Patent Publication Number: US-11051434-B2

Title: Power-module assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 14/687,468 filed Apr. 15, 2015, now U.S. Pat. No. 10,123,465, issued on Nov. 6, 2018, the disclosure of which is hereby incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to power inverters for automotive vehicles. 
     BACKGROUND 
     Vehicles such as battery-electric vehicles (BEVs), plug-in hybrid-electric vehicles (PHEVs) and fully hybrid-electric vehicles (FHEVs) contain a traction battery assembly to act as an energy source for one or more electric machines. The traction battery includes components and systems to assist in managing vehicle performance and operations. A power inverter is electrically connected between the battery and the electric machines to convert the direct current coming from the battery into alternating current compatible with the electric machines. The power inverter may also act as a rectifier to convert alternating current from the electric machines to direct current compatible with the battery. 
     SUMMARY 
     According to one embodiment, a method of forming a power-module assembly includes arranging power stages in a cavity of a container such that the power stages are spaced apart from walls of the container. The method further includes inserting a core between each of the power stages, and installing a manifold on top of the power stages. The method also includes putting resin into the cavity to form a housing of the power-module assembly, and removing the core to reveal coolant chambers between each of the power stages. 
     According to another embodiment, a method of forming a power-module assembly for an automotive power inverter includes arranging a plurality of power stages in a mold cavity of a container such that the power stages are in a linear array with spacing between each of the power stages, and such that the power stages are spaced apart from walls of the container. The method further includes inserting a core into the cavity such that fingers of the core are disposed in the spacing between the power stages. The method also includes inserting a manifold into the cavity such that the manifold is disposed on a top of each of the power stages. The method further includes pouring resin into the cavity to form at least a portion of a housing of the power-module assembly. The method also includes removing the core to reveal a plurality of chambers between each of the power stages. 
     According to yet another embodiment, a method of forming a power-module assembly includes arranging power stages in a mold cavity such that the power stages are spaced apart from walls of the cavity. The method further includes inserting a coolant device between each of the power stages and installing a manifold on top of the power stages and coolant devices such that the devices are in fluid communication with the manifold. The method also includes putting resin into the cavity to form a housing of the power-module assembly. 
     According to another embodiment, a power-module assembly includes a plurality of power stages and a housing. The housing is formed by the process of arranging power stages in a cavity of a container such that the power stages are spaced apart from walls of the container and inserting a core between each of the power stages. The process further includes pouring resin into the cavity to form the housing and removing the core to reveal coolant chambers between each of the power stages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an example hybrid vehicle. 
         FIG. 2  is a schematic diagram of a variable voltage converter and a power inverter. 
         FIG. 3  is a perspective view of a power stage. 
         FIG. 4  is a side view, in cross-section, of the power stage of  FIG. 3  along cut line  4 - 4 . 
         FIG. 5  is a side view of a mold die with the power stages arranged in the mold cavity. 
         FIG. 6  is a front view of the mold die of  FIG. 5 . 
         FIG. 7  is a perspective view of the mold die of  FIGS. 5 and 6 . 
         FIGS. 8A to 8E  illustrate a sequence of operations for manufacturing a power-module assembly according to one embodiment of this disclosure. 
         FIG. 9  is a flow chart for manufacturing the power-module assembly from  FIGS. 8A to 8E . 
         FIGS. 10A to 10D  illustrate a sequence of operations for manufacturing a power-module assembly according to another embodiment of this disclosure. 
         FIG. 11  is a flow chart for manufacturing the power-module assembly from  FIGS. 10A to 10D . 
         FIGS. 12A to 12D  illustrate a sequence of operations for manufacturing a power-module assembly according to yet another embodiment of this disclosure. 
         FIG. 13  is a flow chart for manufacturing the power-module assembly from  FIGS. 12A to 12D . 
         FIG. 14  is a perspective view of a power-module assembly. 
         FIG. 15  is a side view, in cross-section, of the power-module assembly of  FIG. 14  along cut line  15 - 15 . 
