A motor three-phase current overcurrent detection protection circuit and method

Abstract

The application discloses a motor three-phase current overcurrent detection protection circuit and method, wherein the motor three-phase current overcurrent detection protection circuit comprises an MCU controller, a driving IC, a current sampling circuit, a voltage integration circuit and an overcurrent judgment circuit. The current sampling circuit collects three-phase currents output by the driving IC to a driving motor, and sends three-phase current signals rectified into first voltage values to the voltage integration circuit. The voltage integration circuit integrates the first voltage values, and sends obtained second voltage values to the overcurrent judgment circuit. The overcurrent judgment circuit compares the second voltage values with a hardware threshold value, and if the second voltage values are greater than the hardware threshold value, the overcurrent judgment circuit controls the driving IC to stop outputting three-phase currents to the driving motor. By setting the voltage integration circuit, the instantaneous values of the sampled three-phase currents are integrated into voltage values, the influence of instantaneous fluctuation on overcurrent detection is effectively avoided, and the accuracy of overcurrent detection is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor overload protection, and particularly relates to a motor three-phase current overcurrent detection protection circuit and method. BACKGROUND

[0002] The load of a motor is often changing during use, especially in the field of electric vehicles. During driving, the vehicle often needs to brake, and the control system of the vehicle sends instructions to the motor drive assembly according to the load condition. The motor drive assembly provides a current meeting the load requirement to the drive motor according to the instructions of the control system. During this process, if the load changes abnormally, it may cause the motor drive assembly to generate a large current, which may damage the control elements of the motor. Therefore, the current output by the motor drive assembly needs to be sampled to protect the motor from being damaged by overcurrent.

[0003] Currently, overcurrent detection of a motor is mainly achieved by detecting the instantaneous value of the current or voltage of the motor to determine whether the motor is overloaded. However, the winding of the motor is an inductive element, and the current itself has normal fluctuations. Therefore, it is difficult to determine the evaluation index when judging according to the instantaneous value of the current or voltage. If the threshold is set too small, it may lead to misjudgment of overcurrent. If the threshold is set too large, it may lead to missed detection of overcurrent, which cannot effectively protect the motor. SUMMARY

[0004] To solve the technical problem of high overcurrent misjudgment rate of the motor in the prior art, the present application provides a motor three-phase current overcurrent detection protection circuit and method, wherein the motor three-phase current overcurrent detection protection circuit comprises an MCU controller, a drive IC, a current sampling circuit, a voltage integration circuit and an overcurrent judgment circuit. The MCU controller is configured to send a PWM control signal to the drive IC to make the drive IC output three-phase current to a drive motor. The current sampling circuit is configured to collect the three-phase current output by the drive IC, rectify the three-phase current signal into a first voltage value and send the first voltage value to the voltage integration circuit. The voltage integration circuit is configured to integrate the first voltage value and send a second voltage value obtained by integration to the overcurrent judgment circuit. The overcurrent judgment circuit compares the second voltage value with a hardware threshold value. If the second voltage value is greater than the hardware threshold value, the overcurrent judgment circuit controls the drive IC to stop outputting three-phase current to the drive motor.

[0005] Specifically, the voltage integration circuit comprises a first operational amplifier U1, an integration capacitor C1 and an integration elimination module. The integration capacitor C1 cooperates with the first operational amplifier U1 to integrate the first voltage value and generate the second voltage value. The integration elimination module is configured to periodically eliminate the charge of the integration capacitor C1 to make the voltage integration circuit restart the integration operation.

[0006] Specifically, the integral elimination module comprises a first MOS switch, a gate electrode of the first MOS switch is electrically connected with the MCU controller, and the MCU controller periodically sends a high level to the first MOS switch to make the first MOS switch turn on a discharge circuit of the integral capacitor C1.

[0007] Further, the voltage integral circuit is further used for sending the second voltage value to the MCU controller, and the MCU controller is further used for comparing the second voltage value with a software threshold value, and if the second voltage value is greater than the software threshold value, the MCU controller stops sending a PWM control signal to the driving IC to make the driving IC stop outputting three-phase currents to the driving motor.

[0008] Specifically, the current sampling circuit comprises three current sampling sensors and a full-wave rectification module, the three current sampling sensors are used for sampling three-phase currents output by the driving IC, and the full-wave rectification module is used for rectifying three-phase current signals acquired by the three current sampling sensors into the first voltage value.

[0009] Specifically, the current sampling sensor is a Hall sensor.

[0010] The application further provides a motor three-phase current overcurrent detection and protection method, which adopts the motor three-phase current overcurrent detection and protection circuit and comprises the following steps.

[0011] S1, acquiring three-phase current signals output by the driving IC in real time;

[0012] S2, rectifying the three-phase current signals into a first voltage value;

[0013] S3, performing integral operation on the first voltage value to acquire a second voltage value;

[0014] S4, comparing the second voltage value with the hardware threshold value, and if the second voltage value is greater than the hardware threshold value, the overcurrent judgment circuit controls the driving IC to stop outputting currents to the driving motor.

