Motor over-temperature protection circuit for electric power steering system

By designing the motor overtemperature protection circuit of the bridge module and the two-stage amplification module in the electric steering assist system, the problem of insufficient precision in traditional motor temperature monitoring is solved, and higher temperature detection sensitivity and signal accuracy are achieved, effectively preventing the motor from overtemperature.

CN222884570UActive Publication Date: 2025-05-16NINGBO RUYI JOINT CO LTD
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Patent Information

Application Number
CN202421760285.4
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Filing Date
2024-07-24
Publication Date
2025-05-16
Estimated Expiration
2034-07-24

AI Technical Summary

Technical Problem

In traditional electric steering assist systems, the motor temperature monitoring is not accurate enough, and signal distortion is easily caused by nonlinear errors, which cannot effectively prevent the motor from overtemperature.

Method used

A motor overtemperature protection circuit is designed, and a bridge module is used to convert the resistance change of the temperature detection resistance into voltage change, and two-stage amplification is realized through the primary and secondary amplification modules to ensure that the signal remains linear throughout the amplification process and reduce nonlinear distortion.

Benefits of technology

It improves the sensitivity and accuracy of motor temperature detection, ensuring that even slight temperature changes can obtain clear and accurate signal output, effectively avoiding the risk of motor overtemperature.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model discloses a motor over-temperature protection circuit for an electric power steering system, and relates to the field of electric power steering systems. The bridge module is composed of a temperature detection resistor and a plurality of resistors with fixed resistance values; the temperature detection resistor is used for detecting the temperature of the motor; the bridge module is used for converting the resistance change of the temperature detection resistor into voltage change and forming a differential signal; the design of the bridge module improves the sensitivity of temperature detection, and as the resistance value of the temperature detection resistor changes along with the change of the temperature, the change of the temperature can be accurately sensed by monitoring the output voltage of the bridge module, especially under the condition of small temperature difference; in addition, two-stage amplification is achieved through the first-stage amplification module and the second-stage amplification module, signals are enhanced, meanwhile, due to the fact that each stage of amplifier works in the linear working area of the amplifier, the saturation problem possibly encountered by a single high-gain amplifier is avoided, and nonlinear distortion is reduced.
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Description

Technical Field

[0001] The utility model relates to the field of electric power steering systems, in particular to a motor over-temperature protection circuit for electric power steering systems. Background Art

[0002] In the electric power steering system of industrial vehicles, the temperature control of the motor is crucial. Excessive temperature can cause the motor performance to deteriorate or even permanently damage. Traditional temperature protection methods may not accurately monitor the motor temperature due to insufficient amplifier gain or nonlinear errors. Among them, the nonlinear error of the amplifier refers to the inability to maintain a strict proportional relationship between the amplifier output and input, that is, the output signal is not a linear function of the input signal. This nonlinearity may manifest as distortion of the output signal, such as clipping, saturation or compression, especially when the amplifier is close to its maximum output capacity or minimum output capacity. Nonlinear errors will cause signal distortion and reduce signal quality, which is unacceptable for precision measurement and control systems. Single-stage amplifiers may encounter higher gains when designed, making it easier to reach saturation, especially when the input signal amplitude is large or the linear range of the amplifier itself is limited. Nonlinear errors occur when the amplifier operates outside its linear range. Therefore, a more reliable and accurate temperature monitoring and protection mechanism is needed. Utility Model Content

[0003] In order to avoid the problem that the motor temperature cannot be accurately monitored due to nonlinear errors, the utility model proposes a motor over-temperature protection circuit for an electric power steering system, comprising:

[0004] A bridge module, which is composed of a temperature detection resistor and a plurality of resistors with fixed resistance values; the temperature detection resistor is used to detect the temperature of the motor; the bridge module is used to convert the resistance change of the temperature detection resistor into a voltage change and form a differential signal;

[0005] A first closed-loop feedback path and a second closed-loop feedback path formed by resistors of fixed resistance in the bridge module;

[0006] A first-stage amplification module including a first reverse amplifier U9A is used to generate an amplified output signal according to the input of the same-direction input terminal and the input of the reverse input terminal of the first reverse amplifier U9A; the same-direction input terminal of the first reverse amplifier U9A is connected to the original temperature signal generated by the temperature detection resistor, and the output terminal feeds back the output signal to the reverse input terminal of the first reverse amplifier U9A through a first closed-loop feedback path; the reverse input terminal of the first reverse amplifier U9A is also used to connect the differential signal output by the bridge module;

