CN108666973A - A high-precision over-temperature protection circuit with adjustable threshold - Google Patents

Abstract

The invention discloses a high-precision over-temperature protection circuit with adjustable threshold, which belongs to the technical field of electronic circuits. The temperature sensing module includes a diode-type NTC thermistor, the cathode of the diode-type NTC thermistor is used as a temperature detection terminal, and its anode is connected to the first reference current; the subtractor module is used to subtract the anode voltage of the diode-type NTC thermistor from the diode The cathode voltage of the type NTC thermistor is used to obtain the temperature measurement voltage; the input terminal of the threshold value setting module is connected to the reference voltage, and the output terminal outputs the threshold voltage; the threshold value setting module includes a trimming module, which is used to generate trimming code values, modify The code modulation value is used to adjust the threshold voltage; the control output module is used to compare the temperature measurement voltage and the threshold voltage, and generate an over-temperature signal according to the comparison result. The over-temperature protection circuit provided by the invention has the advantages of high detection accuracy, fast detection speed and simple circuit structure, and meanwhile the protection threshold of the circuit can also be adjusted.

Description

A high-precision over-temperature protection circuit with adjustable threshold

technical field

The invention relates to electronic circuit technology, in particular to a high-precision over-temperature protection circuit with adjustable threshold, which can be used in motor drive circuits.

Background technique

Since most integrated circuits integrate many high-power circuits, when the ambient temperature is too high or there is a power short circuit, internal short circuit, etc., the power consumption of the circuit will increase sharply, and the chip temperature will also be too high, resulting in rapid aging or permanent loss of the chip. , so in order to prevent the above situation, it is often necessary to set an over-temperature protection circuit for the chip.

Taking the motor drive circuit as an example, the power MOS is generally used as the switch tube in the motor drive circuit. When the motor is working, the current is relatively large, generally reaching tens of amperes. Once a stall or short circuit occurs, the current will be even greater, so the power MOS is in the When working, a large current must flow, which will cause the temperature of the device to rise. If it cannot be controlled in time, the circuit may be destroyed. Therefore, in the application of power devices, it is necessary to quickly and accurately protect the circuit from over-temperature.

The traditional over-temperature protection circuit is generally built in the driver chip or connected in series with a temperature-sensitive resistor on the power MOS. If the temperature sampling module is set inside the chip, the temperature of the power MOS cannot be accurately sensed, and a large error will be generated. If a temperature-sensitive resistor is connected in series at the source or drain of the power MOS, the power will be increased, and more damage will occur. Great heat.

Contents of the invention

In view of the shortcomings of the traditional over-temperature protection circuit such as large errors and inaccurate measurements, the present invention proposes a high-precision over-temperature protection circuit with adjustable threshold, which has the advantages of accurate and fast temperature sampling, high precision, adjustable threshold and circuit structure Simple and other advantages.

Technical scheme of the present invention is:

A high-precision over-temperature protection circuit with adjustable threshold, including a temperature sensing module, a subtractor module, a threshold setting module and a control output module,

The temperature sensing module includes a diode-type NTC thermistor D1, the cathode of the diode-type NTC thermistor D1 is used as a temperature detection terminal, and its anode is connected to the first reference current Iref1;

The subtractor module is used to subtract the cathode voltage V2 of the diode NTC thermistor D1 from the anode voltage V1 of the diode NTC thermistor D1 to obtain a temperature measurement voltage;

The input end of the threshold setting module is connected to the reference voltage Vref0, and the output end thereof outputs the threshold voltage Vref1;

The threshold setting module includes a trimming module, the trimming module is used to generate a trimming code value, and the trimming code value is used to adjust the threshold voltage Vref1;

The control output module is used for comparing the temperature measuring voltage and the threshold voltage Vref1, and generating an over-temperature signal VOUT according to the comparison result.

