LLC resonant converter arrangement

Abstract

LLC resonant converter arrangement (44, 46), comprising: a first module (12) with a first primary side (16), a first secondary side (18) including a B4C rectifier circuit, and a first resonant circuit (20) coupling the first primary side (16) with the first secondary side (18), 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) with the second secondary side (24), and a capacitor (Co) arranged between a DC output side of the B4C rectifier circuit and a DC output port (28) of the LLC resonant converter arrangement (34, 42, 44), wherein the DC output side of the B4C rectifier circuit is connectable to a DC input side of the capacitor (Co) by a first switch (S1), a DC output side of the B4C rectifier circuit is connectable to the DC input side of the capacitor (Co) downstream of the first switch by a second switch (S2), a secondary winding of a transformer (Tr1) of the first resonant circuit (20) includes a first winding end port (36), a second winding end port (38) and a winding center tap port (40), wherein the first winding end port (36) is connected to a center tap point of a first half-bridge of the B4C rectifier circuit, and the second winding end port (38) and the winding center tap port (40) are alternately connectable to a second half-bridge of the B4C rectifier circuit by a single pole change over switch (SPCO).

Description

[0001] Description

[0002] LLC resonant converter arrangement

[0003] The present invention relates to a LLC resonant converter arrangement for DCDC conversion. In particular, the present invention relates to a stand-alone fault-tolerance integrated fully-redundant LLC resonant converter arrangement for HV / LV DCDC conversion, in particular for use in the automotive sector. The present invention further relates to a method of operating such an arrangement.

[0004] Fail-operational is paramount, in a particular in powertrains related to e-mobility applications, but also in autonomous driving applications ensuring safety, reliability, and compliance with regulations. The implementation of a fail-operational mechanism can be accomplished through either redundancy or through an independent fault-tolerant capability. The reliability of power electronic converters is of significance in mission-critical applications, including electric vehicles, aerospace systems, and other safety related applications.

[0005] When it comes to e-mobility, stand-alone fault-tolerant and fully-redundant HV / LV DCDC converters are essential for the safe and reliable operation of autonomous systems, particularly in advanced autonomous driving (AD) L4 / L5 vehicles. Fault-tolerant and redundant HV / LV DCDC converters ensure consistent power conversion and enhance system resilience by providing backup power paths.

[0006] Current designs of HV / LV DCDC converter arrangements, however, provide either a fault-tolerance capability or a redundancy capability.

[0007] It is thus an object of the present invention to provide an HV / LV DCDC converter arrangement, or more generally an LLC resonant converter arrangement which provides a stand-alone fault-tolerance integrated fully-redundant concept that provides both a stand-alone fault-tolerance and fully-redundant capability. This and other objects, which become apparent upon reading the description, are solved by the subject-matter of the independent claims. Further embodiments and developments are provided in the dependent claims.

[0008] According to a first aspect of the present invention, a LLC resonant converter arrangement, 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 a B4C rectifier circuit including two half-bridges, and a first resonant circuit coupling the first primary side with 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 with the second secondary side. The arrangement further comprises a capacitor arranged between a DC output side of the B4C and a DC output port of the LLC resonant converter arrangement. In the arrangement, the DC output side of the two half-bridges is connectable 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 is connectable to the DC input side of the capacitor downstream of the first switch by a second switch, wherein a transformer of the first resonant circuit on the secondary side of the first module includes a secondary winding, the secondary winding including a first winding end port, a second winding end port and a winding center tap port.

[0009] The first winding end port is connected to a center tap point of a first half-bridge of the two half-bridges, and the second winding end port and the winding center tap port are alternately connectable to a second half-bridge of the two half-bridges by a single pole change over switch (SPCO). Such as switch may also be known as single pole double throw switch (SPDT). In other words, in the B4C rectifier circuit, one winding end port is connected to one of the two half-bridges and the other winding end port or alternatively the winding center tap port is connected to the other one of the two half-bridges.

