CN116780461A

CN116780461A - USB interface protection circuit and terminal equipment

Info

Publication number: CN116780461A
Application number: CN202211193842.4A
Authority: CN
Inventors: 王兴华; 黄允春; 冯英群; 韩超
Original assignee: Honor Device Co Ltd
Current assignee: Honor Device Co Ltd
Priority date: 2022-09-28
Filing date: 2022-09-28
Publication date: 2023-09-19

Abstract

The embodiment of the application provides a USB interface protection circuit and terminal equipment, wherein the terminal equipment comprises a USB interface and at least one functional chip, and the USB interface is connected with the functional chip through a USB access; the USB interface protection circuit comprises a first protection device group; the first protection device group is arranged between the USB interface and the common mode inductor in the USB access; the first protection device group is used for fusing and protecting the USB access. Therefore, the first protection device group arranged between the USB interface and the common mode inductor can effectively protect all devices and functional chips in the USB channel when the USB interface is short-circuited or overloaded and high current flows into the USB channel.

Description

USB interface protection circuit and terminal equipment

Technical Field

The present application relates to the field of electronic technologies, and in particular, to a USB interface protection circuit and a terminal device.

Background

With the development of science, a universal serial bus (Universal Serial Bus, USB) interface has become an interface widely used on portable terminal devices. The terminal equipment can carry out data communication with other external equipment based on the USB interface, and can also be connected with other external equipment or power supply through the USB interface to charge the terminal equipment.

When data communication and charging are carried out, a USB channel is formed between a USB interface in the terminal equipment and a functional chip in the terminal equipment. When two differential signal lines in the USB access are in short circuit or the pins in the USB interface are in short circuit, the USB interface is likely to form a loop with a bidirectional transient diode (Transient Voltage Suppressor, TVS) inside the functional chip due to poor current passing capability of the common-mode inductance, the notch network, the signal switch and other devices, so that the devices on the USB access are damaged, related functions of the USB interface are disabled, and even irreversible damage can be formed to terminal equipment.

Therefore, how to perform short-circuit and overload protection on the USB path in the terminal device is a problem to be solved.

Disclosure of Invention

The embodiment of the application provides a USB interface protection circuit and terminal equipment, which can effectively protect devices in a USB access so as to ensure the safety of a USB interface and an internal functional chip in the terminal equipment.

In a first aspect, the present application provides a USB interface protection circuit, applied to a terminal device, where the terminal device includes a USB interface and at least one functional chip, and the USB interface is connected to the functional chip through a USB path; the USB interface protection circuit comprises a first protection device group;

The first protection device group is arranged between the USB interface and the common mode inductor in the USB path; the first protection device group is used for fusing and protecting the USB access.

Because the common-mode inductor is a front-end device connected with the USB interface in the USB channel, the first protection device group arranged between the USB interface and the common-mode inductor can effectively protect all devices and functional chips in the USB channel when the USB interface is short-circuited or overloaded and high current flows into the USB channel.

When the first protection device group protects the USB access, a fusing protection mode is adopted, and under the condition of short circuit or overload of the USB interface, the current in the USB access is reduced by increasing the impedance of the first protection device group; when the current in the USB path stabilizes, it returns to a low impedance state. Thus, based on the first protection device group, the USB access and the functional chip can be continuously protected.

In one possible implementation, the first protection device group includes an auto-recovery fuse and a voltage stabilizing element group including any one of a varistor and a first bidirectional transient diode TVS;

the first end of the automatic recovery fuse is connected with the USB interface, and the second end of the automatic recovery fuse is connected with the voltage stabilizing element group; the automatic recovery fuse is used for increasing the impedance value of the automatic recovery fuse when the USB access is short-circuited or the current flowing into the USB access is larger than the access current threshold value of the USB access so as to reduce the current value flowing into the common-mode inductor; the voltage stabilizing element group is used for stabilizing the output voltage of the second end of the automatic recovery fuse to be in the working voltage range of the common mode inductance.

Wherein, the automatic recovery fuse has the dual functions of overcurrent and overheat protection and automatic recovery. When the USB interface is short-circuited or overloaded, the heat generated by the large current flowing through the self-recovery fuse can enable the self-recovery fuse to form a high-resistance state, so that the working current in the USB access is rapidly reduced, and the current in the USB access is limited, so that the effect of protecting devices in the USB access is achieved. And after the fault in the USB access or the USB interface is removed, the automatic recovery fuse can be recovered to a low-resistance state and work normally.

Further, in order to avoid unstable voltage input into the common-mode inductor in the overcurrent protection process of the automatic recovery fuse, a voltage stabilizing element group is arranged between the second end of the automatic recovery fuse and the input end of the common-mode inductor. Thus, the input voltage of the common-mode inductor is stabilized in the working voltage range by the voltage stabilizing element group so as to protect the common-mode inductor from being damaged.

In one possible implementation, the USB path includes a first path between a first pin of the USB interface and the functional chip and a second path between a second pin of the USB interface and the functional chip, and the voltage stabilizing element group includes a first voltage stabilizing element, a second voltage stabilizing element, and a third voltage stabilizing element;

The first end of the first voltage stabilizing element is connected with the second end of the automatic recovery fuse in the first passage, and the second end of the first voltage stabilizing element is grounded;

the first end of the second voltage stabilizing element is connected with the second end of the automatic restoration fuse in the second path, and the second end of the second voltage stabilizing element is grounded;

one end of the third voltage stabilizing element is connected with the first passage, and the other end of the third voltage stabilizing element is connected with the second passage.

