Over-current and over-voltage protection circuit

Abstract

The utility model discloses an overcurrent and overvoltage protection circuit, which is characterized in that a threshold comparison signal of an MCU (Microprogrammed Control Unit) is connected with a positive end input pin of a comparator U1, and an output pin of the U1 is connected with a D pin of a trigger D1; an enable signal of the MCU is connected with an OE pin of the D1, a clear signal of the MCU is connected with an LE pin of the D1 and a positive electrode of the diode D4, a protection interrupt signal of the MCU is connected with a negative electrode of the D4, a Q pin of the D1 and one input pin of the AND gate circuit D2, and a load switch signal output end of the MCU is connected with the other input pin of the D2. The output of the D2 is connected with the grid electrode of the MOS tube Q1, the source electrode of the Q1 is connected with the current input interface of the Hall sensor H1, and the sampling analog signal output interface of the H1 is connected with the input pin of the either-or switch D3; the other input pin of the D3 is connected between the series resistor R2 and the resistor R2, and the output pin of the D3 is connected with the negative end input pin of the U1 and the MCU. When an overvoltage or overcurrent fault occurs in the system, a power supply or power output can be closed in time so as to ensure that load equipment and a circuit are not damaged.

Description

Technical Field

[0001] This utility model is mainly applied in the power supply circuit or power drive of electronic devices, belonging to the field of power electronics technology, and relates to an overcurrent and overvoltage protection circuit. Background Technology

[0002] In electronic devices, the requirements for overcurrent and overvoltage protection are becoming increasingly stringent. Different devices have different overcurrent and overvoltage specifications, and even within the same device, the overcurrent and overvoltage thresholds change depending on the operating stage. Currently, the protection thresholds of overcurrent or overvoltage protection circuits are determined after the circuit design is completed. Modifying the protection threshold requires changing the hardware circuitry; it is not possible to dynamically set or modify the protection threshold. Once an overcurrent or overvoltage protection circuit is activated in an electronic device, it cannot be deactivated; recovery can only be achieved by powering down and restarting the system. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an overcurrent and overvoltage protection circuit that uses discrete components in conjunction with a microcontroller (MCU) to achieve overcurrent and overvoltage protection. When an overvoltage or overcurrent fault occurs in the system, the power supply or power output can be shut off in time to ensure that the load equipment and circuits are not damaged.

[0004] The purpose of this utility model is achieved through the following technical solution: an overcurrent and overvoltage protection circuit, including an MCU, a flip-flop D1, a diode D4, an AND gate circuit D2, a comparator U1, a MOSFET Q1, a Hall sensor H1, a load RL, and a two-to-one switch D3;

[0005] The threshold comparison signal output of the MCU is connected to the positive input pin of comparator U1, and the output pin of comparator U1 is connected to the D pin of flip-flop D1. The enable signal output of the MCU is connected to the OE pin of flip-flop D1. The clear signal output of the MCU is connected to the LE pin of flip-flop D1 and the positive terminal of diode D4. The protection interrupt signal output of the MCU is connected to the negative terminal of diode D4, the Q signal pin of flip-flop D1, and one input pin of AND gate D2. The load switch signal output of the MCU is connected to the other input pin of AND gate D2. The positive terminal of diode D4 is also connected to the LE pin of flip-flop D1, and the negative terminal is also connected to the Q signal pin of flip-flop D1.

[0006] The output pin of AND gate D2 is connected to the gate of MOSFET Q1, the drain of MOSFET Q1 is connected to the system load RL, and the other end of the system load RL is connected to the power supply VCC.

[0007] The source of MOSFET Q1 is connected to the current input interface of Hall sensor H1, the current output interface of Hall sensor is grounded, and the sampling analog signal output interface of Hall sensor is connected to one input pin of 2-to-1 switch D3.

[0008] Resistors R2 and R3 are connected in series to form a voltage divider circuit. One end of the voltage divider circuit is connected to the power supply VCC, and the other end is grounded. The other input pin of the 2-to-1 switch D3 is connected between resistors R2 and R3. The output pin of the 2-to-1 switch D3 is connected to the negative input pin of comparator U1 and the sampling signal input pin of the MCU, respectively.

