A protection circuit of a fast charging protocol chip

Abstract

The application discloses a protection circuit of a fast charging protocol chip. The circuit comprises a voltage regulating module, an optocoupler control module, a protection voltage dividing module and a power supply state switching module. The voltage regulating module outputs an internal power supply and a voltage regulating control signal based on a power input terminal. The optocoupler control module is connected between an optocoupler control terminal and a ground terminal, and is used for controlling an external optocoupler feedback branch current. When the internal power supply normally outputs, the voltage regulating module performs normal voltage regulating control on the optocoupler control module. When the internal power supply stops outputting due to a fault, the power supply state switching module responds to a potential change, connects the protection voltage dividing module to the optocoupler control module, and transmits a corresponding voltage dividing voltage of the optocoupler control terminal to the control terminal of the optocoupler control module. The application utilizes an internal resistance network and MOS tube characteristics to form a negative feedback, avoids the problem that the output voltage continuously increases due to the failure of the internal power supply of the chip, effectively prevents the burning of a charging device, and significantly improves the safety of the fast charging system.

Description

Technical Field

[0001] This invention relates to the field of integrated circuits and charging protection technology, and in particular to a protection circuit for a fast charging protocol chip. Background Technology

[0002] Currently, the normal operation of fast charging protocol chips heavily relies on the power supplied by the power input terminal (VIN). In practical applications, when chip pins suffer electrostatic discharge damage, short circuits, or poor soldering, the protocol chip cannot generate internal power. In this failure state, core control units such as the error amplifier inside the chip will malfunction, thus losing the ability to regulate the AC-DC (alternating current to DC) output. Due to the lack of effective failure protection measures in existing technology, once the aforementioned internal control failure occurs, the voltage of the input power supply often becomes uncontrolled and continues to rise, ultimately easily leading to the burnout of the charging device or connected terminal receiving equipment, posing a serious safety hazard. Summary of the Invention

[0003] This invention provides a protection circuit for a fast charging protocol chip. In extreme cases where the internal power supply of the fast charging protocol chip stops due to pin failure, the circuit can respond to potential changes in a timely and autonomous manner and take over control. Through a purely hardware-level negative feedback mechanism, the output voltage is effectively clamped to prevent the output voltage from soaring uncontrollably, thereby avoiding the burning out of the charging device.

[0004] In a first aspect, the present invention provides a protection circuit for a fast charging protocol chip, having an optocoupler control terminal and a ground terminal. The protection circuit includes a voltage regulation module, an optocoupler control module, a protection voltage divider module, and a power supply state switching module.

[0005] The input terminal of the voltage regulating module is connected to the power input terminal, and the output terminal is connected to the optocoupler control module. The voltage regulating module has an internal power supply terminal and is used to output a voltage regulation control signal according to the voltage of the power input terminal.

[0006] The optocoupler control module is connected between the optocoupler control terminal and the ground terminal, and is used to control the conduction current of the external optocoupler feedback branch;

[0007] The protection voltage divider module is connected between the optocoupler control terminal and the ground terminal, and is used to output a voltage divider voltage corresponding to the potential of the optocoupler control terminal.

[0008] The power supply state switching module is connected between the protection voltage divider module and the optocoupler control module, and the control terminal of the power supply state switching module is connected to the internal power supply terminal. The power supply state switching module is used to respond to the potential change of the internal power supply terminal and change the conduction state between the protection voltage divider module and the optocoupler control module.

[0009] When the internal power supply is output, the voltage regulation module regulates the voltage of the optocoupler control module; when the internal power supply stops outputting internal power, the protection voltage divider module is connected to the optocoupler control module via the power supply state switching module to control the optocoupler control module.

[0010] Preferably, the optocoupler control module includes a first MOS transistor;

[0011] The drain of the first MOS transistor is connected to the optocoupler control terminal, the source is connected to the ground terminal, and the gate is connected to the voltage regulation module and the power supply state switching module respectively.