Therefore, the first voltage stabilizing element is arranged on the first path, and the second voltage stabilizing element is arranged on the second path, so that devices in the USB path are prevented from being damaged, and the voltage stability of a single path in the USB path is ensured. Meanwhile, a third voltage stabilizing element is arranged between the first passage and the second passage, so that the phenomenon that the normal operation of each device is influenced due to the fact that the voltage fluctuation in the USB passage is too large is avoided, and the signal stability of a differential signal pair in the USB passage is ensured.

In one possible implementation, the USB interface protection circuit further includes: a first resistor; the first resistor is connected in parallel with the common mode inductor; the first resistor is used for keeping the electric connection between the USB interface and the functional chip after the single-path common-mode inductance in the USB path is disconnected.

Therefore, under the condition that the common mode inductance is abnormal, a passage is formed between the USB interface and the functional chip through the first resistor, and the normal operation of the USB passage is maintained, so that all or part of functions of the functional chip in the terminal equipment can be used by equipment connected with the USB interface, or the terminal equipment can be charged normally by a power supply connected with the USB interface.

In one possible implementation, the USB interface protection circuit further includes a second protection device group; the second protection device group is arranged between the common-mode inductor and the functional chip; the second protection device is used for overvoltage shutoff protection of the USB access.

That is, aiming at the scene that the TVS inside the functional chip has higher clamping starting voltage or long-time Direct Current (DC) is abnormally injected, the abnormal channel can be timely cut off through the second protection device group so as to ensure the safety of the functional chip inside the terminal equipment.

In one possible implementation, the second protection device group includes: a voltage dividing resistor and a comparator; the first end of the voltage dividing resistor is connected with the input end of the notch network in the USB access, and the second end of the voltage dividing resistor is grounded; the divider resistor is used for reducing the input voltage of the notch network; the input end of the comparator is connected with the second end of the divider resistor, and the output end of the comparator is connected with the signal switching element in the USB channel; the comparator is used for switching off the signal switching element when the input voltage of the notch network is larger than a preset switching-off voltage threshold value so as to disconnect the USB access.

Therefore, through the combination of the voltage dividing resistor and the comparator, the abnormal passage can be cut off in time, meanwhile, the stability of the voltage in the USB passage is ensured, and the damage of devices in the USB passage and even functional chips caused by overvoltage is avoided.

In one possible implementation, the second protection device group further includes: a second TVS; the first end of the second TVS is connected with the signal switching element, and the second end of the second TVS is grounded; the second TVS is used for adjusting the voltage value flowing into the functional chip to be in a preset safe voltage range.

Therefore, the voltage in the abnormal channel is adjusted through the second TVS, so that the safety of the functional chip is ensured, and the situation that the functional chip is damaged due to overvoltage of the USB channel is avoided.

In one possible implementation, the functional chip includes a power management integrated circuit; the USB interface protection circuit further includes: a first magnetic bead; the first magnetic beads are used for inhibiting high-frequency noise in the USB access, and the maximum resistance value of the first magnetic beads meets the loop impedance detection requirement of a battery charging protocol in terminal equipment; the first end of the first magnetic bead is connected with a signal switching element in the USB channel, and the second end of the first magnetic bead is connected with the power management integrated circuit.

The magnetic beads have smaller resistance under the action of direct current injection or low-frequency signals, so that the detection requirement of loop impedance during charging of terminal equipment can be met; and the magnetic beads have the characteristic of larger resistance under the action of high-frequency signals, so that the requirement of isolating the power management integrated circuit under the condition of abnormal access can be met. Therefore, the first magnetic beads are arranged at the input end of the power management integrated circuit, so that high-frequency noise and peak interference in a USB (universal serial bus) access can be restrained, and the safety of the power management integrated circuit is ensured; the terminal device can be normally charged.

In one possible implementation, the functional chip includes a power management integrated circuit; the USB interface protection circuit further includes: a second resistor and a second magnetic bead; the second magnetic beads are used for inhibiting high-frequency noise in the USB access, and the maximum resistance of the second magnetic beads and the total resistance of the second resistor meet the loop impedance detection requirement of a battery charging protocol in the terminal equipment; the first end of the second resistor is connected with the signal switching element in the USB passage, the second end of the second resistor is connected with the first end of the second magnetic bead, and the second end of the second magnetic bead is connected with the power management integrated circuit.

Similarly, the magnetic beads have smaller resistance under the action of the low-frequency signal and larger resistance under the action of the high-frequency signal, so that the input end of the power management integrated circuit adopts a magnetic bead string small resistance mode, thereby not only inhibiting high-frequency noise and peak interference in a USB (universal serial bus) channel, ensuring the safety of the power management integrated circuit, but also ensuring the normal charging of terminal equipment.

In a second aspect, the present application further provides a terminal device, including:

a USB interface;

at least one functional chip;

the USB interface is connected with the functional chip through a USB access;

a USB interface protection circuit according to any one of claims 1 to 9 for short-circuit protection and/or overload protection of devices in a USB path.

Therefore, by arranging the USB interface protection circuit on the USB access, devices in the USB access can be effectively protected, and damage to the functional chip caused by abnormality of the USB access is avoided.

