Transistor temperature detection device and electric power steering system
By detecting the potential difference and current of the parasitic diode between the drain and source of the transistor, and combining this with the volt-ampere characteristic, the problem of large internal temperature detection error in the transistor in the prior art is solved, and accurate temperature monitoring is achieved, ensuring the stable operation of the electric power steering system.
Patent Information
- Application Number
- CN202423184426.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2034-12-23
AI Technical Summary
In existing technologies, when detecting transistor temperature by attaching thermocouples to the transistor surface, there is a large error, and the internal temperature of the transistor cannot be accurately monitored.
By utilizing the parasitic diode characteristics between the drain and source of a transistor, and combining a potential difference detection circuit and a current detection circuit, the internal temperature of the transistor can be calculated by detecting the potential difference and current of the parasitic diode and combining the volt-ampere characteristics of the parasitic diode.
This enables accurate monitoring of the internal temperature of the transistor, reduces errors, and ensures the stable operation of the electric power steering system.
Smart Images
Figure CN223756860U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the technical field of automobile parts, and concretely relates to a temperature detection device of transistor and electric power steering system. BACKGROUND
[0002] The transistor generates a lot of heat inside during the working process, and the internal temperature needs to be monitored to avoid damage caused by poor heat dissipation of the transistor.
[0003] For example, the motor drive field effect transistor of the electric power steering system has internal heating phenomenon during the working process, and needs to be monitored to ensure the stable operation of the electric power steering system.
[0004] Currently, a thermocouple is usually pasted near the transistor to detect the surface temperature of the transistor, and then estimate the internal temperature. The current method has the following problems:
[0005] The pasting of the thermocouple can only detect the surface temperature, and when estimating the internal temperature, the error will be too large if the transistor has poor heat dissipation.
[0006] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the utility model, and therefore can include information that does not constitute prior art known to those skilled in the art. CONTENT OF THE UTILITY MODEL
[0007] Therefore, the utility model provides a temperature detection device of transistor and electric power steering system, which detects the internal temperature of the transistor by using the characteristics of the parasitic diode between the drain and the source of the transistor and the voltage-current characteristics of the parasitic diode itself, and has higher accuracy compared with the surface pasting of the thermocouple.
[0008] One aspect of the utility model provides a temperature detection device of transistor, the transistor is connected in series with a load and a sampling resistor, a parasitic diode is formed between the drain and the source of the transistor, and the temperature detection device comprises: a potential difference detection circuit, comprising a first operational amplifier, two input ends of the first operational amplifier are connected with the drain and the source of the transistor respectively, an output end of the first operational amplifier outputs a first sampling voltage, and the potential difference detection circuit is used for detecting the potential difference between the two ends of the parasitic diode when the load regenerative discharge; a current detection circuit, comprising a second operational amplifier, two input ends of the second operational amplifier are connected with the two ends of the sampling resistor respectively, an output end of the second operational amplifier outputs a second sampling voltage, and the current detection circuit is used for detecting the current flowing through the parasitic diode when the load regenerative discharge.
[0009] The utility model discloses a sampling resistance, potential difference detection circuit and current detection circuit are additionally arranged in the loop of transistor and load. The potential difference detection circuit utilizes the differential amplification function of the first operational amplifier to collect the potential difference between the parasitic diode during the regenerative discharge of the load, and specifically, according to the first sampling voltage output by the first operational amplifier and the virtual break and virtual short principle of the operational amplifier, the potential difference between the drain and the source of the transistor connected to the first operational amplifier can be obtained. The current detection circuit utilizes the differential amplification function of the second operational amplifier to collect the potential difference between the sampling resistance during the regenerative discharge of the load, and specifically, according to the second sampling voltage output by the second operational amplifier and the virtual break and virtual short principle of the operational amplifier, the potential difference between the sampling resistance connected to the second operational amplifier can be obtained. Further, according to the series connection of the sampling resistance and the transistor, the current flowing through the parasitic diode during the regenerative discharge of the load can be obtained. According to the detected potential difference between the parasitic diode and the current flowing through the parasitic diode, and in combination with the voltage-current characteristic of the parasitic diode, the temperature of the parasitic diode can be accurately calculated, i.e. the temperature between the PN junctions inside the transistor is obtained.
