A fail-safe super overvoltage protector

Abstract

The application discloses a kind of super strong overvoltage protector of failure safety, it is related to electronic product field, including switching device and clamping device;Switching device and clamping device are packaged as a whole, located in the inside of shell;The inside of shell is provided with lead wire, one end of lead wire is connected with the combination of switching device and clamping device, the other end of lead wire is connected with electrode outside shell, and the welding spot of lead wire and lead wire is used as the failure open circuit device of overvoltage protector.The product size of the present application is miniaturized, and it is patching;The working voltage of electrical performance is high, and the fault tolerance of working voltage is high;Surge capacity is strong;Residual voltage is low, and the protection effect is good;Energy saving and environmental protection, that is, the electrical performance of overvoltage protector, under high working voltage, the leakage current is low, in high temperature environment, the temperature rise of product is small, and the reliability of long-term use is high;Failure open circuit;It has the extensive application demand and broad prospect of adapting to the development trend of present electronic industry.

Description

Technical Field

[0001] This invention relates to the field of electronic products, and more specifically, to a fail-safe, high-strength overvoltage protector. Background Technology

[0002] The development of electronic products is increasingly trending towards lightweighting, miniaturization, and automated production. This, in turn, places higher demands on the miniaturization, surface-mount technology, high energy efficiency, and safety of circuit protection devices for electronic products. To adapt to this trend in the electronics industry, there is a need to develop a fail-safe overvoltage protection device with superior protection capabilities.

[0003] The most common power supply protection method involves connecting the gas discharge tube (GDT) of the switching device and the varistor of the clamping device at the pin in series. Alternatively, connecting the clamping pin varistor and the TSS (solid-state discharge tube) of the switch in series is also a common protection mode in some applications where current carrying capacity requirements are not high. However, a characteristic of these modes is that they are implemented by having independent clamping devices and independent wiring on the PCB board. Another method involves soldering the GDT and varistor of the pin together. This discrete component approach provides circuit protection, which, while offering higher current carrying capacity, is typically bulky, resulting in higher residual voltage. Furthermore, the selection and matching of specific discrete components can be challenging for non-specialist electronic design engineers, and the large PCB footprint makes it difficult to manufacture surface-mount products. To improve protection effectiveness and reduce residual voltage, some manufacturers stack TVS (Transient Voltage Suppressor) chips into a single product. While this method allows for smaller sizes, it is difficult to achieve high current carrying capacity, and the high cost makes it less suitable for widely used applications.

[0004] From the basic characteristics of overvoltage devices, the operating voltage and clamping voltage are directly proportional. The higher the allowable operating voltage, the higher the clamping voltage. Therefore, to reduce residual voltage and improve protection effectiveness, a higher operating voltage cannot be tolerated, resulting in a very small allowable range of operating voltage variation. For example, in some markets where the operating voltage is often 220VAC, the mains voltage can sometimes reach as high as 440VAC. If the operating voltage of the protection device is selected too low, the device may falsely trigger and fail. Conversely, if the operating voltage is too high, the residual voltage will be relatively high, requiring the downstream wiring and devices to withstand higher surge impacts, increasing the cost of downstream cabling, and often failing to achieve the desired protection effect.

[0005] In overvoltage circuit protection devices, the common surge failure mode is short circuit failure. This has drawbacks ranging from simply preventing power to the protected equipment to, in severe cases, causing the circuit or protection device to catch fire due to prolonged high-voltage short circuits. This is the most unacceptable failure mode for circuit protection. To avoid this mode, the current common approach is to use an external current fuse or thermal fuse. When current flows for an extended period, the fuse melts and cuts off the circuit, preventing fire. Alternatively, a thermal fuse can be used to cut off the circuit when the temperature rises to a certain level, ensuring the safety of the circuit or equipment. There are also more advanced solutions, such as soldering a thermal fuse to the overvoltage device. This reduces size, and when the overvoltage device overheats, the temperature is quickly conducted to the thermal fuse, cutting off the circuit promptly. This approach is more compact and faster-responding than the first method. However, these are all remedial measures for short circuits and cannot completely guarantee timely circuit cutting off or complete prevention of fire.

[0006] The following are some applications that are similar to this invention. These solutions are usually based on PCB board routing, and there are also simple combinations of these solutions. However, they only solve part of the problem and cannot solve all of it. They are described in detail below:

[0007] 1. The GDT + MOV (Metal Oxide Varistor) configuration. While this configuration allows for products with low leakage current and high safe operating voltage, as well as high current-carrying capacity, it also has drawbacks: large size, high residual voltage, difficulty in surface mount technology (SMT) products, and a high failure risk. Depending on the component selection and matching, a thermal fuse is typically added to prevent the risk of fire. Figure 3 As shown.

