A feedback compensation circuit for permanent magnet synchronous motor control

Abstract

The application discloses a feedback compensation circuit for permanent magnet synchronous motor control, comprising a phase current sampling module, a temperature detection and compensation module, an inverse electromotive force detection module, and a double operational amplifier chip integrating a first operational amplifier and a second operational amplifier; the application realizes synchronous compensation of temperature feedback and inverse electromotive force detection through a hardware circuit, completely avoids the hysteresis of software compensation, effectively offsets the magnetic field feedback deviation and inverse electromotive force detection distortion caused by temperature drift, greatly improves rotor position recognition accuracy and stability of motor sensorless control, and has high circuit integration and strong anti-interference capability, and is suitable for various permanent magnet synchronous motor driving scenes.

Description

Technical Field

[0001] This invention belongs to the field of motor drive control technology, and relates to a feedback compensation circuit for permanent magnet synchronous motor control. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs), with their advantages of high efficiency, high power density, low torque ripple, and low noise, have become core power components in industrial automation, new energy vehicles, home appliance drives, and robotics. Field-oriented control is the mainstream control scheme for PMSMs, relying on precise phase current sampling (i.e., magnetic field feedback signal) to achieve closed-loop control. Meanwhile, sensorless control technology identifies the rotor position by detecting the zero-crossing point of the motor winding back electromotive force, eliminating the need for mechanical position sensors and significantly reducing system cost, size, and failure rate, thus becoming the mainstream trend in the industry.

[0003] In practical engineering applications, the winding copper resistance and the on-resistance of the drive power devices will show a significant positive temperature coefficient change with the increase of temperature during motor operation. This directly leads to baseline offset and amplitude distortion in phase current sampling (magnetic field feedback), which in turn causes zero-crossing offset and waveform clipping in back EMF detection. Ultimately, this leads to incorrect commutation timing, torque fluctuation, increased operating noise, and even high-speed step loss, seriously affecting the stability and reliability of motor control.

[0004] Current compensation schemes for temperature drift primarily rely on software: temperature sensors collect motor temperature data, and then the MCU uses a preset compensation algorithm to retrospectively correct the calculated back EMF. However, software compensation has inherent drawbacks: First, it suffers from severe lag, failing to synchronize with the microsecond-level transient changes in phase current and back EMF during high-speed motor operation, limiting compensation accuracy to the MCU's processing speed and PWM cycle. Second, the algorithm is highly complex, requiring parameter calibration for different motors and operating conditions, resulting in poor adaptability. Third, existing hardware circuits often separate phase current sampling, temperature detection, and back EMF detection into independent functional modules, leading to complex circuit structures, redundant components, long signal transmission paths, and weak anti-interference capabilities, making it impossible to achieve hardware-level synchronous real-time compensation and failing to meet the requirements of high-precision, high-dynamic-response motor control. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a feedback compensation circuit for permanent magnet synchronous motor control. This circuit integrates three core functions—phase current sampling, real-time temperature detection, and back EMF synchronous compensation—through a pure hardware circuit. It achieves real-time synchronous hardware-level temperature feedback compensation, completely resolving the lag issue of existing software compensation. This effectively offsets magnetic field feedback deviations and back EMF detection distortions caused by temperature drift, while simplifying the circuit structure, improving system integration and anti-interference capabilities, and ensuring the stability and dynamic response performance of sensorless control of the permanent magnet synchronous motor.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A feedback compensation circuit for controlling a permanent magnet synchronous motor includes a phase current sampling module, a temperature detection and compensation module, a back electromotive force (EMF) detection module, and a dual operational amplifier chip U integrating a first operational amplifier and a second operational amplifier. The phase current sampling module is a magnetic field feedback unit for the motor's field-oriented control, including a differential filtering unit, a first differential amplification unit, and a second signal conditioning unit, used to acquire the phase current signal of the permanent magnet synchronous motor windings and output a first sampling signal IW and a bus current sampling signal AD_IBUS. The temperature detection and compensation module includes a sixth current-limiting resistor R14, a negative temperature coefficient thermistor NTC, and a compensation signal coupling unit, used to acquire the motor temperature signal and output a compensation bias signal linearly correlated with the motor temperature. The back EMF detection module includes a third operational amplifier U2. The dual operational amplifier chip U is used to synchronously receive the IW, AD_IBUS, and compensation bias signals, and outputs a back electromotive force detection signal BEMF_W with real-time temperature compensation. The dual operational amplifier chip U is powered by a single power supply. The differential filter unit is connected to the motor current sampling terminal and the differential input terminal of the first operational amplifier. The first differential amplification unit works with the first operational amplifier to output IW. The second signal conditioning unit is connected to the output terminal of the first operational amplifier and works with the second operational amplifier to output AD_IBUS. The input terminal of the temperature detection and compensation module is connected to the output terminal of the second operational amplifier. The NTC is positioned close to the motor windings or power devices. The compensation signal coupling unit is connected to the non-inverting input terminal of the third operational amplifier U2. The inverting input terminal of the third operational amplifier U2 is connected to AD_IBUS, and the output BEMF_W is used for motor rotor position detection and commutation control.