Drawings

Fig. 1 is a schematic diagram of a hardware structure of a terminal device according to an exemplary embodiment of the present application;

FIG. 2 is a pin distribution diagram of a USB interface according to an exemplary embodiment of the present application;

FIG. 3 is a schematic device distribution diagram of a USB channel according to an exemplary embodiment of the present application;

FIG. 4 is a schematic diagram of a first USB interface protection circuit according to an exemplary embodiment of the present application;

FIG. 5 is a schematic diagram of a second USB interface protection circuit according to an exemplary embodiment of the present application;

FIG. 6 is a schematic diagram of a third USB interface protection circuit according to an exemplary embodiment of the present application;

FIG. 7 is a schematic diagram of a fourth USB interface protection circuit according to an exemplary embodiment of the present application;

FIG. 8 is a schematic diagram of a fifth USB interface protection circuit according to an exemplary embodiment of the present application;

FIG. 9 is a schematic diagram of a USB interface charging path according to an exemplary embodiment of the present application;

FIG. 10 is a schematic diagram of a sixth USB interface protection circuit according to an exemplary embodiment of the present application;

FIG. 11 is a schematic diagram of a seventh USB interface protection circuit according to an exemplary embodiment of the present application;

fig. 12 is a schematic diagram of an eighth USB interface protection circuit according to an exemplary embodiment of the present application.

Detailed Description

In order to make the objects, device structures and advantages of the present application more apparent, the structures of the wearable device provided by the present application will be described in further detail with reference to the accompanying drawings and embodiments.

With the continuous development of intelligent terminal technology, a universal serial bus (Universal Serial Bus, USB) interface has become an interface widely used on portable terminal devices. The terminal equipment can carry out data communication with other external equipment based on the USB interface, and can also be connected with other external equipment or power supply through the USB interface to charge the terminal equipment.

The terminal device may be implemented in various forms, and for example, the terminal device described in the present application may include a mobile phone, a tablet computer, a notebook computer, a palm computer, a personal digital assistant (Personal Digital Assistant, PDA), a portable media player (Portable Media Player, PMP), a navigation device, a wearable device, a smart bracelet, a pedometer, and the like.

Referring to the hardware architecture diagram of the terminal device shown in fig. 1, the terminal device 100 may include: an RF (Radio Frequency) unit 101, a wireless fidelity (Wireless Fidelity, wiFi) module 102, an Audio output unit 103, an Audio/Video (a/V) input unit 104, a sensor 105, a display unit 106, a user input unit 107, an interface unit 108, a memory 109, a processor 110, a power supply 111, and the like.

It should be understood that the structure of the terminal device 100 shown in fig. 1 does not constitute a limitation of the terminal device, and the terminal device 100 may include more or less components, or may combine some components, or may be configured in different manners when implemented in particular.

Next, the functions of the respective components in the terminal device 100 will be briefly described with reference to fig. 1.

The radio frequency unit 101 may be used for receiving and transmitting information or signals during communication. Specifically, the downlink information sent by the uplink communication device is received and then sent to the processor 110 for processing; and simultaneously, sending the uplink data to the uplink communication equipment.

In some embodiments, the radio frequency unit 101 includes, but is not limited to, an antenna, at least one amplifier, a transceiver, a coupler, a low noise amplifier, a duplexer, and the like. In addition, the radio frequency unit 101 may also communicate with networks and other devices via wireless communications. The wireless communications may use any communication standard or protocol including, but not limited to, global System for Mobile communications (Global System of Mobile communication, GSM), general packet radio service (General Packet Radio Service, GPRS), code Division multiple Access 2000 (Code Division Multiple Access, CDMA2000), wideband code Division multiple Access (Wideband Code Division Multiple Access, WCDMA), time Division synchronous code Division multiple Access (Time Division-Synchronous Code Division Multiple Access, TD-SCDMA), frequency Division Duplex Long term evolution (Frequency Division Duplexing-Long Term Evolution, FDD-LTE), time Division Duplex Long term evolution (Time Division Duplexing-Long Term Evolution, TDD-LTE), and the like.

WiFi belongs to a short-distance wireless transmission technology, and the terminal equipment 100 can help a user to send and receive e-mails, browse web pages, access streaming media and the like through the WiFi module 102, so that wireless broadband Internet access is provided for the user.

It should be noted that although fig. 1 shows the WiFi module 102, it does not belong to the essential structure of the terminal device 100, and the WiFi module 102 may be omitted without affecting the core functions of the terminal device 100.

The audio output unit 103 may convert audio data received by the radio frequency unit 101 or the WiFi module 102 or stored in the memory 109 into an audio signal and output as sound when the terminal device 100 is in a call signal reception mode, a talk mode, a recording mode, a voice recognition mode, a broadcast reception mode, or the like.

Further, the audio output unit 103 may also provide audio output (e.g., a call signal reception sound, a message reception sound, etc.) related to a specific function performed by the terminal device 100.

In some embodiments, the audio output unit 103 may include a speaker, a buzzer, and the like.

The a/V input unit 104 is used to receive an audio or video signal. The a/V input unit 104 may include a graphics processor (Graphics Processing Unit, GPU) and a microphone,

Wherein the graphics processor processes image data of still pictures or video obtained by an image capturing device (such as a camera) in a video capturing mode or an image capturing mode, the processed image frames may be displayed on the display unit 106. The image frames processed by the graphics processor may be stored in memory 109 (or other storage medium) or transmitted via radio frequency unit 101 or WiFi module 102.

Wherein the microphone can receive sound (audio data) via the microphone in a phone call mode, a recording mode, a voice recognition mode, and the like operation mode, and can process the sound into audio data. The processed audio (voice) data may be converted into a format output that can be transmitted to a communication base station via the radio frequency unit 101 in the case where the terminal device 100 is in a communication mode.

In addition, the microphone may implement various types of noise canceling (or suppressing) algorithms to cancel (or suppress) noise or interference generated in the course of receiving and transmitting the audio signal.