[0010] In some embodiments, the temperature T of the parasitic diode during the regenerative discharge of the load satisfies:
[0011]
[0012] wherein q is the charge of an electron, u D is the potential difference between the parasitic diode, K is the Boltzmann constant, i D is the current flowing through the parasitic diode, I s is the reverse saturation current.
[0013] In this way, the temperature of the parasitic diode inside the transistor is accurately measured by utilizing the influence of temperature on the voltage-current characteristic of the parasitic diode inside the transistor.
[0014] In some embodiments, the potential difference detection circuit further comprises: a first current-limiting resistor connected between the drain of the transistor and the inverting input terminal of the first operational amplifier; a first negative feedback resistor connected between the output terminal and the inverting input terminal of the first operational amplifier; a second current-limiting resistor connected between the source of the transistor and the non-inverting input terminal of the first operational amplifier; and a first pull-down resistor connected to the non-inverting input terminal of the first operational amplifier and grounded.
[0015] The first operational amplifier and the first current-limiting resistor, the second current-limiting resistor, the first negative feedback resistor and the first pull-down resistor form a differential circuit capable of accurately collecting the potential difference between the parasitic diode of the transistor. Specifically, based on the resistance values of the resistors and the first sampling voltage output by the first operational amplifier, and according to the virtual break and virtual short principle of the operational amplifier, the potential difference between the parasitic diode during the regenerative discharge of the load can be accurately calculated.
[0016] In some embodiments, the first current-limiting resistor, the first negative feedback resistor, the second current-limiting resistor and the first pull-down resistor have the same resistance.
[0017] In this way, the calculation of the potential difference across the parasitic diode can be simplified.
[0018] In some embodiments, the current detection circuit further comprises: a third current-limiting resistor connected between the positive terminal of the sampling resistor and the inverting input terminal of the second operational amplifier; a second negative feedback resistor connected between the output terminal and the inverting input terminal of the second operational amplifier; a fourth current-limiting resistor connected between the negative terminal of the sampling resistor and the non-inverting input terminal of the second operational amplifier; and a second pull-down resistor connected to the non-inverting input terminal of the second operational amplifier and grounded.
[0019] The second operational amplifier and the third current-limiting resistor, the fourth current-limiting resistor, the second negative feedback resistor and the second pull-down resistor form a differential circuit that can accurately collect the potential difference across the sampling resistor. Specifically, based on the resistance values of the resistors, the potential difference collected by the second operational amplifier and the output second sampling voltage, the potential difference across the sampling resistor during load discharge can be accurately calculated. In combination with the resistance value of the sampling resistor and the characteristics of the transistor in series with the sampling resistor, the current flowing through the parasitic diode of the transistor during load regenerative discharge can be conveniently calculated.
[0020] In some embodiments, the third current-limiting resistor, the second negative feedback resistor, the fourth current-limiting resistor and the second pull-down resistor have the same resistance.
[0021] In this way, the calculation of the potential difference across the sampling resistor can be simplified.
[0022] In some embodiments, the output terminal of the first operational amplifier and the output terminal of the second operational amplifier are connected to a voltage detector.
[0023] The voltage detector is used to detect the first sampling voltage output by the first operational amplifier and the second sampling voltage output by the second operational amplifier, so as to obtain the potential difference across the parasitic diode and the potential difference across the sampling resistor.
[0024] In some embodiments, the load is connected to a power supply end, and when the power supply end stops supplying power, the load regeneratively discharges.
[0025] When the power supply end stops supplying power, the stored electrical energy in the load is discharged, forming a regenerative current, and the load discharges to the transistor and the sampling resistor.
