A unidirectional DC overvoltage protection element

Abstract

This utility model relates to the field of overvoltage protection components, and particularly to a unidirectional DC overvoltage protection component. This overvoltage protection component includes a thermosetting epoxy resin encapsulation body and, internally, a base, a first connecting layer, a multi-layered TVS chip, a second connecting layer, a varistor, and a support, stacked sequentially. The multi-layered TVS chip has an N-type unipolar structure, with layers connected by connecting tabs. Its positive terminal is connected in series with the varistor via the first connecting layer, and its negative terminal is connected to the base via the second connecting layer. This structure, through the synergistic effect of the TVS chip and the varistor, can quickly respond to forward overvoltages and clamp them to a safe level. Simultaneously, it utilizes the unipolar characteristic to block reverse current, adapting to DC circuit protection requirements. The surface-mount TO218 package is compatible with surface mount technology, improving integration convenience and making it suitable for surge protection scenarios.

Description

Technical Field

[0001] This utility model relates to the field of overvoltage protection components, and in particular to a unidirectional DC overvoltage protection component. Background Technology

[0002] In the field of DC overvoltage protection, especially in the lightning protection scenarios of power electronic equipment such as energy storage power stations and photovoltaic inverters, the installation location often presents a pulsating DC voltage environment. In DC circuit systems, overvoltage (such as surges and voltage spikes) is one of the main causes of damage to electronic equipment, therefore, overvoltage protection components are needed to achieve circuit protection.

[0003] Currently, commonly used overvoltage protection solutions mostly employ TVS chips (transient voltage suppressor diodes) or varistors in individual packages, or in simple combined packages. However, these solutions present several challenges in practical applications. Firstly, traditional through-hole packaged protection components are difficult to adapt to miniaturized, high-density surface-mount circuits, resulting in low circuit integration and limited automated production efficiency. While some surface-mount packaged components offer improved compatibility, their reliance on a single protection device (such as only a TVS chip or only a varistor) makes it difficult to balance fast response speed with high current discharge capability, leading to poor protection performance under high-voltage, high-current surge scenarios. Secondly, DC circuits have stringent requirements for the unidirectional conductivity of protection components. Existing combined components often suffer from insufficient polarity protection stability due to improper connection methods between the TVS chip and the varistor, making them prone to reverse current breakdown. Furthermore, if the stacked structure of multi-layer TVS chips lacks optimized interlayer connection design, excessive contact resistance or poor heat dissipation can affect surge absorption efficiency and component lifespan.

[0004] Therefore, how to develop an overvoltage protection element that is compatible with surface mount technology, has efficient collaborative protection capabilities, and stable unidirectional characteristics is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0005] To overcome the shortcomings of the prior art, this utility model provides a unidirectional DC overvoltage protection element, including a package; a base, a first connection layer, a TVS chip (1), a second connection layer, a varistor and a bracket are stacked in sequence inside the package; The first connecting layer is disposed above the base; The TVS chip is disposed above the first connection layer; The second connection layer is disposed above the multilayer stacked TVS chip; the varistor is disposed above the second connection layer; the support is disposed above the varistor; The TVS chip is an N-type unipolar TVS chip, with its positive electrode connected in series with a varistor through a first connection layer, and its negative electrode connected to the base through a second connection layer.

[0006] Furthermore, the junction capacitance of the TVS chip is in the picofarad range, and when connected in series with the varistor, the current polarity cannot be reversed; the TVS chip has a multi-layer stacked structure, and adjacent TVS chips in the multi-layer stacked structure are connected by a connecting piece.

[0007] Furthermore, the base and the first connecting layer, the first connecting layer and the multi-layer stacked TVS chips, two adjacent TVS chips, the multi-layer stacked TVS chips and the second connecting layer, the second connecting layer and the varistor, and the varistor and the bracket are all connected by solder.

[0008] Furthermore, the solder on the upper and lower surfaces of the TVS chip and the varistor is processed using a vacuum evaporation process.

[0009] Furthermore, the solder between the base and the first connecting layer is formed using a physical rolling process.

[0010] Furthermore, the thickness of the solder is 9-11 μm.

[0011] Furthermore, the solder is one of tin solder, lead-containing solder, and lead-free solder.

[0012] Furthermore, one end of the base extends outward to form a first electrode, and one end of the bracket extends outward to form a second electrode.

[0013] Furthermore, the first connecting layer, the second connecting layer, and the connecting piece are one of molybdenum sheets, copper-molybdenum alloy sheets, and Kovar alloy sheets.

[0014] Furthermore, the varistor is a low-voltage varistor with a length and width of 10–11 mm and a thickness of ≤1 mm; the encapsulation body is formed by encapsulation of thermosetting epoxy resin using TO218.

