An overvoltage detection circuit, method, and protection system for a high-voltage DC bus

Abstract

This invention provides an overvoltage detection circuit, method, and protection system for a high-voltage DC bus. It includes a high-impedance resistor circuit with one end connected to the high-voltage DC bus and the other end grounded via a voltage detection node and a first voltage divider resistor. A voltage regulator comparator circuit compares the detected voltage of the voltage detection node with a reference voltage and outputs a trigger current to the control terminal of a SCR-like structure circuit. The first terminal of the SCR-like structure circuit is connected to the voltage detection node, and its second terminal is grounded. After being triggered by the trigger current, the SCR-like structure circuit enters a positive feedback lockout state and generates a load effect on the voltage detection node, causing the detected voltage to actively collapse. A stable overvoltage detection signal is output from the first terminal. This invention uses discrete components in the circuit design and achieves extremely low circuit cost and equivalent hysteresis control for overvoltage detection through dynamic coupling between the high-impedance input resistor and the feedback current, resulting in reduced circuit cost, high detection stability, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of high voltage overvoltage detection technology, specifically to an overvoltage detection circuit, method, and protection system for a high-voltage DC bus. Background Technology

[0002] Power distribution networks and user-side environments generally exhibit the following characteristics: large voltage fluctuations, frequent lightning surges, single-phase overvoltage caused by three-phase imbalance, significant differences in on-site construction quality, and a large number of outdated existing equipment requiring upgrades. Under these wide voltage fluctuation environments, power data acquisition devices and smart meters not only need to operate stably for extended periods but also withstand surge overvoltage impacts of 500 Vac or even thousands of volts. Therefore, data acquisition and communication equipment and smart meters are widely deployed in unattended systems within distribution networks. These devices are typically equipped with rapid detection and triggering protection mechanisms for abnormal voltage surges in the power grid. This is crucial for preventing equipment failures and improving system reliability.

[0003] Currently, mainstream overvoltage detection technologies mainly include two approaches: those using dedicated overvoltage protection chips (OVP ICs) and those using a software-based "MCU + ADC" approach. The dedicated OVP chip approach typically involves using an AP431 reference source with a comparator, a dedicated AC overvoltage detection IC, or a PWM control chip with integrated OVP functionality. This approach offers advantages such as high threshold accuracy, low temperature drift, and high integration, but also suffers from higher costs, greater sensitivity to EMC, a larger number of external components, and supply chain risks. Therefore, its overall cost-effectiveness is not competitive in the market for electricity meters used on a scale of millions. The software-based "MCU + ADC" approach typically involves acquiring voltage signals via an ADC (A / D converter), combining this with MCU processing logic and software algorithms to determine if the sampled voltage signal exceeds a preset threshold and trigger the corresponding protection mechanism. This approach is highly dependent on program design, its response speed is limited by the sampling period, and it is more susceptible to EMC interference, placing higher demands on system reliability and anti-interference capabilities. In addition, this solution also incurs software certification and subsequent maintenance costs, and has certain limitations in application scenarios with high reliability and stability requirements.

[0004] Therefore, there is an urgent need to innovate an overvoltage detection circuit, method, and protection system for a high-voltage DC bus that can achieve high reliability and extremely low circuit cost without relying on microcontrollers and software development. Summary of the Invention

[0005] To address the common problems in existing technologies, the present invention aims to provide an overvoltage detection circuit, method, and protection system for a high-voltage DC bus. This invention employs discrete components for circuit design and utilizes dynamic coupling design between high-impedance input resistors and feedback current to achieve extremely low circuit cost and equivalent hysteresis control for overvoltage detection, thereby reducing circuit cost and improving detection stability and reliability.

[0006] The present invention achieves the above objectives through the following technical solutions: An overvoltage detection circuit for a high-voltage DC bus includes a high-resistance resistor circuit, a first voltage divider resistor, a voltage regulator comparator circuit, and a SCR-like structure circuit. One end of the high-resistance resistor circuit is connected to the high-voltage DC bus, and the other end is grounded through the first voltage divider resistor via a voltage detection node. The voltage regulator comparator circuit has a reference voltage, and its input terminal is connected to the voltage detection node. It compares the detected voltage of the voltage detection node with the reference voltage and outputs a trigger current to the control terminal of the SCR-like structure circuit based on the comparison result. The first terminal of the SCR-like structure circuit is connected to the voltage detection node, and its second terminal is grounded. After being triggered by the trigger current, the SCR-like structure circuit enters a positive feedback lockout state and generates a load effect on the voltage detection node, causing the detected voltage to actively collapse. A stable overvoltage detection signal is output from the first terminal of the SCR-like structure circuit.

