Abstract:
A power supply connector including a spring loaded member that allows a connector to engage various power receptacles. This engagement of the connector and the power receptacle may reduce a contact resistance between the two components and heat dissipation associated therewith. Thus, the power supply connector reduces the risk of damage to the power supply due to heat dissipation in the power receptacle, power supply connector, or other portion of the power supply.

Description:
RELATED APPLICATIONS 
     This application is related to, and hereby incorporates by reference the entire disclosure of each of the following commonly owned U.S. patent applications, each filed on even date herewith: (1) U.S. patent application Ser. No. 10/984,551, titled “Temperature Sensor for Power Supply,”(2) U.S. patent application Ser. No. 10/984,695, titled “Power Supply Configured to Detect a Power Source,” and (3) U.S. patent application Ser. No. 10/984,552, titled “Microcontroller Controlled Power Supply.” 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to power supplies and, more specifically, to a power supply that includes a connector configured to disable power flow until the connector is properly engaged with a power source. 
     2. Description of the Related Art 
     In order to power many electronic devices, such as household appliances, power supply configured for coupling with an external power source. External power sources may include wall outlets, cigarette lighters in automobiles or other vehicles, and in seat power delivery systems in aircraft. For many types of power sources, the mechanical configuration of a connection portion of the power source is standardized. Thus, power supply manufacturers may develop power supplies according to the applicable standard for a particular type of power source and have a reasonable assurance that the power supply will be compatible with that type of power source. 
     Vehicle cigarette lighters are commonly used to access the power source of a vehicle&#39;s electrical power, which generally comprises a battery and alternator, for example. The receptacle of a vehicle cigarette lighter located in an automobile, water vehicle, or other recreational vehicle, for example, (referred to herein generally as a “vehicle receptacle”) is standardized so that manufacturers may produce power supplies for various electronic devices that may be powered via the vehicle receptacle. However, some vehicles are not in compliance with the standardized vehicle receptacle specifications. Thus, power supplies having standardized vehicle connectors may not properly engage with these out of specification vehicle receptacles. If a connector is incompletely contacting the vehicle receptacle, there is a possibility for an increase of contact resistance between the connector and the receptacle, and a corresponding increase in heat dissipation at the point of increased contact resistance. This increase in heat dissipation may be absorbed by the vehicle connector and may cause melting of components in the connector or the connector housing. In addition, power delivery to the power supply may be interrupted if the connection with the vehicle receptacle is not stable and the electronic device powered by the power supply may be damaged. Accordingly, systems and methods for enhancing a connector&#39;s ability to engage vehicle receptacles are desired. In addition, systems and methods for preventing damage to power supplies due to incomplete or improper connections with vehicle receptacles are desired. 
     SUMMARY OF THE INVENTION 
     In one embodiment, in order to prevent excessive heat dissipation in a power supply connector, the power supply connector is configured to mechanically disconnect the power source from the power supply if a satisfactory connection with the power source is not achieved. In another embodiment, the power supply is configured to monitor a contact resistance between the power supply connector and the power source and disable the power supply, or reduce a power signal transmitted from the power supply, if the contact resistance, or temperature of the connector, exceeds a predetermined threshold. 
     In one embodiment, a connector configured to engagingly mate with a power receptacle of a power source comprises an electrically conductive shaft having a longitudinal axis, the shaft being moveable within the connector along the longitudinal axis and configured to contact the power receptacle, an isolation ring protruding from an outer surface of the shaft, wherein the isolation ring comprises an electrically insulative material, and an electrically conductive housing electrically coupled to a power supply, the housing comprising one or more electrically conductive fingers that are resiliently biased towards the longitudinal axis, wherein the shaft is moveable relative to the housing. 
     In another embodiment, a method of activating a power supply to deliver power from a power source comprises inserting a connector of the power supply into a power receptacle so that a force is applied to a shaft of the connector, in response to the force applied to the shaft of the connector, moving the shaft inward towards a body of the connector thereby causing a conducting finger of the connector to be moved from contact with an insulative portion of the shaft to contact a conductive portion of the shaft, transferring power from the power receptacle to the shaft, transferring power from the shaft to the conducting finger, and transferring power from the conducing finger to the power supply. 
     In another embodiment, a method of disabling power delivered from a power source to a power supply comprises engaging a connector portion of the power supply with a receptacle portion of the power source, changing a position of a the connector of the power supply so that a conducting finger of the connector is moved from contact with a conductive portion of the connector to contact an insulative portion of the connector, and blocking transfer of power from the power source to the power supply due to the contact of the conducting finger with the insulative portion of the connector. 
