A kind of over-temperature protection circuit of lossless voltage clamping element

Abstract

This utility model relates to the field of electronic circuit technology, specifically to an over-temperature protection circuit for a power-free voltage clamping element. It includes: a voltage clamping element; and a normally open temperature control switch, the temperature-sensing part of which is in close contact with the voltage clamping element, and its contacts are connected in parallel with the voltage clamping element. When the voltage clamping element heats up to the activation temperature of the temperature control switch due to current flow, the temperature control switch closes, and the current is shunted through the temperature control switch, causing the voltage clamping element to stop working and cool down. When the temperature drops to the reset temperature, the temperature control switch opens, and the voltage clamping element resumes operation. This utility model ensures that the voltage clamping element can normally absorb transient overvoltages by opening the temperature control switch. When continuous overvoltage or frequent surges cause the clamping element temperature to rise to the activation threshold of the temperature control switch, the current is shunted through the temperature control switch, and the clamping element stops working and cools down due to the reduced current. When the temperature drops to the reset threshold, the temperature control switch opens, and the clamping element resumes operation, forming a cyclic protection.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, specifically to an over-temperature protection circuit for a power-free voltage clamping element. Background Technology

[0002] Voltage clamping components (such as TVS diodes, varistors, and Zener diodes) are widely used in overvoltage protection circuits of electronic equipment to absorb surge voltages, suppress transient overvoltages, and prevent damage to subsequent circuits. However, when a circuit is subjected to continuous overvoltage or frequent surges, voltage clamping components may overheat due to prolonged exposure to high energy, leading to performance degradation or even permanent damage.

[0003] Currently, common protection methods include:

[0004] Passive cooling: This method improves heat dissipation by increasing the area of ​​the heat sink or optimizing the PCB layout, but it cannot fundamentally solve the problem of temperature rise under high current.

[0005] Fuse protection: A fuse is connected in series with the voltage clamping element. When there is an overcurrent, it blows to cut off the circuit. However, it needs to be replaced manually after it blows and cannot be automatically restored.

[0006] PTC resettable fuses can limit overcurrent, but their response speed is slow and changes in resistance may affect the normal operation of the circuit.

[0007] Therefore, all of the above methods have problems such as unintelligent protection, inability to automatically recover, or impact on system stability. Utility Model Content

[0008] This invention provides a zero-power-consumption voltage clamping element over-temperature protection circuit. By opening the temperature control switch, the voltage clamping element is ensured to normally absorb transient overvoltages. When continuous overvoltage or frequent surges cause the clamping element temperature to rise to the temperature control switch's activation threshold, current is diverted through the temperature control switch, and the clamping element stops working and cools down due to the reduced current. When the temperature drops to the reset threshold, the temperature control switch opens, and the clamping element resumes operation, forming a cyclic protection.

[0009] To achieve the above objectives, this utility model provides the following technical solution:

[0010] A zero-power voltage clamping element over-temperature protection circuit includes: a voltage clamping element connected to the input terminal of a transformer; a normally open temperature control switch, the temperature sensing part of which is in close contact with the voltage clamping element, and its contacts are connected in parallel with the voltage clamping element; when the voltage clamping element heats up to the start-up temperature of the temperature control switch due to current flow, the temperature control switch closes, the current is shunted through the temperature control switch, causing the voltage clamping element to stop working and cool down; when the temperature drops to the reset temperature, the temperature control switch opens, and the voltage clamping element resumes operation.

[0011] A zero-power voltage clamping element over-temperature protection circuit includes: a voltage clamping element connected to the output terminal of a transformer; a normally open temperature control switch, the temperature sensing part of which is in close contact with the voltage clamping element, and its contacts are connected in parallel with the output terminal of the transformer; when the voltage clamping element heats up due to current flow to the start temperature of the temperature control switch, the temperature control switch closes, short-circuiting the output terminal of the transformer, increasing the input current of the transformer, and simultaneously reducing the current of the voltage clamping element and cooling down; when the temperature drops to the reset temperature, the temperature control switch opens, and the voltage clamping element resumes operation.

[0012] Preferably, the voltage clamping element is a TVS diode or a varistor.

[0013] Preferably, the temperature control switch is a bimetallic strip temperature control switch.

[0014] Preferably, a fuse or a PTC resettable fuse is connected in series at the input terminal of the transformer.

