PATENT DOCUMENT

Publication Number: US-8339760-B2
Application Number: US-48501909-A
Country: US
Kind Code: B2

Title: Thermal protection circuits and structures for electronic devices and cables

Abstract:
Connectors for cables such as a 30-pin connector are provided. The connectors may have thermal protection circuits and may carry a power supply voltage and a ground voltage. The thermal protection circuits may disable the power supply voltage when the temperature of the connector exceeds a threshold value. The connectors may have structures that encourage any dendritic failure to occur in a preferred location.

Claims:
1. A cable comprising:
 a connector at one end of the cable; 
 a pair of conductors in the connector; and 
 a structure at a given location in the connector that encourages formation of dendritic shorts between the pair of conductors at the given location upon exposure of the connector to moisture. 
 
     
     
       2. The cable defined in  claim 1  wherein the connector includes a printed circuit board and wherein the pair of conductors comprise two traces in the printed circuit board. 
     
     
       3. The cable defined in  claim 2  wherein the printed circuit board includes a mask that covers the traces and wherein the structure that encourages formation of dendritic shorts comprises portions of the printed circuit board and the traces that are not covered by the mask. 
     
     
       4. The cable defined in  claim 2  wherein the two traces are parallel to each other and are separated by a gap and wherein the structure that encourages formation of dendritic shorts comprises a pointed conductive member that extends across part of the gap. 
     
     
       5. The cable defined in  claim 1  further comprising a power cutoff switch that selectively blocks power delivery to the given location. 
     
     
       6. The cable defined in  claim 5  further comprising a temperature sensor in the connector, wherein the power cutoff switch selectively blocks power delivery to the given location based on signals from the temperature sensor. 
     
     
       7. The cable defined in  claim 5  further comprising:
 an additional connector at the other end of the cable; and 
 a plurality of conductors between the connector and the additional connector, wherein the power cutoff switch is interposed between the structure that encourages formation of dendritic shorts and the plurality of conductors between the connector and the additional connector. 
 
     
     
       8. The cable defined in  claim 7  wherein the power cutoff switch comprises an integrated circuit having a temperature sensor that measures the temperature of the connector. 
     
     
       9. Circuitry comprising:
 a first trace that carries a first voltage; 
 a second trace that carries a second voltage and that is separated from the first trace by a gap, wherein the second trace includes an extending member that extends towards the first trace and narrows the gap; and 
 a mask that covers portions of the first and second traces, wherein the mask has a hole over a least a portion of the extending member and wherein the extending member and the hole encourage formation of dendritic shorts upon exposure to moisture. 
 
     
     
       10. The circuitry defined in  claim 9  wherein the first and second traces respectively comprise first and second copper traces. 
     
     
       11. The circuitry defined in  claim 9  further comprising a printed circuit board on which the first and second traces are formed. 
     
     
       12. The circuit defined in  claim 9  wherein the hole in the mask extends over a portion of the first trace opposite the extending member. 
     
     
       13. The circuitry defined in  claim 9  further comprising:
 a cable including a plurality of conductors; and 
 a connector at one end of the cable in which the extending member is located, wherein the connector has pins that receive power supply signals from the conductors through the first and second traces. 
 
     
     
       14. The circuitry defined in  claim 13  wherein the connector comprises a 30-pin connector. 
     
     
       15. The circuitry defined in  claim 9  further comprising:
 a connector in which the extending member is located; 
 a plurality of conductors connected to respective pins in the connector; 
 a temperature sensor that measures temperature in the connector; and 
 a switch between the second trace and a given one of the plurality of conductors, wherein the switch is configured to isolate the second trace from the given conductor when the temperature in the connector exceeds a given threshold. 
 
     
     
       16. A printed circuit board for a connector, the printed circuit board comprising:
 a first trace; and 
 a second trace that is separated from the first trace by a gap, wherein the second trace includes an extending portion that extends towards the first trace and narrows the gap and wherein the extending portion encourages formation of dendritic shorts in the gap between the first and second traces upon exposure of the printed circuit board to moisture. 
 
     
     
       17. The printed circuit board defined in  claim 16  further comprising:
 a mask that covers portions of the first and second traces, wherein the mask has a hole over at least a portion of the extending portion and the first trace. 
 
     
     
       18. The printed circuit board defined in  claim 17  wherein the first and second traces are parallel to each other and wherein the extending portion comprises an extending portion with a point at the narrowest portion of the gap. 
     
     
       19. The printed circuit board defined in  claim 17  further comprising a temperature sensor that measures temperature in the printed circuit board. 
     
     
       20. The printed circuit board defined in  claim 19  further comprising a power cutoff switch that blocks power flow to a given one of the first and second traces when the temperature measured by the temperature sensor exceeds a given threshold for a given period of time.

