Permanent magnet synchronous motor and overcurrent protection circuit thereof

Abstract

The application relates to a permanent magnet synchronous motor and an overcurrent protection circuit thereof. The circuit comprises: a sampling circuit connected with a target motor, used for collecting phase currents of the target motor in different stages; a segmented overcurrent protection threshold setting circuit connected with the target motor, used for determining overcurrent protection threshold values in different stages according to circuit characteristics of the segmented overcurrent protection threshold setting circuit given by the target motor in different stages; and a comparison circuit connected with the sampling circuit and the segmented overcurrent protection threshold setting circuit, used for comparing the phase currents with the overcurrent protection threshold values in corresponding stages, and performing overcurrent protection on the target motor when the phase currents are greater than the overcurrent protection threshold values. The application adopts the segmented overcurrent protection threshold setting circuit, directly changes the voltage size of the overcurrent protection threshold value through the hardware circuit, and solves the technical problem that the overcurrent protection threshold value cannot consider the flexibility, timeliness and effectiveness of motor overcurrent protection when the overcurrent protection threshold value is a fixed value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, and particularly relates to a permanent magnet synchronous motor and an overcurrent protection circuit thereof. BACKGROUND

[0002] With the mature development of the technology in the field of household appliances and the rapid advancement of power electronics technology, permanent magnet synchronous motors are increasingly popular due to their low cost, high efficiency, and low noise. Traditional control uses a Hall sensor to collect rotor position information, and the development of modern control theory has driven the development of sensorless permanent magnet synchronous motor controllers, which use an observer to obtain rotor position information. The problem with using a sensorless control mode is that the starting current is large when a heavy load is started, and the running current is small, which triggers overcurrent protection during the starting phase, resulting in motor starting failure.

[0003] At present, in the related art, the overcurrent protection threshold of a traditional permanent magnet synchronous motor controller is a fixed value, which results in the fact that the motor uses one overcurrent protection point during the starting and running phases, and the flexibility, timeliness, and effectiveness of motor overcurrent protection cannot be taken into account.

[0004] In view of the problem that the overcurrent protection threshold being a fixed value cannot take into account the flexibility, timeliness, and effectiveness of motor overcurrent protection, no effective solution has been proposed at present. SUMMARY

[0005] The present application provides a permanent magnet synchronous motor and an overcurrent protection circuit thereof, to solve the technical problem that the overcurrent protection threshold being a fixed value cannot take into account the flexibility, timeliness, and effectiveness of motor overcurrent protection.

[0006] According to an aspect of an embodiment of the present application, the present application provides an overcurrent protection circuit of a permanent magnet synchronous motor, comprising: a sampling circuit connected with a target motor, configured to collect phase currents of the target motor at different phases; a segmented overcurrent protection threshold setting circuit connected with the target motor, configured to determine overcurrent protection thresholds at different phases according to circuit characteristics of the segmented overcurrent protection threshold setting circuit given by the target motor at different phases; and a comparison circuit connected with the sampling circuit and the segmented overcurrent protection threshold setting circuit, configured to compare the phase currents with the overcurrent protection thresholds at corresponding phases, and to perform overcurrent protection on the target motor in the case that the phase currents are greater than the overcurrent protection thresholds.

[0007] Optionally, the segmented overcurrent protection threshold setting circuit comprises: at least two overcurrent protection threshold setting branches, configured to set overcurrent protection thresholds at respective corresponding phases, and different overcurrent protection threshold setting branches correspond to different phases of the target motor; and a switching unit, configured to turn on different overcurrent protection threshold setting branches according to circuit characteristics of the segmented overcurrent protection threshold setting circuit given by the target motor at different phases.

[0008] Optionally, the overcurrent protection threshold setting branch comprises: a first branch for setting a first overcurrent protection threshold corresponding to the target motor in a starting stage; and a second branch for setting a second overcurrent protection threshold corresponding to the target motor in a running stage.

