A step-down vehicle voltage surge protection circuit

Abstract

This utility model relates to a step-down vehicle voltage surge protection circuit, comprising: an input terminal for receiving power input; an output terminal for connecting an external load; a first resettable fuse, with its first end connected to the input terminal; a second resettable fuse, with its first end connected to its second end and its second end connected to the output terminal; a first transient suppression diode, with one end connected to the second end of the first resettable fuse and the first end of the second resettable fuse, and the other end grounded; and a second transient suppression diode, with one end connected to the second end of the second resettable fuse and the output terminal, and the other end grounded. This utility model achieves step-down voltage protection for downstream electronic equipment through two-stage high and low voltage clamping.

Description

Technical Field

[0001] This utility model relates to the field of automotive electronics technology, and in particular to a step-down type vehicle voltage surge protection circuit. Background Technology

[0002] Automotive systems require P5 surge protection during testing and use. P5 surge protection represents the highest level of protection against power supply transient interference in automotive electronics. In 12V systems or passenger vehicles, the maximum test voltage for P5 surge protection is generally 85V, making implementation relatively easy due to testing requirements and automotive applications. However, for 24V systems, some automakers require surge protection specifications of 174V / 350ms (174V represents the maximum test voltage requirement, and 350ms represents the maximum duration of the energy). When automotive modules require high current operation, many companies use two to three large transient voltage suppressor diodes (TVS) in parallel for input protection. However, this significantly increases costs and complicates circuit board layout. Therefore, finding a cost-effective solution that reduces circuit board space constraints is a pressing issue. Utility Model Content

[0003] To address one of the aforementioned problems in the prior art, this utility model provides a step-down vehicle voltage surge protection circuit, comprising: an input terminal for receiving power input; an output terminal for connecting an external load; a first resettable fuse, with its first end connected to the input terminal; a second resettable fuse, with its first end connected to its second end and its second end connected to the output terminal; a first transient suppression diode, with one end connected to both the second and first ends of the first and second resettable fuses, and its other end grounded; and a second transient suppression diode, with one end connected to both the second and second resettable fuses and the output terminal, and its other end grounded.

[0004] The beneficial effects of this utility model are reflected in the fact that, through the step-down vehicle voltage surge protection circuit provided by this utility model, the first self-resetting fuse, the first transient suppression diode, the second self-resetting fuse, and the second transient suppression diode form a series circuit; the first transient suppression diode, the second self-resetting fuse, and the second transient suppression diode form a parallel circuit; and the second self-resetting fuse and the second transient suppression diode form a series circuit. The surge input voltage is clamped by two stages of different high and low voltages through the first self-resetting fuse, the first transient suppression diode, the second self-resetting fuse, and the second transient suppression diode, achieving step-down voltage protection for downstream electronic equipment. Attached Figure Description

[0005] Figure 1 This invention provides a step-down vehicle voltage surge protection circuit diagram for some embodiments of the present invention.

[0006] Figure 2 Waveform diagrams of surge voltage variation provided for some embodiments of this utility model;

[0007] Figure 3 This is another step-down vehicle voltage surge protection circuit diagram provided for some embodiments of this utility model. Detailed Implementation

[0008] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0009] The step-down vehicle voltage surge protection circuit of this invention can be connected between the vehicle power supply and the vehicle electronic equipment to achieve surge protection for the vehicle electronic equipment. Figure 1 Some embodiments of the present invention are shown. (Refer to...) Figure 1 The step-down vehicle voltage surge protection circuit of this embodiment specifically includes:

[0010] The input terminal VBAT is used to receive power input; specifically, different power inputs are received through the input terminal VBAT of this circuit.

[0011] The output terminal VOUT is used to connect an external load; specifically, the output voltage at the output terminal VOUT is used to supply power to the vehicle's electrical equipment.

[0012] The first self-resetting fuse F1 has its first terminal connected to the input terminal VBAT. Specifically, the self-resetting fuse can be a polymer fuse PPTC (Polymeric Positive Temperature Coefficient), i.e., a polymer positive temperature coefficient element. Under overcurrent fault conditions, the resistance of the self-resetting fuse increases sharply, thereby protecting the downstream circuit; after the fault is cleared, the circuit can automatically return to the conducting state.

[0013] The second self-resetting fuse F2 has its first end connected to the second end of the first self-resetting fuse F1, and its second end connected to the output terminal VOUT. Specifically, the second self-resetting fuse F2 is connected in series with the first self-resetting fuse to achieve graded protection.

[0014] In some specific embodiments, the current sensitivity of the second resettable fuse F2 is higher than that of the first resettable fuse F1. Specifically, for resettable fuses, current sensitivity can be used to distinguish their level of circuit protection. Current sensitivity can be expressed as a time parameter, with the duration representing the operating time when an overcurrent occurs. The shorter the calibrated current sensitivity duration, the shorter the operating time, which means higher current sensitivity. For example, a current sensitivity of 0.1s or 0.2s indicates that the operating time of the resettable fuse in the event of an overcurrent should not exceed 0.1s or 0.2s. For instance, in this embodiment, the current sensitivity of the second resettable fuse F2 can be set to 0.1s, and the current sensitivity of the first resettable fuse F1 can be set to 0.15s. In this case, once an overcurrent occurs, the second resettable fuse F2 will operate before the first resettable fuse F1.

