A new type of lightning surge protection circuit

Abstract

This utility model discloses a novel surge protection circuit for lightning strikes, connected between the live wire, neutral wire, and ground wire. It includes: a surge protection module comprising a varistor for absorbing surge energy and a thermally coupled thermal fuse; and a failure detection and indication module comprising a signal sampling unit, a field-effect transistor (FET) switching unit, a control unit, and an indication unit. The input terminal of the signal sampling unit is connected to the connection node between the thermal fuse and the varistor. The output terminal of the signal sampling unit is connected to the control terminal of the FET switching unit. The output terminal of the FET switching unit generates a status signal and connects to the detection terminal of the control unit. The control unit drives the indication unit to indicate the status based on the level change of the status signal. After the varistor fails, the power supply does not need to be cut off, the product can continue to be used, and the indication unit will notify the user that the surge protection device has failed, allowing the user to take further measures, thus improving safety and user experience.

Description

Technical Field

[0001] This utility model relates to circuit lightning protection technology, and in particular to a new type of lightning surge protection circuit, mainly used for power supply lightning protection. Background Technology

[0002] Currently, the commonly used surge protectors on the market all use varistors to absorb surge energy. Due to the characteristics of varistors, they will be damaged once each time they are subjected to a lightning strike voltage. After a certain number of lightning strikes, the varistor will fail and open circuit.

[0003] When a varistor fails, existing products typically handle the situation in two ways: 1. The entire product is powered off, rendering it unusable. The drawback is that the actual product function remains normal; only the surge protector has failed, resulting in a poor user experience. 2. The entire product is powered on, allowing it to continue operating. However, the user is unaware that the surge protector has failed, exposing the product to the risk of further lightning strikes and potential damage / safety hazards.

[0004] Industry technicians have researched several technologies for detecting lightning strikes. For example, CN204407882 U discloses a groundless LED street light power surge protector that uses an LED to indicate a lightning strike. The LED does not light up when no lightning strike occurs. However, it has a significant drawback: the LED will not light up if the varistor (MOV) fails, preventing users from promptly replacing the varistor. Another example is CN 204407883 U, which discloses an LED street light power surge protector with status indication. It indicates a lightning strike between the neutral (N) and live (L) wires. However, due to the unidirectional conductivity of the diode, it only indicates a strike when the voltage across the neutral (N) wire is higher than that across the live (L) wire. It does not indicate strikes when the voltage across the live (L) wire is higher than that across the neutral (N) wire, or when the live (L) wire strikes against ground (PG) or neutral (N) wire strikes against ground (PG).

[0005] Therefore, a new technical solution needs to be researched to address the above problems. Utility Model Content

[0006] In view of this, the present invention addresses the deficiencies of the existing technology and its main purpose is to provide a new type of surge protection circuit that does not require power cut-off after the varistor fails, allowing the product to continue to be used. The indicator unit also notifies the user that the surge protection device has failed, enabling the user to take further measures to improve safety and user experience.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A novel surge protection circuit for lightning strikes, connected between the live wire, neutral wire, and ground wire, includes: A surge protection module includes a varistor for absorbing surge energy and a thermally coupled temperature fuse to the varistor. The failure detection indication module includes a signal sampling unit, a field-effect transistor switching unit, a control unit, and an indication unit; The input terminal of the signal sampling unit is connected to the connection node between the temperature fuse and the varistor; the output terminal of the signal sampling unit is connected to the control terminal of the field-effect transistor switching unit; the output terminal of the field-effect transistor switching unit generates a status signal and is connected to the detection terminal of the control unit; the control unit drives the indicator unit to perform status indication according to the level change of the status signal.

[0008] As a preferred embodiment, the varistor includes a first varistor, a second varistor, and a third varistor; the first varistor is connected between the live wire and the neutral wire; the second varistor is connected between the neutral wire and the ground wire; the third varistor is connected between the live wire and the ground wire; and the thermal fuse is connected in series with the first varistor.

[0009] As a preferred embodiment, the temperature fuse includes: a first temperature fuse and a second temperature fuse; the first temperature fuse, the first varistor, and the second temperature fuse are connected in series and then connected between the live wire and the neutral wire; the second varistor is connected between the connection point of the first varistor and the second temperature fuse and the ground wire; the third varistor is connected between the connection point of the first temperature fuse and the first varistor and the ground wire.