[0010] The present invention is based at least partially on the idea that such a topology can provide both a fully-integrated redundancy as well as a stand-alone fault-tolerant capability. The redundancy aspect is taken care of a second module which can be used as back-up or top-up for the first module. The second module can be plugged in using the second switch. The fault-tolerant aspect is taken care of in that a drop in output voltage is compensated by increasing, or more precisely, doubling the number of windings in the secondary winding of the first module. The wording “doubling” may be understood in the way that in normal operation, the center tap port of the secondary winding is connected to the DC voltage output port, whereas in case of fault in the first module, followed by a voltage drop, the second winding end port is connected to the DC output port. In the B4C rectifier circuit the second half-bridge of the two half-bridges is used to either connect to the winding center tap port (in normal operation) or the second winding end port (in case of a fault). As compared to a B6C rectifier circuit used in the first secondary side, a third half-bridge can be omitted, saving on two switching elements and the controllers thereof, which overall reduces costs and limits potential sources of faults or failure. As compared to, for example, a center-tapped capacitor, the proposed topology saves on an additional capacitor. Capacitors are a major source of fault or failure in power converter arrangements. Thus, by including only one capacitor instead of two capacitors (in the center-tapped capacitor), the proposed topology increases the overall system power density and ensures an improved overall performance.

[0011] Preferably, the two half-bridges of the first and / or second secondary side are passive half-bridges. Preferably, these half-bridges use diodes as switching elements. Passive half-bridges or in particular diodes are best suited for redundancy and fault-tolerant capabilities as such components are reliable and do not need active controlling.

[0012] Preferably, the first primary side and the second primary side are connected in series or in parallel. Input-parallel output-parallel (IPOP) systems cater to applications requiring large output currents, while input-serial output-parallel (ISOP) systems are suited for cases with high input voltages and lower output voltages. Both topologies are well suited, in particular for applications in the automotive sector. Preferably, the LLC converter arrangement further comprises a control unit configured for controlling the first switch into a closed state and the single pole change over switch into a first state in which the winding center tap port is connected to the second half-bridge of the two half-bridges and the second winding end port is disconnected from the second half-bridge, and controlling the first switch into a closed state and the single pole change over switch into a second state in which the winding center tap port is disconnected from the second half-bridge and the second winding end port is connected to the second half-bridge in case of a fault. This embodiment is based at least partially on the idea that semiconductor faults, or more generally speaking faults of a switching elements of the half-bridge, can lead a device to assume an open-circuit (OC) or short-circuit (SC) state (or drift). In LLC converter arrangements SC faults may present significant risks, as they can cause extensive damage to the power converter. This embodiment is at least partially based on the idea that the LLC resonant converter arrangement reconfigures upon detecting such a fault.

[0013] This embodiment is at least partially based on the idea that the LLC resonant converter arrangement reconfigures upon detecting such a fault.

[0014] In the event of an SC of one of the switching elements in the first primary side, the output voltage drops to 50%, as mentioned earlier. This output voltage drop can be compensated by using an SPCO switch that is used to either connect the winding center tap point or the second winding end port to the second half-bridge of the two half-bridges of the B4C rectifier circuit. This effectively changes the effective number of windings or turns from n: 1 to n: 2 and restores the nominal output voltage. In other words, by doubling the number of windings or turns, the 50% drop can be compensated. Compared to a B6C rectifier circuit, essentially, one half-bridge can be saved using the SPCO switch.

[0015] Preferably, the control unit of the LLC resonant converter arrangement may further be configured for determining a failure of the first module. Herein, under the wording “failure of the first module” is meant that at least two switching elements in one of the first and / or the second half-bridge of the first primary side are broken and / or under fault. In other words, at least two switching elements in the first primary side experience a fault (whether OC or SC, does not matter). In case 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 port of the arrangement and (instead) the second module is connected to the DC output port of the arrangement, by controlling the first switch into an open state and the second switch into a closed state. This reconfiguration is part of the fully-redundant capability of the proposed LLC resonant converter arrangement.

