Power supply under-voltage and over-voltage on-off circuit

Abstract

The utility model discloses a power supply under-voltage and over-voltage on-off circuit, and relates to the field of circuits. A voltage input is connected with an input end of an under-voltage detection unit and a first input end of an under-voltage control unit; a divider resistor is arranged in the under-voltage detection unit, and the under-voltage detection unit is connected to a second input end of the under-voltage control unit through a voltage dividing point; the output end of the under-voltage detection unit and the first output end of the under-voltage control unit are in common ground connection; the control output end of the under-voltage control unit is in cascade connection with the input end of the overvoltage detection unit and the first input end of the overvoltage control unit. A voltage-regulator tube is arranged in the overvoltage detection unit, and the input end of the voltage-regulator tube is connected to the second input end of the overvoltage control unit; the output end of the overvoltage detection unit and the first output end of the overvoltage control unit are in common ground connection, and the control output end of the overvoltage control unit is a circuit output end. Through cooperative use of the divider resistor, the triode and the voltage-regulator tube, on-off of the MOS tube is controlled, voltage output is realized, and circuit stability is improved.

Description

Technical Field

[0001] This application relates to the field of circuits, and in particular to a power supply undervoltage and overvoltage switching circuit. Background Technology

[0002] An on-board pressure sensor is an electronic device that converts physical pressure signals into electrical signals. It monitors the pressure status of various vehicle systems in real time and transmits the data to the electronic control unit (ECU) for precise control and fault warning. Its core function is to ensure vehicle safety, performance stability, and energy efficiency by sensing pressure changes. When the voltage of an on-board pressure sensor increases, the resistive element (such as the strain gauge wire) may overheat, causing resistance characteristics to drift or even melt; the capacitive element may break down and short-circuit, causing circuit failure. When the voltage is insufficient, the sensor's internal drive circuit cannot amplify the signal properly, leading to output distortion or signal loss. Prolonged undervoltage can also accelerate component aging. Overvoltage can cause irreversible deformation of the pressure-sensitive diaphragm. For example, the diaphragm of a piezoresistive MEMS sensor may permanently deform when the pressure exceeds twice the full scale (FS), leading to output deviation or complete failure. Frequent voltage fluctuations in the automotive environment exacerbate this type of mechanical damage.

[0003] In related technologies, traditional protection circuits rely on fixed threshold comparators (such as the fixed VIT- and VIT+ thresholds of the TPS3702), which cannot adapt to the wide range of fluctuations in vehicle power supplies (e.g., transient spikes in a 12V system can reach 40V). Furthermore, a single voltage detection point is susceptible to line impedance, leading to misjudgments. Most solutions employ a step-by-step logic of "detection-judgment-action" (e.g., processing fault signals via DSP), resulting in protection delays in the millisecond range. Transient overvoltages in the vehicle power supply (such as sudden load drops) can damage sensors within microseconds, making this mechanism unsuitable for real-time requirements. Summary of the Invention

[0004] This application provides a power supply undervoltage and overvoltage switching circuit to solve the problems of inaccurate undervoltage measurement and severe damage due to overvoltage in vehicle pressure sensors.

[0005] The circuit includes an undervoltage detection unit, an undervoltage control unit, an overvoltage detection unit, and an overvoltage control unit;

[0006] The voltage input is connected to the input terminal of the undervoltage detection unit and the first input terminal of the undervoltage control unit; the undervoltage detection unit is equipped with a voltage divider resistor, which is connected to the second input terminal of the undervoltage control unit through the voltage divider point; the output terminal of the undervoltage detection unit and the first output terminal of the undervoltage control unit are connected to a common ground.

[0007] The control output terminal of the undervoltage control unit is cascaded with the input terminal of the overvoltage detection unit and the first input terminal of the overvoltage control unit; the overvoltage detection unit is equipped with a voltage regulator tube, and the input terminal of the voltage regulator tube is connected to the second input terminal of the overvoltage control unit;

[0008] The output terminal of the overvoltage detection unit and the first output terminal of the overvoltage control unit are connected to the same ground, and the control output terminal of the overvoltage control unit is the circuit output terminal.