The terminal device 100 further comprises at least one sensor 105, such as a light sensor, a motion sensor and other sensors. Specifically, the light sensor includes an ambient light sensor and a proximity sensor, wherein the ambient light sensor can adjust the brightness of the display panel according to the brightness of ambient light, and the proximity sensor can turn off the display panel and/or the backlight when the terminal device 100 moves to the ear of the user. The accelerometer sensor can detect the acceleration in all directions (generally three axes) and the gravity in a static state, and can be used for the application of recognizing the gesture of equipment, vibration recognition related functions and the like.

In addition, the terminal device 100 may further include other sensors such as fingerprint sensor, pressure sensor, iris sensor, molecular sensor, gyroscope, barometer, hygrometer, thermometer, infrared sensor, etc., which are not described herein.

The display unit 106 is used to display information input by a user or information provided to the user. The display unit 106 may include a display panel, which may be configured in the form of a liquid crystal display (Liquid Crystal Display, LCD), an Organic Light-Emitting Diode (OLED), or the like.

The user input unit 107 may be used to receive input numeric or character information and to generate key signal inputs related to user settings and function control of the terminal device 100. In particular, the user input unit 107 may include a touch panel and other input devices.

The touch panel, also called a touch screen, can collect touch operations on or near the touch panel by a user and drive the corresponding connection device according to a preset program. The touch panel may include two parts, a touch detection device and a touch controller. The touch detection device detects the touch azimuth of a user, detects a signal brought by touch operation and transmits the signal to the touch controller; the touch controller receives touch information from the touch detection device, converts it into touch point coordinates, and sends the touch point coordinates to the processor 110, and can receive and execute commands sent from the processor 110. In addition, the touch panel may be implemented in various types such as resistive, capacitive, infrared, and surface acoustic wave.

Further, the user input unit 107 may also include other input devices including, but not limited to, one or more of a physical keyboard, function keys (e.g., volume control keys, switch keys, etc.), a track ball, a mouse, a joystick, etc., without limitation.

In addition, the touch panel may cover the display panel, and when the touch panel detects a touch operation thereon or thereabout, the touch panel is transferred to the processor 110 to determine the type of touch event, and then the processor 110 provides a corresponding visual output on the display panel according to the type of touch event.

It should be noted that, although in fig. 1, the touch panel and the display panel are two independent components to implement the input and output functions of the mobile terminal, in some embodiments, the touch panel and the display panel may be integrated to implement the input and output functions of the terminal device 100, which is not limited.

The interface unit 108 serves as an interface through which at least one external device can be connected to the terminal apparatus 100. For example, the external device may include a wired or wireless headset port, an external power (or battery charger) port, a wired or wireless data port, a memory card port, a port for connecting a device having an identification module, an audio Input/Output (I/O) port, a video I/O port, an earphone port, a USB interface, and the like.

Specifically, the interface unit 108 may be used to receive input (e.g., data information, power, etc.) from an external device and transmit the received input to one or more elements within the terminal apparatus 100 or may be used to transmit data between the terminal apparatus 100 and the external device.

In some embodiments, the interface unit 108 includes a USB interface, which is an input/output interface for connecting the mobile terminal with an external device, and has various interface types, such as Mini-USB, micro-USB, type-A, type-B, type-C interface, and the like.

Taking the Type-C interface as an example, referring to fig. 2, the Type-C interface uses two groups of pins that are symmetrical up and down, and this design provides a basis for distinguishing between the front and back sides. Based on the original pins, the following pins are added to the Type-C:

(1) A configuration channel (Configuration channel, CC) pin is added for detecting whether the USB device is accessed; detecting the insertion direction of the USB, and establishing a route of a USB data channel according to the detection; after insertion, helping to establish a master-slave relationship between USB devices; discovering and configuring VBUS (VBUS is a power line for supplying power to the USB slave device by the USB master device), and configuring a PD power supply mode of the USB interface; optional standby and auxiliary modes are discovered and configured.

(2) SBU expansion pins are added, and the SBU expansion pins can be used in special signal transmission;

(3) Tx/Rx is a newly added data transmission pin;

(4) D+ and D-differential signal lines are reserved in Type-C for compatibility with older versions.

In addition, the number of the power line VBus and the ground line GND in the Type-C interface is 4, and good physical support is provided for high-current and high-power output of the Type-C interface.

Memory 109 may be used to store software programs as well as various data. In the present invention, the memory 109 of the terminal device 100 stores an application quick start program. The memory 109 may mainly include a storage program area that may store an operating system, application programs required for at least one function (such as a sound playing function, an image playing function, etc.), and a storage data area; the storage data area may store data (such as audio data, phonebook, etc.) created according to the use of the terminal device 100, and the like.

As one example, memory 109 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device.

The processor 110 is a control center of the terminal device 100, connects respective parts of the entire terminal device 100 using various interfaces and lines, and performs various functions of the terminal device 100 and processes data by running or executing software programs and/or modules stored in the memory 109 and calling data stored in the memory 109, thereby performing overall monitoring of the terminal device 100.

Wherein the processor 110 may include one or more processing units. The processor 110 may integrate an application processor that primarily handles operating systems, user interfaces, applications, etc., with a modem processor that primarily handles wireless communications.

It should be noted that, the modem processor may not be integrated into the processor 110, and may be deployed in a stand-alone manner.

The terminal device 100 may also include a power source 111 (e.g., a battery) to power the various components. The power supply 111 may be logically connected to the processor 110 through a power management system, so that functions of managing charging, discharging, power consumption management, etc. are implemented through the power management system. Specifically, the power supply 111 is an internal power management module.

