Over-voltage and under-voltage protection circuit, power supply and electrical equipment

Abstract

The invention relates to the technical field of circuits, and discloses an overvoltage and undervoltage protection circuit, a power supply and electrical equipment, the overvoltage and undervoltage protection circuit comprises an overvoltage protection circuit comprising a first voltage stabilizing diode and a first controlled switch, the negative electrode of the first voltage stabilizing diode is connected with a power supply, the positive electrode is connected with the control end of the first controlled switch, and the first end of the first voltage stabilizing diode is grounded; the under-voltage protection circuit comprises a second voltage stabilizing diode and a second controlled switch, the negative electrode of the second voltage stabilizing diode is connected with the power supply, the positive electrode and the second end of the first controlled switch are respectively connected with the control end of the second controlled switch, and the first end of the second controlled switch is grounded; the control end of the third controlled switch is connected with the second end of the second controlled switch, the first end of the third controlled switch is connected with a power supply, and the second end of the third controlled switch is connected with target electrical equipment. Therefore, when the output voltage of the power supply is larger than an overvoltage value or smaller than an undervoltage value, the voltage stabilization protection function of the circuit is cut off in time.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to an over-voltage and under-voltage protection circuit, a power supply and an electrical device. Background Art

[0002] In the field of electronic applications, in view of some unstable factors in the power supply and use of electrical equipment, it is necessary to design corresponding over-voltage and under-voltage protection circuits to prevent damage to the internal components of the equipment due to external interference. Some internal components of some equipment generally work within a specific voltage range, such as within 36V, but in actual applications, due to overvoltage or undervoltage of the power supply voltage, the internal components of the equipment will be damaged. Based on this, a corresponding protection circuit is proposed to protect electrical equipment from the influence of excessively high or low power supply voltage, thereby ensuring that the electrical equipment can still work normally in an unstable power supply environment.

[0003] At present, the input voltage protection function in the power supply circuit is mainly implemented by the power supply control chip in the circuit. Specifically, the undervoltage protection threshold is set through the undervoltage lockout pin of the power supply control chip. The power supply control chip will not work below the protection threshold. However, the power supply control chip is relatively expensive and lacks protection measures against overvoltage conditions, which poses certain safety hazards. In addition, power supply control chips without undervoltage lockout pins often rely on their own input voltage operating range to cope with input voltage fluctuations. Because their peripheral circuits are complex and have many devices, and it is difficult to effectively suppress overvoltage and undervoltage of all specifications, there are problems such as complex operation and poor versatility, and hardware damage caused by voltage abnormalities cannot be avoided. Summary of the invention

[0004] In view of this, the present invention provides an over-voltage and under-voltage protection circuit, power supply and electrical equipment to solve the problem that the existing protection circuit is complex in design and has poor versatility, making it difficult to effectively protect the power supply of electrical equipment from over-voltage and under-voltage, which in turn causes hardware damage and seriously affects the safe operation of the equipment.

[0005] In a first aspect, the present invention provides an over-voltage and under-voltage protection circuit, the over-voltage and under-voltage protection circuit comprising: An overvoltage protection circuit, the overvoltage protection circuit comprises a first voltage stabilizing diode and a first controlled switch; wherein the cathode of the first voltage stabilizing diode is connected to the power supply, the anode of the first voltage stabilizing diode is connected to the control end of the first controlled switch, and the first end of the first controlled switch is grounded; An undervoltage protection circuit, the undervoltage protection circuit comprises a second voltage stabilizing diode and a second controlled switch; wherein the cathode of the second voltage stabilizing diode is connected to the power supply, the anode of the second voltage stabilizing diode and the second end of the first controlled switch are respectively connected to the control end of the second controlled switch, and the first end of the second controlled switch is grounded; A third controlled switch, the control terminal of the third controlled switch is connected to the second terminal of the second controlled switch, the first terminal of the third controlled switch is connected to the power supply, and the second terminal of the third controlled switch is connected to the target electrical equipment; Wherein, the overvoltage value of the first zener diode and the undervoltage value of the second zener diode are determined according to the operating voltage range of the target electrical equipment; when the output voltage of the power supply is greater than the overvoltage value, the overvoltage protection circuit conducts; when the output voltage of the power supply is less than the undervoltage value, the second controlled switch in the undervoltage protection circuit is cut off.

[0006] The over- and under-voltage protection circuit provided by the present invention designs an overvoltage protection circuit including a first zener diode and a first controlled switch, an undervoltage protection circuit including a second zener diode and a second controlled switch, and a third controlled switch, and determines the overvoltage value and undervoltage value of the corresponding zener diode in combination with the operating voltage of the electrical equipment, realizing the voltage stabilization protection function of timely disconnecting the circuit when the power supply output voltage is greater than the overvoltage value or less than the undervoltage value, and being able to adaptively adjust the overvoltage value of the first zener diode and the undervoltage value of the second zener diode according to actual needs, that is, only by replacing the corresponding zener diode can the over- and under-voltage protection of different devices be realized, with the remarkable advantages of convenient operation and stronger versatility, effectively avoiding hardware damage caused by power supply over- and under-voltage, and greatly ensuring the safe operation of the equipment.

[0007] In an optional embodiment, the over- and under-voltage protection circuit further includes: When the output voltage of the power supply is between the undervoltage value and the overvoltage value, the overvoltage protection circuit is disconnected, and the undervoltage protection circuit conducts.

[0008] In the present invention, when the output voltage of the power supply is between the undervoltage value and the overvoltage value, that is, when the output voltage meets the operating voltage range of the target electrical equipment, the first zener diode does not conduct, causing the overvoltage protection circuit to be disconnected, the second zener diode conducts, and the second controlled switch conducts, making the undervoltage protection circuit in a normal working state and not triggering a protection action. Furthermore, the third controlled switch conducts, ensuring the normal power supply of the rear-end load and maintaining the stable operation of the equipment; at the same time, it can avoid the misoperation of the overvoltage protection circuit, improve the reliability of the safe operation of the equipment, help extend the service life of the equipment, and achieve the balance between the precise protection and efficient power supply of the equipment.

