Power conversion device and control method thereof

Abstract

The invention discloses a power conversion device, a control method of the power conversion device, an electric power steering system and a vehicle, relates to the technical field of power electronics, and aims to enable the power conversion device to adapt to working condition changes and protect a switching tube. The power conversion device comprises a bridge arm, a first current acquisition module, a first voltage acquisition module and a controller. The bridge arm comprises a first switch tube and a second switch tube which are connected in series, and a connection node of the first switch tube and the second switch tube is an output end of the power conversion device; the first voltage acquisition module is connected in parallel with the first switch tube; the controller is used for calculating the first deviation degree of the first switch tube from the first safe working area according to the current collected by the first current collection module and the voltage collected by the first voltage collection module, and sending a control signal to the first switch tube according to the first deviation degree to limit the output current of the power conversion device.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a power conversion device and a control method thereof. Background Art

[0002] The core of the electric power steering (EPS) system in electric vehicles is to use electric motors to replace traditional hydraulic devices to provide steering assistance, making driving easier and smarter.

[0003] Traditional EPS systems protect switching tubes with two methods: overcurrent protection and overheating protection. Overcurrent protection uses a resistor connected in series with the switching tube to sample current. When the sampled current exceeds a threshold, the controller immediately cuts off the switch's drive signal to prevent continued current increase and device burnout. Overheating protection uses a thermistor placed near the switching tube to collect temperature data. When the temperature exceeds the threshold, software thermal compensation is used to provide overheating protection.

[0004] However, traditional overcurrent and overheating protection technologies suffer from lag issues. The fixed threshold in overcurrent protection technology cannot adapt to changing operating conditions (for example, at low temperatures, the motor windings decrease, resulting in a higher actual heat load at the same current). In overheating protection technology, thermistors can only detect temperatures near the switching tube (for example, if the switching tube has heated to 120°C, the thermistor only detects 100°C), failing to accurately reflect the temperature of the switching tube. Summary of the Invention

[0005] The object of the present invention is to provide a power conversion device and a control method thereof, so as to enable the power conversion device to adapt to changes in operating conditions, protect the switching tube, and have no hysteresis.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a power conversion device comprising: a bridge arm, a first current acquisition module, a first voltage acquisition module, and a controller. The bridge arm is connected between a power supply terminal and a ground terminal, and includes a first switching transistor and a second switching transistor connected in series. The connection node between the first switching transistor and the second switching transistor is the output terminal of the power conversion device. The first current acquisition module and the first switching transistor are connected in series between the power supply terminal and the output terminal of the power conversion device, or the first current acquisition module and the first switching transistor are connected in series between the ground terminal and the output terminal of the power conversion device. A first voltage acquisition module is connected in parallel with the first switching transistor. A first terminal of the controller is connected to the output terminal of the first current acquisition module, and a second terminal of the controller is connected to the output terminal of the first voltage acquisition module. The controller is configured to calculate a first deviation degree of the first switching transistor from a first safe operating zone based on the current acquired by the first current acquisition module and the voltage acquired by the first voltage acquisition module, and to send a control signal to the first switching transistor based on the first deviation degree to limit the output current of the power conversion device. The first safe operating zone is the first safe operating zone corresponding to the first switching transistor.

[0008] Based on the above solution, the first current acquisition module acquires the current flowing through the first switching transistor, and the first voltage acquisition module acquires the voltage across the first switching transistor. Both the voltage and current of the first switching transistor are transmitted to the controller. Given the current current and voltage of the first switching transistor, the relevant parameters of the first switching transistor at that moment can be calculated. Based on the calculated relevant parameters, a first degree of deviation of the first switching transistor's operating state from the first safe operating zone at that moment can be calculated. Based on the first degree of deviation, the controller sends a control signal to the first switching transistor to limit the output current of the power conversion device at the next moment. This ensures that the first switching transistor always operates within the first safe operating zone, allowing the power conversion device to adapt to changing operating conditions and protect the first switching transistor. Furthermore, because the power conversion device is limited based on the current current and voltage of the first switching transistor, the protection of the first switching transistor is not affected by hysteresis.

[0009] In one embodiment, the controller is further configured to calculate the on-resistance of the first switching tube based on the current collected by the first current collection module and the voltage collected by the first voltage collection module, determine the junction temperature of the first switching tube based on the on-resistance of the first switching tube, and calculate the first deviation degree based on the current collected by the first current collection module, the voltage collected by the first voltage collection module, the on-resistance of the first switching tube, and the junction temperature of the first switching tube.

[0010] In one embodiment, the controller is further configured to calculate a power limit factor of the first switching tube based on the first deviation degree, calculate a first pre-output current of the power conversion device based on the power limit factor of the first switching tube, and limit the output current of the power conversion device based on the first pre-output current.

