A phase current monitoring circuit and method for a motor drive bridge with temperature compensation

Abstract

The application relates to a phase current monitoring circuit and method of a motor drive bridge with temperature compensation, the circuit comprising a microcontroller, a pre-drive chip, a group of H-bridge lower bridge MOS tubes, a voltage acquisition unit and a temperature acquisition unit; a differential amplifier of the pre-drive chip is used to directly acquire lower bridge MOS tube drain voltages to replace traditional sampling resistors; a gate voltage acquisition module is additionally arranged to acquire MOS tube gate-source voltages; a temperature acquisition module is additionally arranged to monitor MOS tube junction temperatures in real time; based on the acquired drain voltages, gate voltages and real-time temperatures, the MCU dynamically calculates the conduction resistance of the MOS tube under the current temperature in combination with a pre-stored temperature-related MOS tube parameter model, and then accurately calculates the phase current after temperature compensation. The application completely cancels the sampling resistors, reduces the cost, simplifies the heat dissipation design, is beneficial to product miniaturization, effectively solves the MOS tube parameter temperature drift problem through a temperature compensation mechanism, and ensures the accuracy and stability of current sampling in the full-temperature range.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and specifically to a phase current monitoring circuit and method for a motor drive bridge with temperature compensation. Background Technology

[0002] In the field of DC motor drives, especially in applications with high safety requirements such as electric power steering (EPS) systems in automobiles, accurate monitoring of the three-phase (U / V / W) current of the motor is crucial, as it directly affects the accuracy of torque control and the stability of the system. Currently, the mainstream approach involves connecting a low-resistance, high-power sampling resistor in series between the lower arm of the H-bridge and ground, calculating the current by detecting the differential voltage across the resistor. For example, a three-phase fully redundant drive system may require up to six sampling resistors.

[0003] However, this traditional solution has obvious drawbacks: First, multiple high-precision sampling resistors increase material costs; second, a large current flowing through the sampling resistors generates considerable heat, posing a challenge to the heat dissipation design of the circuit board and affecting the long-term reliability of the system; finally, multiple resistors occupy valuable PCB space, which is not conducive to the miniaturization and compact design of motor drivers, especially for special structural layouts such as cylindrical types. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a phase current monitoring circuit and method for a motor drive bridge with temperature compensation, which aims to eliminate sampling resistance, utilize the characteristics of the H-bridge MOSFET for current detection, and ensure measurement accuracy through real-time temperature compensation.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A phase current monitoring circuit for a motor drive bridge with temperature compensation includes a microcontroller, a pre-drive chip, a lower bridge MOSFET group of the H-bridge, a voltage acquisition unit, and a temperature acquisition unit. The H-bridge lower-bridge MOSFET group includes multiple lower-bridge MOSFETs corresponding to each phase of the motor; the pre-drive chip has a built-in differential amplifier unit, the number of which corresponds to the number of lower-bridge MOSFETs, the positive input terminal of each differential amplifier unit is connected to the drain of a corresponding lower-bridge MOSFET, and the negative input terminal of each differential amplifier unit is grounded; the voltage acquisition unit is used to acquire the gate drive voltage of each lower-bridge MOSFET; the temperature acquisition unit is used to acquire the temperature near each lower-bridge MOSFET. The microcontroller is connected to the output terminals of the differential amplifier unit, the voltage acquisition unit, and the temperature acquisition unit, respectively. The microcontroller is configured to calculate the temperature-compensated current values ​​of each phase based on the drain voltage signal output by the differential amplifier unit, the gate voltage signal output by the voltage acquisition unit, the temperature signal output by the temperature acquisition unit, and pre-stored temperature compensation parameters.