[0007] A secondary amplification module including a second reverse amplifier U9B, which is used to generate an amplified output signal according to the input of the same-direction input terminal and the input of the reverse input terminal of the second reverse amplifier U9B, and output it through the output terminal; the same-direction input terminal of the second reverse amplifier U9B is connected to the output terminal of the first reverse amplifier U9A, and the output terminal is connected to the reverse input terminal of the second reverse amplifier U9B through a second closed-loop feedback path;

[0008] An over-temperature detection module connected to the output end of the second reverse amplifier U9B, used to output an over-temperature signal to the single-chip microcomputer when the input signal exceeds the over-temperature threshold;

[0009] The single chip microcomputer is used to execute the over-temperature protection action of the electric steering power system according to the over-temperature signal output by the over-temperature detection module.

[0010] Furthermore, the motor over-temperature protection circuit also includes:

[0011] A voltage regulator; the reference voltage value of the voltage regulator is set by a voltage divider network formed by resistors with fixed resistance values ​​in the bridge module; the voltage regulator provides a reference voltage to the bridge module based on the reference voltage value to stabilize the output voltage of the bridge module.

[0012] Furthermore, the fixed resistance resistors include a fourth resistor R44, a fourth resistor R45 and a fourth resistor R46; and in the bridge module:

[0013] The first pin of the temperature detection resistor PT1 is connected to the reference terminal of the voltage regulator TL431 and one end of the fifth eighth resistor R58 and is grounded, and the second pin is connected to the first-stage amplification module;

[0014] One end of the fourth resistor R44 is connected to the reverse input end of the first reverse amplifier U9A, and the other end is connected to the output end of the first reverse amplifier U9A;

[0015] One end of the fourth fifth resistor R45 is connected to the reverse input end of the second reverse amplifier U9B, and the other end is connected to the output end of the second reverse amplifier U9B;

[0016] One end of the fourth sixth resistor R46 is connected to the power supply voltage (+5V), and the other end is connected to the cathode of the voltage regulator TL431.

[0017] Furthermore, the first-stage amplification module further includes:

[0018] a 49th resistor R49, a 50th resistor R50, a 54th resistor R54, a 55th resistor R55, a 56th resistor R56 and a 58th resistor R58; wherein:

[0019] One end of the fifth-fourth resistor R54 is simultaneously connected to one end of the fifth zero resistor R50 and the other end of the fifth-eighth resistor R58, and the other end is connected to one end of the fourth-fourth resistor R44 and then connected to the reverse input end of the first reverse amplifier U9A; the other end of the fifth zero resistor R50 is connected to one end of the fourth-ninth resistor R49 and the anode of the voltage regulator TL431 in sequence, and then connected to the connection line between the fourth-sixth resistor R46 and the cathode of the voltage regulator TL431; the anode of the voltage regulator TL431 is also connected to the positive power supply (2.5V); the other end of the fourth-ninth resistor R49 is simultaneously connected to the second pin of the temperature detection resistor PT1 and one end of the fifth-sixth resistor R56; the other end of the fifth-sixth resistor R56 is connected to the same-direction input end of the first reverse amplifier U9A; the positive power supply end of the first reverse amplifier U9A is connected to the power supply voltage (+5V), the negative power supply end is grounded, and the output end is connected to the other end of the fourth-fourth resistor R44 and then connected to one end of the fifth-fifth resistor R55; the other end of the fifth-fifth resistor R55 is connected to the secondary amplifier module.

[0020] Furthermore, the secondary amplification module further includes: a fourth first capacitor C41, a fifth second resistor R52 and a fifth third resistor R53; wherein:

[0021] One end of the fourth-first capacitor C41 is connected to the power supply voltage (+5V), and the other end is grounded and connected to one end of the fifth-second resistor R52; the other end of the fifth-second resistor R52 is connected to one end of the fourth-fifth resistor R45 and then connected to the reverse input end of the second reverse amplifier U9B; the same-direction input end of the second reverse amplifier U9B is connected to the other end of the fifth-fifth resistor R55, the positive power supply end is connected to the power supply voltage (+5V), the negative power supply end is grounded, the output end is connected to the other end of the fourth-fifth resistor R45 and then connected to one end of the fifth-third resistor R53; the other end of the fifth-third resistor R53 is connected to the over-temperature detection module.