[0012] The voltage regulation control signal output by the voltage regulation module is output to the gate of the first MOS transistor.

[0013] Preferably, the protection voltage divider module includes a first resistor, a second resistor, and a voltage divider node;

[0014] The first resistor is connected between the optocoupler control terminal and the voltage divider node;

[0015] The second resistor is connected between the voltage divider node and the ground terminal;

[0016] The voltage divider node serves as the output terminal of the protection voltage divider module, and is used to output a voltage divider voltage corresponding to the potential of the optocoupler control terminal.

[0017] Preferably, the power supply state switching module is used to respond to the potential change of the internal power supply terminal and control the conduction state between the protection voltage divider module and the gate of the first MOS transistor;

[0018] When the internal power supply terminal outputs internal power, the power supply state switching module disconnects the connection between the protection voltage divider module and the gate of the first MOS transistor.

[0019] When the internal power supply terminal stops outputting internal power, the power supply state switching module connects the protection voltage divider module to the gate of the first MOS transistor, so that the voltage divided by the protection voltage divider module is transmitted to the gate of the first MOS transistor.

[0020] Preferably, the power supply state switching module includes a second MOSFET;

[0021] The second MOSFET is a P-type MOSFET;

[0022] The source of the second MOS transistor is connected to the voltage divider node, the drain is connected to the gate of the first MOS transistor, and the gate is connected to the internal power supply terminal.

[0023] The second MOSFET is used to respond to the potential change at the internal power supply terminal and control the conduction state between the voltage divider node and the gate of the first MOSFET.

[0024] Preferably, the power supply state switching module further includes a third resistor and a third MOSFET;

[0025] One end of the third resistor is connected to the voltage divider node, and the other end is connected to the drain of the third MOS transistor;

[0026] The third MOS transistor is an N-type MOS transistor, with its source connected to the ground terminal and its gate connected to the internal power supply terminal.

[0027] The third MOS transistor is used to respond to the potential change of the internal power supply terminal and control the conduction state between the third resistor and the ground terminal to change the voltage division of the voltage divider node.

[0028] Preferably, when the internal power supply is stopped from outputting internal power, the second MOS transistor is turned on and the third MOS transistor is turned off. The voltage divided by the protection voltage divider module is transmitted to the gate of the first MOS transistor through the second MOS transistor to control the first MOS transistor to turn on and control the potential of the optocoupler control terminal.

[0029] Preferably, the external optocoupler feedback branch includes a current-limiting resistor and an optocoupler light-emitting diode; it also includes an AC-DC output terminal;

[0030] The current-limiting resistor, the optocoupler light-emitting diode, and the first MOSFET are connected sequentially between the AC / CDC output terminal and the ground terminal.

[0031] The first MOS transistor controls the conduction current of the optocoupler feedback branch according to its gate voltage;

[0032] When the internal power supply is stopped from outputting internal power, the gate voltage of the first MOS transistor is determined by the voltage divider output by the protection voltage divider module, the stable voltage of the optocoupler control terminal is determined by the turn-on threshold of the first MOS transistor, and the limiting voltage of the ACDC output terminal is jointly determined by the stable voltage of the optocoupler control terminal, the voltage drop across the current limiting resistor, and the forward voltage drop of the optocoupler light-emitting diode.

[0033] Preferably, the voltage regulation module includes a low-dropout regulator, an error amplifier, a first sampling resistor, a second sampling resistor, and a reference voltage terminal;

[0034] The input terminal of the low-dropout regulator is connected to the power input terminal, and the output terminal serves as the internal power supply terminal.

[0035] The first sampling resistor and the second sampling resistor are connected in series between the power input terminal and the ground terminal;

[0036] The power supply terminal of the error amplifier is connected to the internal power supply terminal, the first input terminal is connected to the connection node between the first sampling resistor and the second sampling resistor to obtain the sampling voltage, the second input terminal is connected to the reference voltage terminal, and the output terminal is connected to the optocoupler control module.