[0009] Specifically, the undervoltage detection unit is equipped with voltage divider resistors R2 and R3; the voltage input is cascaded with voltage divider resistors R2 and R3 in sequence;

[0010] The input terminal of the voltage divider resistor R3 is set as the voltage divider point and connected to the second input terminal of the undervoltage control unit. The output terminal of the voltage divider resistor R3 is grounded.

[0011] Specifically, the undervoltage control unit includes a PMOS power switch Q1, a transistor Q3, and a bias resistor R1;

[0012] The input terminal of the bias resistor R1 is connected to the source of the power switch Q1, serving as the first input terminal of the undervoltage control unit; the output terminal of the bias resistor R1 is connected to the gate of the power switch Q1, and the drain of the power switch Q1 is the control output terminal of the undervoltage control unit.

[0013] Specifically, the base of transistor Q3 is the second input terminal of the undervoltage control unit, the collector of transistor Q3 is connected to the gate of power switch Q1, and the emitter of transistor Q3 is grounded.

[0014] Specifically, the overvoltage detection unit is equipped with a voltage divider resistor R4 and a Zener diode D1;

[0015] The control output terminal of the undervoltage control unit is cascaded with a voltage divider resistor R4 and a Zener diode D1. The input terminal of the Zener diode D1 is connected to the second input terminal of the overvoltage control unit, and the output terminal of the Zener diode D1 is grounded.

[0016] Specifically, the overvoltage control unit includes a gate resistor R5, a transistor Q4, a PMOS power switch Q2, and a voltage divider resistor R6;

[0017] The input terminal of Zener diode D1 is connected to one end of gate resistor R5, and the other end is connected to the base of transistor Q4. The emitter of transistor Q4 is connected to the source of power switch Q2, serving as the first input terminal of the overvoltage control unit.

[0018] Specifically, the collector of transistor Q4 is connected to the gate of power switch Q2, one end of voltage divider resistor R6 is connected to the collector of transistor Q4, and the other end is grounded.

[0019] Specifically, the drain of power switch Q2 is the control output terminal of the overvoltage control unit.

[0020] Specifically, the bias resistor R1 is 47 kΩ, the voltage divider resistor R2 is 27 kΩ, and the voltage divider resistor R3 is 2.4 kΩ.

[0021] When the base voltage of transistor Q4 is less than the turn-on voltage, transistor Q4 turns on, power switch Q1 turns off, and the circuit is turned off.

[0022] Specifically, the voltage divider resistor R4 is 1 kΩ, the gate resistor R5 is 4.7 kΩ, and the voltage divider resistor R6 is 47 kΩ.

[0023] When the input voltage of the Zener diode D1 is greater than the stable voltage, the transistor Q4 turns on, the power switch Q2 turns off, and the circuit is turned off.

[0024] The beneficial effects of the technical solutions provided in this application include at least the following:

[0025] When the voltage at the second input terminal of the undervoltage control unit is lower than the set threshold voltage (undervoltage), the control output terminal of the undervoltage control unit is in the off state, i.e., VCC_OUT has no output, and the circuit is open. When the voltage at the second input terminal of the undervoltage control unit is higher than the set threshold voltage, the control output terminal of the undervoltage control unit is in the on state. Conversely, when the voltage at the second input terminal of the overvoltage control unit is higher than the set stable voltage (overvoltage), the control output terminal of the overvoltage control unit is in the off state, i.e., VCC_OUT has no output, and the circuit is open. Only when the voltage at the second input terminal of the undervoltage control unit is higher than the set threshold voltage, and the voltage at the second input terminal of the overvoltage control unit is lower than the stable voltage, are both the undervoltage control unit and the overvoltage control unit in the on state, at which time VCC_OUT outputs normally, and the circuit is on.

