Method for determining junction temperature of mosfet in motor controller

Abstract

The invention discloses a method for determining the junction temperature of an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) in a motor controller, which comprises the following steps of: dividing elements in a cooling path of a chip into a plurality of stages of equivalent circuits, and calibrating the thermal resistance value and the thermal capacitance value of each stage of equivalent circuit; acquiring the temperature of the radiator, the heating power of the MOSFET, the heating power of the motor and the heating power of the PCB in real time; and calculating the junction temperature of the MOSFET according to the temperature of the radiator, the heating power of the MOSFET, the heating power of the motor, the heating power of the PCB and the thermal resistance value and the thermal capacitance value of each stage of equivalent circuit. According to the invention, in the process of calculating the junction temperature of the MOSFET, the influence of the heating power of the MOSFET, the heating power of the motor, the heating power of the PCB and the thermal resistance and thermal capacity characteristics of elements in the cooling path of the chip on the junction temperature of the MOSFET is considered, so that the calculated junction temperature of the MOSFET approaches the real junction temperature of the MOSFET.

Description

Technical Field

[0001] The present invention relates to the technical fields of motors and electronic control, and in particular, to a method for determining the junction temperature of a MOSFET in a motor controller. Background Art

[0002] The junction temperature of a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is the actual temperature when the MOSFET is operating. If the MOSFET junction temperature exceeds a set temperature threshold, it will cause the MOSFET to be damaged due to excessive temperature.

[0003] Currently, in a motor controller, a chip encapsulating a MOSFET is disposed on a PCB (Printed Circuit Board) by soldering. At a position adjacent to the chip, a temperature sensor is disposed on the PCB by soldering for measuring the temperature of the PCB, and the PCB temperature is used as the case temperature of the chip. By adjusting the output power of the motor controller, the temperature is made not to exceed the set temperature threshold, thereby ensuring that the MOSFET will not be damaged due to excessive temperature. However, the temperature obtained in this way is actually the PCB temperature at a position adjacent to the chip, rather than the MOSFET junction temperature, and there is a large error between the two, resulting in an inability to obtain the accurate MOSFET junction temperature. Therefore, in order to achieve the purpose of protecting the MOSFET, a large temperature margin needs to be reserved, that is, the temperature threshold needs to be set lower, resulting in an inability to fully utilize the performance of the motor controller. Summary of the Invention

[0004] The starting point of the present invention is to provide a method for determining the junction temperature of a MOSFET in a motor controller, thereby solving the above problems existing in the prior art.

[0005] An embodiment of the present invention provides a method for determining the junction temperature of a MOSFET in a motor controller, the motor controller including a chip encapsulating a MOSFET, a PCB, and a radiator, the chip being disposed on one side of the PCB, the radiator being disposed on the other side of the PCB, the method including:

[0006] Dividing the components in the cooling path of the chip into multiple levels of equivalent circuits, and calibrating the thermal resistance value and heat capacity value of each level of equivalent circuit;

[0007] Real-time obtaining the radiator temperature, the MOSFET heating power, the motor heating power, and the PCB heating power;

[0008] The MOSFET junction temperature is calculated based on the radiator temperature, the MOSFET heat generation power, the motor heat generation power, the PCB heat generation power, and the thermal resistance and heat capacity values of each equivalent circuit stage.

[0009] Optionally, the components in the cooling path of the chip are divided into four equivalent circuit stages, and each equivalent circuit stage includes a thermal resistance and a heat capacity.

[0010] Optionally, the chip encapsulating the MOSFET is used as the first equivalent circuit stage, and the first equivalent circuit stage includes thermal resistance R 1 and heat capacity C 1 ;

[0011] The solder, top-layer copper pour, PCB, and bottom-layer copper pour are used as the second equivalent circuit stage, and the second equivalent circuit stage includes thermal resistance R 2 and heat capacity C 2 ;

[0012] The thermal interface material is used as the third equivalent circuit stage, and the third equivalent circuit stage includes thermal resistance R 3 and heat capacity C 3 ;

[0013] The base plate and the radiator are used as the fourth equivalent circuit stage, and the fourth equivalent circuit stage includes thermal resistance R 4 and heat capacity C 4 .

