PATENT DOCUMENT

Publication Number: US-8498087-B2
Application Number: US-61190009-A
Country: US
Kind Code: B2

Title: Thermal protection circuits for electronic device 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 thermal protection circuits may disable the power supply voltage when liquid is detected in the connector. The thermal protection circuits may disable the power supply voltage permanently or temporarily. In one example, when a cable is reset, the thermal protection circuits may use a record of previous fault events and measurements from thermal and liquid sensors to determine whether to enable or disable the power supply voltage.

Claims:
What is claimed is: 
     
       1. A cable, comprising:
 at least a pair of conductive lines; 
 first and second connectors coupled to respective ends of the lines; and 
 thermal protection circuitry that includes:
 a cutoff switch interposed in at least one of the lines; 
 a fuse, wherein the thermal protection circuitry is configured to close the switch when the fuse is intact; and 
 
 a thermistor configured to blow the fuse through increased current flow in the fuse when temperature of the thermistor has exceeded a threshold temperature. 
 
     
     
       2. The cable defined in  claim 1  further comprising at least one sensor that takes readings. 
     
     
       3. The cable defined in  claim 1  wherein the thermistor is located in the first connector and wherein the cutoff switch is located in the second connector. 
     
     
       4. The cable defined in  claim 1  further comprising a moisture sensor in the first connector, wherein the thermal protection circuitry is configured to blow the fuse when the moisture sensor detects moisture in the first connector. 
     
     
       5. The cable defined in  claim 1  further comprising a moisture sensor in the first connector that includes a pair of conductors separated by a gap, wherein the thermal protection circuitry is configured to blow the fuse when moisture in the first connector electrically couples the pair of conductors together across the gap. 
     
     
       6. The cable defined in  claim 1  wherein the thermal protection circuitry further includes a positive feedback that latches the thermal protection circuit when the temperature of the thermistor has exceeded the threshold temperature. 
     
     
       7. The cable defined in  claim 3  further comprising a third conductive line, wherein the first and second connectors are coupled to respective ends of the third conductive line. 
     
     
       8. The cable defined in  claim 1  wherein the thermistor comprises a thermistor having a negative temperature coefficient. 
     
     
       9. The cable defined in  claim 1  further comprising a moisture sensor in the first connector and a temperature sensor in the first connector, wherein the thermal protection circuitry is configured to blow the fuse when the moisture sensor detects moisture in the first connector and wherein the thermal protection circuitry is configured to blow the fuse when the temperature sensor detects that the temperature of the first connector has exceeded a threshold temperature. 
     
     
       10. A cable, comprising:
 at least a pair of conductive lines; 
 first and second connectors coupled to respective ends of the lines; 
 a cutoff switch interposed in at least one of the lines; 
 moisture sensor circuitry coupled to the cutoff switch and configured to monitor moisture intrusion into a component of the cable; 
 heat detector configured to monitor temperature of the component of the cable; and 
 control circuit configured to use moisture intrusion data from the moisture sensor circuitry and temperature data from the heat detector to determine whether the cutoff switch is to be permanently or temporarily opened, wherein the first and second connectors are electrically decoupled when the cutoff switch is opened. 
 
     
     
       11. The cable defined in  claim 10  wherein the moisture sensor circuitry comprises a pair of conductors separated by a gap. 
     
     
       12. A cable, comprising:
 at least a pair of conductive lines; 
 first and second connectors coupled to respective ends of the lines; 
 a cutoff switch interposed in at least one of the lines; 
 moisture sensor circuitry coupled to the cutoff switch, wherein the moisture sensor circuitry comprises a pair of conductors separated by a gap; and 
 a printed circuit board in the first connector, wherein the printed circuit board has a perimeter and wherein the pair of conductors are formed on at least part of the perimeter of the printed circuit board. 
 
     
     
       13. A cable, comprising:
 at least a pair of conductive lines; 
 first and second connectors coupled to respective ends of the lines; 
 a cutoff switch interposed in at least one of the lines; 
 moisture sensor circuitry coupled to the cutoff switch, wherein the moisture sensor circuitry comprises a pair of conductors separated by a gap; and 
 a printed circuit board in the first connector, wherein the printed circuit board has a perimeter and wherein the pair of conductors are arranged in a ring that extends around a majority of the perimeter of the printed circuit board. 
 
     
     
       14. The cable defined in  claim 11  further comprising a fuse,
 wherein the fuse, the cutoff switch, and the moisture sensor circuitry are part of a thermal protection circuitry, 
 wherein the thermal protection circuitry is configured to close the switch when the fuse is intact, and 
 wherein the thermal protection circuitry is configured to blow the fuse when moisture electrically couples the pair of conductors together across the gap and the control circuit has determined the cutoff switch is to be permanently opened. 
 
