Protection circuit and energy storage system thereof

Abstract

The embodiment of the utility model discloses a protection circuit and an energy storage system thereof. The circuit comprises a switch module configured to receive an input voltage and output the input voltage when the input voltage is conducted; the control module outputs a driving signal to switch on the switch module when the input voltage is greater than a first preset threshold value, and outputs a cut-off signal to switch off the switch module when the input voltage is greater than a second preset threshold value; a self-locking module; the energy storage module is charged when receiving the cut-off signal and outputs a feedback signal to the self-locking module after the voltage is reduced, so that the self-locking module continues to output the cut-off signal; the second preset threshold is greater than the first preset threshold. According to the embodiment of the utility model, the switch is controlled by accurately identifying the input voltage range, the charging circuit is ensured to be disconnected when the voltage is too low or too high, and a continuous self-locking protection mechanism is formed until the input is completely disconnected, so that element damage caused by frequent overvoltage recovery circulation is effectively avoided, the reliability of the photovoltaic energy storage system is improved, and the service life of the photovoltaic energy storage system is prolonged.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic energy storage, and in particular to a protection circuit and its energy storage system. Background Technology

[0002] In modern renewable energy applications, the combination of photovoltaic (PV) power generation systems and energy storage inverters has become an important component of clean energy applications. However, the instability of the output voltage of PV modules poses a significant challenge to system design. When the inverter is charged by PV, the PV voltage fluctuates significantly, and the system needs to operate within a suitable voltage range to ensure efficiency and safety.

[0003] The primary problem facing photovoltaic (PV) inverter systems is the difficulty in starting up due to low voltage. Under low light conditions, such as in the early morning, late afternoon, or on cloudy days, the output voltage of the PV modules often falls below the inverter's minimum startup voltage, preventing the system from activating and wasting available energy. Traditional voltage detection circuits have limited resolution in the low voltage range, making it difficult to accurately distinguish critical states. Even more problematic is that when the voltage approaches the startup threshold, minute fluctuations in sunlight can cause the system to repeatedly start and stop. This start-stop oscillation not only reduces energy efficiency but also significantly shortens the equipment's lifespan.

[0004] Meanwhile, the hazards of excessive voltage should not be ignored. When photovoltaic modules operate under high light and low temperature conditions, the open-circuit voltage may far exceed the rated value, easily exceeding the withstand voltage capacity of the inverter's internal components. Traditional overvoltage protection mechanisms are usually based on fuses or simple circuit breaking structures, with limited response speed, making it difficult to disconnect the circuit in time before critical components fail. More importantly, many existing systems are designed to automatically resume operation after the voltage drops to a safe range. Under frequent fluctuations in light conditions, this can cause the system to repeatedly enter the overvoltage-recovery cycle, significantly increasing component stress, accelerating system aging, and even causing safety accidents. Utility Model Content

[0005] The main technical problem solved by this utility model embodiment is to provide a protection circuit and its energy storage system, which can solve at least some of the defects of existing photovoltaic energy storage systems.

[0006] To solve the above-mentioned technical problems, the present invention provides a protection circuit comprising: a switching module configured to receive an input voltage and output the input voltage when the circuit is on; a control module connected to the switching module and configured to output a drive signal to turn on the switching module when the input voltage is greater than a first preset threshold; and to output a cutoff signal to turn off the switching module when the input voltage is greater than a second preset threshold; a self-locking module connected to the switching module; and an energy storage module connected to the self-locking module and configured to receive the input voltage for charging when the self-locking module receives the cutoff signal, and to output a feedback signal to the self-locking module after the input voltage drops to no greater than the second preset threshold; wherein the self-locking module is configured to output the cutoff signal in response to the feedback signal; and the second preset threshold is greater than the first preset threshold.

[0007] Optionally, the energy storage module stops outputting the feedback signal after the input voltage is disconnected, so that the self-locking module stops outputting the cutoff signal.

[0008] Optionally, the control module includes: a drive unit connected to the switch module, configured to output a drive signal to turn on the switch module when the input voltage is greater than a first preset threshold; and a cut-off unit connected to the switch module, configured to output a cut-off signal to turn off the switch module when the input voltage is greater than a second preset threshold.

[0009] Optionally, the driving unit includes resistor R2 and resistor R9. The first end of resistor R2 is connected to the input voltage, the second end of resistor R2 is connected to the first end of resistor R9 and the first input terminal of the switching module, and the second end of resistor R9 is connected to reference ground.

[0010] Optionally, the cutoff unit includes a Zener diode D3, a diode D1, a resistor R5, and a resistor R8. The cathode of the Zener diode D3 is connected to the input voltage, the anode of the Zener diode D3 is connected to the first terminal of the resistor R5, the second terminal of the resistor R5 is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the first terminal of the resistor R8 and the second input terminal of the switching module, and the second terminal of the resistor R8 is connected to reference ground.

[0011] Optionally, the self-locking module includes: a switching unit connected to the control module and the energy storage module, configured to output a charging signal in response to the cutoff signal, so that the energy storage module receives the input voltage and enters a charging state; and a feedback unit connected to the energy storage module, the switching unit, and the switching module, configured to output the cutoff signal in response to the feedback signal.