[0014] Optionally, the MOSFET junction temperature T junction is calculated according to the following formula:

[0015] ΔT x(k) =ΔT x(k-1) +T S / (τ x+ T S )·[R x ·P xloss(k) -ΔT x(k-1) , τ x =R x C x , x = 1, 2, 3, 4,

[0016] T junction(k) =ΔT 1(k) +ΔT 2(k) +ΔT 3(k) +ΔT 4(k) +T cooler(k) ,

[0017] When x = 1, P loss(k) =P loss_junction(k) ,

[0018] When x = 2, 3, 4, P loss(k) = P loss_junction(k) + P loss_motor(k) + P loss_pcb(k) ,

[0019] where k is the order number of detection, T S is the duration of each detection, T cooler is the radiator temperature, P loss_junction is the heat generation power of the MOSFET, P loss_motor is the heat generation power of the motor, P loss_pcb is the heat generation power of the PCB.

[0020] Optionally, the solder temperature T solder is calculated according to the following formula:

[0021] T solder(k) = ΔT 2(k) + ΔT 3(k) + ΔT 4(k) + T cooler(k) .

[0022] Optionally, the radiator temperature T cooler is obtained in real time by means of a temperature sensor provided on the radiator.

[0023] Optionally, the heat generation power P loss_pcb of the PCB and the heat generation power P loss_motor of the motor are calculated according to the following formula:

[0024] P loss_pcb(k) = (T pcb(k) - T pcb(k-1) ) / R 5 ,

[0025] P loss_motor(k) = (T motor(k) - T motor(k-1) ) / R 6 ,

[0026] where T pcb is the PCB temperature, T motor is the motor temperature, R 5 is the thermal resistance between the PCB position of the temperature sensor set for obtaining the radiator temperature in real time and the PCB position of the chip set, and R 6 is the thermal resistance between the position of the temperature sensor set for obtaining the motor temperature in real time and the PCB position of the chip set.

[0027] Optionally, the temperature sensor for obtaining the motor temperature T motor in real time is provided on the stator of the motor.

[0028] Optionally, the PCB temperature T is obtained in real time by means of a temperature sensor disposed at a position on the PCB adjacent to the chip. pcb .

[0029] Optionally, after obtaining the MOSFET junction temperature, the method further includes:

[0030] Adjusting the output power of the motor controller such that the MOSFET junction temperature does not exceed a set temperature threshold.

[0031] The method for determining the MOSFET junction temperature in a motor controller according to an embodiment of the present invention has at least the following advantages:

[0032] In the present invention, during the process of calculating the MOSFET junction temperature, the influence of the MOSFET heating power, the motor heating power, the PCB heating power, and the thermal resistance and heat capacity characteristics of the components in the chip cooling path on the MOSFET junction temperature is considered, so that the calculated MOSFET junction temperature approaches the true MOSFET junction temperature.

[0033] In the present invention, since the calculated MOSFET junction temperature approaches the true MOSFET junction temperature, there is no need to reserve a large temperature margin, and thus the temperature threshold can be set to approach the theoretical temperature threshold of the MOSFET to fully exert the performance of the motor controller.

[0034] In the present invention, according to the characteristics of the components in the chip cooling path, they are divided into four - level equivalent circuits, and each level of equivalent circuit includes a thermal resistance and a heat capacity, so that an accurate MOSFET junction temperature can be obtained in a simple calculation manner.

[0035] In the present invention, the solder temperature can also be calculated to ensure that the solder temperature does not exceed the solder temperature threshold to avoid affecting the normal operation of the motor controller due to too high a solder temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Other details and advantages of the present invention will become apparent from the detailed description provided below. It should be understood that the following drawings are merely schematic and not drawn to scale, and thus cannot be considered as a limitation to the present application. The following will refer to the drawings for a detailed description, where:

[0037] Figure 1 Schematically shows a flowchart of a method for determining the MOSFET junction temperature in a motor controller according to a specific embodiment of the present invention.

[0038] Figure 2 Schematically shows the division of the components in the chip cooling path into four - level equivalent circuits.

[0039] Figure 3 Schematically shows a thermal network model of a motor controller.

[0040] Figure 4 Schematically shows experimental data of the method according to the present invention. Detailed implementation manners

[0041] Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, many specific details are set forth in order to enable those skilled in the art to more fully understand and implement the present invention. However, it is obvious to those skilled in the art that some of these specific details may not be required for the implementation of the present invention. In addition, it should be understood that the present invention is not limited to the specific embodiments described. On the contrary, the present invention can be implemented by any combination of the features and elements described below, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims, unless expressly recited in the claims.

