Protective circuit for preventing backfeeding at communication port, and charging device

Abstract

The present application relates to the technical field of circuits of low-voltage systems, and discloses a protective circuit for preventing backfeeding at a communication port, and a charging device. The protective 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 sending end of the low-voltage system is connected to the power supply system by means of the first loop, and a communication port receiving end of the low-voltage system is connected to the power supply system by means of the second loop. The first loop at least comprises a waveform shaping circuit, and the second loop at least comprises a low forward voltage drop diode. The protective circuit logic circuit of the present application is simple and easy to implement, requires low cost, occupies a small space, and can effectively protect communication ports of low-voltage systems.

Description

A protection circuit and charging device to prevent cross-current at communication port

[0001] This application claims priority to Chinese patent application No. 202420274735.2 filed on February 4, 2024, entitled “A protection circuit and charging device for preventing cross-current at the communication port”. The entire contents of the above Chinese patent application are incorporated into this application by reference. Technical Field

[0002] 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

[0003] Currently, products such as charging piles or battery swap stations contain a combination of multiple low-voltage systems and permanent power supply systems. The systems are designed independently, and the internal communication method is usually serial communication. In addition, in general, each independent system contains an independent power supply system, which supports power off at any time to reset abnormal conditions. Due to the characteristics of the low-voltage system, the communication pins of the chip of the permanent power supply system will cause the low-voltage system to be unable to completely cut off the power, resulting in functional abnormalities. 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 takes up a large amount of circuit board space. The other is to use a power conversion chip solution. Dedicated power conversion chips are expensive and take up a large space. Therefore, they are not suitable for use in cost-sensitive products and cannot be applied to small systems with limited circuit board design space. Summary of the Invention

[0004] In order to overcome the above-mentioned defects, the present invention proposes a protection circuit to prevent cross-current at the communication port. This scheme uses a simple combinational logic circuit to protect the communication port of the low-voltage system, which can effectively prevent 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.

[0005] In a first aspect, the present application provides a protection circuit for preventing crosstalk at a communication port, comprising a first circuit and a second circuit connected between a power supply system and a low-voltage system;

[0006] 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;

[0007] The first loop includes at least a waveform shaping circuit, and the second loop includes at least a diode.

[0008] In some embodiments, the waveform shaping circuit uses a Schmitt trigger, the communication port transmitting 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.

[0009] In some schemes, the diode specifically adopts a low-voltage drop diode, the communication port receiving end of the low-voltage system is connected to the positive pole of the low-voltage drop diode, the negative pole 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.

[0010] In some embodiments, 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.

[0011] In some embodiments, the power management circuit is used to control the low-voltage output end of the power supply system to output the operating voltage required by the low-voltage system.

[0012] 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 further used to cut off power to the low-voltage system by controlling the switch tube.

[0013] A pull-up resistor is provided on a connection line connecting the communication port of the MCU chip with the first loop and the second loop.

[0014] In some embodiments, the low-voltage system is specifically a Bluetooth control loop or a radio frequency control loop.

[0015] 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.

[0016] In a second aspect, the present application provides a charging device, including a power supply system and the protection circuit for preventing cross-current at the communication port as described above.

[0017] The protection circuit for preventing crosstalk at a communication port provided by this application has the following beneficial effects: The protection circuit logic designed in the embodiments of this application is simple and easy to implement, low-cost, and takes up little space. It can protect the communication port of a low-voltage system, effectively preventing the power supply system from affecting the low-voltage system through the communication port, resulting in an inability to completely power off the low-voltage system. Based on the protection circuit provided by this application, the first and second circuits effectively ensure the power supply isolation between the low-voltage system and the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The disclosure of this application will be more easily understood with reference to the accompanying drawings. Those skilled in the art will readily appreciate that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application. Furthermore, similar numbers in the figures represent similar components, where:

[0019] FIG1 is a schematic diagram of a design structure of an existing protection circuit using a level conversion solution;