[0022] Furthermore, the over-temperature detection module includes:

[0023] The comparator U7B and a voltage dividing unit for setting the comparator U7B to correspond to the overheating threshold; the voltage dividing unit includes a fourth seventh resistor R47 and a fifth seventh resistor R57; wherein:

[0024] One end of the fourth-seventh resistor R47 is connected to the power supply voltage (+5V), and the other end is connected to one end of the fifth-seventh resistor R57 and connected to the inverting input terminal of the comparator U7B; the other end of the fifth-seventh resistor R57 is grounded; the same-direction input terminal of the comparator U7B is connected to the other end of the fifth-third resistor R53, and the output terminal is connected to one end of the fourth-eighth resistor R48 and one end of the fifth-first resistor R51 in sequence and then connected to the single-chip microcomputer; the other end of the fourth-eighth resistor R48 is connected to the power supply voltage (+5V) and connected to the positive terminal of the seventh LED lamp L7; the negative terminal of the seventh LED lamp L7 is connected to the other end of the fifth-first resistor R51.

[0025] Further, the first closed-loop feedback path is formed by: a fourth resistor R44 having one end connected to the inverting input terminal of the first inverting amplifier U9A and the other end connected to the output terminal of the first inverting amplifier U9A;

[0026] The second closed-loop feedback path is formed by a fourth fifth resistor R45 having one end connected to the inverting input terminal of the second inverting amplifier U9B and the other end connected to the output terminal of the second inverting amplifier U9B.

[0027] Compared with the prior art, the utility model has at least the following beneficial effects:

[0028] (1) The utility model includes a bridge module, which is composed of a temperature detection resistor and a plurality of resistors with fixed resistance values; the temperature detection resistor is used to detect the temperature of the motor; the bridge module is used to convert the resistance change of the temperature detection resistor into a voltage change and form a differential signal; the design of the bridge module improves the sensitivity of temperature detection. Since the resistance value of the temperature detection resistor changes with the temperature, by monitoring the output voltage of the bridge module, the temperature change can be accurately sensed, especially in the case of a small temperature difference; in addition, the utility model realizes two-stage amplification through a primary amplification module and a secondary amplification module, which not only enhances the signal, but also because each stage of the amplifier works in its linear working area, it avoids the saturation problem that may be encountered by a single high-gain amplifier and reduces nonlinear distortion. In addition, this circuit design ensures that even with a small temperature change, a clear and accurate signal output can be obtained;

[0029] (2) The utility model can offset the influence of environmental factors, such as power supply fluctuations and external interference, by designing the bridge module, thereby ensuring the accuracy of the measurement results. At the same time, since the bridge module mainly focuses on the voltage difference between the bridge arms rather than the absolute voltage level, it can effectively suppress common mode noise, which helps to improve the anti-interference performance of the circuit;

[0030] (3) In the present invention, the reference voltage value of the voltage regulator is set by a voltage divider network formed by resistors with fixed resistance values ​​in the bridge module; the voltage regulator provides a reference voltage to the bridge module based on the reference voltage value to stabilize the output voltage of the bridge module, thereby ensuring the voltage stability of the bridge module and improving the accuracy of the signal;

[0031] (4) The utility model realizes stable and accurate signal transmission through the designed voltage divider network and voltage stabilizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a circuit diagram of motor over-temperature protection for an electric power steering system. DETAILED DESCRIPTION

[0033] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0034] In order to avoid the problem of inaccurate monitoring of motor temperature due to nonlinear errors, such as Figure 1 As shown, the utility model proposes a motor over-temperature protection circuit for an electric power steering system, comprising:

[0035] A bridge module, which is composed of a temperature detection resistor and a plurality of resistors with fixed resistance values; the temperature detection resistor is used to detect the temperature of the motor; the bridge module is used to convert the resistance change of the temperature detection resistor into a voltage change and form a differential signal;

[0036] In this embodiment, the temperature detection resistor is a PT100 platinum thermal resistor, which has good linearity, stability and accuracy. The resistance of PT100 at 0°C is 100 ohms, and as the temperature rises, the resistance increases according to a specific rule. For example, at 100°C, the resistance is about 138.5 ohms.