[0011] In one embodiment, the first current acquisition module includes: a first resistor, a first voltage detection unit, and a first operational amplifier unit. The first resistor and the first switching tube are connected in series between the power supply terminal and the output terminal of the power conversion device, or the first resistor and the first switching tube are connected in series between the ground terminal and the output terminal of the power conversion device; the first voltage detection unit is connected in parallel with the first resistor; the input terminal of the first operational amplifier unit is connected to the output terminal of the first voltage detection unit, and the output terminal of the first operational amplifier unit is connected to the first terminal of the controller. The first operational amplifier unit is configured to convert the voltage detected by the first voltage detection unit into an analog current signal.

[0012] In one embodiment, the first operational amplifier unit includes an operational amplifier or a pre-driver chip.

[0013] In one embodiment, the power conversion device further includes: a second current acquisition module and a second voltage acquisition module. When the first current acquisition module and the first switching transistor are connected in series between the ground terminal and the output terminal of the power conversion device, the second current acquisition module and the second switching transistor are connected in series between the power supply terminal and the output terminal of the power conversion device. Alternatively, when the first current acquisition module and the first switching transistor are connected in series between the power supply terminal and the output terminal of the power conversion device, the second current acquisition module and the second switching transistor are connected in series between the ground terminal and the output terminal of the power conversion device. A second voltage acquisition module is connected in parallel with the second switching transistor. The third terminal of the controller is connected to the output terminal of the second current acquisition module, and the fourth terminal of the controller is connected to the output terminal of the second voltage acquisition module. The controller is configured to calculate a second deviation degree of the second switching transistor from a second safe operating zone based on the current collected by the second current acquisition module and the voltage collected by the second voltage acquisition module, and to send a control signal to the second switching transistor based on the second deviation degree to limit the output current of the power conversion device. The second safe operating zone is the safe operating zone corresponding to the second switching transistor.

[0014] In one embodiment, the controller is further configured to calculate the on-resistance of the second switching tube based on the current collected by the second current collection module and the voltage collected by the second voltage collection module, determine the junction temperature of the second switching tube based on the on-resistance of the second switching tube, and calculate the second deviation degree based on the current collected by the second current collection module, the voltage collected by the second voltage collection module, the on-resistance of the second switching tube, and the junction temperature of the second switching tube.

[0015] In one embodiment, the controller is further configured to calculate a power limit factor of the second switch tube based on the second deviation degree, calculate a second pre-output current of the power conversion device based on the power limit factor of the second switch tube, and limit the output current of the power conversion device based on the second pre-output current.

[0016] In one embodiment, the second current acquisition module includes: a second resistor, a second voltage detection unit, and a second operational amplifier unit. The second resistor and the second switching tube are connected in series between the power supply terminal and the output terminal of the power conversion device, or the second resistor and the second switching tube are connected in series between the ground terminal and the output terminal of the power conversion device. The second voltage detection unit is connected in parallel with the second resistor. The input terminal of the second operational amplifier unit is connected to the output terminal of the second voltage detection unit, and the output terminal of the second operational amplifier unit is connected to the fourth terminal of the controller. The second operational amplifier unit is configured to convert the voltage detected by the second voltage detection unit into an analog current signal.

[0017] In one embodiment, the second operational amplifier unit includes an operational amplifier or a pre-driver chip.

[0018] In a second aspect, embodiments of the present application provide a method for controlling a power conversion device, applicable to the power conversion device described in the first aspect or any embodiment of the first aspect. The method includes calculating a first deviation degree of a first switching tube from a first safe operating zone based on a current collected by a first current acquisition module and a voltage collected by a first voltage acquisition module. A control signal is sent to the first switching tube based on the first deviation degree to limit the output current of the power conversion device, where the first safe operating zone is the first safe operating zone corresponding to the first switching tube.

[0019] In one embodiment, calculating a first degree of deviation of the first switching tube from the first safe operating area based on the current collected by the first current acquisition module and the voltage collected by the first voltage acquisition module includes: calculating the on-resistance of the first switching tube based on the current collected by the first current acquisition module and the voltage collected by the first voltage acquisition module, determining the junction temperature of the first switching tube based on the on-resistance of the first switching tube, and calculating the first degree of deviation based on the current collected by the first current acquisition module, the voltage collected by the first voltage acquisition module, the on-resistance of the first switching tube, and the junction temperature of the first switching tube.

[0020] In one embodiment, a control signal is sent to the first switching tube according to a first deviation degree to limit the output current of the power conversion device, including: calculating a power limit factor of the first switching tube according to the first deviation degree, calculating a first pre-output current of the power conversion device according to the power limit factor of the first switching tube, and limiting the output current of the power conversion device according to the first pre-output current.

[0021] In a third aspect, an embodiment of the present application provides an electric power steering system, which includes a power-assisted motor and a power conversion device connected to the power-assisted motor. The power conversion device is the power conversion device described in the first aspect or any embodiment of the first aspect.