[0009] In an optional embodiment, the overvoltage protection circuit further includes: a first voltage dividing circuit, the first terminal of the first voltage dividing circuit is connected to the positive electrode of the first zener diode, the output terminal of the first voltage dividing circuit is connected to the control terminal of the first controlled switch, and the second terminal of the first voltage dividing circuit is grounded.

[0010] By designing the first voltage dividing circuit, the present invention can accurately detect the overvoltage state, provide a reliable trigger signal for the protection circuit, further enable the controlled switch to respond accurately, thereby ensuring the reliable operation of the controlled switch, contributing to the realization of an efficient overvoltage protection function, and further enhancing the stability and reliability of the circuit.

[0011] In an alternative embodiment, the undervoltage protection circuit further includes: a second voltage dividing circuit, the first end of the second voltage dividing circuit is connected to the positive electrode of the second zener diode, the output end of the second voltage dividing circuit is connected to the control end of the second controlled switch, and the second end of the second voltage dividing circuit is grounded.

[0012] By designing the second voltage dividing circuit, the present invention can accurately detect the undervoltage state, provide a corresponding reliable trigger signal for the protection circuit, further enable the controlled switch to respond accurately, thereby ensuring the reliable operation of the controlled switch, realizing an efficient undervoltage protection function to a certain extent, and greatly improving the stability and reliability of the circuit.

[0013] In an alternative embodiment, the first controlled switch and / or the second controlled switch is an NPN-type triode; the third controlled switch is an NMOS transistor.

[0014] By using an NPN-type triode and an NMOS transistor, the present invention realizes the over- and undervoltage protection function of the circuit. Without complex integrated circuits or precision components, it has the remarkable advantages of simple circuit structure, low component cost, and easy debugging and maintenance, and can effectively improve the cost performance and practicability of the circuit.

[0015] In an alternative embodiment, the over- and undervoltage protection circuit further includes: a first filtering circuit, and the first filtering circuit is connected between the power supply and the ground.

[0016] The first filtering circuit designed by the present invention can significantly improve the reliability, accuracy, and anti-interference ability of the over- and undervoltage protection circuit, ensure its accurate operation when the voltage is abnormal, and avoid false triggering during normal fluctuations, realizing effective protection for the subsequent circuit.

[0017] In an alternative embodiment, the over- and undervoltage protection circuit further includes: an RC circuit, and the RC circuit is connected between the control end and the first end of the third controlled switch.

[0018] The RC circuit designed by the present invention can significantly improve the working stability and reliability of the controlled switch, further enhance the response accuracy and anti-interference ability of the over- and undervoltage protection circuit to abnormal voltages, and contribute to ensuring the safe and stable operation of the circuit.

[0019] In an alternative embodiment, the over- and undervoltage protection circuit further includes: a second filtering circuit, and the second filtering circuit is connected between the control end and the first end of the second controlled switch.

[0020] The second filtering circuit designed by the present invention can provide stable and reliable driving conditions for the second controlled switch, avoid mis-triggering or malfunction, and protect it from voltage stress damage. Ultimately, it improves the overall performance and reliability of the over-voltage and under-voltage protection circuit. Especially in application scenarios with high noise and large voltage fluctuations, it can greatly ensure the safe and stable operation of the circuit.

[0021] In a second aspect, the present invention provides a power supply, in which an over-voltage and under-voltage protection circuit as described in the first aspect or any corresponding embodiment thereof is configured.

[0022] In a third aspect, the present invention provides an electrical device, and the power supply of the electrical device is configured as the power supply in the second aspect described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 is a circuit schematic diagram of the over-voltage and under-voltage protection circuit according to an embodiment of the present invention; Figure 2 is a structural block diagram of the power supply according to an embodiment of the present invention; Figure 3 is a structural block diagram of the electrical device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0026] In this embodiment, an over-voltage and under-voltage protection circuit is provided. Figure 1 is a circuit schematic diagram of the over-voltage and under-voltage protection circuit according to an embodiment of the present invention, as Figure 1As shown, the over- and under-voltage protection circuit includes: an over-voltage protection circuit, an under-voltage protection circuit, and a third controlled switch. It should be noted that the over-voltage protection circuit is mainly a voltage stabilization circuit designed for the over-voltage situation of the power supply output; the under-voltage protection circuit is mainly a voltage stabilization circuit designed for the under-voltage situation of the power supply output; the third controlled switch is mainly used to control the on / off of the circuit, that is, whether the circuit outputs normally to provide the corresponding working voltage for its subsequent load (i.e., the target electrical device, such as the device or component connected to the back end of the circuit).

[0027] In this embodiment, the over-voltage protection circuit includes a first zener diode and a first controlled switch; wherein, the negative electrode of the first zener diode is connected to the power supply, the positive electrode of the first zener diode is connected to the control end of the first controlled switch, and the first end of the first controlled switch is grounded. It should be noted that the zener diode has the characteristic of maintaining a stable voltage when reverse breakdown occurs; in this embodiment, the first controlled switch is mainly used to control the on / off of the circuit, that is, the change of the control end voltage will affect its conduction state, and its specific type is not limited here and can be adjusted adaptively according to actual needs. For example, the first controlled switch is a semiconductor triode, also known as a bipolar transistor or triode, and its main types include the Negative-Positive-Negative type triode (i.e., NPN type triode) composed of two N-type semiconductors sandwiching a P-type semiconductor and the Positive-Negative-Positive type triode (i.e., PNP type triode) composed of two P-type semiconductors sandwiching an N-type semiconductor; and field effect transistors, such as Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), abbreviated as MOS transistor, which mainly includes two channel types, namely NMOS transistor and PMOS transistor, only for illustration purposes.

