Power module for an inverter and collection circuit

Abstract

The invention relates to a power module (10) for an inverter and a collection circuit (60) having multiple power modules (10). The power module (10) comprises at least two semiconductor switches (54) and a gate drive circuit (59) for the semiconductor switches (54). The gate drive circuit (59) comprises a primary gate drive control (63) and an integrated secondary gate drive circuit portion (58). The integrated secondary gate drive circuit portion (58) comprises a printed circuit board (56) to which the semiconductor switches (54) are bonded side by side in parallel to each other. The primary gate drive control (63) is galvanically isolated from the secondary gate drive circuit portion (58).

Description

[0001] Power module for an inverter and collection circuit

[0002] The invention relates to a power module for an inverter and a collection circuit having multiple power modules.

[0003] Modern transistor topologies, such as GaN-based transistors, enable very high switching speeds to be achieved. In essence, this provides the possibility of efficiency increases of an inverter having such power switches implemented for half bridge power modules. Additionally, GaN HEMTs (High Electron Mobility Transistors), as to their different physical working principle compared to common FETs (Field Effect Transistors) or Bi-polar transistors, have no intrinsic body-diodes and no reverse-recovery charge. This allows tuning the switching loss with the aim of improved efficiency and simultaneously avoiding the disadvantages of parasitic effects caused because of reverse-recovery charge dump.

[0004] However, most GaN transistors have comparatively low gate charge and low threshold voltage. Considering the single chip surface area to amperage, multiple chips per module need to be integrated in parallel to achieve wanted target current ranges. Integration of GaN transistor bare / dies / chips into conventional inverter modules poses several problems. Due to varying dispersion effects of the transistor topologies, a susceptibility of instability is triggered. Ultimately, unwanted effects, such as wide-ranging stray inductance gate loops, high amplitude stray inductance power loops, and high frequency inter-chip noise and oscillations may be caused. If such effects occur in gate-source drive circuits, these effects may lead to short circuit events such that the underlying electronic circuit and components may be severely damaged.

[0005] As these transistor topologies enable for even increased turn-on and turn-of switching speeds by high signal slew-rates, noise effects due to over-voltages are caused thereby, such as electromagnetic interference effects in the gate circuit. In order to reduce or to avoid such interference effects, gate resistors are commonly used as snubbers, which, however, negatively influences the performance and puts a limitation in the gate circuit as well as can effect counter-unwanted transient voltage effects.

[0006] Accordingly, there is a need for power modules and collection circuits having multiple power modules enabling the use of up-to-date transistor topologies such that the underlying circuit is less prone to negative effects affecting the underlying functionality compared to known approaches, such as short circuit events or electromagnetic interference effects.

[0007] The objective technical problem to be solved may be considered to consist in overcoming or at least reducing the disadvantages according to the prior art by providing a power module and an inverter enabling a higher gate robustness, a higher short-circuit robustness, and a high efficiency provided by fewer electric losses when operating the underlying module.

[0008] The problem is solved by the subject matter of the independent claims. Preferred embodiments are indicated within the dependent claims and the following description, each of which, individually or in combination, may represent aspects of the disclosure.

[0009] According to an aspect, a power module for an inverter is provided. The power module comprises at least two semiconductor switches and a gate drive circuit for the semiconductor switches. The gate drive circuit comprises a primary gate drive control and an integrated secondary gate drive circuit portion. The integrated secondary gate drive circuit portion comprises a printed circuit board to which the semiconductor switches are bonded side by side in parallel to each other. The primary gate drive control is galvanically isolated from the secondary gate drive circuit portion.

[0010] The invention is based on the finding that the partition of the gate drive circuit into two portions which are galvanically isolated from each other strongly increases the stability of the circuit underlying the power module including any of the semiconductor switches thereof. This is achieved since parasitic inductances caused by the primary gate drive control can be reduced by a significant amount if not completely eliminated as to the galvanic isolation between the primary gate drive control and the secondary gate drive circuit portion of the gate drive circuit. In particular, the galvanic isolation enables high frequency noise, such as electromagnetic interference effects, to be decreased as compared to prior art approaches. Thus, the chances of spurious and unwanted switching events of power switches being established by the semiconductor switches are greatly reduced at the chip level. Moreover, the reduction of parasitic inductances and this geometric structure also enables the semiconductor device to be arranged in a parallel manner with a very short gate loop. Consequently, the circuit of the power module comprises a highly symmetric layout such that the occurrence of wide-ranging stray inductance gate loops and high amplitude stray inductance power loops is widely suppressed or at least their intensities weakened. For example, the galvanic isolation between different portions of the gate drive circuit enables that the secondary gate drive circuit portion can be arranged closer to the semiconductor switches. Accordingly, if at all stray inductance gate loops arise, such gate loops are reduced in size. Hence, their effects on other components of the power module are reduced. For example, the reduction in size of the stray inductance gate loops also provides for less thermal self-heating effects because of optimized switching loss. Accordingly, a lower cooling power is required in view of the power module which enables a more compact design, a reduction of the installation space, and cost savings.