         FIG. 16  is a perspective view, in cross-section, of the power-module assembly of  FIG. 15  along cut line  16 - 16 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     An example of a PHEV is depicted in  FIG. 1  and referred to generally as a vehicle  16 . The vehicle  16  includes a transmission  12  and is propelled by at least one electric machine  18  with assistance from an internal combustion engine  20 . The electric machine  18  may be an AC electric motor depicted as “motor”  18  in  FIG. 1 . The electric machine  18  receives electrical power and provides torque for vehicle propulsion. The electric machine  18  also functions as a generator for converting mechanical power into electrical power through regenerative braking. 
     The transmission  12  may be a power-split configuration. The transmission  12  includes the first electric machine  18  and a second electric machine  24 . The second electric machine  24  may be an AC electric motor depicted as “generator”  24  in  FIG. 1 . Like the first electric machine  18 , the second electric machine  24  receives electrical power and provides output torque. The second electric machine  24  also functions as a generator for converting mechanical power into electrical power and optimizing power flow through the transmission  12 . In other embodiments, the transmission does not have a power-split configuration. 
     The transmission  12  includes a planetary gear unit  26 , which includes a sun gear  28 , a planet carrier  30  and a ring gear  32 . The sun gear  28  is connected to an output shaft of the second electric machine  24  for receiving generator torque. The planet carrier  30  is connected to an output shaft of the engine  20  for receiving engine torque. The planetary gear unit  26  combines the generator torque and the engine torque and provides a combined output torque about the ring gear  32 . The planetary gear unit  26  functions as a continuously variable transmission, without any fixed or “step” ratios. 
     The transmission  12  may also include a one-way clutch (O.W.C.) and a generator brake  33 . The O.W.C. is coupled to the output shaft of the engine  20  to only allow the output shaft to rotate in one direction. The O.W.C. prevents the transmission  12  from back-driving the engine  20 . The generator brake  33  is coupled to the output shaft of the second electric machine  24 . The generator brake  33  may be activated to “brake” or prevent rotation of the output shaft of the second electric machine  24  and of the sun gear  28 . Alternatively, the O.W.C. and the generator brake  33  may be eliminated and replaced by control strategies for the engine  20  and the second electric machine  24 . 
     The transmission  12  includes a countershaft having intermediate gears including a first gear  34 , a second gear  36  and a third gear  38 . A planetary output gear  40  is connected to the ring gear  32 . The planetary output gear  40  meshes with the first gear  34  for transferring torque between the planetary gear unit  26  and the countershaft. An output gear  42  is connected to an output shaft of the first electric machine  18 . The output gear  42  meshes with the second gear  36  for transferring torque between the first electric machine  18  and the countershaft. A transmission output gear  44  is connected to a driveshaft  46 . The driveshaft  46  is coupled to a pair of driven wheels  48  through a differential  50 . The transmission output gear  44  meshes with the third gear  38  for transferring torque between the transmission  12  and the driven wheels  48 . The transmission also includes a heat exchanger or automatic transmission fluid cooler  49  for cooling the transmission fluid. 
     The vehicle  16  includes an energy storage device, such as a traction battery  52  for storing electrical energy. The battery  52  is a high voltage battery that is capable of outputting electrical power to operate the first electric machine  18  and the second electric machine  24 . The battery  52  also receives electrical power from the first electric machine  18  and the second electric machine  24  when they are operating as generators. The battery  52  is a battery pack made up of several battery modules (not shown), where each battery module contains a plurality of battery cells (not shown). Other embodiments of the vehicle  16  contemplate different types of energy storage devices, such as capacitors and fuel cells (not shown) that supplement or replace the battery  52 . A high voltage bus electrically connects the battery  52  to the first electric machine  18  and to the second electric machine  24 . 