[0015] The first transient voltage suppressor diode, TV1, has one end connected to the second terminal of the first resettable fuse F1 and the first terminal of the second resettable fuse F2, while the other end is grounded. Specifically, a transient voltage suppressor diode (also called a TVS diode) can suppress excessively high voltages exceeding its breakdown protection voltage to protect electrical equipment from voltage spikes. Key performance parameters of a TVS diode include its breakdown protection voltage and clamping voltage. The breakdown protection voltage of a TVS diode refers to its breakdown voltage, which is the critical threshold voltage at which the TVS diode begins to function protectively. When the circuit voltage exceeds the breakdown protection voltage, the TVS diode begins to conduct significantly (entering the avalanche breakdown region). The breakdown protection voltage is usually a range rather than a fixed value. To achieve actual protection, the breakdown protection voltage should be moderately higher than the normal operating voltage of the system. The clamping voltage of a TVS diode refers to the voltage across its terminals when the TVS diode reaches its peak pulse current after protection is triggered. The clamping voltage determines the actual protection capability of the transient voltage suppressor diode. For example, for vehicle systems operating at 24V, a TVS diode with a breakdown protection voltage of 33.3V to 36.8V can be used, and its clamping voltage can be between 30V and 45V. In this case, other electronic devices (loads) connected to the output terminal can be designed with a maximum input voltage higher than 45V to ensure the voltage safety of the electronic devices.

[0016] The second transient suppression diode TV2 has one end connected to the second terminal and the output terminal VOUT of the second resettable fuse F2, and the other end grounded.

[0017] In some specific embodiments, the breakdown protection voltage of the first transient voltage suppressor diode is higher than that of the second transient voltage suppressor diode. Specifically, during continuous system operation, the voltage may continue to rise due to the continuous input of current. By setting different breakdown protection voltages for graded voltage reduction, the protection effect can be improved without affecting the normal operation of the system. For example, the breakdown protection voltage of the second transient voltage suppressor diode TV2 is 33.3V~36.8V, and the breakdown protection voltage of the first transient voltage suppressor diode TV1 is 60V~66.3V. When a high voltage is detected reaching the breakdown protection voltage of TV2, the second transient voltage suppressor diode TV2 starts working first, clamping the voltage between approximately 30V and 45V. If the voltage does not continue to rise at this time, TV2 alone can suppress the voltage. However, due to the influence of current, the voltage may continue to rise and reach the breakdown protection voltage of TV1. Then, TV1 starts working, clamping the voltage between approximately 54V and 87V. By graded voltage reduction, circuit protection can be achieved more flexibly, and the life of the devices can be extended.

[0018] Based on the above circuit, this utility model provides a specific implementation to illustrate its working principle. F2 has a current sensitivity of 0.1s, and F1 has a current sensitivity of 0.15s; the breakdown protection voltage of the second transient suppression diode TV2 is 33.3V~36.8V, and the breakdown protection voltage of the first transient suppression diode TV1 is 60V~66.3V. Its specific working principle is as follows: VBAT power input, high-voltage protection via F1 and TV1, and then a second voltage reduction protection via F2 and TV2. When an overvoltage occurs, TV2 starts working first, clamping the output voltage between 30V and 45V. Simultaneously, because F2 has higher current sensitivity than F1, F2's resistance increases rapidly due to the increased current, preventing TV2's current from continuing to rise. If the voltage continues to rise, when it exceeds TV1's breakdown voltage, TV1 breaks down, and the current increases rapidly and is conducted to ground through TV1. Since TV1's clamping voltage is between 54V and 87V, F2 and TV2 only need to withstand 87V. At this point, a large current flows through F1, causing F1 to rapidly heat up and change from a low-resistance state to a high-resistance state, reducing the current. The excess current is then borne by F1. Because both F1 and F2 are in a high-resistance state at this time, they can withstand higher voltages and resist surge voltages, thus protecting the load circuit after F2. At this point, the connection point voltage between F2 and TV2 is less than 45V. The module connected to the subsequent load only needs to be designed with a maximum input voltage higher than 45V, such as 50V or 60V.

[0019] As described above, the step-down vehicle voltage surge protection circuit provided by this utility model enables F1 to form a series circuit with TV1, F2, and TV2; TV1 to form a parallel circuit with F2 and TV2; and F2 to form a series circuit. The surge input voltage is stepped down through two levels of high and low voltage clamping of F1, TV1, F2, and TV2, thus achieving the effect of voltage protection for downstream electronic equipment.