Specifically, when the over-temperature protection circuit is used to detect the motor drive circuit, the cathode of the diode-type NTC thermistor D1 is closely connected to the drain of the power MOS transistor VD1 of the motor drive circuit.

Specifically, the threshold setting module further includes a first operational amplifier OP1, a first NMOS transistor NM1, a second NMOS transistor NM2, a third NMOS transistor NM3, a fourth NMOS transistor NM4, a fifth NMOS transistor NM5, and a first resistor R1 , the second resistor R2, the third resistor R3, the fourth resistor R4 and the fifth resistor R5,

The positive input terminal of the first operational amplifier OP1 is connected to the reference voltage Vref0, the negative input terminal thereof is connected to the source of the first NMOS transistor NM1 and one end of the first resistor R1, and its output terminal is connected to the gate of the first NMOS transistor NM1. pole; the drain of the first NMOS transistor NM1 is connected to the power supply voltage VCC;

One end of the second resistor R2 is connected to the other end of the first resistor R1 and the drain of the second NMOS transistor NM2, and the other end is connected to one end of the third resistor R3 and the drain of the third NMOS transistor NM3;

One end of the fourth resistor R4 is connected to the other end of the third resistor R3 and the drain of the fourth NMOS transistor NM4, and the other end is connected to the drain of the fifth NMOS transistor NM5 and grounded after passing through the fifth resistor R5;

The trimming module generates a four-bit trimming code value which is respectively connected to the gates of the second NMOS transistor NM2, the third NMOS transistor NM3, the fourth NMOS transistor NM4 and the fifth NMOS transistor NM5, the second NMOS transistor NM2, the third NMOS transistor NM5 The sources of the transistor NM3 , the fourth NMOS transistor NM4 and the fifth NMOS transistor NM5 are interconnected and serve as the output terminal of the threshold setting module to output the threshold voltage Vref1 .

Specifically, the threshold setting module further includes a first operational amplifier OP1, a first NMOS transistor NM1, a sixth NMOS transistor NM6, a seventh NMOS transistor NM7, an eighth NMOS transistor NM8, a ninth NMOS transistor NM9, and a sixth resistor R6 , the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10, the trimming module generates a four-bit trimming code value that is respectively connected to the sixth NMOS transistor NM6, the seventh NMOS transistor NM7, and the eighth NMOS transistor the gates of the transistor NM8 and the ninth NMOS transistor NM9,

The positive input terminal of the first operational amplifier OP1 is connected to the reference voltage Vref0, and its negative input terminal is connected to the source of the first NMOS transistor NM1, the drain of the sixth NMOS transistor NM6 and one end of the sixth resistor R6, and its output The terminal is connected to the gate of the first NMOS transistor NM1; the drain of the first NMOS transistor NM1 is connected to the power supply voltage VCC;

One end of the seventh resistor R7 is connected to the source of the sixth NMOS transistor NM6, the drain of the seventh NMOS transistor NM7, and the other end of the sixth resistor R6, and the other end is connected to the source of the seventh NMOS transistor NM7, the eighth NMOS transistor The drain of NM8 and one end of the eighth resistor R8 are used as the output end of the threshold setting module to output the threshold voltage Vref1;

One end of the ninth resistor R9 is connected to the source of the eighth NMOS transistor NM8, the drain of the ninth NMOS transistor NM9, and the other end of the eighth resistor R8, and the other end is connected to the source of the ninth NMOS transistor NM9 and passed through the tenth resistor Ground after R10;

The trimming module generates a four-bit trimming code value which is respectively connected to the gates of the sixth NMOS transistor NM6 , the seventh NMOS transistor NM7 , the eighth NMOS transistor NM8 and the ninth NMOS transistor NM9 .