Based on the structure of the terminal device 100, the USB interface is used as an input/output interface for connecting the terminal device with an external device, a power supply, a charger, etc., and is easy to wear due to repeated plugging and unplugging in the use process, so that the USB interface is in micro-short circuit or even short circuit. Under the condition of short circuit or overload of the USB interface, when the terminal equipment is charged or signal transmission is carried out through the USB interface, the USB interface is heated, then the USB interface is burnt out, devices in a USB channel connected with the USB interface are burnt out, and functional chips in the terminal equipment are burnt out, so that the safety of the terminal equipment is seriously affected.

Referring to fig. 3, in the terminal device 200, including a USB interface 210 and at least one functional chip 220, a common mode inductor 231, a notch network 232, a signal switching element 233, and the like are connected in series to a USB path connecting the USB interface 210 and the functional chip 220.

The signal switching element may be implemented by a MOS transistor, or may be implemented by other switching elements, which is not limited in the present application.

When DP and DM (Digital Positive & Digital Minus; DM is a data line D of USB, DP is a data line d+ of USB interface 210, DP and DM are paths corresponding to a differential signal pair), or the SBU pin and the VBUS pin in USB interface 210 are shorted, a loop is likely to be formed with transient diodes (Transient Voltage Suppressor, TVS) in functional chip 220 or other modules inside terminal device 200 due to poor current capacity of common mode inductor 231, notch network 232, signal switching element 233, and the like, which causes irreversible damage to functional chip 220, resulting in failure of related functions of USB interface 210.

Based on the protection circuit, the application provides a protection circuit for the USB interface, and a small number of protection devices are added in the USB access to effectively protect the devices in the USB access and functional chips in terminal equipment, so that the functions of the USB interface can be normally used.

Next, a technical solution of the embodiment of the present application and how the technical solution of the embodiment of the present application solves the above technical problems will be described in detail with reference to the accompanying drawings. The embodiments shown below may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

In the following embodiments, the USB interface protection path provided by the present application is applied to the terminal device 200, where the terminal device 200 includes a USB interface 210 and at least one functional chip 220, and the USB interface 210 is connected to the functional chip 220 through the USB path.

It should be noted that, in the drawings corresponding to the embodiments described below, only the deployment mode and the deployment position of the devices in the USB interface protection circuit provided by the present application on the USB path are illustrated, and with respect to the deployment position of the original devices in the USB path, reference may be made to fig. 3, which is not repeated in the following.

In an exemplary embodiment, as shown in fig. 4, the USB interface protection circuit 240 includes a first protection device group 241; the first protection device set 241 is disposed between the USB interface and the common mode inductor in the USB path, and is used for performing fuse protection on the USB path.

In one possible implementation, the first protection device group 241 includes an auto-recovery fuse 2411 and a voltage stabilizing element 2412, the voltage stabilizing element 2412 includes any one of a varistor and a first transient diode TVS.

That is, the first protection device group may be composed of an automatic restoration fuse and a first TVS, or may be composed of an automatic restoration fuse and a varistor, which is not limited in this embodiment.

The first end of the automatic recovery fuse is connected with the USB interface, and the second end of the automatic recovery fuse is connected with the voltage stabilizing element group. Specifically, the automatic recovery fuse is used for increasing the impedance value of the automatic recovery fuse when the USB access is short-circuited or the current flowing into the USB access is larger than the access current threshold value of the USB access so as to reduce the current value flowing into the common-mode inductor. The voltage stabilizing element group is used for stabilizing the output voltage of the second end of the automatic recovery fuse to be in the working voltage range of the common mode inductance.

It should be appreciated that self-healing fuses are typically composed of specially treated polymeric resin (Polymer) and conductive particles (Carbon Black) distributed therein. Under normal operation, the polymer resin tightly binds the conductive particles outside the crystalline structure to form a chain-shaped conductive path, the self-recovery fuse at the moment is in a low-resistance state, and the heat energy generated by the current flowing through the self-recovery fuse on the line is small, so that the crystal structure is not changed. When the circuit is short-circuited or overloaded, the high current flowing through the self-recovery fuse causes the polymeric resin to melt, the volume of the polymeric resin to be rapidly increased, a high-resistance state is formed, and the working current is rapidly reduced, so that the circuit is limited and protected. After the fault is removed, the self-recovery fuse is cooled again for crystallization, the volume is contracted, the conductive particles form a conductive path again, and the self-recovery fuse is recovered to a low-resistance state, so that the protection of a circuit is finished, and manual replacement is not needed.

Therefore, the automatic recovery fuse is arranged on the USB access, the temperature of the USB access is lower when the USB access works normally, the heat generated on the USB access and the heat emitted by the USB access reach balance, the automatic recovery fuse element is in a low-resistance state, and the automatic recovery fuse does not act. When the USB interface is short-circuited or overloaded, the current flowing through the automatic recovery fuse generates a certain degree of heat (the automatic recovery fuse has a resistance value) due to the relation of the current thermal effect, and all or part of the generated heat is dissipated into the environment, so that the temperature of the automatic recovery fuse element can be increased without the dissipated heat. As the current flowing into the automatic recovery fuse through the USB interface increases or the ambient temperature increases, the heat generated by the automatic recovery fuse is larger than the heat emitted, so that the temperature of the automatic recovery fuse element increases suddenly and is in a high-resistance protection state. At this time, the increase in impedance limits the current so that the current in the USB path can drop sharply in a short time, thereby protecting the devices in the USB path from damage. When the voltage applied by the USB interface disappears, the automatic recovery fuse can automatically recover to a low-resistance state.