[0007] The overvoltage detection circuit for the high-voltage DC bus provided by the present invention further includes a rectifier and filter circuit, wherein the rectifier and filter circuit is connected to an external AC power supply and is used to rectify and filter the external AC power supply to form the output of the high-voltage DC bus.

[0008] A first voltage threshold and a second voltage threshold are set. The first voltage threshold is the DC voltage value that causes the SCR-like structure circuit to trigger the corresponding high-voltage DC bus to rise to. The second voltage threshold is the DC voltage value that causes the SCR-like structure circuit to unlock the corresponding high-voltage DC bus to drop to.

[0009] Wherein, the second voltage threshold is less than the first voltage threshold but greater than the upper limit of the operating voltage of the high voltage DC bus.

[0010] According to the overvoltage detection circuit of the high-voltage DC bus provided by the present invention, the high-resistance resistor circuit includes a first high-resistance resistor, a second high-resistance resistor, a third high-resistance resistor and a fourth high-resistance resistor connected in series.

[0011] The operating voltage of the external AC power supply is 220V, the first voltage threshold is set to 550V, and the second voltage threshold is set to 450V; the resistance values ​​of the first high-resistance resistor, the second high-resistance resistor, the third high-resistance resistor, and the fourth high-resistance resistor are all 510KΩ, and the resistance value of the first voltage divider resistor is 28KΩ.

[0012] According to the overvoltage detection circuit of the high-voltage DC bus provided by the present invention, the voltage regulation comparison circuit adopts a Zener diode. The positive terminal of the Zener diode is connected to the voltage detection node, and its negative terminal is connected to the control terminal of the SCR-like structure circuit. The reference voltage is the breakdown voltage of the Zener diode. When the detection voltage rises to the breakdown voltage through threshold comparison, the Zener diode enters the breakdown region and turns on.

[0013] According to the overvoltage detection circuit of the high-voltage DC bus provided by the present invention, the SCR-like structure circuit includes a first transistor circuit and a second transistor circuit. The first transistor circuit and the second transistor circuit are respectively provided with an NPN transistor and a PNP transistor. The base of the NPN transistor is connected to the trigger current, its collector is connected to the base of the second transistor circuit, and its emitter is grounded. The emitter of the PNP transistor is connected to the voltage detection node, and its collector is connected to the base of the NPN transistor.

[0014] The overvoltage detection circuit for a high-voltage DC bus provided by the present invention further includes an optocoupler, wherein the first input terminal of the optocoupler is connected to the voltage detection node, and the second input terminal is connected to the collector of the NPN transistor, for outputting the overvoltage detection signal after opto-isolation.

[0015] According to the overvoltage detection circuit of the high-voltage DC bus provided by the present invention, the first transistor circuit further includes a tenth resistor and a third capacitor, the base of the NPN transistor is grounded through the tenth resistor, and the third capacitor is connected in parallel across the tenth resistor.

[0016] According to the overvoltage detection circuit of the high-voltage DC bus provided by the present invention, the second transistor circuit further includes an eighth resistor, a seventh resistor, and a sixth resistor. The base of the PNP transistor is connected to the collector of the NPN transistor through the eighth resistor, and the seventh resistor is connected in parallel between the PNP transistor and the emitter. The emitter is connected to the voltage detection node through the sixth resistor.

[0017] An overvoltage detection method for a high-voltage DC bus, applied to the overvoltage detection circuit of the high-voltage DC bus, comprising: S1: Connect to an external AC power supply, continuously monitor the overvoltage status of the high-voltage DC bus through the voltage detection node, and determine whether the DC voltage of the external high-voltage DC bus is in a continuous rising phase. If so, the detection voltage of the voltage detection node is linearly proportional to the DC voltage through the voltage divider circuit of the front-stage high-resistance resistor.

[0018] S2: Determine whether the DC voltage has risen to the first voltage threshold. If so, the detection voltage reaches the breakdown voltage of the Zener diode, the Zener diode is reverse-broken and turned on, and the detection voltage rises to the trigger voltage of the SCR-like structure circuit.

[0019] S3: After the SCR-like structure circuit is triggered, it enters a positive feedback lockout state and generates a nonlinear load shunt to the voltage detection node. The detection voltage is actively collapsed from the trigger voltage to the conduction voltage of the SCR-like structure circuit. The SCR-like structure circuit outputs a stable overvoltage detection signal.

[0020] S4: Determine whether the DC voltage has dropped to the second voltage threshold. If so, the input current of the SCR-like structure circuit is less than its holding current, thereby unlocking the circuit and returning to step S2. Otherwise, return to step S3.