Specifically, the subtractor module includes a second operational amplifier OP2, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, and a tenth NMOS transistor NM10,

The eleventh resistor R11 and the twelfth resistor R12 are connected in series and parallel between the minuend input terminal of the subtracter module and the ground, and the series point is connected to the positive input terminal of the second operational amplifier OP2;

The thirteenth resistor R13 and the fourteenth resistor R14 are connected in series and parallel between the subtrahend input terminal of the subtracter module and the source of the tenth NMOS transistor NM10, and the series point is connected to the negative input of the second operational amplifier OP2 end;

The gate of the tenth NMOS transistor NM10 is connected to the output terminal of the second operational amplifier OP2, its drain is connected to the power supply voltage VCC, and its source is used as the output terminal of the subtractor module to output the temperature measurement voltage and connected to the second reference current Iref2.

Specifically, the control output module includes a comparator COMP1, a first inverter INV1, a second inverter INV2, a third inverter INV3, a first PMOS transistor PM1, an eleventh NMOS transistor NM11, a twelfth inverter NMOS transistor NM12, a first Schmitt trigger and a first capacitor C1,

The positive input terminal of the comparator COMP1 is connected to the threshold voltage Vref1, its negative input terminal is connected to the temperature measurement voltage, and its output terminal is connected to the input terminal of the first inverter INV1;

The gate of the first PMOS transistor PM1 is connected to the gate of the eleventh NMOS transistor NM1 and the output terminal of the first inverter INV1, its source is connected to the third reference current Iref3, and its drain is connected to the eleventh NMOS transistor NM11 and the output terminal of the first inverter INV1. The drain of the twelfth NMOS transistor NM12 and the input terminal of the first Schmitt trigger are grounded after passing through the first capacitor C1;

The sources of the eleventh NMOS transistor NM11 and the twelfth NMOS transistor NM12 are grounded;

The input end of the third inverter INV3 is connected to the enable signal EN, and its output end is connected to the gate of the twelfth NMOS transistor NM12;

The input terminal of the second inverter INV2 is connected to the output terminal of the first Schmitt trigger, and its output terminal outputs the over-temperature signal VOUT.

Specifically, the temperature sensing module further includes a fifteenth resistor R15, and the anode of the diode-type NTC thermistor D1 is connected to the subtractor module after passing through the fifteenth resistor R15.

The beneficial effects of the invention are: the over-temperature protection circuit provided by the invention has the advantages of high detection accuracy, fast detection speed and simple circuit structure, and meanwhile the protection threshold of the circuit can also be adjusted.

Description of drawings

FIG. 1 is a realization structure diagram of a high-precision over-temperature protection circuit with an adjustable threshold value proposed by the present invention.

Figure 2 is a schematic diagram of the trimming module.

FIG. 3 is a structural schematic diagram of another implementation of a threshold setting module in a high-precision over-temperature protection circuit with an adjustable threshold proposed by the present invention.

Detailed ways

The working principle of the present invention will be described in detail below according to the drawings and embodiments.

A high-precision over-temperature protection circuit with adjustable threshold value proposed by the present invention includes a temperature sensing module, a subtractor module, a threshold setting module and a control output module, wherein the temperature sensing module includes a diode-type NTC thermistor D1, and the diode-type NTC thermistor D1 is used to The conduction voltage drop of the NTC thermistor D1 decreases with the increase of temperature. The cathode of the diode-type NTC thermistor D1 is used as the temperature detection terminal, and its anode is connected to a constant first reference current Iref1 to generate the first reference The reference circuit of the current Iref1 performs temperature compensation for the first reference current Iref1, so that the first reference current Iref1 does not change with temperature, thereby eliminating the error of the voltage across the diode NTC thermistor D1 caused by the current change.

