A protection circuit and testing device

Abstract

This application discloses a protection circuit and a testing device. The protection circuit provided includes a voltage divider module, a comparator module, and a circuit breaker execution module. The voltage divider module includes a thermistor whose resistance changes with the temperature inside the resistance box, thus affecting the voltage transmitted from the voltage divider module to the comparator module. When the resistance box overheats, the voltage output from the voltage divider module to the comparator module increases, causing the comparator module to output a signal to the circuit breaker execution module. This causes the circuit breaker execution module to disconnect the connection between the resistance box and the test element, improving the safety of the testing device. The testing device can promptly disconnect the connection between the resistance box and the test element, improving the response efficiency to abnormal situations. The overall design effectively solves the problems of reliance on manual response and insufficient disconnection reliability in traditional solutions, making it particularly suitable for equipment safety protection in unattended scenarios and improving the practicality of the protection circuit.

Description

Technical Field

[0001] This application relates to the field of protection circuit technology, and in particular to a protection circuit and testing device. Background Technology

[0002] In the field of electronic product testing, especially when testing with high-power resistors as loads, existing technologies often employ negative temperature coefficient thermistors for overheat monitoring. Specifically, when the equipment power is too high, or the cooling fan stalls or fails, causing the resistor temperature to rise, the thermistor resistance decreases, triggering an indicator light and a buzzer alarm to alert operators of an overheating risk. However, this existing solution has significant shortcomings: First, its application scenarios are highly limited. The alarm mechanism relies entirely on human presence and cannot be applied to unattended operating conditions (such as automated nighttime testing), resulting in monitoring gaps. Second, the overall safety performance is low. If there is no immediate intervention when overheating occurs, the resistor's continued heating may cause it to burn out, and if flammable materials are present nearby, it could even cause a fire. Utility Model Content

[0003] To solve the above-mentioned technical problems, this application provides a protection circuit applied in a testing device. The protection circuit is connected to a resistance box and a test element in the testing device, and is used to disconnect the connection between the resistance box and the test element when the temperature inside the resistance box exceeds the limit.

[0004] The protection circuit includes a power supply, a voltage divider module, a reference module, a comparator module, and a circuit breaker execution module. The first terminal of the voltage divider module is connected to the first output terminal of the power supply, and the second terminal of the voltage divider module is connected to the voltage divider input terminal of the comparator module. The first terminal of the reference module is connected to the first output terminal of the power supply, and the second terminal of the reference module is connected to the reference input terminal of the comparator module. The power input terminal of the comparator module is connected to the first output terminal of the power supply, and the output terminal of the comparator module is connected to the circuit breaker execution module. The ground terminal of the comparator module is grounded. One terminal of the circuit breaker execution module is connected to the second output terminal of the power supply and is connected in series in the connection circuit between the resistance box and the test element.

[0005] The voltage divider module includes a thermistor, which is located in the resistor box.

[0006] The protection circuit further includes a silicon controlled rectifier (SCR), the anode of which is connected to the first output terminal of the power supply, the cathode of which is connected to the circuit breaker module, and the control electrode of which is connected to the output terminal of the comparator module.

[0007] The circuit breaking execution module includes a normally closed contactor, the first end of the winding of the normally closed contactor is connected to the cathode of the silicon controlled rectifier, and the second end of the winding is connected to the second output terminal of the power supply; the first end of the switch contact of the normally closed contactor is connected to the resistor box, and the second end of the switch contact is connected to the test element.

[0008] The protection circuit further includes a first resistor and a transistor. The first end of the first resistor is connected to the cathode of the silicon controlled rectifier, the second end of the first resistor is connected to the first end of the transistor, the second end of the transistor is connected to the first end of the winding, and the third end of the transistor is grounded.

[0009] The protection circuit further includes a switch module, a second resistor, and a third resistor. The first end of the switch module is connected to the first output end of the power supply. The second end of the switch module is connected to the anode of the silicon controlled rectifier through the second resistor. The first end of the third resistor is connected to the cathode of the silicon controlled rectifier, and the second end of the third resistor is grounded.

[0010] The voltage divider module includes a fourth resistor, a first capacitor, and a second capacitor. The first end of the thermistor is connected to the first output terminal of the power supply, and the second end of the thermistor is grounded through the fourth resistor. The first capacitor and the second capacitor are connected in parallel with the fourth resistor, and the second end of the thermistor is connected to the voltage divider input terminal of the comparator module.