[0009] Optionally, the first branch comprises: a third resistor and a fourth resistor connected in series with the third resistor, an input end of the third resistor being connected with the power supply, an output end of the fourth resistor being grounded, and a connection point of the third resistor and the fourth resistor being an output point of the first overcurrent protection threshold.

[0010] Optionally, the second branch comprises: a third resistor, a fourth resistor, and a fifth resistor connected in series with the third resistor and the fourth resistor, an input end of the third resistor being connected with the power supply, an output end of the fourth resistor being grounded, the fifth resistor being connected in series between the third resistor and the fourth resistor, and a connection point of the fourth resistor and the fifth resistor being an output point of the second overcurrent protection threshold.

[0011] Optionally, the switching unit comprises: a first capacitor and a first switch tube, one end of the first capacitor being connected with the power supply of the target motor, the other end of the first capacitor being connected with a gate of the first switch tube, a source of the first switch tube being connected with the fourth resistor, and a drain of the first switch tube being connected with the third resistor.

[0012] Optionally, the first capacitor is configured to: charge when the target motor is in the starting stage at power-on, so that a gate voltage of the first switch tube is greater than a turn-on voltage threshold of the first switch tube, and the first switch tube is turned on; or discharge when the target motor is in the running stage, so that the gate voltage of the first switch tube is less than the turn-on voltage threshold, and the first switch tube is turned off.

[0013] Optionally, the first switch tube is configured to: when the first switch tube is turned on, short-circuit the fifth resistor, so that the first branch is turned on, and the first branch outputs the first overcurrent protection threshold corresponding to the target motor in the starting stage; or when the first switch tube is turned off, turn on the second branch, so that the second branch outputs the second overcurrent protection threshold corresponding to the target motor in the running stage.

[0014] Optionally, the overcurrent protection circuit further comprises a differential circuit configured to determine a duration of the first overcurrent protection threshold in the starting stage, the differential circuit comprising a first resistor, a second resistor, a first diode, and a first capacitor, wherein the first diode, the second resistor, and the first capacitor are connected in parallel, a cathode of the first diode being connected with the power supply of the target motor, an anode being connected with an input end of the first resistor, and an output end of the first resistor being grounded.

[0015] According to another aspect of the embodiments of the present application, the present application provides a permanent magnet synchronous motor comprising the above-mentioned overcurrent protection circuit.

[0016] The above technical solutions provided by the embodiments of the present application have the following advantages compared with related art.

[0017] The overcurrent protection circuit provided by the present application comprises: a sampling circuit connected with the target motor, used for collecting phase currents of the target motor at different stages; a segmented overcurrent protection threshold setting circuit connected with the target motor, used for determining overcurrent protection threshold values at different stages according to circuit characteristics of the segmented overcurrent protection threshold setting circuit given by the target motor at different stages; and a comparison circuit connected with the sampling circuit and the segmented overcurrent protection threshold setting circuit, used for comparing the phase currents with the overcurrent protection threshold values of the corresponding stages, and performing overcurrent protection on the target motor in the case that the phase currents are greater than the overcurrent protection threshold values. The present application uses a hardware circuit to segmentally set overcurrent protection threshold values, directly changes the voltage size of the overcurrent protection threshold values through the hardware circuit, does not need to consider adjusting the bus voltage, can set different overcurrent protection threshold values for different stages of the motor, greatly improves the flexibility, timeliness and effectiveness of motor overcurrent protection, and solves the technical problem that the overcurrent protection threshold values cannot take into account the flexibility, timeliness and effectiveness of motor overcurrent protection. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application together with the specification.

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the accompanying drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0020] Figure 1 An optional overcurrent protection circuit schematic diagram of a permanent magnet synchronous motor according to the embodiments of the present application;

[0021] Figure 2 An optional segmented overcurrent protection threshold setting circuit schematic diagram according to the embodiments of the present application;

[0022] Figure 3 An optional voltage comparison schematic diagram according to the embodiments of the present application. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] In the following description, the use of suffixes such as "module," "part," or "unit" to denote elements is solely for the purpose of illustration and has no specific meaning in itself. Therefore, "module" and "part" may be used interchangeably.