[0022] In a fourth aspect, an embodiment of the present application provides a vehicle, the vehicle including a power battery and an electric power steering system connected to the power battery, the electric power steering system being the electric power steering system described in the third aspect or any one of the embodiments of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 A schematic diagram of a circuit topology of a power conversion device provided in the related art;

[0025] Figure 2 A schematic diagram of a circuit topology of a power conversion device provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0027] Figure 4 A corresponding relationship diagram between the on-resistance of a first switching tube and the junction temperature of the first switching tube provided in an embodiment of the present application;

[0028] Figure 5 A schematic diagram of a first safe operating area of ​​a first switching transistor provided in an embodiment of the present application;

[0029] Figure 6 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0030] Figure 7 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0031] Figure 8 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0032] Figure 9 A flow chart of a control method for a power conversion device provided in an embodiment of the present application;

[0033] Figure 10 A flow chart of another control method for a power conversion device provided in an embodiment of the present application;

[0034] Figure 11 A flow chart of a control method for a power conversion device provided in an embodiment of the present application;

[0035] Figure 12 A schematic diagram of a circuit topology of an electric power steering system provided in an embodiment of the present application;

[0036] Figure 13 A schematic diagram of a circuit topology of a vehicle provided in an embodiment of the present application.

[0037] Reference numerals:

[0038] 1. Vehicle; 20. Electric power steering system;

[0039] 200. Power conversion device; 400. Power assist motor;

[0040] 210, bridge arm; 220, first current acquisition module; 230, first voltage acquisition module;

[0041] 221. First voltage detection unit; 222. First operational amplifier unit;

[0042] 320, a second current acquisition module; 330, a second voltage acquisition module;

[0043] 321, a second voltage detection unit; 322, a second operational amplifier unit;

[0044] Q1, first switch tube; Q2, second switch tube; R1, first resistor; R2, second resistor;

[0045] V, output end of the power conversion device; VBAT, power supply end; GND, ground end; MCU, controller; bat, power battery. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] In the description of the invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "back," "inner," "outer," and the like, indicating directions or positional relationships, are based on the directions or relative positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific direction, be constructed, or operate in a specific direction. Therefore, they should not be construed as limitations on the invention. Unless otherwise specified, the above-mentioned directions may be flexibly set in actual application, provided that the relative positional relationships shown in the accompanying drawings are met.

[0048] 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 quantity of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0049] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "communicated" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections. They may be directly connected, indirectly connected through an intermediary, or internally connected between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0050] In embodiments of the present invention, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of other identical elements in the process, article, or apparatus comprising the element.

[0051] In the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0052] Before explaining the technical solutions provided by the embodiments of the present application, in order to facilitate the understanding of the embodiments of the present application, the present application first specifically describes the problems existing in the related technologies.

[0053] like Figure 1 The figure shows a circuit topology diagram of a power conversion device 100 provided by the related art. The power conversion device 100 includes: a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a sixth switch tube Q6, a first resistor R1, a second resistor R2, a third resistor R3, a first thermistor NCT1, a second thermistor NCT2, a pre-driver chip T and a controller MCU, and the connection method thereof is as follows: Figure 1 shown.

[0054] Taking the overcurrent protection and overheating protection of the second switch Q2 as an example, the second switch Q2 and the first resistor R1 are connected in series between the U-phase output terminal and the ground terminal GND of the power conversion device 100. The function of the first resistor R1 is to sample the current flowing through the second switch Q2. The voltage signal across the first resistor R1 is filtered and connected to the pre-driver chip T. The pre-driver chip T converts the voltage across the first resistor R1 into an analog current signal and transmits the analog current signal to the controller MCU. When the controller MCU detects that the current exceeds the threshold, the controller MCU immediately cuts off the drive signal to the second switch Q2 to prevent the current from continuing to increase and causing the device to burn out, thereby achieving overcurrent protection for the second switch Q2. However, due to the fixed threshold of this overcurrent protection method, the power conversion device cannot adapt to changes in operating conditions (for example, at low temperatures, the motor winding resistance decreases, and at the same current, the actual thermal load of the switch is higher. If the original overcurrent protection threshold remains unchanged, when the switch current reaches the original threshold, the switch has already burned out). As a result, there is a hysteresis in the overcurrent protection of the second switch Q2.

[0055] A first thermistor NTC1 is located near the second switching tube Q2. The first thermistor NTC1 is used to collect the temperature near the second switching tube Q2. The first thermistor NTC1 is connected to the controller MCU. The controller MCU uses the resistance value of the first thermistor NTC1 to determine the temperature of the second switching tube and then implement overheating protection measures. However, because the first thermistor NTC1 can only be placed near the second switching tube Q2, it cannot accurately detect the current temperature of the second switching tube Q2 (for example, the switching tube may have heated up to 120°C, but the thermistor only records 100°C). Therefore, this overheating protection measure also has a lag.