Taking the motor drive circuit as an example, since the power MOS transistor VD1 is generally used as the switch tube in the motor drive circuit, and the drain temperature of the power MOS transistor VD1 is generally the highest, and the drain material is generally metal with good thermal conductivity, so the The cathode of the diode-type NTC thermistor D1 is closely connected to the drain of the power MOS transistor VD1 of the motor drive circuit to detect the temperature of the power MOS transistor VD1. Module, threshold value setting module and control output module are integrated on the outside of the chip, which makes the temperature detected by the temperature sensing module more accurate. When the voltage across the diode NTC thermistor D1 is low and cannot be compared with the threshold voltage Vref1, a fifteenth resistor R15 can be set in the temperature sensing module according to different applications, and the anode of the diode NTC thermistor D1 After passing through the fifteenth resistor R15, it is connected to the subtractor module, so that protective measures can be taken for the circuit at different temperature points as required, making the over-temperature protection more flexible and accurate. The fifteenth resistor R15 must have a very low temperature coefficient, So that the voltage at both ends does not change with temperature, reducing the error.

The current of the power MOS tube is composed of two parts, one part is the motor current, and the other part is the first reference current Iref1 flowing through the diode-type NTC thermistor D1. Because the first reference current Iref1 can be negligibly small relative to the current flowing through the power MOS transistor VD1, the extra power consumption generated by the diode-type NTC thermistor D1 is very small, and the power MOS transistor will not be damaged due to excessive power. VD1 adds extra heat. At the same time, the cathode metal of the diode-type NTC thermistor D1 is directly attached to the drain metal of the power MOS transistor VD1. The metal conducts heat well, and it will transmit the temperature of the power MOS transistor VD1 to the diode-type NTV thermistor D1 more quickly and accurately. , making sampling more accurate and faster.

The working principle of the temperature sensing module is: the gate drive signal VON is used to control the power MOS tube VD1, the drain current of the power MOS tube VD1 is I _D , the temperature of the power MOS tube VD1 will rise with the increase of power, and the diode The anode of the formula NTC thermistor D1 inputs a constant first reference current Iref1, and the voltage drop across it decreases as the temperature increases.

The subtractor module is used to calculate the conduction voltage drop of the diode NTC thermistor D1, its subtrahend input terminal is connected to the anode voltage V1 of the diode NTC thermistor D1, and its subtrahend input terminal is connected to the diode NTC thermistor The cathode voltage V2 of the resistor D1, the temperature measurement voltage is obtained at its output terminal, which is the sum of the voltages across the two ends of the diode-type NTC thermistor D1 (the fifteenth resistor R15 is also protected in some embodiments), eliminating the power MOS tube VD1 source The voltage between the drains interferes with the temperature sampling, and a pure voltage value across the diode-type NTC thermistor D1 that varies linearly with temperature is obtained. As shown in Figure 1 and Figure 3, a circuit implementation structure of the subtractor module is given. The resistance values of the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14 can be adjusted as required Setting, in some embodiments, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14 are set to be exactly the same and have relatively large resistance values. Due to the clamping effect of the input terminal of the operational amplifier, the The voltages of the positive and negative input terminals of the two operational amplifiers OP2 are equal. The anode voltage of the diode-type NTC thermistor D1 is input to the positive input terminal of the second operational amplifier OP2 of the subtractor module through the eleventh resistor R11, and the drain voltage of the power MOS transistor VD1 is input to the second through the thirteenth resistor R13. The negative input terminal of the operational amplifier OP2 outputs the temperature measuring voltage through the source of the tenth NMOS transistor NM10 to the negative input terminal of the comparator COMP1 of the control output module.

Note that the anode voltage of the diode-type NTC thermistor D1 is V1, and the drain voltage of the power MOS transistor VD1 is V2. According to the characteristics of the operational amplifier, the voltage at the positive input terminal of the second operational amplifier can be deduced to be V1/2, so the first The voltage drop on the thirteenth resistor R13 is V2-V1/2, that is, the voltage drop across the fourteenth resistor R14 is V2-V1/2, so the voltage at the source of the tenth NMOS transistor NM10 is:

That is, output the voltage drop across the diode-type NTC thermistor D1 (and the fifteenth resistor R15 in some embodiments) to the negative input terminal of the second operational amplifier OP2 of the subtractor module.