[0025] In related technologies, the overcurrent protection threshold of traditional permanent magnet synchronous motor controllers is a fixed value, which causes the motor to share a single overcurrent protection point during startup and operation, thus failing to take into account the flexibility, timeliness, and effectiveness of motor overcurrent protection.

[0026] To address the problems mentioned in the background art, according to one aspect of the embodiments of this application, an embodiment of an overcurrent protection circuit for a permanent magnet synchronous motor is provided, such as... Figure 1 As shown, the overcurrent protection circuit includes:

[0027] The sampling circuit 100 is connected to the target motor and is used to collect the phase current of the target motor at different stages.

[0028] The segmented overcurrent protection threshold circuit 200 is connected to the target motor and is used to determine the overcurrent protection threshold at different stages based on the circuit characteristics of the segmented overcurrent protection threshold circuit applied to the target motor at different stages.

[0029] The comparator circuit 300 is connected to the sampling circuit and the segmented overcurrent protection threshold setting circuit. It is used to compare the phase current with the overcurrent protection threshold of the corresponding stage, and to provide overcurrent protection for the target motor when the phase current is greater than the overcurrent protection threshold.

[0030] This application uses hardware circuits to set overcurrent protection thresholds in segments. The voltage of the overcurrent protection threshold can be changed directly through hardware circuits without considering adjusting the bus voltage. Different overcurrent protection thresholds can be set for different stages of the motor, which greatly improves the flexibility, timeliness and effectiveness of motor overcurrent protection. This solves the technical problem that a fixed overcurrent protection threshold cannot take into account the flexibility, timeliness and effectiveness of motor overcurrent protection.

[0031] In the embodiments of the present application, the target motor can be a permanent magnet synchronous motor, and of course can be other motors commonly used in household appliances. The different stages of the target motor include but are not limited to the starting stage of the motor, the running stage after the completion of the starting, etc. The phase current of the target motor can be the W-phase current of the motor as shown in Figure 1 , or can be the U-phase current or the V-phase current.

[0032] In the embodiments of the present application, the circuit characteristics of the segmented setting overcurrent protection threshold circuit given to the target motor in different stages can be the working state changes of the capacitors, resistors, switch tubes and other devices in the segmented setting overcurrent protection threshold circuit caused by the power supply working conditions of the target motor.

[0033] In the embodiments of the present application, the comparison circuit is used to compare the phase current with the overcurrent protection threshold of the corresponding stage, and in the case that the phase current is greater than the overcurrent protection threshold, the overcurrent protection is performed on the target motor. Specifically, after the motor is powered on, the current sampling is performed through the sampling resistor R13, the motor W-phase current generates a voltage Vw+ through the sampling resistor R13, and after being filtered through R11 and C4, the voltage is connected to the positive input end of the comparator U1, that is, the collected W-phase current Iw=Vw+ / R13. When the current at the positive input end is greater than the current protection threshold Ioc=VREF / R13, the comparator outputs a high level, at this time, the PWM is turned off through the single-chip microcomputer, and the motor is stopped. The same principle is applied to the U-phase and the V-phase.

[0034] Optionally, the segmented setting overcurrent protection threshold circuit comprises: at least two overcurrent protection threshold setting branches for setting the overcurrent protection threshold in the corresponding stage, and different overcurrent protection threshold setting branches correspond to different stages of the target motor; a switching unit for turning on different overcurrent protection threshold setting branches according to the circuit characteristics of the segmented setting overcurrent protection threshold circuit given to the target motor in different stages.

[0035] In the embodiments of the present application, a plurality of overcurrent protection threshold setting branches can be flexibly set according to the requirements, and different overcurrent protection threshold setting branches correspond to different stages of the target motor. The overcurrent protection threshold setting branches are described below by taking the starting stage and the running stage of the target motor as examples.

[0036] Optionally, the overcurrent protection threshold setting branch comprises: a first branch for setting a first overcurrent protection threshold corresponding to the starting stage of the target motor; and a second branch for setting a second overcurrent protection threshold corresponding to the running stage of the target motor.