     In another embodiment, a system for disabling power delivered from a power source to a power supply comprises means for engaging a connector portion of the power supply with a receptacle portion of the power source, means for changing a position of the connector so that a conducting finger of the connector is moved from contact with a conductive portion of the connector to contact an insulative portion of the connector, and means for blocking transfer of power from the power source to the power supply due to the contact of the conducting finger with the insulative portion of the connector. 
     In another embodiment, a method of reducing a contact resistance between a power receptacle and a power supply connector comprises inserting the power supply connector into the power receptacle so that a shaft of the power supply connector contacts a portion of the power receptacle, engaging the power supply connector with the power receptacle so that the shaft is moved within the power supply connector, and creating an electrically conductive path through the power supply connector in response to movement of the shaft at least a predetermined distance within the power supply connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of the invention will become more apparent from the following description and appended claims taken in conjunction with the following drawings, wherein like reference numbers indicate identical or functionally similar elements. 
         FIG. 1  is a block diagram of a power supply coupled to an electronic device via a changeable connector. 
         FIGS. 2A and 2B  are illustrations of an exemplary plug of a power supply that is configured to engage with a vehicle receptacle. 
         FIGS. 3A and 3B  are illustrations of the plug of a power supply that is configured to be inserted into a power receptacle. 
         FIG. 4  is a perspective view of a connector including the plug ( FIG. 2 ) configured to be inserted in vehicle receptacle. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following is a detailed description of embodiments of the invention. However, the invention can be embodied in a multitude of different ways as defined by the claims. The invention is more general than the embodiments that are explicitly described, and accordingly, is not limited by the specific embodiments. 
       FIG. 1  is a block diagram of a power supply  100  coupled to an electronic device  120  and to a power source  105  via a changeable connector  110  (or simply “connector  110 ”). In the embodiment of  FIG. 1 , the electronic device  120  is any type of device that may be powered by an AC or DC power signal. The electronic device  120  may comprise, for example, a household appliance, a stereo component, a computing device, or any other electronic component. In one embodiment, the power source  105  comprises a cigarette lighter receptacle (also referred to herein as a “vehicle receptacle”) configured to engage the connector  110 , along with the power components coupled to the cigarette lighter, such as the battery and alternator, for example. 
     The connector  110  is mechanically shaped to be coupled with the power source  105 . In one embodiment, the connector  110  comprises a plug having one or more positive and negative leads exposed, wherein the plug may be inserted into a socket, or receptacle, of the power source  105 . In one embodiment, the connector  110  is changeable, such that the connector  110  may be configured to couple with either an in-seat power source receptacle in an aircraft or a vehicle receptacle. 
     In the embodiment of  FIG. 1 , the power supply  100  comprises a power module  102  and a microcontroller  104 . The power module  102  comprises the power delivery components that are configured to generate and supply the voltage to the electronic device  120 . The microcontroller  104  is advantageously coupled to the power module  102  and is configured to control the output voltage level from the power module  102 . In one embodiment, the coupling of the microcontroller  104  to the power module  102  is via one or more amplifiers, diodes, and other electronic components. Those of skill in the art will recognize that various components may be used in the power module  102  to transform and/or convert power from a power source. The systems and methods described herein expressly contemplate the use of any suitable components in the power module  102 . For a more detailed description of the control of a power supply by a microcontroller, refer to commonly owned U.S. patent application Ser. No. 10/984,552, titled “Microprocessor Controlled Power Supply,” filed on even date herewith, which is hereby incorporated by reference in its entirety. 
       FIGS. 2A and 2B  are illustrations of a plug  200  of a power supply that is configured to be inserted into a power receptacle. The exemplary plug  200  is coupled to the power supply  100  and is configured to engage with a power source, such as via a cigarette lighter in a vehicle or an in seat power delivery system in an aircraft.  FIG. 2A  is an elevated side perspective view of a plug  200  in a quiescent position and  FIG. 2B  is a cross-sectional side view of the plug  200  in the quiescent position. In the quiescent position, the plug  200  does not transfer power from a power source to the power supply. In an active position, discussed below with reference to  FIGS. 3A and 3B , the plug  200  is configured to transfer power from a power source to the power supply. 
     The plug  200  comprises a shaft  210  having a tip  215  on one end for contacting a power delivery portion of a power source, such as an electrical contact of a power receptacle, which may be, for example, a vehicle receptacle. However, the receptacle could be any other type, such as an in seat power delivery system in an aircraft or a power outlet in a fixed structure. The shaft includes a longitudinal axis  212  extending through a center of the shaft  210 . The shaft  210 , including the tip  215 , is electrically conductive and is configured to mechanically contact the power receptacle. 