[0012] Optionally, the switching unit includes a switching transistor Q3, the energy storage module includes an electrolytic capacitor EC1, the first terminal of the electrolytic capacitor EC1 is connected to the input voltage, the collector of the switching transistor Q3 is connected to the second terminal of the electrolytic capacitor EC1, the base of the switching transistor Q3 is connected to the second output terminal of the control module, and the emitter of the switching transistor Q3 is connected to a reference ground.

[0013] Optionally, the feedback unit includes a switch Q4, resistors R1, R3, R6, R7, and R10. The emitter of the switch Q4 and the first terminal of the resistor R1 are connected to the input voltage. The base of the switch Q4 is connected to the second terminal of the resistor R1 and the first terminal of the resistor R3. The collector of the switch Q4 is connected to the first terminal of the resistor R6 and the first terminal of the resistor R10. The second terminal of the resistor R3 is connected to the collector of the switch Q3. The second terminal of the resistor R6 is connected to the first terminal of the resistor R7 and the base of the switch Q3. The second terminals of the resistors R10 and R7 are connected to a reference ground.

[0014] Optionally, the switching module includes switching transistors Q1 and Q2, diode D2, resistors R4 and R11, and a voltage regulator reference source U2. The drain of switching transistor Q2 and the first end of resistor R11 are connected to the input voltage. The source of switching transistor Q2 is connected to the anode of diode D2. The cathode of diode D2 is used to output the input voltage. The gate of switching transistor Q2 is connected to the first end of resistor R4 and the second end of resistor R11. The second end of resistor R4 is connected to the cathode of voltage regulator reference source U2. The reference terminal of the cathode of voltage regulator reference source U2 is connected to the collector of switching transistor Q1 and the first output terminal of the control module. The base of switching transistor Q1 is connected to the second output terminal of the control module. The emitter of switching transistor Q1 and the anode of voltage regulator reference source U2 are connected to reference ground.

[0015] Secondly, this utility model provides an energy storage system, including: the protection circuit as described in the first aspect.

[0016] The beneficial effects of this utility model embodiment are as follows: Unlike the prior art, this utility model embodiment achieves accurate identification of the input voltage through the control module, and then controls the switching module to ensure that the charging circuit is not turned on when the voltage is too low; it works stably when the voltage is normal; and it cuts off the charging circuit when the voltage is too high. A continuous self-locking protection mechanism is formed through the self-locking module and the energy storage module. Even if the voltage recovers to a safe range, the switching module remains in the off state until the input is completely disconnected, effectively avoiding component damage caused by frequent overvoltage recovery cycles, and significantly improving the reliability and service life of the photovoltaic energy storage system. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a schematic diagram of the structure of a protection circuit provided in an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of the structure of a control module provided in an embodiment of this application;

[0020] Figure 3 This is a schematic diagram of the structure of a self-locking module provided in an embodiment of this application;

[0021] Figure 4 The circuit structure of the switching module and the control module is shown;

[0022] Figure 5 The circuit structure of the self-locking module and the energy storage module is shown. Detailed Implementation

[0023] To facilitate understanding of this utility model, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this specification are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0025] Reference Figure 1 This utility model provides a protection circuit applicable to photovoltaic energy storage systems. The protection circuit includes a switch module 100, a control module 200, a self-locking module 300, and an energy storage module 400. The connections between the modules are as follows: the control module 200 is connected to the switch module 100; the switch module 100 is connected to the self-locking module 300; and the self-locking module 300 is connected to the energy storage module 400.

[0026] The switching module 100 is configured to receive the input voltage and output the input voltage when it is turned on. In photovoltaic energy storage systems, the input voltage typically comes from the photovoltaic modules and is unstable, varying due to environmental factors such as light intensity and temperature. As the main control unit of the circuit, the switching module 100 determines whether to transmit the input voltage to the system's backend based on signals from the control module 200. The on / off state of the switching module 100 directly determines whether the photovoltaic input voltage can enter the energy storage system for charging.

[0027] The control module 200 is connected to the switch module 100, and its main functions include two aspects: First, when the input voltage is greater than a first preset threshold, it outputs a drive signal to turn on the switch module 100; second, when the input voltage is greater than a second preset threshold, it outputs a cutoff signal to turn off the switch module 100. The control module 200 ensures that the energy storage system operates only within a suitable voltage range by accurately monitoring the input voltage level. The first preset threshold represents the minimum activation voltage of the energy storage system; the system will only be activated and begin operation when the input voltage exceeds this threshold. The second preset threshold represents the maximum safe voltage that the energy storage system can withstand; when the input voltage exceeds this threshold, to protect the system from high-voltage damage, the control module 200 outputs a cutoff signal to turn off the switch module 100.

[0028] When the input voltage is within the normal range, the self-locking module 300 maintains the normal operating state of the switching module 100. However, once the input voltage exceeds the safe range, the self-locking module 300 receives a cutoff signal from the control module 200 and maintains the switching module 100 in the off state. Even if the input voltage subsequently falls back to the safe range, it will not automatically resume the on state. This prevents the energy storage system from repeatedly starting and stopping under frequent input voltage fluctuations, effectively avoiding potential component damage and shortened system lifespan.