[0037] Optionally, as shown in Figure 2As shown in the figure, the first branch includes: a third resistor R3 and a fourth resistor R4 connected in series with the third resistor R3, an input end of the third resistor R3 is connected with a power supply VCC, an output end of the fourth resistor R4 is grounded, and a connection point of the third resistor R3 and the fourth resistor R4 is an output point Vref of the first overcurrent protection threshold.

[0038] In the embodiment of the application, the resistance of the third resistor R3 can be set to 15 kilo-ohms, and the resistance of the fourth resistor R4 can be set to 1 kilo-ohm.

[0039] Optionally, as shown in the figure, Figure 2 As shown in the figure, the second branch includes: a third resistor R3, a fourth resistor R4, and a fifth resistor R5 connected in series with the third resistor R3 and the fourth resistor R4, an input end of the third resistor R3 is connected with a power supply VCC, an output end of the fourth resistor R4 is grounded, the fifth resistor R5 is connected in series between the third resistor R3 and the fourth resistor R4, and a connection point of the fourth resistor R4 and the fifth resistor R5 is an output point Vref of the second overcurrent protection threshold.

[0040] In the embodiment of the application, the resistance of the fifth resistor R5 can be set to 33 kilo-ohms.

[0041] In the embodiment of the application, the motor starting stage and the running stage are two threshold voltages, the first overcurrent protection threshold of the motor starting stage is determined by the resistors R3 and R4, and the second overcurrent protection threshold of the motor running stage is determined by the resistors R3, R4 and R5. The overcurrent protection threshold voltage is set by the hardware circuit segmentation, that is, a larger overcurrent protection threshold voltage is set in the motor starting stage, and a smaller overcurrent protection threshold voltage is set in the motor running stage, so as to ensure the flexibility, timeliness and effectiveness of the motor overcurrent protection.

[0042] Optionally, as shown in the figure, Figure 2 As shown in the figure, the switching unit includes: a first capacitor C1 and a first switch tube Q1, one end of the first capacitor C1 is connected with a power supply VCC of the target motor, the other end of the first capacitor C1 is connected with a gate of the first switch tube Q1, a source of the first switch tube Q1 is connected with the fourth resistor R4, and a drain of the first switch tube Q1 is connected with the third resistor R3. The circuit characteristics of the overcurrent protection threshold circuit set in different stages of the target motor are described below.

[0043] In the embodiment of the application, the capacitance of the first capacitor can be set to 50 micro-farads.

[0044] Optionally, as shown in the figure, Figure 2As shown, the first capacitor C1 is used to charge when the target motor is in the starting stage, so that the gate voltage of the first switch tube Q1 is greater than the threshold of the conduction voltage of the first switch tube Q1, and the first switch tube Q1 is turned on; or discharge when the target motor is in the running stage, so that the gate voltage of the first switch tube Q1 is less than the threshold of the conduction voltage, and the first switch tube Q1 is turned off.

[0045] In the embodiment of the application, the first switch tube Q1 can also be replaced by an NPN triode, and the above-mentioned threshold of the conduction voltage is selected according to the model of the switch tube.

[0046] Optionally, as shown, Figure 2 The first switch tube Q1 is used to short the fifth resistor R5 when the first switch tube Q1 is turned on, so that the first branch is turned on, and the first branch outputs the first overcurrent protection threshold corresponding to the starting stage of the target motor; or when the first switch tube Q1 is turned off, the second branch is turned on, and the second branch outputs the second overcurrent protection threshold corresponding to the running stage of the target motor.

[0047] In the embodiment of the application, when the motor is in the starting stage, the capacitor C1 is charged, the MOS tube Q1 is turned on, the resistor R5 is short-circuited, and VREF is determined by the resistors R3 and R4. VREF = 1 * 5 / 16 = 0.3125v, and the overcurrent protection current is Ioc = 0.3125 / 0.03 = 10.42A. After the capacitor C1 is continuously charged for a period of time, the motor switches to the running state, the MOS tube Q1 is closed, and VREF is determined by the resistors R3, R4 and R5. VREF = 1 * 5 / 49 ≈ 0.102v, and the overcurrent protection current is Ioc = 0.102 / 0.03 = 3.4A.