The threshold setting module generates the threshold voltage Vref1 according to the reference voltage Vref0, and adjusts the threshold voltage Vref1 according to the trimming code value generated by the trimming module. The specific steps are to connect the positive input terminal of the first operational amplifier OP1 to a fixed reference voltage Vref0, The voltage Vref0 is divided by resistors, and then the trimming module controls the conduction of the MOS switch to adjust the generated threshold voltage Vref1. Figure 2 shows a circuit implementation structure for generating a one-bit trimming code value in the trimming module, including the sixteenth resistor R16, the fuse Pfuse, the second PMOS transistor MP2, the third PMOS transistor PM3, and the thirteenth PMOS transistor. The NMOS transistor NM13, the fourteenth NMOS transistor NM14, the fifteenth NMOS transistor NM15, the second Schmitt trigger and the D flip-flop, the gate-drain of the thirteenth NMOS transistor NM13 are interconnected and connected to the fourteenth NMOS transistor NM14 and The gate of the fifteenth NMOS transistor NM15 and the fourth reference current Lref4 are connected to the source of the fourteenth NMOS transistor NM14 and the source of the fifteenth NMOS transistor NM15 and grounded; the gate and drain of the second PMOS transistor PM2 are interconnected and The drain of the fourteenth NMOS transistor NM14 is connected to the gate of the third PMOS transistor PM3, and its source is connected to the power supply voltage VCC after passing through the sixteenth resistor R16; the drain of the third PMOS transistor PM3 is connected to the fifteenth NMOS transistor NM15 The drain and the input end of the second Schmitt trigger, its source is connected to one end of the fuse Pfuse and used as the fuse control end; the other end of the fuse Pfuse is connected to the power supply voltage VCC; the data input end of the D flip-flop is connected to The output terminal of the second Schmitt trigger has its clock input terminal connected to the clock signal CK, its reset terminal connected to the enable signal EN, and its Q output terminal or Q non-output terminal to output a trimming code value.

The principle of the trimming module is a current comparator, in which the fuse Pfuse is a current fuse, and the fuse Pfuse can be blown by adding a high level to the fuse control terminal Pad. Before it is blown, the resistance R of the fuse _Pfuse is approximately At 0, the resistance R _Pfuse of the fuse Pfuse is close to infinity after the fuse is broken, that is, the circuit is broken. The width-to-length ratio of the fourteenth NMOS transistor NM14 and the fifteenth NMOS transistor NM15 are equal, when the fuse Pfuse is not blown, R _Pfuse << R16, VO1 will have a tendency to reduce the current flowing through the third PMOS transistor PM3 , so that the output of VO1 is high level. When the fuse Pfuse is blown, R _Pfuse >> R16, VO1 will increase the current flowing through the third PMOS transistor PM3, and the output of VO1 is low level. If multiple code values need to be modified, only multiple bar code value generating circuits need to be connected in parallel.

As shown in Figure 1, a schematic structural diagram of the threshold setting module in Embodiment 1 is provided. The positive input terminal of the first operational amplifier OP1 is connected to the reference voltage Vref0 to be 1.2V, and the first resistor R1-the fifth resistor R5 convert the reference voltage to Vref0. Vref0 is divided into four voltage values, which are:

The four-bit trimming code value output by the trimming module is connected to the gates of the second NMOS transistor to the fifth NMOS transistor. When the trimming code value is at a high level, the corresponding MOS transistor is turned on, and the output threshold voltage Vref1 is the transistor Drain voltage, but only one of the four trimming code values output each time can be high, that is, only one corresponding MOS transistor can be turned on at a time, so there are only 4 trimming combinations in this way, but this This method of voltage division has good linearity and high precision.

