 and the third switch 3, respectively. The regulating device 12 is configured to correspond to, for example, Figure 2 The control mode shown in a is used to control the individual switches 1, 2, 3. The adjustment device 12 corresponds to Figure 2 The trend in a controls the control contacts of the three switches 1, 2, and 3 to be high or low. When the control signal is high, the corresponding switch is connected to be conductive, corresponding to being turned on, and when the control signal is low, the corresponding switch is connected to be non-conductive, corresponding to being turned off.

[0064] In this time sequence of actuating the switches, electrical power is inductively transferred from the secondary side of the DC voltage converter to the primary side via the transformer consisting of the secondary coil 6 and the primary coil 5. The energy is first stored in the capacitor 4 and then in the primary coil 5 before being delivered to the load connected to the primary voltage connection 11a, 11b.

[0065] Figure 2 b shows the current course I1 in the primary coil 5 and the current course I2 in the secondary coil 6 of the DC voltage converter resulting from the described control mode, wherein: Figure 2 The arrows in a labeled with l1 and l2 in the primary circuit or in the secondary circuit of the DC voltage converter 10 indicate the direction of the current flow at these points of the topology.

[0066] Next, the following describes the operation of the secondary-side third switch 3 starting shortly before the third switch 3 is connected to conduction at time t1. Figure 2 A control mode synthesized Figure 2 b current direction.

[0067] The inductively coupled primary coil 5 on the primary side and the secondary coil 6 on the secondary side can be viewed as equivalent in the electrical replacement diagram used for the subsequent description. The equivalent diagram includes an ideal transmitter between the secondary side and the primary side of the DC voltage converter and a leakage inductance in series with the main inductance on the primary side, wherein the main inductance is connected in parallel with the ideal transmitter.

[0068] At the beginning of the observation, before time t1, the first switch 1 is conducting, while both the second switch 2 and the third switch 3 are not conducting.

[0069] First, a decreasing negative current I1 flows which is driven through the main inductance of the transformer, thereby transferring electrical power to the primary side.

[0070] If the third switch 3 is now connected to conduction at time t1, it is carried out in ZCS mode because the current l2 is very small. With the third switch 3 turned on, the sum of the two voltages U1 and the voltage U2 converted by means of the transformer is applied to the leakage inductance. Since the leakage inductance is very small compared to the main inductance, the current l2 rises steeply in the negative direction and extracts power from the second DC voltage source connected to the secondary voltage connection.

[0071] The voltage U2 converted by means of the transformer is synthesized by the different winding directions of the transformer windings to cause a current increase through the main inductance, which in turn also changes the sign of I1. The duration of the superimposed time period l3, that is, between the time points t1 and t2, can be used to adjust the power transmission, during which the first switch 1 and the third switch 3 are connected together.

[0072] At the end of the time period in which the first switch 1 and the third switch 3 are connected together, the first switch 1 is turned off with low loss at time t2. By turning off the first switch 1, the primary side current I1 caused by the intrinsic diode is commutated to the reverse-conducting second switch 2, so that the second switch S2 is turned on in the ZVS mode almost without loss.

[0073] In this phase, a small negative voltage is applied to the leakage inductance, which is controlled by the voltage U across capacitor 4. 钳位 The negative current I2 is formed by the difference between the voltage U2 converted by the transformer and the negative current I2.

[0074] Almost the entire voltage U2 converted by means of the transformer is present at the main inductor, and the current I1 drops accordingly. Energy is thus stored in the capacitor 4 and in the main inductor.

[0075] At the end of this phase, the current I1 through the second switch 2 has changed its direction. The second switch 2 is thus switched off at time t3 with low losses. The current is then commutated to the reverse diode of the first switch 1 via the main inductor, so that the first switch 1 is switched on at time t3 in ZVS mode with almost no losses.

[0076] The current I2 through the third switch 3 is reduced to a low value and can therefore be switched off at time t3 synchronously with the second switch 2, almost in ZCS mode, with low losses, in particular offset by a time interval relative to the switch-off signal of the switch 2. Alternatively, the third switch 3 can also be switched off passively by reverse recovery of the reverse-conducting diode.

[0077] The negative current I1 in the main inductor now flows to the load connected on the primary side at the primary voltage terminals 11a and 11b. Therefore, in this phase, the power received in the previous phase from the second DC voltage source connected to the secondary side is given to the first DC voltage source or load connected to the primary side. With the third switch 3 being turned on at t'1 in the ZCS mode under low current conditions, the described cycle starts from the beginning.