[0008] 2. TVS stacked configuration. While this configuration allows for products with lower clamping voltages, it also has drawbacks: large size, difficulty in surface mount technology (SMT) products, and a lack of high-voltage, high-current products. Even if such products exist, they are bulky, difficult to mass-produce, and expensive. It also falls under the failure-to-circuit protection mode because TVS provides transient protection. For high-energy surges, the typically external current and temperature fuse configurations are insufficient to ensure timely and safe circuit disconnection.

[0009] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0010] In view of the problems in related technologies, this invention proposes a fail-safe, high-strength overvoltage protector to overcome the aforementioned technical problems existing in the prior art.

[0011] Therefore, the specific technical solution adopted by the present invention is as follows:

[0012] A fail-safe, high-strength overvoltage protector includes:

[0013] Switching device and clamping device; the switching device and clamping device are packaged as one unit and located inside the housing; the housing is provided with leads, one end of which is connected to the combination of the switching device and clamping device, and the other end of which is connected to the external electrode of the overvoltage protector.

[0014] Furthermore, the switching devices are switching devices such as solid-state discharge tube chips, and the clamping devices are clamping devices such as metal oxide rheostats chips.

[0015] Furthermore, the clamping device and the switching device are connected in series.

[0016] Furthermore, the breakdown voltage of the protection device is characterized by the sum of the breakdown voltages of the clamping device and the switching device; the main voltage of the clamping voltage is characterized by the clamping voltage of the clamping device 2.

[0017] Furthermore, integrating the switching device and the clamping device into a single unit includes:

[0018] The switching device and the clamping device are combined in series.

[0019] Furthermore, when a large surge voltage occurs due to overvoltage, the solder joint connecting the lead to the overvoltage protector is selected as the break point for surge failure.

[0020] Furthermore, when an overvoltage condition occurs, the lead wire is selected as the surge failure break point.

[0021] Furthermore, the lead wire is a metal wire such as copper, silver, or gold.

[0022] Furthermore, the current-carrying capacity of switching devices and clamping devices is greater than the surge capacity of leads or solder joints.

[0023] Furthermore, the packaging methods include standard packages such as SMA, SMB, SMC, 3025, and 4032, or any package size based on the internal chip size.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) Miniaturized and surface-mountable. Electrically, it offers high operating voltage and high fault tolerance; strong surge capability; low residual voltage and good protection effect. It is energy-saving and environmentally friendly, exhibiting low leakage current at high operating voltages and low temperature rise in high-temperature environments, resulting in high reliability over long periods. It also prevents open circuit failure. These characteristics make this invention suitable for a wide range of applications and have broad prospects in line with current trends in the electronics industry.

[0026] (2) The product of this invention can easily achieve the effect of ultra-low leakage current under high operating voltage, so the standby power consumption is very low, the long-term working stability and the temperature rise of the device are also very low, which is very consistent with the characteristics of energy saving, environmental protection and high reliability in long-term use. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a fail-safe overvoltage protector according to an embodiment of the present invention;

[0029] Figure 2 This is a dimensional diagram of a fail-safe overvoltage protector according to an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the traditional scheme using a gas discharge tube (GDT) and a varistor (MOV).

[0031] Figure 4 This is a diagram of a commonly used power protection scheme;

[0032] Figure 5 This is one of the schematic diagrams of protection methods for low-current failure;

[0033] Figure 6 This is the second schematic diagram of a protection method for low-current failure;

[0034] Figure 7 This is a basic data diagram of the CMSLD551P102 product;

[0035] Figure 8 This is a diagram showing the electrical performance parameters of the CMSLD551P102 product;

[0036] Figure 9 It is a standard test data chart;

[0037] Figure 10 These are surge test data and failure mode diagrams;

[0038] Figure 11 This is one of the temperature rise test data graphs;

[0039] Figure 12 This is the second chart of temperature rise test data;

[0040] Figure 13 This is a graph of experimental data on damp heat load;

[0041] Figure 14 This is a graph of high-temperature load test data;

[0042] Figure 15 This is a circuit diagram of a type of CMLS product used in BMS applications.

[0043] In the picture:

[0044] 1. Switching device; 2. Clamping device; 3. Housing; 4. Lead wire. Detailed Implementation

[0045] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0046] According to an embodiment of the present invention, a fail-safe, high-voltage overvoltage protector is provided.