[0011] Consequently, a power module layout having parallelized semiconductor switches can be achieved and reliably operated while, compared to prior art approaches, the negative influences of the parasitic inductances are strongly reduced. As the reduced size of the stray inductance gate loops, high switching speeds can be achieved with stray inductance power loops having remarkably minimized amplitudes as compared to prior art approaches. Therefore, an improved noise signature is achieved within the inductance gate loops, i.e. the noise effects are reduced in amplitude as compared to prior art approaches.

[0012] The two semiconductor switches may constitute a single side switch according to a half-bridge topology of an inverter.

[0013] Optionally, a semiconductor switch comprises at least one transistor, such as a high electron mobility transistor (HEMT), a bipolar transistor, or a metal oxide semiconductor field effect transistor (MOSFET).

[0014] The primary gate drive control can be understood so as to regulate a gate signal provided by the secondary gate drive circuit portion to a gate electrode of at least one semiconductor switch. To this end, the primary gate drive control may comprise a pulse width modulator and / or an integrated circuit controlling the functions of the secondary gate drive circuit portion.

[0015] The arrangement of the semiconductor switches within the power module may be symmetric with regard to each other. Accordingly, the symmetry of the power module is further increased such that noise effects are distributed more homogeneous. Hence, the operation properties of a first semiconductor switch do not stand back behind the operation properties of a second semiconductor switch. In addition, no specific components of the power module are singularly affected by noise. The symmetry of the power module also provides for the noise being compensable more efficiently.

[0016] In some embodiments, the primary gate drive control may be established as a low-voltage control. This means that the primary gate drive control may for example be operated a low-voltages, such as at a nominal voltage amplitude of 5 V, 7 V, 9 V, or 12 V. Preferably, a supply voltage required for operating the primary gate drive control is below 48 V, preferably below 24 V. Due to the galvanic isolation, the low-voltage circuit of the primary gate drive control can be reliably separated from the intrinsic circuit portions of the power module. Hence, noise, such as electromagnetic interference, being present in the low-voltage circuit, is prevented from (directly) affecting the underlying internal circuit of the power module because of an additional decoupling filter stage established by the transition from the secondary gate drive circuit portion to the primary gate drive control.

[0017] Accordingly, a decoupling filter stage can also be added in the gate drive circuit within the power module’s gate drive circuit substrate. Additionally, at least one passive snubber stage (R,L,C) can be added as well within the power module to further optimize the power module based on the specific semiconductor properties and configuration (generation).

[0018] Optionally, the primary gate drive control is arranged external to the power module. Accordingly, the source for electronic noise is fully removed from the power module. Thus, the influence of the primary gate drive control on the intrinsic circuits of the power module is reduced.

[0019] Preferably, the primary gate drive control is coupled to the integrated secondary gate drive circuit portion at least based on male connectors extending out of a module encapsulation of the power module encapsulating at least the semiconductor switches and the integrated secondary gate drive circuit portion including the printed circuit board. Hence, a reliable connection between the primary gate drive control and the secondary gate drive circuit portion can be guaranteed. For example, using the male connectors control signals may be one-directionally or bidirectionally transmitted between the various portions of the gate drive circuit.

[0020] In specific embodiments, the male connectors extend orthogonally out of the module encapsulation. This provides for further increase of the symmetry of the power module.

[0021] In some embodiments, the module encapsulation comprises an electrically insulating gel material or an epoxy mold compound. Hence, the module encapsulation may increase the safety of the power module since the clearance and creepage distances needed are effectively increased thereby. Consequently, the clearance and creepage distances may be sufficient for high-voltage applications, such as for electric vehicles or photo-voltaic devices, having voltage amplitudes of up to 800 V, the design of the power module is very compact though.

[0022] Preferably, the secondary gate drive circuit portion comprises a bare die, a packaged integrated circuit, or an embedded die arranged on or within the printed circuit board. This provides the possibility to apply varying gate signals having tailored signal profiles to the gate electrodes of the semiconductor switches. In effect, the control of the semiconductor switches can be adapted according to the respective needs as several parameters of the gate signals provided can be varied by the circuit of the secondary gate drive circuit portion.

[0023] Optionally, the secondary gate drive circuit portion may be enabled to provide different gate signals to the semiconductor switches having different signal profiles. Consequently, the control of the semiconductor switches can be optimized, for example in view of the slew rates underlying switching events of the respective transistors being part of the semiconductor switches. Since the slew rate directly influences the electromagnetic interferences caused as to the switching events, the noise caused by the operation of the power module can be influenced thereby.