Furthermore, the piezoresistor belongs to an overvoltage protection element and is used for clamping voltage when the USB interface bears overvoltage, and absorbing redundant current to protect sensitive devices. The TVS belongs to a diode type high-efficiency protection device, when the two poles of the TVS diode are impacted by reverse transient high energy, the high resistance between the two poles of the TVS diode can be quickly changed into low resistance, the surge power of thousands of watts is absorbed, the voltage clamp between the two poles is positioned at a preset value, and the device in a USB channel is effectively protected from being damaged by various surge pulses.

As an example, the first TVS may employ a unidirectional TVS tube, or a bidirectional TVS tube, which is not limited in this embodiment.

After setting the auto-recovery fuse, the voltage in the USB path may be further stabilized by setting the voltage stabilizing element group 2412. Referring to fig. 4, the USB path includes a first path (DP line or DM line in fig. 4) between a first pin of the USB interface and the functional chip and a second path (DM line or DP line in fig. 4) between a second pin of the USB interface and the functional chip.

As an example, if the USB interface is a Type-C interface, the first pin and the second pin are symmetrical, and the signals transmitted in the first path and the second path are one differential signal pair.

It should be noted that, to ensure that the voltage between the single path and the paths are all in a stable state, the voltage stabilizing element group 2412 provided in the present application may include a first voltage stabilizing element, a second voltage stabilizing element, and a third voltage stabilizing element.

In one possible implementation, as shown in fig. 4, the voltage stabilizing element group 2412 may be disposed in the USB path in the following manner: the first end of the first voltage stabilizing element is connected with the second end of the automatic recovery fuse in the first passage, and the second end of the first voltage stabilizing element is grounded; the first end of the second voltage stabilizing element is connected with the second end of the automatic restoration fuse in the second path, and the second end of the second voltage stabilizing element is grounded; one end of the third voltage stabilizing element is connected with the first passage, and the other end of the third voltage stabilizing element is connected with the second passage.

In another possible implementation, referring to fig. 5, the voltage stabilizing element group 2412 may be disposed in the USB path in the following manner: the first end of the first voltage stabilizing element is connected with the output end of the common mode inductor, and the second end of the first voltage stabilizing element is grounded; the first end of the second voltage stabilizing element is connected with the output end of the common mode inductor, and the second end of the second voltage stabilizing element is grounded; one end of the third voltage stabilizing element is connected with the first passage, and the other end of the third voltage stabilizing element is connected with the second passage.

It should be noted that, whether the voltage stabilizing element group is disposed at the input end of the common-mode inductor or the output end of the common-mode inductor depends on the maximum current value that the common-mode inductor can bear in the USB path. If the current value flowing through the automatic recovery fuse is smaller than the maximum current value which can be born by the common-mode inductor, the voltage stabilizing element group is arranged at the output end of the common-mode inductor; if the current value flowing through the automatic recovery fuse is greater than or equal to the maximum current value which can be born by the common-mode inductor, the voltage stabilizing element group is arranged at the input end of the common-mode inductor so as to play a role in protecting the common-mode inductor.

It should be understood that fig. 4 and 5 are only illustrated with the first voltage stabilizing element, the second voltage stabilizing element, and the third voltage stabilizing element each being a varistor. In practical applications, the varistor may be replaced by the first TVS.

Further, based on the first protection device group in the USB access, when the USB interface has abnormal high voltage or has short circuit, the automatic recovery fuse is automatically disconnected; or, after the voltage dependent resistor/the first TVS is triggered, the fuse is automatically restored to be disconnected, so that the function of protecting a back-end device is achieved, and when the voltage is removed, the fuse is automatically restored, and irreversible damage cannot be generated.

When the device is specifically set, the action current of the automatic recovery fuse needs to be ensured to be far smaller than the damage current of the back-end device, and meanwhile, in order to ensure the high-speed communication performance of the USB access, the action current of the automatic recovery fuse is ensured to be larger than a preset minimum current threshold so as not to influence the performance of the USB access.

In addition, the first protection device set may also be applied to an external circuit of the SBU pin in the USB interface, which is not described herein.

In the first protection device group provided in this embodiment, since the common-mode inductance is a front-end device connected to the USB interface in the USB path, when the USB interface is shorted or overloaded, and an excessive current flows into the USB path, all devices in the USB path and functional chips inside the terminal device can be effectively protected by the first protection device group. When the first protection device group protects the USB access, a fusing protection mode is adopted, so that under the condition that the USB interface is short-circuited or overloaded, the high current in the USB access is reduced by increasing the impedance of the first protection device group. And, in the case that the current in the USB path is stable, the first protection device group is restored to the low impedance state. Thus, based on the first protection device group, the functional chips in the USB access and the terminal equipment can be continuously protected.

In another exemplary embodiment, as shown in fig. 6, the USB interface protection circuit 240 provided by the present application further includes a first resistor 242; the first resistor 242 is connected in parallel with the common mode inductance.

Specifically, the first resistor 242 is used to maintain the electrical connection between the USB interface and the functional chip after the single-path common-mode inductance in the USB path is disconnected.

In this embodiment, the first resistor connected in parallel with the common-mode inductor may form a path between the USB interface and the functional chip under the condition that the common-mode inductor is abnormal, so as to maintain normal operation of the USB path, so that all or part of functions of the functional chip in the terminal device may be used by the device connected with the USB interface, or the terminal device may be charged by the power supply connected with the USB interface.

Based on any of the embodiments, for the scenario of higher TVS clamping starting voltage in the USB path, or the scenario of long-time Direct Current (DC) abnormal injection, the abnormal path needs to be completely cut off, so as to ensure the safety of the functional chip.