[0015] Preferably, the start threshold of the temperature control switch is set to the upper limit of the safe operating temperature of the voltage clamping element, and the reset threshold is set to be 5~70°C lower than the start threshold.

[0016] Preferably, the contacts of the temperature control switch are made of silver alloy or arc-resistant material.

[0017] Preferably, thermally conductive silicone grease or a metal thermal pad is applied between the voltage clamping element and the temperature control switch.

[0018] Preferably, it also includes a resettable thermal fuse thermally coupled to a voltage clamping element for cutting off the circuit when the temperature control switch fails.

[0019] The advantages of this invention are as follows: In this circuit design, the temperature control switch only conducts when the temperature is too high, consuming no power under normal conditions and not affecting circuit efficiency. The bimetallic strip temperature control switch automatically switches on and off based on the temperature threshold, requiring no manual intervention and eliminating the need for fuse replacement. Furthermore, the bimetallic strip has a faster response speed than a PTC and is directly thermally coupled to the clamping element, providing sensitive temperature feedback. The silver alloy contacts are arc-resistant, suitable for frequent switching scenarios. Working in conjunction with a front-end fuse / PTC: input protection reduces the load on the clamping element through current shunting, while output protection triggers the front-end protection device through a short circuit, forming dual protection. Additionally, a resettable thermal fuse can be optionally added as redundant protection in case of temperature control switch failure. Therefore, this circuit design is suitable for various clamping elements such as TVS and varistors, and can be extended to AC / DC power supplies, communication equipment, and other scenarios. Attached Figure Description

[0020] 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 only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the over-temperature protection circuit for the power-free voltage clamping element of this utility model;

[0022] Figure 2 This is a schematic diagram of the over-temperature protection circuit for the power-free voltage clamping element of this utility model.

[0023] In the diagram: 1. Transformer; 2. Voltage clamping element; 3. Temperature control switch. Detailed Implementation

[0024] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and 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.

[0025] according to Figure 1 As shown, a zero-power voltage clamping element over-temperature protection circuit includes: a voltage clamping element 2 connected to the input terminal of a transformer 1, with a fuse or a PTC resettable fuse connected in series at the input terminal of the transformer 1; a normally open temperature control switch 3, the temperature sensing part of which is in close contact with the voltage clamping element 2, and its contacts connected in parallel with the voltage clamping element 2; when the voltage clamping element 2 heats up due to current flow to the start-up temperature of the temperature control switch 3, the temperature control switch 3 closes, the current is shunted through the temperature control switch 3, causing the voltage clamping element 2 to stop working and cool down; when the temperature drops to the reset temperature, the temperature control switch 3 opens, and the voltage clamping element 2 resumes operation.

[0026] This circuit design ensures that the voltage clamping element 2, such as a TVS or varistor, can properly absorb transient overvoltages by opening the temperature control switch 3. When continuous overvoltage or frequent surges cause the clamping element temperature to rise to the activation threshold of the temperature control switch 3, such as 85°C, the bimetallic strip of the temperature control switch 3 closes due to heat, and the current is shunted through the temperature control switch 3. The clamping element stops working and cools down due to the reduced current. When the temperature drops to the reset threshold, such as 70°C, the temperature control switch 3 opens, and the clamping element resumes operation, forming a cyclic protection.

[0027] according to Figure 2As shown, a zero-power voltage clamping element over-temperature protection circuit includes: a voltage clamping element 2 connected to the output terminal of a transformer 1; a normally open temperature control switch 3, the temperature sensing part of which is in close contact with the voltage clamping element 2, and its contacts are connected in parallel with the output terminal of the transformer 1; when the voltage clamping element 2 heats up due to current flow to the start-up temperature of the temperature control switch 3, the temperature control switch 3 closes, short-circuiting the output terminal of the transformer 1, increasing the input current of the transformer 1, and simultaneously reducing the current of the voltage clamping element 2 and cooling down; when the temperature drops to the reset temperature, the temperature control switch 3 opens, and the voltage clamping element 2 resumes operation.

[0028] This circuit design allows the clamping element to operate normally by opening the temperature control switch 3. When the temperature is too high, the temperature control switch 3 closes, short-circuiting the output terminal of transformer 1, causing a surge in input current, triggering the front-end fuse to cut off the circuit, and simultaneously cooling the clamping element due to the reduced current. When the temperature drops, the temperature control switch 3 opens, and the circuit returns to normal.