[0010] As a preferred embodiment, the signal sampling unit includes a rectifier diode and a voltage divider resistor; the anode of the rectifier diode is connected to the junction of the first temperature fuse and the first varistor; the voltage divider resistor is connected between the cathode of the rectifier diode and the field-effect transistor switching unit.

[0011] As a preferred embodiment, the field-effect transistor switching unit is an N-channel field-effect transistor, with its gate connected to the other end of the voltage divider resistor, its source grounded, and its drain serving as the output terminal of the status signal.

[0012] As a preferred embodiment, a pull-up resistor is also included, connected between the drain of the field-effect transistor and a standby power supply.

[0013] As a preferred embodiment, it also includes a Zener diode and a filter capacitor, connected in parallel between the other end of the voltage divider resistor and the neutral line.

[0014] As a preferred embodiment, an air discharge tube is also included, connected between the ground wire and the common connection point of the second and third varistors.

[0015] As a preferred embodiment, the control unit is a microcontroller, the indicator unit is a light-emitting diode (LED), the detection terminal of the microcontroller is connected to the drain of the N-channel MOSFET, the output terminal of the microcontroller is connected to the cathode of the LED, and the anode of the LED is connected to the standby power supply.

[0016] As a preferred embodiment, a main power supply circuit for supplying power to the product is provided on the live wire and the neutral wire, and a fuse is provided on the live wire as a fuse in the main power supply circuit; the rated current of the fuse is greater than the fusing current of the thermal fuse.

[0017] This invention has significant advantages and beneficial effects compared with existing technologies. Specifically, as shown in the above technical solution, it mainly involves installing a surge protection module and a failure detection indication module between the live wire, neutral wire, and ground wire. The surge protection module includes a varistor for absorbing surge energy and a thermally coupled temperature fuse. The failure detection indication module includes a signal sampling unit, a field-effect transistor (FET) switching unit, a control unit, and an indication unit. The input terminal of the signal sampling unit is connected to the connection node between the temperature fuse and the varistor. The output terminal of the signal sampling unit is connected to the control terminal of the FET switching unit. The output terminal of the FET switching unit generates a status signal and connects to the detection terminal of the control unit. The control unit drives the indication unit to indicate the status based on the level change of the status signal. Thus, even after the varistor fails, the power supply does not need to be cut off, the product can continue to be used, and the indication unit alerts the user that the surge protection device has failed, allowing the user to take further measures, improving safety and user experience.

[0018] To more clearly illustrate the structural features and effects of this utility model, the following detailed description of this utility model is provided in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of an embodiment of the present invention. Detailed Implementation

[0020] Please refer to Figure 1 As shown, it illustrates the specific circuit structure of an embodiment of this utility model.

[0021] A novel surge protection circuit for lightning strikes is connected between the live wire, neutral wire, and ground wire. It can issue a warning signal without interrupting power supply after the surge protection device fails. This ensures the continued operation of the main equipment (electrical products) even after the surge protection device fails, and also promptly and clearly informs the user of the surge protection device's failure status so that they can take subsequent maintenance or protective measures. This surge protection circuit includes a surge protection module and a failure detection indication module.

[0022] The surge protection module includes a varistor for absorbing surge energy and a thermally coupled thermal fuse. Thermal coupling is typically achieved by placing the thermal fuse in close contact with the varistor to sense its surface temperature. The failure detection and indication module includes a signal sampling unit, a field-effect transistor (FET) switching unit, a control unit, and an indication unit. The input of the signal sampling unit is connected to the connection point between the thermal fuse and the varistor. The output of the signal sampling unit is connected to the control terminal of the FET switching unit. The output of the FET switching unit generates a status signal and connects to the detection terminal of the control unit. The control unit drives the indication unit to indicate the status based on changes in the level of the status signal. This provides an indication of whether the surge protection device has failed. If the surge protection device fails, a status indication will be given immediately, prompting the user to replace the surge protection device, ensuring the product is always protected by the surge protection device.