Description:
BACKGROUND 
     This invention relates to thermal protection circuits and structures for electronic devices and cables. 
     Portable electronic devices such as portable computers, handheld media players, and cellular telephones typically contain connectors that receive power signals from other electronic devices such as desktop computers and power adapters. The power signals are typically conveyed over cables such as Universal Serial Bus (USB) cables. A user who desires to use a portable electronic device or who desires to charge a battery in the portable electronic device may connect the device to a source of electricity such as a power adapter using a cable. 
     Conventional cables and connectors for cables and electronic devices can fail in the presence of moisture. In particular, when the cables or connectors become wet, conductive dendritic structures form in the dielectric material being used to isolate conductive structures that are at different potentials in the cables or conductors. Once a conductive dendritic structure forms in the dielectric material between the conductors, the two conductors are effectively shorted together. This short circuit condition can lead to excessive current and an undesirable buildup of heat. In some situations, the heat that is produced may melt part of the cable or connector and cause a failure. 
     It would therefore be desirable to be able to provide thermal protection circuits and structures for electronic devices and cables. 
     SUMMARY 
     Electronic devices such as desktop computers, portable computers, handheld devices, and power adapters and cables that interconnect the electronic devices may include thermal protection circuits. The thermal protection circuits may include temperature-sensitive devices such as temperature sensors. Power cutoff switches in the thermal protection circuitry may be used to prevent excessive currents from developing. 
     If desired, a cable may include structures that force moisture-related shorts (e.g., dendritic shorts) to form in a particular location. With this type of arrangement, a power cutoff switch may be provided that can cut off power to the particular location. If desired, the power cutoff switch can be located near the particular location (i.e., adjacent to one or more structures that force moisture-related shorts to form in the particular location). 
     With one suitable arrangement, a cable may include thermal protection circuitry such as a temperature sensor and a power cutoff switch. The cable may include two connectors connected together by a plurality of conductors. If desired, the temperature sensor and the power cutoff switch may be located in a single connector. With this type of arrangement, the power cutoff switch may be configured to cut off power to a portion of the connector when the temperature of the connector exceeds a threshold value. 
     With another arrangement, the temperature sensor may be located in a first connector and the power cutoff switch may be located in a second connector. In this configuration, the power cutoff switch may cut power to the first connector when the temperature sensor determines that the temperature of the first connector has exceeded a threshold temperature. 
     Connectors in the cable may include structures that intentionally encourage dendritic growths. For example, a connector may include a printed circuit board with exposed regions that are not covered by a material such as a solder mask. The printed circuit board may include conductive traces that are arranged to provide an area with a relatively high voltage gradient in the exposed regions. With this type of arrangement, the exposed regions of the printed circuit board may hold moisture so that the moisture is exposed to a relatively high voltage gradient. This may provide relatively favorable conditions for dendrite formation (e.g., conditions favorable to forming shorts between the conductive traces). 
     If desired, the temperature sensor may be provided in one of the electronic devices. In addition or alternatively, the power cutoff switch may be provided in one of the electronic devices. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of illustrative electronic devices that may communicate over a communications path that may include thermal protection circuits in accordance with an embodiment of the present invention. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a media player, cellular telephone, or hybrid device showing how the electronic device may have a connector that mates with other electronic devices and accessories in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a power adapter showing how the electronic device may have a connector that mates with other electronic devices and that conveys power signals to the other electronic devices in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a portable computer that may have one or more connectors that can mate with other electronic devices in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view of an illustrative cable that may form a communications path between two electronic devices and that may include thermal protection circuits and structures in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of a dendritic structure of the type that forms in a conventional connector in the presence of moisture between metal surfaces that are at different potentials in the connector. 
         FIG. 7  is a top view of an illustrative cable that may include a connector that has thermal protection circuitry which can deactivate power supply lines in the connector in response to rising temperatures in the connector in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of an illustrative cable that may include a connector that has a temperature sensor and a power cutoff switch that can deactivate power supply lines in the connector in response to rising temperatures in the connector in accordance with an embodiment of the present invention. 
         FIG. 9  is a top view of an illustrative cable that may include a first connector with a temperature sensor and a second connector with a power cutoff switch that can deactivate power supply lines to the first connector in response to rising temperatures in the first connector in accordance with an embodiment of the present invention. 
         FIG. 10  is a circuit diagram of the illustrative cable of  FIG. 9  showing how the temperature sensor in the first connector may be formed from a thermistor that can be used in controlling latch circuitry in the second connector to deactivate the power supply lines in accordance with an embodiment of the present invention. 
         FIG. 11  is a circuit diagram of the illustrative cable of  FIG. 9  showing how the temperature sensor in the first connector may be formed from circuitry that can control the power cutoff switch in the second connector to deactivate the power supply lines in accordance with an embodiment of the present invention. 
         FIG. 12  is a top view of an illustrative connector that may be a part of a cable such as the cable of  FIG. 5 , that may include structures that encourage dendritic growth to occur in a particular location within the connector, and that may include circuitry which can deactivate power supply lines that pass through the particular location in accordance with an embodiment of the present invention. 
         FIG. 13  is a top view of an illustrative structure that may encourage dendritic growth to occur at a particular location and that may be a part of a connector such as the connector of  FIG. 12  in accordance with an embodiment of the present invention. 
