Abstract:
An electronic device such as an AC/DC power adapter includes a conductive heat dissipation system. The device contains heat generating components and is powered via power supply leads by an external power supply circuit. The device further contains a thermally conductive mass that is thermally coupled to both the heat generating components and to the power supply leads. When the power supply leads are coupled to receive electricity from the external power supply circuit, heat generated by the device is thermally conducted into the external power supply circuit via the power supply leads.

Description:
RELATED APPLICATIONS  
       [0001]     This Patent Application claims priority under 35 U.S.C. 119(e) of the co-pending U.S. Provisional Pat. App. No. 60/609,507, filed Sep. 7, 2004, entitled “Integrated Connector and AC/DC Converter”, which is hereby incorporated by reference. The Patent Application is related to concurrently filed U.S. Pat. App. No. 60/609,507, entitled “Integrated Connector and AC/DC Converter”, which is herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The instant invention relates to a heat dissipating system for electronic devices. More specifically, a heat dissipating system that allows for more compact device packages while maintaining current standards for heat-dissipation, temperature equalization and overheating prevention. In particular, the instant invention reveals a compact AC/DC power converter cooled according to the present invention.  
       BACKGROUND  
       [0003]     Many electronics circuits depend on reliable heat dissipation systems to ensure stable operation and efficiency. Thermal excitement in electrical systems leads to increased noise. Without an effective heat dissipation system, failure or unstable operation is possible.  
         [0004]     Conventional heat dissipation systems depend on one or more of the following strategies: passive convection operating directly on the heat producing components of the electronic device; addition of an active cooling solution, such as a fan or liquid cooling system; placement of a heat sink in conductive contact with the heat producing components, such that the heat sink and the components are then in thermal equilibrium and both dissipate heat through convective means.  
         [0005]     To offer higher capacity heat transfer, new heat dissipation equipment must be more efficient. It is difficult for air-cooled heat sinks to grow in size, because equipment manufacturers are under tremendous competitive pressure to maintain or diminish the size of their equipment packages, all the while filling them with more and more components. In addition, larger heat sinks typically will increase the cost of the heat sink element. Thus, competitive heat dissipation equipment must be relatively compact in size and must perform at levels sufficient to prevent high-performance components from exceeding their operational heat specifications.  
         [0006]     Conventional heat dissipation systems are at odds with these requirements. Heat sinks and active cooling solutions are bulky and require additional space within the device package. Even passive convective cooling requires the allotment of space within the device to allow for air flow.  
         [0007]     Prior work in the art has shown that a solution analogous to a heat sink need not require additional space within the device package. United States Patent Publication No.  2002-0092160  reveals a device wherein the structural frame is composed of a heat conductive material and is thermally coupled to the electronic components therein, whereby the frame and electronic components are at thermal equilibrium and passive convective cooling of the entire system occurs more rapidly than it otherwise would.  
         [0008]     This type of cooling system, relying on heat dissipation through passive convection, is acceptable for low power, battery-operated, portable applications. Higher power electronics create more heat, and dissipation thereof through the exterior of the device package could presumably allow the exterior surface to reach an unsafe temperature. For the same reasons, attaching any form of heat sink to the exterior of a device would not only increase the package bulk, but allow for possible user contact with a hot element used.  
         [0009]     Traditional AC/DC power converters, such as for cellular telephones typically include a plastic housing with air or other insulation surrounding the electronic power convertor circuit. For cooling, such circuits have relied on large device packages and, in some cases, the presence of vents to facilitate passive convective cooling of an enclosed circuit board including a plurality of electronic components mounted on a PCB. This strategy results in a device inconveniently large in size. Furthermore, the convective means of cooling circuitry in an enclosed space, even with vent holes, has poor efficiency, resulting in a high equilibrium operating temperature for the electronic device.  