[0037] The utility model can offset the influence of environmental factors, such as power supply fluctuations and external interference, by designing the bridge module, thereby ensuring the accuracy of the measurement results. At the same time, since the bridge module mainly focuses on the voltage difference between the bridge arms rather than the absolute voltage level, it can effectively suppress common mode noise, which helps to improve the anti-interference performance of the circuit.

[0038] A first closed-loop feedback path and a second closed-loop feedback path formed by resistors of fixed resistance in the bridge module;

[0039] A first-stage amplification module including a first reverse amplifier U9A is used to generate an amplified output signal according to the input of the same-direction input terminal and the input of the reverse input terminal of the first reverse amplifier U9A; the same-direction input terminal of the first reverse amplifier U9A is connected to the original temperature signal generated by the temperature detection resistor, and the output terminal feeds back the output signal to the reverse input terminal of the first reverse amplifier U9A through a first closed-loop feedback path; the reverse input terminal of the first reverse amplifier U9A is also used to connect the differential signal output by the bridge module;

[0040] A secondary amplification module including a second reverse amplifier U9B, which is used to generate an amplified output signal according to the input of the same-direction input terminal and the input of the reverse input terminal of the second reverse amplifier U9B, and output it through the output terminal; the same-direction input terminal of the second reverse amplifier U9B is connected to the output terminal of the first reverse amplifier U9A, and the output terminal is connected to the reverse input terminal of the second reverse amplifier U9B through a second closed-loop feedback path;

[0041] It should be noted that, in this embodiment, the first-stage amplification module can be set to a lower gain, such as 10 times, which is enough to boost the weak signal to a certain level, but not to saturate the amplifier. The second-stage amplification module further amplifies the signal, such as 3 times, so that the final gain is equal to the product of the first and second stage gains, that is, 30 times. This design strategy of the utility model ensures that even under high gain requirements, the signal can maintain good linearity throughout the amplification process, thereby reducing nonlinear errors and improving the accuracy and stability of the overall circuit.

[0042] One arm of the bridge is composed of PT100, and the other three arms are fixed resistors (R44, R45, R46), forming a Wheatstone bridge structure. When the resistance value of PT100 changes, the bridge becomes unbalanced and a voltage difference is generated.

[0043] The fixed resistance resistors include a fourth resistor R44, a fourth resistor R45 and a fourth resistor R46; in the bridge module:

[0044] The first pin of the temperature detection resistor PT1 is connected to the reference terminal of the voltage regulator TL431 and one end of the fifth eighth resistor R58 and is grounded, and the second pin is connected to the first-stage amplification module;

[0045] One end of the fourth resistor R44 is connected to the reverse input end of the first reverse amplifier U9A, and the other end is connected to the output end of the first reverse amplifier U9A;

[0046] One end of the fourth fifth resistor R45 is connected to the reverse input end of the second reverse amplifier U9B, and the other end is connected to the output end of the second reverse amplifier U9B;

[0047] One end of the fourth sixth resistor R46 is connected to the power supply voltage (+5V), and the other end is connected to the cathode of the voltage regulator TL431.

[0048] The first-stage amplification module also includes:

[0049] a 49th resistor R49, a 50th resistor R50, a 54th resistor R54, a 55th resistor R55, a 56th resistor R56 and a 58th resistor R58; wherein:

[0050] One end of the fifth-fourth resistor R54 is simultaneously connected to one end of the fifth zero resistor R50 and the other end of the fifth-eighth resistor R58, and the other end is connected to one end of the fourth-fourth resistor R44 and then connected to the reverse input end of the first reverse amplifier U9A; the other end of the fifth zero resistor R50 is connected to one end of the fourth-ninth resistor R49 and the anode of the voltage regulator TL431 in sequence, and then connected to the connection line between the fourth-sixth resistor R46 and the cathode of the voltage regulator TL431; the anode of the voltage regulator TL431 is also connected to the positive power supply (2.5V); the other end of the fourth-ninth resistor R49 is simultaneously connected to the second pin of the temperature detection resistor PT1 and one end of the fifth-sixth resistor R56; the other end of the fifth-sixth resistor R56 is connected to the same-direction input end of the first reverse amplifier U9A; the positive power supply end of the first reverse amplifier U9A is connected to the power supply voltage (+5V), the negative power supply end is grounded, and the output end is connected to the other end of the fourth-fourth resistor R44 and then connected to one end of the fifth-fifth resistor R55; the other end of the fifth-fifth resistor R55 is connected to the secondary amplifier module.