         FIG. 14  is a circuit diagram of an illustrative cable that may include the connector of  FIG. 12  showing how structures that encourage dendritic growth to occur in a particular location may be used in conjunction with thermal protection circuitry which can deactivate power supply lines in the connector in response to rising temperatures in the connector in accordance with an embodiment of the present invention. 
         FIG. 15  is a top view of an illustrative cable coupled to an electronic device showing how the electronic device may include a temperature sensor located in proximity to a first connector in the cable and how the cable may have a second connector with a power cutoff switch that can be used to deactivate power supply lines to the second connector in response to rising temperatures in the second connector in accordance with an embodiment of the present invention. 
         FIG. 16  is a top view of an illustrative cable coupled between a first electronic device and a second electronic device showing how the first electronic device may include a temperature sensor in proximity to a connector in the cable and the second electronic device may include a power cutoff switch that can deactivate power supply lines to the cable and to the connector in response to rising temperatures in the connector in accordance with an embodiment of the present invention. 
         FIG. 17  is a flow chart of illustrative steps involved in using a cable that may form a communications path between two electronic devices and that may include thermal protection circuits and structures in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic components such as electronic devices and other equipment may be interconnected using wired paths. As an example, a cable may include conductors that convey power signals and data signals between two interconnected electronic devices. A cable may, for example, convey power between a power adapter and a portable electronic device. The cable may include connectors at one or both of its ends. These cable connectors may plug into mating connectors. For example, a cable connector at one end of a cable may plug into a connector in a power adapter and a cable connector at the other end of the cable may plug into a connector in an electronic device. The conductors in the cable couple the connectors at either end of the cable to each other. Pins (or other suitable contacts) may be provided in each connector that mate with corresponding pins in the equipment that mates with the connectors. For example, a cable may have a 30-pin connector. Pins in the 30-pin connector receive power from the conductors in the cable and deliver power with corresponding pins in a media player, cellular telephone, or other electronic device. 
     Cables and their connectors are sometimes inadvertently exposed to moisture. In these circumstances, shorts can form that can lead to excessive temperatures and equipment damage. In a typical failure scenario, a user may spill a liquid onto a connector. When moisture infiltrates the connector, the moisture can interact with the conductive portions of the connector, leading to dendrite growth and short circuits. Initially, dendrites may be too weak to sustain large currents. However, dendrites will eventually grow sufficiently to form a high-current path between the conductive portions of the connector (i.e., conductors at different potentials). The current that flows along the high-current path will sometimes be sufficient to burn plastic housing structures in the connector. Burnt plastic may then lead to conductive carbon deposits that contribute to the undesired short circuit condition. At this point, the connector may be permanently damaged and, if the generated current and heat was sufficient, the device into which the cable connector was plugged or other such equipment may also be damaged. 
     If desired, cables may be provided with thermal protection circuits and structures that help limit the damage caused by moisture-induced dendrite growth and resulting short circuits. Electronic devices may also be provided with thermal protection circuits and structures (in addition to, or instead of, providing the cables with thermal protection circuits and structures). 
     For example, a cable may include thermal protection circuitry that reduces or eliminate power supply signals flowing to a connector in the cable when it is determined that the temperature of the connector has risen above a given threshold. The given threshold may be relatively high, so that any moisture in the connector is removed by heating (i.e., the connector is dried) before the power supply signals are deactivated. Because the connector may be fully dried out by the heating process, the connector will not contain residual pockets of moisture that might result in additional dendrite formation and additional short circuits. 
     With one suitable arrangement, cables may include thermal protection structures in connectors that encourage moisture-related shorts (e.g., shorts resulting from dendritic growths) to occur in one or more specific locations in the connectors. With this type of arrangement, the cables may include one or more switches that can reduce or eliminate power supply signals in those specific locations. 
     An illustrative system in accordance with an embodiment of the present invention is shown in  FIG. 1 . As shown in  FIG. 1 , system  10  may include a first electronic device such as electronic device  12  and a second electronic device such as electronic device  14 . A wired path such as path  16  may be used to connect electronic device  12  to electronic device  14 . In a typical arrangement, path  16  includes one or more conductive lines and a connector at each end. The conductive lines in path  16  may be used to convey signals such as data and power signals over path  16 . There may, in general, be any suitable number of lines in path  16 . For example, there may be two, three, four, five, six, or more than six separate lines. These lines may be part of one or more cables. Cables may include solid wire, stranded wire, shielding, single ground structures, multi-ground structures, twisted pair structures, or any other suitable cabling structures. Extension cord and adapter arrangements may be used as part of path  16 , if desired. Path  16  may be a cable and path  16  may sometimes be referred to herein as cable  16 . 
     Electronic device  12  may be a desktop or portable computer, a portable electronic device such as a cellular telephone or other handheld electronic device that has wireless capabilities, equipment such as a television or audio receiver, a handheld media player, or any other suitable electronic equipment. Electronic device  12  may be provided in the form of stand-alone equipment (e.g., a handheld device that is carried in the pocket of a user) or may be provided as an embedded system. 
     Electronic device  14  may be any suitable device that works in conjunction with electronic device  12 . Examples of electronic device  14  include a portable electronic device, a cellular telephone or other handheld electronic device that has wireless capabilities, equipment such as a television or audio receiver, a handheld media player, or any other suitable electronic equipment. With one suitable arrangement, electronic device  14  may be a power adapter such as a power adapter that converts household power (e.g., alternating-current signals at a nominal voltage of approximately 120 volts or at a nominal voltage of approximately 230 volts, depending on location) or that converts power from an automobile (e.g., direct-current signals at a nominal voltage of approximately 12 volts) to power suitable for use by electronic device  12  (e.g., direct-current power signals at ground and five volts). With this type of arrangement, electronic device  12  may be a portable electronic device such as a portable computer, a cellular telephone, or a media player that receives power from the power adapter  14 . 