[0029] The energy storage module 400 is configured to receive an input voltage for charging when the self-locking module 300 receives a cutoff signal, and to output a feedback signal to the self-locking module 300 after the input voltage drops to no more than a second preset threshold. The energy storage module 400 maintains the operating state of the self-locking module 300 by storing electrical energy, keeping the energy storage system in a shut-off state even after the input voltage has returned to a safe range. Furthermore, according to this embodiment, the energy storage module 400 stops outputting the feedback signal after the input voltage is disconnected, thereby stopping the self-locking module 300 from outputting a cutoff signal. This ensures that the energy storage system can reset and be ready to receive new input after the photovoltaic input is completely disconnected.

[0030] In this embodiment, the self-locking module 300 is configured to output a cutoff signal in response to a feedback signal; the second preset threshold is greater than the first preset threshold to ensure that the energy storage system operates only within a suitable voltage window, i.e., the input voltage is greater than the first preset threshold but does not exceed the second preset threshold. When the input voltage exceeds the second preset threshold, the energy storage system will immediately shut down and remain in the off state until the input voltage is completely disconnected.

[0031] The operation of this protection circuit is as follows: First, the input voltage is input to the control module 200 and the switch module 100 of the protection circuit; the control module 200 monitors the input voltage level; when the input voltage is greater than a first preset threshold but less than a second preset threshold, the control module 200 outputs a drive signal to turn on the switch module 100, and the energy storage system starts to work normally; when the input voltage exceeds the second preset threshold, the control module 200 outputs a cutoff signal, the self-locking module 300 receives the cutoff signal and turns off the switch module 100, and at the same time the energy storage module 400 starts charging; even if the input voltage subsequently drops to a safe range, the energy storage module 400 continues to provide feedback signals to the self-locking module 300 to maintain the off state of the switch module 100; only when the input voltage is completely disconnected does the energy storage module 400 stop outputting feedback signals, the self-locking module 300 then stops outputting cutoff signals, and the energy storage system resets to a state ready to receive new input.

[0032] This protection circuit accurately identifies the input voltage and provides self-locking protection, effectively solving the problem of system damage or low efficiency caused by voltage instability in existing photovoltaic energy storage systems. Compared with traditional protection circuits, the protection circuit provided in this embodiment has higher accuracy, reliability, and safety, which can significantly extend the service life of the photovoltaic energy storage system and improve the overall performance of the energy storage system.

[0033] like Figure 2 As shown, the control module 200 includes a drive unit 210 and a cut-off unit 220, both of which are connected to the switch module 100.

[0034] The drive unit 210 is configured to output a drive signal to turn on the switch module 100 when the input voltage is greater than a first preset threshold. The main function of the drive unit 210 is to ensure that the energy storage system only starts working when the input voltage reaches a certain level, avoiding problems such as instability or low efficiency of the energy storage system due to insufficient voltage. In the energy storage system, the first preset threshold is usually set as the minimum voltage value required for normal operation of the energy storage system, and is reasonably set according to the actual application scenario and the characteristics of the energy storage system components.

[0035] In a photovoltaic energy storage system, when the input voltage is lower than a first preset threshold, the drive unit 210 will not send any drive signal to the switch module 100, the switch module 100 will remain off, and the photovoltaic energy storage system will not operate. As the light intensity increases, the photovoltaic input voltage gradually rises. When the voltage exceeds the first preset threshold, the drive unit 210 generates and sends a drive signal to the switch module 100, causing the switch module 100 to conduct, and the input voltage can be transmitted to the back end of the photovoltaic energy storage system for charging or power supply operations.

[0036] The drive unit 210 can detect whether the input voltage exceeds a first preset threshold through various circuit implementations. For example, a resistor divider network can be used to convert the input voltage into an appropriate detection signal, which is then compared and judged by a comparator or a dedicated voltage detection integrated circuit. When the detection signal exceeds a preset reference value, the drive unit 210 outputs a high level or a signal sufficient to drive the switch module 100, thereby controlling the switch module 100.

[0037] The cutoff unit 220 is configured to output a cutoff signal to turn off the switch module 100 when the input voltage exceeds a second preset threshold. The main function of the cutoff unit 220 is to prevent excessively high input voltage from damaging the energy storage system. In photovoltaic energy storage systems, due to changes in environmental conditions (such as strong sunlight, low temperature, etc.), the output voltage of the photovoltaic modules may exceed the withstand voltage capability of the system modules. Therefore, a protection mechanism must be set up to prevent high voltage from damaging the energy storage system.

[0038] When the input voltage is below the second preset threshold, the cutoff unit 220 is in a non-operating state and does not interfere with the normal operation of the photovoltaic energy storage system. However, once the input voltage exceeds the second preset threshold, the cutoff unit 220 immediately generates and sends a cutoff signal to the switch module 100, forcing the switch module 100 to turn off and cut off the transmission of the input voltage to the back end of the photovoltaic energy storage system, thereby protecting the photovoltaic energy storage system components from high voltage damage.

[0039] The circuit implementation of the cutoff unit 220 can use a Zener diode as a voltage reference. When the input voltage exceeds the Zener diode's voltage regulation value, the Zener diode breaks down and conducts, generating a signal to control the switch module 100 to turn off. Alternatively, a high-precision voltage comparator or a dedicated overvoltage protection integrated circuit can be used. When the detected input voltage exceeds a preset threshold, a trigger signal is output to turn off the switch module 100.