[0006] The beneficial effects of this invention are: it completely eliminates all phase current sampling resistors, significantly reducing material costs and enhancing product market competitiveness; it eliminates the sampling resistor as a major heat source, reducing the power consumption and temperature rise of the entire driver board, simplifying heat dissipation design, and improving the reliability and lifespan of the system in high-temperature environments; it saves sampling resistors and related layout and wiring space, providing greater layout freedom for motor drivers, especially for space-constrained designs such as cylindrical types; it creatively introduces a real-time monitoring and compensation mechanism for MOSFET temperature, solving the core problem of inaccurate current calculation caused by MOSFET on-resistance drift with temperature, ensuring that the alternative solution maintains stable and accurate current acquisition performance under different temperature environments. This invention eliminates sampling resistors, reducing costs, simplifying heat dissipation design, facilitating product miniaturization, and effectively solving the MOSFET parameter temperature drift problem through a temperature compensation mechanism, ensuring the accuracy and stability of current sampling across the entire temperature range.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the microcontroller includes a compensation calculation module, which is configured as follows: Based on the collected temperature signal, the electron mobility and threshold voltage of the lower bridge MOSFET are determined. Based on the determined electron mobility, threshold voltage, and acquired gate voltage signal, the real-time on-resistance value of the lower bridge MOS transistor at the current temperature is calculated using the MOS transistor on-resistance model. Based on the drain voltage signal output by the differential amplifier unit and the calculated real-time on-resistance value, the phase current value after temperature compensation is calculated.

[0009] Furthermore, the on-resistance model of the MOS transistor is as follows: ; in, This is the real-time on-resistance value. For electron mobility, The capacitance of the gate oxide layer of the MOSFET. VGS is the width-to-length ratio of the MOSFET, Vth is the value of the gate voltage signal, and Vth is the threshold voltage.

[0010] Furthermore, the formula for calculating the phase current value after temperature compensation is as follows: I_phase = V_D / Ron(T); Where I_phase is the phase current value after temperature compensation, and V_D is the value of the drain voltage signal.

[0011] Furthermore, the compensation calculation module pre-stores a temperature parameter lookup table, which is used to store the mapping relationship between different temperature signal values ​​and the corresponding electron mobility and threshold voltage.

[0012] Furthermore, the data in the temperature parameter lookup table is obtained through experimental calibration, and the relationship between electron mobility and temperature contained in the temperature parameter lookup table satisfies the following formula: Where T is the temperature to be checked. For the electron mobility to be investigated, For reference temperature, Reference temperature electron mobility at that point This is an empirical constant.

[0013] Furthermore, the voltage acquisition unit includes multiple voltage divider circuits, the input of each voltage divider circuit is connected to the gate drive signal terminal of a lower bridge MOSFET, and the output is connected to the analog-to-digital converter interface of the microcontroller.

[0014] Furthermore, the temperature acquisition unit includes multiple temperature sensor circuits, each temperature sensor circuit containing at least one thermistor with a negative temperature coefficient. The thermistor is located near a lower bridge MOSFET and connected in series with a pull-up resistor to a reference voltage source. The voltage divider node between the thermistor and the pull-up resistor is connected to the analog-to-digital converter interface of the microcontroller.

[0015] Furthermore, the pre-drive chip is a motor pre-drive chip integrating multiple differential operational amplifiers, and the differential amplification unit is the differential operational amplifier.

[0016] To address the aforementioned technical problems, this invention also provides a method for monitoring the phase current of a motor drive bridge with temperature compensation, the specific technical content of which is as follows: A method for monitoring the phase current of a motor drive bridge with temperature compensation, applied to the aforementioned phase current monitoring circuit, includes: The drain voltage signal of each phase of the motor's lower bridge MOSFET, the gate voltage signal of each lower bridge MOSFET, and the real-time temperature of each lower bridge MOSFET are collected synchronously. Based on the collected real-time temperature, gate voltage signals, and pre-stored temperature-related MOS transistor process parameters, the real-time on-resistance of each lower-bridge MOS transistor at the current temperature is calculated. Based on the acquired drain voltage signal and the calculated real-time on-resistance, the temperature-compensated current values ​​for each phase are calculated. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of a phase current monitoring circuit for a motor drive bridge with temperature compensation, according to an embodiment of the present invention. Figure 2 This is a circuit diagram of the prior art in an embodiment of the present invention. Detailed Implementation

[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] Example 1 like Figure 1 As shown, this embodiment provides a phase current monitoring circuit for a motor drive bridge with temperature compensation. The circuit mainly consists of a microcontroller (MCU, as the core of calculation and control), a pre-drive chip, H-bridge lower MOSFETs (M14, M15, M16), a MOS gate voltage acquisition module, a temperature acquisition module, and necessary connection circuits.