[0048] The control logic of the overcurrent protection circuit provided by the embodiment of the application will be described below. Figure 1 and Figure 2 The control logic of the overcurrent protection circuit provided by the embodiment of the application will be described below. Figure 1 and Figure 2As shown, since the motor starting current is greater than the running current, it is necessary to dynamically adjust the overcurrent protection threshold value in the starting stage and the running stage. When the motor is powered on, the motor is in the starting state, and since the gate voltage of Q1 decreases from 5v when the capacitor C1 is charged, the duration is τ=R1*C1, and at this time the state of Q1 is first turned on and then turned off. During the motor starting stage, the capacitor C1 is charged, the MOS tube Q1 is turned on, the resistor R5 is short-circuited, and VREF is determined by resistors R3 and R4. VREF=1*5 / 16=0.3125v, and the overcurrent protection current is Ioc=0.3125 / 0.03=10.42A. After the capacitor C1 is continuously charged for a period of time, the motor switches to the running state, the MOS tube Q1 is turned off, and VREF is determined by resistors R3, R4 and R5. VREF=1*5 / 49≈0.102v, and the overcurrent protection current is Ioc=0.102 / 0.03=3.4A. The duration of the segmented overcurrent protection threshold voltage is determined by the resistor R1 and the capacitor C1. Therefore, the automatic segmented setting of the overcurrent protection threshold value is realized.

[0049] As shown in Figure 3 , the motor is powered on in the starting stage, Q1 is turned on, and the overcurrent protection threshold voltage is 0.3125v. After 300ms, Q1 is turned off, and the motor switches to the running stage, and the overcurrent protection threshold voltage is 0.102v.

[0050] It can be seen that the application adopts hardware circuit segmented setting of the overcurrent protection threshold value, directly changes the voltage size of the overcurrent protection threshold value through the hardware circuit, does not need to consider adjusting the bus voltage, can set different overcurrent protection threshold values for different stages of the motor, greatly improves the flexibility, timeliness and effectiveness of the motor overcurrent protection, and solves the technical problem that the overcurrent protection threshold value cannot consider the flexibility, timeliness and effectiveness of the motor overcurrent protection.

[0051] Optionally, the overcurrent protection circuit further comprises a differential circuit, and the differential circuit is used to determine the duration of the first overcurrent protection threshold value in the starting stage, as shown in Figure 2 , the differential circuit comprises a first resistor R1, a second resistor R2, a first diode D1 and a first capacitor C1, wherein the first diode D1, the second resistor R2 and the first capacitor C1 are connected in parallel, the cathode of the first diode D1 is connected with the power supply of the target motor, the anode is connected with the input end of the first resistor R1, and the output end of the first resistor R1 is grounded.

[0052] In the embodiment of the application, the resistance of the first resistor can be set to 10kΩ, and the resistance of the second resistor can be set to 200kΩ.

[0053] In the embodiment of the application, the duration of the first overcurrent protection threshold value in the starting stage is determined by the differential circuit, that is, the duration is τ=R1*C1, and the circuit is also used to distinguish whether the motor belongs to the starting stage or the running stage.

[0054] It should be noted that the above values of the components are only preferred, and can be set according to actual needs.

[0055] According to another aspect of the embodiments of the present application, the present application provides a permanent magnet synchronous motor comprising the overcurrent protection circuit.

[0056] The present application sets the overcurrent protection threshold value by hardware circuit segmentation, directly changes the voltage size of the overcurrent protection threshold value by hardware circuit, does not need to consider adjusting the bus voltage, can set different overcurrent protection threshold values for different stages of the motor, greatly improves the flexibility, timeliness and effectiveness of the motor overcurrent protection, and solves the technical problem that the overcurrent protection threshold value cannot consider the flexibility, timeliness and effectiveness of the motor overcurrent protection.