[0021] An overvoltage protection system for a high-voltage DC bus includes a switching power supply, a circuit breaker module, an overvoltage detection circuit for the high-voltage DC bus, a main control module, and a backup battery module. The input terminal of the switching power supply is connected to the high-voltage DC bus, and its output terminal is connected to the power supply terminal of the load device through the circuit breaker module. The overvoltage detection circuit is used to monitor the input high-voltage DC power supply in real time and outputs an overvoltage detection signal to the input terminal of the main control module and the backup battery module. The main control module is connected to the control coil of the circuit breaker module and is used to output a switch control signal to open the circuit breaker module according to the overvoltage detection signal. The backup battery module is connected to the power supply terminal of the load device and is used to activate the backup battery power supply according to the overvoltage detection signal.

[0022] Therefore, compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs discrete components in its circuit design to achieve overvoltage detection even with high-resistivity circuits. The overall BOM cost is typically less than 1 / 5 of that of traditional dedicated voltage monitoring ICs, and it does not rely on MCU programs. In industrial low-level modules or terminal devices with shipment volumes in the tens of millions, this cost advantage is decisive in the market. Furthermore, discrete components are highly versatile and have a wide range of alternatives, maintaining high substitutability even during supply chain fluctuations or shortages. They do not depend on proprietary protocols or special pin definitions from specific manufacturers, significantly reducing supply risks.

[0023] 2. This invention fully utilizes the load effect of the voltage detection node to achieve equivalent hysteresis control for overvoltage detection, based on the use of a high-resistivity circuit. After the SCR-like structure circuit is triggered, the positive feedback current will form an additional voltage drop on the high-resistivity sampling network, causing the detection voltage to collapse. This nonlinear load shunt mechanism, compared with the traditional SCR-like structure, transforms the circuit state that originally locks up under low-resistivity source conditions into a hysteresis range with engineering significance on the high-voltage side of the power grid. The circuit structure is simple and the effect is stable.

[0024] 3. This invention employs a discrete bipolar transistor-based SCR-like circuit to achieve positive feedback lockout for overvoltage detection. Compared to traditional highly integrated CMOS voltage monitoring ICs, it exhibits stronger resilience under high-voltage transient impacts. In power grid environments with surge or fast transient burst interference, the high-resistance circuit effectively limits the inrush current, and the parasitic capacitance and junction charge of the transistor base also provide absorption and buffering during transients. Furthermore, the filter capacitor further suppresses high-frequency interference. In harsh electromagnetic compatibility environments, the discrete circuit design of this invention is often more robust than high-precision digital monitoring chips, and is less prone to malfunctions, crashes, or permanent damage.

[0025] 4. The complementary feedback structure formed by the first and second transistor circuits of this invention can quickly trigger and establish a positive feedback loop when the detected voltage exceeds the threshold of the voltage regulator comparator circuit, thereby instantly entering the saturation conduction state. The entire triggering process is responsive and decisive, effectively preventing the optocoupler in the subsequent stage from operating in the semi-conducting linear region, thereby reducing the power consumption and temperature rise of the optocoupler and enhancing the long-term reliability of the circuit.

[0026] 5. This invention isolates the high-voltage side of the power grid from the control section through optocouplers, effectively preventing high voltage from entering the low-voltage control area, and meeting the requirements for creepage distance and clearance in safety standards such as IEC 62368-1, thus ensuring high safety compliance.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0028] Figure 1 This is a circuit diagram of an overvoltage detection circuit for a high-voltage DC bus according to the present invention.

[0029] Figure 2 This is a flowchart of an overvoltage detection method for a high-voltage DC bus according to the present invention.

[0030] Figure 3 This is a schematic diagram of an overvoltage protection system for a high-voltage DC bus according to the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] An embodiment of an overvoltage detection circuit for a high-voltage DC bus See Figure 1 This embodiment relates to an overvoltage detection circuit for a high-voltage DC bus, comprising a high-resistance resistor circuit 20, a first voltage divider resistor R5, a voltage regulator comparator circuit 30, and a SCR-like structure circuit 40. One end of the high-resistance resistor circuit 20 is connected to the high-voltage DC bus, and the other end is grounded through the first voltage divider resistor R5 via a voltage detection node. The voltage regulator comparator circuit 30 sets a reference voltage, and its input terminal is connected to the voltage detection node. It is used to compare the detection voltage V_sense of the voltage detection node with the reference voltage, and outputs a trigger current to the control terminal of the SCR-like structure circuit 40 according to the comparison result. The first terminal of the SCR-like structure circuit 40 is connected to the voltage detection node, and its second terminal is grounded. After being triggered by the trigger current, the SCR-like structure circuit 40 enters a positive feedback lockout state and generates a load effect on the voltage detection node, causing the detection voltage V_sense to actively collapse. A stable overvoltage detection signal OVD_Det is output from the first terminal of the SCR-like structure circuit 40.

[0034] In this embodiment, a rectifier and filter circuit 10 is also included. The rectifier and filter circuit 10 is connected to an external AC power supply and is used to rectify and filter the external AC power supply to form the high-voltage DC bus output.

