Patent Publication Number: US-2009237889-A1

Title: Power Converter Having Multiple Layer Heat Sinks

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims priority to U.S. patent application Ser. No. 11/344,507 filed Jan. 31, 2006. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally related to power converters, and more particularly to power converters adapted to power portable electronic devices. 
     BACKGROUND OF THE INVENTION 
     Power converters are typically used to power and/or recharge the batteries of portable electronic devices including notebook computers, PDA&#39;s, MP3 players, digital cameras, and wireless phones just to name a few. Some of the portable electronic devices are configured to require a significant amount of power, with some notebook computers now consuming up to 140 watts. 
     At the same time, portable electronic device users are demanding that these power converters be smaller and smaller. The miniaturization of these power supplies is constrained by the amount of heat generated during the power conversion, such as in a DC/DC converter, AC/DC converter, DC/AC converter, and an AC/AC converter. Improved efficiency of the power conversion is one way to reduce the heat generated by the power converter. More efficient heat transfer devices are also being designed to better sink generated heat and release it to the ambient. Heat fans and cooling fins are just some types of cooling designs to keep the power converter operating within safe limits, such as established by numerous safety agencies including UL Laboratories. 
     SUMMARY OF INVENTION 
     The present invention achieves technical advantages as a power converter including a printed circuit board (PCB) having a plurality of heat conductive layers configured to sink heat generated by the power converter electronics. Each of these layers are comprised of thermally conductive material configured as planar sheets, each of these thermal layers being coupled to at least one wire to sink heat therefrom, such as via a wire of an input cable and/or output cable. Advantageously, a more compact power converter is realized having improved power output while operating within safety guidelines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a power converter including a printed circuit board having multiple thermal planes; 
         FIG. 2  is a top view of a circuit component layer; and 
         FIGS. 3A-3B  are top views of thermal material layers forming a second and third layer of the printed circuit board shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION 
     Referring now to  FIG. 1  there is shown at  10  an exploded perspective view of a power converter having a multiple layer printed circuit board  11  including layers  12 ,  14 ,  16  and  18 . Top layer  12  includes electrical traces and electrical components forming the power converter circuitry  20 . Disposed thereunder is shown two thermally conductive layers  14  and  16  that are spatially separated from one another, and from the electronics layer  12 , each adapted to sink heat from the first layer during operation of the circuitry  20 . Lower layer  18  is also comprised of components forming another stage of the power converter, or adding to the power converter shown in  20  and serves to operate as a separate power stage altogether, or an adjoining power stage  20 . 
     Referring now to  FIG. 2 , there is shown a top view of the first layer,  14 , seen to include electrically conductive traces and pads for receiving suitable electronic components and interconnecting the same. Further shown are pluralities of vias shown at  22 , the vias are electrically and thermally coupled to the underlying second and third layers and to the first layer  14  with the common vias being shown at  22 . Preferably, these second and third heat sink layers are comprised of a thermally conductive material, such as a metal, and preferably, a highly thermally conductive material such as copper, although other materials are suitable and within the scope of this invention. 
     Advantageously, the pluralities of heat sink layers are provided in the common printed circuit board  11  as shown in  FIG. 1 . In addition, each of these second and third layers are physically separated from each other, but electrically and thermally coupled to each other to sink heat from the first layer, and to efficiently balance and distribute heat therebetween. 
     Referring back to  FIG. 1 , there is shown an input cable  30  and an output cable  40  each coupled to the circuitry  20  of first layer  12  to provide power thereto, and provide therefrom, respectively. At least two electrical conductors are provided in each cable  30  and  40  to provide the power thereto, which power may be an AC or DC power. In addition, at least one thermally conductive member  32  and  42 , preferably a copper wire, is included in respective cable  30  and  40  to facilitate sinking heat from the second and third thermally conductive layers  14  and  16  away from power converter  10 . Thus, heat may be sunk via input cable  30  to the power source, and heat may also be sunk via output cable  40  to the portable electronic device to be powered. 
     Advantageously, due to the multiple heat sink layers, the power converter  10  can be disposed in a housing, (not shown) that has a very thin profile and small overall area. A significant amount of power can be converted using power converter  10 , with the generated heat being universally dispersed to the multiple heat sink layers  14  and  16  without generating a hot spot to the encompassing housing such that power converter  10  operates within safety guidelines, such as those established by UL Laboratories. 
     By way of example, power converter  10  may comprise a 90 watt power converter operating at 90% efficiency, whereby the dimensions of the printed circuit board may be 2.48 by 2.48 inches, disposed in a housing having a thickness of no greater than 0.55 inches and operating less than 85 degrees Celsius. The thermal distribution of the inner layer heat sinks and the heat sinking of the input and output cable allows the power supply to become more like the ideal thermal model in which all heat is uniformly distributed allowing the power supply to dissipate more heat to the environment, thus staying cooler. 
     This design further achieves technical advantages in that the thermal heat sinking properties can be consistently replicated during 5 manufacturing, which provides improved quality control and fewer defective units during manufacturing. 
     Though the invention has been described with respect to a specific preferred embodiment, many variations and modifications will become apparent to those skilled in the art upon reading the present application. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.