[0028] In this embodiment, the first controlled switch and / or the second controlled switch is an NPN type triode. Specifically, referring to Figure 1 , the specific model (i.e., over-voltage value) of the first zener diode (i.e., zener diode D1 in the figure) is determined adaptively with reference to the maximum working voltage of the target electrical device actually connected to the circuit. For example, when the working voltage of the target electrical device is between 10V and 36V, the actual model of zener diode D1 can be determined according to 36V; the first controlled switch is an NPN type triode, abbreviated as triode Q1.

[0029] In this embodiment, the undervoltage protection circuit includes a second zener diode and a second controlled switch; wherein, the negative electrode of the second zener diode is connected to the power supply, and the positive electrode of the second zener diode and the second terminal of the first controlled switch are respectively connected to the control terminal of the second controlled switch, and the first terminal of the second controlled switch is grounded. It should be noted that the relevant content of the second zener diode and the second controlled switch can refer to the relevant content of the first zener diode and the first controlled switch in the previous text respectively, and will not be repeated here. Note that referring to Figure 1 , the specific model (i.e., the undervoltage value) of the second zener diode (i.e., the zener diode D2 in the figure) is determined by referring to the minimum operating voltage adaptability of the target electrical equipment actually connected to the circuit; the second controlled switch is also an NPN-type triode, simply referred to as triode Q2.

[0030] In this embodiment, the control terminal of the third controlled switch is connected to the second terminal of the second controlled switch, the first terminal of the third controlled switch is connected to the power supply, and the second terminal of the third controlled switch is connected to the target electrical equipment. It should be noted that referring to Figure 1 , the third controlled switch in this embodiment is an NMOS transistor. Specifically, the source electrode of the MOS transistor is connected to the power supply, the drain electrode of the MOS transistor is connected to the target electronic device, and the gate electrode of the MOS transistor is connected to the control terminal of the triode Q2 (i.e., the collector of the NPN-type triode). It should be noted that in order to protect the stable output of the MOS transistor, the gate electrode of the MOS transistor is first connected to the current-limiting resistor R6 and then connected to the control terminal of the triode Q2.

[0031] Note that the specific type of the target electrical equipment in this embodiment can be adjusted adaptively according to actual needs. The target electrical equipment includes household electrical equipment, such as conventional household appliances (such as rice cookers) with a working voltage range of 100 - 240V, portable electronic devices (such as portable radios, flashlights, small calculators, etc.) with a working voltage of 10 - 39V, and industrial electrical equipment (whose working voltage is as high as several thousand volts), which is only for illustrative purposes.

[0032] It should be explained that the zener diode has the characteristic of maintaining a stable voltage when it is reversely broken down, that is, the reverse breakdown voltage of the zener diode, also called the regulated voltage value. Specifically, the regulated voltage value of the zener diode must be higher than the highest voltage during normal operation, so that it will not break down under normal voltage and will only act when overvoltage occurs. For example, if the normal operating voltage of the system is 5V, the regulated voltage value is set to about 6V (to leave a certain margin to avoid mis-triggering). In actual applications, due to the influence of temperature in the circuit environment and the normal operating voltage of the subsequent components, the overvoltage value of the first zener diode and the undervoltage value of the second zener diode can also be adaptively determined according to the circuit temperature and the safe voltage of the matching subsequent circuit, so as to ensure that the zener diode works accurately and reliably in the protection circuit.

[0033] In this embodiment, the overvoltage value of the first zener diode and the undervoltage value of the second zener diode are determined according to the operating voltage range of the target electrical device; when the output voltage of the power supply is greater than the overvoltage value, the overvoltage protection circuit conducts; when the output voltage of the power supply is less than the undervoltage value, the second controlled switch in the undervoltage protection circuit is turned off. It should be noted that the overvoltage value of the first zener diode is determined according to the maximum operating voltage of the target electrical device in combination with the actual production model of the zener diode. The specific determination method can be adjusted adaptively according to actual needs. For example, the zener diode model matching the actual production is selected according to the overvoltage value being greater than the maximum operating voltage or greater than a certain percentage of the maximum operating voltage; the undervoltage value of the second zener diode is determined according to the minimum operating voltage of the target electrical device in combination with the actual production model of the zener diode. For example, the zener diode model matching the actual production is selected according to the undervoltage value being less than the minimum operating voltage or less than a certain percentage of the minimum operating voltage. The specific determination method can also be adjusted adaptively according to actual needs, which is only for illustrative purposes.

[0034] The over- and under-voltage protection circuit of the embodiment of the present invention designs an overvoltage protection circuit including a first zener diode and a first controlled switch, an undervoltage protection circuit including a second zener diode and a second controlled switch, and a third controlled switch, and determines the overvoltage value and undervoltage value of the corresponding zener diode in combination with the operating voltage of the electrical device, realizing the voltage stabilization protection function of timely disconnecting the circuit when the power supply output voltage is greater than the overvoltage value or less than the undervoltage value, and can adaptively adjust the overvoltage value of the first zener diode and the undervoltage value of the second zener diode according to actual needs, that is, only by replacing the corresponding zener diode, the over- and under-voltage protection of different devices can be achieved, with the significant advantages of convenient operation and stronger versatility, effectively avoiding hardware damage caused by power over- and under-voltage, and greatly ensuring the safe operation of the device.

[0035] In this embodiment, the overvoltage protection circuit further includes: a first voltage dividing circuit, the first end of the first voltage dividing circuit is connected to the positive electrode of the first zener diode, the output end of the first voltage dividing circuit is connected to the control end of the first controlled switch, and the second end of the first voltage dividing circuit is grounded. It should be noted that the advantages of designing the first voltage dividing circuit in the overvoltage protection circuit in this embodiment include: 1. Precise overvoltage sampling and detection: The first voltage division circuit divides the input voltage, converting the relatively high input voltage into a voltage signal suitable for detection according to the resistance ratio; its first terminal is connected to the positive electrode of the first voltage stabilizing diode, and the reverse breakdown characteristic of the voltage stabilizing diode can be used to determine whether overvoltage occurs; when the input voltage exceeds the preset overvoltage threshold, the divided voltage will cause the first voltage stabilizing diode to break down and conduct reversely, thereby triggering subsequent protection actions; if the threshold is not exceeded, the voltage stabilizing diode remains cut-off and does not affect the normal operation of the circuit. This design can accurately detect the overvoltage state and provide a reliable trigger signal for the protection circuit.