     An illustrative example of electronic device  12  is shown in  FIG. 2 . In the example of  FIG. 2 , device  12  is shown as having a screen such as screen  30  and a user input device such as user interface device  32 . Device  32  may be, for example, a click wheel, a touch pad, keys, switches, or other suitable buttons, a touch screen, etc. Screen  30  may be, for example, a touch screen that covers a large fraction of the front face of device  12 . Audio jack  26  may be provided to allow a user to connect a headset or other accessory to device  12 . Device  12  may include connectors such as connector  28 . Connector  28  may be a 30-pin connector, a Universal Serial Bus (USB) port, a connector that couples to a connector in path  16  of  FIG. 1 , etc. 
     Illustrative examples of electronic device  14  are shown in  FIGS. 3 and 4 . In the example of  FIG. 3 , device  14  is a power adapter that converts electricity into an appropriate form for use by another electronic device  12 . With this type of arrangement, device  14  may include power connectors such as connectors  36  (prongs) that couple to an electricity outlet and a connector such as connector  34 . Connector  34  may be a Universal Serial Bus (USB) port connector, a 30-pin connector, any other suitable connector. Connector  34  may mate with a connector in path  16  of  FIG. 1  and may be used to convey power signals over path  16  from device  14  to device  12  (e.g., for powering device  12  and for charging a battery in device  12 ). 
     In the example of  FIG. 4 , device  14  is a portable computer. Portable computer  14  of  FIG. 4  has a display such as display  30  and user input equipment such as touch pad and keys  32 . As shown in  FIG. 4 , device  14  may have an audio jack such as jack  26  for receiving a mating audio plug. Device  14  may also have connectors such as connector  28  and connector  29 . Connectors  28  and  29  may be 30-pin connectors, Universal Serial Bus (USB) ports, connectors that couple to one or more connectors in path  16  of  FIG. 1 , etc. 
     An illustrative example of a cable that may form a communications path between electronic devices  12  and  14  is shown in  FIG. 5 . In the example of  FIG. 5 , cable  16  includes first connector  38 , second connector  40 , and communications path  42  between connectors  38  and  40 . Connector  38  may be a 30-pin connector that mates with connector  28  ( FIG. 2 ) of electronic device  12 . If desired, connector  40  may be a Universal Serial Bus (USB) connector that can couple to a connector such as connector  29  ( FIG. 4 ) of electronic device  14  and that can be coupled to connector  34  ( FIG. 3 ) of power adapter  14 . Communications path  42  may include any suitable number of conductive lines and may convey signals such as data and power signals between connectors  38  and  40 . If desired, connector  38  may include a male connector portion such as portion  39  that is received by a female connector such as connector  28  ( FIGS. 2 and 4 ) and connector  40  may include a male connector portion such as portion  41  that is received by a female connector such as connector  34  ( FIG. 3 ) or connector  29  ( FIG. 4 ). In general, cable  16  may be formed using any suitable combination of male and female connectors. If desired, one end of cable  16  may be integrated into an electronic device (e.g., a power adapter). 
     As described above, conventional cables and connectors for cables and electronic devices can fail in the presence of excessive moisture. In particular, when the cables or connectors become wet, conductive dendritic structures will form in dielectric material between adjacent conductive structures that are at different potentials in the cables or connectors. Once a conductive dendritic structure forms in the dielectric material between the two conductive structures, the two structures are effectively shorted together, thereby leading to a buildup of heat that may melt surrounding material. 
     A schematic diagram that shows how a dendritic structure forms in a conventional connector is shown in  FIG. 6 . As shown in  FIG. 6 , connector  600  includes a first conductive structure  602  at an electrical potential of zero volts and a second conductive structure  604  at an electrical potential of five volts. Connector  600  also includes a dielectric material  606  that provides electrical insulation between the two conductive structures  602  and  604 . During operation, a voltage develops across conductive structures  602  and  604  (e.g., a five volt voltage difference). In the presence of moisture, this can lead to the formation of dendrites such as dendritic structure  608  in material  606 . Dendritic structure  608  is initially formed from metal (from structures  602  and  604 ) that becomes dissolved and is subsequently pulled across dielectric  606  (via the voltage gradient between structures  602  and  604 ). Once a conductive path is formed between structures  602  and  604  in this way, a large current will flow between the structures  602  and  604  which can carbonize the dielectric  606 . When dielectric  606  is carbonized, carbon material is deposited along dendritic structure  608 . Because the deposited carbon material may be even more conductive than the initial dendritic structure, the result is often a self-sustaining short between structures  602  and  604  which leads to a buildup of further heat in connector  600  and additional damage. 
     An example of a cable that may include a connector with thermal protection circuitry is shown in  FIG. 7 . As shown in  FIG. 7 , cable  16  may include connectors  38  and  40 . With one suitable arrangement, connector  40  may be a male Universal Serial Bus (USB) connector that couples to a female Universal Serial Bus (USB) port such as connector  34  of  FIG. 3  and connector  29  of  FIG. 4 . Connector  38  may be a 30-pin connector that couples to a 30-pin connector such as connector  28  of  FIGS. 2 and 4 . 
     With one arrangement, conductors such as conductors  706  and  708  in path  42  may convey signals between connectors  38  and  40 . For example, conductors  706  and  708  may carry power supply signals between the two connectors of cable  16 . As an example, conductor  706  may carry ground power supply signals and conductor  708  may carry positive power supply signals (e.g., signals at a potential of approximately 5.0 volts above ground). Conductor  706  may be a ground conductor and conductor  708  may be a power conductor. With this type of arrangement, there may be a potential difference in connector  38  between two conductive surfaces that can, under some circumstances, be susceptible to dendritic growth. 
     If desired, connector  38  may include thermal protection circuitry  710 . As one example, thermal protection circuitry  710  may be mounted on a printed circuit board  712  and, if desired, may be mounted between contacts  714  and  716 . Contact  714  may be coupled to conductor  708  and contact  716  may be coupled to pin  717  (e.g., a male pin in connector  38  extending from the connector). There may be a conductive trace between the two contacts  714  and  716 . As one example, the thermal protection circuitry  710  may be mounted along the conductive trace. 
