Switching tube junction temperature detection method, motor controller, motor control system and medium

Abstract

The application discloses a kind of switch tube junction temperature detection method, motor controller, motor control system and medium, method includes: determining direct current bus voltage, and determining the off-pipe voltage drop of at least one phase bridge arm in three-phase inverter bridge when lower pipe is turned off, and determine the three-phase current of motor;According to three-phase current, determine the conduction current of at least one phase bridge arm in three-phase inverter bridge when upper pipe is turned on, and according to direct current bus voltage, off-pipe voltage drop and three-phase current, determine the conduction pipe voltage drop of at least one phase bridge arm in three-phase inverter bridge when upper pipe is turned on;According to conduction pipe voltage drop and conduction current, determine the conduction resistance of at least one phase bridge arm when upper pipe is turned on;According to conduction resistance, determine the junction temperature of at least one phase bridge arm when upper pipe is turned on.The method not only makes that the upper pipe junction temperature obtained has higher accuracy, and can effectively solve the problem of high cost of upper pipe voltage detection caused by upper pipe potential suspension.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a method for detecting the junction temperature of a switching transistor in a motor control system, a motor controller, a computer-readable storage medium, and a motor control system. Background Technology

[0002] In the fields of home appliance motor control and small, lightweight electric vehicle control, motor controllers often employ single-resistor current sampling to control the motor due to cost and space constraints. Simultaneously, discrete components are widely used for switching devices. A common temperature protection method for discrete switching devices involves placing temperature resistors around the device. While this provides temperature sensing capability, the temperature resistors receive the ambient radiant temperature of the switching device. Inaccurate temperature detection is limited by the resistor's installation location, hindering effective temperature protection. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the first objective of this invention is to propose a method for detecting the junction temperature of a switching transistor in a motor control system. This method calculates the on-resistance of the upper transistor based on its on-state voltage drop and on-state current, and then determines the junction temperature based on this resistance. This results in a highly accurate measurement of the upper transistor's junction temperature. Furthermore, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This effectively solves the problem of high voltage detection costs caused by floating potential in the upper transistor when directly detecting its voltage, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0004] The second objective of this invention is to provide a motor controller.

[0005] A third objective of this invention is to provide a computer-readable storage medium.

[0006] The fourth objective of this invention is to provide a motor control system.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for detecting the junction temperature of a switching transistor in a motor control system. The motor control system includes a three-phase inverter bridge that drives the motor. The method includes: determining the DC bus voltage, determining the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge is turned off, and determining the three-phase current of the motor; determining the conduction current when the upper transistor of at least one phase arm of the three-phase inverter bridge is turned on based on the three-phase current, and determining the conduction transistor voltage drop when the upper transistor of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus voltage, the turn-off transistor voltage drop, and the three-phase current; determining the conduction resistance when the upper transistor of at least one phase arm is turned on based on the conduction transistor voltage drop and the conduction current; and determining the junction temperature of the upper transistor of at least one phase arm based on the conduction resistance.

[0008] According to the present invention, the method for detecting the junction temperature of a switching transistor in a motor control system determines the on-resistance of the upper transistor of at least one phase bridge arm when it is turned on based on the on-state voltage drop and on-state current of the upper transistor, and determines the junction temperature of the upper transistor of at least one phase bridge arm based on the on-state resistance. This method provides high accuracy in obtaining the junction temperature of the upper transistor, which is beneficial for temperature protection of the switching device. Simultaneously, the method determines the DC bus voltage, the off-state voltage drop of the lower transistor of at least one phase bridge arm in the three-phase inverter bridge when it is turned off, and the three-phase current of the motor. Based on the three-phase current, the method determines the on-state current of the upper transistor of at least one phase bridge arm in the three-phase inverter bridge when it is turned on, and the method determines the on-state voltage drop of the upper transistor of at least one phase bridge arm in the three-phase inverter bridge based on the DC bus voltage, the off-state voltage drop, and the three-phase current. This effectively solves the problem of high voltage detection cost of the upper transistor due to floating potential when directly detecting the voltage of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0009] According to one embodiment of the present invention, determining the DC bus voltage includes: determining a first sampling window time, wherein the first sampling window time is the time from the underflow interruption time of the PWM triangular wave to the turn-on time of the upper transistor of any one phase arm of the three-phase inverter bridge; and sampling the bus voltage within the first sampling window time to obtain the DC bus voltage.

[0010] According to one embodiment of the present invention, determining the turn-off transistor voltage drop when the lower transistor of at least one phase arm of a three-phase inverter bridge is turned off includes: determining a second sampling window time, a third sampling window time, and a fourth sampling window time, wherein the second sampling window time is the time from the turn-on of the upper transistor of any phase arm of the three-phase inverter bridge after a first preset time delay until the turn-on of the upper transistor of the next phase arm of the three-phase inverter bridge; the third sampling window time is the time from the turn-on of the upper transistor of the next phase arm of the three-phase inverter bridge after a first preset time delay until the turn-on of the upper transistor of the last phase arm of the three-phase inverter bridge; and the fourth sampling window time is the time from the overflow interruption moment of the PWM triangular wave until the turn-off of the upper transistor of any phase arm of the three-phase inverter bridge; and the turn-off transistor voltage drop is sampled during at least one of the second, third, and fourth sampling window times to obtain the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge is turned off.

[0011] According to one embodiment of the present invention, determining the three-phase current of a motor includes: sampling the bus current during a second sampling window time and a third sampling window time to obtain the two-phase current of the motor; and determining the third-phase current of the motor based on the two-phase current of the motor.

[0012] According to one embodiment of the present invention, determining the conduction tube voltage drop when the upper tube of at least one phase arm of a three-phase inverter bridge is turned on based on the DC bus voltage, the turn-off tube voltage drop, and the three-phase current includes: determining the average DC bus current based on the three-phase current, and determining the winding voltage drop based on the average DC bus current and the three-phase winding resistance of the motor; determining the conduction tube voltage drop when the upper tube of at least one phase arm of a three-phase inverter bridge is turned on based on the DC bus voltage, the turn-off tube voltage drop, and the winding voltage drop.

[0013] According to one embodiment of the present invention, determining the average DC bus current based on the three-phase current includes: determining the switching function when the upper tube of each phase arm of the three-phase inverter bridge is turned on; and determining the average DC bus current based on the switching function when the upper tube of each phase arm is turned on and the phase current in the three-phase current.

[0014] According to one embodiment of the present invention, after determining the junction temperature of the upper tube, the method further includes: performing instantaneous over-temperature protection and inverse-time overload protection based on the junction temperature of the upper tube.

[0015] According to one embodiment of the present invention, instantaneous over-temperature protection based on the junction temperature of the upper tube includes: controlling the three-phase inverter bridge to stop output when the junction temperature of the upper tube exceeds a preset maximum protection temperature.

[0016] According to one embodiment of the present invention, inverse-time overload protection based on the upper tube junction temperature includes: determining an inverse-time protection curve and timing the overload protection based on the relationship between the upper tube junction temperature and the inverse-time protection curve; and controlling the three-phase inverter bridge to stop output when the timing period arrives.

[0017] To achieve the above objectives, a second aspect of the present invention provides a motor controller, including a memory, a processor, and a switching transistor junction temperature detection program stored in the memory and executable on the processor. When the processor executes the switching transistor junction temperature detection program, it implements the aforementioned switching transistor junction temperature detection method in the motor control system.

[0018] According to the motor controller of the present invention, based on the aforementioned method for detecting the junction temperature of the switching transistor in the motor control system, the on-resistance of the upper transistor is calculated based on the on-state voltage drop and on-state current of the upper transistor, and the junction temperature of the upper transistor is determined based on the on-state resistance. This results in a high accuracy in obtaining the junction temperature of the upper transistor. At the same time, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This effectively solves the problem of high voltage detection cost of the upper transistor caused by the floating potential of the upper transistor when directly detecting the voltage of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0019] To achieve the above objectives, a third aspect of the present invention provides a computer-readable storage medium storing a junction temperature detection program for a switching transistor in a motor control system. When the junction temperature detection program for a switching transistor in a motor control system is executed by a processor, it implements the aforementioned junction temperature detection method for a switching transistor in a motor control system.