[0026] In some embodiments, the first operational amplifier and the second operational amplifier are powered on and operated when the power supply end stops supplying power.
[0027] Thus, the potential difference detection circuit and the current detection circuit detect the potential difference across the parasitic diode and the current flowing through the parasitic diode at the instant of load regeneration discharge, and the internal temperature of the transistor is obtained accordingly.
[0028] In another aspect, the utility model provides a kind of electric power steering system, the electric power steering system is equipped with the temperature detection device as described in any of the above embodiments;Wherein, the load is the motor winding of the electric power steering system, and the transistor is the motor drive field effect transistor of the electric power steering system.
[0029] The temperature detection device of the utility model monitors the internal temperature of the motor drive field effect transistor of the electric power steering system, and timely early warning is carried out when detecting the abnormal internal temperature of the motor drive field effect transistor, to ensure the stable and reliable operation of the electric power steering system.
[0030] The utility model has at least the following beneficial effects compared with prior art:
[0031] The temperature detection device of the utility model utilizes the characteristic that there is parasitic diode between the drain and the source of transistor, detects the potential difference across the parasitic diode and the current flowing through the parasitic diode when load regeneration discharge through potential difference detection circuit and current detection circuit, and then combines the volt-ampere characteristic of the parasitic diode, to accurately calculate the internal temperature of the transistor.The temperature detection device of the utility model does not affect the normal work of transistor, and can accurately and conveniently monitor the internal temperature of transistor.
[0032] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the utility model. BRIEF DESCRIPTION OF DRAWINGS
[0033] The drawings incorporated into the specification and forming part of the specification, show the embodiments consistent with the utility model, and together with the specification, are used to explain the principles of the utility model. Obviously, the drawings in the following description are only some embodiments of the utility model, and other drawings can be obtained according to these drawings without creative labor for those skilled in the art.
[0034] Figure 1 The circuit module schematic diagram of the temperature detection device of transistor in the embodiment of the utility model is shown;
[0035] Figure 2 The circuit structure schematic diagram of potential difference detection circuit in the embodiment of the utility model is shown;
[0036] Figure 3A circuit structure schematic diagram of the current detection circuit is shown in the embodiment of the utility model.
[0037] Figure 4 A schematic diagram of a discharge loop formed in the motor drive circuit is shown in the embodiment of the utility model. DETAILED DESCRIPTION
[0038] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the implementations set forth herein. Rather, these implementations are provided as non-limiting examples, so that this disclosure will fully convey the scope of the example implementations to those skilled in the art.
[0039] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and together with the description serve to explain the principles of the present application. In the drawings:
[0040] The terms "first", "second", and similar terms do not imply any order, quantity, or importance, but are used to distinguish one element from another, and the terms "include" and "have" are used to indicate that there are constituent elements, and the terms "include" and "have" do not exclude the possibility that other elements are present or added.
[0041] It should be noted that the features of the embodiments of the present application and the features in different embodiments can be combined with each other without conflict.
[0042] Figure 1 A circuit module of the temperature detection device of the transistor is shown in the embodiment of the utility model. Referring to Figure 1 As shown, the transistor Q is connected in series with the load L and the sampling resistor R F The parasitic diode (not specifically shown in the figure) is formed between the drain D and the source S of the transistor Q, and the temperature detection device comprises:
[0043] The potential difference detection circuit 100 comprises a first operational amplifier U1, the two input terminals of the first operational amplifier U1 are connected with the drain D and the source S of the transistor Q respectively, and the output terminal of the first operational amplifier U1 outputs a first sampling voltage U og The potential difference detection circuit 100 is used for detecting the potential difference between the two ends of the parasitic diode when the load L is regenerated and discharged;
[0044] The current detection circuit 200 comprises a second operational amplifier U2, the two input terminals of the second operational amplifier U2 are connected with the two ends of the sampling resistor RF respectively, and the output terminal of the second operational amplifier U2 outputs a second sampling voltage U OThe current detection circuit 200 is used for detecting the current flowing through the parasitic diode when the load L is regenerated and discharged.