[0047] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figures 1-2 As shown, a fail-safe overvoltage protector according to an embodiment of the present invention includes:

[0048] Switching device 1 and clamping device 2 are packaged together as one unit and located inside housing 3. A lead wire 4 is provided inside housing 3. One end of the lead wire 4 is connected to the combination of switching device 1 and clamping device 2, and the other end of the lead wire 4 is connected to the external electrode of the overvoltage protector.

[0049] In one embodiment, the switching device 1 is a switching device such as a solid-state discharge tube (TSS) chip, and the clamping device 2 is a clamping device such as a metal oxide rheostat (MOV) chip.

[0050] In one embodiment, the clamping device 2 and the switching device 1 are connected in series.

[0051] In one embodiment, the breakdown voltage of the overvoltage protector is characterized by the sum of the breakdown voltages of the clamping device 2 and the switching device 1; the main voltage of the clamping voltage is characterized by the clamping voltage of the clamping device 2.

[0052] In one embodiment, the switching device 1 and the clamping device 2 are packaged as a single unit, including:

[0053] The switching device 1 and the clamping device 2 are combined in series.

[0054] In one embodiment, when a large surge voltage occurs due to overvoltage, the solder joint connecting lead 4 to the overvoltage protector is selected as the break point for surge failure.

[0055] In one embodiment, lead 4 is selected as the surge failure break point when an overvoltage condition occurs.

[0056] In one embodiment, lead 4 is a metal wire such as copper, silver, or gold; solder joint is a spot solder joint including solder joint or metal welding joint.

[0057] In one embodiment, the current-carrying capacity of the switching device 1 and the clamping device 2 is greater than the surge current-carrying capacity of the lead 4 or the solder joint.

[0058] In one embodiment, the packaging method includes standard packaging such as SMA packaging, SMB packaging, SMC packaging, 3025 packaging, and 4032 packaging, or any packaging size defined according to the internal chip size.

[0059] To facilitate understanding of the above technical solutions of the present invention, the working principle of the present invention in actual process will be described in detail below.

[0060] The fundamental feature of this invention is the combination of clamping and switching devices, for example, in power supply protection. This invention directly integrates clamping and switching devices into a single package, achieving high current carrying capacity while being thinner and lighter than existing multilayer TVS systems, and also resulting in lower residual voltage.

[0061] Because this invention combines switching and clamping devices, the operating voltage of an overvoltage protector is the sum of the breakdown voltages of the two devices. The clamping voltage is essentially characterized by the residual voltage of the clamping device. Therefore, it achieves a relatively high operating voltage and a relatively low residual voltage. The advantage of this design is that it allows for a high operating voltage and significantly improves the protection of downstream circuitry. For example, in a specific case, a fast-charging customer initially wanted a device with a withstand voltage of 480V and a residual voltage below 800V under a 500A surge. A product made by connecting four TVS chips in series exceeded 10mm in height and had a current carrying capacity of only 300A, failing to meet the customer's size requirements. However, the device made using this invention is less than 5mm in height, has doubled its current carrying capacity to 1000A, and has a residual voltage of less than 800V. The cost is also significantly reduced, and long-term reliability is greatly improved, resulting in a significantly enhanced protection effect. This design is particularly suitable for applications such as small-sized fast-charging devices and low-voltage electrical appliances.

[0062] This invention utilizes an electrical connection line that also provides fail-safe protection. This is achieved by disconnecting the electrical connection line when an overvoltage condition occurs and is about to reach or exceed the protection limit of the overvoltage device, thus preventing a short circuit due to failure. The selection of this failure point depends on the lead-out mechanism; it can be achieved by either choosing the solder joint between the lead and the overvoltage protector, or by using the lead itself as the surge failure break point.

[0063] Taking lead wires as an example, current fuses actually use silver or copper wires to achieve overcurrent protection. Alternatively, in the etching of copper traces on a PCB board, the length and thickness of the copper wires need to be carefully designed to ensure sufficient current flow under normal operating conditions, preventing excessive current from blowing the traces. This invention reverses this principle of copper wire current flow, ensuring both normal current flow capacity under normal operating conditions and timely disconnection of the copper wire under excessive surge conditions, preventing damage to overvoltage devices and subsequent short circuits.