[0009] The protection circuit also includes a pull-up resistor R1. One end of the pull-up resistor R1 is connected between the Q signal pin of the flip-flop D1 and the input pin of the AND gate D2, and the other end is connected to the power supply VCC.

[0010] The beneficial effects of this invention are: by using discrete components in conjunction with a microcontroller (MCU) to implement an overcurrent and overvoltage protection circuit, when an overvoltage or overcurrent fault occurs in the system, the power supply or power output can be shut off in a timely manner to ensure that the load equipment and circuits are not damaged. The current and voltage sampling, threshold comparison, protection signal processing, and switch control of this invention are all implemented by pure hardware circuits without the need for software intervention, ensuring that the overcurrent and overvoltage protection function responds quickly and has high reliability. Attached Figure Description

[0011] Figure 1 This is a circuit diagram of the overcurrent and overvoltage protection circuit of this utility model. Detailed Implementation

[0012] This invention employs discrete components and a microcontroller. The design aims to dynamically set overcurrent and overvoltage thresholds, and dynamically enable and disable overcurrent and overvoltage protection. It also requires an open interface for canceling overcurrent and overvoltage protection signals, ensuring the system continues to maintain overcurrent and overvoltage protection even after the signal is canceled. In this design, current and voltage sampling, threshold comparison, protection signal processing, and switch control must be implemented entirely in hardware, without software intervention, to guarantee fast response and high reliability of the overcurrent and overvoltage protection function.

[0013] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0014] like Figure 1 As shown, an overcurrent and overvoltage protection circuit of this utility model includes an MCU, a flip-flop D1, a diode D4, an AND gate circuit D2, a comparator U1, a MOSFET Q1, a Hall sensor H1, a load RL, and a two-to-one switch D3.

[0015] The threshold comparison signal (DA signal) output of the MCU is connected to the positive input pin (pin 1) of comparator U1, and the output pin (pin 3) of comparator U1 is connected to the D pin of flip-flop D1; the enable signal output of the MCU is connected to the OE pin of flip-flop D1; the clear signal output of the MCU is connected to the LE pin of flip-flop D1 and the positive terminal of diode D4; the protection interrupt signal output of the MCU is connected to the negative terminal of diode D4, the output pin (Q signal pin) of flip-flop D1, and one input pin (pin 2) of AND gate D2; the load switch signal output of the MCU is connected to the other input pin (pin 1) of AND gate D2; the positive terminal of diode D4 is also connected to the LE pin of flip-flop D1, and the negative terminal is also connected to the Q signal pin of flip-flop D1.

[0016] The output pin (pin 3) of AND gate D2 is connected to the gate of MOSFET Q1, the drain of MOSFET Q1 is connected to the system load RL, and the other end of the system load RL is connected to the power supply VCC.

[0017] The source of MOSFET Q1 is connected to the current input interface of Hall sensor H1, the current output interface of Hall sensor is grounded, and the sampling analog signal output interface of Hall sensor is connected to one input pin (pin 2) of 2-to-1 switch D3.

[0018] Resistors R2 and R3 are connected in series to form a voltage divider circuit. One end of the voltage divider circuit is connected to the power supply VCC, and the other end is grounded. The other input pin (pin 1) of the 2-to-1 switch D3 is connected between resistors R2 and R3. The output pin (pin 3) of the 2-to-1 switch D3 is connected to the negative input pin (pin 2) of comparator U1 and the MCU sampling signal input terminal, respectively.

[0019] The protection circuit also includes a pull-up resistor R1. One end of the pull-up resistor R1 is connected between the Q signal pin of the flip-flop D1 and the input pin of the AND gate D2, and the other end is connected to the power supply VCC. The end of the voltage divider circuit connected to the power supply VCC is also connected to the load RL and the pull-up resistor R1.

[0020] The MCU can be an STM32 series microcontroller. The load switch signal, protection interrupt signal, enable signal, and clear signal are all digital signals and can be connected to the MCU's general-purpose GPIO interface. The DA signal connected to pin 1 of U1 is an analog signal and needs to be connected to the MCU's dedicated DA output pin. Generally, GPIO0-15 of STM32 series MCUs can be configured as dedicated DA analog output pins. The signal connected to pin 2 of U1 is an analog signal and needs to be connected to the MCU's dedicated AD input pin. Generally, GPIO0-15 of STM32 series MCUs can be configured as dedicated AD analog input pins for MCU voltage or current acquisition. Users can choose the interface according to their actual needs.