     Thermal protection circuitry  710  may include a temperature-sensitive device such as a temperature sensor and a voltage (power) cutoff switch (as examples). With this type of arrangement, thermal protection circuitry  710  may be configured to detect increasing temperatures in connector  38  (which may be indicative of a dendritic growth creating a short between conductors  706  and  708 ). In response to increasing temperatures in connector  38 , circuitry  710  (e.g., a switch in circuitry  710 ) may be configured to cut off a power supply in connector  38  by electrically isolating contact  714  from contact  716 . With this type of arrangement, the potential of contact  716  may be reduced towards ground. Assuming that the increasing temperatures were a result of a short in connector  38 , circuitry  710  may be able to eliminate the cause of the increasing temperatures (e.g., by cutting off the voltage supply to contact  716 ). In general, thermal protection circuitry such as circuitry  710  may include any suitable temperature-sensitive device for determining when the power cutoff switch cuts off power to connector  38 . For example, circuitry  710  may include a temperature-sensitive fuse or other suitable device that changes state depending on ambient temperature. 
     As shown in  FIG. 8 , thermal protection circuitry such as thermal protection circuitry  710  of  FIG. 7  may include a separate power cutoff switch  800  and temperature sensor  802 . If desired, control circuitry associated with the thermal protection circuitry may be included in switch  800  or in sensor  802 . Temperature sensor  802  may be mounted in any suitable location in connector  38 . 
     As one example, connector  40  may be coupled to a power adapter  14 , connector  38  may be coupled to a portable electronic device  12  with a battery, and cable  16  may be used in conveying electrical power from the power adapter to the portable electronic device (e.g., to charge the battery in the electronic device). In this example, thermal protection circuitry  710  may shut off power to contact  716  and pin  717  (as example) when the temperature in the connector  38  exceeds a threshold level. This may help to protect electronic device  12  from excessive heat. 
     Because the power cutoff in the arrangement of  FIGS. 7 and 8  occurs inside connector  38 , the actions of thermal protection circuitry  710  do not shut off the power supply voltages supplied to connector  38  by conductors  706  and  708  (i.e., upstream voltages remain live). If desired, thermal protection circuitry may be provided that can deactivate one or more of the conductors in path  42  that supply power to connector  38 . With this type of arrangement, the thermal protection circuitry may be able to provide thermal protection from a short in connector  38  regardless of the location of the short (e.g., by shutting off power to the connector  38  from outside the connector  38 ). 
     An example of thermal protection circuitry that may be used to shut off power to connector  38  is shown in  FIG. 9 . As shown in  FIG. 9 , cable  16  may include thermal protection circuitry such as circuit  900  in connector  40  and sensor  902  in connector  38 . Circuit  900  may be a power cutoff switch and circuit  902  may be a temperature sensor (as examples). 
     Thermal protection circuitry such as circuit  900  in connector  40  may be mounted on a printed circuit board such as board  901  and, if desired, may be connected to a temperature sensor  902  in connector  38  over path  904 . Temperature sensor  902  may be mounted on a printed circuit board  903  in connector  38 . With one suitable arrangement, thermal protection circuit  900  may include a switch coupled between contacts  906  and  908  of printed circuit board  901 . As an example, contact  906  may receive a positive power supply voltage from electronic device  14  (e.g., over male connector portion  41  of connector  40 ). During normal operation, switch  900  may electrically connect contact  906  to contact  908  and conductor  910 . In this example, the positive power supply voltage may be conveyed to connector  38  over conductor  910  (e.g., one of a plurality of conductors in path  42 ). 
     Switch  900  may receive control signals from sensor  902  over path  904  that are indicative of the current temperature of connector  38 . When the temperature of connector  38  exceeds a threshold temperature such as a threshold value less than 85° C., a threshold value of 85° C., a threshold value of 90° C., a threshold value of 95° C., a threshold value of 100° C., a threshold value of greater than 100° C., or any other suitable threshold temperature, sensor  902  may send a control signal to switch  900  directing switch  900  to shut off power by forming an open circuit in one or more power supply lines to connector  38 . As an example, switch  900  may isolate contact  906  from contact  908 , thereby cutting off power to the conductor  910  that was previously providing power to connector  38 . With this type of arrangement, thermal protection circuits  900  and  902  may work together to protect connector  38  from overheating. For example, if a dendritic growth in connector  38  shorts conductor  910  to a ground potential, circuits  900  and  902  can detect rising temperatures resulting from the short and can shut power off to connector  38  (e.g., shut off power to conductor  910 ). 
     An illustrative circuit diagram of the arrangement of  FIG. 9  is shown in  FIG. 10 . As shown in  FIG. 10 , cable  16  may convey two or more voltages between external contacts in connector  38  and external contacts in connector  40 . For example, cable  16  may convey a ground voltage between ground (GRND) contact  1000  of connector  40  and ground (GRND) contact  1002  of connector  38 . Cable  16  may convey a positive power supply voltage between contact  1004  of connector  40  and contact  1006  of connector  38  (e.g., the VBUS contacts  1004  and  1006 ). With one suitable arrangement, the positive power supply voltage may be conveyed over conductor  1008  and the ground voltage may be conveyed over conductor  1010 . The circuit diagram of  FIG. 10  also shows how each of the conductors in path  42  may have a non-zero resistance  1014 . 
     As shown in the example of  FIG. 10 , temperature sensor  902  may be formed from a temperature-sensitive resistor such as thermistor  1016  (i.e., a resistor with a resistance that varies with temperature) coupled to power cutoff switch  900  over conductors  1008  and  1018 . 
     Switch  900  may include a number of circuit components such as transistors, resistors, capacitors, etc. that allow switch  900  to block power delivery when desired (i.e., by interrupting the flow of current). Switches such as switch  900  are sometimes referred to as “power cutoff” switches because when a given switch is placed in its open state, the power that would otherwise be delivered is blocked. Switches such as switch  900  may also be referred to as voltage cutoff switches, cutoff switches, switches, current cutoff switches, etc. 
     With one suitable arrangement, power cutoff switch  900  may include three resistors  1020 . Resistors  1020  may have any suitable resistance. As one example, resistors  1020  may each have a resistance of approximately one million ohms. If desired, power cutoff switch  900  may include a capacitor such as capacitor  1022 . As an example, capacitor  1022  may have a capacitance of approximately 0.01 microfarads. Power cutoff switch  900  may also include circuit elements  1024  and  1025  (e.g., n-channel and p-channel transistors). With one arrangement, power cutoff switch  900  may be a latching circuit. 