[0035] Specifically, in this embodiment, the rectifier filter circuit 10 includes a rectifier bridge composed of diodes D3, D4, D5 and D6, and filter capacitors C1 and C2. The input terminal of the rectifier bridge is connected to an external AC power supply, and its DC output terminal positive terminal is connected to one end of the filter capacitor C1 and the high-impedance resistor circuit 20, respectively. One end of the filter capacitor C1 is connected in series with the filter capacitor C2 and grounded.

[0036] Specifically, in this embodiment, the amplitude of the high-voltage DC bus voltage V_line after rectification and filtering has an approximately linear proportional relationship with the voltage of the external AC power supply. Ignoring the voltage drop of the rectifier diodes and the effects of filter ripple, the approximate conversion relationship is:

[0037] in, This refers to the voltage amplitude of the high-voltage DC bus. This refers to the voltage of the external AC power supply.

[0038] Based on the above-mentioned conversion relationship, we can conclude that when the external AC power input is normal, =220Vac, ≈311Vdc; When the external AC power supply is at its normal operating upper limit, =285Vac, ≈403Vdc; When the external AC power supply is in an abnormal boost state. ≈380Vac, ≈537Vdc; When the external AC power supply clears the overvoltage fault, At approximately 300Vac, ≈424Vdc.

[0039] In actual circuits, factors such as the voltage drop of the diodes in the rectifier bridge and the charging and discharging ripple of the filter capacitors need to be considered.

[0040] A first voltage threshold and a second voltage threshold are provided. The first voltage threshold is the DC voltage value that triggers the SCR-like circuit 40 to rise to the corresponding high-voltage DC bus. The second voltage threshold is the DC voltage value that triggers the SCR-like circuit 40 to drop to the corresponding high-voltage DC bus. The second voltage threshold is less than the first voltage threshold but greater than the upper limit of the operating voltage of the high-voltage DC bus.

[0041] Specifically, in this embodiment, after the SCR-like structure circuit 40 enters the positive feedback lockout state, the load effect causes the detection voltage V_sense to actively collapse, reducing the conduction voltage of the SCR-like structure circuit 40 to below its trigger voltage. When the high-voltage DC bus drops below the first voltage threshold, compared to the traditional low-resistance power supply condition where the SCR-like structure needs to reduce the bus input voltage to an extremely low level to release the latch when entering the self-locking state, the detection voltage V_sense in this embodiment, due to the impedance effect, will drop to below the unlocking threshold of the SCR-like structure circuit 40 more quickly when the trigger voltage of the SCR-like structure circuit 40 actively collapses to its conduction voltage, thereby releasing the circuit earlier.

[0042] In this embodiment, the high-resistance circuit 20 includes a first high-resistance resistor R1, a second high-resistance resistor R2, a third high-resistance resistor R3, and a fourth high-resistance resistor R4 connected in series. The first high-resistance resistor R1 and the second high-resistance resistor R2 are connected in parallel across the filter capacitor C1, and the third high-resistance resistor R3 and the fourth high-resistance resistor R4 are connected in parallel across the filter capacitor C2. It also includes a fifth capacitor C5, and the first voltage divider resistor R5 is connected in parallel with the fifth capacitor C5.

[0043] Specifically, in this embodiment, the detection voltage V_sense maintains a linear proportional relationship with the voltage V_line of the high-voltage DC bus through the high-resistance voltage divider series in the high-resistance resistor circuit 20. When the detection voltage V_sense is less than the reference voltage, the subsequent voltage regulator comparator circuit 30 and the SCR-like structure circuit 40 are both inactive and consume almost no current. Therefore, during the abnormal rise phase of the high-voltage DC bus voltage V_line, the detection voltage V_sense and its DC voltage satisfy a linear voltage divider relationship:

[0044] in, To detect the voltage V_sense, k is the voltage division ratio coefficient, which is determined by the ratio of the high-resistance voltage divider resistor in series to the first voltage divider resistor R5.

[0045] Specifically, in this embodiment, the operating voltage of the external AC power supply is 220V, the first voltage threshold is set to 550V, and the second voltage threshold is set to 450V; the resistance values ​​of the first high-resistance resistor R1, the second high-resistance resistor R2, the third high-resistance resistor R3, and the fourth high-resistance resistor R4 are all 510KΩ, and the resistance value of the first voltage divider resistor R5 is 28KΩ.

[0046] In this embodiment, the voltage regulator comparator circuit 30 uses a Zener diode D2. The positive terminal of the Zener diode D2 is connected to the voltage detection node, and its negative terminal is connected to the control terminal of the SCR-like structure circuit 40. The reference voltage is the breakdown voltage of the Zener diode D2. When the detection voltage V_sense rises to the breakdown voltage through threshold comparison, the Zener diode D2 enters the breakdown region and turns on.