[0051] The first closed-loop feedback path is formed by: a fourth resistor R44 having one end connected to the inverting input terminal of the first inverting amplifier U9A and the other end connected to the output terminal of the first inverting amplifier U9A;

[0052] The calculation formula of the gain of the first reverse amplifier U9A is:

[0053] In the formula, Indicates the resistance of the fifth zero resistor R50, A U9A Indicates the gain of the first reverse amplifier U9A;

[0054] The secondary amplification module further includes: a fourth first capacitor C41, a fifth second resistor R52 and a fifth third resistor R53; wherein:

[0055] One end of the fourth-first capacitor C41 is connected to the power supply voltage (+5V), and the other end is grounded and connected to one end of the fifth-second resistor R52; the other end of the fifth-second resistor R52 is connected to one end of the fourth-fifth resistor R45 and then connected to the reverse input end of the second reverse amplifier U9B; the same-direction input end of the second reverse amplifier U9B is connected to the other end of the fifth-fifth resistor R55, the positive power supply end is connected to the power supply voltage (+5V), the negative power supply end is grounded, the output end is connected to the other end of the fourth-fifth resistor R45 and then connected to one end of the fifth-third resistor R53; the other end of the fifth-third resistor R53 is connected to the over-temperature detection module.

[0056] The second closed-loop feedback path is formed by a fourth fifth resistor R45 having one end connected to the inverting input terminal of the second inverting amplifier U9B and the other end connected to the output terminal of the second inverting amplifier U9B.

[0057] It should be noted that the closed-loop feedback allows the circuit to self-regulate and maintain a stable relationship between output and input, and can maintain the stability of the amplification factor even when external conditions such as power supply voltage (+5V) fluctuations or temperature changes.

[0058] The calculation formula of the gain of the second reverse amplifier U9B is:

[0059] In the formula, represents the resistance value of the fifth second resistor R52, A U9B Indicates the amplification factor of the second reverse amplifier U9B;

[0060] The over-temperature detection module connected to the output end of the second reverse amplifier U9B is used to output an over-temperature signal to the single-chip microcomputer when the input signal exceeds the over-temperature threshold; when the input signal is lower than the over-temperature threshold, the output of the comparator U7B remains in a low level state;

[0061] The over-temperature detection module comprises:

[0062] The comparator U7B and a voltage dividing unit for setting the comparator U7B to correspond to the overheating threshold; the voltage dividing unit includes a fourth seventh resistor R47 and a fifth seventh resistor R57; wherein:

[0063] One end of the fourth-seventh resistor R47 is connected to the power supply voltage (+5V), and the other end is connected to one end of the fifth-seventh resistor R57 and connected to the inverting input terminal of the comparator U7B; the other end of the fifth-seventh resistor R57 is grounded; the same-direction input terminal of the comparator U7B is connected to the other end of the fifth-third resistor R53, and the output terminal is connected to one end of the fourth-eighth resistor R48 and one end of the fifth-first resistor R51 in sequence and then connected to the single-chip microcomputer; the other end of the fourth-eighth resistor R48 is connected to the power supply voltage (+5V) and connected to the positive terminal of the seventh LED lamp L7; the negative terminal of the seventh LED lamp L7 is connected to the other end of the fifth-first resistor R51.

[0064] The setting formula for setting the overheat threshold value of the comparator U7B is:

[0065] Where VCC represents the power supply voltage (+5V), represents the resistance value of the 47th resistor R47, Represents the resistance value of the fifth and seventh resistor R57, V th Indicates the overheat threshold.

[0066] The single chip microcomputer is used to execute the over-temperature protection action of the electric steering power system according to the over-temperature signal (high level signal) output by the over-temperature detection module.

[0067] Over-temperature protection actions include: cutting off the power supply to the motor, starting the cooling system in the electric steering system, etc., to prevent the motor from being damaged due to overheating.

[0068] The motor over-temperature protection circuit also includes:

[0069] Voltage regulator; the reference voltage value of the voltage regulator is set by a voltage divider network formed by resistors with fixed resistance values ​​in the bridge module; the voltage regulator provides a reference voltage to the bridge module based on the reference voltage value to stabilize the output voltage of the bridge module. It should be noted that resistors R44 and R45 form a voltage divider network, which are connected to the cathode and reference terminal of the voltage regulator TL431; this voltage divider network determines the output voltage of TL431, that is, the reference voltage value. By adjusting the values ​​of these two resistors, the output voltage of TL431 can be set, thereby providing a stable reference voltage for the bridge module.