[0008] Furthermore, the differential filtering unit includes a first filter capacitor C1, a second filter capacitor C2, a first current-limiting resistor R1, and a second current-limiting resistor R2; the first sampling input terminal COMB is electrically connected to the first terminal of the first filter capacitor C1 and the first terminal of the first current-limiting resistor R1, respectively; the second sampling input terminal NW is electrically connected to the first terminal of the second filter capacitor C2 and the first terminal of the second current-limiting resistor R2, respectively; the second terminals of the first filter capacitor C1 and the second terminal of the second filter capacitor C2 are both grounded; the second terminal of the first current-limiting resistor R1 is electrically connected to the inverting input terminal INA- of the first operational amplifier, and the second terminal of the second current-limiting resistor R2 is electrically connected to the non-inverting input terminal INA+ of the first operational amplifier, thus forming a dual-channel RC low-pass filter circuit.

[0009] Furthermore, the first differential amplifier unit includes a first feedback resistor R3, a first bias resistor R4, and a first bias voltage divider network. The first bias voltage divider network includes a second voltage divider resistor R5 and a third voltage divider resistor R6. The first end of the first feedback resistor R3 is electrically connected to the output terminal OUTA of the first operational amplifier, and the second end of the first feedback resistor R3 is electrically connected to the inverting input terminal INA- of the first operational amplifier, forming a closed-loop negative feedback circuit. The first end of the first bias resistor R4 is electrically connected to the non-inverting input terminal INA+ of the first operational amplifier, and the second end of the first bias resistor R4 is electrically connected to the voltage divider output terminal of the first bias voltage divider network. The first end of the second voltage divider resistor R5 is connected to the power supply VDD, and the second end of the second voltage divider resistor R5 is electrically connected to the first end of the third voltage divider resistor R6. The connection point between the two is the voltage divider output terminal of the first bias voltage divider network, and the second end of the third voltage divider resistor R6 is grounded. The output terminal OUTA of the first operational amplifier is connected in series with a third current limiting resistor R7 to output the first sampling signal IW.

[0010] Furthermore, the second signal conditioning unit includes an input coupling resistor R0, a second feedback resistor R8, a second pull-down resistor R9, a second bias voltage divider network, a fourth current-limiting resistor R12, and a fifth current-limiting resistor R13. The second bias voltage divider network includes a fourth voltage divider resistor R10 and a fifth voltage divider resistor R11. The first terminal of the input coupling resistor R0 is electrically connected to the output terminal OUTA of the first operational amplifier, and the second terminal of the input coupling resistor R0 is electrically connected to the inverting input terminal INB- of the second operational amplifier. The first terminal of the fourth voltage divider resistor R10 is connected to the power supply VDD. The second end of the second voltage divider is electrically connected to the first end of the fifth voltage divider resistor R11. The connection point between the two is the voltage divider output terminal of the second bias voltage divider network. The second end of the fifth voltage divider resistor R11 is grounded. The voltage divider output terminal of the second bias voltage divider network is electrically connected to the non-inverting input terminal INB+ of the second operational amplifier. The first end of the second pull-down resistor R9 is electrically connected to the inverting input terminal INB- of the second operational amplifier. The second end of the second pull-down resistor R9 is grounded. The first end of the second feedback resistor R8 is electrically connected to the output terminal OUTB of the second operational amplifier. The second end of the second feedback resistor R8 is electrically connected to the inverting input terminal INB- of the second operational amplifier, forming a closed-loop negative feedback circuit. The output terminal OUTB of the second operational amplifier is electrically connected to the first end of the fourth current limiting resistor R12. The second end of the fourth current limiting resistor R12 is electrically connected to the first end of the fifth current limiting resistor R13 and the AD sampling output terminal AD_IBUS, respectively. The second end of the fifth current limiting resistor R13 is grounded.

[0011] Furthermore, the compensation signal coupling unit includes a coupling resistor R21 and a filter capacitor C3; the first end of the sixth current-limiting resistor R14 is electrically connected to the output terminal OUTB of the second operational amplifier, and the second end of the sixth current-limiting resistor R14 is electrically connected to the temperature detection signal terminal; the temperature detection signal terminal is electrically connected to the first end of the negative temperature coefficient thermistor NTC and the first end of the coupling resistor R21, and the second end of the negative temperature coefficient thermistor NTC is grounded; the second end of the coupling resistor R21 is electrically connected to the non-inverting input terminal of the third operational amplifier U2, the first end of the filter capacitor C3 is connected to the second end of the coupling resistor R21, and the second end of the filter capacitor C3 is grounded.