[0015] Compared with existing technologies, the unidirectional DC overvoltage protection element provided by this utility model is compatible with existing surface mount technology, improving the convenience of circuit integration and the efficiency of automated production. The thermosetting epoxy resin encapsulation provides excellent mechanical strength, insulation and resistance to damp heat, effectively protecting internal components from external environmental corrosion. The multi-layer stacked TVS chip, combined with the unipolar N-type structure, achieves high surge absorption capability within a limited space, increasing surge protection capability to 60kA or even higher. The unidirectional conductivity of the TVS chip, combined with the varistor, enables the TVS chip to respond quickly and initially clamp overvoltage, while the varistor further dissipates energy. The polarity locking function formed by the series connection of the two ensures the uniqueness of the protection direction, effectively adapting to the needs of DC circuits. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the internal structure of the overvoltage protection element provided by this utility model; Figure 2 This is a schematic diagram of the overall structure of the overvoltage protection element provided by this utility model.

[0018] Figure label: 1-TVS chip; 2-Varistor; 3-Base; 4-Bracket; 5-Package; 6-First connection layer; 7-Connecting piece; 8-Second connection layer; 9-First electrode; 10-Second electrode. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] In the description of this utility model, it should be noted that the terms "upper," "lower," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] To provide a small, high-surge-protection unidirectional DC overvoltage protection component that is compatible with surface-mount TO218 packages and combines the advantages of TVS and MOV, this utility model provides such a... Figure 1-2 An example of a unidirectional DC overvoltage protection element is shown.

[0022] like Figure 1-2As shown, the overvoltage protection element includes a thermosetting epoxy resin encapsulation body 5; a base 3, a first connecting layer 6, a multi-layer stacked TVS chip 1, a second connecting layer 8, a varistor 2, and a bracket 4, which are stacked sequentially inside the encapsulation body 5. The first connecting layer 6 is disposed above the base 3; The multi-layer stacked TVS chip 1 is disposed above the first connection layer 6, and adjacent TVS chip 1 layers are connected by a connecting piece 7. The second connection layer 8 is disposed above the multi-layer stacked TVS chip 1; the varistor 2 is disposed above the second connection layer 8; the bracket 4 is disposed above the varistor 2; The TVS chip 1 is an N-type unipolar TVS chip 1, with its positive electrode connected in series with the varistor 2 through the first connection layer 6, and its negative electrode connected to the base 3 through the second connection layer 8.

[0023] Specifically, when in use, when the component is in normal working condition, the component is installed in a DC circuit, and the current flows in from the base 3, through the first connection layer 6, the multi-layer stacked TVS chip 1, the second connection layer 8, the varistor 2, and the bracket 4 to form a circuit. At this time, the voltage is lower than the trigger threshold, the N-type unipolar TVS chip 1 is in the reverse cutoff state, blocking the small leakage current, and the varistor 2 maintains a high resistance state.

[0024] When the circuit encounters a transient surge, the voltage rises sharply, exceeding the breakdown voltage of TVS chip 1. The surge current first breaks down the bottom TVS chip 1, triggering the adjacent upper-layer chip through the connecting piece 7, achieving rapid conduction. Through the current shunting effect of the multi-layer stacked TVS chips 1, the surge protection capability is improved to ≥60kA. The unidirectional conduction characteristic of TVS forces the current to flow only from the positive terminal (base 3) to the negative terminal (bracket 4), which can avoid polarity reversal. The rapid conduction of TVS chip 1 guides most of the surge current into the circuit, but because its current carrying capacity is limited, the remaining high-energy impact is absorbed by varistor 2. Varistor 2 will activate low clamping. When the residual voltage exceeds the threshold of varistor 2, its resistance drops sharply, clamping the voltage at a safe level.

[0025] When the surge disappears, the circuit voltage drops back down. Due to the N-type unipolar characteristic of TVS chip 1, when the anode voltage is lower than the cathode voltage, TVS automatically returns to the cutoff state. After the clamping voltage is released, varistor 2 returns to the high resistance state.

[0026] Preferred, such as Figure 1 As shown, the multi-layer stacked TVS chip 1 is a three-layer stacked TVS chip 1, and adjacent TVS chip 1 layers are connected by a connecting piece 7.

[0027] Preferably, the base 3 and the bracket 4 are made of copper sheets.

[0028] In one embodiment, the junction capacitance of the TVS chip 1 is in the picofarad range, and when connected in series with the varistor 2, the current polarity cannot be reversed.