[0070] The calculation formula of the reference voltage value of the voltage regulator is:

[0071] Where V k is the voltage at the cathode end of the regulator TL431, represents the resistance value of the fourth fifth resistor R45, represents the resistance value of the fourth resistor R44, and Vref represents the reference voltage value of the voltage regulator;

[0072] In addition, the voltage stabilizer in this embodiment ensures the stability of the power supply voltage (+5V) of the entire circuit to prevent output voltage fluctuations caused by power supply voltage fluctuations, thereby affecting the stability of the A / D conversion result of the single-chip microcomputer.

[0073] The utility model includes a bridge module, which is composed of a temperature detection resistor and a plurality of resistors with fixed resistance values; the temperature detection resistor is used to detect the temperature of the motor; the bridge module is used to convert the resistance change of the temperature detection resistor into a voltage change and form a differential signal; the design of the bridge module improves the sensitivity of temperature detection, and since the resistance value of the temperature detection resistor changes with the temperature, by monitoring the output voltage of the bridge module, the temperature change can be accurately sensed, especially in the case of a small temperature difference; in addition, the utility model realizes two-stage amplification through a primary amplification module and a secondary amplification module, which not only enhances the signal, but also because each stage of the amplifier works in its linear working area, avoids the saturation problem that may be encountered by a single high-gain amplifier, reduces nonlinear distortion, and in addition, this circuit design ensures that even with a small temperature change, a clear and accurate signal output can be obtained.

[0074] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0075] In addition, in the present invention, the descriptions of "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0076] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A motor over-temperature protection circuit for an electric power steering system, characterized in that: include: A bridge module, which is composed of a temperature detection resistor and a plurality of resistors with fixed resistance values; the temperature detection resistor is used to detect the temperature of the motor; the bridge module is used to convert the resistance change of the temperature detection resistor into a voltage change and form a differential signal; A first closed-loop feedback path and a second closed-loop feedback path formed by resistors of fixed resistance in the bridge module; A first-stage amplification module including a first reverse amplifier U9A is used to generate an amplified output signal according to the input of the same-direction input terminal and the input of the reverse input terminal of the first reverse amplifier U9A; the same-direction input terminal of the first reverse amplifier U9A is connected to the original temperature signal generated by the temperature detection resistor, and the output terminal feeds back the output signal to the reverse input terminal of the first reverse amplifier U9A through a first closed-loop feedback path; the reverse input terminal of the first reverse amplifier U9A is also used to connect the differential signal output by the bridge module; A secondary amplification module including a second reverse amplifier U9B, which is used to generate an amplified output signal according to the input of the same-direction input terminal and the input of the reverse input terminal of the second reverse amplifier U9B, and output it through the output terminal; the same-direction input terminal of the second reverse amplifier U9B is connected to the output terminal of the first reverse amplifier U9A, and the output terminal is connected to the reverse input terminal of the second reverse amplifier U9B through a second closed-loop feedback path; An over-temperature detection module connected to the output end of the second reverse amplifier U9B, used to output an over-temperature signal to the single-chip microcomputer when the input signal exceeds the over-temperature threshold; The single chip microcomputer is used to execute the over-temperature protection action of the electric steering power system according to the over-temperature signal output by the over-temperature detection module.

2. The motor over-temperature protection circuit for an electric power steering system according to claim 1, characterized in that: The motor over-temperature protection circuit also includes: A voltage regulator; the reference voltage value of the voltage regulator is set by a voltage divider network formed by resistors with fixed resistance values ​​in the bridge module; the voltage regulator provides a reference voltage to the bridge module based on the reference voltage value to stabilize the output voltage of the bridge module.