[0024] In some embodiments, the printed circuit board comprises redistribution layers or routed conductor tracks having landing bonds bondable pads arranged on the printed circuit board for establishing gate bonds to gate electrodes of the semiconductor switches. This provides the possibility to directly bond (attach) the semiconductor switches to the bondable pets of the printed circuit board. Accordingly, the layout of the power module is very compact. For example, the required installation space is small.

[0025] Optionally, the printed circuit board comprises a glass-reinforced epoxy laminate substrate material, a ceramic substrate material, or a copper / metal-conductor core based substrate material. Accordingly, an additional screening effect is established for decoupling the coupling effects between high voltage and low voltage circuit portions. Hence, the variety of usable materials is broad. For example, a specific material being usable for the printed circuit board is a FR4 PCB material. Here, FR4 denotes a material being of a fire resistance class level 4 type. Therefore, the underlying material of the printed circuit board is highly resistant to taking fire. Accordingly, the robustness and the lifetime of the power module are increased.

[0026] In case the printed circuit board comprises a ceramic substrate material, the printed circuit board may preferably comprise metal tracks. As to the metal tracks, high conductivity paths for transmitting electric signals are provided. Moreover, as to the metal tracks, specific clearance and creepage distances may be established and guaranteed for the embedded tracks in the specific chosen substrate.

[0027] Preferably, the secondary gate drive circuit portion including the printed circuit board is coupled to a directly bonded metal layer of the power module via electrically insulating mechanical support legs such that a clearance sufficient for bonds coupling the semiconductor switches to the printed circuit board is provided between the printed circuit board and the directly bonded metal layer. This means that the printed circuit board of the secondary gate drive circuit portion is distant from the directly bonded metal layer of the power module. The clearance provided in between those components is sufficient for arranging the bonds used for bonding the semiconductor switches within the clearance. Still, sufficient clearance and creepage distances for the respective applications, such as high-voltage applications, are considered. Hence, an arrangement is established which enables the power module to be compact.

[0028] For example, within the usual use case, the printed circuit board of the secondary gate drive circuit portion may be arranged above the directly bonded metal layer. However, beneath the printed circuit board, sufficient space for the bonds for attaching the semiconductor switches is provided. Hence, as the bonds are guided to the printed circuit board from a first side (e.g. the bottom side), electronic circuits can be arranged on a second side being opposite the first side (e.g. a top side). This enables a very compact design and small installation space of the secondary gate drive circuit portion and therewith the power module to be achieved.

[0029] In some embodiments, the printed circuit board is established by two separate parts arranged side by side within a common printed circuit board plane with the semiconductor switches positioned in between both separate parts. Accordingly, the separate parts of the printed circuit board and the semiconductor switches are positioned according to a flat configuration where all of these components are positioned substantially in a single plane or In closely arranged parallel planes. This is also beneficial for the power module having a compact layout and requiring only a small installation space.

[0030] Preferably, at least a first semiconductor switch is provided for a high-side switch of a collection circuit for the inverter and at least a second semiconductor switch is provided for a low-side switch of the collection circuit. The collection circuit comprises multiple power modules. A set of parallel semiconductor chips having at least a first semiconductor switch and a second semiconductor switch are assigned to each of the separate parts of the printed circuit board. A drain electrode of high-side switch is bonded with a DC+ baseplate of the power module. A source electrode of the high-side switch is bonded with drain pads of the low-side switch of the collection circuit and also with an AC baseplate of the power module. A source electrode of the low-side switch is bonded with a DC- baseplate of the power module. This arrangement enables an easy and reliable contacting of the respective electrodes of the switches based on the respective and separate baseplates. The stacked arrangement of the baseplates also provides for magnetic coupling effects between the baseplates. As to the magnetic coupling effects, stray inductance effects are cancelled because of the return current paths. Accordingly, less noise and electromagnetic interference are caused in the power commutation loop. Also, less electric losses are achieved such that the operating efficiency of the power module is improved.

[0031] In an alternative, a high-side switch and a low-side switch of a particular set of parallel semiconductor chips may also be assigned to different parts of the printed circuit board. Thus, the design, especially in view of the positioning of the high-side switches and low-side switches, can be adapted according to the respective needs.

[0032] Optionally, the DC+ baseplate is at least partially arranged beneath the DC- baseplate and also at least partially beneath the AC baseplate with at least one electrically insulating ceramic layer in between each two of them. The electrically insulating ceramic layer guarantees that no short-circuit can be established between the different baseplates. Accordingly, a compact but safe design of the power module is achieved.