[0045] In a transistor Q, such as a field effect transistor (specifically, a MOSFET, metal-oxide-semiconductor field effect transistor), there is a parasitic diode between the drain D and the source S of the transistor Q, which is formed by the PN junction of the transistor Q. In a circuit in which the transistor Q is used as a switch to drive a load L, the regenerated and discharged load L is a known technology. For example, in a motor driving circuit, when the main power supply stops supplying power to the motor winding (i.e., the load L), the stored electrical energy in the motor winding is released, forming a regenerated current flowing through the parasitic diode of the transistor Q.
[0046] The utility model adds sampling resistance R F , potential difference detection circuit 100 and current detection circuit 200 in the loop of transistor Q and load L. The potential difference detection circuit 100 utilizes the differential amplification function of the first operational amplifier U1 to collect the potential difference between the two ends of the parasitic diode when the load L is regenerated and discharged. Specifically, according to the first sampling voltage U og output by the first operational amplifier U1 and the virtual open and short principles of the operational amplifier, the potential difference between the drain D and the source S of the transistor Q connected to the first operational amplifier U1 can be obtained. The current detection circuit 200 utilizes the differential amplification function of the second operational amplifier U2 to collect the potential difference between the two ends of the sampling resistance R F when the load L is regenerated and discharged. Specifically, according to the second sampling voltage U O output by the second operational amplifier U2 and the virtual open and short principles of the operational amplifier, the potential difference between the two ends of the sampling resistance R F connected to the second operational amplifier U2 can be obtained. Further, according to the fact that the sampling resistance R F is connected in series with the transistor Q, the current flowing through the parasitic diode when the load L is regenerated and discharged can be obtained. According to the detected potential difference between the two ends of the parasitic diode and the current flowing through the parasitic diode, combined with the voltage-current characteristic of the parasitic diode, the temperature of the parasitic diode can be accurately calculated, i.e., the temperature between the internal PN junctions of the transistor Q is obtained.
[0047] The temperature detection device of the utility model utilizes the characteristic that there is a parasitic diode between the drain D and the source S of the transistor Q, detects the potential difference between the two ends of the parasitic diode and the current flowing through the parasitic diode when the load L is regenerated and discharged through the potential difference detection circuit 100 and the current detection circuit 200, and then combines the voltage-current characteristic of the parasitic diode to accurately calculate the internal temperature of the transistor Q. The temperature detection device of the utility model does not affect the normal operation of the transistor Q and can accurately and conveniently monitor the internal temperature of the transistor Q.
[0048] In some embodiments, the temperature T of the parasitic diode during the regeneration discharge of the load L satisfies:
[0049]
[0050] where q is the charge of an electron, u D is the potential difference across the parasitic diode, K is the Boltzmann constant, i D is the current flowing through the parasitic diode, and I s is the reverse saturation current.
[0051] Thus, the temperature inside the transistor Q is accurately measured by using the influence of temperature on the voltage-current characteristic of the parasitic diode inside the transistor Q.
[0052] Specifically, according to the voltage-current characteristic of the parasitic diode, the relationship between the potential difference u D across the parasitic diode and the current i D flowing through the parasitic diode is:
[0053]
[0054] For silicon material, the reverse saturation current Is is about 10 pA; the charge of an electron q = 1.6 x 10 -9 C; and the Boltzmann constant k = 1.38 x 10 -23 J / K. Then, according to formula (2), formula (1) can be derived.
[0055] Figure 2 The structure of the potential difference detection circuit 100 is shown, and in combination with Figure 1 and Figure 2 , in some embodiments, the potential difference detection circuit 100 further includes: a first current-limiting resistor R g1 connected between the drain D of the transistor Q and the inverting input terminal of the first operational amplifier U1; a first negative feedback resistor R g2 connected between the output terminal and the inverting input terminal of the first operational amplifier U1; a second current-limiting resistor R g3 connected between the source S of the transistor Q and the non-inverting input terminal of the first operational amplifier U1; and a first pull-down resistor R g4 connected to the non-inverting input terminal of the first operational amplifier U1 and grounded.