[0011] The reference module includes a fifth resistor, a sixth resistor, a third capacitor, and a fourth capacitor. The first end of the fifth resistor is connected to the first output terminal of the power supply, and the second end of the fifth resistor is grounded through the sixth resistor. The third capacitor and the fourth capacitor are connected in parallel with the sixth resistor, and the second end of the fifth resistor is connected to the reference input terminal of the comparison module.

[0012] The protection circuit further includes a seventh resistor and a first diode. The first end of the seventh resistor is connected to the second end of the winding, the second end of the seventh resistor is connected to the cathode of the first diode, and the anode of the first diode is connected to the first end of the winding.

[0013] The protection circuit includes a second diode and a third diode. The anode of the second diode is connected to the output terminal of the comparator module, and the cathode of the second diode is connected to the control electrode of the thyristor rectifier. The anode of the third diode is connected to the output terminal of the comparator module, and the cathode of the third diode is connected to the control electrode of the thyristor rectifier.

[0014] The protection circuit further includes an alarm module and an eighth resistor. The first end of the alarm module is connected to the second output end of the power supply through the eighth resistor, and the second end of the alarm module is connected to the second end of the winding.

[0015] To address the aforementioned technical problems, this application also provides a testing device, including a resistance box, a testing element, and a protection circuit as described above. One end of the protection circuit is connected to the resistance box, and the other end of the protection circuit is connected to the testing element. The protection circuit is used to disconnect the connection between the resistance box and the testing element when the temperature inside the resistance box exceeds the limit.

[0016] The beneficial effects of this application are as follows: Unlike existing technologies, the protection circuit provided in this application is applied in a testing device. The protection circuit is connected to both the resistance box and the test element in the testing device, and is used to disconnect the connection between the resistance box and the test element when the resistance box overheats. The protection circuit includes a power supply, a voltage divider module, a reference module, a comparator module, and a circuit breaker execution module. The first terminal of the voltage divider module is connected to the first output terminal of the power supply, and the second terminal of the voltage divider module is connected to the voltage divider input terminal of the comparator module. The first terminal of the reference module is connected to the first output terminal of the power supply, the second terminal of the reference module is connected to the reference input terminal of the comparator module, the power input terminal of the comparator module is connected to the first output terminal of the power supply, the output terminal of the comparator module is connected to the circuit breaker execution module, and one terminal of the circuit breaker execution module is connected to the second output terminal of the power supply and is connected in series in the connection circuit between the resistance box and the test element. The voltage divider module includes a thermistor located inside the resistance box.

[0017] In this application, the resistance value of the thermistor changes with the temperature inside the resistance box, which in turn affects the voltage transmitted from the voltage divider module to the comparator module. When the resistance box overheats, the voltage output from the voltage divider module to the comparator module increases, causing the comparator module to output a signal to the circuit breaker module. This causes the circuit breaker module to disconnect the connection circuit between the resistance box and the test element, improving the safety of the test device. The test device can promptly disconnect the connection between the resistance box and the test element, improving the response efficiency of abnormal situations in the test device. The overall design effectively solves the problems of reliance on manual response and insufficient disconnection reliability in traditional solutions. It is particularly suitable for equipment safety protection in unattended scenarios, improving the practicality of the protection circuit. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] in:

[0020] Figure 1 This is a schematic diagram of the structure of an embodiment of the testing device of this application;

[0021] Figure 2 This is a schematic diagram of another embodiment of the testing device of this application.

[0022] Reference numerals in the attached diagram: A. Test device; 1. Protection circuit; 11. Power supply; 12. Voltage divider module; 13. Reference module; 14. Comparison module; 15. Circuit breaker module; 16. Alarm module; 2. Resistance box; 3. Test element. Detailed Implementation

[0023] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0024] In the following description, specific details such as particular system architectures, interfaces, and technologies are presented for illustrative purposes rather than for limiting purposes, in order to provide a thorough understanding of this application.

[0025] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] In this application, 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 three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " generally indicates that the preceding and following related objects are in an "or" relationship. Furthermore, "many" in this application means two or more. Moreover, the term "at least one" in this application means any combination of at least two of any one or more of a plurality of objects. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C. Furthermore, the terms "first," "second," and "third" in this application 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.

[0027] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an embodiment of the testing device of this application. To address the aforementioned technical problems, this application mainly proposes a protection circuit 1, applied in the testing device A, such as... Figure 1As shown, the protection circuit 1 is connected to the resistance box 2 and the test element 3 in the test device A, respectively, and is used to disconnect the connection between the resistance box 2 and the test element 3 when the resistance box 2 overheats.