[0012] Furthermore, the back EMF detection module also includes a third feedback resistor R15, a seventh current-limiting resistor R16, an eighth current-limiting resistor R17, a third bias voltage divider network, and a ninth current-limiting resistor R20. The third bias voltage divider network includes a sixth voltage divider resistor R18 and a seventh voltage divider resistor R19. The first terminal of the seventh current-limiting resistor R16 is connected to the AD_IBUS signal, and the second terminal of the seventh current-limiting resistor R16 is electrically connected to the inverting input terminal of the third operational amplifier U2. The first terminal of the third feedback resistor R15 is electrically connected to the output terminal of the third operational amplifier U2, and the second terminal of the third feedback resistor R15 is electrically connected to the inverting input terminal of the third operational amplifier U2, forming a closed-loop negative feedback loop. The circuit consists of: the first terminal of the eighth current-limiting resistor R17 connected to the IW signal, and the second terminal of the eighth current-limiting resistor R17 electrically connected to the non-inverting input terminal of the third operational amplifier U2; the first terminal of the sixth voltage-dividing resistor R18 connected to the power supply VDD, and the second terminal of the sixth voltage-dividing resistor R18 electrically connected to the first terminal of the seventh voltage-dividing resistor R19, with the connection point being the voltage divider output terminal of the third bias voltage divider network; the second terminal of the seventh voltage divider resistor R19 grounded; the voltage divider output terminal of the third bias voltage divider network electrically connected to the non-inverting input terminal of the third operational amplifier U2 through the ninth current-limiting resistor R20; and the output terminal of the third operational amplifier U2 outputs a temperature-compensated back electromotive force detection signal BEMF_W.

[0013] Furthermore, the second voltage divider resistor R5 and the third voltage divider resistor R6 have the same resistance value, providing a DC common-mode bias voltage of 1 / 2 VDD for the first operational amplifier. The differential gain of the first operational amplifier is the ratio of the resistance values ​​of the first feedback resistor R3 and the first current-limiting resistor R1.

[0014] Furthermore, the sixth voltage divider resistor R18 and the seventh voltage divider resistor R19 have the same resistance value, providing a basic DC common-mode bias voltage of 1 / 2 VDD for the third operational amplifier U2. The differential amplification factor of the third operational amplifier U2 is the ratio of the resistance values ​​of the third feedback resistor R15 and the seventh current-limiting resistor R16.

[0015] Furthermore, both the dual operational amplifier chip U and the third operational amplifier U2 are rail-to-rail input / output operational amplifiers, with a power supply VDD of 3.3V or 5V, which is fully compatible with the power supply voltage of the motor control MCU.

[0016] Furthermore, the temperature detection signal terminal is connected to the ADC sampling port of the MCU for real-time monitoring of motor temperature and overheat protection; the AD_IBUS signal is connected to the ADC sampling port of the MCU for field-oriented closed-loop control and overcurrent protection of the motor.

[0017] In summary, the advantages of this invention are: This invention uses a non-inverting summation differential amplifier circuit to directly and synchronously superimpose the temperature detection signal onto the bias circuit of the back EMF detection. Temperature changes and back EMF compensation are executed synchronously, and the compensation response time is consistent with the operational amplifier response speed (microsecond level). This completely avoids the algorithm delay and PWM period limitations of software compensation, perfectly adapts to the high dynamic response requirements of high-speed motor operation, and truly realizes real-time back EMF compensation with synchronous hardware control, solving the core pain points of existing technologies.

[0018] This invention uses a negative temperature coefficient thermistor close to the motor windings / power devices to collect the motor's operating temperature in real time. It converts temperature changes into linear adjustments to the bias voltage, accurately offsetting the baseline shift in magnetic field feedback (phase current sampling) and back EMF detection distortion caused by winding resistance and power device temperature drift. This solves the temperature drift problem at the hardware level, significantly improves the accuracy of rotor position recognition, and fundamentally avoids torque fluctuations, noise, and step loss caused by commutation errors.

[0019] This invention uses a single dual operational amplifier chip to achieve differential amplification and signal conditioning of phase current. The single chip completes the acquisition of magnetic field feedback signal and output of temperature excitation signal. Combined with a single operational amplifier, it realizes back electromotive force detection with temperature compensation. The circuit structure is simplified, the number of components is small, which greatly reduces the system cost and size. At the same time, it shortens the signal transmission path and significantly improves the circuit's anti-interference capability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the circuit structure of the phase current sampling module of the present invention.