[0020] Core connection structure: Current signal acquisition path: The pre-driver chip integrates three differential operational amplifiers (AMP1, AMP2, AMP3), forming the differential amplification unit. The positive input terminal (non-inverting input terminal) of each amplifier is directly connected to the drain of the corresponding lower-phase bridge MOSFET (motor phase line Phase_U, Phase_V, Phase_W), and the negative input terminal (inverting input terminal) is directly grounded (GND). The amplifier output terminal is connected to the dedicated ADC input pin of the MCU.

[0021] Gate voltage signal acquisition path: The gate voltage acquisition module consists of three precision voltage divider networks. Taking phase U as an example, one end of resistor R1 is connected to the lower bridge drive output pin LUO of the pre-drive chip, and the other end is connected to resistor R2 and then grounded. The voltage divider point between R1 and R2 is connected to an ADC pin of the MCU (named AD_LUO). The structure of phase V (R3, R4, AD_LVO) and phase W (R5, R6, AD_LWO) is the same. R1~R6 are all high-stability thin-film resistors with ±1% accuracy.

[0022] Temperature signal acquisition path: The temperature acquisition module consists of three independent thermistor voltage divider circuits. Taking the M14 temperature acquisition as an example, the negative temperature coefficient thermistor NTC1 is placed close to the M14 power transistor casing or heat sink. One end of NTC1 is connected to a high-precision, low-temperature-drift reference voltage source VTK1, and the other end is connected in series with a ±1% accuracy resistor R7 and then grounded. The voltage divider node between NTC1 and R7 is connected to the ADC pin of the MCU (named AD_NTC1). The V phase (NTC2, R8, AD_NTC2) and W phase (NTC3, R9, AD_NTC3) have the same structure.

[0023] The calculation process and methods of a microcontroller (MCU): The MCU integrates a compensation calculation module, which performs temperature-compensated phase current calculations according to the following steps: Step 1: Signal Acquisition The MCU simultaneously or through high-speed polling acquires the following three sets of ADC signals: Three-phase drain voltages: AMP_AD_U, AMP_AD_V, AMP_AD_W (output from AMP1~3).

[0024] Three-phase gate drive voltages: AD_LUO, AD_LVO, AD_LWO (collected by a voltage divider network).

[0025] Three-phase MOSFET temperatures: AD_NTC1, AD_NTC2, AD_NTC3 (collected by NTC voltage divider network).

[0026] Step 2: Parameter Mapping and Temperature Compensation Calculation The MCU's compensation calculation module has a built-in temperature-parameter lookup table. This lookup table was established through calibration experiments and includes the following parameters for different AD_NTC values ​​(corresponding to different temperatures T): Electron mobility: Based on material properties, its relationship with temperature can be approximately described as... Where T is the temperature to be checked. For the electron mobility to be investigated, For reference temperature, Reference temperature The electron mobility at a given temperature (e.g., 25°C) is K, an empirical constant (typically between 1.5 and 2.0). The lookup table stores the AD_NTC values ​​and... The mapping.

[0027] Threshold voltage Vth(T): According to semiconductor physics, it has an approximately linear negative correlation with temperature, Vth(T) = Vth0 - α * (T - T0), where Vth0 is the threshold voltage at the reference temperature T0, and α is the temperature coefficient. A lookup table stores the mapping between AD_NTC values ​​and Vth(T).