FIG. 3 shows a schematic structural diagram of the threshold setting module in the second embodiment. Compared with the threshold setting module in the first embodiment, the connection mode of the MOS tubes is different. In the second embodiment, the sixth NMOS transistor NM6 to the ninth NMOS transistor NM9 are respectively connected in parallel to both ends of the sixth resistor R6 to the ninth resistor R9. The threshold voltage Vref1 is output from the connection point of the seventh resistor R7 and the eighth resistor R8, and the output voltage depends on the resistance between the threshold voltage Vref1 and the ground after the trimming code value is input and the resistance between the inverting input terminal of the first operational amplifier OP1 and the ground ratio. When the MOS transistor connected in parallel at both ends of the resistor is turned on, the resistor is short-circuited, and there are 16 combinations of trimming code values, but the linearity of trimming in this way is not ideal, and the on-resistance of the MOS transistor will also affect the voltage. Accuracy.

The control output module is used to compare the temperature measurement voltage output by the subtractor module with the threshold voltage Vref1 generated by the threshold setting module. When the temperature is higher than the set threshold, the temperature measurement voltage is lower than the threshold voltage Vref1, and the comparator COMP1 outputs a high voltage , the first inverter INV1 outputs a low voltage, and then outputs the over-temperature signal VOUT after delay and shaping. The positive input terminal of the comparator COMP1 in the control output module is connected to the preset threshold voltage Vref1, and the negative input terminal voltage is the voltage difference between the two ends of the diode-type NTC thermistor D1 (some embodiments also include a fifteenth resistor R15). The third reference current Iref3, the first NMOS transistor PM1, the eleventh NMOS transistor NM1 and the first capacitor C1 form a delay loop to generate a certain signal delay, the enable signal EN enables the control output module, and the first Schmitt trigger Output after shaping the waveform. Initially, the temperature is low, the voltage drop across the diode-type NTC thermistor D1 is large, the output of the comparator COMP1 is low, and it is input to the first PMOS transistor PM1 and the eleventh NMOS transistor NM11 through the first inverter INV1 The gate, the eleventh NMOS connected to NM11 is turned on, the first PMOS transistor PM1 is turned off, the drain voltage of the eleventh NMOS transistor NM11 changes from high to low, the first capacitor C1 is discharged, and the drain voltage is low. When the temperature is too high, the voltage difference between the two ends of the diode-type NTC thermistor D1 decreases, and when the temperature measurement voltage V1-V2 is smaller than the threshold voltage Vref1, the output of the comparator COMP1 is high, and is input to the first PMOS through the first inverter INV1 The gates of the transistor PM1 and the eleventh NMOS transistor NM11, the first PMOS transistor PM1 is turned on, the eleventh NMOS transistor NM11 is turned off, the drain voltage of the first PMOS transistor PM1 changes from low to high, and the third reference current Iref3 starts to give the first A capacitor C1 is charged, and the drain voltage of the first PMOS transistor PM1 slowly rises. After being shaped by the first Schmitt trigger, the rising edge of the drain of the first PMOS transistor PM1 generates a certain delay and then outputs an over-temperature signal VOUT to the drive circuit. , and take corresponding protection measures, such as inputting to the motor drive circuit to turn off the power MOS tube VD1, so that the motor drive circuit enters the protection mode.

In summary, the present invention proposes an over-temperature protection circuit that integrates a subtractor module, a threshold value setting module, and a control output module into one chip, and the temperature sensing module uses a temperature-sensitive source diode NTC resistor D1 to detect temperature changes , the diode-type NTC resistor D1 is set outside the chip and close to the component to be tested, so that the detection accuracy is higher, the speed is faster, and the circuit structure is simpler; in addition, the over-temperature protection circuit provided by the present invention can adjust the threshold voltage according to the actual situation , adjust the protection threshold of the circuit by adjusting the resistance value of the fifteenth resistor R15 and the trimming code value generated by the trimming module, which can be applied to any circuit that needs temperature protection.

Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims (7)

1. A high-precision overtemperature protection circuit with adjustable threshold, characterized in that it includes a temperature sensing module, a subtractor module, a threshold setting module and a control output module, The temperature sensing module includes a diode-type NTC thermistor (D1), the cathode of the diode-type NTC thermistor (D1) is used as a temperature detection terminal, and its anode is connected to the first reference current (Iref1); The subtractor module is used to subtract the cathode voltage (V2) of the diode NTC thermistor (D1) from the anode voltage (V1) of the diode NTC thermistor (D1) to obtain the temperature measurement voltage; The input terminal of the threshold setting module is connected to a reference voltage (Vref0), and its output terminal outputs a threshold voltage (Vref1); The threshold setting module includes a trimming module, the trimming module is used to generate a trimming code value, and the trimming code value is used to adjust the threshold voltage (Vref1); The control output module is used for comparing the temperature measurement voltage and the threshold voltage (Vref1), and generating an over-temperature signal (VOUT) according to the comparison result. 2. The high-precision over-temperature protection circuit with adjustable threshold according to claim 1, characterized in that, when the over-temperature protection circuit is used to detect a motor drive circuit, the diode-type NTC thermistor (D1) The cathode is closely connected with the drain of the power MOS transistor (VD1) of the motor drive circuit. 3. The high-precision over-temperature protection circuit with adjustable threshold according to claim 1, characterized in that, the threshold setting module further comprises a first operational amplifier (OP1), a first NMOS transistor (NM1), a second NMOS tube (NM2), third NMOS tube (NM3), fourth NMOS tube (NM4), fifth NMOS tube (NM5), first resistor (R1), second resistor (R2), third resistor (R3), The fourth resistor (R4) and the fifth resistor (R5), The positive input terminal of the first operational amplifier (OP1) is connected to the reference voltage (Vref0), its negative input terminal is connected to the source of the first NMOS transistor (NM1) and one end of the first resistor (R1), and its output terminal Connect the gate of the first NMOS transistor (NM1); the drain of the first NMOS transistor (NM1) is connected to the power supply voltage (VCC); One end of the second resistor (R2) is connected to the other end of the first resistor (R1) and the drain of the second NMOS transistor (NM2), and the other end is connected to one end of the third resistor (R3) and the third NMOS transistor (NM3) the drain; One end of the fourth resistor (R4) is connected to the other end of the third resistor (R3) and the drain of the fourth NMOS transistor (NM4), and the other end is connected to the drain of the fifth NMOS transistor (NM5) and passed through the fifth resistor ( R5) is grounded after; The trimming module generates a four-bit trimming code value that is respectively connected to the gates of the second NMOS transistor (NM2), the third NMOS transistor (NM3), the fourth NMOS transistor (NM4) and the fifth NMOS transistor (NM5). The sources of the second NMOS transistor (NM2), the third NMOS transistor (NM3), the fourth NMOS transistor (NM4) and the fifth NMOS transistor (NM5) are interconnected and output the threshold voltage as the output terminal of the threshold setting module (Vref1). 4. The high-precision over-temperature protection circuit with adjustable threshold according to claim 1, characterized in that, the threshold setting module further comprises a first operational amplifier (OP1), a first NMOS transistor (NM1), a sixth NMOS tube (NM6), seventh NMOS tube (NM7), eighth NMOS tube (NM8), ninth NMOS tube (NM9), sixth resistor (R6), seventh resistor (R7), eighth resistor (R8), The ninth resistor (R9) and the tenth resistor (R10), the trimming module generates a four-bit trimming code value respectively connected to the sixth NMOS transistor (NM6), the seventh NMOS transistor (NM7), the eighth NMOS transistor (NM8 ) and the gate of the ninth NMOS transistor (NM9), The positive input terminal of the first operational amplifier (OP1) is connected to the reference voltage (Vref0), and its negative input terminal is connected to the source of the first NMOS transistor (NM1), the drain of the sixth NMOS