[0020] According to the computer-readable storage medium of the present invention, based on the aforementioned method for detecting the junction temperature of a switching transistor in a motor control system, the on-resistance of the upper transistor is calculated based on the on-state voltage drop and on-state current of the upper transistor, and the junction temperature of the upper transistor is determined based on the on-state resistance. This results in a high accuracy in obtaining the junction temperature of the upper transistor. At the same time, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This effectively solves the problem of high voltage detection cost of the upper transistor caused by the floating potential of the upper transistor when directly detecting the voltage of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0021] To achieve the above objectives, a fourth aspect of the present invention provides a motor control system, comprising: a motor; a three-phase inverter bridge connected between DC buses and driving the motor to operate; a current detection unit configured to detect the DC bus current corresponding to the negative terminal of the DC bus; a first voltage detection unit configured to detect the voltage drop across the lower diode of the U-phase arm of the three-phase inverter bridge; a second voltage detection unit configured to detect the voltage drop across the lower diode of the V-phase arm of the three-phase inverter bridge; and a third voltage detection unit configured to detect the voltage drop across the W-phase arm of the three-phase inverter bridge. The control unit is used to determine the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge is turned off based on the lower transistor voltage drop of each phase arm in the three-phase inverter bridge, and to determine the three-phase current of the motor based on the DC bus current, and to determine the conduction current when the upper transistor of at least one phase arm of the three-phase inverter bridge is turned on based on the three-phase current; the control unit is also used to determine the conduction transistor voltage drop when the upper transistor of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus voltage, the turn-off transistor voltage drop and the three-phase current, and to determine the conduction resistance when the upper transistor of at least one phase arm of the three-phase inverter bridge is turned on based on the conduction transistor voltage drop and the conduction current, and to determine the junction temperature of the upper transistor of at least one phase arm of the three-phase inverter bridge based on the conduction resistance.

[0022] According to the motor control system of the present invention, the control unit determines the on-resistance of the upper tube of at least one phase bridge arm when it is turned on based on the on-state voltage drop and on-state current of the upper tube, and determines the junction temperature of the upper tube of at least one phase bridge arm based on the on-state resistance, so that the obtained junction temperature of the upper tube has high accuracy, which is beneficial for temperature protection of switching devices. At the same time, the control unit determines the DC bus voltage, the off-state voltage drop when the lower tube of at least one phase bridge arm in the three-phase inverter bridge is turned off, and the three-phase current of the motor, and determines the on-state current when the upper tube of at least one phase bridge arm in the three-phase inverter bridge is turned on based on the three-phase current, and determines the on-state voltage drop when the upper tube of at least one phase bridge arm in the three-phase inverter bridge is turned on based on the DC bus voltage, the off-state voltage drop, and the three-phase current. This can effectively solve the problem of high voltage detection cost of the upper tube caused by the floating potential of the upper tube when directly detecting the voltage of the upper tube, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper tube.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a motor control system according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic flowchart of a switching transistor junction temperature detection method according to an embodiment of the present invention;

[0026] Figure 3 This is a graph showing the relationship between the on-resistance and junction temperature of a switching transistor according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of sampling the turn-off voltage drop of the lower transistor, the motor phase current, and the DC bus voltage according to an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram illustrating the process of obtaining the conduction pressure drop of the upper tube according to an embodiment of the present invention;

[0029] Figure 6 This is a graph of the inverse time protection curve according to an embodiment of the present invention. Detailed Implementation

[0030] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0031] In an embodiment of the present invention, the motor control system may include a three-phase inverter bridge, which is used to drive the motor.

[0032] Specifically, refer to Figure 1As shown, the three-phase inverter bridge includes a U-phase bridge arm, a V-phase bridge arm, and a W-phase bridge arm. The U-phase bridge arm includes an upper tube VT1 and a lower tube VT4, the V-phase bridge arm includes an upper tube VT3 and a lower tube VT6, and the W-phase bridge arm includes an upper tube VT5 and a lower tube VT2. The upper transistor VT1 has its first end connected to the positive terminal of the DC bus, the lower transistor VT4 has its first end connected to the second end of the upper transistor VT1, and the second end of the lower transistor VT4 is connected to the negative terminal of the DC bus; the upper transistor VT3 has its first end connected to the positive terminal of the DC bus, the lower transistor VT6 has its first end connected to the second end of the upper transistor VT3, and the second end of the lower transistor VT6 is connected to the negative terminal of the DC bus; the upper transistor VT5 has its first end connected to the positive terminal of the DC bus, the lower transistor VT2 has its first end connected to the second end of the upper transistor VT5, and the second end of the lower transistor VT2 is connected to the negative terminal of the DC bus; the control terminals of the upper transistor VT1, lower transistor VT4, upper transistor VT3, lower transistor VT6, upper transistor VT5, and lower transistor VT2 are respectively connected to a control unit. The control unit may include a microcontroller with memory, a DSP (Digital Signal Processing), or other control devices. This control unit controls the six switching transistors to turn on or off, thereby converting the DC power on the DC bus into AC power, which is then supplied to downstream loads such as motors to enable the motors to operate. The source of DC power can be a battery or AC power rectified; there are no specific restrictions here. A DC bus capacitor is installed between the positive and negative terminals of the DC bus for energy storage and voltage regulation.

[0033] When the control unit controls the six switching transistors to turn on or off for operation, the six switching transistors generate heat, causing their temperatures to rise. In severe cases, this can damage the switching transistors. Therefore, in related technologies, a temperature resistor is placed around the six switching transistors for temperature protection. Although this method provides temperature sensing capability, it is limited in its ability to sense internal temperature changes of the switching transistors because the temperature resistor receives the ambient radiant temperature of the switching transistors. This leads to inaccurate temperature detection and affects the temperature protection of the switching transistors. Based on this, this application provides a switching transistor junction temperature detection method. This method can accurately obtain the junction temperature of the upper transistor, which is beneficial for temperature protection of the switching transistors. At the same time, it can effectively solve the problem of high cost of upper transistor voltage detection caused by floating potential when directly detecting the voltage of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0034] Figure 2 This is a schematic flowchart of a switching transistor junction temperature detection method according to an embodiment of the present invention. (Reference) Figure 2 As shown, the method for detecting the junction temperature of a switching transistor may include the following steps:

[0035] Step S10: Determine the DC bus voltage, determine the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge is turned off, and determine the three-phase current of the motor.

[0036] It should be noted that the turn-off voltage drop refers to the voltage difference between the first and second terminals of the switching transistor when the transistor is turned off. Figure 1 As shown, the turn-off voltage drop of the lower transistor VT4 is the voltage difference between its first and second terminals when VT4 is turned off; the turn-off voltage drop of the lower transistor VT6 is the voltage difference between its first and second terminals when VT6 is turned off; the turn-off voltage drop of the lower transistor VT2 is the voltage difference between its first and second terminals when VT2 is turned off. The three-phase current of the motor includes the U-phase current, V-phase current, and W-phase current.

[0037] Specifically, such as Figure 1 As shown, a voltage detection unit can be set between the positive and negative terminals of the DC bus (i.e., across the two ends of the DC bus capacitor) to detect the DC bus voltage.

[0038] When determining the turn-off voltage drop of the lower transistor, a voltage detection unit can be set up for each lower transistor to detect the turn-off voltage drop. For example... Figure 1 As shown, a first voltage detection unit can be set for the lower transistor VT4 to detect the turn-off voltage drop of the lower transistor VT4; a second voltage detection unit can be set for the lower transistor VT6 to detect the turn-off voltage drop of the lower transistor VT6; and a third voltage detection unit can be set for the lower transistor VT2 to detect the turn-off voltage drop of the lower transistor VT2.

[0039] When determining the three-phase current of the motor, such as Figure 1 As shown, a current sampling resistor and a current detection unit can be set on the negative terminal of the DC bus. The DC bus current is obtained by sampling through the current sampling resistor and the current detection unit. Since the DC bus current is correlated with the motor phase current, the three-phase current of the motor can be obtained based on the DC bus current.

[0040] Step S20: Determine the conduction current when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on based on the three-phase current, and determine the conduction tube voltage drop when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus voltage, the voltage drop of the turn-off tube and the three-phase current.