     The vehicle includes a battery energy control module (BECM)  54  for controlling the battery  52 . The BECM  54  receives input that is indicative of vehicle conditions and battery conditions, such as battery temperature, voltage and current. The BECM  54  calculates and estimates battery parameters, such as battery state of charge and the battery power capability. The BECM  54  provides output (BSOC, P cap ) that is indicative of a battery state of charge (BSOC) and a battery power capability (P cap ) to other vehicle systems and controllers. 
     The vehicle  16  includes a DC-DC converter or variable voltage converter (VVC)  10  and an inverter  56 . The VVC  10  and the inverter  56  are electrically connected between the traction battery  52  and the first electric machine  18 , and between the battery  52  and the second electric machine  24 . The VVC  10  “boosts” or increases the voltage potential of the electrical power provided by the battery  52 . The VVC  10  also “bucks” or decreases the voltage potential of the electrical power provided to the battery  52 , according to one or more embodiments. The inverter  56  inverts the DC power supplied by the main battery  52  (through the VVC  10 ) to AC power for operating the electric machines  18 ,  24 . The inverter  56  also rectifies AC power provided by the electric machines  18 ,  24 , to DC for charging the traction battery  52 . Other embodiments of the transmission  12  include multiple inverters (not shown), such as one invertor associated with each electric machine  18 ,  24 . The VVC  10  includes an inductor assembly  14 . 
     The transmission  12  includes a transmission control module (TCM)  58  for controlling the electric machines  18 ,  24 , the VVC  10  and the inverter  56 . The TCM  58  is configured to monitor, among other things, the position, speed, and power consumption of the electric machines  18 ,  24 . The TCM  58  also monitors electrical parameters (e.g., voltage and current) at various locations within the VVC  10  and the inverter  56 . The TCM  58  provides output signals corresponding to this information to other vehicle systems. 
     The vehicle  16  includes a vehicle system controller (VSC)  60  that communicates with other vehicle systems and controllers for coordinating their function. Although it is shown as a single controller, the VSC  60  may include multiple controllers that may be used to control multiple vehicle systems according to an overall vehicle control logic, or software. 
     The vehicle controllers, including the VSC  60  and the TCM  58  generally includes any number of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM, EPROM and/or EEPROM) and software code to co-act with one another to perform a series of operations. The controllers also include predetermined data, or “look up tables” that are based on calculations and test data and stored within the memory. The VSC  60  communicates with other vehicle systems and controllers (e.g., the BECM  54  and the TCM  58 ) over one or more wired or wireless vehicle connections using common bus protocols (e.g., CAN and LIN). The VSC  60  receives input (PRND) that represents a current position of the transmission  12  (e.g., park, reverse, neutral or drive). The VSC  60  also receives input (APP) that represents an accelerator pedal position. The VSC  60  provides output that represents a desired wheel torque, desired engine speed, and generator brake command to the TCM  58 ; and contactor control to the BECM  54 . 
     The vehicle  16  includes an engine control module (ECM)  64  for controlling the engine  20 . The VSC  60  provides output (desired engine torque) to the ECM  64  that is based on a number of input signals including APP, and corresponds to a driver&#39;s request for vehicle propulsion. 
     If the vehicle  16  is a PHEV, the battery  52  may periodically receive AC energy from an external power supply or grid, via a charge port  66 . The vehicle  16  also includes an on-board charger  68 , which receives the AC energy from the charge port  66 . The charger  68  is an AC/DC converter which converts the received AC energy into DC energy suitable for charging the battery  52 . In turn, the charger  68  supplies the DC energy to the battery  52  during recharging. Although illustrated and described in the context of a PHEV  16 , it is understood that the inverter  56  may be implemented on other types of electric vehicles, such as a HEV or a BEV. 
