Patent Publication Number: US-2004056534-A1

Title: Planar DC-DC converter for multi-volt electrical applications

Description:
RELATED APPLICATIONS  
     [0001] The present application is based on and claims the benefit of U.S. Provisional Application Serial No. 60/385,966 filed on Jun. 3, 2002, entitled PLANAR CONSTRUCTION OF A DC-DC CONVERTER FOR AUTOMOTIVE APPLICATIONS, the entire contents of which are expressly incorporated herein by reference. 
    
    
     
       BACKGROUND INFORMATION  
       [0002] Many of today&#39;s automobiles operate on fourteen-volt electrical systems, in which a fourteen-volt alternator is employed to charge a twelve-volt battery. However, as automobiles become increasingly more “high-tech” and hungry for electricity, the need for increased onboard electrical power in automobiles is growing rapidly.  
       [0003] To respond to the increased demand for electrical power, the automobile industry will soon be introducing cars that operate on fortytwo-volt power systems (fortytwo volts being provided by the alternator to charge thirtysix volt batteries), instead of the conventional fourteen-volt systems of today&#39;s cars. These fortytwo-volt systems will be able to deliver the necessary current to operate many of the “high-tech” computer and electrical systems expected in tomorrow&#39;s automobiles.  
       [0004] However, the change from fourteen-volt systems to fortytwo-volt systems will not be made overnight. Rather, the first fortytwo-volt systems will likely appear in hybrid automobiles capable of operating both fourteen-volt and fortytwo-volt automobile systems and, as such, will likely be provided with both twelve-volt and thirtysix-volt batteries (14-volt and 42-volt systems refer to the charge provided by the alternator of an automobile to charge 12-volt and 36-volt batteries, respectively). In some situations (e.g., if one of the batteries fails), the fourteen-volt battery may be required to provide electrical power to fortytwo-volt systems and/or the fortytwo-volt battery may be required to provide electrical power to fourteen-volt systems. For this purpose, the “hybrid” systems will require DC-DC converters capable of converting voltage from fourteen volts into fortytwo volts, and vice versa.  
       [0005] Referring now to FIG. 1, there is seen a hybrid electrical arrangement  100  according to the prior art. As shown in FIG. 1, electrical arrangement  100  includes a fourteen-volt battery  105  electrically coupled to at least one fourteen-volt electrical system  110  via a fourteen-volt bus  115 , a fortytwo-volt battery  120  electrically coupled to at least one fortytwo-volt electrical system  125  via a fortytwo-volt bus  130 , and a bi-directional DC-DC converter  135  electrically coupled to both fourteen-volt bus  115  and fortytwo-volt bus  130 .  
       [0006] Fourteen-volt electrical system  110  and fortytwo-volt electrical system  125  may include any device configured to be operated, at least in part, by an electrical potential supplied by batteries  105 ,  130 , respectively. For example, with respect to automobile applications, systems  110 ,  125  may include automobile computers, seat positioning motors, windshield wipers, headlights, steering wheel heaters, radios, etc.  
       [0007] In normal operation, fourteen-volt and fortytwo-volt batteries  105 ,  120  provide fourteen-volt and fortytwo-volt potentials to their respective busses  115 ,  130  to power electrical systems  110 ,  125 . However, in at least some operating modes, it may be desirous to have fourteen-volt battery  105  provide power to fortytwo-volt electrical system  125  and/or to have fortytwo-volt battery  120  provide power to fourteen-volt system  110 , for example, if one of batteries  105 ,  120  becomes inoperable. For this purpose, bi-directional DC-DC converter  135  includes an up-converter  140  configured to convert the fourteen-volt electrical potential produced by fourteen-volt battery  105  to the electrical potential of fortytwo-volt bus  130 , and a down-converter  145  configured to convert the fortytwo-volt electrical potential produced by fortytwo-volt battery  120  to the electrical potential of fourteen-volt bus  115 . For this purpose, for example, DC-DC converter  135  may be provided with a control input (not shown). In this manner, bi-directional DC-DC converter  135  may be controllably configured (e.g., by an automobile computer) to permit fourteen-volt battery  105  to operate fortytwo-volt electrical system  125  and/or fortytwo-volt battery  120  to operate fourteen-volt electrical system  110 .  
       [0008] Although the conventional electrical arrangement  100  performs adequately for its intended purpose, it is believed that such a system is cumbersome and consumes much physical space. Furthermore, in various applications, such as automobile applications, operation of DC-DC converter  135  may generate unwanted heat energy, which may destroy or otherwise damage nearby sensitive components.  
       SUMMARY OF THE INVENTION  
       [0009] It is an object of the present invention to overcome the disadvantages of prior art electrical systems described above. For this purpose, the present invention provides an electrical arrangement to supply power to a plurality of electrical systems, in which the DC-DC converter is designed in a planar fashion and mechanically and proximally coupled to at least one of the voltage sources. In this manner, the present invention provides for a compact and space-saving electrical system design.  
       [0010] It is another object of the present invention to provide the electrical system described above, in which the DC-DC converter is mechanically and heat-conductively coupled to a mounting arrangement. By arranging the DC-DC converter is such a manner, the mounting arrangement may dissipate excess heat generated by the DC-DC converter, thereby protecting nearby sensitive components from excess heat.  
       [0011] It is still another object of the present invention to provide the electrical system described above for use in a hybrid automobile system employing fourteen and fortytwo volt electrical systems. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 is a block diagram of an electrical power system according to the prior art.  
     [0013]FIG. 2 is a first exemplary electrical system according to the present invention.  
     [0014]FIG. 3 is a second exemplary electrical system according to the present invention.  
     [0015]FIG. 4 is one embodiment of a bi-directional DC-DC converter. 
    