[0078] In summary, the electrical power is received by the secondary side of the circuit and is given to the primary side of the circuit. Advantageously, all switches are operated either in ZVS mode, such as the first switch 1 and the second switch 2, or in ZCS mode, such as the third switch 3. Small connection losses at these operating points can also be achieved in the control mode or modulation method described here, or a high connection frequency can be achieved in this control cycle. As a result, no additional hardware consumption is generated in the circuit compared to the operation of a DC converter from the primary side to the secondary side.

Claims

1. A DC voltage converter (10) for transferring electric power from the secondary side to the primary side of the DC voltage converter (10), The DC voltage converter has a transformer having a primary coil (5) on the primary side and a secondary coil (6) on the secondary side. in, The primary coil (5) is connected to a first primary voltage connection (11a) on the one hand and to a second primary voltage connection (11b) in series with the first switch (1) on the other hand. wherein a capacitor (4) and a second switch (2) are connected in series in parallel with the primary coil (5); The secondary coil (6) is connected in series with the first secondary voltage interface (9a) on the one hand and with the third switch (3) on the other hand. The DC voltage converter has a regulating device (12) which is configured to: The first switch (1), the second switch (2) and the third switch (3) are repeatedly turned off and on, wherein when the second switch (2) is turned on, the first switch (1) is continuously turned off, and vice versa, so as to generate an alternating current in the primary coil (5); and opening and closing the third switch (3) according to the switch state of the first switch (1), It is characterized in that The regulating device (12) is configured to: The time point of turning on the third switch (3) is set to a time point before the first switch (1) is turned off and the second switch (2) is turned on, so as to enable power flow from the secondary side to the primary side.

2. The DC voltage converter (10) according to claim 1, characterized in that The regulating device (12) is configured to set the time point for switching on the third switch (3) to a time point after the first switch (1) is switched off and the second switch (2) is switched on, so as to enable a power flow from the primary side to the secondary side.

3. The DC voltage converter (10) according to claim 2, characterized in that: The regulating device (12) is configured to set the time point for turning on the third switch (3) to a time point before or after turning off the first switch (1) and turning on the second switch (2) according to a preset power transmission direction, so as to adjust the power flow according to the preset power transmission direction.

4. A DC voltage converter (10) according to any one of the preceding claims, characterized in that At least one of the first switch (1), the second switch (2) or the third switch (3) is manufactured based on silicon technology, silicon carbide technology or gallium nitride technology.

5. A method for controlling a DC voltage converter (10) for transferring electrical power from a secondary side to a primary side of the DC voltage converter (10), in, The DC voltage converter (10) has a transformer having a primary coil (5) on the primary side and a secondary coil (6) on the secondary side. The primary coil (5) is connected to a first primary voltage interface (11a) on the one hand and to a second primary voltage interface (11b) in series with a first switch (1) on the other hand. wherein a capacitor (4) and a second switch (2) are connected in series in parallel with the primary coil (5); The primary coil (6) is connected to a first secondary voltage interface (9a) on the one hand and to a second secondary voltage interface (9b) in series with a third switch (3) on the other hand. The DC voltage converter has a regulating device (12) for controlling the following steps: repeatedly opening and closing the first switch (1), the second switch (2) and the third switch (3), wherein when the second switch (2) is turned on, the first switch (1) is continuously turned off, and vice versa, so as to generate an alternating current in the primary coil (5); opening and closing the third switch (3) according to the switch state of the first switch (1), It is characterized in that The regulating device (12) controls the following other steps: The time point for turning on the third switch (3) is preset to a time point before the first switch (1) is turned off and the second switch (2) is turned on, so as to enable power flow from the secondary side to the primary side.

6. The method according to claim 5, characterized in that The regulating device performs the following further steps: The time point for turning on the third switch (3) is preset to a time point after the first switch (1) is turned off and the second switch (2) is turned on, so as to enable power flow from the primary side to the secondary side.

7. The method according to claim 6, characterized in that The regulating device performs the following further steps: Determine the power transfer direction that can be preset; According to the determined power transfer direction, the time point for turning on the third switch (3) is preset to be a time point before or after turning off the first switch (1) and turning on the second switch (2).

8. Computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of claims 5 to 7.

9. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to implement the method according to any one of claims 5 to 7.

10. A system, comprising: a first DC power source having a first voltage; a second DC power supply having a second voltage, wherein The first voltage is higher than the second voltage; The DC voltage converter according to any one of claims 1 to 4, wherein: The DC voltage converter (10) is electrically connected to the first DC power source on the primary side and to a second DC power source having a second voltage on the secondary side.

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