transistor (NM6) and the drain of the sixth NMOS transistor (NM6). One end of the six resistors (R6), the output end of which is connected to the gate of the first NMOS transistor (NM1); the drain of the first NMOS transistor (NM1) is connected to the power supply voltage (VCC); One end of the seventh resistor (R7) is connected to the source of the sixth NMOS transistor (NM6), the drain of the seventh NMOS transistor (NM7) and the other end of the sixth resistor (R6), and the other end is connected to the seventh NMOS transistor ( The source of NM7), the drain of the eighth NMOS transistor (NM8) and one end of the eighth resistor (R8) output the threshold voltage (Vref1) as the output terminal of the threshold setting module; One end of the ninth resistor (R9) is connected to the source of the eighth NMOS transistor (NM8), the drain of the ninth NMOS transistor (NM9) and the other end of the eighth resistor (R8), and the other end is connected to the ninth NMOS transistor ( The source of NM9) is grounded after passing through the tenth resistor (R10); The trimming module generates a four-bit trimming code value which is respectively connected to the gates of the sixth NMOS transistor (NM6), the seventh NMOS transistor (NM7), the eighth NMOS transistor (NM8) and the ninth NMOS transistor (NM9). 5. The high-precision over-temperature protection circuit with adjustable threshold according to claim 1, characterized in that, the subtractor module includes a second operational amplifier (OP2), an eleventh resistor (R11), a twelfth resistor (R12), the thirteenth resistor (R13), the fourteenth resistor (R14) and the tenth NMOS tube (NM10), The eleventh resistor (R11) and the twelfth resistor (R12) are connected in series between the minuend input terminal of the subtractor module and the ground, and the series point is connected to the positive input of the second operational amplifier (OP2). end; The thirteenth resistor (R13) and the fourteenth resistor (R14) are connected in series between the subtrahend input terminal of the subtractor module and the source of the tenth NMOS transistor (NM10), and the series point is connected to the second operation The negative input of the amplifier (OP2); The gate of the tenth NMOS transistor (NM10) is connected to the output terminal of the second operational amplifier (OP2), its drain is connected to the power supply voltage (VCC), and its source is used as the output terminal of the subtractor module to output the temperature measurement voltage And connect the second reference current (Iref2). 6. The high-precision over-temperature protection circuit with adjustable threshold according to claim 1, characterized in that, the control output module includes a comparator (COMP1), a first inverter (INV1), a second inverter (INV2), the third inverter (INV3), the first PMOS transistor (PM1), the eleventh NMOS transistor (NM11), the twelfth NMOS transistor (NM12), the first Schmitt trigger and the first capacitor (C1), The positive input terminal of the comparator (COMP1) is connected to the threshold voltage (Vref1), its negative input terminal is connected to the temperature measurement voltage, and its output terminal is connected to the input terminal of the first inverter (INV1); The gate of the first PMOS transistor (PM1) is connected to the gate of the eleventh NMOS transistor (NM1) and the output terminal of the first inverter (INV1), its source is connected to the third reference current (Iref3), and its drain Connect the drains of the eleventh NMOS transistor (NM11) and the twelfth NMOS transistor (NM12) and the input end of the first Schmitt trigger and pass through the first capacitor (C1) to ground; The sources of the eleventh NMOS transistor (NM11) and the twelfth NMOS transistor (NM12) are grounded; The input terminal of the third inverter (INV3) is connected to the enable signal (EN), and its output terminal is connected to the gate of the twelfth NMOS transistor (NM12); The input terminal of the second inverter ( INV2 ) is connected to the output terminal of the first Schmitt trigger, and its output terminal outputs the over-temperature signal (VOUT). 7. The high-precision over-temperature protection circuit with adjustable threshold according to claim 1, characterized in that, the temperature sensing module also includes a fifteenth resistor (R15), and the diode-type NTC thermistor (D1) The anode of the anode is connected to the subtractor module after passing through the fifteenth resistor (R15).