         [0010]     This construction method results in large device packages for several reasons. Conventional power conversion circuits include primary and secondary circuits: a primary circuit is connected directly with the AC power input to be converted and power is output through the secondary circuit. Safety regulations require a minimum distance of 6.4 mm between the secondary and primary circuits through air. Further, because government regulations mandate that operating temperatures in such devices not exceed a certain range above the ambient temperature, smaller device packages are not feasible using prior art techniques: a package having a large surface area is often the only means of achieving the needed heat dissipation. Devices constructed according to prior art techniques to have a certain size. This is true since even low powered devices, which might obtain sufficient heat dissipation through a small package, because they are required to meet the through-air requirement of a 6.4 mm spacing.  
         [0011]     In view of this, users must carry an undesirably large power converter to charge their cellular telephone. It is further well known in the art that relatively higher operating temperatures result in relatively higher incidence of device failure and in less efficient operation.  
         [0012]     Because current cooling system designs necessitate large device packages, especially in power conversion devices, many current power converter designs are bulky and inconvenient. Compare the power adapters designed to charge cellular phone batteries with a standard AC power plug. The typical cellular telephone power adapter employs a bulky housing to hold the plug blades and the power conversion circuitry. The relatively large size of the power adapter is necessary because of the heat dissipation requirements outlined above. Exclusive of those requirements, it is apparent that a smaller, more compact device packaging would be advantageous for such power adapters. The advantages of such a construction are especially clear since cellular phone adapters are necessarily portable and thus stand to benefit substantially from a sleeker device packaging.  
         [0013]     In view of the above, there is a demonstrated need for a cooling system capable of handling the large heat loads created in power electronics, but that also allows for compact device packaging and does not present a hazard to the user. This need is especially apparent in the field of power converter manufacturing, where current cooling systems preclude the creation of a compact power converter that is both efficient and reliable.  
       SUMMARY OF THE DISCLOSURE  
       [0014]     The present invention represents an improvement of prior art cooling systems for externally powered electronic devices. It provides all the advantages of an extended external heat sink assembly, allowing for compact device packaging while maintaining a reasonably cool operating temperature. However, the present invention requires no external apparatus aside from the familiar power supply, which in most cases takes the form of a wall outlet.  
         [0015]     In accordance with the embodiments of the present invention, a compact power conversion device is provided. The device comprises a power conversion circuit coupled to receive electric power from a power supply network via power supply leads, and a heat conductive body thermally coupled with the power conversion circuit for substantially efficient heat transfer from the power conversion circuit and to the power supply leads. Wherein the thermal coupling is such that heat generated by the power conversion circuit is transferred to the power supply network. By conduction through the heat conductive body, then the power supply leads and into the wires of the power supply network.  
         [0016]     According to the present invention, one way to achieve the thermal coupling is to mold the heat conductive body around at least a portion of the power conversion circuit and around at least a portion of the power supply leads. In this construction, the power supply leads are coupled by thermal conduction to the power conversion circuit to allow substantially efficient heat transfer from the circuit to the leads. The leads are thermally conductive and transfer heat into the power supply wall socket and subsequently to the wiring in the wall. In further aspects of the present invention, the device has power output leads coupled with the power conversion circuit to transmit the converted power to a distant load.  
         [0017]     In addition to maintaining good heat dissipation characteristics, the present invention discloses several device designs having good structural integrity. In one aspect, the compact power conversion device further comprises a substantially rigid body coupled with the heat conductive body and with the power conversion circuit to provide structural support. In another aspect, the heat conductive body forms also a structural enclosure for the power conversion circuit and the power supply leads. In this case the heat conductive body should conform to accepted strength of materials standards for use as a structural element in an electrical housing.  
         [0018]     In the compact power conversion device of the present invention, the heat conductive body should have at least a minimum thermal conductivity to allow adequate heat dissipation and a low electrical conductivity to prevent short circuits. Further, when the conductive body is used in a structural capacity, or as insulation between the primary and secondary portions of the conversion circuit, it is formed from a UL recognized insulation material.  