     
     
       15. The cable defined in  claim 11 ,
 wherein the control circuit determines the cutoff switch is to be permanently opened when the moisture sensor circuitry has detected moisture intrusion into the component and the heat detector has detected the temperature of the component to exceed a first threshold level, and 
 wherein the control circuit determines the cutoff switch is to be temporarily opened when the moisture sensor circuitry has detected moisture intrusion into the component and the heat detector has detected the temperature of the component to exceed a second threshold level that is lower than the first threshold level. 
 
     
     
       16. The cable defined in  claim 11  wherein the heat detector comprises a thermistor. 
     
     
       17. A method, comprising:
 gathering real time sensor data with sensor circuitry in a cable that has at least a pair of lines with connectors at either end; 
 retrieving information from storage indicative of previously stored sensor data; and 
 determining to permanently or temporarily prevent power flow through at least one of the lines based at least partly on the retrieved information and at least partly on the real time sensor data. 
 
     
     
       18. The method defined in  claim 17  wherein gathering the real time sensor data with the sensor circuitry comprises gathering sensor data with a moisture sensor. 
     
     
       19. The method defined in  claim 17  wherein gathering the real time sensor data with the sensor circuitry comprises gathering real time temperature data with a thermistor and wherein the storage comprises a fuse, the method further comprising:
 blowing the fuse in response to temperature data from the thermistor that indicates that the temperature of one of the connectors has exceeded a threshold temperature. 
 
     
     
       20. The method defined in  claim 17  wherein gathering the real time sensor data with the sensor circuitry comprises gathering real time moisture data with a moisture sensor and gathering real time temperature data with a thermistor, wherein the storage comprises at least first and second fuses, the method further comprising:
 blowing the first fuse in response to real time temperature data from the thermistor that indicates that the temperature of one of the connectors has exceeded a threshold temperature; and 
 blowing the second fuse in response to real time moisture data from the moisture sensor that indicates that moisture has infiltrated one of the connectors.