[0029] Using the above scheme, the TVS chip 1 with picofarad-level junction capacitance is connected in series with the varistor 2. The low capacitance characteristic of the TVS chip 1 ensures signal integrity, while the energy absorption capability of the varistor 2 compensates for the limitation of the current carrying capacity of the TVS chip 1. Together, they achieve fast response and reliable clamping to overvoltage, while preventing reverse current breakdown and enhancing circuit stability.

[0030] In one embodiment, such as Figure 1 As shown, the base 3 is connected to the first connecting layer 6, the first connecting layer 6 is connected to the multi-layer stacked TVS chip 1, the two adjacent TVS chip layers 1 are connected to each other, the multi-layer stacked TVS chip 1 is connected to the second connecting layer 8, the second connecting layer 8 is connected to the varistor 2, and the varistor 2 is connected to the bracket 4 by solder.

[0031] In one embodiment, the solder on the upper and lower surfaces of the TVS chip 1 and the varistor 2 is processed using a vacuum evaporation process.

[0032] The solder layer formed on the surface of TVS chip 1 and varistor 2 using vacuum evaporation process can precisely control the thickness of the solder, forming an ultra-thin solder layer, which enables the entire composite structure to be adapted to the surface mount TO218 package and achieve miniaturization.

[0033] It should be noted that the vacuum evaporation process is existing technology. Those skilled in the art can refer to the vacuum evaporation process method provided in application number CN202410572220.5, entitled "Vacuum Evaporation Process and Physical Calendering Process".

[0034] In one embodiment, the solder between the base 3 and the first connecting layer 6 is formed by a physical rolling process.

[0035] In one embodiment, the solder layer between the varistor 2 and the bracket 4 can be formed by a single-sided physical rolling bracket 4 process, and correspondingly, the solder layer on the other side of the varistor 2 is formed by a vacuum evaporation process.

[0036] In the above scheme, the solder between the base 3 and the first connecting layer 6 is formed by physical rolling process. The solder can be densified by mechanical rolling, the thickness of the solder can be controlled, the density and structural strength of the solder layer can be improved, and the connection stability between the base 3 and the upper structure can be enhanced.

[0037] It should be noted that the physical calendering process is a conventional existing technology, and single-sided or double-sided calendering can be selected according to actual needs.

[0038] In one embodiment, the thickness of the solder is 9-11 μm.

[0039] The above solution, with a thickness of 9-11μm, can fit the internal space of the surface mount TO218 package, solving the problem of excessively thick composite structures caused by traditional thick solder layers. At the same time, the thin solder layer can enhance electrical and thermal conductivity, and improve the surge protection capability of the component.

[0040] In one embodiment, the solder is one of tin solder, lead-containing solder, and lead-free solder.

[0041] Using the above approach, solder can be flexibly selected according to the application scenario. For example, lead-free solder is suitable for fields with strict environmental protection requirements, while lead-containing solder can meet the high-temperature soldering requirements and improve component compatibility.

[0042] It should be noted that those skilled in the art can select the above-mentioned solders according to actual application needs, including but not limited to the solutions provided by this utility model.

[0043] In one embodiment, such as Figure 1 and Figure 2 As shown, one end of the base 3 extends outward to form the first electrode 9, and one end of the bracket 4 extends outward to form the second electrode 10.

[0044] Using the above scheme, the first and second electrodes 10 formed by the extension of the base 3 and the bracket 4 can be directly used as connection terminals of external circuits, simplifying the soldering process between components and PCB boards.

[0045] Preferred, such as Figure 1 As shown, the first electrode 9 and the second electrode 10 are located on both sides of the package 5.

[0046] In one embodiment, the first connecting layer 6, the second connecting layer 8, and the connecting piece 7 are one of a molybdenum sheet, a copper-molybdenum alloy sheet, and a Kovar alloy sheet.

[0047] The above solution uses molybdenum sheets, copper-molybdenum alloy sheets, or Kovar alloy sheets as the connecting layer and connecting piece 7 materials, which have excellent electrical and thermal conductivity, and can efficiently transmit current and dissipate heat. In addition, the thermal expansion coefficient of these materials is well matched with components such as TVS chip 1 and base 3, which can reduce thermal stress caused by temperature changes, avoid cracking or desoldering of the connecting layer, and improve the temperature cycling performance of the components.

[0048] In one embodiment, the varistor 2 is a low-voltage varistor 2, with a length and width of 10–11 mm and a thickness of ≤1 mm.

[0049] Using the above solution, the low-voltage varistor 2 can quickly respond to overvoltage signals near the normal operating voltage of the DC circuit, achieving precise overvoltage triggering and clamping; while the length and width dimensions of 10-11mm and the thickness of ≤1mm can be adapted to the compact space of the TO218 package, avoiding packaging difficulties caused by excessive size. At the same time, the thin design is conducive to the rapid heat dissipation of the varistor 2.