[0036] 2. Stabilize the control terminal voltage to ensure reliable operation of the controlled switch: The output terminal of the first voltage division circuit is connected to the control terminal of the first controlled switch (such as a triode, MOS tube, etc.), and the conduction or cut-off of the controlled switch can be directly controlled by the divided voltage; when the input voltage is normal, the divided voltage keeps the controlled switch conducting and the circuit is normally powered; when overvoltage causes the voltage stabilizing diode to conduct, the voltage output by the voltage division circuit changes (such as being pulled low or pulled high), thereby changing the level of the control terminal of the controlled switch and causing it to quickly turn off, cutting off the power output to achieve overvoltage protection; this connection method ensures the stability and reliability of the control signal, enabling the controlled switch to accurately respond to the overvoltage state.

[0037] 3. Provide a reference potential to ensure the accuracy of voltage division: The second terminal of the first voltage division circuit is grounded, providing a stable reference potential (ground potential) for the voltage division circuit. This makes the divided voltage referenced to the ground, avoiding voltage drift or interference and ensuring the accuracy and stability of voltage division; even if there are certain fluctuations in the input voltage, the grounded terminal can ensure that the voltage signal output by the voltage division circuit is relatively stable, thereby improving the accuracy and reliability of overvoltage detection.

[0038] 4. Simplify the circuit structure and reduce costs: This connection method uses a simple resistor voltage division network in cooperation with a voltage stabilizing diode and a controlled switch to achieve the overvoltage protection function without the need for complex integrated circuits or precision components. The circuit structure is simple, the component cost is low, and it is easy to debug and maintain. It is suitable for cost-sensitive application scenarios and can effectively improve the cost performance and practicality of the circuit.

[0039] In this embodiment, refer to Figure 1, the first voltage dividing circuit includes resistor R1 and resistor R3; wherein, one end of resistor R1 is connected to the positive electrode of zener diode D1, and the other end is connected to the base of transistor Q1; one end of resistor R3 is connected to the base of transistor Q1, and the other end is grounded. It should be noted that since resistor R3 is the voltage dividing resistor of transistor Q1 (i.e., NPN transistor), its specific voltage dividing value needs to be determined according to the conduction voltage of the NPN transistor (this value is determined adaptively based on the actual transistor model. For example, if it conducts when the base voltage is greater than 0.9V, then the conduction voltage is 0.9V). Therefore, the ratio of resistor R1 and resistor R3 needs to satisfy this conduction voltage. For example, the resistance value of resistor R1 is 1K and the resistance value of resistor R3 is 9K, which is only for illustrative purposes. Specifically, in this embodiment, by designing the first voltage dividing circuit, the overvoltage state can be accurately detected, a reliable trigger signal can be provided for the protection circuit, and further the controlled switch can respond accurately, thus ensuring the reliable operation of the controlled switch, helping to achieve an efficient overvoltage protection function, and further enhancing the stability and reliability of the circuit.

[0040] In this embodiment, the undervoltage protection circuit further includes: a second voltage dividing circuit, the first end of the second voltage dividing circuit is connected to the positive electrode of the second zener diode, the output end of the second voltage dividing circuit is connected to the control end of the second controlled switch, and the second end of the second voltage dividing circuit is grounded. Refer to Figure 1 , the second voltage dividing circuit includes resistor R2 and resistor R4; wherein, one end of resistor R2 is connected to the positive electrode of zener diode D2, and the other end is connected to the base of transistor Q2; one end of resistor R4 is connected to the base of transistor Q2, and the other end is grounded. It should be noted that since resistor R4 is the voltage dividing resistor of transistor Q2 (i.e., NPN transistor), its specific voltage dividing value needs to be determined adaptively according to the conduction voltage of the NPN transistor. Therefore, the ratio of resistor R2 and resistor R4 needs to satisfy this conduction voltage. Specifically, in this embodiment, by designing the second voltage dividing circuit, the undervoltage state can be accurately detected, a corresponding reliable trigger signal can be provided for the protection circuit, and further the controlled switch can respond accurately, thus ensuring the reliable operation of the controlled switch, achieving an efficient undervoltage protection function to a certain extent, and greatly improving the stability and reliability of the circuit.

[0041] In this embodiment, the over-undervoltage protection circuit further includes: a first filtering circuit, the first filtering circuit is connected between the power supply and the ground, and it has the following beneficial effects: 1. Filter out power supply noise and ripple to improve detection accuracy: Since the power supply may carry high-frequency noise (such as electromagnetic interference of switching power supplies) or low-frequency ripple (such as voltage fluctuations after rectification); the first filtering circuit (usually composed of components such as capacitors and inductors, and the specific composition can be determined adaptively according to actual needs) can effectively attenuate these interference signals, making the voltage input to the over- and under-voltage protection circuit smoother and purer. Furthermore, it can avoid false detections caused by power supply noise (such as misjudging a spike noise as overvoltage), ensuring that the over- and under-voltage protection circuit only responds to real voltage overlimit situations and improving the accuracy of protection actions.

[0042] 2. Stabilize the power supply voltage to prevent false triggering: In practical applications, the power supply voltage may experience instantaneous fluctuations due to sudden changes in load, power grid fluctuations, etc.; the filtering circuit suppresses these instantaneous changes through energy storage components (such as the charging and discharging of capacitors), keeping the voltage relatively stable. For example, in the case of a short-term power supply voltage fluctuation that does not actually exceed the limit, the filtering circuit can prevent the protection circuit from misjudging it as overvoltage or undervoltage, preventing unnecessary protection actions (such as accidentally cutting off the power supply) and ensuring the normal operation of the circuit.