[0026] Specifically, this solution uses a combination of voltage divider resistors, Zener diodes, and transistors to segment the low and high voltage regions. The voltage divider resistors and transistors cut off the low voltage region, while the Zener diodes and transistors cut off the high voltage region. With the cooperation of the MOSFETs, the circuit is switched on and off, ensuring a stable output band and protecting the pressure sensor from damage. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the power supply undervoltage and overvoltage switching circuit provided in this application;

[0028] Figure 2 This is a schematic diagram of a power supply undervoltage and overvoltage switching circuit provided in another embodiment of this application;

[0029] Figure 3 This is a simulation waveform diagram of key points of the undervoltage control unit with an input power supply voltage of 0-10V.

[0030] Figure 4 The input power supply voltage is 0-10V, and the simulation waveform of the key points of the overvoltage control unit is shown in the figure.

[0031] Figure 5 This is the input power supply voltage 0-10V, and the waveform diagram of the input and output voltage of the entire circuit. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0033] Figure 1 This application provides a power supply undervoltage and overvoltage switching circuit, which includes an undervoltage detection unit, an undervoltage control unit, an overvoltage detection unit, and an overvoltage control unit. The voltage input VCC_IN is connected to the input terminal of the undervoltage detection unit and the first input terminal of the undervoltage control unit. A voltage divider resistor is included in the undervoltage detection unit and connected to the second input terminal of the undervoltage control unit through the voltage divider point. The output terminal of the undervoltage detection unit and the first output terminal of the undervoltage control unit are connected to a common ground, GND.

[0034] The control output of the undervoltage control unit is cascaded with the input of the overvoltage detection unit and the first input of the overvoltage control unit. The overvoltage detection unit contains a Zener diode, and its input is connected to the second input of the overvoltage control unit.

[0035] The output terminal of the overvoltage detection unit and the first output terminal of the overvoltage control unit are connected to the common ground GND. The control output terminal of the overvoltage control unit is the circuit output terminal VCC_OUT.

[0036] In this circuit structure, when the voltage at the second input terminal of the undervoltage control unit is lower than the set threshold voltage (undervoltage), the control output terminal of the undervoltage control unit is in the off state, that is, VCC_OUT has no output, and the circuit is open. When the voltage at the second input terminal of the undervoltage control unit is higher than the set threshold voltage, the control output terminal of the undervoltage control unit is in the on state.

[0037] Conversely, when the voltage at the second input terminal of the overvoltage control unit is higher than the set stable voltage (overvoltage), the control output terminal of the overvoltage control unit is in the off state, that is, VCC_OUT has no output, and the circuit is disconnected.

[0038] Both the undervoltage control unit and the overvoltage control unit are in the on state only when the voltage at the second input terminal of the undervoltage control unit is higher than the set threshold voltage and the voltage at the second input terminal of the overvoltage control unit is lower than the stable voltage. At this time, VCC_OUT outputs normally and the circuit is on.

[0039] This application provides Figure 2The detailed circuit diagram shown illustrates that the undervoltage detection unit includes voltage divider resistors R2 and R3. In this application, voltage divider resistor R2 is set to 27 kΩ, and voltage divider resistor R3 to 2.4 kΩ. Voltage divider resistors R2 and R3 are cascaded in sequence at VCC_IN. A voltage divider point is led out from the input terminal of voltage divider resistor R3, and this point is connected to the second input terminal of the undervoltage control unit. The output terminal of voltage divider resistor R3 is grounded to GND.

[0040] In one possible implementation, the undervoltage control unit may include a PMOS power switch Q1, a transistor Q3, and a bias resistor R1. The bias resistor R1 is chosen to have a resistance of 47 kΩ, and its input terminal VCC_IN is connected to the source of the power switch Q1, serving as the first input terminal of the undervoltage control unit. The output terminal of the bias resistor R1 is connected to the gate of the power switch Q1, and the drain of the power switch Q1 is the control output terminal of the undervoltage control unit. The base of the transistor Q3 is the second input terminal of the undervoltage control unit, the collector of the transistor Q3 is connected to the gate of the power switch Q1, and the emitter of the transistor Q3 is grounded to GND.