[0064] In the battery management system (BMS) protection of new energy vehicles, the charging and discharging of lithium batteries is usually accomplished using MOSFETs. Different voltage charging and discharging power supplies can be made depending on the number of battery strings. To effectively reduce damage to the MOSFETs due to overcharging, high-power TVS diodes with SMC packages, such as a 3kW SMCJ100CA TVS diode, need to be connected in parallel in the charging and discharging circuit. However, failure is a probabilistic event. For example, the probability of failure for one SMCJ100CA TVS diode connected in parallel is 5%, while the probability decreases to 3% for two, and to 0.5% for six. Although more parallel connections generally mean greater safety, they cannot completely eliminate the risk. If one TVS diode fails and short-circuits, all TVS diodes become unusable, and the entire circuit will be unable to supply power. If an electric vehicle happens to be in an off-road location, it will be unable to start. The advantage of this invention is its small size; its shape can use the same solder pads as SMC, but its current carrying capacity is equivalent to that of six SMCJ100CA diodes, greatly reducing wiring space and cost. Furthermore, the product of this invention has low residual voltage, making it convenient for customers to use MOSFETs from different manufacturers and easily matching circuits. Additionally, it is designed to withstand open circuit failures; even if a protection device fails, it will not affect the normal power supply to the battery pack.

[0065] The features of this invention include: achieving multiple superior electrical properties in a small package; and the electrically connected circuits simultaneously functioning as open circuits in case of failure.

[0066] This invention borrows the concept of existing open-circuit failure protection to achieve surge and temperature failure functions in electrical connection lines. Its fail-safe implementation involves pre-designing the current-carrying capacity of the overvoltage device to exceed that of the electrical connection line, ensuring that line failure precedes overvoltage device failure, thus achieving the effect of open-circuit failure. The difference from traditional open-circuit failure protection is that traditional failure mode protection adds an external line open circuit after failure to achieve protection, preventing overvoltage device failure from causing catastrophic consequences such as cascading fires. This invention, however, fundamentally prevents the overvoltage protection device from failing and short-circuiting.

[0067] The design concept of this invention: CMSL (Low Clamping Voltage CMS) is a further development of CMS, maintaining its small size, high current capacity, and surface-mount characteristics while significantly reducing clamping voltage and enhancing protection performance. Advantages of CMSL applications:

[0068] Sufficient operating voltage margin increases safety and reliability, preventing degradation of the varistor over long-term use. It offers better protection than traditional gas discharge tubes and varistors in series, as well as TVS multilayer products. It is fail-safe, failing under high-current surge conditions, and its high voltage and low leakage current reduce the possibility of failure under low current. Suitable for thin and miniaturized applications, and ideal for mass production.

[0069] like Figure 7 The image shows basic data for a product used in fast charging, etc.: CMSLD551P102. CMSLD551P102 dimensions: size equivalent to a semiconductor SMC package, thickness less than 5mm; Dimensions indicates dimensions, Inch indicates inches, Millimeter indicates millimeters. (The image is missing from the original text.) Figure 8The image shows the electrical performance parameters of the CMSLD551P102 product, including device rating and specifications (unless otherwise specified, ambient temperature = 25°C). The CMSLD551P102's electrical performance data shows that it can withstand a 1000A surge of 8 / 20µs at an operating voltage of 560V on a size equivalent to a semiconductor SMC. Under the same size conditions, a TVS has a current carrying capacity of only tens of A. Parameter indicates parameters, Nominal Varistor Voltage indicates breakdown voltage, Maximum Allowable Continuous DC Voltage indicates maximum allowable operating voltage, Maximum Leakage Current indicates maximum leakage current, Maximum Class Current indicates maximum surge current, Operating Temperature Range indicates operating temperature, and Storage Temperature indicates storage temperature. Figure 9 The data shown are some standard test results, which meet the design parameters. Under 550V voltage, the leakage current is less than 5uA. Figure 10 The image shows surge test data and failure modes. Under a single current surge, with a combined surge of 1.2 / 50µs and 8 / 20µs, and a 1kA surge, the residual voltage is below 720V under a 1.5kV surge condition. The failure mode in the extreme test is open circuit. Figures 11-12 As shown, in a temperature rise test, under ambient temperature and 80°C conditions, with 400VAC and 48VAC applied, the product surface temperature did not rise significantly. Figure 13 The data shown is from a damp heat load test conducted under dual 85°C, 1000-hour, AC 400V load conditions. The data is normal and the test passed. Figure 14 The data shown is from a high-temperature load test. First, the test was conducted at 150 degrees Celsius under a 400VAC load for 168 hours. If the temperature was lowered to 125 degrees Celsius and then subjected to lightning strikes for 1000 hours, the data test results were normal. The leakage current was slightly higher than normal, but the voltage was normal. This is considered normal under industry conditions, and the test passed.