[0043] 3. Protect circuit components and enhance reliability: During the long-term operation of the power supply, continuous voltage ripple or high-frequency interference may accelerate the aging or damage of circuit components (such as zener diodes, comparators, sampling resistors, etc.); this circuit can reduce the impact of these interferences on the components, extend the service life of the components, and improve the long-term reliability of the over- and under-voltage protection circuit. For example, a smooth voltage input can reduce the performance degradation of zener diodes due to frequent breakdowns caused by voltage fluctuations.

[0044] 4. Optimize the detection reference to improve protection accuracy: Since over- and under-voltage protection requires accurately comparing the input voltage with the threshold voltage; the filtered and stabilized power supply voltage provides a more reliable reference for the detection circuit (such as a voltage division network, comparator), making the sampled voltage closer to the true value. For example, in undervoltage detection, a stable power supply input can prevent the sampled voltage from being lower than the actual value due to ripple, thus preventing misjudgment as undervoltage; in overvoltage detection, it can prevent the sampled voltage from being falsely high due to noise, ensuring the accurate execution of the protection threshold.

[0045] 5. Suppress common-mode interference and improve anti-interference ability: In this embodiment, the filtering circuit (such as a common-mode filtering capacitor) connected between the power supply and the ground can suppress common-mode interference (interference signals between the power supply and the ground); especially in a complex electromagnetic environment, it reduces the impact of external interference on the power supply, enabling the over- and under-voltage protection circuit to still operate stably under harsh conditions and enhancing the anti-interference ability and adaptability of the system.

[0046] In this embodiment, for the consideration of streamlining the circuit structure and controlling costs, refer to Figure 1, the first filtering circuit includes two capacitors C1 and C2 connected in parallel. Specifically, the first filtering circuit designed in this embodiment not only has the significant advantage of simple circuit structure, but also can significantly improve the reliability, accuracy and anti-interference ability of the over-voltage and under-voltage protection circuit, ensuring its accurate operation when the voltage is abnormal and avoiding false triggering during normal fluctuations, thus achieving effective protection for the subsequent circuit.

[0047] In this embodiment, the over-voltage and under-voltage protection circuit further includes: an RC circuit, which is connected between the control terminal and the first terminal of the third controlled switch, and has the following significant beneficial effects: 1. Suppress voltage spikes and prevent false triggering: In actual applications, when there is an instantaneous voltage mutation in the circuit (such as surges, electromagnetic interference, etc.), the characteristic that the voltage across the capacitor cannot change suddenly can effectively suppress the voltage spike at the control terminal; the resistor limits the rate of change of the current, avoiding false triggering of the controlled switch due to abnormal voltage fluctuations. For example, in an industrial power environment, grid interference may cause the voltage at the control terminal to rise instantaneously, and the RC circuit can ensure that the controlled switch maintains a normal operating state, avoiding misoperation of the over-voltage and under-voltage protection circuit.

[0048] 2. Achieve soft start / soft shutdown and reduce current impact: The time constant formed by the RC circuit can make the voltage at the control terminal of the controlled switch change slowly, realizing soft start or soft shutdown; for example, when the circuit is powered on, the capacitor charges and the voltage at the control terminal gradually rises, and the controlled switch conducts slowly, avoiding the impact of current mutation on circuit components and prolonging the device life. Similarly, when shutting down, the capacitor discharges and the voltage drops slowly, reducing the voltage stress at the moment of shutdown.

[0049] 3. Filter out high-frequency noise and improve circuit stability: Since the capacitor has a low impedance characteristic for high-frequency noise, it can short-circuit high-frequency interference signals to the ground, while the resistor prevents the DC component from being short-circuited, thus filtering out the high-frequency noise at the control terminal; this characteristic is particularly important in scenarios with complex electromagnetic environments (such as factories, substations), ensuring the purity of the control signal of the controlled switch and improving the stability and reliability of the over-voltage and under-voltage protection circuit.

[0050] 4. Protect the controlled switch and extend the device life: In an actual circuit, if the control terminal is subjected to over-voltage or over-current impact, the capacitor can absorb part of the energy, and the resistor limits the current magnitude, avoiding damage to the controlled switch (such as the gate of a MOS transistor, the base of a triode) due to voltage / current overload. For example, the gate withstand voltage of a MOS transistor is limited, and the RC circuit can buffer abnormal voltages, protecting its insulating layer from breakdown and extending the device service life.

[0051] 5. Optimize the control signal to ensure precise operation: The RC circuit can shape and optimize the signal at the control terminal, avoiding overly steep signal edges or oscillations, making the on / off process of the controlled switch smoother, and thus contributing to the precise response of the over- and under-voltage protection circuit to voltage anomalies; when overvoltage or undervoltage occurs, ensure that the controlled switch promptly and accurately executes the protection action (such as cutting off the power supply), improving the overall performance of the protection circuit.

[0052] In this embodiment, considering the output stability of the third controlled switch (i.e., the NMOS transistor), refer to Figure 1 , the RC circuit includes capacitor C4 and resistor R5 (whose specific resistance value is adaptively determined according to actual requirements, such as 5K), which can significantly improve the working stability and reliability of the controlled switch, further enhancing the response accuracy and anti-interference ability of the over- and under-voltage protection circuit to abnormal voltages, and contributing to ensuring the safe and stable operation of the circuit.