Description:
BACKGROUND 
     This invention relates to thermal protection circuits and structures for electronic device 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 from misuse, conductive dendritic structures can 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 device cables. 
     SUMMARY 
     Cables for electronic devices may include thermal protection circuits. The electronic devices may be desktop computers, portable computers, handheld devices, power adapters, or other suitable electronic devices. The cables may interconnect the electronic devices. The thermal protection circuits may include temperature-sensitive devices such as temperature sensors and moisture-sensitive devices such as moisture sensors. Power cutoff switches in the thermal protection circuitry may be used to prevent excessive currents from developing. 
     With one suitable arrangement, a cable may include thermal protection circuitry such as a temperature sensor, a moisture sensor, and a power cutoff switch. The cable may include two connectors connected together by a plurality of conductors. As an example, the moisture sensor may be formed from a pair of exposed conductors in one of the connectors. In this example, the moisture sensor may detect the presence of moisture in the connector by detecting a moisture-related short between the two exposed conductors. The two exposed conductors may be placed at strategic locations in the connector at which water intrusion is likely. The two exposed conductors may surround circuitry in the connector so that any moisture intrusion into the circuitry can be detected. 
     If desired, the temperature and moisture sensors 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 or when moisture is detected in the connector. 
     With another arrangement, the temperature sensor and the moisture 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 off power to the first connector when the temperature sensor determines that the temperature of the first connector has exceeded a threshold temperature or when the moisture sensor detects moisture in the first connector. 
     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 includes 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 top view of an illustrative cable that may include a connector that has thermal protection circuitry for deactivating power supply lines in the connector in response to rising temperatures in the connector in accordance with an embodiment of the present invention. 
         FIG. 7  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. 8  is a circuit diagram of an illustrative cable having thermal protection circuitry in a connector at one end of the cable in accordance with an embodiment of the present invention. 
         FIG. 9  is a circuit diagram of an illustrative cable having thermal protection circuitry that includes a current mirror and a thermistor in a connector at one of the cable in accordance with an embodiment of the present invention. 
         FIG. 10  is a circuit diagram of an illustrative cable having thermal protection circuitry that includes a current mirror, a thermistor, and a positive feedback latching circuit in a connector at one end of the cable in accordance with an embodiment of the present invention. 
         FIG. 11  is a circuit diagram of an illustrative cable having thermal protection circuitry that includes a current mirror, a thermistor, and a positive feedback latching circuit in a first connector in the cable and a power cutoff circuit in a second connector in the cable in accordance with an embodiment of the present invention. 
         FIG. 12  is a circuit diagram of an illustrative cable having thermal protection circuitry that includes a current mirror, a thermistor, a liquid detection circuit, and a positive feedback latching circuit in a first connector in the cable and a power cutoff circuit in a second connector in the cable in accordance with an embodiment of the present invention. 
         FIG. 13  is a schematic diagram of illustrative thermal protection circuitry in part of a cable that forms a communications path between two electronic devices in accordance with an embodiment of the present invention. 
         FIG. 14  is a flow chart of illustrative steps involved in using thermal protection circuitry to selectively enable and disable power supply voltages in a cable that may form a communications path between two electronic devices in accordance with an embodiment of the present invention. 
         FIG. 15  is a flow chart of illustrative steps involved in using thermal protection circuitry that includes detector circuitry and a fuse that may permanently disable power supply voltages in a cable in response to a fault signal from the detector circuitry in accordance with an embodiment of the present invention. 
         FIG. 16  is a circuit diagram of an illustrative liquid sensor that may be a part of a connector in a cable that forms a communications path between two electronic devices 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 to 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 could also be damaged. 
     If desired, cables may be provided with thermal protection circuits and structures that help limit the damage caused by electrical shorts (e.g., damage from moisture-induced dendrite growth and resulting short circuits). Electronic devices may also be provided with thermal protection circuits and structures. 
     For example, a cable may include thermal protection circuitry that reduces or eliminates 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 cut off power supply signals in those specific locations. 
     If desired, cables may include liquid detection circuits that detect liquid intrusion. With one suitable arrangement, a liquid detection circuit in a connector may be connected to a control circuit in the connector that disables power supply signals when liquid is detected. As one example, the liquid detection circuit may be implemented using exposed parallel conductive lines or wires, which are shorted together by liquid when liquid enters the connector. In general, the exposed conductive lines may be run through any suitable portion of the connector (e.g., portions of the connector in which liquid intrusion is more likely to occur). 
     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 couple 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. 