[0040] Under normal operating conditions, when the input voltage is between a first preset threshold and a second preset threshold, the drive unit 210 outputs a drive signal to turn on the switch module 100, while the cutoff unit 220 does not output any signal, and the system operates normally. When the input voltage is below the first preset threshold, the drive unit 210 does not output a drive signal, and the switch module 100 remains off. When the input voltage exceeds the second preset threshold, even if the drive unit 210 outputs a drive signal, the cutoff signal generated by the cutoff unit 220 will force the switch module 100 to turn off, ensuring system safety.

[0041] It is worth noting that the second preset threshold must be greater than the first preset threshold, and the difference between the two constitutes the safe operating voltage window of the photovoltaic energy storage system. The setting of this voltage window needs to comprehensively consider factors such as the electrical characteristics, operating efficiency, and safety margin of the photovoltaic energy storage system components. It should not be too narrow, leading to frequent system start-ups and shutdowns, nor too wide, leading to safety hazards.

[0042] As an example and not a limitation, the control module 200 can be implemented using discrete component circuits or integrated circuits. Discrete component implementations offer advantages such as simple structure, ease of adjustment and maintenance, while integrated circuit implementations are characterized by small size and high reliability. In practical applications, the appropriate implementation method can be selected based on requirements such as cost, space, and reliability.

[0043] In the photovoltaic energy storage system, the control module 200 controls the switching module 100 by accurately identifying the input voltage range, thus achieving effective protection for the photovoltaic energy storage system. Compared with traditional voltage monitoring circuits, the control module structure provided in this embodiment, through the separate design of the drive unit and the cutoff unit, achieves independent monitoring and control of different voltage ranges, improving the accuracy and reliability of the photovoltaic energy storage system. Simultaneously, this structure also provides a good interface for cooperation with the self-locking module and the energy storage module, laying the foundation for the stable operation of the photovoltaic energy storage system.

[0044] This control module structure is suitable for various photovoltaic energy storage systems, especially in scenarios with large input voltage fluctuations. By reasonably setting the first and second preset thresholds, optimization can be performed for different application environments and photovoltaic energy storage system configurations, achieving precise control and effective protection of the photovoltaic energy storage system, extending its service life, and improving energy utilization efficiency.

[0045] like Figure 3 As shown, the self-locking module 300 includes a switching unit 310 and a feedback unit 320. The switching unit 310 is connected to the control module 200 and the energy storage module 400, and the feedback unit 320 is connected to the energy storage module 400, the switching unit 310, and the switching module 100.

[0046] The switching unit 310 is configured to output a charging signal in response to a cutoff signal, so that the energy storage module 400 receives the input voltage and enters a charging state. Upon receiving the cutoff signal from the control module 200, the switching unit 310 quickly activates the energy storage module 400, initiating the charging process. The switching unit 310 acts as a bridge between the control module 200 and the energy storage module 400, translating the overvoltage state detected by the control module 200 into charging control of the energy storage module 400.

[0047] The operation of the switching unit 310 is as follows: When the photovoltaic input voltage is within the normal range, the switching unit 310 is in a non-operating state, which does not affect the normal operation of the photovoltaic energy storage system. Once the photovoltaic input voltage exceeds the set second preset threshold, the control module 200 will immediately output a cutoff signal. After receiving the cutoff signal, the switching unit 310 immediately switches to the operating state and outputs a charging signal to the energy storage module 400, causing the energy storage module 400 to begin receiving the photovoltaic input voltage for charging. The response speed of the switching unit 310 is crucial to the effectiveness of the photovoltaic energy storage system. Therefore, in practical design, it is necessary to select electronic switching devices with fast response characteristics to implement the function of the switching unit 310.

[0048] Feedback unit 320 is connected to energy storage module 400, switching unit 310, and switching module 100, and is configured to output a cutoff signal in response to a feedback signal. Feedback unit 320 receives the feedback signal from energy storage module 400 and generates and maintains the cutoff signal accordingly, continuously shutting off switching module 100 to ensure that the photovoltaic energy storage system will not automatically restart after the input voltage returns to normal, thereby forming effective self-locking protection.

[0049] The operation of feedback unit 320 is as follows: Under normal operating conditions, feedback unit 320 is in standby mode and does not interfere with the normal operation of the photovoltaic energy storage system. When energy storage module 400 starts charging due to overvoltage protection and reaches a certain charge level, energy storage module 400 outputs a feedback signal to feedback unit 320. Upon receiving this feedback signal, feedback unit 320 immediately generates a cutoff signal and outputs it to switch module 100, forcing switch module 100 to remain in the off state. Even if the photovoltaic input voltage has fallen back to a safe range at this time, due to the continuous output of the cutoff signal by feedback unit 320, switch module 100 remains in the off state, and the photovoltaic energy storage system cannot be restarted.

[0050] The cutoff signal output by feedback unit 320 will continue until energy storage module 400 stops providing feedback signals. Energy storage module 400 will stop outputting feedback signals after the input voltage is completely disconnected. At this time, feedback unit 320 will also correspondingly stop outputting the cutoff signal, and the entire photovoltaic energy storage system will return to its restartable initial state. Through this mechanism, the photovoltaic energy storage system achieves true self-locking protection, avoiding damage caused by frequent start-stop cycles due to voltage fluctuations.