     When the resistance of thermistor  902  drops above a below threshold level (corresponding to the temperature in connector  38  rising above a threshold level), the voltage on node  1026  may rise above a level that causes circuitry  900  to shut off power to connector  38  by isolating conductor  1008  from contact  1004 . Alternatively, thermistor  902  may have a resistance which increases with increasing temperatures and circuitry  900  may shut off power to connector  38  when the voltage on node  1026  drops below a threshold value (e.g., when the resistance of thermistor  902  rises above a corresponding threshold resistance). 
     When connector  40  is disconnected from electronic device  14 , the contact  1004  may no longer be powered and the power cutoff switch  900  may reset (e.g., so that if the connector  40  is reconnected to electronic device  14  contact  1004  may be coupled to contact  1006 ). The thermal protection circuitry of cable  16  may be able to cut power off to connector  38  if a short occurs in connector  38  and/or an excessive rise in temperature occurs in connector  38 , thereby protecting connector  38  from excessive damage. 
     In the arrangement of  FIG. 10 , when the temperature of connector  38  rises above a threshold level, the resistance of thermistor  902  may drop. The drop in resistance of thermistor  902  may, in turn, cause the voltage at node  1026  to rise, thereby turning on transistor  1024 . As transistor  1024  is turned on, the voltage on node  1028  will drop. The lower voltage on node  1028  may, in turn, turn off transistor  1025  and isolate contact  1006  from contact  1004  (e.g., shut off power to connector  38 ). 
     Another illustrative circuit that may be associated with the arrangement of  FIG. 9  is shown in  FIG. 11 . As shown in the circuit diagram of  FIG. 11 , connectors  38  and  40  may include contacts  1000 ,  1002 ,  1004 , and  1006 , and may be interconnected by conductors  1008  and  1010 . Similarly, each of the conductors in cable  42  may have a finite resistance  1014 . Temperature sensor  902  in connector  38  may include control circuitry for controlling a power cutoff switch  900  in connector  40 . For example, temperature sensor  902  may be provided as an integrated circuit  1100  that combines a temperature sensor and control circuitry for controlling switch  900 . Circuit  1100  may sometimes be referred to here as control and temperature sensing circuitry  1100 . 
     Power cutoff switch  900  may include a transistor  1106  coupled between contact  1004  in connector  40  and contact  1006  in connector  38  (e.g., between contact  1004  and conductor  1008 ). Transistor  1106  may be used to control whether or not connector  38  is powered. For example, when excessive temperatures are detected by circuitry  1100 , transistor  1106  may be turned off to isolate connector  38  from the positive power supply voltage supplied to cable  16  over contact  1004  (from electronic device  14 ). 
     With one suitable arrangement, control and temperature sensing circuitry such as circuitry  1100  may be powered by power supply signals on conductor  1104  (and by a ground voltage on conductor  1010 ). If desired, conductor  1104  may include a resistor such as resistor  1108  that limits the maximum amount of power that connector  38  can receive from conductor  1104 . With this type of arrangement, a short between conductor  1104  and ground (i.e., conductor  1010 ) in connector  38  may not lead to excessive heat buildup, because of the limiting influence of resistor  1108 . Resistor  1108  may have any suitable resistance (e.g., a resistance that is low enough to provide power to circuitry  1100  and high enough to protect against excessive heat buildup in the event of a short). 
     Control and temperature sensing circuitry  1100  may control transistor  1106  by asserting appropriate signals onto conductor  1102 . For example, when transistor  1106  is implemented as an n-channel transistor, circuitry  1100  may turn off transistor  1106  by applying a ground voltage to conductor  1102  and circuitry  1100  may turn on transistor  1106  by applying a positive power supply voltage to conductor  1102 . 
     Power cutoff switch  900  may, if desired, include resistor  1110 . Resistor  1110  may be used to provide latching functionality to the power cutoff switch  900 . For example, when connector  40  is being connected to an electronic device  14  (after an initial unconnected period), resistor  1110  may help to ensure that transistor  1106  is initially turned on and contact  1004  is coupled to contact  1006  (e.g., that the power cutoff switch  900  is reset). Resistor  1110  may have any suitable resistance. As one example, the resistor  1110  may have a resistance of approximately one million ohms. 
     If desired, connector  38  may include structures that forces dendritic growth to occur first in selected locations within the connector  38 . For example, a structure that encourages moisture-induced dendritic growth may be included in connector  38  at a location that is downstream from the cutoff switch. With this type of arrangement, circuitry in connector  38  may be able to effectively shut off power to the location where the dendritic growth arises (i.e., by opening the switch). This type of configuration may therefore help to avoid the need to provide additional circuitry outside of connector  38  to turn off power flowing into the connector  38  when dendritic growths form in the connector  38 . 
     An example of this type of arrangement is shown in  FIG. 12 . As shown in  FIG. 12 , connector  38  may include a dendritic-growth-promotion structure  1200  that encourages dendritic growth. With one suitable arrangement, dendritic growth structure  1200  may be formed on printed circuit board  712  ( FIG. 7 ). 
     With the arrangement shown in  FIG. 12 , dendritic growth structure  1200  may encourage any dendritic growths that form in connector  38  to form at a location that is downstream from thermal protection circuitry  710  in a conductive path from conductor  708  to pin  717  (e.g., on side  1202  of thermal protection circuitry  710 ). This may help to ensure that circuitry within connector  38  such as circuitry  710  can shut off the power to the portions of the connector that have shorts developing from the dendritic growths. In contrast, if a dendritic growth were to form before thermal protection circuitry  710  (e.g., upstream from circuitry  710  on side  1204  of circuitry  710 ), thermal protection circuitry  710  might not be able to shut off power to the affected areas. The dendritic-growth-promotion structure therefore helps to ensure that any moisture-induced shorts will arise in a location of connector  38  where power delivery to the short can be interrupted when a rise in temperature is detected. 
     With one suitable arrangement, when connector  38  includes a dendritic growth structure  1200  that encourages dendritic growth, thermal protection circuitry  710  may be configured to shut off power to structure  1200  only after the connector  38  exceeds a relatively high temperature. In addition or alternatively, circuitry  710  may be configured to shut off power to structure  1200  only after an extended period of high temperature in connector  38 . Arrangements such as these may be used to dry out connector  38  (as dendritic structures typically form in the presence of moisture) before circuitry  710  shuts off power. Because circuitry  710  is configured to dry out connector  38  in this way before shutting off power to connector  38 , the risk of additional dendritic structures forming (in potentially unprotected areas) may be reduced as the moisture typically required to form dendritic structures may be removed from connector  38 . 