[0047] Specifically, in this embodiment, the breakdown voltage of the Zener diode D2 is 6.3 V. When the detection voltage V_sense rises to approximately 6.3 V, the Zener diode D2 begins to enter the breakdown region and conducts. Current flows through the Zener diode D2 into the branch formed by the tenth resistor R10 and the third capacitor C3, forming a voltage drop at the node of this branch. The detection voltage V_sense rises to near 6.3 V, providing the trigger condition for the SCR-like structure circuit 40. Specifically, since the source impedance of the voltage divider network in the preceding stage is extremely high, the voltage V_line of the high-voltage DC bus only needs to continue to rise slightly, and its corresponding detection voltage V_sense rises to approximately 6.5 V to 6.8 V, which is sufficient to provide enough trigger current to drive the first transistor circuit to quickly enter the saturation state, triggering the positive feedback mechanism to make the second transistor circuit conduct synchronously, and the SCR-like structure circuit 40 enters the regeneration switching stage.

[0048] Specifically, in this embodiment, the Zener diode D2 is used, which is a discrete device and has a lower cost, making it a preferred solution. However, this is not the only circuit structure. A voltage comparator can also be used, with its two input terminals connected to a reference voltage and a detection voltage V_sense, respectively. When the detection voltage V_sense exceeds the reference voltage, its output terminal will quickly flip and output a trigger signal. However, this is an integrated circuit and is more expensive.

[0049] In this embodiment, the SCR-like structure circuit 40 includes a first transistor circuit and a second transistor circuit. The first transistor circuit and the second transistor circuit are respectively provided with an NPN transistor Q1 and a PNP transistor Q2. The base of the NPN transistor Q1 is connected to the trigger current, its collector is connected to the base of the second transistor circuit, and its emitter is grounded. The emitter of the PNP transistor Q2 is connected to the voltage detection node, and its collector is connected to the base of the NPN transistor Q1.

[0050] Specifically, in this embodiment, both NPN transistor Q1 and PNP transistor Q2 are discrete bipolar transistors.

[0051] Specifically, the first transistor circuit in this embodiment also includes a tenth resistor R10 and a third capacitor C3. The base of the NPN transistor Q1 is grounded through the tenth resistor R10, and the third capacitor C3 is connected in parallel across the tenth resistor R10.

[0052] In this embodiment, an optocoupler U1 is also included. The first input terminal of the optocoupler U1 is connected to the voltage detection node, and its second input terminal is connected to the collector of the NPN transistor Q1, which is used to output the overvoltage detection signal OVD_Det after opto-isolation.

[0053] Specifically, this embodiment also includes a ninth resistor R9, an eleventh resistor R11, and a twelfth resistor R12. The first input terminal of the optocoupler U1 is connected to the voltage detection node through the ninth resistor R9, and the eleventh resistor R11 is connected in parallel with the second input terminal. Its output terminal is connected to 3.6V DC power through the twelfth resistor R12.

[0054] In this embodiment, the second transistor circuit further includes an eighth resistor R8, a seventh resistor R7, and a sixth resistor R6. The base of the PNP transistor Q2 is connected to the collector of the NPN transistor Q1 through the eighth resistor R8, and the seventh resistor R7 is connected in parallel between the base and the emitter. The emitter is connected to the voltage detection node through the sixth resistor R6.

[0055] Specifically, in this embodiment, after the Zener diode D2 is broken down and turned on, the current flows through the tenth resistor R10 and the third capacitor C3 to form the base drive channel of the NPN transistor Q1. As the voltage further rises to approximately 6.7V, the base of the NPN transistor Q1 receives sufficient current and quickly enters the saturation conduction state. Its emitter potential is rapidly pulled down, thereby rapidly pulling down the base of the PNP transistor Q2 through the eighth resistor R8, enabling the PNP transistor Q2 to receive forward drive and quickly turn on. After the PNP transistor Q2 turns on, its collector current is injected in reverse into the base of the NPN transistor Q1 through the sixth resistor R6, thereby forming a positive feedback loop. This causes the NPN transistor Q1 and the PNP transistor Q2 to quickly enter the latch-up conduction state, forming a regenerative switching behavior similar to an SCR structure, achieving a steep and well-defined switching characteristic.

[0056] In this process, while the NPN transistor Q1 is continuously turned on, the light-emitting diode inside the optocoupler U1 is driven to turn on. The overvoltage state is transmitted to the twelfth resistor R12 on the isolation side through opto-isolation, and finally the overvoltage detection signal OVD_Det is output. The entire triggering process is fast and the flip is crisp, effectively avoiding the unstable state caused by the linear transition region.