[0023] A main power supply circuit for supplying power to the product is set on the live wire and the neutral wire. A fuse is set on the live wire as a fuse in the main power supply circuit. A 3.3V standby power supply is configured between the live wire L and the neutral wire N to supply power to the switching unit, the control unit and the indicator unit. The varistor includes a first varistor MOV1, a second varistor MOV2, and a third varistor MOV3. The first varistor MOV1 is connected (in parallel) between the live wire L and the neutral wire N to absorb differential-mode lightning surges between them. The thermal fuse is connected in series with the first varistor MOV1. The second varistor MOV2 is connected (in parallel) between the neutral wire N and the ground wire PG. The third varistor MOV3 is connected (in parallel) between the live wire L and the ground wire PG. Thus, regardless of whether the lightning strike is from L to N, L to PG, or N to PG, and regardless of whether it is a positive or negative voltage lightning strike, if any one of MOV1 / MOV2 / MOV3 fails, a status indication (e.g., an illuminated indicator) will be provided, providing comprehensive lightning strike warning functionality.

[0024] The thermal fuses include a first thermal fuse FT1 and a second thermal fuse FT2; the rated current of each fuse (e.g., 3.15A, 250Vac) is greater than the fusing current of the first thermal fuse FT1 and the second thermal fuse FT2. The first thermal fuse FT1 is connected between the live wire L and the ground wire PG, and is connected in series with the third varistor MOV3; the second thermal fuse FT2 is connected between the neutral wire N and the ground wire PG, and is connected in series with the second varistor MOV2; and the first varistor MOV1 is connected in series between the first thermal fuse FT1 and the second thermal fuse FT2. Both the first thermal fuse FT1 and the second thermal fuse FT2 are thermally coupled to the first varistor MOV1, the second varistor MOV2, and the third varistor MOV3; or: the first thermal fuse FT1 is thermally coupled to the first varistor MOV1 and the second varistor MOV2; the second thermal fuse FT2 is thermally coupled to the first varistor MOV1 and the third varistor MOV3. Alternatively, the first thermal fuse FT1 is thermally coupled to a varistor, while the second thermal fuse FT2 is thermally coupled to the remaining two varistors. The first thermal fuse FT1, the first varistor MOV1, and the second thermal fuse FT2 are connected in series between the live wire and the neutral wire; the second varistor MOV2 is connected between the connection point of the first varistor MOV1 and the second thermal fuse FT2 and the ground wire PG; the third varistor MOV3 is connected between the connection point of the first thermal fuse FT1 and the first varistor MOV1 and the ground wire. One end of both the second varistor MOV2 and the third varistor MOV3 is connected to the air discharge tube GD1, and the other ends are respectively connected to the two ends of the first varistor MOV1. The air discharge tube GD1 is connected between the ground wire and the common connection point of the second and third varistors, and can be used to collaboratively discharge amplified energy surges. Thus, the first thermal fuse FT1, the second thermal fuse FT2, the first varistor MOV1, the second varistor MOV2, the third varistor MOV3, and the air discharge tube GD1 jointly achieve the surge protection function, absorbing the lightning current from the power grid. The first varistor MOV1 absorbs the differential mode lightning surge between the L line and the N line, and the second varistor MOV2 and the third varistor MOV3 absorb the lightning surge from the L line and the N line to the ground PG. The first thermal fuse FT1 and the second thermal fuse FT2 are in close contact with the varistor to sense the surface temperature of the varistor.

[0025] The signal sampling unit includes a rectifier diode D1 and voltage divider resistors R2, R3, and R4 (100K). The anode of the rectifier diode D1 is connected to the junction of the first thermal fuse FT1 and the first varistor MOV1. The voltage divider resistors are connected between the cathode of the rectifier diode and the field-effect transistor switching unit.

[0026] The field-effect transistor switching unit is an N-channel field-effect transistor Q1, whose gate is connected to the other end of the voltage divider resistor, whose source is grounded, and whose drain serves as the output terminal of the status signal. It also includes a pull-up resistor connected between the drain of the field-effect transistor and a 3.3V standby power supply.