[0029] The activation threshold of the temperature control switch 3 is set to the upper limit of the safe operating temperature of the voltage clamping element 2, and the reset threshold is set to be 5~70°C lower than the activation threshold. Furthermore, the contacts of the temperature control switch 3 are made of silver alloy or arc-resistant material. Additionally, thermally conductive silicone grease or a metal heat-conducting sheet is applied between the voltage clamping element 2 and the temperature control switch 3. A resettable thermal fuse is further included, thermally coupled to the voltage clamping element 2, to cut off the circuit in the event of a failure of the temperature control switch 3.

[0030] In the above circuit design, the temperature control switch 3 only conducts when the temperature exceeds the limit, consuming no power under normal conditions and not affecting circuit efficiency. The bimetallic strip temperature control switch 3 automatically switches on and off based on the temperature threshold, eliminating the need for manual intervention and resolving the issue of fuse replacement. Furthermore, the bimetallic strip has a faster response speed than a PTC and is directly thermally coupled to the voltage clamping element 2, providing sensitive temperature feedback. The silver alloy contacts are arc-resistant, making them suitable for frequent switching scenarios. Working in conjunction with the front-end fuse / PTC: input protection reduces the load on the clamping element through current shunting, while output protection triggers the front-end protection device through short-circuit triggering, forming dual protection. Additionally, a resettable thermal fuse can be optionally added as redundant protection in case of temperature control switch 3 failure. Therefore, this circuit design is suitable for various clamping elements such as TVS and varistors, and can be extended to AC / DC power supplies, communication equipment, and other scenarios.

[0031] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A power-free voltage clamping element over-temperature protection circuit, characterized in that, include: A voltage clamping element (2) is connected to the input terminal of the transformer (1); The normally open temperature control switch (3) has its temperature sensing part in close contact with the voltage clamping element (2), and its contacts are connected in parallel with the voltage clamping element (2); When the voltage clamping element (2) heats up to the start temperature of the temperature control switch (3) due to the current flowing through it, the temperature control switch (3) closes, and the current is shunted through the temperature control switch (3), causing the voltage clamping element (2) to stop working and cool down; when the temperature drops to the reset temperature, the temperature control switch (3) opens, and the voltage clamping element (2) resumes working.

2. The over-temperature protection circuit for the zero-power voltage clamping element according to claim 1, characterized in that: A fuse or a PTC resettable fuse is connected in series at the input terminal of the transformer (1).

3. A power-free voltage clamping element over-temperature protection circuit, characterized in that, include: A voltage clamping element (2) is connected to the output terminal of the transformer (1); The normally open temperature control switch (3) has its temperature sensing part in close contact with the voltage clamping element (2), and its contacts are connected in parallel with the output terminal of the transformer (1); When the voltage clamping element (2) heats up to the starting temperature of the temperature control switch (3) due to the current flowing through it, the temperature control switch (3) closes, causing a short circuit at the output terminal of the transformer (1), increasing the input current of the transformer (1), and at the same time, the current of the voltage clamping element (2) decreases and the temperature drops; when the temperature drops to the reset temperature, the temperature control switch (3) opens, and the voltage clamping element (2) resumes operation.

4. The over-temperature protection circuit for a power-free voltage clamping element according to claim 1 or 3, characterized in that: The voltage clamping element (2) is a TVS diode or a varistor.

5. The over-temperature protection circuit for a power-free voltage clamping element according to claim 1 or 3, characterized in that: The temperature control switch (3) is a bimetallic strip temperature control switch (3).

6. The over-temperature protection circuit for a power-free voltage clamping element according to claim 1 or 3, characterized in that: The start threshold of the temperature control switch (3) is set to the upper limit of the safe working temperature of the voltage clamping element (2), and the reset threshold is set to be 5~70℃ lower than the start threshold.

7. The over-temperature protection circuit for a power-free voltage clamping element according to claim 1 or 3, characterized in that: The contacts of the temperature control switch (3) are made of silver alloy or arc-resistant material.

8. The over-temperature protection circuit for a power-free voltage clamping element according to claim 1 or 3, characterized in that: The voltage clamping element (2) and the temperature control switch (3) are coated with thermal grease or a metal thermal sheet is used.

9. The over-temperature protection circuit for a power-free voltage clamping element according to claim 1 or 3, characterized in that: It further includes a resettable temperature fuse thermally coupled to a voltage clamping element (2) for cutting off the circuit in the event of failure of the temperature control switch (3).

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