[0041] It should be noted that the conduction current refers to the current flowing through the switching transistor when it is turned on, such as... Figure 1As shown, the conduction current of the upper transistor VT1 is the current flowing through it when VT1 is turned on; the conduction current of the upper transistor VT3 is the current flowing through it when VT3 is turned on; and the conduction current of the upper transistor VT5 is the current flowing through it when VT5 is turned on. Since the motor phase current is related to the turn-on sequence of the switching transistors, the current flowing through the upper transistor when it is turned on, i.e., the conduction current, can be obtained based on the motor phase current.

[0042] like Figure 1 As shown, the motor phase current can be obtained based on the DC bus current. For example, two phase currents of the U-phase current, V-phase current and W-phase current can be obtained directly based on the current flow of the loop when the circuit is turned on, while the other phase current can be obtained based on the single resistor current reconstruction method. Then, the corresponding upper transistor's conduction current is determined according to the motor phase current and the switching transistor's conduction sequence. Therefore, it is not necessary to set a current sampling resistor and current detection unit for each upper transistor, which helps to reduce cost and space occupation.

[0043] Having obtained the DC bus voltage, the turn-off voltage drop of the lower tube, and the three-phase current, the on-state voltage drop of the upper tube can be obtained based on the DC bus voltage, the turn-off voltage drop of the lower tube, and the three-phase current. For example, the voltage difference between the first and second terminals of the upper tube VT1 when it is on, the voltage difference between the first and second terminals of the upper tube VT3 when it is on, and the voltage difference between the first and second terminals of the upper tube VT5 when it is on.

[0044] Step S30: Determine the on-resistance of the upper tube of at least one phase bridge arm when it is turned on based on the voltage drop of the conducting tube and the on-current.

[0045] Specifically, when the on-state voltage drop and on-state current of the switching transistor are obtained, a resistor can be calculated based on the relationship between voltage and current. This resistor is the on-state resistance of the switching transistor when it is turned on. For example... Figure 1 As shown, after obtaining the on-state voltage drop and on-state current of the upper transistor VT1, the on-state resistance of the upper transistor VT1 can be calculated; after obtaining the on-state voltage drop and on-state current of the upper transistor VT3, the on-state resistance of the upper transistor VT3 can be calculated; after obtaining the on-state voltage drop and on-state current of the upper transistor VT5, the on-state resistance of the upper transistor VT5 can be calculated. Specifically, it can be calculated using the following formula (1):

[0046]

[0047] Among them, R dson-real For the on-resistance, V ds I is the voltage drop across the conducting tube, and I is the conducting current.

[0048] Step S40: Determine the junction temperature of the upper tube of at least one phase bridge arm based on the on-resistance.

[0049] Specifically, after obtaining the on-resistance of the switching transistor, the junction temperature of the switching transistor can be obtained based on the relationship between the on-resistance and the junction temperature of the switching transistor. Specifically, the relationship curve between the standard on-resistance of the selected switching transistor and the PN junction temperature of the device can be obtained first (e.g., ...). Figure 3 (As shown), the corresponding curve is then converted into a computer data table value and saved to the aforementioned memory. In practical applications, it can be obtained by looking up the table. For example... Figure 1 As shown, after obtaining the on-resistance of the upper transistor VT1, it is possible to... Figure 3 The characteristic curve of on-resistance versus junction temperature shown can be used to obtain the junction temperature of the upper transistor VT1 through methods such as table lookup; after obtaining the on-resistance of the upper transistor VT3, it can be based on... Figure 3 The characteristic curve of on-resistance versus junction temperature shown can be used to obtain the junction temperature of the upper transistor VT3 through methods such as table lookup; after obtaining the on-resistance of the upper transistor VT5, it can be based on... Figure 3 The characteristic curve of on-resistance versus junction temperature shown can be obtained by looking up tables or other methods to obtain the junction temperature of the upper MOSFET VT5.

[0050] In the above embodiments, by obtaining the internal resistance voltage (i.e., the voltage drop) and conduction current of the upper transistor when it is turned on, and calculating the on-resistance of the upper transistor based on the conduction current and voltage drop, the junction temperature of the upper transistor can be accurately obtained by looking up a table based on the on-resistance. Compared with obtaining the junction temperature of the upper transistor indirectly based on the spatial temperature radiation through a side-mounted temperature resistor, this method can quickly reflect the internal temperature of the upper transistor, which is beneficial for accurate and reliable temperature protection of the upper transistor. Moreover, the method is simple and easy to implement in engineering applications. At the same time, the voltage drop of the upper transistor when it is turned on is obtained indirectly based on the DC bus voltage, the voltage drop of the lower transistor when it is turned off, and the three-phase current of the motor. This can effectively solve the problem of high cost of upper transistor voltage detection caused by the floating potential of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0051] In some embodiments of the present invention, determining the DC bus voltage may include: determining a first sampling window time, the first sampling window time being the time from the underflow interruption of the PWM (Pulse Width Modulation) triangular wave to the turn-on of the upper transistor of any phase arm in the three-phase inverter bridge; and sampling the bus voltage within the first sampling window time to obtain the DC bus voltage.

[0052] It should be noted that the underflow interrupt time refers to the moment when the timer of the triangular wave is interrupted at the bottom of the triangular wave, that is, the moment when the triangular wave reaches its trough.

[0053] Specifically, refer to Figure 4As shown, corresponding to different PWM (Pulse Width Modulation) voltage vector moments U, PWM V, and PWM W, after avoiding current fluctuations caused by switching signal triggering, different acquisition signal moments appear. At the bottom of the triangular wave, the triangular wave timer will experience an underflow interrupt. At this time, PWM U, PWM V, and PWM W are all 0, the upper transistors VT1, VT3, and VT5 of the three-phase bridge arm are all off, and the lower transistors VT4, VT6, and VT2 of the three-phase bridge arm are all on. From this moment until any first turned-on upper transistor turns on (at... Figure 4 In the example shown, the upper tube VT1 of the U-phase bridge arm is the first upper tube to be turned on, and Ta is the turn-on time of the upper tube VT1 of the U-phase bridge arm. The time between these two points is the first sampling window time Ts1. The first sampling window time Ts1 = Ta - T. Since the sampling window time is timed by another timer, the initial time T = 0, i.e., Ts1 = Ta. Within the first sampling window time Ts1, using... Figure 1 The fourth voltage detection unit shown samples the bus voltage to obtain the DC bus voltage Vdc.

[0054] In some embodiments of the present invention, determining the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge is turned off includes: determining a second sampling window time, a third sampling window time, and a fourth sampling window time. The second sampling window time is the time from when the upper transistor of any phase arm of the three-phase inverter bridge is turned on and delayed by a first preset time until the upper transistor of the next phase arm of the three-phase inverter bridge is turned on. The third sampling window time is the time from when the upper transistor of the next phase arm of the three-phase inverter bridge is turned on and delayed by a first preset time until the upper transistor of the last phase arm of the three-phase inverter bridge is turned on. The fourth sampling window time is the time from the overflow interruption moment of the PWM triangular wave until the upper transistor of any phase arm of the three-phase inverter bridge is turned off. During at least one of the second, third, and fourth sampling window times, the turn-off transistor voltage drop is sampled to obtain the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge is turned off.

[0055] It should be noted that the overflow interrupt time refers to the moment when the timer of the triangular wave is interrupted at the top of the triangular wave, that is, the moment when the peak of the triangular wave is reached.

[0056] Specifically, refer to Figure 4 As shown, after the first sampling window time Ts1 ends, the turn-on voltage vector changes. After avoiding the current fluctuation caused by the switching signal trigger, a second sampling window time Ts2 appears. This second sampling window time Ts2 is from the turn-on of any first turned-on upper transistor (in Figure 4In the example shown, the upper tube VT1 of the U-phase bridge arm is the first upper tube to be turned on, and after a first preset time Tdelay, the conduction begins until the second upper tube is turned on (in...). Figure 4 In the example shown, the upper tube VT3 of the V-phase bridge arm is the second upper tube to be turned on, and Tb is the time when the upper tube VT3 of the V-phase bridge arm is turned on. The second sampling window time Ts2 = Tb - Ta - Tdelay.