[0033] Preferably, the electrically insulating ceramic layer which is arranged between the DC+ baseplate and the DC- baseplate is also arranged between the DC- baseplate and the AC baseplate. To this end, the electrically insulating ceramic layer may comprise a step structure (wall portion) at least partially extending from a two-dimensional surface of the electrically insulating ceramic layer. This means that the body of the electrically insulating ceramic layer may comprise a wall portion which is laterally arranged between the AC baseplate and the DC- baseplate. Additionally, if no dedicated step structure is to be implemented, the insulation can also be achieved by conformal dispensing of insulating materials, such as electrically insulating gel or Epoxy mould compound, for example during the last step of power module production.

[0034] In some embodiments, the AC baseplate and the DC- baseplate may be arranged within a single baseplate plane. Hence, the AC baseplate and the DC- baseplate may only partially extend along a cross-sectional surface of the power module. Thereby, the required installation space of the power module can be further decreased as compared to a configuration where both the AC baseplate and the DC- baseplate fully extend along a cross-sectional surface of the power module.

[0035] In some application scenarios, any of the baseplates may be exchanged for another one according to the respective needs. The design of the power module may be flexible in this regard. Of course, if the arrangement of the baseplates is modified, respective coupling structures for contacting the semiconductor switches and the printed circuit board of the secondary gate drive circuit portion may potentially be needed to be adapted. Preferably, a first cooling plate is arranged beneath the DC+ baseplate with at least one additional electrically insulating ceramic layer in between.

[0036] Alternatively or cumulatively, a second cooling plate is arranged above and distant from the printed circuit board.

[0037] Since the power module is configured to be used in high-power scenarios, such as including high voltage scenarios, an effective cooling technique can be established in view of the cooling plates. Thus, electric losses being transformed into thermal energy can be efficiently dissipated from the power module.

[0038] Optionally, the DC+ baseplate and the DC- baseplate establish at least one form fit receptacle for at least one DC-link capacitor. This means that the DC-link capacitor is directly positioned between the DC+ baseplate in the DC- baseplate. As to the form fit receptacle, the position preservation of the DC-link capacitor is guaranteed even though the power module may be subject to movements and vibrations. Hence, reliable electric connections are established between each of the DC-link capacitor and the DC+ baseplate and the DC- baseplate.

[0039] Advantageously, the DC-link capacitor enables the noise established within the power loop due to the operation of the power module, in particular electromagnetic interferences, to at least be reduced and optionally to be compensated for. Put differently, noise effects, such as over-voltages caused due to fast switching events of the semiconductor switches, are reduced or even compensated. Therefore, the electric losses are reduced such that the efficiency of the operation of the power module is increased.

[0040] In a specific embodiment, the power module comprises at least two DC-link capacitors being arranged in form fit receptacles established between the DC+ baseplate and the DC- baseplate, respectively. As to the multiple DC-Link capacitors, a redundancy is provided. The receptacles are to ensure appropriate electrical as well as mechanical support for the capacitors within the power module.

[0041] In some embodiments, a DC+ tab, a DC- tab, and an AC tab are coupled to the DC+ baseplate, the DC- baseplate, and the AC baseplate, respectively. Hence, external signal connectors may be reliably coupled to the respective tabs for operation of the power module. Preferably, the secondary gate drive circuit portion comprises multiple gate resistors and at least one logic circuit such that slew rates for operating the semiconductor switches are variable. This provides the possibility to adapt and vary the switching speed of the switching devices provided by the semiconductor switches. Accordingly, the occurrence of noise and electromagnetic interference can be influenced for the specific application scenario. As to the possibility of reducing the noise, unwanted stray inductances influencing the operation of the semiconductor structures of the semiconductor switches can be at least reduced or even prevented.

[0042] Optionally, bonds used for bonding the semiconductor switches are at least partially arranged beneath the printed circuit board, while complying with clearance and creepage requirements. Therefore the installation space required according to lateral dimensions with respect to the semiconductor switches and the printed circuit board are reduced. Hence, the overall required installation space for the power module is small.

[0043] In some embodiments, bonds used for bonding components are established by wire bonds or ribbon bonds. Therefore, the variability for attaching different components to each other is high. For example, there may be components for which a ribbon bond is more suitable than a wire bond. In such an event, an appropriate type of bond can be used.

[0044] Preferably, the semiconductor switches comprise at least one semiconductor active material of GaN, SiC, Si or a hybrid material combination of multiple semiconductors active materials. Thus, the power module can be used with semiconductor switches having several different active materials. Hence, the variability of the power module is high.

[0045] In particular configurations, in which the power module comprises semiconductor switches having GaN semiconductor structures, the lateral arrangement of the semiconductor guarantees that no reverse recovery time is caused. Therefore, electric losses, such as switching losses, can be reduced as higher switching speeds and / or higher switching frequencies can be achieved compared to prior art approaches making use of SiC and IGBT (Insulated-Gate Bipolar Transistor) semiconductor structures. Optionally, the semiconductor switches are positioned such that they are arranged within a single two-dimensional semiconductor switch plane. Accordingly, the arrangement of the components of the power module is highly symmetric.