[0056] In order to solve the above technical problems, embodiments of the present application provide a power conversion device, a control method for a power conversion device, an electric power steering system, and a vehicle.

[0057] like Figure 2The figure shows a circuit topology diagram of a power conversion device 200 provided in an embodiment of the present application. The power conversion device 200 includes: a bridge arm 210, a first current acquisition module 220, a first voltage acquisition module 230 and a controller MCU.

[0058] The bridge arm 210 is connected between the power supply terminal VBAT and the ground terminal GND. The bridge arm 210 includes a first switch tube Q1 and a second switch tube Q2 connected in series. The connection node between the first switch tube Q1 and the second switch tube Q2 is the output terminal V of the power conversion device.

[0059] The first current acquisition module 220 and the first switch tube Q1 are connected in series between the power supply terminal VBAT and the output terminal V of the power conversion device, or the first current acquisition module 220 and the first switch tube Q1 are connected in series between the ground terminal GND and the output terminal V of the power conversion device. The first voltage acquisition module 230 is connected in parallel with the first switch tube Q1.

[0060] A first terminal of the controller MCU is connected to the output terminal of the first current acquisition module 220, and a second terminal of the controller MCU is connected to the output terminal of the first voltage acquisition module 230. The controller MCU is configured to calculate a first deviation degree of the first switch tube Q1 from a first safe operating zone based on the current collected by the first current acquisition module 220 and the voltage collected by the first voltage acquisition module 230, and to send a control signal to the first switch tube Q1 based on the first deviation degree to limit the output current of the power conversion device. The first safe operating zone is the first safe operating zone corresponding to the first switch tube Q1.

[0061] In one embodiment, the output terminal V of the power conversion device 200 may be a U-phase output terminal, a V-phase output terminal, or a W-phase output terminal, which is not limited in the present application.

[0062] In one embodiment, Figure 3 FIG2 is a circuit topology diagram of another power conversion device 200 provided in an embodiment of the present application. The first current acquisition module 220 includes: a first resistor R1 , a first voltage detection unit 221 and a first operational amplifier unit 222 .

[0063] The first resistor R1 and the first switch tube Q1 are connected in series between the power supply terminal VBAT and the output terminal V of the power conversion device, or the first resistor R1 and the first switch tube Q1 are connected in series between the ground terminal GND and the output terminal of the power conversion device.

[0064] The first voltage detection unit 221 is connected in parallel with the first resistor R1, the input end of the first operational amplifier unit 222 is connected to the output end of the first voltage detection unit 221, and the output end of the first operational amplifier unit 222 is connected to the first end of the controller MCU. The first operational amplifier unit 222 is used to convert the voltage detected by the first voltage detection unit 221 into an analog current signal.

[0065] In one implementation, the first operational amplifier unit 222 includes an operational amplifier or a pre-driver chip.

[0066] In one embodiment, the controller MCU is further configured to calculate the on-resistance of the first switch tube Q1 based on the current collected by the first current collection module 220 and the voltage collected by the first voltage collection module 230. The junction temperature of the first switch tube Q1 is determined based on the on-resistance of the first switch tube Q1. The first deviation degree is calculated based on the current collected by the first current collection module 220, the voltage collected by the first voltage collection module 230, the on-resistance of the first switch tube Q1, and the junction temperature of the first switch tube Q1.

[0067] When the first switch tube Q1 is turned on and the second switch tube Q2 is turned off, the on-resistance of the first switch tube Q1 satisfies the following formula:

[0068] R DS(on) =Vds / Ids

[0069] Among them, RDS(on) is the on-resistance of the first switch tube Q1, Vds is the voltage across the first switch tube Q1, that is, the voltage collected by the first voltage acquisition module 230, and Ids is the current flowing through the first switch tube Q1, that is, the current collected by the first current acquisition module 220.

[0070] like Figure 4 The figure shows a corresponding relationship between the on-resistance of the first switch Q1 and the junction temperature of the first switch Q1, provided by an embodiment of the present application. Tj represents the junction temperature. When the on-resistance of the first switch Q1 is known, the junction temperature of the first switch Q1 can be determined based on the corresponding relationship between the on-resistance and the junction temperature of the first switch Q1. For example, when the on-resistance RDS(on) of the first switch Q1 is 1.1 mΩ, the junction temperature Tj of the first switch Q1 is 40°C.

[0071] Because the embodiment of the present application enables the first switch Q1 to operate within the first safe operating region, the junction temperature fluctuation of the first switch Q1 is also small, which can delay device aging. Furthermore, because the first switch Q1 always operates within the first safe operating region, a first switch of lower specifications can be used for this application, which can save costs.

[0072] The first deviation degree refers to the deviation degree between the current state of the first switch tube Q1 and the first safe operating area of ​​the first switch tube Q1 .