[0057] After the second sampling window time Ts2 ends, the turn-on voltage vector changes. After avoiding the current fluctuation caused by the switching signal trigger, a third sampling window time Ts3 occurs. This third sampling window time Ts3 is from the turn-on of the second turned-on upper transistor (in... Figure 4 In the example shown, the upper tube VT3 of the V-phase bridge arm is the second upper tube to be turned on, and the process begins after a first preset time Tdelay, until the last upper tube is turned on (in...). Figure 4 In the example shown, the upper tube VT5 of the W phase bridge arm is the last upper tube to be turned on, and Tc is the time when the upper tube VT5 of the W phase bridge arm is turned on. The third sampling window time Ts3 = Tc - Tb - Tdelay.

[0058] After the third sampling window time Ts3 ends, a triangular wave overflow interrupt occurs at time Tpwm. That is, at the top of the triangular wave, the timer for the triangular wave overflows. At this time, PWM U, PWM V, and PWM W are all 1, and the upper transistors VT1, VT3, and VT5 of the three-phase bridge arm are all turned on, while the lower transistors VT4, VT6, and VT2 of the three-phase bridge arm are all turned off. From this moment until the first turned-off upper transistor turns off (in... Figure 4 In the example shown, the time between the upper tube VT5 of the W phase bridge arm (which is the first upper tube to be turned off) is taken as the fourth sampling window time Ts4. The fourth sampling window time Ts4 = Tc' - T. Since the initial time T = 0, that is, Ts4 = Tc'.

[0059] After determining the sampling window times Ts2, Ts3, and Ts4, some or all of them can be used as the sampling time for the voltage drop across the turn-off tube of the lower tube. Figure 1 The first voltage detection unit, the second voltage detection unit, and the third voltage detection unit shown sample the voltage of the lower transistor to obtain the turn-off voltage drop of the lower transistor.

[0060] In some embodiments of the present invention, determining the three-phase current of the motor may include: sampling the bus current during a second sampling window and a third sampling window to obtain the two-phase current of the motor; and determining the third-phase current of the motor based on the two-phase current of the motor.

[0061] Specifically, refer to Figure 4As shown, within the second sampling window time Ts2 and the third sampling window time Ts3, the following can be utilized: Figure 1 The current detection unit shown detects the DC bus current. Based on the DC bus current, two of the three-phase currents of the motor are reconstructed. The third phase current can be calculated based on the single-resistor current reconstruction technology, that is, according to the formula Iu+Iv+Iw=0, where Iu is the U-phase current of the motor, Iv is the V-phase current of the motor, and Iw is the W-phase current of the motor.

[0062] Furthermore, as a first example, the U-phase current and the turn-off voltage drop of the lower transistor of the U-phase bridge arm can be obtained within the second sampling window; within the third sampling window, the W-phase current, the turn-off voltage drop of the lower transistor of the U-phase bridge arm, and the turn-off voltage drop of the lower transistor of the V-phase bridge arm can be obtained, or the V-phase current, the turn-off voltage drop of the lower transistor of the U-phase bridge arm, and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained; within the fourth sampling window, the turn-off voltage drops of the lower transistors of the U-phase bridge arm, the V-phase bridge arm, and the W-phase bridge arm can be obtained.

[0063] Specifically, refer to Figure 4 As shown, within the second sampling window time Ts2, since the upper transistor of one phase of the three-phase bridge arm is in a conducting state and the lower transistors of the other two phases are in a conducting state, there is current in the DC bus. At this time, the phase current of the phase containing the upper transistor can be obtained by sampling the DC bus current Idc, and the turn-off voltage drop of the lower transistor of the phase containing the upper transistor can also be sampled. Figure 4 As shown, during the second sampling window time Ts2, the upper tube VT1 of the U-phase bridge arm is in the on state. Therefore, the U-phase current Iu can be obtained by sampling the DC bus current Idc, and the turn-off voltage drop Vdsu_off of the lower tube VT4 can be obtained by sampling the voltage.

[0064] Within the third sampling window time Ts3, since the upper transistors of two phase arms of the three-phase bridge arm are in the conducting state, and the lower transistor of the other phase arm is in the conducting state, there is current in the DC bus. At this time, the phase current of the phase containing the lower transistor can be obtained by sampling the DC bus current Idc, and the turn-off voltage drop of the lower transistor of the phase containing the upper transistor can also be sampled. Figure 4As shown, within the third sampling window time Ts3, both the upper transistor VT1 of the U-phase bridge arm and the upper transistor VT3 of the V-phase bridge arm are in the conducting state. Therefore, the W-phase current Iw can be obtained by sampling the DC bus current Idc, and the turn-off voltage drop Vdsu_off of the lower transistor VT4 and the turn-off voltage drop Vdsv_off of the lower transistor VT6 can be obtained by voltage sampling. Alternatively, within the third sampling window time Ts3, both the upper transistor VT1 of the U-phase bridge arm and the upper transistor VT5 of the W-phase bridge arm are in the conducting state (not shown in the figure). Therefore, the V-phase current IV can be obtained by sampling the DC bus current Idc, and the turn-off voltage drop Vdsu_off of the lower transistor VT4 and the turn-off voltage drop Vdsw_off of the lower transistor VT2 can be obtained by voltage sampling. That is, the second transistor to be turned on may be either the V-phase or the W-phase, and the corresponding phase current and turn-off voltage drop are different when different phases are turned on.

[0065] Within the fourth sampling window time Ts4, since the upper tubes of all three phase bridge arms are in the on state and the lower tubes are in the off state, the off-state voltage drop of each lower tube can be sampled. That is, the off-state voltage drop Vdsu_off of lower tube VT4, the off-state voltage drop Vdsv_off of lower tube VT6, and the off-state voltage drop Vdsw_off of lower tube VT2 can be sampled.

[0066] It should be noted that when the voltage drop sampling of the turn-off transistors of the three lower transistors cannot be completed due to the short fourth sampling window time Ts4, the voltage drop sampling of the corresponding lower transistors at other vector occurrence times can be carried out in a dispersed manner according to the three-phase PWM turn-on relationship, i.e., vector state. For example, the voltage drop across the lower tube VT4 can be sampled within the second sampling window time Ts2 to obtain the turn-off voltage drop Vdsu_off; the voltage drop across the lower tube VT6 can be sampled within the third sampling window time Ts3 to obtain the turn-off voltage drop Vdsv_off; and the voltage drop across the lower tube VT2 can be sampled within the fourth sampling window time Ts4 to obtain the turn-off voltage drop Vdsw_off. Alternatively, the voltage drop across the lower tube VT4 can be sampled within the second sampling window time Ts2 to obtain the turn-off voltage drop Vdsu_off; the voltage drop across the lower tube VT2 can be sampled within the third sampling window time Ts3 to obtain the turn-off voltage drop Vdsw_off; and the voltage drop across the lower tube VT6 can be sampled within the fourth sampling window time Ts4 to obtain the turn-off voltage drop Vdsv_off. This yields the turn-off voltage drop for each lower tube.

[0067] When the U-phase current Iu and W-phase current Iw are obtained using the aforementioned method, the V-phase current Iv can be calculated based on the fact that the sum of the three-phase currents is zero. Similarly, when the U-phase current Iu and V-phase current Iv are obtained using the aforementioned method, the W-phase current Iw can be calculated based on the fact that the sum of the three-phase currents is zero. After obtaining the U-phase current Iu, V-phase current Iv, and W-phase current Iw, the conduction current of the upper tube VT1 can be determined as Iu, the conduction current of the upper tube VT3 as Iv, and the conduction current of the upper tube VT5 as Iw.

[0068] As a second example, the V-phase current and the turn-off voltage drop of the lower transistor of the V-phase bridge arm can be obtained during the second sampling window; during the third sampling window, the U-phase current, the turn-off voltage drop of the lower transistor of the V-phase bridge arm, and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained, or the W-phase current, the turn-off voltage drop of the lower transistor of the U-phase bridge arm, and the turn-off voltage drop of the lower transistor of the V-phase bridge arm can be obtained; during the fourth sampling window, the turn-off voltage drop of the lower transistor of the U-phase bridge arm, the turn-off voltage drop of the lower transistor of the V-phase bridge arm, and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained.

[0069] As a third example, the W-phase current and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained during the second sampling window; during the third sampling window, the U-phase current, the turn-off voltage drop of the lower transistor of the V-phase bridge arm, and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained, or the V-phase current, the turn-off voltage drop of the lower transistor of the U-phase bridge arm, and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained; during the fourth sampling window, the turn-off voltage drop of the lower transistor of the U-phase bridge arm, the turn-off voltage drop of the lower transistor of the V-phase bridge arm, and the turn-off voltage drop of the lower transistor of the W-phase bridge arm can be obtained.