     An example of a structure that may be included in a connector such as connector  38  to encourage dendritic growths to form at a particular location is shown in  FIG. 13 . As shown in the example of  FIG. 13 , dendritic-growth-promotion structure  1200  may be formed on a printed circuit board such as printed circuit board  712  of  FIG. 12 . 
     Dendritic growth structure  1200  may include adjacent traces that are at different potentials. For example, structure  1200  may include a trace  1302  at a ground voltage (e.g., a voltage conveyed over conductor  706 ) and a trace  1304  at a positive power supply voltage (e.g., a voltage conveyed over conductor  708 ). Traces  1302  and  1304  may be formed from any suitable material. As one example, traces  1302  and  1304  may be formed from copper lines on printed circuit board  712 . 
     If desired, printed circuit board  712  may include a solder mask such as solder mask  1306 . Solder mask  1306  may cover all of the portions of the printed circuit board that are shown  FIG. 13  except for opening  1308 . Solder mask  1306  may be formed from a polymer or other material that serves as a protective coating for the traces in printed circuit board  712  such as traces  1302  and  1304 . For example, mask  1306  may be a lacquer-like layer of polymer that provides a protective coating for the traces of printed circuit board  712  and prevents solder from bridging between traces, thereby preventing short circuits caused by solder bridging traces. Mask  1306  may be formed from epoxy that is printed in a pattern onto printed circuit board  712  (e.g., using a silkscreen printing process). Mask  1306  may be formed from a liquid photoimageable solder mask, a dry film photoimageable solder mask, or any other suitable mask. If desired, mask  1306  may be applied to printed circuit board  712  using a silkscreen printing process, a vacuum lamination process, or any other suitable process. If desired, mask  1306  may be thermally cured after being applied to printed circuit board  712 . 
     With one suitable arrangement, one or both of the traces  1302  and  1304  may include structures that increase the voltage gradient between the two traces, thereby encouraging dendritic growth. For example, the positive power supply trace  1304  may include a triangular pointed portion  1310  that extends towards the ground supply trace  1302 . The portion  1310  of trace  1304  may therefore create a region of relatively high voltage gradient (e.g., a large voltage difference across a small gap) between traces  1302  and  1304 . 
     To help encourage dendritic growth, region  1308  of printed circuit board  712  may not be covered by the material of solder mask  1306 . In particular, solder mask  1306  may have portions that define a hole such as hole  1308  over trace  1304 , trace  1302 , and extending pointed member  1310  of trace  1304  (e.g., extending portion  1310 ). As one example, the tip of portion  1310  of trace  1304  and portion  1312  of trace  1302  may be uncovered (e.g., solder mask  1306  may not cover portions  1310  and  1312 ). This type of arrangement may help to promote dendritic formation in the gap between traces  1302  and  1304 . In addition, the exposed portions of printed circuit board  712  such as region  1314  (e.g., a dielectric between traces  1302  and  1304 ) may form a liquid reservoir. Because the formation of dendritic growths is induced by the presence of water, liquid reservoirs such as region  1314  may help to encourage dendritic growths by providing a storage location for liquid and by directing the liquid towards the high voltage gradient (e.g., towards the gap formed between the tip of structure  1310  and the left-hand edge of line  1302  in region  1312 ). The shape of the conductive structures in the solder mask opening of  FIG. 13  is merely illustrative. Any suitable shapes may be used (e.g., with two or more pointed extending regions, with non-triangular extending regions, etc.). 
     An illustrative circuit diagram of the arrangement of  FIG. 13  is shown in  FIG. 14 . As shown in  FIG. 14 , cable  16  may convey two voltages between external contacts in connector  38  and external contacts in connector  40 . For example, cable  16  may convey a ground voltage between ground (GRND) contact  1000  of connector  40  and ground (GRND) contact  1002  of connector  38 . Cable  16  may convey a positive power supply voltage between contact  1004  of connector  40  and contact  1006  of connector  38  (e.g., the VBUS contacts  1004  and  1006 ). With one suitable arrangement, the positive power supply voltage may be conveyed over conductor  1008  and the ground voltage may be conveyed over conductor  1010 . The circuit diagram of  FIG. 14  also shows how each of the conductors in path  42  may have a non-zero resistance  1014 . 
     As shown in the example of  FIG. 14 , thermal protection circuitry  710  ( FIG. 12 ) may be formed in connector  38  at a location that is interposed between dendritic growth structure  1200  and conductor  1008  in path  42 . With this type of arrangement, dendritic growth structure  1200  may encourage dendrites to form in the location of structure  1200  rather than at other locations in connector  38 . If a dendrite does form in structure  1200 , the dendrite may short together conductive lines at the positive voltage of contact  1006  and the ground voltage of contact  1002 , thereby heating up the connector  38 . 
     Thermal protection circuitry  710  may detect a temperature rise in connector  38  and, in response, may shut off power to contact  1006  (e.g., circuitry  710  may isolate conductor  1008  and structure  1200  from each other). With one suitable arrangement, thermal protection circuitry  710  may be configured to shut off power to contact  1006  after the temperature of connector  38  has exceeded a threshold voltage. The threshold voltage may be less than 85° C., 85° C., 90° C., 95° C., 100° C., greater than 100° C., or any other suitable threshold temperature. If desired, the thermal protection circuitry  710  may be configured to shut off power to contact  1006  only after the threshold temperature has been exceeded for a given time period such as 1 minute, 5 minutes, 10 minutes, 30 minutes, etc. With this type of arrangement, thermal protection circuitry  710  may be used to allow connector  38  to heat up enough to dry out the connector  38  and prevent any additional dendrites from forming. 
     If desired, thermal protection circuitry may be provided in electronic device  12 . For example, thermal protection circuitry in system  10  may include a temperature sensor in electronic device  12  that senses the temperature of connector  38  of cable  16  and a power cutoff switch in connector  40  of cable  16  as shown in the example of  FIG. 15 . With this type of arrangement, temperature sensor  1500  in electronic device  12  may be able to sense the temperature of connector  38  of cable  16  and convey signals to cutoff switch  1502  representative of the temperature of connector  38 . If a dendritic structure forms in connector  38  and forms a short that heats up connector  38 , temperature sensor  1500  may detect the increasing temperature and direct power cutoff switch  1502  to shut off power to connector  38  (e.g., to shut off a positive power supply voltage on conductor  708 ). If desired, temperature sensor  1500  may be included in connector  28  of electronic device  12 . 
