LLC resonant transducer arrangement

Abstract

LLC resonant converter arrangement (10, 32), comprising: a first module (12) with a first primary side (16), a first secondary side (18) and a first resonant circuit (20) coupling the first primary side (16) to the first secondary side (18), and a second module (14) with a second primary side (22), a second secondary side (24) and a second resonant circuit (26) coupling the second primary side (22) to the second secondary side (24), a center-tapped capacitor (Co1Co2) arranged between a DC output side of the first secondary side (18) and a DC output terminal (28) of the LLC resonant converter arrangement (10, 32), wherein the DC output side can be connected to a DC input side of the center-tapped capacitor (Co1Co2) by means of a first switch (S1),a DC output side of the second secondary side (24) downstream of the first switch (S1) can be connected by a second switch (S2) to the DC input side of the center-tapped capacitor (Co1Co2), and a center-tapped point of the center-tapped capacitor (Co1Co2) can be connected by a third switch (S5) to a center-tapped point of one of the half-bridges of the first secondary side (18).

Description

[0001] The present invention relates to an LLC resonant converter arrangement for DC-DC conversion. In particular, the present invention relates to a standalone, fault-tolerant, fully redundant LLC resonant converter arrangement for HV / LV DC-DC conversion, particularly for use in the automotive sector. The present invention further relates to a method for operating such an arrangement.

[0002] Fail-operational capability is of utmost importance, especially in powertrains related to electromobility applications, but also in autonomous driving applications, ensuring safety, reliability, and regulatory compliance. Implementing a fail-operational mechanism can be accomplished either through redundancy or through an independent fault tolerance capability. The reliability of power electronic converters is important for mission-critical applications, including electric vehicles, aerospace systems, and other safety-critical applications.

[0003] In the field of electromobility, standalone, fault-tolerant, and fully redundant HV / LV DC-DC converters are essential for the safe and reliable operation of autonomous systems, especially in Advanced Autonomous Driving (AD) L4 / L5 vehicles. Fault-tolerant and redundant HV / LV DC-DC converters ensure consistent power conversion and increase system resilience by providing backup power paths.

[0004] However, current designs of HV / LV DCDC converter arrays provide either fault tolerance capability or redundancy capability.

[0005] It is therefore an object of the present invention to provide an HV / LV DCDC converter arrangement, or more generally, an LLC resonant converter arrangement, that provides a standalone, fault-tolerance-integrated, fully redundant concept that offers both standalone fault tolerance and fully redundant capability. These and other objects, which will become apparent upon reading the description, are achieved by the subject matter of the independent claims. Further embodiments and developments are provided in the dependent claims.

[0006] According to a first aspect of the present invention, an LLC resonant converter arrangement for DCDC conversion, in particular for HV / LV DCDC conversion, is provided. The arrangement comprises a first module with a first primary side including two half-bridges, a first secondary side including two half-bridges, and a first resonant circuit coupling the first primary side to the first secondary side; a second module with a second primary side including two half-bridges, a second secondary side including two half-bridges, and a second resonant circuit coupling the second primary side to the second secondary side; and a center-tapped capacitor arranged between a DC output side of the two half-bridges of the first secondary side and a DC output terminal of the LLC resonant converter arrangement.In the arrangement, the DC output side of the two half-bridges of the first secondary side can be connected to a DC input side of the center-tapped capacitor by a first switch, a DC output side of the two half-bridges of the second secondary side can be connected downstream of the first switch to the DC input side of the center-tapped capacitor by a second switch, and a center-tap point of the center-tapped capacitor can be connected to a center-tap point of one of the two half-bridges of the first secondary side by a third switch.

[0007] The present invention is based, at least in part, on the idea that such a topology can provide both fully integrated redundancy and standalone fault-tolerance capability. The redundancy aspect is covered by a second module, which can be used as a backup or supplement to the first module. The second module can be switched in using the second switch. The standalone fault-tolerance aspect is covered by a center-tapped capacitor, which can be connected at a center-tap point to, for example, mitigate faults in one of the switching elements of the two half-bridges on the first primary side. Overall, this topology enables high-quality, reliable, and functionally safe DCDC conversion, in particular HV / LV DCDC conversion.

[0008] Preferably, the two half-bridges of the first and / or second secondary side are passive half-bridges. These half-bridges preferably use diodes as switching elements. Passive half-bridges, or in particular diodes, are best suited for redundancy and fault tolerance capabilities because such components are reliable and do not require active control.