[0070] It should be noted that the second example involves sampling the phase current and the turn-off voltage drop of the lower transistor when the first switched-on transistor is phase V and the last switched-on transistor is phase U or W. The third example involves sampling the phase current and the turn-off voltage drop of the lower transistor when the first switched-on transistor is phase W and the last switched-on transistor is phase U or V. The sampling principle is the same as... Figure 4 The example shown is similar; please refer to the specific examples. Figure 4 As shown, this will not be elaborated further here. Table 1 presents the relationship between the phase current corresponding to the DC bus current in different sectors and the available turn-off voltage drop sampling for the next lower transistor:

[0071] Table 1

[0072]

[0073] In Table 1, UH represents the conduction status of the upper tube of the U-phase bridge arm, VH represents the conduction status of the upper tube of the V-phase bridge arm, and WH represents the conduction status of the upper tube of the W-phase bridge arm. "1" indicates conduction, and "0" indicates disconnection. Idc is the DC bus current, Vdc is the DC bus voltage, Iu is the U-phase current, Iv is the V-phase current, Iw is the W-phase current, Vdsu_off is the voltage drop across the lower tube of the U-phase bridge arm, Vdsv_off is the voltage drop across the lower tube of the V-phase bridge arm, and Vdsw_off is the voltage drop across the lower tube of the W-phase bridge arm.

[0074] In some embodiments of the present invention, reference is made to Figure 5 As shown, the on-state voltage drop of at least one phase arm of a three-phase inverter bridge is determined based on the DC bus voltage, the turn-off diode voltage drop, and the three-phase current, including:

[0075] Step S201: Determine the average DC bus current based on the three-phase current, and determine the winding voltage drop based on the average DC bus current and the three-phase winding resistance of the motor.

[0076] Specifically, after obtaining the three-phase currents Iu, Iv, and Iw through the aforementioned method, the average DC bus current can be calculated based on the three-phase currents Iu, Iv, and Iw.

[0077] In some embodiments of the present invention, determining the average DC bus current based on the three-phase current includes: determining the switching function when the upper tube of each phase arm of the three-phase inverter bridge is turned on; and determining the average DC bus current based on the switching function when the upper tube of each phase arm is turned on and the phase current in the three-phase current.

[0078] Specifically, the switching functions when the upper tubes of the U-phase bridge arm, V-phase bridge arm, and W-phase bridge arm are turned on are as follows:

[0079]

[0080] Where Sa, Sb, and Sc are the switching functions when the upper tubes of the U-phase, V-phase, and W-phase bridge arms are turned on, respectively; Tpwm is the count value corresponding to the top of the triangular wave; and Ta, Tb, and Tc are the comparison values ​​of the U-phase, V-phase, and W-phase outputs, respectively. Figure 4 The triangular wave count values ​​are shown when the upper tubes of the U-phase bridge arm, V-phase bridge arm, and W-phase bridge arm are turned on.

[0081] DC bus average current I dc_avg It can be calculated using the following formula (3):

[0082] I dc_avg =Sa*Iu+Sb*Iv+Sc*Iw (3)

[0083] Then, the winding voltage drop is calculated based on the average DC bus current and the resistance of the three-phase motor windings, i.e., the winding voltage drop is R*I. dc_avg , where R is the resistance of the three-phase winding.

[0084] Step S202: Determine the conduction tube voltage drop when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus voltage, the turn-off tube voltage drop, and the winding voltage drop.

[0085] It should be noted that the voltage drop of the turn-off transistor of the lower transistor of the three-phase inverter bridge is equal to the terminal voltage of the three phases of the DC bus negative terminal (with the negative terminal as the reference point N), that is, the terminal voltage satisfies the following formula (4):

[0086]

[0087] Where Vun is the voltage at the U-phase terminal, Vvn is the voltage at the V-phase terminal, and Vwn is the voltage at the W-phase terminal.

[0088] Furthermore, the voltage drop across the conductive tube can be calculated using the following formula (5):

[0089] V ds(u,v,w)_up =Vdc-V (u,v,w)n -R*I dc_avg (5)

[0090] Among them, V ds(u,v,w)_up Vdc is the on-state voltage drop of the upper tube, and Vdc is the DC bus voltage. (u,v,w)n R is the terminal voltage, R is the resistance of the three-phase winding, and I is the voltage across the terminals. dc_avg This represents the average current of the DC bus.

[0091] Therefore, the on-state voltage drop of the upper tube can be calculated based on the off-state voltage drop of the lower tube, the DC bus voltage, and the three-phase current of the motor. There is no need to set up a voltage detection unit for the upper tube, which effectively solves the problem of high voltage detection cost of the upper tube due to the floating potential of the upper tube when directly detecting the voltage of the upper tube. This can effectively reduce the cost of detecting and protecting the junction temperature of the upper tube.

[0092] The following example illustrates the process of obtaining the junction temperature of the tube.

[0093] Specifically, with Figure 4Taking the first switching cycle as an example, four sampling window times Ts1, Ts2, Ts3 and Ts4 can be calculated based on the conduction timing. Ts1 = Ta - T, where Ta is the conduction time of the upper tube VT1 of the U-phase bridge arm. Since the sampling window time is timed by another timer, the initial time T = 0, i.e., Ts1 = Ta; Ts2 = Tb - Ta - Tdelay, where Tb is the conduction time of the upper tube VT3 of the V-phase bridge arm, and Tdelay is the first preset time; Ts3 = Tc - Tb - Tdelay, where Tc is the conduction time of the upper tube VT5 of the W-phase bridge arm; Ts4 = Tc' - T, where Tc' is the turn-off time of the upper tube VT5 of the W-phase bridge arm. The initial time T = 0, i.e., Ts4 = Tc'.

[0094] When the triangular wave timer experiences an underflow interrupt (i.e., the PWM underflow interrupt begins), the first sampling window time Ts1 is entered. At this time, the timing of the sampling timer is set to Ta+Tdelay, and the sampling timer is started (the counting pulse of the sampling timer can be at the same frequency as the PWM pulse). Simultaneously, the DC bus voltage is sampled to obtain the DC bus voltage Vdc, which is then saved. When the sampling timer reaches Ta+Tdelay, the second sampling window time Ts2 is entered. At this time, the timing of the sampling timer is set to Ts2+Tdelay, and the sampling timer is started. Simultaneously, the voltage drop across the turn-off transistor VT4 and the DC bus current Idc are sampled, obtaining the voltage drop across the turn-off transistor VT4 Vdsu_off and the U-phase current Iu, which are then saved. When the sampling timer reaches Ts2 + Tdelay, the third sampling window Ts3 begins. At this time, sampling of the turn-off transistor voltage drops of the lower transistors VT4 and VT6, as well as the DC bus current Idc, begins, obtaining the turn-off transistor voltage drops Vdsu_off and Vdsv_off of VT4 and VT6, and the W-phase current Iw, which are then saved. When an overflow interrupt occurs in the triangular wave timer (i.e., the PWM overflow interrupt begins), the fourth sampling window Ts4 begins, and sampling of the turn-off transistor voltage drops of the lower transistors begins. This involves sampling the turn-off transistor voltage drops of one or more lower transistors, for example, sampling the turn-off transistor voltage drops of VT4, VT6, and VT2 to obtain the turn-off transistor voltage drops Vdsu_off, Vdsv_off, and Vdsw_off, which are then saved. This completes the sampling for one switching cycle.

[0095] Then, the V-phase current Iv can be calculated according to Iu+Iv+Iw=0, thereby obtaining the three-phase currents Iu, Iv and Iw of the motor. Based on the relationship between the three-phase current of the motor and the conduction current of the upper tube, the conduction current of the upper tube can be obtained. At the same time, based on the DC bus voltage Vdc, the three-phase currents Iu, Iv and Iw of the motor, and the voltage drops of the turn-off tubes Vdsu_off, Vdsv_off and Vdsw_off of the lower tube, the conduction voltage drops of the upper tubes VT1, VT3 and VT5 can be calculated using the above formulas (2)-(5). Finally, based on the on-state voltage drop and on-state current of the upper tubes VT1, VT3 and VT5, the on-state resistance of the upper tubes VT1, VT3 and VT5 is calculated using the above formula (1). Based on the relationship curve between the on-state resistance and the on-state resistance that matches the model of the upper tube and the junction temperature, the junction temperature of the three upper tubes VT1, VT3 and VT5 is obtained by looking up a table. Thus, the detection of the junction temperature of the upper tubes within one cycle is completed.