[0042] Now refer to Figure 1 , schematically shows a flowchart of a method for determining the junction temperature of a MOSFET in a motor controller. The motor controller includes a chip encapsulating the MOSFET, a PCB, and a heat sink. The chip is disposed on one side of the PCB, and the heat sink is disposed on the other side of the PCB. The method of the present invention can be implemented by any suitable control device, such as a motor controller, and these variations do not exceed the scope of protection of the present invention. As Figure 1 shown, the method includes:

[0043] Step S101: Divide the components in the cooling path of the chip into multiple levels of equivalent circuits, and calibrate the thermal resistance value and heat capacity value of each level of equivalent circuit.

[0044] Step S102: Real-time obtain the heat sink temperature, the MOSFET heating power, the motor heating power, and the PCB heating power.

[0045] Step S103: Calculate and obtain the MOSFET junction temperature according to the heat sink temperature, the MOSFET heating power, the motor heating power, the PCB heating power, and the thermal resistance value and heat capacity value of each level of equivalent circuit.

[0046] In order to calculate the MOSFET junction temperature based on the radiator temperature, MOSFET heating power, motor heating power, PCB heating power, and the thermal resistance and heat capacity values of each stage of the equivalent circuit, the present invention provides the following specific calculation methods. However, those skilled in the art can understand that the MOSFET junction temperature can be calculated according to any suitable method based on the radiator temperature, MOSFET heating power, motor heating power, PCB heating power, and the thermal resistance and heat capacity values of each stage of the equivalent circuit, and these variations do not exceed the protection scope of the present invention.

[0047] Specifically, as Figure 2 shown, the components in the cooling path of the chip can be divided into four stages of equivalent circuits, and each stage of the equivalent circuit includes a thermal resistance R and a heat capacity C. Specifically, the chip encapsulating the MOSFET is used as the first stage of the equivalent circuit, and the first stage of the equivalent circuit includes the thermal resistance R 1 and the heat capacity C 1 ; the solder, top layer copper plating, PCB, and bottom layer copper plating are used as the second stage of the equivalent circuit, and the second stage of the equivalent circuit includes the thermal resistance R 2 and the heat capacity C 2 ; the thermal interface material is used as the third stage of the equivalent circuit, and the third stage of the equivalent circuit includes the thermal resistance R 3 and the heat capacity C 3 ; the base plate and the radiator are used as the fourth stage of the equivalent circuit, and the fourth stage of the equivalent circuit includes the thermal resistance R 4 and the heat capacity C 4 . Among them, the specific values of the thermal resistance and heat capacity of each stage of the equivalent circuit can be calibrated through experiments. Those skilled in the art can understand that although the components in the cooling path of the chip are divided into four stages of equivalent circuits according to the above rules in the present invention, those skilled in the art can also divide the components in the cooling path of the chip into multiple stages of equivalent circuits according to other suitable methods, and these variations do not exceed the protection scope of the present invention.

[0048] Figure 3 Schematically shows the thermal network model of the motor controller. As Figure 3 shown, the factors affecting the MOSFET junction temperature include the MOSFET heating power, motor heating power, PCB heating power, and the thermal resistance and heat capacity characteristics of the first to fourth stages of the equivalent circuit. Therefore, the MOSFET junction temperature T junction can be calculated according to the following formula:

[0049] ΔT x(k) =ΔT x(k-1) +T S / (τ x+ T S )·[Rx·P xloss(k) -ΔT x(k-1) , τ x =Rx C x where \(x = 1, 2, 3, 4\)

[0050] T junction(k) = \(\Delta T\) 1(k) +\(\Delta T\) 2(k) +\(\Delta T\) 3(k) +\(\Delta T\) 4(k) +T cooler(k) ,

[0051] When \(x = 1\), \(P\) loss(k) = \(P\) loss_junction(k) ,

[0052] When \(x = 2, 3, 4\), \(P\) loss(k) = \(P\) loss_junction(k) +\(P\) loss_motor(k) +\(P\) loss_pcb(k) ,

[0053] where \(k\) is the order number of detection, \(T\) S is the duration of each detection, \(T\) cooler is the radiator temperature, \(P\) loss_junction is the heat generation power of the MOSFET, \(P\) loss_motor is the heat generation power of the motor, \(P\) loss_pcb is the heat generation power of the PCB.