     Referring to  FIG. 2 , an electrical schematic of the VVC  10  and the inverter  56  is shown. The VVC  10  may include a first switching unit  70  and a second switching unit  72  for boosting the input voltage (V bat ) to provide output voltage (V dc ). The first switching unit  70  may include a first transistor  74  connected in parallel to a first diode  76 , but with their polarities switched (anti-parallel). The second switching unit  72  may include a second transistor  78  connected anti-parallel to a second diode  80 . Each transistor  74 ,  78  may be any type of controllable switch (e.g., an insulated gate bipolar transistor (IGBT) or field-effect transistor (FET)). Additionally, each transistor  74 ,  78  may be individually controlled by the TCM  58 . The inductor assembly  14  is depicted as an input inductor that is connected in series between the traction battery  52  and the switching units  70 ,  72 . The inductor  14  generates magnetic flux when a current is supplied. When the current flowing through the inductor  14  changes, a time-varying magnetic field is created, and a voltage is induced. Other embodiments of the VVC  10  include alternative circuit configurations (e.g., more than two switches). 
     The inverter  56  may include a plurality of half-bridges  82  that are stacked in an assembly. Each of the half-bridges may be packaged as a power stage. In the illustrated embodiment, the inverter  56  includes six half-bridges, three for the motor  18  and three for the generator  24 . Each of the half bridges  82  may include a positive DC lead  84  that is coupled to a positive DC node from the battery and a negative DC lead  86  that is coupled to a negative DC node from the battery. Each of the half bridges  82  may also include a first switching unit  88  and a second switching unit  90 . The first switching unit  88  may include a first transistor  92  connected in parallel to a first diode  94 . The second switching unit  90  may include a second transistor  96  connected in parallel to a second diode  98 . The first and second transistors  88 ,  96  may be IGBTs or FETs. The first and second switching units  88 ,  90  of the each of the half-bridges  82  convert the DC power of the battery into a single phase AC output at the AC lead  100 . Each of the AC leads  100  are electrically connected to the motor  18  or generator  24 . In the illustrated example, three of the AC leads  100  are electrically connected to the motor  18  and the other three AC leads  100  are electrically connected to the generator  24 . 
     Referring to  FIGS. 3 and 4  each of the half-bridges  82  may be packaged as a power stage. Each of the power stages  82  includes opposing major sides  110 , opposing minor sides  112 , a top  138 , and a bottom  140 . The power stage  82  includes a positive DC power terminal  114 , a negative DC power terminal  116 , an AC power terminal  118 , and signal pins  120  that are each electrically connected with one at least one semiconductor device of the power stage  82 . The location of the terminals and signal pins may vary by embodiment and are not limited to the configuration shown. 
     A first plate  122  is disposed on one of the major sides  110  and a second plate  124  is disposed on the other major side of the power stage  82 . The plates  122 ,  124  may be metallic, plastic, composite, or a combination thereof. The semiconductor devices of the power stage  82  may be filled with an epoxy  127  or other filler to electrically isolate the semiconductor devices from the plates and other components. Note: the epoxy is not cross-hatched for clarity. 
     The power stages  82  may be arranged in a stack forming a power-module assembly. The power-module assembly may be formed by molding a housing around the power stages. Referring to  FIGS. 5, 6, and 7 , a container  126  includes walls  128  and a bottom  130  that cooperate to define a mold cavity  132 . Each of the power stages  82  are arranged within the mold cavity  132  such that the power stages  82  are spaced apart from each other and are spaced apart from the interior surfaces  133  of the cavity  132 . The spaces between the power stages  82  and the cavity  132  are subsequently filled with resin to create the housing. The power stages  82  are arranged with the plates  122 ,  124  of adjacent power stages  82  facing each other. The mold cavity  132  may include slots or holes allowing the terminals ( 114 ,  116 , and  118 ) and signal pins  120  to extend out of the mold cavity  132 . For example, the sidewall  128  may define slots  134  that receive the positive and negative DC terminals  114 ,  116 , and the bottom  130  may define slots  136  for receiving the AC terminals  118 . The slots and holes may act as alignment features to properly position each of the power stages  82  within the die cavity  132 . Note: the power stages  82  in  FIGS. 5 and 6  are illustrated in a simplified form. The container  126  may be die that is part of tool, or may simply be an open box. 