     With another suitable arrangement, thermal protection circuitry may be provided in electronic device  12  and in electronic device  14 . As shown in the example of  FIG. 16 , thermal protection circuitry in system  10  may include temperature sensor  1500  in electronic device  12  (e.g., sensor  1500  in connector  28 ) and a cutoff switch  1600  in electronic device  14 . With this type of arrangement, sensor  1500  may determine the temperature of connector  38  and may relay signals to cutoff switch  1600  indicative of the temperature of connector  38 . When the temperature of connector  38  exceeds a threshold level, cutoff switch  1600  may cut off power to cable  16 . With one suitable arrangement, cutoff switch  1600  may only cut off power signals and data signals may continue to be conveyed between electronic devices  12  and  14 . If desired, cutoff switch  1600  can be incorporated into connector  34  ( FIG. 3 ). With another suitable arrangement, cutoff switch  1600  can be incorporated into connector  29  ( FIG. 4 ). 
     Illustrative steps involved in using thermal protection circuits and structures to protect cable  16  are shown in  FIG. 17 . In the example of  FIG. 17 , cable  16  may be used to convey signals such as power signals between two electronic devices such as electronic devices  12  and  14 . 
     At step  1700 , a user may connect cable  16  to electronic devices  12  and  14  (as examples). As one example, the user may connect connector  40  ( FIG. 5 ) to electronic device  14  and may connect connector  38  to electronic device  12 . The process of connecting cable  16  to electronic devices  12  and  14  may involve creating a wired path in which contacts in the connectors  38  and  40  of cable  16  mate with corresponding contacts in the connectors of electronic devices  12  and  14  and thereby connect the conductive lines of cable  16  between device  12  and device  14 . 
     At step  1702 , cable  16  may convey signals between electronic devices  12  and  14 . As one example, cable  16  may convey power signals from electronic device  14  to electronic device  12  (e.g., to power electronic device  12  and/or to charge a battery in electronic device  12 ). If desired, cable  16  may convey data signals between the electronic devices  12  and  14 . 
     At step  1704 , a temperature sensor may be used to monitor temperature in one of the connectors of cable  16 . For example, a temperature sensor in connector  38  such as a temperature sensor in circuitry  710 , temperature sensor  802 , temperature sensor  902 , or a temperature sensor in circuitry  1100  may be used to monitor temperature in connector  38 . With another suitable arrangement, a temperature sensor  1500  in electronic device  12  may be used to monitor temperature in connector  38 . 
     At step  1706 , connector  38  may be exposed to moisture and, as a result, a dendrite may form in connector  38 . As one example, dendritic-growth-promotion structure  1200  may encourage a dendritic short to form at a particular location in connector  38  when connector  38  is exposed to moisture (e.g., when moisture infiltrates connector  38 ). The formation of a dendrite in connector  38  may lead to a buildup of heat in connector  38 . 
     At step  1708 , the temperature sensor that is monitoring the temperature of connector  38  may detect that the temperature in the connector has exceeded a threshold temperature for a pre-determined time period (as an example). With this type of arrangement, the temperature sensor may be used in determining when the connector  38  has been heated sufficiently to dry out and remove any moisture that could lead to the formation of additional dendrites in connector  38 . 
     At step  1710 , a power cutoff switch such as a switch in circuitry  710 , circuitry  800 , circuitry  900 , or circuitry  1502  of cable  16  may be used to cut off power flow in cable  16 . The power cutoff switch may wait a given period of time after the temperature sensor first detects a temperature above a certain threshold to ensure that any moisture in connector  38  is removed. If desired, the given period of time may be variable based on the actual temperature detected in the connector  38  by the temperature sensor. For example, the given period of time may be relatively short when the actual temperature is above a second higher threshold and may be relatively long when the actual temperature is lower than the second higher threshold. With another suitable arrangement, a power cutoff switch in circuitry  1600  of electronic device  14  may be used to cut off power flow in cable  16 . As one example, a power cutoff switch in circuitry  710  may cut off power to the particular location in connector  38  at which dendritic-growth-promotion structure  1200  encourages formation of dendritic shorts. 
     With another suitable arrangement, power measuring circuitry that measures the amount of power that is lost in transmission between electronic device  12  and  14  through cable  16  may be used in determining whether cable  16  has failed (e.g., when a dendritic short has formed in cable  16  or in one of the connectors  38  and  40 ). If desired, the power measuring circuitry may be used in place of or in addition to the temperature sensors used in any of the examples described herein. The power measuring circuitry may be provided in cable  16 , in electronic device  12 , in electronic device  14 , or in any suitable combination of cable  16  and electronic devices  12  and  14 . 
     As one example, power measuring circuitry in electronic device  14  may measure the amount of power being delivered to cable  16  while power measuring circuitry in electronic device  12  can measure the amount of power being received through cable  16 . Electronic devices  12  and  14  may then communicate to determine the difference between the power being delivered to cable  16  and the power being received through cable  16 . If the amount of power being lost during transmission through cable  16  exceeds a threshold limit (e.g., 1 watt, 5 watts, 10 watts, etc.), electronic device  12  and/or device  14  may determine, based on this information, that a short has likely formed in cable  16  and that cable  16  is likely being heated from the short (e.g., because lost power may typically be transformed into heat). In response to determining that the amount of power being lost exceeds the threshold limit, electronic device  12  and/or device  14  may cut off power flow in cable  16 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20090615
Publication Date: 20121225
Grant Date: 20121225
Priority Date: 20090615
Inventors: RABU STANLEY
LO IDA
FRAZIER CAMERON
SCHMIDT MATHIAS
Assignee: APPLE INC
CPC Classifications: [{"code": "H01R13/6666", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/7137", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R31/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R13/7137", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/6683", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R13/6658", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/6666", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R31/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R13/6658", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/6683", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42470682