[0051] When the switching unit 310 receives the cutoff signal and activates the energy storage module 400, the energy storage module 400 provides a feedback signal to the feedback unit 320, which then generates and maintains the cutoff signal based on this feedback signal. This cutoff signal not only acts on the switching module 100 to keep it off, but also feeds back to the switching unit 310, forming a positive feedback loop and strengthening the self-locking effect.

[0052] In practical circuit implementation, the switching unit 310 can be implemented using semiconductor switching devices such as transistors or field-effect transistors, while the feedback unit 320 can be constructed using components such as comparators, operational amplifiers, or application-specific integrated circuits. For the switching unit 310, the focus is on its response speed and driving capability; for the feedback unit 320, the focus is on its signal processing accuracy and output stability.

[0053] The operating voltage range of the self-locking module 300 needs to match the operating voltage range of the photovoltaic energy storage system. Typically, the self-locking module 300 should be able to operate normally above the minimum activation voltage and withstand the highest possible input voltage. Simultaneously, to ensure the reliability of the self-locking function, the power supply of the self-locking module 300 should have a certain degree of independence, capable of maintaining the self-locked state for a sufficiently long time when the main circuit is disconnected.

[0054] The design of the self-locking module 300 fully considers the characteristics and requirements of the photovoltaic energy storage system's operating environment. Compared with traditional overvoltage protection circuits, the self-locking module structure provided in this embodiment achieves a more reliable overvoltage protection function through the coordinated operation of the switching unit and the feedback unit. Especially in scenarios where frequent changes in light intensity lead to large fluctuations in photovoltaic output voltage, this self-locking function can effectively prevent component aging and damage caused by repeated start-ups and shutdowns, significantly extending the system's service life.

[0055] like Figure 4 As shown, the switching module 100 includes a switching transistor Q1, a switching transistor Q2, a diode D2, resistors R4 and R11, and a voltage regulator reference U2. The drain of the switching transistor Q2 and the first terminal of resistor R11 are connected to the input voltage PV. The source of the switching transistor Q2 is connected to the anode of diode D2, and the cathode of diode D2 is used to output the input voltage, forming the PV_OUT output terminal. The gate of the switching transistor Q2 is connected to the first terminal of resistor R4 and the second terminal of resistor R11. The second terminal of resistor R4 is connected to the cathode of the voltage regulator reference U2. The reference terminal of the cathode of the voltage regulator reference U2 is connected to the collector of the switching transistor Q1 and the first output terminal of the control module (i.e., the output terminal of the drive unit 210). The base of the switching transistor Q1 is connected to the second output terminal of the control module (i.e., the output terminal of the cutoff unit 220). The emitter of the switching transistor Q1 and the anode of the voltage regulator reference U2 are connected to the reference ground.

[0056] Switch Q2 controls whether the PV input voltage is transmitted to the system's backend. Switch Q2 uses a MOSFET device, which features fast switching speed and low on-resistance, enabling efficient transmission of PV input power. Diode D2 is located between the source and output of switch Q2, providing reverse connection protection to ensure that current flows only from the PV input to the output, preventing potential reverse current from damaging the front-end circuitry of the energy storage system.

[0057] Resistors R11 and R4 form the bias network for the gate of transistor Q2. One end of resistor R11 is connected to the PV input voltage, and the other end is connected to the gate of transistor Q2, forming a pull-up resistor. Resistor R4 is connected between the gate of transistor Q2 and the voltage reference U2 to transmit the control signal of U2. Through the synergistic effect of resistors R11 and R4, when the voltage reference U2 is on, the gate of transistor Q2 is pulled low, turning off transistor Q2; when the voltage reference U2 is off, the gate of transistor Q2 is kept high, turning on transistor Q2. The ratio of the resistance values ​​of resistors R11 and R4 determines the gate voltage, thus affecting the conduction state and on-resistance of transistor Q2, and needs to be optimized according to the parameter characteristics of transistor Q2 in actual design.

[0058] The voltage regulator U2 is responsible for determining whether to turn on the switching transistor Q2 based on the voltage signal provided by the drive unit 210. The voltage regulator U2 typically uses an integrated circuit with a precise reference voltage (e.g., 2.5V). When the reference voltage at its cathode exceeds the reference voltage, U2 turns on and stabilizes the reference voltage at the reference voltage level; when the reference voltage is lower than the reference voltage, U2 does not operate. Through the resistor divider network (resistors R2 and R9) of the drive unit 210, the PV input voltage is proportionally divided and sent to the reference terminal of the voltage regulator U2, enabling the voltage regulator U2 to accurately detect whether the PV input voltage has reached the minimum voltage (first preset threshold) required for the energy storage system activation.

[0059] Switch Q1 is responsible for forcibly shutting down the voltage reference source U2 under overvoltage conditions. Switch Q1 is an NPN transistor, with its base connected to the output terminal (node ​​V1) of the cutoff unit 220. When the input voltage exceeds the second preset threshold, V1 goes high, and switch Q1 turns on, pulling the reference terminal of the voltage reference source U2 low to near ground potential, causing the voltage reference source U2 to stop working and thus shutting down switch Q2, cutting off the transmission of the PV input voltage to the system backend. The selection of switch Q1 needs to consider its switching speed, saturation voltage drop, and current gain to ensure that it can quickly and effectively shut down the voltage reference source U2 under overvoltage conditions.