[0037] Preferably, the error amplifier is used to output the voltage regulation control signal based on the comparison result between the sampled voltage at the first input terminal and the reference voltage provided at the reference voltage terminal;

[0038] The first sampling resistor and the second sampling resistor are used to perform voltage division sampling at the power input terminal.

[0039] Compared with existing technologies, the technical solution provided by this invention has the following advantages: This invention utilizes a pure hardware voltage divider network and MOSFET characteristics to form a negative feedback loop. In extreme cases where the chip experiences electrostatic damage, short circuits, or poor soldering leading to internal power loss, it can autonomously respond to potential changes and take over control of the optocoupler without relying on internal operational amplifiers or software mechanisms. This mechanism effectively limits the runaway rise of the external ACDC output voltage by automatically clamping the potential at the optocoupler control terminal, completely eliminating the safety hazard of overvoltage burnout of charging and receiving equipment. Furthermore, this circuit only requires adding three resistors and two MOSFETs to the traditional protocol chip voltage regulation structure, resulting in an extremely simplified overall architecture while also providing overvoltage protection for internal low-voltage nodes under normal operating conditions. Simultaneously, by adjusting the ratio of the voltage divider resistors, the maximum safe voltage threshold protected at the power input terminal (VIN) can be flexibly adjusted. This invention significantly improves the safety and hardware reliability of fast charging systems at extremely low cost. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0043] Figure 1 A schematic diagram of the module structure of a protection circuit for a fast charging protocol chip provided in an embodiment of the present invention;

[0044] Figure 2 Provided for embodiments of the present invention Figure 1 The specific circuit diagram is shown in the figure.

[0045] in, Figure 2 This includes the power input terminal - VIN, optocoupler control terminal - OPTO, ground terminal - GND, first MOSFET - M1, gate of the first MOSFET - VG, internal power supply terminal - avdd, voltage divider node - Vx, first resistor - R1, second resistor - R2, second MOSFET - M2, third resistor - R3, third MOSFET - M3, current limiting resistor - R0, low dropout regulator - LDO, error amplifier - OTA, first sampling resistor - Rx1, second sampling resistor - Rx2, reference voltage terminal - Vref, optocoupler LED - D2, AC / CDC output terminal - output bus / output terminal where VIN is located, transformer secondary winding - T0, rectifier diode - D1, and output filter capacitor - C1. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0048] like Figure 1As shown, this embodiment provides a protection circuit for a fast charging protocol chip, mainly used to solve the serious safety problem of the charging device being burned out due to the failure of the internal power supply (VIN) of the protocol chip, which prevents the AC / DC converter from outputting. The protection circuit has an optocoupler control terminal (OPTO) and a ground terminal (GND). In terms of system architecture, it specifically includes a voltage regulation module, an optocoupler control module, a protection voltage divider module, and a power supply state switching module.

[0049] The voltage regulator module's input is connected to an external power input (VIN), and its output is connected to the optocoupler control module. This module also has an internal power supply terminal (avdd) used to supply power to the chip and output a voltage regulation control signal based on the voltage at the power input (VIN). The optocoupler control module is connected between the optocoupler control terminal (OPTO) and the ground terminal (GND), and its core function is to control the conduction current of the external optocoupler feedback branch. The protection voltage divider module is also connected in parallel between the optocoupler control terminal (OPTO) and the ground terminal (GND), used to output a voltage divider proportional to the potential of the optocoupler control terminal (OPTO) in real time. The power supply state switching module acts as a logic gate for safety control, connected between the protection voltage divider module and the optocoupler control module, and its control terminal is directly electrically connected to the internal power supply terminal (avdd).