[0021] Figure 2 This is a schematic diagram of the circuit structure of the back electromotive force detection module of the present invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The technical solutions described in this embodiment are a clear and complete explanation of the present invention, but not a limitation on the scope of protection of the present invention. Non-creative adjustments made by those skilled in the art based on the core concept of the present invention are all within the scope of protection of the present invention.

[0023] This embodiment provides a feedback compensation circuit for permanent magnet synchronous motor control, applied to a sensorless field orientation control system for permanent magnet synchronous motors. The core is to achieve real-time synchronous compensation of back electromotive force based on temperature feedback through a pure hardware circuit, solving the problems of insufficient accuracy in field feedback and back electromotive force detection caused by software compensation lag and temperature drift in the prior art.

[0024] In this embodiment, the dual operational amplifier chip U is an industrial-grade rail-to-rail input / output dual operational amplifier TP1542, and the third operational amplifier U2 is a single operational amplifier TP1541 from the same series. The power supply VDD is 3.3V, which is fully compatible with the power supply voltage of the motor control MCU and meets the single power supply requirements.

[0025] The pin definitions of the dual operational amplifier chip U are as follows: pin 1 is the output terminal OUTA of the first operational amplifier, pin 2 is the inverting input terminal INA- of the first operational amplifier, pin 3 is the non-inverting input terminal INA+ of the first operational amplifier, pin 4 is the negative terminal of the chip power supply VCC- (grounded GND), pin 5 is the inverting input terminal INB- of the second operational amplifier, pin 6 is the non-inverting input terminal INB+ of the second operational amplifier, pin 7 is the output terminal OUTB of the second operational amplifier, and pin 8 is the positive terminal of the chip power supply VCC+ (connected to the power supply VDD).

[0026] The pin definitions of the third operational amplifier U2 are as follows: pin 1 is the output terminal of the operational amplifier, pin 2 is the inverting input terminal of the operational amplifier, pin 3 is the non-inverting input terminal of the operational amplifier, pin 4 is the negative power supply terminal of the operational amplifier (GND), and pin 8 is the positive power supply terminal of the operational amplifier (connected to the power supply VDD). It adopts a single power supply mode.

[0027] The feedback compensation circuit described in this embodiment includes: 1. Phase current sampling module, including differential filtering unit 11, first differential amplification unit 12, and second signal conditioning unit 13, is used to collect the phase current signal of the W phase winding of permanent magnet synchronous motor, and output W phase current sampling signal IW and bus current sampling signal AD_IBUS to provide accurate magnetic field feedback signal for motor field orientation control.

[0028] The differential filtering unit 11 includes a first filter capacitor C1, a second filter capacitor C2, a first current-limiting resistor R1, and a second current-limiting resistor R2. The first sampling input terminal COMB is connected to the lower end of the sampling resistor of the lower bridge arm of the motor's W-phase winding, and the second sampling input terminal NW is connected to the upper end of the sampling resistor of the lower bridge arm of the motor's W-phase winding. The two input terminals acquire the differential voltage signal (corresponding to the phase current of the W-phase winding) across the sampling resistors. The first sampling input terminal COMB is electrically connected to the first terminal of the first filter capacitor C1 and the first terminal of the first current-limiting resistor R1, respectively; the second sampling input terminal NW is electrically connected to the first terminal of the second filter capacitor C2 and the first terminal of the second current-limiting resistor R2, respectively; the second terminals of the first filter capacitor C1 and the second terminal of the second filter capacitor C2 are both grounded to GND; the second terminal of the first current-limiting resistor R1 is electrically connected to the inverting input terminal INA- of the first operational amplifier, and the second terminal of the second current-limiting resistor R2 is electrically connected to the non-inverting input terminal INA+ of the first operational amplifier.

[0029] The first differential amplifier unit 12 includes a first feedback resistor R3, a first bias resistor R4, and a first bias voltage divider network. The first bias voltage divider network includes a second voltage divider resistor R5 and a third voltage divider resistor R6. The first end of the first feedback resistor R3 is electrically connected to the output terminal OUTA of the first operational amplifier, and the second end of the first feedback resistor R3 is electrically connected to the inverting input terminal INA- of the first operational amplifier, forming a closed-loop negative feedback differential amplifier circuit. The first end of the first bias resistor R4 is electrically connected to the non-inverting input terminal INA+ of the first operational amplifier, and the second end of the first bias resistor R4 is electrically connected to the voltage divider output terminal of the first bias voltage divider network. The first end of the second voltage divider resistor R5 is connected to the power supply VDD, and the second end of the second voltage divider resistor R5 is electrically connected to the first end of the third voltage divider resistor R6. The connection point between the two is the voltage divider output terminal of the first bias voltage divider network, and the second end of the third voltage divider resistor R6 is grounded to GND. The output terminal OUTA of the first operational amplifier is connected in series with the third current limiting resistor R7 to output the first sampling signal IW.