[0046] Preferably, the semiconductor switch plane is arranged parallel to or substantially coincides with the printed circuit board plane. Therefore, the height of the power module according to a direction orthogonal to the printed circuit board plane may be reduced.

[0047] In some embodiments, the semiconductor switches comprise at least one, preferably multiple transistor chips. The transistor chips comprise transistors, such as a high electron mobility transistor (HEMT), an insulated-gate bipolar transistor (IGBT), or a metal oxide semiconductor field effect transistor (MOSFET). Hence, the packing density may be high.

[0048] Preferably, the transistor chips are designed so as to be normally-on. Accordingly, an explicitly predefined switching state of the transistor chips is guaranteed which simplifies the control of the power module.

[0049] According to another aspect, a collection circuit for an inverter having multiple power modules as described herein before is provided.

[0050] Preferably, the power module is configured to provide at least one high-side switch and at least one low-side switch for a half-bridge of the collection circuit. For example, the inverter may comprise a B6-bridge topology having three half bridges. A collection circuit having multiple power modules may be configured to provide the entire bridge circuit of the inverter or only parts thereof. In the latter case, multiple power modules may be combined so as to establish the bridge topology, which may be comprised within the collection circuit.

[0051] Preferably, a single collection circuit may also be configured to establish more than a single high-side switch and a single low-side switch. In this case, the collection circuit may establish multiple half bridges of a bridge topology of the inverter, eventually even the entire bridge topology or a different bridge topology of the inverter. That is, the collection circuit may also provide for any required high-side and low-side switches needed for operating the inverter. Of course, in other alternatives, other topologies of the inverter are possible as well, such as an inverter providing six phases by the combination of two B6-bridge topologies. Depending on the topology of the collection circuit, multiple power modules may then be needed for realizing all half bridges of the inverter.

[0052] The advantages described in view of the power module are readily achieved based on the collection circuit in a corresponding manner as well.

[0053] According to another aspect, an assembly is provided. Preferably, the assembly is suitable for an electric vehicle, a hybrid vehicle, or a photo-voltaic device. The assembly has an inverter and an electric motor. The inverter includes a collection circuit having power modules as described hereinbefore. The electric motor is operated by the inverter.

[0054] The advantages described in view of the power module are readily achieved based on the assembly in a corresponding manner as well.

[0055] All features and embodiments disclosed with respect to any aspect of the present disclosure are combinable alone or in (sub-)combination with any one of the remaining aspects of the present disclosure including each of the preferred embodiments thereof, provided the resulting combination of features is reasonable to a person skilled in the art.

[0056] The forgoing aspects and further advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings. In the drawings,

[0057] Fig. 1 is a schematic drawing of a power module according to an embodiment,

[0058] Fig. 2 and 3 are a schematic exploded drawings of the power module according to an embodiment, and

[0059] Fig. 4 is a schematic drawing of a collection circuit of power modules for an inverter according to an embodiment.

[0060] Fig. 1 is a schematic drawing of a power module 10 according to an embodiment. The power module 10 comprises a housing 12 being at least partially established by an encapsulation 13. The encapsulation 13 comprises an electrically insulating material, such as an electrically insulating gel material or an epoxy mold compound. The encapsulation 13 is arranged such that it also provides a structural support for interior components of the power module. For example, an interior volume of the power module 10 other than the underlying structural components may be filled with the material of the encapsulation 13.

[0061] The power module 10 comprises a top side 14, a bottom side 16, and side walls 18 extending in between the top side 14 and the bottom side 16. Accordingly, the power module 10 comprises a height along the z-direction of the Cartesian coordinate system indicated in the Figure. Moreover, the power module 10 comprises lateral dimensions, namely a width and a length along the x-direction and the y- direction of the coordinate system, respectively.

[0062] The top side 14 of the power module 10 is widely covered by a cooling plate 20 which may be used to couple a cooling device thereto. Accordingly, heat generated during the operation of the power module 10 may be dissipated such that specific operation conditions can be guaranteed for the power module 10, such as an operating temperature range.

[0063] The power module comprises several electrode tabs for connecting external connectors for providing specific voltage signals. For example, at a first portion of the side wall 18, an AC tab 22 is provided extending laterally out of the housing 12 and the encapsulation 13.

[0064] At another portion of the side wall 18, which is located opposite to the portion at which the AC tab 22 is provided, a DC+ tab 24 extends laterally out of the housing 12 and the encapsulation 13. The DC+ tab 24 is arranged between two DC- tabs 26 also extending laterally out of the housing 12 and the encapsulation 13.

