Protection circuit for preventing serial connection of communication port and charging device

Abstract

The utility model discloses a protection circuit and a charging device for preventing serial connection of a communication port, and relates to the technical field of low-voltage system circuits, and the protection circuit comprises a first loop and a second loop which are connected between a power supply system and a low-voltage system. A communication port transmitting end of the low-voltage system is connected to the power supply system through the first loop, and a communication port receiving end of the low-voltage system is connected to the power supply system through the second loop; the first loop at least comprises a waveform shaping circuit, and the second loop at least comprises a low-voltage-drop diode. The protection circuit is simple in logic circuit, easy to implement, low in cost, small in occupied space and capable of effectively protecting the communication port of the low-voltage system.

Description

Technical Field

[0001] The present application relates to the technical field of low-voltage system circuits, and specifically provides a protection circuit and a charging device for preventing cross-current at a communication port of a low-voltage system. Background Art

[0002] At present, products such as charging piles or battery swap stations contain a combination of various low-voltage systems and normal power supply systems. The systems are designed independently, and the communication mode within the board is usually serial communication. In addition, in general, each independent system contains an independent power supply system, which supports cutting off the power supply at any time to reset the abnormal state. Due to the characteristics of the low-voltage system, the communication pins of the chip of the normal power supply system will cause the low-voltage system to be unable to completely cut off the power, resulting in abnormal functions. There are two ways to solve this problem in the industry. One is to use capacitive isolation or electromagnetic isolation. This solution can solve the current problem, but due to the existence of isolation, the communication rate is limited. At the same time, the isolation device is expensive and occupies a large space on the circuit board. The other is to use a power conversion chip solution. The dedicated power conversion chip is expensive and occupies a large space. Therefore, it is not suitable for use in cost-sensitive products, and cannot be applied to small systems with limited circuit board design space. Utility Model Content

[0003] In order to overcome the above-mentioned defects, the utility model proposes a protection circuit to prevent cross-current of the communication port. This scheme protects the communication port of the low-voltage system through a simple combinational logic circuit, which can effectively prevent the power supply system from affecting the low-voltage system through the communication port, resulting in the inability to completely cut off power to the low-voltage system.

[0004] In a first aspect, the present application provides a protection circuit for preventing cross-current at a communication port, comprising a first circuit and a second circuit connected between a power supply system and a low voltage system;

[0005] The communication port transmitting end of the low-voltage system is connected to the power supply system via the first loop, and the communication port receiving end of the low-voltage system is connected to the power supply system via the second loop;

[0006] The first loop includes at least a waveform shaping circuit, and the second loop includes at least a diode.

[0007] Preferably, the waveform shaping circuit adopts a Schmitt trigger, the communication port sending end of the low-voltage system is connected to the input end of the Schmitt trigger, and the output end of the Schmitt trigger is connected to the power supply system via a first resistor.

[0008] Preferably, the diode is a low-voltage drop diode, the communication port receiving end of the low-voltage system is connected to the positive electrode of the low-voltage drop diode, the negative electrode of the low-voltage drop diode is connected to the power supply system, and the communication port receiving end is also connected to the power supply via a second resistor.

[0009] Preferably, the power supply system includes a power management circuit and an MCU chip, and the communication port transmitting end and the communication port receiving end of the low-voltage system are connected to the communication port of the MCU chip via the first loop and the second loop respectively.

[0010] Furthermore, the power management circuit is used to control the low-voltage output end of the power supply system to output the working voltage required by the low-voltage system.

[0011] A switch tube is provided between the low-voltage output end of the power supply system and the low-voltage system, and the power management circuit is also used to cut off power to the low-voltage system by controlling the switch tube.

[0012] A pull-up resistor is arranged on a connection line connecting the communication port of the MCU chip with the first loop and the second loop.

[0013] Preferably, the low-voltage system is specifically a Bluetooth control loop or a radio frequency control loop.