[0009] Preferably, the first primary and the second primary are connected in series or parallel. IPOP (Input-Parallel Output-Parallel) systems are suitable for applications requiring high output currents, while ISOP (Input-Serial Output-Parallel) systems are suitable for cases with high input voltages and lower output voltages. Both topologies are particularly well-suited for automotive applications.

[0010] Preferably, the LLC converter arrangement further comprises a control unit configured to control the first switch to a closed state and the third switch to an open state for operating the first module during normal operation, and configured to control the first switch from a closed state to an open state and the third switch from an open state to a closed state in the event of a fault in one of the two half-bridges on the first primary side. This embodiment is based at least in part on the idea that semiconductor faults, or more generally, faults of a switching element of the half-bridge, can cause a device to enter an open-circuit (OC) or short-circuit (SC) state (or drift). In LLC converter arrangements, SC faults can pose significant risks, as they can lead to significant damage to the power converter.

[0011] This embodiment is based at least in part on the idea that the LLC resonant converter arrangement reconfigures itself upon detection of such a fault. More specifically, upon such a fault, the LLC resonant converter arrangement reconfigures itself from a full bridge (FB) to a half bridge (HB) on the first primary side. For example, if one of the switching elements in one of the two half bridges has an SC fault, the other switching element of the same half bridge must remain open to prevent a short circuit of the input voltage source. Due to the SC fault, the affected switching element on the first primary side is connected to ground and uses the damaged switching element as a circuit path. This can initiate the reconfiguration. Although the unaffected leg of the half bridge of the first primary side continues to operate, the first module under fault conditions only generates half the output voltage compared to the output voltage during normal operation, i.e.without a fault on the first primary side. The embodiment is based at least in part on the idea that this fault requires a modification or reconfiguration of the first secondary side, or more precisely, of the rectifier circuit of the first secondary side. This embodiment is based at least in part on the idea that such a fault and / or such a drop in the output voltage can be mitigated and / or compensated for by allowing the first secondary side to operate as a so-called voltage doubler rectifier (VDR). This embodiment is based at least in part on the idea that by closing the third switch, the center tap of one of the half-bridges of the first secondary side is connected to the center tap of the center-tapped capacitor.As a result of the VDR reconfiguration of the first secondary, the output voltage, which had dropped by 50% due to the fault, doubles and returns to a normal output voltage. The fault can be mitigated, and the output voltage remains (approximately) the same. The half-bridges of the first secondary (which reconfigure into a VDR) can, if necessary, be active switching elements such as MOSFETs or passive switching elements such as diodes.

[0012] Preferably, the control unit of the LLC resonant converter arrangement is further configured to detect a failure of the first module. Here, the term "failure of the first module" means that at least two switching elements in one of the first and / or second half-bridges of the first primary side are defective and / or faulty. In other words, at least two switching elements on the first primary side experience a fault (regardless of whether OC or SC). In the event of a failure of the first primary side, the control unit reconfigures the LLC resonant converter arrangement. The first module is disconnected from the DC output terminal of the arrangement and (instead) the second module is connected to the DC output terminal of the arrangement by controlling the first switch to an open state and the second switch to a closed state. This reconfiguration is part of the fully redundant capability of the proposed LLC resonant converter arrangement.

[0013] In addition, however, the second module can also be used to increase the output power of the LLC resonant converter arrangement. Thus, according to one embodiment, the control unit can be configured to control the second switch to a closed state if additional power is required at the DC output terminal of the LLC resonant converter arrangement. The reason for this is that the LLC resonant converter arrangement is essentially a parallel output arrangement, which allows the power to be doubled when the first and second modules are connected.

[0014] According to a second aspect of the present invention, which may be an independent aspect of the present invention, a method for controlling an LLC resonant converter arrangement according to the first aspect and / or embodiments thereof is provided. The method comprises the following steps: operating the first module in normal operation by controlling the first switch to a closed state and the third switch to an open state, detecting a fault in one of the half-bridges on the first primary side of the first module, and controlling the third switch from an open to a closed state in response to the detected fault.

[0015] Preferably, the method further comprises the steps of: detecting a failure of the first module and controlling the first switch and the third switch to an open state and the second switch to a closed state in response to the detected failure of the first module.