[0096] It should be noted that the junction temperature detection process for other switching cycles is the same as that for the first switching cycle, and will not be repeated here.

[0097] In the above embodiments, during motor control, based on the conduction timing, the sampling window time is calculated at different voltage vector times, and the current of the corresponding phase and the voltage drop of the lower transistor are sampled within the sampling window time. Based on the characteristic that the phase current is zero, the three-phase current is reconstructed under single-resistor current sampling. Then, the conduction current of the lower transistor is obtained from the three-phase current. The conduction resistance can be calculated from the conduction current and the voltage drop. The junction temperature of the lower transistor is obtained from the conduction resistance and the relationship curve between the conduction resistance and the junction temperature. Since the current sampling period is short, it can respond quickly to the temperature change of the switching transistor, thereby overcoming the problems of slow response, poor accuracy and low reliability of indirectly obtaining the junction temperature of the switching transistor through the side temperature resistor. It has high engineering application value.

[0098] It should be noted that, in order to provide comprehensive protection for each switching transistor, a corresponding voltage sampling unit is set for each lower transistor in the aforementioned example. The voltage sampling unit samples the turn-off voltage drop of the lower transistor, and then obtains the on-state voltage drop of each upper transistor based on the turn-off voltage drop of each lower transistor, thereby obtaining the junction temperature of the upper transistor. The sampling method is not limited to sampling the turn-off voltage drop of all lower transistors. The voltage drops of all lower transistors can also be estimated by sampling the turn-off voltage drop of one or two lower transistors, and then the junction temperature of all upper transistors can be estimated, so as to reduce costs.

[0099] According to one embodiment of the present invention, after determining the junction temperature of the upper tube, the switching tube junction temperature detection method may further include: performing instantaneous over-temperature protection and / or inverse-time overload protection based on the junction temperature of the upper tube.

[0100] It should be noted that instantaneous over-temperature protection refers to protection that immediately activates when the junction temperature of the switching transistor meets the over-temperature protection conditions; inverse-time overload protection refers to protection with different operating times at different junction temperatures when the junction temperature of the switching transistor meets the overload protection conditions, with higher junction temperatures resulting in shorter operating times and lower junction temperatures incurring longer operating times. After obtaining the junction temperature of the upper transistor, inverse-time overload protection and / or instantaneous over-temperature protection can be implemented based on this temperature, preferably both protections can be implemented simultaneously.

[0101] In some embodiments, instantaneous over-temperature protection based on the junction temperature of the upper tube may include: controlling the three-phase inverter bridge to stop output when the junction temperature of the upper tube exceeds the preset maximum protection temperature (the preset maximum protection temperature can be set according to the actual situation, and can be determined according to the model of the switching tube).

[0102] Specifically, after obtaining the junction temperature of the upper transistor using the aforementioned method, it is determined whether the junction temperature meets the over-temperature protection conditions, such as whether the junction temperature is greater than or equal to the preset maximum protection temperature Tmax. If the junction temperature is greater than or equal to the preset maximum protection temperature Tmax, it indicates that the current junction temperature has reached the temperature tolerance limit of the switching transistor. If operation continues, it may damage the switching transistor. At this time, the protection action is immediately executed, that is, the three-phase inverter bridge is controlled to stop working, that is, the control signals of the switching transistors of the three-phase inverter bridge, such as PWM signals, are immediately turned off to stop driving the switching transistors to work, so that the three-phase inverter bridge stops working, thereby realizing the instantaneous over-temperature protection of the three-phase inverter bridge, and at the same time, an over-temperature alarm reminder can also be given.

[0103] In some embodiments, inverse-time overload protection based on the upper junction temperature may include: determining an inverse-time protection curve and timing the overload protection based on the relationship between the upper junction temperature and the inverse-time protection curve; and controlling the three-phase inverter bridge to stop output when the timing period arrives. The timing period is inversely correlated with the upper junction temperature; that is, the higher the upper junction temperature, the shorter the timing period, and the lower the upper junction temperature, the longer the timing period.

[0104] Specifically, the inverse time protection curve can be determined based on the characteristics of the switching transistor, namely its temperature characteristic point. For example, three alarm temperatures can be set based on the temperature characteristic point: a first alarm temperature Twarning1, a second alarm temperature Twarning2, and a third alarm temperature Twarning3. The timing period corresponding to the first alarm temperature Twarning1 is 1 minute, the timing period corresponding to the second alarm temperature Twarning2 is 10 seconds, and the timing period corresponding to the third alarm temperature Twarning3 is 1 second. The timing period between the first alarm temperature Twarning1 and the second alarm temperature Twarning2 is less than 1 minute and greater than 10 seconds, and the timing period between the second alarm temperature Twarning2 and the third alarm temperature Twarning3 is less than 10 seconds and greater than 1 second, ultimately forming a curve like this. Figure 6 The inverse time protection curve shown.

[0105] After obtaining the upper tube junction temperature Tj through the aforementioned method, the upper tube junction temperature Tj is judged. When the obtained upper tube temperature Tj is equal to the first alarm temperature Twarning1 in the inverse time protection curve, a 1-minute overload protection timer is started. When the timer reaches 1 minute, the protection action is executed, that is, the three-phase inverter bridge is controlled to stop working, and an overload alarm reminder can also be given.

[0106] When the obtained upper tube junction temperature Tj is greater than the first alarm temperature Twarning1 and less than the second alarm temperature Twarning2 in the inverse time protection curve, the corresponding timing time is obtained according to the upper tube junction temperature and the inverse time protection curve by looking up a table (the inverse time protection curve can be converted into a data table showing the relationship between the upper tube junction temperature and the timing time in advance, and obtained by looking up the table). This timing time is less than 1 minute and greater than 10 seconds. The overload protection timing is started based on the timing time. When the timing time is reached, the protection action is executed, that is, the three-phase inverter bridge is controlled to stop working, and an overload alarm reminder can also be given at the same time.

[0107] When the obtained upper tube temperature Tj is equal to the second alarm temperature Twarning2, a 10-second overload protection timer is activated. When the timer reaches 10 seconds, the protection action is executed, that is, the three-phase inverter bridge is controlled to stop working, and an overload alarm reminder is also given.

[0108] When the obtained upper tube junction temperature Tj is greater than the second alarm temperature Twarning2 and less than the third alarm temperature Twarning3 in the inverse time protection curve, the corresponding timing time is obtained by looking up the table according to the upper tube junction temperature and the inverse time protection curve. This timing time is less than 10 seconds and greater than 1 second. The overload protection timing is started based on the timing time. When the timing time is reached, the protection action is executed, that is, the three-phase inverter bridge is controlled to stop working, and an overload alarm reminder can also be given.

[0109] When the obtained upper tube temperature Tj is equal to the third alarm temperature Twarning3, a 1-second overload protection timer is activated. When the timer reaches 1 second, the protection action is executed, that is, the three-phase inverter bridge is controlled to stop working, and an overload alarm reminder is also given.

[0110] It should be noted that if the upper pipe temperature is not within the overload temperature range within the timed period, i.e., not between the first alarm temperature Twarning1 and the third alarm temperature Twarning3, no protection action will be taken. In other words, after determining the time remaining before overload protection by comparing the obtained upper pipe temperature with each alarm temperature, overload protection will be initiated once the temperature remains within the overload temperature range and the delay time has elapsed, and an overload alarm will be issued simultaneously. Furthermore, the maximum alarm temperature corresponding to inverse-time overload protection is lower than the preset maximum protection temperature corresponding to instantaneous overtemperature protection, such as the third alarm temperature Twarning3 being lower than the preset maximum protection temperature Tmax. It can be understood that instantaneous overtemperature protection can also be considered a special case of inverse-time overload protection, with a corresponding timed period of 0 seconds.