[0050] Performance testing To further illustrate the advantages of the overvoltage protection element of this utility model, the product of this utility model was compared with existing products on the market with a humidity sensitivity level (MSL) test, with the reference standard being JEDEC-J-STD-020C. The test results are shown in Table 1.

[0051] Table 1

[0052] As shown in Table 1, this embodiment uses a surface-mount TO218 package with a humidity sensitivity level of 1. This indicates that the overvoltage protection element provided by this utility model uses thermosetting epoxy resin encapsulation, which provides higher sealing and reliability, meets more stringent moisture protection requirements, is not prone to cracking, and is suitable for scenarios with high environmental reliability requirements.

[0053] The MOV+TVS plug-in product uses epoxy resin powder encapsulation, has a humidity sensitivity level of 5, poor moisture protection performance, can only meet basic moisture protection requirements, and its applicable environment is relatively limited.

[0054] In summary, the unidirectional DC overvoltage protection element provided by this utility model is compatible with existing surface mount technology, improving the convenience of circuit integration and the efficiency of automated production. The thermosetting epoxy resin encapsulation provides excellent mechanical strength, insulation, and resistance to damp heat, effectively protecting internal components from external environmental corrosion. The multi-layer stacked TVS chip, combined with the unipolar N-type structure, achieves high surge absorption capability within a limited space, increasing surge protection capability to 60kA or even higher. The unidirectional conductivity of the TVS chip, combined with the varistor, enables the TVS chip to respond quickly and initially clamp overvoltage, while the varistor further dissipates energy. The polarity locking function formed by the series connection of the two ensures the uniqueness of the protection direction, effectively adapting to the needs of DC circuits.

[0055] Although this document frequently uses terms such as base, first connecting layer, TVS chip, second connecting layer, varistor, and bracket, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would contradict the spirit of this invention.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A unidirectional DC overvoltage protection element, characterized by: Includes a package (5); a base (3), a first connection layer (6), a TVS chip (1), a second connection layer (8), a varistor (2), and a bracket (4) stacked sequentially inside the package (5); The first connecting layer (6) is disposed above the base (3); The TVS chip (1) is disposed above the first connection layer (6); The second connection layer (8) is disposed above the multilayer stacked TVS chip (1); the varistor (2) is disposed above the second connection layer (8); the support (4) is disposed above the varistor (2); The TVS chip (1) is an N-type unipolar TVS chip (1), with its positive electrode connected in series with the varistor (2) through the first connection layer (6), and its negative electrode connected to the base (3) through the second connection layer (8).

2. The unidirectional DC overvoltage protection element according to claim 1, characterized in that: The junction capacitance of the TVS chip (1) is in the picofarad range, and the current polarity cannot be reversed after being connected in series with the varistor (2); the TVS chip (1) is a multi-layer stacked structure, and the adjacent two layers of TVS chips (1) in the multi-layer stacked TVS chip (1) are connected by a connecting piece (7).

3. The unidirectional DC overvoltage protection element according to claim 1, characterized in that: The base (3) is connected to the first connecting layer (6), the first connecting layer (6) is connected to the multi-layer stacked TVS chip (1), the two adjacent TVS chips (1), the multi-layer stacked TVS chip (1) is connected to the second connecting layer (8), the second connecting layer (8) is connected to the varistor (2), and the varistor (2) is connected to the bracket (4) by solder.

4. The unidirectional DC overvoltage protection element according to claim 3, characterized in that: The solder on the upper and lower surfaces of the TVS chip (1) and the varistor (2) is processed by vacuum evaporation.

5. The unidirectional DC overvoltage protection element according to claim 3, characterized in that: The solder between the base (3) and the first connecting layer (6) is formed by physical rolling process.

6. The unidirectional DC overvoltage protection element according to claim 3, characterized in that: The thickness of the solder is 9-11 μm.

7. The unidirectional DC overvoltage protection element according to claim 3, characterized in that: The solder is one of tin solder, lead-containing solder, and lead-free solder.

8. The unidirectional DC overvoltage protection element according to claim 1, characterized in that: The base (3) extends outward at one end to form a first electrode (9), and the bracket (4) extends outward at one end to form a second electrode (10).

9. The unidirectional DC overvoltage protection element according to claim 1, characterized in that: The first connecting layer (6), the second connecting layer (8), and the connecting piece (7) are one of molybdenum sheet, copper-molybdenum alloy sheet, and Kovar alloy sheet.

10. The unidirectional DC overvoltage protection element according to claim 1, characterized in that: The varistor (2) is a low-voltage varistor (2), with a length and width of 10–11 mm and a thickness of ≤1 mm; the encapsulation body (5) is formed by encapsulation of thermosetting epoxy resin using TO218.

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