[0041] In one possible implementation, the overvoltage detection unit includes a voltage divider resistor R4 and a Zener diode D1, with the voltage divider resistor R4 having a resistance of 2.4 kΩ. The control output terminal of the undervoltage control unit is cascaded with the voltage divider resistor R4 and the Zener diode D1, and the input terminal of the Zener diode D1 is connected to the second input terminal of the overvoltage control unit. The output terminal of the Zener diode D1 is grounded to GND.

[0042] In one possible implementation, the overvoltage control unit includes a gate resistor R5, a transistor Q4, a PMOS power switch Q2, and a voltage divider resistor R6. The voltage divider resistor R4 can be set to 1 kΩ, the gate resistor R5 to 4.7 kΩ, and the voltage divider resistor R6 to 47 kΩ. The input terminal of the Zener diode D1 is connected to one end of the gate resistor R5, and the other end is connected to the base of the transistor Q4. The emitter of the transistor Q4 is connected to the source of the power switch Q2, serving as the first input terminal of the overvoltage control unit.

[0043] The collector of transistor Q4 is connected to the gate of power switch Q2. One end of voltage divider resistor R6 is connected to the collector of transistor Q4, and the other end is grounded (GND). The drain of power switch Q2 is the control output terminal VCC_OUT of the overvoltage control unit.

[0044] Based on this circuit structure, when the power supply to the pressure sensor is under-voltage or over-voltage, the circuit can automatically shut off the power supply to the pressure sensor to protect it from damage.

[0045] The following are the voltage values ​​at each device port when VCC_IN is set with different input voltages:

[0046] Figure 3 This is a simulation waveform diagram of key points of the undervoltage control unit with an input power supply voltage of 0-10V. In the figure, the blue line is the input power supply voltage VCC_IN, which is input proportionally; the red line represents the base voltage of transistor Q3; and the green line represents the gate voltage of PMOS power switch Q1.

[0047] The PMOS power switch Q1 is turned on when the gate-source voltage Vgs is greater than the threshold voltage, meaning the gate is turned on at a low level. Due to the effect of the voltage divider resistor R3, the base voltage of Q3 continues to increase, but it does not reach the turn-on state. Therefore, the gate voltage of Q1 continues to increase. After Q3 turns on, the resistor R1 is equivalent to being directly grounded, so the gate voltage of Q1 drops to 0, and Q1 turns on.

[0048] Figure 4 The input power supply voltage is 0-10V. The simulation waveform of the key points of the overvoltage control unit is shown in the figure. The green line in the figure represents the gate voltage of PMOS power switch Q2; the red line represents the base voltage of transistor Q4; and the blue line represents the source voltage of PMOS power switch Q2.

[0049] In the undervoltage state, Zener diode D1 is essentially open-circuited until it reaches its stable voltage. When the voltage returns to the normal range (approximately 3.9V), Q1 will inevitably conduct. At this time, due to the resistance R5, the base voltage of Q4 does not meet the conduction condition, so Q2 also conducts. The gate voltage of Q2 is lower than its source voltage (the source of Q2 is also essentially open-circuited, so the blue and red lines coincide). In the overvoltage state (approximately 6.1V), Zener diode D1 conducts and reaches its regulated voltage; Q4 conducts and its base voltage remains constant thereafter. At this time, the gate and source voltages of Q2 are the same, and it is in the off state. The red and blue lines increase in parallel; the voltage difference is the voltage across the voltage divider resistor R4.

[0050] Figure 5 This is a waveform diagram of the input and output voltages of the entire circuit, with an input power supply voltage of 0-10V. The blue line represents the proportional VCC_IN voltage, and the green line represents the VCC_OUT (i.e., the drain output of Q2) voltage. The normal operating voltage range is 3.9-6.1V. The remaining voltage ranges are in the off state.

[0051] In summary, this solution uses a combination of voltage divider resistors, Zener diodes, and transistors to segment the low and high voltage regions. The voltage divider resistors and transistors cut off the low voltage region, while the Zener diodes and transistors cut off the high voltage region. With the cooperation of the MOSFETs, the circuit can be switched on and off, ensuring a stable output band and protecting the pressure sensor from damage.