[0027] The control unit is a microcontroller U1, also known as a single-chip microcomputer, such as the STC8G model. The indicator unit is a light-emitting diode (LED1). The detection terminal (pin 2, I / O port) of the microcontroller U1 is connected to the drain of the N-channel MOSFET to detect the level of the SURGE signal. The output terminal (pin 8, another I / O port) of the microcontroller U1 is connected to the cathode of the LED1 (the driving current-limiting resistor R6 (1K) of the LED can be connected in series between the other I / O port of the microcontroller U1 and the cathode of the LED1) to drive the LED1 for status indication. The anode of the LED1 is connected to a 3.3V power supply. For the microcontroller U1, pins 3, 5, 6, and 7 are reserved pins and grounded. Using general-purpose discrete components and microcontroller I / O ports, the microcontroller U1 can be any general-purpose MCU with two or more I / O ports, eliminating the need for dedicated chips, resulting in lower costs and easier promotion and application.

[0028] It also includes filter capacitors C1 and C2 (100NF / 50V) and a Zener diode ZD1 (20V) for filtering and regulating the sampled signal. The Zener diode ZD1, resistor R5 (10K), and filter capacitor C2 are connected in parallel between the other end of the voltage divider resistor and the neutral line PG. Filter capacitor C1 is connected between the 3.3V power supply and the neutral line PG. In this embodiment, resistors R2, R3, and R4 are connected in series to form a voltage divider circuit, and these three are connected in series between the cathode of the rectifier diode D1 and the neutral line N; filter capacitors C1 and C2 form a filter circuit to filter out noise interference in the signal.

[0029] Working principle: Its core lies in using the thermal effect of a varistor failure to trigger the thermal fuse to blow, thereby changing the conduction state of the field-effect transistor. The thermal signal is converted into an electrical signal through the thermal fuse, and the field-effect transistor is used for level conversion, which is then recognized by the microcontroller. The microcontroller then drives the indicator unit to indicate the status, thereby alerting the user that the surge protection device has failed. It achieves accurate and reliable indication of the failure status of the surge protection device without cutting off the power supply to the main equipment, combining safety, availability, and high reliability.

[0030] Normal state: The first varistor MOV1 has a high impedance, and the mains voltage is applied across it. This high voltage is rectified by rectifier diode D1 and divided by voltage divider resistors R2 / R3 / R4. The voltage drop across R4 causes the gate-source voltage Vgs of MOSFET Q1 to exceed its turn-on voltage, turning on MOSFET Q1. After MOSFET Q1 turns on, it pulls its drain (SURGE signal point) voltage down to near ground level (approximately 0V). The microcontroller U1 detects the low-level signal, determines that the surge protection function is normal, and does not light up LED1.

[0031] Failure State: When any varistor fails and heats up, causing either the first thermal fuse FT1 or the second thermal fuse FT2 to blow, the high-voltage path of the first varistor MOV1 is cut off. The gate drive voltage Vgs of the field-effect transistor Q1 disappears, and Q1 changes from conducting to cutoff. After Q1 is cut off, its drain voltage is pulled up to a high level of 3.3V by the pull-up resistor R1 (10K). The microcontroller U1 detects the SURGE signal changing from low to high, thus determining that the surge protection device has failed. It then drives the LED1 to light up (after detecting this high-level signal, the microcontroller U1 controls the output of another I / O port connected to LED1 to be low or high, depending on whether LED1 is configured to light up at a low or high level), issuing a visual alarm to the user that the surge protection device has failed and needs maintenance. During this process, the fuse F1 in the main power supply circuit remains intact due to its large rated current, and the main power supply to the product module is not affected.

[0032] As can be seen, the SURGE signal states in its normal state (low level) and failure state (high level) are clearly defined, indicating high reliability. Using a MOSFET as the switching device results in high input impedance and minimal impact on the preceding circuitry. The first thermal fuse FT1, the first varistor MOV1, and the second thermal fuse FT2 are cleverly connected in series to form a series detection structure. The blown fuse FT1 or FT2 can be detected, further enhancing reliability.