[0050] The power supply state switching module is used to sensitively respond to potential changes at the internal power supply terminal (AVDD), thereby changing the signal conduction state between the protection voltage divider module and the optocoupler control module. The specific operating logic is as follows: when the internal power supply terminal (AVDD) is normally outputting internal power, the voltage regulation module takes control and performs routine voltage regulation control on the optocoupler control module; however, when a fault occurs in the chip, such as electrostatic discharge or poor soldering of pins, causing the internal power supply terminal (AVDD) to stop outputting internal power, the protection voltage divider module connects to the optocoupler control module via the power supply state switching module, and the voltage divider takes over and controls the optocoupler control module, thus eliminating the risk of uncontrolled operation.

[0051] like Figure 2 As shown, further, in this embodiment, in order to achieve precise and linear control of the optocoupler branch current, the aforementioned optocoupler control module specifically uses a first MOS transistor (M1). In the specific circuit connection, the drain of the first MOS transistor (M1) is directly connected to the optocoupler control terminal (OPTO) of the circuit, its source is directly connected to the system ground terminal (GND), and its gate (VG) serves as the receiving terminal of the control signal, connected to the output side of the voltage regulation module and the power supply state switching module, respectively.

[0052] When the chip is in normal power supply mode, the voltage regulation module generates a continuously changing voltage regulation control signal and outputs this signal directly to the gate (VG) of the first MOSFET (M1). The first MOSFET (M1) changes the conduction level between its source and drain based on the voltage signal received at its gate, thereby precisely adjusting the current pulled down to ground (GND) of the optocoupler control terminal (OPTO), ultimately achieving dynamic control of the entire fast charging protocol's output voltage.

[0053] Furthermore, in this embodiment, in order to provide a highly reliable hardware-level safety reference voltage when the main control module of the chip completely fails and is powered off, the aforementioned protection voltage divider module is mainly implemented through a pure resistor voltage divider network, specifically including a first resistor (R1), a second resistor (R2), and a voltage divider node (Vx). In the circuit topology connection, the first resistor (R1) is connected between the optocoupler control terminal (OPTO) and the voltage divider node (Vx), and the second resistor (R2) is connected in series between the voltage divider node (Vx) and the ground terminal (GND).

[0054] Relying on the inherent series voltage divider effect of the first resistor (R1) and the second resistor (R2), the voltage divider node (Vx) can continuously sample the current absolute voltage of the optocoupler control terminal (OPTO) according to a fixed resistance ratio. This voltage divider node (Vx) serves as the voltage output terminal of the protection voltage divider module, continuously outputting a voltage divided by a voltage that strictly corresponds to the potential of the optocoupler control terminal (OPTO). This purely hardware architecture does not rely on the internal power supply of the chip, ensuring the effectiveness of protection under extreme failure conditions.

[0055] Furthermore, in this embodiment, the power supply state switching module plays a crucial role in the handover and isolation of control in the entire safety protection system. Its core function is to monitor the potential state of the internal power supply terminal (avdd) in real time in order to control the conduction or cutoff state between the aforementioned protection voltage divider module and the gate (VG) of the first MOS transistor (M1).

[0056] Specifically, when the external power input is normal, causing the internal power supply terminal (avdd) to output internal power normally (i.e., maintain a high level), the power supply state switching module is suppressed and actively disconnects the electrical connection between the protection voltage divider module and the gate (VG) of the first MOSFET (M1), ensuring that the normal voltage regulation control signal is not interfered with by the protection voltage divider during transmission. However, if the power input terminal (VIN) fails, causing the internal power supply terminal (avdd) to stop outputting internal power (i.e., power drops to zero potential or a low level), the power supply state switching module quickly activates, completely reconnecting the protection voltage divider module to the gate (VG) of the first MOSFET (M1). This action allows the safe voltage divider generated at the voltage divider node (Vx) of the protection voltage divider module to be transmitted directly to the gate (VG) of the first MOSFET (M1) without obstruction, achieving seamless control takeover at the moment of power failure.