[0020] Figure 2 The diagram shows the voltage change waveform when encountering a surge using the step-down vehicle voltage surge protection circuit described in this invention. Figure 2 As shown, this illustrates the use of, as Figure 1 The step-down vehicle voltage surge protection circuit shown is used to eliminate the surge process. Specifically, U A U represents the normal operating voltage of the system. S t represents the peak voltage of the surge pulse. r Rise time refers to the time required for the surge pulse voltage to rise from 10% to 90% of its peak value; t d This represents the total time required for the surge pulse voltage to rise from 10% of its peak value to its peak value and then fall back to 10% of its peak value. From Figure 2 The surge voltage can be observed after t dAfter a certain time, the voltage drops significantly to a safe level, demonstrating that the circuit of this invention can quickly cope with surge voltage.

[0021] In some specific embodiments, the step-down vehicle voltage surge protection circuit of this invention may further include: a filter module, one end of which is connected to the input terminal and the first terminal of the first self-resetting fuse, and the other end of which is grounded. Specifically, since excessive current at the moment of power-on may cause the self-resetting fuse to trigger falsely, the filter module can absorb the instantaneous current caused by power fluctuations, prevent false triggering of subsequent circuits, and improve circuit lifespan. In addition, the filter module can also filter out high-frequency power supply noise.

[0022] In specific examples, such as Figure 3 As shown, the filtering module may include two capacitors, C13 and C30, connected in series. Specifically, using capacitors to filter the current can reduce circuit costs.

[0023] In some specific embodiments, the step-down vehicle voltage surge protection circuit of this utility model may further include: a unidirectional conducting element connected between the input and output terminals. Specifically, the unidirectional conducting element enables unidirectional current flow. When the power supply is reversed, the reverse current may damage the resettable fuse or the electronic equipment of the load. The unidirectional conducting element can block the reverse current, preventing the resettable fuse or load from being damaged by reverse voltage, thus extending the circuit life. In addition, when the power supply is suddenly disconnected, the filter capacitor or the capacitor in the resettable fuse may also discharge in reverse, which may also cause the resettable fuse to malfunction. The unidirectional conducting element can also prevent this reverse current.

[0024] In specific examples, such as Figure 3 As shown, a diode D1 can be used as the unidirectional conducting element. Using a diode as the unidirectional conducting element can reduce circuit cost. The unidirectional conducting element can be placed between the input terminal and F1. Figure 3 (not shown), or can be set between F1 and F2 (e.g. Figure 3 As shown in the diagram, specifically, one end of the unidirectional conducting element is connected to the input terminal, and the other end of the unidirectional conducting element is connected to the first terminal of the first resettable fuse; or the second terminal of the first resettable fuse is connected to the first terminal of the second resettable fuse and the first transient suppression diode respectively through the unidirectional conducting element. Different protection effects can be achieved by setting the unidirectional conducting element in different positions.

[0025] In the description of embodiments of this utility model, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of the embodiments of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "assembly" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0027] In the description of the embodiments of this utility model, specific features, structures, materials or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0028] In the description of the embodiments of this utility model, it should be understood that "-" and "~" represent a range between two values, and this range includes the endpoints. For example, "AB" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0029] In the description of the embodiments of this utility model, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0030] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A step-down voltage surge protection circuit for a vehicle, characterized by comprising: include: The input terminal is used to receive power input; The output terminal is used for connecting external loads. A first self-resetting fuse, wherein the first end of the first self-resetting fuse is connected to the input terminal; A second resettable fuse, the first end of which is connected to the second end of the first resettable fuse, and the second end of which is connected to the output terminal; A first transient suppression diode, one end of which is connected to the second end of the first resettable fuse and the first end of the second resettable fuse, and the other end of which is grounded; The second transient suppression diode has one end connected to the second terminal of the second resettable fuse and the output terminal, and the other end grounded.

2. The step-down vehicle voltage surge protection circuit of claim 1, wherein, Also includes: A filtering module, one end of which is connected to the input terminal and the first terminal of the first self-resetting fuse, and the other end of which is grounded.

3. The step-down vehicle voltage surge protection circuit of claim 2, wherein, The filtering module includes two capacitors connected in series.

4. The step-down vehicle voltage surge protection circuit of claim 1, wherein, Also includes: A unidirectional conducting element is connected between the input terminal and the output terminal.

5. The step-down vehicle voltage surge protection circuit of claim 4, wherein, The unidirectional conducting element is a diode.

6. The step-down vehicle voltage surge protection circuit according to claim 4 or 5, characterized in that, One end of the unidirectional conducting element is connected to the input terminal, and the other end of the unidirectional conducting element is connected to the first terminal of the first self-resetting fuse.

7. The step-down vehicle voltage surge protection circuit according to claim 4 or 5, wherein The second end of the first resettable fuse is connected to the first end of the second resettable fuse and the first transient suppression diode through the unidirectional conducting element.

8. The step-down vehicle voltage surge protection circuit of claim 1, wherein, The current sensitivity of the second resettable fuse is higher than that of the first resettable fuse.

9. The step-down vehicle voltage surge protection circuit of claim 1, wherein, The breakdown protection voltage of the first transient suppression diode is higher than that of the second transient suppression diode.

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