         [0019]     Also in the present invention, a power converter is provided. The power converter comprises a circuit for converting an electric signal, power supply leads coupled to provide the electric signal to the circuit, and an electrically inert, thermally conductive mass coupled with the circuit to transfer heat generated by the circuit to the power supply leads. In the power converter according to the present invention, the power supply leads are also thermally coupled to a power supply network such that the heat generated by the circuit is transferred to the power supply network.  
         [0020]     In a further aspect of the present invention a method of cooling an electronic device supplied by an external power source is provided. The method comprises thermally coupling for substantially efficient heat transfer at least a portion of an electronic device to a thermally conductive body, and thermally coupling for substantially efficient heat transfer at least a portion of each of a plurality of power supply leads to the thermally conductive body.  
         [0021]     The method of the present invention further comprises enclosing the electronic device, at least a portion of each of the plurality of power supply leads and the thermally conductive body in any appropriate, rigid shell body, whereby the electronic device is simultaneously embedded in the rigid shell material and in the thermally conductive body.  
         [0022]     In accordance with the method of the present invention, the thermally conductive body should have at least a minimum thermal conductivity to allow adequate heat dissipation and a low electrical conductivity to prevent short circuits. Further, when the thermally conductive body is used in a structural capacity, or as electrical insulation between the primary and secondary portions of the conversion circuit, it is formed from UL recognized electrical insulation material.  
         [0023]     An AC/DC converter assembly is provided in the present invention. The AC/DC converter assembly of the present invention comprises an AC/DC converter circuit having a primary portion and a secondary portion, a plurality of AC plugs coupled with the AC/DC converter circuit, and a housing comprising a thermally conductive and electrically resistive body molded around the AC/DC converter circuit and also around at least a portion of each of the plurality of AC plugs so that the thermally conductive and electrically resistive body is thermally coupled with the AC plugs and the AC/DC converter circuit. In the AC/DC converter assembly of the present invention, thermal energy dissipated in the AC/DC converter circuit is thermally conducted to the AC plugs.  
         [0024]     In accordance with the AC/DC converter assembly of the present invention, the heat conductive body should have at least a minimum thermal conductivity to allow adequate heat dissipation and a low electrical conductivity to prevent shorts. Further, if the conductive body is used in a structural capacity, or as electrical insulation between the primary and secondary portions of the conversion circuit, it is formed from a UL recognized electrical insulation material. In another aspect of the AC/DC converter assembly of the present invention, a UL recognized insulation material is formed around the thermally conductive and electrically resistive body for providing a structural enclosure for the AC/DC converter circuit.  
         [0025]     Also in the present invention a device is provided for cooling one or more electronic circuits supplied by an external power source, where each of the circuits comprises a plurality of circuit elements and the elements further comprise heat producing and non-heat producing elements. The device according to the present invention comprises a thermally conductive mass in direct intimate contact with at least the heat producing elements of the circuits and with the power supply leads.  
         [0026]     The present invention also discloses a system for cooling an electronic device, where the device comprises heat dissipating elements and is supplied by an external power source. According to the present invention, the device comprises means for conductively capturing heat produced by the heat dissipating elements of the device, and means for conducting the heat captured from the heat dissipating elements of the device into the external power source.  
         [0027]     In a further aspect, the present invention describes a power conversion system. The power conversion system comprises a power supply, a power outlet for coupling an arbitrary device into a circuit containing the power supply, an electronic device with a power input, and, an adapter comprising at least one input and at least one output, the inputs comprising an input capable of coupling into the circuit containing the power supply, the outputs comprising an output compatible with the power input of the electronic device, the adapter further comprising heat dissipating elements and non-heat dissipating elements, wherein the heat dissipating elements are thermally coupled for conductive heat transfer to a heat conductive body, further wherein the heat conductive body is configured to be in direct thermal contact with the circuit containing the power supply.  