[0053] In this embodiment, the over- and under-voltage protection circuit further includes: a second filtering circuit, which is connected between the control terminal and the first terminal of the second controlled switch, and has the following significant beneficial effects: 1. Filter out high-frequency noise at the control terminal to avoid mis-triggering: Since the control terminal of the second controlled switch (such as MOS transistors, bipolar transistors, etc.) is usually sensitive to voltage signals (such as the gate input impedance of MOS transistors is extremely high) and is vulnerable to high-frequency noise interference. In this embodiment, the specific composition of the second filtering circuit (usually RC or LC filtering) can attenuate the high-frequency noise at the control terminal, making the control signal input to the controlled switch cleaner. For example, the capacitor presents a low impedance to high-frequency noise and bypasses it to ground, avoiding abnormal voltage fluctuations at the control terminal caused by noise, thereby preventing the controlled switch from being mis-triggered to turn on or off due to noise, and ensuring that the over- and under-voltage protection circuit only responds to real voltage abnormal states.

[0054] 2. Stabilize the voltage at the control terminal and suppress instantaneous interference: Due to instantaneous voltage fluctuations in the power supply or inside the circuit (such as load mutations, surge impacts), instantaneous spikes or dips may occur at the control terminal, causing the controlled switch to malfunction. In this embodiment, the capacitor in the second filtering circuit can store charge, release energy when the control terminal voltage drops instantaneously to maintain voltage stability, and absorb energy when the voltage rises instantaneously to suppress spikes. For example, in the under-voltage protection scenario, if the power supply voltage fluctuates briefly but does not drop below the under-voltage threshold, the filtering circuit can prevent the control terminal voltage from being misjudged as under-voltage and prevent the protection circuit from being mis-triggered to cut off the power supply.

[0055] 3. Achieve smooth transition of control signals and protect switching elements: Since the frequent and rapid on / off of the controlled switch will generate large current or voltage stress, affecting its lifespan. In this embodiment, the time constant of the second filter circuit (especially RC filtering) can make the voltage at the control terminal rise or fall slowly, achieving "soft start" or "soft turn-off" of the controlled switch. For example, the slow change of the MOS transistor gate voltage can reduce the impact of the gate drive current, lower the switching loss, avoid damage to the gate oxide layer due to voltage mutation, and extend the service life of the device.

[0056] 4. Enhance anti-interference ability and adapt to complex electromagnetic environments: Since in strong electromagnetic interference scenarios such as industrial control and power electronics, the control terminal is vulnerable to common-mode or differential-mode interference. In this embodiment, if the second filter circuit includes a capacitor to ground (such as connecting a filter capacitor between the control terminal and ground), it can effectively suppress common-mode interference (i.e., the potential difference fluctuation between the control terminal and ground), ensuring that the control signal is referenced to a stable ground potential and improving the reliability of the circuit in harsh environments.

[0057] 5. Optimize the response accuracy of the protection circuit: Since the core of over-voltage and under-voltage protection is to accurately detect the voltage threshold and control the switch action, the stability of the control terminal signal directly affects the response accuracy. In this embodiment, the voltage at the control terminal after being filtered by the second filter circuit is closer to the true detection result (such as the signal output by the voltage division network or comparator), avoiding detection errors caused by noise. For example, when the voltage is close to the over-voltage or under-voltage threshold, the filter circuit can prevent the control terminal signal from oscillating near the threshold, avoiding frequent switching of the controlled switch, and ensuring that the protection action is decisive and accurate.

[0058] It should be noted that in order to streamline the circuit structure and achieve the function of circuit voltage stabilization and protection in this embodiment, refer to Figure 1 , the second filter circuit includes capacitor C3, which is set between the base and emitter of triode Q2, can provide stable and reliable driving conditions for triode Q2, avoid mis-triggering or mis-operation, and protect it from voltage stress damage, ultimately improving the overall performance and reliability of the over-voltage and under-voltage protection circuit. Especially in application scenarios with high noise and large voltage fluctuations, it can greatly ensure the safe and stable operation of the circuit.

[0059] In this embodiment, the over- and under-voltage protection circuit further includes: when the output voltage of the power supply is between the under-voltage value and the over-voltage value, the over-voltage protection circuit is disconnected, and the under-voltage protection circuit is turned on. It should be noted that the under-voltage protection circuit is turned on and the second controlled switch in the under-voltage protection circuit is turned on. Specifically, in this embodiment, when the output voltage of the power supply is between the under-voltage value and the over-voltage value, that is, when the output voltage meets the working voltage range of the target electrical equipment, the first zener diode is not turned on, causing the over-voltage protection circuit to be disconnected. The second zener diode is turned on and the second controlled switch is turned on, causing the under-voltage protection circuit to be in a normal working state and not trigger a protection action. Furthermore, the third controlled switch is turned on, ensuring the normal power supply of the backend load and maintaining the stable operation of the equipment. At the same time, it can avoid the misoperation of the over-voltage protection circuit, improve the reliability of the safe operation of the equipment, help extend the service life of the equipment, and achieve the balance between the precise protection and efficient power supply of the equipment.

[0060] In a specific embodiment, referring to Figure 1 , the target electrical equipment is a portable small electrical appliance such as a flashlight or an electric toy, and its normal working voltage range is between 10V and 40V. Based on the aforementioned over- and under-voltage protection circuit of this embodiment, a zener diode, an NPN transistor, and an NMOS transistor are used to build the over- and under-voltage protection circuit. When the input voltage VIN is higher than 40V, the circuit is disconnected to provide protection. When the input voltage VIN is lower than 10V, the circuit is also disconnected to provide under-voltage protection. Only when the voltage is between 10V and 40V, VOUT = VIN. Moreover, in this embodiment, different zener diodes can be selected to adjust the over- and under-voltage values, thereby protecting the backend IC devices from voltage damage at the input end and preventing over-discharge of the input battery due to under-voltage.