[0030] In this embodiment, both the second voltage divider resistor R5 and the third voltage divider resistor R6 have a resistance of 10kΩ, providing a DC common-mode bias voltage of 1.65V (1 / 2 VDD) for the first operational amplifier. This ensures that, under single-supply operation, both the positive and negative half-cycles of the bidirectional phase current sampling signal can be fully linearly amplified, avoiding clipping distortion of the negative half-cycle. The differential gain of the first operational amplifier is R3 / R1. In this embodiment, R1=R2=1kΩ and R3=10kΩ, resulting in a gain of 10, which can amplify the weak sampling signal at the millivolt level to the volt level, adapting to the processing requirements of subsequent circuits.

[0031] The second signal conditioning unit 13 includes an input coupling resistor R0, a second feedback resistor R8, a second pull-down resistor R9, a second bias voltage divider network, a fourth current limiting resistor R12, and a fifth current limiting resistor R13. The second bias voltage divider network includes a fourth voltage divider resistor R10 and a fifth voltage divider resistor R11. The first terminal of the input coupling resistor R0 is electrically connected to the output terminal OUTA of the first operational amplifier, and the second terminal of the input coupling resistor R0 is electrically connected to the inverting input terminal INB- of the second operational amplifier. The first terminal of the fourth voltage divider resistor R10 is connected to the power supply VDD, and the second terminal of the fourth voltage divider resistor R10 is electrically connected to the first terminal of the fifth voltage divider resistor R11. The connection point between the two is the voltage divider output terminal of the second bias voltage divider network, and the second terminal of the fifth voltage divider resistor R11 is grounded to GND. The voltage divider output terminal of the second bias voltage divider network is electrically connected to the non-inverting input terminal INB+ of the second operational amplifier. The first terminal of the second pull-down resistor R9 is electrically connected to the inverting input terminal INB- of the second operational amplifier, and the second terminal of the second pull-down resistor R9 is grounded to GND. The first terminal of the second feedback resistor R8 is electrically connected to the output terminal OUTB of the second operational amplifier, and the second terminal of the second feedback resistor R8 is electrically connected to the inverting input terminal INB- of the second operational amplifier. - Electrically connected to form a closed-loop negative feedback amplification circuit; the output terminal OUTB of the second operational amplifier is electrically connected to the first terminal of the fourth current-limiting resistor R12, and the second terminal of the fourth current-limiting resistor R12 is electrically connected to the first terminal of the fifth current-limiting resistor R13 and the AD sampling output terminal AD_IBUS respectively; the second terminal of the fifth current-limiting resistor R13 is grounded to GND.

[0032] In this embodiment, the fourth voltage divider resistor R10 and the fifth voltage divider resistor R11 both have a resistance of 10kΩ, providing a DC common-mode bias voltage of 1.65V for the second operational amplifier; R0=1kΩ, R8=10kΩ, R9=1kΩ, the second operational amplifier performs secondary gain adjustment and level offset adaptation on the phase current signal output by the first operational amplifier, and the output signal is divided by R12 and R13 to output an AD_IBUS signal that is completely matched with the range (0~3.3V) of the MCU 12-bit ADC, realizing the digital acquisition of the magnetic field feedback signal.

[0033] 2. Temperature detection and compensation module, including a sixth current-limiting resistor R14, a negative temperature coefficient thermistor NTC, and a compensation signal coupling unit 21. The compensation signal coupling unit 21 includes a coupling resistor R21 and a filter capacitor C3. The first end of the sixth current-limiting resistor R14 is electrically connected to the output terminal OUTB of the second operational amplifier, and the second end of the sixth current-limiting resistor R14 is electrically connected to the temperature detection signal terminal. The temperature detection signal terminal is electrically connected to the first end of the negative temperature coefficient thermistor NTC and the first end of the coupling resistor R21, respectively. The second end of the negative temperature coefficient thermistor NTC is grounded to GND. The second end of the coupling resistor R21 is electrically connected to the non-inverting input terminal of the third operational amplifier U2. The first end of the filter capacitor C3 is connected to the second end of the coupling resistor R21, and the second end of the filter capacitor C3 is grounded to GND.

[0034] In this embodiment, the negative temperature coefficient thermistor (NTC) is an industrial-grade thermistor with a 10kΩ / 25℃ and a B value of 3950K. It is positioned close to the W-phase winding of the motor and the driving MOSFET. Its resistance decreases linearly with increasing motor temperature and increases linearly with decreasing temperature. The stable voltage output from the second operational amplifier, after being current-limited by R14, serves as the excitation source for the NTC, forming a temperature detection voltage on the NTC that changes linearly with temperature. This voltage is fed into the ADC port of the MCU to achieve real-time monitoring of the motor temperature and overheat protection. On the other hand, it is fed into the non-inverting input of the third operational amplifier of the back EMF detection module through the compensation signal coupling unit to form a compensation bias signal linearly related to the temperature.