[0016] Preferably, the method further comprises the steps of determining that additional power is required at the DC output terminal of the LLC resonant converter arrangement, and controlling the second switch to a closed state in response to the determined additional power requirement.

[0017] According to a third aspect of the present invention, which may be an independent aspect of the present invention, an LLC resonant converter arrangement, in particular for HV / LV DC-DC conversion, is provided. The arrangement comprises: a first module with a first primary side including two half-bridges, a first secondary side including a B6C rectifier circuit with three half-bridges, and a first resonant circuit coupling the first primary side to the first secondary side. The arrangement further comprises a second module with a second primary side including two half-bridges, a second secondary side including two half-bridges, and a second resonant circuit coupling the second primary side to the second secondary side. The arrangement further comprises a capacitor arranged between a DC output side of the B6C rectifier and a DC output terminal of the LLC resonant converter arrangement.In the arrangement, the DC output side of the two half-bridges can be connected to a DC input side of the capacitor by a first switch, a DC output side of the two half-bridges of the second secondary side can be connected downstream of the first switch to the DC input side of the capacitor, wherein a transformer of the first resonant circuit on the secondary side of the first module includes a secondary winding, the secondary winding includes a first winding end terminal, a second winding end terminal and a winding center tap terminal.The first winding end terminal is connected to a center tap point of a first half-bridge of the three half-bridges, the center tap terminal of the secondary winding can be connected to a second half-bridge of the three half-bridges by a third switch, and the second winding end terminal can be connected to a center tap point of a third half-bridge of the three half-bridges by a fourth switch.

[0018] The present invention is based, at least in part, on the idea that such a topology, using the same basic idea as set forth in connection with the first aspect, can provide both fully integrated redundancy and a standalone fault-tolerance capability. The redundancy aspect is covered by a second module that can be used as a backup or supplement to the first module. The second module can be switched on using the second switch. The fault-tolerance aspect is covered by compensating for a drop in the output voltage by increasing, or more precisely, by doubling, the number of windings in the secondary winding of the first module. In other words, in the first aspect, the voltage drop is compensated by the center-tapped connection of the center-tapped capacitor.In the third aspect, the voltage drop is compensated by essentially doubling the windings of the secondary windings. The term "doubling" can be understood to mean that during normal operation, the center tap terminal of the secondary winding is connected to the DC voltage output terminal, while in the event of a fault in the first module followed by a voltage drop, the second winding end terminal is connected to the DC output terminal.

[0019] Preferably, the two half-bridges of the first and / or second secondary side are passive half-bridges. These half-bridges preferably use diodes as switching elements. Passive half-bridges, or in particular diodes, are best suited for redundancy and fault tolerance capabilities because such components are reliable and do not require active control.

[0020] Preferably, the first primary and the second primary are connected in series or parallel. IPOP (Input-Parallel Output-Parallel) systems are suitable for applications requiring high output currents, while ISOP (Input-Serial Output-Parallel) systems are suitable for cases with high input voltages and lower output voltages. Both topologies are particularly well-suited for automotive applications.

[0021] Preferably, the LLC converter arrangement further comprises a control unit configured to control the first switch to a closed state, the third switch to a closed state, and the fourth switch to an open state during normal operation of the first module, and to control the third switch from a closed state to an open state and the fourth switch from an open state to a closed state in the event of a fault of the first primary side.

[0022] As with the previous embodiment, semiconductor failures, or more generally, failures of a half-bridge switching element, can cause a device to enter an open-circuit (OC) or short-circuit (SC) state (or drift). In LLC converter arrangements, SC failures can pose significant risks, as they can lead to significant damage to the power converter.

[0023] This embodiment is based at least in part on the idea that the LLC resonant converter arrangement reconfigures itself upon detection of such a fault.

[0024] In the B6C rectifier circuit, an additional half-bridge or leg is used as the secondary side branch. With an SC of one of the switching elements on the first primary side, the output voltage drops to 50%, as already mentioned. This output voltage drop can be compensated by connecting the second winding end terminal to the secondary side branch (i.e., the additional branch of the B6C rectifier circuit). This changes the effective number of windings or turns from n:1 to n:2, and the rated output voltage is restored. In other words, by doubling the number of windings or turns, the 50% drop can be compensated.

