Serial port transceiver circuit with protection function and electric moped instrument

Abstract

The utility model discloses a serial port transceiver circuit with a protection function and an electric moped instrument. The serial port transmitting and receiving circuit comprises a receiving circuit and a transmitting circuit, the transmitting circuit comprises an MOS tube Q1, a grid electrode of the MOS tube Q1 is connected with a USARTT X end, a source electrode of the MOS tube Q1 is grounded, a drain electrode of the MOS tube Q1 is connected with a + 5V power supply and a grid electrode of an MOS tube Q3, a source electrode of the MOS tube Q3 is grounded, a drain electrode of the MOS tube Q3 is connected with one end of a resistor R2 and a serial port transmitting output end T6, and the other end of the resistor R2 is connected with the serial port transmitting output end T6. The other end of the resistor R2 is connected with a + 5V power supply, and the MOS tube Q3 is also connected with a protection circuit. According to the utility model, on the basis of not changing the basic working principle of the original circuit, only one protection circuit is added, so that the serial communication transmitting circuit has a short-circuit protection effect; and after the short-circuit fault is removed, the circuit can recover a normal communication state.

Description

Technical Field

[0001] The utility model relates to the technical field of electric power-assisted bicycles, and in particular to a serial port transceiver circuit with a protection function and an electric power-assisted bicycle instrument. Background Art

[0002] The serial communication circuit is a commonly used communication circuit between the electric power-assisted bicycle instrument and the controller. The structure of the existing serial communication circuit is as follows: Figure 1 As shown, it converts the serial port level 3.3V to 5V level through two-stage N-MOSFET Q1 and Q3, and improves the serial port output capacity at the same time. This serial port circuit has certain defects. Specifically, if the serial port transmission output terminal T6 is in the working state, the output line connected to the serial port transmission output terminal T6 and the power line are short-circuited due to some reason, Q3 will be short-circuited to the ground during the serial port output low level cycle. A large short-circuit current passes through Q3, which will cause Q3 to fail due to overcurrent, thereby causing communication circuit failure. Utility Model Content

[0003] The purpose of the utility model is to provide a serial port transceiver circuit and an electric power-assisted bicycle instrument with a protection function in view of the deficiencies in the prior art.

[0004] To achieve the above-mentioned purpose, in a first aspect, the utility model provides a serial port transceiver circuit with a protection function, including a receiving circuit and a sending circuit, the sending circuit including a MOS tube Q1 whose gate is connected to a USART_TX terminal, the source of the MOS tube Q1 is grounded, and the drain thereof is respectively connected to a +5V power supply and a gate of a MOS tube Q3, the source of the MOS tube Q3 is grounded, and the drain thereof is respectively connected to one end of a resistor R2 and a serial port sending output terminal T6, the other end of the resistor R2 is connected to a +5V power supply, and the MOS tube Q3 is also connected to a protection circuit.

[0005] Furthermore, the protection circuit includes a resistor R4 and a resistor R6, one end of which is connected to the source of the MOS tube Q3, the other end of the resistor R4 is grounded, the other end of the resistor R6 is respectively connected to the base of the transistor Q2 and one end of the resistor R7, the emitter of the transistor Q2 and the other end of the resistor R7 are both grounded, and the collector of the transistor Q2 is connected to the gate of the MOS tube Q3.

[0006] Furthermore, the resistor R6 is connected in parallel with a capacitor C3.

[0007] Furthermore, the resistance value of the resistor R2 is 1000 ohms, and the resistance value of the resistor R4 is 10 ohms.

[0008] Furthermore, the resistance value of the resistor R6 is 5100 ohms, and the resistance value of the resistor R7 is 10000 ohms.

[0009] In a second aspect, the utility model provides an electric power-assisted bicycle instrument, comprising the above-mentioned serial port transceiver circuit with protection function.

[0010] Beneficial effect: The utility model only adds a protection circuit without changing the basic working principle of the original circuit, so that the serial communication sending circuit has a short-circuit protection function; after the short-circuit fault is eliminated, the circuit can restore to a normal communication state. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural diagram of an existing serial port transceiver circuit;

[0012] Figure 2 It is a structural schematic diagram of a serial port transceiver circuit with a protection function according to an embodiment of the utility model. DETAILED DESCRIPTION

[0013] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The embodiments are implemented based on the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0014] like Figure 2As shown, the embodiment of the utility model provides a serial port transceiver circuit with a protection function, including a receiving circuit and a sending circuit. Among them, the receiving circuit includes a sending circuit including a resistor R9 connected to the USART_RX end, the other end of the resistor R9 is respectively connected to the positive electrode of the diode D3 and one end of the resistor R8, the other end of the resistor R8 is connected to the positive electrode of the 3.3V power supply, the cathode of the diode D3 is connected to the cathode of the diode D4, the anode of the diode D4 is grounded, and the diode D4 is also connected in parallel with a capacitor C4. The above-mentioned receiving circuit is the same as the prior art, and its working principle is not repeated. The sending circuit of the embodiment of the utility model includes a MOS tube Q1 and a MOS tube Q3, wherein the gate of the MOS tube Q1 is connected to the USART_TX end, a resistor R3 can be connected between the gate of the MOS tube Q1 and the USART_TX end, the source of the MOS tube Q1 is grounded, and a resistor R5 can be connected between the gate and the source of the MOS tube Q1. The drain of the MOS transistor Q1 is connected to the +5V power supply and the gate of the MOS transistor Q3, respectively. A resistor R1 can be connected between the drain of the MOS transistor Q1 and the +5V power supply, and a capacitor C1 is preferably connected between the +5V power supply and the ground. The source of the MOS transistor Q3 is grounded, and its drain is connected to the +5V power supply and the serial port transmission output terminal T6, respectively. Specifically, the MOS transistor Q3 is preferably connected to the cathode of the diode D1 through the resistor R2, and the anode of the diode D1 is connected to the +5V power supply. A capacitor C2 is also connected between the serial port transmission output terminal T6 and the ground, and a diode D2 is connected in reverse parallel to the capacitor C2. The MOS transistor Q3 is also connected to a protection circuit.