[0015] Further, the motor three-phase current overcurrent detection and protection method further comprises the following steps.

[0016] S5, comparing the second voltage value with a software threshold value, and if the second voltage value is greater than the software threshold value, the MCU controller stops sending a PWM control signal to the driving IC.

[0017] The technical effect and advantage of the present application: by setting the integral circuit, the instantaneous voltage signal collected by the current sampling circuit is converted into the voltage signal accumulated in the time domain, thereby avoiding the abnormal fluctuation of the instantaneous voltage value from causing the misjudgment of the motor overcurrent, so as to improve the accuracy of the motor overcurrent judgment. At the same time, since the sampled three-phase current signal is rectified by full-wave rectification, the stability of the second voltage value is improved, further improving the accuracy of the motor overcurrent judgment. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The electrical schematic diagram of the overcurrent detection protection circuit. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] Embodiment one

[0021] Reference Figure 1 The embodiment one of the present application provides a motor three-phase current overcurrent detection protection circuit, which comprises an MCU controller, a drive IC, a current sampling circuit, a voltage integral circuit and an overcurrent judgment circuit. The MCU controller is used for sending a PWM control signal to the drive IC, so that the drive IC outputs three-phase current to drive the motor. The current sampling circuit is used for collecting the three-phase current output by the drive IC, and sending the three-phase current signal to the voltage integral circuit after rectifying the three-phase current signal into a first voltage value. The voltage integral circuit is used for integrating the first voltage value, and sending a second voltage value obtained to the overcurrent judgment circuit. The overcurrent judgment circuit compares the second voltage value with a hardware threshold value. If the second voltage value is greater than the hardware threshold value, the overcurrent judgment circuit controls the drive IC to stop outputting the three-phase current to drive the motor.

[0022] By setting the integral circuit, the rapidly changing first voltage value can be integrated in the time domain, converted and amplified into a relatively stable second voltage value, which facilitates the comparison and judgment between voltages, and avoids the influence of the instantaneous voltage fluctuation on the overcurrent judgment, thereby improving the accuracy of the overcurrent judgment.

[0023] Specifically, as an implementation manner, the voltage integral circuit comprises a first operational amplifier U1, an integral capacitor C1 and an integral elimination module. The integral capacitor C1 cooperates with the first operational amplifier U1 to integrate the first voltage value, to generate the second voltage value. The integral elimination module is used for periodically eliminating the charge of the integral capacitor C1, so that the voltage integral circuit restarts the integral operation.

[0024] The principle of the voltage integration circuit is based on the charging and discharging characteristics of the capacitor: when a step voltage is applied to the input end of the integration circuit, the capacitor begins to charge, its impedance gradually increases over time, resulting in a decrease in charging current, and the voltage generated across the capacitor slowly increases, forming a linearly increasing ramp output voltage (i.e., the second voltage value), which continues to increase until the capacitor is fully charged.

[0025] When the motor is working in a normal load state, the drive IC outputs normal three-phase current, the integration capacitor C1 charges at a first speed, and the second voltage value V2 output by the integration circuit increases at a first gradient. The integration elimination module periodically discharges the integration capacitor C1, so that the second voltage value V2 always remains below the hardware threshold Vref1 or the software threshold. When the load of the motor abnormally changes, the three-phase current output by the drive IC overflows, the second voltage value V2 increases at a faster speed, and reaches above the hardware threshold Vref1 or the software threshold before the integration elimination module discharges.

[0026] In order to improve the response speed to overcurrent, the overcurrent judgment circuit compares the second voltage value V2 with the hardware threshold Vref1. When the second voltage value V2 is greater than the hardware threshold Vref1, the overcurrent judgment circuit sends a high-level signal V3 to control the drive IC to stop outputting three-phase current to drive the motor.

[0027] At the same time, the voltage integration circuit also sends the second voltage value V2 to the MCU controller, and the MCU controller compares the second voltage value V2 with the software threshold. If the second voltage value V2 is greater than the software threshold, the MCU controller stops outputting the PWM control signal to the drive IC and sends a fault information. The drive motor is double-protected from the hardware and software levels.

[0028] Specifically, the integration elimination module can be implemented by a MOS switch, for example, a first MOS switch is provided, and the gate electrode of the first MOS switch is electrically connected to the MCU controller. The MCU controller periodically sends a high level to the first MOS switch to turn on the discharge circuit of the integration capacitor C1.

[0029] Current sampling can be achieved by various sensors. In the present application, a Hall sensor is used to obtain the alternating current signal of the three-phase current. The Hall sensor has the advantages of non-contact measurement and can directly measure the voltage signal.