[0057] Specifically, in this embodiment, when the PNP transistor Q2 is turned on, its collector current continuously injects feedback current into the base of the NPN transistor Q1 through the sixth resistor R6, forming a stable positive feedback loop. At this time, the equivalent load of the detection voltage V_sense node is no longer only the first voltage divider resistor R5, but the parallel equivalent impedance formed by the first voltage divider resistor R5 and the resistor in the feedback branch of the second transistor circuit. Due to the significant load effect, more of the current that originally flowed into the first voltage divider resistor R5 and the Zener diode D2 will be shunted and injected into the SCR-like structure circuit 40, thereby further enhancing the conduction condition of the NPN transistor Q1 and maintaining the entire circuit in a stable latch-up state.

[0058] As can be seen, the positive feedback combined with voltage collapse mechanism in this embodiment essentially constitutes a self-locking structure with hysteresis characteristics. That is, once it enters the conduction state, even if there are small fluctuations in the external distribution network voltage or changes in the internal load of the equipment causing certain disturbances in the high-voltage DC bus, the detection circuit will not experience repeated triggering and release jitter, thereby avoiding malfunctions and unstable flipping. Only when the actual overvoltage fault in the external distribution network is eliminated and the voltage V_line of the high-voltage DC bus continues to drop to about 450Vdc, due to the high impedance input resistance of the front stage limiting the current of the injected voltage detection node and the collapse effect of the detection voltage, the feedback current of the SCR-like structure circuit 40 will accelerate to weaken to an insufficient level to maintain the conduction conditions of NPN transistor Q1 and PNP transistor Q2. At this time, the SCR-like structure circuit 40 can quickly exit the latched state, and the detection circuit can quickly unlock and return to the initial standby state.

[0059] An embodiment of an overvoltage detection method for a high-voltage DC bus See Figure 2 This embodiment relates to an overvoltage detection method for a high-voltage DC bus, applied to the overvoltage detection circuit of the high-voltage DC bus, comprising: S1: Connect to an external AC power supply. Continuously monitor the overvoltage status of the high-voltage DC bus through the voltage detection node and determine whether the voltage V_line of the external high-voltage DC bus is in a continuously rising phase. If so, the detection voltage V_sense of the voltage detection node is linearly proportional to the voltage V_line of the high-voltage DC bus through the 20-stage high-resistance resistor circuit in the front stage.

[0060] S2: Determine whether the voltage V_line of the high-voltage DC bus has risen to the first voltage threshold. If so, the detection voltage V_sense reaches the breakdown voltage of the Zener diode D2, the Zener diode D2 is reverse-broken down and turned on, and the detection voltage V_sense is raised to the trigger voltage of the SCR-like structure circuit 40.

[0061] S3: After the SCR-like structure circuit 40 is triggered, it enters a positive feedback lockout state and generates a nonlinear load shunt to the voltage detection node. The detection voltage V_sense is actively collapsed from the trigger voltage to the conduction voltage of the SCR-like structure circuit 40. The SCR-like structure circuit 40 outputs a stable overvoltage detection signal OVD_Det.

[0062] S4: Determine whether the voltage V_line of the high-voltage DC bus has dropped to the second voltage threshold. If so, the input current of the SCR-like structure circuit 40 is less than its holding current, thereby unlocking the circuit and returning to step S2; otherwise, return to step S3.

[0063] Specifically, in this embodiment, the trigger voltage of the SCR structure circuit 40 is 6.3V, and its conduction voltage is 2~3V.

[0064] Specifically, in this embodiment, the shunt current of the first voltage divider resistor R5 is approximately 200µA, and the sustaining current required for the positive feedback lockout of the SCR-like structure circuit 40 is approximately 150µA. When the external distribution network overvoltage fault is eliminated, the voltage Vline of the high-voltage DC bus decreases accordingly, and the detection voltage Vsense linearly coupled to the voltage detection node decreases synchronously with its current. When the voltage Vline of the high-voltage DC bus drops to approximately 450Vdc, the current flowing into the voltage detection node through the high-impedance series voltage divider has decreased to below approximately 210µA. Under these conditions, the current flowing through the branch of the tenth resistor R10 is significantly reduced due to the shunt effect of the first voltage divider resistor R5, and drops to below approximately 150µA. Due to insufficient drive current, the base voltage of the NPN transistor Q1 drops and enters the cutoff state, and the PNP transistor Q2 simultaneously enters the cutoff state; the internal LED of the optocoupler U1 is also turned off, and the overvoltage detection signal OVD_Det is released. At this point, the entire circuit exits the lockout state and returns to the initial standby detection mode.

[0065] Through the above overvoltage detection method, the circuit achieves clear, stable and engineering-significant unlocking threshold control while ensuring rapid triggering and reliable locking, further enhancing the system's reliability and consistency in complex power grid environments.