    
     DETAILED DESCRIPTION  
     [0016] Referring now to FIG. 2, there is seen a first exemplary electrical arrangement  200  according to the present invention. The electrical arrangement  200  comprises a fourteen-volt battery  205  electrically coupled to at least one fourteen-volt electrical system  210  via a fourteen-volt bus  215 , a fortytwo-volt battery  220  electrically coupled to at least one fortytwo-volt electrical system  225  via a fortytwo-volt bus  230 , and a bi-directional DC-DC converter  235  electrically coupled to both fourteen-volt bus  215  and fortytwo-volt bus  230 .  
     [0017] The electrical arrangement  200  requires comparatively less space than conventional DC-DC converters, and further comprises a DC-DC converter  235  that is designed to be a low-profile and mechanically and proximally coupled to a surface (e.g., bottom, side, or top surface) of one of batteries  205 ,  220  (e.g., FIG. 2 shows converter  235  coupled to the bottom surface of battery  205 ).  
     [0018] To achieve a planar construction of DC-DC converter  235 , the converter  235  may be constructed from a plurality planar converter stages, each provided with low impedance planar converter coils, for example, planar coils made of punched solid copper, with the interconnection being effected by Direct Bonded Copper (DBC) or thick film substrate using a bare MOSFET device. To increase magnetic field conduction, each stage may also be provided with a flat ferrite core. Furthermore, ceramic capacitors may be provided for EMI filtering, thereby increasing reliable performance of the planar converter  235 .  
     [0019] It should be appreciated that, although FIG. 2 illustrates a hybrid fourteen-volt/fortytwo-volt arrangement  200 , electrical arrangement  200  may include batteries and electrical systems of different voltage potentials, such as 5-volt, 12-volt, 36-volt, etc. Furthermore, it will be appreciated that DC-DC converter  235  may be mechanically and proximally coupled to fortytwo-volt battery  220 , rather than fourteen-volt battery  105 . For example, DC-DC converter  235  may be mechanically and proximally coupled to the bottom surface of fortytwo-volt battery  220 .  
     [0020] Referring now to FIG. 3, there is seen another exemplary electrical arrangement  300 . Electrical arrangement  300  is similar to electrical arrangement  200 , except that DC-DC converter  235  is mechanically and heat-conductively coupled to a mounting arrangement  305  operable to dissipate heat to the environment. In automobile applications, for example, mounting arrangement  305  may comprise, for example, a portion of the vehicle chassis. In this manner, the mounting arrangement  300  may dissipate excess heat produced by DC-DC converter  235  to the environment. To facilitate an efficient heat-conductive bond between DC-DC converter  235  and mounting arrangement  305 , a heat conductive paste, for example, a silver thermal compound (not shown), may be applied to the surface(s) of DC-DC converter  235  and/or mounting arrangement  305  before mechanically and heat-conductively coupling DC-DC converter  235  to mounting arrangement  300 .  
     [0021] Referring now to FIG. 4, there is seen a DC-DC converter  235  comprising a plurality of electronic components that provide bi-directional DC-DC conversion in a low profile package. For example, flat ferrite  56  is placed adjacent to windings  52 . Additional electronic components  54 ,  58  are electrically connected in a circuit with the windings  52 , providing electronic filtering and input-output for the DC-DC converter  235 , including control input, while maintaining the low profile of the package. By bi-directional, it is meant that the conversion direction can be changed by using a control input. In one example, baseplate  50  is thermally conductive, such as a highly thermally conductive metal, metal alloy or composite baseplate.  
     [0022] The foregoing descriptions and drawings are merely exemplary and should not be considered limiting; the present invention should be limited only by the claims.