     An example of a cable that may include a connector with thermal protection circuitry is shown in  FIG. 6 . As shown in  FIG. 6 , 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  606  and  608  in path  42  may convey signals between connectors  38  and  40 . For example, conductors  606  and  608  may carry power supply signals between the two connectors of cable  16 . As an example, conductor  606  may carry ground power supply signals and conductor  608  may carry positive power supply signals (e.g., signals at a potential of approximately 5.0 volts above ground). Conductor  606  may be a ground conductor and conductor  608  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  610 . As one example, thermal protection circuitry  610  may be mounted on printed circuit board  612  and, if desired, may be mounted between contacts  614  and  616 . Contact  614  may be coupled to conductor  608  and contact  616  may be coupled to pin  617  (e.g., a male pin in connector  38  extending from connector  38 ). There may be a conductive trace between the two contacts  614  and  616 . As one example, thermal protection circuitry  610  may be mounted along the conductive trace. 
     If desired, cable  16  may include structures that force moisture-related shorts (e.g., dendritic shorts) to form in a particular location. For example, connector  38  may include a structure that encourages moisture-related shorts in connector  38  to form near contact  616  so that circuit  610  can shut off power to any shorts that form in connector  38 . With one suitable arrangement, circuit  610  may be configured to shut off power only after connector  38  has been heated enough to dry out any moisture in connector  38 . 
     Thermal protection circuitry  610  may include a temperature-sensitive device such as a temperature sensor, a moisture-sensitive device such as a liquid detector, and a voltage (power) cutoff switch (as examples). With this type of arrangement, thermal protection circuitry  610  may be configured to detect increasing temperatures and/or the presence of moisture in connector  38  (which may be indicative of a short between conductors  606  and  608 ). In response to increasing temperatures and/or the presence of moisture in connector  38 , circuitry  610  (e.g., a switch in circuitry  610 ) may be configured to cut off a power supply in connector  38  by electrically isolating contact  614  from contact  616 . With this type of arrangement, the potential of contact  616  may be reduced towards ground. Assuming that the increasing temperatures were a result of a short in connector  38 , circuitry  610  may be able to eliminate the cause of the increasing temperatures (e.g., by cutting off the voltage supply to contact  616 ). In general, thermal protection circuitry such as circuitry  610  may include any suitable devices (e.g., temperature-sensitive devices and moisture-sensitive devices) for determining when the power cutoff switch cuts off power to connector  38 . For example, circuitry  610  may include a temperature-sensitive fuse or other suitable device that changes state depending on the temperature within connector  38 . If desired, circuitry  610  may include a liquid detector that includes a pair of exposed wires that can be used to detect the presence of liquid (e.g., by detecting when the wires are shorted together by the liquid). 
     An example of thermal protection circuitry that may be used to shut off power to connector  38  is shown in  FIG. 7 . As shown in  FIG. 7 , cable  16  may include thermal protection circuitry such as circuit  700  in connector  40  and sensor  702  in connector  38 . Circuit  700  may be a power cutoff switch and circuit  702  may be a sensor in connector (as examples). Circuitry  702  may include a temperature sensor and may include a liquid sensor. 
     Thermal protection circuitry such as circuit  700  in connector  40  may be mounted on a printed circuit board such as board  701  and, if desired, may be connected to a sensor  702  in connector  38  over path  704 . Sensor  702  may be mounted on a printed circuit board  703  in connector  38 . With one suitable arrangement, thermal protection circuit  700  may include a switch coupled between contacts  706  and  708  of printed circuit board  701 . As an example, contact  706  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  700  may electrically connect contact  706  to contact  708  and conductor  710 . In this example, the positive power supply voltage may be conveyed to connector  38  over conductor  710  (e.g., one of a plurality of conductors in path  42 ). 
     Switch  700  may receive control signals from sensor  702  over path  704 . The control signals may be indicative of the current temperature of connector  38  and may be indicative of the presence of moisture in 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  702  may send a control signal to switch  700  directing switch  700  to shut off power by forming an open circuit in one or more power supply lines to connector  38 . If desired, when moisture is detected within connector  38  by sensor  702 , sensor  702  may send a control signal to switch  700  directing switch  700  to shut off power to connector  38 . As an example, switch  700  may isolate contact  706  from contact  708 , thereby cutting off power to the conductor  710  that was previously providing power to connector  38 . With this type of arrangement, thermal protection circuits  700  and  702  may work together to protect connector  38  from overheating. For example, if a dendritic growth in connector  38  shorts conductor  710  to a ground potential, circuits  700  and  702  can detect rising temperatures resulting from the short and can shut power off to connector  38  (e.g., shut off power to conductor  710 ). 
     An illustrative circuit diagram in which thermal protection circuitry is included in connector  38  is shown in  FIG. 8 . The circuit diagram of  FIG. 8  illustrates a potential implementation of the arrangement of  FIG. 6 . As shown in  FIG. 8 , cable  16  may convey a ground voltage between ground (GRND) contact  800  of connector  40  and ground (GRND) contact  802  of connector  38 . Cable  16  may convey a positive power supply voltage between contact  804  of connector  40  and contact  806  of connector  38  (e.g., the VBUS contacts in connectors  38  and  40 ). 