[0028] The protection circuit 1 includes a power supply 11, a voltage divider module 12, a reference module 13, a comparator module 14, and a circuit breaker execution module 15. The first end of the voltage divider module 12 is connected to the first output terminal of the power supply 11, and the second end of the voltage divider module 12 is connected to the voltage divider input terminal of the comparator module 14. The first end of the reference module 13 is connected to the first output terminal of the power supply 11, and the second end of the reference module 13 is connected to the reference input terminal of the comparator module 14. The power supply input terminal of the comparator module 14 is connected to the first output terminal of the power supply 11, and the output terminal of the comparator module 14 is connected to the circuit breaker execution module 15. The ground terminal of the comparator module 14 is grounded. One end of the circuit breaker execution module 15 is connected to the second output terminal of the power supply 11 and is connected in series in the connection circuit between the resistor box 2 and the test element 3. The first and second output terminals of the power supply 11 output different voltage values; for example, the first output terminal of the power supply 11 can output 5V, while the second output terminal outputs 24V to meet the power requirements of different modules.

[0029] The voltage divider module 12 includes a thermistor, which is located in the resistor box 2.

[0030] Specifically, the reference module 13 can first provide a reference voltage to the comparison module 14. The thermistor can be a negative temperature coefficient thermistor, that is, the resistance of the thermistor decreases when the temperature in the resistance box 2 rises. Consequently, when the temperature in the resistance box 2 rises, because the resistance of the thermistor decreases, the voltage drop across the thermistor is less, and the voltage output by the voltage divider module 12 to the comparison module 14 increases. When the voltage output by the voltage divider module 12 to the comparison module 14 is greater than the reference voltage, the comparison module 14 can output a level signal, such as a high-level signal, to the circuit breaker execution module 15, causing the circuit breaker execution module 15 to disconnect the connection circuit between the resistance box 2 and the test element 3. This realizes timely disconnection of the connection between the resistance box 2 and the test element 3 when the internal temperature of the resistance box 2 exceeds the reference voltage, which is suitable for unattended operation conditions, improves the overall safety performance of the test device A, and enhances the practicality of the protection circuit 1.

[0031] In another embodiment, if the temperature in the resistance box 2 is within the normal range, the voltage output by the voltage divider module 12 to the comparison module 14 is less than the reference voltage output by the reference module 13 to the comparison module 14. Then, the comparison module 14 will output a low-level signal to the circuit breaker execution module 15. The circuit breaker execution module 15 maintains the connection between the resistance box 2 and the test element 3, and the test device A continues to operate.

[0032] In other embodiments, the thermistor can also be a positive temperature coefficient thermistor. When the temperature rises in the resistance box 2, the resistance of the thermistor increases, and the voltage output from the voltage divider module 12 to the comparator module 14 decreases. When the voltage output from the voltage divider module 12 to the comparator module 14 is less than the reference voltage, the comparator module 14 can output a high-level signal to the execution module, causing the circuit breaker execution module 15 to disconnect the connection circuit between the resistance box 2 and the test element 3. This ensures that the connection circuit between the resistance box 2 and the test element 3 is disconnected promptly when the resistance box 2 overheats, improving the practicality of the protection circuit 1.

[0033] Alternatively, please continue reading Figure 2 , Figure 2 This is a schematic diagram of another embodiment of the testing device of this application. The protection circuit 1 includes a silicon controlled rectifier Q1. In one embodiment, the silicon controlled rectifier Q1 is specifically a unidirectional silicon controlled rectifier.

[0034] In this configuration, the anode of the thyristor rectifier Q1 is connected to the first output terminal of the power supply 11, the cathode of the thyristor rectifier Q1 is connected to the circuit breaker module 15, and the control electrode of the thyristor rectifier Q1 is connected to the output terminal of the comparator module 14. The comparator module 14 may include a comparator U.

[0035] Specifically, when the voltage provided by the voltage divider module 12 to the comparator module 14 is greater than the reference voltage provided by the reference module 13 to the comparator module 14, the comparator module 14 can output a high-level signal to the control electrode of the thyristor rectifier Q1, thereby turning on the thyristor rectifier Q1. The thyristor rectifier Q1 outputs a voltage to the circuit breaking execution module 15, causing the circuit breaking execution module 15 to disconnect the connection circuit between the resistor box 2 and the test element 3.