[0073] like Figure 5 Figure 2 shows a schematic diagram of a first safe operating region (SARO) for a first switching transistor according to an embodiment of the present application. The horizontal axis represents the voltage Vds across the first switching transistor Q1, and the vertical axis represents the current Ids flowing through the first switching transistor Q1. The first SARO has five limit lines: the on-resistance Rds(on) limit line, the current limit line, the power limit line, the thermal stability limit line, and the breakdown voltage limit line. When operating in the first SARO, the first switching transistor Q1 is free from the risk of overcurrent or overheating.

[0074] The controller MCU stores the factory parameters of the first safe working area of ​​the first switch tube Q1. When the current Ids, voltage Vds, and on-resistance R of the first switch tube Q1 are known, DS(on) and junction temperature Tj, the first deviation degree can be calculated.

[0075] Specifically, the current Ids, voltage Vds, and on-resistance R of the first switch tube Q1 are actually measured. DS(on) and junction temperature Tj are processed as follows:

[0076] 1) Parameter normalization processing:

[0077]

[0078] Among them, V soa (T j ) represents the allowable voltage value of the first safe operating area at the current junction temperature, I soa (T j ) represents the allowable current value of the first safe operating area at the current junction temperature, T j (max) indicates the maximum junction temperature allowed in the first safe operating area. These values ​​can be obtained by looking up the table in the controller MCU. norm Represents the normalized voltage value, I norm represents the normalized current value, T nrom Indicates the normalized junction temperature value.

[0079] 2) Mode differentiation and dynamic weight coefficient

[0080] When Tj≥105℃, it enters the temperature dominant mode:

[0081] K V =0.25, K I =0.25, K T =0.5

[0082] Among them, KV , K I , K T Indicates the first deviation degree, which includes temperature deviation degree, current deviation degree and temperature deviation degree, K V Indicates the degree of temperature deviation, K I Indicates the degree of current deviation, K T Indicates the degree of temperature deviation.

[0083] When the threshold voltage ΔVds is detected, the voltage dominant mode is entered:

[0084] K V =0.5, K I =0.3, K T =0.2

[0085] Default balance mode:

[0086] K V =0.5, K I =0.3, K T =0.2

[0087] In one embodiment, the controller MCU is further used to calculate a power limit factor of the first switch tube Q1 based on the first deviation degree, calculate a first pre-output current of the power conversion device based on the power limit factor of the first switch tube Q1, and limit the output current of the power conversion device based on the first pre-output current.

[0088] The first deviation degree corresponds to the power limit factor. The power limit factor can represent the power limit range of the first switch Q1. The larger the power limit factor, the greater the power to be limited by the power conversion device 200 at the next moment.

[0089] Specifically, when an abnormality in the threshold current or junction temperature is detected, the system will limit power. The power limit factor α is calculated as follows:

[0090] α=1 / 1+K V ·V norm +K I I norm +K T ·T norm

[0091] Limiting the power of the power conversion device 200 may be achieved by limiting the first pre-output current. In one embodiment, the first pre-output current of the power conversion device 200 satisfies the following formula:

[0092] I out =I ref ×min(α,1)

[0093] Among them, Iout is the first pre-output current of the power conversion device 200, I ref is the target current of the power conversion device 200 originally set at the next moment, α is the power derating factor, and the range of α is 0-1.

[0094] Continue to see Figure 2 , the voltage and current of the first switch tube Q1 are transmitted to the controller MCU. When the current and voltage of the first switch tube Q1 at the current moment are known, the relevant parameters of the first switch tube Q1 at the current moment can be calculated. Based on the calculated relevant parameters, the first degree of deviation of the operating state of the first switch tube Q1 at the current moment from the first safe operating zone can be calculated. The controller sends a control signal to the first switch tube based on the first degree of deviation to limit the output current of the power conversion device at the next moment, thereby ensuring that the first switch tube Q1 always operates in the first safe operating zone, and further ensuring that the power conversion device 200 can adapt to changes in operating conditions and protect the first switch tube Q1. Moreover, because the restrictions on the power conversion device 200 are based on the current and voltage of the first switch tube Q1 at the current moment, and thus limit the output current of the power conversion device 200 at the next moment, the protection of the first switch tube Q1 does not have hysteresis.

[0095] In one embodiment, Figure 6 FIG2 is a circuit topology diagram of another power conversion device 200 provided in an embodiment of the present application. The power conversion device 200 further includes: a second current acquisition module 320 and a second voltage acquisition module 330 .

[0096] When the first current acquisition module 220 and the first switch tube Q1 are connected in series between the ground terminal GND and the output terminal V of the power conversion device, the second current acquisition module 320 and the second switch tube Q2 are connected in series between the power supply terminal VBAT and the output terminal V of the power conversion device. Alternatively, when the first current acquisition module 220 and the first switch tube Q1 are connected in series between the power supply terminal VBAT and the output terminal V of the power conversion device, the second current acquisition module 320 and the second switch tube Q2 are connected in series between the ground terminal GND and the output terminal V of the power conversion device, and the second voltage acquisition module 330 is connected in parallel with the second switch tube Q2.