[0065] In addition, the power module 10 comprises male connectors 30 which extend out of the top side 14 of the housing 12 and the encapsulation 13. According to the present embodiment, the male connectors 30 are oriented orthogonally with respect to the two-dimensional top side 14 extending in the x-direction and the y- direction. That is, the male connectors 30 are oriented along the z-direction. Fig. 2 and 3 are a schematic exploded drawings of the power module 10 according to an embodiment. While figure 2 provides a top view onto the exploded view of the power module 10, figure 3 provides a bottom view onto the exploded view of the power module 10. In the following, the components of the power module 10 will be explained in view of a stacking along the z-direction if not denoted otherwise.

[0066] At the bottom of the power module 10, another cooling plate 20 is provided. That means that the power module 10 can be connected to an external cooling device at opposite sides thereof. Accordingly, an efficient cooling cycle can be established.

[0067] In some embodiments, at least one of the cooling plates 20 may be omitted, which of course depends on the respective geometries of the external cooling devices.

[0068] According to the present embodiment, adjacent to the bottom cooling plate 20, a first electrically insulating ceramic layer 32 is arranged. As to the material of the first electrically insulating ceramic layer 32, an electrical connection between the bottom cooling plate 20 and any of the interior components of the power module 10 is prevented.

[0069] Next, adjacent to the first electrically insulating ceramic layer 32, the DC+ baseplate 34 is provided. The DC+ baseplate 34 comprises an electrically conducting material. The DC+ baseplate 34 also comprises a direct electrically conducting connection to the DC+ tab 24. As to the first electrically insulating ceramic layer 32, an electrical contact between the DC+ baseplate 34 and the bottom cooling plate 20 is prevented.

[0070] Moreover, the DC+ baseplate 34 comprises a first portion 36 of a form fit receptacle 37. Here, the first portion 36 is established by a wall portion extending along the z-direction orthogonally from a two-dimensional surface of the DC+ baseplate 34 extending in an xy-plane.

[0071] Adjacent to the DC+ baseplate 34, a second electrically insulating ceramic layer 38 is arranged. The second electrically insulating ceramic layer 38 comprises a top surface 40 extending in an xy-plane from which a wall portion 42 extends in the z- direction. In addition, several individual ceramic support legs 44 also extend along the z-direction from the top surface 40 of the second electrically insulating ceramic layer 38.

[0072] The second electrically insulating ceramic layer 38 comprises a cutout through which the first portion 36 of the receptacle extends in the z-direction once the power module 10 is assembled together.

[0073] Next, adjacent to the second electrically insulating ceramic layer 38 to individual components are arranged within a single xy-plane, namely, the DC- baseplate 46 and the AC baseplate 52.

[0074] Both, the DC- baseplate 46 and the AC baseplate 52 comprise electrically conducting material and direct connections to the respective DC- tab 26 and AC tab 22, respectively.

[0075] An electrical connection between the DC- baseplate 46 and the AC baseplate 52 is prevented since the gap is formed in between, in which the wall portion 42 of the second electrically insulating ceramic layer 38 is arranged. Moreover, both the DC- baseplate 46 and the AC baseplate 52 comprise several cutouts such that the ceramic support legs 44 extend therethrough in the z-direction.

[0076] In addition, the DC- baseplate 46 comprises a second portion 48 of the receptacle 37. Since the first portion 36 of the receptacle extends in the z-direction through the second electrically insulating ceramic layer 38, the first portion 36 together with the second portion 48 establishes the receptacle 37. Accordingly, the receptacle 37 provides a form fit receptacle for a DC-link capacitor 50. Hence, the DC-link capacitor 50 is connected to the DC- baseplate 46 and its voltage level on one side and to the DC+ baseplate 34 and its voltage level on the other side. Accordingly, the DC-link capacitor 50 can be efficiently used to reduce or compensate for noise and electromagnetic interference.

[0077] Generally, the power module 10 can comprise several receptacles 37 for multiple DC-link capacitors 50. Hence, the noise compensating efficiency can be improved and a redundancy can be provided.

[0078] Adjacent to the DC- baseplate 46 and the AC baseplate 52, several semiconductor switches 54 are arranged in an xy-plane. The semiconductor switches 54 are specifically mounted making use of bond connections (also called bonds). The semiconductor switches 54 comprise several semiconductor structures such as transistors. In the present embodiment, HEMT transistors are used comprising GaN as active material.

[0079] Slightly above the xy-plane in which the semiconductor switches 54 are arranged, a printed circuit board 56 having two individual parts 57 is arranged. The individual parts 57 of the printed circuit board 56 are distant to each other such that a gap in the xy-plane is established in between both parts 57. Inside this gap, the semiconductor switches 54 are at least partially arranged.

