Reversed polarity protection circuit for vehicle-mounted controller

Abstract

The utility model discloses a reversed polarity protection circuit for a vehicle-mounted controller. Comprising an MOS tube M1, a resistor R1, a resistor R3 and diodes D1-D2, one end of the MOS tube M1 is connected with an external storage battery VBAT, the diode D1 and the resistor R3 are connected in series and then are connected in parallel between the MOS tube M1 and the ground together with the resistor R1, the two ends of the MOS tube M1 are connected through the diode D2, the MOS tube M1 is grounded through a load RL, and the output of the MOS tube M1 is connected with an external controller power supply network SUPPOWER. According to the utility model, the storage battery VBAT can be loaded to the controller power supply network SUPPOWER to supply power to the load RL by controlling the opening of the MOS tube under the condition that the voltage basically has no loss, and the MOS tube is ensured to be in a turn-off state to disconnect the power supply under the reverse polarity connection of the power supply, so that the reverse connection short circuit fault of the controller is prevented, and the service life of the controller is prolonged. And the use safety of the vehicle-mounted controller is improved.

Description

Technical Field

[0001] This utility model relates to the field of automotive electronic circuit technology, specifically to a reverse polarity protection circuit for an on-board controller. Background Technology

[0002] The reverse polarity protection of vehicle controllers is a mandatory test item in the national standard. Typical reverse polarity protection uses a diode, leveraging the diode's unidirectional conduction characteristic. This protection method has the following main problems: when the diode is forward-biased, there is a 0.7V forward voltage drop, meaning the minimum starting voltage required by the actual controller needs to be 0.7V higher than the minimum starting voltage of the control chip. Under this condition, some controllers may not meet the minimum starting voltage requirements of special vehicles. Utility Model Content

[0003] To address the problems existing in the background technology, this utility model proposes a reverse polarity protection circuit for vehicle controllers. While meeting the requirements for reverse polarity protection of the controller, the power supply line is controlled by a MOSFET. When the MOSFET is on, its voltage drop is much smaller than that of a diode (0.7V), thereby meeting the minimum starting voltage requirements of some vehicles for the controller.

[0004] The technical solution of this utility model is implemented as follows:

[0005] This utility model includes a MOSFET M1, resistors R1 and R3, and diodes D1 to D2. One end of the MOSFET M1 is connected to an external battery VBAT. Diodes D1 and R3 are connected in series and then in parallel with resistor R1 between the MOSFET M1 and ground. The two ends of the MOSFET M1 are connected through diode D2. The MOSFET M1 is grounded through the load RL. The output of the MOSFET M1 is connected to the external controller power supply network SUP_POWER.

[0006] The drain of the MOSFET M1 is connected to the external battery VBAT. Diode D1 and resistor R3 are connected in series and then in parallel with resistor R1 between the gate of the MOSFET M1 and ground. The gate of the MOSFET M1 is connected to its source through diode D2. The source of the MOSFET M1 is grounded through the load RL. The source of the MOSFET M1 serves as the output terminal for connection to the controller power supply network SUP_POWER.

[0007] The positive terminal of diode D1 is connected to resistor R3, and the negative terminal is connected to the gate of MOSFET M1.

[0008] The positive terminal of diode D2 is connected to the gate of MOSFET M1, and the negative terminal is connected to the source of MOSFET M1.

[0009] The controller power supply network SUP_POWER is specifically implemented by connecting to the vehicle battery through the vehicle wiring harness, thereby supplying power to the ECU controller.

[0010] The load RL refers to the internal load of the controller, specifically the internal loads such as sensors and light switches.

[0011] The MOS transistor M1 is a PMOS transistor.