[0066] An embodiment of an overvoltage protection system for a high-voltage DC bus See Figure 3 This embodiment relates to an overvoltage protection system for a high-voltage DC bus, comprising a switching power supply 100, a circuit breaker module 101, an overvoltage detection circuit 102 for the high-voltage DC bus, a main control module 103, and a backup battery module 104. The input terminal of the switching power supply 100 is connected to the high-voltage DC bus, and its output terminal is connected to the power supply terminal of the load device through the circuit breaker module 101. The overvoltage detection circuit 102 is used to monitor the input high-voltage DC power supply in real time and outputs an overvoltage detection signal OVD_Det to the input terminal of the main control module 103 and the backup battery module 104 respectively. The main control module is connected to the control coil of the circuit breaker module 101 and is used to output a switch control signal to open the circuit breaker module 101 according to the overvoltage detection signal OVD_Det. The backup battery module 104 is connected to the power supply terminal of the load device and is used to activate the backup battery power supply according to the overvoltage detection signal OVD_Det.

[0067] Specifically, this embodiment also includes an alarm module. The main control module 103 outputs an alarm signal to the alarm module based on the overvoltage detection signal OVD_Det. The alarm module includes a buzzer and / or an indicator light for audible and visual alarm. The alarm module enables local overvoltage alarms. By illuminating the indicator light or driving the buzzer, it provides maintenance personnel with a clear fault indication, showing that the system is currently in an overvoltage shutdown state.

[0068] Specifically, in this embodiment, when the overvoltage detection signal OVD_Det is a valid level signal, the system will simultaneously activate five safety protection actions, including: The isolated switching power supply 100, which serves as the main power supply, is hardware-shutdown, putting it into "silent safety mode". The overvoltage detection signal OVD_Det is directly fed back to the enable pin of the internal PWM controller of the isolated switching power supply 100. The internal PWM controller controls the output to stop the internal MOSFET from operating, thereby protecting the internal transformer and secondary components from breakdown and preventing the power supply itself from burning out due to excessive input voltage. The overvoltage detection signal OVD_Det is fed back to the main control module 103. The module uses logic processing and decision-making to determine whether the overvoltage state continues, records the fault log, and issues system commands, such as executing a safety shutdown procedure.

[0069] The load equipment is isolated. The circuit breaker module 101 is activated by the main control module 103 or the logic circuit to disconnect the downstream load equipment. When the main power supply experiences voltage fluctuations or is not completely disconnected, physically disconnecting the load through the circuit breaker can ensure that expensive downstream equipment is protected from damage caused by surge voltage or overvoltage impacts.

[0070] The system performs power switching on the backup battery module 104. The overvoltage detection signal OVD_Det is directly fed back to the backup battery module 104, triggering the backup power supply to start. When the main power supply is shut down due to overvoltage, in order to keep the main control module 103 working and the alarm system running, the system automatically switches to the backup power supply, thereby ensuring that the system remains online and can continuously output alarm signals when a fault occurs.

[0071] As can be seen, the overvoltage protection system in this embodiment detects abnormal high voltage at the input terminal through an overvoltage detection circuit, and achieves multiple safety protections such as power cut-off, load isolation, backup power switching, and alarm triggering in a hardware and software collaborative manner, thereby significantly improving the overall system's operational safety and reliability.

[0072] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. An overvoltage detection circuit for a high-voltage DC bus, characterized in that, include: The circuit includes a high-resistance resistor circuit, a first voltage divider resistor, a voltage regulator comparator circuit, and an SCR-like structure circuit. One end of the high-resistance resistor circuit is connected to a high-voltage DC bus, and the other end is grounded through the first voltage divider resistor via a voltage detection node. The voltage regulator comparator circuit is equipped with a reference voltage, and its input terminal is connected to the voltage detection node. It is used to compare the detected voltage of the voltage detection node with the reference voltage and output a trigger current to the control terminal of the SCR-like structure circuit according to the comparison result. The first terminal of the SCR-like structure circuit is connected to the voltage detection node, and its second terminal is grounded. After being triggered by the trigger current, the SCR-like structure circuit enters a positive feedback lockout state and generates a load effect on the voltage detection node, causing the detection voltage to actively collapse. A stable overvoltage detection signal is output from the first terminal of the SCR-like structure circuit. The SCR-like structure circuit includes a first transistor circuit and a second transistor circuit. The first transistor circuit and the second transistor circuit are respectively provided with an NPN transistor and a PNP transistor. The base of the NPN transistor is connected to the trigger current, its collector is connected to the base of the PNP transistor, and its emitter is grounded. The emitter of the PNP transistor is connected to the voltage detection node, and its collector is connected to the base of the NPN transistor.