[0060] The working principle of the switching module 100 can be divided into three states: When the PV input voltage is lower than the first preset threshold, the voltage at the reference terminal of the voltage regulator U2 is lower than the start-up voltage (e.g., 2.5V) of the voltage regulator U2 through the voltage divider of the driving unit 210 (resistors R2 and R9), so the voltage regulator U2 does not work, the gate voltage of the switching transistor Q2 is insufficient to turn on the switching transistor Q2, and there is no output of PV_OUT.

[0061] When the PV input voltage is between the first preset threshold and the second preset threshold, the voltage at the reference terminal of the voltage regulator U2 exceeds the start-up voltage of the voltage regulator U2 through the voltage division of the drive unit 210. The voltage regulator U2 starts to work and pulls one end of the resistor R4 low, turning on the switch Q2. The PV input voltage is transmitted to PV_OUT through the switch Q2 and the voltage regulator D2, and the energy storage system works normally.

[0062] When the PV input voltage exceeds the second preset threshold, the Zener diode D3 in the cutoff unit 220 is broken down, node V1 becomes high level, the switch Q1 is turned on, pulling the reference terminal of the voltage reference source U2 low, the voltage reference source U2 stops working, the switch Q2 is turned off, the PV input voltage cannot be transmitted to PV_OUT, and the energy storage system enters the protection state.

[0063] The drive unit 210 converts the PV input voltage into a signal level suitable for the operation of the voltage regulator reference source U2 through a voltage divider network composed of resistors R2 and R9, thereby controlling the start-up voltage of the energy storage system. The cut-off unit 220 generates a control signal when the input voltage exceeds the safe range through an overvoltage detection circuit composed of Zener diode D3, diode D1, resistor R5, and resistor R8. This signal forces the voltage regulator reference source U2 and the switching transistor Q2 to be turned off via Q1, thus achieving overvoltage protection.

[0064] The structure of this switching module and control module can effectively cope with the instability of the input voltage, ensuring that the photovoltaic energy storage system operates only within a safe voltage range, thereby improving the reliability and service life of the photovoltaic energy storage system.

[0065] like Figure 5 As shown, the switching unit 310 of the self-locking module includes a switching transistor Q3, and the energy storage module 400 includes an electrolytic capacitor EC1. The first terminal of the electrolytic capacitor EC1 is connected to the input voltage PV, the collector of the switching transistor Q3 is connected to the second terminal of the electrolytic capacitor EC1, the base of the switching transistor Q3 is connected to the second output terminal of the control module (i.e., the signal from the cutoff unit), and the emitter of the switching transistor Q3 is connected to reference ground. Through this structural design, the switching unit 310 can activate the energy storage module 400 and establish a self-locking protection state when it receives an overvoltage signal.

[0066] Switch Q3 adopts an NPN transistor structure, possessing excellent switching characteristics and signal amplification capabilities. The base of switch Q3 receives an overvoltage signal (i.e., a high-level signal at node V1) from the cutoff unit via the second output terminal of the control module. When the PV input voltage is within the normal range, V1 remains low, and switch Q3 is in the off state, not affecting the normal operation of the energy storage system. When the PV input voltage exceeds a preset threshold, V1 becomes high, and the base of switch Q3 receives a valid drive signal, connecting the charging path of electrolytic capacitor EC1, causing EC1 to begin charging.

[0067] Electrolytic capacitor EC1 is responsible for storing electrical energy and maintaining the self-locking protection state under overvoltage conditions. Compared with other types of capacitors, electrolytic capacitors have a larger capacitance and energy density, enabling them to store sufficient charge in a smaller volume and support a longer self-locking state. The first terminal of electrolytic capacitor EC1 is directly connected to the PV input voltage, and the second terminal is connected to the control circuit of switching transistor Q3 through the collector of switching transistor Q3, forming a charge storage and release path.

[0068] When the energy storage system detects an overvoltage condition, the control module's cutoff unit outputs a high-level signal to node V1, turning on switch Q3. Electrolytic capacitor EC1 then begins charging through switch Q3. Charging current flows from the PV input terminal into the first terminal of electrolytic capacitor EC1. After storing charge in EC1, the current flows out from the second terminal of EC1 and through the collector-emitter path of switch Q3 to the reference ground. During charging, the voltage at the second terminal of EC1 gradually increases. This voltage is fed back to the switching module through feedback unit 320, maintaining the switching module in its off state and achieving self-locking protection.

[0069] The selection of the capacitance value of the electrolytic capacitor EC1 is a critical consideration in energy storage module design. An insufficient capacitance value may result in inadequate self-locking time, failing to effectively handle short-term voltage fluctuations; an excessively large capacitance value increases cost and size, and prolongs charging time, potentially affecting protection speed. Generally, the capacitance value of the electrolytic capacitor EC1 needs to be determined comprehensively based on the voltage level of the energy storage system, self-locking protection time requirements, and circuit leakage current level. In practical design, parameters such as the EC1's withstand voltage rating, temperature characteristics, and lifespan also need to be considered to ensure its reliability under various operating conditions.