[0030] The voltage signal acquired by the Hall sensor is a three-phase alternating current signal, while the voltage integrating circuit requires a DC voltage signal as input. Therefore, the current sampling circuit needs to rectify the three-phase alternating current signal. There are two main rectification methods for three-phase current signals: full-bridge rectification and full-wave rectification. Full-bridge rectification uses four diodes to form a bridge structure, converting both the positive and negative half-cycles of the AC current into DC. Its advantages are its simple structure, applicability to various AC inputs, and high efficiency due to full utilization of both positive and negative half-cycles of the AC signal. Its disadvantage is that only two diodes conduct in each cycle, resulting in a larger voltage drop and slightly higher power loss. Full-wave rectification typically refers to a rectification method using a center-tapped transformer and two diodes. It can also convert both positive and negative half-cycles of AC into DC, but it relies on a special transformer structure. Its advantages are that only one diode conducts in each cycle, resulting in a smaller voltage drop, higher efficiency than full-bridge rectification, and smaller output voltage ripple, making it suitable for scenarios with high DC quality requirements.

[0031] The current sampling circuit of the present invention includes three current sampling sensors and a full-wave rectification module. The three current sampling sensors are used to sample the three-phase current output by the driver IC. The full-wave rectification module is used to rectify the three-phase current signals obtained by the three current sampling sensors into a first voltage value. The current sampling sensors are Hall sensors.

[0032] Example 2

[0033] To better achieve the objectives of this invention, this invention also provides a method for detecting and protecting three-phase current overcurrent in a motor, based on the overcurrent detection and protection circuit provided in Embodiment 1. This method includes the following steps:

[0034] S1. Real-time acquisition of the three-phase current signal output by the driver IC;

[0035] S2. Rectify the three-phase current signal into the first voltage value;

[0036] S3. Integrate the first voltage value to obtain the second voltage value;

[0037] S4. Compare the second voltage value with the hardware threshold. If the second voltage value is greater than the hardware threshold, the overcurrent judgment circuit controls the driver IC to stop outputting current to the drive motor.

[0038] Furthermore, the above method may also include the following steps:

[0039] S5. Compare the second voltage value with the software threshold. If the second voltage value is greater than the software threshold, the MCU controller stops sending PWM control signals to the driver IC.

[0040] Finally: the above only for the preferred embodiments of the present application, and not for limiting the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application, should be included in the scope of protection of the present application.

Claims

1. A three-phase current overcurrent detection and protection circuit for a motor, characterized in that, include: MCU controller, driver IC, current sampling circuit, voltage integration circuit, and overcurrent detection circuit; The MCU controller is used to send PWM control signals to the driver IC so that the driver IC outputs three-phase current to the drive motor; The current sampling circuit is used to collect the three-phase current output by the driver IC, and to rectify the three-phase current signal into a first voltage value before sending it to the voltage integration circuit. The voltage integration circuit includes a first operational amplifier U1, an integration capacitor C1, and an integration elimination module. The integration capacitor C1 works with the first operational amplifier U1 to integrate the first voltage value to generate a second voltage value. The integration elimination module is electrically connected to the MCU controller. The MCU controller can periodically control the integration elimination module to clear the charge of the integration capacitor C1 so that the voltage integration circuit can restart the integration operation. The voltage integration circuit is also used to send the second voltage value to the overcurrent judgment circuit and the MCU controller. The overcurrent judgment circuit compares the second voltage value with a hardware threshold. If the second voltage value is greater than the hardware threshold, the overcurrent judgment circuit controls the driver IC to stop outputting three-phase current to the drive motor. The MCU controller compares the second voltage value with a software threshold. If the second voltage value is greater than the software threshold, the MCU controller stops sending PWM control signals to the driver IC so that the driver IC stops outputting three-phase current to the drive motor.

2. The motor three-phase current overcurrent detection and protection circuit according to claim 1, characterized in that, The integral elimination module includes a first MOS switch, the gate of which is electrically connected to the MCU controller. The MCU controller periodically sends a high level to the first MOS switch to turn on the discharge circuit of the integral capacitor C1.

3. The motor three-phase current overcurrent detection and protection circuit according to claim 1, characterized in that, The current sampling circuit includes three current sampling sensors and a full-wave rectification module. The three current sampling sensors are used to sample the three-phase current output by the driver IC, and the full-wave rectification module is used to rectify the three-phase current signals obtained by the three current sampling sensors into the first voltage value.

4. The motor three-phase current overcurrent detection and protection circuit according to claim 3, characterized in that, The current sampling sensor is a Hall sensor.

5. A method for detecting and protecting a three-phase motor overcurrent, comprising the three-phase motor overcurrent detection and protection circuit described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Acquire the three-phase current signal output by the driver IC in real time; S2. Rectify the three-phase current signal into a first voltage value; S3. Integrate the first voltage value to obtain the second voltage value; S4. Compare the second voltage value with the hardware threshold. If the second voltage value is greater than the hardware threshold, the overcurrent judgment circuit controls the driver IC to stop outputting current to the drive motor.

6. The method for detecting and protecting three-phase current overcurrent of a motor according to claim 5, characterized in that, It also includes the following steps: S5. Compare the second voltage value with the software threshold. If the second voltage value is greater than the software threshold, the MCU controller stops sending PWM control signals to the driver IC.

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