[0016] As already mentioned in relation to the first aspect, the second module, may, however, also be used to increase power output of the LLC resonant converter arrangement. As such, according to an embodiment, the control unit may be configured to control the second switch into a closed state in case additional power is required at the DC output port of the LLC resonant converter arrangement. The reason is that the LLC resonant converter arrangement is essentially an output parallel arrangement which allows to double the power upon plugging in the first and the second module.

[0017] According to a second aspect of the present invention, which may be an independent aspect of the present invention, a method of controlling a LLC resonant converter arrangement according to the first aspect and / or embodiments thereof, is provided. The method comprises the steps of: operating the first module in normal operation by controlling the first switch into a closed state and the single pole change over switch into a first state in which the winding center tap port is connected to the second half-bridge of the two half-bridges and the second winding end port is disconnected from the second half-bridge, determining a fault in one of the half-bridges in the first primary side of the first module, and controlling the single pole change over switch into a second state in which the winding center tap port is disconnected from the second half-bridge and the second winding end port is connected to the second half-bridge, in response to the determined fault. Preferably, the method further comprises the steps of: determining a failure of the first module, and controlling the first switch into an open state and the second switch into a closed state in response to the determined failure of the first module.

[0018] Preferably, the method further comprises the steps of determining that additional power is required at the DC output port of the LLC resonant converter arrangement, and controlling the second switch into a closed state in response to the determined additional power requirement.

[0019] Further embodiments and aspects of the present invention are explained using the accompanying schematic figures, which are incorporated herein.

[0020] FIG 1 is a schematic drawing of an example of an LLC resonant converter arrangement, the arrangement being a ISOP arrangement with a B4C rectifier circuit.

[0021] FIG 2 is a schematic drawing of another example of an LLC resonant converter arrangement, the arrangement being an IPOP arrangement with a B4C rectifier circuit.

[0022] Within the figures, same components are referenced by the same numerals.

[0023] Embodiments of the invention will now be described in context with the

[0024] Referring to FIG 1 , a schematic drawing of an LLC resonant converter arrangement 44 in an input-serial output-parallel (ISOP) configuration is shown. LLC resonant converter arrangement 44 may be used as a DCDC converter, in particular is a HV / LV DCDC converter, such as used, for example, in automotive applications.

[0025] LLC resonant converter arrangement 44 includes a first module 12 and a second module 14 arranged in serial. First module 12 includes first primary side 16, a first secondary side 18 and a first resonant circuit 20 coupling the first primary side 16 with first secondary side 18. First resonant circuit 20 includes a capacitance Cr1 , an inductance Lr1 and a transformer Tr1 including magnetizing inductance Lm1. Transformer Tr1 offers electrical isolation at the necessary turns ratio for delivering a desired voltage level. First resonant circuit in 20 is a resonant circuit well known to a person skilled in the art which is why further explanation is not necessary.

[0026] First primary side 16 includes two half bridges, wherein a first branch or leg includes two switching elements Q11 and Q12, and a second branch or leg includes two further switching elements Q13 and Q14. In the exemplary embodiment shown, Q11 -Q14 are MOSFET switching elements. In other embodiments not shown, Q11 -Q14 may be different switching elements. First primary side 16 is connected to a first DC voltage source Vin1. A voltage level of DC voltage source Vin1 is converter to a (lower) DC voltage level at the first secondary side 18 using the first resonant circuit 20, as known to a person skilled in the art.

[0027] First secondary side 18 includes a B4C rectifier circuit including two half-bridges. A first half-bridge of the two half-bridges includes switching elements S11-S12, a second half-bridge of the two half-bridges includes switching elements S13-S14. In the specific embodiment shown, the two half-bridges are active half-bridges including MSOFET switching elements S11 -S14. In other embodiments not shown, the switching elements may be passive switching elements such as diodes.

[0028] Second module 14 includes a second primary side 22, a second secondary side 24 and a second resonant circuit 26 coupling the second primary side 22 with second secondary side 24. Second resonant circuit 26 includes a capacitance Cr2, an inductance Lr2 and a transformer Tr2 including magnetizing inductance Lm2. Transformer Tr2 offers electrical isolation and the necessary turns ratio for delivering a desired voltage level. Second resonant circuit in 26 is a resonant circuit well known to a person skilled in the art which is why further explanation is not necessary.