3. The motor over-temperature protection circuit for an electric power steering system according to claim 2, characterized in that: The fixed resistance resistors include a fourth resistor R44, a fourth resistor R45 and a fourth resistor R46; in the bridge module: The first pin of the temperature detection resistor PT1 is connected to the reference terminal of the voltage regulator TL431 and one end of the fifth eighth resistor R58 and is grounded, and the second pin is connected to the first-stage amplification module; One end of the fourth resistor R44 is connected to the reverse input end of the first reverse amplifier U9A, and the other end is connected to the output end of the first reverse amplifier U9A; One end of the fourth fifth resistor R45 is connected to the reverse input end of the second reverse amplifier U9B, and the other end is connected to the output end of the second reverse amplifier U9B; One end of the fourth sixth resistor R46 is connected to the power supply voltage, and the other end is connected to the cathode of the voltage regulator TL431.

4. The motor over-temperature protection circuit for an electric power steering system according to claim 3, characterized in that: The first-stage amplification module also includes: a 49th resistor R49, a 50th resistor R50, a 54th resistor R54, a 55th resistor R55, a 56th resistor R56 and a 58th resistor R58; wherein: One end of the fifth-fourth resistor R54 is simultaneously connected to one end of the fifth zero resistor R50 and the other end of the fifth-eighth resistor R58, and the other end is connected to one end of the fourth-fourth resistor R44 and then connected to the reverse input end of the first reverse amplifier U9A; the other end of the fifth zero resistor R50 is connected to one end of the fourth-ninth resistor R49 and the anode of the voltage regulator TL431 in sequence, and then connected to the connecting line between the fourth-sixth resistor R46 and the cathode of the voltage regulator TL431; the anode of the voltage regulator TL431 is also connected to the positive power supply; the other end of the fourth-ninth resistor R49 is simultaneously connected to the second pin of the temperature detection resistor PT1 and one end of the fifth-sixth resistor R56; the other end of the fifth-sixth resistor R56 is connected to the same-direction input end of the first reverse amplifier U9A; the positive power supply end of the first reverse amplifier U9A is connected to the power supply voltage, the negative power supply end is grounded, and the output end is connected to the other end of the fourth-fourth resistor R44 and then connected to one end of the fifth-fifth resistor R55; the other end of the fifth-fifth resistor R55 is connected to the secondary amplifier module.

5. The motor over-temperature protection circuit for an electric power steering system according to claim 4, characterized in that: The secondary amplification module further includes: a fourth first capacitor C41, a fifth second resistor R52 and a fifth third resistor R53; wherein: One end of the fourth-first capacitor C41 is connected to the power supply voltage, and the other end is grounded and connected to one end of the fifth-second resistor R52; the other end of the fifth-second resistor R52 is connected to one end of the fourth-fifth resistor R45 and then connected to the reverse input end of the second reverse amplifier U9B; the same-direction input end of the second reverse amplifier U9B is connected to the other end of the fifth-fifth resistor R55, the positive power supply end is connected to the power supply voltage, the negative power supply end is grounded, the output end is connected to the other end of the fourth-fifth resistor R45 and then connected to one end of the fifth-third resistor R53; the other end of the fifth-third resistor R53 is connected to the over-temperature detection module.

6. The motor over-temperature protection circuit for an electric power steering system according to claim 5, characterized in that: The over-temperature detection module comprises: The comparator U7B and a voltage dividing unit for setting the comparator U7B to correspond to the overheating threshold; the voltage dividing unit includes a fourth seventh resistor R47 and a fifth seventh resistor R57; wherein: One end of the fourth-seventh resistor R47 is connected to the power supply voltage, and the other end is connected to one end of the fifth-seventh resistor R57 and connected to the inverting input end of the comparator U7B; the other end of the fifth-seventh resistor R57 is grounded; the same-direction input end of the comparator U7B is connected to the other end of the fifth-third resistor R53, and the output end is connected to one end of the fourth-eighth resistor R48 and one end of the fifth-first resistor R51 in sequence and then connected to the single-chip microcomputer; the other end of the fourth-eighth resistor R48 is connected to the power supply voltage and connected to the positive end of the seventh LED lamp L7; the negative end of the seventh LED lamp L7 is connected to the other end of the fifth-first resistor R51.

7. The motor over-temperature protection circuit for an electric power steering system according to claim 5, characterized in that: The first closed-loop feedback path is formed by: a fourth resistor R44 having one end connected to the inverting input terminal of the first inverting amplifier U9A and the other end connected to the output terminal of the first inverting amplifier U9A; The second closed-loop feedback path is formed by a fourth fifth resistor R45 having one end connected to the inverting input terminal of the second inverting amplifier U9B and the other end connected to the output terminal of the second inverting amplifier U9B.