[0070] The feedback unit 320 of the self-locking module includes a switching transistor Q4, resistors R1, R3, R6, R7, and R10. The emitter of the switching transistor Q4 and the first terminal of resistor R1 are connected to the input voltage PV. The base of the switching transistor Q4 is connected to the second terminal of resistor R1 and the first terminal of resistor R3. The collector of the switching transistor Q4 is connected to the first terminal of resistor R6 and the first terminal of resistor R10. The second terminal of resistor R3 is connected to the collector of the switching transistor Q3 (i.e., connected to the second terminal of electrolytic capacitor EC1). The second terminal of resistor R6 is connected to the first terminal of resistor R7 and the base of the switching transistor Q3. The second terminals of resistor R10 and the second terminals of resistor R7 are connected to reference ground. Through this circuit structure, the feedback unit 320 forms a self-sustaining feedback loop, ensuring the continuous stability of the overvoltage protection state.

[0071] The switching transistor Q4 adopts a PNP transistor structure and is responsible for converting the feedback signal into a continuous control signal after the electrolytic capacitor EC1 is charged. The emitter of the switching transistor Q4 is connected to the PV input voltage to provide the operating power supply; the base forms a bias network through resistors R1 and R3, and the collector is connected to the subsequent circuit and the reference ground through resistors R6 and R10, forming a complete signal transmission path.

[0072] Resistor R1 is connected between the PV input terminal and the base of the switching transistor Q4, forming a pull-down resistor to keep the switching transistor Q4 off in the initial state. Resistor R3 is connected between the base of the switching transistor Q4 and the second terminal of the electrolytic capacitor EC1 (the collector of the switching transistor Q3). It is a key component of the feedback path. When EC1 charges, increasing the voltage at its second terminal, resistor R3 lowers the base voltage of the switching transistor Q4, causing Q4 to turn on, thus forming a self-sustaining loop.

[0073] Resistor R6 is connected between the collector of switching transistor Q4 and the base of switching transistor Q3. It is used to transmit the control signal after switching transistor Q4 is turned on to the base of switching transistor Q3, keeping switching transistor Q3 continuously on. Resistors R7 and R10 are pull-down resistors for the base of switching transistor Q3 and the collector of switching transistor Q4, respectively, to ensure that the corresponding nodes remain at a low level when the signal is insufficient, preventing false triggering.

[0074] The working process of the self-locking module and the energy storage module can be divided into the following stages: when the PV input voltage is within the safe range, the cutoff unit does not output an overvoltage signal, node V1 remains at a low level, the switching transistor Q3 is turned off, the electrolytic capacitor EC1 is not charged, the switching transistor Q4 is also in the off state, and the energy storage system is working normally.

[0075] When the PV input voltage exceeds the second preset threshold, the cutoff unit outputs a high-level signal to node V1, the switch Q3 turns on, and the electrolytic capacitor EC1 starts charging. However, at this time, the voltage of the electrolytic capacitor EC1 has not yet been established, and the switch Q4 is still in the off state.

[0076] As electrolytic capacitor EC1 charges, its second terminal voltage increases, which reduces the base voltage of switching transistor Q4 through resistor R3, causing Q4 to turn on. Once Q4 is on, current is injected into the base of switching transistor Q3 through resistor R6, enhancing Q3's conduction and creating positive feedback. As Q4's conduction deepens, the current supplied to the base of switching transistor Q3 increases, further strengthening Q3's conduction and ultimately achieving complete self-locking.

[0077] Even if the PV input voltage drops back to a safe range at this point, because the electrolytic capacitor EC1 is already charged and the switching transistor Q4 is on, the switching transistor Q3 continues to be on, and the electrolytic capacitor EC1 continues to charge, the energy storage system remains in a protected state. This self-locking state will continue until the PV input is completely disconnected.

[0078] When the PV input is completely disconnected, the electrolytic capacitor EC1 gradually discharges through the circuit leakage current, the voltage decreases, and the switching transistors Q4 and Q3 are turned off in succession. The energy storage system returns to its initial state and is ready to receive new input.

[0079] This self-locking protection mechanism is crucial for the safe and stable operation of photovoltaic systems. Due to changes in sunlight conditions, the output voltage of photovoltaic systems may fluctuate frequently. Conventional overvoltage protection may lead to frequent system start-ups and shutdowns, accelerating module aging. However, with the self-locking mechanism, the energy storage system will remain in a shut-off state after detecting overvoltage until the input is completely disconnected, avoiding the problems caused by frequent start-ups and shutdowns.

[0080] In practical design, a balance needs to be struck between the reliability and sensitivity of the self-locking mechanism. Overly sensitive self-locking may cause the energy storage system to frequently enter a self-locking state due to short-term voltage fluctuations, affecting normal operation; insufficient self-locking sensitivity may prevent effective protection of the energy storage system. Optimal protection can be achieved by appropriately selecting the capacitance value of electrolytic capacitor EC1, the resistance ratios of various resistors, and the parameters of switching transistors Q3 and Q4.

[0081] Compared with traditional overvoltage protection, the self-locking and energy storage mechanism provided in this embodiment has several advantages: First, the self-locking function avoids frequent start-stop due to voltage fluctuations; second, the energy storage module ensures the continuous stability of the protection state; third, the complete power failure recovery mechanism ensures the system's automatic reset capability; and finally, the circuit structure is relatively simple, highly reliable, and low in cost.