[0029] Second primary side 22 includes two half bridges, wherein a first branch or leg includes two switching elements Q21 and Q22, and a second branch or leg includes two further switching elements Q23 and Q24. In the exemplary embodiment shown, Q21 -Q24 are MOSFET switching elements. In other embodiments not shown, Q21 -Q24 may be different switching elements. Second primary side 22 is connected to a second DC voltage source Vin2 and connected in series to first DC voltage source Vin1 . A voltage level of DC voltage source Vin2 is converted to a (lower) DC voltage level at the second secondary side 24 using the second resonant circuit 26, as known to a person skilled in the art.

[0030] Second secondary side 24 includes two half bridges. In the exemplary embodiment shown, the two half bridges of second secondary side 24 are passive half-bridges made of diodes D21-D24. In other embodiments not shown, second secondary side half-bridges may be actively controlled half bridges using MOSFET switching elements or the like.

[0031] LLC resonant converter arrangement 44 further includes a DC output port 28. DC output port 28 is configured for providing a DC output at a desired voltage level for supplying the voltage to an electrical load, schematically illustrated as RL. In the embodiment shown, output voltage levels may be 48V, 24V 12V or other voltage levels.

[0032] LLC resonant converter arrangement 44 further includes DC output port 28. LLC resonant converter arrangement 44 further includes capacitor Co arranged between a DC output side of the two half-bridges of first secondary side 18 and DC output port 28. First switch S1 is arranged between the DC output side of the two half-bridges of the first secondary side 18 and outer DC input side ports of capacitor Co. Second switch S2 is arranged between the DC output side of the two half-bridges of the second secondary side 24 and outer DC input side ports of capacitor Co downstream of first switch S1 .

[0033] First transformer Tr1 includes a first winding on first primary side 16 and a secondary winding on first secondary side 18. Secondary winding includes first winding end port 36, second winding end port 38 and winding center tap port 40. First winding end port 36 is connected to a center tap point of the first half-bridge of the two half-bridges. Second winding end port 38 and winding center tap port 40 are alternately connectable to a center tap point of the second half-bridge of the two half-bridges by a single pole change over switch SPCO also known as a single pole double throw switch. Switch SPCO includes a first state in which winding center tap port 40 is connected to and second winding end port 38 is disconnected from a center tap point of the second half-bridge. Switch SPCO includes a second state in which winding center tap port 40 is disconnected from and second winding end port 38 is connected to the center tap point of the second half-bridge.

[0034] LLC resonant converter arrangement 44 further includes control unit 30. Control unit 30 may be operably connected to first and second modules 12, 14. Control unit 30 is configured for determining a fault in any of the switching elements Q11 -Q24, as well as for determining a required DC voltage output level or drop-off thereof. Control unit 30 is further configured for operating a state of any of the switching elements Q11 -Q24, S11 -S14 of first and second modules 12, 14 as well as switches S1 , S2 and SPCO.

[0035] Under normal operation of first module 12, i.e. if there are no faults in first module 12, control unit 30 may operation Q11 -Q14 as desired, control S1 in a closed state and SPCO into the first state in which winding center tap port 40 is connected to and second winding end port 38 is disconnected from the second half-bridge such that DC output port 28 provides the necessary DC voltage level. If additional power is required, control unit 30 may operate S2 into a closed state to top-up first module 12 by plugging in second module 14.

[0036] In case of one of the switching elements Q11 -Q14 experiencing a fault, in particular an SC fault, control unit 30 may reconfigure LLC resonant converter arrangement 44 such that this fault is compensated.

[0037] As an example, if Q13 experiences an SC fault, control unit 30 controls Q14 to be permanently open. This way second half-bridge of first primary side 16 is grounded and the DC output voltage of the arrangement would drop by 50%. The grounding and / or the voltage drop may be an indicator for control unit 30 to realize and mitigate the fault. Control unit 30 thus controls S1 to remain closed and controls SPCO from the first state into the second state in which winding center tap port 40 is disconnected from and second winding end port 38 is connected to the second half-bridge. The voltage drop is compensated and a fault in first primary side 16 is mitigated.