[0028] Step 3: Real-time On-Resistance Calculation The MCU looks up the current temperature T in a table based on the currently acquired AD_NTC value. And Vth(T). Simultaneously, the gate-source voltage VGS is deduced from signals such as AD_LUO. Combining the known MOSFET process parameters—gate oxide capacitance Cox and aspect ratio (W / L)—the real-time on-resistance Ron_k(T) of each MOSFET is calculated using the MOSFET on-resistance model: ; in, This is the real-time on-resistance value. For electron mobility, The capacitance of the gate oxide layer of the MOSFET. VGS is the width-to-length ratio of the MOSFET, Vth is the value of the gate voltage signal, and Vth is the threshold voltage.

[0029] Step 4: Calculation of current after compensation Finally, Ohm's law is used to calculate the precise U, V, and W phase currents I_phase_U, I_phase_V, and I_phase_W: I_phase_U=(AMP_AD_U-VCM) / (Gain*Ron_M14(T)) I_phase_V=(AMP_AD_V-VCM) / (Gain*Ron_M15(T)) I_phase_W=(AMP_AD_W-VCM) / (Gain*Ron_M16(T)) Where VCM is the common-mode voltage of the pre-driver internal op-amp, and Gain is the op-amp gain, both of which are known circuit constants.

[0030] Through the above process, this invention realizes the use of the MOS transistor itself as a "sampling resistor" and dynamically calculates its on-resistance by monitoring its gate voltage and temperature in real time, ultimately obtaining a high-precision phase current value that is unaffected by temperature.

[0031] Example 2 In this embodiment, the following were removed: Figure 2 The sampling resistors R11, R12, and R13 are connected in series in the three-phase lower bridge in the traditional scheme shown.

[0032] The three-phase U / V / W current of the motor is acquired by monitoring the current passing through three low-impedance, high-power sampling resistors R11, R12, and R13 connected in series in the lower bridge of the three phases. The phase currents I_phase_U, I_phase_V, and I_phase_W are then passed through the three sampling resistors to obtain the differential voltages of the input pre-drive chip current monitoring op-amps AMP1~AMP3. U_phase_differ=R11*I_phase_U; V_phase_differ=R12*I_phase_V; W_phase_differ=R13*I_phase_W; The differential voltage is amplified by three operational amplifiers AMP1~3 inside the pre-driver chip (U_phase_differ, V_phase_differ, and W_phase_differ) and then the output voltage is sent to the MCU for acquisition. The voltage output by the operational amplifiers is as follows: AMP_AD_U=VCM+Gain*U_phase_differ; AMP_AD_V=VCM+Gain*V_phase_diffe; AMP_AD_W=VCM+Gain* W_phase_differ; Where VCM is the internal common-mode voltage of the pre-driver chip, and Gain is the gain factor of the operational amplifier in the pre-driver chip.

[0033] like Figure 1 As shown, in this invention, the original phase current sampling resistors R11, R12, and R13 are removed, and the source and drain voltages of the motor's three-phase lower bridge MOS are connected to the differential input terminals of the pre-driven internal current sampling operational amplifiers AMP1~3. Then: For phase U, the voltage ΔV_AMP1_Differ input to the differential input terminal of AMP1 is: △V_AMP1_Differ=Phase_U-GND; For phase V, the voltage ΔV_AMP2_Differ input to the differential input terminal of AMP2 is: △V_AMP2_Differ=Phase_V-GND; For phase W, the voltage input to the differential input terminal of AMP3 is: △V_AMP3_Differ=Phase_W-GND; The voltages input to the MCU ADC module after amplification by operational amplifiers AMP1~3 are as follows: AMP_AD_U=VCM+Gain*(Phase_U-GND); AMP_AD_V=VCM+Gain*(Phase_V-GND); AMP_AD_W=VCM+Gain*(Phase_W-GND); Where Gain is the gain, and the synchronization of the current calculation is used. The op-amps AMP_AD_U~W are input to different ADC groups, and VCM is the intermediate common-mode voltage inside the pre-driver chip.

