Patent Publication Number: US-10777947-B2

Title: USB cable with thermal protection

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Non-Provisional patent application Ser. No. 15/925,134, filed Mar. 19, 2018, which is a continuation of U.S. Non-Provisional patent application Ser. No. 15/386,144, filed Dec. 21, 2016, granted as U.S. Pat. No. 9,960,545, Issued on May 1, 2018, which claimed the benefit of U.S. Provisional Patent Application No. 62/404,277, filed Oct. 5, 2016, all of which applications are incorporated by reference herein in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to the field of circuit protection devices, and relates more particularly to a universal serial bus cable with integrated thermal protection. 
     BACKGROUND OF THE DISCLOSURE 
     Universal serial bus (USB) cables are increasingly used to deliver power to electronic devices in addition to their more traditional role of facilitating data communication. With the recent advent of the USB-C standard, USB cables can now deliver up to 100 Watts of power, thus facilitating high power applications that were previously unachievable via USB connection. However, it has been observed that the delivery of such high power can result in thermal damage to USB cables, especially in cases where the pins of a USB cable are dirty, bent, or otherwise predisposed to suboptimal connectivity. 
     One technique that has been employed for protecting against overcurrent/overheating in USB cables is the installation of a positive temperature coefficient (PTC) element in series with the power carrying conductors of a USB cable, wherein the PTC element has a resistance that increases as the temperature of the PTC element increases. Thus, as current passing through the PTC element increases above a predefined limit, the PTC element may heat up, causing the resistance of the PTC element to increase and drastically reduce or arrest the flow of current through the USB cable. Damage that would otherwise result from unmitigated fault currents flowing through the USB cable is thereby prevented. 
     While the above-described application of PTC elements in USB cables has provided a practical solution for protecting against overcurrents and overheating in earlier, lower-power (e.g., 5-20 watt) generations of USB cables, similar applications in modern, USB-C standard cables presents significant challenges. Particularly, a PTC element capable of handling 100 watts of power is prohibitively large and expensive for practical commercial application in a USB cable. 
     It is with respect to these and other considerations that the present improvements may be useful. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter. 
     An exemplary embodiment of a cable in accordance with the present disclosure may include a power conductor configured to transmit electrical power between a first device and a second device, a first data conductor configured to transmit data between the first device and the second device, and a first positive temperature coefficient (PTC) element coupled to the first data conductor and configured to mitigate current flowing through the first data conductor if a temperature of the first PTC element rises above a predefined first trip temperature. 
     An exemplary embodiment of a system for over-temperature protection in a cable in accordance with the present disclosure may include a first device and a second device connected to one another by the cable, wherein the cable includes a power conductor configured to transmit electrical power between the first device and the second device, a first data conductor configured to transmit data between the first device and the second device, and a first positive temperature coefficient (PTC) element coupled to the first data conductor and configured to mitigate current flowing through the first data conductor if a temperature of the first PTC element rises above a predefined first trip temperature, wherein at least one of the first device and the second device is configured to reduce an amount of electrical power transmitted via the power conductor upon mitigation of the current flowing through the first data conductor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic diagram illustrating a pin layout of an exemplary embodiment of a cable in accordance with the present disclosure; 
         FIG. 2A  is schematic diagram illustrating portions of the cable shown in  FIG. 1  connected to a pair of devices; 
         FIG. 2B  is schematic diagram illustrating portions of an alternative embodiment of the cable shown in  FIG. 2A ; 
         FIG. 2C  is schematic diagram illustrating portions of another alternative embodiment of the cable shown in  FIG. 2A ; 
         FIG. 3A  is schematic diagram illustrating portions of an alternative embodiment of the cable shown in  FIG. 1  connected to a pair of devices.; 
         FIG. 3B  is schematic diagram illustrating portions of an alternative embodiment of the cable shown in  FIG. 3A ; 
         FIG. 3C  is schematic diagram illustrating portions of another alternative embodiment of the cable shown in  FIG. 3A ; 
         FIG. 4A  is schematic diagram illustrating an exemplary embodiment of another cable in accordance with the present disclosure connected to a pair of devices; 
         FIG. 4B  is schematic diagram illustrating portions of an alternative embodiment of the cable shown in  FIG. 4A ; 
         FIG. 4C  is schematic diagram illustrating portions of another alternative embodiment of the cable shown in  FIG. 4A . 