[0036] Furthermore, based on the characteristics of the thyristor rectifier Q1, after the comparator module 14 outputs a high-level signal to the control electrode of the thyristor rectifier Q1 to turn it on, when the comparator module 14 outputs a low-level signal to the thyristor rectifier Q1 (resistance box 2 is disconnected from test element 3, resistance box 2 stops operating, the internal temperature of resistance box 2 decreases, the resistance of the thermistor increases, and the voltage output by voltage divider module 12 is less than the reference voltage), the thyristor rectifier Q1 can still maintain the conducting state. That is, the resistance box 2 and test element 3 are still disconnected until the connection between the thyristor rectifier Q1 and power supply 11 is disconnected, and the thyristor rectifier Q1 returns to the cut-off state.

[0037] By configuring the thyristor rectifier Q1, the circuit remains open even after the resistor box 2 and test element 3 are disconnected, providing better protection for both. The characteristics of the thyristor rectifier Q1 ensure continuous over-temperature protection. When an over-temperature signal (high-level signal) is detected, the thyristor rectifier Q1 remains in the conducting state until the power supply 11 is disconnected, ensuring that the circuit-breaking execution module 15 continuously disconnects the connection circuit between the resistor box 2 and the test element 3. This design avoids the shortcomings of traditional methods that rely on a continuous electrical signal to maintain the circuit-breaking state, ensuring safe disconnection even after the signal disappears or the system is powered off. Furthermore, the coordination of the voltage divider module 12, the reference module 13, and the comparator module 14 allows for precise control of the triggering timing of the thyristor rectifier Q1, improving the response speed and stability of the over-temperature protection and enhancing the practicality of the protection circuit 1.

[0038] Optionally, the circuit breaking execution module 15 includes a normally closed contactor. The first end of the winding S1 of the normally closed contactor is connected to the cathode of the thyristor rectifier Q1, the second end of the winding S1 is connected to the second output terminal of the power supply 11, the first end of the switch contact (not shown) of the normally closed contactor is connected to the resistor box 2, and the second end of the switch contact is connected to the test element 3.

[0039] Specifically, when the thyristor rectifier Q1 is in the cut-off state (at this time, the internal temperature of the resistor box 2 is within the normal range, the voltage output by the voltage divider module 12 is less than the reference voltage, and the comparator module 14 outputs a low-level signal), the second end circuit of the winding S1 is in the open circuit state, that is, there is no voltage in the winding S1. At this time, the switch contact is in the normally closed state, that is, the resistor box 2 and the test element 3 are in the connected state.

[0040] When the thyristor rectifier Q1 is in the conducting state (at this time, the resistor box 2 is overheated, the voltage output by the voltage divider module 12 is greater than the reference voltage, and the comparator module 14 outputs a high-level signal), the second end of the winding S1 is grounded, and the voltage output by the second output terminal of the power supply 11 can pass through the winding S1. When there is voltage in the winding S1, the switch contacts will open, that is, the resistor box 2 is disconnected from the test element 3. This realizes the automatic disconnection of the connection circuit between the resistor box 2 and the test element 3 when the resistor box 2 is overheated, thus improving the practicality of the protection circuit 1.

[0041] In this embodiment, by connecting the winding S1 of the normally closed contactor to the cathode of the thyristor rectifier Q1, the circuit remains open after the over-temperature protection trips, preventing accidental connection due to power supply fluctuations 11. The physical isolation formed after the switch contacts open effectively prevents the resistor box 2 from continuously heating up and causing a fire risk, making it more suitable for unattended scenarios than a simple audible and visual alarm. The second output terminal of the power supply 11 provides an independent power supply path for the winding S1 of the normally closed contactor, ensuring that the circuit remains open even after the connection between the resistor box 2 and the test element 3 is broken. This dual power supply design improves system reliability and enhances the practicality of the protection circuit 1.

[0042] Optionally, the protection circuit 1 further includes a first resistor R1 and a transistor Q2. The first end of the first resistor R1 is connected to the cathode of the silicon controlled rectifier Q1, the second end of the first resistor R1 is connected to the first end of the transistor Q2, the second end of the transistor Q2 is connected to the first end of the winding S1, and the third end of the transistor Q2 is grounded.

[0043] Specifically, when the thyristor rectifier Q1 is in the on state, part of the voltage output from the cathode of the thyristor rectifier Q1 will be input to the first terminal of the transistor Q2 through the first resistor R1. The first resistor R1 acts as a voltage divider to prevent the transistor Q2 from being damaged by excessive voltage.

[0044] After receiving the voltage, transistor Q2 switches from the cut-off state to the conduction state. At this time, it can be assumed that the first end of winding S1 is grounded, so there is a voltage in winding S1, the switch contact is opened, and the connection circuit between resistor box 2 and test element 3 is broken.