[0014] The Bluetooth control loop includes a Bluetooth chip and a peripheral circuit, and the communication port of the Bluetooth chip is connected to the communication port of the MCU chip via the first loop and the second loop.

[0015] In a second aspect, the present application provides a charging device, including a power supply system, and a protection circuit for preventing cross-current at a communication port as described above.

[0016] The protection circuit for preventing the communication port from being cross-connected provided by the present application has the following beneficial effects: the protection circuit logic circuit designed in the embodiment of the present application is simple and easy to implement, low cost, small space occupation, and can protect the communication port of the low-voltage system, effectively preventing the power supply system from affecting the low-voltage system through the communication port, resulting in the low-voltage system being unable to be completely powered off. Based on the protection circuit provided by the present application, the power supply isolation between the low-voltage system and the power supply system is effectively guaranteed through the first circuit and the second circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The disclosure of the present application will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present application. In addition, similar numbers in the drawings are used to represent similar components, among which:

[0018] Figure 1It is a schematic diagram of the design structure of an existing protection circuit using a level conversion solution;

[0019] Figure 2 It is a schematic diagram of the design structure of an existing protection circuit using an optocoupler isolation solution;

[0020] Figure 3 This is a schematic diagram of an application scenario of a protection circuit for preventing cross-current at a communication port provided by the utility model;

[0021] Figure 4 It is a schematic diagram of the design structure of the first loop of the protection circuit provided by the utility model;

[0022] Figure 5 It is a schematic diagram of the design structure of the second loop of the protection circuit provided by the utility model;

[0023] Figure 6 This is a schematic diagram of a specific application scenario of a protection circuit provided by the utility model;

[0024] Figure 7 yes Figure 6 A circuit structure diagram of a specific implementation method;

[0025] Figure 8 This is a circuit structure diagram of an implementation method of the power supply system provided by the utility model;

[0026] Fig. 9 It is a circuit structure diagram of an implementation method of the low-voltage system provided by the utility model. DETAILED DESCRIPTION

[0027] Some embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0028] In the description of the present invention, the term "A and / or B" means all possible combinations of A and B, such as only A, only B, or A and B. The term "at least one A or B" or "at least one of A and B" has a similar meaning to "A and / or B" and may include only A, only B, or A and B. The singular terms "a", "the" and "the" may also include plural forms.

[0029] In addition, the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the utility model product is usually placed when in use. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the utility model.

[0030] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] There are two existing design schemes for protection circuits of low voltage systems. One is a level conversion scheme, such as Figure 1 As shown, the level conversion solution requires a separate isolated power supply and a level conversion chip. The power supply and chip are isolated to achieve the purpose of non-interference between the input and output of the communication port. This solution uses more components and has a larger package size. It is not suitable for use in small systems with limited circuit board layout space. Another method is to use capacitive isolation or electromagnetic isolation, such as Figure 2 The optocoupler isolation solution shown in the figure uses an isolation device to separate the input and output of the low-voltage system communication port. Due to the use of optocoupler isolation, a necessary avoidance area needs to be provided before and after the isolation on the circuit board (PCB), which is usually 3mm; and the cost of optocoupler isolation is higher than that of non-isolated devices, so it cannot save cost and space in small systems.