[0057] Furthermore, in this embodiment, to ensure that the switching can be automatically and passively completed based on the physical characteristics of semiconductors even under the harsh condition of zero power supply, the core component for switch control in the aforementioned power supply state switching module specifically includes a second MOSFET (M2), and this second MOSFET (M2) is a P-type MOSFET. In terms of pin wiring connections, the source of the second MOSFET (M2) is connected to the aforementioned voltage divider node (Vx), its drain is connected to the gate (VG) of the first MOSFET (M1), and the gate that controls its on / off state is directly electrically connected to the internal power supply terminal (avdd) of the chip.

[0058] By fully utilizing the inherent electrical characteristics of P-type MOSFETs—conduction at low levels and cutoff at high levels—the second MOSFET (M2) can perfectly respond to potential changes at the internal power supply terminal (avdd). When a high-level internal power supply is present at the internal power supply terminal (avdd), the gate of the second MOSFET (M2) is clamped by the high voltage and remains in the cutoff state, completely isolating the voltage divider node (Vx) from the gate (VG) of the first MOSFET (M1). When the internal power supply terminal (avdd) drops to zero potential due to a fault, the gate of the second MOSFET (M2) loses the high-level clamping, and the transistor automatically turns on, thereby quickly connecting the voltage divider node (Vx) to the gate (VG) of the first MOSFET (M1) to achieve state switching.

[0059] Furthermore, in this embodiment, to ensure that internal circuit nodes (especially near the voltage divider node Vx) are not damaged by excessive voltage when the chip is operating normally and requires high voltage output, a third resistor (R3) and a third MOSFET (M3) are further provided in the aforementioned power supply state switching module. In the specific connection structure, one end of the third resistor (R3) is connected to the voltage divider node (Vx), and the other end is connected to the drain of the third MOSFET (M3). This third MOSFET (M3) is an N-type MOSFET with the opposite electrical polarity to the second MOSFET (M2), with its source connected to ground (GND) and its gate directly connected to the internal power supply terminal (avdd).

[0060] The third MOSFET (M3) responds to potential changes at the internal power supply terminal (avdd) and controls the conduction state between the third resistor (R3) and the ground terminal (GND) to change the voltage division of the voltage divider node (Vx). When the chip is operating normally and avdd (i.e., a high level) is present at the internal power supply terminal, the N-type third MOSFET conducts, safely pulling the third resistor into the circuit and grounding it. Due to the presence of avdd, the voltage of the voltage divider node (Vx) is jointly controlled by the optocoupler control terminal (OPTO), the third resistor (R3), and the first resistor (R1). The specific voltage division relationship at this time is: Vx = VOPTO * R3 / (R3 + R1). By properly controlling the ratio of R3 to R1, when the external output voltage is adjusted to a high voltage, it can be ensured that the low-voltage components such as the voltage divider node inside the chip will not be damaged. Among them, R3 is much smaller than R2 (equivalent to ignoring R2).

[0061] Furthermore, in this embodiment, when the fast charging chip suffers extreme damage such as an external short circuit or poor soldering, causing the power input terminal (VIN) to fail and the internal power supply terminal (avdd) to completely stop outputting internal power, the entire protection circuit enters the core safety defense mode. At this time, because the potential of the internal power supply terminal (avdd) drops rapidly to zero, the third MOSFET (M3) driven by the high level immediately turns to the cutoff state, thereby disconnecting the voltage divider discharge branch of the third resistor (R3); at the same time, the zero potential signal causes the P-type second MOSFET (M2) driven by the low level to be fully turned on.

[0062] Since the second MOSFET (M2) is in a fully conducting state, the voltage divider module outputs a voltage divider voltage at the voltage divider node (Vx) based on the current voltage of the optocoupler control terminal (OPTO). This voltage divider can be directly transmitted to the gate (VG) of the first MOSFET (M1) without any obstruction, thereby controlling the first MOSFET (M1) to conduct and forcibly pulling down the potential of the optocoupler control terminal (OPTO) and stabilizing it.