[0025] Preferably, the control unit of the LLC resonant converter arrangement can further be configured to detect a failure of the first module. Here, the term "failure of the first module" means that at least two switching elements in one of the first and / or second half-bridges of the first primary side are defective and / or faulty. In other words, at least two switching elements on the first primary side experience a fault (regardless of whether OC or SC). In the event of a failure of the first primary side, the control unit reconfigures the LLC resonant converter arrangement. The first module is disconnected from the DC output terminal of the arrangement and (instead) the second module is connected to the DC output terminal of the arrangement by controlling the first switch to an open state and the second switch to a closed state. This reconfiguration is part of the fully redundant capability of the proposed LLC resonant converter arrangement.

[0026] However, as already mentioned with regard to the first aspect, the second module can also be used to increase the output power of the LLC resonant converter arrangement. Thus, according to one embodiment, the control unit can be configured to control the second switch to a closed state if additional power is required at the DC output terminal of the LLC resonant converter arrangement. The reason for this is that the LLC resonant converter arrangement is essentially a parallel output arrangement, which allows the power to be doubled when the first and second modules are connected.

[0027] According to a fourth aspect of the present invention, which may be an independent aspect of the present invention, a method for controlling an LLC resonant converter arrangement according to the third aspect and / or embodiments thereof is provided. The method comprises the following steps: operating the first module in normal operation by controlling the first switch and the third switch to a closed state and the fourth switch to an open state, detecting a fault in one of the half-bridges on the first primary side of the first module, and controlling the third switch from a closed to an open state and the fourth switch from an open to a closed state in response to the detected fault.

[0028] Preferably, the method further comprises the steps of: detecting a failure of the first module and controlling the first switch to an open state and the second switch to a closed state in response to the detected failure of the first module.

[0029] Preferably, the method further comprises the steps of determining that additional power is required at the DC output terminal of the LLC resonant converter arrangement, and controlling the second switch to a closed state in response to the determined additional power requirement.

[0030] Further embodiments and aspects of the present invention are explained using the accompanying schematic figures incorporated herein. Fig. 1 is a circuit diagram of an example LLC resonant converter device, the device being an ISOP device with a center-tapped capacitor. Fig. 2 is a circuit diagram of another example of an LLC resonant converter arrangement, the arrangement being an IPOP arrangement with a center-tapped capacitor. Fig. 3 is a circuit diagram of another example of an LLC resonant converter device, the device being an ISOP device with a B6C rectifier circuit. Fig. 4 is a circuit diagram of another example of an LLC resonant converter arrangement, the arrangement being an IPOP arrangement with a B6C rectifier circuit.

[0031] In the figures, identical components are identified by identical numbers. Embodiments of the invention will now be described in connection with the

[0032] With reference to Fig. Figure 1 shows a circuit diagram of an LLC resonant converter arrangement 10 in an ISOP (Input-Serial Output-Parallel) configuration. The LLC resonant converter arrangement 10 can be used as a DC-DC converter, particularly as an HV / LV DC-DC converter, such as those used in automotive applications.

[0033] The LLC resonant converter assembly 10 includes a first module 12 and a second module 14 arranged in series. The first module 12 includes a first primary side 16, a first secondary side 18, and a first resonant circuit 20 coupling the first primary side 16 to the first secondary side 18. The first resonant circuit 20 includes a capacitance Cr1, an inductance Lr1, and a transformer Tr1 including a magnetizing inductance Lm1. The transformer Tr1 provides electrical isolation at the required turns ratio to deliver a desired voltage level. The first resonant circuit 20 is a resonant circuit well known to those skilled in the art, and therefore no further explanation is required.

[0034] The first primary side 16 includes two half-bridges, with a first branch or leg including two switching elements Q11 and Q12 and a second branch or leg including two further switching elements Q13 and Q14. In the illustrated embodiment, Q11-Q14 are MOSFET switching elements. In other embodiments not shown, Q11-Q14 may be other switching elements. The first primary side 16 is connected to a first DC voltage source Vin1. A voltage level of the DC voltage source Vin1 is converted to a (lower) DC voltage level on the first secondary side 18 using the first resonant circuit 20, as is known to those skilled in the art.

[0035] The first secondary side 18 includes two half-bridges. In the illustrated embodiment, the two half-bridges of the first secondary side 18 are passive half-bridges consisting of diodes D11-D14. In other embodiments not shown, the half-bridges on the first secondary side can be actively controlled half-bridges using MOSFET switching elements or the like.