[0097] A third terminal of the controller MCU is connected to the output terminal of the second current acquisition module 320, and a fourth terminal of the controller MCU is connected to the output terminal of the second voltage acquisition module 330. The controller MCU is configured to calculate a second degree of deviation of the second switch tube Q2 from the second safe operating zone based on the current collected by the second current acquisition module 320 and the voltage collected by the second voltage acquisition module 330, and to send a control signal to the second switch tube Q2 based on the second degree of deviation to limit the output current of the power conversion device 200. The second safe operating zone is the safe operating zone corresponding to the second switch tube Q2.

[0098] Figure 6 When the power conversion device 200 is single-phase, the first switch tube Q1 and the second switch tube Q2 are protected at the same time, which can make the power conversion device 200 work safer.

[0099] In one embodiment, Figure 7 FIG. 1 is a circuit topology diagram of another power conversion device 200 provided in an embodiment of the present application. The second current acquisition module 320 includes: a second resistor R2 , a second voltage detection unit 321 , and a second operational amplifier unit 322 .

[0100] The second resistor R2 and the second switch tube Q2 are connected in series between the power supply terminal VBAT and the output terminal V of the power conversion device 200, or the second resistor R2 and the second switch tube Q2 are connected in series between the ground terminal GND and the output terminal V of the power conversion device; the second voltage detection unit 321 is connected in parallel with the second resistor R2.

[0101] The input end of the second operational amplifier unit 322 is connected to the output end of the second voltage detection unit 321, and the output end of the second operational amplifier unit 322 is connected to the fourth end of the controller MCU. The second operational amplifier unit 322 is used to convert the voltage detected by the second voltage detection unit 321 into an analog current signal.

[0102] In one implementation, the second operational amplifier unit 322 includes an operational amplifier or a pre-driver chip.

[0103] In one embodiment, the controller MCU is further configured to calculate the on-resistance of the second switch tube Q2 based on the current collected by the second current acquisition module 320 and the voltage collected by the second voltage acquisition module 330. The junction temperature of the second switch tube Q2 is determined based on the on-resistance of the second switch tube Q2. The second deviation degree is calculated based on the current collected by the second current acquisition module 320, the voltage collected by the second voltage acquisition module 330, the on-resistance of the second switch tube Q2, and the junction temperature of the second switch tube Q2.

[0104] In one embodiment, the controller MCU is further used to calculate a power limit factor of the second switch tube Q2 based on the second deviation degree, calculate a second pre-output current of the power conversion device based on the power limit factor of the second switch tube Q2, and limit the output current of the power conversion device based on the second pre-output current.

[0105] The calculation process of the voltage, current, on-resistance, junction temperature and second deviation degree of the second switch tube Q2 is the same as that of the first switch tube Q1 and will not be repeated here.

[0106] In one embodiment, Figure 8 FIG. 1 is a circuit topology diagram of another power conversion device provided in an embodiment of the present application. Figure 8 This figure shows the circuit topology for protecting each switch when the power conversion device 200 is three-phase. Similarly, when the power conversion device 200 is two-phase, the circuit topology for protecting each switch is the same as for single-phase and three-phase. Because the protection structure of the switch is the same, it will not be described here in detail.

[0107] like Figure 9 The figure shows a flow chart of a control method of a power conversion device provided by an embodiment of the present application. The circuit topology of the power conversion device is as described above. Figures 2 to 8 The circuit topology of the power conversion device shown in any of the accompanying drawings. The control method of the power conversion device includes: S110-S120.

[0108] S110 . Calculate a first deviation degree of the first switch tube Q1 from the first safe operating area according to the current collected by the first current collection module 220 and the voltage collected by the first voltage collection module 230 .

[0109] In one embodiment, Figure 10 The figure shows a flow chart of another control method of a power conversion device provided in an embodiment of the present application, where S110 includes: S111-S113.

[0110] S111 . Calculate the on-resistance of the first switching tube according to the current collected by the first current collection module and the voltage collected by the first voltage collection module.

[0111] S112 : Determine the junction temperature of the first switching tube according to the on-resistance of the first switching tube.

[0112] S113 . Calculate a first deviation degree according to the current collected by the first current collection module, the voltage collected by the first voltage collection module, the on-resistance of the first switching tube, and the junction temperature of the first switching tube.

[0113] S120 : Send a control signal to the first switch tube Q1 according to the first deviation degree to limit the output current of the power conversion device.

[0114] The first safe operating region is a first safe operating region corresponding to the first switch tube Q1 .

[0115] In some embodiments, as Figure 11 The figure shows a flow chart of another control method of a power conversion device provided in an embodiment of the present application, where S120 includes: S121-S123.

[0116] S121. Calculate a power limit factor of the first switch tube according to the first deviation degree.

[0117] S122: Calculate a first pre-output current of the power conversion device according to the power limit factor of the first switch tube.