     As shown in the example of  FIG. 8 , thermal protection circuitry in connector  38  may include a temperature-sensitive resistor such as thermistor  808 , resistors such as resistors  810 ,  812 ,  814 ,  816 , and  818 , a fuse-type resistor such as fuse  820 , and transistors such as transistors  822 ,  824 ,  826 , and  828  (as examples). With one suitable arrangement, transistor  822  may be an enhancement mode p-channel metal-oxide-semiconductor transistor (i.e., a p-channel MOSFET), transistor  824  may be a bipolar pnp transistor, and transistors  826  and  828  may be bipolar npn transistors. 
     Transistor  822  may sometimes be referred to as a voltage cutoff switch, a cutoff switch, a current cutoff switch, a voltage cutoff transistor, a cutoff transistor, a current cutoff transistor, etc. Transistor  822  may be connected between positive power supply contact  804  in connector  40  and positive power supply contact  806  in connector  38 . Transistor  822  may be controlled by signals on node  834  (e.g., signals from node  834  routed to a gate terminal in transistor  822 ). 
     Resistors  810 ,  812 ,  814 ,  816 , and  818  may have any suitable resistances. As one example, resistors  810 ,  812 ,  814 ,  816 , and  818  may have resistances of approximately 2.0 kilo-ohms, 10.0 kilo-ohms, 200.0 ohms, 50.0 ohms, and 1.0 kilo-ohm, respectively. 
     When fuse  820  is intact, fuse  820  may have a resistance of approximately 400.0 milli-ohms. Fuse  820  may be stable when less than 250.0 milliamps of current is flowing through fuse  820 . When the current flowing through fuse  820  surpasses 250.0 milliamps, fuse  820  may become unstable. As one example, fuse  820  may be blown when the current flowing through fuse  820  surpasses a threshold level such as 500.0 milliamps. When fuse  820  is blown (i.e., not intact), fuse  820  will have a nearly infinite resistance and will therefore open the circuit path between node  836  and node  838  (e.g., when blown, fuse  820  will isolate nodes  836  and  838 ). 
     Thermistor  808  may be thermally coupled to connector  38  and to printed circuit board  703  of  FIG. 7  (as an example). As a result, thermistor  808  may be responsive to the temperature of connector  38 . As one example, thermistor  808  may have a negative temperature coefficient (i.e., the resistance of thermistor  808  may decrease as the temperature of thermistor  808  increases). With one suitable arrangement, thermistor  808  may have a resistance of approximately 470.0 kilo-ohms at room temperature (e.g., at approximately 25.0° Celsius). Thermistor  808  may have a resistance that is approximately proportional to the logarithm of the inverse temperature (e.g., a resistance proportional to log(Temperature −1 )). 
     When connector  38  is at or near room temperature (e.g., during normal operations when connector  38  is at approximately 25.0° Celsius), transistor  822  may be turned on and transistors  824 ,  826 , and  828  may be turned off. The voltage on node  840  may be approximately equal to the positive power supply voltage conveyed between contacts  804  and  806 . Because transistors  826  and  824  are turned off, the voltage on node  834  may be approximately equal to the ground power supply voltage on node  838 . The ground voltage on node  834  may, in turn, turn on p-channel metal-oxide-semiconductor transistor  822  (e.g., electrically connect contact  806  to contact  804 ). 
     As connector  38  is heated (e.g., from a short between positive power supply path  830  and ground power supply path  832  or by another heat source), the resistance of thermistor  808  decreases. As the resistance of thermistor  808  decreases, the voltage on node  840  may be pulled low (e.g., the voltage on node  840  may decrease towards the ground voltage on path  832 ). This reduced voltage on node  840  may be applied to the base terminal of transistor  824  and may turn transistor  824  on. As transistor  824  is turned on, the voltage on node  842  may be pulled up towards the positive power supply voltage on path  830 . The raised voltage on node  842  may be applied to the base terminal of transistor  826  and may turn on transistor  826 . 
     As transistors  824  and  826  are turned on, a positive feedback loop may form between that keeps transistors  824  and  826  turned on. Because transistor  824  is now turned on, the current that passes through resistor  816  increases (relative to normal operation). As a result, the voltage on node  844  is raised from the ground voltage of path  832  towards the positive voltage of path  830 . The increasing voltage on node  844  is applied to the base of transistor  828  and transistor  828  is turned on. Transistor  828  may sometimes be referred to herein as a shunt transistor (e.g., a transistor that allows current to flow between paths  830  and  832  without passing through transistors  824  and  826  and thermistor  808 ). 
     The current from transistors  824  and  826  (e.g., the current flowing through resistors  816  and  818 ) may combine with the current flowing through the emitter and collector terminals of transistor  828  and thermistor  808  at node  836 . This combined current flows through fuse  820  and burns out fuse  820  when the temperature of thermistor  808  and connector  38  exceeds a threshold temperature (e.g., when the resistance of thermistor  808  drops below a threshold level). 
     After fuse  820  is blown, the gate of transistor  822  can no longer be held low and transistor  822  is turned off. When transistor  822  is turned off, the positive power supply contact  806  in connector  38  is isolated from path  830  and contact  804  in connector  40 , effectively cutting off power to contact  806 . This type of arrangement may be able to protect connector  38  from thermal damage when a short forms between contacts  802  and  806  (as an example). 