[0111] It should be noted that in some embodiments, after obtaining the junction temperature of the upper transistor, the junction temperature is further filtered before temperature protection is performed based on it. Specifically, in practical applications, due to the complex electromagnetic environment of the application itself, interference spikes such as signal noise from spatial radiation and line conduction may exist during the acquisition of transistor voltage drop signals and phase current signals of each phase motor, causing the junction temperature data to fluctuate within a certain range. In order to ensure that the temperature protection action operates stably within the inverse time protection curve, that is, the protection value needs to be filtered reasonably, therefore, after obtaining the junction temperature of the lower transistor, the junction temperature is also filtered before temperature protection is performed based on it.

[0112] As a concrete example, still using Figure 4The example shown is used as an example. After obtaining the junction temperature of each upper tube VT1, VT3, and VT5, the junction temperature of each upper tube VT1, VT3, and VT5 is compared with the preset maximum protection temperature Tmax. If the junction temperature of any upper tube VT1, VT3, or VT5 is greater than or equal to the preset maximum protection temperature Tmax, the protection action is immediately executed, that is, the three-phase inverter bridge is controlled to stop working and an over-temperature alarm is issued. If the junction temperature of each upper tube VT1, VT3, and VT5 is less than the preset maximum protection temperature Tmax, overload protection is performed on each upper tube based on the inverse time protection curve. For example, when the junction temperature of the upper tube VT1 equals the first alarm temperature Twarning1, a 1-minute overload protection timer is activated. When the timer reaches 1 minute, the protection action is executed, i.e., the three-phase inverter bridge is stopped and an overload alarm is issued. When the junction temperature of the upper tube VT1 is greater than the first alarm temperature Twarning1 but less than the second alarm temperature Twarning2, the corresponding timer is obtained by looking up a table based on the inverse-time protection curve. When the timer reaches 1 minute, the protection action is executed and an overload alarm is issued. And so on. Specific details will not be listed here. The inverse-time overload protection for the upper tubes VT3 and VT5 is the same as that for the upper tube VT1, and will not be elaborated further here.

[0113] In the above embodiments, after obtaining the junction temperature of the upper tube, inverse time overload protection and instantaneous overload protection, i.e., maximum temperature instantaneous protection, are also performed based on the junction temperature. This can effectively prevent the three-phase inverter bridge from being damaged due to excessive temperature and achieve reliable temperature protection for the three-phase inverter bridge.

[0114] In summary, the switching transistor junction temperature detection method according to embodiments of the present invention shares the simultaneous temperature detection and protection of multiple transistors through time-division current sampling technology. It has the advantages of rapid and efficient detection of the internal temperature (junction temperature) of each upper transistor, small temperature deviation, and fast response speed. It overcomes the problems of slow response, poor accuracy, and low reliability that exist in indirectly obtaining the junction temperature of the switching transistor through a side-mounted temperature resistor. Moreover, the method is simple, easy to implement, and has high engineering application value. At the same time, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This can effectively solve the problem of high voltage detection cost of the upper transistor caused by the floating potential of the upper transistor when directly detecting the voltage of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0115] In some embodiments of the present invention, a motor controller is provided, including a processor, a memory, and a switching transistor junction temperature detection program stored in the memory and executable on the processor. When the processor executes the program, it implements the aforementioned switching transistor junction temperature detection method.

[0116] According to the motor controller of this invention, based on the aforementioned switching transistor junction temperature detection method, multiple simultaneous temperature detection and protection are shared through current time-division sampling technology. This method features rapid and efficient detection of the internal temperature (junction temperature) of each upper transistor, with small temperature deviation and fast response speed. It overcomes the problems of slow response, poor accuracy, and low reliability associated with indirectly obtaining the junction temperature of the switching transistor through a side-mounted temperature resistor. Moreover, the method is simple, easy to implement, and has high engineering application value. At the same time, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This effectively solves the problem of high voltage detection cost of the upper transistor caused by the floating potential of the upper transistor when directly detecting its voltage, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0117] In some embodiments of the present invention, a computer-readable storage medium is provided, which stores a switching transistor junction temperature detection program, which, when executed by a processor, implements the aforementioned switching transistor junction temperature detection method.

[0118] According to the computer-readable storage medium of the present invention, based on the aforementioned switching transistor junction temperature detection method, multiple simultaneous temperature detection and protection are shared through current time-division sampling technology. This method features rapid and efficient detection of the internal temperature (junction temperature) of each upper transistor, with small temperature deviation and fast response speed. It overcomes the problems of slow response, poor accuracy, and low reliability associated with indirectly obtaining the junction temperature of the switching transistor through a side-mounted temperature resistor. Furthermore, the method is simple, easy to implement, and has high engineering application value. At the same time, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This effectively solves the problem of high voltage detection cost of the upper transistor caused by the floating potential of the upper transistor when directly detecting its voltage, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0119] In some embodiments of the present invention, a motor control system is also provided, see reference. Figure 1 As shown, the motor control system includes: a motor (not shown in the figure), a three-phase inverter bridge 10, a current detection unit 20, a first voltage detection unit 30, a second voltage detection unit 40, a third voltage detection unit 50, a fourth voltage detection unit 60, and a control unit (not specifically shown in the figure).

[0120] The three-phase inverter bridge 10 is connected between the DC buses and drives the motor to operate. The current detection unit 20 is set to the negative terminal of the DC bus and is used to detect the DC bus current. The first voltage detection unit 30 is set to the lower tube of the U-phase bridge arm in the three-phase inverter bridge 10 and is used to detect the voltage drop of the lower tube of the U-phase bridge arm. The second voltage detection unit 40 is set to the lower tube of the V-phase bridge arm in the three-phase inverter bridge 10 and is used to detect the voltage drop of the lower tube of the V-phase bridge arm. The third voltage detection unit 50 is set to the lower tube of the W-phase bridge arm in the three-phase inverter bridge 10 and is used to detect the voltage drop of the lower tube of the W-phase bridge arm. The fourth voltage detection unit 60 is used to detect the DC bus voltage.

[0121] The control unit is used to determine the turn-off transistor voltage drop when the lower transistor of at least one phase arm of the three-phase inverter bridge 10 is turned off based on the lower transistor voltage drop of each phase arm in the three-phase inverter bridge 10, and to determine the three-phase current of the motor based on the DC bus current, and to determine the conduction current when the upper transistor of at least one phase arm of the three-phase inverter bridge 10 is turned on based on the three-phase current; to determine the conduction transistor voltage drop when the upper transistor of at least one phase arm of the three-phase inverter bridge 10 is turned on based on the DC bus voltage, the turn-off transistor voltage drop and the three-phase current, and to determine the conduction resistance when the upper transistor of at least one phase arm is turned on based on the conduction transistor voltage drop and the conduction current, and to determine the junction temperature of the upper transistor of at least one phase arm based on the conduction resistance.

[0122] According to one embodiment of the present invention, the control unit is further configured to: determine a first sampling window time, wherein the first sampling window time is the time from the underflow interruption time of the PWM triangular wave to the turn-on time of the upper tube of any one phase arm of the three-phase inverter bridge 10; and within the first sampling window time, perform bus voltage sampling to obtain the DC bus voltage.

[0123] According to an embodiment of the present invention, the control unit is specifically configured to: determine a second sampling window time, a third sampling window time, and a fourth sampling window time, wherein the second sampling window time is the time from the turn-on of the upper tube of any one phase arm of the three-phase inverter bridge 10 after a first preset time delay to the turn-on of the upper tube of the next phase arm of the three-phase inverter bridge 10; the third sampling window time is the time from the turn-on of the upper tube of the next phase arm of the three-phase inverter bridge 10 after a first preset time delay to the turn-on of the upper tube of the last phase arm of the three-phase inverter bridge 10; and the fourth sampling window time is the time from the overflow interruption moment of the PWM triangular wave to the turn-off of the upper tube of any one phase arm of the three-phase inverter bridge 10; and within at least one of the second, third, and fourth sampling window times, perform turn-off tube voltage drop sampling to obtain the turn-off tube voltage drop when the lower tube of at least one phase arm of the three-phase inverter bridge 10 is turned off.

[0124] According to one embodiment of the present invention, the control unit is specifically configured to: sample the bus current during the second sampling window time and the third sampling window time to obtain the two-phase current of the motor; and determine the third-phase current of the motor based on the two-phase current of the motor.