[0118] S123: Limit the output current of the power conversion device according to the first pre-output current.

[0119] like Figure 12 The circuit topology diagram of an electric power steering system 20 provided in an embodiment of the present application is shown. The electric power steering system 20 includes a power-assisted motor 400 and a power conversion device 200 connected to the power-assisted motor 400. The circuit topology of the power conversion device 200 is as described above. Figure 2-Figure 3 and Figure 6-Figure 8 The circuit topology of the power conversion device 200 shown in any of the figures.

[0120] like Figure 13 The circuit topology diagram of a vehicle 1 provided in an embodiment of the present application is shown. The vehicle 1 includes a power battery bat and an electric power steering system 20 connected to the power battery bat. The circuit topology of the electric power steering system 20 is as described above. Figure 12 The circuit topology of the electric power steering system 20 is shown in FIG.

[0121] The above detailed description of the power conversion device 200 and the analysis of the beneficial effects can be correspondingly referred to the control method of the power conversion device, the electric power steering system 20 and the vehicle 1 of the embodiment of the present application, and will not be repeated here.

[0122] The above is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A power conversion device (200), characterized in that: include: A bridge arm (210), the bridge arm (210) being connected between a power supply terminal (VBAT) and a ground terminal (GND), the bridge arm (210) comprising a first switch tube (Q1) and a second switch tube (Q2) connected in series, the connection node between the first switch tube (Q1) and the second switch tube (Q2) being the output terminal (V) of the power conversion device (200); a first current acquisition module (220), wherein the first current acquisition module (220) and the first switch tube (Q1) are connected in series between the power supply terminal (VBAT) and the output terminal (V) of the power conversion device (200); or, the first current acquisition module (220) and the first switch tube (Q1) are connected in series between the ground terminal (GND) and the output terminal (V) of the power conversion device (200); a first voltage acquisition module (230), the first voltage acquisition module (230) being connected in parallel with the first switch tube (Q1); a controller (MCU), wherein a first end of the controller (MCU) is connected to an output end of the first current acquisition module (220), and a second end of the controller (MCU) is connected to an output end of the first voltage acquisition module (230); The controller (MCU) is configured to calculate a first deviation degree of the first switch tube (Q1) from a first safe operating zone based on the current collected by the first current collection module (220) and the voltage collected by the first voltage collection module (230), and to send a control signal to the first switch tube (Q1) based on the first deviation degree to limit the output current of the power conversion device (200), wherein the first safe operating zone is a first safe operating zone corresponding to the first switch tube (Q1).

2. The power conversion device (200) according to claim 1, characterized in that The controller (MCU) is further configured to calculate the on-resistance of the first switch tube (Q1) based on the current collected by the first current collection module (220) and the voltage collected by the first voltage collection module (230); determining a junction temperature of the first switching tube (Q1) according to an on-resistance of the first switching tube (Q1); The first deviation degree is calculated based on the current collected by the first current collection module (220), the voltage collected by the first voltage collection module (230), the on-resistance of the first switch tube (Q1), and the junction temperature of the first switch tube (Q1).

3. The power conversion device (200) according to claim 1 or 2, characterized in that: The controller (MCU) is further configured to calculate a power limit factor of the first switch tube (Q1) according to the first deviation degree; Calculating a first pre-output current of the power conversion device (200) according to a power limit factor of the first switch tube (Q1); The output current of the power conversion device (200) is limited according to the first pre-output current.

4. The power conversion device (200) according to claim 1, characterized in that The first current acquisition module (220) comprises: a first resistor (R1), the first resistor (R1) and the first switch tube (Q1) being connected in series between the power supply terminal (VBAT) and the output terminal (V) of the power conversion device (200), or the first resistor (R1) and the first switch tube (Q1) being connected in series between the ground terminal (GND) and the output terminal (V) of the power conversion device (200); a first voltage detection unit (221), the first voltage detection unit (221) being connected in parallel with the first resistor (R1); A first operational amplifier unit (222), wherein the input end of the first operational amplifier unit (222) is connected to the output end of the first voltage detection unit (221), the output end of the first operational amplifier unit (222) is connected to the first end of the controller (MCU), and the first operational amplifier unit (222) is used to convert the voltage detected by the first voltage detection unit (221) into an analog current signal.

5. The power conversion device (200) according to claim 4, characterized in that: The first operational amplifier unit (222) includes an operational amplifier or a pre-driver chip.