     The plug  200  further comprises a housing  220  comprising one or more resilient fingers  225  that are biased towards the longitudinal axis. The resilient fingers  225  are electrically conductive and configured to exert an inward force towards the longitudinal axis  215  of the shaft  210 . The housing includes a power delivery member  228  configured to deliver power to the power supply. The resilient fingers  225  are in electrical contact with the power delivery member  228  so that power delivered to the resilient fingers  225  is transferred to the power delivery member  228 . In operation, power is delivered from the power source to the shaft  210 , to one or more of the resilient fingers  225 , to the power delivery member  228 , and to the power supply. 
     Advantageously, the plug  200  includes features requiring that the plug  200  is properly inserted into a power receptacle before power is transferred from the power source to the power delivery member  228  via the plug  200 . In particular, the plug  200  comprises an isolation ring  214  that surrounds a portion of the shaft  210  and is mechanically connected to the plug  200 . The isolation ring  214  comprises an electrical insulator, such that electrical current does not pass through the isolation ring  214 . In the quiescent state of the plug  200  illustrated in  FIGS. 2A and 2B , the resilient fingers  225  contact the isolation ring  214  and are not in contact with a conductive portion of the shaft  210 . Accordingly, in this quiescent state, the housing  220  is electrically isolated from the shaft  210  and power is not transferred from the power source to the power delivery member  228 . 
       FIGS. 3A and 3B  are illustrations of the plug  200  of a power supply that is configured to be inserted into a power receptacle. In particular,  FIG. 2A  is an elevated side perspective view of a plug  200  in an active position, wherein in the active position power delivered to the shaft  210  is transferred to the power delivery member  228 .  FIG. 3B  is a cross-sectional side view of the plug  200  in the active position. As shown in  FIGS. 3A and 3B , the shaft  200  has been moved towards the power delivery member  228  of the housing  220 . In one embodiment, the shaft  200  is spring loaded within the housing  220  so that by applying a force to the tip  215 , the shaft  200  is moved towards the power delivery member  228 . As the shaft  200  is moved inward, the isolation ring  214  is also moved with reference to the resilient fingers  225 . Due to the shape of the resilient fingers  225 , when the isolation ring  214  has moved inward to a position such as illustrated in  FIGS. 3A and 3B , the resilient fingers  225  mechanically contact the conductive portion of the shaft  210  and any power delivered to the shaft  210  is transferred through the resilient fingers  225  and housing  220  to the power delivery member  228 . Thus, power is delivered to the power supply when the shaft  200  has a sufficient force applied to move the isolation ring  214  so that the resilient fingers  225  contact the shaft  210 . This force may be delivered by a user continuing to push the plug into a vehicle receptacle after the shaft has contacted a surface of the vehicle receptacle. 
     In one embodiment, after the plug  200  is removed from the power receptacle, the shaft  210  is pushed along the longitudinal axis  215  away from the power delivery member  228 . When the shaft  210  returns to a position such that the isolation ring  214  is again in contact with the one or more resilient fingers  225 , the plug  200  is again in it&#39;s quiescent state. Thus, each time the plug  200  is inserted into a power receptacle, the shaft  210  must be moved in order to put the plug  200  into an active state. 
     The design of the above described plug reduces the risk of the plug  200  generating excessive heat that can be caused by an incomplete connection with the power receptacle. For example, some vehicle cigarette lighter power receptacles are shallower than standard power receptacles. Thus, a power supply plug designed for use in standard power receptacles may not have a long enough shaft to electrically connect to a power delivery receptacle, thus providing a potential for increased contact resistance and the heat dissipation that results from the additional contact resistance. In addition, the power supply plug may be inserted into a receptacle so that the shaft is incompletely contacting the power source, thus creating a potential for heat generation in the plug, due to an increase in contact, or crossover, resistance, and possible melting of components in the plug. According to the embodiment described above, plug  200  is in a quiescent mode until the plug is inserted a predetermined distance into the power receptacle. In one embodiment, this predetermined distance is the distance that is determined to be necessary to ensure that the plug  200  is properly contacting the power receptacle of any known power receptacle. 
       FIG. 4  is a perspective view of a connector  110  including plug  200  ( FIG. 2 ) configured to be inserted in vehicle receptacle  310 . As shown in  FIG. 4 , a power delivery member  228  is coupled to the power supply  100  via an electrical cable  320 .  FIG. 4  also illustrates a spring  330  configured to provide a force on the shaft  210  ( FIG. 2 ) of the plug  200 . 
     Specific parts, shapes, materials, functions and modules have been set forth, herein. However, a skilled technologist will realize that there are many ways to fabricate the system of the present invention, and that there are many parts, components, modules or functions that may be substituted for those listed above. While the above detailed description has shown, described, and pointed out the fundamental novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the components illustrated may be made by those skilled in the art, without departing from the spirit or essential characteristics of the invention.