[0032] Therefore, given that Figure 1 and 2The problems with the existing protection circuit scheme for preventing cross-current at the communication port of the low-voltage system are shown. The working principle of a protection circuit for preventing cross-current at the communication port provided in the embodiment of the present application is described as follows: In battery swap stations and charging pile products, there is usually a control circuit with a normal power supply. After the power is cut off in this circuit, the main function of the product is lost and it cannot work normally. For example, the main control MCU circuit is called a normal power supply system. The low-voltage control system is usually a specific function circuit that needs to be initialized or reset by powering off, such as a Bluetooth control circuit, a radio frequency control circuit, etc. The protection circuit of the embodiment of the present application is usually arranged between the normal power supply system and the communication port of the low-voltage system, and the protection circuit includes a first circuit and a second circuit. For example, taking the low-voltage system as a Bluetooth (BLE) control loop as an example, when an abnormality occurs in BLE, in order to ensure that the BLE system can be completely reset, a MOS switch is usually designed to reset the BLE loop power-off. If the anti-sequential protection circuit is not added, due to the external pull-up / internal pull-up circuit of the MCU's pin, the BLE cannot be completely powered off, that is, it cannot be completely reset, and a fault occurs; using the protection circuit provided by the embodiment of the present application, when the low-voltage system is powered off, since the communication port is connected, the communication port pull-up will supply power to the low-voltage system through the communication port. When the low-voltage system is powered off, a high-impedance state is output through the first loop, thereby preventing the low-voltage system from affecting the communication port. The second loop is used as a receiving port, and the general chip pin is in a high-impedance state, so the low-voltage system power supply is used for internal pull-up, and a diode is used to prevent reverse at the external output end through the second loop. When the low-voltage system is powered off, due to the presence of the diode, the leakage current is low and will not affect the low-voltage system.

[0033] The protection circuit for preventing cross-current flow at the communication port provided by the present application (hereinafter referred to as protection circuit) will be described in detail below in conjunction with specific implementation methods.

[0034] Example 1

[0035] like Figure 3 The figure is a schematic diagram of an application scenario of the protection circuit provided in an embodiment of the present application. As shown in the figure, the communication port transmitting end (TX) and the communication port receiving end (RX) of the low-voltage system 300 establish a communication connection with the power supply system 100 via the protection circuit 200. It can be understood that the communication port transmitting end output port (TX OUT) and the communication port receiving end output port (RX OUT) refer to the output ports of TX and RX after passing through the protection circuit 200, respectively.

[0036] The protection circuit provided in the embodiment of the present application includes a first loop and a second loop, wherein the first loop includes at least a waveform shaping circuit, and the second loop includes at least a diode. The communication port transmitting end of the low-voltage system is connected to the power supply system via the first loop, and the communication port receiving end of the low-voltage system is connected to the power supply system via the second loop.

[0037] In one embodiment, the circuit design of the first loop 201 is as follows: Figure 4 shown.

[0038] In the first loop, the first loop is mainly composed of a Schmitt trigger (S) and a first resistor (R1), that is, the waveform shaping circuit specifically adopts a Schmitt trigger (S), the communication port sending end (TX) of the low-voltage system is connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the power supply system via the first resistor (R1), and the Schmitt trigger is also connected to a power supply (VCC) to power it.

[0039] It can be understood that the first circuit uses a Schmitt trigger, the output pin of the low-voltage system is connected to the Schmitt trigger, the Schmitt trigger is consistent with the low-voltage system power supply circuit, and after the low-voltage system is powered off, the Schmitt trigger output is in a high-impedance state, which can prevent the pull-up or output of the power supply system from causing cross-current at the sending end of the low-voltage system communication port.

[0040] In one embodiment, the circuit design of the second loop 202 is as follows: Figure 5 shown.

[0041] In the second loop, the second loop is mainly composed of a low voltage drop diode (D1) and a second resistor (R2), the communication port receiving end (RX) of the low voltage system is connected to the positive electrode of the low voltage drop diode (D1), the negative electrode of the low voltage drop diode is connected to the power supply system, and the communication port receiving end (RX) is also connected to the power supply via the second resistor (R2), wherein the second resistor (R2) can also be called a pull-up resistor according to the function. Further, when the output port (RX_OUT) of the communication port receiving end is suspended, the second loop can realize internal pull-up to ensure the reception level is determined, and achieve reception steady state.

[0042] It can be understood that the second circuit uses a low-voltage drop diode, and the communication port receiving end of the low-voltage system determines a fixed level through an external pull-up circuit. The pull-up power supply is the power supply for the low-voltage system. When the low-voltage system is powered off, the pull-up of the communication port receiving end of the low-voltage system disappears. At the same time, the diode is used to prevent reverse flow, thereby preventing the power supply system from affecting the communication port receiving end of the low-voltage system.