[0063] Furthermore, in this embodiment, the ultimate protection objective of the protection circuit is to limit the high voltage output of the external ACDC circuit by clamping the potential of the optocoupler control terminal (OPTO). This is highly dependent on the closed-loop negative feedback system composed of peripheral circuits. The external optocoupler feedback branch specifically includes a current-limiting resistor (R0) for limiting the maximum current, an optocoupler light-emitting diode (D2) for photoelectric conversion, and an ACDC output terminal. It is sequentially connected to the first MOSFET (M1) inside the chip between the ACDC output terminal and the ground terminal (GND). In this embodiment, the first MOSFET (M1) controls the conduction current of the entire optocoupler feedback branch according to its gate voltage (VG).

[0064] When the internal power supply terminal (avdd) stops outputting internal power, the gate voltage of the first MOSFET (M1) is determined by the voltage divider output from the protection voltage divider module. At this time, the gate voltage of the first MOSFET (M1) is VG = VOPTO * R2 / (R2 + R1). The circuit forms a strong negative feedback: when the voltage at the optocoupler control terminal (OPTO) increases, the gate voltage of M1 increases through voltage division, thereby further turning on M1 and reducing the voltage of OPTO. Since the voltage of VIN is determined by the current flowing through the optocoupler diode, the larger the current, the smaller VIN, successfully suppressing the unlimited voltage spike.

[0065] Based on the electrical characteristics of diodes and MOSFETs, when the circuit reaches equilibrium, the gate voltage of the first MOSFET (M1) is approximately equal to its turn-on threshold Vth. Therefore, the stable voltage at the optocoupler control terminal (OPTO) is clamped at VOPTO = Vth * (R2 + R1) / R2. Furthermore, the limiting voltage at the AC / CDC output terminal (i.e., the maximum protection voltage VIN after limiting) is determined by the stable voltage at the optocoupler control terminal, the voltage drop across the current-limiting resistor (R0), and the forward voltage drop of the optocoupler's LED (D2). The calculation formula is Vin = Vth * (R2 + R1) / R2 + Iopto * R0 + Vd2, where Iopto is the operating current of the optocoupler, and Vd2 is the forward voltage drop of the optocoupler diode.

[0066] Taking a specific application scenario as an example, with the resistor ratio set to (R2+R1) / R2=3, assuming the first MOSFET (M1) has a turn-on threshold voltage Vth=1V, the optocoupler operating current Iopto=400uA, the forward voltage drop Vd2=0.7V, and the current-limiting resistor R0=1KΩ, then the final output power input terminal (VIN) will be hard-clamped at Vin=1*3+400uA*1k+0.7=4.1V. In this protection circuit, the maximum protected voltage VIN can be arbitrarily adjusted by adjusting the ratio of (R2+R1) / R2.

[0067] Furthermore, in this embodiment, in order to provide high-quality system-level stable power supply and high-precision conventional voltage modulation function under normal operating conditions, the voltage regulation module performing normal voltage regulation control adopts a multi-component integrated analog design in its internal hardware architecture. Specifically, the voltage regulation module includes a low-dropout regulator (LDO), an error amplifier (OTA), a first sampling resistor and a second sampling resistor for real-time voltage division sampling of the input voltage, and a reference voltage terminal (Vref) providing a standard voltage reference.

[0068] The input of the low-dropout regulator (LDO) is connected to the chip's power input (VIN), and its output serves as the internal power supply terminal (avdd) providing power to the entire chip. The first and second sampling resistors are connected in series across the power input (VIN) and ground (GND) to form a sampling voltage divider network. The error amplifier (OTA) is connected to the aforementioned internal power supply terminal (avdd) to obtain operating power. Its first input is connected to the connection node between the first and second sampling resistors to accurately obtain the sampling voltage of the current input power supply. Its second input is connected to the reference voltage terminal (Vref), and the amplifier's output is directly connected to the optocoupler control module (i.e., the gate of the first MOSFET M1), forming a classic closed-loop control front end.