2. The overvoltage detection circuit for a high-voltage DC bus according to claim 1, characterized in that: It also includes a rectifier and filter circuit, which is connected to an external AC power supply and is used to rectify and filter the external AC power supply to form the high-voltage DC bus output; A first voltage threshold and a second voltage threshold are set, wherein the first voltage threshold is the DC voltage value that causes the SCR-like structure circuit to trigger the corresponding high-voltage DC bus to rise to. The second voltage threshold is the DC voltage value that the high-voltage DC bus corresponding to the unlocking of the SCR-like structure circuit drops to. Wherein, the second voltage threshold is less than the first voltage threshold but greater than the upper limit of the operating voltage of the high voltage DC bus.

3. The overvoltage detection circuit for a high-voltage DC bus according to claim 2, characterized in that: The high-resistance resistor circuit includes a first high-resistance resistor, a second high-resistance resistor, a third high-resistance resistor, and a fourth high-resistance resistor connected in series. The operating voltage of the external AC power supply is 220V, the first voltage threshold is set to 550V, and the second voltage threshold is set to 450V; the resistance values ​​of the first high-resistance resistor, the second high-resistance resistor, the third high-resistance resistor, and the fourth high-resistance resistor are all 510KΩ, and the resistance value of the first voltage divider resistor is 28KΩ.

4. The overvoltage detection circuit for a high-voltage DC bus according to claim 1, characterized in that, include: The voltage regulator comparator circuit uses a Zener diode. The positive terminal of the Zener diode is connected to the voltage detection node, and its negative terminal is connected to the control terminal of the SCR-like structure circuit. The reference voltage is the breakdown voltage of the Zener diode. When the detection voltage rises to the breakdown voltage through threshold comparison, the Zener diode enters the breakdown region and turns on.

5. The overvoltage detection circuit for a high-voltage DC bus according to claim 1, characterized in that: It also includes an optocoupler, whose first input terminal is connected to the voltage detection node and its second input terminal is connected to the collector of the NPN transistor, for outputting the overvoltage detection signal after photoelectric isolation.

6. The overvoltage detection circuit for a high-voltage DC bus according to claim 1, characterized in that: The first transistor circuit also includes a tenth resistor and a third capacitor. The base of the NPN transistor is grounded through the tenth resistor, and the third capacitor is connected in parallel across the tenth resistor.

7. The overvoltage detection circuit for a high-voltage DC bus according to claim 1, characterized in that: The second transistor circuit also includes an eighth resistor, a seventh resistor, and a sixth resistor. The base of the PNP transistor is connected to the collector of the NPN transistor through the eighth resistor, and the seventh resistor is connected in parallel between the PNP transistor and the emitter. The emitter is connected to the voltage detection node through the sixth resistor.

8. An overvoltage detection method for a high-voltage DC bus, characterized in that, An overvoltage detection circuit applied to a high-voltage DC bus as described in any one of claims 1 to 7, comprising: S1: Connect to an external AC power supply, continuously monitor the overvoltage of the high-voltage DC bus through the voltage detection node, and determine whether the DC voltage of the external high-voltage DC bus is in a continuous rising stage. If so, the detection voltage of the voltage detection node is linearly proportional to the DC voltage through the voltage divider circuit of the front-end high-resistance resistor. S2: Determine whether the DC voltage has risen to the first voltage threshold. If so, the detection voltage reaches the breakdown voltage of the Zener diode, the Zener diode is reverse-broken down and turned on, and the detection voltage rises to the trigger voltage of the SCR-like structure circuit. S3: After the SCR-like structure circuit is triggered, it enters a positive feedback lockout state and generates a nonlinear load shunt to the voltage detection node. The detection voltage is actively collapsed from the trigger voltage to the conduction voltage of the SCR-like structure circuit. The SCR-like structure circuit outputs a stable overvoltage detection signal. S4: Determine whether the DC voltage has dropped to the second voltage threshold. If so, the input current of the SCR-like structure circuit is less than its holding current, thereby unlocking the circuit and returning to step S2; otherwise, return to step S3.

9. An overvoltage protection system for a high-voltage DC bus, characterized in that, include: The system comprises a switching power supply, a circuit breaker module, an overvoltage detection circuit for a high-voltage DC bus as described in any one of claims 1 to 7, a main control module, and a backup battery module. The input terminal of the switching power supply is connected to the high-voltage DC bus, and its output terminal is connected to the power supply terminal of the load device via the circuit breaker module. The overvoltage detection circuit is used to monitor the input high-voltage DC power supply in real time and outputs an overvoltage detection signal to the input terminal of the main control module and the backup battery module, respectively. The main control module is connected to the control coil of the circuit breaker module and is used to output a switch control signal to open the circuit breaker module based on the overvoltage detection signal. The backup battery module is connected to the power supply terminal of the load device and is used to activate the backup battery power supply based on the overvoltage detection signal.

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