[0033] The key design feature of this invention is the installation of a surge protection module and a failure detection indication module between the live wire, neutral wire, and ground wire. The surge protection module includes a varistor for absorbing surge energy and a thermally coupled temperature fuse. The failure detection indication module includes a signal sampling unit, a field-effect transistor (FET) switching unit, a control unit, and an indication unit. The input terminal of the signal sampling unit is connected to the connection node between the temperature fuse and the varistor. The output terminal of the signal sampling unit is connected to the control terminal of the FET switching unit. The output terminal of the FET switching unit generates a status signal and connects to the detection terminal of the control unit. The control unit drives the indication unit to provide status indication based on the level change of the status signal. Thus, even after the varistor fails, the power supply does not need to be cut off, and the product can continue to be used. It combines safety and availability, providing effective lightning protection while avoiding the trouble caused by direct power outages after failure. It also uses an indicator unit to notify the user that the lightning protection device has failed, allowing the user to take further measures. This eliminates the safety blind spot of "unprotected operation" and improves safety and user experience. Since it uses the inherent characteristic of the varistor's failure and heat generation for detection, and triggers the signal through physical melting, it has strong resistance to electrical interference and an extremely low false alarm rate.

[0034] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.

Claims

1. A novel lightning surge protection circuit connected between a live line, a neutral line and a ground line, characterized in that, include: A surge protection module includes a varistor for absorbing surge energy and a thermally coupled temperature fuse to the varistor; The failure detection indication module includes a signal sampling unit, a field-effect transistor switching unit, a control unit, and an indication unit; The input terminal of the signal sampling unit is connected to the connection node between the temperature fuse and the varistor; the output terminal of the signal sampling unit is connected to the control terminal of the field-effect transistor switching unit; the output terminal of the field-effect transistor switching unit generates a status signal and is connected to the detection terminal of the control unit; the control unit drives the indicator unit to perform status indication according to the level change of the status signal.

2. A novel lightning surge protection circuit according to claim 1, characterized in that, The varistor includes a first varistor, a second varistor, and a third varistor; the first varistor is connected between the live wire and the neutral wire; the second varistor is connected between the neutral wire and the ground wire; the third varistor is connected between the live wire and the ground wire; and the temperature fuse is connected in series with the first varistor.

3. A novel surge protection circuit for lightning strikes according to claim 2, characterized in that, The temperature fuse includes a first temperature fuse and a second temperature fuse; The first thermal fuse, the first varistor, and the second thermal fuse are connected in series between the live wire and the neutral wire; the second varistor is connected between the connection point of the first varistor and the second thermal fuse and the ground wire; the third varistor is connected between the connection point of the first thermal fuse and the first varistor and the ground wire.

4. A novel surge protection circuit for lightning strikes according to claim 3, characterized in that, The signal sampling unit includes a rectifier diode and a voltage divider resistor; the anode of the rectifier diode is connected to the connection point of the first temperature fuse and the first varistor; the voltage divider resistor is connected between the cathode of the rectifier diode and the field-effect transistor switching unit.

5. A novel surge protection circuit for lightning strikes according to claim 4, characterized in that, The field-effect transistor switching unit is an N-channel field-effect transistor, whose gate is connected to the other end of the voltage divider resistor, whose source is grounded, and whose drain serves as the output terminal of the status signal.

6. A novel surge protection circuit for lightning strikes according to claim 5, characterized in that, It also includes a pull-up resistor connected between the drain of the field-effect transistor and a standby power supply.

7. A novel surge protection circuit for lightning strikes according to claim 4, characterized in that, It also includes a Zener diode and a filter capacitor, which are connected in parallel between the other end of the voltage divider resistor and the neutral line.

8. A novel surge protection circuit for lightning strikes according to claim 1, characterized in that, It also includes an air discharge tube, which is connected between the ground wire and the common connection point of the second and third varistors.

9. A novel surge protection circuit for lightning strikes according to claim 6, characterized in that, The control unit is a microcontroller, the indicator unit is a light-emitting diode (LED), the detection terminal of the microcontroller is connected to the drain of the N-channel MOSFET, the output terminal of the microcontroller is connected to the cathode of the LED, and the anode of the LED is connected to the standby power supply.

10. A novel surge protection circuit for lightning strikes according to claim 1, characterized in that, The live wire and the neutral wire are provided with a main power supply circuit for supplying power to the product. A fuse is provided on the live wire as a fuse in the main power supply circuit. The rated current of the fuse is greater than the fusing current of the thermal fuse.

Images