     
    
    
     DETAILED DESCRIPTION 
     A data/power transmission cable with integrated thermal protection in accordance with the present disclosure will now be described more fully with reference to the accompanying drawing, in which preferred embodiments of the cable are presented. The cable may, however, be embodied in many different forms and may be configured to conform to various standards (e.g., IEEE standards) and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the cable to those skilled in the art. 
     Referring to  FIG. 1 , a schematic diagram illustrating a pin layout for a USB-C data/power transmission cable  10  (herein after “the cable  10 ”) in accordance with the present disclosure is shown. As dictated by the USB-C standard, the cable  10  includes ground conductors  12 , high speed (USB 2.0, 480 mbps) data conductors  14 , super speed+ (USB 3.1, 10 Gbps) data conductors  16 , power conductors  18 , sideband use conductors  20 , a configuration channel conductor  22  (hereinafter “the CC conductor  22 ”), and a Vconn conductor  24 . Of particular relevance to the present disclosure are the power conductors  18 , the CC conductor  22 , and the Vconn conductor  24 . 
     As will be familiar to those of ordinary skill in the art, the CC conductor  22  allows devices that are connected by the cable  10  to determine whether the devices are, in-fact, connected to each other via the cable  10  and to transmit power and/or data over the cable  10  based on such determination. Specifically, if a device to which the cable  10  is connected detects a predetermined resistance on the CC conductor  22 , such resistance being indicative of a valid connection with another device on the opposing end of the cable  10 , then the device may transmit data and/or power over appropriate conductors of the cable  10 . Conversely, if the device fails to detect a predetermined resistance on the CC conductor  22 , indicating the lack of a valid connection with a device on the opposing end of the cable  10 , then the device will not transmit data or power over the cable  10 . The function of the CC conductor  22  as it relates to the embodiments of the present disclosure will be discussed in greater detail below. 
     As will also be familiar to those of ordinary skill in the art, the Vconn conductor  24  is used to dictate high power (e.g., &gt;20 watts, and typically 100 watts) operation of the cable  10 . Specifically, the Vconn conductor  24  includes an integrated circuit (IC)  36  (see  FIG. 2 ) provided with logic that is configured to indicate to connected devices that the cable  10  is capable of handling high power transmission. For example, if a device that is connected to the cable  10  determines from the IC  36  that the cable  10  is configured to handle high power, the device may subsequently transmit high power over the cable  10  via the power conductors  18 . Conversely, if the connected device does not receive an indication that the cable  10  is configured to handle high power, the device will not transmit high power over the cable  10  and will instead only transmit low power (e.g., 5-20 watts) over the cable  10  via the power conductors  18 . The determination of whether to transmit high power or only low power over the cable  10  is made by a device only upon initial connection of the cable  10  to the device. 
     Referring now to  FIG. 2A , a schematic diagram illustrating the CC conductor  22 , the Vconn conductor  24 , one of the power conductors  18 , and one of the ground conductors  12  of the cable  10  connected to a source device  40  and to a sink device  42  (hereinafter “the source  40 ” and “the sink  42 ”) is shown. It will be understood that the power conductor  18  and the ground conductor  12  shown in  FIG. 2A  are representative of all of the power conductors  18  and ground conductors  12  of the cable  10  shown in  FIG. 1 . The CC conductor  22  may include a positive temperature coefficient (PTC) element  44  connected inline therewith (e.g., via thermal bonding) such that the PTC element  44  is electrically in series with the source  40  and the sink  42  when the cable  10  is connected therebetween. The PTC element  44  may be formed of any type of PTC material (e.g., polymeric PTC material, ceramic PTC material, etc.) configured to have an electrical resistance that increases as the temperature of the PTC element  44  increases. Particularly, the PTC element  44  may be configured to have a predetermined “trip temperature” above which the electrical resistance of the PTC element  44  rapidly and drastically increases (e.g., in a nonlinear fashion) in order to substantially arrest current passing through the CC conductor  22 . In a non-limiting, exemplary embodiment of the cable  10 , the PTC element  44  may have a trip temperature in a range of 176 degrees Fahrenheit to 230 degrees Fahrenheit. 
     While the CC conductor  22  is shown as having only a single PTC element  44  coupled thereto, embodiments of the cable  10  are contemplated in which a plurality of PTC elements are implemented on the CC conductor  22 . For example, referring to  FIG. 2B , the cable  10  may include one PTC element  44  on the CC conductor  22  adjacent one end of the cable  10  (e.g., the end connected to the source  40 ) and a second PTC element  45  on the CC conductor  22  adjacent the opposing end of the cable  10  (e.g., the end connected to the source  42 ). Additionally, or alternatively, referring to  FIG. 2C , it is contemplated that PTC elements  47 ,  48  may be implemented on one or both of the CC conductors  49 ,  51  of the source  40  and the sink  42  that are connected to the CC conductor  22  of the cable  10 , wherein the PTC elements  47 ,  48  function in a manner identical to the PTC element  44  described above to provide the cable  10 , the source  40 , and the sink  42  with thermal protection as further described below. 
     During operation of the cable  10 , if the temperature of the PTC element  44  increases above its trip temperature, such as may result from an overcurrent condition in the cable  10  or from exposure to an external heat source (e.g., the sun, a hot computer chassis, etc.), the PTC element  44  may exhibit high electrical resistance and may arrest current flowing through the CC conductor  22 . Thus, the CC conductor  22  will appear to the source  40  and to the sink  42  to be “open” (i.e., disconnected), thereby causing the source  40  and the sink  42  to cease transmitting data and power via the cable  10 . Subsequently, when the PTC element  44  cools down to a temperature below its trip temperature and becomes electrically conductive again, the CC conductor  22  will appear to the source  40  and to the sink  42  to be “closed” (i.e., connected), and the source  40  and the sink  42  will resume transmitting data and/or power via the cable  10 . The PTC element  44  thus acts as a resettable fuse that mitigates overheating in the cable  10  to prevent thermal damage. Advantageously, since the PTC element  44  is implemented on the CC conductor  22  and not on the power conductor  18 , the PTC element  44  need only be rated to hold nominal electrical currents (e.g., 330 microamps) transmitted on the CC conductor  22  regardless of the amount of current transmitted on the power conductor  18  (e.g., 5 amps). The PTC element  44  may therefore be small and inexpensive, making the cost and the size of the cable  10  commercially practical. 
     Referring now to  FIG. 3A , an embodiment of the cable  10  is shown in which a second PTC element  46  is implemented on the Vconn conductor  24  (e.g., via thermal bonding to the Vconn conductor  24 ). As with PTC element  44  described above, the PTC element  46  may be configured to have an electrical resistance that increases as the temperature of the PTC element  46  increases. Particularly, the PTC element  46  may be configured to have a predetermined “trip temperature” at which the electrical resistance of the PTC element  46  rapidly and drastically increases (e.g., in a nonlinear fashion) in order to substantially arrest current passing through the Vconn conductor  24 . In a non-limiting, exemplary embodiment of the cable  10 , the trip temperature of the PTC element  46  may be lower than that of the PTC element  44  described above and may be in a range of 176 degrees Fahrenheit to 230 degrees Fahrenheit. 
     While the Vconn conductor  24  is shown as having only a single PTC element  46  coupled thereto, embodiments of the cable  10  are contemplated in which a plurality of PTC elements are implemented on the Vconn conductor  24 . For example, referring to  FIG. 3B , the cable  10  may include one PTC element  46  on the Vconn conductor  24  adjacent one end of the cable  10  (e.g., the end connected to the source  40 ) and a second PTC element  53  on the Vconn conductor  24  adjacent the opposing end of the cable  10  (e.g., the end connected to the source  42 ). Additionally, or alternatively, referring to  FIG. 3C , it is contemplated that PTC elements  55 ,  57  may be implemented on one or both of the Vconn conductors  59 ,  61  of the source  40  and the sink  42  that are connected to the Vconn conductor  24  of the cable  10 , wherein the PTC elements  55 ,  57  function in a manner identical to the PTC element  46  described above to provide the cable  10 , the source  40 , and the sink  42  with thermal protection as further described below. 
     The PTC element  46  may serve to prevent high power operation of the cable  10  in high temperature conditions which may present an increased risk of thermal damage to the cable  10  if high power operation were allowed. For example, if, prior to connecting the cable  10  to the source  40  and the sink  42 , the cable  10  has been exposed to high temperatures (e.g., as a result of sitting out in the sun), the temperature of the PTC element  46  may be above its trip temperature. If the USB cable  10  is then connected to the source  40  and to the sink  42  while the PTC element  46  is still “tripped,” it will appear to one or both the source  40  and sink  42  that the Vconn conductor  24  is open, and the source and/or the sink  40 ,  42  will only transmit low power on the power conductor  18 . As described above, the trip temperature of the PTC element  46  may be lower than the trip temperature of the PTC element  44  so that low power operation of cable  10  may be permitted (i.e., the CC conductor  22  will remain closed) at temperatures that would present an increased risk of thermal damage to the cable  10  if the cable  10  were allowed to transmit high power. 
     It will be appreciated that the configuration of the cable  10  described above can be similarly applied to power/data transmission cables that conform to standards other than USB-C. For example, the above-described configuration, which includes a PTC element implemented on a configuration channel conductor of a USB cable for dictating the delivery of power on a separate power conductor of the USB cable, can be similarly implemented in cables that conform to the Apple Lightning standard, the Apple Thunderbolt standard, various generations of the Qualcomm Quick Charge standard, and earlier USB standards. In data/power transmission cables that do not have a direct equivalent to the configuration channel conductors of the USB-C standard (e.g., cables that conform to various generations of the Qualcomm Quick Charge standard), it is contemplated that the data lines of such cables can be utilized in the manner of the CC conductor  22  and the Vconn conductor  24  described above when such cables are being used in a charging-only capacity (an example of such an embodiment is described below). More generally, it is contemplated that the functionality of the cable  10  described above can be similarly achieved in any data/power transmission cable that conforms to existing or future protocols by putting a PTC element on one or more “non-power-carrying” conductors of such cables, where such conductors are used to detect the presence of a source/sink connection and/or a level of charging voltage/current. The embodiments of the present disclosure are not limited in this regard. 
     Referring to  FIG. 4A , a schematic diagram illustrating a non-limiting, exemplary embodiment of a Qualcomm Quick Charge 2.0 cable  50  (hereinafter “the cable  50 ”) in accordance with the present disclosure is shown. As dictated by the Qualcomm Quick Charge 2.0 standard, the cable  50  includes a ground conductor  52 , a D+ data conductor  54 , a D− data conductor  56 , and a power conductor  58 . In a typical application, the cable  50  may be used to connect a source device  60  (e.g., a source of electrical power) to a sink device  62  that is being charged (hereinafter “the source  60 ” and “the sink  62 ”) as shown. 
     As will be familiar to those of ordinary skill in the art, the cable  50  may be used to selectively transmit power at one of several different voltage levels (5V, 9V, 12V, or 20V) from the source  60  to the sink  62 , wherein the voltage level is dictated by the sink  62 . Particularly, if the sink  62  requires power at 5V, the sink  62  will apply 0.6V on the D+ data conductor  54  and will pull the D− data conductor  56  to ground, which causes the source  60  to apply 5V on the power conductor  58 . If the sink  62  requires power at 9V, the sink  62  will apply 3.3V on the D+ data conductor  54  and will apply 0.6V on the D− data conductor  56 , which causes the source  60  to apply 9V on the power conductor  58 . If the sink  62  requires power at 12V, the sink  62  will apply 0.6V on the D+ data conductor  54  and will apply 0.6V on the D− data conductor  56 , which causes the source  60  to apply 12V on the power conductor  58 . If the sink  62  requires power at 20V, the sink  62  will apply 3.3V on the D+ data conductor  54  and will apply 3.3V on the D− data conductor  56 , which causes the source  60  to apply 20V on the power conductor  58 . If one or both of the D+ data conductor  54  and the D− data conductor  56  appears to the source  60  to be disconnected or “open,” the source  60  will default to low power operation and will apply 5V on the power conductor  58 . 
     In accordance with the present disclosure, each of the D+ data conductor  54  and the D− data conductor  56  may include a positive temperature coefficient (PTC) element  64 ,  66  connected inline therewith (e.g., via thermal binding) such that the PTC elements  64 ,  66  are electrically in series with the source  60  and the sink  62  during use of the cable  50 . The PTC elements  64 ,  66  may be formed of any type of PTC material (e.g., polymeric PTC material, ceramic PTC material, etc.) configured to have electrical resistances that increase as the temperatures of the PTC elements  64 ,  66  increase. Particularly, the PTC elements  64 ,  66  may be configured to have predetermined “trip temperatures” above which the electrical resistances of the PTC elements  64 ,  66  rapidly and drastically increase (e.g., in a nonlinear fashion) in order to substantially arrest currents passing through the D+ data conductor  54  and the D− data conductor  56 . In a non-limiting, exemplary embodiment of the cable  50 , the PTC element  64 ,  66  may have a trip temperature in a range of 176 degrees Fahrenheit to 230 degrees Fahrenheit. While the D+ data conductor  54  and the D− data conductor  56  are each shown as having only a single PTC element  64 ,  66  coupled thereto, embodiments of the cable  50  are contemplated in which a plurality of PTC elements are implemented on one or both of the D+ data conductor  54  and the D− data conductor  56 . For example, the cable  10  may include PTC elements on the D+ data conductor  54  and the D− data conductor  56  adjacent one end of the cable  50  as well as PTC elements on the D+ data conductor  54  and the D− data conductor  56  adjacent the opposing end of the cable  50 . 
     While the D+ data conductor  54  and the D− data conductor  56  are each shown as having only a single PTC element  64 ,  66  coupled thereto, embodiments of the cable  50  are contemplated in which a plurality of PTC elements are implemented on one or both of the D+ data conductor  54  and the D− data conductor  56 . For example, referring to  FIG. 4B , the cable  50  may include respective PTC elements  64 ,  66  on the D+ data conductor  54  and the D− data conductor  56  adjacent one end of the cable  50  (e.g., the end connected to the source  40 ) as well as respective PTC elements  68 ,  70  on the D+ data conductor  54  and the D− data conductor  56  adjacent the opposing end of the cable  50  (e.g., the end connected to the source  42 ). Additionally or alternatively, referring to  FIG. 4C , it is contemplated that respective PTC elements  72 ,  74 ,  76 ,  78  may be implemented on one or both of the D+ data conductor  80  and the D− data conductor  82  of the source  40  and/or on one or both of the D+ data conductor  84  and the D− data conductor  86  of the sink  42  that are connected to the D+ data conductor  54  and the D− data conductor  56  of the cable  50 , wherein the PTC elements  72 ,  74 ,  76 ,  78  function in a manner identical to the PTC elements  64 ,  66  described above to provide the cable  50 , the source  60 , and the sink  42  with thermal protection as further described below. 
     During operation of the cable  50 , if the temperature of the PTC element  64  and/or the PTC element  66  increases above its trip temperature, such as may result from an overcurrent condition in the cable  50  or from exposure to an external heat source (e.g., the sun, a hot computer chassis, etc.), the PTC element  64  and/or the PTC element  66  may exhibit high electrical resistance and may arrest current flowing through the D+ data conductor  54  and/or the D− data conductor  56 , respectively. Thus, the D+ data conductor  54  and/or the D− data conductor  56  will appear to the source  60  to be “open” (i.e., disconnected), thereby causing the source  60  to default to low power operation and will apply 5V on the power conductor  58 . High power operation is therefore prevented when the cable  50  is in an overheated state, thereby mitigating damage that might otherwise result if the cable were allowed to transmit high power. 
     When the PTC element  64  and/or the PTC element  66  cools down to a temperature below its trip temperature and becomes electrically conductive again, the D+ data conductor  54  and/or the D− data conductor  56  will appear to the source  40  and to the sink  42  to be “closed” (i.e., connected), and conventional operation of the cable  50  may resume. The PTC elements  64 ,  66  thus act as resettable fuses that mitigate overheating in the cable  50  to prevent thermal damage thereto. Advantageously, since the PTC elements  64 ,  66  are implemented on the D+ data conductor  54  and the D− data conductor  56  and not on the power conductor  58 , the PTC elements  64 ,  66  need only be rated to hold nominal electrical currents (e.g., 8 milliamps) transmitted on the D+ data conductor  54  and the D− data conductor  56  regardless of the amount of current transmitted on the power conductor  58  (e.g., 3 amps). The PTC elements  64 ,  66  may therefore be small and inexpensive, making the cost and the size of the cable  50  commercially practical. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.