[0015] The protection circuit of the embodiment of the utility model includes a resistor R4 and a resistor R6, one end of which is connected to the source of the MOS tube Q3, the other end of the resistor R4 is grounded, the other end of the resistor R6 is connected to the base of the transistor Q2 and one end of the resistor R7 respectively, the emitter of the transistor Q2 and the other end of the resistor R7 are both grounded, and the collector of the transistor Q2 is connected to the gate of the MOS tube Q3. It is also preferred to connect a capacitor C3 in parallel at both ends of the resistor R6. The resistance value of the above-mentioned resistor R2 is preferably 1000 ohms, and the resistance value of the resistor R4 is preferably 10 ohms. The resistance value of the above-mentioned resistor R6 is preferably 5100 ohms, and the resistance value of the resistor R7 is preferably 10000 ohms.

[0016] Normal working state: When the USART_TX end is used as the serial port output high level, through the MOS tube Q1, the output reverse voltage low level acts on the gate of the MOS tube Q3, causing the MOS tube Q3 to be in the cut-off state, so that the serial port transmission output terminal T6 outputs a high level and completes the high level conversion. When the USART_TX end is used as the serial port output low level, through the MOS tube Q1, the output reverse voltage high level acts on the gate of the MOS tube Q3, so that the MOS tube Q3 is in the on state, so that the serial port transmission output terminal T6 outputs a low level. The resistor R4 in the circuit is 10 ohms, which can be ignored relative to the resistor R2 = 1000 ohms. The voltage after the resistor R2 and the resistor R4 are divided is used as the output low level. Under normal working conditions, the voltage generated on the resistor R4 is not enough to turn on the Q2 transistor after the voltage is divided by the resistors R6 and R7, so it will not affect the level conversion of the serial port output.

[0017] Abnormal working state: For example, the output line connected to the serial port transmission output terminal T6 and the power supply voltage are short-circuited, and the power supply voltage generates a large current through the resistor R, and generates a voltage on the resistor R4, which is recorded as VR4. When the VR4 voltage reaches about 1V, the voltage after the voltage division by the resistors R6 and R7 is about 0.7V, which turns on the transistor Q2, thereby lowering the gate potential of the MOS tube Q3. Finally, the conduction current of the MOS tube Q3 is maintained at about 100mA. This current is insufficient and damages the MOS tube Q3, thereby playing a protective role. When the short circuit fault of the serial port transmission output terminal T6 to the power supply is removed, the circuit resumes normal operation. Specifically, by using a DC 60V voltage for testing, the serial port transmission output terminal T6 and the power supply voltage 60V are short-circuited, and the circuit does not fail. The short circuit is canceled and the circuit resumes normal operation.

[0018] Based on the above embodiments, those skilled in the art can easily understand that the utility model also provides an electric power-assisted bicycle instrument, including the above-mentioned serial port transceiver circuit with protection function.

[0019] The above is only a preferred embodiment of the utility model. It should be pointed out that for ordinary technicians in this technical field, other parts not specifically described belong to the prior art or common knowledge. Under the premise of not departing from the principle of the utility model, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the utility model.

Claims

1. A serial port transceiver circuit with a protection function, comprising a receiving circuit and a sending circuit, characterized in that: The sending circuit includes a MOS tube Q1 whose gate is connected to the USART_TX terminal, a source of the MOS tube Q1 is grounded, and a drain thereof is respectively connected to a +5V power supply and a gate of a MOS tube Q3, a source of the MOS tube Q3 is grounded, and a drain thereof is respectively connected to one end of a resistor R2 and a serial port sending output terminal T6, the other end of the resistor R2 is connected to the +5V power supply, and the MOS tube Q3 is also connected to a protection circuit.

2. A serial port transceiver circuit with protection function according to claim 1, characterized in that: The protection circuit includes a resistor R4 and a resistor R6, one end of which is connected to the source of the MOS tube Q3, the other end of the resistor R4 is grounded, the other end of the resistor R6 is connected to the base of the transistor Q2 and one end of the resistor R7 respectively, the emitter of the transistor Q2 and the other end of the resistor R7 are both grounded, and the collector of the transistor Q2 is connected to the gate of the MOS tube Q3.

3. A serial port transceiver circuit with protection function according to claim 2, characterized in that: The resistor R6 is connected in parallel with the capacitor C3.

4. The serial port transceiver circuit with protection function according to claim 2, characterized in that: The resistance value of the resistor R2 is 1000 ohms, and the resistance value of the resistor R4 is 10 ohms.

5. The serial port transceiver circuit with protection function according to claim 2, characterized in that: The resistance value of the resistor R6 is 5100 ohms, and the resistance value of the resistor R7 is 10000 ohms.

6. An electric power-assisted bicycle instrument, characterized in that: The invention comprises the serial port transceiver circuit with protection function as described in any one of claims 1 to 5.

Images