     Another illustrative circuit diagram in which thermal protection circuitry is included in connector  38  is shown in  FIG. 9 . As shown in the example of  FIG. 9 , thermal protection circuitry in connector  38  may include thermistor  808 , resistors such as resistors  902 ,  904 , and  906 , fuse  820 , transistors such as transistors  822 ,  908 ,  910 ,  912 ,  914 , and  916 , and diode  918  (as examples). With one suitable arrangement, transistor  912  may be a depletion mode n-channel metal-oxide-semiconductor transistor (i.e., an re-channel MOSFET), transistors  908  and  910  may be bipolar pnp transistors, and transistors  914  and  916  may be bipolar npn transistors. 
     Resistors  902 ,  904 , and  906  may have any suitable resistances. As one example, resistors  902 ,  904 , and  906  may have resistances of approximately 5.0 mega-ohms, 2.0 mega-ohms, and 2.0 kilo-ohms, respectively. 
     When connector  38  is at or near room temperature (e.g., during normal operations when connector  38  is at approximately 25.0° Celsius), transistor  822  may be turned on and contact  806  may be electrically coupled to contact  804 . During normal operations, transistors  914  and  916  may be turned on by signals passing from path  830  through resistor  904 . Transistors  908  and  910  may form a current mirror. Specifically, transistor  910  may be configured to generate a current through its emitter and collector terminals that is approximately equal to the current passing through the emitter and collector terminators in transistor  908 . Because the resistance of thermistor  808  is relatively large when connector  38  is at or near room temperature, the current flowing through transistor  908 , and therefore the current flowing through transistor  910 , may be relatively small. The majority of the current flowing through transistor  910  may also pass through transistor  916  and resistor  906 , generating a voltage at node  920  that is just above the ground voltage conveyed on path  832 . The voltage on node  920  may turn on transistor  822  and turn off transistor  912 , during normal operations. 
     As connector  38  is heated, the resistance of thermistor  808  decreases. With one arrangement, the thermal protection circuitry in connector  38  may be configured such that, when the temperature of connector  38  reaches a critical temperature, the resistance of transistor  808  matches the resistance of resistor  906 . This is merely one example. As the resistance of thermistor  808  decreases, the current flowing through transistors  914  and  908  increases and the increasing current is mirrored by transistor  910 . The increased current through transistor  910  causes the voltage on node  920  to rise (e.g., because of the increased current through transistor  906 ) which, in turn, applies a positive voltage to the gate of transistor  912 , thereby turning transistor  912  on. When transistor  912  is turned on, current flows from path  830  through diode  918 , transistor  912 , and fuse  820  to path  832 . This current (combined with the currents through transistors  914  and  916 ) burns out fuse  820  and electrically isolates node  926  from path  832 . 
     After fuse  820  is blown, the gate of transistor  822  can no longer be held low and transistor  822  is turned off. In particular, current flowing through transistor  902  may charge the gate of transistor  822  to the voltage of path  830  and thereby turn off transistor  822 . When transistor  822  is turned off, the positive power supply contact  806  in connector  38  is isolated from path  830  and contact  804  in connector  40 , effectively cutting off power to contact  806 . 
     If desired, thermal protection circuitry may be provided in the form shown in  FIG. 10 . As shown in  FIG. 10 , thermal protection circuitry in connector  38  may include a positive feedback circuit with transistor  1004  and resistor  1006 . In addition, diode  918  of  FIG. 9  may be eliminated and transistor  912  of  FIG. 9  may be replaced with a bipolar npn transistor such as transistor  1002 . Transistor  1004  may be a bipolar npn transistor, as one example. Resistor  1006  may have any suitable resistance and, as an example, may have a resistance of approximately 10.0 kilo-ohms. 
     When the temperature of connector  38  increases beyond a critical temperature, the positive feedback circuit may switch on as the connector heats up past the critical temperature, thereby increasing the current through transistor  908 . In particular, as the resistance of thermistor  808  decreases and the current through transistor  908  and mirrored transistor  910  increase, the voltage on node  920  increases and turns on transistor  1004 . When transistor  1004  is turned on, the current flowing through transistors  908  and  910  and the voltage on node  920  rises even more. This type of arrangement creates a latching scenario in which once the resistance of thermistor  808  drops below a critical value, transistor  1004  is turned on until fuse  820  blows. The increased voltage on node  920  is applied to the base terminal of transistor  1002 , thereby turning transistor  1002  on. The combined currents flowing through transistors  1004 ,  914 ,  916 , and  1002  may burn out fuse  820 . Once fuse  820  is burned out, the gate terminal of transistor  822  is no longer biased towards ground, transistor  822  is turned off, and contact  806  is electrically isolated from contact  804 . 
     As described in connection with  FIG. 7 , cable  16  may include thermal protection circuitry in connectors  38  and  40 . An example of this type of arrangement is illustrated in the circuit diagram of  FIG. 11 . As shown in  FIG. 11 , thermal protection circuitry in cable  16  may include a temperature sensing circuit in connector  38  and power cutoff circuitry in connector  40  that cuts off one or more power supply voltages to connector  38  when the temperature of connector  38  exceeds a critical level. For example, if a short develops in connector  38  and heats connector  38  to a potentially damaging temperature, the thermal protection circuitry in connector  40  may cut off power to connector  38 , thereby protecting connector  38  from potential damage. 
     In contrast to the example of  FIG. 10 , thermistor  808 , resistor  906 , and transistor  1004  may be directly connected to path  832  in the example of  FIG. 11 . Fuse  820 , transistors  822  and  1002 , and resistor  902  may be moved from connector  38  to connector  40 . An additional electrical path in cable  42  such as path  1100  may connect the thermal protection circuits in connectors  38  and  40 . 