[0045] When the thyristor rectifier Q1 is in the cut-off state, the first terminal of transistor Q2 does not receive voltage, so transistor Q2 is in the cut-off state. At this time, the first terminal of winding S1 is in the open circuit state, the switch contact is closed, and the resistance box 2 is connected to the test element 3.

[0046] In this embodiment, by combining the first resistor R1 with the transistor Q2, the protection circuit 1 can maintain the conduction state of the silicon controlled rectifier Q1 after over-temperature triggering, ensuring that the switch contacts of the normally closed contactor remain open, thereby isolating the resistor box 2 from the test element 3 and improving the practicality of the protection circuit 1.

[0047] Optionally, the protection circuit 1 also includes a switch module K, a second resistor R2, and a third resistor R3.

[0048] The first terminal of the switch module K is connected to the first output terminal of the power supply 11. The second terminal of the switch module is connected to the anode of the thyristor rectifier Q1 through the second resistor R2. The first terminal of the third resistor R3 is connected to the cathode of the thyristor rectifier Q1, and the second terminal of the third resistor R3 is grounded.

[0049] Among them, the second resistor R2 and the third resistor R3 serve as voltage dividers to ensure the stability of the voltage in the circuit. The switch module K can control the connection state between the thyristor rectifier Q1 and the power supply 11. When the thyristor rectifier Q1 is in the conducting state, the switch module K can be controlled to disconnect the connection between the thyristor rectifier Q1 and the power supply 11, thereby switching the thyristor rectifier Q1 from the conducting state to the cut-off state, and reconnecting the resistor box 2 and the test element 3.

[0050] This embodiment switches the state of the thyristor rectifier Q1 by setting the switch module K, which meets the requirements of unattended operation and improves the practicality of the protection circuit 1.

[0051] Optionally, the voltage divider module 12 includes a fourth resistor R4, a first capacitor C1 and a second capacitor C2, a first terminal of a thermistor RT connected to the first output terminal of the power supply 11, a second terminal of the thermistor RT grounded through the fourth resistor R4, a first capacitor C1 and a second capacitor C2 connected in parallel with the fourth resistor R4, and a second terminal of the thermistor RT connected to the voltage divider input terminal of the comparator module 14.

[0052] In this configuration, the voltage output by the voltage divider module 12 to the comparator module 14 is actually equal to the voltage across the fourth resistor R4. When the temperature inside the resistor box 2 increases, the resistance of the thermistor RT decreases, and the voltage across the thermistor RT decreases. At this time, the voltage across the fourth resistor R4 increases, which means that the voltage output by the voltage divider module 12 to the comparator module 14 increases. The first capacitor C1 and the second capacitor C2 play a role in voltage stabilization and filtering. The capacitance value of the first capacitor C1 can be 100nF, and the capacitance value of the second capacitor C2 can be 10pF. In other embodiments, the capacitance values ​​of the first capacitor C1 and the second capacitor C2 can also be other specific values.

[0053] Optionally, the reference module 13 includes a fifth resistor R5, a sixth resistor R6, a third capacitor C3, and a fourth capacitor C4. The first end of the fifth resistor R5 is connected to the first output terminal of the power supply 11, the second end of the fifth resistor R5 is grounded through the sixth resistor, the third capacitor C3 and the fourth capacitor C4 are connected in parallel with the sixth resistor R6, and the second end of the fifth resistor R5 is connected to the reference input terminal of the comparison module 14.

[0054] The voltage output by the reference module 13 to the comparison module 14 is actually equal to the voltage across the sixth resistor R6. Since both the fifth resistor R5 and the sixth resistor R6 are fixed resistors, the voltage across the sixth resistor R6 is constant. Therefore, it can be used as a reference voltage to compare with the voltage output by the voltage divider module 12 to determine the internal temperature of the resistor box 2.

[0055] In this configuration, the third capacitor C3 and the fourth capacitor C4 serve as voltage regulators and filters. In one embodiment, the capacitance of the third capacitor C3 can be 100nF, and the capacitance of the fourth capacitor C4 can be 10pF. In other embodiments, the capacitance values ​​of the third capacitor C3 and the fourth capacitor C4 can be other specific values. That is, the capacitance value of the third capacitor C3 can be equal to the capacitance value of the first capacitor C1, and the capacitance value of the fourth capacitor C4 can be equal to the capacitance value of the second capacitor C2, to ensure the consistency of the circuit components in the voltage divider module 12 and the reference module 13, thereby improving the accuracy of the comparison module 14's judgment.