[0080] Moreover, the printed circuit board 56 and its individual parts 57 are supported by the ceramic support legs 44. As to the ceramic support legs 44, a height gap (clearance) is established between the printed circuit board 56 and the xy-plane in which both the DC- baseplate 46 and the AC baseplate 52 are arranged. This allows orienting the bonds used for connecting the semiconductor switches 54 such that the bonds are coupled to the bottom side of the printed circuit board 56. In this regard, the printed circuit board 56 comprises redistribution layers or routed conductor tracks having landing bonds bondable pads arranged on the printed circuit board 56 for establishing gate bonds to gate electrodes of the semiconductor switches 54.

[0081] Furthermore, since the bonds used for connecting the semiconductor switches 54 to the printed circuit board 56 are attached to the bottom side of the printed circuit board 56, directly above these connections on the top side of the printed circuit board 56, the secondary gate drive circuit portion 58 of the gate drive circuit 59 is positioned. The secondary gate drive circuit portion 58 comprises a bare die, a packaged integrated circuit, or an embedded die arranged on or within (attached to) the printed circuit board 56.

[0082] In view of the printed circuit board 56 comprising individual parts 57, multiple secondary gate drive circuit portions 58 are provided, where at least one is assigned to each part 57 of the printed circuit board 56. The secondary gate drive circuit portion 58 used for providing gate signals to gate electrodes of the transistors of the semiconductor switches 54 are arranged extremely close to the bond connections used for the signal transmission towards the semiconductor switches 54. Therefore, a very compact connection structure for connecting the semiconductor switches 54 is achieved as the semiconductor switches 54 comprise very short connections in the lateral x- and y-directions and in the z-direction. Consequently, the size of the loop structures is greatly reduced as compared to prior art approaches. Hence, less noise is caused and the efficiency during operation of the power module 10 is greatly improved, for example by reducing electric losses and achieving high switching rates.

[0083] The male connectors 30 are used for coupling the secondary gate drive circuit portion 58 to the primary gate drive control (not shown in Figs. 2 and 3) which is arranged external to the power module 10. To this end, the male connectors 30 extend from the printed circuit board 56. Obviously, the male connectors 30 are coupled to the secondary gate drive circuit portion 58.

[0084] Along the z-direction, the power module 10 is then closed by the housing 12 which comprises the cooling plate 20 at the top side.

[0085] Generally, the printed circuit board 56 comprises a glass-reinforced epoxy laminate substrate material, a ceramic substrate material, or a copper / metal-conductor core based substrate material.

[0086] Although not shown in figures 2 and 3, an interior space of the power module 10 not comprising any components may be filled with an electrically insulating material of the encapsulation 13.

[0087] Fig. 4 is a schematic drawing of a collection circuit 60 having multiple power modules 10 for an inverter according to an embodiment.

[0088] The power module 10 collection circuit 60 has four semiconductor switches 54. The semiconductor switches 54 comprise several transistors such that a bridge circuit having several half bridges 61 is established. Each half bridge 61 comprises a high-side switch and a low-side switch according to a single semiconductor switch 54. The so-designed power module 10 collection circuit 60 may be implemented into an inverter.

[0089] Of course, the semiconductor switches 54 and its bridge circuit is coupled to the AC tab 22, the DC+ tab 24, and the DC- tab 26 for receiving or outputting respective signals. In addition, the power module 10 comprises an external gate drive control high- side circuit 62 and an external gate drive low-side circuit 64. Each of the external gate drive control high-side / low-side circuits 62, 64 is assigned to one of the high- side switches and the low-side switches established by the semiconductor switches 54.

[0090] At least a part of each of the external gate drive control high-side / low-side circuits 62, 64 establishes the respective primary gate drive control 63 of the gate drive circuit 59. Notably, the primary gate drive controls 63 are arranged external to the power module 10.

[0091] The primary gate drive control 63 is coupled to the secondary gate drive circuit portion 58 via the male connectors 30. While the primary gate drive control 63 may regulate general control commands, the secondary gate drive circuit portion 58 comprises multiple gate resistors and at least one logic circuit such that slew rates for operating the semiconductor switches 54 are variable. That is, the secondary gate drive circuit portions 58 are configured for outputting tailored gate signals to the semiconductor dies 54.

[0092] In addition, a common insulation 66 between the primary gate drive control 63 and the secondary gate drive circuit portions 58 is provided. Accordingly, noise which is present in the primary gate drive controls 63 is prevented from directly affecting the major internal components of the power module 10. Consequently, the stability inside the power module 10 is greatly improved while the noise level is reduced. This enables higher switching rates to be used in view of the bridge circuit of the power module 10 such that the efficiency of the power module 10 is improved compared to prior art approaches.

[0093] Bonds 68 are used for gate electrode connections to the printed circuit board 56. Here, wire bonds are used. However, in an alternative, ribbon bonds may be used as well.

[0094] Of course, despite the collection circuit 60, the inverter may comprise additional components as is known in the art.