[0020] FIG2 is a schematic diagram of the design structure of an existing protection circuit using an optocoupler isolation solution;

[0021] FIG3 is a schematic diagram of an application scenario of a protection circuit for preventing crosstalk at a communication port provided by the present invention;

[0022] FIG4 is a schematic diagram of the design structure of the first loop of the protection circuit provided by the present invention;

[0023] FIG5 is a schematic diagram of the design structure of the second loop of the protection circuit provided by the present invention;

[0024] FIG6 is a schematic diagram of a specific application scenario of a protection circuit provided by the present invention;

[0025] FIG7 is a schematic diagram of a circuit structure of a specific implementation of FIG6;

[0026] FIG8 is a schematic diagram of a circuit structure of an implementation of a power supply system provided by the present invention;

[0027] FIG9 is a schematic diagram of a circuit structure of an implementation of a low-voltage system provided by the present invention. DETAILED DESCRIPTION

[0028] Some embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] In the description of the present invention, the term "A and / or B" refers to all possible combinations of A and B, such as just A, just B, or A and B. The term "at least one of A or B" or "at least one of A and B" has a similar meaning to "A and / or B" and may include just A, just B, or A and B. The singular terms "a" and "the" may also include plural forms.

[0030] In addition, the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0031] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0032] There are two existing design schemes for protection circuits in low-voltage systems. One is a level conversion scheme, as shown in Figure 1. This requires a separate isolated power supply and a level conversion chip to isolate the power supply and chip, ensuring that the input and output of the communication port do not interfere with each other. This scheme uses many components and has a large package size, making it unsuitable for use in small systems with limited circuit board layout space. The other is to use capacitive isolation or electromagnetic isolation, such as the optocoupler isolation scheme shown in Figure 2. This scheme uses an isolation device to separate the input and output of the low-voltage system communication port. Because optocoupler isolation is used, the necessary avoidance area before and after the isolation needs to be provided on the circuit board (PCB), usually 3mm. In addition, the cost of optocoupler isolation is higher than that of non-isolated devices, so it cannot save cost and space in small systems.

[0033] Therefore, in view of the problems existing in the existing protection circuit scheme for preventing cross-current of the communication port of the low-voltage system shown in Figures 1 and 2, a protection circuit for preventing cross-current of the communication port is provided in an embodiment of the present application, and its working principle is described as follows: In battery swap stations and charging pile products, there is usually a control circuit with a constant 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 constant power supply system. The low-voltage control system is usually a specific function circuit, which 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 constant 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 an anti-cross-current protection circuit is not added, due to the external pull-up / internal pull-up circuit of the MCU 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 serves as a receiving port, and generally the chip pin is in a high-impedance state. Therefore, the low-voltage system power supply is used as an internal pull-up, and a diode is used to prevent reverse flow at the external output end of 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.

[0034] The protection circuit for preventing cross-current 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.

[0035] Example 1

[0036] As shown in Figure 3, it is a schematic diagram of the 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 through 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.

[0037] The protection circuit provided in the embodiment of the present application includes a first circuit and a second circuit, wherein the first circuit includes at least a waveform shaping circuit, and the second circuit 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 circuit, and the communication port receiving end of the low-voltage system is connected to the power supply system via the second circuit.

[0038] In one implementation, the circuit design of the first loop 201 is shown in FIG4 .

[0039] 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 transmitting 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) for powering it.

[0040] It can be understood that the first circuit uses a Schmitt trigger, and the output pin of the low-voltage system is connected to the Schmitt trigger. The Schmitt trigger is consistent with the power supply circuit of the low-voltage system. 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.

[0041] In one implementation, the circuit design of the second loop 202 is shown in FIG5 .