[0035] 3. Back EMF detection module, including a third operational amplifier U2, a third feedback resistor R15, a seventh current-limiting resistor R16, an eighth current-limiting resistor R17, a third bias voltage divider network, and a ninth current-limiting resistor R20. The third bias voltage divider network includes a sixth voltage divider resistor R18 and a seventh voltage divider resistor R19. The first terminal of the seventh current-limiting resistor R16 is connected to the AD_IBUS signal, and the second terminal of the seventh current-limiting resistor R16 is electrically connected to the inverting input terminal of the third operational amplifier U2. The first terminal of the third feedback resistor R15 is electrically connected to the output terminal of the third operational amplifier U2, and the second terminal of the third feedback resistor R15 is electrically connected to the inverting input terminal of the third operational amplifier U2, forming a closed-loop negative feedback differential amplifier circuit. The first terminal of the eighth current-limiting resistor R17 is connected to the IW signal, and the second terminal of the eighth current-limiting resistor R17 is electrically connected to the non-inverting input terminal of the third operational amplifier U2; the first terminal of the sixth voltage-dividing resistor R18 is connected to the power supply VDD, and the second terminal of the sixth voltage-dividing resistor R18 is electrically connected to the first terminal of the seventh voltage-dividing resistor R19. The connection node between the two is the voltage divider output terminal of the third bias voltage divider network, and the second terminal of the seventh voltage divider resistor R19 is grounded to GND; the voltage divider output terminal of the third bias voltage divider network is electrically connected to the non-inverting input terminal of the third operational amplifier U2 through the ninth current-limiting resistor R20; the output terminal of the coupling resistor R21 of the compensation signal coupling unit is also electrically connected to the non-inverting input terminal of the third operational amplifier U2; the output terminal of the third operational amplifier U2 outputs a back electromotive force detection signal BEMF_W with real-time temperature compensation.

[0036] In this embodiment, the sixth voltage divider resistor R18 and the seventh voltage divider resistor R19 both have a resistance of 10kΩ, providing a basic DC common-mode bias voltage of 1.65V for the third operational amplifier U2, so that the linear amplification range of the circuit completely covers the positive and negative half-cycles of the back EMF signal; R16=1kΩ, R15=10kΩ, the differential amplification factor of the third operational amplifier U2 is 10 times; R17=1kΩ, R20=1kΩ, R21=1kΩ, the three signals (IW, basic bias, and temperature compensation signal) are summed and superimposed in phase at the non-inverting input of the third operational amplifier, completing the synchronous fusion of the temperature compensation signal and the back EMF detection signal.

[0037] In the feedback compensation circuit described in this embodiment, the magnetic field feedback includes: a differential filtering unit performs dual-channel RC low-pass filtering on the differential input signals COMB and NW across the sampling resistor of the motor's W phase to filter out high-frequency electromagnetic interference generated by the PWM switch driven by the motor; the filtered differential signal is then current-limited and sent to the differential input terminal of the first operational amplifier; the first operational amplifier performs linear amplification of the weak phase current differential signal at the millivolt level with a fixed gain through a closed-loop negative feedback circuit; one path of the amplified signal outputs the IW signal through R7 and is sent to the back EMF detection module; the other path is sent to the inverting input terminal of the second operational amplifier through R0.

[0038] The second operational amplifier performs secondary gain adjustment and level adaptation on the phase current signal output by the first operational amplifier, adjusting the signal to the linear input range of the MCU ADC. The output signal is divided by R12 and R13 to obtain the AD_IBUS signal. This signal is sent to the MCU as the core magnetic field feedback signal for field-oriented control, realizing closed-loop torque control and overcurrent protection of the motor.

[0039] Furthermore, the back EMF detection includes: the third operational amplifier U2 forms a non-inverting summing differential amplifier circuit with DC common-mode bias; the AD_IBUS signal (bus current feedback signal) is sent to the inverting input terminal via R16, and the IW signal (W-phase current feedback signal) is sent to the non-inverting input terminal via R17; the circuit accurately amplifies the differential components of the two signals to extract the back EMF signal BEMF_W of the motor's W-phase winding; after this signal is sent to the MCU, the real-time position of the motor rotor can be identified by detecting the zero-crossing point of the back EMF, providing a core basis for the sensorless control of the winding commutation of the permanent magnet synchronous motor, and realizing the stable closed-loop operation of the motor.