[0069] Furthermore, in this embodiment, the dynamic working mechanism and control principle of the aforementioned voltage regulation module during the fast charging protocol adjustment process are explained in detail. When the external input power supply VIN is functioning normally and the internal power supply avdd of the low dropout regulator (LDO) is outputting a stable voltage, the first sampling resistor and the second sampling resistor continuously perform precise voltage division sampling of the power input terminal (VIN). At this time, the error amplifier (OTA), which is in an active state, is used to output the corresponding voltage regulation control signal in real time based on the comparison result between the real-time sampled voltage obtained from the first input terminal and the reference voltage provided by the reference voltage terminal (Vref) at the second input terminal. Due to the presence of the current-limiting resistor R0 and the driving capability of the error amplifier (OTA), the chip can perfectly control the output voltage through the error amplifier (OTA) and the first MOSFET (M1). At this time, the normal output voltage is completely determined by the ratio of the voltage divider resistors and the reference voltage, that is, it satisfies the relationship: Vin=Vref*K, where K is the voltage division ratio of the two sampling resistors. The control signal adjusts the on-resistance of the first MOSFET (M1) in real time and dynamically, thereby precisely adjusting the feedback current of the external optocoupler branch, so that the charging system can fully meet the output level specified by the fast charging protocol.

[0070] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0071] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0072] In the embodiments provided by this invention, it should be understood that the disclosed circuits / terminal devices and methods can be implemented in other ways. For example, the circuit / terminal device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection of circuits or units, and may be electrical, mechanical, or other forms.

[0073] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0074] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or circuit capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0075] The present invention can implement all or part of the processes in the methods of the above embodiments, or it can be accomplished by a computer program product. When the computer program product is run on a terminal device, the terminal device can implement the steps in the various method embodiments described above.

[0076] The embodiments described above are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A protection circuit for a fast charging protocol chip, characterized in that, The protection circuit has an optocoupler control terminal and a ground terminal, and includes a voltage regulation module, an optocoupler control module, a protection voltage divider module, and a power supply state switching module. The input terminal of the voltage regulating module is connected to the power input terminal, and the output terminal is connected to the optocoupler control module. The voltage regulating module has an internal power supply terminal and is used to output a voltage regulation control signal according to the voltage of the power input terminal. The optocoupler control module is connected between the optocoupler control terminal and the ground terminal, and is used to control the conduction current of the external optocoupler feedback branch; The protection voltage divider module is connected between the optocoupler control terminal and the ground terminal, and is used to output a voltage divider voltage corresponding to the potential of the optocoupler control terminal. The power supply state switching module is connected between the protection voltage divider module and the optocoupler control module, and the control terminal of the power supply state switching module is connected to the internal power supply terminal. The power supply state switching module is used to respond to the potential change of the internal power supply terminal and change the conduction state between the protection voltage divider module and the optocoupler control module. When the internal power supply is output, the voltage regulation module regulates the voltage of the optocoupler control module; when the internal power supply stops outputting internal power, the protection voltage divider module is connected to the optocoupler control module via the power supply state switching module to control the optocoupler control module.

2. The protection circuit for the fast charging protocol chip according to claim 1, characterized in that, The optocoupler control module includes a first MOS transistor; The drain of the first MOS transistor is connected to the optocoupler control terminal, the source is connected to the ground terminal, and the gate is connected to the voltage regulation module and the power supply state switching module respectively. The voltage regulation control signal output by the voltage regulation module is output to the gate of the first MOS transistor.

3. The protection circuit for the fast charging protocol chip according to claim 2, characterized in that, The protection voltage divider module includes a first resistor, a second resistor, and a voltage divider node; The first resistor is connected between the optocoupler control terminal and the voltage divider node; The second resistor is connected between the voltage divider node and the ground terminal; The voltage divider node serves as the output terminal of the protection voltage divider module, and is used to output a voltage divider voltage corresponding to the potential of the optocoupler control terminal.