[0042] The second circuit 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), and the negative electrode of the low-voltage drop diode is connected to the power supply system. The communication port receiving end (RX) is also connected to the power supply via the second resistor (R2). According to its function, the second resistor (R2) can also be called a pull-up resistor. Furthermore, when the output port (RX_OUT) of the communication port receiving end is suspended, the second circuit can implement internal pull-up to ensure the reception level is determined, thereby achieving a steady-state reception.

[0043] 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.

[0044] 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.

[0045] Example 2

[0046] Based on the application scenario of the protection circuit shown in FIG1 , the embodiment of the present application provides a specific application scenario of a protection circuit for preventing crosstalk between communication ports. Specifically, as shown in FIG6 , in this application scenario, the power supply system 100 is specifically configured to include a power management circuit 101 and an MCU chip 102, and the low-voltage system 300 is specifically configured as a Bluetooth control circuit. The Bluetooth control circuit includes a Bluetooth chip 301 and its peripheral circuit 302. The power management circuit 101 is used to control the low-voltage output terminal 500 of the power supply system 100 to output the operating voltage required by the low-voltage system 300. Specifically, the power management circuit 101 outputs a 3.3V operating voltage for the Bluetooth module through the low-voltage output terminal 500. A protection circuit 200 is provided at the communication port of the Bluetooth chip 301. 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 circuit and the second circuit). This can prevent the crosstalk 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.

[0047] In this embodiment, a switch is provided between the low-voltage output of the power supply system and the low-voltage system. The power management circuit in the power supply system is also used to control the switch to power off the low-voltage system. Pull-up resistors are provided on the connection lines connecting the communication port transmitting end and the communication port receiving end of the low-voltage system to the communication port of the MCU chip. A specific embodiment is shown in Figure 7. The switch is generally a triode (MOS). The power management circuit controls the MOS to cut off the 3.3V operating voltage provided by the low-voltage output of the power supply system to the Bluetooth chip 301, as shown in the figure as 3V3 BEL. 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 via the protection circuit 200. It is understood that pull-up resistors (R3 and R4) connected to the power supply (VCC) are also provided on the connection lines between the communication port of the MCU chip 102 and the protection circuit 200 (i.e., the first loop and the second loop).

[0048] Furthermore, a specific implementation of the power supply system in this embodiment is shown in Figure 8, which 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 terminal (VIN) of the main chip (U1) is connected to a power supply VCC; a decoupling and filtering circuit consisting of a plurality of capacitors (C20, C21, C22, C10, C11, and C12) is provided between the input terminal (VIN) and the output terminal (VOUT) of the main chip (U1) and the ground; an output terminal (VOUT) of the main chip (U1) is connected to a first transistor (Q1); resistors (R6 and R7) are provided in a series circuit between the first transistor (Q1) and the second transistor (Q2) forming a switch tube; a diode (D2), a resistor (R5), and a capacitor (C30) are provided in parallel with the first transistor (Q1); a diode (D3) and a resistor (R4) are provided in parallel with the second transistor (Q2); and the second transistor (Q2) of the 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.

[0049] Furthermore, a specific implementation of the low-voltage system in the embodiment of the present application is shown in Figure 9, which 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 and second loops 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. The function pin (P0.16) of the Bluetooth chip shown in the figure is 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. 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 being connected 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.

[0050] Example 3

[0051] The present invention also provides a charging device, including a power supply system and the protection circuit provided in Examples 1 and 2 of the present application. The specific implementation methods 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.

[0052] Thus far, the technical solutions of the present application have been described in conjunction with the embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection 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 may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A protection circuit for preventing crosstalk at a communication port, characterized in that: including 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, wherein: 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, wherein: 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, wherein: 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, wherein: 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, wherein: 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 further used to cut off power to the low-voltage system by controlling the switch tube.

7. The protection circuit according to claim 4, wherein: A pull-up resistor is provided 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, wherein: The low-voltage system is specifically a Bluetooth control loop or a radio frequency control loop.

9. The protection circuit according to claim 8, wherein: 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.

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