Based on this, in an exemplary embodiment, as shown in fig. 7, the USB interface protection circuit 240 provided by the present application further includes a second protection device group 243; wherein the second protection device group 243 is disposed between the common mode inductor and the functional chip; the second protection device is used for overvoltage shutoff protection of the USB access.

In one possible implementation, the second set of protection devices 243 includes a divider resistor 2431 and a comparator 2432.

The first end of the voltage dividing resistor is connected with the input end of the notch network in the USB access, and the second end of the voltage dividing resistor is grounded; the input end of the comparator is connected with the second end of the divider resistor, and the output end of the comparator is connected with the signal switching element in the USB channel.

Specifically, in the USB path, the voltage dividing resistor is used to reduce the input voltage of the notch network, and the comparator is used to turn off the signal switching element to disconnect the USB path when the input voltage of the notch network is greater than a preset turn-off voltage threshold.

As one example, the turn-off voltage threshold may be determined based on a normal operating threshold of the notch network and a preset control margin.

In some embodiments, the number of the voltage dividing resistors is three, and each USB path is connected with 2 voltage dividing resistors so as to reduce the voltage value of the input end of the notch network; meanwhile, an amplifier is connected with the voltage dividing resistors of the first path and the second path to determine whether the voltage value in each path is larger than a preset turn-off voltage threshold. And when the voltage value in the channel is larger than the turn-off voltage threshold value, the signal switching element is turned off to thoroughly disconnect the abnormal channel.

It should be noted that, in practical applications, the first path and/or the second path may be controlled by the comparator to switch off. The comparator can also be realized by an operational amplifier so as to achieve the effect of controlling the switching element to be switched off.

As an example, the voltage dividing resistor is preferably a resistor with a large resistance value of more than hundred K levels, so that the quality of high-speed signals in the USB path is not affected. The comparator or the operational amplifier also adopts a high-speed device, and meanwhile, the voltage withstand of the signal switching element is ensured to be reduced, and then the voltage withstand of 20VDC (direct current voltage is 20 volts) is required to be met.

Therefore, through the combination of the voltage dividing resistor and the comparator, not only can the abnormal channel be cut off in time, but also the stability of the voltage in the channel can be ensured, and other devices in the USB channel, even functional chips, are prevented from being damaged by overvoltage.

Further, if a voltage in the USB path is divided by the voltage dividing resistor, and then a voltage inputted to the notch network and thus a voltage in the functional chip is greatly changed, a voltage stabilizing element needs to be provided in the USB path to stabilize the voltage in the path.

In one possible implementation, as shown in fig. 8, the second protection device group 243 further includes: a second TVS (2433 shown in fig. 8); the first end of the second TVS is connected with the signal switching element, and the second end of the second TVS is grounded. The second TVS is used for adjusting the voltage value flowing into the functional chip to be in a preset safe voltage range.

It should be noted that the second TVS may be a unidirectional TVS tube or a bidirectional TVS tube, which is not limited in this embodiment. Fig. 8 is illustrated with a unidirectional TVS tube only and is not intended to limit that it must be a unidirectional TVS tube.

Based on any of the above embodiments, the functional Chip in the embodiments of the present application may include a Power Management Integrated Circuit (PMIC) and a System on a Chip (SOC). The first path and the second path are both connected with the PMIC and the SOC.

In some embodiments, if the first resistors are connected in parallel to two ends of the common-mode inductor, the charging function of the terminal device can be maintained through the first resistors after the single-path common-mode inductor is disconnected.

Referring to fig. 9, in the device fast charge scenario, an isolation resistor with a preset resistance is generally used to isolate the USB path from the PMIC, so as to ensure the quality of the USB eye pattern. However, when the common-mode inductances of the first and second paths are both disconnected, the resistance of the entire USB total loop cannot meet the condition of PMIC detection BC1.2 (i.e., battery fast charge protocol), resulting in a failure to rapidly charge the terminal device through the USB interface.

In an exemplary embodiment, in order to solve the above-mentioned problems, the present application uses magnetic beads to replace isolation resistors, or uses a small-resistance magnetic bead string to reduce DC impedance while meeting the impedance requirement of the USB eye diagram.

In addition, the magnetic beads have very low impedance under the action of direct current injection or low-frequency signals, the requirement of loop impedance detection can be met, BC1.2 can be accurately identified, and PMIC can be effectively isolated when the USB access is abnormal.

In one possible implementation, as shown in fig. 10, the USB interface protection circuit 240 provided by the present application further includes: first magnetic beads 244; the first magnetic bead 244 is used for suppressing high-frequency noise in the USB path, and the maximum resistance of the first magnetic bead meets the loop impedance detection requirement of the battery charging protocol in the terminal device; the first end of the first magnetic bead 244 is connected to a signal switching element in the USB path, and the second end of the first magnetic bead 244 is connected to a power management integrated circuit.

In another possible implementation manner, as shown in fig. 11, the USB interface protection circuit 240 provided by the present application further includes: a second resistor 245 and a second magnetic bead 246; the second magnetic bead 246 is used for suppressing high-frequency noise in the USB path, and the maximum resistance value of the second magnetic bead 246 and the total resistance value of the second resistor 245 meet the loop impedance detection requirement of the battery charging protocol in the terminal device; the first end of the second resistor 245 is connected to the signal switching element in the USB path, the second end of the second resistor bead 245 is connected to the first end of the second magnetic bead 246, and the second end of the second magnetic bead 246 is connected to the power management integrated circuit.