[0043] Based on the protection circuit provided in this embodiment, the power supply isolation between the low-voltage system and the power supply system is effectively guaranteed through the first loop and the second loop.

[0044] Example 2

[0045] The embodiments of this application are Figure 1Based on the application scenario of the protection circuit shown in FIG. 1 , a specific application scenario of the protection circuit for preventing cross-current of the communication port is provided, specifically, Figure 6 In this application scenario, the power supply system 100 is embodied as including a power management circuit 101 and an MCU chip 102, and the low-voltage system 300 is embodied as a Bluetooth control loop, and the Bluetooth control loop includes a Bluetooth chip 301 and its peripheral circuit 302, wherein the power management circuit 101 is used to control the low-voltage output terminal 500 of the power supply system 100 to output the working voltage required by the low-voltage system 300, and specifically, the power management circuit 101 outputs a 3.3V working voltage of the Bluetooth module through the low-voltage output terminal 500. A protection circuit 200 is set at the communication port of the Bluetooth chip 301, and the communication port 400 of the MCU chip 102 needs to be connected to the Bluetooth chip 301 through the protection circuit 200 (i.e., the first loop and the second loop), thereby preventing the cross-current generated between the communication port of the MCU chip and the communication port of the Bluetooth chip from affecting the low-voltage system when the low-voltage system is powered off.

[0046] In this embodiment, a switch tube is provided between the low-voltage output end of the power supply system and the low-voltage system. The power management circuit in the power supply system is also used to cut off the power of the low-voltage system by controlling the switch tube. A pull-up resistor is provided on the connection line connecting the communication port transmitting end and the communication port receiving end of the low-voltage system with the communication port of the MCU chip. A specific implementation method is as follows Figure 7 As shown, the switch tube generally adopts a triode (MOS), and the power management circuit controls the MOS tube to cut off the 3.3V working voltage provided to the Bluetooth chip 301 by the low-voltage output end of the power supply system, as shown in 3V3 BEL in the figure. The communication port transmitting end (TX) and the communication port receiving end (RX) of the Bluetooth chip 301 are connected to the communication port of the MCU chip 102 through the protection circuit 200. It can be understood that the connection line between the communication port of the MCU chip 102 and the protection circuit 200 (i.e., the first loop and the second loop) is also provided with a pull-up resistor (R3 and R4) connected to the power supply (VCC).

[0047] Furthermore, a specific implementation of the power supply system in this embodiment is as follows: Figure 8As shown, it mainly includes an MCU chip and a power management circuit, wherein the power management circuit includes a decoupling and filtering circuit and a switching tube. The decoupling and filtering circuit is composed of multiple capacitors, and the switching tube is composed of two transistors. The power pin (MCU_VCC) of the MCU chip is connected to the power supply (VCC), and the control pin (MCU_CTL) is connected to the power management circuit. It should be understood that the pin of the communication port of the MCU chip is connected to the protection circuit, which is not drawn in the figure. A main chip U1 in a power management circuit is connected in parallel with a fourth diode (D4); an input end (VIN) of the main chip (U1) is connected to a power supply VCC; a decoupling and filtering circuit composed of a plurality of capacitors (C20, C21, C22, C10, C11, C12) is arranged between the input end (VIN) and the output end (VOUT) of the main chip (U1) and the ground; an output end (VOUT) of the main chip (U1) is connected to a first triode (Q1); resistors (R6 and R7) are arranged in a series circuit between the first triode (Q1) and the second triode (Q2) constituting a switch tube; a diode (D2), a resistor (R5) and a capacitor (C30) are arranged in parallel with the first triode (Q1); a diode (D3) and a resistor (R4) are arranged in parallel with the second triode (Q2); and the second triode (Q2) of an MCU chip is connected to a control pin (MCU_CTL) of the MCU chip via a resistor (R3). The power supply system of this embodiment can control the output of a low voltage of 3.3V, as shown in the figure at the low voltage output terminal 3V3BEL.