[0061] It should be noted that the zener diode D1 has the following voltage stabilization characteristics: it conducts when the voltage is greater than 39V and the voltage across its two ends is stabilized at 39V. The zener diode D2 has the following voltage stabilization characteristics: it conducts when the voltage is greater than 9V and the voltage across its two ends is stabilized at 9V. Transistors Q1 and Q2 are both NPN transistors, used to control the on / off of the path, and conduct when the base voltage is greater than 0.9V. U1: MOS transistor, used to control the on / off of the path, and conducts when Vgs is greater than 1V. The resistance values of resistors R1 and R2 are 1K. The resistance values of resistors R3 and R4 are 9K. Capacitors C1 and C2 are used for VIN power supply filtering. Capacitor C3 and resistor R4 are used to protect the MOS transistor. Resistors R5 and R6 are current-limiting resistors.

[0062] In this embodiment, the working mode of the over- and under-voltage protection circuit of the above-mentioned flashlight includes: 1. When the input voltage VIN is greater than 40V, the zener diode D1 conducts and the voltage across its two ends is maintained at 39V. Due to the voltage division effect of R1 and R3, the base voltage of the triode Q1 is greater than 0.9V at this time, and the triode Q1 conducts; the base voltage of the triode Q2 is pulled to 0V, and the triode Q2 does not conduct. The Vgs of the MOS tube U1 = 0 and it does not conduct. Therefore, when the input voltage is greater than 40V, the circuit is disconnected. Specifically, the essence of the overvoltage protection process is the composition of the overvoltage protection circuit for the input voltage VIN greater than 40V: VIN → D1 (the two ends are stabilized at 39V, (VIN - 39V) divides the voltage between R1 and R3) → Q1 (R3 can divide 9 / 10 of the voltage, the base voltage of Q1 is greater than 0.9V and it conducts) → Q2 (the base is pulled down and does not conduct) → Vgs of U1 = 0 (does not conduct) → VOUT = 0.

[0063] 2. When the input voltage VIN is less than 10V and greater than 9V, the zener diode D2 conducts and stabilizes the voltage across its two ends at 9V. However, due to the voltage division effect of R2 and R5, the base voltage of the triode Q2 is less than 0.9V, and the triode Q2 does not conduct. The Vgs of the MOS tube U1 = 0 and it does not conduct; when the input voltage is less than 9V, both the zener diodes D1 and D2 do not conduct, the base voltage of the triode Q2 is 0, the triode Q2 does not conduct, the Vgs of the MOS tube U1 = 0 and it does not conduct. Therefore, when the input voltage is less than 10V, the circuit is disconnected. Specifically, the essence of the undervoltage protection process is the composition of the undervoltage protection circuit (less than 10V): VIN → D2 (the two ends are stabilized at 9V, (VIN - 9V) divides the voltage between R2 and R4) → Q2 (R4 can divide 9 / 10 of the voltage, but less than 0.9V and does not conduct) → Vgs of U1 = 0 (does not conduct) → VOUT = 0.

[0064] 3. When the input voltage VIN is greater than or equal to 10V and less than or equal to 40V, similarly due to the principles of the zener diodes D1 and D2, the voltage division of R1\R3, and the voltage division of R2 / R4, the base voltage of the triode Q1 is less than 0.9V, and the triode Q1 does not conduct; the base voltage of the triode Q2 is greater than 0.9V, the triode Q2 conducts, the Vgs of the MOS tube U1 is greater than 1V, the MOS tube U1 conducts, and VOUT = VIN, and the circuit outputs normally. Specifically, the essence of the overvoltage protection process is the composition of the normal voltage output situation (that is, greater than 10V and less than 40V): Since the voltage division of R3 is less than 0.9V, Q1 does not conduct, the voltage division of R4 is greater than 0.9V, Q2 conducts, the gate voltage of the MOS tube U1 is pulled down, Vgs is greater than 1V, the MOS tube conducts, VOUT = VIN, and the output is normal.

[0065] In summary, the over - undervoltage protection circuit of the embodiment of the present invention has the following advantages: 1. Multi - stage filtering for stable input: The capacitors C1 and C2 in this embodiment form an input filtering circuit, which can effectively filter out high - frequency and low - frequency noises in VIN, reduce power supply ripple, provide a relatively pure input voltage for the subsequent circuit, and improve the overall stability.

[0066] 2. Zener diode reference for anti - voltage - fluctuation: The Zener diodes D1 and D2 in this embodiment provide a stable reference voltage for the base of the triode Q1 through the resistors R1 and R2; even if VIN fluctuates, as long as it is within the working range of the Zener diode, the base voltage of the triode Q1 can be guaranteed to be stable, enhancing the anti - interference ability of the circuit to input voltage fluctuations.

[0067] 3. Triode amplification for precise control: The triodes Q1 and Q2 in this embodiment form a signal amplification and driving link; among them, the triode Q1 amplifies the difference between the reference voltage and the feedback voltage, and the resistor R3 stabilizes its operating point to ensure linear amplification characteristics; the triode Q2 further amplifies the signal to drive the MOS tube; this multi - stage amplification structure can precisely adjust the conduction degree of the MOS tube, quickly respond to over - voltage or under - voltage states, and achieve precise control of VOUT.

[0068] 4. RC damping for oscillation suppression: The capacitor C4 and the resistor R5 in this embodiment are connected in parallel to the gate of the MOS tube to form an RC damping circuit, which can suppress the high - frequency oscillation of the gate voltage of the MOS tube (such as the voltage fluctuation caused by the Miller effect), ensure the stable conduction or turn - off of the MOS tube, and improve the reliability of the circuit.

[0069] 5. Negative feedback and decoupling for enhanced stability: The capacitor C3 and the resistor R4 in this embodiment are connected in parallel (close to the triode Q2), which may play a role in decoupling, and then filter out the high - frequency noise at the base of the triode Q2 to stabilize its bias voltage.

[0070] 6. MOS - tube output for efficient driving: The MOS tube in this embodiment is used as an output adjustment tube, which has the characteristics of high input impedance and small switching loss. It can quickly adjust the on - resistance during over - voltage or under - voltage, achieve efficient regulation of VOUT, is suitable for large - current output scenarios, and has low power consumption.