[0036] The second module 14 includes a second primary side 22, a second secondary side 24, and a second resonant circuit 26 that couples the second primary side 22 to the second secondary side 24. The second resonant circuit 26 includes a capacitance Cr2, an inductance Lr2, and a transformer Tr2 that includes a magnetizing inductance Lm2. The transformer Tr2 provides electrical isolation and the required turns ratio to deliver a desired voltage level. The second resonant circuit 26 is a resonant circuit well known to those skilled in the art, so no further explanation is required.

[0037] The second primary side 22 includes two half-bridges, with a first branch or leg including two switching elements Q21 and Q22 and a second branch or leg including two further switching elements Q23 and Q24. In the embodiment shown, Q21-Q24 are MOSFET switching elements. In other embodiments not shown, Q21-Q24 may be other switching elements. The second primary side 22 is connected to a second DC voltage source Vin2 and connected in series with the first DC voltage source Vin1. A voltage level of the DC voltage source Vin2 is converted to a (lower) DC voltage level on the second secondary side 24 using the second resonant circuit 26, as is known to those skilled in the art.

[0038] The second secondary side 24 includes two half-bridges. In the illustrated embodiment, the two half-bridges of the second secondary side 24 are passive half-bridges consisting of diodes D21-D24. In other embodiments not shown, the half-bridges on the second secondary side may be actively controlled half-bridges using MOSFET switching elements or the like.

[0039] The LLC resonant converter assembly 10 further includes a DC output terminal 28. The DC output terminal 28 is configured to provide a DC output at a desired voltage level for supplying the voltage to an electrical load, schematically represented as RL. In the illustrated embodiment, output voltage levels may be 48 V, 24 V, 12 V, or other voltage levels.

[0040] The LLC resonant converter arrangement 10 further includes a center-tapped capacitor Co1Co2. The center-tapped capacitor Co1Co2 is arranged between a DC output side of the two half-bridges of the first secondary side 18 and the DC output terminal 28. A first switch S1 is arranged between the DC output side of the two half-bridges of the first secondary side 18 and the outer DC input side terminals of the center-tapped capacitor Co1Co2. The first switch S1 is configured to connect or disconnect the DC output side of the two half-bridges of the first secondary side 18 from the DC output terminal 28. A second switch S2 is arranged between the DC output side of the two half-bridges of the second secondary side 24 and the outer DC input side terminals of the center-tapped capacitor Co1Co2 downstream of the first switch S1.The second switch S2 is designed to connect or disconnect the DC output side of the two half-bridges of the second secondary side 24 from the DC output terminal 28.

[0041] A center tap of one of the two half-bridges of the first secondary side 18 is switchably connected to a center tap of the center-tapped capacitor Co1Co2 by a third switch S5. In the illustrated embodiment, a half-bridge with diodes D14 and D13 is switchably connected to the center tap of the center-tapped capacitor Co1Co2.

[0042] The LLC resonant converter arrangement 10 further includes a control unit 30. The control unit 30 can be operatively connected to the first and second modules 12, 14. The control unit 30 is configured to detect a fault in one of the switching elements Q11-Q24 and to determine a required DC voltage output level or its drop. The control unit 30 is further configured to operate a state (in particular an open state and a closed state) of one of the switching elements Q11-Q24 and the switches S1, S2, S5.

[0043] During normal operation of the first module 12, i.e., when there are no faults in the first module 12, the control unit 30 can operate Q11-Q14 as desired, controlling S1 in a closed state and S5 in an open state, so that the DC output terminal 28 provides the required DC voltage level. If additional power is required, the control unit can operate S2 in a closed state to expand the first module 12 by connecting the second module 14.

[0044] If one of the switching elements Q11-Q14 experiences a fault, in particular an SC fault, the control unit 30 can reconfigure the LLC resonant converter arrangement 10 such that this fault is compensated.

[0045] For example, if Q13 experiences an SC fault, the control unit 30 controls Q14 to be permanently open. This grounds the second half-bridge of the first primary side 16, and the DC output voltage of the device would drop by 50%. The ground connection and / or the voltage drop can be an indication for the control unit 30 to detect and mitigate the fault. The control unit 30 thus controls S5 to be closed. The voltage drop is compensated, and a fault on the first primary side 16 is mitigated. Those skilled in the art would understand that the first switch S1 can be in an open or closed state, while the third switch S5 is in a closed state.