[0021] Before the system can operate normally, the microcontroller (MCU) initializes the protection circuit's initial operating state. First, the MCU outputs an enable signal (push-pull high level), enabling the D-type flip-flop D1 to start working. Second, the MCU sets the clear signal to an invalid state (open-drain high level). Third, the MCU outputs a load switch signal to a high level. Fourth, the MCU outputs an analog voltage representing the comparison threshold to the positive input of the comparator (pin 1 of U1) via its internally integrated DAC; this signal is named the threshold comparison signal. At this point, the system is ready to operate, the hardware protection circuit is controllable, and it enters normal operating mode.

[0022] VCC is the system power supply, and RL is the system load. A load loop is formed through MOSFET Q1, Hall sensor H1, and then to GND. MOSFET Q1 acts as the system control switch. In case of overcurrent or overvoltage, the front-end protection circuit outputs a MOSFET turn-off signal via AND gate D2, controlling the MOSFET to disconnect the load loop, thus protecting the circuit. Hall sensor H1 detects the current in the load loop and converts it into a voltage signal. R2 and R3 are connected in series to form a voltage divider circuit, reducing the voltage between VCC and GND proportionally to the resistance values ​​of R2 and R3, achieving VCC voltage division. The voltage signals output by the Hall sensor and the voltage divider circuit are connected to a two-way switch D3. Depending on the design requirements, pins 1 and 3 of the two-way switch can be connected for overvoltage protection, or pins 2 and 3 can be connected for overcurrent protection. The output of pin 3 of the 2-to-1 switch is connected to the negative input of the comparator (pin 2 of U1). The voltage signal output by the Hall sensor or the voltage signal output by the voltage divider circuit is output to the comparator through the 2-to-1 switch. This loop signal is named the protection feedback signal.

[0023] The protection feedback signal and the threshold comparison signal are compared by comparator U1. When the protection feedback signal is less than the threshold comparison signal, the comparator outputs a high-level signal; when the protection feedback signal is greater than the threshold comparison signal, the comparator outputs a low-level signal. The comparison result output by comparator U1 (pin 3 of U1) is connected to pin D of flip-flop D1. The flip-flop can be a D-type flip-flop. The trigger output Q of the D-type flip-flop is connected to the event trigger input LE of the flip-flop through diode D4 to ensure that the low-level pulse output by the comparator can be captured when the system performs a protection action. The protection signal output by the flip-flop (pin Q of D1) is connected to one input of an AND gate (pin 2 of D2), and ANDed with the load switch signal input to the other input of the AND gate circuit, ultimately outputting the switching signal of the MOSFET.

[0024] In the specific design, when selecting comparator U1, it is necessary to consider whether the input voltage range of the comparator, the voltage range of the protection feedback signal, and the analog voltage range of the MCU's DAC output meet the input requirements of comparator U1. Flip-flops can be D-type, RS-type, latching-up, etc. The truth table of a D-type flip-flop is listed here. When the output signal Q of the flip-flop is low, connecting the output signal Q to the trigger signal LE through diode D4 can latch the low-level pulse of the input signal D. The function of diode D4 is to latch the input signal when the output terminal Q of flip-flop D1 is low, and when the output terminal Q is high, the MCU outputs a low-level clear signal, which will not force the output terminal Q to go low. As shown in Table 1, when the LE input of the flip-flop is low, the output signal Q maintains the state of Q0 at the previous moment, that is, it latches the state when the input signal D is low.

[0025] Table 1. Truth Table of Input and Output Values ​​for D-Type Flip-Flop

[0026]

[0027] When the system triggers a protection action, the trigger enters a latched state. Without external intervention, the trigger will not exit the latched state. When selecting a trigger, an open-drain output trigger should be chosen, driven by a resistor R1 at a high level. When the trigger is in the latched state, the MCU controls the OE pin of trigger D1 to be low (open-drain) and the clear signal LE to be high (open-drain), causing the trigger to exit the latched state. Then, the MCU controls the OE pin of trigger D1 to be high (push-pull), thereby canceling the protection signal and allowing the system to continue to have overcurrent or overvoltage protection functions.