         [0028]     Also, the present invention includes a method of manufacturing a power adaptor. The method of manufacturing includes the steps of providing a power conversion circuit, including a plurality of power supply leads, power conversion components, and power output leads, and of molding a heat conductive material around the power conversion components to form a plug structure and integrated strain relief structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]      FIG. 1  is a perspective view of the device in an assembled state.  
         [0030]      FIG. 2  is a partial cross sectional view of the preferred embodiment of the device wherein the device packaging is formed of multiple materials, at least one material being used in primarily structural way and at least one material being used primarily for heat transfer.  
         [0031]      FIG. 3  is a partial cross sectional view of an alternate embodiment of the device wherein the device packaging is formed of thermally conductive material, used for both heat transfer and also structure. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0032]     For illustration purposes only, and by way of example, the present invention is shown to be employed for an AC/DC converter. As will be seen below, the cooling system for the electronic device of the present invention can be easily employed in the fabrication of other electronic devices, such as, and without limitation, power amplifiers and computing devices.  
         [0033]     The invention will be described in detail below in the context of an application for an AC/DC converter; however, such disclosure is not intended to limit the scope of the present invention to such an application of the present invention.  
         [0034]      FIG. 1  shows a compact power conversion device  100  according to the present invention. The power conversion device  100  includes a substantially rigid body  130  from one end of which extend two power supply leads  110  and  120  that in create a standard male AC plug. The power supply leads  110  and  120  and can include apertures as shown or to be solid. The power supply leads  110  and  120  and can both be the same size as shown or have polarity such that one blade is wider. A third power supply lead can be used as a conventional ground terminal. From the opposite end of the substantially rigid body  130  extends a power cord  140  which terminates in a DC power coupling  150 . As can be seen, the device bears a strong resemblance to a common AC power cord. The substantially rigid body  130  is shown with a particular industrial design. This industrial design is representative only and can be modified without departing from the invention. Also owing to the present invention, the device is substantially the same as a common AC power cord.  
         [0035]     In  FIG. 2 , a partial cross sectional view of a power conversion device  200  is shown to include a substantially rigid body  230  from one end of which extend two power supply leads  210  and  220  that together form a standard male AC power plug. The device of  FIG. 2  can but need not be the same as that shown in  FIG. 1 . From the opposite end of the substantially rigid body  230  extends a power cord  240  which terminates in a DC power coupling  245 . The power cord  240  contains the power output leads  276  which are coupled with the power conversion circuit  270 . The power conversion circuit  270  is shown schematically only with circuit elements represented by blocks; any conventional circuit could work using the present invention. The power conversion circuit  270  includes primary  272  and secondary  274  portions. Further, the body is seen to contain electrically and thermally conductive ends  215  of both power supply leads  210  and  220 . Also illustrated is the gap  225  of at least 0.4 mm between the primary  272  and secondary  274  sides of the power conversion circuit  270 . The gap  225  being filled with the material that the substantially rigid body  230  is comprised of, which is preferably a UL recognized electrical insulation material that provides the minimum required electrical insulation between the primary  272  and secondary  274  sides of the power conversion circuit  270 . The power conversion circuit  270  is also shown to include heat generating components  260  within the primary portion  272 . In the preferred embodiment, the structural body  230  is coupled to a heat conductive body  250  which is further thermally coupled for substantially efficient heat transfer to the heat generating components  260  and to the thermally conductive ends  215  of the power supply leads  210 ,  220  so that the heat generated in the heat generating components  260  is transferred into the power supply leads  210 ,  220  and from there to the power supply network (not shown) such as conventional power outlets and wall wiring. The thermal coupling is preferably accomplished by molding the heat conductive body  250  around the heat generating components  260  and the thermally conductive ends  215 , but could be accomplished by any reasonable means. According to the present invention, the heat conductive body has at least a minimum thermal conductivity allow adequate heat dissipation and a low electrical conductivity to prevent shorts.  