[0012] The beneficial effects of this utility model are:

[0013] This invention enables the battery VBAT to be supplied to the controller's power supply network SUP_POWER with minimal voltage loss by controlling the MOSFET's on-state, thereby powering the load RL. In the case of reverse polarity connection, the circuit ensures the MOSFET is off, thus disconnecting the power supply and preventing reverse short circuit faults in the controller. This reverse polarity circuit improves the safety of the vehicle controller. Attached Figure Description

[0014] Figure 1 This is a reverse polarity protection circuit for an on-board controller. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] like Figure 1 As shown, the specific circuit includes MOSFET M1, resistors R1 and R3, and diodes D1 to D2. One end of MOSFET M1 is connected to the external battery VBAT. Diode D1 and resistor R3 are connected in series and then in parallel with resistor R1 between MOSFET M1 and ground. The two ends of MOSFET M1 are connected through diode D2. MOSFET M1 is grounded through the load RL. The output of MOSFET M1 is connected to the external controller power supply network SUP_POWER.

[0017] More specifically, such as Figure 1 As shown, the circuit includes a MOSFET M1, resistors R1 and R3, a load RL, and diodes D1 to D2. The drain of pin 1 of the MOSFET M1 is connected to the external battery VBAT. Diode D1 and resistor R3 are connected in series and then in parallel with resistor R1 between the gate of pin 3 of the MOSFET M1 and ground. The gate of pin 3 of the MOSFET M1 is connected to its own source through diode D2. The source of pin 3 of the MOSFET M1 is grounded through the load RL. The source of pin 3 of the MOSFET M1 serves as the output terminal for connection to the controller power supply network SUP_POWER.

[0018] Specifically, the source of pin 3 of MOSFET M1 is connected to pin 2 of one end of load RL and the negative terminal of pin 2 of diode D2, and is used as an output terminal to connect to the controller power supply network SUP_POWER; pin 1 of the other end of load RL is grounded; the gate of pin 2 of MOSFET is connected to the cathode of pin 2 of diode D2, pin 1 of resistor R1, and pin 1 of diode D1; pin 2 of resistor R1 is grounded; the anode of pin 2 of diode D1 is connected to pin 1 of resistor R3; and pin 2 of resistor R3 is grounded.

[0019] The anode of diode D1 is connected to resistor R3, and the cathode is connected to the gate of pin 3 of MOSFET M1. The anode of diode D2 is connected to the gate of pin 3 of MOSFET M1, and the cathode is connected to the source of pin 3 of MOSFET M1.

[0020] The controller power supply network SUP_POWER is specifically implemented by connecting to the vehicle battery through the vehicle wiring harness, thereby supplying power to the ECU controller. The load RL is the internal load of the controller, specifically internal sensors, light switches, and other loads. MOSFET M1 is a PMOS transistor.

[0021] In the specific implementation, MOSFET M1 is a PMOS transistor, specifically model RSQ015P10HZG; diode D2 is a Zener diode, model UFZVFHTE-1715B; and diode D1 is a switching diode, model S-LBAS21HT1G. Resistor R1 can be set to 1MΩ, and resistor R3 can be set to 10KΩ.

[0022] In this invention, the MOSFET M1 is used to turn on or off the external battery VBAT power supply. The Zener diode D2 is used to ensure that the voltage difference between the gate of pin 2 and the source of pin 3 of the PMOS transistor does not exceed 15V. The resistor R1 is used for current limiting and pull-down to stabilize the potential. Diode D1 is connected in series with resistor R3 in parallel with resistor R1 to bypass resistor R1 and ensure that the PMOS transistor does not turn on when reverse connected.

[0023] The circuit of this invention has two operating modes, including a forward operating mode and a reverse protection mode. The specific operating processes of the two operating modes are as follows:

[0024] In positive working mode:

[0025] At the instant the external battery VBAT is powered on, the battery voltage VBAT is 13V, which is applied to the controller power supply network SUP_POWER through the body diode of the PMOS transistor M1, resulting in a voltage of 13V - 0.7V = 12.3V. At this moment, there are two possibilities: the Zener diode D2 does not break down, or the Zener diode D2 breaks down.

[0026] When the Zener diode D2 does not break down, the voltage at the gate of pin 2 of PMOS transistor M1 is the voltage divider between diode D2 and resistor R1. Considering that the internal resistance of diode D2 is approximately 10MΩ when it does not break down, the voltage across its terminals is VG = 12.3 * (1MΩ / (1MΩ + 10MΩ)) = 1.118V. At this time, the voltage difference between the gate and source of PMOS transistor M1 is VGS = VG - VS = 1.18V - 12.3V = -11.12V < -2.5V. This ensures that PMOS transistor M1 is fully turned on, making the battery voltage VBAT and the voltage of the controller power supply network SUP_POWER the same at 13V with almost no voltage drop.