Claims

Claims1. A power module (10) for an inverter, the power module (10) comprising at least two semiconductor switches (54) and a gate drive circuit (59) for the semiconductor switches (54), wherein the gate drive circuit (59) comprises a primary gate drive control (63) and an integrated secondary gate drive circuit portion (58), wherein the integrated secondary gate drive circuit portion (58) comprises a printed circuit board (56) to which the semiconductor switches (54) are bonded side by side in parallel to each other, and wherein the primary gate drive control (63) is galvanically isolated from the secondary gate drive circuit portion (58).

2. The power module (10) of claim 1 , wherein the primary gate drive control (63) is arranged external to the power module (10).

3. The power module (10) of claim 1 or 2, wherein the primary gate drive control (63) is coupled to the integrated secondary gate drive circuit portion (58) at least based on male connectors (30) extending out of a module encapsulation (13) of the power module (10) encapsulating at least the semiconductor switches (54) and the integrated secondary gate drive circuit portion (58) including the printed circuit board (56).

4. The power module (10) of claim 3, wherein the module encapsulation (13) comprises an electrically insulating gel material or an epoxy mold compound.

5. The power module (10) of any one of the preceding claims, wherein the secondary gate drive circuit portion (58) comprises a bare die, a packaged integrated circuit, or an embedded die arranged on or within the printed circuit board (56).

6. The power module (10) of any one of the preceding claims, wherein the printed circuit board (56) comprises redistribution layers or routed conductor tracks having landing bonds bondable pads arranged on the printed circuit board (56) for establishing gate bonds to gate electrodes of the semiconductor switches (54).

7. The power module (10) of any one of the preceding claims, wherein the printed circuit board (56) comprises a glass-reinforced epoxy laminate substrate material, a ceramic substrate material, or a copper / metal-conductor core based substrate material.

8. The power module (10) of any one of the preceding claims, wherein the secondary gate drive circuit portion (58) including the printed circuit board (56) is coupled to a directly bonded metal layer of the power module (10) via electrically insulating mechanical support legs (44) such that a clearance sufficient for bonds (68) coupling the semiconductor switches (54) to the printed circuit board (56) is provided between the printed circuit board (56) and the directly bonded metal layer.

9. The power module (10) of any one of the preceding claims, wherein the printed circuit board (56) is established by two separate parts (57) arranged side by side within a common printed circuit board plane with the semiconductor switches (54) at least partially positioned in between both separate parts (56).

10. The power module (10) of claim 9, wherein at least a first semiconductor switch (54) is provided for a high-side switch of a collection circuit (60) for the inverter and at least a second semiconductor switch (54) is provided for a low-side switch of the collection circuit (60), wherein a set of parallel semiconductor chips having at least a first semiconductor switch (54) and a second semiconductor switch (54) are assigned to each of the separate parts (57) of the printed circuit board (56), wherein a drain electrode of high-side switch is bonded with a DC+ baseplate (34) of the power module (10), wherein a source electrode of the high- side switch is bonded with drain pads of the low-side switch of the collection circuit (60) and also with an AC baseplate (52) of the power module (10), and wherein a source electrode of the low-side switch is bonded with a DC- baseplate (46) of the power module (10).11 . The power module (10) of claim 10, wherein the DC+ baseplate (34) is at least partially arranged beneath the DC- baseplate (46) and also at least partially beneath the AC baseplate (52) with at least one electrically insulating ceramic layer (38) in between each two of them.

12. The power module (10) of claim 10 or 1 1 , wherein a first cooling plate (20) is arranged beneath the DC+ baseplate (34) with at least one additional electrically insulating ceramic layer (32) in between, and / or wherein a second cooling plate (20) is arranged above and distant from the printed circuit board (56).

13. The power module (10) of any one claims 10 to 12, wherein the DC+ baseplate (34) and the DC- baseplate (46) establish at least one form fit receptacle (37) for at least one DC-link capacitor (50).

14. The power module (10) of any one claims 10 to 13, wherein a DC+ tab (24), a DC- tab (26), and an AC tab (22) are coupled to the DC+ baseplate (34), the DC- baseplate (46), and the AC baseplate (52), respectively.

15. The power module (10) of any one of the preceding claims, wherein the secondary gate drive circuit portion (58) comprises multiple gate resistors and at least one logic circuit such that slew rates for operating the semiconductor switches (54) are variable.

16. The power module (10) of any one of the preceding claims, wherein bonds (68) used for bonding the semiconductor switches (54) are at least partially arranged beneath the printed circuit board (56).

17. The power module (10) of any one of the preceding claims, wherein bonds (68) used for bonding components are established by wire bonds or ribbon bonds.

18. The power module (10) of any one of the preceding claims, wherein the semiconductor switches (54) comprise at least one semiconductor active material of GaN, SiC, Si or a hybrid material combination of multiple semiconductors active materials.

19. A collection circuit (60) for an inverter having multiple power modules (10) according to any one of the preceding claims.

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