     Path  1100  may electrically connect node  1102  together with node  1104 . During normal operations (e.g., when the resistance of thermistor  808  is high), the voltage on node  1104  may be at or near a ground voltage and transistor  822  may be turned on, thereby delivering power to path  830  and contact  806 . When the resistance of thermistor  808  drops below a critical level in the circuit of  FIG. 11 , the voltage on node  1104  rises towards the power supply voltage carried on path  830 , turns on transistor  1002 , and blows out fuse  820 . Once fuse  820  is blown, transistor  822  is turned off and contact  804  is electrically isolated from path  830 , contact  806 , and connector  38 . The arrangement of  FIG. 11  may help to ensure that power is completely cut off to connector  38 , thereby eliminating any potential for an electrical short in connector  38  to damage connector  38  (once transistor  822  is turned off). 
     If desired, circuits of the type shown in  FIGS. 8 ,  9 ,  10 , and  11  may be provided with liquid detection circuitry. An example of how the circuit of  FIG. 11  may be provided with liquid detection circuitry is illustrated by  FIG. 12 . As shown in  FIG. 12 , the circuitry in connector  38  may include transistor  1200  and liquid detection circuit  1202 . 
     The collector terminal of transistor  1200  (e.g., a bipolar npn transistor) may be electrically connected to node  1201 . With this type of arrangement, the combined current flowing through transistors  1004 ,  1006 , and  1200  will be mirrored by transistor  910 . 
     When liquid detection circuit  1202  is exposed to liquid, contacts  1204  and  1206  of circuit  1202  may be shorted together. When contacts  1204  and  1206  are shorted together, current will flow through transistor  1200  to ground path  832 . In contrast, when contacts  1204  and  1206  are not shorted together, no current will flow through transistor  1200 . The current that flows through transistor  1200 , when liquid shorts contacts  1204  and  1206  together, will cause the voltage on node  1208  to rise, thereby turning on latching transistor  1004  and turning on transistor  1002 , which in turn blows fuse  820 . Once fuse  820  is blown, transistor  822  is turned off and power is no longer delivered to connector  38  over path  830 . 
     The circuits of  FIGS. 8 ,  9 ,  10 , and  11  are merely examples of how thermal protection circuitry may be included in cable  16 . When unmodified from the description presented above, each of the circuits may have certain benefits and disadvantages relative to the other circuits. 
     For example, the circuit of  FIG. 8  is the simplest design and includes the smallest number of components (out of  FIGS. 8 ,  9 ,  10 , and  11 ) but has a relatively high shutdown current (e.g., approximately 23.0 microamperes when the temperature of connector  38  reaches approximately 40° Celsius), has a temperature trip point that is relatively dependent on the voltage of path  830 , and the temperature trip point increases as the voltage of path  830  decreases. 
     The circuit of  FIG. 9  has a relatively low shutdown current (e.g., approximately 9.0 microamperes at approximately 40° Celsius), a trip point that is independent of the voltage of path  830 , a moderate number of components, and a circuit that turns off pass transistor  912  as fuse  820  is blown, but has no positive feedback (i.e., the circuit is non-latching), includes a metal-oxide-semiconductor pass transistor such as transistor  912  (compared to inexpensive bipolar pass transistor  828 ), and includes an additional reverse current blocking diode such as diode  918 . 
     The circuit of  FIG. 10  includes positive feedback that latches the circuit when a temperature fault is detected. This helps to ensure the circuit stays on long enough to blow fuse  820 . The circuit does not include a reverse current blocking diode, but does have a slightly higher component count that the circuit of  FIG. 9 . 
     The circuit of  FIG. 11  may provide a high level of protection by ensuring that the entire positive power supply path (i.e., path  830 ) is shut off inside connector  38  (e.g., by shutting off power outside connector  38 ), but generally requires additional components such as a circuit board in connector  40  and an additional conductor in path  40 . 
     A schematic diagram of thermal protection circuitry that may be provided as a part of a cable such as cable  16  of  FIG. 5  is shown in  FIG. 13 . As shown in  FIG. 13 , the thermal protection circuitry may include control circuit  1300 , memory  1306 , and one or more detectors such as liquid detector  1302  and heat detector  1304 . Control circuit  1300  may use information obtained from detectors  1302  and  1304  and information stored in memory  1306  in controlling switching circuitry  1316 . Switching circuit  1316  may control whether or not power contacts  1308  and  1312  (e.g., power contacts VBUS and GRND in a connector such as connector  40  of  FIG. 5 ) are connected to power contacts  1310  and  1314  (e.g., power contacts VBUS and GRND in a connector such as connector  38  of  FIG. 5 ). 
     Memory  1306  may include any suitable type of memory. Examples of memory  1306  include single-bit nonvolatile memory circuits such as a fuse and multi-bit nonvolatile memory circuits. If desired, memory  1306  may be implemented using volatile memory circuits. 
     With one suitable arrangement, control circuit  1300  may use detector  1302  to determine when the temperature of a component such as connector  38  exceeds a threshold level. In response, control circuit  1300  may record information in memory  1306  that indicates that the temperature of the component has exceeded the threshold level and may also send a command to circuit  1316  to electrically isolate contact  1308  from contact  1310  and, if desired, electrically isolate contact  1312  from contact  1314 . 
     Similarly, control circuit  1300  may use detector  1304  to determine when liquid enters a component such as connector  38 . In response, control  1300  may record information in memory  1306  that indicates that liquid has entered the connector and may send a command to circuit  1316  to electrically isolate contacts  1308 ,  1310 ,  1312 , and  1314 . 