[0125] According to one embodiment of the present invention, the control unit is specifically configured to: determine the average DC bus current based on the three-phase current, and determine the winding voltage drop based on the average DC bus current and the three-phase winding resistance of the motor; and determine the conduction tube voltage drop when the upper tube of at least one phase arm of the three-phase inverter bridge 10 is turned on based on the DC bus voltage, the turn-off tube voltage drop, and the winding voltage drop.

[0126] According to one embodiment of the present invention, the control unit is specifically used to: determine the switching function when the upper tube of each phase arm of the three-phase inverter bridge 10 is turned on; and determine the average DC bus current based on the switching function when the upper tube of each phase arm is turned on and the phase current in the three-phase current.

[0127] According to one embodiment of the present invention, the control unit is further configured to: after determining the junction temperature of the upper tube, perform instantaneous over-temperature protection and inverse-time overload protection based on the junction temperature of the upper tube.

[0128] According to one embodiment of the present invention, the control unit is specifically used to: control the three-phase inverter bridge 10 to stop output when the junction temperature of the upper tube is greater than the preset maximum protection temperature.

[0129] According to one embodiment of the present invention, the control unit is specifically used to: determine the inverse time protection curve, and perform overload protection timing based on the relationship between the upper tube junction temperature and the inverse time protection curve; when the timing period arrives, control the three-phase inverter bridge 10 to stop output.

[0130] It should be noted that for the description of the motor control system in this application, please refer to the description of the switching transistor junction temperature detection method in this application, which will not be repeated here.

[0131] The motor control system according to embodiments of the present invention shares multiple simultaneous temperature detection and protection through current time-division sampling technology. It has the characteristics of fast and efficient detection of the internal temperature (junction temperature) of each upper transistor, small temperature deviation, and fast response speed. It overcomes the problems of slow response, poor accuracy, and low reliability of indirectly obtaining the junction temperature of the switching transistor through a side temperature resistor. Moreover, the method is simple, easy to implement, and has high engineering application value. At the same time, the on-state voltage drop of the upper transistor is obtained based on the DC bus voltage, the off-state voltage drop of the lower transistor, and the three-phase current. This can effectively solve the problem of high voltage detection cost of the upper transistor caused by the floating potential of the upper transistor when directly detecting the voltage of the upper transistor, thereby effectively reducing the cost of detecting and protecting the junction temperature of the upper transistor.

[0132] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0133] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0134] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0135] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0136] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0137] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for detecting the junction temperature of a switching transistor in a motor control system, characterized in that, The motor control system includes a three-phase inverter bridge for driving the motor, and the method includes: Determine the DC bus voltage, the turn-off voltage drop when the lower switch of at least one phase arm of the three-phase inverter bridge is turned off, and the three-phase current of the motor. The conduction current when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on is determined based on the three-phase current, and the conduction tube voltage drop when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on is determined based on the DC bus voltage, the voltage drop of the turn-off tube, and the three-phase current. The on-resistance when the upper tube of at least one phase bridge arm is turned on is determined based on the voltage drop across the conducting tube and the on-current. The junction temperature of the upper tube of the at least one phase bridge arm is determined based on the on-resistance.

2. The method according to claim 1, characterized in that, Determining the DC bus voltage includes: Determine the first sampling window time, wherein the first sampling window time is the time from the underflow interruption time of the PWM triangular wave to the time when the upper tube of any one phase arm of the three-phase inverter bridge is turned on; During the first sampling window, the bus voltage is sampled to obtain the DC bus voltage.

3. The method according to claim 1, characterized in that, Determining the turn-off voltage drop when the lower switch of at least one phase arm of the three-phase inverter bridge is turned off includes: The second sampling window time, the third sampling window time, and the fourth sampling window time are determined. The second sampling window time is the time from when the upper tube of any one phase arm of the three-phase inverter bridge is turned on and delayed by a first preset time until the upper tube of the next phase arm of the three-phase inverter bridge is turned on. The third sampling window time is the time from when the upper tube of the next phase arm of the three-phase inverter bridge is turned on and delayed by a first preset time until the upper tube of the last phase arm of the three-phase inverter bridge is turned on. The fourth sampling window time is the time from when the overflow interruption of the PWM triangular wave occurs until the upper tube of any one phase arm of the three-phase inverter bridge is turned off. During at least one of the second sampling window time, the third sampling window time, and the fourth sampling window time, the turn-off tube voltage drop is sampled to obtain the turn-off tube voltage drop when the lower tube of at least one phase arm of the three-phase inverter bridge is turned off.

4. The method according to claim 3, characterized in that, Determining the three-phase current of the motor includes: During the second sampling window time and the third sampling window time, the bus current is sampled to obtain the two-phase current of the motor; The third phase current of the motor is determined based on the two-phase current of the motor.

5. The method according to any one of claims 1-4, characterized in that, Determining the conduction diode voltage drop when the upper diode of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus voltage, the turn-off diode voltage drop, and the three-phase current includes: The average DC bus current is determined based on the three-phase current, and the winding voltage drop is determined based on the average DC bus current and the three-phase winding resistance of the motor. The conduction tube voltage drop when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on is determined based on the DC bus voltage, the voltage drop of the turn-off tube, and the voltage drop of the winding.

6. The method according to claim 5, characterized in that, Determining the average DC bus current based on the three-phase current includes: Determine the switching function when the upper tube of each phase arm of the three-phase inverter bridge is turned on; The average DC bus current is determined based on the switching function when the upper tube of each phase bridge arm is turned on and the current of each phase in the three-phase current.

7. The method according to claim 1, characterized in that, After determining the junction temperature of the upper tube, the method further includes: Instantaneous over-temperature protection and inverse-time overload protection are performed based on the junction temperature of the upper tube.

8. The method according to claim 7, characterized in that, Instantaneous over-temperature protection based on the upper tube junction temperature includes: When the junction temperature of the upper tube exceeds the preset maximum protection temperature, the three-phase inverter bridge is controlled to stop outputting.

9. The method according to claim 7, characterized in that, Inverse-time overload protection based on the upper tube junction temperature includes: Determine the inverse time protection curve and perform overload protection timing based on the relationship between the upper tube junction temperature and the inverse time protection curve; When the timer expires, the three-phase inverter bridge is controlled to stop outputting.

10. A motor controller, characterized in that, The method includes a memory, a processor, and a switching transistor junction temperature detection program stored in the memory and executable on the processor. When the processor executes the switching transistor junction temperature detection program, it implements the switching transistor junction temperature detection method in the motor control system according to any one of claims 1-9.

11. A computer-readable storage medium, characterized in that, It stores a junction temperature detection program for a switching transistor in a motor control system. When the processor executes the junction temperature detection program for a switching transistor in a motor control system, it implements the junction temperature detection method for a switching transistor in a motor control system according to any one of claims 1-9.

12. A motor control system, characterized in that, include: Electric motor; A three-phase inverter bridge is connected between DC buses and drives the motor to work. A current detection unit is provided, which is set to the negative terminal of the DC bus and is used to detect the DC bus current. The first voltage detection unit is set in accordance with the lower tube of the U-phase bridge arm in the three-phase inverter bridge and is used to detect the voltage drop of the lower tube of the U-phase bridge arm. The second voltage detection unit is set corresponding to the lower tube of the V-phase bridge arm in the three-phase inverter bridge and is used to detect the voltage drop of the lower tube of the V-phase bridge arm. The third voltage detection unit is set in accordance with the lower tube of the W-phase bridge arm in the three-phase inverter bridge and is used to detect the voltage drop of the lower tube of the W-phase bridge arm. The fourth voltage detection unit is used to detect the DC bus voltage; The control unit is used to determine the turn-off tube voltage drop when the lower tube of at least one phase arm of the three-phase inverter bridge is turned off based on the lower tube voltage drop of each phase arm of the three-phase inverter bridge, and to determine the three-phase current of the motor based on the DC bus current, and to determine the conduction current when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on based on the three-phase current. The control unit is further configured to: determine the on-state voltage drop when the upper tube of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus voltage, the voltage drop of the turn-off tube, and the three-phase current; determine the on-resistance when the upper tube of the at least one phase arm is turned on based on the voltage drop of the turn-off tube and the on-state current; and determine the junction temperature of the upper tube of the at least one phase arm based on the on-resistance.

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