[0056] The first operational amplifier U1 and the first current-limiting resistor R g1 , the second current-limiting resistor R g3 , the first negative feedback resistor R g2 , and the first pull-down resistor R g4 form a differential circuit that can accurately collect the potential difference across the parasitic diode of the transistor Q. Specifically, based on the resistance values of the resistors and the first sampling voltage Uog According to the virtual open and short principles of the operational amplifier, the potential difference across the parasitic diode during the regenerative discharge of the load L can be accurately calculated.
[0057] In some embodiments, the first current-limiting resistor R g1 , the first negative feedback resistor R g2 , the second current-limiting resistor R g3 , and the first pull-down resistor R g4 have the same resistance. In this way, the calculation of the potential difference across the parasitic diode can be simplified.
[0058] Let the voltage at the inverting input of the first operational amplifier U1 be U D , and the voltage at the non-inverting input be U S . Then the potential difference across the parasitic diode U DS = U D - U S . The first sampling voltage U og output by the first operational amplifier U1 can be directly measured. According to the virtual open and short principles of the operational amplifier, the following equation (3) is obtained:
[0059]
[0060] where the first current-limiting resistor R g1 , the first negative feedback resistor R g2 , the second current-limiting resistor R g3 , and the first pull-down resistor R g4 have the same resistance, i.e., R g1 = R g2 = R g3 = R g4 . Solving equation (3) gives: U DS = U D - U S = U og . That is, the first sampling voltage U og output by the first operational amplifier U1 is the potential difference across the parasitic diode.
[0061] Figure 3 The structure of the current detection circuit 200 is shown, and in combination with the structures shown in Figure 1 and Figure 3 , in some embodiments, the current detection circuit 200 further includes: a third current-limiting resistor R F1 connected between the positive pole R Fa of the sampling resistor RF and the inverting input of the second operational amplifier U2; a second negative feedback resistor R F2 connected between the output and the inverting input of the second operational amplifier U2; a fourth current-limiting resistor R F3, connected to the negative pole R Fb of the sampling resistor RF F4 , connected to the positive input of the second operational amplifier U2 and grounded.
[0062] Through the second operational amplifier U2 and the third current-limiting resistor R F1 , the fourth current-limiting resistor R F3 , the second negative feedback resistor R F2 and the second pull-down resistor R F4 , a differential circuit is formed, which can accurately collect the potential difference across the sampling resistor R F . Specifically, based on the resistance values of the resistors, the potential difference collected by the second operational amplifier U2 and the output second sampling voltage U O , the potential difference across the sampling resistor R F when the load L is discharged can be accurately calculated. In combination with the resistance value of the sampling resistor R F and the characteristics of the transistor Q in series with the sampling resistor R F , the current flowing through the parasitic diode of the transistor Q when the load L is regenerated discharged can be conveniently calculated.
[0063] In some embodiments, the resistance values of the third current-limiting resistor R F1 , the second negative feedback resistor R F2 , the fourth current-limiting resistor R F3 and the second pull-down resistor R F4 are equal. In this way, the calculation of the potential difference across the sampling resistor R F can be simplified.
[0064] Let the voltage at the inverting input of the second operational amplifier U2 be U RF1 and the voltage at the non-inverting input be U RF2 . Then the potential difference U F across the sampling resistor R RF is U RF1 - U RF2 . The second sampling voltage U O output by the second operational amplifier U2 can be directly measured. According to the virtual break and virtual short principles of the operational amplifier, the following equation (4) is obtained:
[0065]
[0066] where the resistance values of the third current-limiting resistor R F1 , the second negative feedback resistor R F2 , the fourth current-limiting resistor R F3 and the second pull-down resistor R F4 are equal, i.e. R F1 = R F2 = RF3 = R F4 Solving equation (4) can obtain: U RF = U RF1 - U RF2 = U O That is, the second sampling voltage U O outputted by the second operational amplifier U2 is the potential difference between the two ends of the sampling resistor R F .