[0054] In addition, as Figure 3 shown, the factors affecting the solder temperature include the heat generation power of the MOSFET, the heat generation power of the motor, the heat generation power of the PCB, and the thermal resistance and heat capacity characteristics of the first to fourth stage equivalent circuits. Therefore, the solder temperature \(T\) solder can be calculated according to the following formula:

[0055] \(T\) solder(k) = \(\Delta T\) 2(k) +\(\Delta T\) 3(k) +\(\Delta T\) 4(k) +T cooler(k) .

[0056] The heat generation power of the MOSFET mainly includes conduction loss, switching loss, drive loss, and parasitic diode loss. Those skilled in the art can obtain the heat generation power of the MOSFET by means of any suitable existing detection and calculation methods, and these variations do not exceed the protection scope of the present invention.

[0057] Furthermore, as Figure 3 shown, the heat generation power \(P\) loss_pcb of the PCB and the heat generation power \(P\) loss_motor of the motor can be calculated according to the following formula:

[0058] \(P\) loss_pcb(k) = (\(T\) pcb(k) -\(T\) pcb(k-1) ) / \(R\)5 ,

[0059] P loss_motor(k) = (T motor(k) - T motor(k-1) ) / R 6 ,

[0060] wherein, T pcb is the PCB temperature, T motor is the motor temperature, and R 5 is the thermal resistance between the PCB location where a temperature sensor is set for obtaining the radiator temperature in real time and the PCB location where the chip is set, and R 6 is the thermal resistance between the location where a temperature sensor is set for obtaining the motor temperature in real time and the PCB location where the chip is set.

[0061] Specifically, the radiator temperature T cooler , the motor temperature T motor and the PCB temperature T pcb can be obtained by means of temperature sensors set at corresponding positions of the motor. For example, the radiator temperature T cooler can be obtained in real time by means of a temperature sensor set on the radiator, the motor temperature T motor can be obtained in real time by means of a temperature sensor set on the stator of the motor, and the PCB temperature T pcb can be obtained in real time by means of a temperature sensor set at a position adjacent to the chip on the PCB.

[0062] After calculating the MOSFET junction temperature, the output power of the motor controller can be adjusted so that the MOSFET junction temperature does not exceed the set junction temperature threshold.

[0063] In addition, after calculating the solder temperature, the output power of the motor controller can also be adjusted so that the solder temperature does not exceed the set solder temperature threshold.

[0064] Figure 4 Experiment data according to the method of the present invention are schematically shown. During the experiment, the MOSFET junction temperature is measured in real time while calculating the MOSFET junction temperature by using the method of the present invention. As Figure 4 shown, the error between the MOSFET junction temperature calculated according to the method of the present invention and the measured MOSFET junction temperature is very small, and the error approaches zero as the motor controller continues to operate. Therefore, the MOSFET junction temperature calculated by using the method of the present invention can be approximately equal to the true MOSFET junction temperature.

[0065] Compared with the prior art, the method for determining the MOSFET junction temperature in the motor controller according to the embodiments of the present invention has at least the following advantages:

[0066] In the present invention, during the process of calculating the junction temperature of the MOSFET, the influence of the heating power of the MOSFET, the heating power of the motor, the heating power of the PCB, and the thermal resistance and heat capacity characteristics of the components in the cooling path of the chip on the junction temperature of the MOSFET is considered, so that the calculated junction temperature of the MOSFET approaches the true junction temperature of the MOSFET.

[0067] In the present invention, since the calculated junction temperature of the MOSFET approaches the true junction temperature of the MOSFET, there is no need to reserve a large temperature margin, so that the temperature threshold can be set to approach the theoretical temperature threshold of the MOSFET, in order to give full play to the performance of the motor controller.

[0068] In the present invention, according to the characteristics of the components in the cooling path of the chip, they are divided into four - level equivalent circuits, and each level of equivalent circuit includes a thermal resistance and a heat capacity, so that an accurate MOSFET junction temperature can be obtained by a simple calculation method.

[0069] In the present invention, the solder temperature can also be calculated to ensure that the solder temperature is not higher than the solder temperature threshold, so as to avoid affecting the normal operation of the motor controller due to too high solder temperature.

[0070] It should be noted that the above description is only an example, rather than a limitation of the present invention. In other embodiments of the present invention, the method may have more, fewer or different steps, and the relationships such as the sequence, inclusion and function between the steps may be different from those described and illustrated. For example, usually multiple steps can be combined into a single step, and a single step can also be split into multiple steps. For those of ordinary skill in the art, without creative work, the changes in the sequence of each step are also within the protection scope of the present invention.