[0027] When Zener diode D2 breaks down, the voltage difference between the gate (pin 2) and source (pin 1) of PMOS transistor M1 is -15V, i.e., VGS = -15V < -2.5V. This ensures that PMOS transistor M1 is fully turned on, making the battery voltage VBAT match the voltage of the controller power supply network SUP_POWER at 13V. Resistor R1 limits the current to prevent excessive current flowing through Zener diode D2, which could damage it.

[0028] In reverse protection mode:

[0029] The battery VBAT is grounded, and the ground is the power supply of 13.5V. At this time, the 13.5V power supply goes through resistor R3 to diode D1, and then through Zener diode D2 to the load RL. Zener diode D2 is conducting normally, and the voltage difference across diode D2 is 0.7V. Therefore, VGS = 0.7V > -2.5V, which does not meet the PMOS turn-on condition. This disconnects the battery VBAT from the controller power supply network SUP_POWER, thus preventing a short circuit between the power supply and ground.

[0030] In this mode, the function of the resistor R3 and diode D1 in series is to ensure that the current in the circuit is greater than the minimum conduction current of diode D2. With this module, the circuit current will be limited by the 1M resistance of R1, resulting in a circuit current that is too small. It cannot guarantee that the forward current requirement of the Zener diode D2 will be met. In this case, the voltage difference across diode D2 cannot be guaranteed to be a certain constant value of 0.7V. There is a risk of unexpected conduction of PMOS transistor M1, and the purpose of reverse polarity protection cannot be achieved.

[0031] Therefore, this invention can control the MOSFET to enable the battery VBAT to be loaded onto the controller power supply network SUP_POWER with almost no voltage loss, thereby supplying power to the load RL.

[0032] With the power supply connected in reverse polarity, the circuit ensures that the MOSFET is in the off state, thus disconnecting the power supply and preventing short circuit faults in the controller. This reverse polarity circuit improves the safety of the vehicle controller.

Claims

1. A reverse polarity protection circuit for an on-board controller, characterized in that: It includes MOSFET M1, resistors R1 and R3, and diodes D1 to D2. One end of MOSFET M1 is connected to an external battery VBAT. Diode D1 and resistor R3 are connected in series and then in parallel with resistor R1 between MOSFET M1 and ground. The two ends of MOSFET M1 are connected through diode D2. MOSFET M1 is grounded through load RL. The output of MOSFET M1 is connected to the external controller power supply network SUP_POWER.

2. A reverse polarity protection circuit for a vehicle control unit according to claim 1, wherein: The drain of the MOSFET M1 is connected to the external battery VBAT. Diode D1 and resistor R3 are connected in series and then in parallel with resistor R1 between the gate of the MOSFET M1 and ground. The gate of the MOSFET M1 is connected to its source through diode D2. The source of the MOSFET M1 is grounded through the load RL. The source of the MOSFET M1 serves as the output terminal for connection to the controller power supply network SUP_POWER.

3. The reverse polarity protection circuit for an in-vehicle controller according to claim 1, wherein: The positive terminal of diode D1 is connected to resistor R3, and the negative terminal is connected to the gate of MOSFET M1.

4. The reverse polarity protection circuit for an in-vehicle controller according to claim 1, characterized by: The positive terminal of diode D2 is connected to the gate of MOSFET M1, and the negative terminal is connected to the source of MOSFET M1.

5. The reverse polarity protection circuit for an in-vehicle controller according to claim 1, characterized by: The controller power supply network SUP_POWER is connected to the vehicle battery via the vehicle wiring harness, thereby supplying power to the ECU controller.

6. The reverse polarity protection circuit for an in-vehicle controller according to claim 1, wherein: The load RL is the internal load of the controller.

7. The reverse polarity protection circuit for an in-vehicle controller according to claim 1, wherein: The MOS transistor M1 is a PMOS transistor.

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