[0028] The load switch signal serves as an auxiliary control signal for MOSFET Q1, controlling the load power supply switch. It is processed together with the flip-flop's output signal via an AND gate. Regardless of whether a protection action occurs, the MOSFET remains in the off state. The flip-flop's output signal Q is routed to the MCU as a protection interrupt signal. When a protection action occurs, the MCU receives the interrupt signal of the protection pulse. The protection feedback signal is connected to the MCU, allowing the MCU to acquire the system's current voltage or current via its internally integrated ADC.

[0029] After the system is powered on and ready to operate, the MCU controls the enable signal to be high. The MCU first controls the clear signal to be high, and then controls the clear signal to be low, which can disable the trigger latch function, that is, disable the overcurrent or overvoltage protection function of the entire system. When the overcurrent or overvoltage protection function is disabled, the MCU controls the clear signal to be high to re-enable the protection function. When the overcurrent or overvoltage protection function is disabled, the MCU can directly control the on / off state of the MOSFET by controlling the high and low levels of the load switch signal, which can realize software control of the load switch.

[0030] By applying this design, the system completes Figure 1 The schematic diagram is shown. The threshold comparison signal can be output through the DAC integrated on the microcontroller. After processing by the hardware circuit, the threshold comparison signal and the protection feedback signal ultimately control the on / off state of the MOSFET to protect the load equipment and circuit. The threshold comparison signal output by the MCU is the DAC output signal. After the system is powered on and ready to work, the MCU controls the enable and clear signals to turn the system's overcurrent or overvoltage protection functions on or off. After the protection action is activated, the MCU controls the OE and LE pins of flip-flop D1 to exit the latched state, thus canceling the protection signal. This allows for troubleshooting and maintenance of the system under power-on faults. After the system enters normal operating mode, the protection action circuit is completed by the following components or modules: voltage and current acquisition, signal comparison, latching, and MOSFET control. These circuits are all implemented by hardware circuits without software involvement, resulting in fast protection action response and high reliability. The protection action circuit leads out protection interrupt signals and protection feedback signals to the MCU for signal processing.

[0031] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of this invention, and should be understood that the scope of protection of this invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on these technical teachings disclosed in this invention without departing from the essence of this invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An overcurrent and overvoltage protection circuit, characterized in that, Includes MCU, flip-flop D1, diode D4, AND gate circuit D2, comparator U1, MOSFET Q1, Hall sensor H1, load RL and 2-to-1 switch D3; The threshold comparison signal output of the MCU is connected to the positive input pin of comparator U1, and the output pin of comparator U1 is connected to the D pin of flip-flop D1. The enable signal output of the MCU is connected to the OE pin of flip-flop D1. The clear signal output of the MCU is connected to the LE pin of flip-flop D1 and the positive terminal of diode D4. The protection interrupt signal output of the MCU is connected to the negative terminal of diode D4, the Q signal pin of flip-flop D1, and one input pin of AND gate D2. The load switch signal output of the MCU is connected to the other input pin of AND gate D2. The positive terminal of diode D4 is also connected to the LE pin of flip-flop D1, and the negative terminal is also connected to the Q signal pin of flip-flop D1. The output pin of AND gate D2 is connected to the gate of MOSFET Q1, the drain of MOSFET Q1 is connected to the system load RL, and the other end of the system load RL is connected to the power supply VCC. The source of MOSFET Q1 is connected to the current input interface of Hall sensor H1, the current output interface of Hall sensor is grounded, and the sampling analog signal output interface of Hall sensor is connected to one input pin of 2-to-1 switch D3. Resistors R2 and R3 are connected in series to form a voltage divider circuit. One end of the voltage divider circuit is connected to the power supply VCC, and the other end is grounded. The other input pin of the 2-to-1 switch D3 is connected between resistors R2 and R3. The output pin of the 2-to-1 switch D3 is connected to the negative input pin of comparator U1 and the sampling signal input pin of the MCU, respectively.

2. The overcurrent and overvoltage protection circuit according to claim 1, characterized in that, The protection circuit also includes a pull-up resistor R1. One end of the pull-up resistor R1 is connected between the Q signal pin of the flip-flop D1 and the input pin of the AND gate D2, and the other end is connected to the power supply VCC.

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