[0056] In this embodiment, the voltage division relationship between the resistors in the voltage divider module 12 and the reference module 13 can promptly reflect the internal temperature of the resistor box 2. Furthermore, the parallel capacitor design can effectively filter out noise interference from the power supply 11, keeping the voltage division signal of the fourth resistor R4 and the reference voltage stable and avoiding false triggering caused by voltage fluctuations. This design makes the over-temperature protection more reliable and stable, improving the practicality of the protection circuit 1.

[0057] In one embodiment, please refer to Figure 2 The protection circuit 1 may include two voltage divider modules 12 connected in parallel. The thermistors RT of each voltage divider module 12 can be positioned on opposite sides of the resistance box 2, enabling multi-point monitoring of the resistance box 2. This solves the problem of low response efficiency of thermistors RT to the temperature of resistors far away in traditional technologies, improving the response efficiency of the protection circuit 1 to the temperature of the resistance box 2 and enhancing its practicality. In other embodiments, the protection circuit 1 may also include more than two voltage divider modules 12. The thermistors in different voltage divider modules 12 can be positioned at different locations inside the resistance box 2 to perform multi-point temperature monitoring of the resistance box 2, improving the reliability and safety of the testing device A.

[0058] Specifically, the two voltage divider modules 12 can be defined as a first voltage divider module 12 and a second voltage divider module 12. The second terminal of the thermistor RT in the first voltage divider module 12 is connected to the first voltage divider input terminal of the comparator module 14, and the second terminal of the thermistor RT in the second voltage divider module 12 is connected to the second voltage divider input terminal of the comparator module 14. Furthermore, when the voltage output from the first voltage divider module 12 to the comparator module 14 is greater than the reference voltage, the comparator module 14 can output a high-level signal to the control electrode of the thyristor rectifier Q1 through its first output terminal. Conversely, when the voltage output from the second voltage divider module 12 to the comparator module 14 is greater than the reference voltage, the comparator module 14 can output a high-level signal to the thyristor rectifier Q1 through its second output terminal to indicate that the internal temperature of the resistance box 2 is too high, thus disconnecting the resistance box 2 from the test element 3.

[0059] In this embodiment, multiple voltage divider modules 12 are set, with thermistors in each module 12 located at different positions within the resistance box 2, enabling multi-point monitoring of the internal temperature of the resistance box 2. This multi-point monitoring mechanism improves the overall accuracy of the protection and ensures that even if some thermistors fail, other detection points can still trigger the protection mechanism, significantly improving the reliability of over-temperature protection and enhancing the practicality of the protection circuit 1.

[0060] Optionally, the protection circuit 1 further includes a first diode D1 and a seventh resistor R7. The first end of the seventh resistor R7 is connected to the second end of the winding S1, the second end of the seventh resistor R7 is connected to the cathode of the first diode D1, and the anode of the first diode D1 is connected to the first end of the winding S1.

[0061] Specifically, when the switch contacts of the normally closed contactor are closed, that is, when the first end of the winding S1 is open, the current output from the second output terminal of the power supply 11 will pass through the seventh resistor R7 and the first diode D1. The seventh resistor R7 and the first diode D1 are used to release the electrical energy on the winding S1, so that the switch contacts of the normally closed contactor will quickly close.

[0062] When the switch contacts of the normally closed contactor are open, that is, when the first end of the winding S1 is grounded, the current will not pass through the seventh resistor R7, but through the winding S1, due to the connection direction of the first diode D1.

[0063] In this embodiment, the seventh resistor R7 and the first diode D1 serve to regulate voltage and protect polarity in the circuit, ensuring that the current flows along a preset path under specific operating conditions. When the voltage across winding S1 changes, the circuit maintains a stable operating state through the voltage division of the resistor and the unidirectional conduction characteristic of the diode, thus improving the safety of protection circuit 1.

[0064] Optionally, the protection circuit 1 also includes a second diode D2 and a third diode D3.

[0065] The anode of the second diode D2 is connected to the output terminal of the comparator module 14, specifically the first output terminal as described above. The cathode of the second diode is connected to the control electrode of the silicon controlled rectifier Q1. The anode of the third diode D3 is connected to the output terminal of the comparator module 14, specifically the second output terminal as described above. The cathode of the third diode D3 is connected to the control electrode of the silicon controlled rectifier Q1.