     If desired, control circuit  1300  may use memory  1306  in combination with detectors  1302  and  1304  in determining whether or not it is safe to electrically couple contacts  1308 ,  1310 ,  1312 , and  1314  together. For example, when detector  1304  detects that the temperature of the component exceeds a first threshold level, control circuit  1300  may permanently isolate contacts  1308  and  1310  from contacts  1312  and  1314 . In contrast, when detector  1304  detects that the temperature of the component has only exceeded a second lower threshold level, control circuit  1300  may temporarily isolate contacts  1308  and  1310  from contacts  1312  and  1314  (e.g., until the temperature of the connector drops to a safe level or until the circuitry is reset). Similarly, when detector  1302  detects liquid intrusion in the component, control circuit  1300  may temporarily isolate contacts  1308  and  1310  from contacts  1312  and  1314  (e.g., until the liquid intrusion is no longer detected or until the circuitry is reset). These are merely illustrative examples. 
       FIG. 14  shows illustrative steps that control circuit  1300  of  FIG. 13  may use in determining whether or not to enable power (e.g., determining whether contacts  1308  and  1310  are electrically coupled to or isolated from contacts  1312  and  1314 ). 
     As shown by line  1400 , when cable  16  and control circuit  1300  first receive power (e.g., when connector  40  of  FIG. 5  is connected to electronic device  14  of  FIG. 1 ), control circuit  1300  may monitor detector circuitry such as detectors  1302  and  1304  in step  1402 . 
     In step  1404 , control circuit  1300  may record results from the detector circuitry. For example, control circuit  1300  may record measurements from detectors  1302  and  1304  in memory  1306 . If desired, control circuit  1300  may record multiple measurements from the detectors over time in volatile memory and/or non-volatile memory. For example, control circuit  1300  may blow a fuse when the temperature of connector  38  exceeds a critical level. As another example, control circuit  1300  may store data in volatile memory when liquid is detected in connector  38  (e.g., so that the data is erased when memory  1306  is powered down). 
     In step  1406 , control circuit  1300  may compare current measurements from the detector circuitry and stored results (i.e., the results stored in step  1404 ). Based on this comparison, control circuit  1300  may either maintain or enable power supply voltages (as illustrated by line  1408 ) or circuit  1300  may disable power supply voltages (as illustrated by line  1410 ). With one suitable arrangement, control circuit  1300  may analyze temperature and liquid intrusion patterns over time to determine if power should be cutoff to connector  38 . For example, control circuit  1300  may determine when a sudden spike in temperature occurs that may be indicative of a short in connector  38  and, in response, may cut off power to connector  38  even before the temperature of connector  38  exceeds a threshold temperature. 
     If desired, control circuit  1300  may shut off power to connector  38  until control circuit  1300  is reset (e.g., connector  40  is disconnected and reconnected to device  14 ). With another suitable arrangement, control circuit  1300  may have to be reset more than once (e.g., 2 times, 5 times, 10 times, etc.) before control circuit  1300  restores power to connector  38 . 
       FIG. 15  shows illustrative steps that control circuit  1300  of  FIG. 13  may use in monitoring detector circuitry in connector  38 . In the example of  FIG. 15 , memory  1306  may include a fuse (e.g., non-volatile memory). 
     When cable  16  is powered up, control circuit  1300  may check the status of the fuse in memory  1306  in step  1500 . When the fuse in memory  1306  is blown, control circuit  1300  may shut down cable  16  in step  1502 . When the fuse is not blown, control circuit  1300  may continue to step  1504 . 
     In step  1504 , control circuit  1300  may monitor detector circuitry in connector  38  such as liquid detector  1302  and heat detector  1304 . As illustrated by line  1505 , when no faults are detected in connector  38 , control circuit  1300  may loop back to check the status of the fuse in step  1500 . As illustrated by line  1506 , when a fault is detected (e.g., when a short is detected using liquid detector  1302  and/or heat detector  1304 ), control circuit  1300  may blow the fuse in memory  1306  in step  1508 . 
     As described in connection with  FIG. 12 , thermal protection circuitry in connector  38  may include one or more liquid detection circuits. An example of a liquid detection circuit that may be included in connector  38  is shown in  FIG. 16 . As shown in  FIG. 16 , connector  38  may include a circuit board such as circuit board  1608  with a plurality of conductive pins  1600  connecting to portion  39  (e.g., a male connector portion extending from connector  38 ). A liquid detector such as detector  1602  may be mounted on circuit board  1608 . Detector  1602  (e.g., liquid detection circuit  1202  shown in  FIG. 12 ) may include a pair of parallel wires such as wires  1604  and  1606  (e.g., contacts  1204  and  1204  in the  FIG. 12  example). Wires  1604  and  1606  may be placed along the perimeter of circuit board  1608  (as illustrated in  FIG. 16 ). If desired, wires  1604  and  1606  may be placed in areas where liquid instruction is most likely to occur such as adjacent to pins  1601 . Detector  1602  may detect the presence of liquid in connector  38  when liquid shorts together wires  1604  and  1606  at a given point along the length of wires  1604  and  1606  (e.g., when liquid electrically bridges the relatively small gap between parallel wires  1604  and  1606 ). 
     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: 20091103
Publication Date: 20130730
Grant Date: 20130730
Priority Date: 20091103
Inventors: RABU STANLEY
HOLLABAUGH JAMES M.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01R31/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R13/7137", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R13/7137", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R31/065", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 43925898