[0067] Further, the current I F flowing through the two ends of the sampling resistor R F = U O ÷ R F , wherein R F is a known accurate resistance value. Thus, the current flowing through the parasitic diode when the load L is regenerated and discharged is I F , that is, i D = I F .
[0068] In some embodiments, the output end of the first operational amplifier U1 and the output end of the second operational amplifier U2 are connected with a voltage detector.
[0069] The voltage detector is used to detect the first sampling voltage U og outputted by the first operational amplifier U1 and the second sampling voltage U O outputted by the second operational amplifier U2, so as to obtain the potential difference between the two ends of the parasitic diode and the potential difference between the two ends of the sampling resistor R F . When the temperature detection device is applied in a vehicle, the voltage detector is, for example, a main controller of the vehicle, which can directly measure the first sampling voltage U og and the second sampling voltage U O .
[0070] In some embodiments, as shown in Figure 1 , the load L is connected with a power supply end VDD, and when the power supply end VDD stops supplying power, the load L is regenerated and discharged.
[0071] When the power supply end VDD stops supplying power, the electrical energy stored in the load L is released to form a regenerated current, and the load L is discharged to the transistor Q and the sampling resistor R F . At this time, the transistor Q can be turned off or turned on, depending on the regeneration mode of the circuit, which is not limited by the utility model. The utility model detects the voltage and current in the circuit when the power supply end VDD stops supplying power, so as to realize energy saving and cost reduction.
[0072] In some embodiments, the first operational amplifier U1 and the second operational amplifier U2 are powered on when the power supply end VDD stops supplying power. In this way, the potential difference detection circuit 100 and the current detection circuit 200 detect the potential difference across the parasitic diode and the current flowing through the parasitic diode at the moment when the load L regeneratively discharges, and thereby obtain the internal temperature of the transistor Q.
[0073] The utility model embodiment further provides an electric power assisted steering system, the electric power assisted steering system is provided with the temperature detection device as any of the above embodiments, wherein the load is a motor winding of the electric power assisted steering system, and the transistor is a motor drive field effect transistor of the electric power assisted steering system.
[0074] The motor drive field effect transistor is a key component in the motor drive circuit of the electric power assisted steering system, and whether it can work normally directly relates to whether the electric power assisted steering system can safely operate. In the working process of the motor drive field effect transistor, the internal PN junction generates Joule heat under the action of current. If the heat is serious, the performance of the motor drive field effect transistor will be affected, and even the motor drive field effect transistor will be disabled, causing driving safety problems.
[0075] The motor drive circuit can adopt an H-bridge circuit, Figure 4 A discharge loop formed in the motor drive circuit when the motor winding regeneratively discharges is shown, wherein the other irrelevant transistors in the dashed box are hidden. Referring to Figure 4 , the motor drive field effect transistors Q3 and Q2 are connected in series with the motor winding L1, and the sampling resistor R F is also connected in series in the discharge loop. The drain D3 and the source S3 of the motor drive field effect transistor Q3, and the drain D2 and the source S2 of the motor drive field effect transistor Q2 are respectively connected to the potential difference detection circuit 100 shown in Figure 1 and Figure 2 . The positive pole R F and the negative pole R Fb of the sampling resistor R Fa are connected to the current detection circuit 200 shown in Figure 1 and Figure 3 . When the main power supply V_PHASE stops supplying power to the motor winding L1, the stored electrical energy in the motor winding L1 is released, forming a regenerative current (referring to the arrow shown in Figure 4 ) flowing through the parasitic diode of the motor drive field effect transistors Q3 and Q2 and the sampling resistor R F . Through the potential difference detection circuit 100 and the current detection circuit 200, the potential difference across the parasitic diode of the motor drive field effect transistors Q3 and Q2 and the current flowing through the parasitic diode can be accurately detected, and the internal temperature of the motor drive field effect transistors Q3 and Q2 can be accurately calculated in combination with the volt-ampere characteristic of the parasitic diode.