6. The power conversion device (200) according to claim 1, characterized in that The power conversion device (200) further includes: The second current acquisition module (320) is connected in series between the ground terminal (GND) and the output terminal (V) of the power conversion device (200) with the first current acquisition module (220) and the first switch tube (Q1), and the second current acquisition module (320) and the second switch tube (Q2) are connected in series between the power supply terminal (VBAT) and the output terminal (V) of the power conversion device (200); or When the first current acquisition module (220) and the first switch tube (Q1) are connected in series between the power supply terminal (VBAT) and the output terminal (V) of the power conversion device (200), the second current acquisition module (320) and the second switch tube (Q2) are connected in series between the ground terminal (GND) and the output terminal (V) of the power conversion device (200); a second voltage acquisition module (330), the second voltage acquisition module (330) being connected in parallel with the second switch tube (Q2); The third terminal of the controller (MCU) is connected to the output terminal of the second current acquisition module (320), and the fourth terminal of the controller (MCU) is connected to the output terminal of the second voltage acquisition module (330); The controller (MCU) is configured to calculate a second degree of deviation of the second switch tube (Q2) from a second safe operating zone based on the current collected by the second current collection module (320) and the voltage collected by the second voltage collection module (330), and to send a control signal to the second switch tube (Q2) based on the second degree of deviation to limit the output current of the power conversion device (200), wherein the second safe operating zone is a safe operating zone corresponding to the second switch tube (Q2).

7. The power conversion device (200) according to claim 6, characterized in that The controller (MCU) is further configured to calculate the on-resistance of the second switch tube (Q2) based on the current collected by the second current collection module (320) and the voltage collected by the second voltage collection module (330); determining a junction temperature of the second switching tube (Q2) according to an on-resistance of the second switching tube (Q2); The second deviation degree is calculated based on the current collected by the second current collection module (320), the voltage collected by the second voltage collection module (330), the on-resistance of the second switch tube (Q2), and the junction temperature of the second switch tube (Q2).

8. The power conversion device (200) according to claim 6 or 7, characterized in that: The controller (MCU) is further configured to calculate a power limit factor of the second switch tube (Q2) according to the second deviation degree; Calculating a second pre-output current of the power conversion device (200) according to the power limit factor of the second switch tube (Q2); The output current of the power conversion device (200) is limited according to the second pre-output current.

9. The power conversion device (200) according to claim 6, characterized in that: The second current acquisition module (320) comprises: a second resistor (R2), wherein the second resistor (R2) and the second switch tube (Q2) are connected in series between the power supply terminal (VBAT) and the output terminal (V) of the power conversion device (200); or, the second resistor (R2) and the second switch tube (Q2) are connected in series between the ground terminal (GND) and the output terminal (V) of the power conversion device (200); a second voltage detection unit (321), the second voltage detection unit (321) being connected in parallel with the second resistor (R2); A second operational amplifier unit (322), wherein the input end of the second operational amplifier unit (322) is connected to the output end of the second voltage detection unit (321), the output end of the second operational amplifier unit (322) is connected to the fourth end of the controller (MCU), and the second operational amplifier unit (322) is used to convert the voltage detected by the second voltage detection unit (321) into an analog current signal.

10. The power conversion device (200) according to claim 9, characterized in that: The second operational amplifier unit (322) includes an operational amplifier or a pre-driver chip.

11. A control method for a power conversion device (200), characterized in that: Applied to the power conversion device (200) according to any one of claims 1 to 5, the method comprising: Calculating a first deviation degree of the first switch tube (Q1) from a first safe operating area based on the current collected by the first current collection module (220) and the voltage collected by the first voltage collection module (230); A control signal is sent to the first switch tube (Q1) according to the first deviation degree to limit the output current of the power conversion device (200), and the first safe operating area is the first safe operating area corresponding to the first switch tube (Q1).

12. The control method of the power conversion device (200) according to claim 11, characterized in that: Calculating a first deviation degree of the first switch tube (Q1) from a first safe operating area based on the current collected by the first current collection module (220) and the voltage collected by the first voltage collection module (230) comprises: Calculating the on-resistance of the first switch tube (Q1) based on the current collected by the first current collection module (220) and the voltage collected by the first voltage collection module (230); determining a junction temperature of the first switching tube (Q1) according to an on-resistance of the first switching tube (Q1); The first deviation degree is calculated based on the current collected by the first current collection module (220), the voltage collected by the first voltage collection module (230), the on-resistance of the first switch tube (Q1), and the junction temperature of the first switch tube (Q1).

13. The control method of the power conversion device (200) according to claim 11, characterized in that: The sending of a control signal to the first switch tube (Q1) according to the first deviation degree to limit the output current of the power conversion device (200) includes: calculating a power limit factor of the first switch tube (Q1) according to the first deviation degree; Calculating a first pre-output current of the power conversion device (200) according to a power limit factor of the first switch tube (Q1); The output current of the power conversion device (200) is limited according to the first pre-output current.

14. An electric power steering system (20), characterized in that: The electric power steering system (20) comprises a power-assisted motor (400) and a power conversion device (200) according to any one of claims 1 to 10, connected to the power-assisted motor (400).

15. A vehicle (1), characterized in that The vehicle (1) comprises a power battery (bat), and an electric power steering system (20) according to claim 14 connected to the power battery (bat).

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