       FIGS. 8A to 8E  illustrate a sequence of operations for manufacturing a power-module assembly according to the flowchart  146  shown in  FIG. 9 . At operation  148  the power stages  82  are arranged within the mold cavity  132  as described above and as shown in  FIG. 8A . In some embodiments the container  126  is part of the finished product. In other embodiments the container is a component of the tooling and is not part of the finished product. At operation  150  a mold core  160  is inserted into the mold cavity  132  as shown in  FIG. 8B . The mold core  160  may include a planar top portion  162  disposed on top of each of the power stages  82 , and fingers  164  disposed between adjacent power stages  82 . The mold core  160  displaces volume within the mold cavity to create internal cavities within the power-module assembly. The mold core may be made out of extruded polystyrene foam (e.g. Styrofoam®), sugar, salt, sand, or wax. 
     At operation  152  a first phase of resin is poured into the mold cavity  132  as shown in  FIG. 8C . In embodiments where the container  126  is not part of the finished product, a release agent may be applied to the cavity walls to prevent the resin from sticking to the container  126 . During the first phase, liquid resin  163  may be poured into the mold cavity  132  until the resin rises to the top  138  of the power stages  82 . The mold core  160  displaces the resin  163  to create resin free areas, which will become internal cavities in the power-module assembly. After pouring, the container  126  is set aside until the resin cures or hardens. The container  126  may be placed in an oven or other heating process to facilitate curing of the resin. The resin may be an epoxy, or other polymer. 
     The hardened resin forms a housing  168  that encapsulates the power stages  82  as shown in  FIG. 8D . After the resin hardens, the mold core  160  is removed to reveal a plurality of coolant chambers  171  disposed between each of the power stages  82  at operation  154 . Each of the coolant chambers  171  are defined by a first plate  122 , a second plate  124 , a bottom  165  of the housing  168 , and sidewalls  166  of the housing  168 . The coolant chambers  171  are configured to circulate coolant therein to cool the power stages  82  during operation of the inverter. In some embodiments, a flow guide assembly may be inserted into each of the coolant chambers  171 . The flow guides may include fins to facilitate coolant circulation within the chambers  171 . The core  160  may be removed by pouring a solvent into the cavity  132  to dissolve the core  160 . The method used to remove the core will depend on the type of core used. 
     At operation  156  a manifold  170  is disposed on top of the power modules  82  as shown in  FIG. 8D . The manifold  170  includes a bottom  172  that defines ports  174 . Each of the ports is in fluid communication with one of the coolant chambers  171 . The ports  174  may project downwardly from the bottom  172  and extend into the coolant chambers. The manifold  170  includes an inlet (not visible) and an outlet  178 . The inlet and outlet may extend through a slot defined in the container  126 . The inlet and outlet are configured to connect with supply and return lines to connect the manifold  170  with the coolant system (not shown). 
     At operation  158  a second phase of resin is poured into the mold cavity  132  as shown in  FIG. 8E . During the second phase, liquid resin  163  is poured into the mold cavity  132  until the resin rises to a predetermined height within the cavity  132 . The resin from the second phase encapsulates the manifold  170  to form the upper portion of the housing. The resin may be the same type of resin that was used during the first phase. The resin may cure at room temperature or may be placed in an oven depending upon the type of resin used and the desired cure time. After the resin hardens, the power-module assembly may either be removed from the container  126 , or remains in the container depending upon the embodiment 
       FIGS. 10A to 10D  illustrate a sequence of operations for forming another power-module assembly according to the flowchart  190  show in  FIG. 11 . At operation  192  the power stages  82  are arranged within the mold cavity  202  as described above and as shown in  FIG. 10A . At operation  194  a plurality of coolant devices  204  are inserted between adjacent power stages  82  as shown in  FIG. 10A . Each of the devices  204  includes a housing  206  that defines a coolant chamber  208 . The housing  206  may include an open top or may include a top having openings allowing coolant to enter and exit into the coolant chamber  208 . Flow guide assemblies may be inserted into the chambers  208  to facilitate cooling. 