[0066] As mentioned above, when the voltage output by the first voltage divider module 12 to the comparator module 14 is greater than the reference voltage, the first output terminal of the comparator module 14 will output a high-level signal to the thyristor rectifier Q1. At this time, the high-level signal will reach the control electrode of the thyristor rectifier Q1 through the second diode D2. Due to the unidirectional conduction of the third diode D3, the high-level signal will not affect the second output terminal of the comparator module 14 through the third diode D3.

[0067] When the voltage output by the second voltage divider module 12 to the comparator module 14 is greater than the reference voltage, the second output terminal of the comparator module 14 will output a high-level signal to the thyristor rectifier Q1 through the third diode D3. Due to the unidirectional conduction of the second diode D2, the high-level signal will not affect the first output terminal of the comparator module 14 through the second diode D2.

[0068] In this embodiment, by setting a second diode D2 and a third diode D3, the safety of the output signal of the comparator module 14 is ensured even when the protection circuit 1 includes multiple voltage divider modules 12. Simultaneously, the unidirectional conduction characteristic of the diodes ensures that the over-temperature detection signal of the comparator module 14 can be stably transmitted to the SCR control terminal, avoiding false triggering caused by interference between multiple signals and improving the reliability and practicality of the protection circuit 1.

[0069] Optionally, the protection circuit 1 also includes an alarm module 16 and an eighth resistor R8. The first end of the alarm module 16 is connected to the second output end of the power supply 11 through the eighth resistor R8, and the second end of the alarm module 16 is connected to the second end of the winding S1.

[0070] Specifically, the eighth resistor R8 can be used as a current-limiting or voltage-dividing element to regulate the operating current or voltage of the alarm module 16. The alarm module 16 can be a buzzer, indicator light, or audible and visual alarm device. When the protection circuit 1 is triggered, the alarm module 16 receives power from the power supply 11 through the eighth resistor R8 and forms a loop through the second end of the winding S1, thereby issuing an alarm signal.

[0071] In this embodiment, by connecting the alarm module 16 to the second output terminal of the power supply 11 and the winding S1, the circuit status can be fed back in real time and an audible and visual warning can be provided, thereby improving the visibility and warning effect when the test device A is abnormal.

[0072] In summary, the protection circuit 1 provided in this application embodiment uses a thermistor RT to monitor the temperature change of the resistance box 2 in real time and convert it into an electrical signal. Combined with the voltage divider module 12, the reference module 13, and the comparison module 14, it forms a precise temperature detection mechanism, enabling automatic over-temperature protection without manual intervention. The circuit-breaking execution module 15, based on the continuous conduction characteristic of the thyristor rectifier Q1, ensures that it remains disconnected after an abnormal temperature, preventing reconnection due to bounce or malfunction of the normally closed contactor's switch contacts. The multi-point thermistor arrangement enhances the comprehensiveness of temperature monitoring, and the comparison logic between the voltage divider and the reference voltage enhances the accuracy of temperature judgment. The overall design effectively solves the problems of reliance on manual response and insufficient disconnection reliability in traditional solutions, making it particularly suitable for equipment safety protection in unattended scenarios.

[0073] This application also provides a test apparatus A, please refer to... Figure 1 or Figure 2 The test device A provided in this application includes a resistance box 2, a test element 3 and a protection circuit 1. One end of the protection circuit 1 is connected to the resistance box 2 and the other end of the protection circuit 1 is connected to the test element 3. The protection circuit 1 is used to disconnect the connection between the resistance box 2 and the test element 3 when the resistance box 2 overheats.

[0074] In its specific implementation, the protection circuit 1 includes components such as a thermistor RT, a comparator module 14, a silicon controlled rectifier Q1, and a normally closed contactor. The thermistors RT are distributed at multiple locations for temperature detection. The comparator module 14 determines the temperature status through a voltage divider module 12 and a reference module 13. The silicon controlled rectifier Q1 remains in the conducting state after being triggered, and the normally closed contactor's switch contacts remain in the open state after being opened. Multiple sets of thermistors RT can be combined to achieve multi-point monitoring.

[0075] In the test device A of this application embodiment, multiple thermistors are set in the resistance box 2 to achieve multiple judgments of temperature anomalies, which improves the detection reliability compared with single-point monitoring. When the temperature exceeds a preset threshold, the protection circuit 1 is triggered to disconnect the resistance box 2 from the test element 3 and maintain the open circuit state between the resistance box 2 and the test element 3. This self-holding mechanism effectively prevents secondary risks caused by repeated temperature fluctuations. The test device A can automatically cut off the power supply 11 in unattended scenarios to avoid equipment damage or fire risks caused by continuous temperature rise. At the same time, it can maintain a safe state without manual intervention after disconnection, improving the automation level and safety of the testing process.