[0046] If at least two switching elements of Q11-Q14 experience a fault, in particular an SC fault, the control unit 30 reconfigures the LLC resonant converter 10 such that the first module 12 is disconnected from the DC output terminal 28 and the redundant second module 14 is connected to the DC output terminal 28 to take over for the first module 12.

[0047] Thus, the LLC resonant converter arrangement 10 provides a fully redundant and fault-tolerant converter arrangement in which errors and / or failures in the first module 12 can be compensated.

[0048] With reference to Fig. 2 shows a circuit diagram of an LLC resonant converter arrangement 32. The LLC resonant converter arrangement 32 is similar to the LLC resonant converter arrangement 10 of Fig. 1, except that the LLC resonant converter arrangement 32 is an IPOP (Input-Parallel Output-Parallel) arrangement, while the LLC resonant converter arrangement 10 of Fig. 1 is an ISOP (Input-Serial Output-Parallel) arrangement. Therefore, Fig. 2 the first and second modules 12, 14 are connected in series and not in parallel, as in Fig. 1. The function and operation of the control unit 30 can be described in conjunction with Fig. 1. For example, the control unit 30 may operate the switches S1, S2, and S5 such that a fault and / or failure in the first module 12 may be mitigated.

[0049] With reference to Fig. Figure 3 shows a circuit diagram of an LLC resonant converter arrangement 34. The LLC resonant converter arrangement 34 is similar to the LLC resonant converter arrangements 10, 32, except that the LLC resonant converter arrangement 34 does not include a center-tapped capacitor to mitigate a drop in the DC output voltage, but instead includes a B6C rectifier circuit.

[0050] More specifically, the LLC resonant converter assembly 34 includes a first module 12 and a second module 14 arranged in series. The first module 12 includes a first primary side 16, a first secondary side 18, and a first resonant circuit 20 coupling the first primary side 16 to the first secondary side 18. The first primary side 16 includes two half-bridges, with a first branch or leg including two switching elements Q11 and Q12 and a second branch or leg including two further switching elements Q13 and Q14. In the embodiment shown, Q11-Q14 are MOSFET switching elements. In other embodiments not shown, Q11-Q14 may be other switching elements. The first primary side 16 is connected to a first DC voltage source Vin1. A voltage level of the DC voltage source Vin1 is converted on the first secondary side 18 into a (lower) DC voltage level using the first resonant circuit 20, as is known to those skilled in the art.

[0051] The first secondary side 18 includes three half-bridges arranged in a B6C rectifier circuit arrangement. In the illustrated embodiment, the three half-bridges of the first secondary side 18 use MOSFET switching elements, with S11-S12 arranged in a first half-bridge or first leg, S13-S14 arranged in a second half-bridge or second leg, and S13-S14 arranged in a third half-bridge or third leg.

[0052] The second module 14 includes a second primary side 22, a second secondary side 24, and a second resonant circuit 26 that couples the second primary side 22 to the second secondary side 24. The second primary side 22 includes two half-bridges, with a first branch or leg including two switching elements Q21 and Q22 and a second branch or leg including two further switching elements Q23 and Q24. In the embodiment shown, Q21-Q24 are MOSFET switching elements. In other embodiments not shown, Q21-Q24 may be other switching elements. The second primary side 22 is connected to a second DC voltage source Vin2 and connected in series with the first DC voltage source Vin1. A voltage level of the DC voltage source Vin2 is converted to a (lower) DC voltage level on the second secondary side 24 using the second resonant circuit 26, as is known to those skilled in the art.

[0053] The second secondary side 24 includes two half-bridges. In the illustrated embodiment, the two half-bridges of the second secondary side 24 are passive half-bridges consisting of diodes D21-D24. In other embodiments not shown, the half-bridges on the second secondary side may be actively controlled half-bridges using MOSFET switching elements or the like.

[0054] The LLC resonant converter assembly 34 further includes a DC output terminal 28. The DC output terminal 28 is configured to provide a DC output at a desired voltage level for supplying the voltage to an electrical load, schematically represented as RL. In the illustrated embodiment, output voltage levels may be 48 V, 24 V, 12 V, or other voltage levels.

[0055] The LLC resonant converter arrangement 34 further includes a capacitor Co arranged between a DC output side of the two half-bridges of the first secondary side 18 and the DC output terminal 28. A first switch S1 is arranged between the DC output side of the two half-bridges of the first secondary side 18 and the outer DC input side terminals of the capacitor Co. The first switch S1 is configured to connect or disconnect the DC output side of the two half-bridges of the first secondary side 18 from the DC output terminal 28. A second switch S2 is arranged between the DC output side of the two half-bridges of the second secondary side 24 and the outer DC input side terminals of the capacitor Co downstream of the first switch S1. The second switch S2 is configured to connect or disconnect the DC output side of the two half-bridges of the second secondary side 24 from the DC output terminal 28.