[0034] To calculate the current for the MCU, it is necessary to estimate the internal resistance of M14~M16 after they are turned on. According to the NMOS on-resistance formula, the on-resistance of MOSFETs M14~M16 is: ; ; ; In the above formula, Electron mobility is a process parameter of MOS. This refers to the gate oxide capacitance of a MOS transistor. VGS_M14, VGS_M15, and VGS_M16 represent the width-to-length ratio of the MOS transistors M14, M15, and M16, respectively. The source of the MOS transistor is grounded. To acquire the gate voltage value of the MOS transistor, the gate of the MOS transistor is connected to the drive outputs of the pre-driver chip, LOO, LWO. The three drive output signals are input to the MOS gate voltage acquisition module for voltage division. The divided voltage is then input to the MCUADC acquisition module. The divided voltage is as follows: AD_LUO = LUO * R2 / (R1 + R2); AD_LVO=LVO*R4 / (R3+R4); AD_LWO=LWO*R6 / (R5+R6); To ensure the accuracy of the sampled voltage, resistors R1 to R6 should be selected with an accuracy of ±1%.

[0035] In the formula, due to electron mobility The threshold voltage Vth is a temperature-dependent parameter, corresponding to different MOS temperatures and electron mobility. Since the threshold voltage Vth varies with temperature, this patented solution collects the temperature of the MOS in real time, allowing the MCU to adjust the electron mobility in real time based on the temperature. The values ​​of the threshold voltage Vth allow for more accurate calculation of the MOS on-resistance. The MOS temperature acquisition module consists of resistors R7~R9 and NTC1~NTC3. R7~R9 are resistors with an accuracy of ±1%, and NTC1~NTC3 are temperature acquisition resistors with a negative temperature coefficient and an accuracy of ±1%, placed close to MOS M14, M15, and M16 respectively. VTK1 is a high-precision and stable pull-up reference power supply. The temperature acquisition voltage values ​​AD_NTC1~AD_NTC3 are shown below: AD_NTC1=VTK1*NTC1 / (R7+NTC1); AD_NTC2=VTK1*NTC2 / (R8+NTC2); AD_NTC3=VTK1*NTC3 / (R9+NTC3); The MCU transmits the temperature data to... Figure 1 The MCU's compensation calculation module uses a lookup table method to obtain the NTC temperature value corresponding to different AD values.

[0036] electron mobility The relationship with temperature is as follows: Where T0 is the ambient temperature. The value represents the electron mobility at room temperature, and 1.5 is the preferred value for K.

[0037] The relationship between the threshold voltage Vth and temperature is as follows: Where Vth0 is the threshold under normal temperature conditions.

[0038] The MCU's compensation calculation module can use a lookup table to find the threshold voltage and electron mobility under the corresponding temperature conditions to estimate the on-resistance of the H-bridge MOS transistors. Adding a temperature-dependent factor, the on-resistances of MOS transistors M14, M15, and M16 under different temperature conditions are as follows: Among them, Ron_M14(T), Ron_M15(T), and Ron_M16(T) are the on-resistances of MOSFETs M14, M15, and M16, respectively; VGS_M14(T), VGS_M15(T), and VGS_M16(T) are the gate-source voltage differences of MOSFETs M14, M15, and M16, respectively.

[0039] Based on the above formula for calculating the on-resistance, the three-phase current values ​​after temperature calibration can be obtained: I_phase_U=(Phase_U-GND) / Ron_M14(T) I_phase_V=(Phase_V-GND) / Ron_M15(T) I_phase_W=(Phase_W-GND) / Ron_M16(T) In the formula, GND is the grounding terminal voltage; I_phase_U, I_phase_V, and I_phase_W are the current values ​​of the three phases U, V, and W, respectively.