[0076] The temperature detection device is used for monitoring the internal temperature of the motor driving field effect tube of the electric power steering system, and timely early warning is performed when the internal temperature of the motor driving field effect tube is detected to be abnormal, so that stable and reliable operation of the electric power steering system is ensured.
[0077] The above is a further detailed description of the utility model in combination with specific preferred embodiments, and the specific implementation of the utility model cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the utility model belongs, without departing from the concept of the utility model, a number of simple deductions or substitutions can be made, and all of them should be regarded as belonging to the protection scope of the utility model.
Claims
1. A temperature detecting device of a transistor, characterized by comprising: The transistor is connected in series with a load and a sampling resistor, a parasitic diode is formed between the drain and the source of the transistor, and the temperature detection device comprises: a potential difference detection circuit comprising a first operational amplifier, two input ends of the first operational amplifier being connected to the drain and the source of the transistor respectively, and an output end of the first operational amplifier outputting a first sampling voltage, the potential difference detection circuit being configured to detect a potential difference across the parasitic diode during regenerative discharge of the load; a current detection circuit comprising a second operational amplifier, two input ends of the second operational amplifier being connected to two ends of the sampling resistor respectively, and an output end of the second operational amplifier outputting a second sampling voltage, the current detection circuit being configured to detect a current flowing through the parasitic diode during regenerative discharge of the load.
2. The temperature detecting device according to claim 1, wherein The temperature T of the parasitic diode during regenerative discharge of the load satisfies: where q is the charge of an electron, u D is the potential difference across the parasitic diode, K is the Boltzmann constant, i D is the current flowing through the parasitic diode, I s is the reverse saturation current.
3. The temperature detecting device according to claim 1, wherein The potential difference detection circuit further comprises: a first current-limiting resistor connected between the drain of the transistor and an inverting input end of the first operational amplifier; a first negative feedback resistor connected between the output end and the inverting input end of the first operational amplifier; a second current-limiting resistor connected between the source of the transistor and a non-inverting input end of the first operational amplifier; a first pull-down resistor connected to the non-inverting input end of the first operational amplifier and grounded.
4. The temperature detecting device according to claim 3, wherein The first current-limiting resistor, the first negative feedback resistor, the second current-limiting resistor and the first pull-down resistor have equal resistance values.
5. The temperature detecting device according to claim 1, wherein The current detection circuit further comprises: a third current-limiting resistor connected between a positive electrode of the sampling resistor and an inverting input end of the second operational amplifier; a second negative feedback resistor connected between the output end and the inverting input end of the second operational amplifier; a fourth current-limiting resistor connected between a negative electrode of the sampling resistor and a non-inverting input end of the second operational amplifier; a second pull-down resistor connected to the non-inverting input end of the second operational amplifier and grounded.
6. The temperature detecting device according to claim 5, wherein The third current-limiting resistor, the second negative feedback resistor, the fourth current-limiting resistor and the second pull-down resistor have equal resistance values.
7. The temperature detecting device according to claim 1, wherein The output end of the first operational amplifier and the output end of the second operational amplifier are connected to a voltage detector.
8. The temperature detecting device according to any one of claims 1 to 7, wherein The load is connected to a power supply end, and the load is configured to be regeneratively discharged when the power supply end stops supplying power.
9. The temperature detecting device according to claim 8, wherein The first operational amplifier and the second operational amplifier are powered on and operated when the power supply end stops supplying power.
10. An electric power assisted steering system characterised in that, The temperature detection device is configured as claimed in any one of claims 1-9. The load is a motor winding of the electric power steering system, and the transistor is a motor drive field effect transistor of the electric power steering system.