[0056] A first transformer Tr1 includes a primary winding on the first primary side 16 and a secondary winding on the first secondary side 18. The secondary winding includes a first winding end terminal 36, a second winding end terminal 38, and a winding center tap terminal 40. The first winding end terminal 36 is connected to a center tap point of the first half-bridge of the three half-bridges of the B6C rectifier circuit. The winding center tap terminal 40 can be switchably connected to a center tap point of the second half-bridge of the three half-bridges by a third switch S8. The second winding end terminal 38 can be switchably connected to a center tap point of the third half-bridge of the three half-bridges by a fourth switch S7.

[0057] The LLC resonant converter arrangement 34 further includes a control unit 30. The control unit 30 can be operatively connected to the first and second modules 12, 14. The control unit 30 is configured to detect a fault in one of the switching elements Q11-Q24 and to determine a required DC voltage output level or its drop. The control unit 30 is further configured to operate a state (in particular an open state and a closed state) of one of the switching elements Q11-Q24 and the switches S1, S2, S7, S8.

[0058] During normal operation of the first module 12, i.e., when there are no faults in the first module 12, the control unit 30 can operate Q11-Q14 as desired, controlling S1 and S8 in a closed state and S7 in an open state, so that the DC output terminal 28 provides the required DC voltage level. If additional power is required, the control unit can operate S2 in a closed state to expand the first module 12 by connecting the second module 14.

[0059] If one of the switching elements Q11-Q14 experiences a fault, in particular an SC fault, the control unit 30 can reconfigure the LLC resonant converter arrangement 34 such that this fault is compensated.

[0060] For example, if Q13 experiences an SC fault, the control unit 30 controls Q14 to be permanently open. This grounds the second half-bridge of the first primary side 16, and the DC output voltage of the device would drop by 50%. The ground connection and / or the voltage drop can be an indication for the control unit 30 to detect and mitigate the fault. The control unit 30 thus controls S1 to remain closed, S8 to open, and S7 to close. The voltage drop is compensated, and a fault on the first primary side 16 is mitigated.

[0061] If at least two switching elements of Q11-Q14 experience a fault, in particular an SC fault, the control unit 30 reconfigures the LLC resonant converter 34 such that the first module 12 is disconnected from the DC output terminal 28 and the redundant second module 14 is connected to the DC output terminal 28 to take over for the first module 12.

[0062] Thus, the LLC resonant converter arrangement 34 provides a fully redundant and fault-tolerant converter arrangement in which errors and / or failures in the first module 12 can be compensated.

[0063] With reference to Fig. 4 shows a circuit diagram of an LLC resonant converter arrangement 42. The LLC resonant converter arrangement 42 is similar to the LLC resonant converter arrangement 34 of Fig. 3, except that the LLC resonant converter arrangement 42 is an IPOP (Input-Parallel Output-Parallel) arrangement, while the LLC resonant converter arrangement 34 of Fig. 3 is an ISOP (Input-Serial Output-Parallel) arrangement. Therefore, Fig. 4 the first and second modules 12, 14 are connected in series and not in parallel, as in Fig. 3. The function and operation of the control unit 30 can be described in conjunction with Fig. 3. For example, the control unit 30 may operate the switches S1, S2, S7, and S8 in such a way that a fault and / or failure in the first module 12 may be mitigated.

[0064] Although the above LLC resonant converter arrangements have been described with respect to either an ISOP or an IPOP configuration, those skilled in the art would understand that such LLC resonant converter arrangements can also be adapted for ISOS (Input-Serial Output-Serial) or IPOS (Input-Parallel Output-Serial) configurations.