[0082] This self-locking module and energy storage module structure are suitable for applications with stringent voltage control requirements, such as photovoltaic energy storage systems and battery management systems. Through collaborative work with the control module and switching module, they form a complete voltage protection system capable of effectively handling various abnormal voltage conditions and ensuring the safe and stable operation of the equipment.

[0083] Based on the protection circuit provided in the above embodiments, this application also provides an energy storage system, which includes the protection circuit provided in any of the above embodiments.

[0084] It should be noted that while the preferred embodiments of this utility model are provided in the specification and accompanying drawings, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of this utility model; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of this utility model. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this utility model specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A protection circuit, characterized by, The application relates to a switching module, a control module, a self-locking module and an energy storage module. The switching module is configured to receive an input voltage and output the input voltage when turned on. The control module is connected with the switching module and configured to output a driving signal to turn on the switching module when the input voltage is greater than a first preset threshold value. The control module is also configured to output a cutoff signal to turn off the switching module when the input voltage is greater than a second preset threshold value. The self-locking module is connected with the switching module. The energy storage module is connected with the self-locking module and configured to receive the input voltage to charge when the self-locking module receives the cutoff signal. The energy storage module is also configured to output a feedback signal to the self-locking module after the input voltage is reduced to not greater than the second preset threshold value. The self-locking module is configured to output the cutoff signal in response to the feedback signal.

2. The circuit of claim 1, wherein, The second preset threshold value is greater than the first preset threshold value.

3. The circuit of claim 1, wherein, The energy storage module stops outputting the feedback signal after the input voltage is disconnected, so that the self-locking module stops outputting the cutoff signal. The control module comprises a driving unit and a cutoff unit. The driving unit is connected with the switching module and configured to output a driving signal to turn on the switching module when the input voltage is greater than a first preset threshold value.

4. The circuit of claim 3, wherein, The cutoff unit is connected with the switching module and configured to output a cutoff signal to turn off the switching module when the input voltage is greater than a second preset threshold value. The driving unit comprises a resistor R2 and a resistor R9.

5. The circuit of claim 3, wherein, A first end of the resistor R2 is connected with the input voltage, a second end of the resistor R2 is connected with a first end of the resistor R9 and a first input end of the switching module, and a second end of the resistor R9 is connected with a reference ground. The cutoff unit comprises a Zener diode D3, a diode D1, a resistor R5 and a resistor R8.

6. The circuit of claim 1, wherein, A cathode of the Zener diode D3 is connected with the input voltage, an anode of the Zener diode D3 is connected with a first end of the resistor R5, a second end of the resistor R5 is connected with an anode of the diode D1, a cathode of the diode D1 is connected with a first end of the resistor R8 and a second input end of the switching module, and a second end of the resistor R8 is connected with a reference ground. The self-locking module comprises a switching unit and a feedback unit. The switching unit is connected with the control module and the energy storage module and configured to output a charging signal in response to the cutoff signal, so that the energy storage module receives the input voltage to enter a charging state.

7. The circuit of claim 6, wherein, The feedback unit is connected with the energy storage module, the switching unit and the switching module and configured to output the cutoff signal in response to the feedback signal.

8. The circuit of claim 7, wherein, The switching unit comprises a switching tube Q3, the energy storage module comprises an electrolytic capacitor EC1, a first end of the electrolytic capacitor EC1 is connected with the input voltage, a collector of the switching tube Q3 is connected with a second end of the electrolytic capacitor EC1, a base of the switching tube Q3 is connected with a second output end of the control module, and an emitter of the switching tube Q3 is connected with a reference ground. The feedback unit comprises a switching tube Q4, a resistor R1, a resistor R3, a resistor R6, a resistor R7 and a resistor R10. The emitter of the switch tube Q4 and the first end of the resistor R1 are connected with the input voltage, the base of the switch tube Q4 is connected with the second end of the resistor R1 and the first end of the resistor R3, the collector of the switch tube Q4 is connected with the first end of the resistor R6 and the first end of the resistor R10, the second end of the resistor R3 is connected with the collector of the switch tube Q3, the second end of the resistor R6 is connected with the first end of the resistor R7 and the base of the switch tube Q3, the second end of the resistor R10 and the second end of the resistor R7 are connected with reference ground.

9. The circuit according to any of claims 1-8, characterized in that, The switch module comprises a switch tube Q1, a switch tube Q2, a diode D2, a resistor R4, a resistor R11 and a voltage reference source U2, The drain of the switch tube Q2 and the first end of the resistor R11 are connected with the input voltage, the source of the switch tube Q2 is connected with the anode of the diode D2, the cathode of the diode D2 is used for outputting the input voltage, the gate of the switch tube Q2 is connected with the first end of the resistor R4 and the second end of the resistor R11, the second end of the resistor R4 is connected with the cathode of the voltage reference source U2, the reference end of the cathode of the voltage reference source U2 is connected with the collector of the switch tube Q1 and the first output end of the control module, the base of the switch tube Q1 is connected with the second output end of the control module, the emitter of the switch tube Q1 and the anode of the voltage reference source U2 are connected with reference ground.

10. An energy storage system characterized by, The protection circuit comprises: The protection circuit according to any one of claims 1-9.

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