[0070] The product of this invention is suitable for applications requiring miniaturization and high power, such as fast charging, as well as applications requiring low standby power consumption. Currently, the standby power consumption of general PD fast charging is 150mW, but some companies have reduced the standby power consumption of PD fast charging to 35mW. This invention can achieve the 35mW requirement by matching the standby power consumption of domestic PDs.

[0071] The product of this invention is also suitable for use in battery management systems for new energy sources, and as a CMLS product for MOSFET protection in the charging and discharging circuits of a BMS, capable of replacing high-power TVS, specifically as follows: Figure 15 As shown, during overshoot, a high voltage exceeding the MOSFET's tolerance will be applied to both ends of the MOSFET. If no protection is provided, it will cause surge damage to the MOSFET. With the addition of CMS2, when an overvoltage occurs, CMS will clamp the voltage to a certain value to ensure the safety of the MOSFET.

[0072] Table 1 shows a comparison of surge and residual voltage data for high-power TVS and CMSL.

[0073] The test data shows that, using the product of this invention, one CMSL can replace many TVSs, and has a lower protection voltage. This saves on the number of TVSs used, reduces wiring space, and lowers costs. On the other hand, it also provides safer protection and reduces the surge withstand capability requirements of MOSFETs, making the circuit cost lower and safer.

[0074] Table 1 Comparison of surge and residual voltage data for high-power TVS, CMS, and CMSL

[0075]

[0076] In addition to the typical applications mentioned above, CMSL is also in demand in industries such as low-voltage electrical appliances, security, communications, automotive electronics, and new energy.

[0077] Low-voltage electrical appliances used under 220VAC require small size, high current carrying capacity, and low residual voltage, ensuring safety and reliability. Security and communication applications require 48V power supply protection, demanding residual voltage less than 100V, normal operation at 125°C, and open-circuit protection. Automotive fast-charging electronics require 800V-1000V-1200V-1500V, with internal power requirements ranging from 12V-24V-48V, also demanding residual voltage less than 100V, normal operation at 125°C, and fail-safe open-circuit protection. New energy photovoltaic inverters, with voltages ranging from 48V to 220V, require even lower residual voltage and higher current carrying capacity, along with fail-safe open-circuit protection, and all require CMSL (Complex Compatibility Study).

[0078] In summary, the product of this invention has a small size, saving wiring space; high surge capability, able to withstand greater surge impact; low clamping, providing better protection; good high-temperature performance, with all indicators meeting the specification design standards at an ambient temperature of 125 degrees Celsius; energy-saving and environmentally friendly, meeting the requirements for low standby power consumption such as fast charging, i.e., reducing standby power consumption from 350mW to 80mW; and safe to use in case of failure and open circuit.

[0079] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fail-safe, high-strength overvoltage protector, characterized in that, include: Switching device (1) and clamping device (2); The switching device (1) and the clamping device (2) are encapsulated as a single unit and located inside the housing (3); The housing (3) is provided with a lead wire (4) inside. One end of the lead wire (4) is connected to the combination of the switching device (1) and the clamping device (2), and the other end of the lead wire (4) is connected to the external electrode of the overvoltage protector. The breakdown voltage of the overvoltage protector is determined by the sum of the breakdown voltages of the clamping device (2) and the switching device (1), and the main voltage of the clamping voltage is characterized by the clamping voltage of the clamping device (2). When an overvoltage occurs, select the lead (4) as the surge failure break point or select the solder joint connecting the lead (4) and the overvoltage protector as the surge failure break point; The lead (4) is a metal wire, including copper wire, silver wire or gold wire; the solder joint includes solder joint and metal solder joint; the current carrying capacity of the switching device (1) and the clamping device (2) is greater than the current carrying capacity of the lead (4) or the solder joint.

2. The fail-safe, high-voltage overvoltage protector according to claim 1, characterized in that, The switching device (1) includes a solid-state discharge tube chip, and the clamping device (2) includes a metal oxide rheostat chip.

3. The fail-safe, high-voltage overvoltage protector according to claim 1, characterized in that, The clamping device (2) and the switching device (1) are connected in series.

4. The fail-safe, high-voltage overvoltage protector according to claim 1, characterized in that, The process of encapsulating the switching device (1) and the clamping device (2) into one unit includes: The switching device (1) and the clamping device (2) are combined in series.

5. A fail-safe, high-voltage overvoltage protector according to claim 1, characterized in that, The package size can be any package size defined based on the size of the internal chip, including: SMA package, SMB package, SMC package, 3025 package and 4032 package.

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