[0071] In summary, the above over - under - voltage protection circuit in this embodiment uses NPN - type triodes and NMOS tubes to achieve the over - under - voltage protection function of the circuit. It does not require complex integrated circuits or precision components, has the significant advantages of simple circuit structure, low component cost, easy debugging and maintenance, can effectively cope with input voltage fluctuations, ensure the stability of VOUT, and at the same time has strong anti - interference ability, fast response speed, high efficiency, etc.

[0072] In this embodiment, a power supply is also provided. The power supply is configured with an over-voltage and under-voltage protection circuit for implementing the above-mentioned embodiments and preferred embodiments, and those that have been described will not be elaborated again. Specifically, Figure 2 is the structural block diagram of the power supply according to the embodiment of the present invention. As Figure 2 shown, an over-voltage and under-voltage protection circuit 201 is configured in the power supply. Specifically, by configuring the over-voltage and under-voltage protection circuit in the power supply of this embodiment, the voltage stabilization protection function of timely disconnecting the circuit when the output voltage is greater than the over-voltage value or less than the under-voltage value can be realized.

[0073] In this embodiment, an electrical device is also provided. The power supply of the electrical device is configured to include a power supply with an over-voltage and under-voltage protection circuit for implementing the above-mentioned embodiments and preferred embodiments, and those that have been described will not be elaborated again. Specifically, Figure 3 is the structural block diagram of the electrical device according to the embodiment of the present invention. As Figure 3 shown, the power supply of the electrical device is the power supply 3 configured with the over-voltage and under-voltage protection circuit 201.

[0074] It should be noted that the specific type of the electrical device in this embodiment is not limited here and can be adaptively adjusted according to actual needs. For example, the electrical device is a low-voltage small household appliance, such as an electric shaver, an electric toothbrush, and a beauty instrument included in personal care; a portable juicer, a mini electric cooker, and a small bread maker included in kitchen small appliances; an electronic scale, a mini projector, and a water dispenser included in daily practical devices; only for illustration and not limited thereto, and it can be adaptively adjusted according to actual needs. Specifically, integrating the above-mentioned over-voltage and under-voltage protection circuit of this embodiment on the electrical device, that is, this type of electrical device can realize the voltage stabilization protection function of timely disconnecting the circuit when the power supply output voltage is greater than the over-voltage value or less than the under-voltage value by selecting a power supply configured with an over-voltage and under-voltage protection circuit for power supply, and only needs to replace the corresponding voltage stabilizing diode to realize the over-voltage and under-voltage protection of different devices. It has the significant advantages of convenient operation and stronger versatility, can effectively avoid hardware damage caused by power supply over-voltage and under-voltage, greatly ensure the safe operation of the device, meet the high-efficiency use requirements of the device, and improve the user experience to a certain extent.

[0075] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An over- and under-voltage protection circuit, characterized in that, The over- and under-voltage protection circuit includes: An over-voltage protection circuit, which includes a first zener diode and a first controlled switch; wherein, the negative electrode of the first zener diode is connected to the power supply, the positive electrode of the first zener diode is connected to the control end of the first controlled switch, and the first end of the first controlled switch is grounded; An under-voltage protection circuit, which includes a second zener diode and a second controlled switch; wherein, the negative electrode of the second zener diode is connected to the power supply, the positive electrode of the second zener diode and the second end of the first controlled switch are respectively connected to the control end of the second controlled switch, and the first end of the second controlled switch is grounded; A third controlled switch, the control end of the third controlled switch is connected to the second end of the second controlled switch, the first end of the third controlled switch is connected to the power supply, and the second end of the third controlled switch is connected to the target electrical equipment; Wherein, the over-voltage value of the first zener diode and the under-voltage value of the second zener diode are determined according to the operating voltage range of the target electrical equipment; when the output voltage of the power supply is greater than the over-voltage value, the over-voltage protection circuit conducts; when the output voltage of the power supply is less than the under-voltage value, the second controlled switch in the under-voltage protection circuit is cut off.

2. The over- and under-voltage protection circuit according to claim 1, characterized in that, The over- and under-voltage protection circuit further includes: When the output voltage of the power supply is between the under-voltage value and the over-voltage value, the over-voltage protection circuit is disconnected, and the under-voltage protection circuit conducts.

3. The over-voltage and under-voltage protection circuit according to claim 1, characterized in that, The over-voltage protection circuit further includes: a first voltage dividing circuit, the first end of the first voltage dividing circuit is connected to the positive electrode of the first zener diode, the output end of the first voltage dividing circuit is connected to the control end of the first controlled switch, and the second end of the first voltage dividing circuit is grounded.

4. The over- and under-voltage protection circuit according to claim 1, characterized in that, The under-voltage protection circuit further includes: a second voltage dividing circuit, the first end of the second voltage dividing circuit is connected to the positive electrode of the second zener diode, the output end of the second voltage dividing circuit is connected to the control end of the second controlled switch, and the second end of the second voltage dividing circuit is grounded.

5. The over- and under-voltage protection circuit according to claim 1, characterized in that The first controlled switch and / or the second controlled switch is an NPN-type triode; The third controlled switch is an NMOS transistor.

6. The over-voltage and under-voltage protection circuit according to any one of claims 1 to 5, characterized in that The over- and under-voltage protection circuit further includes: a first filtering circuit, which is connected between the power supply and the ground.

7. The over- and under-voltage protection circuit according to claim 1 or 5, characterized in that, The over- and under-voltage protection circuit further includes: an RC circuit, which is connected between the control end and the first end of the third controlled switch.

8. The over- and under-voltage protection circuit according to claim 1, 4 or 5, characterized in that The over- and under-voltage protection circuit further includes: a second filtering circuit, which is connected between the control end and the first end of the second controlled switch.

9. A power supply, characterized in that, The power supply is configured with the over- and under-voltage protection circuit according to any one of claims 1 to 8.

10. An electrical device, characterized in that, The power supply of the electrical equipment is configured as the power supply according to claim 9.

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