[0048] Furthermore, a specific implementation of the low-voltage system in the embodiment of the present application is as follows: Fig. 9 As shown, it mainly includes a Bluetooth chip and its peripheral circuits, wherein the communication port transmitting end (TX) and the communication port receiving end (RX) of the Bluetooth chip are respectively provided with resistors (R11) and (R12). It should be understood that the Bluetooth chip is connected to the first loop and the second loop of the protection circuit through the TX and RX shown in the figure. In addition, multiple pins of the Bluetooth chip are also directly connected to the low-voltage output end (3V3BEL) of the power supply system, such as the function pin (P0.16) of the Bluetooth chip shown in the figure connected to the working status indication circuit composed of a diode (D5) and a resistor (R8), and the battery status management pin (VBAT) of the Bluetooth chip is directly connected to the low-voltage output end (3V3 BEL) of the low-voltage system, and the state reset pin (RESET) of the Bluetooth chip is connected to the low-voltage output end (3V3 BEL) of the low-voltage system through a resistor R9. By connecting to the low-voltage output end (3V3 BEL) of the low-voltage system of the power supply system, the required working voltage can be provided for each pin of the Bluetooth chip and the peripheral circuit.

[0049] Example 3

[0050] The utility model also provides a charging device, including a power supply system and a protection circuit provided in Embodiments 1 and 2 of the present application, wherein the specific implementation of the power supply system and the protection circuit can be referred to the description in the previous embodiments and will not be repeated here.

[0051] So far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present application.

Claims

1. A protection circuit for preventing cross-current at a communication port, characterized in that: It includes a first circuit and a second circuit connected between the power supply system and the low voltage system; The communication port transmitting end of the low-voltage system is connected to the power supply system via the first loop, and the communication port receiving end of the low-voltage system is connected to the power supply system via the second loop; The first loop includes at least a waveform shaping circuit, and the second loop includes at least a diode.

2. The protection circuit according to claim 1, characterized in that: The waveform shaping circuit adopts a Schmitt trigger, the communication port sending end of the low-voltage system is connected to the input end of the Schmitt trigger, and the output end of the Schmitt trigger is connected to the power supply system via a first resistor.

3. The protection circuit according to claim 1, characterized in that: The diode specifically adopts a low voltage drop diode, the communication port receiving end of the low voltage system is connected to the positive electrode of the low voltage drop diode, the negative electrode of the low voltage drop diode is connected to the power supply system, and the communication port receiving end is also connected to the power supply via a second resistor.

4. The protection circuit according to claim 1, characterized in that: The power supply system includes a power management circuit and an MCU chip. The communication port transmitting end and the communication port receiving end of the low-voltage system are connected to the communication port of the MCU chip via the first loop and the second loop respectively.

5. The protection circuit according to claim 4, characterized in that: The power management circuit is used to control the low-voltage output end of the power supply system to output the working voltage required by the low-voltage system.

6. The protection circuit according to claim 5, characterized in that: A switch tube is provided between the low-voltage output end of the power supply system and the low-voltage system, and the power management circuit is also used to cut off power to the low-voltage system by controlling the switch tube.

7. The protection circuit according to claim 4, characterized in that: A pull-up resistor is arranged on a connection line connecting the communication port of the MCU chip with the first loop and the second loop.

8. The protection circuit according to claim 4, characterized in that: The low voltage system is specifically a Bluetooth control loop or a radio frequency control loop.

9. The protection circuit according to claim 8, characterized in that: The Bluetooth control loop includes a Bluetooth chip and a peripheral circuit, and the communication port of the Bluetooth chip is connected to the communication port of the MCU chip via the first loop and the second loop.

10. A charging device, characterized in that: It comprises a power supply system and a protection circuit for preventing cross-current at a communication port as claimed in any one of claims 1 to 9.

Images