     The resin may be poured in a single phase or in multiple phases. For example, at operation  196  a first phase of resin is poured into the mold cavity  202  as shown in  FIG. 10B . During the first phase, liquid resin  212  is poured into the mold cavity  202  until the resin rises near the top of the coolant devices  204 . The resin may be left to cure at room temperature or placed in a heated environment. 
     At operation  198  a manifold  210  is disposed on top of the power stages  82  and the coolant devices  204 . A bottom of the manifold  210  includes ports that are in fluid communication with each of the coolant chambers  208 . After installing the manifold  210 , a second phase of resin is poured into the cavity  202  at operation  200  as shown in  FIG. 10D . The resin from the second phase encapsulates the manifold  210  to form the upper portion of the power-module assembly. After the resin hardens, the power-module assembly may (or may not) be removed from the container. 
       FIGS. 12A to 12D  illustrate a sequence of operations for forming yet another power-module assembly according to the flowchart  211  show in  FIG. 11 . At operation  213  the power stages  82  are arranged within a container  126  with the terminals and signal pin extending through openings defined in the walls of the container as shown in  FIG. 12A . At operation  214  a sealant is applied around the holes and terminals to seal the cavity  132 . For example, a sealant is applied around terminal  118  to seal the opening  136  and prevent leaking of any resin during the molding process. The sealant, for example, may be a silicone or an epoxy that is applied around each of the openings. Alternatively, the container  126  may be dipped in a sealant bath to seal all of the openings. At operation  216  a mold core  224  is inserted between each of the power stages  82  as shown in  FIG. 12B . The mold core  224  may be inserted between the power stages  82  after the power stages are arranged in the container  126 , or may be arranged between the power stages  82  prior to the power stages  82  being arranged within container  126 . At operation  218  the manifold is inserted into the cavity and installed on top of the power stages  82  as shown in  FIG. 12C . At operation  220  resin  228  is poured into the cavity  132  and allowed to harden. At operation  222  the mold core  224  is removed to reveal coolant chambers  226  interleaved between the power stages  82  as shown in  FIG. 12D . 
     Flow charts  146 ,  190 , and  211  illustrate methods that utilize a prefabricated manifold. But, in alternative embodiments, the present disclosure contemplates forming the manifold with resin as part of the process. Here, either an additional or modified core is arranged within the cavity prior to pouring of the resin. The core displaces volume that will become the manifold once the core is removed. After the resin is poured and set, the core is removed to reveal the manifold. 
     Referring to  FIGS. 14, 15 and 16 , a power inverter for a motor vehicle includes a power-module assembly  230 , a capacitor module (not shown), and a gate board (not shown). The power-module assembly  230  may be a power-module assembly manufactured according to flowchart  146  for example. The power-module assembly  230  may include a housing  168  formed of hardened resin. In some embodiments, the housing  168  is a combination of hardened resin and the container  126 . The housing  168  encapsulates a plurality of power stages  82  and a manifold  170 . A plurality of coolant chambers  171  are interleaved with the power stages  82 . The manifold  170  is in fluid communication with each of the coolant chambers  171  via the fluid ports  174  that may extend into a respective chamber  171 . The inlet stub  176  and the outlet stub  178  of the manifold  170  extend outwardly through the housing  168  so that the manifold can be connected with the coolant circulation system. The positive DC terminals  114  and the negative DC terminals  116  projects outwardly through a side of the housing  168 . The DC terminals may be electrically connected to the capacitor module. The AC terminals  118  project outwardly through a bottom of the housing  168  and may be electrically connected to the electric machines  18 ,  24 . The signal pins  120  project outwardly through a side of the housing  168  and may be electrically connected to the gate board. 
     An optional flow guide assembly  232  may be disposed within one or more of the coolant chambers  171 . The flow guide assembly  232  may include fins  234  that direct coolant circulating within the chambers  171 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.