It should be noted that, on the premise of ensuring that the maximum resistance value of the second magnetic bead and the total resistance value of the second resistor meet the loop impedance detection requirement of the battery charging protocol in the terminal equipment, the resistance value of the second resistor may be smaller.

In this embodiment, the magnetic beads have smaller resistance under the action of the low-frequency signal and larger resistance under the action of the high-frequency signal, so that the input end of the power management integrated circuit adopts a magnetic bead string resistance mode, which not only can inhibit high-frequency noise and peak interference in the USB path, but also can ensure the safety of the power management integrated circuit and ensure that the terminal equipment can be charged normally.

In summary, as shown in fig. 12, the present application provides a terminal device, where the terminal device includes an SB interface and at least one functional chip, and the USB interface is connected to the functional chip through a USB path.

The USB interface protection circuit comprises a first protection device group, a first resistor, a second protection device group and magnetic beads, so that the USB access is subjected to fusing protection, overvoltage shutoff and supplementary optimization (magnetic beads), devices in the USB access are effectively protected, and meanwhile safety of a USB interface and an internal functional chip in the terminal equipment is guaranteed.

It should be noted that, the deployment manner and the function of the device shown in fig. 12 may be referred to the above embodiments, and will not be described herein.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The foregoing is merely a specific implementation of the embodiment of the present application, and is not intended to limit the scope of the embodiment of the present application, and any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solution of the embodiment of the present application should be included in the scope of the embodiment of the present application.

Claims

1. The USB interface protection circuit is characterized by being applied to terminal equipment, wherein the terminal equipment comprises a USB interface and at least one functional chip, and the USB interface is connected with the functional chip through a USB access; the USB interface protection circuit comprises a first protection device group;

the first protection device group is arranged between the USB interface and the common mode inductor in the USB access; the first protection device group is used for fusing and protecting the USB access.

2. The USB interface protection circuit according to claim 1 wherein the first protection device group includes an auto-recovery fuse and a voltage stabilizing element group including any one of a varistor and a first transient diode TVS;

the first end of the automatic recovery fuse is connected with the USB interface, and the second end of the automatic recovery fuse is connected with the voltage stabilizing element group;

the automatic recovery fuse is used for increasing the impedance value of the automatic recovery fuse when the USB access is short-circuited or the current flowing into the USB access is larger than the access current threshold value of the USB access so as to reduce the current value flowing into the common-mode inductor; the voltage stabilizing element group is used for stabilizing the output voltage of the second end of the automatic recovery fuse to be in the working voltage range of the common mode inductor.

3. The USB interface protection circuit of claim 2, wherein the USB path includes a first path between a first pin of the USB interface and the functional chip and a second path between a second pin of the USB interface and the functional chip, the voltage stabilizing element group includes a first voltage stabilizing element, a second voltage stabilizing element, and a third voltage stabilizing element;

the first end of the second voltage stabilizing element is connected with the second end of the automatic restoration fuse in the second passage, and the second end of the second voltage stabilizing element is grounded;

4. A USB interface protection circuit according to any one of claims 1 to 3 wherein the USB interface protection circuit further comprises: a first resistor; the first resistor is connected with the common mode inductor in parallel; the first resistor is used for maintaining the electric connection between the USB interface and the functional chip after the single-path common mode inductance in the USB path is disconnected.

5. The USB interface protection circuit of claim 4, further comprising a second set of protection devices;

the second protection device group is arranged between the common-mode inductor and the functional chip; the second protection device is used for performing overvoltage shutoff protection on the USB access.

6. The USB interface protection circuit of claim 5, wherein the second protection device group comprises: a voltage dividing resistor and a comparator;

the first end of the voltage dividing resistor is connected with the input end of the notch network in the USB access, and the second end of the voltage dividing resistor is grounded; the divider resistor is used for reducing the input voltage of the notch network;

the input end of the comparator is connected with the second end of the divider resistor, and the output end of the comparator is connected with the signal switching element in the USB channel; the comparator is used for turning off the signal switching element when the input voltage of the notch network is larger than a preset turn-off voltage threshold value so as to disconnect the USB access.

7. The USB interface protection circuit of claim 6, wherein the second protection device group further comprises: a second TVS; a first end of the second TVS is connected with the signal switching element, and a second end of the second TVS is grounded;

the second TVS is configured to adjust the voltage value flowing into the functional chip to be within a preset safe voltage range.

8. The USB interface protection circuit of claim 4, wherein the functional chip includes a power management integrated circuit; the USB interface protection circuit further includes: a first magnetic bead; the first magnetic beads are used for inhibiting high-frequency noise in the USB access, and the maximum resistance of the first magnetic beads meets the loop impedance detection requirement of a battery charging protocol in the terminal equipment;

The first end of the first magnetic bead is connected with the signal switching element in the USB channel, and the second end of the first magnetic bead is connected with the power management integrated circuit.

9. The USB interface protection circuit of claim 4, wherein the functional chip includes a power management integrated circuit; the USB interface protection circuit further includes: a second resistor and a second magnetic bead; the second magnetic beads are used for inhibiting high-frequency noise in the USB access, and the maximum resistance of the second magnetic beads and the total resistance of the second resistor meet the loop impedance detection requirement of a battery charging protocol in the terminal equipment;

the first end of the second resistor is connected with the signal switching element in the USB channel, the second end of the second resistor is connected with the first end of the second magnetic bead, and the second end of the second magnetic bead is connected with the power management integrated circuit.

10. A terminal device, comprising:

a USB interface;

at least one functional chip;

the USB interface is connected with the functional chip through a USB access;

a USB interface protection circuit according to any one of claims 1 to 9 for short-circuit protection and/or overload protection of devices in the USB path.