[0040] Furthermore, the core temperature real-time synchronous compensation includes: During motor operation, an increase in temperature leads to an increase in the winding copper resistance and the on-resistance of the drive power devices, causing a positive shift in the baseline of phase current sampling. This, in turn, causes the zero-crossing point of the back EMF detection to be advanced and the amplitude to be distorted, resulting in commutation errors. In this invention, when the motor temperature rises, the NTC resistance close to the winding / power devices decreases linearly with the temperature increase, and the voltage at the temperature detection signal terminal decreases linearly accordingly. This decreased voltage is synchronously sent to the non-inverting input of the third operational amplifier U2 through the coupling resistor R21, linearly lowering the total bias voltage at the non-inverting input to accurately offset the positive shift in the sampling baseline caused by the temperature increase. Conversely, when the motor temperature decreases, the NTC resistance increases linearly, and the voltage at the temperature detection signal terminal increases accordingly, synchronously raising the total bias voltage at the non-inverting input of the third operational amplifier to offset the negative shift in the sampling baseline at low temperatures.

[0041] The entire compensation process is completed in real time synchronously through pure hardware circuits, without the computational delay of software algorithms. The compensation response time is consistent with the response speed of the operational amplifier (≤1μs), which is fully adapted to the microsecond-level dynamic changes during high-speed motor operation. It truly realizes real-time compensation of back EMF by synchronous hardware control, fundamentally solving the problems of magnetic field feedback deviation and insufficient back EMF detection accuracy caused by temperature drift.

Claims

1. A feedback compensation circuit for controlling a permanent magnet synchronous motor, characterized in that, It includes a phase current sampling module, a temperature detection and compensation module, a back EMF detection module, and a dual operational amplifier chip integrating a first operational amplifier and a second operational amplifier; The phase current sampling module is a magnetic field feedback unit for the magnetic field orientation control of the motor, including a differential filtering unit, a first differential amplification unit, and a second signal conditioning unit, used to collect the phase current signal of the permanent magnet synchronous motor winding and output the first sampling signal and the bus current sampling signal. The temperature detection and compensation module includes a sixth current-limiting resistor, a negative temperature coefficient thermistor, and a compensation signal coupling unit, which are used to acquire motor temperature signals and output a compensation bias signal that is linearly related to motor temperature. The back EMF detection module includes a third operational amplifier, which is used to simultaneously receive the first sampling signal, the bus current sampling signal and the compensation bias signal, and output a W back EMF detection signal with real-time temperature compensation. The dual operational amplifier chip is powered by a single power supply. The differential filtering unit is connected to the motor current sampling terminal and the differential input terminal of the first operational amplifier. The first differential amplification unit works with the first operational amplifier to output the first sampling signal. The second signal conditioning unit is connected to the output terminal of the first operational amplifier and works with the second operational amplifier to output the bus current sampling signal. The input terminal of the temperature detection and compensation module is connected to the output terminal of the second operational amplifier. The negative temperature coefficient thermistor is placed close to the motor winding or power device. The compensation signal coupling unit is connected to the non-inverting input terminal of the third operational amplifier. The inverting input terminal of the third operational amplifier is connected to the bus current sampling signal. The output W back electromotive force detection signal is used for motor rotor position detection and commutation control.

2. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, The differential filtering unit includes a first filter capacitor, a second filter capacitor, a first current-limiting resistor, and a second current-limiting resistor; the first sampling input terminal is electrically connected to the first terminal of the first filter capacitor and the first terminal of the first current-limiting resistor, respectively; the second sampling input terminal is electrically connected to the first terminal of the second filter capacitor and the first terminal of the second current-limiting resistor, respectively; the second terminals of the first and second filter capacitors are both grounded; the second terminal of the first current-limiting resistor is electrically connected to the inverting input terminal of the first operational amplifier, and the second terminal of the second current-limiting resistor is electrically connected to the non-inverting input terminal of the first operational amplifier, thus forming a dual-channel RC low-pass filter circuit.

3. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, The first differential amplifier unit includes a first feedback resistor, a first bias resistor, and a first bias voltage divider network. The first bias voltage divider network includes a second voltage divider resistor and a third voltage divider resistor. The first end of the first feedback resistor is electrically connected to the output terminal of the first operational amplifier, and the second end of the first feedback resistor is electrically connected to the inverting input terminal of the first operational amplifier, forming a closed-loop negative feedback circuit. The first end of the first bias resistor is electrically connected to the non-inverting input terminal of the first operational amplifier, and the second end of the first bias resistor is electrically connected to the voltage divider output terminal of the first bias voltage divider network. The first end of the second voltage divider resistor is connected to the power supply, and the second end of the second voltage divider resistor is electrically connected to the first end of the third voltage divider resistor. The connection node between the two is the voltage divider output terminal of the first bias voltage divider network, and the second end of the third voltage divider resistor is grounded. The output terminal of the first operational amplifier is connected in series with a third current-limiting resistor to output a first sampling signal.

4. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, The second signal conditioning unit includes an input coupling resistor, a second feedback resistor, a second pull-down resistor, a second bias voltage divider network, a fourth current-limiting resistor, and a fifth current-limiting resistor. The second bias voltage divider network includes a fourth voltage divider resistor and a fifth voltage divider resistor. The first end of the input coupling resistor is electrically connected to the output terminal of the first operational amplifier, and the second end of the input coupling resistor is electrically connected to the inverting input terminal of the second operational amplifier. The first end of the fourth voltage divider resistor is connected to the power supply, and the second end of the fourth voltage divider resistor is electrically connected to the first end of the fifth voltage divider resistor. The connection point between the two is the voltage divider output terminal of the second bias voltage divider network. The second end of the fifth voltage divider resistor is connected to... Ground; the voltage divider output of the second bias voltage divider network is electrically connected to the non-inverting input of the second operational amplifier; the first end of the second pull-down resistor is electrically connected to the inverting input of the second operational amplifier, and the second end of the second pull-down resistor is grounded; the first end of the second feedback resistor is electrically connected to the output of the second operational amplifier, and the second end of the second feedback resistor is electrically connected to the inverting input of the second operational amplifier, forming a closed-loop negative feedback circuit; the output of the second operational amplifier is electrically connected to the first end of the fourth current-limiting resistor, and the second end of the fourth current-limiting resistor is electrically connected to the first end of the fifth current-limiting resistor and the AD sampling output; the second end of the fifth current-limiting resistor is grounded.

5. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, The compensation signal coupling unit includes a coupling resistor and a filter capacitor; the first end of the sixth current-limiting resistor is electrically connected to the output terminal of the second operational amplifier, and the second end of the sixth current-limiting resistor is electrically connected to the temperature detection signal terminal; the temperature detection signal terminal is electrically connected to the first end of the negative temperature coefficient thermistor and the first end of the coupling resistor, respectively, and the second end of the negative temperature coefficient thermistor is grounded; the second end of the coupling resistor is electrically connected to the non-inverting input terminal of the third operational amplifier, the first end of the filter capacitor is connected to the second end of the coupling resistor, and the second end of the filter capacitor is grounded.

6. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, The back EMF detection module further includes a third feedback resistor, a seventh current-limiting resistor, an eighth current-limiting resistor, a third bias voltage divider network, and a ninth current-limiting resistor. The third bias voltage divider network includes a sixth voltage divider resistor and a seventh voltage divider resistor. The first end of the seventh current-limiting resistor is connected to a signal, and the second end of the seventh current-limiting resistor is electrically connected to the inverting input of the third operational amplifier. The first end of the third feedback resistor is electrically connected to the output of the third operational amplifier, and the second end of the third feedback resistor is electrically connected to the inverting input of the third operational amplifier, forming a closed-loop negative feedback circuit. The first end of the eighth current-limiting resistor is connected to a signal, and the second end of the eighth current-limiting resistor is electrically connected to the non-inverting input of the third operational amplifier. The first end of the sixth voltage divider resistor is connected to the power supply, and the second end of the sixth voltage divider resistor is electrically connected to the first end of the seventh voltage divider resistor. The connection point between the two is the voltage divider output of the third bias voltage divider network, and the second end of the seventh voltage divider resistor is grounded. The voltage divider output of the third bias voltage divider network is electrically connected to the non-inverting input of the third operational amplifier through the ninth current-limiting resistor. The output of the third operational amplifier outputs a temperature-compensated back EMF detection signal.

7. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 3, characterized in that, The second voltage divider resistor and the third voltage divider resistor have the same resistance value, providing a 1 / 2 VDD DC common-mode bias voltage for the first operational amplifier. The differential gain of the first operational amplifier is the ratio of the resistance values ​​of the first feedback resistor and the first current-limiting resistor.

8. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 6, characterized in that, The sixth and seventh voltage divider resistors have the same resistance value, providing a basic DC common-mode bias voltage of 1 / 2 VDD for the third operational amplifier. The differential gain of the third operational amplifier is the ratio of the resistance values ​​of the third feedback resistor and the seventh current-limiting resistor.

9. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, Both the dual operational amplifier chip and the third operational amplifier are rail-to-rail input / output operational amplifiers, with a power supply of 3.3V or 5V, which is fully compatible with the power supply voltage of the motor control MCU.

10. The feedback compensation circuit for permanent magnet synchronous motor control according to claim 1, characterized in that, The temperature detection signal is connected to the ADC sampling port of the MCU for real-time monitoring of motor temperature and overheat protection; the bus current sampling signal is connected to the ADC sampling port of the MCU for field-oriented closed-loop control and overcurrent protection of the motor.

Images