         [0036]     In  FIG. 3 , a partial cross sectional view of a power conversion device  300  is shown to include a structural enclosure  330  from one end of which extend two power supply leads  310  and  320  that together form a standard male AC power plug. From the opposite end of the structural enclosure  330  extends a power cord  340  which terminates in a DC power coupling  345 . The power cord  340  contains the power output leads  376  which are coupled with the power conversion circuit  370 . The power conversion circuit  370  includes primary  372  and secondary  374  portions. Further, the body is seen to contain electrically and thermally conductive ends  315  of both power supply leads  310  and  320 . Also illustrated is the gap  325  of at least 0.4 mm between the primary  372  and secondary  374  sides of the power conversion circuit  370 . The gap  325  being filled with the material that the structural enclosure  330  is comprised of, which is preferably a UL recognized electrical insulation material that provides the minimum required electrical insulation between the primary  372  and secondary  374  sides of the power conversion circuit  370 . The power conversion circuit  370  is also shown to include heat generating components  360  within the primary portion  372 . In this embodiment, the structural body  330  is comprised of an electrically inert, thermally conductive material which is further thermally coupled for substantially efficient heat transfer to the heat generating components  360  and to the thermally conductive ends  315  of the power supply leads  310 ,  320  so that the heat generated in the heat generating components  360  is transferred into the power supply network (not shown) through the power supply leads  310 ,  320 . The thermal coupling is preferably accomplished by molding the structural enclosure  330  around the heat generating components  360  and the thermally conductive ends  315 , but could be accomplished by any reasonable means. According to the present invention, the structural enclosure  330  has a sufficient thermal conductivity to allow adequate heat dissipation and a low electrical conductivity to prevent shorts.  
         [0037]     Also in accordance with the present invention, a method of cooling an electronic device supplied by an external power source is provided, which will now be discussed with reference to the above devices, and to  FIGS. 2 and 3 . The method of the present invention comprises thermally coupling for substantially efficient heat transfer at least a portion of an electronic device to a thermally conductive body, and thermally coupling for substantially efficient heat transfer at least a portion of each of a plurality of power supply leads to the thermally conductive body. Referring to  FIG. 2 , an electronic device  200  is constructed according to the method of the present invention. A portion of the electrical circuit  270  is thermally coupled to the thermally conductive body  270 , which is also thermally coupled to the power supply leads  210 ,  220  for substantially efficient heat transfer. In the device  200 , the structural integrity of the device package is maintained by the rigid shell body  230 . Referring to  FIG. 3 , an electrical device  300  is constructed according to the method of the present invention. A portion of the electrical circuit  370  is thermally coupled to the thermally conductive body  330 , which is also thermally coupled to the power supply leads  310 ,  320  for substantially efficient heat transfer. In the device  300 , the thermally conductive body  330  also provides a structurally sound device package. In the method of the present invention, the structural materials are preferably comprised of a UL recognized insulation material. Also, in the method of the present invention the thermally conductive materials used to thermally couple the power supply leads to the electrical device have at least a minimum thermal conductivity to allow adequate heat dissipation and a low electrical conductivity to prevent shorts.  
         [0038]     Because the device of the present invention comprises a solid mass of material molded around the circuit components of a power converter, a much more compact size is achieved than is present in prior art devices or possible with prior art designs. Though safety regulations dictate a 6.4 mm spacing through air between primary and secondary circuitry in a power converter, only 0.4 mm spacing is required through any homogeneous UL recognized electrical insulation material. In the preferred embodiment of the present invention, a UL recognized insulation material is used to provide the structure of the compact power conversion device. Though other materials are contemplated in the present invention, because of current regulations other contemplated materials that are non-UL recognized at the time of invention cannot be considered equivalent. Of course, any future materials meeting the approval of UL or some similar regulatory authority, would have to be considered equivalents.  
         [0039]     The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of the principles of construction and operation of the invention. As such, references, herein, to specific embodiments and details thereof are not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications can be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention.