Patent Description:
The increased amount of power delivered by the USB Type-C connector system, which may be upwards of <NUM> watts, may present safety issues not realized in other systems which handle lower amounts of power. For instance, in the event one or more of the power supply lines, known as VBUS lines, within the USB Type-C connector system become short circuited to the ground, such as by a buildup of dust within a USB Type-C port or some other conductive object entering a port, the port may become overheated. The overheated USB Type-C port may lead to the port, or other components connected to, or in the vicinity of, the port burning or incurring other damage as a result of the excessive heat. In addition, there is a risk of a user suffering from burns or being shocked if they contact that overheated port or the other affected components.

<CIT>, with respect to an USB-C Type interface, discloses an overtemperature protection circuit and a data line, wherein a temperature sensing module outputs a sensing voltage according to an ambient temperature, a first path terminal of the first switching element receives an input voltage, a first control terminal of the first switching element receives the induced voltage, a second via terminal of the first switching elements connected to a common terminal of the first voltage dividing resistor and the second voltage dividing resistor, and a third path terminal of the second switching element receives an input voltage. A second control terminal of the second switching element is connected to a second via terminal of the first switching element, when the ambient temperature of the temperature sensing module is lower than the sensed temperature of the temperature sensing module, the induced voltage output from the temperature sensing module disconnects the first switching element to control the second switching element to conduct, when the ambient temperature of the temperature sensing module is higher than or equal to the sensed temperature of the temperature sensing module. The sensed voltage output by the temperature sensing module further causes the first switching element to be turned on to control the second switching element to be turned off, thereby disconnecting the circuit to prevent the device from being overheated.

<CIT> relates to a battery pack including a first switching element which shuts off a discharging current flowing to a battery cell and a second switching element which shuts off a charging current. A positive temperature coefficient thermistor is inserted between a gate control terminal of a protective control circuit and a gate of at least one of the switching elements, and a resistor is connected between the gate and a source of the switching element. The positive temperature coefficient thermistor is thermally connected to one or more of the first and second switching elements and/or to the battery cell. Thus, an abnormally overheated state of one or more of the switching elements or the battery cell leads to an increase in the resistance of the positive temperature coefficient thermistor causing shut-off of the switching element thereby protecting the battery pack.

<CIT> discloses a switching power converter, provided with an overvoltage protection circuit that softly switches on a power bus switch during a soft-start period responsive to a device connecting to a data cable for receiving power over a power bus coupled to the power bus switch.

The proposed solution relates to a system as defined by claim <NUM>.

In one scenario, a diode is positioned on the first configuration channel line between the first resistor and the junction point.

In some embodiments, the voltage divider outputs a voltage at the second junction point.

In some embodiments, the short circuit protection circuit further comprises a third resistor connected to a third configuration channel line, wherein the third resistor is connected to the drain of the FET. In one example, the short circuit protection circuit further comprises a diode positioned on the second configuration channel line between the third resistor and the junction point. In some instances, the short circuit protection circuit further comprises a capacitor, wherein the capacitor is connected on a first end to a second junction on the configuration channel line located between the diode and the second resistor and the capacitor is connected on a second end to the ground line. In some instances, the capacitor stabilizes the voltage at the junction point.

In some embodiments, the FET is configured to turn on when a voltage at the gate is above a threshold value and turn off when the voltage at the gate is below the threshold value. In some examples, power is delivered over a power supply line extending from the first connector when the FET is on and no power is delivered over the power supply line when the FET is off.

In some embodiments, the voltage divider outputs a lower voltage at the second junction point when the thermistor is at a higher temperature than when the thermistor is at a lower temperature.

In some embodiments, the short circuit protection circuit further comprises a third diode, wherein the diode connects a power supply line extending from the first connector to the junction point. In some examples, the short circuit protection circuit further comprises a low-dropout regulator (LDO) positioned inline between the junction point and the voltage divider, wherein the LDO stabilizes a voltage at the voltage divider and/or lowers the voltage provided at the junction point.

In some embodiments, the FET is metal-oxide-semiconductor field-effect transistor (MOSFET).

Embodiment illustrated in <FIG> and associated passages in the description does not form part of the invention as claimed but is presented as illustrative purposes".

The technology relates generally to circuit designs for reducing the risk of a short circuited power supply line damaging a port. Such circuitry may be implemented in any number of devices where power is supplied through a USB Type-C system. In this regard, power delivery through the USB Type-C system requires a valid connection be made between two USB Type-C ports before power is supplied. According to this disclosure, and as described in detail herein, the circuitry leverages the way a valid connection is detected, as well as the heat generated by a short circuited power supply line, to turn off the power supplied through the power supply line. For example, the circuitry utilizes a voltage divider including a negative temperature coefficient (NTC) thermistor to control the operation of the transistor. When the thermistor is heated up as the result of the short circuited power supply line, the transistor may be switched off. In the off position, the transistor makes it appear that a valid connection is not present between two ports which are otherwise validly connected. As a result, the power supply line may be turned off to prevent excessive heat from damaging the port.

The short circuit protection circuit (SCPC) includes a pair of resistors which operate as a voltage divider. One or more of the resistors may be a thermistor that has a variable resistance which is dependent upon its temperature. In this regard, the higher the temperature of the thermistor the lower the resistance of the thermistor. As such, the voltage output by the voltage divider decreases as the thermistor <NUM> heats up.

The SCPC also includes a transistor, such as a MOSFET, which is controlled by the voltage of the voltage divider. In this regard, when the voltage output by the voltage divider is sufficiently high, as described herein, the transistor turns on. Upon the transistor turning on, a valid connection between the USB Type-C ports may be determined, such as by a controller or other such processor, and power may be delivered over the power supply line.

In instances where the voltage divider is insufficient, such as in instances where the thermistor heats up beyond a certain threshold, the transistor may turn off. Upon turning off, a valid connection between the USB Type-C ports may no longer be determined by a controller, or other such processor, and power delivery over the power supply line may be turned off.

The features described may reduce the risk of a short circuited power supply line damaging a port or components connected to, or in the vicinity of the port. In addition, the circuitry described may reduce the risk of a user suffering from burns or being shocked from an overheated port or other components. In some instances, the circuitry may allow power to be supplied over a shorted power supply line as long as the heat generated by the short circuited power supply line remains within a safe temperature range.

A USB Type-C port may include two sets of pins which are rotationally-symmetrical to allow a connector to be reversibly connected to the port. For example, and as shown in example USB Type-C port <NUM> of <FIG>, the port contains two sets of <NUM> pins, A1-A12 and B1-B12. Pins A1, A12, B1 and B12 (GND) may be ground contacts. Pins A2 and B2 (TX1+) and A3 and B3 (TX1-) can form respective pairs of high speed transmission paths. Pins A4, B4, A9, and B9 can be bus power (VBUS) contacts. Pins A5 and B5 (CC1, CC2) can form a configuration channel (CC) path. Pins A6, A7, B6, and B7 (D+, D-) may form a differential pair path. Pins A8 and B8 can form a side band use (SBU1, SBU2). Pins A10 and A11 (RX2-, RX2+), B10 and B11 (RX1-, RX1+) may form high speed transmission differential pair. Although the USB Type-C ports discussed herein are described as female receptacles configured to receive a male connector, the USB Type-C ports may be a male receptacle configured to receive a female connector, or the USB Type-C ports may be configured as male or female connectors configured to attach to female or male receptacles. The technology discussed herein may also be implemented in other buses and connectors, such as connectors which have separate control lines which control the delivery of power.

<FIG> provides a typical USB Type-C system including two USB Type-C ports, including a downstream facing port (DFP) and an upstream facing port (UFP). The DFP may be configured to provide power to the UFP over one or more power supply lines after a valid connection between the DFP and UFP is made. For example, USB Type-C system <NUM> shown in <FIG> includes DFP <NUM> and UFP <NUM>. USB Type-C compliant cable <NUM> connects CC pin <NUM> of the DFP <NUM> with CC pin <NUM> of the UFP <NUM> together. As USB Type-C cable <NUM> contains only a single CC line, if the cable <NUM> is reversed in the DFP <NUM> and/or the UFP <NUM>, connections between different CC pins may be made. For instance, CC pin <NUM> may be connected to CC pin <NUM> or CC pin <NUM> may be connected to CC pin <NUM> or <NUM>.

The cable <NUM> also connects VBUS pin <NUM> of the DFP <NUM> with VBUS pin <NUM> of the UFP <NUM>. Although only a single VBUS line <NUM> is shown in <FIG>, power may be delivered over more than one VBUS line and between more than one pair of VBUS pins between the DFP <NUM> and UFP <NUM>. Other connectors may be used in conjunction with or in place of cable <NUM> to connect DFP <NUM> and UFP <NUM>. While the ground lines <NUM>, <NUM>, and <NUM> are shown as independent lines, it should be understood that each of the UFP <NUM> and DFP <NUM>, as well as components connected thereto, may share a common ground line. In this regard, cable <NUM> may provide a connection between one or more ground pins in the DFP <NUM> and UFP <NUM> (not shown) to tie the various grounds (i.e., <NUM>, <NUM>, <NUM>, etc.,) together.

A valid connection between the DFP <NUM> and UFP <NUM> may be indicated by a particular voltage being present at one or more configuration channel (CC) pins within the DFP <NUM>. In this regard, a controller or other processor, such as controller <NUM> may monitor the configuration channel (CC) pins <NUM>, <NUM> for a particular voltage. The particular voltage may be a predefined voltage or a voltage within a range of voltages, such as a voltage between. 5V and 3V, or more or less. Upon detecting the particular voltage, the controller <NUM> may trigger a power source, such as power source <NUM> to deliver power over the VBUS line <NUM>.

The voltage at the CC pins <NUM> and/or <NUM> may be based upon the voltage generated by a power source and the resistance of resistors connected to the CC pins. For example, and as further shown in <FIG>, CC pins <NUM> and <NUM> of the DFP <NUM> are connected to power source <NUM> via pull-up resistors <NUM> and <NUM>, respectively and CC pins <NUM> and <NUM> of the UFP are connected to ground <NUM> via pull-down resistors <NUM> and <NUM>, respectively. The power source <NUM>, which may be the same or different than power source <NUM>, may continually, or intermittently, generate a voltage of <NUM>-<NUM> volts, or more or less.

The pull-up resistors and the pull-down resistors may form a voltage divider which divides the voltage provided by power source <NUM> to present a particular voltage at one of the CC pins. For example, when CC pins <NUM> and <NUM> are connected by cable <NUM> as shown in <FIG>, pull-up resistor <NUM> and pull-down resistor <NUM> may form a voltage divider which presents a particular voltage at CC pins <NUM> and <NUM>. In instances where the cable <NUM> is reversed, a voltage divider may be formed by different pairs of resistors, such as resistor <NUM> and <NUM> or resistor <NUM> and resistor <NUM> or <NUM>. The resistance of the pull-up resistors <NUM>, <NUM> may be indicative of the current sourcing capability of a power supply <NUM> and may be between 4kS2 and 56kQ, or more or less. The resistance of pull-down resistors may be around 5kQ, or more or less.

In operation, when the DFP <NUM> is not connected to UFP <NUM>, the voltage at the unterminated CC pins <NUM>, <NUM> may be between <NUM>-5V, or more or less. In instances where the UFP <NUM> is connected to the DFP <NUM>, such as shown in <FIG>, the voltage of CC pin <NUM> may be the particular voltage, such as a voltage between. 5V and 3V, and pin <NUM> may be 0V, or more or less. The controller <NUM> may detect the particular voltage at CC pin <NUM> and trigger, or otherwise activate power source <NUM>, which in turn may deliver power to the UFP <NUM> via the VBUS <NUM>. Power source <NUM> may continue to provide voltage as long as the particular voltage is detected at pin <NUM> by the controller. That is to say, power source <NUM> provides voltage over the VBUS <NUM> as long as a valid connection is detected between DFP <NUM> and UFP <NUM>.

As used herein, the circuitry and components located before the DFP <NUM>, including pull-up resistors <NUM>, <NUM>, and power sources <NUM> and <NUM>, is considered downstream circuitry. The circuitry located after the UFP <NUM>, including the pull-down resistors <NUM>, <NUM> is considered upstream circuitry. Although <FIG> shows the downstream circuitry as being outside the DFP <NUM> and the upstream circuitry as being outside the UFP <NUM>, some or all of the downstream circuitry may be integrated into the DFP <NUM> and some or all of the upstream circuitry may be integrated into the UFP <NUM>.

<FIG> provides a circuit diagram illustrating a circuit design of a short circuit protection circuit (SCPC) <NUM> integrated into the upstream circuitry. The SCPC <NUM> includes diode <NUM> positioned in parallel with pull-down resistor <NUM> on line CC1 <NUM> and diode <NUM> positioned in parallel with pull-down resistor <NUM> on line CC2 <NUM>. Diodes <NUM> and <NUM> tie together at junction <NUM>. The diodes <NUM> and <NUM> may prevent current from flowing from the SCPC <NUM> back towards the CC pins <NUM> and <NUM>.

A capacitor may be used to minimize voltage fluctuation at junction <NUM> with the SCPC <NUM>. For example, capacitor <NUM> is positioned inline between junction <NUM> and ground. The capacitor <NUM> may have a relatively small capacitance, such as <NUM>. 1µF, or more or less. During a voltage change at junction <NUM>, such as during a switch over from CC1 or CC2, and/or during VBUS being powered upon a qualified pull down via MOSFET <NUM> and pull-down resistor <NUM> or <NUM>, capacitor <NUM> may release a stored charge to maintain a consistent voltage at junction <NUM>.

A pair of resistors in the SCPC <NUM>, including resistor <NUM> and negative temperature coefficient (NTC) thermistor <NUM>, is used as a voltage divider to generate a voltage at junction <NUM>. The voltage output by the voltage divider is dependent upon the temperature of the thermistor. In this regard, the thermistor has a variable resistance which is dependent upon its temperature, with a higher temperature resulting in a lower resistance. In other words, when thermistor <NUM> heats up its resistance decreases. Thermistor <NUM>, which ties junction <NUM> to ground, may have a variable resistance between 100kΩ and 0Ω, or more or less, depending upon its temperature. Resistor <NUM>, which may be around 150kS2, or more or less, is positioned between junction <NUM> and junction <NUM>.

The thermistor <NUM> may be positioned close to the VBUS pins of the UFP <NUM> so that heat at the VBUS pin affects the resistance of the thermistor. For instance, when the VBUS <NUM> is short circuited to ground, a buildup of heat may occur at the VBUS pins of the UFP <NUM>, and in some instances, the VBUS <NUM> itself may generate excessive heat. This increased heat may cause the thermistor <NUM> to heat up and the resistance of the thermistor to decrease.

The SCPC <NUM> includes a MOSFET <NUM> with its drain attached to junction <NUM> and source attached to ground <NUM>. The gate of the MOSFET <NUM> is attached to junction <NUM>. When the gate of the MOSFET <NUM> is subjected to a certain voltage, such as. 6V or more or less, the MOSFET may be turned on, thereby allowing current to travel between the drain and the source. In this regard, when gate of the MOSFET <NUM> is subjected to the certain voltage, current flows from junction <NUM> to ground <NUM>. As a result, the pull-down resistors <NUM>, <NUM> are connected to ground when the MOSFET <NUM> is on and unterminated when the MOSFET <NUM> is off. As explained above, the voltage at junction <NUM>, to which the gate of the MOSFET is attached, is determined by the value of the voltage divider formed by resistor <NUM> and thermistor <NUM>. Although SCPC <NUM> is shown as including a MOSFET, other field effect transistors may also be used.

A third diode <NUM> may be positioned between the VBUS <NUM> and junction <NUM>. Diode <NUM> may provide junction <NUM> with the voltage on the VBUS <NUM> when the VBUS is powered. In this regard, the voltage provided on the VBUS <NUM> may be larger and/or more stable than the voltage provided over the CC pins, <NUM> and <NUM>. As such, the voltage divider created by resistor <NUM> and thermistor <NUM> may operate more reliably with the voltage from the VBUS <NUM> than the voltage provided over the CC pins, <NUM> and <NUM>. Diode <NUM> also prevents current from flowing back towards the VBUS from the SCPC <NUM>.

<FIG> illustrates the operation of the SCPC <NUM> when the UFP <NUM> is connected to a DFP (not shown) and a voltage is provided to pin CC1 <NUM> by a power source, such as power source <NUM>. For example, current, illustrated by the dashed line, flows through diode <NUM> to the voltage divider formed by resistor <NUM> and thermistor <NUM>. The voltage presented at junction <NUM> by the voltage divider may be about <NUM>. 8V, or more or less depending upon the voltage provided by the power source.

The voltage presented at junction <NUM> by the voltage divider turns on the MOSFET <NUM>, as further illustrated in <FIG>. As a result of turning on the MOSFET <NUM>, junction <NUM> is grounded which pulls pull-down resistor <NUM> to ground. Current passing through pull-down resistor <NUM> generates a particular voltage at CC pin <NUM>, such as a voltage between. As CC pin <NUM> is connected to a corresponding CC pin on the DFP, a controller, such as controller <NUM> may detect the particular voltage at the CC pin of the DFP and trigger, or otherwise activate a power source to deliver power to the UFP <NUM> via the VBUS <NUM>. In instances where voltage is provided to pin CC2 <NUM>, the operation of the SCPC <NUM> will be similar, however current will flow through diode <NUM> and pull-down resistor <NUM> instead of diode <NUM> and pull-down resistor <NUM>.

<FIG> illustrates the operation of the SCPC <NUM> when the VBUS <NUM> is short circuited. As discussed above, when the VBUS <NUM> is shorted, excessive heat is generated at the VBUS pins of the UFP <NUM>. As the heat generated by the VBUS pin rises, the heat that is generated propagates to the thermistor <NUM> and increases the thermistor's temperature. The increased temperature of the thermistor <NUM> reduces of the resistance of the thermistor. The reduced resistance of thermistor <NUM> reduces the voltage at junction <NUM> presented by the voltage divider created by resistor <NUM> and thermistor <NUM>.

Upon the voltage at junction <NUM> crossing below a certain voltage, such as <NUM>. 6V, or more or less, the gate of the MOSFET <NUM> may be turned off. Turning off the MOSFET <NUM> may release the connection between pull-down resistors <NUM>, <NUM> and ground thereby preventing current, illustrated by the dashed line, from flowing through the pull-down resistors. When the pull-down resistors <NUM>, <NUM> are disconnected from ground, the voltage presented at the CC pins <NUM>, <NUM> may be 3V, or more or less. When no power is delivered over the VBUS <NUM>, the temperature of the thermistor <NUM> may cool. When the thermistor <NUM> cools to a certain temperature, its resistance may increase to a level high enough to create a voltage between the voltage divider sufficient to turn the MOSFET <NUM> back on.

As the CC pins <NUM>, <NUM> are connected to corresponding CC pins on the DFP, a controller, such as controller <NUM>, may detect that the particular voltages at the CC pins of the DFP are greater than the particular value required to trigger power delivery on the VBUS. As a result, the controller may determine that a valid connection is no longer present and cease power delivery to the UFP <NUM> via the VBUS <NUM>.

In some instances a low dropout regulator (LDO) and associated capacitor may be integrated into the SCPC <NUM> to provide a regulated voltage to the voltage divider formed by resistor <NUM> and thermistor <NUM>. For example, and as illustrated in <FIG>, an LDO may be positioned after junction <NUM> and tied to resistor <NUM> at junction <NUM>. Capacitor <NUM> ties junction <NUM> to ground. Capacitor <NUM> may have a relatively small capacitance, such as <NUM>. 1µF, or more or less. During a voltage change at junction <NUM>, capacitor <NUM> may release a stored charge to maintain a consistent voltage at junction <NUM>. The LDO may also present a lower voltage to the voltage divider than provided by the VBUS, such that the voltage output at junction <NUM> may be lower to turn the MOSFET when the thermistor <NUM> at a lower temperature that if a higher voltage was presented to the voltage divider.

The SCPC <NUM> is a non-latching and self-recovering circuit. In this regard, turning off power on the VBUS <NUM> allows the temperature of the thermistor to decrease, thereby increasing the resistance of the thermistor. The increase of resistance within the thermistor may cause the voltage divider (i.e., resistor <NUM> and thermistor <NUM>) to generate a voltage at junction <NUM> which turns MOSFET <NUM> back on. Turning the MOSFET <NUM> back on may result in power again being delivered to the VBUS <NUM>. The MOSFET <NUM> may remain on until the heat generated by the short circuited VBUS <NUM> again causes the resistance of the thermistor to decrease to a point where the voltage supplied to the MOSFET is unable to keep the MOSFET <NUM> on. This cycle of the MOSFET <NUM> turning on and off as a result of the temperature and resistance of the thermistor rising and falling may continue indefinitely.

In some instances, upon a short circuit event occurring on the VBUS, the VBUS may not sustain full voltage, such as 5V, or more or less. The reduced voltage on VBUS may provide the divider with a lower voltage, thereby allowing the voltage across <NUM> to be lower. As such, the MOSFET may turn off when the thermistor <NUM> is at a lower voltage, than if full voltage was provided to the voltage divider.

In some instances, a controller or other such processor may monitor the voltage at junction <NUM>. For instance, an electronic device which is connected to UFP <NUM> may receive a temperature sense signal line (T_sns, shown in <FIG>,) which provides the voltage of the voltage divider formed by resistor <NUM> and thermistor <NUM>. Based on the voltage, the electronic device may be able to determine the resistance and temperature of the thermistor <NUM>. For example, and as shown in <FIG>, resistor <NUM> and thermistor <NUM> are powered by VBUS, which may provide a regulated voltage of 5V, or more or less, through diode <NUM>. The voltage drop on thermistor <NUM> and at junction <NUM> is a function of temperature of the thermistor <NUM>. Thus, depending on the voltage of the T_sns signal line at junction <NUM>, the temperature and voltage of the thermistor <NUM> may be determined. This temperature and voltage information may be used for diagnostic and monitoring purposes to provide warnings or to take action upon the temperature rising or voltage falling outside a threshold value.

While the examples described above primarily relate to USB Type-C connector systems, it should be understood that the power line short circuit protection circuit may be implemented in any of a number of connector systems which provide power over a supply line based on the detection of a particular voltage on another line of the system.

Claim 1:
A system, comprising:
a first port (<NUM>) having a first set of pins (<NUM>, <NUM>, <NUM>);
a second port (<NUM>) having a second set of pins (<NUM>, <NUM>, <NUM>), wherein the second port (<NUM>) is configured to electrically connect to the first port (<NUM>) via one or more electrical connections between the first set of pins and the second set of pins;
a power supply line (<NUM>) extending from a second pin in the second port (<NUM>),
a power supply for providing a voltage to a first configuration channel line at a first pin in the first port (<NUM>), wherein the first pin in the first port is connected to the first pin in the second port (<NUM>) and the first pin in the second port (<NUM>) is connected to a second configuration line (<NUM>, <NUM>);
a first resistor (<NUM>; <NUM>) connected to the second configuration channel line (<NUM>; <NUM>);
a short circuit protection circuit (<NUM>) connected to the second port (<NUM>) comprising:
a voltage divider connected to a junction point (<NUM>) on the second configuration channel line (<NUM>, <NUM>) and comprising a second resistor (<NUM>) and a thermistor (<NUM>), wherein the thermistor is connected to a ground line (<NUM>); and
a field effect transistor (<NUM>), FET, connected to the first resistor (<NUM>; <NUM>); and
a controller (<NUM>) configured to detect the voltage on the first configuration channel line at the first pin in the first port (<NUM>), wherein when the controller (<NUM>) detects a voltage on the first pin in the first port being above a threshold value, the controller triggers power delivery on the power supply line (<NUM>).