[0038] In case of at least two switching elements of Q11 -Q14 experiencing a fault, in particular an SC fault, control unit 30 reconfigures LLC resonant converter 44 such that first module 12 is disconnected from DC output port 28 and redundant second module 14 is connected to DC output port 28 to take over for first module 12.

[0039] Thus, LLC resonant converter arrangement 44 provides a fully redundant and fault-tolerant LLC resonant converter arrangement, wherein fault and / or failures in first module 12 can be compensated.

[0040] Referring to FIG 2, a schematic drawing of an LLC resonant converter arrangement 46 is shown. LLC resonant converter arrangement 46 is similar to LLC resonant converter arrangement 44 of FIG 1 except that that LLC resonant converter arrangement 46 is an input-parallel output-parallel (IPOP) arrangement, whereas LLC resonant converter arrangement 44 of FIG 1 is an input-serial output-parallel (ISOP) arrangement. Thus, in FIG 2, first and second modules 12, 14 are connected in series and not in parallel as shown in FIG 1 . Function and operation of control unit 30 may be the same as described in connection with FIG 1. For example, control unit 30 may operate switches S1 , S2, and SPCO such that a fault and / or a failure in first module 12 can be mitigated.

[0041] Although the above mentioned LLC resonant converter arrangements 44, 46 were described in relation to either a ISOP or IPOP configuration, a person skilled in the art, would understand, that such LLC resonant converter arrangements may be also adapted to input-serial output-serial (ISOS) or input-parallel output-serial (IPOS) 9configurations.

Claims

Patent claims1. LLC resonant converter arrangement (44, 46) for DCDC conversion, comprising: a first module (12) with a first primary side (16) including two half-bridges, a first secondary side (18) including a B4C rectifier circuit including two half-bridges, and a first resonant circuit (20) coupling the first primary side (16) with the first secondary side (18), a second module (14) with 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) with the second secondary side (24), and a capacitor (Co) arranged between a DC output side of the B4C rectifier circuit and a DC output port (28) of the LLC resonant converter arrangement (34, 42, 44), wherein the DC output side of the two half-bridges is connectable 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) is connectable to the DC input side of the capacitor (Co) downstream of the first switch by a second switch (S2), a secondary winding of a transformer (Tr1 ) of the first resonant circuit (20) includes a first winding end port (36), a second winding end port (38) and a winding center tap port (40), wherein the first winding end port (36) is connected to a center tap point of a first half-bridge of the two half-bridges, and the second winding end port (38) and the winding center tap port (40) are alternately connectable to a second half-bridge of the two half-bridges by a single pole change over switch (SPCO).

2. LLC resonant converter arrangement (44, 46) of claim 1 , comprising: a control unit (30) wherein the control unit (30) is configured for controlling the first switch (S1 ) into a closed state and the single pole change over switch (SPCO) into a first state in which the winding center tap port (40) is connected to the second half-bridgeof the two half-bridges and the second winding end port (38) is disconnected from the second half-bridge, and controlling the first switch (S1 ) into a closed state and the single pole change over switch (SPCO) into a second state in which the winding center tap port (40) is disconnected from the second half-bridge and the second winding end port (38) is connected to the second half-bridge in case of a fault in one of the half-bridges in the first primary side (16).

3. LLC resonant converter arrangement (44, 46) of claim 2, wherein the control unit (30) is further configured for determining a failure of the first module (12) and controlling the first switch (S1 ) into an open state and the second switch (S2) into a closed state in response to the determined failure of the first module.

4. LLC resonant converter arrangement (44, 46) of any one of claims 2-3, wherein the control unit (30) is further configured for controlling the second switch (S2) in a closed state in case additional power is required at the DC output port (28) of the LLC resonant converter arrangement (34, 42, 44).

5. LLC resonant converter arrangement (44, 46) of any 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.

6. LLC resonant converter arrangement (44, 46) of any 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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