[0076] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A protection circuit, characterized in that, When applied in a testing device, the protection circuit is connected to the resistance box and the test element in the testing device respectively, and is used to disconnect the connection between the resistance box and the test element when the temperature inside the resistance box is too high. The protection circuit includes a power supply, a voltage divider module, a reference module, a comparator module, and a circuit breaker execution module. The first terminal of the voltage divider module is connected to the first output terminal of the power supply, and the second terminal of the voltage divider module is connected to the voltage divider input terminal of the comparator module. The first terminal of the reference module is connected to the first output terminal of the power supply, and the second terminal of the reference module is connected to the reference input terminal of the comparator module. The power input terminal of the comparator module is connected to the first output terminal of the power supply, and the output terminal of the comparator module is connected to the circuit breaker execution module. The ground terminal of the comparator module is grounded. One terminal of the circuit breaker execution module is connected to the second output terminal of the power supply and is connected in series in the connection circuit between the resistance box and the test element. The voltage divider module includes a thermistor, which is located in the resistor box.

2. The protection circuit according to claim 1, characterized in that, The protection circuit also includes a silicon controlled rectifier (SCR), the anode of which is connected to the first output terminal of the power supply, the cathode of which is connected to the circuit breaker module, and the control electrode of which is connected to the output terminal of the comparator module.

3. The protection circuit according to claim 2, characterized in that, The circuit breaking execution module includes a normally closed contactor, the first end of the winding of the normally closed contactor is connected to the cathode of the silicon controlled rectifier, and the second end of the winding is connected to the second output terminal of the power supply; the first end of the switch contact of the normally closed contactor is connected to the resistor box, and the second end of the switch contact is connected to the test element.

4. The protection circuit according to claim 3, characterized in that, The protection circuit further includes a first resistor and a transistor. The first end of the first resistor is connected to the cathode of the silicon controlled rectifier, the second end of the first resistor is connected to the first end of the transistor, the second end of the transistor is connected to the first end of the winding, and the third end of the transistor is grounded.

5. The protection circuit according to claim 3, characterized in that, The protection circuit further includes a switch module, a second resistor, and a third resistor. The first end of the switch module is connected to the first output end of the power supply. The second end of the switch module is connected to the anode of the silicon controlled rectifier through the second resistor. The first end of the third resistor is connected to the cathode of the silicon controlled rectifier, and the second end of the third resistor is grounded.

6. The protection circuit according to claim 1, characterized in that, The voltage divider module includes a fourth resistor, a first capacitor, and a second capacitor. The first end of the thermistor is connected to the first output terminal of the power supply, and the second end of the thermistor is grounded through the fourth resistor. The first capacitor and the second capacitor are connected in parallel with the fourth resistor, and the second end of the thermistor is connected to the voltage divider input terminal of the comparator module. The reference module includes a fifth resistor, a sixth resistor, a third capacitor, and a fourth capacitor. The first end of the fifth resistor is connected to the first output terminal of the power supply, and the second end of the fifth resistor is grounded through the sixth resistor. The third capacitor and the fourth capacitor are connected in parallel with the sixth resistor, and the second end of the fifth resistor is connected to the reference input terminal of the comparison module.

7. The protection circuit according to claim 3, characterized in that, The protection circuit further includes a seventh resistor and a first diode. The first end of the seventh resistor is connected to the second end of the winding, the second end of the seventh resistor is connected to the cathode of the first diode, and the anode of the first diode is connected to the first end of the winding.

8. The protection circuit according to claim 2, characterized in that, The protection circuit includes a second diode and a third diode. The anode of the second diode is connected to the output terminal of the comparator module, and the cathode of the second diode is connected to the control electrode of the thyristor rectifier. The anode of the third diode is connected to the output terminal of the comparator module, and the cathode of the third diode is connected to the control electrode of the thyristor rectifier.

9. The protection circuit according to claim 3, characterized in that, The protection circuit also includes an alarm module and an eighth resistor. The first end of the alarm module is connected to the second output end of the power supply through the eighth resistor, and the second end of the alarm module is connected to the second end of the winding.

10. A testing apparatus, characterized in that, The device includes a resistance box, a test element, and a protection circuit as described in any one of claims 1-9, wherein one end of the protection circuit is connected to the resistance box, and the other end of the protection circuit is connected to the test element, and the protection circuit is used to disconnect the connection between the resistance box and the test element when the temperature inside the resistance box exceeds the limit.

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