4. The protection circuit for the fast charging protocol chip according to claim 3, characterized in that, The power supply state switching module is used to respond to the potential change of the internal power supply terminal and control the conduction state between the protection voltage divider module and the gate of the first MOS transistor. When the internal power supply terminal outputs internal power, the power supply state switching module disconnects the connection between the protection voltage divider module and the gate of the first MOS transistor. When the internal power supply terminal stops outputting internal power, the power supply state switching module connects the protection voltage divider module to the gate of the first MOS transistor, so that the voltage divided by the protection voltage divider module is transmitted to the gate of the first MOS transistor.

5. The protection circuit for the fast charging protocol chip according to claim 4, characterized in that, The power supply state switching module includes a second MOSFET; The second MOSFET is a P-type MOSFET; The source of the second MOS transistor is connected to the voltage divider node, the drain is connected to the gate of the first MOS transistor, and the gate is connected to the internal power supply terminal. The second MOSFET is used to respond to the potential change at the internal power supply terminal and control the conduction state between the voltage divider node and the gate of the first MOSFET.

6. The protection circuit for the fast charging protocol chip according to claim 5, characterized in that, The power supply state switching module also includes a third resistor and a third MOSFET; One end of the third resistor is connected to the voltage divider node, and the other end is connected to the drain of the third MOS transistor; The third MOS transistor is an N-type MOS transistor, with its source connected to the ground terminal and its gate connected to the internal power supply terminal. The third MOS transistor is used to respond to the potential change of the internal power supply terminal and control the conduction state between the third resistor and the ground terminal to change the voltage division of the voltage divider node.

7. The protection circuit for the fast charging protocol chip according to claim 6, characterized in that, When the internal power supply is stopped from outputting internal power, the second MOS transistor is turned on and the third MOS transistor is turned off. The voltage divided by the protection voltage divider module is transmitted to the gate of the first MOS transistor through the second MOS transistor to control the first MOS transistor to turn on and control the potential of the optocoupler control terminal.

8. The protection circuit for the fast charging protocol chip according to claim 7, characterized in that, The external optocoupler feedback branch includes a current-limiting resistor and an optocoupler light-emitting diode; it also includes an AC-CDC output terminal. The current-limiting resistor, the optocoupler light-emitting diode, and the first MOSFET are connected sequentially between the AC / CDC output terminal and the ground terminal. The first MOS transistor controls the conduction current of the optocoupler feedback branch according to its gate voltage; When the internal power supply is stopped from outputting internal power, the gate voltage of the first MOS transistor is determined by the voltage divider output by the protection voltage divider module, the stable voltage of the optocoupler control terminal is determined by the turn-on threshold of the first MOS transistor, and the limiting voltage of the ACDC output terminal is jointly determined by the stable voltage of the optocoupler control terminal, the voltage drop across the current limiting resistor, and the forward voltage drop of the optocoupler light-emitting diode.

9. The protection circuit for the fast charging protocol chip according to claim 1, characterized in that, The voltage regulation module includes a low-dropout regulator, an error amplifier, a first sampling resistor, a second sampling resistor, and a reference voltage terminal; The input terminal of the low-dropout regulator is connected to the power input terminal, and the output terminal serves as the internal power supply terminal. The first sampling resistor and the second sampling resistor are connected in series between the power input terminal and the ground terminal; The power supply terminal of the error amplifier is connected to the internal power supply terminal, the first input terminal is connected to the connection node between the first sampling resistor and the second sampling resistor to obtain the sampling voltage, the second input terminal is connected to the reference voltage terminal, and the output terminal is connected to the optocoupler control module.

10. The protection circuit for the fast charging protocol chip according to claim 9, characterized in that, The error amplifier is used to output the voltage regulation control signal based on the comparison result between the sampled voltage at the first input terminal and the reference voltage provided at the reference voltage terminal; The first sampling resistor and the second sampling resistor are used to perform voltage division sampling at the power input terminal.

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