Claims

[1] LLC resonant converter arrangement (10, 32) for DCDC conversion, comprising: - a first module (12) having a first primary side (16) including two half-bridges, a first secondary side (18) including two half-bridges, and a first resonant circuit (20) coupling the first primary side (16) to the first secondary side (18), - a second module (14) having a second primary side (22) comprising two half-bridges, a second secondary side (24) comprising two half-bridges, and a second resonant circuit (26) coupling the second primary side (22) to the second secondary side (24), - a center-tapped capacitor (Co1Co2) arranged between a DC output side of the two half-bridges of the first secondary side (18) and a DC output terminal (28) of the LLC resonant converter arrangement (10, 32), wherein - the DC output side of the two half-bridges of the first secondary side (18) can be connected to a DC input side of the center-tapped capacitor (Co1Co2) by a first switch (S1), - a DC output side of the two half-bridges of the second secondary side (24) downstream of the first switch (S1) is connectable to the DC input side of the center-tapped capacitor (Co1Co2) by a second switch (S2), and - a center tap point of the center-tapped capacitor (Co1Co2) can be connected by a third switch (S5) to a center tap point of one of the two half-bridges of the first secondary side (18). [2] LLC resonant converter arrangement (10, 32) according to claim 1, further comprising: - a control unit (30) designed to: - controlling the first switch (S1) into a closed state and the third switch (S5) into an open state for operating the first module (12) in normal operation, and - Controlling the third switch (S5) from an open state to a closed state in the event of a fault in one of the two half-bridges on the first primary side. [3] LLC resonant converter arrangement (10, 32) according to claim 2, wherein the control unit (30) is further configured to detect a failure of the first module (12) and to control the first switch (S1) and the third switch (S5) to an open state and the second switch (S2) to a closed state in response to the detected failure of the first module. [4] LLC resonant converter arrangement (10, 32) according to one of claims 2-3, wherein the control unit (30) is further configured to control the second switch (S2) into a closed state if additional power is required at the DC output terminal (28) of the LLC resonant converter arrangement (10, 32). [5] LLC resonant converter arrangement (34, 42) for DCDC conversion, comprising: - a first module (12) having a first primary side (16) including two half-bridges, a first secondary side (18) including a B6C rectifier circuit with three half-bridges, and a first resonant circuit (20) coupling the first primary side (16) to the first secondary side (18), - a second module (14) having a second primary side (22) including two half-bridges, a second secondary side (24) including two half-bridges, and a second resonant circuit (26) coupling the second primary side (22) to the second secondary side (24), and - a capacitor (Co) arranged between a DC output side of the B6C rectifier circuit and a DC output terminal (28) of the LLC resonant converter arrangement (34, 42, 44), wherein - the DC output side of the two half-bridges can be connected to a DC input side of the capacitor (Co) by a first switch (S1), - a DC output side of the two half-bridges of the second secondary side (24) downstream of the first switch can be connected to the DC input side of the capacitor (Co) by a second switch (S2), and - a secondary winding of a transformer (Tr1) of the first resonant circuit (20) includes a first winding end terminal (36), a second winding end terminal (38) and a winding center tap terminal (40), wherein - the first winding end terminal (36) is connected to a center tap point of a first half-bridge of the three half-bridges, the winding center tap terminal (40) of the secondary winding is connectable to a second half-bridge of the three by a third switch (S8), and the second winding end terminal (38) is connectable to a center tap point of a third half-bridge of the three half-bridges by a fourth switch (S7). [6] LLC resonant converter arrangement (34, 42) according to claim 5, further comprising: - a control unit (30), wherein the control unit (30) is designed to: - controlling the first switch (S1) into a closed state, the third switch (S8) into a closed state and the fourth switch (S7) into an open state during normal operation of the first module (12) and - controlling the third switch (S8) from a closed state to an open state and the fourth switch (S7) from an open state to a closed state in the event of a fault in one of the half-bridges on the first primary side (16). [7] LLC resonant converter arrangement (34, 42) according to claim 6, wherein the control unit (30) is further configured to detect a failure of the first module (12) and control the first switch (S1) to an open state and the second switch (S2) to a closed state in response to the detected failure of the first module. [8] LLC resonant converter arrangement (34, 42) according to one of claims 6-7, wherein the control unit (30) is further configured to control the second switch (S2) into a closed state if additional power is required at the DC output terminal (28) of the LLC resonant converter arrangement (34, 42). [9] LLC resonant converter arrangement (10, 32, 34, 42) according to one of the preceding claims, wherein the two half-bridges of the first secondary side (18) and / or the second secondary side (24) are passive half-bridges, preferably diodes. [10] LLC resonant converter arrangement (10, 32, 34, 42) according to one of the preceding claims, wherein the first primary side (16) and the second primary side (22) are connected in series or in parallel.

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