[0071] The technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor or a microcontroller to execute all or part of the steps of the methods described in various embodiments of the present invention.

[0072] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above - mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer - readable storage medium. When the program is executed, it executes the steps including the above - mentioned method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other various media that can store program codes.

[0073] Although the present invention has been disclosed above in its preferred embodiments, the present invention is not limited thereto. Any person skilled in the art, without departing from the spirit and scope of the present invention, makes various changes and modifications, which should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A method for determining the junction temperature of a MOSFET in a motor controller, wherein the motor controller comprises a chip encapsulating the MOSFET, a PCB and a heat sink, wherein the chip is arranged on one side of the PCB and the heat sink is arranged on the other side of the PCB, wherein: The method comprises: Dividing the elements in the cooling path of the chip into multiple levels of equivalent circuits, and calibrating the thermal resistance and thermal capacity of each level of equivalent circuit; Get the heat sink temperature, MOSFET heating power, motor heating power and PCB heating power in real time; The MOSFET junction temperature is calculated based on the heat sink temperature, MOSFET heat power, motor heat power, PCB heat power, and the thermal resistance and thermal capacitance of each stage of the equivalent circuit.

2. The method according to claim 1, wherein: The elements in the cooling path of the chip are divided into four levels of equivalent circuits, each level of equivalent circuit includes a thermal resistance R and a thermal capacitance C.

3. The method according to claim 2, wherein: A chip encapsulated with a MOSFET is used as a first-level equivalent circuit, wherein the first-level equivalent circuit includes a thermal resistance R1 and a thermal capacitance C1; The solder, the top copper layer, the PCB and the bottom copper layer are used as a second-level equivalent circuit, wherein the second-level equivalent circuit includes a thermal resistance R2 and a thermal capacitance C2; The thermal interface material is used as a third-level equivalent circuit, wherein the third-level equivalent circuit includes a thermal resistance R3 and a thermal capacitance C3; The base plate and the heat sink are used as a fourth-level equivalent circuit, and the fourth-level equivalent circuit includes a thermal resistor R4 and a thermal capacitor C4.

4. The method according to claim 2, wherein: Calculate the MOSFET junction temperature T according to the following formula junction : ΔT x(k) =ΔT x(k-1) +T S / (τ x+ T S ) · [R x· P xloss(k) -ΔT x(k-1) ],τ x =R x C x ,x=1,2,3,4, T junction(k) =ΔT 1(k) +ΔT 2(k) +ΔT 3(k) +ΔT 4(k) +T cooler(k) , When x=1, P loss(k) =P loss_junction(k) , When x=2,3,4,P loss(k) =P loss_junction(k) +P loss_motor(k) +P loss_pcb(k) , Where k is the order of detection, T S is the duration of each detection, T cooler is the heat sink temperature, P loss_junction is the MOSFET heat generation power, P loss_motor is the motor heating power, P loss_pcb It is the heating power of PCB.

5. The method according to claim 4, wherein: Calculate the solder temperature T according to the following formula solder : T solder(k) =ΔT 2(k) +ΔT 3(k) +ΔT 4(k) +T cooler(k) 。 6. The method according to claim 4, wherein: The radiator temperature T is obtained in real time by means of a temperature sensor arranged on the radiator. cooler .

7. The method according to claim 6, wherein: Calculate the PCB heating power P according to the following formula loss_pcb and motor heating power P loss_motor : P loss_pcb(k) =(T pcb(k) -T pcb(k-1) ) / R5, P loss_motor(k) =(T motor(k) -T motor(k-1) ) / R6, Among them, T pcb is the PCB temperature, T motor is the motor temperature, R5 is the thermal resistance from the PCB position of the temperature sensor set for real-time acquisition of the radiator temperature to the PCB position of the chip, and R6 is the thermal resistance from the position of the temperature sensor set for real-time acquisition of the motor temperature to the PCB position of the chip.

8. The method according to claim 7, wherein: Used to obtain the motor temperature T in real time motor The temperature sensor is arranged on the stator of the motor.

9. The method according to claim 7, wherein: The PCB temperature T is obtained in real time by means of a temperature sensor disposed at a position of the PCB adjacent to the chip. pcb .

10. The method according to any one of claims 1 to 9, after obtaining the MOSFET junction temperature, the method further comprises: The output power of the motor controller is adjusted so that the MOSFET junction temperature does not exceed the set temperature threshold.

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