[0052] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A power supply undervoltage and overvoltage switching circuit, characterized in that, Includes an undervoltage detection unit, an undervoltage control unit, an overvoltage detection unit, and an overvoltage control unit; The voltage input is connected to the input terminal of the undervoltage detection unit and the first input terminal of the undervoltage control unit; the undervoltage detection unit is equipped with a voltage divider resistor, which is connected to the second input terminal of the undervoltage control unit through the voltage divider point; the output terminal of the undervoltage detection unit and the first output terminal of the undervoltage control unit are connected to a common ground. The control output terminal of the undervoltage control unit is cascaded with the input terminal of the overvoltage detection unit and the first input terminal of the overvoltage control unit; the overvoltage detection unit is equipped with a voltage regulator tube, and the input terminal of the voltage regulator tube is connected to the second input terminal of the overvoltage control unit; The output terminal of the overvoltage detection unit and the first output terminal of the overvoltage control unit are connected to the same ground, and the control output terminal of the overvoltage control unit is the circuit output terminal.

2. The power supply under / over voltage cut-off circuit according to claim 1, wherein The undervoltage detection unit is equipped with voltage divider resistors R2 and R3; the voltage input is cascaded with voltage divider resistors R2 and R3 in sequence. The input terminal of the voltage divider resistor R3 is set as the voltage divider point and connected to the second input terminal of the undervoltage control unit. The output terminal of the voltage divider resistor R3 is grounded.

3. The power supply under / over voltage cut-off circuit according to claim 2, wherein The undervoltage control unit includes a PMOS power switch Q1, a transistor Q3, and a bias resistor R1; The input terminal of the bias resistor R1 is connected to the source of the power switch Q1, serving as the first input terminal of the undervoltage control unit; the output terminal of the bias resistor R1 is connected to the gate of the power switch Q1, and the drain of the power switch Q1 is the control output terminal of the undervoltage control unit.

4. The power supply under / over voltage cut-off circuit according to claim 3, wherein The base of transistor Q3 is the second input terminal of the undervoltage control unit, the collector of transistor Q3 is connected to the gate of power switch Q1, and the emitter of transistor Q3 is grounded.

5. The power supply under / over voltage cut-off circuit according to claim 1, wherein The overvoltage detection unit is equipped with a voltage divider resistor R4 and a Zener diode D1. The control output terminal of the undervoltage control unit is cascaded with a voltage divider resistor R4 and a Zener diode D1. The input terminal of the Zener diode D1 is connected to the second input terminal of the overvoltage control unit, and the output terminal of the Zener diode D1 is grounded.

6. The power supply under / over voltage cut-off circuit according to claim 5, wherein The overvoltage control unit includes a gate resistor R5, a transistor Q4, a PMOS power switch Q2, and a voltage divider resistor R6. The input terminal of Zener diode D1 is connected to one end of gate resistor R5, and the other end is connected to the base of transistor Q4. The emitter of transistor Q4 is connected to the source of power switch Q2, serving as the first input terminal of the overvoltage control unit.

7. The power supply under / over voltage cut-off circuit according to claim 4, wherein The collector of transistor Q4 is connected to the gate of power switch Q2. One end of voltage divider resistor R6 is connected to the collector of transistor Q4, and the other end is grounded.

8. The power supply under / over voltage cut-off circuit according to claim 7, wherein The drain of power switch Q2 is the control output terminal of the overvoltage control unit.

9. The under- and over-voltage power supply circuit of claim 3, wherein, The bias resistor R1 is 47 kΩ, the voltage divider resistor R2 is 27 kΩ, and the voltage divider resistor R3 is 2.4 kΩ. When the base voltage of transistor Q4 is less than the turn-on voltage, transistor Q4 turns on, power switch Q1 turns off, and the circuit is turned off.

10. The under- and over-voltage power supply circuit of claim 6, wherein, The voltage divider resistor R4 is 1 kΩ, the gate resistor R5 is 4.7 kΩ, and the voltage divider resistor R6 is 47 kΩ. When the input voltage of the Zener diode D1 is greater than the stable voltage, the transistor Q4 turns on, the power switch Q2 turns off, and the circuit is turned off.

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