[0057] The above only describes specific embodiments of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A current protection circuit for a permanent magnet synchronous motor, characterized by, The application relates to a motor overcurrent protection threshold setting circuit. The motor overcurrent protection threshold setting circuit comprises: a sampling circuit connected with a target motor, which is used for collecting phase currents of the target motor at different stages; a segmented overcurrent protection threshold setting circuit connected with the target motor, which is used for determining overcurrent protection thresholds at different stages according to circuit characteristics of the segmented overcurrent protection threshold setting circuit given by the target motor at different stages; and a comparison circuit connected with the sampling circuit and the segmented overcurrent protection threshold setting circuit, which is used for comparing the phase currents with the overcurrent protection thresholds at corresponding stages and performing overcurrent protection on the target motor when the phase currents are greater than the overcurrent protection thresholds. The segmented overcurrent protection threshold setting circuit comprises: at least two overcurrent protection threshold setting branches, which are used for setting the overcurrent protection thresholds at respective corresponding stages, and different overcurrent protection threshold setting branches correspond to different stages of the target motor; and a switching unit, which is used for turning on different overcurrent protection threshold setting branches according to circuit characteristics of the segmented overcurrent protection threshold setting circuit given by the target motor at different stages. The switching unit comprises: a first capacitor and a first switch tube, one end of the first capacitor is connected with a power supply of the target motor, the other end of the first capacitor is connected with a gate of the first switch tube, a source of the first switch tube is connected with a fourth resistor in the overcurrent protection threshold setting branch, and a drain of the first switch tube is connected with a third resistor in the overcurrent protection threshold setting branch. The overcurrent protection threshold setting branch comprises: A first branch, which is used for setting a first overcurrent protection threshold corresponding to a starting stage of the target motor; and 2. The circuit of claim 1, wherein, A second branch, which is used for setting a second overcurrent protection threshold corresponding to a running stage of the target motor. The first branch comprises: A third resistor and a fourth resistor connected in series with the third resistor, an input end of the third resistor is connected with a power supply, an output end of the fourth resistor is grounded, and a connection point of the third resistor and the fourth resistor is an output point of the first overcurrent protection threshold.

3. The circuit of claim 2, wherein, The second branch comprises: The third resistor, the fourth resistor and a fifth resistor connected in series with the third resistor and the fourth resistor, an input end of the third resistor is connected with a power supply, an output end of the fourth resistor is grounded, the fifth resistor is connected in series between the third resistor and the fourth resistor, and a connection point of the fourth resistor and the fifth resistor is an output point of the second overcurrent protection threshold.

4. The circuit of claim 3, wherein, The first capacitor is used for: Charging when the target motor is in the starting stage, so that the gate voltage of the first switch tube is greater than the turn-on voltage threshold of the first switch tube, and the first switch tube is turned on; or 5. The circuit of claim 4, wherein, Discharging when the target motor is in the running stage, so that the gate voltage of the first switch tube is less than the turn-on voltage threshold, and the first switch tube is turned off. The first switch tube is used for: Short-circuiting the fifth resistor when the first switch tube is turned on, so that the first branch is turned on, the first branch outputs the first overcurrent protection threshold corresponding to the starting stage of the target motor; or Short-circuiting the fifth resistor when the first switch tube is turned off, so that the second branch is turned on, the second branch outputs the second overcurrent protection threshold corresponding to the running stage of the target motor.

6. The circuit of claim 5, wherein, ​ ​ When the first switch is off, the second branch is turned on, and the second branch outputs the second over-current protection threshold corresponding to the running stage of the target motor.

7. A circuit as claimed in any one of claims 4 to 6, characterised in that, The over-current protection circuit further comprises a differential circuit for determining the duration of the first over-current protection threshold in the starting stage, and the differential circuit comprises a first resistor, a second resistor, a first diode and the first capacitor, wherein the first diode, the second resistor and the first capacitor are connected in parallel, the cathode of the first diode is connected to the power supply of the target motor, the anode of the first diode is connected to the input end of the first resistor, and the output end of the first resistor is grounded. 8.A permanent magnet synchronous motor comprising the over-current protection circuit according to any one of claims 1 to 7.

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