[0040] The final three-phase current values ​​(U, V, W) after temperature compensation calculation are as follows: In the formula, R2, R4, and R6 represent the resistance values ​​of resistors R2, R4, and R6, respectively.

[0041] Example 3 This embodiment proposes further optimized and extended implementation schemes to address more complex scenarios or improve performance.

[0042] Extended Circuit Topology: The current monitoring scheme of this invention is not only applicable to standard three-phase H-bridge drives, but can also be extended to multi-phase (such as five-phase, six-phase) motor drives, dual H-bridge redundant drive systems, or single-phase H-bridge drives. Only the corresponding differential amplifier units, grid voltage, and temperature acquisition channels need to be added according to the number of phases; the core calculation and compensation method remains unchanged. This is of direct value for applications requiring higher reliability or specific performance requirements (such as steer-by-wire systems).

[0043] Temperature compensation algorithm optimization: The MCU's compensation calculation module can adopt a more advanced compensation strategy.

[0044] Online self-calibration: When the motor starts or is unloaded, it can perform a cross-validation using a known small current or other sensors (such as a bus current sensor), and conduct a micro-investigation to find table or model parameters to offset errors caused by MOSFET aging and batch differences.

[0045] Interpolation and model fitting: The temperature-parameter lookup table can be replaced by piecewise linear interpolation or higher-order polynomial fitting instead of simple piecewise lookup, so as to improve the calculation accuracy of parameters at non-calibration points (between calibration temperature points).

[0046] Distributed temperature prediction: In applications where the temperatures of the three lower-bridge MOSFETs are highly consistent, it is advisable to reduce the number of temperature sensors (e.g., using two sensors) and estimate the temperature of the third MOSFET using a thermal model to reduce costs.

[0047] Implementation: The compensation calculation module function of the MCU can be implemented entirely by the MCU's general-purpose processor (CPU) through software algorithms, or it can be implemented on an MCU with a hardware floating-point unit (FPU) to improve speed. For applications with extremely high performance requirements, the compensation algorithm can also be implemented in hardware logic in a dedicated digital signal processor (DSP) or field-programmable gate array (FPGA) to obtain the deterministic minimum calculation delay.

[0048] Integration with motor control loop: The high-precision phase current values ​​I_phase_U, I_phase_V, and I_phase_W obtained through compensation calculations in this solution can be directly and seamlessly input into the current loop of motor control algorithms (such as FOC vector control) for closed-loop control. This eliminates the current loop gain error caused by temperature drift in traditional sampling resistor solutions, helping to improve the torque control accuracy and stability of the motor over a wide temperature range.

[0049] Compared with the prior art, the present invention has the following advantages: Cost reduction: The complete elimination of all phase current sampling resistors significantly reduces material costs and enhances the product's market competitiveness.

[0050] Simplified thermal design and improved reliability: Eliminating the sampling resistor, a major heat source, reduces the power consumption and temperature rise of the entire driver board, simplifies the heat dissipation design, and improves the system's reliability and lifespan in high-temperature environments.

[0051] Facilitates miniaturization: It saves space for sampling resistors and related layout wiring, providing greater layout freedom for motor drives, especially for space-constrained designs such as cylindrical types.

[0052] Accuracy Guarantee: A real-time monitoring and compensation mechanism for MOSFET temperature is creatively introduced, solving the core problem of inaccurate current calculation caused by the drift of MOSFET on-resistance with temperature, ensuring that the alternative solution can maintain stable and accurate current acquisition performance under different temperature environments.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the concept and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phase current monitoring circuit for a motor drive bridge with temperature compensation, characterized in that, It includes a microcontroller, a pre-driver chip, an H-bridge lower bridge MOSFET group, a voltage acquisition unit, and a temperature acquisition unit; The H-bridge lower-bridge MOSFET group includes multiple lower-bridge MOSFETs corresponding to each phase of the motor; the pre-drive chip has a built-in differential amplifier unit, the number of which corresponds to the number of lower-bridge MOSFETs, the positive input terminal of each differential amplifier unit is connected to the drain of a corresponding lower-bridge MOSFET, and the negative input terminal of each differential amplifier unit is grounded; the voltage acquisition unit is used to acquire the gate drive voltage of each lower-bridge MOSFET; the temperature acquisition unit is used to acquire the temperature near each lower-bridge MOSFET. The microcontroller is connected to the output terminals of the differential amplifier unit, the voltage acquisition unit, and the temperature acquisition unit, respectively. The microcontroller is configured to calculate the temperature-compensated current values ​​of each phase based on the drain voltage signal output by the differential amplifier unit, the gate voltage signal output by the voltage acquisition unit, the temperature signal output by the temperature acquisition unit, and pre-stored temperature compensation parameters.

2. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 1, characterized in that, The microcontroller includes a compensation calculation module, which is configured as follows: Based on the collected temperature signal, the electron mobility and threshold voltage of the lower bridge MOSFET are determined. Based on the determined electron mobility, threshold voltage, and acquired gate voltage signal, the real-time on-resistance value of the lower bridge MOS transistor at the current temperature is calculated using the MOS transistor on-resistance model. Based on the drain voltage signal output by the differential amplifier unit and the calculated real-time on-resistance value, the phase current value after temperature compensation is calculated.

3. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 2, characterized in that, The on-resistance model of the MOS transistor is as follows: ； in, This is the real-time on-resistance value. For electron mobility, The capacitance of the gate oxide layer of the MOSFET. VGS is the width-to-length ratio of the MOSFET, Vth is the value of the gate voltage signal, and Vth is the threshold voltage.

4. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 3, characterized in that, The formula for calculating the phase current value after temperature compensation is as follows: I_phase = V_D / Ron(T); Where I_phase is the phase current value after temperature compensation, and V_D is the value of the drain voltage signal.

5. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 2, characterized in that, The compensation calculation module has a pre-stored temperature parameter lookup table, which is used to store the mapping relationship between different temperature signal values ​​and the corresponding electron mobility and threshold voltage.

6. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 5, characterized in that, The data in the temperature parameter lookup table were obtained through experimental calibration, and the relationship between electron mobility and temperature contained in the temperature parameter lookup table satisfies the following formula: Where T is the temperature to be checked. For the electron mobility to be investigated, For reference temperature, Reference temperature electron mobility at that point This is an empirical constant.

7. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 1, characterized in that, The voltage acquisition unit includes multiple voltage divider circuits. The input of each voltage divider circuit is connected to the gate drive signal terminal of a lower bridge MOSFET, and the output is connected to the analog-to-digital converter interface of the microcontroller.

8. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 1, characterized in that, The temperature acquisition unit includes multiple temperature sensor circuits, each temperature sensor circuit containing at least one thermistor with a negative temperature coefficient. The thermistor is located near a lower bridge MOSFET and connected in series with a pull-up resistor to a reference voltage source. The voltage divider node between the thermistor and the pull-up resistor is connected to the analog-to-digital converter interface of the microcontroller.

9. The phase current monitoring circuit of the motor drive bridge with temperature compensation according to claim 7, characterized in that, The pre-drive chip is a motor pre-drive chip that integrates multiple differential operational amplifiers, and the differential amplification unit is the differential operational amplifier.

10. A method for monitoring the phase current of a motor drive bridge with temperature compensation, characterized in that, The circuit is applied to the phase current monitoring circuit as described in any one of claims 1-9, comprising: The drain voltage signal of each phase of the motor's lower bridge MOSFET, the gate voltage signal of each lower bridge MOSFET, and the real-time temperature of each lower bridge MOSFET are collected synchronously. Based on the collected real-time temperature, gate voltage signals, and pre-stored temperature-related MOS transistor process parameters, the real-time on-resistance of each lower-bridge MOS transistor at the current temperature is calculated. Based on the acquired drain voltage signal and the calculated real-time on-resistance, the temperature-compensated current values ​​for each phase are calculated.

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